Radar and microphysical characteristics of convective storms simulated from a numerical model using a new microphysical parameterization

NASA Technical Reports Server (NTRS)

Ferrier, Brad S.; Tao, Wei-Kuo; Simpson, Joanne

1991-01-01

The basic features of a new and improved bulk-microphysical parameterization capable of simulating the hydrometeor structure of convective systems in all types of large-scale environments (with minimal adjustment of coefficients) are studied. Reflectivities simulated from the model are compared with radar observations of an intense midlatitude convective system. Simulated reflectivities using the novel four-class ice scheme with a microphysical parameterization rain distribution at 105 min are illustrated. Preliminary results indicate that this new ice scheme works efficiently in simulating midlatitude continental storms.

Use of Collocated KWAJEX Satellite, Aircraft, and Ground Measurements for Understanding Ambiguities in TRMM Radiometer Rain Profile Algorithm

NASA Technical Reports Server (NTRS)

Smith, Eric A.; Fiorino, Steven

2002-01-01

Coordinated ground, aircraft, and satellite observations are analyzed from the 1999 TRMM Kwajalein Atoll field experiment (KWAJEX) to better understand the relationships between cloud microphysical processes and microwave radiation intensities in the context of physical evaluation of the Level 2 TRMM radiometer rain profile algorithm and uncertainties with its assumed microphysics-radiation relationships. This talk focuses on the results of a multi-dataset analysis based on measurements from KWAJEX surface, air, and satellite platforms to test the hypothesis that uncertainties in the passive microwave radiometer algorithm (TMI 2a12 in the nomenclature of TRMM) are systematically coupled and correlated with the magnitudes of deviation of the assumed 3-dimensional microphysical properties from observed microphysical properties. Re-stated, this study focuses on identifying the weaknesses in the operational TRMM 2a12 radiometer algorithm based on observed microphysics and radiation data in terms of over-simplifications used in its theoretical microphysical underpinnings. The analysis makes use of a common transform coordinate system derived from the measuring capabilities of the aircraft radiometer used to survey the experimental study area, i.e., the 4-channel AMPR radiometer flown on the NASA DC-8 aircraft. Normalized emission and scattering indices derived from radiometer brightness temperatures at the four measuring frequencies enable a 2-dimensional coordinate system that facilities compositing of Kwajalein S-band ground radar reflectivities, ARMAR Ku-band aircraft radar reflectivities, TMI spacecraft radiometer brightness temperatures, PR Ku-band spacecraft radar reflectivities, bulk microphysical parameters derived from the aircraft-mounted cloud microphysics laser probes (including liquid/ice water contents, effective liquid/ice hydrometeor radii, and effective liquid/ice hydrometeor variances), and rainrates derived from any of the individual ground, aircraft, or satellite algorithms applied to the radar or radiometer measurements, or their combination. The results support the study's underlying hypothesis, particularly in context of ice phase processes, in that the cloud regions where the 2a12 algorithm's microphysical database most misrepresents the microphysical conditions as determined by the laser probes, are where retrieved surface rainrates are most erroneous relative to other reference rainrates as determined by ground and aircraft radar. In reaching these conclusions, TMI and PR brightness temperatures and reflectivities have been synthesized from the aircraft AMPR and ARMAR measurements with the analysis conducted in a composite framework to eliminate measurement noise associated with the case study approach and single element volumes obfuscated by heterogeneous beam filling effects. In diagnosing the performance of the 2a12 algorithm, weaknesses have been found in the cloud-radiation database used to provide microphysical guidance to the algorithm for upper cloud ice microphysics. It is also necessary to adjust a fractional convective rainfall factor within the algorithm somewhat arbitrarily to achieve satisfactory algorithm accuracy.

Evaluation of simulated tropical convective updraft hydrometeor properties using aircraft observations

NASA Astrophysics Data System (ADS)

Stanford, McKenna W.

The High Altitude Ice Crystals - High Ice Water Content (HAIC-HIWC) field campaign produced aircraft retrievals of total condensed water content (TWC), hydrometeor particle size distributions, and vertical velocity (w) in high ice water content regions of tropical mesoscale convective systems (MCSs). These observations are used to evaluate deep convective updraft properties in high-resolution nested Weather Research and Forecasting (WRF) simulations of observed MCSs. Because simulated hydrometeor properties are highly sensitive to the parameterization of microphysics, three commonly used microphysical parameterizations are tested, including two bulk schemes (Thompson and Morrison) and one bin scheme (Fast Spectral Bin Microphysics). A commonly documented bias in cloud-resolving simulations is the exaggeration of simulated radar reflectivities aloft in tropical MCSs. This may result from overly strong convective updrafts that loft excessive condensate mass and from simplified approximations of hydrometeor size distributions, properties, species separation, and microphysical processes. The degree to which the reflectivity bias is a separate function of convective dynamics, condensate mass, and hydrometeor size has yet to be addressed. This research untangles these components by comparing simulated and observed relationships between w, TWC, and hydrometer size as a function of temperature. All microphysics schemes produce median mass diameters that are generally larger than observed for temperatures between -10 °C and -40 °C and TWC > 1 g m-3. Observations produce a prominent mode in the composite mass size distribution around 300 microm, but under most conditions, all schemes shift the distribution mode to larger sizes. Despite a much greater number of samples, all simulations fail to reproduce observed high TWC or high w conditions between -20 °C and -40 °C in which only a small fraction of condensate mass is found in relatively large particle sizes. Increasing model resolution and employing explicit cloud droplet nucleation decrease the size bias, but not nearly enough to reproduce observations. Because simulated particle sizes are too large across all schemes when controlling for temperature, w, and TWC, this bias is hypothesized to partly result from errors in parameterized microphysical processes in addition to overly simplified hydrometeor properties such as mass-size relationships and particle size distribution parameters.

Evidence of Mineral Dust Altering Cloud Microphysics and Precipitation

NASA Technical Reports Server (NTRS)

Min, Qilong; Li, Rui; Lin, Bing; Joseph, Everette; Wang, Shuyu; Hu, Yongxiang; Morris, Vernon; Chang, F.

2008-01-01

Multi-platform and multi-sensor observations are employed to investigate the impact of mineral dust on cloud microphysical and precipitation processes in mesoscale convective systems. It is clearly evident that for a given convection strength,small hydrometeors were more prevalent in the stratiform rain regions with dust than in those regions that were dust free. Evidence of abundant cloud ice particles in the dust sector, particularly at altitudes where heterogeneous nucleation process of mineral dust prevails, further supports the observed changes of precipitation. The consequences of the microphysical effects of the dust aerosols were to shift the precipitation size spectrum from heavy precipitation to light precipitation and ultimately suppressing precipitation.

Validation of Microphysical Schemes in a CRM Using TRMM Satellite

NASA Astrophysics Data System (ADS)

Li, X.; Tao, W.; Matsui, T.; Liu, C.; Masunaga, H.

2007-12-01

The microphysical scheme in the Goddard Cumulus Ensemble (GCE) model has been the most heavily developed component in the past decade. The cloud-resolving model now has microphysical schemes ranging from the original Lin type bulk scheme, to improved bulk schemes, to a two-moment scheme, to a detailed bin spectral scheme. Even with the most sophisticated bin scheme, many uncertainties still exist, especially in ice phase microphysics. In this study, we take advantages of the long-term TRMM observations, especially the cloud profiles observed by the precipitation radar (PR), to validate microphysical schemes in the simulations of Mesoscale Convective Systems (MCSs). Two contrasting cases, a midlatitude summertime continental MCS with leading convection and trailing stratiform region, and an oceanic MCS in tropical western Pacific are studied. The simulated cloud structures and particle sizes are fed into a forward radiative transfer model to simulate the TRMM satellite sensors, i.e., the PR, the TRMM microwave imager (TMI) and the visible and infrared scanner (VIRS). MCS cases that match the structure and strength of the simulated systems over the 10-year period are used to construct statistics of different sensors. These statistics are then compared with the synthetic satellite data obtained from the forward radiative transfer calculations. It is found that the GCE model simulates the contrasts between the continental and oceanic case reasonably well, with less ice scattering in the oceanic case comparing with the continental case. However, the simulated ice scattering signals for both PR and TMI are generally stronger than the observations, especially for the bulk scheme and at the upper levels in the stratiform region. This indicates larger, denser snow/graupel particles at these levels. Adjusting microphysical schemes in the GCE model according the observations, especially the 3D cloud structure observed by TRMM PR, result in a much better agreement.

Ice phase in altocumulus clouds over Leipzig: remote sensing observations and detailed modeling

NASA Astrophysics Data System (ADS)

Simmel, M.; Bühl, J.; Ansmann, A.; Tegen, I.

2015-09-01

The present work combines remote sensing observations and detailed cloud modeling to investigate two altocumulus cloud cases observed over Leipzig, Germany. A suite of remote sensing instruments was able to detect primary ice at rather high temperatures of -6 °C. For comparison, a second mixed phase case at about -25 °C is introduced. To further look into the details of cloud microphysical processes, a simple dynamics model of the Asai-Kasahara (AK) type is combined with detailed spectral microphysics (SPECS) forming the model system AK-SPECS. Vertical velocities are prescribed to force the dynamics, as well as main cloud features, to be close to the observations. Subsequently, sensitivity studies with respect to ice microphysical parameters are carried out with the aim to quantify the most important sensitivities for the cases investigated. For the cases selected, the liquid phase is mainly determined by the model dynamics (location and strength of vertical velocity), whereas the ice phase is much more sensitive to the microphysical parameters (ice nucleating particle (INP) number, ice particle shape). The choice of ice particle shape may induce large uncertainties that are on the same order as those for the temperature-dependent INP number distribution.

Ice phase in altocumulus clouds over Leipzig: remote sensing observations and detailed modelling

NASA Astrophysics Data System (ADS)

Simmel, M.; Bühl, J.; Ansmann, A.; Tegen, I.

2015-01-01

The present work combines remote sensing observations and detailed cloud modeling to investigate two altocumulus cloud cases observed over Leipzig, Germany. A suite of remote sensing instruments was able to detect primary ice at rather warm temperatures of -6 °C. For comparison, a second mixed phase case at about -25 °C is introduced. To further look into the details of cloud microphysical processes a simple dynamics model of the Asai-Kasahara type is combined with detailed spectral microphysics forming the model system AK-SPECS. Vertical velocities are prescribed to force the dynamics as well as main cloud features to be close to the observations. Subsequently, sensitivity studies with respect to ice microphysical parameters are carried out with the aim to quantify the most important sensitivities for the cases investigated. For the cases selected, the liquid phase is mainly determined by the model dynamics (location and strength of vertical velocity) whereas the ice phase is much more sensitive to the microphysical parameters (ice nuclei (IN) number, ice particle shape). The choice of ice particle shape may induce large uncertainties which are in the same order as those for the temperature-dependent IN number distribution.

Improving a Spectral Bin Microphysical Scheme Using TRMM Satellite Observations

NASA Technical Reports Server (NTRS)

Li, Xiaowen; Tao, Wei-Kuo; Matsui, Toshihisa; Liu, Chuntao; Masunaga, Hirohiko

2010-01-01

Comparisons between cloud model simulations and observations are crucial in validating model performance and improving physical processes represented in the mod Tel.hese modeled physical processes are idealized representations and almost always have large rooms for improvements. In this study, we use data from two different sensors onboard TRMM (Tropical Rainfall Measurement Mission) satellite to improve the microphysical scheme in the Goddard Cumulus Ensemble (GCE) model. TRMM observed mature-stage squall lines during late spring, early summer in central US over a 9-year period are compiled and compared with a case simulation by GCE model. A unique aspect of the GCE model is that it has a state-of-the-art spectral bin microphysical scheme, which uses 33 different bins to represent particle size distribution of each of the seven hydrometeor species. A forward radiative transfer model calculates TRMM Precipitation Radar (PR) reflectivity and TRMM Microwave Imager (TMI) 85 GHz brightness temperatures from simulated particle size distributions. Comparisons between model outputs and observations reveal that the model overestimates sizes of snow/aggregates in the stratiform region of the squall line. After adjusting temperature-dependent collection coefficients among ice-phase particles, PR comparisons become good while TMI comparisons worsen. Further investigations show that the partitioning between graupel (a high-density form of aggregate), and snow (a low-density form of aggregate) needs to be adjusted in order to have good comparisons in both PR reflectivity and TMI brightness temperature. This study shows that long-term satellite observations, especially those with multiple sensors, can be very useful in constraining model microphysics. It is also the first study in validating and improving a sophisticated spectral bin microphysical scheme according to long-term satellite observations.

Dwarfs in the Deepest Fields at Noon: Studying Size and Shape of Low-mass Galaxies out to z 3 in Five HST Legacy Fields

NASA Astrophysics Data System (ADS)

Guo, Yicheng

2017-08-01

Galaxies with stellar mass 100x-1000x times smaller than our Milky Way (hereafter dwarf galaxies or DGs) are important for understanding galaxy formation and evolution by being the most sensitive probes of both the macro-physics of dark matter halos and the micro-physics of the different physical mechanisms that regulate star formation and shape galaxies. Currently, however, observations of distant DGs have been hampered by small samples and poor quality due to their faintness. We propose an archival study of the size, morphology, and structures of DGs out to z 3.0 by combining the archived data from five of the deepest regions that HST has ever observed: eXtreme Deep Field (XDF, updated from HUDF) and the Hubble Legacy Fields (HLFs). Our program would be the first to advance the morphology studies of DGs to the Cosmic Noon (z 2), and hence place unprecedented constraints on models of galaxy structure formation. Equally important is the data product of our program: multi-wavelength photometry and morphology catalogs for all detected galaxies in these fields. These catalogs would be a timely treasure for the public to prepare for the coming JWST era by providing detailed information of small, faint, but important objects in some deepest HST fields for JWST observations.

Microphysical and Radiative Characteristics of Convective Clouds during COHMEX.

NASA Astrophysics Data System (ADS)

Fulton, Richard; Heymsfield, Gerald M.

1991-01-01

The use of passive remote microwave radiance measurements above cloud tops for rainrate estimation is complicated by the complex nature of cloud microphysics. The knowledge of the microphysical structure of clouds, specifically the hydrometeor types, shapes, sizes, and their vertical distribution, is important because radiative emission and scattering effects are dependent upon the hydrometeor distribution. This paper has two purposes: first, to document the structure and evolution of two strong thunderstorms in Alabama using radar multiparameter data; and second, to relate the inferred microphysics to the resulting upwelling microwave radiance observed concurrently by high altitude aircraft. These measurements were collected during the COHMEX field program in the summer of 1986. The radar analysis includes a description of the parameters reflectivity Z, differential reflectivity ZDR, linear depolarization ratio LDR, and hail signal HS for two thunderstorm cases on 11 July 1986. The simultaneous aircraft data includes passive microwave brightness temperature (TB) measurements at four frequencies ranging from 18 to 183 GHz as well as visible and infrared data.The remote radar observations reveal the existence of large ice particles within the storms which is likely to have caused the observed low microwave brightness temperatures. By relating the evolution of the radar measureables to the microwave TB's it has been found that knowledge of the storm microphysics and its evolution is important to adequately understand the microwave TB's.

Arctic biomass burning aerosol event-microphysical property retrieval

NASA Astrophysics Data System (ADS)

Böckmann, Christine; Ritter, Christoph; Ortiz-Amezcua, Pablo

2018-04-01

An intense biomass-burning (BB) event from North America in July 2015 was observed over Ny-Ålesund (Spitsbergen, European Arctic). An extreme air pollution took place and aerosol optical depth (AOD) of more than 1 at 500nm occurs in middle and lower troposphere. We analyse data from the multi-wavelength Raman-lidar KARL of Alfred Wegener Institute to derive microphysical properties of the aerosol of one interesting layer from 3186 to 3306 m via regularization. We found credible and confidential microphysical parameters.

Numerical Analysis Using WRF-SBM for the Cloud Microphysical Structures in the C3VP Field Campaign: Impacts of Supercooled Droplets and Resultant Riming on Snow Microphysics

NASA Technical Reports Server (NTRS)

Iguchi, Takamichi; Matsui, Toshihisa; Shi, Jainn J.; Tao, Wei-Kuo; Khain, Alexander P.; Hao, Arthur; Cifelli, Robert; Heymsfield, Andrew; Tokay, Ali

2012-01-01

Two distinct snowfall events are observed over the region near the Great Lakes during 19-23 January 2007 under the intensive measurement campaign of the Canadian CloudSat/CALIPSO validation project (C3VP). These events are numerically investigated using the Weather Research and Forecasting model coupled with a spectral bin microphysics (WRF-SBM) scheme that allows a smooth calculation of riming process by predicting the rimed mass fraction on snow aggregates. The fundamental structures of the observed two snowfall systems are distinctly characterized by a localized intense lake-effect snowstorm in one case and a widely distributed moderate snowfall by the synoptic-scale system in another case. Furthermore, the observed microphysical structures are distinguished by differences in bulk density of solid-phase particles, which are probably linked to the presence or absence of supercooled droplets. The WRF-SBM coupled with Goddard Satellite Data Simulator Unit (G-SDSU) has successfully simulated these distinctive structures in the three-dimensional weather prediction run with a horizontal resolution of 1 km. In particular, riming on snow aggregates by supercooled droplets is considered to be of importance in reproducing the specialized microphysical structures in the case studies. Additional sensitivity tests for the lake-effect snowstorm case are conducted utilizing different planetary boundary layer (PBL) models or the same SBM but without the riming process. The PBL process has a large impact on determining the cloud microphysical structure of the lake-effect snowstorm as well as the surface precipitation pattern, whereas the riming process has little influence on the surface precipitation because of the small height of the system.

Introducing Convective Cloud Microphysics to a Deep Convection Parameterization Facilitating Aerosol Indirect Effects

NASA Astrophysics Data System (ADS)

Alapaty, K.; Zhang, G. J.; Song, X.; Kain, J. S.; Herwehe, J. A.

2012-12-01

Short lived pollutants such as aerosols play an important role in modulating not only the radiative balance but also cloud microphysical properties and precipitation rates. In the past, to understand the interactions of aerosols with clouds, several cloud-resolving modeling studies were conducted. These studies indicated that in the presence of anthropogenic aerosols, single-phase deep convection precipitation is reduced or suppressed. On the other hand, anthropogenic aerosol pollution led to enhanced precipitation for mixed-phase deep convective clouds. To date, there have not been many efforts to incorporate such aerosol indirect effects (AIE) in mesoscale models or global models that use parameterization schemes for deep convection. Thus, the objective of this work is to implement a diagnostic cloud microphysical scheme directly into a deep convection parameterization facilitating aerosol indirect effects in the WRF-CMAQ integrated modeling systems. Major research issues addressed in this study are: What is the sensitivity of a deep convection scheme to cloud microphysical processes represented by a bulk double-moment scheme? How close are the simulated cloud water paths as compared to observations? Does increased aerosol pollution lead to increased precipitation for mixed-phase clouds? These research questions are addressed by performing several WRF simulations using the Kain-Fritsch convection parameterization and a diagnostic cloud microphysical scheme. In the first set of simulations (control simulations) the WRF model is used to simulate two scenarios of deep convection over the continental U.S. during two summer periods at 36 km grid resolution. In the second set, these simulations are repeated after incorporating a diagnostic cloud microphysical scheme to study the impacts of inclusion of cloud microphysical processes. Finally, in the third set, aerosol concentrations simulated by the CMAQ modeling system are supplied to the embedded cloud microphysical scheme to study impacts of aerosol concentrations on precipitation and radiation fields. Observations available from the ARM microbase data, the SURFRAD network, GOES imagery, and other reanalysis and measurements will be used to analyze the impacts of a cloud microphysical scheme and aerosol concentrations on parameterized convection.

Improving Representation of Convective Transport for Scale-Aware Parameterization – Part I: Convection and Cloud Properties Simulated with Spectral Bin and Bulk Microphysics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fan, Jiwen; Liu, Yi-Chin; Xu, Kuan-Man

2015-04-27

The ultimate goal of this study is to improve representation of convective transport by cumulus parameterization for meso-scale and climate models. As Part I of the study, we perform extensive evaluations of cloud-resolving simulations of a squall line and mesoscale convective complexes in mid-latitude continent and tropical regions using the Weather Research and Forecasting (WRF) model with spectral-bin microphysics (SBM) and with two double-moment bulk microphysics schemes: a modified Morrison (MOR) and Milbrandt and Yau (MY2). Compared to observations, in general, SBM gives better simulations of precipitation, vertical velocity of convective cores, and the vertically decreasing trend of radar reflectivitymore » than MOR and MY2, and therefore will be used for analysis of scale-dependence of eddy transport in Part II. The common features of the simulations for all convective systems are (1) the model tends to overestimate convection intensity in the middle and upper troposphere, but SBM can alleviate much of the overestimation and reproduce the observed convection intensity well; (2) the model greatly overestimates radar reflectivity in convective cores (SBM predicts smaller radar reflectivity but does not remove the large overestimation); and (3) the model performs better for mid-latitude convective systems than tropical system. The modeled mass fluxes of the mid latitude systems are not sensitive to microphysics schemes, but are very sensitive for the tropical case indicating strong microphysics modification to convection. Cloud microphysical measurements of rain, snow and graupel in convective cores will be critically important to further elucidate issues within cloud microphysics schemes.« less

Vertical structure and microphysical characteristics of precipitation on the high terrain and lee side of the Olympic Mountains

NASA Astrophysics Data System (ADS)

Zagrodnik, J. P.; McMurdie, L. A.; Houze, R.

2017-12-01

As mid-latitude cyclones pass over coastal mountain ranges, the processes producing their clouds and precipitation are modified when they encounter complex terrain, leading to a maximum in precipitation fallout on the windward slopes and a minimum on the lee side. The precipitation that does reach the high terrain and lee side of a mountain range can be theoretically determined by a complex interaction between the dynamics of air lifting over the terrain, the thermodynamics of moist air, and the microphysical time required to grow particles large enough to fall out. To date, there have been few observational studies that have focused on the nonlinear microphysical processes contributing to the variability of precipitation that is received on the lee side slopes of a mountain range such as the Olympic Mountains. The 2015-16 Olympic Mountains Experiment (OLYMPEX) collected unprecedented observations on the high terrain and lee side of the Olympic Mountains including frequent soundings on Vancouver Island, dual-polarization Doppler radar, multi-frequency airborne radar, and ground-based particle size and crystal habit observations at the higher elevation Hurricane Ridge site. We utilize these observations to examine the evolution of the vertical structure and microphysical precipitation characteristics over the high terrain and leeside within the context of large-scale dynamic and thermodynamic conditions that evolve during the passage of cold season mid-latitude cyclones. The primary goal is to determine the degree to which the observed variability in lee side precipitation amount and microphysical properties are controlled by variations in temperature, flow speed and direction, shear, and stability associated with characteristic synoptic storm sectors and frontal passages.

Heavy rain forecasts in mesoscale convective system in July 2016 in Belarus

NASA Astrophysics Data System (ADS)

Lapo, Palina; Barodka, Siarhei; Krasouski, Aliaksandr

2017-04-01

During the last decade, the frequency of severe weather phenomena, such as heavy precipitation, hail and squalls, over Europe is observed to increase, which is attributed to climate change in the region. Such hazardous weather events over the territory of Belarus every year, having significant economic and social effects. Of special interest for further studies are mesoscale convective systems, which can be described as long-lived cloud complexes including groups of cumulonimbus clouds and squall lines. Passage of such systems is accompanied with intense thunderstorms, showers and squally wind. In this study, we investigate a case of Mesoscale Convective System (MCS) passage over the territory of Belarus, which occurred 13 July 2016. During this Mesoscale Convective Complex passage, heavy precipitation (up to 43 mm), squally winds and intense thunderstorms have been observed. Another feature of this MCS was the hook-shaped weather radar signature known as a "hook echo", seen on the Doppler weather radar Minsk-2. Tornadoes and powerful mesocyclones are often characterized by the presence of a hook echo on radar. Also we have performed simulations of the convective complex passage with the WRF-ARW mesoscale atmospheric modelling system using 6 different microphysics parameterizations. Our main objectives are to study the conditions of this Mesoscale Convective Systems (MCSs) development, to consider the microphysical structure of clouds in the MCS, and to identify which microphysics package provides the best forecast of precipitation for this case of MCS in terms of its geographical distribution and precipitation amount in towns and cities where highest levels of precipitation have been observed. We present analysis of microphysical structure of this MCS along with evaluation of precipitation forecasts obtained with different microphysics parametrizations as compared to real observational data. In particular, we may note that results of almost all microphysics simulations indicate underestimation of precipitation areas in the region of interest.

Numerical Study of the Role of Microphysical Latent Heating and Surface Heat Fluxes in a Severe Precipitation Event in the Warm Sector over Southern China

NASA Astrophysics Data System (ADS)

Yin, Jin-Fang; Wang, Dong-Hai; Liang, Zhao-Ming; Liu, Chong-Jian; Zhai, Guo-Qing; Wang, Hong

2018-02-01

Simulations of the severe precipitation event that occurred in the warm sector over southern China on 08 May 2014 are conducted using the Advanced Weather Research and Forecasting (WRF-ARWv3.5.1) model to investigate the roles of microphysical latent heating and surface heat fluxes during the severe precipitation processes. At first, observations from surface rain gauges and ground-based weather radars are used to evaluate the model outputs. Results show that the spatial distribution of 24-h accumulated precipitation is well reproduced, and the temporal and spatial distributions of the simulated radar reflectivity agree well with the observations. Then, several sensitive simulations are performed with the identical model configurations, except for different options in microphysical latent heating and surface heat fluxes. From the results, one of the significant findings is that the latent heating from warm rain microphysical processes heats the atmosphere in the initial phase of the precipitation and thus convective systems start by self-triggering and self-organizing, despite the fact that the environmental conditions are not favorable to the occurrence of precipitation event at the initial phase. In the case of the severe precipitation event over the warm sector, both warm and ice microphysical processes are active with the ice microphysics processes activated almost two hours later. According to the sensitive results, there is a very weak precipitation without heavy rainfall belt when microphysical latent heating is turned off. In terms of this precipitation event, the warm microphysics processes play significant roles on precipitation intensity, while the ice microphysics processes have effects on the spatial distribution of precipitation. Both surface sensible and latent heating have effects on the precipitation intensity and spatial distribution. By comparison, the surface sensible heating has a strong influence on the spatial distribution of precipitation, and the surface latent heating has only a slight impact on the precipitation intensity. The results indicate that microphysical latent heating might be an important factor for severe precipitation forecast in the warm sector over southern China. Surface sensible heating can have considerable influence on the precipitation spatial distribution and should not be neglected in the case of weak large-scale conditions with abundant water vapor in the warm sector.

Intercomparison of microphysical datasets collected from CAIPEEX observations and WRF simulation

NASA Astrophysics Data System (ADS)

Pattnaik, S.; Goswami, B.; Kulkarni, J.

2009-12-01

In the first phase of ongoing Cloud Aerosol Interaction and Precipitation Enhancement Experiment (CAIPEEX) program of Indian Institute of Tropical Meteorology (IITM), intensive cloud microphysical datasets are collected over India during the May through September, 2009. This study is designed to evaluate the forecast skills of existing cloud microphysical parameterization schemes (i.e. single moment/double moments) within the WRF-ARW model (Version 3.1.1) during different intensive observation periods (IOP) over the targeted regions spreading all across India. Basic meteorological and cloud microphysical parameters obtained from the model simulations are validated against the observed data set collected during CAIPEEX program. For this study, we have considered three IOP phases (i.e. May 23-27, June 11-15, July 3-7) carried out over northern, central and western India respectively. This study emphasizes the thrust to understand the mechanism of evolution, intensification and distribution of simulated precipitation forecast upto day four (i.e. 96 hour forecast). Efforts have also been made to carryout few important microphysics sensitivity experiments within the explicit schemes to investigate their respective impact on the formation and distribution of vital cloud parameters (e.g. cloud liquid water, frozen hydrometeors) and model rainfall forecast over the IOP regions. The characteristic features of liquid and frozen hydrometers in the pre-monsoon and monsoon regimes are examined from model forecast as well as from CAIPEEX observation data set for different IOPs. The model is integrated in a triply nested fashion with an innermost nest explicitly resolved at a horizontal resolution of 4km.In this presentation preliminary results from aforementioned research initiatives will be introduced.

A study of cloud microphysics and precipitation over the Tibetan Plateau by radar observations and cloud-resolving model simulations: Cloud Microphysics over Tibetan Plateau

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gao, Wenhua; Sui, Chung-Hsiung; Fan, Jiwen

Cloud microphysical properties and precipitation over the Tibetan Plateau (TP) are unique because of the high terrains, clean atmosphere, and sufficient water vapor. With dual-polarization precipitation radar and cloud radar measurements during the Third Tibetan Plateau Atmospheric Scientific Experiment (TIPEX-III), the simulated microphysics and precipitation by the Weather Research and Forecasting model (WRF) with the Chinese Academy of Meteorological Sciences (CAMS) microphysics and other microphysical schemes are investigated through a typical plateau rainfall event on 22 July 2014. Results show that the WRF-CAMS simulation reasonably reproduces the spatial distribution of 24-h accumulated precipitation, but has limitations in simulating time evolutionmore » of precipitation rates. The model-calculated polarimetric radar variables have biases as well, suggesting bias in modeled hydrometeor types. The raindrop sizes in convective region are larger than those in stratiform region indicated by the small intercept of raindrop size distribution in the former. The sensitivity experiments show that precipitation processes are sensitive to the changes of warm rain processes in condensation and nucleated droplet size (but less sensitive to evaporation process). Increasing droplet condensation produces the best area-averaged rain rate during weak convection period compared with the observation, suggesting a considerable bias in thermodynamics in the baseline simulation. Increasing the initial cloud droplet size causes the rain rate reduced by half, an opposite effect to that of increasing droplet condensation.« less

Campaign datasets for Biomass Burning Observation Project (BBOP)

DOE Data Explorer

Kleinman,Larry; Mei,Fan; Arnott,William; Buseck,Peter; Chand,Duli; Comstock,Jennifer; Dubey,Manvendra; Lawson,Paul; Long,Chuck; Onasch,Timothy; Sedlacek,Arthur; Senum,Gunnar; Shilling,John; Springston,Stephen; Tomlinson,Jason; Wang,Jian

2014-04-24

This field campaign will address multiple uncertainties in aerosol intensive properties, which are poorly represented in climate models, by means of aircraft measurements in biomass burning plumes. Key topics to be investigated are: 1. Aerosol mixing state and morphology 2. Mass absorption coefficients (MACs) 3. Chemical composition of non-refractory material associated with light-absorbing carbon (LAC) 4. Production rate of secondary organic aerosol (SOA) 5. Microphysical processes relevant to determining aerosol size distributions and single scattering albedo (SSA) 6. CCN activity. These topics will be investigated through measurements near active fires (0-5 hours downwind), where limited observations indicate rapid changes in aerosol properties, and in biomass burning plumes aged >5 hours. Aerosol properties and their time evolution will be determined as a function of fire type, defined according to fuel and the mix of flaming and smoldering combustion at the source.

Studying Precipitation Processes in WRF with Goddard Bulk Microphysics in Comparison with Other Microphysical Schemes

NASA Technical Reports Server (NTRS)

Tao, W.K.; Shi, J.J.; Braun, S.; Simpson, J.; Chen, S.S.; Lang, S.; Hong, S.Y.; Thompson, G.; Peters-Lidard, C.

2009-01-01

A Goddard bulk microphysical parameterization is implemented into the Weather Research and Forecasting (WRF) model. This bulk microphysical scheme has three different options, 2ICE (cloud ice & snow), 3ICE-graupel (cloud ice, snow & graupel) and 3ICE-hail (cloud ice, snow & hail). High-resolution model simulations are conducted to examine the impact of microphysical schemes on different weather events: a midlatitude linear convective system and an Atlantic hurricane. The results suggest that microphysics has a major impact on the organization and precipitation processes associated with a summer midlatitude convective line system. The Goddard 3ICE scheme with the cloud ice-snow-hail configuration agreed better with observations ill of rainfall intensity and having a narrow convective line than did simulations with the cloud ice-snow-graupel and cloud ice-snow (i.e., 2ICE) configurations. This is because the Goddard 3ICE-hail configuration has denser precipitating ice particles (hail) with very fast fall speeds (over 10 m/s) For an Atlantic hurricane case, the Goddard microphysical scheme (with 3ICE-hail, 3ICE-graupel and 2ICE configurations) had no significant impact on the track forecast but did affect the intensity slightly. The Goddard scheme is also compared with WRF's three other 3ICE bulk microphysical schemes: WSM6, Purdue-Lin and Thompson. For the summer midlatitude convective line system, all of the schemes resulted in simulated precipitation events that were elongated in southwest-northeast direction in qualitative agreement with the observed feature. However, the Goddard 3ICE-hail and Thompson schemes were closest to the observed rainfall intensities although the Goddard scheme simulated more heavy rainfall (over 48 mm/h). For the Atlantic hurricane case, none of the schemes had a significant impact on the track forecast; however, the simulated intensity using the Purdue-Lin scheme was much stronger than the other schemes. The vertical distributions of model-simulated cloud species (e.g., snow) are quite sensitive to the microphysical schemes, which is an issue for future verification against satellite retrievals. Both the Purdue-Lin and WSM6 schemes simulated very little snow compared to the other schemes for both the midlatitude convective line and hurricane case. Sensitivity tests with these two schemes showed that increasing the snow intercept, turning off the auto-conversion from snow to graupel, eliminating dry growth, and reducing the transfer processes from cloud-sized particles to precipitation-sized ice collectively resulted in a net increase in those schemes' snow amounts.

Evaluation of Mixed-Phase Microphysics Within Winter Storms using Field Data and In Situ Observations

NASA Technical Reports Server (NTRS)

Colle, Brian A.; Yu, Ruyi; Molthan, Andrew L.; Nesbitt, Stephen

2014-01-01

It is hypothesized that microphysical predictions have greater uncertainties/errors when there are complex interactions that result from mixedphased processes like riming. Use Global Precipitation Measurement (GPM) Mission ground validation studies in Ontario, Canada to verify and improve parameterizations

Passive microwave structure of severe tornadic storms on 16 November 1987

NASA Technical Reports Server (NTRS)

Heymsfield, Gerald M.; Fulton, Richard

1994-01-01

Passive microwave observations using the Special Sensor Microwave/Imager (SSM/I) are presented for severe tornadic storms in the lower midwestern United States on 16 November 1987. These measurements are compared with Geostationary Operational Environmental Satellite infrared (IR) measurements for the same case. The IR observations had a classic 'V' cold feature commonly associated with severe Midwest thunderstorms. The minimum microwave brightness temperatures at 86 GHz, which primarily respond to ice scattering by larger ice particles, were located in the convective region and the warm interior of the anvil top, between the arms of the IR V feature. The interior warm region was the only portion of the entire anvil region that had high 86-GHz polarization difference temperatures. Microphysical implications of these multispectral observations are discussed. The observations suggest that there are large variations of ice microphysical characteristics spatially and vertically in the anvil region. These observations are discussed in the context of previous dynamical and microphysical hypotheses on the IR V feature.

The variability of tropical ice cloud properties as a function of the large-scale context from ground-based radar-lidar observations over Darwin, Australia

NASA Astrophysics Data System (ADS)

Protat, A.; Delanoë, J.; May, P. T.; Haynes, J.; Jakob, C.; O'Connor, E.; Pope, M.; Wheeler, M. C.

2011-08-01

The high complexity of cloud parameterizations now held in models puts more pressure on observational studies to provide useful means to evaluate them. One approach to the problem put forth in the modelling community is to evaluate under what atmospheric conditions the parameterizations fail to simulate the cloud properties and under what conditions they do a good job. It is the ambition of this paper to characterize the variability of the statistical properties of tropical ice clouds in different tropical "regimes" recently identified in the literature to aid the development of better process-oriented parameterizations in models. For this purpose, the statistical properties of non-precipitating tropical ice clouds over Darwin, Australia are characterized using ground-based radar-lidar observations from the Atmospheric Radiation Measurement (ARM) Program. The ice cloud properties analysed are the frequency of ice cloud occurrence, the morphological properties (cloud top height and thickness), and the microphysical and radiative properties (ice water content, visible extinction, effective radius, and total concentration). The variability of these tropical ice cloud properties is then studied as a function of the large-scale cloud regimes derived from the International Satellite Cloud Climatology Project (ISCCP), the amplitude and phase of the Madden-Julian Oscillation (MJO), and the large-scale atmospheric regime as derived from a long-term record of radiosonde observations over Darwin. The vertical variability of ice cloud occurrence and microphysical properties is largest in all regimes (1.5 order of magnitude for ice water content and extinction, a factor 3 in effective radius, and three orders of magnitude in concentration, typically). 98 % of ice clouds in our dataset are characterized by either a small cloud fraction (smaller than 0.3) or a very large cloud fraction (larger than 0.9). In the ice part of the troposphere three distinct layers characterized by different statistically-dominant microphysical processes are identified. The variability of the ice cloud properties as a function of the large-scale atmospheric regime, cloud regime, and MJO phase is large, producing mean differences of up to a factor 8 in the frequency of ice cloud occurrence between large-scale atmospheric regimes and mean differences of a factor 2 typically in all microphysical properties. Finally, the diurnal cycle of the frequency of occurrence of ice clouds is also very different between regimes and MJO phases, with diurnal amplitudes of the vertically-integrated frequency of ice cloud occurrence ranging from as low as 0.2 (weak diurnal amplitude) to values in excess of 2.0 (very large diurnal amplitude). Modellers should now use these results to check if their model cloud parameterizations are capable of translating a given atmospheric forcing into the correct statistical ice cloud properties.

Diurnal Variation of Tropical Ice Cloud Microphysics: Evidence from Global Precipitation Measurement Microwave Imager Polarimetric Measurements

NASA Astrophysics Data System (ADS)

Gong, Jie; Zeng, Xiping; Wu, Dong L.; Li, Xiaowen

2018-01-01

The diurnal variation of tropical ice clouds has been well observed and examined in terms of the occurring frequency and total mass but rarely from the viewpoint of ice microphysical parameters. It accounts for a large portion of uncertainties in evaluating ice clouds' role on global radiation and hydrological budgets. Owing to the advantage of precession orbit design and paired polarized observations at a high-frequency microwave band that is particularly sensitive to ice particle microphysical properties, 3 years of polarimetric difference (PD) measurements using the 166 GHz channel of Global Precipitation Measurement Microwave Imager (GPM-GMI) are compiled to reveal a strong diurnal cycle over tropical land (30°S-30°N) with peak amplitude varying up to 38%. Since the PD signal is dominantly determined by ice crystal size, shape, and orientation, the diurnal cycle observed by GMI can be used to infer changes in ice crystal properties. Moreover, PD change is found to lead the diurnal changes of ice cloud occurring frequency and total ice mass by about 2 h, which strongly implies that understanding ice microphysics is critical to predict, infer, and model ice cloud evolution and precipitation processes.

A Robust Multi-Scale Modeling System for the Study of Cloud and Precipitation Processes

NASA Technical Reports Server (NTRS)

Tao, Wei-Kuo

2012-01-01

During the past decade, numerical weather and global non-hydrostatic models have started using more complex microphysical schemes originally developed for high resolution cloud resolving models (CRMs) with 1-2 km or less horizontal resolutions. These microphysical schemes affect the dynamic through the release of latent heat (buoyancy loading and pressure gradient) the radiation through the cloud coverage (vertical distribution of cloud species), and surface processes through rainfall (both amount and intensity). Recently, several major improvements of ice microphysical processes (or schemes) have been developed for cloud-resolving model (Goddard Cumulus Ensemble, GCE, model) and regional scale (Weather Research and Forecast, WRF) model. These improvements include an improved 3-ICE (cloud ice, snow and graupel) scheme (Lang et al. 2010); a 4-ICE (cloud ice, snow, graupel and hail) scheme and a spectral bin microphysics scheme and two different two-moment microphysics schemes. The performance of these schemes has been evaluated by using observational data from TRMM and other major field campaigns. In this talk, we will present the high-resolution (1 km) GeE and WRF model simulations and compared the simulated model results with observation from recent field campaigns [i.e., midlatitude continental spring season (MC3E; 2010), high latitude cold-season (C3VP, 2007; GCPEx, 2012), and tropical oceanic (TWP-ICE, 2006)].

Lidar investigations on the optical and dynamical properties of cirrus clouds in the upper troposphere and lower stratosphere regions at a tropical station, Gadanki, India (13.5°N, 79.2°E)

NASA Astrophysics Data System (ADS)

Krishnakumar, Vasudevannair; Satyanarayana, Malladi; Radhakrishnan, Soman R.; Dhaman, Reji K.; Jayeshlal, Glory Selvan; Motty, Gopinathan Nair S.; Pillai, Vellara P. Mahadevan; Raghunath, Karnam; Ratnam, Madineni Venkat; Rao, Duggirala Ramakrishna; Sudhakar, Pindlodi

2014-01-01

High altitude cirrus clouds are composed mainly of ice crystals with a variety of sizes and shapes. They have a large influence on Earth's energy balance and global climate. Recent studies indicate that the formation, dissipation, life time, optical, and micro-physical properties are influenced by the dynamical conditions of the surrounding atmosphere like background aerosol, turbulence, etc. In this work, an attempt has been made to quantify some of these characteristics by using lidar and mesosphere-stratosphere-troposphere (MST) radar. Mie lidar and 53 MHz MST radar measurements made over 41 nights during the period 2009 to 2010 from the tropical station, Gadanki, India (13.5°N, 79.2°E). The optical and microphysical properties along with the structure and dynamics of the cirrus are presented as observed under different atmospheric conditions. The study reveals the manifestation of different forms of cirrus with a preferred altitude of formation in the 13 to 14 km altitude. There are considerable differences in the properties obtained among 2009 and 2010 showing significant anomalous behavior in 2010. The clouds observed during 2010 show relatively high asymmetry and large multiple scattering effects. The anomalies found during 2010 may be attributed to the turbulence noticed in the surrounding atmosphere. The results show a clear correlation between the crystal morphology in the clouds and the dynamical conditions of the prevailing atmosphere during the observational period.

Two Distinct Modes in One-Day Rainfall Event during MC3E Field Campaign: Analyses of Disdrometer Observations and WRF-SBM Simulation

NASA Technical Reports Server (NTRS)

Iguchi, Takamichi; Matsui, Toshihisa; Tokay, Ali; Kollias, Pavlos; Tao, Wei-Kuo

2012-01-01

A unique microphysical structure of rainfall is observed by the surface laser optical Particle Size and Velocity (Parsivel) disdrometers on 25 April 2011 during Midlatitude Continental Convective Clouds Experiment (MC3E). According to the systematic differences in rainfall rate and bulk effective droplet radius, the sampling data can be divided into two groups; the rainfall mostly from the deep convective clouds has relatively high rainfall rate and large bulk effective droplet radius, whereas the reverse is true for the rainfall from the shallow wrm clouds. The Weather Research and Forecasting model coupled with spectral bin microphysics (WRF-SBM) successfully reproduces the two distinct modes in the observed rainfall microphysical structure. The results show that the up-to-date model can demonstrate how the cloud physics and the weather condition on the day are involved in forming the unique rainfall characteristic.

Two distinct modes in one-day rainfall event during MC3E field campaign: Analyses of disdrometer observations and WRF-SBM simulation

NASA Astrophysics Data System (ADS)

Iguchi, Takamichi; Matsui, Toshihisa; Tokay, Ali; Kollias, Pavlos; Tao, Wei-Kuo

2012-12-01

A unique microphysical structure of rainfall is observed by the surface laser optical Particle Size and Velocity (Parsivel) disdrometers on 25 April 2011 during Midlatitude Continental Convective Clouds Experiment (MC3E). According to the systematic differences in rainfall rate and bulk effective droplet radius, the sampling data can be divided into two groups; the rainfall mostly from the deep convective clouds has relatively high rainfall rate and large bulk effective droplet radius, whereas the reverse is true for the rainfall from the shallow warm clouds. The Weather Research and Forecasting model coupled with spectral bin microphysics (WRF-SBM) successfully reproduces the two distinct modes in the observed rainfall microphysical structure. The results show that the up-to-date model can demonstrate how the cloud physics and the weather condition on the day are involved in forming the unique rainfall characteristic.

Diurnal Variation of Tropical Ice Cloud Microphysics inferred from Global Precipitation Measurement Microwave Imager (GPM-GMI)'s Polarimetric Measurement

NASA Astrophysics Data System (ADS)

Gong, J.; Zeng, X.; Wu, D. L.; Li, X.

2017-12-01

Diurnal variation of tropical ice cloud has been well observed and examined in terms of the area of coverage, occurring frequency, and total mass, but rarely on ice microphysical parameters (habit, size, orientation, etc.) because of lack of direct measurements of ice microphysics on a high temporal and spatial resolutions. This accounts for a great portion of the uncertainty in evaluating ice cloud's role on global radiation and hydrological budgets. The design of Global Precipitation Measurement (GPM) mission's procession orbit gives us an unprecedented opportunity to study the diurnal variation of ice microphysics on the global scale for the first time. Dominated by cloud ice scattering, high-frequency microwave polarimetric difference (PD, namely the brightness temperature difference between vertically- and horizontally-polarized paired channel measurements) from the GPM Microwave Imager (GMI) has been proven by our previous study to be very valuable to infer cloud ice microphysical properties. Using one year of PD measurements at 166 GHz, we found that cloud PD exhibits a strong diurnal cycle in the tropics (25S-25N). The peak PD amplitude varies as much as 35% over land, compared to only 6% over ocean. The diurnal cycle of the peak PD value is strongly anti-correlated with local ice cloud occurring frequency and the total ice mass with a leading period of 3 hours for the maximum correlation. The observed PD diurnal cycle can be explained by the change of ice crystal axial ratio. Using a radiative transfer model, we can simulate the observed 166 GHz PD-brightness temperature curve as well as its diurnal variation using different axial ratio values, which can be caused by the diurnal variation of ice microphysical properties including particle size, percentage of horizontally-aligned non-spherical particles, and ice habit. The leading of the change of PD ahead of ice cloud mass and occurring frequency implies the important role microphysics play in the formation and dissipation processes of ice clouds and frozen precipitations.

Evaluation of Microphysics and Cumulus Schemes of WRF for Forecasting of Heavy Monsoon Rainfall over the Southeastern Hilly Region of Bangladesh

NASA Astrophysics Data System (ADS)

Hasan, Md Alfi; Islam, A. K. M. Saiful

2018-05-01

Accurate forecasting of heavy rainfall is crucial for the improvement of flood warning to prevent loss of life and property damage due to flash-flood-related landslides in the hilly region of Bangladesh. Forecasting heavy rainfall events is challenging where microphysics and cumulus parameterization schemes of Weather Research and Forecast (WRF) model play an important role. In this study, a comparison was made between observed and simulated rainfall using 19 different combinations of microphysics and cumulus schemes available in WRF over Bangladesh. Two severe rainfall events during 11th June 2007 and 24-27th June 2012, over the eastern hilly region of Bangladesh, were selected for performance evaluation using a number of indicators. A combination of the Stony Brook University microphysics scheme with Tiedtke cumulus scheme is found as the most suitable scheme for reproducing those events. Another combination of the single-moment 6-class microphysics scheme with New Grell 3D cumulus schemes also showed reasonable performance in forecasting heavy rainfall over this region. The sensitivity analysis confirms that cumulus schemes play a greater role than microphysics schemes for reproducing the heavy rainfall events using WRF.

Impacts of Microphysical Scheme on Convective and Stratiform Characteristics in Two High Precipitation Squall Line Events

NASA Technical Reports Server (NTRS)

Wu, Di; Dong, Xiquan; Xi, Baike; Feng, Zhe; Kennedy, Aaron; Mullendore, Gretchen; Gilmore, Matthew; Tao, Wei-Kuo

2013-01-01

This study investigates the impact of snow, graupel, and hail processes on simulated squall lines over the Southern Great Plains in the United States. The Weather Research and Forecasting (WRF) model is used to simulate two squall line events in Oklahoma during May 2007, and the simulations are validated against radar and surface observations. Several microphysics schemes are tested in this study, including the WRF 5-Class Microphysics (WSM5), WRF 6-Class Microphysics (WSM6), Goddard Cumulus Ensemble (GCE) Three Ice (3-ice) with graupel, Goddard Two Ice (2-ice), and Goddard 3-ice hail schemes. Simulated surface precipitation is sensitive to the microphysics scheme when the graupel or hail categories are included. All of the 3-ice schemes overestimate the total precipitation with WSM6 having the largest bias. The 2-ice schemes, without a graupel/hail category, produce less total precipitation than the 3-ice schemes. By applying a radar-based convective/stratiform partitioning algorithm, we find that including graupel/hail processes increases the convective areal coverage, precipitation intensity, updraft, and downdraft intensities, and reduces the stratiform areal coverage and precipitation intensity. For vertical structures, simulations have higher reflectivity values distributed aloft than the observed values in both the convective and stratiform regions. Three-ice schemes produce more high reflectivity values in convective regions, while 2-ice schemes produce more high reflectivity values in stratiform regions. In addition, this study has demonstrated that the radar-based convective/stratiform partitioning algorithm can reasonably identify WRF-simulated precipitation, wind, and microphysical fields in both convective and stratiform regions.

Use of Combined A-Train Observations to Validate GEOS Model Simulated Dust Distributions During NAMMA

NASA Technical Reports Server (NTRS)

Nowottnick, E.

2007-01-01

During August 2006, the NASA African Multidisciplinary Analyses Mission (NAMMA) field experiment was conducted to characterize the structure of African Easterly Waves and their evolution into tropical storms. Mineral dust aerosols affect tropical storm development, although their exact role remains to be understood. To better understand the role of dust on tropical cyclogenesis, we have implemented a dust source, transport, and optical model in the NASA Goddard Earth Observing System (GEOS) atmospheric general circulation model and data assimilation system. Our dust source scheme is more physically based scheme than previous incarnations of the model, and we introduce improved dust optical and microphysical processes through inclusion of a detailed microphysical scheme. Here we use A-Train observations from MODIS, OMI, and CALIPSO with NAMMA DC-8 flight data to evaluate the simulated dust distributions and microphysical properties. Our goal is to synthesize the multi-spectral observations from the A-Train sensors to arrive at a consistent set of optical properties for the dust aerosols suitable for direct forcing calculations.

Simultaneous Estimation of Microphysical Parameters and Atmospheric State Variables With Radar Data and Ensemble Square-root Kalman Filter

NASA Astrophysics Data System (ADS)

Tong, M.; Xue, M.

2006-12-01

An important source of model error for convective-scale data assimilation and prediction is microphysical parameterization. This study investigates the possibility of estimating up to five fundamental microphysical parameters, which are closely involved in the definition of drop size distribution of microphysical species in a commonly used single-moment ice microphysics scheme, using radar observations and the ensemble Kalman filter method. The five parameters include the intercept parameters for rain, snow and hail/graupel, and the bulk densities of hail/graupel and snow. Parameter sensitivity and identifiability are first examined. The ensemble square-root Kalman filter (EnSRF) is employed for simultaneous state and parameter estimation. OSS experiments are performed for a model-simulated supercell storm, in which the five microphysical parameters are estimated individually or in different combinations starting from different initial guesses. When error exists in only one of the microphysical parameters, the parameter can be successfully estimated without exception. The estimation of multiple parameters is found to be less robust, with end results of estimation being sensitive to the realization of the initial parameter perturbation. This is believed to be because of the reduced parameter identifiability and the existence of non-unique solutions. The results of state estimation are, however, always improved when simultaneous parameter estimation is performed, even when the estimated parameters values are not accurate.

Microphysics, Radiation and Surface Processes in the Goddard Cumulus Ensemble (GCE) Model

NASA Technical Reports Server (NTRS)

Tao, Wei-Kuo

2002-01-01

In this talk, five specific major GCE improvements: (1) ice microphysics, (2) longwave and shortwave radiative transfer processes, (3) land surface processes, (4) ocean surface fluxes and (5) ocean mixed layer processes are presented. The performance of these new GCE improvements will be examined. Observations are used for model validation.

Microphysical parameters of cirrus clouds using lidar at a tropical station, Gadanki, Tirupati (13.5° N, 79.2°E), India

NASA Astrophysics Data System (ADS)

Satyanarayana, M.; Radhakrishnan, S.-R.; Krishnakumar, V.; Mahadevan Pillai, V. P.; Raghunath, K.

2008-12-01

Cirrus clouds have been identified as one of the most uncertain component in the atmospheric research. It is known that cirrus clouds modulate the earth's climate through direct and indirect modification of radiation. The role of cirrus clouds depends mainly on their microphysical properties. To understand cirrus clouds better, we must observe and characterize their properties. In-situ observation of such clouds is a challenging experiment, as the clouds are located at high altitudes. Active remote sensing method based on lidar can detect high and thin cirrus clouds with good spatial and temporal resolution. We present the result obtained on the microphysical properties of the cirrus clouds at two Tropical stations namely Gadhanki, Tirupati (13.50 N, 79.20 E), India and Trivandrum (13.50 N, 770 E) Kerala, India from the ground based pulsed Nd: YAG lidar systems installed at the stations. A variant of the widely used Klett's lidar inversion method with range dependent scattering ratio is used for the present study for the retrieval of aerosol extinction and microphysical parameters of cirrus cloud.

Ice formation in altocumulus clouds over Leipzig: Remote sensing measurements and detailed model simulations

NASA Astrophysics Data System (ADS)

Simmel, Martin; Bühl, Johannes; Ansmann, Albert; Tegen, Ina

2014-05-01

Over Leipzig, altocumulus clouds are frequently observed using a suite of remote sensing instruments. These observations cover a wide range of heights, temperatures, and microphysical properties of the clouds ranging from purely liquid to heavily frozen. For the current study, two cases were chosen to test the sensitivity of these clouds with respect to several microphysical and dynamical parameters such as aerosol properties (CCN, IN), ice particle shape as well as turbulence. The mixed-phase spectral microphysical model SPECS was coupled to a dynamical model of the Asai-Kasahara type resulting in the model system AK-SPECS. The relatively simple dynamics allows for a fine vertical resolution needed for the rather shallow cloud layers observed. Additionally, the proper description of hydrometeor sedimentation is important especially for the fast growing ice crystals to realistically capture their interaction with the vapour and liquid phase (Bergeron-Findeisen process). Since the focus is on the cloud microphysics, the dynamics in terms of vertical velocity profile is prescribed for the model runs and the feedback of the microphysics on dynamics by release or consumption of latent heat due to phase transfer is not taken into account. The microphysics focuses on (1) ice particle shape allowing hexagonal plates and columns with size-dependant axis ratios and (2) the ice nuclei (IN) budget realized with a prognostic temperature resolved field of potential IN allowing immersion freezing only when active IN and supercooled drops above a certain size threshold are present within a grid cell. Sensitivity studies show for both cases that ice particle shape seems to have the major influence on ice mass formation under otherwise identical conditions. This is due to the effect (1) on terminal fall velocity of the individual ice particle allowing for longer presence times in conditions supersaturated with respect to ice and (2) on water vapour deposition which is enhanced due to increased capacitance because of deviation from the spherical shape.

New, Improved Goddard Bulk-Microphysical Schemes for Studying Precipitation Processes in WRF

NASA Technical Reports Server (NTRS)

Tao, Wei-Kuo

2007-01-01

An improved bulk microphysical parameterization is implemented into the Weather Research and Forecasting ()VRF) model. This bulk microphysical scheme has three different options, 2ICE (cloud ice & snow), 3ICE-graupel (cloud ice, snow & graupel) and 3ICE-hail (cloud ice, snow & hail). High-resolution model simulations are conducted to examine the impact of microphysical schemes on two different weather events (a midlatitude linear convective system and an Atlantic hurricane). The results suggest that microphysics has a major impact on the organization and precipitation processes associated with a summer midlatitude convective line system. The Goddard 3ICE scheme with a cloud ice-snow-hail configuration agreed better with observations in terms of rainfall intensity and a narrow convective line than did simulations with a cloud ice-snow-graupel or cloud ice-snow (i.e., 2ICE) configuration. This is because the 3ICE-hail scheme includes dense ice precipitating (hail) particle with very fast fall speed (over 10 in For an Atlantic hurricane case, the Goddard microphysical schemes had no significant impact on the track forecast but did affect the intensity slightly. The improved Goddard schemes are also compared with WRF's three other 3ICE bulk microphysical schemes: WSM6, Purdue-Lin and Thompson. For the summer midlatitude convective line system, all of the schemes resulted in simulated precipitation events that were elongated in the southwest-northeast direction in qualitative agreement with the observed feature. However, the Goddard 3ICE scheme with the hail option and the Thompson scheme agree better with observations in terms of rainfall intensity, expect that the Goddard scheme simulated more heavy rainfall (over 48 mm/h). For the Atlantic hurricane case, none of the schemes had a significant impact on the track forecast; however, the simulated intensity using the Purdue-Lin scheme was much stronger than the other schemes. The vertical distributions of model simulated cloud species (i.e., snow) are quite sensitive to microphysical schemes, which is an important issue for future verification against satellite retrievals. Both the Purdue-Lin and WSM6 schemes simulated very little snow compared to the other schemes for both the midlatitude convective line and hurricane cases. Sensitivity tests are performed for these two WRF schemes to identify that snow productions could be increased by increasing the snow intercept, turning off the auto-conversion from snow to graupel and reducing the transfer processes from cloud-sized particles to precipitation-sized ice.

The Kinematic and Microphysical Control of Storm Integrated Lightning Flash Extent

NASA Technical Reports Server (NTRS)

Carey, Lawrence; Koshak, William; Petersen, Harold; Schultz, Elise; Schultz, Chris; Matthee, Retha; Bain, Lamont

2012-01-01

The objective of this preliminary study is to investigate the kinematic and microphysical control of lightning properties, particularly those that may govern the production of nitrogen oxides (NOx) in thunderstorms, such as flash rate, type and extent. The mixed-phase region is where the noninductive charging (NIC) process is thought to generate most storm electrification during rebounding collisions between ice particles in the presence of supercooled water. As a result, prior radar-based studies have demonstrated that lightning flash rate is well correlated to kinematic and microphysical properties in the mixed-phase region of thunderstorms such as updraft volume, graupel mass, or ice mass flux. There is also some evidence that lightning type is associated with the convective state. Intracloud (IC) lightning tends to dominate during the updraft accumulation of precipitation ice mass while cloud-to-ground (CG) lightning is more numerous during the downdraft-driven descent of radar echo associated with graupel and hail. More study is required to generalize these relationships, especially regarding lightning type, in a wide variety of storm modes and meteorological conditions. Less is known about the co-evolving relationship between storm kinematics, microphysics, morphology and three-dimensional flash extent, despite its importance for lightning NOx production. To address this conceptual gap, the NASA MSFC Lightning Nitrogen Oxides Model (LNOM) is applied to North Alabama Lightning Mapping Array (NALMA) and Vaisala National Lightning Detection NetworkTM (NLDN) observations following ordinary convective cells through their lifecycle. LNOM provides estimates of flash type, channel length distributions, lightning segment altitude distributions (SADs) and lightning NOx production profiles. For this study, LNOM is applied in a Lagrangian sense to well isolated convective cells on 3 April 2007 (single cell and multi-cell hailstorm, non-severe multicell) and 6 July 2007 (non-severe multi-cell) over Northern Alabama. The LNOM lightning characteristics are compared to the evolution of updraft and precipitation properties inferred from dual-Doppler and polarimetric radar analyses applied to observations from a nearby Doppler radar network, including the UA Huntsville Advanced Radar for Meteorological and Operational Research (ARMOR, C-band, polarimetric). The LNOM estimated SAD and lightning NOx production profiles are placed in the context of radar derived profiles of vertical motion, precipitation types and amounts. Finally, these analyses are used to determine if storm integrated flash channel extent is as well correlated to volumetric updraft and precipitation ice characteristics in the mixed phase region as flash rate for these individual convective cells.

The Microphysical Properties of Convective Precipitation Over the Tibetan Plateau by a Subkilometer Resolution Cloud-Resolving Simulation

NASA Astrophysics Data System (ADS)

Gao, Wenhua; Liu, Liping; Li, Jian; Lu, Chunsong

2018-03-01

The microphysical properties of convective precipitation over the Tibetan Plateau are unique because of the extremely high topography and special atmospheric conditions. In this study, the ground-based cloud radar and disdrometer observations as well as high-resolution Weather Research and Forecasting simulations with the Chinese Academy of Meteorological Sciences microphysics and four other microphysical schemes are used to investigate the microphysics and precipitation mechanisms of a convection event on 24 July 2014. The Weather Research and Forecasting-Chinese Academy of Meteorological Sciences simulation reasonably reproduces the spatial distribution of 24-hr accumulated rainfall, yet the temporal evolution of rain rate has a delay of 1-3 hr. The model reflectivity shares the common features with the cloud radar observations. The simulated raindrop size distributions demonstrate more of small- and large-size raindrops produced with the increase of rain rate, suggesting that changeable shape parameter should be used in size distribution. Results show that abundant supercooled water exists through condensation of water vapor above the freezing layer. The prevailing ice crystal microphysical processes are depositional growth and autoconversion of ice crystal to snow. The dominant source term of snow/graupel is riming of supercooled water. Sedimentation of graupel can play a vital role in the formation of precipitation, but melting of snow is rather small and quite different from that in other regions. Furthermore, water vapor budgets suggest that surface moisture flux be the principal source of water vapor and self-circulation of moisture happen at the beginning of convection, while total moisture flux convergence determine condensation and precipitation during the convective process over the Tibetan Plateau.

What can the CMB tell about the microphysics of cosmic reheating?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Drewes, Marco, E-mail: marcodrewes@googlemail.com

In inflationary cosmology, cosmic reheating after inflation sets the initial conditions for the hot big bang. We investigate how CMB data can be used to study the effective potential and couplings of the inflaton during reheating to constrain the underlying microphysics. If there is a phase of preheating that is driven by a parametric resonance or other instability, then the thermal history and expansion history during the reheating era depend on a large number of microphysical parameters in a complicated way. In this case the connection between CMB observables and microphysical parameters can only established with intense numerical studies. Suchmore » studies can help to improve CMB constraints on the effective inflaton potential in specific models, but parameter degeneracies usually make it impossible to extract meaningful best-fit values for individual microphysical parameters. If, on the other hand, reheating is driven by perturbative processes, then it can be possible to constrain the inflaton couplings and the reheating temperature from CMB data. This provides an indirect probe of fundamental microphysical parameters that most likely can never be measured directly in the laboratory, but have an immense impact on the evolution of the cosmos by setting the stage for the hot big bang.« less

Idealized Simulations of a Squall Line from the MC3E Field Campaign Applying Three Bin Microphysics Schemes: Dynamic and Thermodynamic Structure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xue, Lulin; Fan, Jiwen; Lebo, Zachary J.

The squall line event on May 20, 2011, during the Midlatitude Continental Convective Clouds (MC3E) field campaign has been simulated by three bin (spectral) microphysics schemes coupled into the Weather Research and Forecasting (WRF) model. Semi-idealized three-dimensional simulations driven by temperature and moisture profiles acquired by a radiosonde released in the pre-convection environment at 1200 UTC in Morris, Oklahoma show that each scheme produced a squall line with features broadly consistent with the observed storm characteristics. However, substantial differences in the details of the simulated dynamic and thermodynamic structure are evident. These differences are attributed to different algorithms and numericalmore » representations of microphysical processes, assumptions of the hydrometeor processes and properties, especially ice particle mass, density, and terminal velocity relationships with size, and the resulting interactions between the microphysics, cold pool, and dynamics. This study shows that different bin microphysics schemes, designed to be conceptually more realistic and thus arguably more accurate than bulk microphysics schemes, still simulate a wide spread of microphysical, thermodynamic, and dynamic characteristics of a squall line, qualitatively similar to the spread of squall line characteristics using various bulk schemes. Future work may focus on improving the representation of ice particle properties in bin schemes to reduce this uncertainty and using the similar assumptions for all schemes to isolate the impact of physics from numerics.« less

A comparison between rate-and-state friction and microphysical models, based on numerical simulations of fault slip

NASA Astrophysics Data System (ADS)

van den Ende, M. P. A.; Chen, J.; Ampuero, J.-P.; Niemeijer, A. R.

2018-05-01

Rate-and-state friction (RSF) is commonly used for the characterisation of laboratory friction experiments, such as velocity-step tests. However, the RSF framework provides little physical basis for the extrapolation of these results to the scales and conditions of natural fault systems, and so open questions remain regarding the applicability of the experimentally obtained RSF parameters for predicting seismic cycle transients. As an alternative to classical RSF, microphysics-based models offer means for interpreting laboratory and field observations, but are generally over-simplified with respect to heterogeneous natural systems. In order to bridge the temporal and spatial gap between the laboratory and nature, we have implemented existing microphysical model formulations into an earthquake cycle simulator. Through this numerical framework, we make a direct comparison between simulations exhibiting RSF-controlled fault rheology, and simulations in which the fault rheology is dictated by the microphysical model. Even though the input parameters for the RSF simulation are directly derived from the microphysical model, the microphysics-based simulations produce significantly smaller seismic event sizes than the RSF-based simulation, and suggest a more stable fault slip behaviour. Our results reveal fundamental limitations in using classical rate-and-state friction for the extrapolation of laboratory results. The microphysics-based approach offers a more complete framework in this respect, and may be used for a more detailed study of the seismic cycle in relation to material properties and fault zone pressure-temperature conditions.

Long-delayed bright dancing sprite with large horizontal displacement from its parent flash

NASA Astrophysics Data System (ADS)

Yang, J.; Lu, G.; Lee, L. J.; Feng, G.

2015-12-01

A long-delayed very bright dancing sprite with large horizontal displacement from its parent flash was observed. The dancing sprite lasted only 60 ms, and the morphology consisted of three fields with two slim dim sprite elements in the first two fields and a very bright large sprite element in the third field, different from other observations. The bright sprite displaced at least 38 km from its parent flash and occurred over comparatively higher cloud top region. The parent flash was positive, with only one return stroke (~24 kA) and obvious continuing current process, and the charge moment change of the stroke was small (roughly the threshold for sprite production). All of the sprite elements occurred during the continuing current period, and the bright sprite induced considerable current. The sprite dancing features may be linked to parent storm electrical structure, dynamics and microphysics, and the parent CG discharge process which was consistent with VHF observations.

A Comparison between Airborne and Mountaintop Cloud Microphysics

NASA Astrophysics Data System (ADS)

David, R.; Lowenthal, D. H.; Hallar, A. G.; McCubbin, I.; Avallone, L. M.; Mace, G. G.; Wang, Z.

2014-12-01

Complex terrain has a large impact on cloud dynamics and microphysics. Several studies have examined the microphysical details of orographically-enhanced clouds from either an aircraft or from a mountain top location. However, further research is needed to characterize the relationships between mountain top and airborne microphysical properties. During the winter of 2011, an airborne study, the Colorado Airborne Mixed-Phase Cloud Study (CAMPS), and a ground-based field campaign, the Storm Peak Lab (SPL) Cloud Property Validation Experiment (StormVEx) were conducted in the Park Range of the Colorado Rockies. The CAMPS study utilized the University of Wyoming King Air (UWKA) to provide airborne cloud microphysical and meteorological data on 29 flights totaling 98 flight hours over the Park Range from December 15, 2010 to February 28, 2011. The UWKA was equipped with instruments that measured both cloud droplet and ice crystal size distributions, liquid water content, total water content (vapor, liquid, and ice), and 3-dimensional wind speed and direction. The Wyoming Cloud Radar and Lidar were also deployed during the campaign. These measurements are used to characterize cloud structure upwind and above the Park Range. StormVEx measured cloud droplet, ice crystal, and aerosol size distributions at SPL, located on the west summit of Mt. Werner at 3220m MSL. The observations from SPL are used to determine mountain top cloud microphysical properties at elevations lower than the UWKA was able to sample in-situ. Comparisons showed that cloud microphysics aloft and at the surface were consistent with respect to snow growth processes while small crystal concentrations were routinely higher at the surface, suggesting ice nucleation near cloud base. The effects of aerosol concentrations and upwind stability on mountain top and downwind microphysics are considered.

Effects of Wildfire Pollution on the Microphysical and Electrical Properties of Pyrocumulus

NASA Astrophysics Data System (ADS)

Duff, R.; Grant, L. D.; van den Heever, S. C.

2014-12-01

Pyrocumulus clouds form over wildfires when hot, smoke-filled air rises, cools and condenses. These clouds have higher cloud condensation nuclei (CCN) concentrations, which affect their microphysical and electrical properties. It is important to better understand pyrocumulus cloud microphysical characteristics and lightning formation, which have implications for the prediction of wildfire growth as well as the radiative and chemical characteristics of the upper troposphere. A recent observational study documented an electrified pyrocumulus over the May 2012 Hewlett Gulch fire located to the west of Fort Collins, Colorado. This cloud produced approximately 20 intracloud lightning flashes, and its electrical activity differed from surrounding convection that was not directly impacted by the fire and associated smoke. The goal of this research is to investigate aerosol-induced cloud-scale microphysical differences between clean clouds and polluted pyrocumulus to better characterize the mechanisms that cause pyrocumulus electrification. In order to address this goal, idealized cloud-resolving model simulations were performed using the Regional Atmospheric Modeling System (RAMS). The model environment was initialized with an average of the 12Z 16 May and 00Z 17 May 2012 observed Denver soundings to represent the conditions when the Hewlett Gulch pyrocumulus occurred. Five simulations were performed using surface aerosol concentrations from 100 to 5000 #/mg. The results demonstrate that in moderately polluted pyrocumulus, rain processes are suppressed while graupel production increases. Extremely polluted pyrocumulus, however, experience a complete shut-down of graupel production, which favors the production of large amounts of liquid water and smaller ice species such as ice crystals and snowflakes. The processes responsible for these microphysical changes, as well as inferred pyrocumulus electrification mechanisms, will be compared with those discussed in previous observational studies of this case.

The great Indian haze revisited: aerosol distribution effects on microphysical and optical properties of warm clouds over peninsular India

NASA Astrophysics Data System (ADS)

Ghanti, R.; Ghosh, S.

2010-03-01

The Indian subcontinent is undergoing a phase of rapid urbanisation. Inevitable fallout of this process is a concomitant increase in air pollution much of which can be attributed to the infamous great Indian haze phenomena. One observes that the aerosol size distributions vary considerably along the Bay of Bengal (BOB), Arabian Sea (AS) and the Indian Ocean (IO), although, the dynamical attributes are very similar, particularly over the BOB and the AS during this season. Unlike major European studies (e.g. Aerosol Characterization Experiment-2, Ghosh et al., 2005), there are no cloud microphysical modelling studies to complement these observational results for the Indian sub-continent. Ours is the first modelling study over this important region where a time-tested model (O'Dowd et al., 1999a; Ghosh et al., 2007; Rap et al., 2009) is used to obtain cloud microphysical and optical properties from observed aerosol size distributions. Un-activated aerosol particles and very small cloud droplets have to be treated specially to account for non-ideal effects-our model does this effectively yielding realistic estimate of cloud droplet number concentrations (Nc). Empirical relationships linking aerosol concentration to (Nc) yield a disproportionately higher Nc suggesting that such empirical formulations should be used with caution. Our modelling study reveals that the cloud's microphysical and optical properties are very similar along the AS and the BOB despite them having disparate dry aerosol spectral distributions. This is non-intuitive, as one would expect changes in microphysical development with widely different aerosol distributions. There is some increase in cloud droplet numbers with increased haze concentrations but much less than a simple proportion would indicate.

Representing Precipitation Ice Species With Both Spherical and Nonspherical Particles for Radiative Transfer Modeling of Microphysics-Consistent Cloud Microwave Scattering Properties

NASA Astrophysics Data System (ADS)

Sieron, Scott B.; Zhang, Fuqing; Clothiaux, Eugene E.; Zhang, Lily N.; Lu, Yinghui

2018-04-01

Cloud microwave scattering properties for the Community Radiative Transfer Model (CRTM) have previously been created to be consistent with the particle size distributions specified by the WSM6 single-moment microphysics scheme. Here substitution of soft sphere scattering properties with nonspherical particle scattering properties is explored in studies of Hurricane Karl (2010). A nonsphere replaces a sphere of the same maximum dimension, and the number of particles of a given size is scaled by the ratio of the sphere to nonsphere mass to keep the total mass of a given particle size unchanged. The replacement of homogeneous soft sphere snow particles is necessary to resolve a highly evident issue in CRTM simulations: precipitation-affected brightness temperatures are generally warmer at 183 GHz than at 91.7 GHz, whereas the reverse is seen in observations. Using sector snowflakes resolve this issue better than using columns/plates, bullet rosettes, or dendrites. With sector snowflakes, both of these high frequencies have low simulated brightness temperatures compared to observations, providing a clear and consistent suggestion that snow is being overproduced in the examined simulation using WSM6 microphysics. Graupel causes cold biases at lower frequencies which can be reduced by either reducing graupel water contents or replacing the microphysics-consistent spherical graupel particles with sector snowflakes. However, soft spheres are likely the better physical representation of graupel particles. The hypotheses that snow and graupel are overproduced in simulations using WSM6 microphysics shall be examined more systematically in future studies through additional cases and ensemble data assimilation of all-sky microwave radiance observations.

Evaluation of AIRS cloud properties using MPACE data

NASA Astrophysics Data System (ADS)

Wu, Xuebao; Li, Jun; Menzel, W. Paul; Huang, Allen; Baggett, Kevin; Revercomb, Henry

2005-12-01

Retrieval of cloud properties from the Atmospheric Infrared Sounder (AIRS) aboard the NASA Aqua satellite has been investigated. The cloud products from the collocated MODerate resolution Imaging Spectroradiometer (MODIS) data are used to characterize the AIRS sub-pixel cloud information such as cloud phase, cloud coverage, and cloud layer information. A Minimum Residual (MR) approach is used to retrieve cloud microphysical properties once the cloud top pressure (CTP) and effective cloud amount (ECA) are determined from AIRS CO2 absorption channels between 720 and 790 cm-1. The cloud microphysical properties can be retrieved by minimizing the differences between the observations and the calculations using AIRS longwave window channels between 790 and 1130 cm-1. AIRS is used to derive cloud properties during the Mixed Phase Arctic Cloud Experiment (MPACE) field campaign. Comparison with measurements obtained from lidar data is made for a test day, showing that AIRS cloud property retrievals agree with in situ lidar observations. Due to the large solar zenith angle, the MODIS operational retrieval approach is not able to provide cloud microphysics north of Barrow, Alaska; however, AIRS provides cloud microphysical properties with its high spectral resolution IR measurements.

Cold Season QPF: Sensitivities to Snow Parameterizations and Comparisons to NASA CloudSat Observations

NASA Technical Reports Server (NTRS)

Molthan, A. L.; Haynes, J. A.; Jedlovec, G. L.; Lapenta, W. M.

2009-01-01

As operational numerical weather prediction is performed at increasingly finer spatial resolution, precipitation traditionally represented by sub-grid scale parameterization schemes is now being calculated explicitly through the use of single- or multi-moment, bulk water microphysics schemes. As computational resources grow, the real-time application of these schemes is becoming available to a broader audience, ranging from national meteorological centers to their component forecast offices. A need for improved quantitative precipitation forecasts has been highlighted by the United States Weather Research Program, which advised that gains in forecasting skill will draw upon improved simulations of clouds and cloud microphysical processes. Investments in space-borne remote sensing have produced the NASA A-Train of polar orbiting satellites, specially equipped to observe and catalog cloud properties. The NASA CloudSat instrument, a recent addition to the A-Train and the first 94 GHz radar system operated in space, provides a unique opportunity to compare observed cloud profiles to their modeled counterparts. Comparisons are available through the use of a radiative transfer model (QuickBeam), which simulates 94 GHz radar returns based on the microphysics of cloudy model profiles and the prescribed characteristics of their constituent hydrometeor classes. CloudSat observations of snowfall are presented for a case in the central United States, with comparisons made to precipitating clouds as simulated by the Weather Research and Forecasting Model and the Goddard single-moment microphysics scheme. An additional forecast cycle is performed with a temperature-based parameterization of the snow distribution slope parameter, with comparisons to CloudSat observations provided through the QuickBeam simulator.

Black carbon mixing state impacts on cloud microphysical properties: effects of aerosol plume and environmental conditions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ching, Ping Pui; Riemer, Nicole; West, Matthew

2016-05-27

Black carbon (BC) is usually mixed with other aerosol species within individual aerosol particles. This mixture, along with the particles' size and morphology, determines the particles' optical and cloud condensation nuclei properties, and hence black carbon's climate impacts. In this study the particle-resolved aerosol model PartMC-MOSAIC was used to quantify the importance of black carbon mixing state for predicting cloud microphysical quantities. Based on a set of about 100 cloud parcel simulations a process level analysis framework was developed to attribute the response in cloud microphysical properties to changes in the underlying aerosol population ("plume effect") and the cloud parcelmore » cooling rate ("parcel effect"). It shows that the response of cloud droplet number concentration to changes in BC emissions depends on the BC mixing state. When the aerosol population contains mainly aged BC particles an increase in BC emission results in increasing cloud droplet number concentrations ("additive effect"). In contrast, when the aerosol population contains mainly fresh BC particles they act as sinks for condensable gaseous species, resulting in a decrease in cloud droplet number concentration as BC emissions are increased ("competition effect"). Additionally, we quantified the error in cloud microphysical quantities when neglecting the information on BC mixing state, which is often done in aerosol models. The errors ranged from -12% to +45% for the cloud droplet number fraction, from 0% to +1022% for the nucleation-scavenged black carbon (BC) mass fraction, from -12% to +4% for the effective radius, and from -30% to +60% for the relative dispersion.« less

Evaluation of Unified Model Microphysics in High-resolution NWP Simulations Using Polarimetric Radar Observations

NASA Astrophysics Data System (ADS)

Johnson, Marcus; Jung, Youngsun; Dawson, Daniel; Supinie, Timothy; Xue, Ming; Park, Jongsook; Lee, Yong-Hee

2018-07-01

The UK Met Office Unified Model (UM) is employed by many weather forecasting agencies around the globe. This model is designed to run across spatial and time scales and known to produce skillful predictions for large-scale weather systems. However, the model has only recently begun running operationally at horizontal grid spacings of ˜1.5 km [e.g., at the UK Met Office and the Korea Meteorological Administration (KMA)]. As its microphysics scheme was originally designed and tuned for large-scale precipitation systems, we investigate the performance of UM microphysics to determine potential inherent biases or weaknesses. Two rainfall cases from the KMA forecasting system are considered in this study: a Changma (quasi-stationary) front, and Typhoon Sanba (2012). The UM output is compared to polarimetric radar observations in terms of simulated polarimetric radar variables. Results show that the UM generally underpredicts median reflectivity in stratiform rain, producing high reflectivity cores and precipitation gaps between them. This is partially due to the diagnostic rain intercept parameter formulation used in the one-moment microphysics scheme. Model drop size is generally both underand overpredicted compared to observations. UM frozen hydrometeors favor generic ice (crystals and snow) rather than graupel, which is reasonable for Changma and typhoon cases. The model performed best with the typhoon case in terms of simulated precipitation coverage.

Lightning and Precipitation: Observational Analysis of LIS and PR

NASA Technical Reports Server (NTRS)

Adamo, C.; Solomon, R.; Goodman, S.; Dietrich, S.; Mugnai, A.

2003-01-01

Lightning flash rate can identify areas of convective rainfall when the storms are dominated by ice-phase precipitation. Modeling and observational studies indicate that cloud electrification and microphysics are very closely related and it is of great interest to understand the relationship between lightning and cloud microphysical quantities. Analyzing data from the Lightning Image Sensor (LIS) and the Precipitation Radar (PR), we show a quantitative relationship between microphysical characteristics of thunderclouds and lightning flash rate. We have performed a complete analysis of all data available over the Mediterranean during the TRMM mission and show a range of reflective profiles as a function of lightning activity for both convective and stratiform regimes as well as seasonal variations. Due to the increasing global coverage of lightning detection networks, this kind of study can used to extend the knowledge about thunderstorms and discriminate between different regimes in regions where radar measurements are readilly available.

Relationship between macroscopic and microphysical properties for mixed-phase and ice clouds over the Southern Ocean in ORCAS campaign

NASA Astrophysics Data System (ADS)

Diao, M.; Jensen, J. B.

2017-12-01

Mixed-phase and ice clouds play very important roles in regulating the atmospheric radiation over the Southern Ocean. Previously, in-situ observations over this remote region are limited, and a few of the available observation-based analyses mainly focused on the cloud microphysical properties. The relationship between macroscopic and microphysical properties for both mixed-phase and ice clouds have not been thoroughly investigated based on in-situ observations. In this work, the aircraft-based observations from the NSF O2/N2 Ratio and CO2 Airborne Southern Ocean (ORCAS) field campaign (Jan - Feb 2016) will be used to analyze the cloud macroscopic properties on the microscale to mesoscale, including the distributions of cloud chord length, the patchiness of clouds, and the spatial ratios of adjacent cloud segments in mixed phase and pure ice phase. In addition, these macroscopic properties will be analyzed in relation to the relative humidity (RH) background, such as the average and maximum RH inside clouds, as well as the probability density function (PDF) of in-cloud RH. We found that the clouds with larger horizontal scales are often associated with larger magnitudes of average and maximum in-cloud RH values. In addition, when decomposing the contributions from the spatial variabilities of water vapor and temperature to the variability of RH, the water vapor heterogeneities are found to have the most dominant impact on RH variability. Sensitivities of the cloud macroscopic and microphysical properties to the horizontal resolutions of the observations will be shown, including the impacts on the patchiness of clouds, cloud fraction, frequencies of ice supersaturation, and the PDFs of RH. These sensitivity analyses will provide useful information on the comparisons among multi-scale observations and simulations.

Microphysics-based black carbon aging in a global CTM: constraints from HIPPO observations and implications for global black carbon budget

NASA Astrophysics Data System (ADS)

He, Cenlin; Li, Qinbin; Liou, Kuo-Nan; Qi, Ling; Tao, Shu; Schwarz, Joshua P.

2016-03-01

We develop and examine a microphysics-based black carbon (BC) aerosol aging scheme that accounts for condensation, coagulation, and heterogeneous chemical oxidation processes in a global 3-D chemical transport model (GEOS-Chem) by interpreting the BC measurements from the HIAPER Pole-to-Pole Observations (HIPPO, 2009-2011) using the model. We convert aerosol mass in the model to number concentration by assuming lognormal aerosol size distributions and compute the microphysical BC aging rate (excluding chemical oxidation aging) explicitly from the condensation of soluble materials onto hydrophobic BC and the coagulation between hydrophobic BC and preexisting soluble particles. The chemical oxidation aging is tested in the sensitivity simulation. The microphysical aging rate is ˜ 4 times higher in the lower troposphere over source regions than that from a fixed aging scheme with an e-folding time of 1.2 days. The higher aging rate reflects the large emissions of sulfate-nitrate and secondary organic aerosol precursors hence faster BC aging through condensation and coagulation. In contrast, the microphysical aging is more than 5-fold slower than the fixed aging in remote regions, where condensation and coagulation are weak. Globally, BC microphysical aging is dominated by condensation, while coagulation contribution is largest over eastern China, India, and central Africa. The fixed aging scheme results in an overestimate of HIPPO BC throughout the troposphere by a factor of 6 on average. The microphysical scheme reduces this discrepancy by a factor of ˜ 3, particularly in the middle and upper troposphere. It also leads to a 3-fold reduction in model bias in the latitudinal BC column burden averaged along the HIPPO flight tracks, with largest improvements in the tropics. The resulting global annual mean BC lifetime is 4.2 days and BC burden is 0.25 mg m-2, with 7.3 % of the burden at high altitudes (above 5 km). Wet scavenging accounts for 80.3 % of global BC deposition. We find that, in source regions, the microphysical aging rate is insensitive to aerosol size distribution, condensation threshold, and chemical oxidation aging, while it is the opposite in remote regions, where the aging rate is orders of magnitude smaller. As a result, global BC burden and lifetime show little sensitivity (< 5 % change) to these three factors.

Aerosol Properties Downwind of Biomass Burns Field Campaign Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Buseck, Peter R

We determined the morphological, chemical, and thermal properties of aerosol particles generated by biomass burning during the Biomass Burning Observation Project (BBOP) campaign during the wildland fire season in the Pacific Northwest from July to mid-September, 2013, and in October, 2013 from prescribed agricultural burns in the lower Mississippi River Valley. BBOP was a field campaign of the U.S. Department of Energy (DOE)’s Atmospheric Radiation Measurement (ARM) Climate Research Facility. The morphological information was both two-dimensional, as is typical of most microscopy images and that have many of the characteristic of shadows in that they lack depth data, and three-dimensionalmore » (3D). The electron tomographic measurements will provided 3D data, including the presence and nature of pores and interstices, and whether the individual particles are coated by or embedded within other materials. These microphysical properties were determined for particles as a function of time and distance from the respective sources in order to obtain detailed information regarding the time evolution of changes during aging.« less

Remote measurement of cloud microphysics and its influence in predicting high impact weather events

NASA Astrophysics Data System (ADS)

Bipasha, Paul S.; Jinya, John

2016-05-01

Understanding the cloud microphysical processes and precise retrieval of parameters governing the same are crucial for weather and climate prediction. Advanced remote sensing sensors and techniques offer an opportunity for monitoring micro-level developments in cloud structure. . Using the observations from a visible and near-infrared lidar onboard CALIPSO satellite (part of A-train) , the spatial variation of cloud structure has been studied over the Tropical monsoon region . It is found that there is large variability in the cloud microphysical parameters manifesting in distinct precipitation regimes. In particular, the severe storms over this region are driven by processes which range from the synoptic to the microphysical scale. Using INSAT-3D data, retrieval of cloud microphysical parameters like effective radius (CER) and optical depth (COD) were carried out for tropical cyclone Phailine. It was observed that there is a general increase of CER in a top-down direction, characterizing the progressively increasing number and size of precipitation hydrometeors while approaching the cloud base. The distribution of CER relative to cloud top temperature for growing convective clouds has been investigated to reveal the evolution of the particles composing the clouds. It is seen that the relatively high concentration of large particles in the downdraft zone is closely related to the precipitation efficiency of the system. Similar study was also carried using MODIS observations for cyclones over Indian Ocean (2010-2013), in which we find that that the mean effective radius is 24 microns with standard deviation 4.56, mean optical depth is 21 with standard deviation 13.98, mean cloud fraction is 0.92 with standard deviation 0.13 and mainly ice phase is dominant. Thus the remote observations of microstructure of convective storms provide very crucial information about the maintenance and potential devastation likely to be associated with it. With the synergistic observations from A-Train , geostationary and futuristic imaging spectroscopic sensors, a multi-dimensional, and multi-scalar exploration of cloud systems is anticipated leading to accurate prediction of high impact weather events.

Precipitation microphysics characteristics of a Typhoon Matmo (2014) rainband after landfall over eastern China based on polarimetric radar observations

NASA Astrophysics Data System (ADS)

Wang, Mingjun; Zhao, Kun; Xue, Ming; Zhang, Guifu; Liu, Su; Wen, Long; Chen, Gang

2016-10-01

The evolution of microphysical characteristics of a rainband in Typhoon Matmo (2014) over eastern China, through its onset, developing, mature, and dissipating stages, is documented using observations from an S band polarimetric Doppler radar and a two-dimensional video disdrometer (2DVD). The drop size distributions observed by the 2DVD and retrieved from the polarimetric radar measurements indicate that the convection in the rainband generally contains smaller drops and higher number concentrations than the typical maritime type convection described in Bringi et al. (2003). The average mass-weighted mean diameter (Dm) of convective precipitation in the rainband is about 1.41 mm, and the average logarithmic normalized intercept (Nw) is 4.67 log10 mm-1 m-3. To further investigate the dominant microphysical processes, the evolution of the vertical structures of polarimetric variables is examined. Results show that complex ice processes are involved above the freezing level, while it is most likely that the accretion and/or coalescence processes dominate below the freezing level throughout the rainband life cycle. A combined examination of the polarimetric measurements and profiles of estimated vertical liquid and ice water contents indicates that the conversion of cloud water into rainwater through cloud water accretion by raindrops plays a dominant role in producing heavy rainfall. The high estimated precipitation efficiency of 50% also suggests that cloud water accretion is the dominant mechanism for producing heavy rainfall. This study represents the first time that radar and 2DVD observations are used together to characterize the microphysical characteristics and precipitation efficiency for typhoon rainbands in China.

Uncertainty and feasibility of dynamical downscaling for modeling tropical cyclones for storm surge simulation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Zhaoqing; Taraphdar, Sourav; Wang, Taiping

This paper presents a modeling study conducted to evaluate the uncertainty of a regional model in simulating hurricane wind and pressure fields, and the feasibility of driving coastal storm surge simulation using an ensemble of region model outputs produced by 18 combinations of three convection schemes and six microphysics parameterizations, using Hurricane Katrina as a test case. Simulated wind and pressure fields were compared to observed H*Wind data for Hurricane Katrina and simulated storm surge was compared to observed high-water marks on the northern coast of the Gulf of Mexico. The ensemble modeling analysis demonstrated that the regional model wasmore » able to reproduce the characteristics of Hurricane Katrina with reasonable accuracy and can be used to drive the coastal ocean model for simulating coastal storm surge. Results indicated that the regional model is sensitive to both convection and microphysics parameterizations that simulate moist processes closely linked to the tropical cyclone dynamics that influence hurricane development and intensification. The Zhang and McFarlane (ZM) convection scheme and the Lim and Hong (WDM6) microphysics parameterization are the most skillful in simulating Hurricane Katrina maximum wind speed and central pressure, among the three convection and the six microphysics parameterizations. Error statistics of simulated maximum water levels were calculated for a baseline simulation with H*Wind forcing and the 18 ensemble simulations driven by the regional model outputs. The storm surge model produced the overall best results in simulating the maximum water levels using wind and pressure fields generated with the ZM convection scheme and the WDM6 microphysics parameterization.« less

Explicit prediction of hail using multimoment microphysics schemes for a hailstorm of 19 March 2014 in eastern China

NASA Astrophysics Data System (ADS)

Luo, Liping; Xue, Ming; Zhu, Kefeng; Zhou, Bowen

2017-07-01

In the late afternoon of 19 March 2014, a severe hailstorm swept through eastern central Zhejiang province, China. The storm produced golf ball-sized hail, strong winds, and lighting, lasting approximately 1 h over the coastal city of Taizhou. The Advanced Regional Prediction System is used to simulate the hailstorm using different configurations of the Milbrandt-Yau microphysics scheme that predict one, two, or three moments of the hydrometeor particle size distribution. Simulated fields, including accumulated precipitation and maximum estimated hail size (MESH), are verified against rain gauge observations and radar-derived MESH, respectively. For the case of the 19 March 2014 storms, the general evolution is better predicted with multimoment microphysics schemes than with the one-moment scheme; the three-moment scheme produces the best forecast. Predictions from the three-moment scheme qualitatively agree with observations in terms of size and amount of hail reaching the surface. The life cycle of the hailstorm is analyzed, using the most skillful, three-moment forecast. Based upon the tendency of surface hail mass flux, the hailstorm life cycle can be divided into three stages: developing, mature, and dissipating. Microphysical budget analyses are used to examine microphysical processes and characteristics during these three stages. The vertical structures within the storm and their link to environmental shear conditions are discussed; together with the rapid fall of hailstones, these structures and conditions appear to dictate this pulse storm's short life span. Finally, a conceptual model for the life cycle of pulse hailstorms is proposed.

Implementation of an Aerosol-Cloud Microphysics-Radiation Coupling into the NASA Unified WRF: Simulation Results for the 6-7 August 2006 AMMA Special Observing Period

NASA Technical Reports Server (NTRS)

Shi, J. J.; Matsui, T.; Tao, W.-K.; Tan, Q.; Peters-Lidard, C.; Chin, M.; Pickering, K.; Guy, N.; Lang, S.; Kemp, E. M.

2014-01-01

Aerosols affect the Earth's radiation balance directly and cloud microphysical processes indirectly via the activation of cloud condensation and ice nuclei. These two effects have often been considered separately and independently, hence the need to assess their combined impact given the differing nature of their effects on convective clouds. To study both effects, an aerosol-microphysics-radiation coupling, including Goddard microphysics and radiation schemes, was implemented into the NASA Unified Weather Research and Forecasting model (NU-WRF). Fully coupled NU-WRF simulations were conducted for a mesoscale convective system (MCS) that passed through the Niamey, Niger area on 6-7 August 2006 during an African Monsoon Multidisciplinary Analysis (AMMA) special observing period. The results suggest that rainfall is reduced when aerosol indirect effects are included, regardless of the aerosol direct effect. Daily mean radiation heating profiles in the area traversed by the MCS showed the aerosol (mainly mineral dust) direct effect had the largest impact near cloud tops just above 200 hectopascals where short-wave heating increased by about 0.8 Kelvin per day; the weakest long-wave cooling was at around 250 hectopascals. It was also found that more condensation and ice nuclei as a result of higher aerosol/dust concentrations led to increased amounts of all cloud hydrometeors because of the microphysical indirect effect, and the radiation direct effect acts to reduce precipitating cloud particles (rain, snow and graupel) in the middle and lower cloud layers while increasing the non-precipitating particles (ice) in the cirrus anvil. However, when the aerosol direct effect was activated, regardless of the indirect effect, the onset of MCS precipitation was delayed about 2 hours, in conjunction with the delay in the activation of cloud condensation and ice nuclei. Overall, for this particular environment, model set-up and physics configuration, the effect of aerosol radiative heating due to mineral dust overwhelmed the effect of the aerosols on microphysics.

A Microphysics-Based Black Carbon Aging Scheme in a Global Chemical Transport Model: Constraints from HIPPO Observations

NASA Astrophysics Data System (ADS)

He, C.; Li, Q.; Liou, K. N.; Qi, L.; Tao, S.; Schwarz, J. P.

2015-12-01

Black carbon (BC) aging significantly affects its distributions and radiative properties, which is an important uncertainty source in estimating BC climatic effects. Global models often use a fixed aging timescale for the hydrophobic-to-hydrophilic BC conversion or a simple parameterization. We have developed and implemented a microphysics-based BC aging scheme that accounts for condensation and coagulation processes into a global 3-D chemical transport model (GEOS-Chem). Model results are systematically evaluated by comparing with the HIPPO observations across the Pacific (67°S-85°N) during 2009-2011. We find that the microphysics-based scheme substantially increases the BC aging rate over source regions as compared with the fixed aging timescale (1.2 days), due to the condensation of sulfate and secondary organic aerosols (SOA) and coagulation with pre-existing hydrophilic aerosols. However, the microphysics-based scheme slows down BC aging over Polar regions where condensation and coagulation are rather weak. We find that BC aging is primarily dominated by condensation process that accounts for ~75% of global BC aging, while the coagulation process is important over source regions where a large amount of pre-existing aerosols are available. Model results show that the fixed aging scheme tends to overestimate BC concentrations over the Pacific throughout the troposphere by a factor of 2-5 at different latitudes, while the microphysics-based scheme reduces the discrepancies by up to a factor of 2, particularly in the middle troposphere. The microphysics-based scheme developed in this work decreases BC column total concentrations at all latitudes and seasons, especially over tropical regions, leading to large improvement in model simulations. We are presently analyzing the impact of this scheme on global BC budget and lifetime, quantifying its uncertainty associated with key parameters, and investigating the effects of heterogeneous chemical oxidation on BC aging.

Studies of Radiation and Microphysics in Cirrus and Marine Stratocumulus Clouds

NASA Technical Reports Server (NTRS)

1999-01-01

Two tasks were completed during this period. In the first, we examined the polarization of millimeter-wavelength radar beams scattered by ice crystals. Because of their non-spherical shape and size, ice crystals depolarize the incident polarized radar beam. In principle, this depolarization can be used to identify ice from liquid water, as well as provide some information on size. However, the amount of de-polarization is small, producing only a weak signal at the receiver. Our task was to determine the magnitude of such a signal and decide if our radar would be capable of measuring it under typical cirrus conditions. The theoretical study was carried out by Henrietta Lemke, a visiting graduate student from Germany. She had prior experience using a discrete dipole code to compute scattering depolarization. Dr. Kultegin Aydin of the Penn State Electrical Engineering Department, who is also expert in this area, consulted with us on this project at no cost to the project. Our conclusion was that the depolarization signal is too weak to be usefully measured by our system. Therefore we proceeded no further in this study. The second task involved the study of the effect of stratus microphysics on surface cloud forcing. Manajit Sengupta, a graduate student, and the project PI jointly carried out this task. The study used data culled from over a year of continuous radar and radiometer observations at the Atmospheric Radiation Measurement (ARM) site in Oklahoma. The study compared solar radiation calculations made using constant microphysics with calculations made using a retrieved mean particle size. The results showed that on average the constant microphysics produced the correct forcing when compared with the observed forcing. We conclude, therefore, that there is little impetus on radiation grounds alone to include explicit microphysics in climate models. The question of pollutant particle emission impacts on microphysics remains to be resolved. A manuscript is in preparation and will be submitted this year.

Use of cloud radar Doppler spectra to evaluate stratocumulus drizzle size distributions in large-eddy simulations with size-resolved microphysics

DOE PAGES

Remillard, J.; Fridlind, Ann M.; Ackerman, A. S.; ...

2017-09-20

Here, a case study of persistent stratocumulus over the Azores is simulated using two independent large-eddy simulation (LES) models with bin microphysics, and forward-simulated cloud radar Doppler moments and spectra are compared with observations. Neither model is able to reproduce the monotonic increase of downward mean Doppler velocity with increasing reflectivity that is observed under a variety of conditions, but for differing reasons. To a varying degree, both models also exhibit a tendency to produce too many of the largest droplets, leading to excessive skewness in Doppler velocity distributions, especially below cloud base. Excessive skewness appears to be associated withmore » an insufficiently sharp reduction in droplet number concentration at diameters larger than ~200 μm, where a pronounced shoulder is found for in situ observations and a sharp reduction in reflectivity size distribution is associated with relatively narrow observed Doppler spectra. Effectively using LES with bin microphysics to study drizzle formation and evolution in cloud Doppler radar data evidently requires reducing numerical diffusivity in the treatment of the stochastic collection equation; if that is accomplished sufficiently to reproduce typical spectra, progress toward understanding drizzle processes is likely.« less

Use of cloud radar Doppler spectra to evaluate stratocumulus drizzle size distributions in large-eddy simulations with size-resolved microphysics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Remillard, J.; Fridlind, Ann M.; Ackerman, A. S.

Here, a case study of persistent stratocumulus over the Azores is simulated using two independent large-eddy simulation (LES) models with bin microphysics, and forward-simulated cloud radar Doppler moments and spectra are compared with observations. Neither model is able to reproduce the monotonic increase of downward mean Doppler velocity with increasing reflectivity that is observed under a variety of conditions, but for differing reasons. To a varying degree, both models also exhibit a tendency to produce too many of the largest droplets, leading to excessive skewness in Doppler velocity distributions, especially below cloud base. Excessive skewness appears to be associated withmore » an insufficiently sharp reduction in droplet number concentration at diameters larger than ~200 μm, where a pronounced shoulder is found for in situ observations and a sharp reduction in reflectivity size distribution is associated with relatively narrow observed Doppler spectra. Effectively using LES with bin microphysics to study drizzle formation and evolution in cloud Doppler radar data evidently requires reducing numerical diffusivity in the treatment of the stochastic collection equation; if that is accomplished sufficiently to reproduce typical spectra, progress toward understanding drizzle processes is likely.« less

Mobile Disdrometer Observations of Nocturnal Mesoscale Convective Systems During PECAN

NASA Astrophysics Data System (ADS)

Bodine, D. J.; Rasmussen, K. L.

2015-12-01

Understanding microphysical processes in nocturnal mesoscale convective systems (MCSs) is an important objective of the Plains Elevated Convection At Night (PECAN) experiment, which occurred from 1 June - 15 July 2015 in the central Great Plains region of the United States. Observations of MCSs were collected using a large array of mobile and fixed instrumentation, including ground-based radars, soundings, PECAN Integrated Sounding Arrays (PISAs), and aircraft. In addition to these observations, three mobile Parsivel disdrometers were deployed to obtain drop-size distribution (DSD) measurements to further explore microphysical processes in convective and stratiform regions of nocturnal MCSs. Disdrometers were deployed within close range of a multiple frequency network of mobile and fixed dual-polarization radars (5 - 30 km range), and near mobile sounding units and PISAs. Using mobile disdrometer and multiple-wavelength, dual-polarization radar data, microphysical properties of convective and stratiform regions of MCSs are investigated. The analysis will also examine coordinated Range-Height Indicator (RHI) scans over the disdrometers to elucidate vertical DSD structure. Analysis of dense observations obtained during PECAN in combination with mobile disdrometer DSD measurements contributes to a greater understanding of the structural characteristics and evolution of nocturnal MCSs.

New, Improved Bulk-microphysical Schemes for Studying Precipitation Processes in WRF. Part 1; Comparisons with Other Schemes

NASA Technical Reports Server (NTRS)

Tao, W.-K.; Shi, J.; Chen, S. S> ; Lang, S.; Hong, S.-Y.; Thompson, G.; Peters-Lidard, C.; Hou, A.; Braun, S.;

The sensitivity to the microphysical schemes on the skill of forecasting the track and intensity of tropical cyclones using WRF-ARW model

NASA Astrophysics Data System (ADS)

Choudhury, Devanil; Das, Someshwar

2017-06-01

The Advanced Research WRF (ARW) model is used to simulate Very Severe Cyclonic Storms (VSCS) Hudhud (7-13 October, 2014), Phailin (8-14 October, 2013) and Lehar (24-29 November, 2013) to investigate the sensitivity to microphysical schemes on the skill of forecasting track and intensity of the tropical cyclones for high-resolution (9 and 3 km) 120-hr model integration. For cloud resolving grid scale (<5 km) cloud microphysics plays an important role. The performance of the Goddard, Thompson, LIN and NSSL schemes are evaluated and compared with observations and a CONTROL forecast. This study is aimed to investigate the sensitivity to microphysics on the track and intensity with explicitly resolved convection scheme. It shows that the Goddard one-moment bulk liquid-ice microphysical scheme provided the highest skill on the track whereas for intensity both Thompson and Goddard microphysical schemes perform better. The Thompson scheme indicates the highest skill in intensity at 48, 96 and 120 hr, whereas at 24 and 72 hr, the Goddard scheme provides the highest skill in intensity. It is known that higher resolution domain produces better intensity and structure of the cyclones and it is desirable to resolve the convection with sufficiently high resolution and with the use of explicit cloud physics. This study suggests that the Goddard cumulus ensemble microphysical scheme is suitable for high resolution ARW simulation for TC's track and intensity over the BoB. Although the present study is based on only three cyclones, it could be useful for planning real-time predictions using ARW modelling system.

Cloud microphysics modification with an online coupled COSMO-MUSCAT regional model

NASA Astrophysics Data System (ADS)

Sudhakar, D.; Quaas, J.; Wolke, R.; Stoll, J.; Muehlbauer, A. D.; Tegen, I.

2015-12-01

Abstract: The quantification of clouds, aerosols, and aerosol-cloud interactions in models, continues to be a challenge (IPCC, 2013). In this scenario two-moment bulk microphysical scheme is used to understand the aerosol-cloud interactions in the regional model COSMO (Consortium for Small Scale Modeling). The two-moment scheme in COSMO has been especially designed to represent aerosol effects on the microphysics of mixed-phase clouds (Seifert et al., 2006). To improve the model predictability, the radiation scheme has been coupled with two-moment microphysical scheme. Further, the cloud microphysics parameterization has been modified via coupling COSMO with MUSCAT (MultiScale Chemistry Aerosol Transport model, Wolke et al., 2004). In this study, we will be discussing the initial result from the online-coupled COSMO-MUSCAT model system with modified two-moment parameterization scheme along with COSP (CFMIP Observational Simulator Package) satellite simulator. This online coupled model system aims to improve the sub-grid scale process in the regional weather prediction scenario. The constant aerosol concentration used in the Seifert and Beheng, (2006) parameterizations in COSMO model has been replaced by aerosol concentration derived from MUSCAT model. The cloud microphysical process from the modified two-moment scheme is compared with stand-alone COSMO model. To validate the robustness of the model simulation, the coupled model system is integrated with COSP satellite simulator (Muhlbauer et al., 2012). Further, the simulations are compared with MODIS (Moderate Resolution Imaging Spectroradiometer) and ISCCP (International Satellite Cloud Climatology Project) satellite products.

A Mixed Phase Tale: New Ways of using in-situ cloud observations to reduce climate model biases in Southern Ocean

NASA Astrophysics Data System (ADS)

Gettelman, A.; Stith, J. L.

2014-12-01

Southern ocean clouds are a critical part of the earth's energy budget, and significant biases in the climatology of these clouds exist in models used to predict climate change. We compare in situ measurements of cloud microphysical properties of ice and liquid over the S. Ocean with constrained output from the atmospheric component of an Earth System Model. Observations taken during the HIAPER (the NSF/NCAR G-V aircraft) Pole-to-Pole Observations (HIPPO) multi-year field campaign are compared with simulations from the atmospheric component of the Community Earth System Model (CESM). Remarkably, CESM is able to accurately simulate the locations of cloud formation, and even cloud microphysical properties are comparable between the model and observations. Significantly, the simulations do not predict sufficient supercooled liquid. Altering the model cloud and aerosol processes to better reproduce the observations of supercooled liquid acts to reduce long-standing biases in S. Ocean clouds in CESM, which are typical of other models. Furthermore, sensitivity tests show where better observational constraints on aerosols and cloud microphysics can reduce uncertainty and biases in global models. These results are intended to show how we can connect large scale simulations with field observations in the S. Ocean to better understand Southern Ocean cloud processes and reduce biases in global climate simulations.

Trends in aerosol abundances and distributions

NASA Technical Reports Server (NTRS)

Turco, R. P.; Mccormick, M. P.; Clancy, R. T.; Curran, R.; Deluisi, J.; Hamill, P.; Kent, G.; Rosen, J. M.; Toon, O. B.; Yue, G.

1989-01-01

The properties of aerosols that reside in the upper atmosphere are described. Special emphasis is given to the influence these aerosols have on ozone observation systems, mainly through radiative effects, and on ambient ozone concentrations, mainly through chemical effects. It has long been appreciated that stratospheric particles can interfere with the remote sensing of ozone distribution. The mechanism and magnitude of this interference are evaluated. Separate sections deal with the optical properties of upper atmospheric aerosols, long-term trends in stratospheric aerosols, perturbations of the stratospheric aerosol layer by volcanic eruptions, and estimates of the impacts that such particles have on remotely measured ozone concentrations. Another section is devoted to a discussion of the polar stratospheric clouds (PSC's). These unique clouds, recently discovered by satellite observation, are now thought to be intimately connected with the Antarctic ozone hole. Accordingly, interest in PSC's has grown considerably in recent years. This chapter describes what we know about the morphology, physical chemistry, and microphysics of PSC's.

3D And 4D Cloud Lifecycle Investigations Using Innovative Scanning Radar Analysis Methods. Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kollias, Pavlos

2017-04-23

With the vast upgrades to the ARM program radar measurement capabilities in 2010 and beyond, our ability to probe the 3D structure of clouds and associated precipitation has increased dramatically. This project build on the PI's and co-I's expertisein the analysis of radar observations. The first research thrust aims to document the 3D morphological (as depicted by the radar reflectivity structure) and 3D dynamical (cloud$-$scale eddies) structure of boundary layer clouds. Unraveling the 3D dynamical structure of stratocumulus and shallow cumulus clouds requires decomposition of the environmental wind contribution and particle sedimentation velocity from the observed radial Doppler velocity. Themore » second thrust proposes to unravel the mechanism of cumulus entrainment (location, scales) and its impact on microphysics utilizing radar measurements from the vertically pointing and new scanning radars at the ARM sites. The third research thrust requires the development of a cloud$-$tracking algorithm that monitors the properties of cloud.« less

Building the GPM-GV Column from the GPM Cold season Precipitation Experiment (Invited)

NASA Astrophysics Data System (ADS)

Nesbitt, S. W.; Duffy, G. A.; Gleicher, K.; McFarquhar, G. M.; Kulie, M.; Williams, C. R.; Petersen, W. A.; Munchak, S. J.; Tokay, A.; Skofronick Jackson, G.; Chandrasekar, C. V.; Kollias, P.; Hudak, D. R.; Tanelli, S.

2013-12-01

Within the context of the Drop Size Distribution Working Group (DSDWG) of the Global Precipitation Mission-Ground Validation (GPM-GV) program, a major science and satellite precipitation algorithm validation focus is on quantitatively determining the variability of microphysical properties of precipitation in the vertical column, as well as the radiative properties of those particles at GPM-relevant microwave frequencies. The GPM Cold season Precipitation Experiment, or GCPEx, was conducted to address both of these objectives in mid-latitude winter precipitation. Radar observations at C, X, Ku, Ka, and W band from ground based scanning radars, profiling radars, and aircraft, as well as an aircraft passive microwave imager from GCPEx, conducted in early 2012 near Barrie, Ontario, Canada, can be used to constrain the observed reflectivites and brightness temperatures in snow as well as construct radar dual frequency ratios (DFRs) that can be used to identify regimes of microwave radiative properties in observed hydrometeor columns. These data can be directly matched with aircraft and ground based in situ microphysical probes, such as 2-D and bulk aircraft probes and surface disdrometers, to place the microphysical and microwave scattering and emission properties of the snow in context throughout the column of hydrometeors. In this presentation, particle scattering regimes will be identified in GCPEx hydrometeor columns storm events using a clustering technique in a multi-frequency DFR-near Rayleigh radar reflectivity phase space using matched ground-based and aircraft-based radar and passive microwave data. These data will be interpreted using matched in situ disdrometer and aircraft probe microphysical data (particle size distributions, habit identification, fall speed, mass-diameter relationships) derived during the events analyzed. This database is geared towards evaluating scattering simulations and the choice of integral particle size distributions for snow precipitation retrieval algorithms for ground and spaceborne radars at relevant wavelengths. A comparison of results for different cases with varying synoptic forcing and microphysical evolution will be presented.

The 20-22 January 2007 Snow Events over Canada: Microphysical Properties

NASA Technical Reports Server (NTRS)

Tao. W.K.; Shi, J.J.; Matsui, T.; Hao, A.; Lang, S.; Peters-Lidard, C.; Skofronick-Jackson, G.; Petersen, W.; Cifelli, R.; Rutledge, S.

2009-01-01

One of the grand challenges of the Global Precipitation Measurement (GPM) mission is to improve precipitation measurements in mid- and high-latitudes during cold seasons through the use of high-frequency passive microwave radiometry. Toward this end, the Weather Research and Forecasting (WRF) model with the Goddard microphysics scheme is coupled with a Satellite Data Simulation Unit (WRF-SDSU) that has been developed to facilitate over-land snowfall retrieval algorithms by providing a virtual cloud library and microwave brightness temperature (Tb) measurements consistent with the GPM Microwave Imager (GMI). This study tested the Goddard cloud microphysics scheme in WRF for snowstorm events (January 20-22, 2007) that took place over the Canadian CloudSAT/CALIPSO Validation Project (C3VP) ground site (Centre for Atmospheric Research Experiments - CARE) in Ontario, Canada. In this paper, the performance of the Goddard cloud microphysics scheme both with 2ice (ice and snow) and 3ice (ice, snow and graupel) as well as other WRF microphysics schemes will be presented. The results are compared with data from the Environment Canada (EC) King Radar, an operational C-band radar located near the CARE site. In addition, the WRF model output is used to drive the Goddard SDSU to calculate radiances and backscattering signals consistent with direct satellite observations for evaluating the model results.

Upper-level enhancement of microphysical processes in extratropical cyclones observed during OLYMPEX

NASA Astrophysics Data System (ADS)

Rowe, A.; McMurdie, L. A.; Houze, R.; Zagrodnik, J. P.; Schuldt, T.; Chaplin, M.

2017-12-01

Data collected during the Olympic Mountains Experiment (OLYMPEX) of fall 2015-winter 2016 offer a unique opportunity to document enhancement of precipitation on the windward side of a mountain range as mid-latitude cyclones encountered the complex terrain of the Olympic Mountains. During the campaign, extensive instrumentation was deployed, including ground-based dual-polarization Doppler radars on the windward and leeward sides of the mountains and research aircraft providing in situ microphysical measurements and triple-frequency radar data over the ground-based sites and highest elevations. These datasets provide unprecedented detail on microphysical and dynamical processes associated with precipitation enhancement. Previous studies of precipitation enhancement over mountains have focused on surface rainfall amounts. However, the airflow over the terrain affects precipitation throughout the vertical columns of the atmosphere passing over the mountains. The OLYMPEX data were collected in a way that allows the mechanisms leading to enhancement to be examined at all levels. In particular, NASA's S-band and the NSF/CSWR DOW6 X-band dual-polarization radars provided high-resolution vertical cross sections in sectors upwind and over the mountains. The degree of upper-level enhancement seen in these radar data was most pronounced when the integrated vapor transport was strong, stability was moist neutral, and melting levels were relatively high. These conditions were often found within the warm sectors of the mid-latitude cyclones observed in OLYMPEX. Within widespread stratiform echo, radar data revealed layers of enhanced differential reflectivity aloft in addition to the enhanced reflectivity. In situ microphysical probe data from the University of North Dakota Citation aircraft were obtained in the context of these ground-based radar observations, which along with observations from the APR3 radar aboard the DC8 research aircraft, provide a unique dataset for investigating these ice-based microphysical processes aloft, including over the high terrain. Insights from these coincident datasets include the role of generating cells in production of supercooled liquid water and riming aloft within the warm sector during a heavy rain event.

Investigating the Sensitivity of Nucleation Parameterization on Ice Growth

NASA Astrophysics Data System (ADS)

Gaudet, L.; Sulia, K. J.

2017-12-01

The accurate prediction of precipitation from lake-effect snow events associated with the Great Lakes region depends on the parameterization of thermodynamic and microphysical processes, including the formation and subsequent growth of frozen hydrometeors. More specifically, the formation of ice hydrometeors has been represented through varying forms of ice nucleation parameterizations considering the different nucleation modes (e.g., deposition, condensation-freezing, homogeneous). These parameterizations have been developed from in-situ measurements and laboratory observations. A suite of nucleation parameterizations consisting of those published in Meyers et al. (1992) and DeMott et al. (2010) as well as varying ice nuclei data sources are coupled with the Adaptive Habit Model (AHM, Harrington et al. 2013), a microphysics module where ice crystal aspect ratio and density are predicted and evolve in time. Simulations are run with the AHM which is implemented in the Weather Research and Forecasting (WRF) model to investigate the effect of ice nucleation parameterization on the non-spherical growth and evolution of ice crystals and the subsequent effects on liquid-ice cloud-phase partitioning. Specific lake-effect storms that were observed during the Ontario Winter Lake-Effect Systems (OWLeS) field campaign (Kristovich et al. 2017) are examined to elucidate this potential microphysical effect. Analysis of these modeled events is aided by dual-polarization radar data from the WSR-88D in Montague, New York (KTYX). This enables a comparison of the modeled and observed polarmetric and microphysical profiles of the lake-effect clouds, which involves investigating signatures of reflectivity, specific differential phase, correlation coefficient, and differential reflectivity. Microphysical features of lake-effect bands, such as ice, snow, and liquid mixing ratios, ice crystal aspect ratio, and ice density are analyzed to understand signatures in the aforementioned modeled dual-polarization radar variables. Hence, this research helps to determine an ice nucleation scheme that will best model observations of lake-effect clouds producing snow off of Lake Ontario and Lake Erie, and analyses will highlight the sensitivity of the evolution of the cases to a given nucleation scheme.

Evaluation of Cloud Microphysics Simulated using a Meso-Scale Model Coupled with a Spectral Bin Microphysical Scheme through Comparison with Observation Data by Ship-Borne Doppler and Space-Borne W-Band Radars

NASA Technical Reports Server (NTRS)

Iguchi, T.; Nakajima, T.; Khain, A. P.; Saito, K.; Takemura, T.; Okamoto, H.; Nishizawa, T.; Tao, W.-K.

2012-01-01

Equivalent radar reflectivity factors (Ze) measured by W-band radars are directly compared with the corresponding values calculated from a three-dimensional non-hydrostatic meso-scale model coupled with a spectral-bin-microphysical (SBM) scheme for cloud. Three case studies are the objects of this research: one targets a part of ship-borne observation using 95 GHz Doppler radar over the Pacific Ocean near Japan in May 2001; other two are aimed at two short segments of space-borne observation by the cloud profiling radar on CloudSat in November 2006. The numerical weather prediction (NWP) simulations reproduce general features of vertical structures of Ze and Doppler velocity. A main problem in the reproducibility is an overestimation of Ze in ice cloud layers. A frequency analysis shows a strong correlation between ice water contents (IWC) and Ze in the simulation; this characteristic is similar to those shown in prior on-site studies. From comparing with the empirical correlations by the prior studies, the simulated Ze is overestimated than the corresponding values in the studies at the same IWC. Whereas the comparison of Doppler velocities suggests that large-size snowflakes are necessary for producing large velocities under the freezing level and hence rules out the possibility that an overestimation of snow size causes the overestimation of Ze. Based on the results of several sensitivity tests, we conclude that the source of the overestimation is a bias in the microphysical calculation of Ze or an overestimation of IWC. To identify the source of the problems needs further validation research with other follow-up observations.

Evaluation of high-level clouds in cloud resolving model simulations with ARM and KWAJEX observations

DOE PAGES

Liu, Zheng; Muhlbauer, Andreas; Ackerman, Thomas

2015-11-05

In this paper, we evaluate high-level clouds in a cloud resolving model during two convective cases, ARM9707 and KWAJEX. The simulated joint histograms of cloud occurrence and radar reflectivity compare well with cloud radar and satellite observations when using a two-moment microphysics scheme. However, simulations performed with a single moment microphysical scheme exhibit low biases of approximately 20 dB. During convective events, two-moment microphysical overestimate the amount of high-level cloud and one-moment microphysics precipitate too readily and underestimate the amount and height of high-level cloud. For ARM9707, persistent large positive biases in high-level cloud are found, which are not sensitivemore » to changes in ice particle fall velocity and ice nuclei number concentration in the two-moment microphysics. These biases are caused by biases in large-scale forcing and maintained by the periodic lateral boundary conditions. The combined effects include significant biases in high-level cloud amount, radiation, and high sensitivity of cloud amount to nudging time scale in both convective cases. The high sensitivity of high-level cloud amount to the thermodynamic nudging time scale suggests that thermodynamic nudging can be a powerful ‘‘tuning’’ parameter for the simulated cloud and radiation but should be applied with caution. The role of the periodic lateral boundary conditions in reinforcing the biases in cloud and radiation suggests that reducing the uncertainty in the large-scale forcing in high levels is important for similar convective cases and has far reaching implications for simulating high-level clouds in super-parameterized global climate models such as the multiscale modeling framework.« less

Microphysics-based black carbon aging in a global CTM: constraints from HIPPO observations and implications for global black carbon budget

NASA Astrophysics Data System (ADS)

He, C.; Li, Q.; Liou, K. N.; Qi, L.; Tao, S.; Schwarz, J. P.

2015-11-01

We develop and examine a microphysics-based black carbon (BC) aerosol aging scheme that accounts for condensation and coagulation processes in a global 3-D chemical transport model (GEOS-Chem) by interpreting the BC measurements from the HIAPER Pole-to-Pole Observations (HIPPO, 2009-2011) using the model. We convert aerosol mass in the model to number concentration by assuming lognormal aerosol size distributions and compute the microphysical BC aging rate explicitly from the condensation of soluble materials onto hydrophobic BC and the coagulation between hydrophobic BC and preexisting soluble particles. The resulting aging rate is ∼ 4 times higher in the lower troposphere over source regions than that from a fixed aging scheme with an e-folding time of 1.2 days. The higher aging rate reflects the large emissions of sulfate-nitrate and secondary organic aerosol precursors hence faster BC aging through condensation and coagulation. In contrast, the microphysical aging is more than fivefold slower than the fixed aging in remote regions, where condensation and coagulation are weak. Globally BC microphysical aging is dominated by condensation, while coagulation contribution is largest over East China, India, and Central Africa. The fixed aging scheme results in an overestimate of HIPPO BC throughout the troposphere by a factor of 6 on average. The microphysical scheme reduces this discrepancy by a factor of ∼ 3, particularly in the middle and upper troposphere. It also leads to a threefold reduction in model bias in the latitudinal BC column burden averaged along the HIPPO flight tracks, with largest improvements in the tropics. The resulting global annual mean BC lifetime is 4.2 days and BC burden is 0.25 mg m-2, with 7.3 % of the burden at high altitudes (above 5 km). Wet scavenging accounts for 80.3 % of global BC deposition. We find that in source regions the microphysical aging rate is insensitive to aerosol size distribution, condensation threshold, and chemical oxidation aging, while it is the opposite in remote regions, where the aging rate is orders of magnitude smaller. As a result, global BC burden and lifetime show little sensitivity (< 5 % change) to these three factors.

The Influence of Microphysical Cloud Parameterization on Microwave Brightness Temperatures

NASA Technical Reports Server (NTRS)

Skofronick-Jackson, Gail M.; Gasiewski, Albin J.; Wang, James R.; Zukor, Dorothy J. (Technical Monitor)

2000-01-01

The microphysical parameterization of clouds and rain-cells plays a central role in atmospheric forward radiative transfer models used in calculating passive microwave brightness temperatures. The absorption and scattering properties of a hydrometeor-laden atmosphere are governed by particle phase, size distribution, aggregate density., shape, and dielectric constant. This study identifies the sensitivity of brightness temperatures with respect to the microphysical cloud parameterization. Cloud parameterizations for wideband (6-410 GHz observations of baseline brightness temperatures were studied for four evolutionary stages of an oceanic convective storm using a five-phase hydrometeor model in a planar-stratified scattering-based radiative transfer model. Five other microphysical cloud parameterizations were compared to the baseline calculations to evaluate brightness temperature sensitivity to gross changes in the hydrometeor size distributions and the ice-air-water ratios in the frozen or partly frozen phase. The comparison shows that, enlarging the rain drop size or adding water to the partly Frozen hydrometeor mix warms brightness temperatures by up to .55 K at 6 GHz. The cooling signature caused by ice scattering intensifies with increasing ice concentrations and at higher frequencies. An additional comparison to measured Convection and Moisture LA Experiment (CAMEX 3) brightness temperatures shows that in general all but, two parameterizations produce calculated T(sub B)'s that fall within the observed clear-air minima and maxima. The exceptions are for parameterizations that, enhance the scattering characteristics of frozen hydrometeors.

Application of TRMM PR and TMI Measurements to Assess Cloud Microphysical Schemes in the MM5 Model for a Winter Storm

NASA Technical Reports Server (NTRS)

Han, Mei; Braun, Scott A.; Olson, William S.; Persson, P. Ola G.; Bao, Jian-Wen

2009-01-01

Seen by the human eye, precipitation particles are commonly drops of rain, flakes of snow, or lumps of hail that reach the ground. Remote sensors and numerical models usually deal with information about large collections of rain, snow, and hail (or graupel --also called soft hail ) in a volume of air. Therefore, the size and number of the precipitation particles and how particles interact, evolve, and fall within the volume of air need to be represented using physical laws and mathematical tools, which are often implemented as cloud and precipitation microphysical parameterizations in numerical models. To account for the complexity of the precipitation physical processes, scientists have developed various types of such schemes in models. The accuracy of numerical weather forecasting may vary dramatically when different types of these schemes are employed. Therefore, systematic evaluations of cloud and precipitation schemes are of great importance for improvement of weather forecasts. This study is one such endeavor; it pursues quantitative assessment of all the available cloud and precipitation microphysical schemes in a weather model (MM5) through comparison with the observations obtained by National Aeronautics and Space Administration (NASA) s and Japan Aerospace Exploration Agency (JAXA) s Tropical Rainfall Measuring Mission (TRMM) precipitation radar (PR) and microwave imager (TMI). When satellite sensors (like PR or TMI) detect information from precipitation particles, they cannot directly observe the microphysical quantities (e.g., water species phase, density, size, and amount etc.). Instead, they tell how much radiation is absorbed by rain, reflected away from the sensor by snow or graupel, or reflected back to the satellite. On the other hand, the microphysical quantities in the model are usually well represented in microphysical schemes and can be converted to radiative properties that can be directly compared to the corresponding PR and TMI observations. This study employs this method to evaluate the accuracy of the simulated radiative properties by the MM5 model with different microphysical schemes. It is found that the representations of particle density, size, and mass in the different schemes in the MM5 model determine the model s performance when predicting a winter storm over the eastern Pacific Ocean. Schemes lacking moderate density particles (i.e. graupel), with snow flakes that are too large, or with excessive mass of snow or graupel lead to degraded prediction of the radiative properties as observed by the TRMM satellite. This study demonstrates the uniqueness of the combination of both an active microwave sensor (PR) and passive microwave sensor (TMI) onboard TRMM on assessing the accuracy of numerical weather forecasting. It improves our understanding of the physical and radiative properties of different types of precipitation particles and provides suggestions for better representation of cloud and precipitation processes in numerical models. It would, ultimately, contribute to answering questions like "Why did it not rain when the forecast says it would?"

Improving the representation of mixed-phase cloud microphysics in the ICON-LEM

NASA Astrophysics Data System (ADS)

Tonttila, Juha; Hoose, Corinna; Milbrandt, Jason; Morrison, Hugh

2017-04-01

The representation of ice-phase cloud microphysics in ICON-LEM (the Large-Eddy Model configuration of the ICOsahedral Nonhydrostatic model) is improved by implementing the recently published Predicted Particle Properties (P3) scheme into the model. In the typical two-moment microphysical schemes, such as that previously used in ICON-LEM, ice-phase particles must be partitioned into several prescribed categories. It is inherently difficult to distinguish between categories such as graupel and hail based on just the particle size, yet this partitioning may significantly affect the simulation of convective clouds. The P3 scheme avoids the problems associated with predefined ice-phase categories that are inherent in traditional microphysics schemes by introducing the concept of "free" ice-phase categories, whereby the prognostic variables enable the prediction of a wide range of smoothly varying physical properties and hence particle types. To our knowledge, this is the first application of the P3 scheme in a large-eddy model with horizontal grid spacings on the order of 100 m. We will present results from ICON-LEM simulations with the new P3 scheme comprising idealized stratiform and convective cloud cases. We will also present real-case limited-area simulations focusing on the HOPE (HD(CP)2 Observational Prototype Experiment) intensive observation campaign. The results are compared with a matching set of simulations employing the two-moment scheme and the performance of the model is also evaluated against observations in the context of the HOPE simulations, comprising data from ground based remote sensing instruments.

Topical Meeting on Microphysics of Surfaces, Beams, and Adsorbates Held at Santa Fe, New Mexico on 4-6 February 1985.

DTIC Science & Technology

1985-12-18

during excimer laser ablation. Results are %%% Study on the Mechanism of Ion-Assisted Etching, F. H. M. correlated with interferometric measurements of...report on real time interferometric measurements of free electron density and laser induced .,- fluorescence studies of atoms and molecules in the...compared with morphology exam- Ined with Nomarski micrographs and SEM. In addition, the struc- ture and composition of the deposited lines were analysed

Performance of the Goddard Multiscale Modeling Framework with Goddard Ice Microphysical Schemes

NASA Technical Reports Server (NTRS)

Chern, Jiun-Dar; Tao, Wei-Kuo; Lang, Stephen E.; Matsui, Toshihisa; Li, J.-L.; Mohr, Karen I.; Skofronick-Jackson, Gail M.; Peters-Lidard, Christa D.

2016-01-01

The multiscale modeling framework (MMF), which replaces traditional cloud parameterizations with cloud-resolving models (CRMs) within a host atmospheric general circulation model (GCM), has become a new approach for climate modeling. The embedded CRMs make it possible to apply CRM-based cloud microphysics directly within a GCM. However, most such schemes have never been tested in a global environment for long-term climate simulation. The benefits of using an MMF to evaluate rigorously and improve microphysics schemes are here demonstrated. Four one-moment microphysical schemes are implemented into the Goddard MMF and their results validated against three CloudSat/CALIPSO cloud ice products and other satellite data. The new four-class (cloud ice, snow, graupel, and frozen drops/hail) ice scheme produces a better overall spatial distribution of cloud ice amount, total cloud fractions, net radiation, and total cloud radiative forcing than earlier three-class ice schemes, with biases within the observational uncertainties. Sensitivity experiments are conducted to examine the impact of recently upgraded microphysical processes on global hydrometeor distributions. Five processes dominate the global distributions of cloud ice and snow amount in long-term simulations: (1) allowing for ice supersaturation in the saturation adjustment, (2) three additional correction terms in the depositional growth of cloud ice to snow, (3) accounting for cloud ice fall speeds, (4) limiting cloud ice particle size, and (5) new size-mapping schemes for snow and graupel. Despite the cloud microphysics improvements, systematic errors associated with subgrid processes, cyclic lateral boundaries in the embedded CRMs, and momentum transport remain and will require future improvement.

Modeling the Impact of Drizzle and 3D Cloud Structure on Remote Sensing of Effective Radius

NASA Technical Reports Server (NTRS)

Platnick, Steven; Zinner, Tobias; Ackerman, S.

2008-01-01

Remote sensing of cloud particle size with passive sensors like MODIS is an important tool for cloud microphysical studies. As a measure of the radiatively relevant droplet size, effective radius can be retrieved with different combinations of visible through shortwave infrared channels. MODIS observations sometimes show significantly larger effective radii in marine boundary layer cloud fields derived from the 1.6 and 2.1 pm channel observations than for 3.7 pm retrievals. Possible explanations range from 3D radiative transport effects and sub-pixel cloud inhomogeneity to the impact of drizzle formation on the droplet distribution. To investigate the potential influence of these factors, we use LES boundary layer cloud simulations in combination with 3D Monte Carlo simulations of MODIS observations. LES simulations of warm cloud spectral microphysics for cases of marine stratus and broken stratocumulus, each for two different values of cloud condensation nuclei density, produce cloud structures comprising droplet size distributions with and without drizzle size drops. In this study, synthetic MODIS observations generated from 3D radiative transport simulations that consider the full droplet size distribution will be generated for each scene. The operational MODIS effective radius retrievals will then be applied to the simulated reflectances and the results compared with the LES microphysics.

Microphysical growth state of ice particles and large-scale electrical structure of clouds

NASA Technical Reports Server (NTRS)

Williams, Earle; Zhang, Renyi; Boccippio, Dennis

1994-01-01

Cloud temperature, liquid water content, and vertical air velocity are all considered in evaluating the microphysical growth state of ice phase precipitation particles in the atmosphere. The large-scale observations taken together with in situ measurements indicated that the most prevalent growth condition for large ice particles in active convection is sublimation during riming, whereas the most prevalent growth condition in stratiform precipitation is vapor deposition. The large-scale electrical observations lend further support to the idea that particles warmed by riming into sublimation charge negatively and particles in vapor deposition charge positively in collisions with small ice particles.

Marine stratocumulus cloud characteristics from multichannel satellite measurements

NASA Technical Reports Server (NTRS)

Durkee, Philip A.; Mineart, Gary M.

1990-01-01

Understanding the effects of aerosols on the microphysical characteristics of marine stratocumulus clouds, and the resulting influence on cloud radiative properties, is a primary goal of FIRE. The potential for observing variations of cloud characteristics that might be related to variations of available aerosols is studied. Some results from theoretical estimates of cloud reflectance are presented. Also presented are the results of comparisons between aircraft measured microphysical characteristics and satellite detected radiative properties of marine stratocumulus clouds. These results are extracted from Mineart where the analysis procedures and a full discussion of the observations are presented. Only a brief description of the procedures and the composite results are presented.

Simulating mixed-phase Arctic stratus clouds: sensitivity to ice initiation mechanisms

NASA Astrophysics Data System (ADS)

Sednev, I.; Menon, S.; McFarquhar, G.

2008-06-01

The importance of Arctic mixed-phase clouds on radiation and the Arctic climate is well known. However, the development of mixed-phase cloud parameterization for use in large scale models is limited by lack of both related observations and numerical studies using multidimensional models with advanced microphysics that provide the basis for understanding the relative importance of different microphysical processes that take place in mixed-phase clouds. To improve the representation of mixed-phase cloud processes in the GISS GCM we use the GISS single-column model coupled to a bin resolved microphysics (BRM) scheme that was specially designed to simulate mixed-phase clouds and aerosol-cloud interactions. Using this model with the microphysical measurements obtained from the DOE ARM Mixed-Phase Arctic Cloud Experiment (MPACE) campaign in October 2004 at the North Slope of Alaska, we investigate the effect of ice initiation processes and Bergeron-Findeisen process (BFP) on glaciation time and longevity of single-layer stratiform mixed-phase clouds. We focus on observations taken during 9th-10th October, which indicated the presence of a single-layer mixed-phase clouds. We performed several sets of 12-h simulations to examine model sensitivity to different ice initiation mechanisms and evaluate model output (hydrometeors' concentrations, contents, effective radii, precipitation fluxes, and radar reflectivity) against measurements from the MPACE Intensive Observing Period. Overall, the model qualitatively simulates ice crystal concentration and hydrometeors content, but it fails to predict quantitatively the effective radii of ice particles and their vertical profiles. In particular, the ice effective radii are overestimated by at least 50%. However, using the same definition as used for observations, the effective radii simulated and that observed were more comparable. We find that for the single-layer stratiform mixed-phase clouds simulated, process of ice phase initiation due to freezing of supercooled water in both saturated and undersaturated (w.r.t. water) environments is as important as primary ice crystal origination from water vapor. We also find that the BFP is a process mainly responsible for the rates of glaciation of simulated clouds. These glaciation rates cannot be adequately represented by a water-ice saturation adjustment scheme that only depends on temperature and liquid and solid hydrometeors' contents as is widely used in bulk microphysics schemes and are better represented by processes that also account for supersaturation changes as the hydrometeors grow.

Simulating mixed-phase Arctic stratus clouds: sensitivity to ice initiation mechanisms

NASA Astrophysics Data System (ADS)

Sednev, I.; Menon, S.; McFarquhar, G.

2009-07-01

The importance of Arctic mixed-phase clouds on radiation and the Arctic climate is well known. However, the development of mixed-phase cloud parameterization for use in large scale models is limited by lack of both related observations and numerical studies using multidimensional models with advanced microphysics that provide the basis for understanding the relative importance of different microphysical processes that take place in mixed-phase clouds. To improve the representation of mixed-phase cloud processes in the GISS GCM we use the GISS single-column model coupled to a bin resolved microphysics (BRM) scheme that was specially designed to simulate mixed-phase clouds and aerosol-cloud interactions. Using this model with the microphysical measurements obtained from the DOE ARM Mixed-Phase Arctic Cloud Experiment (MPACE) campaign in October 2004 at the North Slope of Alaska, we investigate the effect of ice initiation processes and Bergeron-Findeisen process (BFP) on glaciation time and longevity of single-layer stratiform mixed-phase clouds. We focus on observations taken during 9-10 October, which indicated the presence of a single-layer mixed-phase clouds. We performed several sets of 12-h simulations to examine model sensitivity to different ice initiation mechanisms and evaluate model output (hydrometeors' concentrations, contents, effective radii, precipitation fluxes, and radar reflectivity) against measurements from the MPACE Intensive Observing Period. Overall, the model qualitatively simulates ice crystal concentration and hydrometeors content, but it fails to predict quantitatively the effective radii of ice particles and their vertical profiles. In particular, the ice effective radii are overestimated by at least 50%. However, using the same definition as used for observations, the effective radii simulated and that observed were more comparable. We find that for the single-layer stratiform mixed-phase clouds simulated, process of ice phase initiation due to freezing of supercooled water in both saturated and subsaturated (w.r.t. water) environments is as important as primary ice crystal origination from water vapor. We also find that the BFP is a process mainly responsible for the rates of glaciation of simulated clouds. These glaciation rates cannot be adequately represented by a water-ice saturation adjustment scheme that only depends on temperature and liquid and solid hydrometeors' contents as is widely used in bulk microphysics schemes and are better represented by processes that also account for supersaturation changes as the hydrometeors grow.

Twomey effect observed from collocated microphysical and remote sensing measurements over shallow cumulus

NASA Astrophysics Data System (ADS)

Werner, F.; Ditas, F.; Siebert, H.; Simmel, M.; Wehner, B.; Pilewskie, P.; Schmeissner, T.; Shaw, R. A.; Hartmann, S.; Wex, H.; Roberts, G. C.; Wendisch, M.

2014-02-01

Clear experimental evidence of the Twomey effect for shallow trade wind cumuli near Barbados is presented. Effective droplet radius (reff) and cloud optical thickness (τ), retrieved from helicopter-borne spectral cloud-reflected radiance measurements, and spectral cloud reflectivity (γλ) are correlated with collocated in situ observations of the number concentration of aerosol particles from the subcloud layer (N). N denotes the concentration of particles larger than 80 nm in diameter and represents particles in the activation mode. In situ cloud microphysical and aerosol parameters were sampled by the Airborne Cloud Turbulence Observation System (ACTOS). Spectral cloud-reflected radiance data were collected by the Spectral Modular Airborne Radiation measurement sysTem (SMART-HELIOS). With increasing N a shift in the probability density functions of τ and γλ toward larger values is observed, while the mean values and observed ranges of retrieved reff decrease. The relative susceptibilities (RS) of reff, τ, and γλ to N are derived for bins of constant liquid water path. The resulting values of RS are in the range of 0.35 for reff and τ, and 0.27 for γλ. These results are close to the maximum susceptibility possible from theory. Overall, the shallow cumuli sampled near Barbados show characteristics of homogeneous, plane-parallel clouds. Comparisons of RS derived from in situ measured reff and from a microphysical parcel model are in close agreement.

GHI calculation sensitivity on microphysics, land- and cumulus parameterization in WRF over the Reunion Island

NASA Astrophysics Data System (ADS)

De Meij, A.; Vinuesa, J.-F.; Maupas, V.

2018-05-01

The sensitivity of different microphysics and dynamics schemes on calculated global horizontal irradiation (GHI) values in the Weather Research Forecasting (WRF) model is studied. 13 sensitivity simulations were performed for which the microphysics, cumulus parameterization schemes and land surface models were changed. Firstly we evaluated the model's performance by comparing calculated GHI values for the Base Case with observations for the Reunion Island for 2014. In general, the model calculates the largest bias during the austral summer. This indicates that the model is less accurate in timing the formation and dissipation of clouds during the summer, when higher water vapor quantities are present in the atmosphere than during the austral winter. Secondly, the model sensitivity on changing the microphysics, cumulus parameterization and land surface models on calculated GHI values is evaluated. The sensitivity simulations showed that changing the microphysics from the Thompson scheme (or Single-Moment 6-class scheme) to the Morrison double-moment scheme, the relative bias improves from 45% to 10%. The underlying reason for this improvement is that the Morrison double-moment scheme predicts the mass and number concentrations of five hydrometeors, which help to improve the calculation of the densities, size and lifetime of the cloud droplets. While the single moment schemes only predicts the mass for less hydrometeors. Changing the cumulus parameterization schemes and land surface models does not have a large impact on GHI calculations.

Aerosol-Cloud Interactions and Cloud Microphysical Properties in the Asir Region of Saudi Arabia

NASA Astrophysics Data System (ADS)

Kucera, P. A.; Axisa, D.; Burger, R. P.; Li, R.; Collins, D. R.; Freney, E. J.; Buseck, P. R.

2009-12-01

In recent advertent and inadvertent weather modification studies, a considerable effort has been made to understand the impact of varying aerosol properties and concentration on cloud properties. Significant uncertainties exist with aerosol-cloud interactions for which complex microphysical processes link the aerosol and cloud properties. Under almost all environmental conditions, increased aerosol concentrations within polluted air masses will enhance cloud droplet concentration relative to that in unperturbed regions. The interaction between dust particles and clouds are significant, yet the conditions in which dust particles become cloud condensation nuclei (CCN) are uncertain. In order to quantify this aerosol effect on clouds and precipitation, a field campaign was launched in the Asir region, located adjacent to the Red Sea in the southwest region of Saudi Arabia. Ground measurements of aerosol size distributions, hygroscopic growth factors, CCN concentrations as well as aircraft measurements of cloud hydrometeor size distributions were observed in the Asir region in August 2009. The presentation will include a summary of the analysis and results with a focus on aerosol-cloud interactions and cloud microphysical properties observed during the convective season in the Asir region.

The potential effects of volcanic aerosols on cirrus cloud microphysics

NASA Technical Reports Server (NTRS)

Jensen, Eric J.; Toon, Owen B.

1992-01-01

The potential impact of volcanic aerosols on nucleation of ice crystals in upper tropospheric cirrus clouds is examined from a microphysical perspective. The sulfuric acid aerosols which form in the stratosphere are presumably transported into the troposphere by sedimentation and tropopause folding. The tropospheric volcanic aerosol size distribution is estimated from 10-micron lidar backscatter and in situ measurements. Microphysical simulations suggest that at temperatures below about -50 C the concentration of ice crystals which nucleate may be as much as a factor of 5 larger when volcanic aerosols are present. The simulations suggest that the presence of volcanic aerosols may increase the net radiative forcing (surface warming) of certain types of cirrus near the tropopause by as much as 8 W/sq m. Further observations are required to determine whether these effects actually occur, and their global impact.

A Comprehensive Two-moment Warm Microphysical Bulk Scheme :

NASA Astrophysics Data System (ADS)

Caro, D.; Wobrock, W.; Flossmann, A.; Chaumerliac, N.

The microphysic properties of gaz, aerosol particles, and hydrometeors have impli- cations at local scale (precipitations, pollution peak,..), at regional scale (inundation, acid rains,...), and also, at global scale (radiative forcing,...). So, a multi-scale study is necessary to understand and forecast in a good way meteorological phenomena con- cerning clouds. However, it cannot be carried with detailed microphysic model, on account of computers limitations. So, microphysical bulk schemes have to estimate the n´ large scale z properties of clouds due to smaller scale processes and charac- teristics. So, the development of such bulk scheme is rather important to go further in the knowledge of earth climate and in the forecasting of intense meteorological phenomena. Here, a quasi-spectral microphysic warm scheme has been developed to predict the concentrations and mixing ratios of aerosols, cloud droplets and raindrops. It considers, explicitely and analytically, the nucleation of droplets (Abdul-Razzak et al., 2000), condensation/evaporation (Chaumerliac et al., 1987), the breakup and collision-coalescence processes with the Long (1974) Ss kernels and the Berry and ´ Reinhardt (1974) Ss autoconversion parameterization, but also, the aerosols and gaz ´ scavenging. First, the parameterization has been estimated in the simplest dynamic framework of an air parcel model, with the results of the detailed scavenging model, DESCAM (Flossmann et al., 1985). Then, it has been tested, in the dynamic frame- work of a kinematic model (Szumowski et al., 1998) dedicated to the HaRP cam- paign (Hawaiian Rainband Project, 1990), with the observations and with the results of the two dimensional detailed microphysic scheme, DESCAM 2-D (Flossmann et al., 1988), implement in the CLARK model (Clark and Farley, 1984).

Evaluating the effects of the Pacific Decadal Oscillation on winter precipitation in The Cascades using a mixed-physics WRF ensemble

NASA Astrophysics Data System (ADS)

Buxton, Carly S.

In most of Washington and Oregon, USA, mountain snowpack stores water which will be available through spring and early summer, when water demand in the region is at its highest. Therefore, understanding the numerous factors that influence winter precipitation variability is a key component in water resource planning. This project examines the effects of the Pacific Decadal Oscillation (PDO) on winter precipitation in the Pacific Northwest U.S. using the WRF-ARW regional climate model. A significant component of this work was evaluating the many options that WRF-ARW provides for representing sub-grid scale cloud microphysical processes. Because the "best" choice of microphysics parameterization can vary depending on the application, this project also seeks to determine which option leads to the most accurate simulation of winter precipitation (when compared to observations) in the complex terrain of the Pacific Northwest. A series of test runs were performed with eight different combinations of physics parameterizations, and the results of these test runs were used to narrow the number of physics options down to three for the final runs. Mean total precipitation and coefficient of variation of the final model runs were compared against observational data. As RCMs tend to do, WRF over-predicts mean total precipitation compared to observations, but the double-moment microphysics schemes, Thompson and Morrison, over-predict to a lesser extent than the single-moment scheme. Two WRF microphysics schemes, Thompson and Lin, were more likely to have a coefficient of variation within the range of observations. Overall, the Thompson scheme produced the most accurate simulation as compared to observations. To focus on the effects of the PDO, WRF simulations were performed for two ten-member ensembles, one for positive PDO Decembers, and one for negative PDO Decembers. WRF output of total precipitation was compared to both station and gridded observational data. During positive PDO conditions, there is a strong latitudinal signal at low elevations, while during negative PDO conditions, there is a strong latitudinal signal at high elevations. This shift in where the PDO signal is most visible is due to changes in mid-level westerly winds and upper-level circulation and temperature advection. Under positive PDO conditions, wind direction and moisture transport are the most important factors, and frequent warm, moist southwesterly winds cause a PDO signal at low elevations. Under negative PDO conditions, differences in westerly wind speed, and therefore orographic precipitation enhancement, lead to a latitudinal PDO signal at high elevations. This PDO signal is robust, appearing in both the WRF simulations and observational data, and the differences due to PDO phase exceed the differences due to choice of microphysics scheme, WRF internal variability, and observational data uncertainty.

High-Resolution NU-WRF Simulations of a Deep Convective-Precipitation System During MC3E: Part I: Comparisons Between Goddard Microphysics Schemes and Observations

NASA Technical Reports Server (NTRS)

Tao, Wei-Kuo; Wu, Di; Lang, Stephen; Chern, Jiun-Dar; Peters-Lidard, Christa; Fridlind, Ann; Matsui, Toshihisa

2016-01-01

The Goddard microphysics was recently improved by adding a fourth ice class (frozen dropshail). This new 4ICE scheme was developed and tested in the Goddard Cumulus Ensemble (GCE) model for an intense continental squall line and a moderate, less organized continental case. Simulated peak radar reflectivity profiles were improved in intensity and shape for both cases, as were the overall reflectivity probability distributions versus observations. In this study, the new Goddard 4ICE scheme is implemented into the regional-scale NASA Unified-Weather Research and Forecasting (NU-WRF) model, modified and evaluated for the same intense squall line, which occurred during the Midlatitude Continental Convective Clouds Experiment (MC3E). NU-WRF simulated radar reflectivities, total rainfall, propagation, and convective system structures using the 4ICE scheme modified herein agree as well as or significantly better with observations than the original 4ICE and two previous 3ICE (graupel or hail) versions of the Goddard microphysics. With the modified 4ICE, the bin microphysics-based rain evaporation correction improves propagation and in conjunction with eliminating the unrealistic dry collection of icesnow by hail can replicate the erect, narrow, and intense convective cores. Revisions to the ice supersaturation, ice number concentration formula, and snow size mapping, including a new snow breakup effect, allow the modified 4ICE to produce a stronger, better organized system, more snow, and mimic the strong aggregation signature in the radar distributions. NU-WRF original 4ICE simulated radar reflectivity distributions are consistent with and generally superior to those using the GCE due to the less restrictive domain and lateral boundaries.

Evaluating the Performance of the Goddard Multi-Scale Modeling Framework against GPM, TRMM and CloudSat/CALIPSO Products

NASA Astrophysics Data System (ADS)

Chern, J. D.; Tao, W. K.; Lang, S. E.; Matsui, T.; Mohr, K. I.

2014-12-01

Four six-month (March-August 2014) experiments with the Goddard Multi-scale Modeling Framework (MMF) were performed to study the impacts of different Goddard one-moment bulk microphysical schemes and large-scale forcings on the performance of the MMF. Recently a new Goddard one-moment bulk microphysics with four-ice classes (cloud ice, snow, graupel, and frozen drops/hail) has been developed based on cloud-resolving model simulations with large-scale forcings from field campaign observations. The new scheme has been successfully implemented to the MMF and two MMF experiments were carried out with this new scheme and the old three-ice classes (cloud ice, snow graupel) scheme. The MMF has global coverage and can rigorously evaluate microphysics performance for different cloud regimes. The results show MMF with the new scheme outperformed the old one. The MMF simulations are also strongly affected by the interaction between large-scale and cloud-scale processes. Two MMF sensitivity experiments with and without nudging large-scale forcings to those of ERA-Interim reanalysis were carried out to study the impacts of large-scale forcings. The model simulated mean and variability of surface precipitation, cloud types, cloud properties such as cloud amount, hydrometeors vertical profiles, and cloud water contents, etc. in different geographic locations and climate regimes are evaluated against GPM, TRMM, CloudSat/CALIPSO satellite observations. The Goddard MMF has also been coupled with the Goddard Satellite Data Simulation Unit (G-SDSU), a system with multi-satellite, multi-sensor, and multi-spectrum satellite simulators. The statistics of MMF simulated radiances and backscattering can be directly compared with satellite observations to assess the strengths and/or deficiencies of MMF simulations and provide guidance on how to improve the MMF and microphysics.

Impacts of a Stochastic Ice Mass-Size Relationship on Squall Line Ensemble Simulations

NASA Astrophysics Data System (ADS)

Stanford, M.; Varble, A.; Morrison, H.; Grabowski, W.; McFarquhar, G. M.; Wu, W.

2017-12-01

Cloud and precipitation structure, evolution, and cloud radiative forcing of simulated mesoscale convective systems (MCSs) are significantly impacted by ice microphysics parameterizations. Most microphysics schemes assume power law relationships with constant parameters for ice particle mass, area, and terminal fallspeed relationships as a function of size, despite observations showing that these relationships vary in both time and space. To account for such natural variability, a stochastic representation of ice microphysical parameters was developed using the Predicted Particle Properties (P3) microphysics scheme in the Weather Research and Forecasting model, guided by in situ aircraft measurements from a number of field campaigns. Here, the stochastic framework is applied to the "a" and "b" parameters of the unrimed ice mass-size (m-D) relationship (m=aDb) with co-varying "a" and "b" values constrained by observational distributions tested over a range of spatiotemporal autocorrelation scales. Diagnostically altering a-b pairs in three-dimensional (3D) simulations of the 20 May 2011 Midlatitude Continental Convective Clouds Experiment (MC3E) squall line suggests that these parameters impact many important characteristics of the simulated squall line, including reflectivity structure (particularly in the anvil region), surface rain rates, surface and top of atmosphere radiative fluxes, buoyancy and latent cooling distributions, and system propagation speed. The stochastic a-b P3 scheme is tested using two frameworks: (1) a large ensemble of two-dimensional idealized squall line simulations and (2) a smaller ensemble of 3D simulations of the 20 May 2011 squall line, for which simulations are evaluated using observed radar reflectivity and radial velocity at multiple wavelengths, surface meteorology, and surface and satellite measured longwave and shortwave radiative fluxes. Ensemble spreads are characterized and compared against initial condition ensemble spreads for a range of variables.

A microphysics guide to cirrus clouds - Part 1: Cirrus types

NASA Astrophysics Data System (ADS)

Krämer, Martina; Rolf, Christian; Luebke, Anna; Afchine, Armin; Spelten, Nicole; Costa, Anja; Meyer, Jessica; Zöger, Martin; Smith, Jessica; Herman, Robert L.; Buchholz, Bernhard; Ebert, Volker; Baumgardner, Darrel; Borrmann, Stephan; Klingebiel, Marcus; Avallone, Linnea

2016-03-01

The microphysical and radiative properties of cirrus clouds continue to be beyond understanding and thus still represent one of the largest uncertainties in the prediction of the Earth's climate (IPCC, 2013). Our study aims to provide a guide to cirrus microphysics, which is compiled from an extensive set of model simulations, covering the broad range of atmospheric conditions for cirrus formation and evolution. The model results are portrayed in the same parameter space as field measurements, i.e., in the Ice Water Content-Temperature (IWC-T) parameter space. We validate this cirrus analysis approach by evaluating cirrus data sets from 17 aircraft campaigns, conducted in the last 15 years, spending about 94 h in cirrus over Europe, Australia, Brazil as well as South and North America. Altogether, the approach of this study is to track cirrus IWC development with temperature by means of model simulations, compare with observations and then assign, to a certain degree, cirrus microphysics to the observations. Indeed, the field observations show characteristics expected from the simulated Cirrus Guide. For example, high (low) IWCs are found together with high (low) ice crystal concentrations Nice. An important finding from our study is the classification of two types of cirrus with differing formation mechanisms and microphysical properties: the first cirrus type forms directly as ice (in situ origin cirrus) and splits in two subclasses, depending on the prevailing strength of the updraft: in slow updrafts these cirrus are rather thin with lower IWCs, while in fast updrafts thicker cirrus with higher IWCs can form. The second type consists predominantly of thick cirrus originating from mixed phase clouds (i.e., via freezing of liquid droplets - liquid origin cirrus), which are completely glaciated while lifting to the cirrus formation temperature region (< 235 K). In the European field campaigns, slow updraft in situ origin cirrus occur frequently in low- and high-pressure systems, while fast updraft in situ cirrus appear in conjunction with jet streams or gravity waves. Also, liquid origin cirrus mostly related to warm conveyor belts are found. In the US and tropical campaigns, thick liquid origin cirrus which are formed in large convective systems are detected more frequently.

Aerosol and Cloud Microphysical Characteristics of Rifts and Gradients in Maritime Stratocumulus Clouds

NASA Technical Reports Server (NTRS)

Sharon, Tarah M.; Albrecht, Bruce A.; Jonsson, Haflidi H.; Minnis, Patrick; Khaiyer, Mandana M.; Van Reken, Timothy; Seinfeld, John; Flagan, Rick

2008-01-01

A cloud rift is characterized as a large-scale, persistent area of broken, low reflectivity stratocumulus clouds usually surrounded by a solid deck of stratocumulus. A rift observed off the coast of Monterey Bay, California on 16 July 1999 was studied to compare the aerosol and cloud microphysical properties in the rift with those of the surrounding solid stratus deck. Variables measured from an instrumented aircraft included temperature, water vapor, and cloud liquid water. These measurements characterized the thermodynamic properties of the solid deck and rift areas. Microphysical measurements made included aerosol, cloud drop and drizzle drop concentrations and cloud condensation nuclei (CCN) concentrations. The microphysical characteristics in a solid stratus deck differ substantially from those of a broken, cellular rift where cloud droplet concentrations are a factor of 2 lower than those in the solid cloud. Further, CCN concentrations were found to be about 3 times greater in the solid cloud area compared with those in the rift and aerosol concentrations showed a similar difference as well. Although drizzle was observed near cloud top in parts of the solid stratus cloud, the largest drizzle rates were associated with the broken clouds within the rift area. In addition to marked differences in particle concentrations, evidence of a mesoscale circulation near the solid cloud rift boundary is presented. This mesoscale circulation provides a mechanism for maintaining a rift, but further study is required to understand the initiation of a rift and the conditions that may cause it to fill.

Forest fire smoke layers observed in the free troposphere over Portugal with a multiwavelength Raman lidar: optical and microphysical properties.

PubMed

Nepomuceno Pereira, Sérgio; Preißler, Jana; Guerrero-Rascado, Juan Luis; Silva, Ana Maria; Wagner, Frank

2014-01-01

Vertically resolved optical and microphysical properties of biomass burning aerosols, measured in 2011 with a multiwavelength Raman lidar, are presented. The transportation time, within 1-2 days (or less), pointed towards the presence of relatively fresh smoke particles over the site. Some strong layers aloft were observed with particle backscatter and extinction coefficients (at 355 nm) greater than 5 Mm(-1)sr(-1) and close to 300 Mm(-1), respectively. The particle intensive optical properties showed features different from the ones reported for aged smoke, but rather consistent with fresh smoke. The Ångström exponents were generally high, mainly above 1.4, indicating a dominating accumulation mode. Weak depolarization values, as shown by the small depolarization ratio of 5% or lower, were measured. Furthermore, the lidar ratio presented no clear wavelength dependency. The inversion of the lidar signals provided a set of microphysical properties including particle effective radius below 0.2 μm, which is less than values previously observed for aged smoke particles. Real and imaginary parts of refractive index of about 1.5-1.6 and 0.02i, respectively, were derived. The single scattering albedo was in the range between 0.85 and 0.93; these last two quantities indicate the nonnegligible absorbing characteristics of the observed particles.

WRF Simulations of the 20-22 January 2007 Snow Events over Eastern Canada: Comparison with In-Situ and Satellite Observations

NASA Technical Reports Server (NTRS)

Shi, J. J.; Tao, W.-K.; Matsui, T.; Cifelli, R.; Huo, A.; Lang, S.; Tokay, A.; Peters-Lidard, C.; Jackson, G.; Rutledge, S.;

Vertical distribution of microphysical properties of Arctic springtime low-level mixed-phase clouds over the Greenland and Norwegian seas

NASA Astrophysics Data System (ADS)

Mioche, Guillaume; Jourdan, Olivier; Delanoë, Julien; Gourbeyre, Christophe; Febvre, Guy; Dupuy, Régis; Monier, Marie; Szczap, Frédéric; Schwarzenboeck, Alfons; Gayet, Jean-François

2017-10-01

This study aims to characterize the microphysical and optical properties of ice crystals and supercooled liquid droplets within low-level Arctic mixed-phase clouds (MPCs). We compiled and analyzed cloud in situ measurements from four airborne spring campaigns (representing 18 flights and 71 vertical profiles in MPCs) over the Greenland and Norwegian seas mainly in the vicinity of the Svalbard archipelago. Cloud phase discrimination and representative vertical profiles of the number, size, mass and shape of ice crystals and liquid droplets are established. The results show that the liquid phase dominates the upper part of the MPCs. High concentrations (120 cm-3 on average) of small droplets (mean values of 15 µm), with an averaged liquid water content (LWC) of 0.2 g m-3 are measured at cloud top. The ice phase dominates the microphysical properties in the lower part of the cloud and beneath it in the precipitation region (mean values of 100 µm, 3 L-1 and 0.025 g m-3 for diameter, particle concentration and ice water content (IWC), respectively). The analysis of the ice crystal morphology shows that the majority of ice particles are irregularly shaped or rimed particles; the prevailing regular habits found are stellars and plates. We hypothesize that riming and diffusional growth processes, including the Wegener-Bergeron-Findeisen (WBF) mechanism, are the main growth mechanisms involved in the observed MPCs. The impact of larger-scale meteorological conditions on the vertical profiles of MPC properties was also investigated. Large values of LWC and high concentration of smaller droplets are possibly linked to polluted situations and air mass origins from the south, which can lead to very low values of ice crystal size and IWC. On the contrary, clean situations with low temperatures exhibit larger values of ice crystal size and IWC. Several parameterizations relevant for remote sensing or modeling studies are also determined, such as IWC (and LWC) - extinction relationship, ice and liquid integrated water paths, ice concentration and liquid water fraction according to temperature.

The first observed cloud echoes and microphysical parameter retrievals by China's 94-GHz cloud radar

NASA Astrophysics Data System (ADS)

Wu, Juxiu; Wei, Ming; Hang, Xin; Zhou, Jie; Zhang, Peichang; Li, Nan

2014-06-01

By using the cloud echoes first successfully observed by China's indigenous 94-GHz SKY cloud radar, the macrostructure and microphysical properties of drizzling stratocumulus clouds in Anhui Province on 8 June 2013 are analyzed, and the detection capability of this cloud radar is discussed. The results are as follows. (1) The cloud radar is able to observe the time-varying macroscopic and microphysical parameters of clouds, and it can reveal the microscopic structure and small-scale changes of clouds. (2) The velocity spectral width of cloud droplets is small, but the spectral width of the cloud containing both cloud droplets and drizzle is large. When the spectral width is more than 0.4 m s-1, the radar reflectivity factor is larger (over -10 dBZ). (3) The radar's sensitivity is comparatively higher because the minimum radar reflectivity factor is about -35 dBZ in this experiment, which exceeds the threshold for detecting the linear depolarized ratio (LDR) of stratocumulus (commonly -11 to -14 dBZ; decreases with increasing turbulence). (4) After distinguishing of cloud droplets from drizzle, cloud liquid water content and particle effective radius are retrieved. The liquid water content of drizzle is lower than that of cloud droplets at the same radar reflectivity factor.

Evaluating Simulated Tropical Convective Cores using HAIC-HIWC Microphysics and Dynamics Observations

NASA Astrophysics Data System (ADS)

Stanford, M.; Varble, A.; Zipser, E. J.; Strapp, J. W.; Leroy, D.; Schwarzenboeck, A.; Korolev, A.; Potts, R.

2016-12-01

A model intercomparison study is conducted to identify biases in simulated tropical convective core microphysical properties using two popular bulk parameterization schemes (Thompson and Morrison) and the Fast Spectral Bin Microphysics (FSBM) scheme. In-situ aircraft measurements of total condensed water content (TWC) and particle size distributions are compared with output from high-resolution WRF simulations of 4 mesoscale convective system (MCS) cases during the High Altitude Ice Crystals-High Ice Water Content (HAIC-HIWC) field campaign conducted in Darwin, Australia in 2014 and Cayenne, French Guiana in 2015. Observations of TWC collected using an isokinetic evaporator probe (IKP) optimized for high IWC measurements in conjunction with particle image processing from two optical array probes aboard the Falcon-20 research aircraft were used to constrain mass-size relationships in the observational dataset. Hydrometeor mass size distributions are compared between retrievals and simulations providing insight into the well-known high bias in simulated convective radar reflectivity. For TWC > 1 g m-3 between -10 and -40°C, simulations generally produce significantly greater median mass diameters (MMDs). Observations indicate that a sharp particle size mode occurs at 300 μm for large TWC values (> 2 g m-3) regardless of temperature. All microphysics schemes fail to reproduce this feature, and relative contributions of different hydrometeor species to this size bias vary between schemes. Despite far greater sample sizes, simulations also fail to produce high TWC conditions with very little of the mass contributed by large particles for a range of temperatures, despite such conditions being observed. Considering vapor grown particles alone in comparison with observations fails to correct the bias present in all schemes. Decreasing horizontal resolution from 1 km to 333 m shifts graupel and rain size distributions to slightly smaller sizes, but increased resolution alone will clearly not eliminate model biases. Results instead indicate that biases in both hydrometeor size distribution assumptions and parameterized processes also exist and need to be addressed before cloud and precipitation properties of convective systems can be adequately predicted.

Aerosol Microphysical and Radiative Effects on Continental Cloud Ensembles

DOE PAGES

Wang, Yuan; Vogel, Jonathan M.; Lin, Yun; ...

2018-01-10

Aerosol-cloud-radiation interactions represent one of the largest uncertainties in the current climate assessment. Much of the complexity arises from the non-monotonic responses of clouds, precipitation and radiative fluxes to aerosol perturbations under various meteorological conditions. Here, an aerosol-aware Weather Research and Forecasting (WRF) model is used to investigate the microphysical and radiative effects of aerosols in three weather systems during the March 2000 Cloud Intensive Observational Period campaign at the Southern Great Plains site of the US Atmospheric Radiation Measurement Program. Three cloud ensembles with different meteorological conditions are simulated, including a low-pressure deep convective cloud system, a series ofmore » lessprecipitating stratus and shallow cumulus, and a cold frontal passage. The WRF simulations are evaluated by the available observations of cloud fraction, liquid water path, precipitation, and surface temperature. The microphysical properties of cloud hydrometeors, such as their mass and number concentrations, generally show monotonic trends as a function of cloud condensation nuclei concentrations. Aerosol radiative effects do not interfere the trends of cloud microphysics, except for the stratus and shallow cumulus cases where aerosol semi-direct effects are identified. The precipitation changes by aerosols vary with the cloud types and their evolving stages, with more prominent aerosol invigoration effect and associated enhanced precipitation from the convective sources. Furthermore, the simulated aerosol direct effect suppresses precipitation in all three cases but does not overturn the direction of precipitation changes by the aerosol indirect effect. Cloud fraction exhibits much smaller sensitivity (typically less than 2%) to aerosol perturbations than the cloud microphysics, and the responses vary with aerosol concentrations and cloud regimes. The surface shortwave radiation shows a monotonic decrease by increasing aerosols, while the magnitude of the decrease depends on the cloud type. Surface temperature changes closely follow the modulation of the surface radiation fluxes.« less

Aerosol Microphysical and Radiative Effects on Continental Cloud Ensembles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Yuan; Vogel, Jonathan M.; Lin, Yun

Aerosol-cloud-radiation interactions represent one of the largest uncertainties in the current climate assessment. Much of the complexity arises from the non-monotonic responses of clouds, precipitation and radiative fluxes to aerosol perturbations under various meteorological conditions. Here, an aerosol-aware Weather Research and Forecasting (WRF) model is used to investigate the microphysical and radiative effects of aerosols in three weather systems during the March 2000 Cloud Intensive Observational Period campaign at the Southern Great Plains site of the US Atmospheric Radiation Measurement Program. Three cloud ensembles with different meteorological conditions are simulated, including a low-pressure deep convective cloud system, a series ofmore » lessprecipitating stratus and shallow cumulus, and a cold frontal passage. The WRF simulations are evaluated by the available observations of cloud fraction, liquid water path, precipitation, and surface temperature. The microphysical properties of cloud hydrometeors, such as their mass and number concentrations, generally show monotonic trends as a function of cloud condensation nuclei concentrations. Aerosol radiative effects do not interfere the trends of cloud microphysics, except for the stratus and shallow cumulus cases where aerosol semi-direct effects are identified. The precipitation changes by aerosols vary with the cloud types and their evolving stages, with more prominent aerosol invigoration effect and associated enhanced precipitation from the convective sources. Furthermore, the simulated aerosol direct effect suppresses precipitation in all three cases but does not overturn the direction of precipitation changes by the aerosol indirect effect. Cloud fraction exhibits much smaller sensitivity (typically less than 2%) to aerosol perturbations than the cloud microphysics, and the responses vary with aerosol concentrations and cloud regimes. The surface shortwave radiation shows a monotonic decrease by increasing aerosols, while the magnitude of the decrease depends on the cloud type. Surface temperature changes closely follow the modulation of the surface radiation fluxes.« less

Insights on TTL Dehydration Mechanisms from Microphysical Modelling of Aircraft Observations

NASA Technical Reports Server (NTRS)

Ueyama, R.; Pfister, L.; Jensen, E.

2014-01-01

The Tropical Tropopause Layer (TTL), a transition layer between the upper troposphere and lower stratosphere in the tropics, serves as the entryway of various trace gases into the stratosphere. Of particular interest is the transport of water vapor through the TTL, as WV is an important greenhouse gas and also plays a significant role in stratospheric chemistry by affecting polar stratospheric cloud formation and the ozone budget. While the dominant control of stratospheric water vapor by tropical cold point temperatures via the "freeze-drying" process is generally well understood, the details of the TTL dehydration mechanisms, including the relative roles of deep convection, atmospheric waves and cloud microphysical processes, remain an active area of research. The dynamical and microphysical processes that influence TTL water vapor concentrations are investigated in simulations of cloud formation and dehydration along air parcel trajectories. We first confirm the validity of our Lagrangian models in a case study involving measurements from the Airborne Tropical TRopopause EXperiment (ATTREX) flights over the central and eastern tropical Pacific in Oct-Nov 2011 and Jan-Feb 2013. ERA-Interim winds and seasonal mean heating rates from Yang et al. (2010) are used to advance parcels back in time from the flight tracks, and time-varying vertical profiles of water vapor along the diabatic trajectories are calculated in a one-dimensional cloud model as in Jensen and Pfister (2004) but with more reliable temperature field, wave and convection schemes. The simulated water vapor profiles demonstrate a significant improvement over estimates based on the Lagrangian Dry Point, agreeing well with aircraft observations when the effects of cloud microphysics, subgrid-scale gravity waves and convection are included. Following this approach, we examine the dynamical and microphysical control of TTL water vapor in the 30ºS-30ºN latitudinal belt and elucidate the dominant processes in the winter and summer seasons. Implications of the TTL dehydration processes for the regulation of global stratospheric humidity will be discussed.

Understanding the Relationships Between Lightning, Cloud Microphysics, and Airborne Radar-derived Storm Structure During Hurricane Karl (2010)

NASA Technical Reports Server (NTRS)

Reinhart, Brad; Fuelberg, Henry; Blakeslee, Richard; Mach, Douglas; Heymsfield, Andrew; Bansemer, Aaron; Durden, Stephen L.; Tanelli, Simone; Heymsfield, Gerald; Lambrigtsen, Bjorn

2013-01-01

This study explores relationships between lightning, cloud microphysics, and tropical cyclone (TC) storm structure in Hurricane Karl (16 September 2010) using data collected by the NASA DC-8 and Global Hawk (GH) aircraft during NASA's Genesis and Rapid Intensification Processes (GRIP) experiment. The research capitalizes on the unique opportunity provided by GRIP to synthesize multiple datasets from two aircraft and analyze the microphysical and kinematic properties of an electrified TC. Five coordinated flight legs through Karl by the DC-8 and GH are investigated, focusing on the inner-core region (within 50km of the storm center) where the lightning was concentrated and the aircraft were well coordinated. GRIP datasets are used to compare properties of electrified and nonelectrified inner-core regions that are related to the noninductive charging mechanism, which is widely accepted to explain the observed electric fields within thunderstorms. Three common characteristics of Karl's electrified regions are identified: 1) strong updrafts of 10-20ms21, 2) deep mixed-phase layers indicated by reflectivities.30 dBZ extending several kilometers above the freezing level, and 3) microphysical environments consisting of graupel, very small ice particles, and the inferred presence of supercooled water. These characteristics describe an environment favorable for in situ noninductive charging and, hence, TC electrification. The electrified regions in Karl's inner core are attributable to a microphysical environment that was conducive to electrification because of occasional, strong convective updrafts in the eyewall.

MODIS Microphysical Regimes for Examining Apparent Aerosol Effects on Clouds and Precipitation

NASA Astrophysics Data System (ADS)

Oreopoulos, L.; Cho, N.; Lee, D.; Kato, S.; Lebsock, M. D.; Yuan, T.; Huffman, G. J.

2014-12-01

We use a 10-year record of MODIS Terra and Aqua Level-3 joint histograms of cloud optical thickness (COT) and cloud effective radius (CER) to derive so-called cloud microphysical regimes by means of clustering analysis. The regimes reveal the dominant modes of COT and CER co-variations around the globe for both liquid and ice phases. The clustering analysis is capable of separating regimes so that each is dominated by one of the two water phases and can be associated with previously derived "dynamical" regimes. The microphysical regimes serve as an appropriate basis to study possible effects of aerosols on cloud microphysical changes and precipitation. To this end, we employ MODIS aerosol loading measurements either in terms of aerosol index or aerosol optical depth and spatiotemporally matched precipitation (from either GPCP, TRMM or CloudSat) to examine intra-regime variability, regime transitions from morning (Terra) to afternoon (Aqua), and regime precipitation characteristics for locally low, average, and high aerosol loadings. Breakdowns by ocean/land and geographical zone (e.g., tropics vs. midlatitudes) are essential for physical interpretation of the results. The analysis conducted so far reveals notable differences in apparent characteristics of low- and high-cloud dominated microphysical regimes when in different aerosol environments. The presentation will attempt to examine whether the picture painted by our work is consistent with prevailing expectations, rooted to either modeling or prior observational studies, on how clouds and precipitation respond to distinct aerosol environments.

Investigation of Microphysical Parameters within Winter and Summer Type Precipitation Events over Mountainous [Complex] Terrain

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stalker, James R.; Bossert, James E.

1997-12-31

In this study we investigate complex terrain effects on precipitation with RAMS for both in winter and summer cases from a microphysical perspective. We consider a two dimensional east-west topographic cross section in New Mexico representative of the Jemez mountains on the west and the Sangre de Cristo mountains on the east. Located between these two ranges is the Rio Grande Valley. In these two dimensional experiments, variations in DSDs are considered to simulate total precipitation that closely duplicate observed precipitation.

Observations of Stratiform Lightning Flashes and Their Microphysical and Kinematic Environments

NASA Technical Reports Server (NTRS)

Lang, Timothy J.; Williams, Earle

2016-01-01

During the Midlatitude Continental Convective Clouds Experiment (MC3E), combined observations of clouds and precipitation were made from airborne and ground-based in situ and remote sensing platforms. These observations were coordinated for multiple mesoscale convective systems (MCSs) that passed over the MC3E domain in northern Oklahoma. Notably, during a storm on 20 May 2011 in situ and remote sensing airborne observations were made near the times and locations of stratiform positive cloud-to-ground (+CG) lightning flashes. These +CGs resulted from extremely large stratiform lightning flashes that were hundreds of km in length and lasted several seconds. This dataset provides an unprecedented look at kinematic and microphysical environments in the vicinity of large, powerful, and long-lived stratiform lightning flashes. We will use this dataset to understand the influence of low liquid water contents (LWCs) in the electrical charging of MCS stratiform regions.

Observations of Stratiform Lightning Flashes and Their Microphysical and Kinematic Environments

NASA Technical Reports Server (NTRS)

Lang, Timothy J.; Williams, Earle

2017-01-01

During the Midlatitude Continental Convective Clouds Experiment (MC3E), combined observations of clouds and precipitation were made from airborne and ground-based in situ and remote sensing platforms. These observations were coordinated for multiple mesoscale convective systems (MCSs) that passed over the MC3E domain in northern Oklahoma. Notably, during a storm on 20 May 2011 in situ and remote sensing airborne observations were made near the times and locations of stratiform positive cloud-to-ground (+CG) lightning flashes. These +CGs resulted from extremely large stratiform lightning flashes that were hundreds of km in length and lasted several seconds. This dataset provides an unprecedented look at kinematic and microphysical environments in the vicinity of large, powerful, and long-lived stratiform lightning flashes. We will use this dataset to understand the influence of low liquid water contents (LWCs) in the electrical charging of MCS stratiform regions.

Derivation of Aerosol Profiles for MC3E Convection Studies and Use in Simulations of the 20 May Squall Line Case

NASA Technical Reports Server (NTRS)

Fridlind, Ann M.; Li, Xiaowen; Wu, Di; van Lier-Walqui, Marcus; Ackerman, Andrew S.; Tao, Wei-Kuo; McFarquhar, Greg M.; Wu, Wei; Dong, Xiquan; Wang, Jingyu;

Collaborative Research: Reducing tropical precipitation biases in CESM — Tests of unified parameterizations with ARM observations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Larson, Vincent; Gettelman, Andrew; Morrison, Hugh

In state-of-the-art climate models, each cloud type is treated using its own separate cloud parameterization and its own separate microphysics parameterization. This use of separate schemes for separate cloud regimes is undesirable because it is theoretically unfounded, it hampers interpretation of results, and it leads to the temptation to overtune parameters. In this grant, we are creating a climate model that contains a unified cloud parameterization and a unified microphysics parameterization. This model will be used to address the problems of excessive frequency of drizzle in climate models and excessively early onset of deep convection in the Tropics over land.more » The resulting model will be compared with ARM observations.« less

Observations of marine stratocumulus clouds during FIRE

NASA Technical Reports Server (NTRS)

Albrecht, Bruce A.; Randall, David A.; Nicholls, Stephen

1988-01-01

The First International Satellite Cloud Climatology Project Regional Experiment (FIRE) to study extensive fields of stratocumulus clouds off the coast of California is presented. Measurements on the regional and detailed local scales were taken, allowing for a wide interpretation of the mean, turbulent, microphysical, radiative, and chemical characteristics of stratocumulus. Multiple aircraft and ground-based remote-sensing systems were used to study the time evolution of the boundary layer structure over a three-week period, and probes from tethered balloons were used to measure turbulence and to collect cloud-microphysical and cloud-radiative data. The observations provide a base for studying the generation maintenance and dissipation of stratocumulus clouds, and could aid in developing numerical models and improved methods for retrieving cloud properties by satellite.

Simulations of precipitation using the Community Earth System Model (CESM): Sensitivity to microphysics time step

NASA Astrophysics Data System (ADS)

Murthi, A.; Menon, S.; Sednev, I.

2011-12-01

An inherent difficulty in the ability of global climate models to accurately simulate precipitation lies in the use of a large time step, Δt (usually 30 minutes), to solve the governing equations. Since microphysical processes are characterized by small time scales compared to Δt, finite difference approximations used to advance microphysics equations suffer from numerical instability and large time truncation errors. With this in mind, the sensitivity of precipitation simulated by the atmospheric component of CESM, namely the Community Atmosphere Model (CAM 5.1), to the microphysics time step (τ) is investigated. Model integrations are carried out for a period of five years with a spin up time of about six months for a horizontal resolution of 2.5 × 1.9 degrees and 30 levels in the vertical, with Δt = 1800 s. The control simulation with τ = 900 s is compared with one using τ = 300 s for accumulated precipitation and radi- ation budgets at the surface and top of the atmosphere (TOA), while keeping Δt fixed. Our choice of τ = 300 s is motivated by previous work on warm rain processes wherein it was shown that a value of τ around 300 s was necessary, but not sufficient, to ensure positive definiteness and numerical stability of the explicit time integration scheme used to integrate the microphysical equations. However, since the entire suite of microphysical processes are represented in our case, we suspect that this might impose additional restrictions on τ. The τ = 300 s case produces differences in large-scale accumulated rainfall from the τ = 900 s case by as large as 200 mm, over certain regions of the globe. The spatial patterns of total accumulated precipitation using τ = 300 s are in closer agreement with satellite observed precipitation, when compared to the τ = 900 s case. Differences are also seen in the radiation budget with the τ = 300 (900) s cases producing surpluses that range between 1-3 W/m2 at both the TOA and surface in the global means. In order to gain some insight into the possible causes of the observed differences, future work would involve performing additional sensitivity tests using the single column model version of CAM 5.1 to gauge the effect of τ on calculations of source terms and mixing ratios used to calculate precipitation in the budget equations.

Microphysics in West African squall line with an Xband polarimetric radar and an Hydrometeor Identification Scheme: comparison with in situ measurements

NASA Astrophysics Data System (ADS)

Cazenave, F.; Gosset, M.; Kacou, M.; Alcoba, M.; Fontaine, E.

2015-12-01

A better knowledge on the microphysics of tropical continental convective systems is needed in order to improve quantitative precipitation measurements in the Tropics. Satellite passive microwave estimation of tropical rainfall could be improved with a better parameterization of the icy hydrometeors in the Bayesian RAIN estimation algorithm (BRAIN, Viltard et al., 2006) used over continental tropics. To address this important issue specific campaigns that combine aircraft based in situ microphysics probing and polarimetric radar have been organized as part of the CNES/ISRO satellite mission Megha-Tropiques. The first microphysics validation campaign was set up in Niamey in August 2010. The field deployment included the AMMA-CATH 56 rain gages, 3 disdrometers, 2 meteorological radars including the C-band MIT and the Xport X-band dual polarisation radar, and a 4 weeks campaign with the instrumented Falcon 20 from the french operator for environmental research aircrafts equipped with several microphysics probes and the 94Ghz cloud radar RASTA. The objective is to combine scales and methods to converge towards a parameterization of the ice size, mass and density laws inside continental Mesoscale Convective System (MCS). The Particle IDentification algorithm (PID) developed by the Colorado State University (CSU) adapted to the band X by B. Dolan (Dolan et al. 2009) is used to classify seven kind of particles: drizzle or light rain, moderate to heavy rain, wet and dry graupel, wet and dry aggregates and ice crystals. On a limited number of systems, the airborne microphysics sensors provide a detailed in situ reference on the Particle Size Distribution (PSD) that can be compared with the radar PID in the radar pixels located along the flight trajectory. An original approach has been developed for the radar - in situ comparison: it consists in simulating synthetic radar variables from the microphysics probe information and compare the 2 data sets in a common 'radar space'. The consistency between the 2 types of observation is good considering the differences in sampling. The time evolution of the hydrometeor types and their relative proportion in the convective and stratiform regions are analyzed for the 13rd August 2010 MCS.

TRMM Common Microphysics Products: A Tool for Evaluating Spaceborne Precipitation Retrieval Algorithms

NASA Technical Reports Server (NTRS)

Kingsmill, David E.; Yuter, Sandra E.; Hobbs, Peter V.; Rangno, Arthur L.; Heymsfield, Andrew J.; Stith, Jeffrey L.; Bansemer, Aaron; Haggerty, Julie A.; Korolev, Alexei V.

2004-01-01

A customized product for analysis of microphysics data collected from aircraft during field campaigns in support of the TRMM program is described. These Common Microphysics Products (CMP's) are designed to aid in evaluation of TRMM spaceborne precipitation retrieval algorithms. Information needed for this purpose (e.g., particle size spectra and habit, liquid and ice water content) was derived using a common processing strategy on the wide variety of microphysical instruments and raw native data formats employed in the field campaigns. The CMP's are organized into an ASCII structure to allow easy access to the data for those less familiar with and without the tools to accomplish microphysical data processing. Detailed examples of the CMP show its potential and some of its limitations. This approach may be a first step toward developing a generalized microphysics format and an associated community-oriented, non-proprietary software package for microphysics data processing, initiatives that would likely broaden community access to and use of microphysics datasets.

Structural and parameteric uncertainty quantification in cloud microphysics parameterization schemes

NASA Astrophysics Data System (ADS)

van Lier-Walqui, M.; Morrison, H.; Kumjian, M. R.; Prat, O. P.; Martinkus, C.

2017-12-01

Atmospheric model parameterization schemes employ approximations to represent the effects of unresolved processes. These approximations are a source of error in forecasts, caused in part by considerable uncertainty about the optimal value of parameters within each scheme -- parameteric uncertainty. Furthermore, there is uncertainty regarding the best choice of the overarching structure of the parameterization scheme -- structrual uncertainty. Parameter estimation can constrain the first, but may struggle with the second because structural choices are typically discrete. We address this problem in the context of cloud microphysics parameterization schemes by creating a flexible framework wherein structural and parametric uncertainties can be simultaneously constrained. Our scheme makes no assuptions about drop size distribution shape or the functional form of parametrized process rate terms. Instead, these uncertainties are constrained by observations using a Markov Chain Monte Carlo sampler within a Bayesian inference framework. Our scheme, the Bayesian Observationally-constrained Statistical-physical Scheme (BOSS), has flexibility to predict various sets of prognostic drop size distribution moments as well as varying complexity of process rate formulations. We compare idealized probabilistic forecasts from versions of BOSS with varying levels of structural complexity. This work has applications in ensemble forecasts with model physics uncertainty, data assimilation, and cloud microphysics process studies.

Depolarization Lidar Determination Of Cloud-Base Microphysical Properties

NASA Astrophysics Data System (ADS)

Donovan, D. P.; Klein Baltink, H.; Henzing, J. S.; de Roode, S.; Siebesma, A. P.

2016-06-01

The links between multiple-scattering induced depolarization and cloud microphysical properties (e.g. cloud particle number density, effective radius, water content) have long been recognised. Previous efforts to use depolarization information in a quantitative manner to retrieve cloud microphysical cloud properties have also been undertaken but with limited scope and, arguably, success. In this work we present a retrieval procedure applicable to liquid stratus clouds with (quasi-)linear LWC profiles and (quasi-)constant number density profiles in the cloud-base region. This set of assumptions allows us to employ a fast and robust inversion procedure based on a lookup-table approach applied to extensive lidar Monte-Carlo multiple-scattering calculations. An example validation case is presented where the results of the inversion procedure are compared with simultaneous cloud radar observations. In non-drizzling conditions it was found, in general, that the lidar- only inversion results can be used to predict the radar reflectivity within the radar calibration uncertainty (2-3 dBZ). Results of a comparison between ground-based aerosol number concentration and lidar-derived cloud base number considerations are also presented. The observed relationship between the two quantities is seen to be consistent with the results of previous studies based on aircraft-based in situ measurements.

Final Report fir DE-SC0005507 (A1618): The Development of an Improved Cloud Microphysical Product for Model and Remote Sensing Evaluation using RACORO Observations

DOE Office of Scientific and Technical Information (OSTI.GOV)

McFarquhar, Greg M.

2012-09-21

We proposed to analyze data collected during the Routine Aerial Facilities (AAF) Clouds with Low Optical Water Depths (CLOWD) Optical Radiative Observations (RACORO) in order to develop an integrated product of cloud microphysical properties (number concentration of drops in different size bins, total liquid drop concentration integrated over all bin sizes, liquid water content LWC, extinction of liquid clouds, effective radius of water drops, and radar reflectivity factor) that could be used to evaluate large-eddy simulations (LES), general circulation models (GCMs) and ground-based remote sensing retrievals, and to develop cloud parameterizations with the end goal of improving the modeling ofmore » cloud processes and properties and their impact on atmospheric radiation. We have completed the development of this microphysical database. We investigated the differences in the size distributions measured by the Cloud and Aerosol Spectrometer (CAS) and the Forward Scattering Probe (FSSP), between the one dimensional cloud imaging probe (1DC) and the two-dimensional cloud imaging probe (2DC), and between the bulk LWCs measured by the Gerber probe against those derived from the size resolved probes.« less

A study of the 3D radiative transfer effect in cloudy atmospheres

NASA Astrophysics Data System (ADS)

Okata, M.; Teruyuki, N.; Suzuki, K.

2015-12-01

Evaluation of the effect of clouds in the atmosphere is a significant problem in the Earth's radiation budget study with their large uncertainties of microphysics and the optical properties. In this situation, we still need more investigations of 3D cloud radiative transer problems using not only models but also satellite observational data.For this purpose, we have developed a 3D-Monte-Carlo radiative transfer code that is implemented with various functions compatible with the OpenCLASTR R-Star radiation code for radiance and flux computation, i.e. forward and backward tracing routines, non-linear k-distribution parameterization (Sekiguchi and Nakajima, 2008) for broad band solar flux calculation, and DM-method for flux and TMS-method for upward radiance (Nakajima and Tnaka 1998). We also developed a Minimum cloud Information Deviation Profiling Method (MIDPM) as a method for a construction of 3D cloud field with MODIS/AQUA and CPR/CloudSat data. We then selected a best-matched radar reflectivity factor profile from the library for each of off-nadir pixels of MODIS where CPR profile is not available, by minimizing the deviation between library MODIS parameters and those at the pixel. In this study, we have used three cloud microphysical parameters as key parameters for the MIDPM, i.e. effective particle radius, cloud optical thickness and top of cloud temperature, and estimated 3D cloud radiation budget. We examined the discrepancies between satellite observed and mode-simulated radiances and three cloud microphysical parameter's pattern for studying the effects of cloud optical and microphysical properties on the radiation budget of the cloud-laden atmospheres.

Dynamic downscaling over western Himalayas: Impact of cloud microphysics schemes

NASA Astrophysics Data System (ADS)

Tiwari, Sarita; Kar, Sarat C.; Bhatla, R.

2018-03-01

Due to lack of observation data in the region of inhomogeneous terrain of the Himalayas, detailed climate of Himalayas is still unknown. Global reanalysis data are too coarse to represent the hydroclimate over the region with sharp orography gradient in the western Himalayas. In the present study, dynamic downscaling of the European Centre for Medium-Range Weather Forecast (ECMWF) Reanalysis-Interim (ERA-I) dataset over the western Himalayas using high-resolution Weather Research and Forecast (WRF) model has been carried out. Sensitivity studies have also been carried out using convection and microphysics parameterization schemes. The WRF model simulations have been compared against ERA-I and available station observations. Analysis of the results suggests that the WRF model has simulated the hydroclimate of the region well. It is found that in the simulations that the impact of convection scheme is more during summer months than in winter. Examination of simulated results using various microphysics schemes reveal that the WRF single-moment class-6 (WSM6) scheme simulates more precipitation on the upwind region of the high mountain than that in the Morrison and Thompson schemes during the winter period. Vertical distribution of various hydrometeors shows that there are large differences in mixing ratios of ice, snow and graupel in the simulations with different microphysics schemes. The ice mixing ratio in Morrison scheme is more than WSM6 above 400 hPa. The Thompson scheme favors formation of more snow than WSM6 or Morrison schemes while the Morrison scheme has more graupel formation than other schemes.

Intercomparison and Evaluation of Global Aerosol Microphysical Properties Among Aerocom Models of a Range of Complexity

NASA Technical Reports Server (NTRS)

Mann, G. W.; Carslaw, K. S.; Reddington, C. L.; Pringle, K. J.; Schulz, M.; Asmi, A.; Spracklen, D. V.; Ridley, D. A.; Woodhouse, M. T.; Lee, L. A.;

Microphysical characterization of winter cloud systems during a research flight campaign

NASA Astrophysics Data System (ADS)

Fernández-González, Sergio; Sánchez, José Luis; Valero, Francisco; Gascón, Estíbaliz; Merino, Andrés; Hermida, Lucía; López, Laura; Marcos, José Luis; García-Ortega, Eduardo

2015-04-01

The lack of accuracy in the knowledge of cloud microphysics leads to aviation risks, which have caused numerous crashes, mainly owing to aircraft icing (e.g., an EMB-120 crashed in Detroit, Michigan in 1997, and an ATR-72 crashed near Roselawn, Indiana in 1994). Further, this lack is a source of uncertainty in numerical weather forecasting models, since commonly used parameterizations often overestimate ice water content and underestimate supercooled liquid water. This makes the collection of data on cloud microphysical characteristics very useful toward improving the forecasting of icing conditions. Ten research flights were conducted during the winters of 2011/12 and 2012/13. Their goal was to determine dominant microphysical conditions of winter cloud systems traversing the Guadarrama Mountains in the central Iberian Peninsula. The aircraft was a C-212-200, equipped with a Cloud, Aerosol, and Precipitation Spectrometer (CAPS) under the left wing. Data of temperature and Liquid Water Content (LWC), registered by the CAPS probe, were used in the study. Furthermore, we thoroughly analyzed images taken by a Cloud Imaging Probe Grayscale (CIP-GS), capable of measuring hydrometeors between 25 and 1,550 µm in size, and representing them in a 2D image. The various types of hydrometeors observed during these flights are described, along with microphysical processes inferred from the CIP-GS images. ACKNOWLEDGEMENTS S. Fernández-González acknowledges grant support from the FPU program (AP 2010-2093). This study was also supported by grants from GRANIMETRO (CGL2010-15930) and MICROMETEO (IPT-310000-2010-22). The authors thank INTA for the research flights.

Evidence for Tropopause Layer Moistening by Convection During CRYSTAL-FACE

NASA Technical Reports Server (NTRS)

Ackerman, A.; Fridlind, A.; Jensen, E.; Miloshevich, L.; Heymsfield, G.; McGill, M.

2003-01-01

Measurements and analysis of the impact of deep convection on tropopause layer moisture are easily confounded by difficulties making precise observations with sufficient spatial coverage before and after convective events and difficulties distinguishing between changes due to local convection versus large-scale advection. The interactions between cloud microphysics and dynamics in the convective transport of moisture into the tropopause layer also result in a sufficiently complex and poorly characterized system to allow for considerable freedom in theoretical models of stratosphere-troposphere exchange. In this work we perform detailed large-eddy simulations with an explicit cloud microphysics model to study the impact of deep convection on tropopause layer moisture profiles observed over southern Florida during CRYSTALFACE. For four days during the campaign (July 11, 16, 28, and 29) we initialize a 100-km square domain with temperature and moisture profiles measured prior to convection at the PARSL ground site, and initiate convection with a warm bubble that produces an anvil at peak elevations in agreement with lidar and radar observations on that day. Comparing the moisture field after the anvils decay with the initial state, we find that convection predominantly moistens the tropopause layer (as defined by minimum temperature and minimum potential temperature lapse rate), although some drying is also predicted in localized layers. We will also present results of sensitivity tests designed to separate the roles of cloud microphysics and dynamics.

A General Uncertainty Quantification Methodology for Cloud Microphysical Property Retrievals

NASA Astrophysics Data System (ADS)

Tang, Q.; Xie, S.; Chen, X.; Zhao, C.

2014-12-01

The US Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) program provides long-term (~20 years) ground-based cloud remote sensing observations. However, there are large uncertainties in the retrieval products of cloud microphysical properties based on the active and/or passive remote-sensing measurements. To address this uncertainty issue, a DOE Atmospheric System Research scientific focus study, Quantification of Uncertainties in Cloud Retrievals (QUICR), has been formed. In addition to an overview of recent progress of QUICR, we will demonstrate the capacity of an observation-based general uncertainty quantification (UQ) methodology via the ARM Climate Research Facility baseline cloud microphysical properties (MICROBASE) product. This UQ method utilizes the Karhunen-Loéve expansion (KLE) and Central Limit Theorems (CLT) to quantify the retrieval uncertainties from observations and algorithm parameters. The input perturbations are imposed on major modes to take into account the cross correlations between input data, which greatly reduces the dimension of random variables (up to a factor of 50) and quantifies vertically resolved full probability distribution functions of retrieved quantities. Moreover, this KLE/CLT approach has the capability of attributing the uncertainties in the retrieval output to individual uncertainty source and thus sheds light on improving the retrieval algorithm and observations. We will present the results of a case study for the ice water content at the Southern Great Plains during an intensive observing period on March 9, 2000. This work is performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

A tandem approach for collocated measurements of microphysical and radiative cirrus properties

NASA Astrophysics Data System (ADS)

Klingebiel, Marcus; Ehrlich, André; Finger, Fanny; Röschenthaler, Timo; Jakirlić, Suad; Voigt, Matthias; Müller, Stefan; Maser, Rolf; Wendisch, Manfred; Hoor, Peter; Spichtinger, Peter; Borrmann, Stephan

2017-09-01

Microphysical and radiation measurements were collected with the novel AIRcraft TOwed Sensor Shuttle (AIRTOSS) - Learjet tandem platform. The platform is a combination of an instrumented Learjet 35A research aircraft and an aerodynamic bird, which is detached from and retracted back to the aircraft during flight via a steel wire with a length of 4000 m. Both platforms are equipped with radiative, cloud microphysical, trace gas, and meteorological instruments. The purpose of the development of this tandem set-up is to study the inhomogeneity of cirrus as well as other stratiform clouds. Sophisticated numerical flow simulations were conducted in order to optimally integrate an axially asymmetric Cloud Combination Probe (CCP) inside AIRTOSS. The tandem platform was applied during measurements at altitudes up to 36 000 ft (10 970 m) in the framework of the AIRTOSS - Inhomogeneous Cirrus Experiment (AIRTOSS-ICE). Ten flights were performed above the North Sea and Baltic Sea to probe frontal and in situ formed cirrus, as well as anvil outflow cirrus. For one flight, cirrus microphysical and radiative properties displayed significant inhomogeneities resolved by both measurement platforms. The CCP data show that the maximum of the observed particle number size distributions shifts with decreasing altitude from 30 to 300 µm, which is typical for frontal, midlatitude cirrus. Theoretical considerations imply that cloud particle aggregation inside the studied cirrus is very unlikely. Consequently, diffusional growth was identified to be the dominant microphysical growth process. Measurements of solar downward and upward irradiances at 670 nm wavelength were conducted above, below, and in the cirrus on both the Learjet and AIRTOSS. The observed variability of the downward irradiance below the cirrus reflects the horizontal heterogeneity of the observed thin cirrus. Vertically resolved solar heating rates were derived by either using single-platform measurements at different altitudes or by making use of the collocated irradiance measurements at different altitudes of the tandem platform. Due to unavoidable biases of the measurements between the individual flight legs, the single-platform approach failed to provide a realistic solar heating rate profile, while the uncertainties of the tandem approach are reduced. Here, the solar heating rates range up to 6 K day-1 at top of the cirrus layer.

MODIS Cloud Products Derived from Terra and Aqua During CRYSTAL-FACE

NASA Technical Reports Server (NTRS)

King, Michael D.; Platnick, S.; Riedi, J. C.; Ackerman, S. A.; Menzel, W. P.

2003-01-01

The Moderate Resolution Imaging Spectroradiometer (MODIS), developed as part of the Earth Observing System (EOS) and launched on Terra in December 1999 and Aqua in May 2002, is designed to meet the scientific needs for satellite remote sensing of clouds, aerosols, water vapor, and land and ocean surface properties. During the CRYSTAL-FACE experiment, numerous aircraft coordinated both in situ and remote sensing observations with the Terra and Aqua spacecraft. In this paper we will emphasize the optical, microphysical, and physical properties of both liquid water and ice clouds obtained from an analysis of the satellite observations over Florida and the Gulf of Mexico during July 2002. We will present the frequency distribution of liquid water and ice cloud microphysical properties throughout the region, separating the results over land and ocean. Probability distributions of effective radius and cloud optical thickness will also be shown.

Chemistry and Microphysics of Lower Stratospheric Aerosols Determined by Satellite Remote Sensing

NASA Astrophysics Data System (ADS)

Zasetsky, A. Y.; Khalizov, A.; Sloan, J.

2003-12-01

Observations of broadband Infrared satellites such as ILAS-II (Ministry of the Environment, Japan, launched 14 December 2002) and SciSat-1 (Canadian Space Agency, launched 12 August 2003) can provide details of the chemical composition and particle size of atmospheric aerosols by direct inversion without recourse to models. During the past decade, we have developed mathematical methods to achieve this inversion by working with FTIR observations of model atmospheric aerosols in cryogenic flowtubes. More recently, we have converted these to operational algorithms for use in the above missions. In this presentation, we will briefly outline these procedures and illustrate their capabilities using laboratory data. These laboratory results show that the chemical compositions, phases and sizes of ensembles of particles can be obtained simultaneously using these procedures. We will also report chemical and microphysical properties of lower stratospheric clouds and aerosols derived by applying these procedures to observations from space.

Derivation of aerosol profiles for MC3E convection studies and use in simulations of the 20 May squall line case

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fridlind, Ann M.; Li, Xiaowen; Wu, Di

Advancing understanding of deep convection microphysics via mesoscale modeling studies of well-observed case studies requires observation-based aerosol inputs. Here, we derive hygroscopic aerosol size distribution input profiles from ground-based and airborne measurements for six convection case studies observed during the Midlatitude Continental Convective Cloud Experiment (MC3E) over Oklahoma. We demonstrate use of an input profile in simulations of the only well-observed case study that produced extensive stratiform outflow on 20 May 2011. At well-sampled elevations between –11 and –23 °C over widespread stratiform rain, ice crystal number concentrations are consistently dominated by a single mode near ~400 µm in randomly oriented maximummore » dimension ( D max). The ice mass at –23 °C is primarily in a closely collocated mode, whereas a mass mode near D max ~1000 µm becomes dominant with decreasing elevation to the –11 °C level, consistent with possible aggregation during sedimentation. However, simulations with and without observation-based aerosol inputs systematically overpredict mass peak D max by a factor of 3–5 and underpredict ice number concentration by a factor of 4–10. Previously reported simulations with both two-moment and size-resolved microphysics have shown biases of a similar nature. Furthermore, the observed ice properties are notably similar to those reported from recent tropical measurements. Based on several lines of evidence, we speculate that updraft microphysical pathways determining outflow properties in the 20 May case are similar to a tropical regime, likely associated with warm-temperature ice multiplication that is not well understood or well represented in models.« less

Derivation of aerosol profiles for MC3E convection studies and use in simulations of the 20 May squall line case

NASA Astrophysics Data System (ADS)

Fridlind, Ann M.; Li, Xiaowen; Wu, Di; van Lier-Walqui, Marcus; Ackerman, Andrew S.; Tao, Wei-Kuo; McFarquhar, Greg M.; Wu, Wei; Dong, Xiquan; Wang, Jingyu; Ryzhkov, Alexander; Zhang, Pengfei; Poellot, Michael R.; Neumann, Andrea; Tomlinson, Jason M.

2017-05-01

Advancing understanding of deep convection microphysics via mesoscale modeling studies of well-observed case studies requires observation-based aerosol inputs. Here, we derive hygroscopic aerosol size distribution input profiles from ground-based and airborne measurements for six convection case studies observed during the Midlatitude Continental Convective Cloud Experiment (MC3E) over Oklahoma. We demonstrate use of an input profile in simulations of the only well-observed case study that produced extensive stratiform outflow on 20 May 2011. At well-sampled elevations between -11 and -23 °C over widespread stratiform rain, ice crystal number concentrations are consistently dominated by a single mode near ˜ 400 µm in randomly oriented maximum dimension (Dmax). The ice mass at -23 °C is primarily in a closely collocated mode, whereas a mass mode near Dmax ˜ 1000 µm becomes dominant with decreasing elevation to the -11 °C level, consistent with possible aggregation during sedimentation. However, simulations with and without observation-based aerosol inputs systematically overpredict mass peak Dmax by a factor of 3-5 and underpredict ice number concentration by a factor of 4-10. Previously reported simulations with both two-moment and size-resolved microphysics have shown biases of a similar nature. The observed ice properties are notably similar to those reported from recent tropical measurements. Based on several lines of evidence, we speculate that updraft microphysical pathways determining outflow properties in the 20 May case are similar to a tropical regime, likely associated with warm-temperature ice multiplication that is not well understood or well represented in models.

Derivation of aerosol profiles for MC3E convection studies and use in simulations of the 20 May squall line case

DOE PAGES

Fridlind, Ann M.; Li, Xiaowen; Wu, Di; ...

2017-05-15

Advancing understanding of deep convection microphysics via mesoscale modeling studies of well-observed case studies requires observation-based aerosol inputs. Here, we derive hygroscopic aerosol size distribution input profiles from ground-based and airborne measurements for six convection case studies observed during the Midlatitude Continental Convective Cloud Experiment (MC3E) over Oklahoma. We demonstrate use of an input profile in simulations of the only well-observed case study that produced extensive stratiform outflow on 20 May 2011. At well-sampled elevations between –11 and –23 °C over widespread stratiform rain, ice crystal number concentrations are consistently dominated by a single mode near ~400 µm in randomly oriented maximummore » dimension ( D max). The ice mass at –23 °C is primarily in a closely collocated mode, whereas a mass mode near D max ~1000 µm becomes dominant with decreasing elevation to the –11 °C level, consistent with possible aggregation during sedimentation. However, simulations with and without observation-based aerosol inputs systematically overpredict mass peak D max by a factor of 3–5 and underpredict ice number concentration by a factor of 4–10. Previously reported simulations with both two-moment and size-resolved microphysics have shown biases of a similar nature. Furthermore, the observed ice properties are notably similar to those reported from recent tropical measurements. Based on several lines of evidence, we speculate that updraft microphysical pathways determining outflow properties in the 20 May case are similar to a tropical regime, likely associated with warm-temperature ice multiplication that is not well understood or well represented in models.« less

Derivation of Aerosol Profiles for MC3E Convection Studies and Use in Simulations of the 20 May Squall Line Case

NASA Technical Reports Server (NTRS)

Fridlind, Ann M.; Xiaowen, Li; Wu, Di; Van Lier-Walqui, Marcus; Ackerman, Andrew S.; Tao, Wei-Kuo; McFarquhar, Greg M.; Wu, Wei; Dong, Xiquan; Wang, Jingyu;

Schneefernerhaus as a mountain research station for clouds and turbulence - Part 2: Cloud microphysics and fine-scale turbulence

NASA Astrophysics Data System (ADS)

Siebert, H.; Shaw, R. A.; Ditas, J.; Schmeissner, T.; Malinowski, S. P.; Bodenschatz, E.; Xu, H.

2015-01-01

Mountain research stations are advantageous not only for long-term sampling of cloud properties, but also for measurements that prohibitively difficult to perform on airborne platforms due to the true air speed or adverse factors such as weight and complexity of the equipment necessary. Some cloud-turbulence measurements, especially Lagrangian in nature, fall into this category. We report results from simultaneous, high-resolution and collocated measurements of cloud microphysical and turbulence properties during several warm cloud events at the Umweltforschungsstation Schneefernerhaus (UFS) on Zugspitze in the German Alps. The data gathered was found to be representative of observations made with similar instrumentation in free clouds. The turbulence observed, shared all features known for high Reynolds number flows: it exhibited approximately Gaussian fluctuations for all three velocity components, a clearly defined inertial subrange following Kolmogorov scaling (power spectrum, and second and third order Eulerian structure functions), and highly intermittent velocity gradients, as well as approximately lognormal kinetic energy dissipation rates. The clouds were observed to have liquid water contents of order 1 g m-3, and size distributions typical of continental clouds, sometimes exhibiting long positive tails indicative of large drop production through turbulent mixing or coalescence growth. Dimensionless parameters relevant to cloud-turbulence interactions, the Stokes number and settling parameter, are in the range typically observed in atmospheric clouds. Observed fluctuations in droplet number concentration and diameter suggest a preference for inhomogeneous mixing. Finally, enhanced variance in liquid water content fluctuations is observed at high frequencies, and the scale break occurs at a value consistent with the independently estimated phase relaxation time from microphysical measurements.

High-resolution measurement of cloud microphysics and turbulence at a mountaintop station

NASA Astrophysics Data System (ADS)

Siebert, H.; Shaw, R. A.; Ditas, J.; Schmeissner, T.; Malinowski, S. P.; Bodenschatz, E.; Xu, H.

2015-08-01

Mountain research stations are advantageous not only for long-term sampling of cloud properties but also for measurements that are prohibitively difficult to perform on airborne platforms due to the large true air speed or adverse factors such as weight and complexity of the equipment necessary. Some cloud-turbulence measurements, especially Lagrangian in nature, fall into this category. We report results from simultaneous, high-resolution and collocated measurements of cloud microphysical and turbulence properties during several warm cloud events at the Umweltforschungsstation Schneefernerhaus (UFS) on Zugspitze in the German Alps. The data gathered were found to be representative of observations made with similar instrumentation in free clouds. The observed turbulence shared all features known for high-Reynolds-number flows: it exhibited approximately Gaussian fluctuations for all three velocity components, a clearly defined inertial subrange following Kolmogorov scaling (power spectrum, and second- and third-order Eulerian structure functions), and highly intermittent velocity gradients, as well as approximately lognormal kinetic energy dissipation rates. The clouds were observed to have liquid water contents on the order of 1 g m-3 and size distributions typical of continental clouds, sometimes exhibiting long positive tails indicative of large drop production through turbulent mixing or coalescence growth. Dimensionless parameters relevant to cloud-turbulence interactions, the Stokes number and settling parameter are in the range typically observed in atmospheric clouds. Observed fluctuations in droplet number concentration and diameter suggest a preference for inhomogeneous mixing. Finally, enhanced variance in liquid water content fluctuations is observed at high frequencies, and the scale break occurs at a value consistent with the independently estimated phase relaxation time from microphysical measurements.

Microphysics of Clouds with the Relaxed Arakawa-Schubert Scheme (McRAS). Part I: Design and Evaluation with GATE Phase III Data.

NASA Astrophysics Data System (ADS)

Sud, Y. C.; Walker, G. K.

1999-09-01

A prognostic cloud scheme named McRAS (Microphysics of Clouds with Relaxed Arakawa-Schubert Scheme) has been designed and developed with the aim of improving moist processes, microphysics of clouds, and cloud-radiation interactions in GCMs. McRAS distinguishes three types of clouds: convective, stratiform, and boundary layer. The convective clouds transform and merge into stratiform clouds on an hourly timescale, while the boundary layer clouds merge into the stratiform clouds instantly. The cloud condensate converts into precipitation following the autoconversion equations of Sundqvist that contain a parametric adaptation for the Bergeron-Findeisen process of ice crystal growth and collection of cloud condensate by precipitation. All clouds convect, advect, as well as diffuse both horizontally and vertically with a fully interactive cloud microphysics throughout the life cycle of the cloud, while the optical properties of clouds are derived from the statistical distribution of hydrometeors and idealized cloud geometry.An evaluation of McRAS in a single-column model (SCM) with the Global Atmospheric Research Program Atlantic Tropical Experiment (GATE) Phase III data has shown that, together with the rest of the model physics, McRAS can simulate the observed temperature, humidity, and precipitation without discernible systematic errors. The time history and time mean in-cloud water and ice distribution, fractional cloudiness, cloud optical thickness, origin of precipitation in the convective anvils and towers, and the convective updraft and downdraft velocities and mass fluxes all simulate a realistic behavior. Some of these diagnostics are not verifiable with data on hand. These SCM sensitivity tests show that (i) without clouds the simulated GATE-SCM atmosphere is cooler than observed; (ii) the model's convective scheme, RAS, is an important subparameterization of McRAS; and (iii) advection of cloud water substance is helpful in simulating better cloud distribution and cloud-radiation interaction. An evaluation of the performance of McRAS in the Goddard Earth Observing System II GCM is given in a companion paper (Part II).

Simulations of NLC formation using a microphysical model driven by three-dimensional dynamics

NASA Astrophysics Data System (ADS)

Kirsch, Annekatrin; Becker, Erich; Rapp, Markus; Megner, Linda; Wilms, Henrike

2014-05-01

Noctilucent clouds (NLCs) represent an optical phenomenon occurring in the polar summer mesopause region. These clouds have been known since the late 19th century. Current physical understanding of NLCs is based on numerous observational and theoretical studies, in recent years especially observations from satellites and by lidars from ground. Theoretical studies based on numerical models that simulate NLCs with the underlying microphysical processes are uncommon. Up to date no three-dimensional numerical simulations of NLCs exist that take all relevant dynamical scales into account, i.e., from the planetary scale down to gravity waves and turbulence. Rather, modeling is usually restricted to certain flow regimes. In this study we make a more rigorous attempt and simulate NLC formation in the environment of the general circulation of the mesopause region by explicitly including gravity waves motions. For this purpose we couple the Community Aerosol and Radiation Model for Atmosphere (CARMA) to gravity-wave resolving dynamical fields simulated beforehand with the Kuehlungsborn Mechanistic Circulation Model (KMCM). In our case, the KMCM is run with a horizontal resolution of T120 which corresponds to a minimum horizontal wavelength of 350 km. This restriction causes the resolved gravity waves to be somewhat biased to larger scales. The simulated general circulation is dynamically controlled by these waves in a self-consitent fashion and provides realistic temperatures and wind-fields for July conditions. Assuming a water vapor mixing ratio profile in agreement with current observations results in reasonable supersaturations of up to 100. In a first step, CARMA is applied to a horizontal section covering the Northern hemisphere. The vertical resolution is 120 levels ranging from 72 to 101 km. In this paper we will present initial results of this coupled dynamical microphysical model focussing on the interaction of waves and turbulent diffusion with NLC-microphysics.

A new retrieval method for the ice water content of cirrus using data from the CloudSat and CALIPSO

NASA Astrophysics Data System (ADS)

Pan, Honglin; Bu, Lingbing; Kumar, K. Raghavendra; Gao, Haiyang; Huang, Xingyou; Zhang, Wentao

2017-08-01

The CloudSat and CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) are the members of satellite observation system of A-train to achieve the quasi-synchronization observation on the same orbit. With the help of active (CALIOP and CPR) and passive payloads from these two satellites, respectively, unprecedented detailed information of microphysical properties of ice cloud can be retrieved. The ice water content (IWC) is regarded as one of the most important microphysical characteristics of cirrus for its prominent role in cloud radiative forcing. In this paper, we proposed a new joint (Combination) retrieval method using the full advantages of different well established retrieval methods, namely the LIDAR method (for the region Lidar-only), the MWCR method (for the region Radar-only), and Wang method (for the region Lidar-Radar) proposed by Wang et al. (2002). In retrieval of cirrus IWC, empirical formulas of the exponential type were used for both thinner cirrus (detected by Lidar-only), thicker cirrus (detected by radar-only), and the part of cirrus detected by both, respectively. In the present study, the comparison of various methods verified that our proposed new joint method is more comprehensive, rational and reliable. Further, the retrieval information of cirrus is complete and accurate for the region that Lidar cannot penetrate and Radar is insensitive. On the whole, the retrieval results of IWC showed certain differences retrieved from the joint method, Ca&Cl, and ICARE which can be interpreted from the different hypothesis of microphysical characteristics and parameters used in the retrieval method. In addition, our joint method only uses the extinction coefficient and the radar reflectivity factor to calculate the IWC, which is simpler and reduces to some extent the accumulative error. In future studies, we will not only compare the value of IWC but also explore the detailed macrophysical and microphysical characteristics of cirrus.

Zooming in on cirrus with the Canadian Regional Climate Model

NASA Astrophysics Data System (ADS)

Stefanof, C.; Stefanof, A.; Beaulne, A.; Munoz Alpizar, R.; Szyrmer, W.; Blanchet, J.

2004-05-01

The Canadian Regional Climate Model plus a microphysical scheme: two-moments microphysics with three hydrometeor categories (cloud liquid water, pristine ice crystals and larger precipitation crystals) is used to test the simulation in forecast mode using ECMWF data at 0.4 X 0.4 degree. We are zooming in on cirrus at higher resolutions (9, 1.8, 0.36 km). We are currently using the data set measured in APEX-E3, measurements of radar, lidar, passive instruments and interpreted microphysics for some flights (G-II, C404, B200). The radar and lidar data are available for high level cirrus. The south west of Japon is the flight region. The dates are March 20, March 27 and April 2, 2003. We first focus on the March 27 frontal system. We did a rigorous synoptical analysis for the cases. The cirrus at 360 m resolution are simulated. The cloud structure and some similarities between model simulation and observations will be presented.

Observed and Simulated Radiative and Microphysical Properties of Tropical Convective Storms

NASA Technical Reports Server (NTRS)

DelGenio, Anthony D.; Hansen, James E. (Technical Monitor)

2001-01-01

Increases in the ice content, albedo and cloud cover of tropical convective storms in a warmer climate produce a large negative contribution to cloud feedback in the GISS GCM. Unfortunately, the physics of convective upward water transport, detrainment, and ice sedimentation, and the relationship of microphysical to radiative properties, are all quite uncertain. We apply a clustering algorithm to TRMM satellite microwave rainfall retrievals to identify contiguous deep precipitating storms throughout the tropics. Each storm is characterized according to its size, albedo, OLR, rain rate, microphysical structure, and presence/absence of lightning. A similar analysis is applied to ISCCP data during the TOGA/COARE experiment to identify optically thick deep cloud systems and relate them to large-scale environmental conditions just before storm onset. We examine the statistics of these storms to understand the relative climatic roles of small and large storms and the factors that regulate convective storm size and albedo. The results are compared to GISS GCM simulated statistics of tropical convective storms to identify areas of agreement and disagreement.

Aerosol Microphysical Effects on Cloud Fraction over the Nighttime Arctic Ocean

NASA Astrophysics Data System (ADS)

Zamora, L. M.; Kahn, R. A.; Stohl, A.; Eckhardt, S.

2017-12-01

Cloud fraction is a key component affecting the surface energy balance in the Arctic. Aerosol microphysical processes can affect cloud fraction, for example through cloud lifetime effects. However, the importance of aerosol impacts on cloud fraction is not well constrained on a regional scale at high latitudes. Here we discuss a new method for identifying and comparing clean and aerosol-influenced cloud characteristics using a combination of multi-year remote sensing data (CALIPSO, CloudSat) and the FLEXPART aerosol model. We use this method to investigate a variety of aerosol microphysical impacts on nighttime Arctic Ocean clouds on regional and local scales. We observe differences in factors that can impact cloud lifetime, including cloud thickness and phase, within a subset of clean vs. polluted clouds. We will also discuss cumulative cloud fraction differences in clean and non-clean environments, as well as their likely impact on longwave cloud radiative effects at the Arctic Ocean surface during polar night.

Simulation of the Upper Clouds and Hazes of Venus Using a Microphysical Cloud Model

NASA Astrophysics Data System (ADS)

McGouldrick, K.

2012-12-01

Several different microphysical and chemical models of the clouds of Venus have been developed in attempts to reproduce the in situ observations of the Venus clouds made by Pioneer Venus, Venera, and Vega descent probes (Turco et al., 1983 (Icarus 53:18-25), James et al, 1997 (Icarus 129:147-171), Imamura and Hashimoto, 2001 (J. Atm. Sci. 58:3597-3612), and McGouldrick and Toon, 2007 (Icarus 191:1-24)). The model of McGouldrick and Toon has successfully reproduced observations within the condensational middle and lower cloud decks of Venus (between about 48 and 57 km altitude, experiencing conditions similar to Earth's troposphere) and it now being extended to also simulate the microphysics occurring in the upper cloud deck (between altitudes of about 57 km and 70 km, experiencing conditions similar to Earth's stratosphere). In the upper clouds, aerosols composed of a solution of sulfuric acid in water are generated from the reservoir of available water vapor and sulfuric acid vapor that is photochemically produced. The manner of particle creation (e.g., activation of cloud condensation nuclei, or homogeneous or heterogeneous nucleation) is still incompletely understood, and the atmospheric environment has been measured to be not inconsistent with frozen aerosol particles (either sulfuric acid monohydrate or water ice). The material phase, viscosity, and surface tension of the aerosols (which are strongly dependent up on the local temperature and water vapor concentration) can affect the coagulation efficiencies of the aerosol, leading to variations in the size distributions, and other microphysical and radiative properties. Here, I present recent work exploring the effects of nucleation rates and coalescence efficiencies on the simulated Venus upper clouds.

Microphysics and dynamics of the gamma-ray burst 121024A

NASA Astrophysics Data System (ADS)

Varela, K.; van Eerten, H.; Greiner, J.; Schady, P.; Elliott, J.; Sudilovsky, V.; Krühler, T.; van der Horst, A. J.; Bolmer, J.; Knust, F.; Agurto, C.; Azagra, F.; Belloche, A.; Bertoldi, F.; De Breuck, C.; Delvaux, C.; Filgas, R.; Graham, J. F.; Kann, D. A.; Klose, S.; Menten, K. M.; Nicuesa Guelbenzu, A.; Rau, A.; Rossi, A.; Schmidl, S.; Schuller, F.; Schweyer, T.; Tanga, M.; Weiss, A.; Wiseman, P.; Wyrowski, F.

2016-05-01

Aims: The aim of the study is to constrain the physics of gamma-ray bursts (GRBs) by analysing the multi-wavelength afterglow data set of GRB 121024A that covers the full range from radio to X-rays. Methods: Using multi-epoch broad-band observations of the GRB 121024A afterglow, we measured the three characteristic break frequencies of the synchrotron spectrum. We used six epochs of combined XRT and GROND data to constrain the temporal slopes, the dust extinction, the X-ray absorption, and the spectral slope with high accuracy. Two more epochs of combined data from XRT, GROND, APEX, CARMA, and EVLA were used to set constraints on the break frequencies and therefore on the micro-physical and dynamical parameters. Results: The XRT and GROND light curves show a simultaneous and achromatic break at around 49 ks. As a result, the crossing of the synchrotron cooling break is no suitable explanation for the break in the light curve. The multi-wavelength data allow us to test two plausible scenarios explaining the break: a jet break, and the end of energy injection. The jet-break scenario requires a hard electron spectrum, a very low cooling break frequency, and a non-spreading jet. The energy injection avoids these problems, but requires ɛe > 1 (k = 2), spherical outflow, and ɛB < 10-9. Conclusions: In light of the extreme microphysical parameters required by the energy-injection model, we favour a jet-break scenario where νm < νsa to explain the observations. This scenario gives physically meaningful microphysical parameters, and it also naturally explains the reported detection of linear and circular polarisation.

Impact of large-scale dynamics on the microphysical properties of midlatitude cirrus

DOE Office of Scientific and Technical Information (OSTI.GOV)

Muhlbauer, Andreas; Ackerman, Thomas P.; Comstock, Jennifer M.

2014-04-16

In situ microphysical observations 3 of mid-latitude cirrus collected during the Department of Energy Small Particles in Cirrus (SPAR-TICUS) field campaign are combined with an atmospheric state classification for the Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) site to understand statistical relationships between cirrus microphysics and the large-scale meteorology. The atmospheric state classification is informed about the large-scale meteorology and state of cloudiness at the ARM SGP site by combining ECMWF ERA-Interim reanalysis data with 14 years of continuous observations from the millimeter-wavelength cloud radar. Almost half of the cirrus cloud occurrences in the vicinity of the ARM SGPmore » site during SPARTICUS can be explained by three distinct synoptic condi- tions, namely upper-level ridges, mid-latitude cyclones with frontal systems and subtropical flows. Probability density functions (PDFs) of cirrus micro- physical properties such as particle size distributions (PSDs), ice number con- centrations and ice water content (IWC) are examined and exhibit striking differences among the different synoptic regimes. Generally, narrower PSDs with lower IWC but higher ice number concentrations are found in cirrus sam- pled in upper-level ridges whereas cirrus sampled in subtropical flows, fronts and aged anvils show broader PSDs with considerably lower ice number con- centrations but higher IWC. Despite striking contrasts in the cirrus micro- physics for different large-scale environments, the PDFs of vertical velocity are not different, suggesting that vertical velocity PDFs are a poor predic-tor for explaining the microphysical variability in cirrus. Instead, cirrus mi- crophysical contrasts may be driven by differences in ice supersaturations or aerosols.« less

Retrieval of cloud microphysical parameters from INSAT-3D: a feasibility study using radiative transfer simulations

NASA Astrophysics Data System (ADS)

Jinya, John; Bipasha, Paul S.

2016-05-01

Clouds strongly modulate the Earths energy balance and its atmosphere through their interaction with the solar and terrestrial radiation. They interact with radiation in various ways like scattering, emission and absorption. By observing these changes in radiation at different wavelength, cloud properties can be estimated. Cloud properties are of utmost importance in studying different weather and climate phenomena. At present, no satellite provides cloud microphysical parameters over the Indian region with high temporal resolution. INSAT-3D imager observations in 6 spectral channels from geostationary platform offer opportunity to study continuous cloud properties over Indian region. Visible (0.65 μm) and shortwave-infrared (1.67 μm) channel radiances can be used to retrieve cloud microphysical parameters such as cloud optical thickness (COT) and cloud effective radius (CER). In this paper, we have carried out a feasibility study with the objective of cloud microphysics retrieval. For this, an inter-comparison of 15 globally available radiative transfer models (RTM) were carried out with the aim of generating a Look-up- Table (LUT). SBDART model was chosen for the simulations. The sensitivity of each spectral channel to different cloud properties was investigated. The inputs to the RT model were configured over our study region (50°S - 50°N and 20°E - 130°E) and a large number of simulations were carried out using random input vectors to generate the LUT. The determination of cloud optical thickness and cloud effective radius from spectral reflectance measurements constitutes the inverse problem and is typically solved by comparing the measured reflectances with entries in LUT and searching for the combination of COT and CER that gives the best fit. The products are available on the website www.mosdac.gov.in

Specific findings on ice crystal microphysical properties from in-situ observation

NASA Astrophysics Data System (ADS)

Coutris, Pierre; Leroy, Delphine; Fontaine, Emmanuel; Schwarzenboeck, Alfons; Strapp, J. Walter

2017-04-01

This study focuses on microphysical properties of ice particles populating high ice water content areas in Mesoscale Convective Systems (MCS). These clouds have been extensively sampled during the High Altitude Ice Crystal - High Ice Water Content international projects (HAIC-HIWC, Dezitter et al. 2013, Strapp et al. 2015) with the objective of characterizing ice particle properties such as size distribution, radar reflectivity and ice water content. The in-situ data collected during these campaigns at different temperature levels and in different type of MCS (oceanic, continental) make the HAIC-HIWC data set a unique opportunity to study ice particle microphysical properties. Recently, a new approach to retrieve ice particle mass from in-situ measurements has been developed: a forward model that relates ice particles' mass to Particle Size Distribution (PSD) and Ice Water Content (IWC) is formulated as a linear system of equations and the retrieval process consists in solving the inverse problem with numerical optimization tools (Coutris et al. 2016). In this study, this new method is applied to HAIC-HIWC data set and main outcomes are discussed. First, the method is compared to a classical power-law based method using data from one single flight performed in Darwin area on February, 7th 2014. The observed differences in retrieved quantities such as ice particle mass, ice water content or median mass diameter, highlight the potential benefit of abandoning the power law simplistic assumption. The method is then applied to data measured at different cloud temperatures ranging from -40°C to -10°C during several flights of both Darwin 2014 and Cayenne 2015 campaigns. Specific findings about ice microphysical properties such as variations of effective density with particle size and the influence of cloud temperature on particle effective density are presented.

Supersaturation, droplet spectra, and turbulent mixing in clouds

NASA Technical Reports Server (NTRS)

Gerber, H.

1990-01-01

Much effort has recently gone into explaining the observed broad precoalescence size distribution of droplets in cloud and fogs, because this differs from the results of condensational growth calculations which lead to much narrower distributions. A good example of droplet size-distribution broadening was observed on flight 17 (25 July) of the NRL tethered balloon during the 1987 FIRE San Nicolas Island IFO. These observations caused the interactions between cloud microphysics and turbulent mixing to be re-examined. The findings of Broadwell and Breidenthal (1982) who conducted laboratory and theoretical studies of mixing in shear flow, and those of Baker et al. (1984) who applied the earlier work to mixing in clouds, were used. Rather than looking at the 25 July case at SNI, earlier fog observations made at SUNY (6 Oct. 1982) which also indicated that shear-induced mixing was taking place, and which had a better collection of microphysical measurements including more precise supersaturation measurements and detailed vertical profiles of meteorological parameters were chosen instead.

Improvements in sub-grid, microphysics averages using quadrature based approaches

NASA Astrophysics Data System (ADS)

Chowdhary, K.; Debusschere, B.; Larson, V. E.

2013-12-01

Sub-grid variability in microphysical processes plays a critical role in atmospheric climate models. In order to account for this sub-grid variability, Larson and Schanen (2013) propose placing a probability density function on the sub-grid cloud microphysics quantities, e.g. autoconversion rate, essentially interpreting the cloud microphysics quantities as a random variable in each grid box. Random sampling techniques, e.g. Monte Carlo and Latin Hypercube, can be used to calculate statistics, e.g. averages, on the microphysics quantities, which then feed back into the model dynamics on the coarse scale. We propose an alternate approach using numerical quadrature methods based on deterministic sampling points to compute the statistical moments of microphysics quantities in each grid box. We have performed a preliminary test on the Kessler autoconversion formula, and, upon comparison with Latin Hypercube sampling, our approach shows an increased level of accuracy with a reduction in sample size by almost two orders of magnitude. Application to other microphysics processes is the subject of ongoing research.

Microphysical and macrophysical characteristics of ice and mixed-phase clouds compared between in-situ observations from the NSF ORCAS campaign and the NCAR Community Atmospheric Model

NASA Astrophysics Data System (ADS)

Diao, M.; D'Alessandro, J.; Wu, C.; Liu, X.; Jensen, J. B.

2016-12-01

Large spatial coverage of ice and mixed-phase clouds is frequently observed in the higher latitudinal regions, especially over the Arctic and Antarctica. However, because the microphysical properties in the ice and mixed-phase clouds are highly variable in space, major challenges still remain in understanding the characteristics of ice and mixed-phase clouds on the microscale, as well as representing the sub-grid scale variabilities of relative humidity in the General Circulation Models. In this work, we use the in-situ, airborne observations from the NSF O2/N2 Ratio and CO2 Airborne Southern Ocean (ORCAS) Study (January - February 2016) to analyze the microphysical and macrophysical characteristics of ice and mixed-phase clouds over the Southern Ocean. A total of 18 flights onboard the NSF Gulfstream-V research aircraft are used to quantify the cloud properties and relative humidity distributions at various temperatures, pressures and aerosol background. New QC/QA water vapor data of the Vertical Cavity Surface Emitting Laser based on the laboratory calibration in summer 2016 will be presented. The statistical distributions of cloud microphysical properties and relative humidity with respect to ice (RHi) derived from in-situ observations will be compared with the NCAR Community Atmospheric Model Version 5 (CAM5). The horizontal extent of ice and mixed-phase clouds, and their formation and evolution will be derived based on the method of Diao et al. (2013). The occurrence frequency of ice supersaturation (i.e., RHi > 100%) will be examined in relation to various chemical tracers (i.e., O3 and CO) and total aerosol number concentrations (e.g., aerosols > 0.1 μm and > 0.5 μm) at clear-sky and in-cloud conditions. We will quantify whether these characteristics of ISS are scale-dependent from the microscale to the mesoscale. Overall, our work will evaluate the spatial variabilities of RHi inside/outside of ice and mixed-phase clouds, the frequency and magnitude of ice supersaturation, as well as the correlations between ice water content and liquid water content in the CAM5 simulations.

Microphysics, Radiation and Surface Processes in the Goddard Cumulus Ensemble (GCE) Model

NASA Technical Reports Server (NTRS)

Tao, Wei-Kuo; Starr, David (Technical Monitor)

2002-01-01

One of the most promising methods to test the representation of cloud processes used in climate models is to use observations together with Cloud Resolving Models (CRMs). The CRMs use more sophisticated and realistic representations of cloud microphysical processes, and they can reasonably well resolve the time evolution, structure, and life cycles of clouds and cloud systems (size about 2-200 km). The CRMs also allow explicit interaction between out-going longwave (cooling) and in-coming solar (heating) radiation with clouds. Observations can provide the initial conditions and validation for CRM results. The Goddard Cumulus Ensemble (GCE) Model, a CRM, has been developed and improved at NASA/Goddard Space Flight Center over the past two decades. The GCE model has been used to understand the following: 1) water and energy cycles and their roles in the tropical climate system; 2) the vertical redistribution of ozone and trace constituents by individual clouds and well organized convective systems over various spatial scales; 3) the relationship between the vertical distribution of latent heating (phase change of water) and the large-scale (pre-storm) environment; 4) the validity of assumptions used in the representation of cloud processes in climate and global circulation models; and 5) the representation of cloud microphysical processes and their interaction with radiative forcing over tropical and midlatitude regions. Four-dimensional cloud and latent heating fields simulated from the GCE model have been provided to the TRMM Science Data and Information System (TSDIS) to develop and improve algorithms for retrieving rainfall and latent heating rates for TRMM and the NASA Earth Observing System (EOS). More than 90 referred papers using the GCE model have been published in the last two decades. Also, more than 10 national and international universities are currently using the GCE model for research and teaching. In this talk, five specific major GCE improvements: (1) ice microphysics, (2) longwave and shortwave radiative transfer processes, (3) land surface processes, (4) ocean surface fluxes and (5) ocean mixed layer processes are presented. The performance of these new GCE improvements will be examined. Observations are used for model validation.

Performance of Precipitation Algorithms During IPHEx and Observations of Microphysical Characteristics in Complex Terrain

NASA Astrophysics Data System (ADS)

Erlingis, J. M.; Gourley, J. J.; Kirstetter, P.; Anagnostou, E. N.; Kalogiros, J. A.; Anagnostou, M.

2015-12-01

An Intensive Observation Period (IOP) for the Integrated Precipitation and Hydrology Experiment (IPHEx), part of NASA's Ground Validation campaign for the Global Precipitation Measurement Mission satellite took place from May-June 2014 in the Smoky Mountains of western North Carolina. The National Severe Storms Laboratory's mobile dual-pol X-band radar, NOXP, was deployed in the Pigeon River Basin during this time and employed various scanning strategies, including more than 1000 Range Height Indicator (RHI) scans in coordination with another radar and research aircraft. Rain gauges and disdrometers were also positioned within the basin to verify precipitation estimates and estimation of microphysical parameters. The performance of the SCOP-ME post-processing algorithm on NOXP data is compared with real-time and near real-time precipitation estimates with varying spatial resolutions and quality control measures (Stage IV gauge-corrected radar estimates, Multi-Radar/Multi-Sensor System Quantitative Precipitation Estimates, and CMORPH satellite estimates) to assess the utility of a gap-filling radar in complex terrain. Additionally, the RHI scans collected in this IOP provide a valuable opportunity to examine the evolution of microphysical characteristics of convective and stratiform precipitation as they impinge on terrain. To further the understanding of orographically enhanced precipitation, multiple storms for which RHI data are available are considered.

Two moment dust and water ice in the MarsWRF GCM

NASA Astrophysics Data System (ADS)

Lee, Christopher; Richardson, Mark I.; Newman, Claire E.; Mischna, Michael A.

2016-10-01

A new two moment dust and water ice microphysics scheme has been developed for the MarsWRF General Circulation Model based on the Morrison and Gettelman (2008) scheme, and includes temperature dependent nucleation processes and energetically constrained condensation and evaporation. Dust consumed in the formation of water ice is also tracked by the model.The two moment dust scheme simulates dust particles in the Martian atmosphere using a Gamma distribution with fixed radius for lifted particles. Within the atmosphere the particle distribution is advected and sedimented within the two moment framework, obviating the requirement for lossy conversion between the continuous Gamma distribution and discritized bins found in some Mars microphysics schemes. Water ice is simulated using the same Gamma distribution and advected and sedimented in the same way. Water ice nucleation occurs heterogeneously onto dust particles with temperature dependent contact parameters (e.g. Trainer et al., 2009) and condensation and evaporation follows energetic constraints (e.g. Pruppacher and Klett, 1980; Montmessin et al., 2002) allowing water ice particles to grow in size where necessary. Dust particles are tracked within the ice cores as nucleation occurs, and dust cores advect and sediment along with their parent ice particle distributions. Radiative properties of dust and water particles are calculated as a function of the effective radius of the particles and the distribution width. The new microphysics scheme requires 5 tracers to be tracked as the moments of the dust, water ice, and ice core. All microphysical processes are simulated entirely within the two moment framework without any discretization of particle sizes.The effect of this new microphysics scheme on dust and water ice cloud distribution will be discussed and compared with observations from TES and MCS.

Using a Multiwavelength Suite of Microwave Instruments to Investigate the Microphysical Structure of Deep Convective Cores

NASA Technical Reports Server (NTRS)

Battaglia, A.; Mroz, K.; Lang, Tim; Tridon, F.; Tanelli, S.; Tian, Lin; Heymsfield, Gerald M.

2016-01-01

Due to the large natural variability of its microphysical properties, the characterization of solid precipitation is a longstanding problem. Since in situ observations are unavailable in severe convective systems, innovative remote sensing retrievals are needed to extend our understanding of such systems. This study presents a novel technique able to retrieve the density, mass, and effective diameter of graupel and hail in severe convection through the combination of airborne microwave remote sensing instruments. The retrieval is applied to measure solid precipitation properties within two convective cells observed on 2324 May 2014 over North Carolina during the IPHEx campaign by the NASA ER-2 instrument suite. Between 30 and 40 degrees of freedom of signal are associated with the measurements, which is insufficient to provide full microphysics profiling. The measurements have the largest impact on the retrieval of ice particle sizes, followed by ice water contents. Ice densities are mainly driven by a priori assumptions, though low relative errors in ice densities suggest that in extensive regions of the convective system, only particles with densities larger than 0.4 gcm3 are compatible with the observations. This is in agreement with reports of large hail on the ground and with hydrometeor classification derived from ground-based polarimetric radars observations. This work confirms that multiple scattering generated by large ice hydrometeors in deep convection is relevant for airborne radar systems already at Ku band. A fortiori, multiple scattering will play a pivotal role in such conditions also for Ku band spaceborne radars (e.g., the GPM Dual Precipitation Radar).

Optimizing observations of drizzle onset with millimeter-wavelength radars

DOE PAGES

Acquistapace, Claudia; Kneifel, Stefan; Löhnert, Ulrich; ...

2017-05-12

Cloud Doppler radars are increasingly used to study cloud and precipitation microphysical processes. Typical bulk cloud properties such as liquid or ice content are usually derived using the first three standard moments of the radar Doppler spectrum. Recent studies demonstrated the value of higher moments for the reduction of retrieval uncertainties and for providing additional insights into microphysical processes. Large effort has been undertaken, e.g., within the Atmospheric Radiation Measurement (ARM) program to ensure high quality of radar Doppler spectra. However, a systematic approach concerning the accuracy of higher moment estimates and sensitivity to basic radar system settings, such asmore » spectral resolution, integration time and beam width, are still missing. Here In this study, we present an approach on how to optimize radar settings for radar Doppler spectra moments in the specific context of drizzle detection. The process of drizzle development has shown to be particularly sensitive to higher radar moments such as skewness. We collected radar raw data (I/Q time series) from consecutive zenith-pointing observations for two liquid cloud cases observed at the cloud observatory JOYCE in Germany. The I/Q data allowed us to process Doppler spectra and derive their moments using different spectral resolutions and integration times during identical time intervals. This enabled us to study the sensitivity of the spatiotemporal structure of the derived moments to the different radar settings. The observed signatures were further investigated using a radar Doppler forward model which allowed us to compare observed and simulated sensitivities and also to study the impact of additional hardware-dependent parameters such as antenna beam width. For the observed cloud with drizzle onset we found that longer integration times mainly modify spectral width ( S w) and skewness ( S k), leaving other moments mostly unaffected. An integration time of 2 s seems to be an optimal compromise: both observations and simulations revealed that a 10 s integration time – as it is widely used for European cloud radars – leads to a significant turbulence-induced increase of S w and reduction of S k compared to 2 s integration time. This can lead to significantly different microphysical interpretations with respect to drizzle water content and effective radius. A change from 2 s to even shorter integration times (0. 4 s) has much smaller effects on S w and S k. We also find that spectral resolution has a small impact on the moment estimations, and thus on the microphysical interpretation of the drizzle signal. Even the coarsest spectral resolution studied, 0. 08 ms -1, seems to be appropriate for calculation moments of drizzling clouds. Moreover, simulations provided additional insight into the microphysical interpretation of the skewness signatures observed: in low (high)-turbulence conditions, only drizzle larger than 20 µm (40 µm) can generate S k values above the S k noise level (in our case 0.4). Higher S k values are also obtained in simulations when smaller beam widths are adopted.« less

Radiation Transfer in the Atmosphere: Scattering

NASA Technical Reports Server (NTRS)

Mishchenko, M.; Travis, L.; Lacis, Andrew A.

2014-01-01

Sunlight illuminating the Earth's atmosphere is scattered by gas molecules and suspended particles, giving rise to blue skies, white clouds, and optical displays such as rainbows and halos. By scattering and absorbing the shortwave solar radiation and the longwave radiation emitted by the underlying surface, cloud and aerosol particles strongly affect the radiation budget of the terrestrial climate system. As a consequence of the dependence of scattering characteristics on particle size, morphology, and composition, scattered light can be remarkably rich in information on particle properties and thus provides a sensitive tool for remote retrievals of macro- and microphysical parameters of clouds and aerosols.

Comparisons of Cloud Properties over the Southern Ocean between In situ Observations and WRF Simulations

NASA Astrophysics Data System (ADS)

D'Alessandro, J.; Diao, M.; Wu, C.; Liu, X.

2017-12-01

Numerical weather models often struggle at representing clouds since small scale cloud processes must be parameterized. For example, models often utilize simple parameterizations for transitioning from liquid to ice, usually set as a function of temperature. However, supercooled liquid water (SLW) often persists at temperatures much lower than threshold values used in microphysics parameterizations. Previous observational studies of clouds over the Southern Ocean have found high frequencies of SLW (e.g., Morrison et al., 2011). Many of these studies have relied on satellite retrievals, which provide relatively low resolution observations and are often associated with large uncertainties due to assumptions of microphysical properties (e.g., particle size distributions). Recently, the NSF/NCAR O2/N2 Ratio and CO2 Airborne Southern Ocean Study (ORCAS) campaign took observations via the NSF/NCAR HIAPER research aircraft during January and February of 2016, providing in situ observations over the Southern Ocean (50°W to 92°W). We compare simulated results from the Weather Research and Forecasting (WRF) model with in situ observations from ORCAS. Differences between observations and simulations are evaluated via statistical analyses. Initial results from ORCAS reveal a high frequency of SLW at temperatures as low as -15°C, and the existence of SLW around -30°C. Recent studies have found that boundary layer clouds are underestimated by WRF in regions unaffected by cyclonic activity (Huang et al., 2014), suggesting a lack of low-level moisture due to local processes. To explore this, relative humidity distributions are examined and controlled by cloud microphysical characteristics (e.g., total water content) and relevant ambient properties (e.g., vertical velocity). A relatively low frequency of simulated SLW may in part explain the discrepancies in WRF, as cloud-top SLW results in stronger radiative cooling and turbulent motions conducive for long-lived cloud regimes. Results presented in this study will help improve our understanding of Southern Ocean clouds and the observed discrepancies seen in WRF simulations.

Evaluating Microphysics in Cloud-Resolving Models using TRMM and Ground-based Precipitation Radar Observations

NASA Astrophysics Data System (ADS)

Krueger, S. K.; Zulauf, M. A.; Li, Y.; Zipser, E. J.

2005-05-01

Global satellite datasets such as those produced by ISCCP, ERBE, and CERES provide strong observational constraints on cloud radiative properties. Such observations have been widely used for model evaluation, tuning, and improvement. Cloud radiative properties depend primarily on small, non-precipitating cloud droplets and ice crystals, yet the dynamical, microphysical and radiative processes which produce these small particles often involve large, precipitating hydrometeors. There now exists a global dataset of tropical cloud system precipitation feature (PF) properties, collected by TRMM and produced by Steve Nesbitt, that provides additional observational constraints on cloud system properties. We are using the TRMM PF dataset to evaluate the precipitation microphysics of two simulations of deep, precipitating, convective cloud systems: one is a 29-day summertime, continental case (ARM Summer 1997 SCM IOP, at the Southern Great Plains site); the second is a tropical maritime case: the Kwajalein MCS of 11-12 August 1999 (part of a 52-day simulation). Both simulations employed the same bulk, three-ice category microphysical parameterization (Krueger et al. 1995). The ARM simulation was executed using the UCLA/Utah 2D CRM, while the KWAJEX simulation was produced using the 3D CSU CRM (SAM). The KWAJEX simulation described above is compared with both the actual radar data and the TRMM statistics. For the Kwajalein MCS of 11 to 12 August 1999, there are research radar data available for the lifetime of the system. This particular MCS was large in size and rained heavily, but it was weak to average in measures of convective intensity, against the 5-year TRMM sample of 108. For the Kwajalein MCS simulation, the 20 dBZ contour is at 15.7 km and the 40 dBZ contour at 14.5 km! Of all 108 MCSs observed by TRMM, the highest value for the 40 dBZ contour is 8 km. Clearly, the high reflectivity cores are off scale compared with observed cloud systems in this area. A similar conclusion can be reached by comparing the simulated microwave brightness temperatures with observed brightness temperatures at 85 GHz and 37 GHz. In each case, the simulations are more extreme than all observed MCSs in the region over the 5 year period. The situation is similar but less egregious for the southern Great Plains simulation. Inspection of the cloud microphysics output files reveals the source of the discrepancy between simulation and observations in the upper troposphere. The simulations have very large graupel concentrations between about 5-10 km, as high as 10 g/kg graupel mixing ratio. This guarantees that there are very high radar reflectivities extending into the upper troposphere, and unrealistically low microwave brightness temperatures. We also performed a set of short (6-h) numerical simulations of the life cycle of a single convection cell to examine the sensitivity of the simulated graupel fields to the intercept parameter and the density of the graupel. The control case used the same values as the ARM and KWAJEX simulations. Reducing the intercept parameter by a factor of 100 reduced the maximum graupel mixing ratios but increased the maximum dBZ values. This suggests that the discrepencies between the simulations and the observations must involve the graupel growth rates.

Contrails and contrail-cirrus microphysics

DOT National Transportation Integrated Search

2008-01-25

Theme 4 of the ACCRI, Contrails and Contrail-Specific Microphysics, reviews the current : state of understanding of the science of contrails: 1) how they are formed, 2) their microphysical properties as they evolve, 3) how they develop into con...

Synergistic observations of convective cloud life-cycle during the Mid-latitude Continental Convective Clouds Experiment (MC3E)

NASA Astrophysics Data System (ADS)

Jensen, M. P.; Petersen, W. A.; Giangrande, S.; Heymsfield, G. M.; Kollias, P.; Rutledge, S. A.; Schwaller, M.; Zipser, E. J.

2011-12-01

The Midlatitude Continental Convective Clouds Experiment (MC3E) took place from 22 April through 6 June 2011 centered at the U.S. Department of Energy's Atmospheric Radiation Measurement (ARM) Southern Great Plains Central Facility in north-central Oklahoma. This campaign was a joint effort between the ARM and the National Aeronautics and Space Administration's (NASA) Global Precipitation Measurement mission Ground Validation program. It was the first major field campaign to take advantage of numerous new radars and other remote sensing instrumentation purchased through the American Recovery and Reinvestment Act of 2009. The measurement strategy for this field campaign was to provide a well-defined forcing dataset for modeling efforts coupled with detailed observations of cloud/precipitation dynamics and microphysics within the domain highlighted by advanced multi-scale, multi-frequency radar remote sensing. These observations are aimed at providing important insights into eight different components of convective simulation and microphysical parameterization: (1) pre-convective environment, (2) convective initiation, (3) updraft/downdraft dynamics, (4) condensate transport/detrainment/entrainment, (5) precipitation and cloud microphysics, (6) influence on the environment, (7) influence on radiation, and (8) large-scale forcing. In order to obtain the necessary dataset, the MC3E surface-based observational network included six radiosonde launch sites each launching 4-8 sondes per day, three X-band scanning ARM precipitation radars, a C-band scanning ARM precipitation radar, the NASA N-Pol (S-band) scanning radar, the NASA D3R Ka/Ku-band radar, the Ka/W-band scanning ARM cloud radar, vertically pointing radar systems at Ka-, S- and UHF band, a network of over 20 disdrometers and rain gauges and the full complement of radiation, cloud and atmospheric state observations available at the ARM facility. This surface-based network was complemented by aircraft measurements by the NASA ER-2 high altitude aircraft which included a radar system (Ka/Ku band) and multiple passive microwave radiometers (10-183 GHz) and the University of North Dakota Citation which included a full suite of in situ microphysics instruments. The campaign was successful in providing observations over a wide variety of convective cloud types, from shallow non-precipitating cloud fields to shallow-to-deep transitions to mature deep convective systems some of which included severe weather. We will present an overview of the convective cloud conditions that were observed, the status MC3E datastreams and a summary of some of the preliminary results.

Effects of microphysics parameterization on simulations of summer heavy precipitation in the Yangtze-Huaihe Region, China

NASA Astrophysics Data System (ADS)

Kan, Yu; Chen, Bo; Shen, Tao; Liu, Chaoshun; Qiao, Fengxue

2017-09-01

It has been a longstanding problem for current weather/climate models to accurately predict summer heavy precipitation over the Yangtze-Huaihe Region (YHR) which is the key flood-prone area in China with intensive population and developed economy. Large uncertainty has been identified with model deficiencies in representing precipitation processes such as microphysics and cumulus parameterizations. This study focuses on examining the effects of microphysics parameterization on the simulation of different type of heavy precipitation over the YHR taking into account two different cumulus schemes. All regional persistent heavy precipitation events over the YHR during 2008-2012 are classified into three types according to their weather patterns: the type I associated with stationary front, the type II directly associated with typhoon or with its spiral rain band, and the type III associated with strong convection along the edge of the Subtropical High. Sixteen groups of experiments are conducted for three selected cases with different types and a local short-time rainstorm in Shanghai, using the WRF model with eight microphysics and two cumulus schemes. Results show that microphysics parameterization has large but different impacts on the location and intensity of regional heavy precipitation centers. The Ferrier (microphysics) -BMJ (cumulus) scheme and Thompson (microphysics) - KF (cumulus) scheme most realistically simulates the rain-bands with the center location and intensity for type I and II respectively. For type III, the Lin microphysics scheme shows advantages in regional persistent cases over YHR, while the WSM5 microphysics scheme is better in local short-term case, both with the BMJ cumulus scheme.

Synergistic Measurement of Ice Cloud Microphysics using C- and Ka-Band Radars

NASA Astrophysics Data System (ADS)

Ewald, F.; Gross, S.; Hagen, M.; Li, Q.; Zinner, T.

2017-12-01

Ice clouds play an essential role in the climate system since they have a large effect on the Earth's radiation budget. Uncertainties associated with their spatial and temporal distribution as well as their optical and microphysical properties still account for large uncertainties in climate change predictions. Substantial improvement of our understanding of ice clouds was achieved with the advent of cloud radars into the field of ice cloud remote sensing. Here, highly variable ice crystal size distributions are one of the key issues remaining to be resolved. With radar reflectivity scaling with the sixth moment of the particle size, the assumed ice crystal size distribution has a large impact on the results of microphysical retrievals. Different ice crystal sizes distributions can, however, be distinguished, when cloud radars of different wavelength are used simultaneously.For this study, synchronous RHI scans were performed for a common measurement range of about 30 km between two radar instruments using different wavelengths: the dual-polarization C-band radar POLDIRAD operated at DLR and the Mira-36 Ka-band cloud radar operated at the University of Munich. For a measurement period over several months, the overlapping region for ice clouds turned out to be quite large. This gives evidence on the presence of moderate-sized ice crystals for which the backscatter is sufficient high to be visible in the C-band as well. In the range between -10 to +10 dBz, reflectivity measurements from both radars agreed quite well indicating the absence of large ice crystals. For reflectivities above +10 dBz, we observed differences with smaller values at the Ka-band due to Mie scattering effects at larger ice crystals.In this presentation, we will show how this differential reflectivity can be used to gain insight into ice cloud microphysics on the basis of electromagnetic scattering calculations. We will further explore ice cloud microphysics using the full polarization agility of the C-band radar and compare the results to simultaneous linear depolarization measurements with the Ka-band radar. In summary, we will explore if the scientific understanding of ice cloud microphysics can be advanced by the combination of C- and Ka-band radars.

Modelling ice microphysics of mixed-phase clouds

NASA Astrophysics Data System (ADS)

Ahola, J.; Raatikainen, T.; Tonttila, J.; Romakkaniemi, S.; Kokkola, H.; Korhonen, H.

2017-12-01

The low-level Arctic mixed-phase clouds have a significant role for the Arctic climate due to their ability to absorb and reflect radiation. Since the climate change is amplified in polar areas, it is vital to apprehend the mixed-phase cloud processes. From a modelling point of view, this requires a high spatiotemporal resolution to capture turbulence and the relevant microphysical processes, which has shown to be difficult.In order to solve this problem about modelling mixed-phase clouds, a new ice microphysics description has been developed. The recently published large-eddy simulation cloud model UCLALES-SALSA offers a good base for a feasible solution (Tonttila et al., Geosci. Mod. Dev., 10:169-188, 2017). The model includes aerosol-cloud interactions described with a sectional SALSA module (Kokkola et al., Atmos. Chem. Phys., 8, 2469-2483, 2008), which represents a good compromise between detail and computational expense.Newly, the SALSA module has been upgraded to include also ice microphysics. The dynamical part of the model is based on well-known UCLA-LES model (Stevens et al., J. Atmos. Sci., 56, 3963-3984, 1999) which can be used to study cloud dynamics on a fine grid.The microphysical description of ice is sectional and the included processes consist of formation, growth and removal of ice and snow particles. Ice cloud particles are formed by parameterized homo- or heterogeneous nucleation. The growth mechanisms of ice particles and snow include coagulation and condensation of water vapor. Autoconversion from cloud ice particles to snow is parameterized. The removal of ice particles and snow happens by sedimentation and melting.The implementation of ice microphysics is tested by initializing the cloud simulation with atmospheric observations from the Indirect and Semi-Direct Aerosol Campaign (ISDAC). The results are compared to the model results shown in the paper of Ovchinnikov et al. (J. Adv. Model. Earth Syst., 6, 223-248, 2014) and they show a good match. One of the advantages of UCLALES-SALSA is that it can be used to quantify the effect of aerosol scavenging on cloud properties in a precise way.

Potential Retrieval of Aerosol Microphysics From Multistatic Space-Borne Lidar

NASA Astrophysics Data System (ADS)

Levitan, Nathaniel; Gross, Barry; Moshary, Fred; Wu, Yonghua

2018-04-01

HSRL lidars are being considered for deployment to space to retrieve aerosol microphysics. The literature is mostly focused on the monostatic configuration; but, in this paper, we explore whether additional information for the retrieval of microphysics can be obtained by adding a second detector in a bistatic configuration. The information gained from the additional measurements can under certain conditions reduce the ill-posed nature of aerosol microphysics retrieval and reducing the uncertainty in the retrievals.

The Impact of Microphysics on Intensity and Structure of Hurricanes

NASA Technical Reports Server (NTRS)

Tao, Wei-Kuo; Shi, Jainn; Lang, Steve; Peters-Lidard, Christa

2006-01-01

During the past decade, both research and operational numerical weather prediction models, e.g. Weather Research and Forecast (WRF) model, have started using more complex microphysical schemes originally developed for high-resolution cloud resolving models (CRMs) with a 1-2 km or less horizontal resolutions. WFW is a next-generation mesoscale forecast model and assimilation system that has incorporated modern software framework, advanced dynamics, numeric and data assimilation techniques, a multiple moveable nesting capability, and improved physical packages. WFW model can be used for a wide range of applications, from idealized research to operational forecasting, with an emphasis on horizontal grid sizes in the range of 1-10 km. The current WRF includes several different microphysics options such as Lin et al. (1983), WSM 6-class and Thompson microphysics schemes. We have recently implemented three sophisticated cloud microphysics schemes into WRF. The cloud microphysics schemes have been extensively tested and applied for different mesoscale systems in different geographical locations. The performances of these schemes have been compared to those from other WRF microphysics options. We are performing sensitivity tests in using WW to examine the impact of six different cloud microphysical schemes on hurricane track, intensity and rainfall forecast. We are also performing the inline tracer calculation to comprehend the physical processes @e., boundary layer and each quadrant in the boundary layer) related to the development and structure of hurricanes.

Using Directional Emissivity as a Probe of Particle Microphysical Properties

NASA Astrophysics Data System (ADS)

Pitman, K. M.; Wolff, M. J.; Bandfield, J. L.; Clayton, G. C.

2002-09-01

Real surfaces are not expected to be diffuse emitters, thus observed emissivity values are a function of viewing geometry. This fact has strong implications for analyses of the MGS/TES emission phase function (EPF) sequences and the upcoming Mars Exploration Rover mini-TES dataset. As reviewed previously [1], in the absence of strong thermal gradients, directional emissivity may be obtained via a combination of reciprocity and Kirchhoff's Law. Here we focus on the potential utility of directional emissivity as a direct probe of surface particle microphysical properties. We explore the effects of particle size and composition on observed radiances in the TES spectral regime using a combination of multiple scattering radiative transfer and Mie scattering algorithms. Comparisons of these simulated spectra to TES EPF observations of typical surface units (e.g., high and low albedo regions) will also be made. This work is supported through NASA grant NAGS-9820 (MJW) and LSU Board of Regents (KMP). [1] Pitman, K.M., et al. (2001), AAS-DPS meeting # 33, # 36.01.

Simulations of cloud-radiation interaction using large-scale forcing derived from the CINDY/DYNAMO northern sounding array

DOE PAGES

Wang, Shuguang; Sobel, Adam H.; Fridlind, Ann; ...

2015-09-25

The recently completed CINDY/DYNAMO field campaign observed two Madden-Julian oscillation (MJO) events in the equatorial Indian Ocean from October to December 2011. Prior work has indicated that the moist static energy anomalies in these events grew and were sustained to a significant extent by radiative feedbacks. We present here a study of radiative fluxes and clouds in a set of cloud-resolving simulations of these MJO events. The simulations are driven by the large scale forcing dataset derived from the DYNAMO northern sounding array observations, and carried out in a doubly-periodic domain using the Weather Research and Forecasting (WRF) model. simulatedmore » cloud properties and radiative fluxes are compared to those derived from the S-Polka radar and satellite observations. Furthermore, to accommodate the uncertainty in simulated cloud microphysics, a number of single moment (1M) and double moment (2M) microphysical schemes in the WRF model are tested.« less

Intel Xeon Phi accelerated Weather Research and Forecasting (WRF) Goddard microphysics scheme

NASA Astrophysics Data System (ADS)

Mielikainen, J.; Huang, B.; Huang, A. H.-L.

2014-12-01

The Weather Research and Forecasting (WRF) model is a numerical weather prediction system designed to serve both atmospheric research and operational forecasting needs. The WRF development is a done in collaboration around the globe. Furthermore, the WRF is used by academic atmospheric scientists, weather forecasters at the operational centers and so on. The WRF contains several physics components. The most time consuming one is the microphysics. One microphysics scheme is the Goddard cloud microphysics scheme. It is a sophisticated cloud microphysics scheme in the Weather Research and Forecasting (WRF) model. The Goddard microphysics scheme is very suitable for massively parallel computation as there are no interactions among horizontal grid points. Compared to the earlier microphysics schemes, the Goddard scheme incorporates a large number of improvements. Thus, we have optimized the Goddard scheme code. In this paper, we present our results of optimizing the Goddard microphysics scheme on Intel Many Integrated Core Architecture (MIC) hardware. The Intel Xeon Phi coprocessor is the first product based on Intel MIC architecture, and it consists of up to 61 cores connected by a high performance on-die bidirectional interconnect. The Intel MIC is capable of executing a full operating system and entire programs rather than just kernels as the GPU does. The MIC coprocessor supports all important Intel development tools. Thus, the development environment is one familiar to a vast number of CPU developers. Although, getting a maximum performance out of MICs will require using some novel optimization techniques. Those optimization techniques are discussed in this paper. The results show that the optimizations improved performance of Goddard microphysics scheme on Xeon Phi 7120P by a factor of 4.7×. In addition, the optimizations reduced the Goddard microphysics scheme's share of the total WRF processing time from 20.0 to 7.5%. Furthermore, the same optimizations improved performance on Intel Xeon E5-2670 by a factor of 2.8× compared to the original code.

Global Simulations of Ice nucleation and Ice Supersaturation with an Improved Cloud Scheme in the Community Atmosphere Model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gettelman, A.; Liu, Xiaohong; Ghan, Steven J.

2010-09-28

A process-based treatment of ice supersaturation and ice-nucleation is implemented in the National Center for Atmospheric Research (NCAR) Community Atmosphere Model (CAM). The new scheme is designed to allow (1) supersaturation with respect to ice, (2) ice nucleation by aerosol particles and (3) ice cloud cover consistent with ice microphysics. The scheme is implemented with a 4-class 2 moment microphysics code and is used to evaluate ice cloud nucleation mechanisms and supersaturation in CAM. The new model is able to reproduce field observations of ice mass and mixed phase cloud occurrence better than previous versions of the model. Simulations indicatemore » heterogeneous freezing and contact nucleation on dust are both potentially important over remote areas of the Arctic. Cloud forcing and hence climate is sensitive to different formulations of the ice microphysics. Arctic radiative fluxes are sensitive to the parameterization of ice clouds. These results indicate that ice clouds are potentially an important part of understanding cloud forcing and potential cloud feedbacks, particularly in the Arctic.« less

COMMIT in 7-SEAS/BASELInE: Operation of and Observations from a Novel, Mobile Laboratory for Measuring In-Situ Properties of Aerosols and Gases

NASA Technical Reports Server (NTRS)

Pantina, Peter; Tsay, Si-Chee; Hsiao, Ta-Chih; Loftus, Adrian M.; Kuo, Ferret; Ou-Yang, Chang-Feng; Sayer, Andrew M.; Wang, Shen-Hsiang; Lin, Neng-Huei; Hsu, N. Christina;

Simulations of arctic mixed-phase clouds in forecasts with CAM3 and AM2 for M-PACE

DOE PAGES

Xie, Shaocheng; Boyle, James; Klein, Stephen A.; ...

2008-02-27

[1] Simulations of mixed-phase clouds in forecasts with the NCAR Atmosphere Model version 3 (CAM3) and the GFDL Atmospheric Model version 2 (AM2) for the Mixed-Phase Arctic Cloud Experiment (M-PACE) are performed using analysis data from numerical weather prediction centers. CAM3 significantly underestimates the observed boundary layer mixed-phase cloud fraction and cannot realistically simulate the variations of liquid water fraction with temperature and cloud height due to its oversimplified cloud microphysical scheme. In contrast, AM2 reasonably reproduces the observed boundary layer cloud fraction while its clouds contain much less cloud condensate than CAM3 and the observations. The simulation of themore » boundary layer mixed-phase clouds and their microphysical properties is considerably improved in CAM3 when a new physically based cloud microphysical scheme is used (CAM3LIU). The new scheme also leads to an improved simulation of the surface and top of the atmosphere longwave radiative fluxes. Sensitivity tests show that these results are not sensitive to the analysis data used for model initialization. Increasing model horizontal resolution helps capture the subgrid-scale features in Arctic frontal clouds but does not help improve the simulation of the single-layer boundary layer clouds. AM2 simulated cloud fraction and LWP are sensitive to the change in cloud ice number concentrations used in the Wegener-Bergeron-Findeisen process while CAM3LIU only shows moderate sensitivity in its cloud fields to this change. Furthermore, this paper shows that the Wegener-Bergeron-Findeisen process is important for these models to correctly simulate the observed features of mixed-phase clouds.« less

Simulations of Arctic mixed-phase clouds in forecasts with CAM3 and AM2 for M-PACE

NASA Astrophysics Data System (ADS)

Xie, Shaocheng; Boyle, James; Klein, Stephen A.; Liu, Xiaohong; Ghan, Steven

2008-02-01

Simulations of mixed-phase clouds in forecasts with the NCAR Atmosphere Model version 3 (CAM3) and the GFDL Atmospheric Model version 2 (AM2) for the Mixed-Phase Arctic Cloud Experiment (M-PACE) are performed using analysis data from numerical weather prediction centers. CAM3 significantly underestimates the observed boundary layer mixed-phase cloud fraction and cannot realistically simulate the variations of liquid water fraction with temperature and cloud height due to its oversimplified cloud microphysical scheme. In contrast, AM2 reasonably reproduces the observed boundary layer cloud fraction while its clouds contain much less cloud condensate than CAM3 and the observations. The simulation of the boundary layer mixed-phase clouds and their microphysical properties is considerably improved in CAM3 when a new physically based cloud microphysical scheme is used (CAM3LIU). The new scheme also leads to an improved simulation of the surface and top of the atmosphere longwave radiative fluxes. Sensitivity tests show that these results are not sensitive to the analysis data used for model initialization. Increasing model horizontal resolution helps capture the subgrid-scale features in Arctic frontal clouds but does not help improve the simulation of the single-layer boundary layer clouds. AM2 simulated cloud fraction and LWP are sensitive to the change in cloud ice number concentrations used in the Wegener-Bergeron-Findeisen process while CAM3LIU only shows moderate sensitivity in its cloud fields to this change. This paper shows that the Wegener-Bergeron-Findeisen process is important for these models to correctly simulate the observed features of mixed-phase clouds.

Sensitivity of a Cloud-Resolving Model to the Bulk and Explicit Bin Microphysical Schemes. Part 1; Validations with a PRE-STORM Case

NASA Technical Reports Server (NTRS)

Li, Xiao-Wen; Tao, Wei-Kuo; Khain, Alexander P.; Simpson, Joanne; Johnson, Daniel E.

2004-01-01

A cloud-resolving model is used to study sensitivities of two different microphysical schemes, one is the bulk type, and the other is an explicit bin scheme, in simulating a mid-latitude squall line case (PRE-STORM, June 10-11, 1985). Simulations using different microphysical schemes are compared with each other and also with the observations. Both the bulk and bin models reproduce the general features during the developing and mature stage of the system. The leading convective zone, the trailing stratiform region, the horizontal wind flow patterns, pressure perturbation associated with the storm dynamics, and the cool pool in front of the system all agree well with the observations. Both the observations and the bulk scheme simulation serve as validations for the newly incorporated bin scheme. However, it is also shown that, the bulk and bin simulations have distinct differences, most notably in the stratiform region. Weak convective cells exist in the stratiform region in the bulk simulation, but not in the bin simulation. These weak convective cells in the stratiform region are remnants of the previous stronger convections at the leading edge of the system. The bin simulation, on the other hand, has a horizontally homogeneous stratiform cloud structure, which agrees better with the observations. Preliminary examinations of the downdraft core strength, the potential temperature perturbation, and the evaporative cooling rate show that the differences between the bulk and bin models are due mainly to the stronger low-level evaporative cooling in convective zone simulated in the bulk model. Further quantitative analysis and sensitivity tests for this case using both the bulk and bin models will be presented in a companion paper.

A case study of microphysical structures and hydrometeor phase in convection using radar Doppler spectra at Darwin, Australia

NASA Astrophysics Data System (ADS)

Riihimaki, L. D.; Comstock, J. M.; Luke, E.; Thorsen, T. J.; Fu, Q.

2017-07-01

To understand the microphysical processes that impact diabatic heating and cloud lifetimes in convection, we need to characterize the spatial distribution of supercooled liquid water. To address this observational challenge, ground-based vertically pointing active sensors at the Darwin Atmospheric Radiation Measurement site are used to classify cloud phase within a deep convective cloud. The cloud cannot be fully observed by a lidar due to signal attenuation. Therefore, we developed an objective method for identifying hydrometeor classes, including mixed-phase conditions, using k-means clustering on parameters that describe the shape of the Doppler spectra from vertically pointing Ka-band cloud radar. This approach shows that multiple, overlapping mixed-phase layers exist within the cloud, rather than a single region of supercooled liquid. Diffusional growth calculations show that the conditions for the Wegener-Bergeron-Findeisen process exist within one of these mixed-phase microstructures.

Aerosol effects on cloud water amounts were successfully simulated by a global cloud-system resolving model.

PubMed

Sato, Yousuke; Goto, Daisuke; Michibata, Takuro; Suzuki, Kentaroh; Takemura, Toshihiko; Tomita, Hirofumi; Nakajima, Teruyuki

2018-03-07

Aerosols affect climate by modifying cloud properties through their role as cloud condensation nuclei or ice nuclei, called aerosol-cloud interactions. In most global climate models (GCMs), the aerosol-cloud interactions are represented by empirical parameterisations, in which the mass of cloud liquid water (LWP) is assumed to increase monotonically with increasing aerosol loading. Recent satellite observations, however, have yielded contradictory results: LWP can decrease with increasing aerosol loading. This difference implies that GCMs overestimate the aerosol effect, but the reasons for the difference are not obvious. Here, we reproduce satellite-observed LWP responses using a global simulation with explicit representations of cloud microphysics, instead of the parameterisations. Our analyses reveal that the decrease in LWP originates from the response of evaporation and condensation processes to aerosol perturbations, which are not represented in GCMs. The explicit representation of cloud microphysics in global scale modelling reduces the uncertainty of climate prediction.

Comment on 'The effect of liquid water on thunderstorm charging' by C.P.R. Saunders et al

NASA Technical Reports Server (NTRS)

Williams, Earle; Zhang, Renyi

1993-01-01

This paper is a comment on the claims made in the paper by Saunders et al. (1991), which reports on a laboratory simulation of ice particle charging in thunderstorms, concerning the microphysical condition of riming ice particles and the conditions for sublimation and negative charging in thunderclouds. It is argued that the interpretation of Saunders is contrary to the findings of Williams et al. (1991), which support the hypothesis that sublimating graupel charge negatively (in collision with smaller ice particles) and graupel in deposition charge positively. Based on microphysical calculations as well as observations in thunderclouds, it is concluded that, while sublimation of the rimer surface and negative charging do not appear to account for the laboratory observations reported by Saunders et al., these authors do not have sufficient evidence for rejecting the sublimation hypothesis presented by Williams et al. (1991) for thunderstorms.

Tropical Cloud Properties and Radiative Heating Profiles

DOE Data Explorer

Mather, James

2008-01-15

We have generated a suite of products that includes merged soundings, cloud microphysics, and radiative fluxes and heating profiles. The cloud microphysics is strongly based on the ARM Microbase value added product (Miller et al., 2003). We have made a few changes to the microbase parameterizations to address issues we observed in our initial analysis of the tropical data. The merged sounding product is not directly related to the product developed by ARM but is similar in that it uses the microwave radiometer to scale the radiosonde column water vapor. The radiative fluxes also differ from the ARM BBHRP (Broadband Heating Rate Profile) product in terms of the radiative transfer model and the sampling interval.

Boundary Layer Thermodynamics and Cloud Microphysics for a Mixed Stratocumulus and Cumulus Cloud Field Observed during ACE-ENA

NASA Astrophysics Data System (ADS)

Jensen, M. P.; Miller, M. A.; Wang, J.

2017-12-01

The first Intensive Observation Period of the DOE Aerosol and Cloud Experiments in the Eastern North Atlantic (ACE-ENA) took place from 21 June through 20 July 2017 involving the deployment of the ARM Gulfstream-159 (G-1) aircraft with a suite of in situ cloud and aerosol instrumentation in the vicinity of the ARM Climate Research Facility Eastern North Atlantic (ENA) site on Graciosa Island, Azores. Here we present preliminary analysis of the thermodynamic characteristics of the marine boundary layer and the variability of cloud properties for a mixed cloud field including both stratiform cloud layers and deeper cumulus elements. Analysis combines in situ atmospheric state observations from the G-1 with radiosonde profiles and surface meteorology from the ENA site in order to characterize the thermodynamic structure of the marine boundary layer including the coupling state and stability. Cloud/drizzle droplet size distributions measured in situ are combined with remote sensing observations from a scanning cloud radar, and vertically pointing cloud radar and lidar provide quantification of the macrophysical and microphysical properties of the mixed cloud field.

Observing microphysical structures and hydrometeor phase in convection with ARM active sensors

NASA Astrophysics Data System (ADS)

Riihimaki, L.; Comstock, J. M.; Luke, E. P.; Thorsen, T. J.; Fu, Q.

2016-12-01

The existence and distribution of super-cooled liquid water within convective clouds impacts the microphysical processes responsible for cloud radiative and lifetime effects. Yet few observations of cloud phase are available within convection and associated stratiform anvils. Here we identify super-cooled liquid layers within convection and associated stratiform clouds using measured radar Doppler spectra from vertically pointing Ka-band cloud radar and Raman Lidar, capitalizing on the strengths of both instruments. Observations from these sensors are used to show that liquid exists in patches within the cloud, rather than in uniform layers, impacting the growth and formation of ice. While a depolarization lidar like the Raman Lidar is a trusted measurement for identifying super-cooled liquid, the lidar attenuates at an optical depth of around three, limiting its ability to probe the full cloud. The use of the radar Doppler spectra is particularly valuable for this purpose because it allows observations within optically thicker clouds. We demonstrate a new method for identifying super-cooled liquid objectively from the radar Doppler spectra using machine-learning techniques.

Hydrometeor Trajectories and Distributions in a Simulation of TC Rapid Intensification (RI)

NASA Astrophysics Data System (ADS)

Zhu, Z.; Zhu, P.

2010-12-01

It has long been recognized that the microphysics scheme used in a numerical simulation of tropical cyclones (TC) can greatly affect the precipitation distribution, intensity and thermodynamic structure of the simulated TC. This suggests that the mixing ratios, concentrations and size distributions of hydrometeor(snow, graupel,rain,cloud ice) are important factors in the evolution of TC . The transport of hydrometeor may have a strong influence on these factors through its interactions with the growth and the latent heat forcing of hydrometeor and the wind filed, hence is a key to understanding TC microphysics. Schematic hydrometeor trajectories were first constructed using 3-D wind field and particle fallspeeds derived from airborne radar observations in a steady-state mature hurricane,Alicia(1983). Since then, little effort has been put in understanding hydrometeor transport in TC, especially the potential link between its evolution and the intensity and structure changes in a non-steady-state TC. This study is focused on investigating such a link by means of numerical simulations of TC Rapid Intensification(RI) using WRF model. We use the tracer utility in WRF to construct hydrometeor trajectories. Most of the popular microphysics schemes are tested, and the most reasonable test( which is determined by comparing the simulated TC intensity and structure with airborne radar observations) and the ensemble mean of all the tests are picked for detailed examinations.

Large Contribution of Coarse Mode to Aerosol Microphysical and Optical Properties: Evidence from Ground-Based Observations of a Transpacific Dust Outbreak at a High-Elevation North American Site

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kassianov, E.; Pekour, M.; Flynn, C.

Our work is motivated by previous studies of the long-range trans-Atlantic transport of Saharan dust and the observed quasi-static nature of coarse mode aerosol with a volume median diameter (VMD) of approximately 3.5 µm. We examine coarse mode contributions from the trans-Pacific transport of Asian dust to North American aerosol microphysical and optical properties using a dataset collected at the high-elevation, mountain-top Storm Peak Laboratory (SPL, 3.22 km above sea level [ASL]) and the nearby Atmospheric Radiation Measurement (ARM) Mobile Facility (AMF, 2.76 km ASL). Data collected during the SPL Cloud Property Validation Experiment (STORMVEX, March 2011) are complemented bymore » quasi-global high-resolution model simulations coupled with aerosol chemistry. We identify dust event associated mostly with Asian plume (about 70% of dust mass) where the coarse mode with moderate (~4 µm) VMD is distinct and contributes substantially to aerosol microphysical (up to 70% for total volume) and optical (up to 45% for total scattering and aerosol optical depth) properties. Our results, when compared with previous Saharan dust studies, suggest a fairly invariant behavior of coarse mode dust aerosols. If confirmed in additional studies, this invariant behavior may simplify considerably model parameterizations for complex and size-dependent processes associated with dust transport and removal.« less

Magnetic neutron star cooling and microphysics

NASA Astrophysics Data System (ADS)

Potekhin, A. Y.; Chabrier, G.

2018-01-01

Aims: We study the relative importance of several recent updates of microphysics input to the neutron star cooling theory and the effects brought about by superstrong magnetic fields of magnetars, including the effects of the Landau quantization in their crusts. Methods: We use a finite-difference code for simulation of neutron-star thermal evolution on timescales from hours to megayears with an updated microphysics input. The consideration of short timescales (≲1 yr) is made possible by a treatment of the heat-blanketing envelope without the quasistationary approximation inherent to its treatment in traditional neutron-star cooling codes. For the strongly magnetized neutron stars, we take into account the effects of Landau quantization on thermodynamic functions and thermal conductivities. We simulate cooling of ordinary neutron stars and magnetars with non-accreted and accreted crusts and compare the results with observations. Results: Suppression of radiative and conductive opacities in strongly quantizing magnetic fields and formation of a condensed radiating surface substantially enhance the photon luminosity at early ages, making the life of magnetars brighter but shorter. These effects together with the effect of strong proton superfluidity, which slows down the cooling of kiloyear-aged neutron stars, can explain thermal luminosities of about a half of magnetars without invoking heating mechanisms. Observed thermal luminosities of other magnetars are still higher than theoretical predictions, which implies heating, but the effects of quantizing magnetic fields and baryon superfluidity help to reduce the discrepancy.

The Impact of Microphysics on Intensity and Structure of Hurricanes and Mesoscale Convective Systems

NASA Technical Reports Server (NTRS)

Tao, Wei-Kuo; Shi, Jainn J.; Jou, Ben Jong-Dao; Lee, Wen-Chau; Lin, Pay-Liam; Chang, Mei-Yu

2007-01-01

During the past decade, both research and operational numerical weather prediction models, e.g. Weather Research and Forecast (WRF) model, have started using more complex microphysical schemes originally developed for high-resolution cloud resolving models (CRMs) with a 1-2 km or less horizontal resolutions. WRF is a next-generation mesoscale forecast model and assimilation system that has incorporated modern software framework, advanced dynamics, numeric and data assimilation techniques, a multiple moveable nesting capability, and improved physical packages. WRF model can be used for a wide range of applications, from idealized research to operational forecasting, with an emphasis on horizontal grid sizes in the range of 1-10 km. The current WRF includes several different microphysics options such as Purdue Lin et al. (1983), WSM 6-class and Thompson microphysics schemes. We have recently implemented three sophisticated cloud microphysics schemes into WRF. The cloud microphysics schemes have been extensively tested and applied for different mesoscale systems in different geographical locations. The performances of these schemes have been compared to those from other WRF microphysics options. We are performing sensitivity tests in using WRF to examine the impact of six different cloud microphysical schemes on precipitation processes associated hurricanes and mesoscale convective systems developed at different geographic locations [Oklahoma (IHOP), Louisiana (Hurricane Katrina), Canada (C3VP - snow events), Washington (fire storm), India (Monsoon), Taiwan (TiMREX - terrain)]. We will determine the microphysical schemes for good simulated convective systems in these geographic locations. We are also performing the inline tracer calculation to comprehend the physical processes (i.e., boundary layer and each quadrant in the boundary layer) related to the development and structure of hurricanes and mesoscale convective systems.

Effect of sea breeze circulation on aerosol mixing state and radiative properties in a desert setting

NASA Astrophysics Data System (ADS)

Derimian, Yevgeny; Choël, Marie; Rudich, Yinon; Deboudt, Karine; Dubovik, Oleg; Laskin, Alexander; Legrand, Michel; Damiri, Bahaiddin; Koren, Ilan; Unga, Florin; Moreau, Myriam; Andreae, Meinrat O.; Karnieli, Arnon

2017-09-01

Chemical composition, microphysical, and optical properties of atmospheric aerosol deep inland in the Negev Desert of Israel are found to be influenced by daily occurrences of sea breeze flow from the Mediterranean Sea. Abrupt increases in aerosol volume concentration and shifts of size distributions towards larger sizes, which are associated with increase in wind speed and atmospheric water content, were systematically recorded during the summertime at a distance of at least 80 km from the coast. Chemical imaging of aerosol samples showed an increased contribution of highly hygroscopic particles during the intrusion of the sea breeze. Besides a significant fraction of marine aerosols, the amount of internally mixed marine and mineral dust particles was also increased during the sea breeze period. The number fraction of marine and internally mixed particles during the sea breeze reached up to 88 % in the PM1-2. 5 and up to 62 % in the PM2. 5-10 size range. Additionally, numerous particles with residuals of liquid coating were observed by SEM/EDX analysis. Ca-rich dust particles that had reacted with anthropogenic nitrates were evidenced by Raman microspectroscopy. The resulting hygroscopic particles can deliquesce at very low relative humidity. Our observations suggest that aerosol hygroscopic growth in the Negev Desert is induced by the daily sea breeze arrival. The varying aerosol microphysical and optical characteristics perturb the solar and thermal infrared radiations. The changes in aerosol properties induced by the sea breeze, relative to the background situation, doubled the shortwave radiative cooling at the surface (from -10 to -20.5 W m-2) and increased by almost 3 times the warming of the atmosphere (from 5 to 14 W m-2), as evaluated for a case study. Given the important value of observed liquid coating of particles, we also examined the possible influence of the particle homogeneity assumption on the retrieval of aerosol microphysical characteristics. The tests suggest that sensitivity to the coating appears if backward scattering and polarimetric measurements are available for the inversion algorithm. This may have an important implication for retrievals of aerosol microphysical properties in remote sensing applications.

UV Raman lidar measurements of relative humidity for the characterization of cirrus cloud microphysical properties

NASA Astrophysics Data System (ADS)

di Girolamo, P.; Summa, D.; Lin, R.-F.; Maestri, T.; Rizzi, R.; Masiello, G.

2009-11-01

Raman lidar measurements performed in Potenza by the Raman lidar system BASIL in the presence of cirrus clouds are discussed. Measurements were performed on 6 September 2004 in the frame of the Italian phase of the EAQUATE Experiment. The major feature of BASIL is represented by its capability to perform high-resolution and accurate measurements of atmospheric temperature and water vapour, and consequently relative humidity, both in daytime and night-time, based on the application of the rotational and vibrational Raman lidar techniques in the UV. BASIL is also capable to provide measurements of the particle backscatter and extinction coefficient, and consequently lidar ratio (at the time of these measurements, only at one wavelength), which are fundamental to infer geometrical and microphysical properties of clouds. A case study is discussed in order to assess the capability of Raman lidars to measure humidity in presence of cirrus clouds, both below and inside the cloud. While air inside the cloud layers is observed to be always under-saturated with respect to water, both ice super-saturation and under-saturation conditions are found inside these clouds. Upper tropospheric moistening is observed below the lower cloud layer. The synergic use of the data derived from the ground based Raman Lidar and of spectral radiances measured by the NAST-I Airborne Spectrometer allows the determination of the temporal evolution of the atmospheric cooling/heating rates due to the presence of the cirrus cloud. Lidar measurements beneath the cirrus cloud layer have been interpreted using a 1-D cirrus cloud model with explicit microphysics. The 1-D simulations indicate that sedimentation-moistening has contributed significantly to the moist anomaly, but other mechanisms are also contributing. This result supports the hypothesis that the observed mid-tropospheric humidification is a real feature which is strongly influenced by the sublimation of precipitating ice crystals. Results illustrated in this study demonstrate that Raman lidars, like the one used in this study, can resolve the spatial and temporal scales required for the study of cirrus cloud microphysical processes and appear sensitive enough to reveal and quantify upper tropospheric humidification associated with cirrus cloud sublimation.

UV Raman lidar measurements of relative humidity for the characterization of cirrus cloud microphysical properties

NASA Astrophysics Data System (ADS)

di Girolamo, P.; Summa, D.; Lin, R.-F.; Maestri, T.; Rizzi, R.; Masiello, G.

2009-07-01

Raman lidar measurements performed in Potenza by the Raman lidar system BASIL in the presence of cirrus clouds are discussed. Measurements were performed on 6 September 2004 in the frame of Italian phase of the EAQUATE Experiment. The major feature of BASIL is represented by its capability to perform high-resolution and accurate measurements of atmospheric temperature and water vapour, and consequently relative humidity, both in daytime and night-time, based on the application of the rotational and vibrational Raman lidar techniques in the UV. BASIL is also capable to provide measurements of the particle backscatter and extinction coefficient, and consequently lidar ratio (at the time of these measurements only at one wavelength), which are fundamental to infer geometrical and microphysical properties of clouds. A case study is discussed in order to assess the capability of Raman lidars to measure humidity in presence of cirrus clouds, both below and inside the cloud. While air inside the cloud layers is observed to be always under-saturated with respect to water, both ice super-saturation and under-saturation conditions are found inside these clouds. Upper tropospheric moistening is observed below the lower cloud layer. The synergic use of the data derived from the ground based Raman Lidar and of spectral radiances measured by the NAST-I Airborne Spectrometer allows to determine the temporal evolution of the atmospheric cooling/heating rates due to the presence of the cirrus cloud anvil. Lidar measurements beneath the cirrus cloud layer have been interpreted using a 1-D cirrus cloud model with explicit microphysics. The 1-D simulations indicates that sedimentation-moistening has contributed significantly to the moist anomaly, but other mechanisms are also contributing. This result supports the hypothesis that the observed mid-tropospheric humidification is a real feature which is strongly influenced by the sublimation of precipitating ice crystals. Results illustrated in this study demonstrate that Raman lidars, like the one used in this study, can resolve the spatial and temporal scales required for the study of cirrus cloud microphysical processes and appears sensitive enough to reveal and quantify upper tropospheric humidification associated with cirrus cloud sublimation.

Microphysical effects determine macrophysical response for aerosol impacts on deep convective clouds

NASA Astrophysics Data System (ADS)

Fan, Jiwen; Leung, L. Ruby; Rosenfeld, Daniel; Chen, Qian; Li, Zhanqing; Zhang, Jinqiang; Yan, Hongru

2013-11-01

Deep convective clouds (DCCs) play a crucial role in the general circulation, energy, and hydrological cycle of our climate system. Aerosol particles can influence DCCs by altering cloud properties, precipitation regimes, and radiation balance. Previous studies reported both invigoration and suppression of DCCs by aerosols, but few were concerned with the whole life cycle of DCC. By conducting multiple monthlong cloud-resolving simulations with spectral-bin cloud microphysics that capture the observed macrophysical and microphysical properties of summer convective clouds and precipitation in the tropics and midlatitudes, this study provides a comprehensive view of how aerosols affect cloud cover, cloud top height, and radiative forcing. We found that although the widely accepted theory of DCC invigoration due to aerosol's thermodynamic effect (additional latent heat release from freezing of greater amount of cloud water) may work during the growing stage, it is microphysical effect influenced by aerosols that drives the dramatic increase in cloud cover, cloud top height, and cloud thickness at the mature and dissipation stages by inducing larger amounts of smaller but longer-lasting ice particles in the stratiform/anvils of DCCs, even when thermodynamic invigoration of convection is absent. The thermodynamic invigoration effect contributes up to ∼27% of total increase in cloud cover. The overall aerosol indirect effect is an atmospheric radiative warming (3-5 Wṡm-2) and a surface cooling (-5 to -8 Wṡm-2). The modeling findings are confirmed by the analyses of ample measurements made at three sites of distinctly different environments.

Microphysical characteristics of squall-line stratiform precipitation and transition zones inferred using an ice particle property-evolving model

NASA Astrophysics Data System (ADS)

Jensen, A. A.; Harrington, J. Y.; Morrison, H.

2017-12-01

A quasi-idealized 3D squall line (based on a June 2007 Oklahoma case) is simulated using a novel bulk microphysics scheme called the Ice-Spheroids Habit Model with Aspect-ratio Evolution (ISHMAEL). In ISHMAEL, the evolution of ice particle properties, such as mass, shape, maximum diameter, density, and fall speed, are tracked as these properties evolve from vapor growth, sublimation, riming, and melting. Thus, ice properties evolve from various microphysical processes without needing separate unrimed and rimed ice categories. Simulation results show that ISHMAEL produces both a squall-line transition zone and an enhanced stratiform precipitation region. The ice particle properties produced in this simulation are analyzed and compared to observations to determine the characteristics of ice that lead to the development of these squall-line features. It is shown that rimed particles advected rearward from the convective region produce the enhanced stratiform precipitation region. The development of the transition zone results from hydrometer sorting: the evolution of ice particle properties in the convective region produces specific fall speeds that favor significant ice advecting rearward of the transition zone before reaching the melting level, causing a local minimum in precipitation rate and reflectivity there. Microphysical sensitivity studies, for example turning rime splintering off, that lead to changes in ice particle properties reveal that the fall speed of ice particles largely determines both the location of the enhanced stratiform precipitation region and whether or not a transition zone forms.

An evaluation of WRF microphysics schemes for simulating the warm-type heavy rain over the Korean peninsula

NASA Astrophysics Data System (ADS)

Song, Hwan-Jin; Sohn, Byung-Ju

2018-01-01

The Korean peninsula is the region of distinctly showing the heavy rain associated with relatively low storm height and small ice water content in the upper part of cloud system (i.e., so-called warm-type heavy rainfall). The satellite observations for the warmtype rain over Korea led to a conjecture that the cloud microphysics parameterization suitable for the continental deep convection may not work well for the warm-type heavy rainfall over the Korean peninsula. Therefore, there is a growing need to examine the performance of cloud microphysics schemes for simulating the warm-type heavy rain structures over the Korean peninsula. This study aims to evaluate the capabilities of eight microphysics schemes in the Weather Research and Forecasting (WRF) model how warmtype heavy rain structures can be simulated, in reference to the Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) reflectivity measurements. The results indicate that the WRF Double Moment 6-class (WDM6) scheme simulated best the vertical structure of warm-type heavy rain by virtue of a reasonable collisioncoalescence process between liquid droplets and the smallest amount of snow. Nonetheless the WDM6 scheme appears to have limitations that need to be improved upon for a realistic reflectivity structure, in terms of the reflectivity slope below the melting layer, discontinuity in reflectivity profiles around the melting layer, and overestimation of upper-level reflectivity due to high graupel content.

An Evaluation of WRF Microphysics Schemes for Simulating the Warm-Type Heavy Rain over the Korean Peninsula

NASA Astrophysics Data System (ADS)

Song, Hwan-Jin; Sohn, Byung-Ju

2018-05-01

The Korean peninsula is the region of distinctly showing the heavy rain associated with relatively low storm height and small ice water content in the upper part of cloud system (i.e., so-called warm-type heavy rainfall). The satellite observations for the warm-type rain over Korea led to a conjecture that the cloud microphysics parameterization suitable for the continental deep convection may not work well for the warm-type heavy rainfall over the Korean peninsula. Therefore, there is a growing need to examine the performance of cloud microphysics schemes for simulating the warm-type heavy rain structures over the Korean peninsula. This study aims to evaluate the capabilities of eight microphysics schemes in the Weather Research and Forecasting (WRF) model how warm-type heavy rain structures can be simulated, in reference to the Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) reflectivity measurements. The results indicate that the WRF Double Moment 6-class (WDM6) scheme simulated best the vertical structure of warm-type heavy rain by virtue of a reasonable collision-coalescence process between liquid droplets and the smallest amount of snow. Nonetheless the WDM6 scheme appears to have limitations that need to be improved upon for a realistic reflectivity structure, in terms of the reflectivity slope below the melting layer, discontinuity in reflectivity profiles around the melting layer, and overestimation of upper-level reflectivity due to high graupel content.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ovchinnikov, Mikhail; Ackerman, Andrew; Avramov, Alex

Large-eddy simulations of mixed-phase Arctic clouds by 11 different models are analyzed with the goal of improving understanding and model representation of processes controlling the evolution of these clouds. In a case based on observations from the Indirect and Semi-Direct Aerosol Campaign (ISDAC), it is found that ice number concentration, Ni, exerts significant influence on the cloud structure. Increasing Ni leads to a substantial reduction in liquid water path (LWP) and potential cloud dissipation, in agreement with earlier studies. By comparing simulations with the same microphysics coupled to different dynamical cores as well as the same dynamics coupled to differentmore » microphysics schemes, it is found that the ice water path (IWP) is mainly controlled by ice microphysics, while the inter-model differences in LWP are largely driven by physics and numerics of the dynamical cores. In contrast to previous intercomparisons, all models here use the same ice particle properties (i.e., mass-size, mass-fall speed, and mass-capacitance relationships) and a common radiation parameterization. The constrained setup exposes the importance of ice particle size distributions (PSD) in influencing cloud evolution. A clear separation in LWP and IWP predicted by models with bin and bulk microphysical treatments is documented and attributed primarily to the assumed shape of ice PSD used in bulk schemes. Compared to the bin schemes that explicitly predict the PSD, schemes assuming exponential ice PSD underestimate ice growth by vapor deposition and overestimate mass-weighted fall speed leading to an underprediction of IWP by a factor of two in the considered case.« less

Microphysical effects determine macrophysical response for aerosol impacts on deep convective clouds.

PubMed

Fan, Jiwen; Leung, L Ruby; Rosenfeld, Daniel; Chen, Qian; Li, Zhanqing; Zhang, Jinqiang; Yan, Hongru

2013-11-26

Deep convective clouds (DCCs) play a crucial role in the general circulation, energy, and hydrological cycle of our climate system. Aerosol particles can influence DCCs by altering cloud properties, precipitation regimes, and radiation balance. Previous studies reported both invigoration and suppression of DCCs by aerosols, but few were concerned with the whole life cycle of DCC. By conducting multiple monthlong cloud-resolving simulations with spectral-bin cloud microphysics that capture the observed macrophysical and microphysical properties of summer convective clouds and precipitation in the tropics and midlatitudes, this study provides a comprehensive view of how aerosols affect cloud cover, cloud top height, and radiative forcing. We found that although the widely accepted theory of DCC invigoration due to aerosol's thermodynamic effect (additional latent heat release from freezing of greater amount of cloud water) may work during the growing stage, it is microphysical effect influenced by aerosols that drives the dramatic increase in cloud cover, cloud top height, and cloud thickness at the mature and dissipation stages by inducing larger amounts of smaller but longer-lasting ice particles in the stratiform/anvils of DCCs, even when thermodynamic invigoration of convection is absent. The thermodynamic invigoration effect contributes up to ~27% of total increase in cloud cover. The overall aerosol indirect effect is an atmospheric radiative warming (3-5 W m(-2)) and a surface cooling (-5 to -8 W m(-2)). The modeling findings are confirmed by the analyses of ample measurements made at three sites of distinctly different environments.

Microphysical Analysis using Airborne 2-D Cloud and Precipitation Imaging Probe Data

NASA Astrophysics Data System (ADS)

Guy, N.; Jorgensen, D.; Witte, M.; Chuang, P. Y.; Black, R. A.

2013-12-01

The NOAA P-3 instrumented aircraft provided in-situ cloud and precipitation microphysical observations during the DYNAMO (Dynamics of the Madden-Julian Oscillation) field experiment. The Particle Measuring System 2D cloud (2D-C) and precipitation (2D-P) probes collected data for particles between 12.5 μm - 1.55 mm (25 μm resolution) and 100 μm - 6.2 mm (100 μm resolution), respectively. Spectra from each instrument were combined to provide a broad distribution of precipitation particle sizes. The 'method of moments' technique was used to analyze drop size distribution (DSD) spectra, which were modeled by fitting a three-parameter (slope, shape, and intercept) gamma distribution to the spectra. The characteristic shape of the mean spectrum compares to previous maritime measurements. DSD variability will be presented with respect to the temporal evolution of cloud populations during a Madden-Julian Oscillation (MJO) event, as well as in-situ aircraft vertical wind velocity measurements. Using the third and sixth moments, rainfall rate (R) and equivalent radar reflectivity factor (Z), respectively, were computed for each DSD. Linear regression was applied to establish a Z-R relationship for the data for the estimation of precipitation. The study indicated unique characteristics of microphysical processes for this region. These results are important to continue to define the cloud population characteristics in the climatological MJO region. Improved representation of the cloud characteristics on the microphysical scale will serve as a check to model parameterizations, helping to improve numerical simulations.

Aerosol indirect effects from ground-based retrievals over the rain shadow region in Indian subcontinent

NASA Astrophysics Data System (ADS)

Harikishan, G.; Padmakumari, B.; Maheskumar, R. S.; Pandithurai, G.; Min, Q. L.

2016-03-01

Aerosol-induced changes in cloud microphysical and radiative properties have been studied for the first time using ground-based and airborne observations over a semiarid rain shadow region. The study was conducted for nonprecipitating, ice-free clouds during monsoon (July to September) and postmonsoon (October) months, when cloud condensation nuclei (CCN) concentrations over the region of interest increased monotonically and exhibited characteristics of continental origin. A multifilter rotating shadowband radiometer and microwave radiometric profiler were used to retrieve the cloud optical depth and liquid water path (LWP), respectively, from which cloud effective radius (CER) was obtained. CER showed wide variability from 10-18 µm and a decreasing trend toward the postmonsoon period. During monsoon, the estimated first aerosol indirect effect (AIE) increased from 0.01 to 0.23 with increase in LWP. AIE at different super saturations (SS) showed maximum value (significant at 95%) at 0.4% SS and higher LWP bin (250-300 g/m2). Also, statistically significant AIE values were found at 0.6% and 0.8% SSs but at lower LWP bin (200-250 g/m2). The relationship between CCN and CER showed high correlation at 0.4% SS at higher LWP bin, while at higher SSs good correlations were observed at lower LWPs. Data combined from ground-based and aircraft observations showed dominance of microphysical effect at aerosol concentrations up to 1500 cm-3 and radiative effect at higher concentrations. This combined cloud microphysical and aerosol radiative effect is more prominent during postmonsoon period due to an increase in aerosol concentration.

High-Resolution NU-WRF Simulations of a Deep Convective-Precipitation System During MC3E. Part 1; Comparisons Between Goddard Microphysics Schemes and Observations

NASA Technical Reports Server (NTRS)

Tao, Wei-Kuo; Wu, Di; Lang, Stephen; Chern, Jiundar; Peters-Lidard, Christa; Fridlind, Ann; Matsui, Toshihisa

2015-01-01

The Goddard microphysics scheme was recently improved by adding a 4th ice class (frozen dropshail). This new 4ICE scheme was implemented and tested in the Goddard Cumulus Ensemble model (GCE) for an intense continental squall line and a moderate,less-organized continental case. Simulated peak radar reflectivity profiles were improved both in intensity and shape for both cases as were the overall reflectivity probability distributions versus observations. In this study, the new Goddard 4ICE scheme is implemented into the regional-scale NASA Unified - Weather Research and Forecasting model (NU-WRF) and tested on an intense mesoscale convective system that occurred during the Midlatitude Continental Convective Clouds Experiment (MC3E). The NU42WRF simulated radar reflectivities, rainfall intensities, and vertical and horizontal structure using the new 4ICE scheme agree as well as or significantly better with observations than when using previous versions of the Goddard 3ICE (graupel or hail) schemes. In the 4ICE scheme, the bin microphysics-based rain evaporation correction produces more erect convective cores, while modification of the unrealistic collection of ice by dry hail produces narrow and intense cores, allowing more slow-falling snow to be transported rearward. Together with a revised snow size mapping, the 4ICE scheme produces a more horizontally stratified trailing stratiform region with a broad, more coherent light rain area. In addition, the NU-WRF 4ICE simulated radar reflectivity distributions are consistent with and generally superior to those using the GCE due to the less restrictive open lateral boundaries

The diagnosis of severe thunderstorms with high-resolution WRF model

NASA Astrophysics Data System (ADS)

Litta, A. J.; Mohanty, U. C.; Idicula, Sumam Mary

2012-04-01

Thunderstorm, resulting from vigorous convective activity, is one of the most spectacular weather phenomena in the atmosphere. A common feature of the weather during the pre-monsoon season over the Indo-Gangetic Plain and northeast India is the outburst of severe local convective storms, commonly known as `Nor'westers'(as they move from northwest to southeast). The severe thunderstorms associated with thunder, squall lines, lightning and hail cause extensive losses in agricultural, damage to structure and also loss of life. In this paper, sensitivity experiments have been conducted with the Non-hydrostatic Mesoscale Model (NMM) to test the impact of three microphysical schemes in capturing the severe thunderstorm event occurred over Kolkata on 15 May 2009. The results show that the WRF-NMM model with Ferrier microphysical scheme appears to reproduce the cloud and precipitation processes more realistically than other schemes. Also, we have made an attempt to diagnose four severe thunderstorms that occurred during pre-monsoon seasons of 2006, 2007 and 2008 through the simulated radar reflectivity fields from NMM model with Ferrier microphysics scheme and validated the model results with Kolkata Doppler Weather Radar (DWR) observations. Composite radar reflectivity simulated by WRF-NMM model clearly shows the severe thunderstorm movement as observed by DWR imageries, but failed to capture the intensity as in observations. The results of these analyses demonstrated the capability of high resolution WRF-NMM model in the simulation of severe thunderstorm events and determined that the 3 km model improve upon current abilities when it comes to simulating severe thunderstorms over east Indian region.

Evaluation of Cloud-Resolving and Limited Area Model Intercomparison Simulations Using TWP-ICE Observations. Part 2 ; Precipitation Microphysics

NASA Technical Reports Server (NTRS)

Varble, Adam; Zipser, Edward J.; Fridland, Ann M.; Zhu, Ping; Ackerman, Andrew S.; Chaboureau, Jean-Pierre; Fan, Jiwen; Hill, Adrian; Shipway, Ben; Williams, Christopher

2014-01-01

Ten 3-D cloud-resolving model (CRM) simulations and four 3-D limited area model (LAM) simulations of an intense mesoscale convective system observed on 23-24 January 2006 during the Tropical Warm Pool-International Cloud Experiment (TWP-ICE) are compared with each other and with observations and retrievals from a scanning polarimetric radar, colocated UHF and VHF vertical profilers, and a Joss-Waldvogel disdrometer in an attempt to explain a low bias in simulated stratiform rainfall. Despite different forcing methodologies, similar precipitation microphysics errors appear in CRMs and LAMs with differences that depend on the details of the bulk microphysics scheme used. One-moment schemes produce too many small raindrops, which biases Doppler velocities low, but produces rainwater contents (RWCs) that are similar to observed. Two-moment rain schemes with a gamma shape parameter (mu) of 0 produce excessive size sorting, which leads to larger Doppler velocities than those produced in one-moment schemes but lower RWCs. Two-moment schemes also produce a convective median volume diameter distribution that is too broad relative to observations and, thus, may have issues balancing raindrop formation, collision-coalescence, and raindrop breakup. Assuming a mu of 2.5 rather than 0 for the raindrop size distribution improves one-moment scheme biases, and allowing mu to have values greater than 0 may improve excessive size sorting in two-moment schemes. Underpredicted stratiform rain rates are associated with underpredicted ice water contents at the melting level rather than excessive rain evaporation, in turn likely associated with convective detrainment that is too high in the troposphere and mesoscale circulations that are too weak. A limited domain size also prevents a large, well-developed stratiform region like the one observed from developing in CRMs, although LAMs also fail to produce such a region.

Modeling Aerosol Microphysical and Radiative Effects on Clouds and Implications for the Effects of Black and Brown Carbon on Clouds

NASA Astrophysics Data System (ADS)

Ten Hoeve, J. E.; Jacobson, M. Z.

2010-12-01

Satellite observational studies have found an increase in cloud fraction (CF) and cloud optical depth (COD) with increasing aerosol optical depth (AOD) followed by a decreasing CF/COD with increasing AOD at higher AODs over the Amazon Basin. The shape of this curve is similar to that of a boomerang, and thus the effect has been dubbed the "boomerang effect.” The increase in CF/COD with increasing AOD at low AODs is ascribed to the first and second indirect effects and is referred to as a microphysical effect of aerosols on clouds. The decrease in CF/COD at higher AODs is ascribed to enhanced warming of clouds due to absorbing aerosols, either as inclusions in drops or interstitially between drops. This is referred to as a radiative effect. To date, the interaction of the microphysical and radiative effects has not been simulated with a regional or global computer model. Here, we simulate the boomerang effect with the nested global-through-urban climate, air pollution, weather forecast model, GATOR-GCMOM, for the Amazon biomass burning season of 2006. We also compare the model with an extensive set of data, including satellite data from MODIS, TRMM, and CALIPSO, in situ surface observations, upper-air data, and AERONET data. Biomass burning emissions are obtained from the Global Fire Emissions Database (GFEDv2), and are combined with MODIS land cover data along with biomass burning emission factors. A high-resolution domain, nested within three increasingly coarser domains, is employed over the heaviest biomass burning region within the arc of deforestation. Modeled trends in cloud properties with aerosol loading compare well with MODIS observed trends, allowing causation of these observed correlations, including of the boomerang effect, to be determined by model results. The impact of aerosols on various cloud parameters, such as cloud optical thickness, cloud fraction, cloud liquid water/ice content, and precipitation, are shown through differences between simulations that include and exclude biomass burning emissions. This study suggests by cause and effect through numerical modeling that aerosol radiative effects counteract microphysical effects at high AODs, a result previously shown by correlation alone. As such, computer models that exclude treatment of cloud radiative effects are likely to overpredict the indirect effects of aerosols on clouds and underestimate the warming due to aerosols containing black carbon.

Meteorological and Aerosol effects on Marine Cloud Microphysical Properties

NASA Astrophysics Data System (ADS)

Sanchez, K. J.; Russell, L. M.; Modini, R. L.; Frossard, A. A.; Ahlm, L.; Roberts, G.; Hawkins, L. N.; Schroder, J. C.; Wang, Z.; Lee, A.; Abbatt, J.; Lin, J.; Nenes, A.; Wonaschuetz, A.; Sorooshian, A.; Noone, K.; Jonsson, H.; Albrecht, B. A.; Desiree, T. S.; Macdonald, A. M.; Seinfeld, J.; Zhao, R.

2015-12-01

Both meteorology and microphysics affect cloud formation and consequently their droplet distributions and shortwave reflectance. The Eastern Pacific Emitted Aerosol Cloud Experiment (EPEACE) and the Stratocumulus Observations of Los-Angeles Emissions Derived Aerosol-Droplets (SOLEDAD) studies provide detailed measurements in 6 case studies of both cloud thermodynamic properties and initial particle number distribution and composition, as well as the resulting cloud drop distribution and composition. This study uses simulations of a detailed chemical and microphysical aerosol-cloud parcel (ACP) model with explicit kinetic drop activation to reproduce the observed cloud droplet distribution and composition. Four of the cases examined had a sub-adiabatic lapse rate, which was shown to have fewer droplets due to decreased maximum supersaturation, lower LWC and higher cloud base height, consistent with previous findings. These detailed case studies provided measured thermodynamics and microphysics that constrained the simulated droplet size distribution sufficiently to match the droplet number within 6% and the size within 19% for 4 of the 6 cases, demonstrating "closure" or consistency of the measured composition with the measured CCN spectra and the inferred and modeled supersaturation. The contribution of organic components to droplet formation shows small effects on the droplet number and size in the 4 marine cases that had background aerosol conditions with varying amounts of coastal, ship or other non-biogenic sources. In contrast, the organic fraction and hygroscopicity increased the droplet number and size in the cases with generated smoke and cargo ship plumes that were freshly emitted and not yet internally mixed with the background particles. The simulation results show organic hygroscopicity causes small effects on cloud reflectivity (<0.7%) with the exception of the cargo ship plume and smoke plume which increased absolute cloud reflectivity fraction by 0.02 and 0.20 respectively. In addition, the ACP model simulations are compared to those from a numerical parameterization of cloud droplet activation that is suitable for GCMs and show droplet concentrations are comparable between the two methods.

The use of a potential lightning index in multi-microphysical cloud-resolving simulations of a V-shape convective system.

NASA Astrophysics Data System (ADS)

Lagasio, Martina; Parodi, Antonio; Procopio, Renato; Rachidi, Farhad; Fiori, Elisabetta

2017-04-01

Lightning activity is a characteristic phenomenon of severe weather as confirmed by many studies on different weather regimes that reveal strong interplay between lightning phenomena and extreme rainfall process in thunderstorms. The improvement of the so-called total (i.e. cloud-to-ground and intra-cloud) lightning observation systems in the last decades has allowed to investigate the relationship between the lightning flash rate and the kinematic and microphysical properties of severe hydro-meteorological events characterized by strong convection. V-shape back-building Mesoscale Convective Systems (MCSs) occurring over short periods of time have hit several times the Liguria region located in north-western Italy in the period between October 2010 and November 2014, generating flash-flood events responsible for hundreds of fatalities and millions of euros of damage. All these events showed an area of intense precipitation sweeping an arc of a few degrees around the warm conveyor belt originating about 50-60 km from the Liguria coastline. A second main ingredient was the presence of a convergence line, which supported the development and the maintenance of the aforementioned back-building process. Other common features were the persistence of such geometric configuration for many hours and the associated strong lightning activity. A methodological approach for the evaluation of these types of extreme rainfall and lightning convective events is presented for a back-building MCS event occurred in Genoa in 2014. A microphysics driven ensemble of WRF simulations at cloud-permitting grid spacing (1 km) with different microphysics parameterizations is used and compared to the available observational radar and lightning data. To pursue this aim, the performance of the Lightning Potential Index (LPI) as a measure of the potential for charge generation and separation that leads to lightning occurrence in clouds, is computed and analyzed to gain further physical insight in these V-shape convective processes and to understand its predictive ability.

Microphysical Analysis of a Warm Front Using and Linking Radar and In-Situ Data.

NASA Astrophysics Data System (ADS)

Keppas, S.

2017-12-01

The northward movement of the Azores anticyclone over the ENE coast of Canada on 20th January 2009 caused the formation of a well-organized low pressure system in North Atlantic Ocean. That system was followed by a trough which approached the UK from the WNW on 21st January 2009. The corresponding warm front affected the UK with multiple rainbands. We present an analysis of the microphysical properties of the afore-mentioned situation using radar and in-situ data. The ground-based radars are located in Chilbolton (South England) and operate at 3 and 35 GHz frequency. Chilbolton's radar high resolution (0.4 Km in vertical and 0.3 Km in horizontal dimension) and dual-polarization technology offers a view of the different features of the hydrometeors over large scales. The in-situ measurements have been taken during a flight over the SW England in the framework of the APPRAISE Clouds project, funded by the Natural Environment Research Council (NERC). The data from microphysical probes (CDP, 2D-S, CIP15, CIP100) provide a complete picture of hydrometeor properties (cloud droplets, ice particles and snow) are used for the microphysical analysis of this well- defined warm front. Using these datasets, features we try to identify and analyse regions, within mixed-phase clouds, of embedded convection, long ice fall streaks and the warm conveyor belt. We also try to explain the way that the warm conveyor belt affects the ice multiplication processes and the formation of some particular ice-particles, which we called ice-lollies due to their similarities in shape. The main goals of this work are: a. the identification and interpretation of areas with specific ice crystal habits by comparing radar and in-situ observations and b. the determination of the polarimetric and microphysical characteristics of a warm front.

An explicit microphysics thunderstorm model.

Treesearch

R. Solomon; C.M. Medaglia; C. Adamo; S. Dietrick; A. Mugnai; U. Biader Ceipidor

2005-01-01

The authors present a brief description of a 1.5-dimensional thunderstorm model with a lightning parameterization that utilizes an explicit microphysical scheme to model lightning-producing clouds. The main intent of this work is to describe the basic microphysical and electrical properties of the model, with a small illustrative section to show how the model may be...

Improving microphysics in a convective parameterization: possibilities and limitations

NASA Astrophysics Data System (ADS)

Labbouz, Laurent; Heikenfeld, Max; Stier, Philip; Morrison, Hugh; Milbrandt, Jason; Protat, Alain; Kipling, Zak

2017-04-01

The convective cloud field model (CCFM) is a convective parameterization implemented in the climate model ECHAM6.1-HAM2.2. It represents a population of clouds within each ECHAM-HAM model column, simulating up to 10 different convective cloud types with individual radius, vertical velocities and microphysical properties. Comparisons between CCFM and radar data at Darwin, Australia, show that in order to reproduce both the convective cloud top height distribution and the vertical velocity profile, the effect of aerodynamic drag on the rising parcel has to be considered, along with a reduced entrainment parameter. A new double-moment microphysics (the Predicted Particle Properties scheme, P3) has been implemented in the latest version of CCFM and is compared to the standard single-moment microphysics and the radar retrievals at Darwin. The microphysical process rates (autoconversion, accretion, deposition, freezing, …) and their response to changes in CDNC are investigated and compared to high resolution CRM WRF simulations over the Amazon region. The results shed light on the possibilities and limitations of microphysics improvements in the framework of CCFM and in convective parameterizations in general.

Workshop on Spanning Regional-to-Global Pollution

NASA Technical Reports Server (NTRS)

Thompson, Anne M.; Newman, Paul A.; Gleason, James F.; Brune, William H.; Dickerson, Russell R.

2002-01-01

Pollution is often considered a localized phenomenon, but it is now clear that it travels from region-to-region, country to country, and even continent to continent. In addition to urban pollution in developed countries, large emissions from developing nations and large-scale biomass fires add to the global pollution burden. Ozone and aerosols are two components of pollution that contribute to radiative forcing of the earth s climate. In turn, as climate changes, rates of chemical and microphysical reactions may be perturbed. Considering the earth as a coupled chemical-microphysical-climate system poses challenges for models and observations alike. These issues were the topic of a Workshop held in May 2002 at NASA GSFC s Laboratory for Atmospheres. Highlights of the Workshop are summarized in this article.

A macrophysical life cycle description for precipitating systems

NASA Astrophysics Data System (ADS)

Evaristo, Raquel; Xie, Xinxin; Troemel, Silke; Diederich, Malte; Simon, Juergen; Simmer, Clemens

2014-05-01

The lack of understanding of cloud and precipitation processes is still the overarching problem of climate simulation, and prediction. The work presented is part of the HD(CP)2 project (High Definition Clouds and Precipitation for Advancing Climate Predictions) which aims at building a very high resolution model in order to evaluate and exploit regional hindcasts for the purpose of parameterization development. To this end, an observational object-based climatology for precipitation systems will be built, and shall later be compared with a twin model-based climatological data base for pseudo precipitation events within an event-based model validation approach. This is done by identifying internal structures, described by means of macrophysical descriptors used to characterize the temporal development of tracked rain events. 2 pre-requisites are necessary for this: 1) a tracking algorithm, and 2) 3D radar/satellite composite. Both prerequisites are ready to be used, and have already been applied to a few case studies. Some examples of these macrophysical descriptors are differential reflectivity columns, bright band fraction and trend, cloud top heights, the spatial extent of updrafts or downdrafts or the ice content. We will show one case study from August 5th 2012, when convective precipitation was observed simultaneously by the BOXPOL and JUXPOL X-band polarimetric radars. We will follow the main paths identified by the tracking algorithm during this event and identify in the 3D composite the descriptors that characterize precipitation development, their temporal evolution, and the different macrophysical processes that are ultimately related to the precipitation observed. In a later stage these observations will be compared to the results of hydrometeor classification algorithm, in order to link the macrophysical and microphysical aspects of the storm evolution. The detailed microphysical processes are the subject of a closely related work also presented in this session: Microphysical processes observed by X band polarimetric radars during the evolution of storm systems, by Xinxin Xie et al.

Aerosol Impacts on California Winter Clouds and Precipitation during CalWater 2011: Local Pollution versus Long-Range Transported Dust

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fan, Jiwen; Leung, Lai-Yung R.; DeMott, Paul J.

2014-01-03

Mineral dust aerosols often observed over California in winter and spring, associated with long-range transport from Asia and Sahara, have been linked to enhanced precipitation based on observations. Local anthropogenic pollution, on the other hand, was shown in previous observational and modeling studies to reduce precipitation. Here we incorporate recent developments in ice nucleation parameterizations to link aerosols with ice crystal formation in a spectral-bin cloud microphysical model coupled with the Weather Research and Forecasting (WRF) model, to examine the relative and combined impacts of dust and local pollution particles on cloud properties and precipitation type and intensity. Simulations aremore » carried out for two cloud cases with contrasting meteorology and cloud dynamics that occurred on February 16 (FEB16) and March 02 (MAR02) from the CalWater 2011 field campaign. In both cases, observations show the presence of dust and biological particles in a relative pristine environment. The simulated cloud microphysical properties and precipitation show reasonable agreement with aircraft and surface measurements. Model sensitivity experiments indicate that in the pristine environment, the dust and biological aerosol layers increase the accumulated precipitation by 10-20% from the Central Valley to the Sierra Nevada Mountains for both FEB16 and MAR02 due to a ~40% increase in snow formation, validating the observational hypothesis. Model results show that local pollution increases precipitation over the windward slope of the mountains by few percent due to increased snow formation when dust is present but reduces precipitation by 5-8% if dust is removed on FEB16. The effects of local pollution on cloud microphysics and precipitation strongly depend on meteorology including the strength of the Sierra Barrier Jet, and cloud dynamics. This study further underscores the importance of the interactions between local pollution, dust, and environmental conditions for assessing aerosol effects on cold season precipitation in California.« less

The microphysical properties of convective precipitation over the Tibetan Plateau by a high-resolution cloud-resolving simulation

NASA Astrophysics Data System (ADS)

Gao, W.; Liu, L.; Hu, Z.

2017-12-01

The microphysical properties of precipitating convective systems over the Tibetan Plateau (TP) are unique because of the extremely high topography and special atmospheric conditions. In this study, the ground-based millimeter cloud radar and optical disdrometer observations during the Third Tibetan Plateau Atmospheric Scientific Experiment (TIPEX-III), and the high-resolution (600-m horizontal grid size) simulations with the Chinese Academy of Meteorological Sciences microphysics (CAMS) are used to investigate the microphysics and precipitation mechanism of a convection event on 24 July 2014. The model reasonably reproduces the spatial distribution of 24-h accumulated rainfall yet the temporal evolution of rainfall rate has a two hours delay. The simulated raindrop size distribution (RSD) is in general agreement with the disdrometer measurement, and the number concentration for small raindrop is a certain degree overestimated. The RSD over the TP is wider than that over plain at the same latitude, implying that the precipitation may be more easily produced in the former. Results demonstrate that the leading ice crystal microphysical processes are the depositional growth of ice crystal and autoconversion of ice crystal to snow. The dominant source term of snow/graupel in convection is the accretion of cloud water by snow/graupel (riming) due to the plentiful supercooled cloud water over there. Note that the accretion of snow by rain to form graupel has a great contribution to graupel number concentration as the existence of large liquid particles in cold region over the TP. In addition, the microphysics-produced graupel fall out completely through the sedimentation process and accumulate near the melting layer with the rate of 0.09 g kg-1s-1. They then melt immediately to form rain water in warm region and half of them can finally reach the ground to form precipitation (the rest evaporated). Furthermore, the water vapor budgets analyses reveal that the surface evaporation is the principal source of water vapor at the beginning of convection. While during the development of convection, the total vapor flux convergence (horizontal and vertical) supplies about 90% of the net condensation (condensation and deposition) and has the similar phase with the area-averaged rainfall rate, indicating its important role in TP convective precipitation.

The role of microphysics in the development of mesoscale areas of high winds around occluded cyclones

NASA Astrophysics Data System (ADS)

Baker, T. P.; Knippertz, P.; Blyth, A.

2012-04-01

Extratropical cyclones are an integral part of the weather in north-western Europe and can be associated with heavy precipitation and strong winds. While synoptic-scale aspects of these storms are often satisfactorily forecast several days in advance, mesoscale features within these systems such as bands of heavy rain or localized wind maxima, which are often the cause of the most damaging effects, are significantly less well understood and predicted by operational forecasts. Accurate predictions of the location, timing and intensity of these features are, however, highly important for the mitigation of the adverse effects that they bring. This is one of the motivations for the UK consortium DIAMET (DIAbatic influences on Mesoscale structures in ExtraTropical storms) that is focused on improving the understanding and predictability of these potentially damaging mesoscale features embedded within larger synoptic-scale extratropical storms. The project is based around a number of field campaigns using the Facility for Airborne Atmospheric Measurements (FAAM) BAe146 research aircraft along with other remote and in-situ measurements. An overview of the project will be presented by Geraint Vaughan in this session. This study analyses the effects of microphysics on the mesoscale dynamics within extratropical storms, in particular the high wind areas around occluded fronts wrapped around the core of a matured cyclonic storm. It has been hypothesized that evaporation and melting of hydrometeors in this region can lead to downward momentum transport and thereby increase near-surface winds (sometimes referred to as sting jets). The main tool for this study is the Weather Research and Forecasting (WRF) model. High-resolution simulations are run for several cases from the DIAMET field campaigns to examine how the development of strong winds around occluded fronts is affected by the microphysics. The model results using different microphysics schemes are compared with the observational data from the BAe146 aircraft and other sources such as wind profilers and radiosondes. In initial model simulations of a secondary frontal wave observed during the 2009 T-NAWDEX pilot flights, the microphysics in the parameterization scheme used has a large impact on the winds observed around the hook of the occlusion. The advanced double-moment Morrison and Thompson schemes show 12-hour mean 10m winds about 50% higher than the simpler WSM3 (WRF single moment) scheme in this area. These results suggest that ice processes could play an important role in the downward transport of momentum in this part of the cyclone. Further results from this and other cases from the field campaigns will be presented at the conference.

Long-delayed bright dancing sprite with large Horizontal displacement from its parent flash

NASA Astrophysics Data System (ADS)

Yang, Jing; Lu, Gaopeng; Lee, Li-Jou; Feng, Guili

2015-07-01

We reported in this paper the observation of a very bright long-delayed dancing sprite with distinct horizontal displacement from its parent stroke. The dancing sprite lasted only 60 ms, and the morphology consisted of three fields with two slim dim sprite elements in the first two fields and a very bright large element in the third field, different from other observations where the dancing sprites usually contained multiple elements over a longer time interval, and the sprite shape and brightness in the video field are often similar to the previous fields. The bright sprite was displaced at least 38 km from its parent cloud-to-ground (CG) stroke and occurred over comparatively higher cloud top region. The parent flash of this compact dancing sprite was of positive polarity, with only one return stroke (approximately +24 kA) and obvious continuing current process, and the charge moment change of stroke was small (barely above the threshold for sprite production). All the sprite elements occurred during the continuing current stage, and the bright long-delayed sprite element induced a considerable current pulse. The dancing feature of this sprite may be linked to the electrical charge structure, dynamics and microphysics of parent storm, and the inferred development of parent CG flash was consistent with previous very high-frequency (VHF) observations of lightning in the same region.

Progress Towards Achieving the Challenge of Indian Summer Monsoon Climate Simulation in a Coupled Ocean-Atmosphere Model

NASA Astrophysics Data System (ADS)

Hazra, Anupam; Chaudhari, Hemantkumar S.; Saha, Subodh Kumar; Pokhrel, Samir; Goswami, B. N.

2017-10-01

Simulation of the spatial and temporal structure of the monsoon intraseasonal oscillations (MISOs), which have effects on the seasonal mean and annual cycle of Indian summer monsoon (ISM) rainfall, remains a grand challenge for the state-of-the-art global coupled models. Biases in simulation of the amplitude and northward propagation of MISOs and related dry rainfall bias over ISM region in climate models are limiting the current skill of monsoon prediction. Recent observations indicate that the convective microphysics of clouds may be critical in simulating the observed MISOs. The hypothesis is strongly supported by high fidelity in simulation of the amplitude and space-time spectra of MISO by a coupled climate model, when our physically based modified cloud microphysics scheme is implemented in conjunction with a modified new Simple Arakawa Schubert (nSAS) convective parameterization scheme. Improved simulation of MISOs appears to have been aided by much improved simulation of the observed high cloud fraction and convective to stratiform rain fractions and resulted into a much improved simulation of the ISM rainfall, monsoon onset, and the annual cycle.

The Exoplanet Cloud Atlas

NASA Astrophysics Data System (ADS)

Gao, Peter; Marley, Mark S.; Morley, Caroline; Fortney, Jonathan J.

2017-10-01

Clouds have been readily inferred from observations of exoplanet atmospheres, and there exists great variability in cloudiness between planets, such that no clear trend in exoplanet cloudiness has so far been discerned. Equilibrium condensation calculations suggest a myriad of species - salts, sulfides, silicates, and metals - could condense in exoplanet atmospheres, but how they behave as clouds is uncertain. The behavior of clouds - their formation, evolution, and equilibrium size distribution - is controlled by cloud microphysics, which includes processes such as nucleation, condensation, and evaporation. In this work, we explore the cloudy exoplanet phase space by using a cloud microphysics model to simulate a suite of cloud species ranging from cooler condensates such as KCl/ZnS, to hotter condensates like perovskite and corundum. We investigate how the cloudiness and cloud particle sizes of exoplanets change due to variations in temperature, metallicity, gravity, and cloud formation mechanisms, and how these changes may be reflected in current and future observations. In particular, we will evaluate where in phase space could cloud spectral features be observable using JWST MIRI at long wavelengths, which will be dependent on the cloud particle size distribution and cloud species.

An observation of sea-spray microphysics by airborne Doppler radar

NASA Astrophysics Data System (ADS)

Fairall, C. W.; Pezoa, S.; Moran, K.; Wolfe, D.

2014-05-01

This paper describes observations and analysis of Doppler radar data from a down-looking 94 GHz (W-Band) system operated from a NOAA WP-3 Orion research aircraft in Tropical Storm (TS) Karen. The flight took place on 5 October 2013; Karen had weakened with maximum winds around 20 m s-1. Doppler spectral moments from the radar were processed to retrieve sea-spray microphysical properties (drop size and liquid water mass concentration) profiles in the height range 75-300 m above the sea surface. In the high wind speed regions of TS Karen (U10 > 15 m s-1), sea spray was observed with a nominal mass-mode radius of about 40 µm, a radar-weighted gravitational fall velocity of about 1 m s-1, and a mass concentration of about 10-3 gm-3 at 75 m. Spray-drop mass concentration declined with height to values of about 10-4 gm-3 at 300 m. Drop mass decreased slightly more slowly with increasing height than predicted by surface-layer similarity theory for a balance of turbulent diffusion vs fall velocity.

Understanding Ice Supersaturation, Particle Growth, and Number Concentration in Cirrus Clouds

NASA Technical Reports Server (NTRS)

Comstock, Jennifer M.; Lin, Ruei-Fong; Starr, David O'C.; Yang, Ping

2008-01-01

Many factors control the ice supersaturation and microphysical properties in cirrus clouds. We explore the effects of dynamic forcing, ice nucleation mechanisms, and ice crystal growth rate on the evolution and distribution of water vapor and cloud properties in nighttime cirrus clouds using a one-dimensional cloud model with bin microphysics and remote sensing measurements obtained at the Department of Energy's Atmospheric Radiation Measurement (ARM) Climate Research Facility located near Lamont, OK. We forced the model using both large-scale vertical ascent and, for the first time, mean mesoscale velocity derived from radar Doppler velocity measurements. Both heterogeneous and homogeneous nucleation processes are explored, where a classical theory heterogeneous scheme is compared with empirical representations. We evaluated model simulations by examining both bulk cloud properties and distributions of measured radar reflectivity, lidar extinction, and water vapor profiles, as well as retrieved cloud microphysical properties. Our results suggest that mesoscale variability is the primary mechanism needed to reproduce observed quantities. Model sensitivity to the ice growth rate is also investigated. The most realistic simulations as compared with observations are forced using mesoscale waves, include fast ice crystal growth, and initiate ice by either homogeneous or heterogeneous nucleation. Simulated ice crystal number concentrations (tens to hundreds particles per liter) are typically two orders of magnitude smaller than previously published results based on aircraft measurements in cirrus clouds, although higher concentrations are possible in isolated pockets within the nucleation zone.

Microphysical and Kinematic Characteristics of Regions of Flash Initiation in a Supercell Storm and a Multicell Storm Observed During the DC3 Field Program

NASA Astrophysics Data System (ADS)

DiGangi, E.; MacGorman, D. R.; Ziegler, C.; Betten, D.; Biggerstaff, M. I.

2017-12-01

Lightning initiation in thunderstorms requires that the local electric field magnitude exceed breakdown values somewhere, and this tends to occur between regions of positive and negative charge, where the largest electric field magnitudes tend to occur. Past studies have demonstrated that, near updrafts, storms with very strong updrafts tend to elevate regions of charge and of flash initiations higher, as well as to have more flashes initiated by small pockets of charge, than in storms with much weaker updrafts. In all thunderstorms, the source of these charge regions is generally thought to be microscopic charge separation via the relative growth rate noninductive mechanism, followed by macroscopic charge separation via sedimentation, although other charge generation mechanisms can contribute to charge in some regions. Charge generation and lightning initiation are therefore inherently dependent on the microphysical and kinematic characteristics of a given storm. This study compares the results of a hydrometeor classification algorithm applied to C-band mobile radar data with mixing ratios calculated by a diabatic Lagrangian analysis retrieval from the dual-Doppler wind fields for two storms, the 29-30 May 2012 supercell storm and the 21 June 2012 multicell storm, observed during the Deep Convective Clouds and Chemistry experiment. Using these data, we then compare the inferred microphysical and kinematic characteristics of regions in which the Oklahoma Lightning Mapping Array indicated that flashes were initiated in these two very different storms.

Simulation of particle size distributions in Polar Mesospheric Clouds from Microphysical Models

NASA Astrophysics Data System (ADS)

Thomas, G. E.; Merkel, A.; Bardeen, C.; Rusch, D. W.; Lumpe, J. D.

2009-12-01

The size distribution of ice particles is perhaps the most important observable aspect of microphysical processes in Polar Mesospheric Cloud (PMC) formation and evolution. A conventional technique to derive such information is from optical observation of scattering, either passive solar scattering from photometric or spectrometric techniques, or active backscattering by lidar. We present simulated size distributions from two state-of-the-art models using CARMA sectional microphysics: WACCM/CARMA, in which CARMA is interactively coupled with WACCM3 (Bardeen et al, 2009), and stand-alone CARMA forced by WACCM3 meteorology (Merkel et al, this meeting). Both models provide well-resolved size distributions of ice particles as a function of height, location and time for realistic high-latitude summertime conditions. In this paper we present calculations of the UV scattered brightness at multiple scattering angles as viewed by the AIM Cloud Imaging and Particle Size (CIPS) satellite experiment. These simulations are then considered discretely-sampled “data” for the scattering phase function, which are inverted using a technique (Lumpe et al, this meeting) to retrieve particle size information. We employ a T-matrix scattering code which applies to a wide range of non-sphericity of the ice particles, using the conventional idealized prolate/oblate spheroidal shape. This end-to-end test of the relatively new scattering phase function technique provides insight into both the retrieval accuracy and the information content in passive remote sensing of PMC.

Three dimensional modeling of cirrus during the 1991 FIRE IFO 2: Detailed process study

NASA Technical Reports Server (NTRS)

Jensen, Eric J.; Toon, Owen B.; Westphal, Douglas L.

1993-01-01

A three-dimensional model of cirrus cloud formation and evolution, including microphysical, dynamical, and radiative processes, was used to simulate cirrus observed in the FIRE Phase 2 Cirrus field program (13 Nov. - 7 Dec. 1991). Sulfate aerosols, solution drops, ice crystals, and water vapor are all treated as interactive elements in the model. Ice crystal size distributions are fully resolved based on calculations of homogeneous freezing of solution drops, growth by water vapor deposition, evaporation, aggregation, and vertical transport. Visible and infrared radiative fluxes, and radiative heating rates are calculated using the two-stream algorithm described by Toon et al. Wind velocities, diffusion coefficients, and temperatures were taken from the MAPS analyses and the MM4 mesoscale model simulations. Within the model, moisture is transported and converted to liquid or vapor by the microphysical processes. The simulated cloud bulk and microphysical properties are shown in detail for the Nov. 26 and Dec. 5 case studies. Comparisons with lidar, radar, and in situ data are used to determine how well the simulations reproduced the observed cirrus. The roles played by various processes in the model are described in detail. The potential modes of nucleation are evaluated, and the importance of small-scale variations in temperature and humidity are discussed. The importance of competing ice crystal growth mechanisms (water vapor deposition and aggregation) are evaluated based on model simulations. Finally, the importance of ice crystal shape for crystal growth and vertical transport of ice are discussed.

Observations and Modeling of the Green Ocean Amazon 2014/15. CHUVA Field Campaign Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Machado, L. A. T.

2016-03-01

The physical processes inside clouds are one of the most unknown components of weather and climate systems. A description of cloud processes through the use of standard meteorological parameters in numerical models has to be strongly improved to accurately describe the characteristics of hydrometeors, latent heating profiles, radiative balance, air entrainment, and cloud updrafts and downdrafts. Numerical models have been improved to run at higher spatial resolutions where it is necessary to explicitly describe these cloud processes. For instance, to analyze the effects of global warming in a given region it is necessary to perform simulations taking into account allmore » of the cloud processes described above. Another important application that requires this knowledge is satellite precipitation estimation. The analysis will be performed focusing on the microphysical evolution and cloud life cycle, different precipitation estimation algorithms, the development of thunderstorms and lightning formation, processes in the boundary layer, and cloud microphysical modeling. This project intends to extend the knowledge of these cloud processes to reduce the uncertainties in precipitation estimation, mainly from warm clouds, and, consequently, improve knowledge of the water and energy budget and cloud microphysics.« less

Impact of convection on stratospheric humidity and upper tropospheric clouds

NASA Astrophysics Data System (ADS)

Ueyama, R.; Schoeberl, M. R.; Jensen, E. J.; Pfister, L.; Avery, M. A.

2017-12-01

The role of convection on stratospheric water vapor and upper tropospheric cloud fraction is investigated using two sets of complementary transport and microphysical models driven by MERRA-2 and ERA-Interim meteorological analyses: (1) computationally efficient ensembles of forward trajectories with simplified cloud microphysics, and (2) one-dimensional simulations with detailed microphysics along back trajectories. Convective influence along the trajectories is diagnosed based on TRMM/GPM rainfall products and geostationary infrared satellite cloud-top measurements, with convective cloud-top height adjusted to match the CloudSat, CALIPSO, and CATS measurements. We evaluate and constrain the model results by comparison with satellite observations (e.g., Aura MLS, CALIPSO CALIOP) and high-altitude aircraft campaigns (e.g., ATTREX, POSIDON). Convection moistens the lower stratosphere by approximately 10-15% and increases the cloud fraction in the upper troposphere by 35-50%. Convective moistening is dominated by the saturating effect of parcels; convectively-lofted ice has a negligible impact on lower stratospheric humidity. We also find that the highest convective clouds have a disproportionately large impact on stratospheric water vapor because stratospheric relative humidity is low. Implications of these model results on the role of convection on present and future climate will be discussed.

Evaluation of Warm-Rain Microphysical Parameterizations in Cloudy Boundary Layer Transitions

NASA Astrophysics Data System (ADS)

Nelson, K.; Mechem, D. B.

2014-12-01

Common warm-rain microphysical parameterizations used for marine boundary layer (MBL) clouds are either tuned for specific cloud types (e.g., the Khairoutdinov and Kogan 2000 parameterization, "KK2000") or are altogether ill-posed (Kessler 1969). An ideal microphysical parameterization should be "unified" in the sense of being suitable across MBL cloud regimes that include stratocumulus, cumulus rising into stratocumulus, and shallow trade cumulus. The recent parameterization of Kogan (2013, "K2013") was formulated for shallow cumulus but has been shown in a large-eddy simulation environment to work quite well for stratocumulus as well. We report on our efforts to implement and test this parameterization into a regional forecast model (NRL COAMPS). Results from K2013 and KK2000 are compared with the operational Kessler parameterization for a 5-day period of the VOCALS-REx field campaign, which took place over the southeast Pacific. We focus on both the relative performance of the three parameterizations and also on how they compare to the VOCALS-REx observations from the NOAA R/V Ronald H. Brown, in particular estimates of boundary-layer depth, liquid water path (LWP), cloud base, and area-mean precipitation rate obtained from C-band radar.

A study on the entrainment and mixing process in the continental stratocumulus clouds measured during the RACORO campaign

DOE PAGES

Yeom, Jae Min; Yum, Seong Soo; Liu, Yangang; ...

2017-04-20

Entrainment and mixing processes and their effects on cloud microphysics in the continental stratocumulus clouds observed in Oklahoma during the RACORO campaign are analyzed in the frame of homogeneous and inhomogeneous mixing concepts by combining the approaches of microphysical correlation, mixing diagram, and transition scale (number). A total of 110 horizontally penetrated cloud segments is analyzed in this paper. Mixing diagram and cloud microphysical relationship analyses show homogeneous mixing trait of positive relationship between liquid water content (L) and mean volume of droplets (V) (i.e., smaller droplets in more diluted parcel) in most cloud segments. Relatively small temperature and humiditymore » differences between the entraining air from above the cloud top and cloudy air and relatively large turbulent dissipation rate are found to be responsible for this finding. The related scale parameters (i.e., transition length and transition scale number) are relatively large, which also indicates high likelihood of homogeneous mixing. Finally, clear positive relationship between L and vertical velocity (W) for some cloud segments is suggested to be evidence of vertical circulation mixing, which may further enhance the positive relationship between L and V created by homogeneous mixing.« less

Simulation of Asia Dust and Cloud Interaction Over Pacific Ocean During Pacdex

NASA Astrophysics Data System (ADS)

Long, X.; Huang, J.; Cheng, C.; Wang, W.

2007-12-01

The effect of dust plume on the Pacific cloud systems and the associated radiative forcing is an outstanding problem for understanding climate change. Many studies showing that dust aerosol might be a good absorber for solar radiation, at the same time dust aerosols could affect the cloud's formation and precipitation by its capability as cloud condensation nuclei (CCN) and ice forming nuclei (IFN). But the role of aerosols in clouds and precipitation is very complex. Simulation of interaction between cloud and dust aerosols requires recognition that the aerosol cloud system comprises coupled components of dynamics, aerosol and cloud microphysics, radiation processes. In this study, we investigated the interaction between dust aerosols and cloud with WRF which coupled with detailed cloud microphysics processes and dust process. The observed data of SACOL (Semi-Arid Climate and Environment Observatory of Lanzhou University) and PACDEX (Pacific Dust Experiment) is used as the initialization which include the vertical distributions and concentration of dust particles. Our results show that dust aerosol not only impacts cloud microphysical processes but also cloud microstructure; Dust aerosols can act as effective ice nuclei and intensify the ice-forming processes.

Microphysics, Radiation and Surface Processes in the Goddard Cumulus Ensemble (GCE) Model

NASA Technical Reports Server (NTRS)

Tao, Wei-Kuo; Simpson, J.; Baker, D.; Braun, S.; Chou, M.-D.; Ferrier, B.; Johnson, D.; Khain, A.; Lang, S.; Lynn, B.

2001-01-01

The response of cloud systems to their environment is an important link in a chain of processes responsible for monsoons, frontal depression, El Nino Southern Oscillation (ENSO) episodes and other climate variations (e.g., 30-60 day intra-seasonal oscillations). Numerical models of cloud properties provide essential insights into the interactions of clouds with each other, with their surroundings, and with land and ocean surfaces. Significant advances are currently being made in the modeling of rainfall and rain-related cloud processes, ranging in scales from the very small up to the simulation of an extensive population of raining cumulus clouds in a tropical- or midlatitude-storm environment. The Goddard Cumulus Ensemble (GCE) model is a multi-dimensional nonhydrostatic dynamic/microphysical cloud resolving model. It has been used to simulate many different mesoscale convective systems that occurred in various geographic locations. In this paper, recent GCE model improvements (microphysics, radiation and surface processes) will be described as well as their impact on the development of precipitation events from various geographic locations. The performance of these new physical processes will be examined by comparing the model results with observations. In addition, the explicit interactive processes between cloud, radiation and surface processes will be discussed.

A study on the entrainment and mixing process in the continental stratocumulus clouds measured during the RACORO campaign

NASA Astrophysics Data System (ADS)

Yeom, Jae Min; Yum, Seong Soo; Liu, Yangang; Lu, Chunsong

2017-09-01

Entrainment and mixing processes and their effects on cloud microphysics in the continental stratocumulus clouds observed in Oklahoma during the RACORO campaign are analyzed in the frame of homogeneous and inhomogeneous mixing concepts by combining the approaches of microphysical correlation, mixing diagram, and transition scale (number). A total of 110 horizontally penetrated cloud segments is analyzed. Mixing diagram and cloud microphysical relationship analyses show homogeneous mixing trait of positive relationship between liquid water content (L) and mean volume of droplets (V) (i.e., smaller droplets in more diluted parcel) in most cloud segments. Relatively small temperature and humidity differences between the entraining air from above the cloud top and cloudy air and relatively large turbulent dissipation rate are found to be responsible for this finding. The related scale parameters (i.e., transition length and transition scale number) are relatively large, which also indicates high likelihood of homogeneous mixing. Clear positive relationship between L and vertical velocity (W) for some cloud segments is suggested to be evidence of vertical circulation mixing, which may further enhance the positive relationship between L and V created by homogeneous mixing.

A study on the entrainment and mixing process in the continental stratocumulus clouds measured during the RACORO campaign

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yeom, Jae Min; Yum, Seong Soo; Liu, Yangang

Entrainment and mixing processes and their effects on cloud microphysics in the continental stratocumulus clouds observed in Oklahoma during the RACORO campaign are analyzed in the frame of homogeneous and inhomogeneous mixing concepts by combining the approaches of microphysical correlation, mixing diagram, and transition scale (number). A total of 110 horizontally penetrated cloud segments is analyzed in this paper. Mixing diagram and cloud microphysical relationship analyses show homogeneous mixing trait of positive relationship between liquid water content (L) and mean volume of droplets (V) (i.e., smaller droplets in more diluted parcel) in most cloud segments. Relatively small temperature and humiditymore » differences between the entraining air from above the cloud top and cloudy air and relatively large turbulent dissipation rate are found to be responsible for this finding. The related scale parameters (i.e., transition length and transition scale number) are relatively large, which also indicates high likelihood of homogeneous mixing. Finally, clear positive relationship between L and vertical velocity (W) for some cloud segments is suggested to be evidence of vertical circulation mixing, which may further enhance the positive relationship between L and V created by homogeneous mixing.« less

Quantification of uncertainty in aerosol optical thickness retrieval arising from aerosol microphysical model and other sources, applied to Ozone Monitoring Instrument (OMI) measurements

NASA Astrophysics Data System (ADS)

Määttä, A.; Laine, M.; Tamminen, J.; Veefkind, J. P.

2014-05-01

Satellite instruments are nowadays successfully utilised for measuring atmospheric aerosol in many applications as well as in research. Therefore, there is a growing need for rigorous error characterisation of the measurements. Here, we introduce a methodology for quantifying the uncertainty in the retrieval of aerosol optical thickness (AOT). In particular, we concentrate on two aspects: uncertainty due to aerosol microphysical model selection and uncertainty due to imperfect forward modelling. We apply the introduced methodology for aerosol optical thickness retrieval of the Ozone Monitoring Instrument (OMI) on board NASA's Earth Observing System (EOS) Aura satellite, launched in 2004. We apply statistical methodologies that improve the uncertainty estimates of the aerosol optical thickness retrieval by propagating aerosol microphysical model selection and forward model error more realistically. For the microphysical model selection problem, we utilise Bayesian model selection and model averaging methods. Gaussian processes are utilised to characterise the smooth systematic discrepancies between the measured and modelled reflectances (i.e. residuals). The spectral correlation is composed empirically by exploring a set of residuals. The operational OMI multi-wavelength aerosol retrieval algorithm OMAERO is used for cloud-free, over-land pixels of the OMI instrument with the additional Bayesian model selection and model discrepancy techniques introduced here. The method and improved uncertainty characterisation is demonstrated by several examples with different aerosol properties: weakly absorbing aerosols, forest fires over Greece and Russia, and Sahara desert dust. The statistical methodology presented is general; it is not restricted to this particular satellite retrieval application.

Remote Sensing the Vertical Profile of Cloud Droplet Effective Radius, Thermodynamic Phase, and Temperature

NASA Technical Reports Server (NTRS)

Martins, J. V.; Marshak, A.; Remer, L. A.; Rosenfeld, D.; Kaufman, Y. J.; Fernandez-Borda, R.; Koren, I.; Correia, A. L.; Zubko, V.; Artaxo, P.

2011-01-01

Cloud-aerosol interaction is a key issue in the climate system, affecting the water cycle, the weather, and the total energy balance including the spatial and temporal distribution of latent heat release. Information on the vertical distribution of cloud droplet microphysics and thermodynamic phase as a function of temperature or height, can be correlated with details of the aerosol field to provide insight on how these particles are affecting cloud properties and their consequences to cloud lifetime, precipitation, water cycle, and general energy balance. Unfortunately, today's experimental methods still lack the observational tools that can characterize the true evolution of the cloud microphysical, spatial and temporal structure in the cloud droplet scale, and then link these characteristics to environmental factors and properties of the cloud condensation nuclei. Here we propose and demonstrate a new experimental approach (the cloud scanner instrument) that provides the microphysical information missed in current experiments and remote sensing options. Cloud scanner measurements can be performed from aircraft, ground, or satellite by scanning the side of the clouds from the base to the top, providing us with the unique opportunity of obtaining snapshots of the cloud droplet microphysical and thermodynamic states as a function of height and brightness temperature in clouds at several development stages. The brightness temperature profile of the cloud side can be directly associated with the thermodynamic phase of the droplets to provide information on the glaciation temperature as a function of different ambient conditions, aerosol concentration, and type. An aircraft prototype of the cloud scanner was built and flew in a field campaign in Brazil.

Assessment of biomass burning smoke influence on environmental conditions for multi-year tornado outbreaks by combining aerosol-aware microphysics and fire emission constraints.

PubMed

Saide, Pablo E; Thompson, Gregory; Eidhammer, Trude; da Silva, Arlindo M; Pierce, R Bradley; Carmichael, Gregory R

2016-09-16

We use the WRF system to study the impacts of biomass burning smoke from Central America on several tornado outbreaks occurring in the US during spring. The model is configured with an aerosol-aware microphysics parameterization capable of resolving aerosol-cloud-radiation interactions in a cost-efficient way for numerical weather prediction (NWP) applications. Primary aerosol emissions are included and smoke emissions are constrained using an inverse modeling technique and satellite-based AOD observations. Simulations turning on and off fire emissions reveal smoke presence in all tornado outbreaks being studied and show an increase in aerosol number concentrations due to smoke. However, the likelihood of occurrence and intensification of tornadoes is higher due to smoke only in cases where cloud droplet number concentration in low level clouds increases considerably in a way that modifies the environmental conditions where the tornadoes are formed (shallower cloud bases and higher low-level wind shear). Smoke absorption and vertical extent also play a role, with smoke absorption at cloud-level tending to burn-off clouds and smoke absorption above clouds resulting in an increased capping inversion. Comparing these and WRF-Chem simulations configured with a more complex representation of aerosol size and composition and different optical properties, microphysics and activation schemes, we find similarities in terms of the simulated aerosol optical depths and aerosol impacts on near-storm environments. This provides reliability on the aerosol-aware microphysics scheme as a less computationally expensive alternative to WRF-Chem for its use in applications such as NWP and cloud-resolving simulations.

Assessment of Biomass Burning Smoke Influence on Environmental Conditions for Multi-Year Tornado Outbreaks by Combining Aerosol-Aware Microphysics and Fire Emission Constraints

NASA Technical Reports Server (NTRS)

Saide, Pablo E.; Thompson, Gregory; Eidhammer, Trude; Da Silva, Arlindo M.; Pierce, R. Bradley; Carmichael, Gregory R.

2016-01-01

We use the WRF system to study the impacts of biomass burning smoke from Central America on several tornado outbreaks occurring in the US during spring. The model is configured with an aerosol-aware microphysics parameterization capable of resolving aerosol-cloud-radiation interactions in a cost-efficient way for numerical weather prediction (NWP) applications. Primary aerosol emissions are included and smoke emissions are constrained using an inverse modeling technique and satellite-based AOD observations. Simulations turning on and off fire emissions reveal smoke presence in all tornado outbreaks being studied and show an increase in aerosol number concentrations due to smoke. However, the likelihood of occurrence and intensification of tornadoes is higher due to smoke only in cases where cloud droplet number concentration in low level clouds increases considerably in a way that modifies the environmental conditions where the tornadoes are formed (shallower cloud bases and higher low-level wind shear). Smoke absorption and vertical extent also play a role, with smoke absorption at cloud-level tending to burn-off clouds and smoke absorption above clouds resulting in an increased capping inversion. Comparing these and WRF-Chem simulations configured with a more complex representation of aerosol size and composition and different optical properties, microphysics and activation schemes, we find similarities in terms of the simulated aerosol optical depths and aerosol impacts on near-storm environments. This provides reliability on the aerosol-aware microphysics scheme as a less computationally expensive alternative to WRFChem for its use in applications such as NWP and cloud-resolving simulations.

Microphysical effects determine macrophysical response for aerosol impacts on deep convective clouds

PubMed Central

Fan, Jiwen; Leung, L. Ruby; Rosenfeld, Daniel; Chen, Qian; Li, Zhanqing; Zhang, Jinqiang; Yan, Hongru

2013-01-01

Deep convective clouds (DCCs) play a crucial role in the general circulation, energy, and hydrological cycle of our climate system. Aerosol particles can influence DCCs by altering cloud properties, precipitation regimes, and radiation balance. Previous studies reported both invigoration and suppression of DCCs by aerosols, but few were concerned with the whole life cycle of DCC. By conducting multiple monthlong cloud-resolving simulations with spectral-bin cloud microphysics that capture the observed macrophysical and microphysical properties of summer convective clouds and precipitation in the tropics and midlatitudes, this study provides a comprehensive view of how aerosols affect cloud cover, cloud top height, and radiative forcing. We found that although the widely accepted theory of DCC invigoration due to aerosol’s thermodynamic effect (additional latent heat release from freezing of greater amount of cloud water) may work during the growing stage, it is microphysical effect influenced by aerosols that drives the dramatic increase in cloud cover, cloud top height, and cloud thickness at the mature and dissipation stages by inducing larger amounts of smaller but longer-lasting ice particles in the stratiform/anvils of DCCs, even when thermodynamic invigoration of convection is absent. The thermodynamic invigoration effect contributes up to ∼27% of total increase in cloud cover. The overall aerosol indirect effect is an atmospheric radiative warming (3–5 W⋅m−2) and a surface cooling (−5 to −8 W⋅m−2). The modeling findings are confirmed by the analyses of ample measurements made at three sites of distinctly different environments. PMID:24218569

Aerosol microphysical and radiative effects on continental cloud ensembles

NASA Astrophysics Data System (ADS)

Wang, Yuan; Vogel, Jonathan M.; Lin, Yun; Pan, Bowen; Hu, Jiaxi; Liu, Yangang; Dong, Xiquan; Jiang, Jonathan H.; Yung, Yuk L.; Zhang, Renyi

2018-02-01

Aerosol-cloud-radiation interactions represent one of the largest uncertainties in the current climate assessment. Much of the complexity arises from the non-monotonic responses of clouds, precipitation and radiative fluxes to aerosol perturbations under various meteorological conditions. In this study, an aerosol-aware WRF model is used to investigate the microphysical and radiative effects of aerosols in three weather systems during the March 2000 Cloud Intensive Observational Period campaign at the US Southern Great Plains. Three simulated cloud ensembles include a low-pressure deep convective cloud system, a collection of less-precipitating stratus and shallow cumulus, and a cold frontal passage. The WRF simulations are evaluated by several ground-based measurements. The microphysical properties of cloud hydrometeors, such as their mass and number concentrations, generally show monotonic trends as a function of cloud condensation nuclei concentrations. Aerosol radiative effects do not influence the trends of cloud microphysics, except for the stratus and shallow cumulus cases where aerosol semi-direct effects are identified. The precipitation changes by aerosols vary with the cloud types and their evolving stages, with a prominent aerosol invigoration effect and associated enhanced precipitation from the convective sources. The simulated aerosol direct effect suppresses precipitation in all three cases but does not overturn the aerosol indirect effect. Cloud fraction exhibits much smaller sensitivity (typically less than 2%) to aerosol perturbations, and the responses vary with aerosol concentrations and cloud regimes. The surface shortwave radiation shows a monotonic decrease by increasing aerosols, while the magnitude of the decrease depends on the cloud type.

Correlations among the Optical Properties of Cirrus-Cloud Particles: Microphysical Interpretation

NASA Technical Reports Server (NTRS)

Reichardt, J.; Reichardt, S.; Hess, M.; McGee, T. J.; Bhartia, P. K. (Technical Monitor)

2002-01-01

Cirrus measurements obtained with a ground-based polarization Raman lidar at 67.9 deg N in January 1997 reveal a strong positive correlation between the particle optical properties, specifically depolarization ratio delta(sub par) and extinction- to-backscatter (lidar) ratio S, for delta(sub par) less than approximately 40%, and an anti-correlation for delta(sub par) greater than approximately 40%. Over the length of the measurements the particle properties vary systematically. Initially, delta (sub par) approximately equals 60% and S approximately equals 10sr are observed. Then, with decreasing delta(sub par), S first increases to approximately 27sr (delta(sub par) approximately equals 40%) before decreasing to values around 10sr again (delta(sub par) approximately equals 20%). The analysis of lidar humidity and radiosonde temperature data shows that the measured optical properties stem from scattering by dry solid ice particles, while scattering by supercooled droplets, or by wetted or subliming ice particles can be excluded. For the microphysical interpretation of the lidar measurements, ray-tracing computations of particle scattering properties have been used. The comparison with the theoretical data suggests that the observed cirrus data can be interpreted in terms of size, shape, and, under the assumption that the lidar measurements of consecutive cloud segments can be mapped on the temporal development of a single cloud parcel moving along its trajectory, growth of the cirrus particles: Near the cloud top in the early stage of cirrus development, light scattering by nearly isometric particles that have the optical characteristics of hexagonal columns (short, column-like particles) is dominant. Over time the ice particles grow, and as the cloud base height extends to lower altitudes characterized by warmer temperatures they become morphologically diverse. For large S and depolarization values of approximately 40%, the scattering contributions of column- and plate-like particles are roughly the same. In the lower ranges of the cirrus clouds, light scattering is predominantly by plate-like ice particles. This interpretation assumes random orientation of the cirrus particles. Simulations with a simple model suggest, however, that the positive correlation between S and delta(sub par) which is observed for depolarization ratios less than 40% mainly at low cloud altitudes, can be alternatively explained by horizontal alignment of a fraction of the cirrus particle population.

Investigation of fog structure affected by gravity waves and turbulence in the mountainous region of Pyeongchang, Korea, the place for the 2018 Winter Olympics and Paralympics

NASA Astrophysics Data System (ADS)

La, I.; Yum, S. S.; Yeom, J. M.; Gultepe, I.

2017-12-01

Since microphysical and dynamical processes of fog are not well-known and have non-linear relationships among processes that are related to fog formation, improving the accuracy of the fog forecasting/nowcasting system is challenging. For these reasons, understanding the fog mechanism is needed to develop the fog forecasting system. So, we focus on understanding fog-turbulence interactions and fog-gravity wave interactions. Many studies noted that turbulence plays important roles in fog. However, a discrepancy between arguments for the effect of turbulent mixing on fog formation exists. Several studies suggested that turbulent mixing suppresses fog formation. Some other studies reported that turbulent mixing contributes to fog formation. On the other hand, several quasi-periodic oscillations of temperature, visibility, and vertical velocity, which have period of 10-20 minutes, were observed to be related to gravity waves in fog; because gravity waves play significant dynamic roles in the atmosphere. Furthermore, a numerical study suggested that gravity waves, simulated near the top of the fog layer, may affect fog microphysics. Thus, we investigate the effects of turbulent mixing on fog formation and the influences of gravity waves on fog microphysics to understand fog structure in Pyeongchang. In these studies, we analyze the data that are obtained from doppler lidar and 3.5 m meteorological observation tower including 3D-ultrasonic anemometer, IR sensor, and fog monitor during ICE-POP (International Collaborative Experiments for Pyeongchang 2018 Olympic and Paralympic winter games) campaign. In these instruments, doppler lidar is a good instrument to observe the gravity waves near the fog top, while in situ measurements have small spatial coverage. The instruments are installed at the mountainous terrain of Pyeongchang, Korea. More details will be presented at the conference.

Simulations of Cloud-Radiation Interaction Using Large-Scale Forcing Derived from the CINDY/DYNAMO Northern Sounding Array

NASA Technical Reports Server (NTRS)

Wang, Shuguang; Sobel, Adam H.; Fridlind, Ann; Feng, Zhe; Comstock, Jennifer M.; Minnis, Patrick; Nordeen, Michele L.

2015-01-01

The recently completed CINDY/DYNAMO field campaign observed two Madden-Julian oscillation (MJO) events in the equatorial Indian Ocean from October to December 2011. Prior work has indicated that the moist static energy anomalies in these events grew and were sustained to a significant extent by radiative feedbacks. We present here a study of radiative fluxes and clouds in a set of cloud-resolving simulations of these MJO events. The simulations are driven by the large-scale forcing data set derived from the DYNAMO northern sounding array observations, and carried out in a doubly periodic domain using the Weather Research and Forecasting (WRF) model. Simulated cloud properties and radiative fluxes are compared to those derived from the S-PolKa radar and satellite observations. To accommodate the uncertainty in simulated cloud microphysics, a number of single-moment (1M) and double-moment (2M) microphysical schemes in the WRF model are tested. The 1M schemes tend to underestimate radiative flux anomalies in the active phases of the MJO events, while the 2M schemes perform better, but can overestimate radiative flux anomalies. All the tested microphysics schemes exhibit biases in the shapes of the histograms of radiative fluxes and radar reflectivity. Histograms of radiative fluxes and brightness temperature indicate that radiative biases are not evenly distributed; the most significant bias occurs in rainy areas with OLR less than 150 W/ cu sq in the 2M schemes. Analysis of simulated radar reflectivities indicates that this radiative flux uncertainty is closely related to the simulated stratiform cloud coverage. Single-moment schemes underestimate stratiform cloudiness by a factor of 2, whereas 2M schemes simulate much more stratiform cloud.

Tropopause Inversion Layer and Stratosphere-Troposphere Exchange in Baroclinic Life Cycles: The Role of Diabatic Processes

NASA Astrophysics Data System (ADS)

Kunkel, D.; Hoor, P. M.; Wirth, V.

2014-12-01

Observations and model simulations of temperature and tracer profiles in the extratropical upper troposphere/lower stratosphere (UTLS) show the presence of an inversion layer just above the thermal tropopause, i.e., the tropopause inversion layer (TIL), which is situated in a region affected by stratosphere-troposphere exchange (STE). Moreover, from a dynamical perspective the extratropical UTLS is highly affected by baroclinic life cycles. Since both the TIL and STE emerge, amongst many other features, during simulated baroclinic life cycles, we study whether there is a relationship between the TIL and STE. We use the non-hydrostatic model COSMO in an idealized mid-latitude channel configuration to simulate baroclinic life cycles. In a first step contributions of individual diabatic processes from turbulence, radiation, and cloud microphysics to the formation of the TIL are analyzed. These results are compared to those from adiabatic simulations in which the TIL forms during the life cycles with the limitation of being less sharp than in observations. Furthermore, passive tropospheric and stratospheric tracers are used to identify STE. Regions of STE are then analyzed with respect to the temporal evolution of the static stability above the tropopause. The results suggest that radiative effects, especially from water vapor, have the largest additional contribution to the TIL formation, while additional individual effects of cloud microphysics are almost negligible. STE occurs in all diabatic simulations but its strength depends highly on how the underlying diabatic process can affect the thermal and dynamical structure in the tropopause region. Weak STE is found when considering cloud microphysics, while STE is stronger in case of using turbulence and radiation. Tropopause-based vertical profiles of the tropospheric tracers show in some cases similarities with observed tracer profiles of CO.

Active sensor synergy for arctic cloud microphysics

NASA Astrophysics Data System (ADS)

Sato, Kaori; Okamoto, Hajime; Katagiri, Shuichiro; Shiobara, Masataka; Yabuki, Masanori; Takano, Toshiaki

2018-04-01

In this study, we focus on the retrieval of liquid and ice-phase cloud microphysics from spaceborne and ground-based lidar-cloud radar synergy. As an application of the cloud retrieval algorithm developed for the EarthCARE satellite mission (JAXA-ESA) [1], the derived statistics of cloud microphysical properties in high latitudes and their relation to the Arctic climate are investigated.

A case study of microphysical structures and hydrometeor phase in convection using radar Doppler spectra at Darwin, Australia

DOE Office of Scientific and Technical Information (OSTI.GOV)

Riihimaki, Laura D.; Comstock, Jennifer M.; Luke, Edward

To understand the microphysical processes that impact diabatic heating and cloud lifetimes in convection, we need to characterize the spatial distribution of supercooled liquid water. To address this observational challenge, vertically pointing active sensors at the Darwin Atmospheric Radiation Measurement (ARM) site are used to classify cloud phase within a deep convective cloud in a shallow to deep convection transitional case. The cloud cannot be fully observed by a lidar due to signal attenuation. Thus we develop an objective method for identifying hydrometeor classes, including mixed-phase conditions, using k-means clustering on parameters that describe the shape of the Doppler spectramore » from vertically pointing Ka band cloud radar. This approach shows that multiple, overlapping mixed-phase layers exist within the cloud, rather than a single region of supercooled liquid, indicating complexity to how ice growth and diabatic heating occurs in the vertical structure of the cloud.« less

The Influence of Aerosols on the Shortwave Cloud Radiative Forcing from North Pacific Oceanic Clouds: Results from the Cloud Indirect Forcing Experiment (CIFEX)

NASA Technical Reports Server (NTRS)

Wilcox, Eric M.; Roberts, Greg; Ramanathan, V.

2006-01-01

Aerosols over the Northeastern Pacific Ocean enhance the cloud drop number concentration and reduce the drop size for marine stratocumulus and cumulus clouds. These microphysical effects result in brighter clouds, as evidenced by a combination of aircraft and satellite observations. In-situ measurements from the Cloud Indirect Forcing Experiment (CIFEX) indicate that the mean cloud drop number concentration in low clouds over the polluted marine boundary layer is greater by 53/cu cm compared to clean clouds, and the mean cloud drop effective radius is smaller by 4 microns. We link these in-situ measurements of cloud modification by aerosols, for the first time, with collocated satellite broadband radiative flux observations from the Clouds and the Earth's Radiant Energy System (CERES) to show that these microphysical effects of aerosols enhance the top-of-atmosphere cooling by -9.9+/-4.3 W/sq m for overcast conditions.

Observed microphysical structure of nimbostratus in northeast cold vortex over China

NASA Astrophysics Data System (ADS)

Zhao, Zhen; Lei, Hengchi

2014-06-01

Airborne measurements were collected during a stepwise ascent within a nimbostratus cloud associated with a northeast cold vortex in Jilin Province over China on 20 June 2005 to study cloud structure and ice particle spectra. The microphysical structure of the nimbostratus was elucidated by King liquid water probe and Particle Measuring Systems (PMS) probes aboard the research aircraft. The PMS 2D images provide detailed information on crystal habits. A thick layer of supercooled cloud is observed and Hallett-Mossop ice multiplication process is used to explain very high ice particle concentrations in the temperature region between - 3 °C and - 6 °C. From near cloud top to melting layer, ice crystals shape in the form of columns, needles, aggregations and plates. In addition, significant horizontal variability was evident on the scale of few hundred meters. Ice particle spectra in this cloud were adequately described by exponential relationships. Relationship between the intercept (N0) and slope (λ) parameters of an exponential size distribution was well characterized by a power law.

A case study of microphysical structures and hydrometeor phase in convection using radar Doppler spectra at Darwin, Australia

DOE PAGES

Riihimaki, Laura D.; Comstock, J. M.; Luke, E.; ...

2017-07-12

To understand the microphysical processes that impact diabatic heating and cloud lifetimes in convection, we need to characterize the spatial distribution of supercooled liquid water. To address this observational challenge, ground-based vertically pointing active sensors at the Darwin Atmospheric Radiation Measurement site are used to classify cloud phase within a deep convective cloud. The cloud cannot be fully observed by a lidar due to signal attenuation. Therefore, we developed an objective method for identifying hydrometeor classes, including mixed-phase conditions, using k-means clustering on parameters that describe the shape of the Doppler spectra from vertically pointing Ka-band cloud radar. Furthermore, thismore » approach shows that multiple, overlapping mixed-phase layers exist within the cloud, rather than a single region of supercooled liquid. Diffusional growth calculations show that the conditions for the Wegener-Bergeron-Findeisen process exist within one of these mixed-phase microstructures.« less

A case study of microphysical structures and hydrometeor phase in convection using radar Doppler spectra at Darwin, Australia

DOE Office of Scientific and Technical Information (OSTI.GOV)

Riihimaki, Laura D.; Comstock, J. M.; Luke, E.

To understand the microphysical processes that impact diabatic heating and cloud lifetimes in convection, we need to characterize the spatial distribution of supercooled liquid water. To address this observational challenge, ground-based vertically pointing active sensors at the Darwin Atmospheric Radiation Measurement site are used to classify cloud phase within a deep convective cloud. The cloud cannot be fully observed by a lidar due to signal attenuation. Therefore, we developed an objective method for identifying hydrometeor classes, including mixed-phase conditions, using k-means clustering on parameters that describe the shape of the Doppler spectra from vertically pointing Ka-band cloud radar. Furthermore, thismore » approach shows that multiple, overlapping mixed-phase layers exist within the cloud, rather than a single region of supercooled liquid. Diffusional growth calculations show that the conditions for the Wegener-Bergeron-Findeisen process exist within one of these mixed-phase microstructures.« less

Minimalist model of ice microphysics in mixed-phase stratiform clouds

NASA Astrophysics Data System (ADS)

Yang, Fan; Ovchinnikov, Mikhail; Shaw, Raymond A.

2013-07-01

The question of whether persistent ice crystal precipitation from supercooled layer clouds can be explained by time-dependent, stochastic ice nucleation is explored using an approximate, analytical model and a large-eddy simulation (LES) cloud model. The updraft velocity in the cloud defines an accumulation zone, where small ice particles cannot fall out until they are large enough, which will increase the residence time of ice particles in the cloud. Ice particles reach a quasi-steady state between growth by vapor deposition and fall speed at cloud base. The analytical model predicts that ice water content (wi) has a 2.5 power-law relationship with ice number concentration (ni). wi and ni from a LES cloud model with stochastic ice nucleation confirm the 2.5 power-law relationship, and initial indications of the scaling law are observed in data from the Indirect and Semi-Direct Aerosol Campaign. The prefactor of the power law is proportional to the ice nucleation rate and therefore provides a quantitative link to observations of ice microphysical properties.

Parameterizing microphysical effects on variances and covariances of moisture and heat content using a multivariate probability density function: a study with CLUBB (tag MVCS)

DOE PAGES

Griffin, Brian M.; Larson, Vincent E.

2016-11-25

Microphysical processes, such as the formation, growth, and evaporation of precipitation, interact with variability and covariances (e.g., fluxes) in moisture and heat content. For instance, evaporation of rain may produce cold pools, which in turn may trigger fresh convection and precipitation. These effects are usually omitted or else crudely parameterized at subgrid scales in weather and climate models.A more formal approach is pursued here, based on predictive, horizontally averaged equations for the variances, covariances, and fluxes of moisture and heat content. These higher-order moment equations contain microphysical source terms. The microphysics terms can be integrated analytically, given a suitably simplemore » warm-rain microphysics scheme and an approximate assumption about the multivariate distribution of cloud-related and precipitation-related variables. Performing the integrations provides exact expressions within an idealized context.A large-eddy simulation (LES) of a shallow precipitating cumulus case is performed here, and it indicates that the microphysical effects on (co)variances and fluxes can be large. In some budgets and altitude ranges, they are dominant terms. The analytic expressions for the integrals are implemented in a single-column, higher-order closure model. Interactive single-column simulations agree qualitatively with the LES. The analytic integrations form a parameterization of microphysical effects in their own right, and they also serve as benchmark solutions that can be compared to non-analytic integration methods.« less

The Impact of Aerosols on Cloud and Precipitation Processes: Cloud-Resolving Model Simulations

NASA Technical Reports Server (NTRS)

Tao, Wei-Kuo; Li, X.; Khain, A.; Simpson, S.; Johnson, D.; Remer, L.

2004-01-01

Cloud microphysics is inevitably affected by the smoke particle (CCN, cloud condensation nuclei) size distributions below the clouds. Therefore, size distributions parameterized as spectral bin microphysics are needed to explicitly study the effects of atmospheric aerosol concentration on cloud development, rainfall production, and rainfall rates for convective clouds. Recently, two detailed spectral-bin microphysical schemes were implemented into the Goddard Cumulus Ensembel (GCE) model. The formulation for the explicit spectral-bin microphysical processes is based on solving stochastic kinetic equations for the size distribution functions of water droplets (i.e., cloud droplets and raindrops), and several types of ice particles [i.e. pristine ice crystals (columnar and plate-like), snow (dendrites and aggregates), graupel and frozen drops/hail]. Each type is described by a special size distribution function containing many categories (i.e. 33 bins). Atmospheric aerosols are also described using number density size distribution functions. A spectral-bin microphysical model is very expensive from a computational point of view and has only been implemented into the 2D version of the GCE at the present time. The model is tested by studying the evolution of deep tropical clouds in the west Pacific warm pool region and in the mid-latitude continent with different concentrations of CCN: a low "c1ean"concentration and a high "dirty" concentration. In addition, differences and similarities between bulk microphysics and spectral-bin microphysical schemes will be examined and discussed.

The Impact of Aerosols on Cloud and Precipitation Processes: Cloud-resolving Model Simulations

NASA Technical Reports Server (NTRS)

Tao, Wei-Kuo; Li, X.; Khain, A.; Simpson, S.; Johnson, D.; Remer, L.

2004-01-01

Cloud microphysics is inevitably affected by the smoke particle (CCN, cloud condensation nuclei) size distributions below the clouds. Therefore, size distributions parameterized as spectral bin microphysics are needed to explicitly study the effects of atmospheric aerosol concentration on cloud development, r d a U production, and rainfall rates for convective clouds. Recently, two detailed spectral-bin microphysical schemes were implemented into the Goddard Cumulus Ensembe1 (GCE) model. The formulation for the explicit spectral-bin microphysical processes is based on solving stochastic kinetic equations for the size distribution functions of water droplets (i.e., cloud droplets and raindrops), and several types of ice particles [i.e. pristine ice crystals (columnar and platelike), snow (dendrites and aggregates), graupel and frozen drops/hail]. Each type is described by a special size distribution function containing many categories (i.e. 33 bins). Atmospheric aerosols are also described using number density size-distribution functions. A spectral-bin microphysical model is very expensive from a computational point of view and has only been implemented into the 2D version of the GCE at the present time. The model is tested by studying the evolution of deep tropical clouds in the west Pacific warm pool region and in the mid-latitude continent with different concentrations of CCN: a low "c1ean"concentration and a high "dirty" concentration. In addition, differences and similarities between bulk microphysics and spectral-bin microphysical schemes will be examined and discussed.

Characterization of ice nucleating particles during continuous springtime measurements in Prudhoe Bay: an Arctic oilfield location

NASA Astrophysics Data System (ADS)

Creamean, J.; Spada, N. J.; Kirpes, R.; Pratt, K.

2017-12-01

Aerosols that serve as ice nucleating particles (INPs) have the potential to modulate cloud microphysical properties. INPs can thus subsequently impact cloud radiative forcing in addition to modification of precipitation formation processes. In regions such as the Arctic, aerosol-cloud interactions are severely understudied yet have significant implications for surface radiation reaching the sea ice and snow surfaces. Further, uncertainties in model representations of heterogeneous ice nucleation are a significant hindrance to simulating Arctic mixed-phase cloud processes. Characterizing a combination of aerosol chemical, physical, and ice nucleating properties is pertinent to evaluating of the role of aerosols in altering Arctic cloud microphysics. We present preliminary results from an aerosol sampling campaign called INPOP (Ice Nucleating Particles at Oliktok Point), which took place at a U.S. Department of Energy's Atmospheric Radiation Measurement (DOE ARM) facility on the North Slope of Alaska. Three time- and size-resolved aerosol samplers were deployed from 1 Mar to 31 May 2017 and were co-located with routine measurements of aerosol number, size, chemical, and radiative property measurements conducted by DOE ARM at their Aerosol Observing System (AOS). Offline analysis of samples collected at a daily time resolution included composition and morphology via single-particle analysis and drop freezing measurements for INP concentrations, while analysis of 12-hourly samples included mass, optical, and elemental composition. We deliberate the possible influences on the aerosol and INP population from the Prudhoe Bay oilfield resource extraction and daily operations in addition to what may be local background or long-range transported aerosol. To our knowledge our results represent some of the first INP characterization measurements in an Arctic oilfield location and can be used as a benchmark for future INP characterization studies in Arctic locations impacted by local resource extraction pollution. Ultimately, these results can be used to evaluate the impacts of oil exploration activities on Arctic cloud aerosol composition and possible linkages to Arctic cloud ice formation.

New Cloud and Precipitation Research Avenues Enabled by low-cost Phased-array Radar Technology

NASA Astrophysics Data System (ADS)

Kollias, P.; Oue, M.; Fridlind, A. M.; Matsui, T.; McLaughlin, D. J.

2017-12-01

For over half a century, radars operating in a wide range of frequencies have been the primary source of observational insights of clouds and precipitation microphysics and dynamics and contributed to numerous significant advancements in the field of cloud and precipitation physics. The development of multi-wavelength and polarization diversity techniques has further strengthened the quality of microphysical and dynamical retrievals from radars and has assisted in overcoming some of the limitations imposed by the physics of scattering. Atmospheric radars have historically employed a mechanically-scanning dish antenna and their ability to point to, survey, and revisit specific points or regions in the atmosphere is limited by mechanical inertia. Electronically scanned, or phased-array, radars capable of high-speed, inertialess beam steering, have been available for several decades, but the cost of this technology has limited its use to military applications. During the last 10 years, lower power and lower-cost versions of electronically scanning radars have been developed, and this presents an attractive and affordable new tool for the atmospheric sciences. The operational and research communities are currently exploring phased array advantages in signal processing (i.e. beam multiplexing, improved clutter rejection, cross beam wind estimation, adaptive sensing) and science applications (i.e. tornadic storm morphology studies). Here, we will present some areas of atmospheric research where inertia-less radars with ability to provide rapid volume imaging offers the potential to advance cloud and precipitation research. We will discuss the added value of single phased-array radars as well as networks of these radars for several problems including: multi-Doppler wind retrieval techniques, cloud lifetime studies and aerosol-convection interactions. The performance of current (dish) and future (e-scan) radar systems for these atmospheric studies will be evaluated using numerical model output and a sophisticated radar simulator package.

In search of the best match: probing a multi-dimensional cloud microphysical parameter space to better understand what controls cloud thermodynamic phase

NASA Astrophysics Data System (ADS)

Tan, Ivy; Storelvmo, Trude

2015-04-01

Substantial improvements have been made to the cloud microphysical schemes used in the latest generation of global climate models (GCMs), however, an outstanding weakness of these schemes lies in the arbitrariness of their tuning parameters, which are also notoriously fraught with uncertainties. Despite the growing effort in improving the cloud microphysical schemes in GCMs, most of this effort has neglected to focus on improving the ability of GCMs to accurately simulate the present-day global distribution of thermodynamic phase partitioning in mixed-phase clouds. Liquid droplets and ice crystals not only influence the Earth's radiative budget and hence climate sensitivity via their contrasting optical properties, but also through the effects of their lifetimes in the atmosphere. The current study employs NCAR's CAM5.1, and uses observations of cloud phase obtained by NASA's CALIOP lidar over a 79-month period (November 2007 to June 2014) guide the accurate simulation of the global distribution of mixed-phase clouds in 20∘ latitudinal bands at the -10∘ C, -20∘C and -30∘C isotherms, by adjusting six relevant cloud microphysical tuning parameters in the CAM5.1 via Quasi-Monte Carlo sampling. Among the parameters include those that control the Wegener-Bergeron-Findeisen (WBF) timescale for the conversion of supercooled liquid droplets to ice and snow in mixed-phase clouds, the fraction of ice nuclei that nucleate ice in the atmosphere, ice crystal sedimentation speed, and wet scavenging in stratiform and convective clouds. Using a Generalized Linear Model as a variance-based sensitivity analysis, the relative contributions of each of the six parameters are quantified to gain a better understanding of the importance of their individual and two-way interaction effects on the liquid to ice proportion in mixed-phase clouds. Thus, the methodology implemented in the current study aims to search for the combination of cloud microphysical parameters in a GCM that produce the most accurate reproduction of observations of cloud thermodynamic phase, while simultaneously assessing the weaknesses of the parameterizations in the model. We find that the simulated proportion of liquid to ice in mixed-phase clouds is dominated by the fraction of active ice nuclei in the atmosphere and the WBF timescale. In a follow-up to this study, we apply these results to a fully-coupled GCM, CESM, and find that cloud thermodynamic phase has profound ramifications for the uncertainty associated with climate sensitivity estimates.

Inference of cirrus cloud properties using satellite-observed visible and infrared radiances. I - Parameterization of radiance fields

NASA Technical Reports Server (NTRS)

Minnis, Patrick; Liou, Kuo-Nan; Takano, Yoshihide

1993-01-01

The impact of using phase functions for spherical droplets and hexagonal ice crystals to analyze radiances from cirrus is examined. Adding-doubling radiative transfer calculations are employed to compute radiances for different cloud thicknesses and heights over various backgrounds. These radiances are used to develop parameterizations of top-of-the-atmosphere visible reflectance and IR emittance using tables of reflectances as a function of cloud optical depth, viewing and illumination angles, and microphysics. This parameterization, which includes Rayleigh scattering, ozone absorption, variable cloud height, and an anisotropic surface reflectance, reproduces the computed top-of-the-atmosphere reflectances with an accruacy of +/- 6 percent for four microphysical models: 10-micron water droplet, small symmetric crystal, cirrostratus, and cirrus uncinus. The accuracy is twice that of previous models.

Studies of Dark Spots and Their Companion Clouds on the Ice Giant Planets

NASA Astrophysics Data System (ADS)

Bhure, Sakhee; Sankar, Ramanakumar; Hadland, Nathan; Palotai, Csaba J.; Le Beau, Raymond P.; Koutas, Nikko

2017-10-01

Observations of ice giant planets in our Solar System have shown several large-scale dark spots with varying lifespans. Some of these features were directly observed, others were diagnosed from their orographic companion clouds. Historically, numerical simulations have been able to model certain characteristics of these storms such as the shape variability of the Neptune Great Dark Spot (GDS-89) (Deng and Le Beau, 2006), but have not been able to match observed drift rates and lifespans using the standard zonal wind profiles (Hammel et al. 2009). Common amongst these studies has been the lack of condensable species in the atmosphere and an explicit treatment of cloud microphysics. Yet, observations show that dark spots can affect neighboring cloud features, such as in the case of bright companion clouds or the “Berg” on Uranus. An analysis of the cloud structure is therefore required to gain a better understanding of the underlying atmospheric physics and dynamics of these vortices.For our simulations, we use the Explicit Planetary Isentropic Coordinate (EPIC) general circulation model (Dowling et al. 1998, 2006) and adapt its jovian cloud microphysics module which successfully reproduced the cloud structure of jovian storms, such as the Great Red Spot and the Oval BA (Palotai and Dowling 2008, Palotai et al. 2014). EPIC was recently updated to account for the condensation of methane and hydrogen sulfide (Palotai et al. 2016), which allows us to account for both the high-altitude methane ice-cloud and the deep atmosphere hydrogen sulfide ice-cloud layers.In this work, we simulate large-scale vortices on Uranus and Neptune with varying cloud microphysical parameters such as the deep abundance and the ambient supersaturation. We examine the effect of cloud formation on their lifespan and drift rates to better understand the underlying processes which drive these storms.

A Theoretical Framework for Examining Geographical Variability in the Microphysical Mechanisms of Precipitation Development.

DTIC Science & Technology

1986-06-01

Energy and Natural Resources SWS Contract Report 391 FINAL REPORT A THEORETICAL FRAMEWORK FOR EXAMINING GEOGRAPHICAL VARIABILITY IN THE MICROPHYSICAL...U) A Theoretical Framework for Examining Geographical Variability in the Microphysical Mechanisms of Precipitation Development 12. PERSONAL AUTHOR(S...concentration. Oter key parameters include the degree of entrainment and stability of the environment. I 5 - T17 Unclassified ,.-. . A THEORETICAL FRAMEWORK FOR

DOE Office of Scientific and Technical Information (OSTI.GOV)

Griffin, Brian M.; Larson, Vincent E.

Microphysical processes, such as the formation, growth, and evaporation of precipitation, interact with variability and covariances (e.g., fluxes) in moisture and heat content. For instance, evaporation of rain may produce cold pools, which in turn may trigger fresh convection and precipitation. These effects are usually omitted or else crudely parameterized at subgrid scales in weather and climate models.A more formal approach is pursued here, based on predictive, horizontally averaged equations for the variances, covariances, and fluxes of moisture and heat content. These higher-order moment equations contain microphysical source terms. The microphysics terms can be integrated analytically, given a suitably simplemore » warm-rain microphysics scheme and an approximate assumption about the multivariate distribution of cloud-related and precipitation-related variables. Performing the integrations provides exact expressions within an idealized context.A large-eddy simulation (LES) of a shallow precipitating cumulus case is performed here, and it indicates that the microphysical effects on (co)variances and fluxes can be large. In some budgets and altitude ranges, they are dominant terms. The analytic expressions for the integrals are implemented in a single-column, higher-order closure model. Interactive single-column simulations agree qualitatively with the LES. The analytic integrations form a parameterization of microphysical effects in their own right, and they also serve as benchmark solutions that can be compared to non-analytic integration methods.« less

Comparison of convective clouds observed by spaceborne W-band radar and simulated by cloud-resolving atmospheric models

NASA Astrophysics Data System (ADS)

Dodson, Jason B.

Deep convective clouds (DCCs) play an important role in regulating global climate through vertical mass flux, vertical water transport, and radiation. For general circulation models (GCMs) to simulate the global climate realistically, they must simulate DCCs realistically. GCMs have traditionally used cumulus parameterizations (CPs). Much recent research has shown that multiple persistent unrealistic behaviors in GCMs are related to limitations of CPs. Two alternatives to CPs exist: the global cloud-resolving model (GCRM), and the multiscale modeling framework (MMF). Both can directly simulate the coarser features of DCCs because of their multi-kilometer horizontal resolutions, and can simulate large-scale meteorological processes more realistically than GCMs. However, the question of realistic behavior of simulated DCCs remains. How closely do simulated DCCs resemble observed DCCs? In this study I examine the behavior of DCCs in the Nonhydrostatic Icosahedral Atmospheric Model (NICAM) and Superparameterized Community Atmospheric Model (SP-CAM), the latter with both single-moment and double-moment microphysics. I place particular emphasis on the relationship between cloud vertical structure and convective environment. I also emphasize the transition between shallow clouds and mature DCCs. The spatial domains used are the tropical oceans and the contiguous United States (CONUS), the latter of which produces frequent vigorous convection during the summer. CloudSat is used to observe DCCs, and A-Train and reanalysis data are used to represent the large-scale environment in which the clouds form. The CloudSat cloud mask and radar reflectivity profiles for CONUS cumuliform clouds (defined as clouds with a base within the planetary boundary layer) during boreal summer are first averaged and compared. Both NICAM and SP-CAM greatly underestimate the vertical growth of cumuliform clouds. Then they are sorted by three large-scale environmental variables: total preciptable water (TPW), surface air temperature (SAT), and 500hPa vertical velocity (W500), representing the dynamical and thermodynamical environment in which the clouds form. The sorted CloudSat profiles are then compared with NICAM and SP-CAM profiles simulated with the Quickbeam CloudSat simulator. Both models have considerable difficulty representing the relationship of SAT and clouds over CONUS. For TPW and W500, shallow clouds transition to DCCs at higher values than observed. This may be an indication of the models' inability to represent the formation of DCCs in marginal convective environments. NICAM develops tall DCCs in highly favorable environments, but SP-CAM appears to be incapable of developing tall DCCs in almost any environment. The use of double moment microphysics in SP-CAM improves the frequency of deep clouds and their relationship with TPW, but not SAT. Both models underpredict radar reflectivity in the upper cloud of mature DCCs. SP-CAM with single moment microphysics has a particularly unrealistic DCC reflectivity profile, but with double moment microphysics it improves substantially. SP-CAM with double-moment microphysics unexpectedly appears to weaken DCC updraft strength as TPW increases, but otherwise both NICAM and SP-CAM represent the environment-versus-DCC relationships fairly realistically.

The Impact of Microphysical Schemes on Intensity and Track of Hurricane

NASA Technical Reports Server (NTRS)

Tao, W. K.; Shi, J. J.; Chen, S. S.; Lang, S.; Lin, P.; Hong, S. Y.; Peters-Lidard, C.; Hou, A.

2010-01-01

During the past decade, both research and operational numerical weather prediction models [e.g. Weather Research and Forecasting Model (WRF)] have started using more complex microphysical schemes originally developed for high-resolution cloud resolving models (CRMs) with a 1-2 km or less horizontal resolutions. The WRF is a next-generation meso-scale forecast model and assimilation system that has incorporated a modern software framework, advanced dynamics, numeric and data assimilation techniques, a multiple moveable nesting capability, and improved physical packages. The WRF model can be used for a wide range of applications, from idealized research to operational forecasting, with an emphasis on horizontal grid sizes in the range of 1-10 km. The current WRF includes several different microphysics options. At Goddard, four different cloud microphysics schemes (warm rain only, two-class of ice, two three-class of ice with either graupel or hail) are implemented into the WRF. The performances of these schemes have been compared to those from other WRF microphysics scheme options for an Atlantic hurricane case. In addition, a brief review and comparison on the previous modeling studies on the impact of microphysics schemes and microphysical processes on intensity and track of hurricane will be presented. Generally, almost all modeling studies found that the microphysics schemes did not have major impacts on track forecast, but did have more effect on the intensity. All modeling studies found that the simulated hurricane has rapid deepening and/or intensification for the warm rain-only case. It is because all hydrometeors were very large raindrops, and they fell out quickly at and near the eye-wall region. This would hydrostatically produce the lowest pressure. In addition, these modeling studies suggested that the simulated hurricane becomes unrealistically strong by removing the evaporative cooling of cloud droplets and melting of ice particles. This is due to the much weaker downdraft simulated. However, there are many differences between different modeling studies and these differences were identified and discussed.

The Cloud Ice Mountain Experiment (CIME) 1998: experiment overview and modelling of the microphysical processes during the seeding by isentropic gas expansion

NASA Astrophysics Data System (ADS)

Wobrock, Wolfram; Flossmann, Andrea I.; Monier, Marie; Pichon, Jean-Marc; Cortez, Laurent; Fournol, Jean-François; Schwarzenböck, Alfons; Mertes, Stephan; Heintzenberg, Jost; Laj, Paolo; Orsi, Giordano; Ricci, Loretta; Fuzzi, Sandro; Brink, Harry Ten; Jongejan, Piet; Otjes, René

The second field campaign of the Cloud Ice Mountain Experiment (CIME) project took place in February 1998 on the mountain Puy de Dôme in the centre of France. The content of residual aerosol particles, of H 2O 2 and NH 3 in cloud droplets was evaluated by evaporating the drops larger than 5 μm in a Counterflow Virtual Impactor (CVI) and by measuring the residual particle concentration and the released gas content. The same trace species were studied behind a round jet impactor for the complementary interstitial aerosol particles smaller than 5 μm diameter. In a second step of experiments, the ambient supercooled cloud was converted to a mixed phase cloud by seeding the cloud with ice particles by the gas release from pressurised gas bottles. A comparison between the physical and chemical characteristics of liquid drops and ice particles allows a study of the fate of the trace constituents during the presence of ice crystals in the cloud. In the present paper, an overview is given of the CIME 98 experiment and the instrumentation deployed. The meteorological situation during the experiment was analysed with the help of a cloud scale model. The microphysics processes and the behaviour of the scavenged aerosol particles before and during seeding are analysed with the detailed microphysical model ExMix. The simulation results agreed well with the observations and confirmed the assumption that the Bergeron-Findeisen process was dominating during seeding and was influencing the partitioning of aerosol particles between drops and ice crystals. The results of the CIME 98 experiment give an insight on microphysical changes, redistribution of aerosol particles and cloud chemistry during the Bergeron-Findeisen process when acting also in natural clouds.

Assessment of biomass burning smoke influence on environmental conditions for multiyear tornado outbreaks by combining aerosol-aware microphysics and fire emission constraints

NASA Astrophysics Data System (ADS)

Saide, Pablo E.; Thompson, Gregory; Eidhammer, Trude; da Silva, Arlindo M.; Pierce, R. Bradley; Carmichael, Gregory R.

2016-09-01

We use the Weather Research and Forecasting (WRF) system to study the impacts of biomass burning smoke from Central America on several tornado outbreaks occurring in the U.S. during spring. The model is configured with an aerosol-aware microphysics parameterization capable of resolving aerosol-cloud-radiation interactions in a cost-efficient way for numerical weather prediction (NWP) applications. Primary aerosol emissions are included, and smoke emissions are constrained using an inverse modeling technique and satellite-based aerosol optical depth observations. Simulations turning on and off fire emissions reveal smoke presence in all tornado outbreaks being studied and show an increase in aerosol number concentrations due to smoke. However, the likelihood of occurrence and intensification of tornadoes is higher due to smoke only in cases where cloud droplet number concentration in low-level clouds increases considerably in a way that modifies the environmental conditions where the tornadoes are formed (shallower cloud bases and higher low-level wind shear). Smoke absorption and vertical extent also play a role, with smoke absorption at cloud-level tending to burn-off clouds and smoke absorption above clouds resulting in an increased capping inversion. Comparing these and WRF-Chem simulations configured with a more complex representation of aerosol size and composition and different optical properties, microphysics, and activation schemes, we find similarities in terms of the simulated aerosol optical depths and aerosol impacts on near-storm environments. This provides reliability on the aerosol-aware microphysics scheme as a less computationally expensive alternative to WRF-Chem for its use in applications such as NWP and cloud-resolving simulations.

Assessment of biomass burning smoke influence on environmental conditions for multi-year tornado outbreaks by combining aerosol-aware microphysics and fire emission constraints

PubMed Central

Saide, Pablo E.; Thompson, Gregory; Eidhammer, Trude; da Silva, Arlindo M.; Pierce, R. Bradley; Carmichael, Gregory R.

2018-01-01

We use the WRF system to study the impacts of biomass burning smoke from Central America on several tornado outbreaks occurring in the US during spring. The model is configured with an aerosol-aware microphysics parameterization capable of resolving aerosol-cloud-radiation interactions in a cost-efficient way for numerical weather prediction (NWP) applications. Primary aerosol emissions are included and smoke emissions are constrained using an inverse modeling technique and satellite-based AOD observations. Simulations turning on and off fire emissions reveal smoke presence in all tornado outbreaks being studied and show an increase in aerosol number concentrations due to smoke. However, the likelihood of occurrence and intensification of tornadoes is higher due to smoke only in cases where cloud droplet number concentration in low level clouds increases considerably in a way that modifies the environmental conditions where the tornadoes are formed (shallower cloud bases and higher low-level wind shear). Smoke absorption and vertical extent also play a role, with smoke absorption at cloud-level tending to burn-off clouds and smoke absorption above clouds resulting in an increased capping inversion. Comparing these and WRF-Chem simulations configured with a more complex representation of aerosol size and composition and different optical properties, microphysics and activation schemes, we find similarities in terms of the simulated aerosol optical depths and aerosol impacts on near-storm environments. This provides reliability on the aerosol-aware microphysics scheme as a less computationally expensive alternative to WRF-Chem for its use in applications such as NWP and cloud-resolving simulations. PMID:29619287

Micro-Physical characterisation of Convective & Stratiform Rainfall at Tropics

NASA Astrophysics Data System (ADS)

Sreekanth, T. S.

Large Micro-Physical characterisation of Convective & Stratiform Rainfall at Tropics begin{center} begin{center} Sreekanth T S*, Suby Symon*, G. Mohan Kumar (1) , and V Sasi Kumar (2) *Centre for Earth Science Studies, Akkulam, Thiruvananthapuram (1) D-330, Swathi Nagar, West Fort, Thiruvananthapuram 695023 (2) 32. NCC Nagar, Peroorkada, Thiruvananthapuram ABSTRACT Micro-physical parameters of rainfall such as rain drop size & fall speed distribution, mass weighted mean diameter, Total no. of rain drops, Normalisation parameters for rain intensity, maximum & minimum drop diameter from different rain intensity ranges, from both stratiform and convective rain events were analysed. Convective -Stratiform classification was done by the method followed by Testud et al (2001) and as an additional information electrical behaviour of clouds from Atmospheric Electric Field Mill was also used. Events which cannot be included in both types are termed as 'mixed precipitation' and identified separately. For the three years 2011, 2012 & 2013, rain events from both convective & stratiform origin are identified from three seasons viz Pre-Monsoon (March-May), Monsoon (June-September) and Post-Monsoon (October-December). Micro-physical characterisation was done for each rain events and analysed. Ground based and radar observations were made and classification of stratiform and convective rainfall was done by the method followed by Testud et al (2001). Radar bright band and non bright band analysis was done for confimation of stratifom and convective rain respectievely. Atmospheric electric field data from electric field mill is also used for confirmation of convection during convective events. Statistical analyses revealed that the standard deviation of rain drop size in higher rain rates are higher than in lower rain rates. Normalised drop size distribution is ploted for selected events from both forms. Inter relations between various precipitation parameters were analysed in three seasons.

Illustration of microphysical processes in Amazonian deep convective clouds in the gamma phase space: introduction and potential applications

NASA Astrophysics Data System (ADS)

Cecchini, Micael A.; Machado, Luiz A. T.; Wendisch, Manfred; Costa, Anja; Krämer, Martina; Andreae, Meinrat O.; Afchine, Armin; Albrecht, Rachel I.; Artaxo, Paulo; Borrmann, Stephan; Fütterer, Daniel; Klimach, Thomas; Mahnke, Christoph; Martin, Scot T.; Minikin, Andreas; Molleker, Sergej; Pardo, Lianet H.; Pöhlker, Christopher; Pöhlker, Mira L.; Pöschl, Ulrich; Rosenfeld, Daniel; Weinzierl, Bernadett

2017-12-01

The behavior of tropical clouds remains a major open scientific question, resulting in poor representation by models. One challenge is to realistically reproduce cloud droplet size distributions (DSDs) and their evolution over time and space. Many applications, not limited to models, use the gamma function to represent DSDs. However, even though the statistical characteristics of the gamma parameters have been widely studied, there is almost no study dedicated to understanding the phase space of this function and the associated physics. This phase space can be defined by the three parameters that define the DSD intercept, shape, and curvature. Gamma phase space may provide a common framework for parameterizations and intercomparisons. Here, we introduce the phase space approach and its characteristics, focusing on warm-phase microphysical cloud properties and the transition to the mixed-phase layer. We show that trajectories in this phase space can represent DSD evolution and can be related to growth processes. Condensational and collisional growth may be interpreted as pseudo-forces that induce displacements in opposite directions within the phase space. The actually observed movements in the phase space are a result of the combination of such pseudo-forces. Additionally, aerosol effects can be evaluated given their significant impact on DSDs. The DSDs associated with liquid droplets that favor cloud glaciation can be delimited in the phase space, which can help models to adequately predict the transition to the mixed phase. We also consider possible ways to constrain the DSD in two-moment bulk microphysics schemes, in which the relative dispersion parameter of the DSD can play a significant role. Overall, the gamma phase space approach can be an invaluable tool for studying cloud microphysical evolution and can be readily applied in many scenarios that rely on gamma DSDs.

Microphysical characterization of long-range transported biomass burning particles from North America at three EARLINET stations

NASA Astrophysics Data System (ADS)

Ortiz-Amezcua, Pablo; Guerrero-Rascado, Juan Luis; José Granados-Muñoz, María; Benavent-Oltra, José Antonio; Böckmann, Christine; Samaras, Stefanos; Stachlewska, Iwona S.; Janicka, Łucja; Baars, Holger; Bohlmann, Stephanie; Alados-Arboledas, Lucas

2017-05-01

Strong events of long-range transported biomass burning aerosol were detected during July 2013 at three EARLINET (European Aerosol Research Lidar Network) stations, namely Granada (Spain), Leipzig (Germany) and Warsaw (Poland). Satellite observations from MODIS (Moderate Resolution Imaging Spectroradiometer) and CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) instruments, as well as modeling tools such as HYSPLIT (Hybrid Single-Particle Lagrangian Integrated Trajectory) and NAAPS (Navy Aerosol Analysis and Prediction System), have been used to estimate the sources and transport paths of those North American forest fire smoke particles. A multiwavelength Raman lidar technique was applied to obtain vertically resolved particle optical properties, and further inversion of those properties with a regularization algorithm allowed for retrieving microphysical information on the studied particles. The results highlight the presence of smoke layers of 1-2 km thickness, located at about 5 km a.s.l. altitude over Granada and Leipzig and around 2.5 km a.s.l. at Warsaw. These layers were intense, as they accounted for more than 30 % of the total AOD (aerosol optical depth) in all cases, and presented optical and microphysical features typical for different aging degrees: color ratio of lidar ratios (LR532 / LR355) around 2, α-related ångström exponents of less than 1, effective radii of 0.3 µm and large values of single scattering albedos (SSA), nearly spectrally independent. The intensive microphysical properties were compared with columnar retrievals form co-located AERONET (Aerosol Robotic Network) stations. The intensity of the layers was also characterized in terms of particle volume concentration, and then an experimental relationship between this magnitude and the particle extinction coefficient was established.

An intercomparison of methods for solving the stochastic collection equation with a focus on cloud radar Doppler spectra in drizzling stratocumulus

NASA Astrophysics Data System (ADS)

Lee, H.; Fridlind, A. M.; Ackerman, A. S.; Kollias, P.

2017-12-01

Cloud radar Doppler spectra provide rich information for evaluating the fidelity of particle size distributions from cloud models. The intrinsic simplifications of bulk microphysics schemes generally preclude the generation of plausible Doppler spectra, unlike bin microphysics schemes, which develop particle size distributions more organically at substantial computational expense. However, bin microphysics schemes face the difficulty of numerical diffusion leading to overly rapid large drop formation, particularly while solving the stochastic collection equation (SCE). Because such numerical diffusion can cause an even greater overestimation of radar reflectivity, an accurate method for solving the SCE is essential for bin microphysics schemes to accurately simulate Doppler spectra. While several methods have been proposed to solve the SCE, here we examine those of Berry and Reinhardt (1974, BR74), Jacobson et al. (1994, J94), and Bott (2000, B00). Using a simple box model to simulate drop size distribution evolution during precipitation formation with a realistic kernel, it is shown that each method yields a converged solution as the resolution of the drop size grid increases. However, the BR74 and B00 methods yield nearly identical size distributions in time, whereas the J94 method produces consistently larger drops throughout the simulation. In contrast to an earlier study, the performance of the B00 method is found to be satisfactory; it converges at relatively low resolution and long time steps, and its computational efficiency is the best among the three methods considered here. Finally, a series of idealized stratocumulus large-eddy simulations are performed using the J94 and B00 methods. The reflectivity size distributions and Doppler spectra obtained from the different SCE solution methods are presented and compared with observations.

Influence of Superparameterization and a Higher-Order Turbulence Closure on Rainfall Bias Over Amazonia in Community Atmosphere Model Version 5: How Parameterization Changes Rainfall

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Kai; Fu, Rong; Shaikh, Muhammad J.

We evaluate the Community Atmosphere Model Version 5 (CAM5) with a higher-order turbulence closure scheme, named Cloud Layers Unified By Binomials (CLUBB), and a Multiscale Modeling Framework (MMF) with two different microphysics configurations to investigate their influences on rainfall simulations over Southern Amazonia. The two different microphysics configurations in MMF are the one-moment cloud microphysics without aerosol treatment (SAM1MOM) and two-moment cloud microphysics coupled with aerosol treatment (SAM2MOM). Results show that both MMF-SAM2MOM and CLUBB effectively reduce the low biases of rainfall, mainly during the wet season. The CLUBB reduces low biases of humidity in the lower troposphere with furthermore » reduced shallow clouds. The latter enables more surface solar flux, leading to stronger convection and more rainfall. MMF, especially MMF-SAM2MOM, unstablizes the atmosphere with more moisture and higher atmospheric temperatures in the atmospheric boundary layer, allowing the growth of more extreme convection and further generating more deep convection. MMF-SAM2MOM significantly increases rainfall in the afternoon, but it does not reduce the early bias of the diurnal rainfall peak; LUBB, on the other hand, delays the afternoon peak time and produces more precipitation in the early morning, due to more realistic gradual transition between shallow and deep convection. MMF appears to be able to realistically capture the observed increase of relative humidity prior to deep convection, especially with its two-moment configuration. In contrast, in CAM5 and CAM5 with CLUBB, occurrence of deep convection in these models appears to be a result of stronger heating rather than higher relative humidity.« less

Evaluating the Performance of Single and Double Moment Microphysics Schemes During a Synoptic-Scale Snowfall Event

NASA Technical Reports Server (NTRS)

Molthan, Andrew L.

2011-01-01

Increases in computing resources have allowed for the utilization of high-resolution weather forecast models capable of resolving cloud microphysical and precipitation processes among varying numbers of hydrometeor categories. Several microphysics schemes are currently available within the Weather Research and Forecasting (WRF) model, ranging from single-moment predictions of precipitation content to double-moment predictions that include a prediction of particle number concentrations. Each scheme incorporates several assumptions related to the size distribution, shape, and fall speed relationships of ice crystals in order to simulate cold-cloud processes and resulting precipitation. Field campaign data offer a means of evaluating the assumptions present within each scheme. The Canadian CloudSat/CALIPSO Validation Project (C3VP) represented collaboration among the CloudSat, CALIPSO, and NASA Global Precipitation Measurement mission communities, to observe cold season precipitation processes relevant to forecast model evaluation and the eventual development of satellite retrievals of cloud properties and precipitation rates. During the C3VP campaign, widespread snowfall occurred on 22 January 2007, sampled by aircraft and surface instrumentation that provided particle size distributions, ice water content, and fall speed estimations along with traditional surface measurements of temperature and precipitation. In this study, four single-moment and two double-moment microphysics schemes were utilized to generate hypothetical WRF forecasts of the event, with C3VP data used in evaluation of their varying assumptions. Schemes that incorporate flexibility in size distribution parameters and density assumptions are shown to be preferable to fixed constants, and that a double-moment representation of the snow category may be beneficial when representing the effects of aggregation. These results may guide forecast centers in optimal configurations of their forecast models for winter weather and identify best practices present within these various schemes.

HOLIMO II: a digital holographic instrument for ground-based in-situ observations of microphysical properties of mixed-phase clouds

NASA Astrophysics Data System (ADS)

Henneberger, J.; Fugal, J. P.; Stetzer, O.; Lohmann, U.

2013-05-01

Measurements of the microphysical properties of mixed-phase clouds with high spatial resolution are important to understand the processes inside these clouds. This work describes the design and characterization of the newly developed ground-based field instrument HOLIMO II (HOLographic Imager for Microscopic Objects II). HOLIMO II uses digital in-line holography to in-situ image cloud particles in a well defined sample volume. By an automated algorithm, two-dimensional images of single cloud particles between 6 and 250 μm in diameter are obtained and the size spectrum, the concentration and water content of clouds are calculated. By testing the sizing algorithm with monosized beads a systematic overestimation near the resolution limit was found, which has been used to correct the measurements. Field measurements from the high altitude research station Jungfraujoch, Switzerland, are presented. The measured number size distributions are in good agreement with parallel measurements by a fog monitor (FM-100, DMT, Boulder USA). The field data shows that HOLIMO II is capable of measuring the number size distribution with a high spatial resolution and determines ice crystal shape, thus providing a method of quantifying variations in microphysical properties. A case study over a period of 8 h has been analyzed, exploring the transition from a liquid to a mixed-phase cloud, which is the longest observation of a cloud with a holographic device. During the measurement period, the cloud does not completely glaciate, contradicting earlier assumptions of the dominance of the Wegener-Bergeron-Findeisen (WBF) process.

HOLIMO II: a digital holographic instrument for ground-based in situ observations of microphysical properties of mixed-phase clouds

NASA Astrophysics Data System (ADS)

Henneberger, J.; Fugal, J. P.; Stetzer, O.; Lohmann, U.

2013-11-01

Measurements of the microphysical properties of mixed-phase clouds with high spatial resolution are important to understand the processes inside these clouds. This work describes the design and characterization of the newly developed ground-based field instrument HOLIMO II (HOLographic Imager for Microscopic Objects II). HOLIMO II uses digital in-line holography to in situ image cloud particles in a well-defined sample volume. By an automated algorithm, two-dimensional images of single cloud particles between 6 and 250 μm in diameter are obtained and the size spectrum, the concentration and water content of clouds are calculated. By testing the sizing algorithm with monosized beads a systematic overestimation near the resolution limit was found, which has been used to correct the measurements. Field measurements from the high altitude research station Jungfraujoch, Switzerland, are presented. The measured number size distributions are in good agreement with parallel measurements by a fog monitor (FM-100, DMT, Boulder USA). The field data shows that HOLIMO II is capable of measuring the number size distribution with a high spatial resolution and determines ice crystal shape, thus providing a method of quantifying variations in microphysical properties. A case study over a period of 8 h has been analyzed, exploring the transition from a liquid to a mixed-phase cloud, which is the longest observation of a cloud with a holographic device. During the measurement period, the cloud does not completely glaciate, contradicting earlier assumptions of the dominance of the Wegener-Bergeron-Findeisen (WBF) process.

The microphysical properties of ice fog measured in urban environments of Interior Alaska

NASA Astrophysics Data System (ADS)

Schmitt, Carl G.; Stuefer, Martin; Heymsfield, Andrew J.; Kim, Chang Ki

2013-10-01

microphysical properties of ice fog were measured at two sites during a small field campaign in January and February of 2012 in Interior Alaska. The National Center for Atmospheric Research Video Ice Particle Sampler probe and Formvar (polyvinyl formal)-coated microscope slides were used to sample airborne ice particles at two polluted sites in the Fairbanks region. Both sites were significantly influenced by anthropogenic emission and additional water vapor from nearby open water power plant cooling ponds. Measurements show that ice fog particles were generally droxtal shaped (faceted, quasi-spherical) for sub-10 µm particles, while plate-shaped crystals were the most frequently observed particles between 10 and 50 µm. A visibility cutoff of 3 km was used to separate ice fog events from other observations which were significantly influenced by larger (50-150 µm) diamond dust particles. The purpose of this study is to more realistically characterize ice fog microphysical properties in order to facilitate better model predictions of the onset of ice fog in polluted environments. Parameterizations for mass and projected area are developed and used to estimate particle terminal velocity. Dimensional characteristics are based on particle geometry and indicated that ice fog particles have significantly lower densities than water droplets as well as reduced cross-sectional areas, the net result being that terminal velocities are estimated to be less than half the value of those calculated for water droplets. Particle size distributions are characterized using gamma functions and have a shape factor (μ) of between -0.5 and -1.0 for polluted ice fog conditions.

Evaluation of Model Microphysics within Precipitation Bands of Extratropical Cyclones

NASA Technical Reports Server (NTRS)

Colle, Brian A.; Yu, Ruyi; Molthan, Andrew L.; Nesbitt, Steven

2013-01-01

Recent studies evaluating the bulk microphysical schemes (BMPs) within cloud resolving models (CRMs) have indicated large uncertainties and errors in the amount and size distributions of snow and cloud ice aloft. The snow prediction is sensitive to the snow densities, habits, and degree of riming within the BMPs. Improving these BMPs is a crucial step toward improving both weather forecasting and climate predictions. Several microphysical schemes in the Weather Research and Forecasting (WRF) model down to 1.33-km grid spacing are evaluated using aircraft, radar, and ground in situ data from the Global Precipitation Mission Coldseason Precipitation Experiment (GCPEx) experiment, as well as a few years (15 winter storms) of surface measurements of riming, crystal habit, snow density, and radar measurements at Stony Brook, NY (SBNY on north shore of Long Island) during the 2009-2012 winter seasons. Surface microphysical measurements at SBNY were taken every 15 to 30 minutes using a stereo microscope and camera, and snow depth and snow density were also recorded. During these storms, a vertically-pointing Ku-band radar was used to observe the vertical evolution of reflectivity and Doppler vertical velocities. A Particle Size and Velocity (PARSIVEL) disdrometer was also used to measure the surface size distribution and fall speeds of snow at SBNY. For the 15 cases at SBNY, the WSM6, Morrison (MORR), Thompson (THOM2), and Stony Brook (SBU-YLIN) BMPs were validated. A non-spherical snow assumption (THOM2 and SBU-YLIN) simulated a more realistic distribution of reflectivity than spherical snow assumptions in the WSM6 and MORR schemes. The MORR, WSM6, and SBU-YLIN schemes are comparable to the observed velocity distribution in light and moderate riming periods. The THOM2 is approx 0.25 m/s too slow with its velocity distribution in these periods. In heavier riming, the vertical Doppler velocities in the WSM6, THOM2, and MORR schemes were approx 0.25 m/s too slow, while the SBU-YLIN was 0.25 to 0.5 m/s too fast. Overall, the BMPs simulate a size distribution close to the observed for D < 4 mm in the dendritic, plates, and mixed habit periods. The model BMPs underestimate the size distribution when large aggregates were observed. For D > 6 mm in the dendrites, side planes, and mixed habit periods, the BMPs are likely not simulating enough aggregation to create a larger size distribution, although the MORR (double moment) scheme seemed to perform best. These SBNY results will be compared with some results from GCPEx for a warm frontal snow band observed at 18 February 2012.

Evaluation of Model Microphysics Within Precipitation Bands of Extratropical Cyclones

NASA Technical Reports Server (NTRS)

Colle, Brian A.; Molthan, Andrew; Yu, Ruyi; Stark, David; Yuter, Sandra; Nesbitt, Steven

2013-01-01

Recent studies evaluating the bulk microphysical schemes (BMPs) within cloud resolving models (CRMs) have indicated large uncertainties and errors in the amount and size distributions of snow and cloud ice aloft. The snow prediction is sensitive to the snow densities, habits, and degree of riming within the BMPs. Improving these BMPs is a crucial step toward improving both weather forecasting and climate predictions. Several microphysical schemes in the Weather Research and Forecasting (WRF) model down to 1.33-km grid spacing are evaluated using aircraft, radar, and ground in situ data from the Global Precipitation Mission Coldseason Precipitation Experiment (GCPEx) experiment, as well as a few years (15 winter storms) of surface measurements of riming, crystal habit, snow density, and radar measurements at Stony Brook, NY (SBNY on north shore of Long Island) during the 2009-2012 winter seasons. Surface microphysical measurements at SBNY were taken every 15 to 30 minutes using a stereo microscope and camera, and snow depth and snow density were also recorded. During these storms, a vertically-pointing Ku-band radar was used to observe the vertical evolution of reflectivity and Doppler vertical velocities. A Particle Size and Velocity (PARSIVEL) disdrometer was also used to measure the surface size distribution and fall speeds of snow at SBNY. For the 15 cases at SBNY, the WSM6, Morrison (MORR), Thompson (THOM2), and Stony Brook (SBU-YLIN) BMPs were validated. A non-spherical snow assumption (THOM2 and SBU-YLIN) simulated a more realistic distribution of reflectivity than spherical snow assumptions in the WSM6 and MORR schemes. The MORR, WSM6, and SBU-YLIN schemes are comparable to the observed velocity distribution in light and moderate riming periods. The THOM2 is 0.25 meters per second too slow with its velocity distribution in these periods. In heavier riming, the vertical Doppler velocities in the WSM6, THOM2, and MORR schemes were 0.25 meters per second too slow, while the SBU-YLIN was 0.25 to 0.5 meters per second too fast. Overall, the BMPs simulate a size distribution close to the observed for D < 4 mm in the dendritic, plates, and mixed habit periods. The model BMPs underestimate the size distribution when large aggregates were observed. For D > 6 mm in the dendrites, side planes, and mixed habit periods, the BMPs are likely not simulating enough aggregation to create a larger size distribution, although the MORR (double moment) scheme seemed to perform best. These SBNY results will be compared with some results from GCPEx for a warm frontal snow band observed at 18 February 2012.

Understanding the Microphysical Properties of Developing Cloud Clusters during TCS-08

DTIC Science & Technology

2010-09-30

Typhoon Mawar (2005) from the western North Pacific to demonstrate considerable differences in both the development of (Fig. 4), and the microphysical...traces of simulated Typhoon Mawar (2005) showing sea-level pressure on the left axis and maximum wind speed on the right axis. There is considerable...differences in both the speed at which Mawar develops and the final minimum sea-level pressure depending on which microphysics (cloud-resolving

Evaluating Cloud Initialization in a Convection-permit NWP Model

NASA Astrophysics Data System (ADS)

Li, Jia; Chen, Baode

2015-04-01

In general, to avoid "double counting precipitation" problem, in convection permit NWP models, it was a common practice to turn off convective parameterization. However, if there were not any cloud information in the initial conditions, the occurrence of precipitation could be delayed due to spin-up of cloud field or microphysical variables. In this study, we utilized the complex cloud analysis package from the Advanced Regional Prediction System (ARPS) to adjust the initial states of the model on water substance, such as cloud water, cloud ice, rain water, et al., that is, to initialize the microphysical variables (i.e., hydrometers), mainly based on radar reflectivity observations. Using the Advanced Research WRF (ARW) model, numerical experiments with/without cloud initialization and convective parameterization were carried out at grey-zone resolutions (i.e. 1, 3, and 9 km). The results from the experiments without convective parameterization indicate that model ignition with radar reflectivity can significantly reduce spin-up time and accurately simulate precipitation at the initial time. In addition, it helps to improve location and intensity of predicted precipitation. With grey-zone resolutions (i.e. 1, 3, and 9 km), using the cumulus convective parameterization scheme (without radar data) cannot produce realistic precipitation at the early time. The issues related to microphysical parametrization associated with cloud initialization were also discussed.

Evaluation of a new microphysical aerosol module in the ECMWF Integrated Forecasting System

NASA Astrophysics Data System (ADS)

Woodhouse, Matthew; Mann, Graham; Carslaw, Ken; Morcrette, Jean-Jacques; Schulz, Michael; Kinne, Stefan; Boucher, Olivier

2013-04-01

The Monitoring Atmospheric Composition and Climate II (MACC-II) project will provide a system for monitoring and predicting atmospheric composition. As part of the first phase of MACC, the GLOMAP-mode microphysical aerosol scheme (Mann et al., 2010, GMD) was incorporated within the ECMWF Integrated Forecasting System (IFS). The two-moment modal GLOMAP-mode scheme includes new particle formation, condensation, coagulation, cloud-processing, and wet and dry deposition. GLOMAP-mode is already incorporated as a module within the TOMCAT chemistry transport model and within the UK Met Office HadGEM3 general circulation model. The microphysical, process-based GLOMAP-mode scheme allows an improved representation of aerosol size and composition and can simulate aerosol evolution in the troposphere and stratosphere. The new aerosol forecasting and re-analysis system (known as IFS-GLOMAP) will also provide improved boundary conditions for regional air quality forecasts, and will benefit from assimilation of observed aerosol optical depths in near real time. Presented here is an evaluation of the performance of the IFS-GLOMAP system in comparison to in situ aerosol mass and number measurements, and remotely-sensed aerosol optical depth measurements. Future development will provide a fully-coupled chemistry-aerosol scheme, and the capability to resolve nitrate aerosol.

What does reflection from cloud sides tell us about vertical distribution of cloud droplets?

NASA Technical Reports Server (NTRS)

Marshak, A.; Kaufman, Yoram; Martins, V.; Zubko, Victor

2006-01-01

In order to accurately measure the interaction of clouds with aerosols, we have to resolve the vertical distribution of cloud droplet sizes and determine the temperature of glaciation for clean and polluted clouds. Knowledge of the droplet vertical profile is also essential for understanding precipitation. So far, all existing satellites either measure cloud microphysics only at cloud top (e.g., MODIS) or give a vertical profile of precipitation sized droplets (e.g., Cloudsat). What if one measures cloud microphysical properties in the vertical by retrieving them from the solar and infrared radiation reflected or emitted from cloud sides? This was the idea behind CLAIM-3D (A 3D - cloud aerosol interaction mission) recently proposed by NASA GSFC. This presentation will focus on the interpretation of the radiation reflected from cloud sides. In contrast to plane-parallel approximation, a conventional approach to all current operational retrievals, 3D radiative transfer will be used for interpreting the observed reflectances. As a proof of concept, we will show a few examples of radiation reflected from cloud fields generated by a simple stochastic cloud model with prescribed microphysics. Instead of fixed values of the retrieved effective radii, the probability density functions of droplet size distributions will serve as possible retrievals.

Arctic Stratospheric Temperature In The Winters 1999/2000 and 2000/2001: A Quantitative Assessment and Microphysical Implications

NASA Astrophysics Data System (ADS)

Buss, S.; Wernli, H.; Peter, T.; Kivi, R.; Bui, T. P.; Kleinböhl, A.; Schiller, C.

Stratospheric winter temperatures play a key role in the chain of microphysical and chemical processes that lead to the formation of polar stratospheric clouds (PSCs), chlorine activation and eventually to stratospheric ozone depletion. Here the tempera- ture conditions during the Arctic winters 1999/2000 and 2000/2001 are quantitatively investigated using observed profiles of water vapour and nitric acid, and tempera- tures from high-resolution radiosondes and aircraft observations, global ECMWF and UKMO analyses and mesoscale model simulations over Scandinavia and Greenland. The ECMWF model resolves parts of the gravity wave activity and generally agrees well with the observations. However, for the very cold temperatures near the ice frost point the ECMWF analyses have a warm bias of 1-6 K compared to radiosondes. For the mesoscale model HRM, this bias is generally reduced due to a more accurate rep- resentation of gravity waves. Quantitative estimates of the impact of the mesoscale temperature perturbations indicates that over Scandinavia and Greenland the wave- induced stratospheric cooling (as simulated by the HRM) affects only moderately the estimated chlorine activation and homogeneous NAT particle formation, but strongly enhances the potential for ice formation.

The Kinematic and Microphysical Control of Storm Integrated Lightning Flash Extent

NASA Technical Reports Server (NTRS)

Carey, Lawrence D.; Peterson, Harold S.; Schultz, Elise V.; Matthee, Retha; Schultz, Christopher J.; Petersen, Walter A,; Bain, Lamont

2012-01-01

Objective: To investigate the kinematic and microphysical control of lightning properties, particularly those that may govern the production of nitrogen oxides (NOx) in thunderstorms, such as flash rate, type (intracloud [IC] vs. cloud-to-ground [CG] ) and extent. Data and Methodology: a) NASA MSFC Lightning Nitrogen Oxides Model (LNOM) is applied to North Alabama Lightning Mapping Array (NALMA) and Vaisala National Lightning Detection Network(TradeMark) (NLDN) observations following ordinary convective cells through their lifecycle. b) LNOM provides estimates of flash type, channel length distributions, lightning segment altitude distributions (SADs) and lightning NOx production profiles (Koshak et al. 2012). c) LNOM lightning characteristics are compared to the evolution of updraft and precipitation properties inferred from dual-Doppler (DD) and polarimetric radar analyses of UAHuntsville Advanced Radar for Meteorological and Operational Research (ARMOR, Cband, polarimetric) and KHTX (S-band, Doppler).

Coastal Observations of Weather Features in Senegal during the AMMA SOP-3 Period

NASA Technical Reports Server (NTRS)

Jenkins, G.; Kucera, P.; Joseph, E.; Fuentes, J.; Gaye, A.; Gerlach, J.; Roux, F.; Viltard, N.; Papazzoni, M.; Protat, A.;

Microphysics, Meteorology, Microwave and Modeling of Mediterranean Storms: The M(sup 5) Problem

NASA Technical Reports Server (NTRS)

Smith, Eric A.; Fiorino, Steven; Mugnai, Alberto; Panegrossi, Giulia; Tripoli, Gregory; Starr, David (Technical Monitor)

2001-01-01

Comprehensive understanding of the microphysical nature of Mediterranean storms requires a combination of in situ meteorological data analysis and radar-passive microwave data analysis, effectively integrated with numerical modeling studies at various scales, particularly from synoptic scale down to mesoscale. The microphysical properties of and their controls on severe storms are intrinsically related to meteorological processes under which storms have evolved, processes which eventually select and control the dominant microphysical properties themselves. Insofar as hazardous Mediterranean storms, highlighted by the September 25-28/1992 Genova flood event, the October 5-7/1998 Friuli flood event, and the October 13-15/2000 Piemonte flood event (all taking place in northern Italy), developing a comprehensive microphysical interpretation requires an understanding of the multiple phases of storm evolution and the heterogeneous nature of precipitation fields within the storm domains. This involves convective development, stratiform transition and decay, orographic lifting, and sloped frontal lifting proc esses. This also involves vertical motions and thermodynamical instabilities governing physical processes that determine details of the liquid/ice water contents, size distributions, and fall rates of the various modes of hydrometeors found within the storm environments. This paper presents detailed 4-dimensional analyses of the microphysical elements of the three severe Mediterranean storms identified above, investigated with the aid of SSM/I and TRMM satellite measurements (and other remote sensing measurements). The analyses are guided by nonhydrostatic mesoscale model simulations at high resolution of the intense rain producing portions of the storm environments. The results emphasize how meteorological controls taking place at the large scale, coupled with localized terrain controls, ultimately determine the most salient features of the bulk microphysical properties of the storms. These results have bearing on precipitation remote sensing from space, and the role of modeling in designing precipitation retrieval algorithms.

Coupling Spectral-bin Cloud Microphysics with the MOSAIC Aerosol Model in WRF-Chem: Methodology and Results for Marine Stratocumulus Clouds

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gao, Wenhua; Fan, Jiwen; Easter, Richard C.

Aerosol-cloud interaction processes can be represented more physically with bin cloud microphysics relative to bulk microphysical parameterizations. However, due to computational power limitations in the past, bin cloud microphysics was often run with very simple aerosol treatments. The purpose of this study is to represent better aerosol-cloud interaction processes in the Chemistry version of Weather Research and Forecast model (WRF-Chem) at convection-permitting scales by coupling spectral-bin cloud microphysics (SBM) with the MOSAIC sectional aerosol model. A flexible interface is built that exchanges cloud and aerosol information between them. The interface contains a new bin aerosol activation approach, which replaces themore » treatments in the original SBM. It also includes the modified aerosol resuspension and in-cloud wet removal processes with the droplet loss tendencies and precipitation fluxes from SBM. The newly coupled system is evaluated for two marine stratocumulus cases over the Southeast Pacific Ocean with either a simplified aerosol setup or full-chemistry. We compare the aerosol activation process in the newly-coupled SBM-MOSAIC against the SBM simulation without chemistry using a simplified aerosol setup, and the results show consistent activation rates. A longer time simulation reinforces that aerosol resuspension through cloud drop evaporation plays an important role in replenishing aerosols and impacts cloud and precipitation in marine stratocumulus clouds. Evaluation of the coupled SBM-MOSAIC with full-chemistry using aircraft measurements suggests that the new model works realistically for the marine stratocumulus clouds, and improves the simulation of cloud microphysical properties compared to a simulation using MOSAIC coupled with the Morrison two-moment microphysics.« less

The role of ice particles in the microphysics and dynamics of deep convective storms in various latitudes

NASA Astrophysics Data System (ADS)

Huang, Y. C.; Wang, P. K.

2017-12-01

The role of ice particles in the microphysics and dynamics of deep convective storms in various latitudes Yi-Chih Huang and Pao K. Wang Ice particles contribute to the microphysics and dynamics of severe storms in various regions of the world to a degree that is not commonly recognized. This study is motivated by the need to understand the role of ice particles plays in the development of severe storms so that their impact on various aspects of the storm behavior can be properly assessed. In this study, we perform numerical simulations of thunderstorms using a cloud resolving model WISCDYMM that includes parameterized microphysical processes to understand the role played by ice processes. We simulate thunderstorms occurred over various regions of the world including tropics, substropics and midlatitudes. We then perform statistical analysis of the simulated results to show the formation of various categories of hydrometeors to reveal the importance of ice processes. We will show that ice hydrometeors (cloud ice, snow, graupel/hail) account for 80% of the total hydrometeor mass for the High Plains storms but 50% for the subtropical storms. In addition, the melting of large ice particles (graupel and hail) is the major production process of rain in tropical storms although the ratio of ice-phase mass is responsible for only 40% of the total hydrometeor mass. Furthermore, hydrometeors have their own special microphysical processes in development and depletion over various latitudes. Microphysical structures depend on atmospheric dynamical and thermodynamical conditions which determine the partitioning of hydrometeors. This knowledge would benefit the microphysics parameterization in cloud models and cumulus parameterization in global circulation models.

Coupling spectral-bin cloud microphysics with the MOSAIC aerosol model in WRF-Chem: Methodology and results for marine stratocumulus clouds

NASA Astrophysics Data System (ADS)

Gao, Wenhua; Fan, Jiwen; Easter, R. C.; Yang, Qing; Zhao, Chun; Ghan, Steven J.

2016-09-01

Aerosol-cloud interaction processes can be represented more physically with bin cloud microphysics relative to bulk microphysical parameterizations. However, due to computational power limitations in the past, bin cloud microphysics was often run with very simple aerosol treatments. The purpose of this study is to represent better aerosol-cloud interaction processes in the Chemistry version of Weather Research and Forecast model (WRF-Chem) at convection-permitting scales by coupling spectral-bin cloud microphysics (SBM) with the MOSAIC sectional aerosol model. A flexible interface is built that exchanges cloud and aerosol information between them. The interface contains a new bin aerosol activation approach, which replaces the treatments in the original SBM. It also includes the modified aerosol resuspension and in-cloud wet removal processes with the droplet loss tendencies and precipitation fluxes from SBM. The newly coupled system is evaluated for two marine stratocumulus cases over the Southeast Pacific Ocean with either a simplified aerosol setup or full-chemistry. We compare the aerosol activation process in the newly coupled SBM-MOSAIC against the SBM simulation without chemistry using a simplified aerosol setup, and the results show consistent activation rates. A longer time simulation reinforces that aerosol resuspension through cloud drop evaporation plays an important role in replenishing aerosols and impacts cloud and precipitation in marine stratocumulus clouds. Evaluation of the coupled SBM-MOSAIC with full-chemistry using aircraft measurements suggests that the new model works realistically for the marine stratocumulus clouds, and improves the simulation of cloud microphysical properties compared to a simulation using MOSAIC coupled with the Morrison two-moment microphysics.

Lidar stand-alone retrieval of atmospheric aerosol microphysical properties during SLOPE

NASA Astrophysics Data System (ADS)

Ortiz-Amezcua, Pablo; Samaras, Stefanos; Böckmann, Christine; Antonio Benavent-Oltra, Jose; Luis Guerrero-Rascado, Juan; Román, Roberto; Alados-Arboledas, Lucas

2018-04-01

Two cases from SLOPE campaign at Granada are analyzed in terms of particle microphysical properties using novel software developed at Potsdam University. Multiwavelength Raman lidar measurements of particle extinction and backscatter coefficients as well as linear particle depolarization ratios are used as input for the software. The result of the retrieval is a 2-dimensional particle volume distribution as a function of radius and aspect ratio, from which the particle microphysical properties are obtained.

Investigation of Turbulent Entrainment-Mixing Processes With a New Particle-Resolved Direct Numerical Simulation Model

DOE PAGES

Gao, Zheng; Liu, Yangang; Li, Xiaolin; ...

2018-02-19

Here, a new particle-resolved three dimensional direct numerical simulation (DNS) model is developed that combines Lagrangian droplet tracking with the Eulerian field representation of turbulence near the Kolmogorov microscale. Six numerical experiments are performed to investigate the processes of entrainment of clear air and subsequent mixing with cloudy air and their interactions with cloud microphysics. The experiments are designed to represent different combinations of three configurations of initial cloudy area and two turbulence modes (decaying and forced turbulence). Five existing measures of microphysical homogeneous mixing degree are examined, modified, and compared in terms of their ability as a unifying measuremore » to represent the effect of various entrainment-mixing mechanisms on cloud microphysics. Also examined and compared are the conventional Damköhler number and transition scale number as a dynamical measure of different mixing mechanisms. Relationships between the various microphysical measures and dynamical measures are investigated in search for a unified parameterization of entrainment-mixing processes. The results show that even with the same cloud water fraction, the thermodynamic and microphysical properties are different, especially for the decaying cases. Further analysis confirms that despite the detailed differences in cloud properties among the six simulation scenarios, the variety of turbulent entrainment-mixing mechanisms can be reasonably represented with power-law relationships between the microphysical homogeneous mixing degrees and the dynamical measures.« less

Investigation of Turbulent Entrainment-Mixing Processes With a New Particle-Resolved Direct Numerical Simulation Model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gao, Zheng; Liu, Yangang; Li, Xiaolin

Here, a new particle-resolved three dimensional direct numerical simulation (DNS) model is developed that combines Lagrangian droplet tracking with the Eulerian field representation of turbulence near the Kolmogorov microscale. Six numerical experiments are performed to investigate the processes of entrainment of clear air and subsequent mixing with cloudy air and their interactions with cloud microphysics. The experiments are designed to represent different combinations of three configurations of initial cloudy area and two turbulence modes (decaying and forced turbulence). Five existing measures of microphysical homogeneous mixing degree are examined, modified, and compared in terms of their ability as a unifying measuremore » to represent the effect of various entrainment-mixing mechanisms on cloud microphysics. Also examined and compared are the conventional Damköhler number and transition scale number as a dynamical measure of different mixing mechanisms. Relationships between the various microphysical measures and dynamical measures are investigated in search for a unified parameterization of entrainment-mixing processes. The results show that even with the same cloud water fraction, the thermodynamic and microphysical properties are different, especially for the decaying cases. Further analysis confirms that despite the detailed differences in cloud properties among the six simulation scenarios, the variety of turbulent entrainment-mixing mechanisms can be reasonably represented with power-law relationships between the microphysical homogeneous mixing degrees and the dynamical measures.« less

A Hierarchical Modeling Study of the Interactions Among Turbulence, Cloud Microphysics, and Radiative Transfer in the Evolution of Cirrus Clouds

NASA Technical Reports Server (NTRS)

Curry, Judith; Khvorostyanov, V. I.

2005-01-01

This project used a hierarchy of cloud resolving models to address the following science issues of relevance to CRYSTAL-FACE: What ice crystal nucleation mechanisms are active in the different types of cirrus clouds in the Florida area and how do these different nucleation processes influence the evolution of the cloud system and the upper tropospheric humidity? How does the feedback between supersaturation and nucleation impact the evolution of the cloud? What is the relative importance of the large-scale vertical motion and the turbulent motions in the evolution of the crystal size spectra? How does the size spectra impact the life-cycle of the cloud, stratospheric dehydration, and cloud radiative forcing? What is the nature of the turbulence and waves in the upper troposphere generated by precipitating deep convective cloud systems? How do cirrus microphysical and optical properties vary with the small-scale dynamics? How do turbulence and waves in the upper troposphere influence the cross-tropopause mixing and stratospheric and upper tropospheric humidity? The models used in this study were: 2-D hydrostatic model with explicit microphysics that can account for 30 size bins for both the droplet and crystal size spectra. Notably, a new ice crystal nucleation scheme has been incorporated into the model. Parcel model with explicit microphysics, for developing and evaluating microphysical parameterizations. Single column model for testing bulk microphysics parameterizations

Analysis and evaluation of WRF microphysical schemes for deep moist convection over south-eastern South America (SESA) using microwave satellite observations and radiative transfer simulations

NASA Astrophysics Data System (ADS)

Sol Galligani, Victoria; Wang, Die; Alvarez Imaz, Milagros; Salio, Paola; Prigent, Catherine

2017-10-01

In the present study, three meteorological events of extreme deep moist convection, characteristic of south-eastern South America, are considered to conduct a systematic evaluation of the microphysical parameterizations available in the Weather Research and Forecasting (WRF) model by undertaking a direct comparison between satellite-based simulated and observed microwave radiances. A research radiative transfer model, the Atmospheric Radiative Transfer Simulator (ARTS), is coupled with the WRF model under three different microphysical parameterizations (WSM6, WDM6 and Thompson schemes). Microwave radiometry has shown a promising ability in the characterization of frozen hydrometeors. At high microwave frequencies, however, frozen hydrometeors significantly scatter radiation, and the relationship between radiation and hydrometeor populations becomes very complex. The main difficulty in microwave remote sensing of frozen hydrometeor characterization is correctly characterizing this scattering signal due to the complex and variable nature of the size, composition and shape of frozen hydrometeors. The present study further aims at improving the understanding of frozen hydrometeor optical properties characteristic of deep moist convection events in south-eastern South America. In the present study, bulk optical properties are computed by integrating the single-scattering properties of the Liu(2008) discrete dipole approximation (DDA) single-scattering database across the particle size distributions parameterized by the different WRF schemes in a consistent manner, introducing the equal mass approach. The equal mass approach consists of describing the optical properties of the WRF snow and graupel hydrometeors with the optical properties of habits in the DDA database whose dimensions might be different (Dmax') but whose mass is conserved. The performance of the radiative transfer simulations is evaluated by comparing the simulations with the available coincident microwave observations up to 190 GHz (with observations from Tropical Rainfall Measuring Mission's (TRMM) Microwave Imager (TMI), Microwave Humidity Sounder (MHS) and Special Sensor Microwave Imager/Sounder (SSMI/S)) using the χ2 test. Good agreement is obtained with all observations provided special care is taken to represent the scattering properties of the snow and graupel species.

Advection of Microphysical Scalars in Terminal Area Simulation System (TASS)

NASA Technical Reports Server (NTRS)

Ahmad, Nashat N.; Proctor, Fred H.

2011-01-01

The Terminal Area Simulation System (TASS) is a large eddy scale atmospheric flow model with extensive turbulence and microphysics packages. It has been applied successfully in the past to a diverse set of problems ranging from prediction of severe convective events (Proctor et al. 2002), tracking storms and for simulating weapons effects such as the dispersion and fallout of fission debris (Bacon and Sarma 1991), etc. More recently, TASS has been used for predicting the transport and decay of wake vortices behind aircraft (Proctor 2009). An essential part of the TASS model is its comprehensive microphysics package, which relies on the accurate computation of microphysical scalar transport. This paper describes an evaluation of the Leonard scheme implemented in the TASS model for transporting microphysical scalars. The scheme is validated against benchmark cases with exact solutions and compared with two other schemes - a Monotone Upstream-centered Scheme for Conservation Laws (MUSCL)-type scheme after van Leer and LeVeque's high-resolution wave propagation method. Finally, a comparison between the schemes is made against an incident of severe tornadic super-cell convection near Del City, Oklahoma.

Representation of Nucleation Mode Microphysics in a Global Aerosol Model with Sectional Microphysics

NASA Technical Reports Server (NTRS)

Lee, Y. H.; Pierce, J. R.; Adams, P. J.

2013-01-01

In models, nucleation mode (1 nm

Constraints on vertical transport near the polar summer mesopause from PMC observations and modelling

NASA Astrophysics Data System (ADS)

Wilms, H.; Rapp, M.; Kirsch, A.

2016-12-01

The comparison of microphysical simulations of polar mesospheric cloud properties with ground based and satellite borne observations suggests that vertical wind variance imposed by gravity waves is an important prerequisite to realistically model PMC properties. This paper reviews the available observational evidence of vertical wind measurements at the polar summer mesopause (including their frequency content). Corresponding results are compared to vertical wind variance from several global models and implications for the transport of trace constituents in this altitude region are discussed.

Retrieval of microphysical characteristics of particles in atmospheres of distant comets from ground-based polarimetry

NASA Astrophysics Data System (ADS)

Dlugach, Janna M.; Ivanova, Oleksandra V.; Mishchenko, Michael I.; Afanasiev, Viktor L.

2018-01-01

We summarize unique aperture data on the degree of linear polarization observed for distant comets C/2010 S1, C/2010 R1, C/2011 KP36, C/2012 J1, C/2013 V4, and C/2014 A4 with heliocentric distances exceeding 3 AU. Observations have been carried out at the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences (Nizhnij Arkhyz, Russia) during the period from 2011 to 2016. The measured negative polarization proves to be significantly larger in absolute value than what is typically observed for comets close to the Sun. We compare the new observational data with the results of numerical modeling performed with the T-matrix and superposition T-matrix methods. In our computer simulations, we assume the cometary coma to be an optically thin cloud containing particles in the form of spheroids, fractal aggregates composed of spherical monomers, and mixtures of spheroids and aggregate particles. We obtain a good semi-quantitative agreement between all polarimetric data for the observed distant comets and the results of numerical modeling for the following models of the cometary dust: (i) a mixture of submicrometer water-ice oblate spheroids with aggregates composed of submicrometer silicate monomers; and (ii) a mixture of submicrometer water-ice oblate spheroids and aggregates consisting of both silicate and organic monomers. The microphysical parameters of these models are presented and discussed.

ISDAC Microphysics

DOE Data Explorer

McFarquhar, Greg

2011-07-25

Best estimate of cloud microphysical parameters derived using data collected by the cloud microphysical probes installed on the National Research Council (NRC) of Canada Convair-580 during ISDAC. These files contain phase, liquid and ice crystal size distributions (Nw(D) and Ni(D) respectively), liquid water content (LWC), ice water content (IWC), extinction of liquid drops (bw), extinction of ice crystals (bi), effective radius of water drops (rew) and of ice crystals (rei) and median mass diameter of liquid drops (Dmml) and of ice crystals (Dmmi) at 30 second resolution.

Laboratory Investigations of Mesospheric Ice Surfaces: Absence of Dangling Bonds in the Presence of Atomic Oxygen

NASA Astrophysics Data System (ADS)

Boulter, J. E.; Morgan, C. G.; Marschall, J.

2006-05-01

Remote observations of PMCs have become more sophisticated and have increased in geographic and temporal coverage, while numerical models have advanced in detail and predictive power. Together, these advances enable new questions of PMC morphology, optical properties, and microphysical processes in their formation and dissipation. Laboratory investigations also advance this understanding, simulating physical and chemical processes unique to this atmospheric region under comparable conditions. In this work, ice deposition experiments in the presence of microwave discharge-dissociated molecular oxygen suggest heterogeneous interactions between dangling OH bonds on the ice surface and atomic oxygen. Ice films deposited on a gold substrate at temperatures of 115, 130, and 140 K from oxygen/water gas mixtures representative of the summertime polar mesosphere exhibit infrared absorption features characteristic of dangling bonds, whereas films grown in the presence of atomic oxygen do not. Dangling bond spectral features are shown to diminish rapidly when the microwave discharge is activated during ice deposition. Similar decreases were not seen when the gas stream was heated or when the ice film was slowly annealed from 130 to 160 K. One interpretation of these results is that atomic oxygen binds to dangling bond sites during ice growth, a phenomenon that may also occur during the formation of ice particles observed just below the cold summertime mesopause.

Investigation of hydrometeor classification uncertainties through the POLARRIS polarimetric radar simulator

NASA Astrophysics Data System (ADS)

Dolan, B.; Rutledge, S. A.; Barnum, J. I.; Matsui, T.; Tao, W. K.; Iguchi, T.

2017-12-01

POLarimetric Radar Retrieval and Instrument Simulator (POLARRIS) is a framework that has been developed to simulate radar observations from cloud resolving model (CRM) output and subject model data and observations to the same retrievals, analysis and visualization. This framework not only enables validation of bulk microphysical model simulated properties, but also offers an opportunity to study the uncertainties associated with retrievals such as hydrometeor classification (HID). For the CSU HID, membership beta functions (MBFs) are built using a set of simulations with realistic microphysical assumptions about axis ratio, density, canting angles, size distributions for each of ten hydrometeor species. These assumptions are tested using POLARRIS to understand their influence on the resulting simulated polarimetric data and final HID classification. Several of these parameters (density, size distributions) are set by the model microphysics, and therefore the specific assumptions of axis ratio and canting angle are carefully studied. Through these sensitivity studies, we hope to be able to provide uncertainties in retrieved polarimetric variables and HID as applied to CRM output. HID retrievals assign a classification to each point by determining the highest score, thereby identifying the dominant hydrometeor type within a volume. However, in nature, there is rarely just one a single hydrometeor type at a particular point. Models allow for mixing ratios of different hydrometeors within a grid point. We use the mixing ratios from CRM output in concert with the HID scores and classifications to understand how the HID algorithm can provide information about mixtures within a volume, as well as calculate a confidence in the classifications. We leverage the POLARRIS framework to additionally probe radar wavelength differences toward the possibility of a multi-wavelength HID which could utilize the strengths of different wavelengths to improve HID classifications. With these uncertainties and algorithm improvements, cases of convection are studied in a continental (Oklahoma) and maritime (Darwin, Australia) regime. Observations from C-band polarimetric data in both locations are compared to CRM simulations from NU-WRF using the POLARRIS framework.

Polarimetric Radar Characteristics of Simulated and Observed Intense Convection Between Continental and Maritime Environment

NASA Astrophysics Data System (ADS)

Matsui, T.; Dolan, B.; Tao, W. K.; Rutledge, S. A.; Iguchi, T.; Barnum, J. I.; Lang, S. E.

2017-12-01

This study presents polarimetric radar characteristics of intense convective cores derived from observations as well as a polarimetric-radar simulator from cloud resolving model (CRM) simulations from Midlatitude Continental Convective Clouds Experiment (MC3E) May 23 case over Oklahoma and a Tropical Warm Pool-International Cloud Experiment (TWP-ICE) Jan 23 case over Darwin, Australia to highlight the contrast between continental and maritime convection. The POLArimetric Radar Retrieval and Instrument Simulator (POLARRIS) is a state-of-art T-matrix-Mueller-Matrix-based polarimetric radar simulator that can generate synthetic polarimetric radar signals (reflectivity, differential reflectivity, specific differential phase, co-polar correlation) as well as synthetic radar retrievals (precipitation, hydrometeor type, updraft velocity) through the consistent treatment of cloud microphysics and dynamics from CRMs. The Weather Research and Forecasting (WRF) model is configured to simulate continental and maritime severe storms over the MC3E and TWP-ICE domains with the Goddard bulk 4ICE single-moment microphysics and HUCM spectra-bin microphysics. Various statistical diagrams of polarimetric radar signals, hydrometeor types, updraft velocity, and precipitation intensity are investigated for convective and stratiform precipitation regimes and directly compared between MC3E and TWP-ICE cases. The result shows MC3E convection is characterized with very strong reflectivity (up to 60dBZ), slight negative differential reflectivity (-0.8 0 dB) and near-zero specific differential phase above the freezing levels. On the other hand, TWP-ICE convection shows strong reflectivity (up to 50dBZ), slight positive differential reflectivity (0 1.0 dB) and differential phase (0 0.8 dB/km). Hydrometeor IDentification (HID) algorithm from the observation and simulations detect hail-dominant convection core in MC3E, while graupel-dominant convection core in TWP-ICE. This land-ocean contrast agrees with the previous studies using the radar and radiometer signals from TRMM satellite climatology associated with warm-cloud depths and vertical structure of buoyancy.

Use of Field Observations for Understanding Controls of Polar Low Cloud Microphysical Properties

NASA Astrophysics Data System (ADS)

McFarquhar, G. M.

2016-12-01

Although arctic clouds have a net warming effect on the Arctic surface, their radiative effect is sensitive to cloud microphysical properties, namely the sizes, phases and shapes of cloud particles. Such cloud properties are influenced by the numbers, compositions and sizes of aerosols, meteorological conditions, and surface characteristics. Uncertainty in representing cloud-aerosol interactions in varying environmental conditions and associated feedbacks is a major cause in our lack of understanding of why the Arctic is warming faster than the rest of the Earth. Here, the understanding of cloud-aerosol interactions gained from past arctic field experiments is reviewed. Such studies have characterized the structure of single-layer mixed phase clouds that are ubiquitous in the Arctic and investigated different aerosol indirect effect mechanisms acting in these clouds. But, it is still unknown what controls the amount of supercooled water in arctic clouds (especially in complex frequently occurring multi-layer clouds), how probability distributions of cloud properties and radiative heating and their subsequent impact on temperature profiles and underlying snow and sea ice cover vary with aerosol loading and composition in different surface and meteorological conditions, how the composition and concentration of arctic aerosols and cloud microphysical properties vary annually and interannually, and how cloud-aerosol-radiative interactions can be better represented in models with varying temporal and spatial scales. These needs can be addressed in two ways. First, there is a need for comprehensive and routine aircraft, UAV and tethered balloon measurements in the presence of ground, air or space-based remote sensors over a variety of surface and meteorological conditions. Second, planned observational campaigns (the Measurements of Aerosols Radiation and Clouds over the Southern Oceans MARCUS and the Southern Oceans Cloud Radiation Transport Experimental Study SOCRATES) should provide cloud, aerosol, radiative and precipitation observations over the pristine and continually cloudy Southern Oceans that are remote from natural and continental anthropogenic aerosol sources should provide a process-oriented understanding of cloud-aerosol interactions in liquid and ice clouds.

Microphysical Structures of Hurricane Irma Observed by Polarimetric Radar

NASA Astrophysics Data System (ADS)

Didlake, A. C.; Kumjian, M. R.

2017-12-01

This study examines dual-polarization radar observations of Hurricane Irma as its center passed near the WSR-88D radar in Puerto Rico, capturing needed microphysical information of a mature tropical cyclone. Twenty hours of observations continuously sampled the inner core precipitation features. These data were analyzed by annuli and azimuth, providing a bulk characterization of the primary eyewall, secondary eyewall, and rainbands as they varied around the storm. Polarimetric radar variables displayed distinct signatures of convective and stratiform precipitation in the primary eyewall and rainbands that were organized in a manner consistent with the expected kinematic asymmetry of a storm in weak environmental wind shear but with moderate low-level storm-relative flow. In the front quadrants of the primary eyewall, vertical profiles of differential reflectivity (ZDR) exhibit increasing values with decreasing height consistent with convective precipitation processes. In particular, the front-right quadrant exhibits a signature in reflectivity (ZH) and ZDR indicating larger, sparser drops, which is consistent with a stronger updraft present in this quadrant. In the rear quadrants, a sharply peaked ZDR maximum occurs within the melting layer, which is attributed of stratiform processes. In the rainbands, the convective to stratiform transition can be seen traveling from the front-right to the front-left quadrant. The front-right quadrant exhibits lower co-polar correlation coefficient (ρHV) values in the 3-8 km altitude layer, suggesting larger vertical spreading of various hydrometeors that occurs in convective vertical motions. The front-left quadrant exhibits larger ρHV values, suggesting less diversity of hydrometeor shapes, consistent with stratiform processes. The secondary eyewall did not exhibit a clear signature of processes preferred in a specific quadrant, and a temporal analysis of the secondary eyewall revealed a complex evolution of its structure. These results provide important microphysical insight that are critical for understanding the inner core processes modulating tropical cyclone intensity and structure.

Testing ice microphysics parameterizations in the NCAR Community Atmospheric Model Version 3 using Tropical Warm Pool-International Cloud Experiment data

DOE PAGES

Wang, Weiguo; Liu, Xiaohong; Xie, Shaocheng; ...

2009-07-23

Here, cloud properties have been simulated with a new double-moment microphysics scheme under the framework of the single-column version of NCAR Community Atmospheric Model version 3 (CAM3). For comparison, the same simulation was made with the standard single-moment microphysics scheme of CAM3. Results from both simulations compared favorably with observations during the Tropical Warm Pool–International Cloud Experiment by the U.S. Department of Energy Atmospheric Radiation Measurement Program in terms of the temporal variation and vertical distribution of cloud fraction and cloud condensate. Major differences between the two simulations are in the magnitude and distribution of ice water content within themore » mixed-phase cloud during the monsoon period, though the total frozen water (snow plus ice) contents are similar. The ice mass content in the mixed-phase cloud from the new scheme is larger than that from the standard scheme, and ice water content extends 2 km further downward, which is in better agreement with observations. The dependence of the frozen water mass fraction on temperature from the new scheme is also in better agreement with available observations. Outgoing longwave radiation (OLR) at the top of the atmosphere (TOA) from the simulation with the new scheme is, in general, larger than that with the standard scheme, while the surface downward longwave radiation is similar. Sensitivity tests suggest that different treatments of the ice crystal effective radius contribute significantly to the difference in the calculations of TOA OLR, in addition to cloud water path. Numerical experiments show that cloud properties in the new scheme can respond reasonably to changes in the concentration of aerosols and emphasize the importance of correctly simulating aerosol effects in climate models for aerosol-cloud interactions. Further evaluation, especially for ice cloud properties based on in-situ data, is needed.« less

Seasonal cycles on Titan from a Coupled Aerosol Microphysical and Global Circulation Model

NASA Astrophysics Data System (ADS)

Larson, Erik J.; Toon, Owen B.

2010-04-01

Understanding the aerosols on Titan is imperative for understanding the atmosphere as a whole. The aerosols affect the albedo, optical depth, and heating and cooling rates which in turn affects the winds on Titan. Correctly representing them in atmospheric models is crucial to understanding this atmosphere. Several groups have used GCMs to model Titan's atmosphere. Hourdin et al. (1995) were able to reproduce the super-rotating prograde winds. Rannou et al. (2004) found the aerosols accumulated at the poles, which increased the temperature gradient. The increased temperature gradient intensified the zonal winds. Friedson et al. (2009) produced a three- dimensional model for Titan using the NCAR CAM3 model, to which we coupled the aerosol microphysics model CARMA. Until now, there has not been a three- dimensional model that couples radiation, dynamics and aerosol microphysics to study the atmospheric properties of Titan. We have also made the aerosols produced by CARMA interactive with the radiation code in CAM. Preliminary results show that this model is capable of reproducing the seasonal changes in aerosols on Titan and many of the associated phenomena. For instance, the radiatively interactive aerosols are lifted more in the summer hemisphere than the non-interactive aerosols, which is necessary to reproduce the observed seasonal cycle of the albedo (Hutzell et al 1996). However, treating aerosols as spheres with Mie theory is inconsistent with laboratory and observational data that suggest the aerosols are fractal aggregates. We are currently incorporating fractal particle physics into the model. Changing the particles to fractals will affect the radiative properties of the particles, their distribution in the atmosphere, and should improve our fits to the data.

Retrieval of radiative and microphysical properties of clouds from multispectral infrared measurements

NASA Astrophysics Data System (ADS)

Iwabuchi, Hironobu; Saito, Masanori; Tokoro, Yuka; Putri, Nurfiena Sagita; Sekiguchi, Miho

2016-12-01

Satellite remote sensing of the macroscopic, microphysical, and optical properties of clouds are useful for studying spatial and temporal variations of clouds at various scales and constraining cloud physical processes in climate and weather prediction models. Instead of using separate independent algorithms for different cloud properties, a unified, optimal estimation-based cloud retrieval algorithm is developed and applied to moderate resolution imaging spectroradiometer (MODIS) observations using ten thermal infrared bands. The model considers sensor configurations, background surface and atmospheric profile, and microphysical and optical models of ice and liquid cloud particles and radiative transfer in a plane-parallel, multilayered atmosphere. Measurement and model errors are thoroughly quantified from direct comparisons of clear-sky observations over the ocean with model calculations. Performance tests by retrieval simulations show that ice cloud properties are retrieved with high accuracy when cloud optical thickness (COT) is between 0.1 and 10. Cloud-top pressure is inferred with uncertainty lower than 10 % when COT is larger than 0.3. Applying the method to a tropical cloud system and comparing the results with the MODIS Collection 6 cloud product shows good agreement for ice cloud optical thickness when COT is less than about 5. Cloud-top height agrees well with estimates obtained by the CO2 slicing method used in the MODIS product. The present algorithm can detect optically thin parts at the edges of high clouds well in comparison with the MODIS product, in which these parts are recognized as low clouds by the infrared window method. The cloud thermodynamic phase in the present algorithm is constrained by cloud-top temperature, which tends not to produce results with an ice cloud that is too warm and liquid cloud that is too cold.

What Does Reflection from Cloud Sides Tell Us About Vertical Distribution of Cloud Droplet Sizes?

NASA Technical Reports Server (NTRS)

Marshak, Alexander; Martins, J. Vanderlei; Zubko, Victor; Kaufman, Yoram, J.

2005-01-01

Cloud development, the onset of precipitation and the effect of aerosol on clouds depend on the structure of the cloud profiles of droplet size and phase. Aircraft measurements of cloud profiles are limited in their temporal and spatial extent. Satellites were used to observe cloud tops not cloud profiles with vertical profiles of precipitation-sized droplets anticipated from Cloudsat. The recently proposed CLAIM-3D satellite mission (cloud aerosol interaction mission in 3D) suggests to measure profiles of cloud microphysical properties by retrieving them from the solar and infrared radiation reflected or emitted from cloud sides. Inversion of measurements from the cloud sides requires rigorous understanding of the 3-dimensional (3D) properties of clouds. Here we discuss the reflected sunlight from the cloud sides and top at two wavelengths: one nonabsorbing to solar radiation (0.67 micrometers) and one with liquid water efficient absorption of solar radiation (2.1 micrometers). In contrast to the plane-parallel approximation, a conventional approach to all current operational retrievals, 3D radiative transfer is used for interpreting the observed reflectances. General properties of the radiation reflected from the sides of an isolated cloud are discussed. As a proof of concept, the paper shows a few examples of radiation reflected from cloud fields generated by a simple stochastic cloud model with the prescribed vertically resolved microphysics. To retrieve the information about droplet sizes, we propose to use the probability density function of the droplet size distribution and its first two moments instead of the assumption about fixed values of the droplet effective radius. The retrieval algorithm is based on the Bayesian theorem that combines prior information about cloud structure and microphysics with radiative transfer calculations.

Marine Stratocumulus Properties from the FPDR - PDI as a Function of Aerosol during ORACLES

NASA Astrophysics Data System (ADS)

Small Griswold, J. D.; Heikkila, A.

2016-12-01

Aerosol-cloud interactions in the southeastern Atlantic (SEA) region were investigated during year 1 of the ObseRvations of Aerosols above CLouds and their intEractionS (ORACLES) field project in Aug-Sept 2016. This region is of interest due to seasonally persistent marine stratocumulus cloud decks that are an important component of the climate system due to their radiative and hydrologic impacts. The SEA deck is unique due to the interactions between these clouds and transported biomass burning aerosol during the July-October fire season. These biomass burning aerosol play multiple roles in modifying the cloud deck through interactions with radiation as absorbing aerosol and through modifications to cloud microphysical properties as cloud condensation nuclei. This work uses in situcloud data obtained with a Flight Probe Dual Range - Phase Doppler Interferometer (FPDR - PDI), standard aerosol instrumentation on board the NASA P-3, and reanalysis data to investigate Aerosol-Cloud Interactions (ACI). The FPDR - PDI provides unique cloud microphysical observations of individual cloud drop arrivals allowing for the computation of a variety of microphysical cloud properties including individual drop size, cloud drop number concentration, cloud drop size distributions, liquid water content, and cloud thickness. The FPDR - PDI measurement technique also provides droplet spacing and drop velocity information which is used to investigate turbulence and entrainment mixing processes. We use aerosol information such as average background aerosol amount (low, mid, high) and location relative to cloud (above or mixing) to sort FPDR - PDI cloud properties. To control for meteorological co-variances we further sort the data within aerosol categories by lower tropospheric stability, vertical velocity, and surface wind direction. We then determine general marine stratocumulus cloud characteristics under each of the various aerosol categories to investigate ACI in the SEA.

What does Reflection from Cloud Sides tell us about Vertical Distribution of Cloud Droplet Sizes?

NASA Technical Reports Server (NTRS)

Marshak, A.; Martins, J. V.; Zubko, V.; Kaufman, Y. J.

2006-01-01

Cloud development, the onset of precipitation and the effect of aerosol on clouds depend on the structure of the cloud profiles of droplet size and phase. Aircraft measurements of cloud profiles are limited in their temporal and spatial extent. Satellites were used to observe cloud tops not cloud profiles with vertical profiles of precipitation-sized droplets anticipated from CloudSat. The recently proposed CLAIM-3D satellite mission (cloud aerosol interaction mission in 3-D) suggests to measure profiles of cloud microphysical properties by retrieving them from the solar and infrared radiation reflected or emitted from cloud sides. Inversion of measurements from the cloud sides requires rigorous understanding of the 3-dimentional(3-D) properties of clouds. Here we discuss the reflected sunlight from the cloud sides and top at two wavelengths: one nonabsorbing to solar radiation (0.67 microns) and one with liquid water efficient absorption of solar radiation (2.1 microns). In contrast to the plane-parallel approximation, a conventional approach to all current operational retrievals, 3-D radiative transfer is used for interpreting the observed reflectances. General properties of the radiation reflected from the sides of an isolated cloud are discussed. As a proof of concept, the paper shows a few examples of radiation reflected from cloud fields generated by a simple stochastic cloud model with the prescribed vertically resolved microphysics. To retrieve the information about droplet sizes, we propose to use the probability density function of the droplet size distribution and its first two moments instead of the assumption about fixed values of the droplet effective radius. The retrieval algorithm is based on the Bayesian theorem that combines prior information about cloud structure and microphysics with radiative transfer calculations.

Retrieval of Macro- and Micro-Physical Properties of Oceanic Hydrosols from Polarimetric Observations

NASA Technical Reports Server (NTRS)

Ibrahim, Amir; Gilerson, Alexander; Chowdhary, Jacek; Ahmed, Samir

2016-01-01

Remote sensing has mainly relied on measurements of scalar radiance and its spectral and angular features to retrieve micro- and macro-physical properties of aerosols/hydrosols. However, it is recognized that measurements that include the polarimetric characteristics of light provide more intrinsic information about particulate scattering. To take advantage of this, we used vector radiative transfer (VRT) simulations and developed an analytical relationship to retrieve the macro and micro-physical properties of the oceanic hydrosols. Specifically, we investigated the relationship between the observed degree of linear polarization (DoLP) and the ratio of attenuation-to- absorption coefficients (c/a) in water, from which the scattering coefficient can be readily computed (b equals c minus a), after retrieving a. This relationship was parameterized for various scattering geometries, including sensor zenith/azimuth angles relative to the Sun's principal plane, and for varying Sun zenith angles. An inversion method was also developed for the retrieval of the microphysical properties of hydrosols, such as the bulk refractive index and the particle size distribution. The DoLP vs c/a relationship was tested and validated against in-situ measurements of underwater light polarization obtained by a custom-built polarimeter and measurements of the coefficients a and c, obtained using an in-water WET (Western Environmental Technologies) Labs ac-s (attenuation coefficients In-Situ Spectrophotometer) instrument package. These measurements confirmed the validity of the approach, with retrievals of attenuation coefficients showing a high coefficient of determination depending on the wavelength. We also performed a sensitivity analysis of the DoLP at the Top of Atmosphere (TOA) over coastal waters showing the possibility of polarimetric remote sensing application for ocean color.

Meteorology, Macrophysics, Microphysics, Microwaves, and Mesoscale Modeling of Mediterranean Mountain Storms: The M8 Laboratory

NASA Technical Reports Server (NTRS)

Starr, David O. (Technical Monitor); Smith, Eric A.

2002-01-01

Comprehensive understanding of the microphysical nature of Mediterranean storms can be accomplished by a combination of in situ meteorological data analysis and radar-passive microwave data analysis, effectively integrated with numerical modeling studies at various scales, from synoptic scale down through the mesoscale, the cloud macrophysical scale, and ultimately the cloud microphysical scale. The microphysical properties of and their controls on severe storms are intrinsically related to meteorological processes under which storms have evolved, processes which eventually select and control the dominant microphysical properties themselves. This involves intense convective development, stratiform decay, orographic lifting, and sloped frontal lifting processes, as well as the associated vertical motions and thermodynamical instabilities governing physical processes that affect details of the size distributions and fall rates of the various types of hydrometeors found within the storm environment. Insofar as hazardous Mediterranean storms, highlighted in this study by three mountain storms producing damaging floods in northern Italy between 1992 and 2000, developing a comprehensive microphysical interpretation requires an understanding of the multiple phases of storm evolution and the heterogeneous nature of precipitation fields within a storm domain. This involves convective development, stratiform transition and decay, orographic lifting, and sloped frontal lifting processes. This also involves vertical motions and thermodynamical instabilities governing physical processes that determine details of the liquid/ice water contents, size disi:ributions, and fall rates of the various modes of hydrometeors found within hazardous storm environments.

A 2D Microphysical Analysis of Aerosol Nucleation in the Polar Winter Stratosphere: Implications for H2SO4 Photolysis and Nucleation Mechanisms

NASA Technical Reports Server (NTRS)

Mills, Michael J.; Toon, Owen B.; Mills, Michael J.; Solomon, Susan

1997-01-01

Each spring a layer of small particles forms between 20 and 30 km in the polar regions. Results are presented from a 2D microphysical model of sulfate aerosol, which provide the first self-consistent explanation of the observed "CN layer." Photochemical conversion of sulfuric acid to SO2 in the upper stratosphere and mesosphere is necessary for this layer to form. Recent laboratory measurements of H2SO4 and SO3 photolysis rates are consistent with such conversion, though an additional source of SO2 may be required. Nucleation throughout the polar winter extends the top of the aerosol layer to higher altitudes, despite strong downward transport of ambient air. This finding may be important to heterogeneous chemistry at the top of the aerosol layer in polar winter and spring.

How do Polar Stratospheric Clouds Form?

NASA Technical Reports Server (NTRS)

Drdla, Katja; Gandrud, Bruce; Baumgardner, Darrel; Herman, Robert; Gore, Warren J. (Technical Monitor)

2000-01-01

SOLVE measurements have been compared with results from a microphysical model to understand the composition and formation of the polar stratospheric clouds (PSCs) observed during SOLVE. Evidence that the majority of the particles remain liquid throughout the winter will be presented. However, a small fraction of the particles do freeze, and the presence of these frozen particles can not be explained by current theories, in which the only freezing mechanism is homogeneous freezing to ice below the ice frost point. Alternative formation mechanisms, in particular homogeneous freezing above the ice frost point and heterogeneous freezing, have been explored using the microphysical model. Both nitric acid trihydrate (NAT) and nitric acid dihydrate (NAD) have been considered as possible compositions for the solid-phase nitric acid aerosols. Comparisons between the model results and the SOLVE measurements will be used to constrain the possible formation mechanisms. Other effects of these frozen particles will also be discussed, in particular denitrification.

Outcome regimes of binary raindrop collisions

NASA Astrophysics Data System (ADS)

Testik, Firat Y.

2009-11-01

This study delineates the physical conditions that are responsible for the occurrence of main outcome regimes (i.e., bounce, coalescence, and breakup) for binary drop collisions with a precipitation microphysics perspective. Physical considerations based on the collision kinetic energy and the surface energies of the colliding drops lead to the development of a theoretical regime diagram for the drop/raindrop collision outcomes in the We- p plane ( We — Weber number, p — raindrop diameter ratio). This theoretical regime diagram is supported by laboratory experimental observations of drop collisions using high-speed imaging. Results of this fundamental study bring in new insights into the quantitative understanding of drop dynamics, applications of which extend beyond precipitation microphysics. In particular, results of this drop collision study are expected to give impetus to the physics-based dynamic modeling of the drop size distributions that is essential for various typical modern engineering applications, including numerical modeling of evolution of raindrop size distribution in rain shaft.

Laboratory measurements of resistivity in warm dense plasmas relevant to the microphysics of brown dwarfs

DOE PAGES

Booth, N.; Robinson, A. P. L.; Hakel, P.; ...

2015-11-06

Since the observation of the first brown dwarf in 1995, numerous studies have led to a better understanding of the structures of these objects. Here we present a method for studying material resistivity in warm dense plasmas in the laboratory, which we relate to the microphysics of brown dwarfs through viscosity and electron collisions. Here we use X-ray polarimetry to determine the resistivity of a sulphur-doped plastic target heated to Brown Dwarf conditions by an ultra-intense laser. The resistivity is determined by matching the plasma physics model to the atomic physics calculations of the measured large, positive, polarization. Furthermore, themore » inferred resistivity is larger than predicted using standard resistivity models, suggesting that these commonly used models will not adequately describe the resistivity of warm dense plasma related to the viscosity of brown dwarfs.« less

Final Technical Report for "Reducing tropical precipitation biases in CESM"

DOE Office of Scientific and Technical Information (OSTI.GOV)

Larson, Vincent

In state-of-the-art climate models, each cloud type is treated using its own separate cloud parameterization and its own separate microphysics parameterization. This use of separate schemes for separate cloud regimes is undesirable because it is theoretically unfounded, it hampers interpretation of results, and it leads to the temptation to overtune parameters. In this grant, we have created a climate model that contains a unified cloud parameterization (“CLUBB”) and a unified microphysics parameterization (“MG2”). In this model, all cloud types --- including marine stratocumulus, shallow cumulus, and deep cumulus --- are represented with a single equation set. This model improves themore » representation of convection in the Tropics. The model has been compared with ARM observations. The chief benefit of the project is to provide a climate model that is based on a more theoretically rigorous formulation.« less

The Midlatitude Continental Convective Clouds Experiment (MC3E)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jensen, Mark P.; Petersen, Walt A.; Bansemer, Aaron

The Midlatitude Continental Convective Clouds Experiment (MC3E), a field program jointly led by the U.S. Department of Energy’s Atmospheric Radiation Measurement program and the NASA Global Precipitation Measurement (GPM) Mission, was conducted in south-central Oklahoma during April – May 2011. MC3E science objectives were motivated by the need to improve understanding of midlatitude continental convective cloud system lifecycles, microphysics, and GPM precipitation retrieval algorithms. To achieve these objectives a multi-scale surface- and aircraft-based in situ and remote sensing observing strategy was employed. A variety of cloud and precipitation events were sampled during the MC3E, of which results from three deepmore » convective events are highlighted. Vertical structure, air motions, precipitation drop-size distributions and ice properties were retrieved from multi-wavelength radar, profiler, and aircraft observations for an MCS on 11 May. Aircraft observations for another MCS observed on 20 May were used to test agreement between observed radar reflectivities and those calculated with forward-modeled reflectivity and microwave brightness temperatures using in situ particle size distributions and ice water content. Multi-platform observations of a supercell that occurred on 23 May allowed for an integrated analysis of kinematic and microphysical interactions. A core updraft of 25 ms-1 supported growth of hail and large rain drops. Data collected during the MC3E campaign is being used in a number of current and ongoing research projects and is available through the DOE ARM and NASA data archives.« less

Stratospheric Heterogeneous Chemistry and Microphysics: Model Development, Validation and Applications

NASA Technical Reports Server (NTRS)

Turco, Richard P.

1996-01-01

The objectives of this project are to: define the chemical and physical processes leading to stratospheric ozone change that involve polar stratospheric clouds (PSCS) and the reactions occurring on the surfaces of PSC particles; study the formation processes, and the physical and chemical properties of PSCS, that are relevant to atmospheric chemistry and to the interpretation of field measurements taken during polar stratosphere missions; develop quantitative models describing PSC microphysics and heterogeneous chemical processes; assimilate laboratory and field data into these models; and calculate the extent of chemical processing on PSCs and the impact of specific microphysical processes on polar composition and ozone depletion. During the course of the project, a new coupled microphysics/physical-chemistry/ photochemistry model for stratospheric sulfate aerosols and nitric acid and ice PSCs was developed and applied to analyze data collected during NASA's Arctic Airborne Stratospheric Expedition-II (AASE-II) and other missions. In this model, detailed treatments of multicomponent sulfate aerosol physical chemistry, sulfate aerosol microphysics, polar stratospheric cloud microphysics, PSC ice surface chemistry, as well as homogeneous gas-phase chemistry were included for the first time. In recent studies focusing on AASE measurements, the PSC model was used to analyze specific measurements from an aircraft deployment of an aerosol impactor, FSSP, and NO(y) detector. The calculated results are in excellent agreement with observations for particle volumes as well as NO(y) concentrations, thus confirming the importance of supercooled sulfate/nitrate droplets in PSC formation. The same model has been applied to perform a statistical study of PSC properties in the Northern Hemisphere using several hundred high-latitude air parcel trajectories obtained from Goddard. The rates of ozone depletion along trajectories with different meteorological histories are presently being systematically evaluated to identify the principal relationships between ozone loss and aerosol state. Under this project, we formulated a detailed quantitative model that predicts the multicomponent composition of sulfate aerosols under stratospheric conditions, including sulfuric, nitric, hydrochloric, hydrofluoric and hydrobromic acids. This work defined for the first time the behavior of liquid ternary-system type-1b PSCS. The model also allows the compositions and reactivities of sulfate aerosols to be calculated over the entire range of environmental conditions encountered in the stratosphere (and has been incorporated into a trajectory/microphysics model-see above). Important conclusions that derived from this work over the last few years include the following: the HNO3 content of liquid-state aerosols dominate PSCs below about 195 K; the freezing of nitric acid ice from sulfate aerosol solutions is likely to occur within a few degrees K of the water vapor frost point; the uptake and reactions of HCl in liquid aerosols is a critical component of PSC heterogeneous chemistry. In a related application of this work, the inefficiency of chlorine injection into the stratosphere during major volcanic eruptions was explained on the basis of nucleation of sulfuric acid aerosols in rising volcanic plumes leading to the formation of supercooled water droplets on these aerosols, which efficiently scavenges HCl via precipitation.

Implementation of aerosol-cloud interactions in the regional atmosphere-aerosol model COSMO-MUSCAT(5.0) and evaluation using satellite data

NASA Astrophysics Data System (ADS)

Dipu, Sudhakar; Quaas, Johannes; Wolke, Ralf; Stoll, Jens; Mühlbauer, Andreas; Sourdeval, Odran; Salzmann, Marc; Heinold, Bernd; Tegen, Ina

2017-06-01

The regional atmospheric model Consortium for Small-scale Modeling (COSMO) coupled to the Multi-Scale Chemistry Aerosol Transport model (MUSCAT) is extended in this work to represent aerosol-cloud interactions. Previously, only one-way interactions (scavenging of aerosol and in-cloud chemistry) and aerosol-radiation interactions were included in this model. The new version allows for a microphysical aerosol effect on clouds. For this, we use the optional two-moment cloud microphysical scheme in COSMO and the online-computed aerosol information for cloud condensation nuclei concentrations (Cccn), replacing the constant Cccn profile. In the radiation scheme, we have implemented a droplet-size-dependent cloud optical depth, allowing now for aerosol-cloud-radiation interactions. To evaluate the models with satellite data, the Cloud Feedback Model Intercomparison Project Observation Simulator Package (COSP) has been implemented. A case study has been carried out to understand the effects of the modifications, where the modified modeling system is applied over the European domain with a horizontal resolution of 0.25° × 0.25°. To reduce the complexity in aerosol-cloud interactions, only warm-phase clouds are considered. We found that the online-coupled aerosol introduces significant changes for some cloud microphysical properties. The cloud effective radius shows an increase of 9.5 %, and the cloud droplet number concentration is reduced by 21.5 %.

SSH-2 measurements of cirrus at 18-28 micrometers from the King Air during FIRE 2

NASA Technical Reports Server (NTRS)

Griffin, Michael K.

1993-01-01

In November of 1991, the First ISCCP (International Satellite Cloud Climatology Project) Regional Experiment (FIRE) Phase II cirrus study took place at Coffeyville, Kansas. The field experiment incorporated instrumentation from surface, aircraft, and satellite to attempt to define the optical, radiative, and microphysical characteristics of these high altitude, predominantly ice clouds. The NCAR King Air research aircraft was outfitted with a variety of radiative and microphysical instrumentation for the FIRE II project. Included for this project was the SSH-2, a 16-channel passive radiometer. The SSH-2 was originally designed as a space-qualified infrared (IR) temperature and water vapor sounder for deployment onboard the Defense Meteorological Satellite Program (DMSP) series of environmental satellites. For this experiment, only those channels associated with the water vapor profiling function have been examined although downwelling radiance measurements were taken at all channels during the project. With supporting information from the aircraft telemetry observations it may be possible to relate these SSH-2 measurements to cloud radiative and microphysical properties. The following sections will describe the spectral characteristics of the instrument, the calibration scheme used to convert the raw measured counts into calibrated radiances, and the case studies that will be covered in this paper. This will be followed by a discussion of the results of this preliminary investigation and a description of future work to be done.

Radiative-dynamical and microphysical processes of thin cirrus clouds controlling humidity of air entering the stratosphere

NASA Astrophysics Data System (ADS)

Dinh, Tra; Fueglistaler, Stephan

2016-04-01

Thin cirrus clouds in the tropical tropopause layer (TTL) are of great interest due to their role in the control of water vapor and temperature in the TTL. Previous research on TTL cirrus clouds has focussed mainly on microphysical processes, specifically the ice nucleation mechanism and dehydration efficiency. Here, we use a cloud resolving model to analyse the sensitivity of TTL cirrus characteristics and impacts with respect to microphysical and radiative processes. A steady-state TTL cirrus cloud field is obtained in the model forced with dynamical conditions typical for the TTL (2-dimensional setup with a Kelvin-wave temperature perturbation). Our model results show that the dehydration efficiency (as given by the domain average relative humidity in the layer of cloud occurrence) is relatively insensitive to the ice nucleation mechanism, i.e. homogeneous versus heterogeneous nucleation. Rather, TTL cirrus affect the water vapor entering the stratosphere via an indirect effect associated with the cloud radiative heating and dynamics. Resolving the cloud radiative heating and the radiatively induced circulations approximately doubles the domain average ice mass. The cloud radiative heating is proportional to the domain average ice mass, and the observed increase in domain average ice mass induces a domain average temperature increase of a few Kelvin. The corresponding increase in water vapor entering the stratosphere is estimated to be about 30 to 40%.

Indian Summer Monsoon Drought 2009: Role of Aerosol and Cloud Microphysics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hazra, Anupam; Taraphdar, Sourav; Halder, Madhuparna

2013-07-01

Cloud dynamics played a fundamental role in defining Indian summer monsoon (ISM) rainfall during drought in 2009. The anomalously negative precipitation was consistent with cloud properties. Although, aerosols inhibited the growth of cloud effective radius in the background of sparse water vapor, their role is secondary. The primary role, however, is played by the interactive feedback between cloud microphysics and dynamics owing to reduced efficient cloud droplet growth, lesser latent heating release and shortage of water content. Cloud microphysical processes were instrumental for the occurrence of ISM drought 2009.

Combined observational and modeling efforts of aerosol-cloud-precipitation interactions over Southeast Asia

NASA Astrophysics Data System (ADS)

Loftus, Adrian; Tsay, Si-Chee; Nguyen, Xuan Anh

2016-04-01

Low-level stratocumulus (Sc) clouds cover more of the Earth's surface than any other cloud type rendering them critical for Earth's energy balance, primarily via reflection of solar radiation, as well as their role in the global hydrological cycle. Stratocumuli are particularly sensitive to changes in aerosol loading on both microphysical and macrophysical scales, yet the complex feedbacks involved in aerosol-cloud-precipitation interactions remain poorly understood. Moreover, research on these clouds has largely been confined to marine environments, with far fewer studies over land where major sources of anthropogenic aerosols exist. The aerosol burden over Southeast Asia (SEA) in boreal spring, attributed to biomass burning (BB), exhibits highly consistent spatiotemporal distribution patterns, with major variability due to changes in aerosol loading mediated by processes ranging from large-scale climate factors to diurnal meteorological events. Downwind from source regions, the transported BB aerosols often overlap with low-level Sc cloud decks associated with the development of the region's pre-monsoon system, providing a unique, natural laboratory for further exploring their complex micro- and macro-scale relationships. Compared to other locations worldwide, studies of springtime biomass-burning aerosols and the predominately Sc cloud systems over SEA and their ensuing interactions are underrepresented in scientific literature. Measurements of aerosol and cloud properties, whether ground-based or from satellites, generally lack information on microphysical processes; thus cloud-resolving models are often employed to simulate the underlying physical processes in aerosol-cloud-precipitation interactions. The Goddard Cumulus Ensemble (GCE) cloud model has recently been enhanced with a triple-moment (3M) bulk microphysics scheme as well as the Regional Atmospheric Modeling System (RAMS) version 6 aerosol module. Because the aerosol burden not only affects cloud droplet size and number concentration, but also the spectral width of the cloud droplet size distribution, the 3M scheme is well suited to simulate aerosol-cloud-precipitation interactions within a three-dimensional regional cloud model. Moreover, the additional variability predicted on the hydrometeor distributions provides beneficial input for forward models to link the simulated microphysical processes with observations as well as to assess both ground-based and satellite retrieval methods. In this presentation, we provide an overview of the 7 South East Asian Studies / Biomass-burning Aerosols and Stratocumulus Environment: Lifecycles and Interactions Experiment (7-SEAS/BASELInE) operations during the spring of 2013. Preliminary analyses of pre-monsoon Sc system lifecycles observed during the first-ever deployment of a ground-based cloud radar to northern Vietnam will be also be presented. Initial results from GCE model simulations of these Sc using double-moment and the new 3M bulk microphysics schemes under various aerosol loadings will be used to showcase the 3M scheme as well as provide insight into how the impact of aerosols on cloud and precipitation processes in stratocumulus over land may manifest themselves in simulated remote-sensing signals. Applications and future work involving ongoing 7-SEAS campaigns aimed at improving our understanding of aerosol-cloud-precipitation interactions of will also be discussed.

Measurement needs guided by synthetic radar scans in high-resolution model output

NASA Astrophysics Data System (ADS)

Varble, A.; Nesbitt, S. W.; Borque, P.

2017-12-01

Microphysical and dynamical process interactions within deep convective clouds are not well understood, partly because measurement strategies often focus on statistics of cloud state rather than cloud processes. While processes cannot be directly measured, they can be inferred with sufficiently frequent and detailed scanning radar measurements focused on the life cycleof individual cloud regions. This is a primary goal of the 2018-19 DOE ARM Cloud, Aerosol, and Complex Terrain Interactions (CACTI) and NSF Remote sensing of Electrification, Lightning, And Mesoscale/microscale Processes with Adaptive Ground Observations (RELAMPAGO) field campaigns in central Argentina, where orographic deep convective initiation is frequent with some high-impact systems growing into the tallest and largest in the world. An array of fixed and mobile scanning multi-wavelength dual-polarization radars will be coupled with surface observations, sounding systems, multi-wavelength vertical profilers, and aircraft in situ measurements to characterize convective cloud life cycles and their relationship with environmental conditions. While detailed cloud processes are an observational target, the radar scan patterns that are most ideal for observing them are unclear. They depend on the locations and scales of key microphysical and dynamical processes operating within the cloud. High-resolution simulations of clouds, while imperfect, can provide information on these locations and scales that guide radar measurement needs. Radar locations are set in the model domain based on planned experiment locations, and simulatedorographic deep convective initiation and upscale growth are sampled using a number of different scans involving RHIs or PPIs with predefined elevation and azimuthal angles that approximately conform with radar range and beam width specifications. Each full scan pattern is applied to output atsingle model time steps with time step intervals that depend on the length of time required to complete each scan in the real world. The ability of different scans to detect key processes within the convective cloud life cycle are examined in connection with previous and subsequent dynamical and microphysical transitions. This work will guide strategic scan patterns that will be used during CACTI and RELAMPAGO.

Exploiting Cloud Radar Doppler Spectra of Mixed-Phase Clouds during ACCEPT Field Experiment to Identify Microphysical Processes

NASA Astrophysics Data System (ADS)

Kalesse, H.; Myagkov, A.; Seifert, P.; Buehl, J.

2015-12-01

Cloud radar Doppler spectra offer much information about cloud processes. By analyzing millimeter radar Doppler spectra from cloud-top to -base in mixed-phase clouds in which super-cooled liquid-layers are present we try to tell the microphysical evolution story of particles that are present by disentangling the contributions of the solid and liquid particles to the total radar returns. Instead of considering vertical profiles, dynamical effects are taken into account by following the particle population evolution along slanted paths which are caused by horizontal advection of the cloud. The goal is to identify regions in which different microphysical processes such as new particle formation (nucleation), water vapor deposition, aggregation, riming, or sublimation occurr. Cloud radar measurements are supplemented by Doppler lidar and Raman lidar observations as well as observations with MWR, wind profiler, and radio sondes. The presence of super-cooled liquid layers is identified by positive liquid water paths in MWR measurements, the vertical location of liquid layers (in non-raining systems and below lidar extinction) is derived from regions of high-backscatter and low depolarization in Raman lidar observations. In collocated cloud radar measurements, we try to identify cloud phase in the cloud radar Doppler spectrum via location of the Doppler peak(s), the existence of multi-modalities or the spectral skewness. Additionally, within the super-cooled liquid layers, the radar-identified liquid droplets are used as air motion tracer to correct the radar Doppler spectrum for vertical air motion w. These radar-derived estimates of w are validated by independent estimates of w from collocated Doppler lidar measurements. A 35 GHz vertically pointing cloud Doppler radar (METEK MIRA-35) in linear depolarization (LDR) mode is used. Data is from the deployment of the Leipzig Aerosol and Cloud Remote Observations System (LACROS) during the Analysis of the Composition of Clouds with Extended Polarization Techniques (ACCEPT) field experiment in Cabauw, Netherlands in Fall 2014. There, another MIRA-35 was operated in simultaneous transmission and simultaneous reception (STSR) mode for obtaining measurements of differential reflectivity (ZDR) and correlation coefficient ρhv.

The Impact of Microphysical Schemes on Hurricane Intensity and Track

NASA Technical Reports Server (NTRS)

Tao, Wei-Kuo; Shi, Jainn Jong; Chen, Shuyi S.; Lang, Stephen; Lin, Pay-Liam; Hong, Song-You; Peters-Lidard, Christa; Hou, Arthur

2011-01-01

During the past decade, both research and operational numerical weather prediction models [e.g. the Weather Research and Forecasting Model (WRF)] have started using more complex microphysical schemes originally developed for high-resolution cloud resolving models (CRMs) with 1-2 km or less horizontal resolutions. WRF is a next-generation meso-scale forecast model and assimilation system. It incorporates a modern software framework, advanced dynamics, numerics and data assimilation techniques, a multiple moveable nesting capability, and improved physical packages. WRF can be used for a wide range of applications, from idealized research to operational forecasting, with an emphasis on horizontal grid sizes in the range of 1-10 km. The current WRF includes several different microphysics options. At NASA Goddard, four different cloud microphysics options have been implemented into WRF. The performance of these schemes is compared to those of the other microphysics schemes available in WRF for an Atlantic hurricane case (Katrina). In addition, a brief review of previous modeling studies on the impact of microphysics schemes and processes on the intensity and track of hurricanes is presented and compared against the current Katrina study. In general, all of the studies show that microphysics schemes do not have a major impact on track forecasts but do have more of an effect on the simulated intensity. Also, nearly all of the previous studies found that simulated hurricanes had the strongest deepening or intensification when using only warm rain physics. This is because all of the simulated precipitating hydrometeors are large raindrops that quickly fall out near the eye-wall region, which would hydrostatically produce the lowest pressure. In addition, these studies suggested that intensities become unrealistically strong when evaporative cooling from cloud droplets and melting from ice particles are removed as this results in much weaker downdrafts in the simulated storms. However, there are many differences between the different modeling studies, which are identified and discussed.

Final Technical Report for Interagency Agreement No. DE-SC0005453 “Characterizing Aerosol Distributions, Types, and Optical and Microphysical Properties using the NASA Airborne High Spectral Resolution Lidar (HSRL) and the Research Scanning Polarimeter (RSP)”

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hostetler, Chris; Ferrare, Richard

Measurements of the vertical profile of atmospheric aerosols and aerosol optical and microphysical characteristics are required to: 1) determine aerosol direct and indirect radiative forcing, 2) compute radiative flux and heating rate profiles, 3) assess model simulations of aerosol distributions and types, and 4) establish the ability of surface and space-based remote sensors to measure the indirect effect. Consequently the ASR program calls for a combination of remote sensing and in situ measurements to determine aerosol properties and aerosol influences on clouds and radiation. As part of our previous DOE ASP project, we deployed the NASA Langley airborne High Spectralmore » Resolution Lidar (HSRL) on the NASA B200 King Air aircraft during major field experiments in 2006 (MILAGRO and MaxTEX), 2007 (CHAPS), 2009 (RACORO), and 2010 (CalNex and CARES). The HSRL provided measurements of aerosol extinction (532 nm), backscatter (532 and 1064 nm), and depolarization (532 and 1064 nm). These measurements were typically made in close temporal and spatial coincidence with measurements made from DOE-funded and other participating aircraft and ground sites. On the RACORO, CARES, and CalNEX missions, we also deployed the NASA Goddard Institute for Space Studies (GISS) Research Scanning Polarimeter (RSP). RSP provided intensity and degree of linear polarization over a broad spectral and angular range enabling column-average retrievals of aerosol optical and microphysical properties. Under this project, we analyzed observations and model results from RACORO, CARES, and CalNex and accomplished the following objectives. 1. Identified aerosol types, characterize the vertical distribution of the aerosol types, and partition aerosol optical depth by type, for CARES and CalNex using HSRL data as we have done for previous missions. 2. Investigated aerosol microphysical and macrophysical properties using the RSP. 3. Used the aerosol backscatter and extinction profiles measured by the HSRL to characterize the planetary boundary layer height (PBL) and the transition zone thickness, for the RACORO and CARES and CalNex campaigns as we have done for previous campaigns. 4. Investigated how optical properties measured by HSRL vary near clouds. 5. Assessed model simulations of aerosol spatial distributions and optical and microphysical properties.« less

Microphysical Model Studies of Venus Clouds

NASA Astrophysics Data System (ADS)

Meade, P. E.; Bullock, M. A.; Grinspoon, D. H.

2004-11-01

We have adapted a standard cloud microphysics model to construct a self-consistent microphysical model of Venus' cloud layer which reproduces and extends previous studies (e.g. James et al. 1997). Our model is based on the Community Aerosol and Radiation Model Atmosphere (CARMA), which is a widely used computer code for terrestrial cloud microphysics, derived from the work of Toon et al. (1988). The standard code has been adapted to treat H2O and H2SO4 as co-condensing vapor species onto aqueous H2SO4 cloud droplets, as well as the nucleation of condensation nuclei to droplets. Vapor condensation and evaporation follows the method of James et al. (1997). Microphysical processes included in this model include nucleation of condensation nuclei, condensation and evaporation of H2O and H2SO4 vapor, and droplet coagulation. Vertical transport occurs though advection, eddy diffusion, sedimentation for both droplets and condensation nuclei. The cloud model is used to explore the sensitivity of Venus' cloud layer to environmental changes. Observations of the Venus' lower cloud from the Pioneer Venus, Venera, and Galileo spacecraft have suggested that the properties of the lower cloud may be time-variable, and at times may be entirely absent (Carlson et al. 1993, Grinspoon et al. 1993, Esposito et al. 1997). Our model explores the dependence of such behavior on environment factors such as variations in water or SO2 abundance. We have also calculated the optical properties of the model atmosphere using both the conventional optical constants for H2SO4 (Palmer and Williams, 1975), and the new data of Tisdale et al. (1998). This work has been supported by NASA's Exobiology Program. References Carlson, R.W., et al., 1993. Planetary and Space Science, 41, 477-486. Esposito, L.W., et al., 1997. In Venus II, eds. S.W. Bougher et al., pp. 415-458, University of Arizona Press, Tucson. Grinspoon, D.H., et al., 1993. Planetary and Space Science, 41 (July 1993), 515-542. James, E. P., et al., 1997. Icarus, 129, 147-171. Palmer, K.F., and D. Williams, 1975. Applied Optics, 14, 208-219. Tisdale, R.T., et al., 1998. Journal of Geophysical Research, 103, 25,353-25,370. Toon , O. B., et al., 1988. J. Atmos. Sci., 45, 2123-2143.

The Impact of Aerosols on Cloud and Precipitation Processes: Cloud-Resolving Model Simulations

NASA Technical Reports Server (NTRS)

Tao, Wei-Kuo; Li, X.; Khain, A.; Simpson, S.

2005-01-01

Cloud microphysics are inevitable affected by the smoke particle (CCN, cloud condensation nuclei) size distributions below the clouds, Therefore, size distributions parameterized as spectral bin microphysics are needed to explicitly study the effect of atmospheric aerosol concentration on cloud development, rainfall production, and rainfall rates for convective clouds. Recently, a detailed spectral-bin microphysical scheme was implemented into the the Goddard Cumulus Ensemble (GCE) model. The formulation for the explicit spectral-bim microphysical processes is based on solving stochastic kinetic equations for the size distribution functions of water droplets (i.e., cloud droplets and raindrops), and several types of ice particles [i.e., pristine ice crystals (columnar and plate-like), snow (dendrites and aggregates), graupel and frozen drops/hail]. Each type is described by a special size distribution function containing many categories (i.e., 33 bins). Atmospheric aerosols are also described using number density size-distribution functions.

Precipitation in a boiling soup: is microphysics driving the statistical properties of intense turbulent convection?

NASA Astrophysics Data System (ADS)

Parodi, A.; von Hardenberg, J.; Provenzale, A.

2012-04-01

Intense precipitation events are often associated with strong convective phenomena in the atmosphere. A deeper understanding of how microphysics affects the spatial and temporal variability of convective processes is relevant for many hydro-meteorological applications, such as the estimation of rainfall using remote sensing techniques and the ability to predict severe precipitation processes. In this paper, high-resolution simulations (0.1-1 km) of an atmosphere in radiative-convective equilibrium are performed using the Weather Research and Forecasting (WRF) model by prescribing different microphysical parameterizations. The dependence of fine-scale spatio-temporal properties of convective structures on microphysical details are investigated and the simulation results are compared with the known properties of radar maps of precipitation fields. We analyze and discuss similarities and differences and, based also on previous results on the dependence of precipitation statistics on the raindrop terminal velocity, try to draw some general inferences.

The implications of dust ice nuclei effect on cloud top temperature in a complex mesoscale convective system.

PubMed

Li, Rui; Dong, Xue; Guo, Jingchao; Fu, Yunfei; Zhao, Chun; Wang, Yu; Min, Qilong

2017-10-23

Mineral dust is the most important natural source of atmospheric ice nuclei (IN) which may significantly mediate the properties of ice cloud through heterogeneous nucleation and lead to crucial impacts on hydrological and energy cycle. The potential dust IN effect on cloud top temperature (CTT) in a well-developed mesoscale convective system (MCS) was studied using both satellite observations and cloud resolving model (CRM) simulations. We combined satellite observations from passive spectrometer, active cloud radar, lidar, and wind field simulations from CRM to identify the place where ice cloud mixed with dust particles. For given ice water path, the CTT of dust-mixed cloud is warmer than that in relatively pristine cloud. The probability distribution function (PDF) of CTT for dust-mixed clouds shifted to the warmer end and showed two peaks at about -45 °C and -25 °C. The PDF for relatively pristine cloud only show one peak at -55 °C. Cloud simulations with different microphysical schemes agreed well with each other and showed better agreement with satellite observations in pristine clouds, but they showed large discrepancies in dust-mixed clouds. Some microphysical schemes failed to predict the warm peak of CTT related to heterogeneous ice formation.

Ship-based Observations of Turbulence and Stratocumulus Cloud Microphysics in the SE Pacific Ocean from the VOCALS Field Program

NASA Astrophysics Data System (ADS)

Fairall, C. W.; Williams, C.; Grachev, A. A.; Brewer, A.; Choukulkar, A.

2013-12-01

The VAMOS (VOCALS) field program involved deployment of several measurement systems based on ships, land and aircraft over the SE Pacific Ocean. The NOAA Ship Ronald H. Brown was the primary platform for surface based measurements which included the High Resolution Doppler Lidar (HRDL) and the motion-stabilized 94-GHz cloud Doppler radar (W-band radar). In this paper, the data from the W-band radar will be used to study the turbulent and microphysical structure of the stratocumulus clouds prevalent in the region. The radar data consists of a 3 Hz time series of radar parameters (backscatter coefficient, mean Doppler shift, and Doppler width) at 175 range gates (25-m spacing). Several statistical methods to de-convolve the turbulent velocity and gravitational settling velocity are examined and an optimized algorithm is developed. 20 days of observations are processed to examine in-cloud profiles of mean turbulent statistics (vertical velocity variance, skewness, dissipation rate) in terms of surface fluxes and estimates of entrainment and cloudtop radiative cooling. The clean separation of turbulent and fall velocities will allow us to compute time-averaged drizzle-drop size spectra within and below the cloud that are significantly superior to previous attempts with surface-based marine cloud radar observations.

An observational study of entrainment rate in deep convection

DOE PAGES

Guo, Xiaohao; Lu, Chunsong; Zhao, Tianliang; ...

2015-09-22

This study estimates entrainment rate and investigates its relationships with cloud properties in 156 deep convective clouds based on in-situ aircraft observations during the TOGA-COARE (Tropical Ocean Global Atmosphere Coupled Ocean Atmosphere Response Experiment) field campaign over the western Pacific. To the authors’ knowledge, this is the first study on the probability density function of entrainment rate, the relationships between entrainment rate and cloud microphysics, and the effects of dry air sources on the calculated entrainment rate in deep convection from an observational perspective. Results show that the probability density function of entrainment rate can be well fitted by lognormal,more » gamma or Weibull distribution, with coefficients of determination being 0.82, 0.85 and 0.80, respectively. Entrainment tends to reduce temperature, water vapor content and moist static energy in cloud due to evaporative cooling and dilution. Inspection of the relationships between entrainment rate and microphysical properties reveals a negative correlation between volume-mean radius and entrainment rate, suggesting the potential dominance of homogeneous mechanism in the clouds examined. The entrainment rate and environmental water vapor content show similar tendencies of variation with the distance of the assumed environmental air to the cloud edges. Their variation tendencies are non-monotonic due to the relatively short distance between adjacent clouds.« less

An observational study of entrainment rate in deep convection

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guo, Xiaohao; Lu, Chunsong; Zhao, Tianliang

This study estimates entrainment rate and investigates its relationships with cloud properties in 156 deep convective clouds based on in-situ aircraft observations during the TOGA-COARE (Tropical Ocean Global Atmosphere Coupled Ocean Atmosphere Response Experiment) field campaign over the western Pacific. To the authors’ knowledge, this is the first study on the probability density function of entrainment rate, the relationships between entrainment rate and cloud microphysics, and the effects of dry air sources on the calculated entrainment rate in deep convection from an observational perspective. Results show that the probability density function of entrainment rate can be well fitted by lognormal,more » gamma or Weibull distribution, with coefficients of determination being 0.82, 0.85 and 0.80, respectively. Entrainment tends to reduce temperature, water vapor content and moist static energy in cloud due to evaporative cooling and dilution. Inspection of the relationships between entrainment rate and microphysical properties reveals a negative correlation between volume-mean radius and entrainment rate, suggesting the potential dominance of homogeneous mechanism in the clouds examined. The entrainment rate and environmental water vapor content show similar tendencies of variation with the distance of the assumed environmental air to the cloud edges. Their variation tendencies are non-monotonic due to the relatively short distance between adjacent clouds.« less

Spatial and Temporal Distribution of Tropospheric Clouds and Aerosols Observed by MODIS Onboard the Terra and Aqua Satellites

NASA Technical Reports Server (NTRS)

King, Michael D.; Platnick, Steven; Remer, Lorraine A.; Kaufman, Yoram J.

2004-01-01

Remote sensing of cloud and aerosol optical properties is routinely obtained using the Moderate Resolution Imaging Spectroradiometer (MODIS) onboard the Terra and Aqua satellites. Techniques that are being used to enhance our ability to characterize the global distribution of cloud and aerosol properties include well-calibrated multispectral radiometers that rely on visible, near-infrared, and thermal infrared channels. The availability of thermal channels to aid in cloud screening for aerosol properties is an important additional piece of information that has not always been incorporated into sensor designs. In this paper, we describe the radiative properties of clouds as currently determined from satellites (cloud fraction, optical thickness, cloud top pressure, and cloud effective radius), and highlight the global and regional cloud microphysical properties currently available for assessing climate variability and forcing. These include the latitudinal distribution of cloud optical and radiative properties of both liquid water and ice clouds, as well as joint histograms of cloud optical thickness and effective radius for selected geographical locations around the world. In addition, we will illustrate the radiative and microphysical properties of aerosol particles that are currently available from space-based observations, and show selected cases in which aerosol particles are observed to modify the cloud optical properties.

Multi-Spectral Cloud Retrievals from Moderate Image Spectrometer (MODIS)

NASA Technical Reports Server (NTRS)

Platnick, Steven

2004-01-01

MODIS observations from the NASA EOS Terra spacecraft (1030 local time equatorial sun-synchronous crossing) launched in December 1999 have provided a unique set of Earth observation data. With the launch of the NASA EOS Aqua spacecraft (1330 local time crossing! in May 2002: two MODIS daytime (sunlit) and nighttime observations are now available in a 24-hour period allowing some measure of diurnal variability. A comprehensive set of remote sensing algorithms for cloud masking and the retrieval of cloud physical and optical properties has been developed by members of the MODIS atmosphere science team. The archived products from these algorithms have applications in climate modeling, climate change studies, numerical weather prediction, as well as fundamental atmospheric research. In addition to an extensive cloud mask, products include cloud-top properties (temperature, pressure, effective emissivity), cloud thermodynamic phase, cloud optical and microphysical parameters (optical thickness, effective particle radius, water path), as well as derived statistics. An overview of the instrument and cloud algorithms will be presented along with various examples, including an initial analysis of several operational global gridded (Level-3) cloud products from the two platforms. Statistics of cloud optical and microphysical properties as a function of latitude for land and Ocean regions will be shown. Current algorithm research efforts will also be discussed.

Arctic Mixed-phase Clouds Simulated by a Cloud-Resolving Model: Comparison with ARM Observations and Sensitivity to Microphysics Parameterizations

NASA Technical Reports Server (NTRS)

Xu, Kuan-Man; Luo, Yali; Morrison, Hugh; Mcfarquhar, G.M.

2008-01-01

Single-layer mixed-phase stratiform (MPS) Arctic clouds, which formed under conditions of large surface heat flux combined with general subsidence during a subperiod of the Atmospheric Radiation Measurement (ARM) Program Mixed-Phase Arctic Cloud Experiment (M-PACE), are simulated with a cloud resolving model (CRM). The CRM is implemented with either an advanced two-moment (M05) or a commonly used one-moment (L83) bulk microphysics scheme and a state-of-the-art radiative transfer scheme. The CONTROL simulation, that uses the M05 scheme and observed aerosol size distribution and ice nulei (IN) number concentration, reproduces the magnitudes and vertical structures of cloud liquid water content (LWC), total ice water content (IWC), number concentration and effective radius of cloud droplets as suggested by the M-PACE observations. It underestimates ice crystal number concentrations by an order of magnitude and overestimates effective radius of ice crystals by a factor of 2-3. The OneM experiment, that uses the L83 scheme, produces values of liquid water path (LWP) and ice plus snow water path (ISWP) that were about 30% and 4 times, respectively, of those produced by the CONTROL. Its vertical profile of IWC exhibits a bimodal distribution in contrast to the constant distribution of IWC produced in the CONTROL and observations.

Comparison of PARASOL Observations with Polarized Reflectances Simulated Using Different Ice Habit Mixtures

NASA Technical Reports Server (NTRS)

Cole, Benjamin H.; Yang, Ping; Baum, Bryan A.; Riedi, Jerome; Labonnote, Laurent C.; Thieuleux, Francois; Platnick, Steven

2012-01-01

Insufficient knowledge of the habit distribution and the degree of surface roughness of ice crystals within ice clouds is a source of uncertainty in the forward light scattering and radiative transfer simulations required in downstream applications involving these clouds. The widely used MODerate Resolution Imaging Spectroradiometer (MODIS) Collection 5 ice microphysical model assumes a mixture of various ice crystal shapes with smooth-facets except aggregates of columns for which a moderately rough condition is assumed. When compared with PARASOL (Polarization and Anisotropy of Reflectances for Atmospheric Sciences coupled with Observations from a Lidar) polarized reflection data, simulations of polarized reflectance using smooth particles show a poor fit to the measurements, whereas very rough-faceted particles provide an improved fit to the polarized reflectance. In this study a new microphysical model based on a mixture of 9 different ice crystal habits with severely roughened facets is developed. Simulated polarized reflectance using the new ice habit distribution is calculated using a vector adding-doubling radiative transfer model, and the simulations closely agree with the polarized reflectance observed by PARASOL. The new general habit mixture is also tested using a spherical albedo differences analysis, and surface roughening is found to improve the consistency of multi-angular observations. It is suggested that an ice model incorporating an ensemble of different habits with severely roughened surfaces would potentially be an adequate choice for global ice cloud retrievals.

A Self-consistent Cloud Model for Brown Dwarfs and Young Giant Exoplanets: Comparison with Photometric and Spectroscopic Observations

NASA Astrophysics Data System (ADS)

Charnay, B.; Bézard, B.; Baudino, J.-L.; Bonnefoy, M.; Boccaletti, A.; Galicher, R.

2018-02-01

We developed a simple, physical, and self-consistent cloud model for brown dwarfs and young giant exoplanets. We compared different parametrizations for the cloud particle size, by fixing either particle radii or the mixing efficiency (parameter f sed), or by estimating particle radii from simple microphysics. The cloud scheme with simple microphysics appears to be the best parametrization by successfully reproducing the observed photometry and spectra of brown dwarfs and young giant exoplanets. In particular, it reproduces the L–T transition, due to the condensation of silicate and iron clouds below the visible/near-IR photosphere. It also reproduces the reddening observed for low-gravity objects, due to an increase of cloud optical depth for low gravity. In addition, we found that the cloud greenhouse effect shifts chemical equilibrium, increasing the abundances of species stable at high temperature. This effect should significantly contribute to the strong variation of methane abundance at the L–T transition and to the methane depletion observed on young exoplanets. Finally, we predict the existence of a continuum of brown dwarfs and exoplanets for absolute J magnitude = 15–18 and J-K color = 0–3, due to the evolution of the L–T transition with gravity. This self-consistent model therefore provides a general framework to understand the effects of clouds and appears well-suited for atmospheric retrievals.

Orographic Modification of Precipitation Processes in a Tropical Cyclone Moving over a Continental Mountain Range

NASA Astrophysics Data System (ADS)

DeHart, Jennifer C.

Airborne radar reflectivity data and numerical simulations are examined to determine how tropical cyclone precipitation processes are impacted by landfall over a continental mountain range. Analysis of the high-resolution radar data collected within Hurricane Karl (2010) during the Genesis and Rapid Intensification Processes (GRIP) shows that radar reflectivity enhancement in regions of upslope flow is constrained to low-levels. Reflectivity enhancement is not uniform and discrete regions of enhanced precipitation are embedded within a broad echo. In conjunction with an upstream dropsonde that exhibits weak instability, the radar data suggest a mix of gentle ascent and shallow convection occur. Regions of downslope flow are characterized by precipitation originating further aloft with little modification near low levels. Satellite data further indicate that deep convection develops after the high clouds dissipate, indicating that the evolving thermodynamic environment favors orographic modification processes beyond collection of orographically-generated cloud water. Numerical simulations examine how modification processes controlling precipitation are affected by the height of an idealized plateau. When terrain is minimal, the tropical cyclone decays slowly, the upper-level warm core remains robust, the moist neutral environment persists, and precipitation processes are largely concentrated within the eyewall and rainband. Movement over a tall topographic barrier induces rapid decay, which erodes the warm core and moist neutral environment. A mix of forced ascent and buoyant motions contribute to enhanced warm rain processes over the terrain. Overall, all microphysical quantities are greater for the tall plateau storm, but concentrations within the innermost core decay rapidly along with the storm. It is shown that the simulated tropical cyclone precipitation is heavily influenced by overestimated graupel production, which is a common problem of microphysical schemes. Surface precipitation is comparable between the two experiments, suggesting that strong decay of the storm affects the upper limit of precipitation. Similar precipitation patterns between the observations and tall plateau simulation suggest that the model obtains realistic precipitation through incorrect microphysical processes, but a lack of microphysical observations prevent full assessment of that hypothesis. Overall, this dissertation demonstrates that decay due to landfall over complex terrain affects the inner core thermodynamic and kinematic environment, which in turn affects the type and organization of precipitation processes that occur.

Influence of Meteorological Regimes on Cloud Microphysics Over Ross Island, Antarctica

NASA Astrophysics Data System (ADS)

Glennon, C.; Wang, S. H.; Scott, R. C.; Bromwich, D. H.; Lubin, D.

2017-12-01

The Antarctic provides a sharp contrast in cloud microphysics from the high Arctic, due to orographic lifting and resulting strong vertical motions induced by mountain ranges and other varying terrain on several spatial scales. The Atmospheric Radiation Measurement (ARM) West Antarctic Radiation Experiment (AWARE) deployed advanced cloud remote sensing equipment to Ross Island, Antarctica, from December 2015 until January 2016. This equipment included scanning and zenith radars operating in the Ka and X bands, a high spectral resolution lidar (HSRL), and a polarized micropulse lidar (MPL). A major AWARE objective is to provide state-of-the-art data for improving cloud microphysical parameterizations in climate models. To further this objective we have organized and classified the local Ross Island meteorology into distinct regimes using k-means clustering on ERA-Interim reanalysis data. We identify synoptic categories producing unique regimes of cloud cover and cloud microphysical properties over Ross Island. Each day of observations can then be associated with a specific meteorological regime, thus assisting modelers with identifying case studies. High-resolution (1 km) weather forecasts from the Antarctic Mesoscale Prediction System (AMPS) are sorted into these categories. AMPS-simulated anomalies of cloud fraction, near-surface air temperature, and vertical velocity at 500-mb are composited and compared with ground-based radar and lidar-derived cloud properties to identify mesoscale meteorological processes driving Antarctic cloud formation. Synoptic lows over the Ross and Amundsen Seas drive anomalously warm conditions at Ross Island by injecting marine air masses inland over the West Antarctic Ice Sheet (WAIS). This results in ice and mixed-phase orographic cloud systems arriving at Ross Island from the south to southeast along the Transantarctic Mountains. In contrast, blocking over the Amundsen Sea region brings classical liquid-dominated mixed-phase and thin liquid water clouds from the Southern Ocean. Low pressure systems over the Bellingshausen Sea produce outflow of cold, dry continental polar air, yielding predominantly tenuous ice cloud at Ross Island.

Particle backscatter and relative humidity measured across cirrus clouds and comparison with microphysical cirrus modelling

NASA Astrophysics Data System (ADS)

Brabec, M.; Wienhold, F. G.; Luo, B. P.; Vömel, H.; Immler, F.; Steiner, P.; Hausammann, E.; Weers, U.; Peter, T.

2012-10-01

Advanced measurement and modelling techniques are employed to estimate the partitioning of atmospheric water between the gas phase and the condensed phase in and around cirrus clouds, and thus to identify in-cloud and out-of-cloud supersaturations with respect to ice. In November 2008 the newly developed balloon-borne backscatter sonde COBALD (Compact Optical Backscatter and AerosoL Detector) was flown 14 times together with a CFH (Cryogenic Frost point Hygrometer) from Lindenberg, Germany (52° N, 14° E). The case discussed here in detail shows two cirrus layers with in-cloud relative humidities with respect to ice between 50% and 130%. Global operational analysis data of ECMWF (roughly 1° × 1° horizontal and 1 km vertical resolution, 6-hourly stored fields) fail to represent ice water contents and relative humidities. Conversely, regional COSMO-7 forecasts (6.6 km × 6.6 km, 5-min stored fields) capture the measured humidities and cloud positions remarkably well. The main difference between ECMWF and COSMO data is the resolution of small-scale vertical features responsible for cirrus formation. Nevertheless, ice water contents in COSMO-7 are still off by factors 2-10, likely reflecting limitations in COSMO's ice phase bulk scheme. Significant improvements can be achieved by comprehensive size-resolved microphysical and optical modelling along backward trajectories based on COSMO-7 wind and temperature fields, which allow accurate computation of humidities, homogeneous ice nucleation, resulting ice particle size distributions and backscatter ratios at the COBALD wavelengths. However, only by superimposing small-scale temperature fluctuations, which remain unresolved by the numerical weather prediction models, can we obtain a satisfying agreement with the observations and reconcile the measured in-cloud non-equilibrium humidities with conventional ice cloud microphysics. Conversely, the model-data comparison provides no evidence that additional changes to ice-cloud microphysics - such as heterogeneous nucleation or changing the water vapour accommodation coefficient on ice - are required.

A Multi-Moment Bulkwater Ice Microphysics Scheme with Consideration of the Adaptive Growth Habit and Apparent Density for Pristine Ice in the WRF Model

NASA Astrophysics Data System (ADS)

Tsai, T. C.; Chen, J. P.; Dearden, C.

2014-12-01

The wide variety of ice crystal shapes and growth habits makes it a complicated issue in cloud models. This study developed the bulk ice adaptive habit parameterization based on the theoretical approach of Chen and Lamb (1994) and introduced a 6-class hydrometeors double-moment (mass and number) bulk microphysics scheme with gamma-type size distribution function. Both the proposed schemes have been implemented into the Weather Research and Forecasting model (WRF) model forming a new multi-moment bulk microphysics scheme. Two new moments of ice crystal shape and volume are included for tracking pristine ice's adaptive habit and apparent density. A closure technique is developed to solve the time evolution of the bulk moments. For the verification of the bulk ice habit parameterization, some parcel-type (zero-dimension) calculations were conducted and compared with binned numerical calculations. The results showed that: a flexible size spectrum is important in numerical accuracy, the ice shape can significantly enhance the diffusional growth, and it is important to consider the memory of growth habit (adaptive growth) under varying environmental conditions. Also, the derived results with the 3-moment method were much closer to the binned calculations. A field campaign of DIAMET was selected to simulate in the WRF model for real-case studies. The simulations were performed with the traditional spherical ice and the new adaptive shape schemes to evaluate the effect of crystal habits. Some main features of narrow rain band, as well as the embedded precipitation cells, in the cold front case were well captured by the model. Furthermore, the simulations produced a good agreement in the microphysics against the aircraft observations in ice particle number concentration, ice crystal aspect ratio, and deposition heating rate especially within the temperature region of ice secondary multiplication production.

Factors Influencing Aerosol Concentrations and Properties over the Tropical Eastern Pacific: Observations from TC4

NASA Astrophysics Data System (ADS)

Anderson, B. E.; Chen, G.; Thornhill, K. L.; Winstead, E. L.; Dibb, J.; Scheuer, E.; Lathem, T.

2007-12-01

The NASA Tropical Composition Cloud and Climate Coupling (TC4) mission was conducted during summer 2007 and had the primary objective of gaining a better understanding of composition and dynamics of the upper troposphere over the tropical eastern pacific region. Based in San Jose, Costa Rica, the mission employed instrumented aircraft along with ground, balloon, and satellite borne sensors to determine the spatial distribution of trace gas and aerosol species as well as moisture and clouds between the surface and roughly 16 km altitude over Central America, the eastern Pacific, the western Caribbean and northern South America. Because of its heavy payload and long endurance capability, the NASA DC-8 aircraft was the primary sampling platform for the lower-tropospheric altitude regime (i.e., below 12 km). It carried both remote and in situ instruments and was used to characterize cloud inflow and outflow as well as the microphysical properties of maritime convective systems. Because of their roles in regulating atmospheric radiation transfer and cloud formation and microphysics, flight plans placed particular emphasis on determining the sources and properties of the aerosol particles present within the region. A preliminary analysis of the DC-8 data set suggests that the following sources/processes had the greatest impact on aerosol number and mass loading: dust transport from Africa; sea salt production over the ocean; urban and biogenic emissions over the continent; secondary aerosol formation in volcanic plumes; nucleation in cloud outflow; and cloud scavenging. In this presentation, we will examine the microphysical, optical and hydration properties of each aerosol type and assess the overall impact of the source/sink processes to the regional aerosol budget. We will also contrast the microphysical properties of the Saharan Dust sampled over the Caribbean with those measured in fresh dust layers over the eastern Atlantic from the DC-8 during the summer 2006, NASA African Monsoon Multidisciplinary Activity (NAMMA).

Evaluation of Cloud-Resolving Model Intercomparison Simulations Using TWP-ICE Observations: Precipitation and Cloud Structure

NASA Technical Reports Server (NTRS)

Varble, Adam; Fridlind, Ann M.; Zipser, Edward J.; Ackerman, Andrew S.; Chaboureau, Jean-Pierre; Fan, Jiwen; Hill, Adrian; McFarlane, Sally A.; Pinty, Jean-Pierre; Shipway, Ben

2011-01-01

The Tropical Warm Pool.International Cloud Experiment (TWP ]ICE) provided extensive observational data sets designed to initialize, force, and constrain atmospheric model simulations. In this first of a two ]part study, precipitation and cloud structures within nine cloud ]resolving model simulations are compared with scanning radar reflectivity and satellite infrared brightness temperature observations during an active monsoon period from 19 to 25 January 2006. Seven of nine simulations overestimate convective area by 20% or more leading to general overestimation of convective rainfall. This is balanced by underestimation of stratiform rainfall by 5% to 50% despite overestimation of stratiform area by up to 65% because of a preponderance of very low stratiform rain rates in all simulations. All simulations fail to reproduce observed radar reflectivity distributions above the melting level in convective regions and throughout the troposphere in stratiform regions. Observed precipitation ]sized ice reaches higher altitudes than simulated precipitation ]sized ice despite some simulations that predict lower than observed top ]of ]atmosphere infrared brightness temperatures. For the simulations that overestimate radar reflectivity aloft, graupel is the cause with one ]moment microphysics schemes whereas snow is the cause with two ]moment microphysics schemes. Differences in simulated radar reflectivity are more highly correlated with differences in mass mean melted diameter (Dm) than differences in ice water content. Dm is largely dependent on the mass ]dimension relationship and gamma size distribution parameters such as size intercept (N0) and shape parameter (m). Having variable density, variable N0, or m greater than zero produces radar reflectivities closest to those observed.

Microphysical, Macrophysical and Radiative Signatures of Volcanic Aerosols in Trade Wind Cumulus Observed by the A-Train

NASA Technical Reports Server (NTRS)

Yuan, T.; Remer, L. A.; Yu, H.

2011-01-01

Increased aerosol concentrations can raise planetary albedo not only by reflecting sunlight and increasing cloud albedo, but also by changing cloud amount. However, detecting aerosol effect on cloud amount has been elusive to both observations and modeling due to potential buffering mechanisms and convolution of meteorology. Here through a natural experiment provided by long-tem1 degassing of a low-lying volcano and use of A-Train satellite observations, we show modifications of trade cumulus cloud fields including decreased droplet size, decreased precipitation efficiency and increased cloud amount are associated with volcanic aerosols. In addition we find significantly higher cloud tops for polluted clouds. We demonstrate that the observed microphysical and macrophysical changes cannot be explained by synoptic meteorology or the orographic effect of the Hawaiian Islands. The "total shortwave aerosol forcin", resulting from direct and indirect forcings including both cloud albedo and cloud amount. is almost an order of magnitude higher than aerosol direct forcing alone. Furthermore, the precipitation reduction associated with enhanced aerosol leads to large changes in the energetics of air-sea exchange and trade wind boundary layer. Our results represent the first observational evidence of large-scale increase of cloud amount due to aerosols in a trade cumulus regime, which can be used to constrain the representation of aerosol-cloud interactions in climate models. The findings also have implications for volcano-climate interactions and climate mitigation research.

The Kinematic and Microphysical Control of Storm Integrated Lightning Flash Extent

NASA Technical Reports Server (NTRS)

Carey, Lawrence D.; Koshak, William J.; Peterson, Harold S.; Shultz, Elise; Matthee, Retha; Shultz, Christopher J.; Petersen, Walter A.; Bain, Lamont

2013-01-01

To investigate the kinematic and microphysical control of lightning properties, particularly those that may govern the production of nitrogen oxides (NO(x)) in thunderstorms, such as flash rate, type (intracloud (IC) vs. cloud-to-ground (CG)) and extent.

Retrieval of effective cloud field parameters from radiometric data

NASA Astrophysics Data System (ADS)

Paulescu, Marius; Badescu, Viorel; Brabec, Marek

2017-06-01

Clouds play a key role in establishing the Earth's climate. Real cloud fields are very different and very complex in both morphological and microphysical senses. Consequently, the numerical description of the cloud field is a critical task for accurate climate modeling. This study explores the feasibility of retrieving the effective cloud field parameters (namely the cloud aspect ratio and cloud factor) from systematic radiometric measurements at high frequency (measurement is taken every 15 s). Two different procedures are proposed, evaluated, and discussed with respect to both physical and numerical restrictions. None of the procedures is classified as best; therefore, the specific advantages and weaknesses are discussed. It is shown that the relationship between the cloud shade and point cloudiness computed using the estimated cloud field parameters recovers the typical relationship derived from measurements.

Parameterizations of the Vertical Variability of Tropical Cirrus Cloud Microphysical and Optical Properties

NASA Technical Reports Server (NTRS)

Twohy, Cynthia; Heymsfield, Andrew; Gerber, Hermann

2005-01-01

Our multi-investigator effort was targeted at the following areas of interest to CRYSTAL-FACE: (1) the water budgets of anvils, (2) parameterizations of the particle size distributions and related microphysical and optical properties (3) characterizations of the primary ice particle habits, (4) the relationship of the optical properties to the microphysics and particle habits, and (5) investigation of the ice-nuclei types and mechanisms in anvil cirrus. Dr. Twohy's effort focused on (l), (2), and (5), with the measurement and analysis of ice water content and cirrus residual nuclei using the counterflow virtual impactor (CVI).

Microphysical Timescales in Clouds and their Application in Cloud-Resolving Modeling

NASA Technical Reports Server (NTRS)

Zeng, Xiping; Tao, Wei-Kuo; Simpson, Joanne

2007-01-01

Independent prognostic variables in cloud-resolving modeling are chosen on the basis of the analysis of microphysical timescales in clouds versus a time step for numerical integration. Two of them are the moist entropy and the total mixing ratio of airborne water with no contributions from precipitating particles. As a result, temperature can be diagnosed easily from those prognostic variables, and cloud microphysics be separated (or modularized) from moist thermodynamics. Numerical comparison experiments show that those prognostic variables can work well while a large time step (e.g., 10 s) is used for numerical integration.

How to assess the impact of a physical parameterization in simulations of moist convection?

NASA Astrophysics Data System (ADS)

Grabowski, Wojciech

2017-04-01

A numerical model capable in simulating moist convection (e.g., cloud-resolving model or large-eddy simulation model) consists of a fluid flow solver combined with required representations (i.e., parameterizations) of physical processes. The later typically include cloud microphysics, radiative transfer, and unresolved turbulent transport. Traditional approaches to investigate impacts of such parameterizations on convective dynamics involve parallel simulations with different parameterization schemes or with different scheme parameters. Such methodologies are not reliable because of the natural variability of a cloud field that is affected by the feedback between the physics and dynamics. For instance, changing the cloud microphysics typically leads to a different realization of the cloud-scale flow, and separating dynamical and microphysical impacts is difficult. This presentation will present a novel modeling methodology, the piggybacking, that allows studying the impact of a physical parameterization on cloud dynamics with confidence. The focus will be on the impact of cloud microphysics parameterization. Specific examples of the piggybacking approach will include simulations concerning the hypothesized deep convection invigoration in polluted environments, the validity of the saturation adjustment in modeling condensation in moist convection, and separation of physical impacts from statistical uncertainty in simulations applying particle-based Lagrangian microphysics, the super-droplet method.

Spatial and Temporal Distribution of Tropospheric Clouds and Aerosols Observed by MODIS Onboard the Terra and Aqua Satellites

NASA Technical Reports Server (NTRS)

King, Michael D.; Platnick, Steven; Menzel, W. Paul; Ackerman, Steven A.; Remer, Lorraine A.

2006-01-01

Remote sensing of cloud and aerosol optical properties is routinely obtained using the Moderate Resolution Imaging Spectroradiometer (MODIS) onboard the Terra and Aqua satellites. Instruments that are being used to enhance our ability to characterize the global distribution of cloud and aerosol properties include well-calibrated multispectral radiometers that measure in the visible, near-infrared, and thermal infrared. The availability of thermal channels to enhance detection of cloud when estimating aerosol properties is an important improvement. In this paper, we describe the radiative properties of clouds as currently determined from satellites (cloud fraction, optical thickness, cloud top pressure, and cloud particle effective radius) and highlight the global/regional cloud microphysical properties currently available for assessing climate variability and forcing. These include the latitudinal distribution of cloud optical and radiative properties of both liquid water and ice clouds, as well as joint histograms of cloud optical thickness and effective particle radius for selected geographical locations around the world. In addition, we will illustrate the radiative and microphysical properties of aerosol particles (in cloud free regions) that are currently available from space-based observations, and show the latitudinal distribution of aerosol optical properties over both land and ocean surfaces.

G-band atmospheric radars: new frontiers in cloud physics

NASA Astrophysics Data System (ADS)

Battaglia, A.; Westbrook, C. D.; Kneifel, S.; Kollias, P.; Humpage, N.; Löhnert, U.; Tyynelä, J.; Petty, G. W.

2014-01-01

Clouds and associated precipitation are the largest source of uncertainty in current weather and future climate simulations. Observations of the microphysical, dynamical and radiative processes that act at cloud-scales are needed to improve our understanding of clouds. The rapid expansion of ground-based super-sites and the availability of continuous profiling and scanning multi-frequency radar observations at 35 and 94 GHz have significantly improved our ability to probe the internal structure of clouds in high temporal-spatial resolution, and to retrieve quantitative cloud and precipitation properties. However, there are still gaps in our ability to probe clouds due to large uncertainties in the retrievals. The present work discusses the potential of G-band (frequency between 110 and 300 GHz) Doppler radars in combination with lower frequencies to further improve the retrievals of microphysical properties. Our results show that, thanks to a larger dynamic range in dual-wavelength reflectivity, dual-wavelength attenuation and dual-wavelength Doppler velocity (with respect to a Rayleigh reference), the inclusion of frequencies in the G-band can significantly improve current profiling capabilities in three key areas: boundary layer clouds, cirrus and mid-level ice clouds, and precipitating snow.

G band atmospheric radars: new frontiers in cloud physics

NASA Astrophysics Data System (ADS)

Battaglia, A.; Westbrook, C. D.; Kneifel, S.; Kollias, P.; Humpage, N.; Löhnert, U.; Tyynelä, J.; Petty, G. W.

2014-06-01

Clouds and associated precipitation are the largest source of uncertainty in current weather and future climate simulations. Observations of the microphysical, dynamical and radiative processes that act at cloud scales are needed to improve our understanding of clouds. The rapid expansion of ground-based super-sites and the availability of continuous profiling and scanning multi-frequency radar observations at 35 and 94 GHz have significantly improved our ability to probe the internal structure of clouds in high temporal-spatial resolution, and to retrieve quantitative cloud and precipitation properties. However, there are still gaps in our ability to probe clouds due to large uncertainties in the retrievals. The present work discusses the potential of G band (frequency between 110 and 300 GHz) Doppler radars in combination with lower frequencies to further improve the retrievals of microphysical properties. Our results show that, thanks to a larger dynamic range in dual-wavelength reflectivity, dual-wavelength attenuation and dual-wavelength Doppler velocity (with respect to a Rayleigh reference), the inclusion of frequencies in the G band can significantly improve current profiling capabilities in three key areas: boundary layer clouds, cirrus and mid-level ice clouds, and precipitating snow.

Using Nadir and Directional Emissivity as a Probe of Particle Microphysical Properties

NASA Astrophysics Data System (ADS)

Pitman, Karly M.; Wolff, Michael J.; Bandfield, Joshua L.; Clayton, Geoffrey C.

Real surfaces are not expected to be diffuse emitters, thus observed emissivity values of surface dust deposits are a function of viewing geometry. Attempts to model infrared emission spectral profiles of surface dust deposits at nadir have not yet matured to match the sophistication of astrophysical dust radiative transfer codes. In the absence of strong thermal gradients, directional emissivity may be obtained theoretically via a combination of reciprocity and Kirchhoff's Law. Owing to a lack of laboratory data on directional emissivity for comparison, theorists have not explored the potential utility of directional emissivity as a direct probe of surface dust microphysical properties. Motivated by future analyses of MGS/TES emission phase function (EPF) sequences and the upcoming Mars Exploration Rover mini-TES dataset, we explore the effects of dust particle size and composition on observed radiances at nadir and off-nadir geometries in the TES spectral regime using a combination of multiple scattering radiative transfer and Mie scattering algorithms. Comparisons of these simulated spectra to laboratory spectra of standard mineral assemblages will also be made. This work is supported through NASA grant NAGS-9820 (MJW) and LSU Board of Regents (KMP).

Ground-based observations of aerosol-cloud interactions in the North East of the United States

NASA Astrophysics Data System (ADS)

Li, S.; Joseph, E.; Min, Q.

2015-12-01

Five years ground-based observations (2006 to 2010) of aerosol and cloud properties derived from passive radiometric sensors deployed at an atmospheric measurement field station in the Baltimore-Washington corridor operated by Howard University were used to examine aerosol indirect effect on cloud optical depth (COD), liquid water path (LWP), cloud droplet effective radius (Re) and cloud droplet number concentration (Nd). A higher frequency of clouds with small Re (<7µm) was found during summer of 2006 and 2007 along with higher frequency of abundant aerosol loading (AOD>0.5). The five-year data are screened for summer boundary layer clouds only and are separated into clean and polluted cases based on aerosol particulate matter with aerodynamic diameter≤2.5µm (PM2.5) value. Evidence of aerosol indirect effect on cloud microphysics is found where for the polluted cases the mean (and median) values of Nd distributions were elevated while the mean (and median) values of Re were decreased as compared to those for the clean cases under various LWP ranges. Relatively, the aerosol indirect effects on modifying cloud microphysical properties are found more significant with large LWP than with small LWP.

Observed microphysical changes in Arctic mixed-phase clouds when transitioning from sea-ice to open ocean

NASA Astrophysics Data System (ADS)

Young, Gillian; Jones, Hazel M.; Crosier, Jonathan; Bower, Keith N.; Darbyshire, Eoghan; Taylor, Jonathan W.; Liu, Dantong; Allan, James D.; Williams, Paul I.; Gallagher, Martin W.; Choularton, Thomas W.

2016-04-01

The Arctic sea-ice is intricately coupled to the atmosphere[1]. The decreasing sea-ice extent with the changing climate raises questions about how Arctic cloud structure will respond. Any effort to answer these questions is hindered by the scarcity of atmospheric observations in this region. Comprehensive cloud and aerosol measurements could allow for an improved understanding of the relationship between surface conditions and cloud structure; knowledge which could be key in validating weather model forecasts. Previous studies[2] have shown via remote sensing that cloudiness increases over the marginal ice zone (MIZ) and ocean with comparison to the sea-ice; however, to our knowledge, detailed in-situ data of this transition have not been previously presented. In 2013, the Aerosol-Cloud Coupling and Climate Interactions in the Arctic (ACCACIA) campaign was carried out in the vicinity of Svalbard, Norway to collect in-situ observations of the Arctic atmosphere and investigate this issue. Fitted with a suite of remote sensing, cloud and aerosol instrumentation, the FAAM BAe-146 aircraft was used during the spring segment of the campaign (Mar-Apr 2013). One case study (23rd Mar 2013) produced excellent coverage of the atmospheric changes when transitioning from sea-ice, through the MIZ, to the open ocean. Clear microphysical changes were observed, with the cloud liquid-water content increasing by almost four times over the transition. Cloud base, depth and droplet number also increased, whilst ice number concentrations decreased slightly. The surface warmed by ~13 K from sea-ice to ocean, with minor differences in aerosol particle number (of sizes corresponding to Cloud Condensation Nuclei or Ice Nucleating Particles) observed, suggesting that the primary driver of these microphysical changes was the increased heat fluxes and induced turbulence from the warm ocean surface as expected. References: [1] Kapsch, M.L., Graversen, R.G. and Tjernström, M. Springtime atmospheric energy transport and the control of Arctic summer sea-ice extent. Nature Clim. Change 3, 744-748, doi:10.1038/nclimate1884 (2013) [2] Palm, S. P., Strey, S. T., Spinhirne, J., and Markus, T.: Influence of Arctic sea ice extent on polar cloud fraction and vertical structure and implications for regional climate. Journal of Geophysical Research (Atmospheres), 115, D21209, doi:10.1029/2010JD013900 (2010)

Microphysical properties of cirrus clouds between 75°N and 25°S derived from extensive airborne in-situ observations

NASA Astrophysics Data System (ADS)

Krämer, Martina

2016-04-01

Numerous airborne field campaigns were performed in the last decades to record cirrus clouds microphysical properties. Beside the understanding of the processes of cirrus formation and evolution, an additional motivation for those studies is to provide a database to evaluate the representation of cirrus clouds in global climate models. This is of importance for an improved certainty of climate predictions, which are affected by the poor understanding of the microphysical processes of ice clouds (IPCC, 2013). To this end, the observations should ideally cover the complete respective parameter range and not be influenced by instrumental artifacts. However, due to the difficulties in measuring cirrus properties on fast-flying, high-altitude aircraft, some issues with respect to the measurements %evolved have arisen. In particular, concerns about the relative humidity in and around cirrus clouds and the ice crystal number concentrations were under discussion. Too high ice supersaturations as well as ice number concentrations were often reported. These issues have made more challenging the goal of compiling a large database using data from a suite of different instruments that were used on different campaigns. In this study, we have have addressed these challenges and compiled a large data set of cirrus clouds, sampled during eighteen field campaigns between 75°N and 25°S, representing measurements fulfilling the above mentioned requirements. The most recent campaigns were performed in 2014; namely, the ATTREX campaign with the research aircraft Global Hawk and the ML-CIRRUS and ACRIDICON campaigns with HALO. % The observations include ice water content (IWC: 130 hours of observations), ice crystal numbers (N_ice: 83 hours), ice crystal mean mass size (Rice: 83 hours) and relative humidity (RH_ice) in- and outside of cirrus clouds (78 and 140 hours). % We will present the parameters as PDFs versus temperature and derive medians and core ranges (including the most frequent observations) for each parameter. The new large data sets confirm the earlier results presented by Schiller et al. (JGR, 2008), Krämer et al. (ACP, 2009) and Luebke et al. (ACP, 2013), which are all based on much smaller datasets. Further, we will show the geographical and altitude distribution of IWC, N_ice, R_ice and RH_ice.

NASA's space physics theory program - An opportunity for collaboration

NASA Technical Reports Server (NTRS)

Vinas, Adolfo F.

1990-01-01

The field of theoretical space physics offers a unique opportunity to Latin American scientists for collaborative participation in NASA programs where the greatly increased complexity of both experimental observations and theoretical simulations requires in-depth comparisons between theory and observational data. The key problem areas identified by NASA for aggressive work in the decade of the 1990s are the nature of flows and turbulence, acceleration and transport of particles, the coupling of microphysics and macrophysics, the coupling of local and global dynamics, and nonclassical plasmas.

FIRE Science Results 1988

NASA Technical Reports Server (NTRS)

Mcdougal, David S. (Editor); Wagner, H. Scott (Editor)

1990-01-01

FIRE (First ISCCP Regional Experiment) is a U.S. cloud-radiation program that seeks to address the issues of a basic understanding and parameterizations of cirrus and marine stratocumulus cloud systems and ISCCP data products. The papers describe research analysis of data collected at the 1986 Cirrus Intensive Field Observations (IFO), the 1987 Marine Stratocumulus IFO, and the Extended Time Observations. The papers are grouped into sessions on satellite studies, lidar/radiative properties/microphysical studies, radiative properties, thermodynamic and dynamic properties, case studies, and large scale environment and modeling studies.

Solar Wind/Magnetosphere/Ionosphere Coupling and the Temporal and Spatial Evolution of Boundary Layers using Cluster, Polar and other ISTP Satellites

NASA Technical Reports Server (NTRS)

Maynard, Nelson C.

2004-01-01

Our analysis concerns macro and meso-scale aspects of coupling between the IMF and the magnetosphere-ionosphere system, as opposed to the microphysics of determining how electron gyrotropy is broken and merging actually occurs. We correlate observed behaviors at Cluster and at Polar with temporal variations in other regions, such as in the ionosphere as measured by SuperDARN. Addressing problems with simultaneous observations from diverse locations properly constrains our interpretations.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Matthew R. Kumjian; Giangrande, Scott E.; Mishra, Subashree

Polarimetric radar observations increasingly are used to understand cloud microphysical processes, which is critical for improving their representation in cloud and climate models. In particular, there has been recent focus on improving representations of ice collection processes (e.g., aggregation, riming), as these influence precipitation rate, heating profiles, and ultimately cloud life cycles. However, distinguishing these processes using conventional polarimetric radar observations is difficult, as they produce similar fingerprints. This necessitates improved analysis techniques and integration of complementary data sources. Furthermore, the Midlatitude Continental Convective Clouds Experiment (MC3E) provided such an opportunity.

Acid rain: Microphysical model

NASA Technical Reports Server (NTRS)

Dingle, A. N.

1980-01-01

A microphysical model was used to simulate the case of a ground cloud without dilution by entrainment and without precipitation. The numerical integration techniques of the model are presented. The droplet size spectra versus time and the droplet molalities for each value of time are discussed.

Spectrophotometric properties of materials observed by Pancam on the Mars Exploration Rovers: 2. Opportunity

USGS Publications Warehouse

Johnson, J. R.; Grundy, W.M.; Lemmon, M.T.; Bell, J.F.; Johnson, M.J.; Deen, R.; Arvidson, R. E.; Farrand, W. H.; Guinness, E.; Hayes, A.G.; Herkenhoff, K. E.; Seelos, F.; Soderblom, J.; Squyres, S.

2006-01-01

The Panoramic Camera (Pancam) on the Mars Exploration Rover Opportunity acquired visible/near-infrared multispectral observations of soils and rocks under varying viewing and illumination geometries that were modeled using radiative transfer theory to improve interpretations of the microphysical and surface scattering nature of materials in Meridiani Planum. Nearly 25,000 individual measurements were collected of rock and soil units identified by their color and morphologic properties over a wide range of phase angles (0-150??) at Eagle crater, in the surrounding plains, in Endurance crater, and in the plains between Endurance and Erebus craters through Sol 492. Corrections for diffuse skylight incorporated sky models based on observations of atmospheric opacity throughout the mission. Disparity maps created from Pancam stereo images allowed inclusion of local facet orientation estimates. Outcrop rocks overall exhibited the highest single scattering albedos (???0.9 at 753 nm), and most spherule-rich soils exhibited the lowest (???0.6 at 753 nm). Macroscopic roughness among outcrop rocks varied but was typically larger than spherule-rich soils. Data sets with sufficient phase angle coverage (resulting in well-constrained Hapke parameters) suggested that models using single-term and two-term Henyey-Greenstein phase functions exhibit a dominantly broad backscattering trend for most undisturbed spherule-rich soils. Rover tracks and other compressed soils exhibited forward scattering, while outcrop rocks were intermediate in their scattering behaviors. Some phase functions exhibited wavelength-dependent trends that may result from variations in thin deposits of airfall dust that occurred during the mission. Copyright 2006 by the American Geophysical Union.

The hydrometeor partitioning and microphysical processes over the Pacific Warm Pool in numerical modeling

NASA Astrophysics Data System (ADS)

Huang, Yi-Chih; Wang, Pao K.

2017-01-01

Numerical modeling is conducted to study the hydrometeor partitioning and microphysical source and sink processes during a quasi-steady state of thunderstorms over the Pacific Warm Pool by utilizing the microphysical model WISCDYMM to simulate selected storm cases. The results show that liquid-phase hydrometeors dominate thunderstorm evolution over the Pacific Warm Pool. The ratio of ice-phase mass to liquid-phase mass is about 41%: 59%, indicating that ice-phase water is not as significant over the Pacific Warm Pool as the liquid water compared to the larger than 50% in the subtropics and 80% in the US High Plains in a previous study. Sensitivity tests support the dominance of liquid-phase hydrometeors over the Pacific Warm Pool. The major rain sources are the key hail sinks: melting of hail and shedding from hail; whereas the crucial rain sinks are evaporation and accretion by hail. The major snow sources are Bergeron-Findeisen process, transfer of cloud ice to snow and accretion of cloud water; whereas the foremost sink of snow is accretion by hail. The essential hail sources are accretions of rain, cloud water, and snow; whereas the critical hail sinks are melting of hail and shedding from hail. The contribution and ranking of sources and sinks of these precipitates are compared with the previous study. Hydrometeors have their own special microphysical processes in the development and depletion over the Pacific Warm Pool. Microphysical budgets depend on atmospheric dynamical and thermodynamical conditions which determine the partitioning of hydrometeors. This knowledge would benefit the microphysics parameterization in cloud models and cumulus parameterization in global circulation models.

Intel Many Integrated Core (MIC) architecture optimization strategies for a memory-bound Weather Research and Forecasting (WRF) Goddard microphysics scheme

NASA Astrophysics Data System (ADS)

Mielikainen, Jarno; Huang, Bormin; Huang, Allen H.

2014-10-01

The Goddard cloud microphysics scheme is a sophisticated cloud microphysics scheme in the Weather Research and Forecasting (WRF) model. The WRF is a widely used weather prediction system in the world. It development is a done in collaborative around the globe. The Goddard microphysics scheme is very suitable for massively parallel computation as there are no interactions among horizontal grid points. Compared to the earlier microphysics schemes, the Goddard scheme incorporates a large number of improvements. Thus, we have optimized the code of this important part of WRF. In this paper, we present our results of optimizing the Goddard microphysics scheme on Intel Many Integrated Core Architecture (MIC) hardware. The Intel Xeon Phi coprocessor is the first product based on Intel MIC architecture, and it consists of up to 61 cores connected by a high performance on-die bidirectional interconnect. The Intel MIC is capable of executing a full operating system and entire programs rather than just kernels as the GPU do. The MIC coprocessor supports all important Intel development tools. Thus, the development environment is familiar one to a vast number of CPU developers. Although, getting a maximum performance out of MICs will require using some novel optimization techniques. Those optimization techniques are discusses in this paper. The results show that the optimizations improved performance of the original code on Xeon Phi 7120P by a factor of 4.7x. Furthermore, the same optimizations improved performance on a dual socket Intel Xeon E5-2670 system by a factor of 2.8x compared to the original code.

A Comparison of Cloud Microphysical and Optical Properties during TOGA-COARE

NASA Technical Reports Server (NTRS)

Strawa, A. W.; Pueschel, R. F.; Pilewskie, P.; Valero, F. P. J.; Gore, Warren J. (Technical Monitor)

1996-01-01

The impact of cirrus clouds on climate is an issue of research interest currently. Whether cirrus clouds heat or cool the Earth-atmosphere system depends on the cloud shortwave albedo and infrared reflectance and absorptance. These in turn are determined by the size distribution, phase, and composition of particles in the clouds. The TOGA-COARE campaign presented an excellent opportunity to study cirrus clouds and their influence on climate. In this campaign, a microphysics instrument package was flown aboard the DC-8 aircraft at medium altitudes in cirrus clouds. This package included a 2D Greyscale Cloud Particle Probe, a Forward Scattering Spectrometer Aerosol Probe, and an ice crystal replicator. At the same time the ER-2 equipped with a radiation measurement system flew coordinated flight tracks above the DC-8 at very high altitude. The radiation measurement made were short and long wave fluxes, as well as narrowband fluxes, both upwelling and downwelling. In addition LIDAR data is available. The existence of these data sets allows for a the comparison of radiation measurement with microphysical measurements. For example, the optical depth and effective radius retrieved from the ER-2 radiation measurements can be compared to the microphysical data. Conversely, the optical properties and fluxes produced by the clouds can be calculated from the microphysical measurements and compared to those measured aboard the ER-2. The assumptions required to make these comparisons are discussed. Typical microphysical results show a prevalence of micron-sized particles, in addition to the cloud particles that exceed 100 mm. The large number of small particles or "haze" cause the effective cloud radii to shift to smaller sizes, leading to changes in optical parameters.

Vertical profile of fog microphysics : a case study

NASA Astrophysics Data System (ADS)

Burnet, Frédéric; Brilouet, Pierre-Etienne; Mazoyer, Marie; Bourrianne, Thierry; Etcheberry, Jean-Michel; Gaillard, Brigitte; Legain, Dominique; Tzanos, Diane; Barrié, Joel; Barrau, Sébastien; Defoy, Stephan

2016-04-01

The occurrence and development of fogs result from the non-linear interaction of competing radiative, thermodynamic, microphysical and dynamical processes and the forecasting of their life cycle still remains a challenging issue. Several field campaigns have been carried out at the SIRTA observatory in the Paris suburb area (France). These experiments have shown that fog events exhibit large differences of the microphysical properties and various evolutions during their life cycle. To better understand relationships between the different processes and to validate numerical simulations it is necessary however to document the vertical profile of the fog microphysics. A CDP (Cloud Droplet Spectrometer) from DMT (Droplet Measurement Technology, Boulder, CO) has been modified to allow measurements of the droplet size distribution in fog layers with a tethered balloon. This instrumental set-up has been used during a field campaign during the winter 2013-214 in the Landes area in the South West of France. To validate the vertical profiles provided by the modified CDP, a mast was equipped with microphysical instruments at 2 altitude levels with an another CDP at 24 m and a Fog Monitor FM100 at 42 m. The instrumental set-up deployed during this campaign is presented. Data collected during a fog event that occurred during the night of 5-6 March 2014 are analysed. We show that microphysical properties such as droplet number concentration, LWC and mean droplet size, exhibit different time evolution during the fog life cycle depending on the altitude level. Droplet size distribution measurements are also investigated. They reveal sharp variations along the vertical close to the top of the fog layer. In addition it is shown that the shape of the size distributions at the top follows a time evolution typical of a quasi-adiabatic droplet growth.

The emergence of time's arrows and special science laws from physics.

PubMed

Loewer, Barry

2012-02-06

In this paper, I will argue that there is an important connection between two questions concerning how certain features of the macro world emerge from the laws and processes of fundamental microphysics and suggest an approach to answering these questions. The approach involves a kind of emergence but quite different from 'top-down' emergence discussed at the conference, for which an earlier version of this paper was written. The two questions are (i) How do 'the arrows of time' emerge from microphysics? (ii) How do macroscopic special science laws and causation emerge from microphysics? Answering these questions is especially urgent for those, who like myself, think that a certain version of physicalism, which I call 'micro-physical completeness' (MC), is true. According to MC, there are fundamental dynamical laws that completely govern (deterministically or probabilistically), the evolution of all micro-physical events and there are no additional ontologically independent dynamical or causal special science laws. In other words, there is no ontologically independent 'top-down' causation. Of course, MC does not imply that physicists now or ever will know or propose the complete laws of physics. Or even if the complete laws were known we would know how special science properties and laws reduce to laws and properties of fundamental physics. Rather, MC is a contingent metaphysical claim about the laws of our world. After a discussion of the two questions, I will argue the key to showing how it is possible for the arrows of time and the special science laws to emerge from microphysics and a certain account of how thermodynamics is related to fundamental dynamical laws.

Numerical Simulations of Precipitation Processes, Microphysics, and Microwave Radiative Properties of flood Producing Storms in Mediterranean & Adriatic Basins

NASA Technical Reports Server (NTRS)

Smith, Eric A.; Einaudi, Franco (Technical Monitor)

2001-01-01

A comprehensive understanding of the meteorological and microphysical nature of Mediterranean storms requires a combination of in situ data analysis, radar data analysis, and satellite data analysis, effectively integrated with numerical modeling studies at various scales. An important aspect of understanding microphysical controls of severe storms, is first understanding the meteorological controls under which a storm has evolved, and then using that information to help characterize the dominant microphysical processes. For hazardous Mediterranean storms, highlighted by the October 5-6, 1998 Friuli flood event in northern Italy, a comprehensive microphysical interpretation requires an understanding of the multiple phases of storm evolution. This involves intense convective development, Sratiform decay, orographic lifting, and sloped frontal lifting processes, as well as the associated vertical motions and thermodynamical instabilities governing physical processes that effect details of the size distributions and fall rates of the various types of hydrometeors found within the storm environment. This talk overviews the microphysical elements of a severe Mediterranean storm in such a context, investigated with the aid of TRMM satellite and other remote sensing measurements, but guided by a nonhydrostatic mesoscale model simulation of the Friuli flood event. The data analysis for this paper was conducted by my research groups at the Global Hydrology and Climate Center in Huntsville, AL and Florida State University in Tallahassee, and in collaboration with Dr. Alberto Mugnai's research group at the Institute of Atmospheric Physics in Rome. The numerical modeling was conducted by Professor Oreg Tripoli and Ms. Giulia Panegrossi at the University of Wisconsin in Madison, using Professor Tripoli's nonhydrostatic modeling system (NMS). This is a scalable, fully nested mesoscale model capable of resolving nonhydrostatic circulations from regional scale down to cloud scale and below.

A new approach to modeling aerosol effects on East Asian climate: Parametric uncertainties associated with emissions, cloud microphysics, and their interactions: AEROSOL EFFECTS ON EAST ASIAN CLIMATE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yan, Huiping; Qian, Yun; Zhao, Chun

2015-09-09

In this study, we adopt a parametric sensitivity analysis framework that integrates the quasi-Monte Carlo parameter sampling approach and a surrogate model to examine aerosol effects on the East Asian Monsoon climate simulated in the Community Atmosphere Model (CAM5). A total number of 256 CAM5 simulations are conducted to quantify the model responses to the uncertain parameters associated with cloud microphysics parameterizations and aerosol (e.g., sulfate, black carbon (BC), and dust) emission factors and their interactions. Results show that the interaction terms among parameters are important for quantifying the sensitivity of fields of interest, especially precipitation, to the parameters. Themore » relative importance of cloud-microphysics parameters and emission factors (strength) depends on evaluation metrics or the model fields we focused on, and the presence of uncertainty in cloud microphysics imposes an additional challenge in quantifying the impact of aerosols on cloud and climate. Due to their different optical and microphysical properties and spatial distributions, sulfate, BC, and dust aerosols have very different impacts on East Asian Monsoon through aerosol-cloud-radiation interactions. The climatic effects of aerosol do not always have a monotonic response to the change of emission factors. The spatial patterns of both sign and magnitude of aerosol-induced changes in radiative fluxes, cloud, and precipitation could be different, depending on the aerosol types, when parameters are sampled in different ranges of values. We also identify the different cloud microphysical parameters that show the most significant impact on climatic effect induced by sulfate, BC and dust, respectively, in East Asia.« less

Improving the Representation of Snow Crystal Properties Within a Single-Moment Microphysics Scheme

NASA Technical Reports Server (NTRS)

Molthan, Andrew L.; Petersen, Walter A.; Case, Jonathan L.; Dembek, S. R.

2010-01-01

As computational resources continue their expansion, weather forecast models are transitioning to the use of parameterizations that predict the evolution of hydrometeors and their microphysical processes, rather than estimating the bulk effects of clouds and precipitation that occur on a sub-grid scale. These parameterizations are referred to as single-moment, bulk water microphysics schemes, as they predict the total water mass among hydrometeors in a limited number of classes. Although the development of single moment microphysics schemes have often been driven by the need to predict the structure of convective storms, they may also provide value in predicting accumulations of snowfall. Predicting the accumulation of snowfall presents unique challenges to forecasters and microphysics schemes. In cases where surface temperatures are near freezing, accumulated depth often depends upon the snowfall rate and the ability to overcome an initial warm layer. Precipitation efficiency relates to the dominant ice crystal habit, as dendrites and plates have relatively large surface areas for the accretion of cloud water and ice, but are only favored within a narrow range of ice supersaturation and temperature. Forecast models and their parameterizations must accurately represent the characteristics of snow crystal populations, such as their size distribution, bulk density and fall speed. These properties relate to the vertical distribution of ice within simulated clouds, the temperature profile through latent heat release, and the eventual precipitation rate measured at the surface. The NASA Goddard, single-moment microphysics scheme is available to the operational forecast community as an option within the Weather Research and Forecasting (WRF) model. The NASA Goddard scheme predicts the occurrence of up to six classes of water mass: vapor, cloud ice, cloud water, rain, snow and either graupel or hail.

A model predicting the evolution of ice particle size spectra and radiative properties of cirrus clouds. Part 2: Dependence of absorption and extinction on ice crystal morphology

NASA Technical Reports Server (NTRS)

Mitchell, David L.; Arnott, W. Patrick

1994-01-01

This study builds upon the microphysical modeling described in Part 1 by deriving formulations for the extinction and absorption coefficients in terms of the size distribution parameters predicted from the micro-physical model. The optical depth and single scatter albedo of a cirrus cloud can then be determined, which, along with the asymmetry parameter, are the input parameters needed by cloud radiation models. Through the use of anomalous diffraction theory, analytical expressions were developed describing the absorption and extinction coefficients and the single scatter albedo as functions of size distribution parameters, ice crystal shapes (or habits), wavelength, and refractive index. The extinction coefficient was formulated in terms of the projected area of the size distribution, while the absorption coefficient was formulated in terms of both the projected area and mass of the size distribution. These properties were formulated as explicit functions of ice crystal geometry and were not based on an 'effective radius.' Based on simulations of the second cirrus case study described in Part 1, absorption coefficients predicted in the near infrared for hexagonal columns and rosettes were up to 47% and 71% lower, respectively, than absorption coefficients predicted by using equivalent area spheres. This resulted in single scatter albedos in the near-infrared that were considerably greater than those predicted by the equivalent area sphere method. Reflectances in this region should therefore be underestimated using the equivalent area sphere approach. Cloud optical depth was found to depend on ice crystal habit. When the simulated cirrus cloud contained only bullet rosettes, the optical depth was 142% greater than when the cloud contained only hexagonal columns. This increase produced a doubling in cloud albedo. In the near-infrared (IR), the single scatter albedo also exhibited a significant dependence on ice crystal habit. More research is needed on the geometrical properties of ice crystals before the influence of ice crystal shape on cirrus radiative properties can be adequately understood. This study provides a way of coupling the radiative properties of absorption, extinction, and single scatter albedo to the microphysical properties of cirrus clouds. The dependence of extinction and absorption on ice crystal shape was not just due to geometrical differences between crystal types, but was also due to the effect these differences had on the evolution of ice particle size spectra. The ice particle growth model in Part 1 and the radiative properties treated here are based on analytical formulations, and thus represent a computationally efficient means of modeling the microphysical and radiative properties of cirrus clouds.

Large-Eddy Simulation of Shallow Cumulus over Land: A Composite Case Based on ARM Long-Term Observations at Its Southern Great Plains Site

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Yunyan; Klein, Stephen A.; Fan, Jiwen

Based on long-term observations by the Atmospheric Radiation Measurement program at its Southern Great Plains site, a new composite case of continental shallow cumulus (ShCu) convection is constructed for large-eddy simulations (LES) and single-column models. The case represents a typical daytime nonprecipitating ShCu whose formation and dissipation are driven by the local atmospheric conditions and land surface forcing and are not influenced by synoptic weather events. The case includes early morning initial profiles of temperature and moisture with a residual layer; diurnally varying sensible and latent heat fluxes, which represent a domain average over different land surface types; simplified large-scalemore » horizontal advective tendencies and subsidence; and horizontal winds with prevailing direction and average speed. Observed composite cloud statistics are provided for model evaluation. The observed diurnal cycle is well reproduced by LES; however, the cloud amount, liquid water path, and shortwave radiative effect are generally underestimated. LES are compared between simulations with an all-or-nothing bulk microphysics and a spectral bin microphysics. The latter shows improved agreement with observations in the total cloud cover and the amount of clouds with depths greater than 300 m. When compared with radar retrievals of in-cloud air motion, LES produce comparable downdraft vertical velocities, but a larger updraft area, velocity, and updraft mass flux. Both observations and LES show a significantly larger in-cloud downdraft fraction and downdraft mass flux than marine ShCu.« less

Large-Eddy Simulation of Shallow Cumulus over Land: A Composite Case Based on ARM Long-Term Observations at Its Southern Great Plains Site

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Yunyan; Klein, Stephen A.; Fan, Jiwen

Based on long-term observations by the Atmospheric Radiation Measurement program at its Southern Great Plains site, a new composite case of continental shallow cumulus (ShCu) convection is constructed for large-eddy simulations (LES) and single-column models. The case represents a typical daytime non-precipitating ShCu whose formation and dissipation are driven by the local atmospheric conditions and land-surface forcing, and are not influenced by synoptic weather events. The case includes: early-morning initial profiles of temperature and moisture with a residual layer; diurnally-varying sensible and latent heat fluxes which represent a domain average over different land-surface types; simplified large-scale horizontal advective tendencies andmore » subsidence; and horizontal winds with prevailing direction and average speed. Observed composite cloud statistics are provided for model evaluation. The observed diurnal cycle is well-reproduced by LES, however the cloud amount, liquid water path, and shortwave radiative effect are generally underestimated. LES are compared between simulations with an all-or-nothing bulk microphysics and a spectral bin microphysics. The latter shows improved agreement with observations in the total cloud cover and the amount of clouds with depths greater than 300 meters. When compared with radar retrievals of in-cloud air motion, LES produce comparable downdraft vertical velocities, but a larger updraft area, velocity and updraft mass flux. Finally, both observation and LES show a significantly larger in-cloud downdraft fraction and downdraft mass flux than marine ShCu.« less

Large-Eddy Simulation of Shallow Cumulus over Land: A Composite Case Based on ARM Long-Term Observations at Its Southern Great Plains Site

DOE PAGES

Zhang, Yunyan; Klein, Stephen A.; Fan, Jiwen; ...

2017-09-19

Based on long-term observations by the Atmospheric Radiation Measurement program at its Southern Great Plains site, a new composite case of continental shallow cumulus (ShCu) convection is constructed for large-eddy simulations (LES) and single-column models. The case represents a typical daytime non-precipitating ShCu whose formation and dissipation are driven by the local atmospheric conditions and land-surface forcing, and are not influenced by synoptic weather events. The case includes: early-morning initial profiles of temperature and moisture with a residual layer; diurnally-varying sensible and latent heat fluxes which represent a domain average over different land-surface types; simplified large-scale horizontal advective tendencies andmore » subsidence; and horizontal winds with prevailing direction and average speed. Observed composite cloud statistics are provided for model evaluation. The observed diurnal cycle is well-reproduced by LES, however the cloud amount, liquid water path, and shortwave radiative effect are generally underestimated. LES are compared between simulations with an all-or-nothing bulk microphysics and a spectral bin microphysics. The latter shows improved agreement with observations in the total cloud cover and the amount of clouds with depths greater than 300 meters. When compared with radar retrievals of in-cloud air motion, LES produce comparable downdraft vertical velocities, but a larger updraft area, velocity and updraft mass flux. Finally, both observation and LES show a significantly larger in-cloud downdraft fraction and downdraft mass flux than marine ShCu.« less

The Midlatitude Continental Convective Clouds Experiment (MC3E)

DOE PAGES

Jensen, M. P.; Petersen, W. A.; Bansemer, A.; ...

2015-12-18

The Midlatitude Continental Convective Clouds Experiment (MC3E), a field program jointly led by the U.S. Department of Energy’s Atmospheric Radiation Measurement program and the NASA Global Precipitation Measurement (GPM) Mission, was conducted in south-central Oklahoma during April – May 2011. MC3E science objectives were motivated by the need to improve understanding of midlatitude continental convective cloud system lifecycles, microphysics, and GPM precipitation retrieval algorithms. To achieve these objectives a multi-scale surface- and aircraft-based in situ and remote sensing observing strategy was employed. A variety of cloud and precipitation events were sampled during the MC3E, of which results from three deepmore » convective events are highlighted. Vertical structure, air motions, precipitation drop-size distributions and ice properties were retrieved from multi-wavelength radar, profiler, and aircraft observations for an MCS on 11 May. Aircraft observations for another MCS observed on 20 May were used to test agreement between observed radar reflectivities and those calculated with forward-modeled reflectivity and microwave brightness temperatures using in situ particle size distributions and ice water content. Multi-platform observations of a supercell that occurred on 23 May allowed for an integrated analysis of kinematic and microphysical interactions. A core updraft of 25 ms -1 supported growth of hail and large rain drops. As a result, data collected during the MC3E campaign is being used in a number of current and ongoing research projects and is available through the DOE ARM and NASA data archives.« less

The Midlatitude Continental Convective Clouds Experiment (MC3E)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jensen, M. P.; Petersen, W. A.; Bansemer, A.

The Midlatitude Continental Convective Clouds Experiment (MC3E), a field program jointly led by the U.S. Department of Energy’s Atmospheric Radiation Measurement program and the NASA Global Precipitation Measurement (GPM) Mission, was conducted in south-central Oklahoma during April – May 2011. MC3E science objectives were motivated by the need to improve understanding of midlatitude continental convective cloud system lifecycles, microphysics, and GPM precipitation retrieval algorithms. To achieve these objectives a multi-scale surface- and aircraft-based in situ and remote sensing observing strategy was employed. A variety of cloud and precipitation events were sampled during the MC3E, of which results from three deepmore » convective events are highlighted. Vertical structure, air motions, precipitation drop-size distributions and ice properties were retrieved from multi-wavelength radar, profiler, and aircraft observations for an MCS on 11 May. Aircraft observations for another MCS observed on 20 May were used to test agreement between observed radar reflectivities and those calculated with forward-modeled reflectivity and microwave brightness temperatures using in situ particle size distributions and ice water content. Multi-platform observations of a supercell that occurred on 23 May allowed for an integrated analysis of kinematic and microphysical interactions. A core updraft of 25 ms -1 supported growth of hail and large rain drops. As a result, data collected during the MC3E campaign is being used in a number of current and ongoing research projects and is available through the DOE ARM and NASA data archives.« less

Heterogeneous Formation of Polar Stratospheric Clouds- Part 1: Nucleation of Nitric Acid Trihydrate (NAT)

NASA Technical Reports Server (NTRS)

Hoyle, C. R.; Engel, I.; Luo, B. P.; Pitts, M. C.; Poole, L. R.; Grooss, J.-U.; Peter, T.

2013-01-01

Satellite-based observations during the Arctic winter of 2009/2010 provide firm evidence that, in contrast to the current understanding, the nucleation of nitric acid trihydrate (NAT) in the polar stratosphere does not only occur on preexisting ice particles. In order to explain the NAT clouds observed over the Arctic in mid-December 2009, a heterogeneous nucleation mechanism is required, occurring via immersion freezing on the surface of solid particles, likely of meteoritic origin. For the first time, a detailed microphysical modelling of this NAT formation pathway has been carried out. Heterogeneous NAT formation was calculated along more than sixty thousand trajectories, ending at Cloud Aerosol Lidar with Orthogonal Polarization (CALIOP) observation points. Comparing the optical properties of the modelled NAT with these observations enabled a thorough validation of a newly developed NAT nucleation parameterisation, which has been built into the Zurich Optical and Microphysical box Model (ZOMM). The parameterisation is based on active site theory, is simple to implement in models and provides substantial advantages over previous approaches which involved a constant rate of NAT nucleation in a given volume of air. It is shown that the new method is capable of reproducing observed polar stratospheric clouds (PSCs) very well, despite the varied conditions experienced by air parcels travelling along the different trajectories. In a companion paper, ZOMM is applied to a later period of the winter, when ice PSCs are also present, and it is shown that the observed PSCs are also represented extremely well under these conditions.

Morphology and mixing state of atmospheric particles: Links to optical properties and cloud processing

NASA Astrophysics Data System (ADS)

China, Swarup

Atmospheric particles are ubiquitous in Earth's atmosphere and impact the environment and the climate while affecting human health and Earth's radiation balance, and degrading visibility. Atmospheric particles directly affect our planet's radiation budget by scattering and absorbing solar radiation, and indirectly by interacting with clouds. Single particle morphology (shape, size and internal structure) and mixing state (coating by organic and inorganic material) can significantly influence the particle optical properties as well as various microphysical processes, involving cloud-particle interactions and including heterogeneous ice nucleation and water uptake. Conversely, aerosol cloud processing can affect the morphology and mixing of the particles. For example, fresh soot has typically an open fractal-like structure, but aging and cloud processing can restructure soot into more compacted shapes, with different optical and ice nucleation properties. During my graduate research, I used an array of electron microscopy and image analysis tools to study morphology and mixing state of a large number of individual particles collected during several field and laboratory studies. To this end, I investigated various types of particles such as tar balls (spherical carbonaceous particles emitted during biomass burning) and dust particles, but with a special emphasis on soot particles. In addition, I used the Stony Brook ice nucleation cell facility to investigate heterogeneous ice nucleation and water uptake by long-range transported particles collected at the Pico Mountain Observatory, in the Archipelago of the Azores. Finally, I used ice nucleation data from the SAAS (Soot Aerosol Aging Study) chamber study at the Pacific Northwest National Laboratory to understand the effects that ice nucleation and supercooled water processing has on the morphology of residual soot particles. Some highlights of our findings and implications are discussed next. We found that the morphology of fresh soot emitted by vehicles depends on the driving conditions (i.e.; the vehicle specific power). Soot emitted by biomass burning is often heavily coated by other materials while processing of soot in urban environment exhibits complex mixing. We also found that long-range transported soot over the ocean after atmospheric processing is very compacted. In addition, our results suggest that freezing process can facilitate restructuring of soot and results into collapsed soot. Furthermore, numerical simulations showed strong influence on optical properties when fresh open fractal-like soot evolved to collapsed soot. Further investigation of long-range transported aged particles exhibits that they are efficient in water uptake and can induce ice nucleation in colder temperature. Our results have implications for assessing the impact of the morphology and mixing state of soot particles on human health, environment and climate. Our findings can provide guidance to numerical models such as particle-resolved mixing state models to account for, and better understand, vehicular emissions and soot evolution since its emission to atmospheric processing in urban environment and finally in remote regions after long-range transport. Morphology and mixing state information can be used to model observational-constrained optical properties. The details of morphology and mixing state of soot particles are crucial to assess the accuracy of climate models in describing the contribution of soot radiative forcing and their direct and indirect climate effects. Finally, our observations of ice nucleation ability by aged particles show that nucleated particles are internally mixed and coated with several materials.

CRYSTAL-FACE Analysis and Simulations of the July 23rd Extended Anvil Case

NASA Technical Reports Server (NTRS)

Starr, David

2003-01-01

A key focus of CRYSTAL-FACE (Cirrus Regional Study of Tropical Anvils and cirrus Layers - Florida Area Cirrus Experiment) was the generation and subsequent evolution of cirrus outflow from deep convective cloud systems. Present theoretical background and motivations will be discussed. An integrated look at the observations of an extended cirrus anvil cloud system observed on 23 July 2002 will be presented, including lidar and millimeter radar observation; from NASA s ER-2 and in-situ observations from NASA s WB-57 and University of North Dakota Citation. The observations will be compared to results of simulations using 1-D and 2-D high-resolution (100 meter) cloud resolving models. The CRMs explicitly account for cirrus microphysical development by resolving the evolving ice crystal size distribution (bin model) in time and space. Both homogeneous and heterogeneous nucleation are allowed in the model. The CRM simulations are driven using the output of regional simulations using MM5 that produces deep convection similar to what was observed. The MM5 model employs a 2 km inner grid (32 layers) over a 360 km domain, nested within a 6-km grid over a 600-km domain. Initial and boundary conditions for the 36-hour MM5 simulation are taken from NCEP Eta model analysis at 32 km resolution. Key issues to be explored are the settling of the observed anvil versus the model simulations, and comparisons of dynamical properties, such as vertical motions, occurring in the observations and models. The former provides an integrated measure of the validity of the model microphysics (fallspeed) while the latter is the key factor in forcing continued ice generation.

Re-formulation and Validation of Cloud Microphysics Schemes

NASA Astrophysics Data System (ADS)

Wang, J.; Georgakakos, K. P.

2007-12-01

The research focuses on improving quantitative precipitation forecasts by removing significant uncertainties in current cloud microphysics schemes embedded in models such as WRF and MM5 and cloud-resolving models such as GCE. Reformulation of several production terms in these microphysics schemes was found necessary. When estimating four graupel production terms involved in the accretion between rain, snow and graupel, current microphysics schemes assumes that all raindrops and snow particles are falling at their appropriate mass-weighted mean terminal velocities and thus analytic solutions are able to be found for these production terms. Initial analysis and tests showed that these approximate analytic solutions give significant and systematic overestimates of these terms, and, thus, become one of major error sources of the graupel overproduction and associated extreme radar reflectivity in simulations. These results are corroborated by several reports. For example, the analytic solution overestimates the graupel production by collisions between raindrops and snow by up to 230%. The structure of "pure" snow (not rimed) and "pure graupel" (completely rimed) in current microphysics schemes excludes intermediate forms between "pure" snow and "pure" graupel and thus becomes a significant reason of graupel overproduction in hydrometeor simulations. In addition, the generation of the same density graupel by both the freezing of supercooled water and the riming of snow may cause underestimation of graupel production by freezing. A parameterization scheme of the riming degree of snow is proposed and then a dynamic fallspeed-diameter relationship and density- diameter relationship of rimed snow is assigned to graupel based on the diagnosed riming degree. To test if these new treatments can improve quantitative precipitation forecast, the Hurricane Katrina and a severe winter snowfall event in the Sierra Nevada Range are selected as case studies. A series of control simulation and sensitivity tests was conducted for these two cases. Two statistical methods are used to compare simulated radar reflectivity by the model with that detected by ground-based and airborne radar at different height levels. It was found that the changes made in current microphysical schemes improve QPF and microphysics simulation significantly.

Examination of turbulent entrainment-mixing mechanisms using a combined approach

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lu, C.; Liu, Y.; Niu, S.

2011-10-01

Turbulent entrainment-mixing mechanisms are investigated by applying a combined approach to the aircraft measurements of three drizzling and two nondrizzling stratocumulus clouds collected over the U.S. Department of Energy's Atmospheric Radiation Measurement Southern Great Plains site during the March 2000 cloud Intensive Observation Period. Microphysical analysis shows that the inhomogeneous entrainment-mixing process occurs much more frequently than the homogeneous counterpart, and most cases of the inhomogeneous entrainment-mixing process are close to the extreme scenario, having drastically varying cloud droplet concentration but roughly constant volume-mean radius. It is also found that the inhomogeneous entrainment-mixing process can occur both near the cloudmore » top and in the middle level of a cloud, and in both the nondrizzling clouds and nondrizzling legs in the drizzling clouds. A new dimensionless number, the scale number, is introduced as a dynamical measure for different entrainment-mixing processes, with a larger scale number corresponding to a higher degree of homogeneous entrainment mixing. Further empirical analysis shows that the scale number that separates the homogeneous from the inhomogeneous entrainment-mixing process is around 50, and most legs have smaller scale numbers. Thermodynamic analysis shows that sampling average of filament structures finer than the instrumental spatial resolution also contributes to the dominance of inhomogeneous entrainment-mixing mechanism. The combined microphysical-dynamical-thermodynamic analysis sheds new light on developing parameterization of entrainment-mixing processes and their microphysical and radiative effects in large-scale models.« less

The Mixed-Phase Arctic Cloud Experiment (M-PACE)

NASA Technical Reports Server (NTRS)

Verlinde, J.; Harrington, J. Y.; McFarquhar, G. M.; Yannuzzi, V. T.; Avramov, A.; Greenberg, S.; Johnson, N.; Zhang, G.; Poellot, M. R.; Mather, J. H.;

Simulations of Hurricane Nadine (2012) during HS3 Using the NASA Unified WRF with Aerosol-Cloud Microphysics-Radiation Coupling

NASA Astrophysics Data System (ADS)

Shi, J. J.; Braun, S. A.; Sippel, J. A.; Tao, W. K.; Tao, Z.

2014-12-01

The impact of the SAL on the development and intensification of hurricanes has garnered significant attention in recent years. Many past studies have shown that synoptic outbreaks of Saharan dust, which usually occur from late spring to early fall and can extend from western Africa across the Atlantic Ocean into the Caribbean, can have impacts on hurricane genesis and subsequent intensity change. The Hurricane and Severe Storm Sentinel (HS3) mission is a multiyear NASA field campaign with the goal of improving understanding of hurricane formation and intensity change. One of HS3's primary science goals is to obtain measurements to help determine the extent to which the Saharan air layer impacts storm intensification. HS3 uses two of NASA's unmanned Global Hawk aircrafts equipped with three instruments each to measure characteristics of the storm environment and inner core. The Goddard microphysics and longwave/shortwave schemes in the NASA Unified Weather Research and Forecasting (NU-WRF) model have been coupled in real-time with the Goddard Chemistry Aerosol Radiation and Transport (GOCART) model in WRF-Chem to account for the direct (radiation) and indirect (microphysics) impact. NU-WRF with interactive aerosol-cloud-radiation physics is used to generate 30-member ensemble simulations of Nadine (2012) with and without the aerosol interactions. Preliminary conclusions related to the impact of the SAL on the evolution of Nadine from the HS3 observations and model output will be described.

The effect of mineral dust and soot aerosols on ice microphysics near the foothills of the Himalayas: A numerical investigation

NASA Astrophysics Data System (ADS)

Hazra, Anupam; Padmakumari, B.; Maheskumar, R. S.; Chen, Jen-Ping

2016-05-01

This study investigates the influence of different ice nuclei (IN) species and their number concentrations on cloud ice production. The numerical simulation with different species of ice nuclei is investigated using an explicit bulk-water microphysical scheme in a Mesoscale Meteorological Model version 5 (MM5). The species dependent ice nucleation parameterization that is based on the classical nucleation theory has been implemented into the model. The IN species considered include dust and soot with two different concentrations (Low and High). The simulated cloud microphysical properties like droplet number concentration and droplet effective radii as well as macro-properties (equivalent potential temperature and relative humidity) are comparable with aircraft observations. When higher dust IN concentrations are considered, the simulation results showed good agreement with the cloud ice and cloud water mixing ratio from aircraft measurements during Cloud Aerosol Interactions and Precipitation Enhancement Experiment (CAIPEEX) and Modern Era Retrospective Analysis for Research and Applications (MERRA) reanalysis. Relative importance of IN species is shown as compared to the homogeneous freezing nucleation process. The tendency of cloud ice production rates is also analyzed and found that dust IN is more efficient in producing cloud ice when compared to soot IN. The dust IN with high concentration can produce more surface precipitation than soot IN at the same concentration. This study highlights the need to improve the ice nucleation parameterization in numerical models.

Dynamical Downscaling of Global Circulation Models With the Weather Research and Forecast Model in the Northern Great Plains

NASA Astrophysics Data System (ADS)

Burtch, D.; Mullendore, G. L.; Kennedy, A. D.; Simms, M.; Kirilenko, A.; Coburn, J.

2015-12-01

Understanding the impacts of global climate change on regional scales is crucial for accurate decision-making by state and local governments. This is especially true in North Dakota, where climate change can have significant consequences on agriculture, its traditionally strongest economic sector. This region of the country shows a high variability in precipitation, especially in the summer months and so the focus of this study is on warm season processes over decadal time scales. The Weather Research and Forecast (WRF) model is used to dynamically downscale two Global Circulation Models (GCMs) from the CMIP5 ensemble in order to determine the microphysical parameterization and nudging techniques (spectral or analysis) best suited for this region. The downscaled domain includes the entirety of North Dakota at a horizontal resolution of 5 km. In addition, smaller domains of 1 km horizontal resolution are centered over regions of focused hydrological importance. The dynamically downscaled simulations are compared with both gridded observational data and statistically downscaled data to evaluate the performance of the simulations. Preliminary results have shown a marked difference between the two downscaled GCMs in terms of temperature and precipitation bias. Choice of microphysical parameterization has not shown to create any significant differences in the temperature fields. However, the precipitation fields do appear to be most affected by the microphysical parameterization, regardless of the choice of GCM. Implications on the unique water resource challenges faced in this region will also be discussed.

Design, Evaluation and GCM-Performance of a New Parameterization for Microphysics of Clouds with Relaxed Arakawa-Schubert Scheme (McRas)

NASA Technical Reports Server (NTRS)

Sud, Y. C.; Walker, G. K.

1998-01-01

A prognostic cloud scheme named McRAS (Microphysics of clouds with Relaxed Arakawa-Schubert Scheme) was developed with the aim of improving cloud-microphysics, and cloud-radiation interactions in GCMs. McRAS distinguishes convective, stratiform, and boundary-layer clouds. The convective clouds merge into stratiform clouds on an hourly time-scale, while the boundary-layer clouds do so instantly. The cloud condensate transforms into precipitation following the auto-conversion relations of Sundqvist that contain a parametric adaptation for the Bergeron-Findeisen process of ice crystal growth and collection of cloud condensate by precipitation. All clouds convect, advect, and diffuse both horizontally and vertically with a fully active cloud-microphysics throughout its life-cycle, while the optical properties of clouds are derived from the statistical distribution of hydrometeors and idealized cloud geometry. An evaluation of McRAS in a single column model (SCM) with the GATE Phase III data has shown that McRAS can simulate the observed temperature, humidity, and precipitation without discernible systematic errors. An evaluation with the ARM-CART SCM data in a cloud model intercomparison exercise shows reasonable but not an outstanding accurate simulation. Such a discrepancy is common to almost all models and is related, in part, to the input data quality. McRAS was implemented in the GEOS II GCM. A 50 month integration that was initialized with the ECMWF analysis of observations for January 1, 1987 and forced with the observed sea-surface temperatures and sea-ice distribution and vegetation properties (biomes, and soils), with prognostic soil moisture, snow-cover, and hydrology showed a very realistic simulation of cloud process, incloud water and ice, and cloud-radiative forcing (CRF). The simulated ITCZ showed a realistic time-mean structure and seasonal cycle, while the simulated CRF showed sensitivity to vertical distribution of cloud water which can be easily altered by the choice of time constant and incloud critical cloud water amount regulators for auto-conversion. The CRF and its feedbacks also have a profound effect on the ITCZ. Even though somewhat weaker than observed, the McRAS-GCM simulation produces robust 30-60 day oscillations in the 200 hPa velocity potential. Two ensembles of 4-summer (July, August, September) simulations, one each for 1987 and 1988 show that the McRAS-GCM simulates realistic and statistically significant precipitation differences over India, Central America, and tropical Africa. Several seasonal simulations were performed with McRAS-GEOS II GCM for the summer (June-July- August) and winter (December-January-February) periods to determine how the simulated clouds and CRFs would be affected by: i) advection of clouds; ii) cloud top entrainment instability, iii) cloud water inhomogeneity correction, and (iv) cloud production and dissipation in different cloud-processes. The results show that each of these processes contributes to the simulated cloud-fraction and CRF.

Development of an atmospheric infrared radiation model with high clouds for target detection

NASA Astrophysics Data System (ADS)

Bellisario, Christophe; Malherbe, Claire; Schweitzer, Caroline; Stein, Karin

2016-10-01

In the field of target detection, the simulation of the camera FOV (field of view) background is a significant issue. The presence of heterogeneous clouds might have a strong impact on a target detection algorithm. In order to address this issue, we present here the construction of the CERAMIC package (Cloudy Environment for RAdiance and MIcrophysics Computation) that combines cloud microphysical computation and 3D radiance computation to produce a 3D atmospheric infrared radiance in attendance of clouds. The input of CERAMIC starts with an observer with a spatial position and a defined FOV (by the mean of a zenithal angle and an azimuthal angle). We introduce a 3D cloud generator provided by the French LaMP for statistical and simplified physics. The cloud generator is implemented with atmospheric profiles including heterogeneity factor for 3D fluctuations. CERAMIC also includes a cloud database from the French CNRM for a physical approach. We present here some statistics developed about the spatial and time evolution of the clouds. Molecular optical properties are provided by the model MATISSE (Modélisation Avancée de la Terre pour l'Imagerie et la Simulation des Scènes et de leur Environnement). The 3D radiance is computed with the model LUCI (for LUminance de CIrrus). It takes into account 3D microphysics with a resolution of 5 cm-1 over a SWIR bandwidth. In order to have a fast computation time, most of the radiance contributors are calculated with analytical expressions. The multiple scattering phenomena are more difficult to model. Here a discrete ordinate method with correlated-K precision to compute the average radiance is used. We add a 3D fluctuations model (based on a behavioral model) taking into account microphysics variations. In fine, the following parameters are calculated: transmission, thermal radiance, single scattering radiance, radiance observed through the cloud and multiple scattering radiance. Spatial images are produced, with a dimension of 10 km x 10 km and a resolution of 0.1 km with each contribution of the radiance separated. We present here the first results with examples of a typical scenarii. A 1D comparison in results is made with the use of the MATISSE model by separating each radiance calculated, in order to validate outputs. The code performance in 3D is shown by comparing LUCI to SHDOM model, referency code which uses the Spherical Harmonic Discrete Ordinate Method for 3D Atmospheric Radiative Transfer model. The results obtained by the different codes present a strong agreement and the sources of small differences are considered. An important gain in time is observed for LUCI versus SHDOM. We finally conclude on various scenarios for case analysis.

Atmospheric microphysical experiments on an orbital platform

NASA Technical Reports Server (NTRS)

Eaton, L. R.

1974-01-01

The Zero-Gravity Atmospheric Cloud Physics Laboratory is a Shuttle/Spacelab payload which will be capable of performing a large range of microphysics experiments. This facility will complement terrestrial cloud physics research by allowing many experiments to be performed which cannot be accomplished within the confines of a terrestrial laboratory. This paper reviews the general Cloud Physics Laboratory concept and the experiment scope. The experimental constraints are given along with details of the proposed equipment. Examples of appropriate experiments range from three-dimensional simulation of the earth and planetary atmosphere and of ocean circulation to cloud electrification processes and the effects of atmospheric pollution materials on microphysical processes.

Cirrus and Water Vapor Transport in the Tropical Tropopause Layer

NASA Astrophysics Data System (ADS)

Dinh, Tra Phuong

Simulations of tropical-tropopause-layer (TTL) cirrus under the influence of a large-scale equatorial Kelvin wave have been performed in two dimensions. These simulations show that, even under the influence of the large-scale wave, radiatively induced dynamics in TTL cirrus plays an important role in the transport of water vapor in the vertical direction. In a typical TTL cirrus, the heating that results from absorption of radiation by ice crystals induces a mesoscale circulation. Advection of ice and water vapor by the radiatively induced circulation leads to the persistence of the cloud and upward advection of the cloudy air. Upward advection of the cloudy air is equivalent to upward transport of water vapor when the air above the cloud is drier than the cloudy air, and downward transport otherwise. In TTL cirrus, microphysical processes also contribute to transport of water vapor in the vertical direction. Ice nucleation and growth, followed by sedimentation and sublimation, always lead to downward transport of water vapor. The magnitude of the downward transport by microphysical processes increases with the relative humidity of the air surrounding the cloud. Moisture in the surrounding environment is important because there is continuous interactions between the cloudy and environmental air throughout the cloud boundary. In our simulations, when the air surrounding the cloud is subsaturated, hence drier than the cloudy air, the magnitude of the downward transport due to microphysical processes is smaller than that of the upward transport due to the radiatively induced advection of water vapor. The net result is upward transport of water vapor, and equivalently hydration of the lower stratosphere. On the other hand, when the surrounding air is supersaturated, hence moister than the cloudy air, microphysical and radiatively induced dynamical processes work in concert to induce downward transport of water vapor, that is dehydration of the lower stratosphere. TTL cirrus processes also depend sensitively on the deposition coefficient of water vapor on ice crystals. The deposition coefficient determines the depositional growth rate of ice crystals, hence microphysical and radiative properties of the cloud. In our simulations, larger values of the deposition coefficient correspond to less ice crystals nucleated during homogeneous freezing, larger ice crystal sizes, faster ice sedimentation, smaller radiative heating rate and weaker dynamics. These results indicate that detailed observations of the relative humidity in the vicinity of TTL cirrus and accurate laboratory measurements of the deposition coefficient are necessary to quantify the impact of TTL cirrus in the dehydration of the stratosphere. This research highlights the complex role of microphysical, radiative and dynamical processes in the transport of water vapor within TTL cirrus. It shows that under certain realistic conditions, TTL cirrus may lead to upward transport of water vapor, which results in moistening of the lower stratosphere. Thus it is not accurate to always associate TTL cirrus with stratospheric dehydration.

Using the JPL Tropical Cyclone Information System to study the climatology of hurricane precipitation structure from 10 years of passive microwave satellite observations in the Atlantic

NASA Astrophysics Data System (ADS)

Hristova-Veleva, Svetla; Haddad, Ziad; Knosp, Brian; Lambrigtsen, Bjorn; Li, P. Peggy; Poulsen, William; Seo, Eun-Kyoung; Shen, Tsae-Pyng; Turk, Francis J.; Vu, Quoc

2013-04-01

In spite of recent improvements in hurricane track forecast accuracy, currently there are still many unanswered questions about the physical processes that determine hurricane genesis, and evolution. Furthermore, a significant amount of work remains to be done in validating and improving hurricane forecast models. None of this can be accomplished without a comprehensive set of multi-parameter observations that are relevant to both the large-scale and the storm-scale processes in the atmosphere and in the ocean. Despite the significant amount of satellite observations today, they are still underutilized in hurricane research and operations, due to complexity and volume. To facilitate hurricane research, we developed the JPL Tropical Cyclone Information System (TCIS) of multi-instrument satellite observations pertaining to: i) the thermodynamic and microphysical structure of the storms; ii) the air-sea interaction processes; iii) the larger-scale environment as depicted by the SST and the Total Precipitable Water of the environment (Hristova-Veleva et al., 2008, 2011). Our goal was to create a one-stop place to provide the researchers with an extensive set of observed hurricane data, and their graphical representation, organized in an easy way to determine when coincident observations from multiple instruments are available. In this study we use the 10+ years of passive microwave observations of Atlantic hurricanes to create composite structures that are segregated by hurricane category and by intensification rate. The use of composite structures provides a statistically robust framework (e.g. Rogers et al., 2012). We analyze the storm asymmetry as depicted by several factors - brightness temperatures and their derivatives such as a newly-develop Rain Indicator and a new convective/stratiform separation that is based on the value and the spatial variability of this Rain Indicator. The goal is to determine whether the storm morphology (in particular, the storm asymmetry or lack thereof) carries predictive skills regarding the potential for intensification. The presentation will describe the JPL TCIS and the results of our analysis of the passive microwave satellite observations of the Atlantic hurricanes. Refernces: Hristova-Veleva, S. M., C. Ao, Y. Chao, V. Dang, R. Fovell, M. Garay, Z. Haddad, B. Knosp, B. Lambrigtsen, P. P. Li, K. J. Park, W. Poulsen, H. Su, S. Tanelli, D. Vane, Q. A. Vu, J. Willis, D. L. Wu, 2008: "Using the JPL Tropical Cyclone Information System for Research and Applications", AMS 28th Hurricane and Tropical Meteorology Conference, Orlando, FL, 28Apr.-02May 2008 Hristova-Veleva, S. M., A. Chau, Z. Haddad, B. Knosp, B. Lambrigtsen, P. P. Li, E. Rodriguez, T. -. P. Shen, B. Stiles, H. Su, J. Turk, and Q. Vu, 2011: "Impact of microphysical parameterizations on the structure and intensity of simulated hurricanes: Using satellite data to determine the parameterizations that produce most realistic storms", 14th Conference on Mesoscale Processes, 1-4 August 2011, Los Angeles, California Rogers, R., S. Lorsolo, P. Reasor, J. Gamache, F. Marks, 2012: Multiscale Analysis of Tropical Cyclone Kinematic Structure from Airborne Doppler Radar Composites. Mon. Wea. Rev., 140, 77-99.

Improved MICROBASE Product with Uncertainties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Meng

The data set contains four primary microphysics, including liquid water content, ice water content, liquid effective radius, and ice effective radius. Bit QC and data quality QC are also calculated. Quantification of uncertainties (incorporating the work of Zhao et al. 2013) are included for all four microphysics.

Intercomparison of aerosol-cloud-precipitation interactions in stratiform orographic mixed-phase clouds

NASA Astrophysics Data System (ADS)

Muhlbauer, A.; Hashino, T.; Xue, L.; Teller, A.; Lohmann, U.; Rasmussen, R. M.; Geresdi, I.; Pan, Z.

2010-09-01

Anthropogenic aerosols serve as a source of both cloud condensation nuclei (CCN) and ice nuclei (IN) and affect microphysical properties of clouds. Increasing aerosol number concentrations is hypothesized to retard the cloud droplet coalescence and the riming in mixed-phase clouds, thereby decreasing orographic precipitation. This study presents results from a model intercomparison of 2-D simulations of aerosol-cloud-precipitation interactions in stratiform orographic mixed-phase clouds. The sensitivity of orographic precipitation to changes in the aerosol number concentrations is analysed and compared for various dynamical and thermodynamical situations. Furthermore, the sensitivities of microphysical processes such as coalescence, aggregation, riming and diffusional growth to changes in the aerosol number concentrations are evaluated and compared. The participating numerical models are the model from the Consortium for Small-Scale Modeling (COSMO) with bulk microphysics, the Weather Research and Forecasting (WRF) model with bin microphysics and the University of Wisconsin modeling system (UWNMS) with a spectral ice habit prediction microphysics scheme. All models are operated on a cloud-resolving scale with 2 km horizontal grid spacing. The results of the model intercomparison suggest that the sensitivity of orographic precipitation to aerosol modifications varies greatly from case to case and from model to model. Neither a precipitation decrease nor a precipitation increase is found robustly in all simulations. Qualitative robust results can only be found for a subset of the simulations but even then quantitative agreement is scarce. Estimates of the aerosol effect on orographic precipitation are found to range from -19% to 0% depending on the simulated case and the model. Similarly, riming is shown to decrease in some cases and models whereas it increases in others, which implies that a decrease in riming with increasing aerosol load is not a robust result. Furthermore, it is found that neither a decrease in cloud droplet coalescence nor a decrease in riming necessarily implies a decrease in precipitation due to compensation effects by other microphysical pathways. The simulations suggest that mixed-phase conditions play an important role in buffering the effect of aerosol perturbations on cloud microphysics and reducing the overall susceptibility of clouds and precipitation to changes in the aerosol number concentrations. As a consequence the aerosol effect on precipitation is suggested to be less pronounced or even inverted in regions with high terrain (e.g., the Alps or Rocky Mountains) or in regions where mixed-phase microphysics is important for the climatology of orographic precipitation.

Microphysical modelling of volcanic plumes / Comparisons against groundbased and spaceborne lidar data

NASA Astrophysics Data System (ADS)

Jumelet, Julien; Bekki, Slimane; Keckhut, Philippe

2017-04-01

We present a high-resolution isentropic microphysical transport model dedicated to stratospheric aerosols and clouds. The model is based on the MIMOSA model (Modélisation Isentrope du transport Méso-échelle de l'Ozone Stratosphérique par Advection) and adds several modules: a fully explicit size-resolving microphysical scheme to transport aerosol granulometry as passive tracers and an optical module, able to calculate the scattering and extinction properties of particles at given wavelengths. Originally designed for polar stratospheric clouds (composed of sulfuric acid, nitric acid and water vapor), the model is fully capable of rendering the structure and properties of volcanic plumes at the finer scales, assuming complete SO2 oxydation. This link between microphysics and optics also enables the model to take advantage of spaceborne lidar data (i.e. CALIOP) by calculating the 532nm aerosol backscatter coefficient, taking it as the control variable to provide microphysical constraints during the transport. This methodology has been applied to simulate volcanic plumes during relatively recent volcanic eruptions, from the 2010 Merapi to the 2015 Calbuco eruption. Optical calculations are also used for direct comparisons between the model and groundbased lidar stations for validation as well as characterization purposes. We will present the model and the simulation results, along with a focus on the sensitivity to initialisation parameters, considering the need for quasi-real time modelling and forecasts in the case of future eruptions.

Sensitivity of the simulation of tropical cyclone size to microphysics schemes

NASA Astrophysics Data System (ADS)

Chan, Kelvin T. F.; Chan, Johnny C. L.

2016-09-01

The sensitivity of the simulation of tropical cyclone (TC) size to microphysics schemes is studied using the Advanced Hurricane Weather Research and Forecasting Model (WRF). Six TCs during the 2013 western North Pacific typhoon season and three mainstream microphysics schemes-Ferrier (FER), WRF Single-Moment 5-class (WSM5) and WRF Single-Moment 6-class (WSM6)-are investigated. The results consistently show that the simulated TC track is not sensitive to the choice of microphysics scheme in the early simulation, especially in the open ocean. However, the sensitivity is much greater for TC intensity and inner-core size. The TC intensity and size simulated using the WSM5 and WSM6 schemes are respectively higher and larger than those using the FER scheme in general, which likely results from more diabatic heating being generated outside the eyewall in rainbands. More diabatic heating in rainbands gives higher inflow in the lower troposphere and higher outflow in the upper troposphere, with higher upward motion outside the eyewall. The lower-tropospheric inflow would transport absolute angular momentum inward to spin up tangential wind predominantly near the eyewall, leading to the increment in TC intensity and size (the inner-core size, especially). In addition, the inclusion of graupel microphysics processes (as in WSM6) may not have a significant impact on the simulation of TC track, intensity and size.

The Impact of Aerosols on Cloud and Precipitation Processes: Cloud-Resolving Model Simulations

NASA Technical Reports Server (NTRS)

Tao, Wei-Kuo; Li, X.; Khain, A.; Simpson, S.

2004-01-01

Cloud microphysics are inevitably affected by the smoke particle (CCN, cloud condensation nuclei) size distributions below the clouds. Therefore, size distributions parameterized as spectral bin microphysics are needed to explicitly study the effects of atmospheric aerosol concentration on cloud development, rainfall production, and rainfall rates for convective clouds. Recently, two detailed spectral-bin microphysical schemes were implemented into the Goddard Cumulus Ensemble (GCE) model. The formulation for the explicit spectral-bin microphysical processes is based on solving stochastic kinetic equations for the size distribution functions of water droplets (i.e., cloud droplets and raindrops), and several types of ice particles (i.e., pristine ice crystals (columnar and plate-like), snow (dendrites and aggregates), graupel and frozen drops/hail). Each type is described by a special size distribution function containing many categories (i.e. 33 bins). Atmospheric aerosols are also described using number density size-distribution functions. A spectral-bin microphysical model is very expensive from a computational point of view and has only been implemented into the 2D version of the GCE at the present time. The model is tested by studying the evolution of deep cloud systems in the west Pacific warm pool region, in the sub-tropics (Florida) and in the mid-latitude using identical thermodynamic conditions but with different concentrations of CCN: a low 'clean' concentration and a high 'dirty' concentration.

Satellite Remote Sensing of Aerosol Forcing

NASA Technical Reports Server (NTRS)

Remer, Lorraine; Kaufman, Yoram; Ramaprasad, Jaya; Procopio, Aline; Levin, Zev

1999-01-01

Aerosol and cloud impacts on the earth's climate become a recent hot topic in climate studies. Having near future earth observing satellites, EOS-AM1 (Earth Observing System-AM1), ENVISAT (Environmental Satellites) and ADEOS-2 (Advanced Earth Observation Satellite-2), it will be a good timing to discuss how to obtain and use the microphysical parameters of aerosols and clouds for studying their climate impacts. Center for Climate System Research (CCSR) of the University of Tokyo invites you to 'Symposium on synergy between satellite-remote sensing and climate modeling in aerosol and cloud issues.' Here, we like to discuss the current and future issues in the remote sensing of aerosol and cloud microphysical parameters and their climate modeling studies. This workshop is also one of workshop series on aerosol remote sensing held in 1996, Washington D. C., and Meribel, France in 1999. It should be reminded that NASDA/ADEOS-1 & -2 (National Space Development Agency of Japan/Advanced Earth Observation Satellite-1 & -2) Workshop will be held in the following week (Dec. 6-10, 1999), so that this opportunity will be a perfect period for you to attend two meetings for satellite remote sensing in Japan. A weekend in Kyoto, the old capital of Japan, will add a nice memory to your visiting Japan. *Issues in the symposium: 1) most recent topics in aerosol and cloud remot sensing, and 2) utility of satellite products on climate modeling of cloud-aerosol effects.

Application of the CloudSat and NEXRAD Radars Toward Improvements in High Resolution Operational Forecasts

NASA Technical Reports Server (NTRS)

Molthan, A. L.; Haynes, J. A.; Case, J. L.; Jedlovec, G. L.; Lapenta, W. M.

2008-01-01

As computational power increases, operational forecast models are performing simulations with higher spatial resolution allowing for the transition from sub-grid scale cloud parameterizations to an explicit forecast of cloud characteristics and precipitation through the use of single- or multi-moment bulk water microphysics schemes. investments in space-borne and terrestrial remote sensing have developed the NASA CloudSat Cloud Profiling Radar and the NOAA National Weather Service NEXRAD system, each providing observations related to the bulk properties of clouds and precipitation through measurements of reflectivity. CloudSat and NEXRAD system radars observed light to moderate snowfall in association with a cold-season, midlatitude cyclone traversing the Central United States in February 2007. These systems are responsible for widespread cloud cover and various types of precipitation, are of economic consequence, and pose a challenge to operational forecasters. This event is simulated with the Weather Research and Forecast (WRF) Model, utilizing the NASA Goddard Cumulus Ensemble microphysics scheme. Comparisons are made between WRF-simulated and observed reflectivity available from the CloudSat and NEXRAD systems. The application of CloudSat reflectivity is made possible through the QuickBeam radiative transfer model, with cautious application applied in light of single scattering characteristics and spherical target assumptions. Significant differences are noted within modeled and observed cloud profiles, based upon simulated reflectivity, and modifications to the single-moment scheme are tested through a supplemental WRF forecast that incorporates a temperature dependent snow crystal size distribution.

Evaluation of and Suggested Improvements to the WSM6 Microphysics in WRF- ARW Using Synthetic and Observed GOES-13 Imagery

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grasso, Lewis; Lindsey, Daniel T.; Lim, Kyo-Sun

Synthetic satellite imagery can be employed to evaluate simulated cloud fields. Past studies have revealed that the Weather Research and Forecasting (WRF) WRF Single-Moment 6-class (WSM6) microphysics in WRF-ARW produces less upper level ice clouds within synthetic images compared to observations. Synthetic Geostationary Operational Environmental Satellite (GOES)-13 imagery at 10.7 μm of simulated cloud fields from the 4 km National Severe Storms Laboratory (NSSL) WRF-ARW is compared to observed GOES-13 imagery. Histograms suggest that too few points contain upper level simulated ice clouds. In particular, side-by-side examples are shown of synthetic and observed convective anvils. Such images illustrate the lackmore » of anvil cloud associated with convection produced by the NSSL WRF-ARW. A vertical profile of simulated hydrometeors suggests that too much cloud water mass may be converted into graupel mass, effectively reducing the main source of ice mass in a simulated anvil. Further, excessive accretion of ice by snow removes ice from an anvil by precipitation settling. Idealized sensitivity tests reveal that a 50% reduction of the conversion of cloud water mass to graupel and a 50% reduction of the accretion rate of ice by snow results in a significant increase in anvil ice of a simulated storm. Such results provide guidance as to which conversions could be reformulated, in a more physical manner, to increase simulated ice mass in the upper troposphere.« less

In Situ Microphysical and Scattering Properties of Falling Snow in GPM-GCPEx

NASA Astrophysics Data System (ADS)

Duffy, G.; Nesbitt, S. W.; McFarquhar, G. M.; Poellot, M.; Chandrasekar, C. V.; Hudak, D. R.

2013-12-01

The Global Precipitation Measurement Cold-season Precipitation Experiment (GPM-GCPEx) field campaign was conducted near Egbert, Ontario, Canada in January-February 2012 to study the physical characteristics and microwave radiative properties of the column of hydrometeors in cold season precipitation events. Extensive in situ aircraft profiling was conducted with the University of North Dakota (UND) Citation aircraft within the volume of several remote sensing instruments within a wide variety of precipitation events, from snow to freezing drizzle. Several of the primary goals of GCPEx include improving our understanding of the microphysical characteristics of falling snow and how those characteristics relate to the multi-wavelength radiative characteristics In this study, particle size distribution parameters, effective particle densities, and habit distributions are determined using in-situ cloud measurements obtained on the UND citation using the High Volume Precipitation Spectrometer, the Cloud Particle Imager, and the Cloud Imaging Probe. These quantities are matched compared to multi-frequency radar measurements from the Environment Canada King City C-Band and NASA D3R Ku-Ka Band dual polarization radars. These analysis composites provide the basis for direct evaluation of particle size distributions and observed multi-wavelength and multi-polarization radar observations, including radar reflectivity, differential reflectivity, and dual wavelength ratio) in falling snow at weather radar and GPM radar frequencies. Theoretical predictions from Mie, Rayleigh-Gans, and more complex snowflake aggregate scattering model predictions using observed particle size distributions are compared with observed radar scattering characteristics along the Citation flight track.

Statistical Evaluation of CRM-Simulated Cloud and Precipitation Structures Using Multi- sensor TRMM Measurements and Retrievals

NASA Astrophysics Data System (ADS)

Posselt, D.; L'Ecuyer, T.; Matsui, T.

2009-05-01

Cloud resolving models are typically used to examine the characteristics of clouds and precipitation and their relationship to radiation and the large-scale circulation. As such, they are not required to reproduce the exact location of each observed convective system, much less each individual cloud. Some of the most relevant information about clouds and precipitation is provided by instruments located on polar-orbiting satellite platforms, but these observations are intermittent "snapshots" in time, making assessment of model performance challenging. In contrast to direct comparison, model results can be evaluated statistically. This avoids the requirement for the model to reproduce the observed systems, while returning valuable information on the performance of the model in a climate-relevant sense. The focus of this talk is a model evaluation study, in which updates to the microphysics scheme used in a three-dimensional version of the Goddard Cumulus Ensemble (GCE) model are evaluated using statistics of observed clouds, precipitation, and radiation. We present the results of multiday (non-equilibrium) simulations of organized deep convection using single- and double-moment versions of a the model's cloud microphysical scheme. Statistics of TRMM multi-sensor derived clouds, precipitation, and radiative fluxes are used to evaluate the GCE results, as are simulated TRMM measurements obtained using a sophisticated instrument simulator suite. We present advantages and disadvantages of performing model comparisons in retrieval and measurement space and conclude by motivating the use of data assimilation techniques for analyzing and improving model parameterizations.

HoloGondel: in situ cloud observations on a cable car in the Swiss Alps using a holographic imager

NASA Astrophysics Data System (ADS)

Beck, Alexander; Henneberger, Jan; Schöpfer, Sarah; Fugal, Jacob; Lohmann, Ulrike

2017-02-01

In situ observations of cloud properties in complex alpine terrain where research aircraft cannot sample are commonly conducted at mountain-top research stations and limited to single-point measurements. The HoloGondel platform overcomes this limitation by using a cable car to obtain vertical profiles of the microphysical and meteorological cloud parameters. The main component of the HoloGondel platform is the HOLographic Imager for Microscopic Objects (HOLIMO 3G), which uses digital in-line holography to image cloud particles. Based on two-dimensional images the microphysical cloud parameters for the size range from small cloud particles to large precipitation particles are obtained for the liquid and ice phase. The low traveling velocity of a cable car on the order of 10 m s-1 allows measurements with high spatial resolution; however, at the same time it leads to an unstable air speed towards the HoloGondel platform. Holographic cloud imagers, which have a sample volume that is independent of the air speed, are therefore well suited for measurements on a cable car. Example measurements of the vertical profiles observed in a liquid cloud and a mixed-phase cloud at the Eggishorn in the Swiss Alps in the winters 2015 and 2016 are presented. The HoloGondel platform reliably observes cloud droplets larger than 6.5 µm, partitions between cloud droplets and ice crystals for a size larger than 25 µm and obtains a statistically significantly size distribution for every 5 m in vertical ascent.

Solar Effects on Global Climate Due to Cosmic Rays and Solar Energetic Particles

NASA Technical Reports Server (NTRS)

Turco, R. P.; Raeder, J.; DAuria, R.

2005-01-01

Although the work reported here does not directly connect solar variability with global climate change, this research establishes a plausible quantitative causative link between observed solar activity and apparently correlated variations in terrestrial climate parameters. Specifically, we have demonstrated that ion-mediated nucleation of atmospheric particles is a likely, and likely widespread, phenomenon that relates solar variability to changes in the microphysical properties of clouds. To investigate this relationship, we have constructed and applied a new model describing the formation and evolution of ionic clusters under a range of atmospheric conditions throughout the lower atmosphere. The activation of large ionic clusters into cloud nuclei is predicted to be favorable in the upper troposphere and mesosphere, and possibly in the lower stratosphere. The model developed under this grant needs to be extended to include additional cluster families, and should be incorporated into microphysical models to further test the cause-and-effect linkages that may ultimately explain key aspects of the connections between solar variability and climate.

Theoretical study of mixing in liquid clouds – Part 1: Classical concepts

DOE PAGES

Korolev, Alexei; Khain, Alex; Pinsky, Mark; ...

2016-07-28

The present study considers final stages of in-cloud mixing in the framework of classical concept of homogeneous and extreme inhomogeneous mixing. Simple analytical relationships between basic microphysical parameters were obtained for homogeneous and extreme inhomogeneous mixing based on the adiabatic consideration. It was demonstrated that during homogeneous mixing the functional relationships between the moments of the droplets size distribution hold only during the primary stage of mixing. Subsequent random mixing between already mixed parcels and undiluted cloud parcels breaks these relationships. However, during extreme inhomogeneous mixing the functional relationships between the microphysical parameters hold both for primary and subsequent mixing.more » The obtained relationships can be used to identify the type of mixing from in situ observations. The effectiveness of the developed method was demonstrated using in situ data collected in convective clouds. It was found that for the specific set of in situ measurements the interaction between cloudy and entrained environments was dominated by extreme inhomogeneous mixing.« less

Improved intraseasonal variability in the NASA GEOS AGCM with 2-moment microphysics and a shallow cumulus parameterization

NASA Astrophysics Data System (ADS)

Arnold, N.; Barahona, D.

2017-12-01

Atmospheric general circulation models (AGCMs) have long struggled to realistically represent tropical intraseasonal variability. Here we report progress in simulating the Madden Julian Oscillation (MJO) with the NASA Goddard Earth Observing System (GEOS) AGCM, in free-running simulations utilizing a new two-moment microphysics scheme and the University of Washington shallow cumulus parameterization. Lag composites of intraseasonal signals show significantly improved eastward propagation over the Indian Ocean and maritime region, with increased eastward precipitation variance and more coherent large-scale structure. The dynamics of the MJO are analyzed using a vertically resolved moisture budget, assuming weak temperature gradient conditions. We find that positive longwave radiative heating anomalies associated with high clouds contribute to low-level ascent and moistening, coincident with intraseasonal precipitation anomalies. Horizontal advection generally damps intraseasonal moisture anomalies, but at some longitudes contributes to their eastward tendency. Shallow convection is enhanced to the east of the intraseasonal precipitation maximum, and its associated moistening of the lower free troposphere encourages eastward propagation of deep convection.

Microphysical Consequences of the Spatial Distribution of Ice Nucleation in Mixed-Phase Stratiform Clouds

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Fan; Ovchinnikov, Mikhail; Shaw, Raymond A.

Mixed-phase stratiform clouds can persist even with steady ice precipitation fluxes, and the origin and microphysical properties of the ice crystals are of interest. Vapor deposition growth and sedimentation of ice particles along with a uniform volume source of ice nucleation, leads to a power law relation between ice water content wi and ice number concentration ni with exponent 2.5. The result is independent of assumptions about the vertical velocity structure of the cloud and is therefore more general than the related expression of Yang et al. [2013]. The sensitivity of the wi-ni relationship to the spatial distribution of icemore » nucleation is confirmed by Lagrangian tracking and ice growth with cloud-volume, cloud-top, and cloud-base sources of ice particles through a time-dependent cloud field. Based on observed wi and ni from ISDAC, a lower bound of 0.006 m^3/s is obtained for the ice crystal formation rate.« less

Cirrus clouds and climate feedback: Is the sky falling and should we go tell the king

NASA Technical Reports Server (NTRS)

Stephens, Graeme L.

1990-01-01

It is widely believed that thin cirrus clouds act to enhance the greenhouse effect owing to a particular combination of their optical properties. It is demonstrated how this effect is perhaps based on inadequate resolution of the physics of cirrus clouds and that the more likely impact of cirrus clouds to climate change remains somewhat elusive. These conclusions are developed within the context of a specific feedback mechanism incorporated into a simple mechanistic climate model. A specific scientific question addressed is whether or not the observed relationship between the ice water content and temperature of cirrus provides any significant feedback to the CO2 greenhouse warming. A related question also examined concerns the specific role of cloud microphysics and radiation in this feedback. This raises several pertinent issues about the understanding of cirrus clouds and their likely role in climate change as there presently exists a considerable uncertainty about the microphysics of these clouds (size and shape of ice crystals) and their radiative influences.

Minimalist Model of Ice Microphysics in Mixed-phase Stratiform Clouds

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, F.; Ovchinnikov, Mikhail; Shaw, Raymond A.

The question of whether persistent ice crystal precipitation from super cooled layer clouds can be explained by time-dependent, stochastic ice nucleation is explored using an approximate, analytical model, and a large-eddy simulation (LES) cloud model. The updraft velocity in the cloud defines an accumulation zone, where small ice particles cannot fall out until they are large enough, which will increase the residence time of ice particles in the cloud. Ice particles reach a quasi-steady state between growth by vapor deposition and fall speed at cloud base. The analytical model predicts that ice water content (wi) has a 2.5 power lawmore » relationship with ice number concentration ni. wi and ni from a LES cloud model with stochastic ice nucleation also confirm the 2.5 power law relationship. The prefactor of the power law is proportional to the ice nucleation rate, and therefore provides a quantitative link to observations of ice microphysical properties.« less

On the ambiguity in relativistic tidal deformability

NASA Astrophysics Data System (ADS)

Gralla, Samuel E.

2018-04-01

The LIGO collaboration recently reported the first gravitational-wave constraints on the tidal deformability of neutron stars. I discuss an inherent ambiguity in the notion of relativistic tidal deformability that, while too small to affect the present measurement, may become important in the future. I propose a new way to understand the ambiguity and discuss future prospects for reliably linking observed gravitational waveforms to compact object microphysics.

Understanding the Microphysical Properties of Developing Cloud Clusters During TCS-08

DTIC Science & Technology

2012-09-30

sensed satellite data In addition to the lightning data , geostationary infrared brightness temperatures and MODIS data have been used to analyze...detailed investigation of genesis using remote-sensed observations from platforms that are maintained on a more permanent basis including satellite -based...searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments

Biofuel blending reduces particle emissions from aircraft engines at cruise conditions

NASA Astrophysics Data System (ADS)

Moore, Richard H.; Thornhill, Kenneth L.; Weinzierl, Bernadett; Sauer, Daniel; D'Ascoli, Eugenio; Kim, Jin; Lichtenstern, Michael; Scheibe, Monika; Beaton, Brian; Beyersdorf, Andreas J.; Barrick, John; Bulzan, Dan; Corr, Chelsea A.; Crosbie, Ewan; Jurkat, Tina; Martin, Robert; Riddick, Dean; Shook, Michael; Slover, Gregory; Voigt, Christiane; White, Robert; Winstead, Edward; Yasky, Richard; Ziemba, Luke D.; Brown, Anthony; Schlager, Hans; Anderson, Bruce E.

2017-03-01

Aviation-related aerosol emissions contribute to the formation of contrail cirrus clouds that can alter upper tropospheric radiation and water budgets, and therefore climate. The magnitude of air-traffic-related aerosol-cloud interactions and the ways in which these interactions might change in the future remain uncertain. Modelling studies of the present and future effects of aviation on climate require detailed information about the number of aerosol particles emitted per kilogram of fuel burned and the microphysical properties of those aerosols that are relevant for cloud formation. However, previous observational data at cruise altitudes are sparse for engines burning conventional fuels, and no data have previously been reported for biofuel use in-flight. Here we report observations from research aircraft that sampled the exhaust of engines onboard a NASA DC-8 aircraft as they burned conventional Jet A fuel and a 50:50 (by volume) blend of Jet A fuel and a biofuel derived from Camelina oil. We show that, compared to using conventional fuels, biofuel blending reduces particle number and mass emissions immediately behind the aircraft by 50 to 70 per cent. Our observations quantify the impact of biofuel blending on aerosol emissions at cruise conditions and provide key microphysical parameters, which will be useful to assess the potential of biofuel use in aviation as a viable strategy to mitigate climate change.

Biofuel blending reduces particle emissions from aircraft engines at cruise conditions.

PubMed

Moore, Richard H; Thornhill, Kenneth L; Weinzierl, Bernadett; Sauer, Daniel; D'Ascoli, Eugenio; Kim, Jin; Lichtenstern, Michael; Scheibe, Monika; Beaton, Brian; Beyersdorf, Andreas J; Barrick, John; Bulzan, Dan; Corr, Chelsea A; Crosbie, Ewan; Jurkat, Tina; Martin, Robert; Riddick, Dean; Shook, Michael; Slover, Gregory; Voigt, Christiane; White, Robert; Winstead, Edward; Yasky, Richard; Ziemba, Luke D; Brown, Anthony; Schlager, Hans; Anderson, Bruce E

2017-03-15

Aviation-related aerosol emissions contribute to the formation of contrail cirrus clouds that can alter upper tropospheric radiation and water budgets, and therefore climate. The magnitude of air-traffic-related aerosol-cloud interactions and the ways in which these interactions might change in the future remain uncertain. Modelling studies of the present and future effects of aviation on climate require detailed information about the number of aerosol particles emitted per kilogram of fuel burned and the microphysical properties of those aerosols that are relevant for cloud formation. However, previous observational data at cruise altitudes are sparse for engines burning conventional fuels, and no data have previously been reported for biofuel use in-flight. Here we report observations from research aircraft that sampled the exhaust of engines onboard a NASA DC-8 aircraft as they burned conventional Jet A fuel and a 50:50 (by volume) blend of Jet A fuel and a biofuel derived from Camelina oil. We show that, compared to using conventional fuels, biofuel blending reduces particle number and mass emissions immediately behind the aircraft by 50 to 70 per cent. Our observations quantify the impact of biofuel blending on aerosol emissions at cruise conditions and provide key microphysical parameters, which will be useful to assess the potential of biofuel use in aviation as a viable strategy to mitigate climate change.

A Cloud Microphysics Model for the Gas Giant Planets

NASA Astrophysics Data System (ADS)

Palotai, Csaba J.; Le Beau, Raymond P.; Shankar, Ramanakumar; Flom, Abigail; Lashley, Jacob; McCabe, Tyler

2016-10-01

Recent studies have significantly increased the quality and the number of observed meteorological features on the jovian planets, revealing banded cloud structures and discrete features. Our current understanding of the formation and decay of those clouds also defines the conceptual modes about the underlying atmospheric dynamics. The full interpretation of the new observational data set and the related theories requires modeling these features in a general circulation model (GCM). Here, we present details of our bulk cloud microphysics model that was designed to simulate clouds in the Explicit Planetary Hybrid-Isentropic Coordinate (EPIC) GCM for the jovian planets. The cloud module includes hydrological cycles for each condensable species that consist of interactive vapor, cloud and precipitation phases and it also accounts for latent heating and cooling throughout the transfer processes (Palotai and Dowling, 2008. Icarus, 194, 303-326). Previously, the self-organizing clouds in our simulations successfully reproduced the vertical and horizontal ammonia cloud structure in the vicinity of Jupiter's Great Red Spot and Oval BA (Palotai et al. 2014, Icarus, 232, 141-156). In our recent work, we extended this model to include water clouds on Jupiter and Saturn, ammonia clouds on Saturn, and methane clouds on Uranus and Neptune. Details of our cloud parameterization scheme, our initial results and their comparison with observations will be shown. The latest version of EPIC model is available as open source software from NASA's PDS Atmospheres Node.

Biomass burning influences on atmospheric composition: A case study to assess the impact of aerosol data assimilation

NASA Astrophysics Data System (ADS)

Keslake, Tim; Chipperfield, Martyn; Mann, Graham; Flemming, Johannes; Remy, Sam; Dhomse, Sandip; Morgan, Will

2016-04-01

The C-IFS (Composition Integrated Forecast System) developed under the MACC series of projects and to be continued under the Copernicus Atmospheric Monitoring System, provides global operational forecasts and re-analyses of atmospheric composition at high spatial resolution (T255, ~80km). Currently there are 2 aerosol schemes implemented within C-IFS, a mass-based scheme with externally mixed particle types and an aerosol microphysics scheme (GLOMAP-mode). The simpler mass-based scheme is the current operational system, also used in the existing system to assimilate satellite measurements of aerosol optical depth (AOD) for improved forecast capability. The microphysical GLOMAP scheme has now been implemented and evaluated in the latest C-IFS cycle alongside the mass-based scheme. The upgrade to the microphysical scheme provides for higher fidelity aerosol-radiation and aerosol-cloud interactions, accounting for global variations in size distribution and mixing state, and additional aerosol properties such as cloud condensation nuclei concentrations. The new scheme will also provide increased aerosol information when used as lateral boundary conditions for regional air quality models. Here we present a series of experiments highlighting the influence and accuracy of the two different aerosol schemes and the impact of MODIS AOD assimilation. In particular, we focus on the influence of biomass burning emissions on aerosol properties in the Amazon, comparing to ground-based and aircraft observations from the 2012 SAMBBA campaign. Biomass burning can affect regional air quality, human health, regional weather and the local energy budget. Tropical biomass burning generates particles primarily composed of particulate organic matter (POM) and black carbon (BC), the local ratio of these two different constituents often determining the properties and subsequent impacts of the aerosol particles. Therefore, the model's ability to capture the concentrations of these two carbonaceous aerosol types, during the tropical dry season, is essential for quantifying these wide ranging impacts. Comparisons to SAMBBA aircraft observations show that while both schemes underestimate POM and BC mass concentrations, the GLOMAP scheme provides a more accurate simulation. When satellite AOD is assimilated into the GEMS-AER scheme, the model is successfully adjusted, capturing observed mass concentrations to a good degree of accuracy.

Polarimetric radar and aircraft observations of saggy bright bands during MC3E

DOE PAGES

Matthew R. Kumjian; Giangrande, Scott E.; Mishra, Subashree; ...

2016-03-19

Polarimetric radar observations increasingly are used to understand cloud microphysical processes, which is critical for improving their representation in cloud and climate models. In particular, there has been recent focus on improving representations of ice collection processes (e.g., aggregation, riming), as these influence precipitation rate, heating profiles, and ultimately cloud life cycles. However, distinguishing these processes using conventional polarimetric radar observations is difficult, as they produce similar fingerprints. This necessitates improved analysis techniques and integration of complementary data sources. Furthermore, the Midlatitude Continental Convective Clouds Experiment (MC3E) provided such an opportunity.

Statistical retrieval of thin liquid cloud microphysical properties using ground-based infrared and microwave observations

NASA Astrophysics Data System (ADS)

Marke, Tobias; Ebell, Kerstin; Löhnert, Ulrich; Turner, David D.

2016-12-01

In this article, liquid water cloud microphysical properties are retrieved by a combination of microwave and infrared ground-based observations. Clouds containing liquid water are frequently occurring in most climate regimes and play a significant role in terms of interaction with radiation. Small perturbations in the amount of liquid water contained in the cloud can cause large variations in the radiative fluxes. This effect is enhanced for thin clouds (liquid water path, LWP <100 g/m2), which makes accurate retrieval information of the cloud properties crucial. Due to large relative errors in retrieving low LWP values from observations in the microwave domain and a high sensitivity for infrared methods when the LWP is low, a synergistic retrieval based on a neural network approach is built to estimate both LWP and cloud effective radius (reff). These statistical retrievals can be applied without high computational demand but imply constraints like prior information on cloud phase and cloud layering. The neural network retrievals are able to retrieve LWP and reff for thin clouds with a mean relative error of 9% and 17%, respectively. This is demonstrated using synthetic observations of a microwave radiometer (MWR) and a spectrally highly resolved infrared interferometer. The accuracy and robustness of the synergistic retrievals is confirmed by a low bias in a radiative closure study for the downwelling shortwave flux, even for marginally invalid scenes. Also, broadband infrared radiance observations, in combination with the MWR, have the potential to retrieve LWP with a higher accuracy than a MWR-only retrieval.

Airborne observations of the microphysical structure of two contrasting cirrus clouds

NASA Astrophysics Data System (ADS)

O'Shea, S. J.; Choularton, T. W.; Lloyd, G.; Crosier, J.; Bower, K. N.; Gallagher, M.; Abel, S. J.; Cotton, R. J.; Brown, P. R. A.; Fugal, J. P.; Schlenczek, O.; Borrmann, S.; Pickering, J. C.

2016-11-01

We present detailed airborne in situ measurements of cloud microphysics in two midlatitude cirrus clouds, collected as part of the Cirrus Coupled Cloud-Radiation Experiment. A new habit recognition algorithm for sorting cloud particle images using a neural network is introduced. Both flights observed clouds that were related to frontal systems, but one was actively developing while the other dissipated as it was sampled. The two clouds showed distinct differences in particle number, habit, and size. However, a number of common features were observed in the 2-D stereo data set, including a distinct bimodal size distribution within the higher-temperature regions of the clouds. This may result from a combination of local heterogeneous nucleation and large particles sedimenting from aloft. Both clouds had small ice crystals (<100 µm) present at all levels However, this small ice mode is not present in observations from a holographic probe. This raises the possibility that the small ice observed by optical array probes may at least be in part an instrument artifact due to the counting of out-of-focus large particles as small ice. The concentrations of ice crystals were a factor 10 higher in the actively growing cloud with the stronger updrafts, with a mean concentration of 261 L-1 compared to 29 L-1 in the decaying case. Particles larger than 700 µm were largely absent from the decaying cirrus case. A comparison with ice-nucleating particle parameterizations suggests that for the developing case the ice concentrations at the lowest temperatures are best explained by homogenous nucleation.

Enhancing our Understanding of Snowfall Modes with Ground-Based Observations

NASA Astrophysics Data System (ADS)

Pettersen, C.; Kulie, M.; Petersen, W. A.; Bliven, L. F.; Wood, N.

2016-12-01

Snowfall can be broadly categorized into deep and shallow events based on the vertical distribution of the precipitating ice. Remotely sensed data refine these precipitation categories and aid in discerning the underlying macro- and microphysical mechanisms. The unique patterns in the remotely sensed instruments observations can potentially connect distinct modes of snowfall to specific processes. Though satellites can observe and recognize these patterns in snowfall, these measurements are limited - particularly in cases of shallow and light precipitation, as the snow may be too close to the surface or below the detection limits of the instrumentation. By enhancing satellite measurements with ground-based instrumentation, whether with limited-term field campaigns or long-term strategic sites, we can further our understanding and assumptions about different snowfall modes and how they are measured from spaceborne instruments. Presented are three years of data from a ground-based instrument suite consisting of a MicroRain Radar (MRR; optimized for snow events) and a Precipitation Imaging Package (PIP). These instruments are located at the Marquette, Michigan National Weather Service Weather Forecast Office to: a) use coincident meteorological measurements and observations to enhance our understanding of the thermodynamic drivers and b) showcase these instruments in an operational setting to enhance forecasts of shallow snow events. Three winters of MRR and PIP measurements are partitioned, based on meteorological surface observations, into two-dimensional histograms of reflectivity and particle size distribution data. These statistics improve our interpretation of deep versus shallow precipitation. Additionally, these statistical techniques are applied to similar datasets from Global Precipitation Measurement field campaigns for further insight into cloud and precipitation macro- and microphysical processes.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kalesse, Heike; Szyrmer, Wanda; Kneifel, Stefan

In this paper, Radar Doppler spectra measurements are exploited to study a riming event when precipitating ice from a seeder cloud sediment through a supercooled liquid water (SLW) layer. The focus is on the "golden sample" case study for this type of analysis based on observations collected during the deployment of the Atmospheric Radiation Measurement Program's (ARM) mobile facility AMF2 at Hyytiälä, Finland, during the Biogenic Aerosols – Effects on Clouds and Climate (BAECC) field campaign. The presented analysis of the height evolution of the radar Doppler spectra is a state-of-the-art retrieval with profiling cloud radars in SLW layers beyondmore » the traditional use of spectral moments. Dynamical effects are considered by following the particle population evolution along slanted tracks that are caused by horizontal advection of the cloud under wind shear conditions. In the SLW layer, the identified liquid peak is used as an air motion tracer to correct the Doppler spectra for vertical air motion and the ice peak is used to study the radar profiles of rimed particles. A 1-D steady-state bin microphysical model is constrained using the SLW and air motion profiles and cloud top radar observations. The observed radar moment profiles of the rimed snow can be simulated reasonably well by the model, but not without making several assumptions about the ice particle concentration and the relative role of deposition and aggregation. In conclusion, this suggests that in situ observations of key ice properties are needed to complement the profiling radar observations before process-oriented studies can effectively evaluate ice microphysical parameterizations.« less

Evaluation of WRF physical parameterizations against ARM/ASR Observations in the post-cold-frontal region to improve low-level clouds representation in CAM5

NASA Astrophysics Data System (ADS)

Lamraoui, F.; Booth, J. F.; Naud, C. M.

2017-12-01

The representation of subgrid-scale processes of low-level marine clouds located in the post-cold-frontal region poses a serious challenge for climate models. More precisely, the boundary layer parameterizations are predominantly designed for individual regimes that can evolve gradually over time and does not accommodate the cold front passage that can overly modify the boundary layer rapidly. Also, the microphysics schemes respond differently to the quick development of the boundary layer schemes, especially under unstable conditions. To improve the understanding of cloud physics in the post-cold frontal region, the present study focuses on exploring the relationship between cloud properties, the local processes and large-scale conditions. In order to address these questions, we explore the WRF sensitivity to the interaction between various combinations of the boundary layer and microphysics parameterizations, including the Community Atmospheric Model version 5 (CAM5) physical package in a perturbed physics ensemble. Then, we evaluate these simulations against ground-based ARM observations over the Azores. The WRF-based simulations demonstrate particular sensitivities of the marine cold front passage and the associated post-cold frontal clouds to the domain size, the resolution and the physical parameterizations. First, it is found that in multiple different case studies the model cannot generate the cold front passage when the domain size is larger than 3000 km2. Instead, the modeled cold front stalls, which shows the importance of properly capturing the synoptic scale conditions. The simulation reveals persistent delay in capturing the cold front passage and also an underestimated duration of the post-cold-frontal conditions. Analysis of the perturbed physics ensemble shows that changing the microphysics scheme leads to larger differences in the modeled clouds than changing the boundary layer scheme. The in-cloud heating tendencies are analyzed to explain this sensitivity.

Application of advanced data assimilation techniques to the study of cloud and precipitation feedbacks in the tropical climate system

NASA Astrophysics Data System (ADS)

Posselt, Derek J.

The research documented in this study centers around two topics: evaluation of the response of precipitating cloud systems to changes in the tropical climate system, and assimilation of cloud and precipitation information from remote-sensing platforms. The motivation for this work proceeds from the following outstanding problems: (1) Use of models to study the response of clouds to perturbations in the climate system is hampered by uncertainties in cloud microphysical parameterizations. (2) Though there is an ever-growing set of available observations, cloud and precipitation assimilation remains a difficult problem, particularly in the tropics. (3) Though it is widely acknowledged that cloud and precipitation processes play a key role in regulating the Earth's response to surface warming, the response of the tropical hydrologic cycle to climate perturbations remains largely unknown. The above issues are addressed in the following manner. First, Markov chain Monte Carlo (MCMC) methods are used to quantify the sensitivity of the NASA Goddard Cumulus Ensemble (GCE) cloud resolving model (CRM) to changes in its cloud odcrnpbymiC8l parameters. TRMM retrievals of precipitation rate, cloud properties, and radiative fluxes and heating rates over the South China Sea are then assimilated into the GCE model to constrain cloud microphysical parameters to values characteristic of convection in the tropics, and the resulting observation-constrained model is used to assess the response of the tropical hydrologic cycle to surface warming. The major findings of this study are the following: (1) MCMC provides an effective tool with which to evaluate both model parameterizations and the assumption of Gaussian statistics used in optimal estimation procedures. (2) Statistics of the tropical radiation budget and hydrologic cycle can be used to effectively constrain CRM cloud microphysical parameters. (3) For 2D CRM simulations run with and without shear, the precipitation efficiency of cloud systems increases with increasing sea surface temperature, while the high cloud fraction and outgoing shortwave radiation decrease.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nicoll, Ken A.; O'Connor, E.

Large-scale properties of clouds such as lifetime, optical thickness, and precipitation are all dependent on small-scale cloud microphysical processes. Such processes determine when droplets will grow or shrink, their size, and the number of cloud droplets. Although our understanding of cloud microphysics has vastly improved over the past several decades with the development of remote sensing methods such as lidar and radar, there remain a number of processes that are not well understood, such as the effect of electrical charge on cloud microphysics. To understand the various processes and feedback mechanisms, high-vertical–resolution observations are required. Radiosondes provide an ideal platformmore » for providing routine vertical profiles of in situ measurements at any location (with a vertical resolution of a few meters). Modified meteorological radiosondes have been extensively developed at the University of Reading for measuring cloud properties, to allow measurements beyond the traditional thermodynamic quantities (pressure, temperature and relative humidity) to be obtained cost-effectively. This project aims to investigate a number of cloud processes in which in situ cloud observations from these modified radiosondes can provide information either complementary to or not obtainable by lidar/radar systems. During two intensive operational periods (IOPs) in May and August 2014 during deployment to Hyytiälä, Finland, the Atmospheric Radiation Measurement (ARM) Climate Research Facility’s Second ARM Mobile Facility (AMF2) launched a total of 24 instrumented radiosondes through a number of different cloud types ranging from low-level stratiform cloud to cumulonimbus. Twelve balloon flights of an accelerometer turbulence sensor were made, which detected significant turbulence on eleven of these flights. Most of the turbulent episodes encountered were due to convective processes, but several were associated with the transition from troposphere to stratosphere at the tropopause. Similarities in the location of turbulent layers were generally found between the balloon turbulence sensor and the Ka-band radar, but with discrepancies between the orders of magnitude of turbulence detected. The reason for these discrepancies is the subject of future work.« less

The global aerosol-climate model ECHAM-HAM, version 2: sensitivity to improvements in process representations

NASA Astrophysics Data System (ADS)

Zhang, K.; O'Donnell, D.; Kazil, J.; Stier, P.; Kinne, S.; Lohmann, U.; Ferrachat, S.; Croft, B.; Quaas, J.; Wan, H.; Rast, S.; Feichter, J.

2012-03-01

This paper introduces and evaluates the second version of the global aerosol-climate model ECHAM-HAM. Major changes have been brought into the model, including new parameterizations for aerosol nucleation and water uptake, an explicit treatment of secondary organic aerosols, modified emission calculations for sea salt and mineral dust, the coupling of aerosol microphysics to a two-moment stratiform cloud microphysics scheme, and alternative wet scavenging parameterizations. These revisions extend the model's capability to represent details of the aerosol lifecycle and its interaction with climate. Sensitivity experiments are carried out to analyse the effects of these improvements in the process representation on the simulated aerosol properties and global distribution. The new parameterizations that have largest impact on the global mean aerosol optical depth and radiative effects turn out to be the water uptake scheme and cloud microphysics. The former leads to a significant decrease of aerosol water contents in the lower troposphere, and consequently smaller optical depth; the latter results in higher aerosol loading and longer lifetime due to weaker in-cloud scavenging. The combined effects of the new/updated parameterizations are demonstrated by comparing the new model results with those from the earlier version, and against observations. Model simulations are evaluated in terms of aerosol number concentrations against measurements collected from twenty field campaigns as well as from fixed measurement sites, and in terms of optical properties against the AERONET measurements. Results indicate a general improvement with respect to the earlier version. The aerosol size distribution and spatial-temporal variance simulated by HAM2 are in better agreement with the observations. Biases in the earlier model version in aerosol optical depth and in the Ångström parameter have been reduced. The paper also points out the remaining model deficiencies that need to be addressed in the future.

Exploring Alternative Parameterizations for Snowfall with Validation from Satellite and Terrestrial Radars

NASA Technical Reports Server (NTRS)

Molthan, Andrew L.; Petersen, Walter A.; Case, Jonathan L.; Dembek, Scott R.

2009-01-01

Increases in computational resources have allowed operational forecast centers to pursue experimental, high resolution simulations that resolve the microphysical characteristics of clouds and precipitation. These experiments are motivated by a desire to improve the representation of weather and climate, but will also benefit current and future satellite campaigns, which often use forecast model output to guide the retrieval process. The combination of reliable cloud microphysics and radar reflectivity may constrain radiative transfer models used in satellite simulators during future missions, including EarthCARE and the NASA Global Precipitation Measurement. Aircraft, surface and radar data from the Canadian CloudSat/CALIPSO Validation Project are used to check the validity of size distribution and density characteristics for snowfall simulated by the NASA Goddard six-class, single moment bulk water microphysics scheme, currently available within the Weather Research and Forecast (WRF) Model. Widespread snowfall developed across the region on January 22, 2007, forced by the passing of a mid latitude cyclone, and was observed by the dual-polarimetric, C-band radar King City, Ontario, as well as the NASA 94 GHz CloudSat Cloud Profiling Radar. Combined, these data sets provide key metrics for validating model output: estimates of size distribution parameters fit to the inverse-exponential equations prescribed within the model, bulk density and crystal habit characteristics sampled by the aircraft, and representation of size characteristics as inferred by the radar reflectivity at C- and W-band. Specified constants for distribution intercept and density differ significantly from observations throughout much of the cloud depth. Alternate parameterizations are explored, using column-integrated values of vapor excess to avoid problems encountered with temperature-based parameterizations in an environment where inversions and isothermal layers are present. Simulation of CloudSat reflectivity is performed by adopting the discrete-dipole parameterizations and databases provided in literature, and demonstrate an improved capability in simulating radar reflectivity at W-band versus Mie scattering assumptions.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boybeyi, Zafer

The Department of Energy (DOE) awarded George Mason University (GMU) with a research project. This project started on June, 2009 and ended July 2014. Main objectives of this research project are; a) to assess the indirect and semi-direct aerosol effects on microphysical structure and radiative properties of Arctic clouds, b) to assess the impact of feedback between the aerosol-cloud interactions and atmospheric boundary layer (ABL) processes on the surface energy balance, c) to better understand and characterize the important unresolved microphysical processes, aerosol effects, and ABL processes and feedbacks, over meso-γ spatial (~1-2 km) and temporal scales (a few minutesmore » to days), and d) to investigate the scale dependency of microphysical parameterizations and its effect on simulations.« less

Comparisons of cirrus cloud properties between polluted and pristine air based on in-situ observations from the NSF HIPPO, EU INCA and NASA ATTREX campaigns

NASA Astrophysics Data System (ADS)

Diao, M.; Schumann, U.; Jensen, J. B.; Minikin, A.

2015-12-01

The radiative forcing of cirrus clouds is influenced by microphysical (e.g., ice crystal number concentration and size distribution) and macroscopic properties. Currently it is still unclear how the formation of cirrus clouds and their microphysical properties are influenced by anthropogenic emissions. In this work, we use airborne in-situ observations to compare cirrus cloud properties between polluted and pristine regions. Our dataset includes: the NSF HIAPER Pole-to-Pole Observations (HIPPO) Global campaign (2009-2011), the EU Interhemispheric Differences In Cirrus Properties from Anthropogenic Emissions (INCA) campaign (2000) and the NASA Airborne Tropical Tropopause Experiment (ATTREX) campaign (2014). The combined dataset include observations of both extratropical (HIPPO and INCA) and tropical (ATTREX) cirrus, over the Northern and Southern Hemispheres. We use the in-situ measured carbon monoxide (CO) mixing ratio as a pollution indicator, and compare ice microphysical properties (i.e., ice crystal number concentration (Nc) and number-weighted mean diameter (Dc)) between air masses with higher and lower CO. All analyses are restricted to T ≤ -40°C. By analyzing ice crystals (Fast-2DC, 87.5-1600 µm) in HIPPO, we found that Dc decreases with increasing CO concentration at multiple constant pressure levels. In addition, analysis of INCA data shows that Nc and extinction of small ice particles (FSSP 3-20 µm) increases with increasing CO. Particles < 87.5 µm in Fast-2DC data are not considered due to uncertainty in sample volume, and the FSSP measurements are subject to possible shattering. We further analyze the ice crystals (SPEC FCDP, 1-50 µm) in the tropical tropopause layer in ATTREX. At -70°C to -90°C, we found that the average Nc (Dc) increases (decreases) at higher CO. Overall, our results suggest that extratropical and tropical cirrus are likely to have more numerous small ice particles, when sampled in the more polluted background. Back trajectory analysis will be used to separate cirrus formed by recent convection from the in-situ generated ones. Other pollution tracers will also be used to examine if similar features exist. Overall, these analyses will help to improve the estimation of the impacts from anthropogenic emissions on cirrus cloud formation.

Aerosol-cloud interactions in mixed-phase convective clouds - Part 1: Aerosol perturbations

NASA Astrophysics Data System (ADS)

Miltenberger, Annette K.; Field, Paul R.; Hill, Adrian A.; Rosenberg, Phil; Shipway, Ben J.; Wilkinson, Jonathan M.; Scovell, Robert; Blyth, Alan M.

2018-03-01

Changes induced by perturbed aerosol conditions in moderately deep mixed-phase convective clouds (cloud top height ˜ 5 km) developing along sea-breeze convergence lines are investigated with high-resolution numerical model simulations. The simulations utilise the newly developed Cloud-AeroSol Interacting Microphysics (CASIM) module for the Unified Model (UM), which allows for the representation of the two-way interaction between cloud and aerosol fields. Simulations are evaluated against observations collected during the COnvective Precipitation Experiment (COPE) field campaign over the southwestern peninsula of the UK in 2013. The simulations compare favourably with observed thermodynamic profiles, cloud base cloud droplet number concentrations (CDNC), cloud depth, and radar reflectivity statistics. Including the modification of aerosol fields by cloud microphysical processes improves the correspondence with observed CDNC values and spatial variability, but reduces the agreement with observations for average cloud size and cloud top height. Accumulated precipitation is suppressed for higher-aerosol conditions before clouds become organised along the sea-breeze convergence lines. Changes in precipitation are smaller in simulations with aerosol processing. The precipitation suppression is due to less efficient precipitation production by warm-phase microphysics, consistent with parcel model predictions. In contrast, after convective cells organise along the sea-breeze convergence zone, accumulated precipitation increases with aerosol concentrations. Condensate production increases with the aerosol concentrations due to higher vertical velocities in the convective cores and higher cloud top heights. However, for the highest-aerosol scenarios, no further increase in the condensate production occurs, as clouds grow into an upper-level stable layer. In these cases, the reduced precipitation efficiency (PE) dominates the precipitation response and no further precipitation enhancement occurs. Previous studies of deep convective clouds have related larger vertical velocities under high-aerosol conditions to enhanced latent heating from freezing. In the presented simulations changes in latent heating above the 0°C are negligible, but latent heating from condensation increases with aerosol concentrations. It is hypothesised that this increase is related to changes in the cloud field structure reducing the mixing of environmental air into the convective core. The precipitation response of the deeper mixed-phase clouds along well-established convergence lines can be the opposite of predictions from parcel models. This occurs when clouds interact with a pre-existing thermodynamic environment and cloud field structural changes occur that are not captured by simple parcel model approaches.

Uniwavelength lidar sensitivity to spherical aerosol microphysical properties for the interpretation of Lagrangian stratospheric observations

NASA Astrophysics Data System (ADS)

Jumelet, Julien; David, Christine; Bekki, Slimane; Keckhut, Philippe

2009-01-01

The determination of stratospheric particle microphysical properties from multiwavelength lidar, including Rayleigh and/or Raman detection, has been widely investigated. However, most lidar systems are uniwavelength operating at 532 nm. Although the information content of such lidar data is too limited to allow the retrieval of the full size distribution, the coupling of two or more uniwavelength lidar measurements probing the same moving air parcel may provide some meaningful size information. Within the ORACLE-O3 IPY project, the coordination of several ground-based lidars and the CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation) space-borne lidar is planned during measurement campaigns called MATCH-PSC (Polar Stratospheric Clouds). While probing the same moving air masses, the evolution of the measured backscatter coefficient (BC) should reflect the variation of particles microphysical properties. A sensitivity study of 532 nm lidar particle backscatter to variations of particles size distribution parameters is carried out. For simplicity, the particles are assumed to be spherical (liquid) particles and the size distribution is represented with a unimodal log-normal distribution. Each of the four microphysical parameters (i.e. log-normal size distribution parameters, refractive index) are analysed separately, while the three others are remained set to constant reference values. Overall, the BC behaviour is not affected by the initial values taken as references. The total concentration (N0) is the parameter to which BC is least sensitive, whereas it is most sensitive to the refractive index (m). A 2% variation of m induces a 15% variation of the lidar BC, while the uncertainty on the BC retrieval can also reach 15%. This result underlines the importance of having both an accurate lidar inversion method and a good knowledge of the temperature for size distribution retrieval techniques. The standard deviation ([sigma]) is the second parameter to which BC is most sensitive to. Yet, the impact of m and [sigma] on BC variations is limited by the realistic range of their variations. The mean radius (rm) of the size distribution is thus the key parameter for BC, as it can vary several-fold. BC is most sensitive to the presence of large particles. The sensitivity of BC to rm and [sigma] variations increases when the initial size distributions are characterized by low rm and large [sigma]. This makes lidar more suitable to detect particles growing on background aerosols than on volcanic aerosols.

A Combined Retrieval of Aerosol Microphysical Properties using active HSRL and Passive Polarimeter Multi-sensor Data

NASA Astrophysics Data System (ADS)

Liu, X.; Stamnes, S.; Ferrare, R. A.; Hostetler, C. A.; Burton, A. S.; Chemyakin, E.; Sawamura, P.; Mueller, D.

2017-12-01

Vertically resolved measurements of aerosol optical, microphysical, and macrophysical parameters are required to better understand the influence of aerosols on climate and air quality. We will describe an Optimal Estimation (OE) retrieval framework which can perform aerosol property retrievals in three modes: 1) lidar-only, 2) polarimeter-only, and 3) combined lidar-polarimeter muti-sensor system. The lidar data can be profile measurements by any high spectral resolution lidar (HSRL) and/or Raman lidar with multiple wavelengths of aerosol backscattering (β) and extinction (α). The polarimeter data can be any multi-angle and multi-wavelength measurements with 2 or 3 polarization components. We will show aerosol microphysical retrieval results from the HSRL-2 data measured from various NASA airborne field campaigns including the recent ORACLES mission. We will also show the OE retrieval results from the polarimeter-only mode. Finally, we will demonstrate how the information content of the aerosol microphysical retrieval is increased by combining the active HSRL and passive polarimeter data in our simultaneous OE retrieval system.

Meteorological Observations and System Performance From the NASA D3R's First 5 Years

NASA Technical Reports Server (NTRS)

Chandrasekar, V.; Beauchamp, Robert M.; Vega, Manuel; Chen, Haonan; Kumar, Mohit; Joshil, Shashank; Schwaller, Mathew; Petersen, Walter; Wolff, David

2017-01-01

The NASA dual-frequency, dual-polarization, Doppler radar (D3R) was conceived and developed to support ground validation (GV) operations of the Global Precipitation Measurement (GPM) mission. The D3R operates in the same frequencies bands, Ku- and Ka-band, as GPMs dual-frequency precipitation radar enabling direct comparisons of microphysical observations of precipitation. To support the GPM GVmission, D3R substantively participated in four field campaigns in North America with diverse geographic features covering both winter and summer conditions.

Optimization of microphysics in the Unified Model, using the Micro-genetic algorithm.

NASA Astrophysics Data System (ADS)

Jang, J.; Lee, Y.; Lee, H.; Lee, J.; Joo, S.

2016-12-01

This study focuses on parameter optimization of microphysics in the Unified Model (UM) using the Micro-genetic algorithm (Micro-GA). We need the optimization of microphysics in UM. Because, Microphysics in the Numerical Weather Prediction (NWP) model is important to Quantitative Precipitation Forecasting (QPF). The Micro-GA searches for optimal parameters on the basis of fitness function. The five parameters are chosen. The target parameters include x1, x2 related to raindrop size distribution, Cloud-rain correlation coefficient, Surface droplet number and Droplet taper height. The fitness function is based on the skill score that is BIAS and Critical Successive Index (CSI). An interface between UM and Micro-GA is developed and applied to three precipitation cases in Korea. The cases are (ⅰ) heavy rainfall in the Southern area because of typhoon NAKRI, (ⅱ) heavy rainfall in the Youngdong area, and (ⅲ) heavy rainfall in the Seoul metropolitan area. When the optimized result is compared to the control result (using the UM default value, CNTL), the optimized result leads to improvements in precipitation forecast, especially for heavy rainfall of the late forecast time. Also, we analyze the skill score of precipitation forecasts in terms of various thresholds of CNTL, Optimized result, and experiments on each optimized parameter for five parameters. Generally, the improvement is maximized when the five optimized parameters are used simultaneously. Therefore, this study demonstrates the ability to improve Korean precipitation forecasts by optimizing microphysics in UM.

On The Cloud Processing of Aerosol Particles: An Entraining Air Parcel Model With Two-dimensional Spectral Cloud Microphysics and A New Formulation of The Collection Kernel

NASA Astrophysics Data System (ADS)

Bott, Andreas; Kerkweg, Astrid; Wurzler, Sabine

A study has been made of the modification of aerosol spectra due to cloud pro- cesses and the impact of the modified aerosols on the microphysical structure of future clouds. For this purpose an entraining air parcel model with two-dimensional spectral cloud microphysics has been used. In order to treat collision/coalescence processes in the two-dimensional microphysical module, a new realistic and continuous formu- lation of the collection kernel has been developed. Based on experimental data, the kernel covers the entire investigated size range of aerosols, cloud and rain drops, that is the kernel combines all important coalescence processes such as the collision of cloud drops as well as the impaction scavenging of small aerosols by big raindrops. Since chemical reactions in the gas phase and in cloud drops have an important impact on the physico-chemical properties of aerosol particles, the parcel model has been extended by a chemical module describing gas phase and aqueous phase chemical reactions. However, it will be shown that in the numerical case studies presented in this paper the modification of aerosols by chemical reactions has a minor influence on the microphysical structure of future clouds. The major process yielding in a second cloud event an enhanced formation of rain is the production of large aerosol particles by collision/coalescence processes in the first cloud.

Aerosol indirect effect from turbulence-induced broadening of cloud-droplet size distributions.

PubMed

Chandrakar, Kamal Kant; Cantrell, Will; Chang, Kelken; Ciochetto, David; Niedermeier, Dennis; Ovchinnikov, Mikhail; Shaw, Raymond A; Yang, Fan

2016-12-13

The influence of aerosol concentration on the cloud-droplet size distribution is investigated in a laboratory chamber that enables turbulent cloud formation through moist convection. The experiments allow steady-state microphysics to be achieved, with aerosol input balanced by cloud-droplet growth and fallout. As aerosol concentration is increased, the cloud-droplet mean diameter decreases, as expected, but the width of the size distribution also decreases sharply. The aerosol input allows for cloud generation in the limiting regimes of fast microphysics ([Formula: see text]) for high aerosol concentration, and slow microphysics ([Formula: see text]) for low aerosol concentration; here, [Formula: see text] is the phase-relaxation time and [Formula: see text] is the turbulence-correlation time. The increase in the width of the droplet size distribution for the low aerosol limit is consistent with larger variability of supersaturation due to the slow microphysical response. A stochastic differential equation for supersaturation predicts that the standard deviation of the squared droplet radius should increase linearly with a system time scale defined as [Formula: see text], and the measurements are in excellent agreement with this finding. The result underscores the importance of droplet size dispersion for aerosol indirect effects: increasing aerosol concentration changes the albedo and suppresses precipitation formation not only through reduction of the mean droplet diameter but also by narrowing of the droplet size distribution due to reduced supersaturation fluctuations. Supersaturation fluctuations in the low aerosol/slow microphysics limit are likely of leading importance for precipitation formation.

LACIS-T - A humid wind tunnel for investigating the Interactions between Cloud Microphysics and Turbulence

NASA Astrophysics Data System (ADS)

Voigtländer, Jens; Niedermeier, Dennis; Siebert, Holger; Shaw, Raymond; Schumacher, Jörg; Stratmann, Frank

2017-04-01

To improve the fundamental and quantitative understanding of the interactions between cloud microphysical and turbulent processes, the Leibniz Institute for Tropospheric Research (TROPOS) has built up a new humid wind tunnel (LACIS-T). LACIS-T allows for the investigation of cloud microphysical processes, such as cloud droplet activation and freezing, under-well defined thermodynamic and turbulent flow conditions. It therewith allows for the straight forward continuation, extension, and completion of the cloud microphysics related investigations carried out at the Leipzig Aerosol Cloud Interaction Simulator (LACIS) under laminar flow conditions. Characterization of the wind tunnel with respect to flow, thermodynamics, and droplet microphysics is carried out with probes mounted inside (pitot tube and hot-wire anemometer for mean velocity and fluctuations, Pt100 sensor for mean temperature, cold-wire sensor for temperature fluctuations is in progress, as well as a dew-point mirror for mean water vapor concentration, a Lyman-alpha sensor for water vapor fluctuations is in progress) the measurement section, and from outside with optical detection methods (a laser light sheet is available for cloud droplet visualization, a digital holography system for detection of cloud droplet size distributions will be installed for tests in February 2017), respectively. Computational fluid dynamics (CFD) simulations have been carried out for defining suitable experimental conditions and assisting the interpretation of the experimental data. In this work, LACIS-T, its fundamental operating principle, and first preliminary results from ongoing characterization efforts will be presented.

Cloud Microphysics Budget in the Tropical Deep Convective Regime

NASA Technical Reports Server (NTRS)

Li, Xiao-Fan; Sui, C.-H.; Lau, K.-M.; Einaudi, Franco (Technical Monitor)

2001-01-01

Cloud microphysics budgets in the tropical deep convective regime are analyzed based on a 2-D cloud resolving simulation. The model is forced by the large-scale vertical velocity and zonal wind and large-scale horizontal advections derived from TOGA COARE for a 20-day period. The role of cloud microphysics is first examined by analyzing mass-weighted mean heat budget and column-integrated moisture budget. Hourly budgets show that local changes of mass-weighted mean temperature and column-integrated moisture are mainly determined by the residuals between vertical thermal advection and latent heat of condensation and between vertical moisture advection and condensation respectively. Thus, atmospheric thermodynamics depends on how cloud microphysical processes are parameterized. Cloud microphysics budgets are then analyzed for raining conditions. For cloud-vapor exchange between cloud system and its embedded environment, rainfall and evaporation of raindrop are compensated by the condensation and deposition of supersaturated vapor. Inside the cloud system, the condensation of supersaturated vapor balances conversion from cloud water to raindrop, snow, and graupel through collection and accretion processes. The deposition of supersaturated vapor balances conversion from cloud ice to snow through conversion and riming processes. The conversion and riming of cloud ice and the accretion of cloud water balance conversion from snow to graupel through accretion process. Finally, the collection of cloud water and the melting of graupel increase raindrop to compensate the loss of raindrop due to rainfall and the evaporation of raindrop.

Fingerprints of a riming event on cloud radar Doppler spectra: observations and modeling

DOE PAGES

Kalesse, Heike; Szyrmer, Wanda; Kneifel, Stefan; ...

2016-03-09

In this paper, Radar Doppler spectra measurements are exploited to study a riming event when precipitating ice from a seeder cloud sediment through a supercooled liquid water (SLW) layer. The focus is on the "golden sample" case study for this type of analysis based on observations collected during the deployment of the Atmospheric Radiation Measurement Program's (ARM) mobile facility AMF2 at Hyytiälä, Finland, during the Biogenic Aerosols – Effects on Clouds and Climate (BAECC) field campaign. The presented analysis of the height evolution of the radar Doppler spectra is a state-of-the-art retrieval with profiling cloud radars in SLW layers beyondmore » the traditional use of spectral moments. Dynamical effects are considered by following the particle population evolution along slanted tracks that are caused by horizontal advection of the cloud under wind shear conditions. In the SLW layer, the identified liquid peak is used as an air motion tracer to correct the Doppler spectra for vertical air motion and the ice peak is used to study the radar profiles of rimed particles. A 1-D steady-state bin microphysical model is constrained using the SLW and air motion profiles and cloud top radar observations. The observed radar moment profiles of the rimed snow can be simulated reasonably well by the model, but not without making several assumptions about the ice particle concentration and the relative role of deposition and aggregation. In conclusion, this suggests that in situ observations of key ice properties are needed to complement the profiling radar observations before process-oriented studies can effectively evaluate ice microphysical parameterizations.« less

Aerosol-Cloud Interactions during Tropical Deep Convection: Evidence for the Importance of Free Tropospheric Aerosols

NASA Technical Reports Server (NTRS)

Ackerman, A.; Jensen, E.; Stevens, D.; Wang, D.; Heymsfield, A.; Miloshevich, L.; Twohy, C.; Poellot, M.; VanReken, T.; Fridland, Ann

2003-01-01

NASA's 2002 CRYSTAL-FACE field experiment focused on the formation and evolution of tropical cirrus cloud systems in southern Florida. Multiple aircraft extensively sampled cumulonimbus dynamical and microphysical properties, as well as characterizing ambient aerosol populations both inside and outside the full depth of the convective column. On July 18, unique measurements were taken when a powerful updraft was traversed directly by aircraft, providing a window into the primary source region of cumulonimbus anvil crystals. Observations of the updraft, entered at approximately l0 km altitude and -34 C, indicated more than 200 cloud particles per mL at vertical velocities exceeding 20 m/s and the presence of significant condensation nuclei and liquid water within the core. In this work, aerosol and cloud phase observations are integrated by simulating the updraft conditions using a large-eddy resolving model with 3 explicit multiphase microphysics, including treatment of size-resolved aerosol fields, aerosol activation and freezing, and evaporation of cloud particles back to the aerosol phase. Simulations were initialized with observed thermodynamic and aerosol size distributions profiles and convection was driven by surface fluxes assimilated from the ARPS forecast model. Model results are consistent with the conclusions that most crystals are homogeneously frozen droplets and that entrained free tropospheric aerosols may contribute a significant fraction of the crystals. Thus most anvil crystals appear to be formed aloft in updraft cores, well above cloud base. These conclusions are supported by observations of hydrometeor size distribution made while traversing the dore, as well as aerosol and cloud particle size distributions generally observed by aircraft below 4km and crystal properties generally observed by aircraft above 12km.

Retrievals of Ice Cloud Microphysical Properties of Deep Convective Systems using Radar Measurements

NASA Astrophysics Data System (ADS)

Tian, J.; Dong, X.; Xi, B.; Wang, J.; Homeyer, C. R.

2015-12-01

This study presents innovative algorithms for retrieving ice cloud microphysical properties of Deep Convective Systems (DCSs) using Next-Generation Radar (NEXRAD) reflectivity and newly derived empirical relationships from aircraft in situ measurements in Wang et al. (2015) during the Midlatitude Continental Convective Clouds Experiment (MC3E). With composite gridded NEXRAD radar reflectivity, four-dimensional (space-time) ice cloud microphysical properties of DCSs are retrieved, which is not possible from either in situ sampling at a single altitude or from vertical pointing radar measurements. For this study, aircraft in situ measurements provide the best-estimated ice cloud microphysical properties for validating the radar retrievals. Two statistical comparisons between retrieved and aircraft in situ measured ice microphysical properties are conducted from six selected cases during MC3E. For the temporal-averaged method, the averaged ice water content (IWC) and median mass diameter (Dm) from aircraft in situ measurements are 0.50 g m-3 and 1.51 mm, while the retrievals from radar reflectivity have negative biases of 0.12 g m-3 (24%) and 0.02 mm (1.3%) with correlations of 0.71 and 0.48, respectively. For the spatial-averaged method, the IWC retrievals are closer to the aircraft results (0.51 vs. 0.47 g m-3) with a positive bias of 8.5%, whereas the Dm retrievals are larger than the aircraft results (1.65 mm vs. 1.51 mm) with a positive bias of 9.3%. The retrieved IWCs decrease from ~0.6 g m-3 at 5 km to ~0.15 g m-3 at 13 km, and Dm values decrease from ~2 mm to ~0.7 mm at the same levels. In general, the aircraft in situ measured IWC and Dm values at each level are within one standard derivation of retrieved properties. Good agreements between microphysical properties measured from aircraft and retrieved from radar reflectivity measurements indicate the reasonable accuracy of our retrievals.

Intercomparison of aerosol-cloud-precipitation interactions in stratiform orographic mixed-phase clouds

NASA Astrophysics Data System (ADS)

Muhlbauer, A.; Hashino, T.; Xue, L.; Teller, A.; Lohmann, U.; Rasmussen, R. M.; Geresdi, I.; Pan, Z.

2010-04-01

Anthropogenic aerosols serve as a source of both cloud condensation nuclei (CCN) and ice nuclei (IN) and affect microphysical properties of clouds. Increasing aerosol number concentrations is hypothesized to retard the cloud droplet collision/coalescence and the riming in mixed-phase clouds, thereby decreasing orographic precipitation. This study presents results from a model intercomparison of 2-D simulations of aerosol-cloud-precipitation interactions in stratiform orographic mixed-phase clouds. The sensitivity of orographic precipitation to changes in the aerosol number concentrations is analyzed and compared for various dynamical and thermodynamical situations. Furthermore, the sensitivities of microphysical processes such as collision/coalescence, aggregation and riming to changes in the aerosol number concentrations are evaluated and compared. The participating models are the Consortium for Small-Scale Modeling's (COSMO) model with bulk-microphysics, the Weather Research and Forecasting (WRF) model with bin-microphysics and the University of Wisconsin modeling system (UWNMS) with a spectral ice-habit prediction microphysics scheme. All models are operated on a cloud-resolving scale with 2 km horizontal grid spacing. The results of the model intercomparison suggest that the sensitivity of orographic precipitation to aerosol modifications varies greatly from case to case and from model to model. Neither a precipitation decrease nor a precipitation increase is found robustly in all simulations. Qualitative robust results can only be found for a subset of the simulations but even then quantitative agreement is scarce. Estimates of the second indirect aerosol effect on orographic precipitation are found to range from -19% to 0% depending on the simulated case and the model. Similarly, riming is shown to decrease in some cases and models whereas it increases in others which implies that a decrease in riming with increasing aerosol load is not a robust result. Furthermore, it is found that neither a decrease in cloud droplet coalescence nor a decrease in riming necessarily implies a decrease in precipitation due to compensation effects by other microphysical pathways. The simulations suggest that mixed-phase conditions play an important role in reducing the overall susceptibility of clouds and precipitation with respect to changes in the aerosols number concentrations. As a consequence the indirect aerosol effect on precipitation is suggested to be less pronounced or even inverted in regions with high terrain (e.g., the Alps or Rocky Mountains) or in regions where mixed-phase microphysics climatologically plays an important role for orographic precipitation.

Evaluating cloud retrieval algorithms with the ARM BBHRP framework

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mlawer,E.; Dunn,M.; Mlawer, E.

2008-03-10

Climate and weather prediction models require accurate calculations of vertical profiles of radiative heating. Although heating rate calculations cannot be directly validated due to the lack of corresponding observations, surface and top-of-atmosphere measurements can indirectly establish the quality of computed heating rates through validation of the calculated irradiances at the atmospheric boundaries. The ARM Broadband Heating Rate Profile (BBHRP) project, a collaboration of all the working groups in the program, was designed with these heating rate validations as a key objective. Given the large dependence of radiative heating rates on cloud properties, a critical component of BBHRP radiative closure analysesmore » has been the evaluation of cloud microphysical retrieval algorithms. This evaluation is an important step in establishing the necessary confidence in the continuous profiles of computed radiative heating rates produced by BBHRP at the ARM Climate Research Facility (ACRF) sites that are needed for modeling studies. This poster details the continued effort to evaluate cloud property retrieval algorithms within the BBHRP framework, a key focus of the project this year. A requirement for the computation of accurate heating rate profiles is a robust cloud microphysical product that captures the occurrence, height, and phase of clouds above each ACRF site. Various approaches to retrieve the microphysical properties of liquid, ice, and mixed-phase clouds have been processed in BBHRP for the ACRF Southern Great Plains (SGP) and the North Slope of Alaska (NSA) sites. These retrieval methods span a range of assumptions concerning the parameterization of cloud location, particle density, size, shape, and involve different measurement sources. We will present the radiative closure results from several different retrieval approaches for the SGP site, including those from Microbase, the current 'reference' retrieval approach in BBHRP. At the NSA, mixed-phase clouds and cloud with a low optical depth are prevalent; the radiative closure studies using Microbase demonstrated significant residuals. As an alternative to Microbase at NSA, the Shupe-Turner cloud property retrieval algorithm, aimed at improving the partitioning of cloud phase and incorporating more constrained, conditional microphysics retrievals, also has been evaluated using the BBHRP data set.« less

Microphysical Properties of Frozen Particles Inferred from Global Precipitation Measurement (GPM) Microwave Imager (GMI) Polarimetric Measurements

NASA Technical Reports Server (NTRS)

Gong, Jie; Wu, Dongliang

2017-01-01

Scattering differences induced by frozen particle microphysical properties are investigated, using the vertically (V) and horizontally (H) polarized radiances from the Global Precipitation Measurement (GPM) Microwave Imager (GMI) 89 and 166GHz channels. It is the first study on global frozen particle microphysical properties that uses the dual-frequency microwave polarimetric signals. From the ice cloud scenes identified by the 183.3 3GHz channel brightness temperature (TB), we find that the scatterings of frozen particles are highly polarized with V-H polarimetric differences (PD) being positive throughout the tropics and the winter hemisphere mid-latitude jet regions, including PDs from the GMI 89 and 166GHz TBs, as well as the PD at 640GHz from the ER-2 Compact Scanning Submillimeter-wave Imaging Radiometer (CoSSIR) during the TC4 campaign. Large polarization dominantly occurs mostly near convective outflow region (i.e., anvils or stratiform precipitation), while the polarization signal is small inside deep convective cores as well as at the remote cirrus region. Neglecting the polarimetric signal would result in as large as 30 error in ice water path retrievals. There is a universal bell-curve in the PD TB relationship, where the PD amplitude peaks at 10K for all three channels in the tropics and increases slightly with latitude. Moreover, the 166GHz PD tends to increase in the case where a melting layer is beneath the frozen particles aloft in the atmosphere, while 89GHz PD is less sensitive than 166GHz to the melting layer. This property creates a unique PD feature for the identification of the melting layer and stratiform rain with passive sensors. Horizontally oriented non-spherical frozen particles are thought to produce the observed PD because of different ice scattering properties in the V and H polarizations. On the other hand, changes in the ice microphysical habitats or orientation due to turbulence mixing can also lead to a reduced PD in the deep convective cores. The current GMI polarimetric measurements themselves cannot fully disentangle the possible mechanisms.

The Role of Aerosols on Precipitation Processes: Cloud Resolving Model Simulations

NASA Technical Reports Server (NTRS)

Tao, Wei-Kuo; Li, X.; Matsui, T.

2012-01-01

Cloud microphysics is inevitably affected by the smoke particle (CCN, cloud condensation nuclei) size distributions below the clouds. Therefore, size distributions parameterized as spectral bin microphysics are needed to explicitly study the effects of atmospheric aerosol concentration on cloud development, rainfall production, and rainfall rates for convective clouds. Recently, a detailed spectral-bin microphysical scheme was implemented into the Goddard Cumulus Ensemble (GCE) model. The formulation for the explicit spectral bin microphysical processes is based on solving stochastic kinetic equations for the size distribution functions of water droplets (i.e., cloud droplets and raindrops), and several types of ice particles [i.e. pristine ice crystals (columnar and plate-like), snow (dendrites and aggregates), graupel and frozen drops/hail]. Each type is described by a special size distribution function containing many categories (i.e., 33 bins). Atmospheric aerosols are also described using number density size-distribution functions. The model is tested by studying the evolution of deep cloud systems in the west Pacific warm pool region, the sub-tropics (Florida) and midlatitudes using identical thermodynamic conditions but with different concentrations of CCN: a low "clean" concentration and a high "dirty" concentration. Results indicate that the low CCN concentration case produces rainfall at the surface sooner than the high CeN case but has less cloud water mass aloft. Because the spectral-bin model explicitly calculates and allows for the examination of both the mass and number concentration of species in each size category, a detailed analysis of the instantaneous size spectrum can be obtained for these cases. It is shown that since the low (CN case produces fewer droplets, larger sizes develop due to greater condensational and collection growth, leading to a broader size spectrum in comparison to the high CCN case. Sensitivity tests were performed to identify the impact of ice processes, radiation and large-scale influence on cloud-aerosol interactive processes, especially regarding surface rainfall amounts and characteristics (i.e., heavy or convective versus light or stratiform types). In addition, an inert tracer was included to follow the vertical redistribution of aerosols by cloud processes. We will also give a brief review from observational evidence on the role of aerosol on precipitation processes.

Direct observation of localized radial oxygen migration in functioning tantalum oxide memristors

DOE PAGES

Kumar, Suhas; Graves, Catherine E.; Strachan, John Paul; ...

2016-02-02

Oxygen migration in tantalum oxide, a promising next-generation storage material, is studied using in operando x-ray absorption spectromicroscopy and is used to microphysically describe accelerated evolution of conduction channel and device failure. Furthermore, the resulting ring-like patterns of oxygen concentration are modeled using thermophoretic forces and Fick diffusion, establishing the critical role of temperature-activated oxygen migration that has been under question lately.

Aerosol absorption measurements and retrievals in shadow2 campaign

NASA Astrophysics Data System (ADS)

Hu, Qiaoyun; Goloub, Philippe; Podvin, Thierry; Veselovskiy, Igor; Lopatin, Anton; Dubovik, Oleg; Torres, Benjamìn; Revilini, Laura; Crumeyrolle, Suzanne; Lapionak, Tatsiana; Deroo, Christine

2018-04-01

Dust, maritime and dust-smoke mixture events observed during SHADOW2 (SaHAran Dust Over West Africa) field campaign are selected and analyzed by using Raman and GARRLiC retrievals. The derived aerosol optical and microphysical properties will be shown. Dust absorption profile and on ground level are derived from GARRLiC retrievals and Aethalometer measurements, respectively. Our results provide a closer insight about dust absorbing properties.

Validation of Satellite Aerosol Retrievals from AERONET Ground-Based Measurements

NASA Technical Reports Server (NTRS)

Holben, Brent; Remer, Lorraine; Torres, Omar; Zhao, Tom; Smith, David E. (Technical Monitor)

2001-01-01

Accurate and comprehensive assessment of the parameters that control key atmospheric and biospheric processes including assessment of anthropogenic effects on climate change is a fundamental measurement objective of NASA's EOS program (King and Greenstone, 1999). Satellite assessment programs and associated global climate models require validation and additional parameterization with frequent reliable ground-based observations. A critical and highly uncertain element of the measurement program is characterization of tropospheric aerosols requiring basic observations of aerosols optical and microphysical properties. Unfortunately as yet we do not know the aerosol burden man is contributing to the atmosphere and thus we will have no definitive measure of change for the future. This lack of aerosol assessment is the impetus for some of the EOS measurement activities (Kaufman et al., 1997; King et al., 1999) and the formation of the AERONET program (Holben et al., 1998). The goals of the AERONET program are to develop long term monitoring at globally distributed sites providing critical data for multiannual trend changes in aerosol loading and optical properties with the specific goal of providing a data base for validation of satellite derived aerosol optical properties. The AERONET program has evolved into an international federated network of approximately 100 ground-based remote sensing monitoring stations to characterize the optical and microphysical properties of aerosols.

The Sectional Stratospheric Sulfate Aerosol module (S3A-v1) within the LMDZ general circulation model: description and evaluation against stratospheric aerosol observations

NASA Astrophysics Data System (ADS)

Kleinschmitt, Christoph; Boucher, Olivier; Bekki, Slimane; Lott, François; Platt, Ulrich

2017-09-01

Stratospheric aerosols play an important role in the climate system by affecting the Earth's radiative budget as well as atmospheric chemistry, and the capabilities to simulate them interactively within global models are continuously improving. It is important to represent accurately both aerosol microphysical and atmospheric dynamical processes because together they affect the size distribution and the residence time of the aerosol particles in the stratosphere. The newly developed LMDZ-S3A model presented in this article uses a sectional approach for sulfate particles in the stratosphere and includes the relevant microphysical processes. It allows full interaction between aerosol radiative effects (e.g. radiative heating) and atmospheric dynamics, including e.g. an internally generated quasi-biennial oscillation (QBO) in the stratosphere. Sulfur chemistry is semi-prescribed via climatological lifetimes. LMDZ-S3A reasonably reproduces aerosol observations in periods of low (background) and high (volcanic) stratospheric sulfate loading, but tends to overestimate the number of small particles and to underestimate the number of large particles. Thus, it may serve as a tool to study the climate impacts of volcanic eruptions, as well as the deliberate anthropogenic injection of aerosols into the stratosphere, which has been proposed as a method of geoengineering to abate global warming.

In situ observations of snow particle size distributions over a cold frontal rainband within an extratropical cyclone

NASA Astrophysics Data System (ADS)

Yang, Jiefan; Lei, Hengchi

2016-02-01

Cloud microphysical properties of a mixed phase cloud generated by a typical extratropical cyclone in the Tongliao area, Inner Mongolia on 3 May 2014, are analyzed primarily using in situ flight observation data. This study is mainly focused on ice crystal concentration, supercooled cloud water content, and vertical distributions of fit parameters of snow particle size distributions (PSDs). The results showed several discrepancies of microphysical properties obtained during two penetrations. During penetration within precipitating cloud, the maximum ice particle concentration, liquid water content, and ice water content were increased by a factor of 2-3 compared with their counterpart obtained during penetration of a nonprecipitating cloud. The heavy rimed and irregular ice crystals obtained by 2D imagery probe as well as vertical distributions of fitting parameters within precipitating cloud show that the ice particles grow during falling via riming and aggregation process, whereas the lightly rimed and pristine ice particles as well as fitting parameters within non-precipitating cloud indicate the domination of sublimation process. During the two cloud penetrations, the PSDs were generally better represented by gamma distributions than the exponential form in terms of the determining coefficient ( R 2). The correlations between parameters of exponential /gamma form within two penetrations showed no obvious differences compared with previous studies.

FINAL REPORT (DE-FG02-97ER62338): Single-column modeling, GCM parameterizations, and ARM data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Richard C. J. Somerville

2009-02-27

Our overall goal is the development of new and improved parameterizations of cloud-radiation effects and related processes, using ARM data at all three ARM sites, and the implementation and testing of these parameterizations in global models. To test recently developed prognostic parameterizations based on detailed cloud microphysics, we have compared SCM (single-column model) output with ARM observations at the SGP, NSA and TWP sites. We focus on the predicted cloud amounts and on a suite of radiative quantities strongly dependent on clouds, such as downwelling surface shortwave radiation. Our results demonstrate the superiority of parameterizations based on comprehensive treatments ofmore » cloud microphysics and cloud-radiative interactions. At the SGP and NSA sites, the SCM results simulate the ARM measurements well and are demonstrably more realistic than typical parameterizations found in conventional operational forecasting models. At the TWP site, the model performance depends strongly on details of the scheme, and the results of our diagnostic tests suggest ways to develop improved parameterizations better suited to simulating cloud-radiation interactions in the tropics generally. These advances have made it possible to take the next step and build on this progress, by incorporating our parameterization schemes in state-of-the-art three-dimensional atmospheric models, and diagnosing and evaluating the results using independent data. Because the improved cloud-radiation results have been obtained largely via implementing detailed and physically comprehensive cloud microphysics, we anticipate that improved predictions of hydrologic cycle components, and hence of precipitation, may also be achievable.« less

Collaborative Research: Quantifying the Uncertainties of Aerosol Indirect Effects and Impacts on Decadal-Scale Climate Variability in NCAR CAM5 and CESM1

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nenes, Athanasios

The goal of this proposed project is to assess the climatic importance and sensitivity of aerosol indirect effect (AIE) to cloud and aerosol processes and feedbacks, which include organic aerosol hygroscopicity, cloud condensation nuclei (CCN) activation kinetics, Giant CCN, cloud-scale entrainment, ice nucleation in mixed-phase and cirrus clouds, and treatment of subgrid variability of vertical velocity. A key objective was to link aerosol, cloud microphysics and dynamics feedbacks in CAM5 with a suite of internally consistent and integrated parameterizations that provide the appropriate degrees of freedom to capture the various aspects of the aerosol indirect effect. The proposal integrated newmore » parameterization elements into the cloud microphysics, moist turbulence and aerosol modules used by the NCAR Community Atmospheric Model version 5 (CAM5). The CAM5 model was then used to systematically quantify the uncertainties of aerosol indirect effects through a series of sensitivity tests with present-day and preindustrial aerosol emissions. New parameterization elements were developed as a result of these efforts, and new diagnostic tools & methodologies were also developed to quantify the impacts of aerosols on clouds and climate within fully coupled models. Observations were used to constrain key uncertainties in the aerosol-cloud links. Advanced sensitivity tools were developed and implements to probe the drivers of cloud microphysical variability with unprecedented temporal and spatial scale. All these results have been published in top and high impact journals (or are in the final stages of publication). This proposal has also supported a number of outstanding graduate students.« less

Extreme Rainfall from Hurricane Harvey (2017): Intercomparisons of WRF Simulations and Polarimetric Radar Fields

NASA Astrophysics Data System (ADS)

Yang, L.; Smith, J. A.; Liu, M.; Baeck, M. L.; Chaney, M. M.; Su, Y.

2017-12-01

Hurricane Harvey made landfall on 25 August 2017 and produced more than a meter of rain during a four-day period over eastern Texas, making it the wettest tropical cyclone on record in the United States. Extreme rainfall from Harvey was predominantly related to the dynamics and structure of outer rain bands. In this study, we provide details of the extreme rainfall produced by Hurricane Harvey. The principal research questions that motivate this study are: (1) what are the key microphysical properties of extreme rainfall from landfalling tropical cyclones and (2) what are the capabilities and deficiencies of existing bulk microphysics parameterizations from the physical models in capturing them. Our analyses are centered on intercomparisons of high-resolution simulations using the Weather Research and Forecasting (WRF) model and polarimetric radar fields from KHGX (Houston, Texas) WSR-88D. The WRF simulations accurately capture the track and intensity of Hurricane Harvey. Multi-rainband structure and its key evolution features are also well represented in the simulations. Two microphysics parameterizations (WSM6 and WDM6) are tested in this study. Radar reflectivity and differential reflectivity fields simulated by the WRF model are compared with polarimetric radar observations. An important feature for the extreme rainfall from Hurricane Harvey is the sharp boundary of spatial rainfall accumulation along the coast (with torrential rainfall distributed over Houston and its surrounding inland areas). We will examine the role of land-sea contrasts in dictating storm structure and evolution from both WRF simulations and polarimetric radar fields. Implications for improving hurricane rainfall forecasts and estimates will be provided.

Impact of different parameterization schemes on simulation of mesoscale convective system over south-east India

NASA Astrophysics Data System (ADS)

Madhulatha, A.; Rajeevan, M.

2018-02-01

Main objective of the present paper is to examine the role of various parameterization schemes in simulating the evolution of mesoscale convective system (MCS) occurred over south-east India. Using the Weather Research and Forecasting (WRF) model, numerical experiments are conducted by considering various planetary boundary layer, microphysics, and cumulus parameterization schemes. Performances of different schemes are evaluated by examining boundary layer, reflectivity, and precipitation features of MCS using ground-based and satellite observations. Among various physical parameterization schemes, Mellor-Yamada-Janjic (MYJ) boundary layer scheme is able to produce deep boundary layer height by simulating warm temperatures necessary for storm initiation; Thompson (THM) microphysics scheme is capable to simulate the reflectivity by reasonable distribution of different hydrometeors during various stages of system; Betts-Miller-Janjic (BMJ) cumulus scheme is able to capture the precipitation by proper representation of convective instability associated with MCS. Present analysis suggests that MYJ, a local turbulent kinetic energy boundary layer scheme, which accounts strong vertical mixing; THM, a six-class hybrid moment microphysics scheme, which considers number concentration along with mixing ratio of rain hydrometeors; and BMJ, a closure cumulus scheme, which adjusts thermodynamic profiles based on climatological profiles might have contributed for better performance of respective model simulations. Numerical simulation carried out using the above combination of schemes is able to capture storm initiation, propagation, surface variations, thermodynamic structure, and precipitation features reasonably well. This study clearly demonstrates that the simulation of MCS characteristics is highly sensitive to the choice of parameterization schemes.

Raman Spectroscopy and Microphysics of Single PSC Precursor Particles Suspended in a Quadrupole Trap

NASA Astrophysics Data System (ADS)

Sonnenfroh, D. M.; Hunter, A. J.; Rawlins, W. T.

2001-12-01

Polar stratospheric clouds (PSCs) consist primarily of solid nitric acid trihydrate (NAT) particles, which are thought to nucleate via HNO3 uptake on background sulfuric acid particles at temperatures below 195 K. The mechanism for this process is uncertain, and depends on whether the sulfuric acid particles are solid or liquid at these temperatures. Previous results from laboratory and field measurements are mixed; our previous single-particle laboratory experiments showed that binary H2SO4/H2O particles at stratospheric compositions are essentially metastable in the liquid phase when cooled to PSC temperatures. Currently, we are investigating the detailed microphysics of binary (H2SO4/H2O) and ternary (HNO3/H2SO4/H2O) single particles suspended in an electrodynamic levitator, using optical elastic scattering and Raman spectroscopy to observe changes in phase and composition. Single-particle Raman spectra for supercooled binary particles exhibit spectral distributions which alter markedly with decreasing temperature down to 190 K. The variations signify increasing dissociation of HSO4(-) to SO4(-2) with decreasing temperature, consistent with measurements for bulk solutions. Upon gradual warming of supercooled liquid binary particles, some of them freeze briefly in a narrow "window" of the phase diagram, near 210 K and 60 weight per cent H2SO4. We will discuss the Raman spectroscopy and microphysical behavior of the liquid and frozen particles for both the binary and ternary systems. This research was supported by the NASA Atmospheric Effects of Aviation Program.

Electric Fields, Cloud Microphysics, and Reflectivity in Anvils of Florida Thunderstorms

NASA Technical Reports Server (NTRS)

Dye, J. E.; Bateman, M. G.; Christian, H. J.; Grainger, C. A.; Hall, W. D.; Krider, E. P.; Lewis, S. A.; Mach, D. M.; Merceret, F. J.; Willett, J. C.;

Performance of multi-physics ensembles in convective precipitation events over northeastern Spain

NASA Astrophysics Data System (ADS)

García-Ortega, E.; Lorenzana, J.; Merino, A.; Fernández-González, S.; López, L.; Sánchez, J. L.

2017-07-01

Convective precipitation with hail greatly affects southwestern Europe, causing major economic losses. The local character of this meteorological phenomenon is a serious obstacle to forecasting. Therefore, the development of reliable short-term forecasts constitutes an essential challenge to minimizing and managing risks. However, deterministic outcomes are affected by different uncertainty sources, such as physics parameterizations. This study examines the performance of different combinations of physics schemes of the Weather Research and Forecasting model to describe the spatial distribution of precipitation in convective environments with hail falls. Two 30-member multi-physics ensembles, with two and three domains of maximum resolution 9 and 3km each, were designed using various combinations of cumulus, microphysics and radiation schemes. The experiment was evaluated for 10 convective precipitation days with hail over 2005-2010 in northeastern Spain. Different indexes were used to evaluate the ability of each ensemble member to capture the precipitation patterns, which were compared with observations of a rain-gauge network. A standardized metric was constructed to identify optimal performers. Results show interesting differences between the two ensembles. In two domain simulations, the selection of cumulus parameterizations was crucial, with the Betts-Miller-Janjic scheme the best. In contrast, the Kain-Fristch cumulus scheme gave the poorest results, suggesting that it should not be used in the study area. Nevertheless, in three domain simulations, the cumulus schemes used in coarser domains were not critical and the best results depended mainly on microphysics schemes. The best performance was shown by Morrison, New Thomson and Goddard microphysics.

Combining laboratory results, numerical modeling, and in situ measurements to investigate the relative contributions of homogeneous and heterogeneous nucleation to ice formation in the tropical tropopause layer

NASA Astrophysics Data System (ADS)

Jensen, E. J.; Karcher, B.; Ueyama, R.; Pfister, L.; Bui, T. V.; Diskin, G. S.; DiGangi, J. P.; Woods, S.; Lawson, P.; Froyd, K. D.; Murphy, D. M.

2017-12-01

Laboratory experiments over the past decade have advanced our understanding of the physical state and ice nucleation efficacy of aerosols with atmospherically-relevant compositions at low temperatures. We use these laboratory results along with measurements of upper-tropospheric aerosol composition to develop a parameterization if the ice nuclei number, and activity dependence on ice supersaturation and temperature in the cold tropical tropopause layer (TTL, 13-18 km). We show that leading candidates for aerosol types serving as effective ice nuclei are glassy organic-containing aerosols, crystalline ammonium sulfate, and mineral dust. We apply the low-temperature heterogeneous ice nucleation parameterization in a detailed model of TTL transport and cirrus formation. The model treats heterogeneous ice nucleation and homogeneous freezing of aqueous aerosols, deposition growth and sublimation of ice crystals, and sedimentation of ice crystals. The model is driven by meteorological fields with high-frequency waves superimposed, and simulated cirrus microphysical properties are statistically compared with recent measurements of TTL cirrus microphysical properties and ice supersaturation from recent high-altitude aircraft campaigns. We show that effective ice nuclei concentrations on the order of 50-100/L can dominate over homogeneous freezing production of TTL cirrus ice crystals. Glassy organic-containing aerosols or crystalline ammonium sulfate could conceivably provide more abundant sources of ice nuclei, but the simulations indicate that high concentrations of effective IN would prevent observed occurrence of large supersaturations and high ice concentrations. We will also show the impact of heterogeneous ice nuclei on TTL cirrus microphysical properties and occurrence frequencies.

Improving the Representation of Snow Crystal Properties within a Single-Moment Microphysics Scheme

NASA Technical Reports Server (NTRS)

Molthan, Andrew L.; Petersen, Walter A.; Case, Jonathan L.; Dembek, Scott R.

2010-01-01

The assumptions of a single-moment microphysics scheme (NASA Goddard) were evaluated using a variety of surface, aircraft and radar data sets. Fixed distribution intercepts and snow bulk densities fail to represent the vertical variability and diversity of crystal populations for this event. Temperature-based equations have merit, but they can be adversely affected by complex temperature profiles that are inverted or isothermal. Column-based approaches can mitigate complex profiles of temperature but are restricted by the ability of the model to represent cloud depth. Spheres are insufficient for use in CloudSat reflectivity comparisons due to Mie resonance, but reasonable for Rayleigh scattering applications. Microphysics schemes will benefit from a greater range of snow crystal characteristics to accommodate naturally occurring diversity.

Microphysical Modeling of Mineral Clouds in GJ1214 b and GJ436 b: Predicting Upper Limits on the Cloud-top Height

NASA Astrophysics Data System (ADS)

Ohno, Kazumasa; Okuzumi, Satoshi

2018-05-01

The ubiquity of clouds in the atmospheres of exoplanets, especially of super-Earths, is one of the outstanding issues for the transmission spectra survey. Understanding the formation process of clouds in super-Earths is necessary to interpret the observed spectra correctly. In this study, we investigate the vertical distributions of particle size and mass density of mineral clouds in super-Earths using a microphysical model that takes into account the vertical transport and growth of cloud particles in a self-consistent manner. We demonstrate that the vertical profiles of mineral clouds significantly vary with the concentration of cloud condensation nuclei and atmospheric metallicity. We find that the height of the cloud top increases with increasing metallicity as long as the metallicity is lower than the threshold. If the metallicity is larger than the threshold, the cloud-top height no longer increases appreciably with metallicity because coalescence yields larger particles of higher settling velocities. We apply our cloud model to GJ1214 b and GJ436 b, for which recent transmission observations suggest the presence of high-altitude opaque clouds. For GJ436 b, we show that KCl particles can ascend high enough to explain the observation. For GJ1214 b, by contrast, the height of KCl clouds predicted from our model is too low to explain its flat transmission spectrum. Clouds made of highly porous KCl particles could explain the observations if the atmosphere is highly metal-rich, and hence the particle microstructure might be a key to interpret the flat spectrum of GJ1214 b.

CLaMS-Ice: Large-scale cirrus cloud simulations in comparison with observations

NASA Astrophysics Data System (ADS)

Costa, Anja; Rolf, Christian; Grooß, Jens-Uwe; Spichtinger, Peter; Afchine, Armin; Spelten, Nicole; Dreiling, Volker; Zöger, Martin; Krämer, Martina

2016-04-01

Cirrus clouds are an element of uncertainty in the climate system and have received increasing attention since the last IPCC reports. The interactions of different freezing mechanisms, sedimentation rates, updraft velocity fluctuations and other factors that determine the formation and evolution of those clouds is still not fully understood. Thus, a reliable representation of cirrus clouds in models representing real atmospheric conditions is still a challenging task. At last year's EGU, Rolf et al. (2015) introduced the new large-scale microphysical cirrus cloud model CLaMS-Ice: based on trajectories calculated with CLaMS (McKenna et al., 2002 and Konopka et al. 2007), it simulates the development of cirrus clouds relying on the cirrus bulk model by Spichtinger and Gierens (2009). The qualitative agreement between CLaMS-Ice simulations and observations could be demonstrated at that time. Now we present a detailed quantitative comparison between standard ECMWF products, CLaMS-Ice simulations, and in-situ measurements obtained during the ML-Cirrus campaign 2014. We discuss the agreement of the parameters temperature (observational data: BAHAMAS), relative humidity (SHARC), cloud occurrence, cloud particle concentration, ice water content and cloud particle radii (all NIXE-CAPS). Due to the precise trajectories based on ECMWF wind and temperature fields, CLaMS-Ice represents the cirrus cloud vertical and horizontal coverage more accurately than the ECMWF ice water content (IWC) fields. We demonstrate how CLaMS-Ice can be used to evaluate different input settings (e.g. amount of ice nuclei, freezing thresholds, sedimentation settings) that lead to cirrus clouds with the microphysical properties observed during ML-Cirrus (2014).

Observations of CO above Venus cloud top near 4.53 μm

NASA Astrophysics Data System (ADS)

Marcq, E.; Encrenaz, T.; Widemann, T.; Bertaux, J. L.

2013-09-01

Venus' cloud top region exhibits a higher level of variability both in space and time than previously thought. The interplay between photochemistry, dynamics and cloud microphysics requires more observational constraints in order to be fully grasped. Recent observations of sulfur dioxide (SO2) variability [2, 8, 7, 9] have evidenced both short-term, longterm and latitudinal variability whose origin remains mysterious (volcanogenic emissions? dynamic variability?). A better knowledge of the variability of other minor species would be highly welcome in this context. Carbon monoxide (CO), whose pattern of sinks and sources is opposite to SO2, is a prime candidate.

Multisensor Observation and Simulation of Snowfall During the 2003 Wakasa Bay Field Experiment

NASA Technical Reports Server (NTRS)

Johnson, Benjamin T.; Petty, Grant W.; Skofronick-Jackson, Gail; Wang, James W.

2005-01-01

This research seeks to assess and improve the accuracy of microphysical assumptions used in satellite passive microwave radiative transfer models and retrieval algorithms by exploiting complementary observations from satellite radiometers, such as TRMM/AMSR-E/GPM, and coincident aircraft instruments, such as the next generation precipitation radar (PR-2). We focus in particular on aircraft data obtained during the Wakasa Bay field experiment, Japan 2003, pertaining to surface snowfall events. The observations of vertical profiles of reflectivity and Doppler-derived fall speeds are used in conjunction with the radiometric measurements to identify 1-D profiles of precipitation particle types, sizes, and concentrations that are consistent with the observations.

Impact of Aerosols on Convective Clouds and Precipitation

NASA Technical Reports Server (NTRS)

Tao, Wei-Kuo; Chen, Jen-Ping; Li, Zhanqing; Wang, Chien; Zhang, Chidong

2011-01-01

Aerosols are a critical factor in the atmospheric hydrological cycle and radiation budget. As a major reason for clouds to form and a significant attenuator of solar radiation, aerosols affect climate in several ways. Current research suggests that aerosol effects on clouds could further extend to precipitation, both through the formation of cloud particles and by exerting persistent radiative forcing on the climate system that disturbs dynamics. However, the various mechanisms behind these effects, in particular the ones connected to precipitation, are not yet well understood. The atmospheric and climate communities have long been working to gain a better grasp of these critical effects and hence to reduce the significant uncertainties in climate prediction resulting from such a lack of adequate knowledge. The central theme of this paper is to review past efforts and summarize our current understanding of the effect of aerosols on precipitation processes from theoretical analysis of microphysics, observational evidence, and a range of numerical model simulations. In addition, the discrepancy between results simulated by models, as well as that between simulations and observations will be presented. Specifically, this paper will address the following topics: (1) fundamental theories of aerosol effects on microphysics and precipitation processes, (2) observational evidence of the effect of aerosols on precipitation processes, (3) signatures of the aerosol impact on precipitation from large-scale analyses, (4) results from cloud-resolving model simulations, and (5) results from large-scale numerical model simulations. Finally, several future research directions on aerosol - precipitation interactions are suggested.

Shallow Cumulus Variability at the ARM Eastern North Atlantic Site

NASA Astrophysics Data System (ADS)

Lamer, K.; Kollias, P.; Ghate, V. P.; Luke, E. P.

2016-12-01

Cumulus clouds play a critical role in modulating the radiative and hydrological budget of the lower troposphere. These clouds, which are ubiquitous in regions of large-scale subsidence over the oceans, tend to be misrepresented in global climate models. Island-based, long-term, high-resolution ground-based observations can provide valuable insights on the factors controlling their macroscopic and microphysical properties and subsequenlty assist in model evaluation and guidance. Previous studies, limited to fair-weather cumuli over land, revealed that their fractional coverage is only weakly correlated with several parameters; the best ones being complex dynamical characteristics of the subcloud layer (vertical velocity skewness and eddy coherence). Other studies noted a relationship between cumuli depth and their propensity to precipitate. The current study will expand on such analysis by performing detail characterization of the full spectrum of shallow cumulus fields from non-precipitating to precipitating in the context of the large-scale forcing (i.e. thermodynamic structure and subsidence rates). Two years of ground-based remote sensing observations collected at the Atmospheric Radiation Measurement (ARM) Eastern North Atlantic (ENA) site are used to document macroscopic (cloud depth, cord length, cover), microphysical (liquid water path, cloud base rain rate) and dynamical (cloud base mass flux, eddy dissipation rate) cumuli properties. The observed variability in shallow cumulus is examined in relation to the variability of the large-scale environment as captured by the humidity profile, the magnitude of the low-level horizontal winds and near-surface aerosol conditions.

Impact of Aerosols on Convective Clouds and Precipitation

NASA Technical Reports Server (NTRS)

Tao, Wei-Kuo; Chen, Jen-Ping; Li, Zhanqing; Wang, Chien; Zhang, Chidong

2012-01-01

Aerosols are a critical factor in the atmospheric hydrological cycle and radiation budget. As a major agent for clouds to form and a significant attenuator of solar radiation, aerosols affect climate in several ways. Current research suggests that aerosol effects on clouds could further extend to precipitation, both through the formation of cloud particles and by exerting persistent radiative forcing on the climate system that disturbs dynamics. However, the various mechanisms behind these effects, in particular the ones connected to precipitation, are not yet well understood. The atmospheric and climate communities have long been working to gain a better grasp of these critical effects and hence to reduce the significant uncertainties in climate prediction resulting from such a lack of adequate knowledge. Here we review past efforts and summarize our current understanding of the effect of aerosols on convective precipitation processes from theoretical analysis of microphysics, observational evidence, and a range of numerical model simulations. In addition, the discrepancy between results simulated by models, as well as that between simulations and observations, are presented. Specifically, this paper addresses the following topics: (1) fundamental theories of aerosol effects on microphysics and precipitation processes, (2) observational evidence of the effect of aerosols on precipitation processes, (3) signatures of the aerosol impact on precipitation from largescale analyses, (4) results from cloud-resolving model simulations, and (5) results from large-scale numerical model simulations. Finally, several future research directions for gaining a better understanding of aerosol--cloud-precipitation interactions are suggested.

Changes in Stratiform Clouds of Mesoscale Convective Complex Introduced by Dust Aerosols

NASA Technical Reports Server (NTRS)

Lin, B.; Min, Q.-L.; Li, R.

2010-01-01

Aerosols influence the earth s climate through direct, indirect, and semi-direct effects. There are large uncertainties in quantifying these effects due to limited measurements and observations of aerosol-cloud-precipitation interactions. As a major terrestrial source of atmospheric aerosols, dusts may serve as a significant climate forcing for the changing climate because of its effect on solar and thermal radiation as well as on clouds and precipitation processes. Latest satellites measurements enable us to determine dust aerosol loadings and cloud distributions and can potentially be used to reduce the uncertainties in the estimations of aerosol effects on climate. This study uses sensors on various satellites to investigate the impact of mineral dust on cloud microphysical and precipitation processes in mesoscale convective complex (MCC). A trans-Atlantic dust outbreak of Saharan origin occurring in early March 2004 is considered. For the observed MCCs under a given convective strength, small hydrometeors were found more prevalent in the dusty stratiform regions than in those regions that were dust free. Evidence of abundant cloud ice particles in the dust regions, particularly at altitudes where heterogeneous nucleation of mineral dust prevails, further supports the observed changes of clouds and precipitation. The consequences of the microphysical effects of the dust aerosols were to shift the size spectrum of precipitation-sized hydrometeors from heavy precipitation to light precipitation and ultimately to suppress precipitation and increase the lifecycle of cloud systems, especially over stratiform areas.

Revisiting Intel Xeon Phi optimization of Thompson cloud microphysics scheme in Weather Research and Forecasting (WRF) model

NASA Astrophysics Data System (ADS)

Mielikainen, Jarno; Huang, Bormin; Huang, Allen

2015-10-01

The Thompson cloud microphysics scheme is a sophisticated cloud microphysics scheme in the Weather Research and Forecasting (WRF) model. The scheme is very suitable for massively parallel computation as there are no interactions among horizontal grid points. Compared to the earlier microphysics schemes, the Thompson scheme incorporates a large number of improvements. Thus, we have optimized the speed of this important part of WRF. Intel Many Integrated Core (MIC) ushers in a new era of supercomputing speed, performance, and compatibility. It allows the developers to run code at trillions of calculations per second using the familiar programming model. In this paper, we present our results of optimizing the Thompson microphysics scheme on Intel Many Integrated Core Architecture (MIC) hardware. The Intel Xeon Phi coprocessor is the first product based on Intel MIC architecture, and it consists of up to 61 cores connected by a high performance on-die bidirectional interconnect. The coprocessor supports all important Intel development tools. Thus, the development environment is familiar one to a vast number of CPU developers. Although, getting a maximum performance out of MICs will require using some novel optimization techniques. New optimizations for an updated Thompson scheme are discusses in this paper. The optimizations improved the performance of the original Thompson code on Xeon Phi 7120P by a factor of 1.8x. Furthermore, the same optimizations improved the performance of the Thompson on a dual socket configuration of eight core Intel Xeon E5-2670 CPUs by a factor of 1.8x compared to the original Thompson code.

Aerosol indirect effect from turbulence-induced broadening of cloud-droplet size distributions

PubMed Central

Chandrakar, Kamal Kant; Cantrell, Will; Chang, Kelken; Ciochetto, David; Niedermeier, Dennis; Ovchinnikov, Mikhail; Shaw, Raymond A.; Yang, Fan

2016-01-01

The influence of aerosol concentration on the cloud-droplet size distribution is investigated in a laboratory chamber that enables turbulent cloud formation through moist convection. The experiments allow steady-state microphysics to be achieved, with aerosol input balanced by cloud-droplet growth and fallout. As aerosol concentration is increased, the cloud-droplet mean diameter decreases, as expected, but the width of the size distribution also decreases sharply. The aerosol input allows for cloud generation in the limiting regimes of fast microphysics (τc<τt) for high aerosol concentration, and slow microphysics (τc>τt) for low aerosol concentration; here, τc is the phase-relaxation time and τt is the turbulence-correlation time. The increase in the width of the droplet size distribution for the low aerosol limit is consistent with larger variability of supersaturation due to the slow microphysical response. A stochastic differential equation for supersaturation predicts that the standard deviation of the squared droplet radius should increase linearly with a system time scale defined as τs−1=τc−1+τt−1, and the measurements are in excellent agreement with this finding. The result underscores the importance of droplet size dispersion for aerosol indirect effects: increasing aerosol concentration changes the albedo and suppresses precipitation formation not only through reduction of the mean droplet diameter but also by narrowing of the droplet size distribution due to reduced supersaturation fluctuations. Supersaturation fluctuations in the low aerosol/slow microphysics limit are likely of leading importance for precipitation formation. PMID:27911802

Aerosol indirect effect from turbulence-induced broadening of cloud-droplet size distributions

DOE PAGES

Chandrakar, Kamal Kant; Cantrell, Will; Chang, Kelken; ...

2016-11-28

Here, the influence of aerosol concentration on cloud droplet size distribution is investigated in a laboratory chamber that enables turbulent cloud formation through moist convection. The experiments allow steady-state microphysics to be achieved, with aerosol input balanced by cloud droplet growth and fallout. As aerosol concentration is increased the cloud droplet mean diameter decreases as expected, but the width of the size distribution also decreases sharply. The aerosol input allows for cloud generation in the limiting regimes of fast microphysics (τ c < τ t) for high aerosol concentration, and slow microphysics (τ c > τ t) for low aerosolmore » concentration; here, τ c is the phase relaxation time and τ t is the turbulence correlation time. The increase in the width of the droplet size distribution for the low aerosol limit is consistent with larger variability of supersaturation due to the slow microphysical response. A stochastic differential equation for supersaturation predicts that the standard deviation of the squared droplet radius should increase linearly with a system time scale defined as τ s -1 =τ c -1 + τ t -1, and the measurements are in excellent agreement with this finding. This finding underscores the importance of droplet size dispersion for the aerosol indirect effect: increasing aerosol concentration not only suppresses precipitation formation through reduction of the mean droplet diameter, but perhaps more importantly, through narrowing of the droplet size distribution due to reduced supersaturation fluctuations. Supersaturation fluctuations in the low aerosol / slow microphysics limit are likely of leading importance for precipitation formation.« less

Aerosol indirect effect from turbulence-induced broadening of cloud-droplet size distributions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chandrakar, Kamal Kant; Cantrell, Will; Chang, Kelken

Here, the influence of aerosol concentration on cloud droplet size distribution is investigated in a laboratory chamber that enables turbulent cloud formation through moist convection. The experiments allow steady-state microphysics to be achieved, with aerosol input balanced by cloud droplet growth and fallout. As aerosol concentration is increased the cloud droplet mean diameter decreases as expected, but the width of the size distribution also decreases sharply. The aerosol input allows for cloud generation in the limiting regimes of fast microphysics (τ c < τ t) for high aerosol concentration, and slow microphysics (τ c > τ t) for low aerosolmore » concentration; here, τ c is the phase relaxation time and τ t is the turbulence correlation time. The increase in the width of the droplet size distribution for the low aerosol limit is consistent with larger variability of supersaturation due to the slow microphysical response. A stochastic differential equation for supersaturation predicts that the standard deviation of the squared droplet radius should increase linearly with a system time scale defined as τ s -1 =τ c -1 + τ t -1, and the measurements are in excellent agreement with this finding. This finding underscores the importance of droplet size dispersion for the aerosol indirect effect: increasing aerosol concentration not only suppresses precipitation formation through reduction of the mean droplet diameter, but perhaps more importantly, through narrowing of the droplet size distribution due to reduced supersaturation fluctuations. Supersaturation fluctuations in the low aerosol / slow microphysics limit are likely of leading importance for precipitation formation.« less

Aerosol indirect effect from turbulence-induced broadening of cloud-droplet size distributions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chandrakar, Kamal Kant; Cantrell, Will; Chang, Kelken

2016-11-28

The influence of aerosol concentration on cloud droplet size distribution is investigated in a laboratory chamber that enables turbulent cloud formation through moist convection. The experiments allow steady-state microphysics to be achieved, with aerosol input balanced by cloud droplet growth and fallout. As aerosol concentration is increased the cloud droplet mean diameter decreases as expected, but the width of the size distribution also decreases sharply. The aerosol input allows for cloud generation in the limiting regimes of fast microphysics (τ c < τ t) for high aerosol concentration, and slow microphysics (τ c > τ t) for low aerosol concentration;more » here, τ c is the phase relaxation time and τ t is the turbulence correlation time. The increase in the width of the droplet size distribution for the low aerosol limit is consistent with larger variability of supersaturation due to the slow microphysical response. A stochastic differential equation for supersaturation predicts that the standard deviation of the squared droplet radius should increase linearly with a system time scale defined as τ s -1 =τ c -1 + τ t -1, and the measurements are in excellent agreement with this finding. This finding underscores the importance of droplet size dispersion for the aerosol indirect effect: increasing aerosol concentration not only suppresses precipitation formation through reduction of the mean droplet diameter, but perhaps more importantly, through narrowing of the droplet size distribution due to reduced supersaturation fluctuations. Supersaturation fluctuations in the low aerosol / slow microphysics limit are likely of leading importance for precipitation formation.« less

Cloud-resolving model intercomparison of an MC3E squall line case: Part I-Convective updrafts: CRM Intercomparison of a Squall Line

DOE PAGES

Fan, Jiwen; Han, Bin; Varble, Adam; ...

2017-09-06

An intercomparison study of a midlatitude mesoscale squall line is performed using the Weather Research and Forecasting (WRF) model at 1 km horizontal grid spacing with eight different cloud microphysics schemes to investigate processes that contribute to the large variability in simulated cloud and precipitation properties. All simulations tend to produce a wider area of high radar reflectivity (Z e > 45 dBZ) than observed but a much narrower stratiform area. Furthermore, the magnitude of the virtual potential temperature drop associated with the gust front passage is similar in simulations and observations, while the pressure rise and peak wind speedmore » are smaller than observed, possibly suggesting that simulated cold pools are shallower than observed. Most of the microphysics schemes overestimate vertical velocity and Z e in convective updrafts as compared with observational retrievals. Simulated precipitation rates and updraft velocities have significant variability across the eight schemes, even in this strongly dynamically driven system. Differences in simulated updraft velocity correlate well with differences in simulated buoyancy and low-level vertical perturbation pressure gradient, which appears related to cold pool intensity that is controlled by the evaporation rate. Simulations with stronger updrafts have a more optimal convective state, with stronger cold pools, ambient low-level vertical wind shear, and rear-inflow jets. We found that updraft velocity variability between schemes is mainly controlled by differences in simulated ice-related processes, which impact the overall latent heating rate, whereas surface rainfall variability increases in no-ice simulations mainly because of scheme differences in collision-coalescence parameterizations.« less

Comparing Aircraft Observations of Snowfall to Forecasts Using Single or Two Moment Bulk Water Microphysics Schemes

NASA Technical Reports Server (NTRS)

Molthan, Andrew L.

2010-01-01

High resolution weather forecast models with explicit prediction of hydrometeor type, size distribution, and fall speed may be useful in the development of precipitation retrievals, by providing representative characteristics of frozen hydrometeors. Several single or double-moment microphysics schemes are currently available within the Weather Research and Forecasting (WRF) model, allowing for the prediction of up to three ice species. Each scheme incorporates different assumptions regarding the characteristics of their ice classes, particularly in terms of size distribution, density, and fall speed. In addition to the prediction of hydrometeor content, these schemes must accurately represent the vertical profile of water vapor to account for possible attenuation, along with the size distribution, density, and shape characteristics of ice crystals that are relevant to microwave scattering. An evaluation of a particular scheme requires the availability of field campaign measurements. The Canadian CloudSat/CALIPSO Validation Project (C3VP) obtained measurements of ice crystal shapes, size distributions, fall speeds, and precipitation during several intensive observation periods. In this study, C3VP observations obtained during the 22 January 2007 synoptic-scale snowfall event are compared against WRF model output, based upon forecasts using four single-moment and two double-moment schemes available as of version 3.1. Schemes are compared against aircraft observations by examining differences in size distribution, density, and content. In addition to direct measurements from aircraft probes, simulated precipitation can also be converted to equivalent, remotely sensed characteristics through the use of the NASA Goddard Satellite Data Simulator Unit. Outputs from high resolution forecasts are compared against radar and satellite observations emphasizing differences in assumed crystal shape and size distribution characteristics.

Retrieve Optically Thick Ice Cloud Microphysical Properties by Using Airborne Dual-Wavelength Radar Measurements

NASA Technical Reports Server (NTRS)

Wang, Zhien; Heymsfield, Gerald M.; Li, Lihua; Heymsfield, Andrew J.

2005-01-01

An algorithm to retrieve optically thick ice cloud microphysical property profiles is developed by using the GSFC 9.6 GHz ER-2 Doppler Radar (EDOP) and the 94 GHz Cloud Radar System (CRS) measurements aboard the high-altitude ER-2 aircraft. In situ size distribution and total water content data from the CRYSTAL-FACE field campaign are used for the algorithm development. To reduce uncertainty in calculated radar reflectivity factors (Ze) at these wavelengths, coincident radar measurements and size distribution data are used to guide the selection of mass-length relationships and to deal with the density and non-spherical effects of ice crystals on the Ze calculations. The algorithm is able to retrieve microphysical property profiles of optically thick ice clouds, such as, deep convective and anvil clouds, which are very challenging for single frequency radar and lidar. Examples of retrieved microphysical properties for a deep convective clouds are presented, which show that EDOP and CRS measurements provide rich information to study cloud structure and evolution. Good agreement between IWPs derived from an independent submillimeter-wave radiometer, CoSSIR, and dual-wavelength radar measurements indicates accuracy of the IWC retrieved from the two-frequency radar algorithm.

Study of cloud properties using airborne and satellite measurements

NASA Astrophysics Data System (ADS)

Boscornea, Andreea; Stefan, Sabina; Vajaiac, Sorin Nicolae

2014-08-01

The present study investigates cloud microphysics properties using aircraft and satellite measurements. Cloud properties were drawn from data acquired both from in situ measurements with state of the art airborne instrumentation and from satellite products of the MODIS06 System. The used aircraft was ATMOSLAB - Airborne Laboratory for Environmental Atmospheric Research, property of the National Institute for Aerospace Research "Elie Carafoli" (INCAS), Bucharest, Romania, which is specially equipped for this kind of research. The main tool of the airborne laboratory is a Cloud, Aerosol and Precipitation Spectrometer - CAPS (30 bins, 0.51- 50 μm). The data was recorded during two flights during the winter 2013-2014, over a flat region in the south-eastern part of Romania (between Bucharest and Constanta). The analysis of cloud particle size variations and cloud liquid water content provided by CAPS can explain cloud processes, and can also indicate the extent of aerosols effects on clouds. The results, such as cloud coverage and/or cloud types, microphysical parameters of aerosols on the one side and the cloud microphysics parameters obtained from aircraft flights on the other side, was used to illustrate the importance of microphysics cloud properties for including the radiative effects of clouds in the regional climate models.

Radar Sounder

DTIC Science & Technology

1988-09-01

S’ardard Form 298 Rev 2-89) • " Del " 1 , -iNS, 19 , q f .If - ACKNOWLEDGMENTS The authors would like to acknowledge the support of numerous...plates, etc.); estimation of rain rate and the observation of the horizontal and vertical structure of rain. The data from the radar sounder will be...crytal habit. The microphysical properties and vertical structure of the clouds are needed for applications of interest to the Air Force such as

Accretion in active galactic nuclei and disk-jet coupling

NASA Astrophysics Data System (ADS)

Czerny, B.; You, B.

2016-02-01

We review the current state of understanding how accretion onto a black hole proceeds and what the key elements needed to form relativistic jets are. Theoretical progress is severely undermined by the lack of thorough understanding of the microphysics involved in accretion discs and in the formation of jets, particularly in the presence of strong magnetic fields. Therefore, all proposed solutions are still models that need to be validated by observational constraints.

Proton pinhole imaging on the National Ignition Facility

NASA Astrophysics Data System (ADS)

Zylstra, A. B.; Park, H.-S.; Ross, J. S.; Fiuza, F.; Frenje, J. A.; Higginson, D. P.; Huntington, C.; Li, C. K.; Petrasso, R. D.; Pollock, B.; Remington, B.; Rinderknecht, H. G.; Ryutov, D.; Séguin, F. H.; Turnbull, D.; Wilks, S. C.

2016-11-01

Pinhole imaging of large (mm scale) carbon-deuterium (CD) plasmas by proton self-emission has been used for the first time to study the microphysics of shock formation, which is of astrophysical relevance. The 3 MeV deuterium-deuterium (DD) fusion proton self-emission from these plasmas is imaged using a novel pinhole imaging system, with up to five different 1 mm diameter pinholes positioned 25 cm from target-chamber center. CR39 is used as the detector medium, positioned at 100 cm distance from the pinhole for a magnification of 4 ×. A Wiener deconvolution algorithm is numerically demonstrated and used to interpret the images. When the spatial morphology is known, this algorithm accurately reproduces the size of features larger than about half the pinhole diameter. For these astrophysical plasma experiments on the National Ignition Facility, this provides a strong constraint on simulation modeling of the experiment.

Proton pinhole imaging on the National Ignition Facility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zylstra, Alex B.; Park, H. -S.; Ross, J. S.

Here, pinhole imaging of large (mm scale) carbon-deuterium (CD) plasmas by proton self-emission has been used for the first time to study the microphysics of shock formation, which is of astrophysical relevance. The 3 MeV deuterium-deuterium (DD) fusion proton self-emission from these plasmas is imaged using a novel pinhole imaging system, with up to five different 1 mm diameter pinholes positioned 25 cm from target-chamber center. CR39 is used as the detector medium, positioned at 100 cm distance from the pinhole for a magnification of 4×. A Wiener deconvolution algorithm is numerically demonstrated and used to interpret the images. Whenmore » the spatial morphology is known, this algorithm accurately reproduces the size of features larger than about half the pinhole diameter. For these astrophysical plasma experiments on the National Ignition Facility, this provides a strong constraint on simulation modeling of the experiment.« less

Proton pinhole imaging on the National Ignition Facility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zylstra, A. B., E-mail: zylstra@lanl.gov; Park, H.-S.; Ross, J. S.

Pinhole imaging of large (mm scale) carbon-deuterium (CD) plasmas by proton self-emission has been used for the first time to study the microphysics of shock formation, which is of astrophysical relevance. The 3 MeV deuterium-deuterium (DD) fusion proton self-emission from these plasmas is imaged using a novel pinhole imaging system, with up to five different 1 mm diameter pinholes positioned 25 cm from target-chamber center. CR39 is used as the detector medium, positioned at 100 cm distance from the pinhole for a magnification of 4 ×. A Wiener deconvolution algorithm is numerically demonstrated and used to interpret the images. Whenmore » the spatial morphology is known, this algorithm accurately reproduces the size of features larger than about half the pinhole diameter. For these astrophysical plasma experiments on the National Ignition Facility, this provides a strong constraint on simulation modeling of the experiment.« less

Detection of mesoscale convective complexes using multispectral RGB technique of Himawari-8 (Case Study: Jakarta, 20 February 2017)

NASA Astrophysics Data System (ADS)

Fatkhuroyan; Wati, T.

2018-05-01

Mesoscale Convective Complexes (MCC) is a well-organized convective cloud that has big size and long lifetime. The aim of the study is to detect and to monitor the development of MCC around Jakarta on 20th February 2017 using satellite Himawari-8. This study uses the analyzing method of the infrared channel and multispectral imagery RGB Technique to monitor the development of radiative, morphology and cloud position which describe the cloud top microphysics, structure and movement of the MCC. On 20th February 2017, the result from Himawari-8 shows that there are many dense-clouds with small ice particle and cloud top temperature could be < -50°C which can be seen as red and yellow dot colour by RGB Technique. The MCC caused a severe storm at Jakarta and its surrounding area.

Proton pinhole imaging on the National Ignition Facility

DOE PAGES

Zylstra, Alex B.; Park, H. -S.; Ross, J. S.; ...

2016-07-29

Here, pinhole imaging of large (mm scale) carbon-deuterium (CD) plasmas by proton self-emission has been used for the first time to study the microphysics of shock formation, which is of astrophysical relevance. The 3 MeV deuterium-deuterium (DD) fusion proton self-emission from these plasmas is imaged using a novel pinhole imaging system, with up to five different 1 mm diameter pinholes positioned 25 cm from target-chamber center. CR39 is used as the detector medium, positioned at 100 cm distance from the pinhole for a magnification of 4×. A Wiener deconvolution algorithm is numerically demonstrated and used to interpret the images. Whenmore » the spatial morphology is known, this algorithm accurately reproduces the size of features larger than about half the pinhole diameter. For these astrophysical plasma experiments on the National Ignition Facility, this provides a strong constraint on simulation modeling of the experiment.« less

Proton pinhole imaging on the National Ignition Facility.

PubMed

Zylstra, A B; Park, H-S; Ross, J S; Fiuza, F; Frenje, J A; Higginson, D P; Huntington, C; Li, C K; Petrasso, R D; Pollock, B; Remington, B; Rinderknecht, H G; Ryutov, D; Séguin, F H; Turnbull, D; Wilks, S C

2016-11-01

Pinhole imaging of large (mm scale) carbon-deuterium (CD) plasmas by proton self-emission has been used for the first time to study the microphysics of shock formation, which is of astrophysical relevance. The 3 MeV deuterium-deuterium (DD) fusion proton self-emission from these plasmas is imaged using a novel pinhole imaging system, with up to five different 1 mm diameter pinholes positioned 25 cm from target-chamber center. CR39 is used as the detector medium, positioned at 100 cm distance from the pinhole for a magnification of 4 ×. A Wiener deconvolution algorithm is numerically demonstrated and used to interpret the images. When the spatial morphology is known, this algorithm accurately reproduces the size of features larger than about half the pinhole diameter. For these astrophysical plasma experiments on the National Ignition Facility, this provides a strong constraint on simulation modeling of the experiment.

Individual aerosol particles in ambient and updraft conditions below convective cloud bases in the Oman mountain region

NASA Astrophysics Data System (ADS)

Semeniuk, T. A.; Bruintjes, R. T.; Salazar, V.; Breed, D. W.; Jensen, T. L.; Buseck, P. R.

2014-03-01

An airborne study of cloud microphysics provided an opportunity to collect aerosol particles in ambient and updraft conditions of natural convection systems for transmission electron microscopy (TEM). Particles were collected simultaneously on lacey carbon and calcium-coated carbon (Ca-C) TEM grids, providing information on particle morphology and chemistry and a unique record of the particle's physical state on impact. In total, 22 particle categories were identified, including single, coated, aggregate, and droplet types. The fine fraction comprised up to 90% mixed cation sulfate (MCS) droplets, while the coarse fraction comprised up to 80% mineral-containing aggregates. Insoluble (dry), partially soluble (wet), and fully soluble particles (droplets) were recorded on Ca-C grids. Dry particles were typically silicate grains; wet particles were mineral aggregates with chloride, nitrate, or sulfate components; and droplets were mainly aqueous NaCl and MCS. Higher numbers of droplets were present in updrafts (80% relative humidity (RH)) compared with ambient conditions (60% RH), and almost all particles activated at cloud base (100% RH). Greatest changes in size and shape were observed in NaCl-containing aggregates (>0.3 µm diameter) along updraft trajectories. Their abundance was associated with high numbers of cloud condensation nuclei (CCN) and cloud droplets, as well as large droplet sizes in updrafts. Thus, compositional dependence was observed in activation behavior recorded for coarse and fine fractions. Soluble salts from local pollution and natural sources clearly affected aerosol-cloud interactions, enhancing the spectrum of particles forming CCN and by forming giant CCN from aggregates, thus, making cloud seeding with hygroscopic flares ineffective in this region.

Formation of highly porous aerosol particles by atmospheric freeze-drying in ice clouds

PubMed Central

Adler, Gabriela; Koop, Thomas; Haspel, Carynelisa; Taraniuk, Ilya; Moise, Tamar; Koren, Ilan; Heiblum, Reuven H.; Rudich, Yinon

2013-01-01

The cycling of atmospheric aerosols through clouds can change their chemical and physical properties and thus modify how aerosols affect cloud microphysics and, subsequently, precipitation and climate. Current knowledge about aerosol processing by clouds is rather limited to chemical reactions within water droplets in warm low-altitude clouds. However, in cold high-altitude cirrus clouds and anvils of high convective clouds in the tropics and midlatitudes, humidified aerosols freeze to form ice, which upon exposure to subsaturation conditions with respect to ice can sublimate, leaving behind residual modified aerosols. This freeze-drying process can occur in various types of clouds. Here we simulate an atmospheric freeze-drying cycle of aerosols in laboratory experiments using proxies for atmospheric aerosols. We find that aerosols that contain organic material that undergo such a process can form highly porous aerosol particles with a larger diameter and a lower density than the initial homogeneous aerosol. We attribute this morphology change to phase separation upon freezing followed by a glass transition of the organic material that can preserve a porous structure after ice sublimation. A porous structure may explain the previously observed enhancement in ice nucleation efficiency of glassy organic particles. We find that highly porous aerosol particles scatter solar light less efficiently than nonporous aerosol particles. Using a combination of satellite and radiosonde data, we show that highly porous aerosol formation can readily occur in highly convective clouds, which are widespread in the tropics and midlatitudes. These observations may have implications for subsequent cloud formation cycles and aerosol albedo near cloud edges. PMID:24297908

Formation of highly porous aerosol particles by atmospheric freeze-drying in ice clouds.

PubMed

Adler, Gabriela; Koop, Thomas; Haspel, Carynelisa; Taraniuk, Ilya; Moise, Tamar; Koren, Ilan; Heiblum, Reuven H; Rudich, Yinon

2013-12-17

The cycling of atmospheric aerosols through clouds can change their chemical and physical properties and thus modify how aerosols affect cloud microphysics and, subsequently, precipitation and climate. Current knowledge about aerosol processing by clouds is rather limited to chemical reactions within water droplets in warm low-altitude clouds. However, in cold high-altitude cirrus clouds and anvils of high convective clouds in the tropics and midlatitudes, humidified aerosols freeze to form ice, which upon exposure to subsaturation conditions with respect to ice can sublimate, leaving behind residual modified aerosols. This freeze-drying process can occur in various types of clouds. Here we simulate an atmospheric freeze-drying cycle of aerosols in laboratory experiments using proxies for atmospheric aerosols. We find that aerosols that contain organic material that undergo such a process can form highly porous aerosol particles with a larger diameter and a lower density than the initial homogeneous aerosol. We attribute this morphology change to phase separation upon freezing followed by a glass transition of the organic material that can preserve a porous structure after ice sublimation. A porous structure may explain the previously observed enhancement in ice nucleation efficiency of glassy organic particles. We find that highly porous aerosol particles scatter solar light less efficiently than nonporous aerosol particles. Using a combination of satellite and radiosonde data, we show that highly porous aerosol formation can readily occur in highly convective clouds, which are widespread in the tropics and midlatitudes. These observations may have implications for subsequent cloud formation cycles and aerosol albedo near cloud edges.

Effects of Convective Aggregation on Radiative Cooling and Precipitation in a CRM

NASA Astrophysics Data System (ADS)

Naegele, A. C.; Randall, D. A.

2017-12-01

In the global energy budget, the atmospheric radiative cooling (ARC) is approximately balanced by latent heating, but on regional scales, the ARC and precipitation rates are inversely related. We use a cloud-resolving model to explore how the relationship between precipitation and the ARC is affected by convective aggregation, in which the convective activity is confined to a small portion of the domain that is surrounded by a much larger region of dry, subsiding air. Sensitivity tests show that the precipitation rate and ARC are highly sensitive to both SST and microphysics; a higher SST and 1-moment microphysics both act to increase the domain-averaged ARC and precipitation rates. In all simulations, both the domain-averaged ARC and precipitation rates increased due to convective aggregation, resulting in a positive temporal correlation. Furthermore, the radiative effect of clouds in these simulations is to decrease the ARC. This finding is consistent with our observational results of the cloud effect on the ARC, and has implications for convective aggregation and the geographic extent in which it can occur.

Challenges for Cloud Modeling in the Context of Aerosol–Cloud–Precipitation Interactions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lebo, Zachary J.; Shipway, Ben J.; Fan, Jiwen

The International Cloud Modeling Workshop (CMW) has been a longstanding tradition in the cloud microphysics modeling community and is typically held the week prior to the International Conference on Clouds and Precipitation (ICCP). For the Ninth CMW, more than 40 participants from 10 countries convened at the Met Office in Exeter, United Kingdom. The workshop included 4 detailed case studies (described in more detail below) rooted in recent field campaigns. The overarching objective of these cases was to utilize new observations to better understand inter-model differences and model deficiencies, explore new modeling techniques, and gain physical insight into the behaviormore » of clouds. As was the case at the Eighth CMW, there was a general theme of understanding the role of aerosol impacts in the context of cloud-precipitation interactions. However, an additional objective was the focal point of several cases at the most recent workshop: microphysical-dynamical interactions. Many of the cases focused less on idealized small-domain simulations (as was the general focus of previous workshops) and more on large-scale nested configurations examining effects at various scales.« less

New approaches to quantifying aerosol influence on the cloud radiative effect

DOE PAGES

Feingold, Graham; McComiskey, Allison; Yamaguchi, Takanobu; ...

2016-02-01

The topic of cloud radiative forcing associated with the atmospheric aerosol has been the focus of intense scrutiny for decades. The enormity of the problem is reflected in the need to understand aspects such as aerosol composition, optical properties, cloud condensation, and ice nucleation potential, along with the global distribution of these properties, controlled by emissions, transport, transformation, and sinks. Equally daunting is that clouds themselves are complex, turbulent, microphysical entities and, by their very nature, ephemeral and hard to predict. Atmospheric general circulation models represent aerosol–cloud interactions at ever-increasing levels of detail, but these models lack the resolution tomore » represent clouds and aerosol–cloud interactions adequately. There is a dearth of observational constraints on aerosol–cloud interactions. In this paper, we develop a conceptual approach to systematically constrain the aerosol–cloud radiative effect in shallow clouds through a combination of routine process modeling and satellite and surface-based shortwave radiation measurements. Finally, we heed the call to merge Darwinian and Newtonian strategies by balancing microphysical detail with scaling and emergent properties of the aerosol–cloud radiation system.« less

Global Multispectral Cloud Retrievals from MODIS

NASA Technical Reports Server (NTRS)

King, Michael D.; Platnick, Steven; Ackerman, Steven A.; Menzel, W. Paul; Riedi, Jerome C.; Baum, Bryan A.

2003-01-01

The Moderate Resolution Imaging Spectroradiometer (MODIS) was developed by NASA and launched onboard the Terra spacecraft on December 18,1999 and Aqua spacecraft on May 4,2002. It achieved its final orbit and began Earth observations on February 24, 2000 for Terra and June 24, 2002 for Aqua. A comprehensive set of remote sensing algorithms for cloud masking and the retrieval of cloud physical and optical properties has been developed by members of the MODIS atmosphere science team. The archived products from these algorithms have applications in climate change studies, climate modeling, numerical weather prediction, as well as fundamental atmospheric research. In addition to an extensive cloud mask, products include cloud-top properties (temperature, pressure, effective emissivity), cloud thermodynamic phase, cloud optical and microphysical parameters (optical thickness, effective particle radius, water path), as well as derived statistics. We will describe the various cloud properties being analyzed on a global basis from both Terra and Aqua, and will show characteristics of cloud optical and microphysical properties as a function of latitude for land and ocean separately, and contrast the statistical properties of similar cloud types in various parts of the world.