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Sample records for mesoscale convective system

  1. Deep convection in mesoscale convective systems

    NASA Technical Reports Server (NTRS)

    Goodman, S. J.

    1985-01-01

    A study was undertaken to examine the evolution of radar echoes and lightning attending the convective storms in mesoscale convective systems (MCS) and the relationships between the spatial and temporal evolution of deep convection and the storm environment, precipitation, severe weather, and lightning. The total number of ground discharges ranges from 10,000 to 30,000 over the life cycle of the MCS with peak sustained rates (for up to 10 consecutive hours) in excess of 2000 per hour. The peak lightning activity occurs from 5 to 20 hours after the first storms and anywhere from 7 hours prior to 7 hours after the time of the maximum areal extent of the MCS for very similar synoptic environments. Thus, it appears that mesoscale and sub-synoptic scale mechanisms are responsible for these large temporal variation in lightning activity. In addition, we have found that the lightning rates in MCS's are not related to either the size or the duration of the MCS. Preliminary results suggest that the MCA's with embedded squall lines produce the greatest flash rates.

  2. Global Variability of Mesoscale Convective System

    NASA Technical Reports Server (NTRS)

    Yuan, J.; Houze, R. A., Jr.

    2010-01-01

    Mesoscale convective systems (MCSs) in the tropics produce extensive anvil clouds, which significantly affect the transfer of radiation. This study develops an objective method to identify MCSs and their anvils by combining data from three A-train satellite instruments: Moderate Resolution Imaging Spectroradiometer (MODIS) for cloud-top size and coldness, Advanced Microwave Scanning Radiometer for Earth Observing System (AMSR-E) for rain area size and intensity, and CloudSat for horizontal and vertical dimensions of anvils. The authors distinguish three types of MCSs: small and large separated MCSs and connected MCSs. The latter are MCSs sharing a contiguous rain area. Mapping of the objectively identified MCSs shows patterns of MCSs that are consistent with previous studies of tropical convection, with separated MCSs dominant over Africa and the Amazon regions and connected MCSs favored over the warm pool of the Indian and west Pacific Oceans. By separating the anvil from the raining regions of MCSs, this study leads to quantitative global maps of anvil coverage. These maps are consistent with the MCS analysis, and they lay the foundation for estimating the global radiative effects of anvil clouds. CloudSat radar data show that the modal thickness of MCS anvils is about 4--5 km. Anvils are mostly confined to within 1.5--2 times the equivalent radii of the primary rain areas of the MCSs. Over the warm pool, they may extend out to about 5 times the rain area radii. The warm ocean MCSs tend to have thicker non-raining and lightly raining anvils near the edges of their actively raining regions, indicating that anvils are generated in and spread out from the primary raining regions of the MCSs. Thicker anvils are nearly absent over continental regions.

  3. Numerical Archetypal Parameterization for Mesoscale Convective Systems

    NASA Astrophysics Data System (ADS)

    Yano, J. I.

    2015-12-01

    Vertical shear tends to organize atmospheric moist convection into multiscale coherent structures. Especially, the counter-gradient vertical transport of horizontal momentum by organized convection can enhance the wind shear and transport kinetic energy upscale. However, this process is not represented by traditional parameterizations. The present paper sets the archetypal dynamical models, originally formulated by the second author, into a parameterization context by utilizing a nonhydrostatic anelastic model with segmentally-constant approximation (NAM-SCA). Using a two-dimensional framework as a starting point, NAM-SCA spontaneously generates propagating tropical squall-lines in a sheared environment. A high numerical efficiency is achieved through a novel compression methodology. The numerically-generated archetypes produce vertical profiles of convective momentum transport that are consistent with the analytic archetype.

  4. Thermodynamic properties of mesoscale convective systems observed during BAMEX

    SciTech Connect

    Correia, James; Arritt, R.

    2008-11-01

    Dropsonde observations from the Bow-echo and Mesoscale convective vortex EXperiment (BAMEX) are used to document the spatio-temporal variability of temperature, moisture and wind within mesoscale convective systems (MCSs). Onion type sounding structures are found throughout the stratiform region of MCSs but the temperature and moisture variability is large. Composite soundings were constructed and statistics of thermodynamic variability were generated within each sub-region of the MCS. The calculated air vertical velocity helped identify subsaturated downdrafts. We found that lapse rates within the cold pool varied markedly throughout the MCS. Layered wet bulb potential temperature profiles seem to indicate that air within the lowest several km comes from a variety of source regions. We also found that lapse rate transitions across the 0 C level were more common than isothermal, melting layers. We discuss the implications these findings have and how they can be used to validate future high resolution numerical simulations of MCSs.

  5. Kinematics and thermodynamics of a midlatitude, continental mesoscale convective system and its mesoscale vortex

    NASA Astrophysics Data System (ADS)

    Knievel, Jason Clark

    The author examines a mesoscale convective system (MCS) and the mesoscale convective vortex (MCV) it generated. The MCS, which comprised a leading convective line and trailing stratiform region, traversed Kansas and Oklahoma on 1 August 1996, passing through the NOAA Wind Profiler Network, as well as four sites from which soundings were being taken every three hours during a field project. The unusually rich data set permitted study of the MCS and MCV over nine hours on scales between those of operational rawinsondes and Doppler radars. The author used a spatial bandpass filter to divide observed wind into synoptic and mesoscale components. The environment-relative, mesoscale wind contained an up- and downdraft and divergent outflows in the lower and upper troposphere. The mesoscale wind was asymmetric about the MCS, consistent with studies of gravity waves generated by heating typical of that in many MCSs. According to a scale-discriminating vorticity budget, both the synoptic and mesoscale winds contributed to the prominent resolved sources of vorticity in the MCV: tilting and convergence. Unresolved sources were also large. The author speculates that an abrupt change in the main source of vorticity in an MCV may appear as an abrupt change in its altitude of maximum vorticity. Distributions of temperature and humidity in the MCS were consistent with its mesoscale circulations. In the terminus of the mesoscale downdraft, advection of drier, potentially warmer air exceeded humidifying and cooling from rain, so profiles of temperature and dew point exhibit onion and double-onion patterns. The mesoscale updraft was approximately saturated with a moist adiabatic lapse rate. Mesoscale drafts and convective drafts vertically mixed the troposphere, partially homogenizing equivalent potential temperature. The MCV contained a column of high potential vorticity in the middle troposphere, with a cold core below the freezing level and a warm core above---a pattern

  6. Genesis of Typhoon Nari (2001) from a mesoscale convective system

    NASA Astrophysics Data System (ADS)

    Zhang, Da-Lin; Tian, Liqing; Yang, Ming-Jen

    2011-12-01

    In this study, the origin and genesis of Typhoon Nari (2001) as well as its erratic looping track, are examined using large-scale analysis, satellite observations, and a 4 day nested, cloud-resolving simulation with the finest grid size of 1.33 km. Observational analysis reveals that Nari could be traced 5 days back to a diurnally varying mesoscale convective system with growing cyclonic vorticity and relative humidity in the lower troposphere and that it evolved from a mesoscale convective vortex (MCV) as moving over a warm ocean under the influence of a subtropical high, a weak westerly baroclinic disturbance, an approaching-and-departing Typhoon Danas to the east, and the Kuroshio Current. Results show that the model reproduces the genesis, final intensity, looping track, and the general convective activity of Nari during the 4 day period. It also captures two deep subvortices at the eye-eyewall interface that are similar to those previously observed, a few spiral rainbands, and a midget storm size associated with Nari's relatively dry and stable environment. We find that (1) continuous convective overturning within the MCV stretches the low-level vorticity and moistens a deep mesoscale column that are both favorable for genesis; (2) Nari's genesis does not occur until after the passage of the baroclinic disturbance; (3) convective asymmetry induces a smaller-sized vortex circulation from the preexisting MCV; (4) the vortex-vortex interaction with Danas leads to Nari's looping track and temporal weakening; and (5) midlevel convergence associated with the subtropical high and Danas accounts for the generation of a nearly upright eyewall.

  7. Lightning characteristics of derecho producing mesoscale convective systems

    NASA Astrophysics Data System (ADS)

    Bentley, Mace L.; Franks, John R.; Suranovic, Katelyn R.; Barbachem, Brent; Cannon, Declan; Cooper, Stonie R.

    2015-11-01

    Derechos, or widespread, convectively induced wind storms, are a common warm season phenomenon in the Central and Eastern United States. These damaging and severe weather events are known to sweep quickly across large spatial regions of more than 400 km and produce wind speeds exceeding 121 km h-1. Although extensive research concerning derechos and their parent mesoscale convective systems already exists, there have been few investigations of the spatial and temporal distribution of associated cloud-to-ground lightning with these events. This study analyzes twenty warm season (May through August) derecho events between 2003 and 2013 in an effort to discern their lightning characteristics. Data used in the study included cloud-to-ground flash data derived from the National Lightning Detection Network, WSR-88D imagery from the University Corporation for Atmospheric Research, and damaging wind report data obtained from the Storm Prediction Center. A spatial and temporal analysis was conducted by incorporating these data into a geographic information system to determine the distribution and lightning characteristics of the environments of derecho producing mesoscale convective systems. Primary foci of this research include: (1) finding the approximate size of the lightning activity region for individual and combined event(s); (2) determining the intensity of each event by examining the density and polarity of lightning flashes; (3) locating areas of highest lightning flash density; and (4) to provide a lightning spatial analysis that outlines the temporal and spatial distribution of flash activity for particularly strong derecho producing thunderstorm episodes.

  8. Lightning characteristics of derecho producing mesoscale convective systems

    NASA Astrophysics Data System (ADS)

    Bentley, Mace L.; Franks, John R.; Suranovic, Katelyn R.; Barbachem, Brent; Cannon, Declan; Cooper, Stonie R.

    2016-06-01

    Derechos, or widespread, convectively induced wind storms, are a common warm season phenomenon in the Central and Eastern United States. These damaging and severe weather events are known to sweep quickly across large spatial regions of more than 400 km and produce wind speeds exceeding 121 km h-1. Although extensive research concerning derechos and their parent mesoscale convective systems already exists, there have been few investigations of the spatial and temporal distribution of associated cloud-to-ground lightning with these events. This study analyzes twenty warm season (May through August) derecho events between 2003 and 2013 in an effort to discern their lightning characteristics. Data used in the study included cloud-to-ground flash data derived from the National Lightning Detection Network, WSR-88D imagery from the University Corporation for Atmospheric Research, and damaging wind report data obtained from the Storm Prediction Center. A spatial and temporal analysis was conducted by incorporating these data into a geographic information system to determine the distribution and lightning characteristics of the environments of derecho producing mesoscale convective systems. Primary foci of this research include: (1) finding the approximate size of the lightning activity region for individual and combined event(s); (2) determining the intensity of each event by examining the density and polarity of lightning flashes; (3) locating areas of highest lightning flash density; and (4) to provide a lightning spatial analysis that outlines the temporal and spatial distribution of flash activity for particularly strong derecho producing thunderstorm episodes.

  9. Multicloud parametrization of mesoscale convective systems for the ITCZ

    NASA Astrophysics Data System (ADS)

    Khouider, B.; Moncrieff, M. W.

    2014-12-01

    Mesoscale convective systems (MCS), aligned approximately parallel to the background low-level wind shear, are ubiquitous in the Eastern Pacific intertropical convergence zone (ITCZ). They are believed to control the local Hadley circulation and have a nontrivial momentum feedback on the ambient shear. They also play a central role in the two-way interactions between convection and the synoptic and planetary scale waves. They do so by serving as both the building block for organized convection, which involves congestus cloud decks that moisten and precondition the environment for deep convection which in turn is lagged by stratiform anvils, and as a conveyer belt for convective momentum transport (CMT). Here, we propose an extension of the multicloud model of Khouider and Majda (2006) to make the stratiform anvils more sensitive to the background wind shear profile. We do so by invoking two layers of moisture in the free troposphere instead of one, in addition to the boundary layer. Linear stability, in a wind shear background consisting of both mid-level and low-level easterly jets, representing, simultaneously, the Tropical Easterly and African Easterly jets, features the usual synoptic scale instability of the multicloud model plus two new instability bands at the meso-alpha and meso-beta scales, respectively. The meso-alpha and meso-beta modes constitute a paradigm for the dynamics of shear parallel convective systems with the meso-alpha waves being the quasi-stationary systems. In this talk we will present limited domain 3D simulations, without rotation, of realistic shear parallel lines of convection with parallel stratifrom anvils moving eastward, with a steering level in the upper troposphere, as a mesoscale envelope of the individual convective cells moving inwards, with a steering level in the lower troposphere. This provides, among other things, an excellent example of nontrivial CMT effect on the background low-level wind. It results in a narrow channel

  10. Budget study of a mesoscale convective system - Model simulation

    NASA Technical Reports Server (NTRS)

    Tao, Wei-Kuo; Simpson, Joanne; Mccumber, Michael

    1988-01-01

    A tropical squall-type cloud cluster is examined as an example of a mesoscale convective complex. The precipitation growth processes and air circulations that develop in the convective and stratiform regions are studied using a data set generated from a time-dependent numerical cloud model. The relationship of the stratiform region of the mesoscale convective complex is discussed. The vertical profiles of heating and drying are calculated. Comparisons are made between simulations with and without ice-phase microphysical processes and a simulation with forcing by weaker lifting at middle and upper levels.

  11. Explicit simulation of a midlatitude Mesoscale Convective System

    SciTech Connect

    Alexander, G.D.; Cotton, W.R.

    1996-04-01

    We have explicitly simulated the mesoscale convective system (MCS) observed on 23-24 June 1985 during PRE-STORM, the Preliminary Regional Experiment for the Stormscale Operational and Research and Meterology Program. Stensrud and Maddox (1988), Johnson and Bartels (1992), and Bernstein and Johnson (1994) are among the researchers who have investigated various aspects of this MCS event. We have performed this MCS simulation (and a similar one of a tropical MCS; Alexander and Cotton 1994) in the spirit of the Global Energy and Water Cycle Experiment Cloud Systems Study (GCSS), in which cloud-resolving models are used to assist in the formulation and testing of cloud parameterization schemes for larger-scale models. In this paper, we describe (1) the nature of our 23-24 June MCS dimulation and (2) our efforts to date in using our explicit MCS simulations to assist in the development of a GCM parameterization for mesoscale flow branches. The paper is organized as follows. First, we discuss the synoptic situation surrounding the 23-24 June PRE-STORM MCS followed by a discussion of the model setup and results of our simulation. We then discuss the use of our MCS simulation. We then discuss the use of our MCS simulations in developing a GCM parameterization for mesoscale flow branches and summarize our results.

  12. 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.

  13. The impact of mesoscale data on the simulation of a mesoscale convective weather system

    NASA Technical Reports Server (NTRS)

    Fritsch, J. M.; Zhang, D.-L.

    1985-01-01

    The objectives are: (1) to demonstrate the sensitivity of a numerical simulation of a mesoscale convective weather system to the initial conditions; and (2) to provide further evidence of the need for a high resolution observing system that is compatible with numerical-model initial data requirements. To this end, a series of nine numerical-model sensitivity experiments were conducted in which one or more variables from one or more observations (soundings) were omitted and/or adjusted in the model initialization. Two types of surroundings were available for manipulation in the sensitivity experiments. Specifically, for the particular event being simulated (the 1977 Johnstown flash flood), an independent mesoanalysis was available from Bosart and Sanders (1981). In his analysis, Bosart produced a fine-resolution three-dimensional array of data from which soundings that helped to define mesoscale features could be extracted. These 'nonconventional' soundings were added to the conventional sounding data routinely available for model initialization.

  14. Defining Mesoscale Convective Systems by Their 85-GHz Ice-Scattering Signatures.

    NASA Astrophysics Data System (ADS)

    Mohr, Karen I.; Zipser, Edward J.

    1996-06-01

    Mesoseale Convective systems are composed of numerous deep convective cells with varying amounts of large, convectively produced ice particles aloft. The magnitude of the 85-GHz brightness temperature depression resulting from scattering by large ice is believed to be related to the convective intensity and to the magnitude of the convective fluxes through a deep layer. The 85-GHz ice-scattering signature can be used to map the distribution of organized mesoscale regions of convectively produced large ice particles. The purpose of this article is to demonstrate the usefulness of the 85-GHz ice-scattering signature for describing the frequency, convective intensity, and geographic distribution of mesoscale convective systems.Objective criteria were developed to identify mesoscale convective systems from raw data from January, April, July, and October 1993. To minimize the effects of background contamination and to ensure that bounded areas contained convective elements, a "mesoscale convective system" was defined as an area bounded by 250 K of at least 2000 km2 of 85 GHz, with a minimum brightness temperature 225 K. Mesoscale convective systems extracted from the raw data were sorted and plotted by their areas and by their minimum brightness temperatures. Four area and brightness temperature classes were used to account for a spectrum of organized convection ranging from small to very large and from less organized to highly organized. The populations of mesoscale convective systems by this study's definition were consistent with infrared-based climatologies and large-scale seasonal dynamics. Land/water differences were high-lighted by the plots of minimum brightness temperature. Most of the intense mesoscale convective systems were located on or near land and seemed to occur most frequently in particular areas in North America, South America, Africa, and India.

  15. Mesoscale aspects of convective storms

    NASA Technical Reports Server (NTRS)

    Fujita, T. T.

    1981-01-01

    The structure, evolution and mechanisms of mesoscale convective disturbances are reviewed and observation techniques for "nowcasting" their nature are discussed. A generalized mesometeorological scale is given, classifying both low and high pressure systems. Mesoscale storms are shown often to induce strong winds, but their wind speeds are significantly less than those accompanied by submesoscale disturbances, such as tornadoes, downbursts, and microbursts. Mesoscale convective complexes, severe storm wakes, and flash floods are considered. The understanding of the evolution of supercells is essential for improving nowcasting capabilities and a very accurate combination of radar and satellite measurements is required.

  16. Cloud-to-ground lightning and Mesoscale Convective Systems

    NASA Astrophysics Data System (ADS)

    Mattos, Enrique V.; Machado, Luiz A. T.

    2011-03-01

    This work analyzes some physical and microphysical properties of Mesoscale Convective Systems (MCSs) and cloud-to-ground lightning. Satellite data from the GOES-10 infrared and NOAA-18 and TRMM microwave channels and lightning information from the Brazilian lightning detection network (BrasilDAT) were utilized for the period from 2007 to 2009. Based on an automatic MCSs detection method, 720 MCSs life cycles were identified during the period and in the region of study, with a lightning detection efficiency of over 90%. During the diurnal cycle, maximum electrical activity occurred close to the time of maximum convective cloud fraction (18 UTC), and 3 h after the maximum normalized area expansion rate. Diurnal cycles of both properties were modulated by diurnal heating, and thus could be used to monitor diurnal variability of lightning occurrence. The electrical activity was more intense for the widest (Pearson's correlation of 0.96) and deeper (Pearson's correlation of 0.84) clouds, which reached 390 km size and 17 km maximum cloud top height. Area growth during the initial phase of MCSs exerted a strong influence on their size and duration, and thus also showed a potential for defining the possibility of electrical activity during their life cycle. The average lightning life cycle exhibited a maximum close to MCSs maturation, while the maximum average lightning density occurred in the MCSs initial life cycle stage. The growth rate of electrical activity during the early stages can indicate the strength of convection and the possible duration of systems with lightning occurrence. Strong condensation processes and mass flux during the growth phase of the systems can provide favorable conditions for cloud electrification and lightning occurrence. A comparison of high microwave frequencies with lightning data showed a strong relationship of vertically integrated ice content and particle size with lightning occurrence, with Pearson's correlation of 0.86 and 0

  17. Transient luminous events above two mesoscale convective systems

    NASA Astrophysics Data System (ADS)

    Lang, Timothy; Rutledge, Steve; Lyons, Walt; Cummer, Steve; Li, Jingbo; Macgorman, Don

    2010-05-01

    Two warm-season mesoscale convective systems (MCSs) were analyzed with respect to production of transient luminous events (TLEs), mainly sprites. Sprites were documented over the lightning mapping array (LMA) network in Oklahoma, USA, using highly sensitive optical cameras operated at Yucca Ridge in Ft. Collins, Colorado, as part of our Sprites 2007 field campaign. Information about charge moment changes in lightning flashes was obtained by the National Charge Moment Change Network (CMCN). Cloud-to-ground lightning data were obtained from the National Lightning Detection Network (NLDN). The 20 June 2007 symmetric MCS produced 282 observed TLEs over a 4-h period, during which time the storm's intense convection weakened and its stratiform region strengthened. In contrast to previous sprite studies, the stratiform charge layer involved in producing the TLE-parent positive cloud-to-ground (+CG) lightning flash was situated at upper levels as opposed to near the melting level. This layer was physically connected to an even higher upper-level convective positive charge region via a downward-sloping pathway. The average altitude discharged by TLE-parent flashes during TLE activity was 8.2 km above mean sea level (MSL; -25 °C). The 9 May 2007 asymmetric MCS produced 25 observed TLEs over a 2-h period, during which the storm's convection rapidly weakened before recovering later. The 9 May storm best fit the conventional model of low-altitude positive charge playing the dominant role in sprite production; however, the average altitude discharged during the TLE phase of flashes still was higher than the melting level: 6.1 km MSL (-15 °C). The average TLE-parent +CG flash in the symmetric 20 June case initiated at higher altitude, discharged a substantially larger area, had a larger peak current, and tapped positive charge at higher altitude compared to the asymmetric 9 May case. Analysis of full charge moment change (CMC) data from TLE-parent +CGs in these two cases

  18. Numerical simulations and analyses of mesoscale convective systems during MC3E with data assimilation at a convective permitting scale

    NASA Astrophysics Data System (ADS)

    Pu, Z.; Lin, C.; Wei, L.

    2012-12-01

    Our previous studies demonstrate that assimilation of surface mesonet observations and atmospheric profiles results in improved numerical simulations and predictability of mesoscale convective systems and their related atmospheric boundary layer conditions. In this study, numerical simulations of mesoscale convective systems observed during the Midlatitude Continental Convective Clouds Experiment (MC3E) field campaign are conducted with the mesoscale community Weather Research and Forecasting (WRF) model at a convective permitting scale. First, five time periods, with convective systems evolved are identified over the Oklahoma-Kansas area. High-resolution numerical simulations are conducted with the WRF model for those five periods. A multiple-level nested domain technique is used to achieve the cloud-permitting scale simulation. Specifically, the model domains are set up for 3 nested domains with horizontal resolutions at 12 km, 4 km and 1.33 km, respectively. The model initial and boundary conditions are derived from the NCEP Northern American Mesoscale model (NAM) analysis. Results show that the WRF model reproduces the convective initiations and relatively reasonable evolution of those convective systems during most of the simulation periods, although errors are present in all numerical simulations when compared the model simulated convective initiation time, location and quantitative precipitation with observations. As an early investigation, sensitivity of numerical simulations of mesoscale convective systems to WRF model physical parameterization schemes is examined. For the cases during 12 UTC 19 May to 12 UTC 21 May 2011, it is found that the numerical simulation results are very sensitive to the choice of microphysical schemes in the WRF model. However, even with the best numerical simulation, errors are still found in terms of the prediction of convective initiation time, location and quantitative precipitation, indicating the need for data assimilation

  19. FURTHER CASE STUDIES ON THE IMPACT OF MESOSCALE CONVECTIVE SYSTEMS ON REGIONAL OZONE AND HAZE DISTRIBUTIONS

    EPA Science Inventory

    The report is a continuation of an earlier effort to study the impact of mesoscale convective precipitation systems upon distributions of aerosol and photochemical oxidant pollutants in the planetary boundary layer (PBL). Analyses of surface visibility and ozone data revealed a d...

  20. Characteristics of mesoscale-convective-system-produced extreme rainfall over southeastern South Korea: 7 July 2009

    NASA Astrophysics Data System (ADS)

    Jeong, Jong-Hoon; Lee, Dong-In; Wang, Chung-Chieh; Han, In-Seong

    2016-04-01

    An extreme-rainfall-producing mesoscale convective system (MCS) associated with the Changma front in southeastern South Korea was investigated using observational data. This event recorded historic rainfall and led to devastating flash floods and landslides in the Busan metropolitan area on 7 July 2009. The aim of the present study is to analyse the influences for the synoptic and mesoscale environment, and the reasons that the quasi-stationary MCS causes extreme rainfall. Synoptic and mesoscale analyses indicate that the MCS and heavy rainfall occurred in association with a stationary front which resembled a warm front in structure. A strong southwesterly low-level jet (LLJ) transported warm and humid air and supplied the moisture toward the front, and the air rose upwards above the frontal surface. As the moist air was conditionally unstable, repeated upstream initiation of deep convection by back-building occurred at the coastline, while old cells moved downstream parallel to the convective line with training effect. Because the motion of convective cells nearly opposed the backward propagation, the system as a whole moved slowly. The back-building behaviour was linked to the convectively generated cold pool and its outflow boundary, which played a role in the propagation and maintenance of the rainfall system. As a result, the quasi-stationary MCS caused a prolonged duration of heavy rainfall, leading to extreme rainfall over the Busan metropolitan area.

  1. Evaluating and Understanding Parameterized Convective Processes and Their Role in the Development of Mesoscale Precipitation Systems

    NASA Technical Reports Server (NTRS)

    Fritsch, J. Michael (Principal Investigator); Kain, John S.

    1995-01-01

    Research efforts during the first year focused on numerical simulations of two convective systems with the Penn State/NCAR mesoscale model. The first of these systems was tropical cyclone Irma, which occurred in 1987 in Australia's Gulf of Carpentaria during the AMEX field program. Comparison simulations of this system were done with two different convective parameterization schemes (CPS's), the Kain-Fritsch (1993 - KF) and the Betts-Miller (Betts 1986- BM) schemes. The second system was the June 10-11 1985 squall line simulation, which occurred over the Kansas-Oklahoma region during the PRE-STORM experiment. Simulations of this system using the KF scheme were examined in detail.

  2. Evaluating and Understanding Parameterized Convective Processes and Their Role in the Development of Mesoscale Precipitation Systems

    NASA Technical Reports Server (NTRS)

    Fritsch, J. Michael; Kain, John S.

    1996-01-01

    Research efforts focused on numerical simulations of two convective systems with the Penn State/NCAR mesoscale model. The first of these systems was tropical cyclone Irma, which occurred in 1987 in Australia's Gulf of Carpentaria during the AMEX field program. Comparison simulations of this system were done with two different convective parameterization schemes (CPS's), the Kain-Fritsch (KF) and the Betts-Miller (BM) schemes. The second system was the June 10-11, 1985 squall line simulation, which occurred over the Kansas-Oklahoma region during the PRE-STORM experiment. Simulations of this system using the KF scheme were examined in detail.

  3. Explicit simulation and parameterization of mesoscale convective systems. Final report, November 1, 1993--April 30, 1997

    SciTech Connect

    Cotton, W.R.

    1997-08-12

    This research has focused on the development of a parameterization scheme for mesoscale convective systems (MCSs), to be used in numerical weather prediction models with grid spacing too coarse to explicitly simulate such systems. This is an extension to cumulus parameterization schemes, which have long been used to account for the unresolved effects of convection in numerical models. Although MCSs generally require an extended sequence of numerous deep convective cells in order to develop into their characteristic sizes and to persist for their typical durations, their effects on the large scale environment are significantly different than that due to the collective effects of numerous ordinary deep convective cells. These differences are largely due to a large stratiform cloud that develops fairly early in the MCS life-cycle, where mesoscale circulations and dynamics interact with the environment in ways that call for a distinct MCS parameterization. Comparing an MCS and a collection of deep convection that ingests the same amount of boundary layer air and moisture over an extended several hour period, the MCS will generally generates more stratiform rainfall, produce longer-lasting and optically thicker cirrus, and result in different vertical distributions of large-scale tendencies due to latent heating and moistening, momentum transfers, and radiational heating.

  4. Convectively induced mesoscale weather systems in the tropical and warm-season midlatitude atmosphere

    NASA Astrophysics Data System (ADS)

    Smull, Bradley F.

    1995-07-01

    As anticipated by Nelson [1991] in the last U.S. National Report, mesoscale meteorology has continued to be an area of vigorous research activity. Progress is evinced by a growing number of process-oriented studies capitalizing on expanded observational capabilities, as well as more theoretical treatments employing numerical simulations of increasing sophistication. While the majority of papers within the scope of this review fall into the category of basic research, the field's maturation is evident in the emergence of a growing number of applications to operational weather forecasting. Even as our ability to anticipate shifts in synoptic scale upper-air patterns and associated baroclinic developments has steadily improved, lagging skill with regard to quantitative forecasts of precipitation—particularly in situations where deep moist convection is prevalent—has sustained research in warm-season mesoscale meteorology. Each spring and summer midlatitude populations are exposed to life-threatening natural weather phenomena in the form of lightning, tornadoes, straight-line winds, hail, and flash floods. This point was driven home during the summer of 1993, when an extraordinarily persistent series of mesoscale convective systems (MCSs) led to unusually severe and widespread flooding throughout the Mississippi and Missouri river basins. In addition to this obvious impact on regional climate, the 1990's have brought an increased appreciation for the less direct yet potentially significant role that tropical convection may play in shaping global climate through phenomena such as the El Niño-Southern Oscillation (ENSO).

  5. 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.

  6. Numerical Simulation and Analysis of a Series of Mesoscale Convective Systems

    NASA Astrophysics Data System (ADS)

    Bresch, James Francis

    A case in which a series of mesoscale convective systems (MCSs) traversed across Kansas and Oklahoma (3 -4 June 1985) was examined using observations and the MM4 model. The first MCS in the series (MCS1) began north of a stationary front in a region of strong low-level warm advection and moisture convergence near the terminus of a low-level jet (LLJ). Simulations of this system evolved realistically and show that the elevated convection fed on air riding over the frontal inversion. This source air originated in the heated boundary layer over Texas and Oklahoma the previous afternoon. The system-relative circulation of the mature system did not exhibit a front -to-rear upper-level flow nor extensive trailing stratiform region as has been observed with other systems. The second MCS (MCS2) was linked to an upper-level jet streak throughout its lifetime. In agreement with observations, the simulation produced the two precipitation bands within MCS2 that gave it the appearance of a miniature occluded cyclone. The north-south band, located in the southern half of the system, consisted of surface-based convection forced by low-level convergence of convective downdrafts with the environmental flow, while the northeast -southwest band in the northern part of the system was comprised of elevated convection occurring in a frontogenetic zone. Convection in this region was initially triggered by a LLJ induced by transverse ageostrophic circulations about an approaching upper-level jet streak. The strong LLJ was decoupled from the surface by the frontal inversion and was able to advect high-theta_ E air northwestward, destabilizing the airmass. The simulation of MCS1 was found to be sensitive to the initial low-level moisture distribution, suggesting that accurate prediction of elevated convection requires initial conditions that include mesoscale details aloft. In agreement with a previous study, the simulation was found to be quite sensitive to the convective trigger function

  7. The Contribution of Mesoscale Motions to the Mass and Heat Fluxes of an Intense Tropical Convective System.

    NASA Astrophysics Data System (ADS)

    Leary, Colleen A.; Houze, Robert A., Jr.

    1980-04-01

    The existence of extensive precipitating anvil clouds in intense tropical convection suggests that vertical air motions associated with the anvil clouds play a significant role in the mass and heat budgets of these systems. This paper uses three different sets of assumptions about the water budget of an idealized mesoscale convective system to test the sensitivity of diagnostic calculations of vertical transports of mass and heat to the inclusion or exclusion of anvil clouds and their associated mesoscale vertical air motions. The properties of the mesoscale updraft and downdraft are evaluated using observations and the results of modeling studies. When a mesoscale updraft and downdraft are included in the diagnostic calculations, the profiles of vertical transports of mass and moist static energy are both qualitatively and quantitatively different from the results when mesoscale vertical air motions are excluded. Inclusion of mesoscale vertical motions in the diagnostic calculations leads to smaller upward mass transports below 4 km, larger upward mass sports above 4 km, less cooling below 4 km, and more cooling between 4.5 and 6.5 km than are obtained when mesoscale motions are not included in the calculations. These results imply that the effect of mesoscale vertical air motions on cloud mass flux and net beating profiles should be considered when parameterizing the effects of tropical convection on the larger scale environment.

  8. Characteristics of cloud-to-ground lightning strikes in the stratiform regions of mesoscale convective systems

    NASA Astrophysics Data System (ADS)

    Wang, Fei; Zhang, Yijun; Liu, Hengyi; Yao, Wen; Meng, Qing

    2016-09-01

    To better understand the characteristics of cloud-to-ground lightning (CG) strikes in the stratiform regions of mesoscale convective systems (MCSs), radar and CG data from 10 MCS cases in China were comprehensively analyzed. Results show that stratiform CGs have characteristics distinct from those of convective CGs. A significant polarity bias appears in convective CGs, but the polarity bias in stratiform CGs is either undetectable or opposite that of the bias of convective CGs. The medians of the first return stroke current for positive and negative stratiform CGs have mean values of 59.7 kA and - 37.3 kA, respectively; these values are 26% and 24% higher than the corresponding mean values for positive and negative convective CGs, respectively. In contrast to stratiform CGs, the first return strokes of convective CGs have polarized currents. Most convective CGs have relatively low currents, but most CGs with maximum currents in MCSs also fall within convective CGs. In the 10 MCSs studied, most stratiform CGs strike the ground at or near the edge of a region whose maximum reflectivity (≥ 30 dBZ) occurs at 3-6 km height. The characteristics of reflectivity across this region are consistent with the reflectivity characteristics of the brightband; thus, this study provides important evidence for the relationship between the brightband and stratiform CGs. A charging mechanism based on the melting of ice particles is speculated to be the key to initiating stratiform lightning. This mechanism could induce the propagation of lightning from the convective region to the stratiform region, thereby explaining the observed strikes on the ground nearby.

  9. Transient Luminous Events and the 9 May 2007 Oklahoma Mesoscale Convective System

    NASA Astrophysics Data System (ADS)

    Lang, T. J.; Rutledge, S. A.; Lyons, W.; Cummer, S.; Meyer, J.; Holzworth, R.; Macgorman, D.

    2008-12-01

    On 9 May 2007 an asymmetric mesoscale convective system (MCS) passed through the domain of the Oklahoma Lightning Mapping Array while producing 26 transient luminous events (TLEs) in a 2-hour period, which were observed at the Yucca Ridge Field Station in northeastern Colorado. During the observation period (03-05 UTC), the MCS consisted of a short NW-SE-oriented line with a stratiform region to its north. This stratiform region also contained intense embedded convection, and rotated cyclonically as a mesoscale convective vortex. The MCS was dominated by negative cloud-to-ground (CG) lightning, with 95% of the 3037 detected National Lightning Detection Network (NLDN) strokes being negative, and total flash rate sometimes exceeded 100 flashes per minute. Twenty-four of the 26 TLEs observed in this case coincided with parent positive CG strokes detected by the NLDN (the other two likely were associated with undetected positive CGs). Eighteen of these events had valid impulse charge moment change (iCMC) retrievals by the National Charge Moment Change Network. Thirteen of these had iCMC values in excess of 100 C km, roughly consistent with past studies that suggest iCMC values ~100 C km or greater are favorable for generating TLEs. Fifty-eight percent of the TLE- producing positive CG strokes also were detected by the World Wide Lightning Location Network, which suggests that this global network may have promising utility in TLE research studies. Both convective regions (southern convective line, and embedded convection in the stratiform region) produced TLE parent flashes, although most TLE producers initiated in the stratiform-embedded convection. TLE parent flashes initiated around 5.7 km MSL in the embedded convection, but slightly higher (7.5 km) in the southern convective line. Both sets of TLE parent flashes tended to propagate near 6 km MSL in the stratiform region while producing their TLEs. In general, TLE flash altitudes were lower (by ~2 km or more) and

  10. Analysis of the initiation of a mesoscale convective system based on heat and moisture budget calculations

    NASA Astrophysics Data System (ADS)

    Kalthoff, Norbert; Adler, Bianca; Gantner, Leonhard

    2010-05-01

    COSMO runs were performed to simulate a mesoscale convective system (MCS), which was observed on 11 June, 2006 (pre-onset phase of the monsoon, SOP 1). Different simulation scenarios were investigated including a realistic soil moisture distribution (i), a simulation with increased soil moisture (ii) and a homogeneous soil moisture and soil texture in the whole investigation area (iii). The simulations showed that convection was initiated in all experiments. However, the amount of cells and its origin differed. While in experiment (i) and (iii) several cells were initiated and merged into an organized convective system, in experiment (ii) only a small, short-lived cell was simulated. In order to study the conditions which led to the different evolution, heat and moisture budgets were calculated. The boxes for which budgets were calculated included the whole area, where convective cells were initiated, as well as isolated cells only. The different contributions of the components of the budgets and its differences between the three scenarios were discussed. Special attention was laid on the impact of the components of the budgets (e.g. heat flux convergence, horizontal advection) on the evolution of convection-related parameters (CAPE, CIN) and thermally induced circulation systems.

  11. Evaluating and Understanding Parameterized Convective Processes and their Role in the Development of Mesoscale Precipitation Systems

    NASA Technical Reports Server (NTRS)

    Fritsch, J. Michael; Kain, John S.

    1997-01-01

    Research efforts during the second year have centered on improving the manner in which convective stabilization is achieved in the Penn State/NCAR mesoscale model MM5. Ways of improving this stabilization have been investigated by (1) refining the partitioning between the Kain-Fritsch convective parameterization scheme and the grid scale by introducing a form of moist convective adjustment; (2) using radar data to define locations of subgrid-scale convection during a dynamic initialization period; and (3) parameterizing deep-convective feedbacks as subgrid-scale sources and sinks of mass. These investigations were conducted by simulating a long-lived convectively-generated mesoscale vortex that occurred during 14-18 Jul. 1982 and the 10-11 Jun. 1985 squall line that occurred over the Kansas-Oklahoma region during the PRE-STORM experiment. The long-lived vortex tracked across the central Plains states and was responsible for multiple convective outbreaks during its lifetime.

  12. Transport and chemistry of formaldehyde by mesoscale convective systems in West Africa during AMMA 2006

    NASA Astrophysics Data System (ADS)

    Borbon, AgnèS.; Ruiz, M.; Bechara, J.; Aumont, B.; Chong, M.; Huntrieser, H.; Mari, C.; Reeves, C. E.; Scialom, Georges; Hamburger, T.; Stark, H.; Afif, C.; Jambert, C.; Mills, G.; Schlager, H.; Perros, P. E.

    2012-06-01

    In situ measurements of formaldehyde (CH2O) onboard four European research aircraft in August 2006 as part of the African Monsoon Multidisciplinary Analysis (AMMA) experiment in West Africa are used (1) to examine the redistribution of CH2O by mesoscale convective systems (MCS) in the tropical upper troposphere (UT), (2) to evaluate the scavenging efficiency (SE) of CH2O by MCS and (3) to quantify the impact of CH2O on UT photooxidant production downwind of MCS. The intercomparison of CH2O measurements is first tested, providing a unique and consistent 3-D-spatially resolved CH2O database in background and convective conditions. While carbon monoxide (CO) is vertically uplifted by deep convection up to 12 km, CH2O is also affected by cloud processing as seen from its ratio relative to CO with altitude. A new observation-based model is established to quantify the SE of CH2O. This model shows that convective entrainment of free tropospheric air cannot be neglected since it contributes to 40% of the convective UT air. For the 4 studied MCS, SE shows a large variability within a 4% to 39% range at a relative standard deviation of 30%, which is consistent with MCS features. A time-dependent photochemical box model is applied to convective UT air. After convection, 60% of CH2O is due to its photochemical production rather than to its direct transport. Model results indicate that CH2O directly injected by convection does not impact ozone and HOx production in the tropical UT of West Africa. NOx and anthropogenic hydrocarbon precursors dominate the secondary production of CH2O, ozone and HOx.

  13. Thermodynamic sensitivities in observed and simulated extreme-rain-producing mesoscale convective systems

    NASA Astrophysics Data System (ADS)

    Schumacher, R. S.; Peters, J. M.

    2015-12-01

    Mesoscale convective systems (MCSs) are responsible for a large fraction of warm-season extreme rainfall events over the continental United States, as well as other midlatitude regions globally. The rainfall production in these MCSs is determined by numerous factors, including the large-scale forcing for ascent, the organization of the convection, cloud microphysical processes, and the surrounding thermodynamic and kinematic environment. Furthermore, heavy-rain-producing MCSs are most common at night, which means that well-studied mechanisms for MCS maintenance and organization such as cold pools (gravity currents) are not always at work. In this study, we use numerical model simulations and recent field observations to investigate the sensitivity of low-level MCS structures, and their influences on rainfall, to the details of the thermodynamic environment. In particular, small alterations to the initial conditions in idealized and semi-idealized simulations result in comparatively large precipitation changes, both in terms of the intensity and the spatial distribution. The uncertainties in the thermodynamic enviroments in the model simulations will be compared with high-resolution observations from the Plains Elevated Convection At Night (PECAN) field experiment in 2015. The results have implications for the paradigms of "surface-based" versus "elevated" convection, as well as for the predictability of warm-season convective rainfall.

  14. Characterization of mesoscale convective systems over the eastern Pacific during boreal summer

    NASA Astrophysics Data System (ADS)

    Berthet, Sarah; Rouquié, Bastien; Roca, Rémy

    2015-04-01

    The eastern Pacific Ocean is one of the most active tropical disturbances formation regions on earth. This preliminary study is part of a broader project that aims to investigate how mesoscale convective systems (MCS) may be related to these synoptic disturbances with emphasis on local initiation of tropical depressions. As a first step, the main characteristics of the MCS over the eastern Pacific are documented with the help of the recently developed TOOCAN tracking algorithm (Fiolleau and Roca, 2013) applied to the infrared satellite imagery data from GOES-W and -E for the period JJAS 2012-2014. More specifically, the spatial distribution of the MCS population, the statistics of their spatial extensions and durations, as well as their trajectories and propagation speeds are summarized. In addition the environment of the MCS will be investigated using various Global Precipitation Mission datasets and the Megha-Tropiques/SAPHIR humidity microwave sounder derived products. Reference: Fiolleau T. and R. Roca, (2013), An Algorithm For The Detection And Tracking Of Tropical Mesoscale Convective Systems Using Infrared Images From Geostationary Satellite, Transactions on Geoscience and Remote Sensing, doi: 10.1109/TGRS.2012.2227762.

  15. Sensitivity of a mesoscale convective system to soil moisture perturbations in West Africa

    NASA Astrophysics Data System (ADS)

    Gantner, L.; Adler, B.; Kalthoff, N.

    2010-09-01

    The response of a mesoscale convective system (MCS) to soil moisture inhomogeneities in West Africa is investigated in a sensitivity study. Convection permitting simulations with the COSMO-Model driven by ECMWF analyses were performed. Several scenarios were investigated, including homogeneous soil type and soil moisture, and homogeneous soil type with a north-south oriented band in which the soil moisture is either reduced or increased. Precipitation related to the MCS was continuously strong in the homogeneous case. When the MCS approached the band with reduced soil moisture precipitation decreased because of higher convective inhibition (CIN) ahead of the band. Over the drier band precipitation increased again. The moist band caused an increase of precipitation before the MCS reached the band and a decrease in the area with higher soil moisture caused by very high CIN values. Soil moisture inhomogeneities induced thermal circulations which led to modified conditions in the lower troposphere and to changes in CIN and accounted for the modification of precipitation of an MCS. In the dry band case, a precipitating cell already developed in the western part of band in the late afternoon, where convergence, generated by thermal circulations and supported by downward mixing of momentum from the African Easterly Jet, triggered convection.

  16. Response of mesoscale convective system (MCS) and cold pool formation to dust-radiative effects

    NASA Astrophysics Data System (ADS)

    Waylonis, M. T.; Chen, S. H.

    2014-12-01

    This study examines the role of dust in the development of a mesoscale convective system (MCS) over the central-west Sahara, and how cold pools from the MCS feedback to dust emissions. Few studies have simulated the direct-radiative effects of dust on cloud development. Moderate Resolution Imaging Spectrometer (MODIS) and Multi-angle Imaging Spectrometer (MISR) Retrieved aerosol optical depth and Meteosat Second Generation dust enhancement product were used to examine a dust outbreak that occurred between 13 and 15 August 2005 and revealed that an moist intrusion into the Sahara caused a MCS to form and resulted in dust emission due to cold pool outflow from the MCS. A dust model based on the Weather Research and Forecasting model was developed to include dust emissions, transport, dry and moist deposition, and radiation interactions and was used to simulate the case. Dust-radiation interactions were found to enhance convective strength through low-level heating, which increased convective available potential energy and low-level convergence. The increased intensity of the convection led to stronger and more widespread cold pool formation, which in turn emitted more dust into the atmosphere.

  17. Mesoscale convective complexes in Africa

    SciTech Connect

    Laing, A.G.; Fritsch, J.M. )

    1993-08-01

    Digitized full-disk infrared satellite imagery from the European geostationary satellite (Meteosat) for 1986 and 1987 was used to construct a climatology of mesoscale convective complexes (MCCs) in Africa. One hundred ninety-five systems formed over Africa and its near vicinity during the two-year study period. From this database, characteristics of Africa MCCs were calculated. The results indicate that these MCCs display many of the same characteristics as those found in the Americas, the Indian subcontinent, and the western Pacific region. The systems are predominantly nocturnal and tend to form over or in the immediate vicinity of land. The average lifetime of African MCCs is about 11.5 h. The size distributions of the African systems are also extremely similar to those of the Americas, the Indian subcontinent, and the western Pacific region with most systems exhibiting areas between 2 [times] 10[sup 5] and 3 [times] 10[sup 5] km[sup 2]. The monthly frequency distribution of African systems indicates that peak activity tends to occur during the period of most intense insolation. Like the MCCs in the western Pacific region and the Americas, the African MCCs tend to propagate toward the low-level high-[theta][sub e] air that feeds the convective systems. Systems over northern Africa moved toward the west-southwest, with a few developing into tropical cyclones over the Atlantic. Systems over southeastern Africa generally moved toward the northeast and east. It is concluded that the satellite-observed systems over Africa are essentially the same phenomena as the MCC populations observed over the Americas, the Indian monsoon region, and the western Pacific region. In addition, the large number of MCCs found worldwide (approximately 300-400 per year) indicate that they may be significant contributors to the global tropospheric energy budget and hydrological cycle. 46 refs., 9 figs., 1 tab.

  18. Propagation of Mesoscale Convective Systems over India in the Boreal Summer Monsoon Season

    NASA Astrophysics Data System (ADS)

    Phadtare, J. A.; Bhat, G. S.

    2015-12-01

    With an automated cloud tracking algorithm, we have analysed the propagation of mesoscale convective systems (MCSs) over Indian region in the boreal summer monsoon season (June-September). We used half hourly infrared images of a geostationary satellite KALPANA-I for the study. The data covers four monsoon seasons (2010,12,13,and 14). Mesoscale convective systems (MCSs) over the Indian land show a prominent westward propagation, which is opposite to the lower tropospheric monsoonal westerlies. The mechanism associated with these propagations seems robust, i.e. it appears in all the events. The propagation seems to be a result of internal dynamics of MCS, and not forced by any external agent. The mechanism is prevalent through out the monsoon season, but absent in pre- and post-monsoon season. The zonal convective streaks associated with the large MCSs have a spatial and temporal scales of 1000 km and 1 day respectively, with a westward speed of 18 m/s. These streaks resemble the westward propagating inertial-gravity (WIG) type of wave propagation. Thus, we speculate that, the MCSs over India in the summer monsoon season trigger WIG waves. And the subsequent propagation of MCS is coupled to this wave signal. Most of the large MCSs are associated with the synoptic scale monsoon depressions. Mean propagation of MCSs over Bay of Bengal (BoB) is of more complex nature. There seems to be more than one propagation mechanism which are active over BoB in the summer monsoon season. The selection of propagation mechanism by the BoB MCSs might depend on the phase of diurnal cycle or intra-seasonal oscillation, MCS size, and its location over the bay.

  19. Assessment of mesoscale convective systems using IR brightness temperature in the southwest of Iran

    NASA Astrophysics Data System (ADS)

    Rafati, Somayeh; Karimi, Mostafa

    2016-04-01

    In this research, the spatial and temporal distribution of Mesoscale Convective Systems was assessed in the southwest of Iran using Global merged satellite IR brightness temperature (acquired from Meteosat, GOES, and GMS geostationary satellites) and synoptic station data. Event days were selected using a set of storm reports and precipitation criteria. The following criteria are used to determine the days with occurrence of convective systems: (1) at least one station reported 6-h precipitation exceeding 10 mm and (2) at least three stations reported phenomena related to convection (thunderstorm, lightning, and shower). MCSs were detected based on brightness temperature, maximum areal extent, and duration thresholds (228 K, 10,000 km2, and 3 h, respectively). An MCS occurrence classification system is developed based on mean sea level, 850 and 500 hPa pressure patterns. The results indicated that the highest frequency of MCSs occurred in December and April. Assessment of MCSs spatial frequency showed that MCS occurrence is strongly correlated with topography in April and May unlike the cold months. In other words, the role of Zagros Mountains in developing MCSs varies based on the season so that its impact increases with enhancement of mean monthly temperature. In addition, the occurrence of MCSs depends closely on the configuration of the Sudan Low in the southwest of Iran.

  20. A synoptic climatology of derecho producing mesoscale convective systems in the North-Central Plains

    NASA Astrophysics Data System (ADS)

    Bentley, Mace L.; Mote, Thomas L.; Byrd, Stephen F.

    2000-09-01

    Synoptic-scale environments favourable for producing derechos, or widespread convectively induced windstorms, in the North-Central Plains are examined with the goal of providing pattern-recognition/diagnosis techniques. Fifteen derechos were identified across the North-Central Plains region during 1986-1995. The synoptic environment at the initiation, mid-point and decay of each derecho was then evaluated using surface, upper-air and National Center for Atmospheric Research (NCAR)/National Center for Environmental Prediction (NCEP) reanalysis datasets.Results suggest that the synoptic environment is critical in maintaining derecho producing mesoscale convective systems (DMCSs). The synoptic environment in place downstream of the MCS initiation region determines the movement and potential strength of the system. Circulation around surface low pressure increased the instability gradient and maximized leading edge convergence in the initiation region of nearly all events regardless of DMCS location or movement. Other commonalities in the environments of these events include the presence of a weak thermal boundary, high convective instability and a layer of dry low-to-mid-tropospheric air. Of the two corridors sampled, northeastward moving derechos tend to initiate east of synoptic-scale troughs, while southeastward moving derechos form on the northeast periphery of a synoptic-scale ridge. Other differences between these two DMCS events are also discussed.

  1. Contrasting a non-developing African mesoscale convective system with the precursor to Hurricane Helene (2006)

    NASA Astrophysics Data System (ADS)

    Rivera, G.; Fuentes, J. D.; Evans, J. L.; Hamilton, H. L.

    2015-12-01

    Mesoscale convective systems (MCSs) in West Africa traverse strong thermodynamic gradients during their westward propagation from land to ocean. Some of the systems continue to develop after crossing the coastline and may ultimately develop into tropical cyclones, while others do not. Understanding the lifecycle behavior of these convective systems and the factors that contribute to their continuous development as they transition from a continental environment to a marine environment poses a challenge. We examine the difference between two MCSs, one that continued to develop when it crossed the West African coast and one that did not, using European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA Interim) and Tropical Rainfall Measurement Mission (TRMM) 3B42 data. The non-developing MCS that intensified briefly while over land, weakened as soon as it crossed the coast. Preliminary results show that the developing MCS interacted with two cyclonic vortices, one associated with an African Easterly Wave that was propagating towards the coast and the other vortex generated by the topography near the coast.

  2. Dominant processes of extreme rainfall-producing mesoscale convective system over southeastern Korea: 7 July 2009 case

    NASA Astrophysics Data System (ADS)

    Jeong, J.-H.; Lee, D.-I.; Wang, C.-C.; Han, I.-S.

    2015-10-01

    An extreme rainfall-producing mesoscale convective system (MCS) associated with the Changma front in southeastern Korea was investigated using observational data. This event recorded historic rainfall and led to devastating flash floods and landslides in the Busan metropolitan area on 7 July 2009. The aim of the present study is to analyze and better understand the synoptic and mesoscale environment, and the behavior of quasi-stationary MCS causing extreme rainfall. Synoptic and mesoscale analyses indicate that the MCS and heavy rainfall occurred association with a stationary front which resembled a warm front in structure. A strong southwesterly low-level jet (LLJ) transported warm and humid air and supplied the moisture toward the front, and the air rose upwards above the frontal surface. As the moist air was conditionally unstable, repeated upstream initiation of deep convection by back-building occurred at the coastline, while old cells moved downstream parallel to the convective line with training effect. Because the motion of convective cells nearly opposed the backward propagation, the system as a whole moved slowly. The back-building behavior was linked to the convectively produced cold pool and its outflow boundary, which played an essential role in the propagation and maintenance of the rainfall system. As a result, the quasi-stationary MCS caused a prolonged duration of heavy rainfall, leading to extreme rainfall over the Busan metropolitan area.

  3. Investigations of The Structure of Mesoscale Convective Systems Over The Sea of Japan

    NASA Astrophysics Data System (ADS)

    Mezrin, M. Yu.; Starokoltsev, E. V.; Fujiyoshi, Yasushi

    Under the Joint Research Agreement between the Central Aerological Observatory of the Russian Federal Service for Hydrometeorology and Environmental Monitoring, Russia (CAO) and Japan Science and Technology Corporation, Japan (JST), investigations of the structure and formation/development mechanisms of mesoscale convective systems in the Sea of Japan area were carried out in January- February 2001 from board a Russian research aircraft IL-18. The aircraft was equipped with navigation and research instruments to investigate diverse atmospheric and cloud parameters, including instrumentation to study turbulent transport of moisture, heat, etc. The meteorological situation was characterized by a surge of cold, dry continental air to the rear of a cold front (i.e., from Siberia to the open surface of the Sea of Japan). Horizontal measurements were made during flights at altitudes of 100, 500, 1500, and 3000 m, between Vladivistok, Russia, and Sado Island of Japan. As a result of the investigations of turbulent moisture transport at a 100-m level, mesostructure features of the transport were observed having a horizontal scale of about 30 km and an amplitude of about 0.100 g/m2s. The shape and magnitude of such features repeated at a 500-m level, their position shifting windward with time. This phenomenon was evidently caused by cylindrical convection, whose spatial structure showed in the arrangement of cloud streets formed at a 1500-m level. Satellite pictures of the cloud streets were used.

  4. Relative influence of meteorological conditions and aerosols on the lifetime of mesoscale convective systems

    NASA Astrophysics Data System (ADS)

    Chakraborty, Sudip; Fu, Rong; Massie, Steven T.; Stephens, Graeme

    2016-07-01

    Using collocated measurements from geostationary and polar-orbital satellites over tropical continents, we provide a large-scale statistical assessment of the relative influence of aerosols and meteorological conditions on the lifetime of mesoscale convective systems (MCSs). Our results show that MCSs’ lifetime increases by 3–24 h when vertical wind shear (VWS) and convective available potential energy (CAPE) are moderate to high and ambient aerosol optical depth (AOD) increases by 1 SD (1σ). However, this influence is not as strong as that of CAPE, relative humidity, and VWS, which increase MCSs’ lifetime by 3–30 h, 3–27 h, and 3–30 h per 1σ of these variables and explain up to 36%, 45%, and 34%, respectively, of the variance of the MCSs’ lifetime. AOD explains up to 24% of the total variance of MCSs’ lifetime during the decay phase. This result is physically consistent with that of the variation of the MCSs’ ice water content (IWC) with aerosols, which accounts for 35% and 27% of the total variance of the IWC in convective cores and anvil, respectively, during the decay phase. The effect of aerosols on MCSs’ lifetime varies between different continents. AOD appears to explain up to 20–22% of the total variance of MCSs’ lifetime over equatorial South America compared with 8% over equatorial Africa. Aerosols over the Indian Ocean can explain 20% of total variance of MCSs’ lifetime over South Asia because such MCSs form and develop over the ocean. These regional differences of aerosol impacts may be linked to different meteorological conditions.

  5. Relative influence of meteorological conditions and aerosols on the lifetime of mesoscale convective systems.

    PubMed

    Chakraborty, Sudip; Fu, Rong; Massie, Steven T; Stephens, Graeme

    2016-07-01

    Using collocated measurements from geostationary and polar-orbital satellites over tropical continents, we provide a large-scale statistical assessment of the relative influence of aerosols and meteorological conditions on the lifetime of mesoscale convective systems (MCSs). Our results show that MCSs' lifetime increases by 3-24 h when vertical wind shear (VWS) and convective available potential energy (CAPE) are moderate to high and ambient aerosol optical depth (AOD) increases by 1 SD (1σ). However, this influence is not as strong as that of CAPE, relative humidity, and VWS, which increase MCSs' lifetime by 3-30 h, 3-27 h, and 3-30 h per 1σ of these variables and explain up to 36%, 45%, and 34%, respectively, of the variance of the MCSs' lifetime. AOD explains up to 24% of the total variance of MCSs' lifetime during the decay phase. This result is physically consistent with that of the variation of the MCSs' ice water content (IWC) with aerosols, which accounts for 35% and 27% of the total variance of the IWC in convective cores and anvil, respectively, during the decay phase. The effect of aerosols on MCSs' lifetime varies between different continents. AOD appears to explain up to 20-22% of the total variance of MCSs' lifetime over equatorial South America compared with 8% over equatorial Africa. Aerosols over the Indian Ocean can explain 20% of total variance of MCSs' lifetime over South Asia because such MCSs form and develop over the ocean. These regional differences of aerosol impacts may be linked to different meteorological conditions. PMID:27313203

  6. Large Charge Moment Change Lightning in an Oklahoma Mesoscale Convective System

    NASA Technical Reports Server (NTRS)

    Lang, Timothy J.; Cummer, Steven; Beasley, William; Flores-Rivera, Lizxandra; Lyons, Walt; MacGorman, Donald

    2014-01-01

    On 31 May 2013, a line of severe thunderstorms developed during the local afternoon in central Oklahoma, USA. One of the supercells produced the El Reno tornado, which caused significant damage and killed several people. During the 2300 UTC hour (during the mature supercell stage and just after the tornado began), the storm produced several positive cloud-to-ground (+CG) lightning strokes that featured large (> 75 C km) impulse charge moment changes (iCMCs - charge moment during the first 2 ms after the return stroke). These discharges occurred mainly in convection, in contrast to the typical pattern of large-CMC and sprite-parent +CGs occurring mainly in stratiform precipitation regions. After this time, the line of thunderstorms evolved over several hours into a large mesoscale convective system (MCS). By the 0700 UTC hour on 1 June 2013, the large- CMC pattern had changed markedly. Large-CMC negative CGs, which were absent early in the storm's lifetime, occurred frequently within convection. Meanwhile, large- CMC +CGs had switched to occurring mainly within the broad stratiform region that had developed during the intervening period. The evolution of the large-CMC lightning in this case will be examined using a mix of polarimetric data from individual radars, national mosaics of radar reflectivity, the Oklahoma Lightning Mapping Array (OKLMA), the Charge Moment Change Network (CMCN), and the National Lightning Detection Network (NLDN). A major goal of this study is understanding how storm structure and evolution affected the production of large-CMC lightning. It is anticipated that this will lead to further insight into how and why storms produce the powerful lightning that commonly causes sprites in the upper atmosphere.

  7. Large Charge Moment Change Lightning in an Oklahoma Mesoscale Convective System

    NASA Technical Reports Server (NTRS)

    Lang, Timothy J.; Cummer, Steven; Petersen, Danyal; Flores-Rivera, Lizxandra; Lyons, Walt; MacGorman, Donald; Beasley, William

    2014-01-01

    On 31 May 2013, a line of severe thunderstorms developed during the local afternoon in central Oklahoma, USA. One of the supercells produced the El Reno tornado, which caused significant damage and killed several people. During the 2300 UTC hour (during the mature supercell stage and just after the tornado began), the storm produced several positive cloud-to-ground (+CG) lightning strokes that featured large (> 100 C km) impulse charge moment changes (iCMCs; charge moment during the first 2 ms after the return stroke). These discharges occurred mainly in convection, in contrast to the typical pattern of large-CMC and sprite-parent +CGs occurring mainly in stratiform precipitation regions. After this time, the line of thunderstorms evolved over several hours into a large mesoscale convective system (MCS). By the 0700 UTC hour on 1 June 2013, the large-CMC pattern had changed markedly. Large-CMC negative CGs, which were absent early in the storm's lifetime, occurred frequently within convection. Meanwhile, large-CMC +CGs had switched to occurring mainly within the broad stratiform region that had developed during the intervening period. The evolution of the large-CMC lightning in this case will be examined using a mix of national mosaics of radar reflectivity, the Oklahoma Lightning Mapping Array (OKLMA), the Charge Moment Change Network (CMCN), and the National Lightning Detection Network (NLDN). A major goal of this study is understanding how storm structure and evolution affected the production of large-CMC lightning. It is anticipated that this will lead to further insight into how and why storms produce the powerful lightning that commonly causes sprites in the upper atmosphere.

  8. Analysis of ice crystals occuring in the upper high levels of tropical mesoscale convective systems

    NASA Astrophysics Data System (ADS)

    Delplanque, Alexandre

    2015-04-01

    In 2010 several test flights were performed in tropical marine meso-scale convective systems at flight levels between 10.5 and 10.8 km. Ice crystals were observed with a high speed CDD camera (image pixel resolution: 15 μ m, time resolution 0.007 s) hereafter called the Airbus nephelometer. In-cloud observations were not restricted to the stratiform regions of the MCS but also convective cores were intensely sampled. High number concentrations of ice crystals (N > 1000 L-1) and IWC of more than 4 g.m-3 could be observed. The main objective of our study is the retrieval of the ice water mass from ice particle number distribution and crystal habits, both observed by the Airbus nephelometer. The shape of ice particles was supposed to correspond to the form of oblate spheroids. A statistical study of the aspect ratio of crystal images was performed comparing two different geometrical approaches for the aspect ratio of their semi axis. One uses the ratio of minimum to maximum length, the other is based on the aspect ratio which best fits the crystal image. Different regions of the MCS present different mean aspect ratios measured at small scale (200 m). Variations of the aspect ratio seem to be associated with different nucleation and growth histories for the crystals. For regions with 'young' ice crystals, an anti-correlation between the aspect ratio and ice number concentration was observed. This observation is compared with the results obtained from simple diffusional growth modeling. To better quantify the characteristics of high concentrations of small ice crystal MCS regions, we propose to use the size distribution of the mean aspect ratio (from 100 μ m to 1 mm), to distinguish quite different behaviors for 'young' and 'mature' convective regions.

  9. A Modeling Study of Heating and Drying Effects of Convective Clouds in an Extratropical Mesoscale Convective System.

    NASA Astrophysics Data System (ADS)

    Ogura, Yoshi; Jiang, Jih-Yih

    1985-12-01

    The two-dimensional version of the cumulus ensemble model developed by Soong and Ogura is applied both to a prestorm situation and to the mature stage of the extratropical mesoscale convective system (MCS) that developed on 10-11 April 1979 (AVE-SESAME-79 I) over the central United States. The objective is to investigate the statistical properties of convection, developing in response to an imposed large-scale forcing, and the thermodynamic feedback effect of clouds on the large-scale environment in midlatitudes. The result is compared to that recently obtained by Tao for a tropical rainband.The outstanding result of the model integration for 17 h of physical time is that statistical properties of clouds averaged horizontally over 128 km of the model domain undergo temporal variations for a given time-independent large-scale forcing, rather than settling down into a steady state. When applied to a prestorm situation, the model predicts heavy precipitation that continues to fall for the first 5 h, followed by a 4 h period without precipitation. A second burst of deep convection then occurs. An analysis of the result reveals that the pause of precipitation occurs when the subcloud layer is dried up primarily due to the net vertical transport of moisture associated with clouds. Convection again starts developing when the moisture in the subcloud layer is replenished by the imposed large-scale forcing. The precipitation rate averaged over the precipitation period is found to exceed the supply of moisture by the large-scale forcing. The result implies that the fraction of moisture convergence in a vertical air column that contributes to moisten the environmental atmosphere in Kuo's cumulus parameterization scheme can be negative.Further, the result indicates the following: 1) The updraft mass flux increases with height until it reaches the local maximum at 350 mb, indicating that the cloud population is dominated by deep clouds, in contrast to the bimodal or broad

  10. Nonhydrostatic effects in numerical modeling of mesoscale convective systems and baroclinic waves

    NASA Technical Reports Server (NTRS)

    Cohen, Charles

    1993-01-01

    The present investigation is concerned with the role of convection upon mesoscale modeling results, particularly when the grid resolution becomes small enough that there is not a clear scale separation between the explicitly resolved circulations and the parameterized clouds. In those situations, the vertical accelerations in explicitly resolved circulations become strong enough that the hydrostatic assumption may no longer be valid. These concerns arise from interests in improving mesoscale modeling per se and in improving the subgrid-scale parameterizations in global models. The hydrostatic and the nonhydrostatic options of the Colorado State University Regional Atmospheric Modeling System were used to simulate dry gravity currents in two dimensions, using several different horizontal grid sizes. With horizontal grid intervals of 10 km or less, nonhydrostatic simulations produce wider and colder heads and weaker but wider forced updrafts than do the hydrostatic simulations. Comparing the hydrostatic and nonhydrostatic models show that the difference between the vertical mass fluxes is much less than the difference between the vertical velocities. When the grid is fine enough to resolve the head of the gravity current, horizontal convergence at the gust front extends upwards almost to the head of the cold air. Vertical mass flux in the forced updraft at the front varies with horizontal grid size mainly as a function of the height of the simulated head. For coarser grids, which do not resolve the head, vertical mass flux at all heights decreases with increasing horizontal grid size. A comparison on nonhydrostatic simulations with horizontal grid intervals of 1 km and 2 km illustrates how decreasing the grid size does not necessarily increase the intensity of the resolved circulation. The smaller grid enables the simulated gravity current to entrain a bubble of warm air behind the head, which results in a weaker circulation with a shorter head and weaker updraft.

  11. Simulation of quasi-linear mesoscale convective systems in northern China: Lightning activities and storm structure

    NASA Astrophysics Data System (ADS)

    Li, Wanli; Qie, Xiushu; Fu, Shenming; Su, Debin; Shen, Yonghai

    2016-01-01

    Two intense quasi-linear mesoscale convective systems (QLMCSs) in northern China were simulated using the WRF (Weather Research and Forecasting) model and the 3D-Var (three-dimensional variational) analysis system of the ARPS (Advanced Regional Prediction System) model. A new method in which the lightning density is calculated using both the precipitation and non-precipitation ice mass was developed to reveal the relationship between the lightning activities and QLMCS structures. Results indicate that, compared with calculating the results using two previous methods, the lightning density calculated using the new method presented in this study is in better accordance with observations. Based on the calculated lightning densities using the new method, it was found that most lightning activity was initiated on the right side and at the front of the QLMCSs, where the surface wind field converged intensely. The CAPE was much stronger ahead of the southeastward progressing QLMCS than to the back it, and their lightning events mainly occurred in regions with a large gradient of CAPE. Comparisons between lightning and non-lightning regions indicated that lightning regions featured more intense ascending motion than non-lightning regions; the vertical ranges of maximum reflectivity between lightning and non-lightning regions were very different; and the ice mixing ratio featured no significant differences between the lightning and non-lightning regions.

  12. Global Variability of Mesoscale Convective System Anvil Structure from A-Train Satellite Data

    NASA Technical Reports Server (NTRS)

    Yuan, Jian; Houze, Robert A.

    2010-01-01

    Mesoscale convective systems (MCSs) in the tropics produce extensive anvil clouds, which significantly affect the transfer of radiation. This study develops an objective method to identify MCSs and their anvils by combining data from three A-train satellite instruments: Moderate Resolution Imaging Spectroradiometer (MODIS) for cloud-top size and coldness, Advanced Microwave Scanning Radiometer for Earth Observing System (AMSR-E) for rain area size and intensity, and CloudSat for horizontal and vertical dimensions of anvils. The authors distinguish three types of MCSs: small and large separated MCSs and connected MCSs. The latter are MCSs sharing a contiguous rain area. Mapping of the objectively identified MCSs shows patterns of MCSs that are consistent with previous studies of tropical convection, with separated MCSs dominant over Africa and the Amazon regions and connected MCSs favored over the warm pool of the Indian and west Pacific Oceans. By separating the anvil from the raining regions of MCSs, this study leads to quantitative global maps of anvil coverage. These maps are consistent with the MCS analysis, and they lay the foundation for estimating the global radiative effects of anvil clouds. CloudSat radar data show that the modal thickness of MCS anvils is about 4-5 km. Anvils are mostly confined to within 1.5-2 times the equivalent radii of the primary rain areas of the MCSs. Over the warm pool, they may extend out to about 5 times the rain area radii. The warm ocean MCSs tend to have thicker non-raining and lightly raining anvils near the edges

  13. Mean state and kinematic properties of mesoscale convective systems over West Africa

    NASA Astrophysics Data System (ADS)

    Ogungbenro, Stephen B.; Ajayi, V. O.; Adefolalu, D. O.

    2016-04-01

    A 17-year (1984 to 2000) dataset of brightness temperature (T b) was employed to study the spatial and temporal scales of mesoscale convective systems (MCS) over West Africa. The kinematic properties of MCS were tested using wind products. A threshold brightness temperature (T b) of ≤213 K and spatial coverage specifications of more than 5000 km2 were used as two set criteria for initiating MCS tracking. MCS occurrences vary in seasons and locations over West Africa, and their activities vary with different weather zones. They can appear at any time of the day, but this study revealed a significant preference for early morning hours and night hours over continental West Africa. The well-organized systems occur between July and September in the Sahel, and between May and September in the Savanna band. MCS activities in the Gulf of Guinea peak between March and April, while the Savanna and Sahel zones peak between June and August. The produced annual atlas gives a spatial account of areas of MCS dominance in West Africa. The presence of African Easterly Jet (AEJ) and Tropical Easterly Jet (TEJ), and deep monsoon depth all characterize an environment where MCS thrive. Kinematic study of a typical MCS reveals that the monsoon depth increases at the passage of MCS, with cyclonic vorticity dominating from the surface to 300 hpa while anticyclonic vorticity was observed around 200 hpa, and this confirms the importance of low level convergence and upper level divergence as the major requirements for storm mobilization and maintenance.

  14. Mesoscale convective systems in Spain: instability conditions and moisture sources involved

    NASA Astrophysics Data System (ADS)

    Queralt, S.; Hernandez, E.; Gallego, D.; Lorente, P.

    2008-04-01

    Source-receptor water vapor content areas are analyzed for a particular case of deep mesoscale convective system (MCS) developed over the Mediterranean margin of Spain in October 1982. The aim of this work is to study simultaneously the atmospheric instability conditions and water vapour fluxes which finally resulted in very severe precipitation rates, reaching up to 600 mm in a single day. Humidity amounts and transport are quantified along the trajectories computed from a lagrangian particle simulation model (FLEXPART6.2). To evaluate the precipitation probability, the water vapor content and both thermodynamic and dynamic atmospheric instability components were assessed. The October 1982 Iberian MCS occurred as a consequence of a deep cutoff low detected between 500 and 200 hPa levels. The dynamical instability was measured through potential vorticity anomalies and Q vector divergence, which presented their maximum and minimum centers respectively over south-eastern Iberia. Synoptic and dynamic instability conditions were obtained from the ERA-40 reanalysis dataset. It is observed that during this severe weather episode, the specific humidity increased along the lowest and easternmost trajectories, which are mainly spread over the Mediterranean Sea.

  15. Development of a regional rain retrieval algorithm for exclusive mesoscale convective systems over peninsular India

    NASA Astrophysics Data System (ADS)

    Dutta, Devajyoti; Sharma, Sanjay; Das, Jyotirmay; Gairola, R. M.

    2012-06-01

    The present study emphasize the development of a region specific rain retrieval algorithm by taking into accounts the cloud features. Brightness temperatures (Tbs) from various TRMM Microwave Imager (TMI) channels are calibrated with near surface rain intensity as observed from the TRMM - Precipitation Radar. It shows that Tb-R relations during exclusive-Mesoscale Convective System (MCS) events have greater dynamical range compared to combined events of non-MCS and MCS. Increased dynamical range of Tb-R relations for exclusive-MCS events have led to the development of an Artificial Neural Network (ANN) based regional algorithm for rain intensity estimation. By using the exclusive MCSs algorithm, reasonably good improvement in the accuracy of rain intensity estimation is observed. A case study of a comparison of rain intensity estimation by the exclusive-MCS regional algorithm and the global TRMM 2A12 rain product with a Doppler Weather Radar shows significant improvement in rain intensity estimation by the developed regional algorithm.

  16. A mesoscale gravity wave event observed during CCOPE. II - Interactions between mesoscale convective systems and the antecedent waves. [Cooperative Convection Precipitation Experiment

    NASA Technical Reports Server (NTRS)

    Koch, Steven E.; Golus, Robert E.; Dorian, Paul B.

    1988-01-01

    The interactions between preexisting gravity waves and convective systems were investigated using data obtained by the Cooperative Convection Precipitation Experiment observational network in Montana on July 11-12, 1981. The results indicate that strong convection substantially affects gravity waves locally by augmenting the wave amplitude, reducing its wavelength, distorting the wave shape, altering the wave phase velocity, and greatly weakening the in-phase covariance between the perturbation wind and pressure fields. These convective effects upon gravity waves are explained in terms of hydrostatic and nonhydrostatic pressure forces and gust front processes associated with thunderstorms.

  17. Investigation into a displacement bias in numerical weather prediction models' forecasts of mesoscale convective systems

    NASA Astrophysics Data System (ADS)

    Yost, Charles

    Although often hard to correctly forecast, mesoscale convective systems (MCSs) are responsible for a majority of warm-season, localized extreme rain events. This study investigates displacement errors often observed by forecasters and researchers in the Global Forecast System (GFS) and the North American Mesoscale (NAM) models, in addition to the European Centre for Medium Range Weather Forecasts (ECMWF) and the 4-km convection allowing NSSL-WRF models. Using archived radar data and Stage IV precipitation data from April to August of 2009 to 2011, MCSs were recorded and sorted into unique six-hour intervals. The locations of these MCSs were compared to the associated predicted precipitation field in all models using the Method for Object-Based Diagnostic Evaluation (MODE) tool, produced by the Developmental Testbed Center and verified through manual analysis. A northward bias exists in the location of the forecasts in all lead times of the GFS, NAM, and ECMWF models. The MODE tool found that 74%, 68%, and 65% of the forecasts were too far to the north of the observed rainfall in the GFS, NAM and ECMWF models respectively. The higher-resolution NSSL-WRF model produced a near neutral location forecast error with 52% of the cases too far to the south. The GFS model consistently moved the MCSs too quickly with 65% of the cases located to the east of the observed MCS. The mean forecast displacement error from the GFS and NAM were on average 266 km and 249 km, respectively, while the ECMWF and NSSL-WRF produced a much lower average of 179 km and 158 km. A case study of the Dubuque, IA MCS on 28 July 2011 was analyzed to identify the root cause of this bias. This MCS shattered several rainfall records and required over 50 people to be rescued from mobile home parks from around the area. This devastating MCS, which was a classic Training Line/Adjoining Stratiform archetype, had numerous northward-biased forecasts from all models, which are examined here. As common with

  18. Vertical Structures of Anvil Clouds of Tropical Mesoscale Convective Systems Observed by CloudSat

    NASA Technical Reports Server (NTRS)

    Yuan, J.; Houze, R. A., Jr.; Heymsfield, A.

    2011-01-01

    A global study of the vertical structures of the clouds of tropical mesoscale convective systems (MCSs) has been carried out with data from the CloudSat Cloud Profiling Radar. Tropical MCSs are found to be dominated by cloud-top heights greater than 10 km. Secondary cloud layers sometimes occur in MCSs, but outside their primary raining cores. The secondary layers have tops at 6--8 and 1--3 km. High-topped clouds extend outward from raining cores of MCSs to form anvil clouds. Closest to the raining cores, the anvils tend to have broader distributions of reflectivity at all levels, with the modal values at higher reflectivity in their lower levels. Portions of anvil clouds far away from the raining core are thin and have narrow frequency distributions of reflectivity at all levels with overall weaker values. This difference likely reflects ice particle fallout and therefore cloud age. Reflectivity histograms of MCS anvil clouds vary little across the tropics, except that (i) in continental MCS anvils, broader distributions of reflectivity occur at the uppermost levels in the portions closest to active raining areas; (ii) the frequency of occurrence of stronger reflectivity in the upper part of anvils decreases faster with increasing distance in continental MCSs; and (iii) narrower-peaked ridges are prominent in reflectivity histograms of thick anvil clouds close to the raining areas of connected MCSs (superclusters). These global results are consistent with observations at ground sites and aircraft data. They present a comprehensive test dataset for models aiming to simulate process-based upper-level cloud structure around the tropics.

  19. Vertical Structures of Anvil Clouds of Tropical Mesoscale Convective Systems Observed by CloudSat

    NASA Technical Reports Server (NTRS)

    Hence, Deanna A.; Houze, Robert A.

    2011-01-01

    A global study of the vertical structures of the clouds of tropical mesoscale convective systems (MCSs) has been carried out with data from the CloudSat Cloud Profiling Radar. Tropical MCSs are found to be dominated by cloud-top heights greater than 10 km. Secondary cloud layers sometimes occur in MCSs, but outside their primary raining cores. The secondary layers have tops at 6 8 and 1 3 km. High-topped clouds extend outward from raining cores of MCSs to form anvil clouds. Closest to the raining cores, the anvils tend to have broader distributions of reflectivity at all levels, with the modal values at higher reflectivity in their lower levels. Portions of anvil clouds far away from the raining core are thin and have narrow frequency distributions of reflectivity at all levels with overall weaker values. This difference likely reflects ice particle fallout and therefore cloud age. Reflectivity histograms of MCS anvil clouds vary little across the tropics, except that (i) in continental MCS anvils, broader distributions of reflectivity occur at the uppermost levels in the portions closest to active raining areas; (ii) the frequency of occurrence of stronger reflectivity in the upper part of anvils decreases faster with increasing distance in continental MCSs; and (iii) narrower-peaked ridges are prominent in reflectivity histograms of thick anvil clouds close to the raining areas of connected MCSs (superclusters). These global results are consistent with observations at ground sites and aircraft data. They present a comprehensive test dataset for models aiming to simulate process-based upper-level cloud structure around the tropics.

  20. Evolution of Mesoscale Convective System over the South Western Peninsular India: Observations from Microwave Radiometer and Simulations using WRF

    NASA Astrophysics Data System (ADS)

    Uma, K. N.; Krishna Moorthy, K.; Sijikumar, S.; Renju, R.; Tinu, K. A.; Raju, Suresh C.

    2012-07-01

    Meso-scale Convective Systems (MCS) are important in view of their large cumulous build-up, vertical extent, short horizontal extent and associated thundershowers. The Microwave Radiometer Profiler (MRP) over the equatorial coastal station Thiruvanathapuram (Trivandrum, 8.55oN, 76.9oE), has been utilized to understand the genesis of Mesoscale convective system (MCS), that occur frequently during the pre-monsoon season. Examination of the measurement of relative humidity, temperature and cloud liquid water measurements, over the zenith and two scanning elevation angles (15o) viewing both over the land and the sea respectively revealed that the MCS generally originate over the land during early afternoon hours, propagate seawards over the observational site and finally dissipate over the sea, with accompanying rainfall and latent heat release. The simulations obtained using Advanced Research-Weather Research and Forecast (WRF-ARW) model effectively reproduces the thermodynamical and microphysical properties of the MCS. The time duration and quantity of rainfall obtained by the simulations also well compared with the observations. Analysis also suggests that wind shear in the upper troposphere is responsible for the growth and the shape of the convective cloud.

  1. Mesoscale Convective Systems Which Do and Do Not Produce Sprites: Results From STEPS 2000

    NASA Astrophysics Data System (ADS)

    Lyons, W. A.; Andersen, L. M.; Nelson, T. E.; Cummer, S. A.; Jauget, N. C.; Huffines, G. R.

    2005-12-01

    During the Severe Thunderstorm Electrification and Precipitation Study (STEPS) conducted during the summer of 2000 over the High Plains, we addressed two basic questions. First, what are the characteristics of those positive cloud-to-ground strokes (+CGs) which produce transient luminous events (TLEs), especially sprites, halos and elves? It was found the vast majority TLEs optically confirmed over High Plains storms were associated with large charge moment change events (DMq), exceeding thresholds of several hundred C km, substantially larger than the DMq for "normal" lightning. This finding is entirely consistent with present theoretical models of sprite ignition at ~75 km due to conventional breakdown. The second question addressed concerned what types of storms produced these unusual CG discharges. Not all mesoscale convective systems (MCSs) produce TLEs, or if they do, do so only for certain stages in their life cycle. Why? Meteorological analyses of TLE-producing systems had determined that the TLE parent +CGs were concentrated mostly in the stratiform region of their parent storms. Initial and updated analyses for Lightning Mapping Array data from the New Mexico Tech system suggested that the majority of the charge in the parent +CGs was removed from relatively low altitudes in the storm, typically 3 to 5 km AGL. After summarizing the characteristics of over 1500 TLEs and their parent MCSs, some clear criteria have become evident. First the cloud top canopy must be larger than 20,000 sq. km at the 50C level, and the coldest temperature must be at least -55C. Second, the peak reflectivity somewhere in the parent storm must exceed 55 dBZ. This requirement for a very tall and also intense storm initially seems at odds with the known environment of TLE parent CGs (low in the startiform region). Yet, as will be discussed, the emerging conceptual models of TLEs within trailing stratiform regions suggests the overall picture is indeed consistent with what is known

  2. Charge transfer and in-cloud structure of large-charge-moment positive lightning strokes in a mesoscale convective system

    NASA Astrophysics Data System (ADS)

    Lu, Gaopeng; Cummer, Steven A.; Li, Jingbo; Han, Feng; Blakeslee, Richard J.; Christian, Hugh J.

    2009-08-01

    Lightning observations in the very high frequency band and measurements of ultra low frequency magnetic fields are analyzed to investigate the charge transfer and in-cloud structure of eight positive cloud-to-ground (+CG) strokes in a mesoscale convective system. Although no high altitude images were recorded, these strokes contained large charge moment changes (1500-3200 C·km) capable of producing nighttime sprites. Even though the convective region of the storm was where the flashes originated and where the CG strokes could occur, the charge transferred to ground was mainly from the stratiform region. The post-stroke long continuing currents were connected to highly branched negative leader extension into the stratiform region. While the storm dissipated, the altitude of negative leader propagation in the stratiform area dropped gradually from 8 to 5 km, indicating that in some and perhaps all of these strokes, it was the upper positive charge in the stratiform region that was transferred.

  3. Impact of a Stochastic Parameterization of Cumulus Convection Using Cellular Automata in a Meso-Scale Ensemble Prediction System.

    NASA Astrophysics Data System (ADS)

    Bengtsson, L.

    2014-12-01

    A common way of addressing forecast uncertainty in Numerical Weather Prediction (NWP) models is to use ensemble prediction. The idea behind ensemble predictionis to simulate the sensitivity of the forecast to the initial and boundary conditions, as well as model construction error, such as sub-grid physical parameterizations. Existing methods used in order to account for such model consturction uncertainty include; multi-model ensembles, adding random perturbations to the tendencies produced by the parameterizations, or perturbing parameters within the parameterizations. Although such methods are successful in a probabilistic sense, individual ensemble members can be degraded in a deterministic sense by adding random non-physical perturbations. Furthermore, different ensemble members can have different bias (and skill) since they are based on separate models and/or parameters. Another way of accounting for model uncertainty (due to sub-grid variability) is to introduce random variability in the convection parameterization itself. Here we will present the impact of the stochastic deep convection parameterization using cellular automata described in Bengtsson et. al. 2013, as implemented in the high resolution meso-scale ensemble prediction system HarmonEPS. The questions we would like to answer are; can we improve the forecast skill both in a deterministic and probabilistic sense using the stochastic convection scheme? Can the stochastic parameterization in terms of the spread/skill relationship compete with the multi-model approach? Furthermore, the stochastic parameterization proposed in Bengtsson et. al. 2013 addresses lateral communication between model grid-boxes by using a cellular automaton. It was demonstrated that the scheme in a deterministic model is capable of contributing to the organization of convective squall-lines and meso-scale convective systems. We study if and how uncertainties with origin on the sub-grid scale transfer to the larger atmospheric

  4. Controls on phase composition and ice water content in a convection-permitting model simulation of a tropical mesoscale convective system

    NASA Astrophysics Data System (ADS)

    Franklin, Charmaine N.; Protat, Alain; Leroy, Delphine; Fontaine, Emmanuel

    2016-07-01

    Simulations of tropical convection from an operational numerical weather prediction model are evaluated with the focus on the model's ability to simulate the observed high ice water contents associated with the outflow of deep convection and to investigate the modelled processes that control the phase composition of tropical convective clouds. The 1 km horizontal grid length model that uses a single-moment microphysics scheme simulates the intensification and decay of convective strength across the mesoscale convective system. However, deep convection is produced too early, the OLR (outgoing longwave radiation) is underestimated and the areas with reflectivities > 30 dBZ are overestimated due to too much rain above the freezing level, stronger updraughts and larger particle sizes in the model. The inclusion of a heterogeneous rain-freezing parameterisation and the use of different ice size distributions show better agreement with the observed reflectivity distributions; however, this simulation still produces a broader profile with many high-reflectivity outliers demonstrating the greater occurrence of convective cells in the simulations. Examining the phase composition shows that the amount of liquid and ice in the modelled convective updraughts is controlled by the following: the size of the ice particles, with larger particles growing more efficiently through riming and producing larger IWC (ice water content); the efficiency of the warm rain process, with greater cloud water contents being available to support larger ice growth rates; and exclusion or limitation of graupel growth, with more mass contained in slower falling snow particles resulting in an increase of in-cloud residence times and more efficient removal of LWC (liquid water content). In this simulated case using a 1 km grid length model, horizontal mass divergence in the mixed-phase regions of convective updraughts is most sensitive to the turbulence formulation. Greater mixing of environmental air

  5. Attributes of mesoscale convective systems at the land-ocean transition in Senegal during NASA African Monsoon Multidisciplinary Analyses 2006

    NASA Astrophysics Data System (ADS)

    Delonge, Marcia S.; Fuentes, Jose D.; Chan, Stephen; Kucera, Paul A.; Joseph, Everette; Gaye, Amadou T.; Daouda, Badiane

    2010-05-01

    In this study we investigate the development of a mesoscale convective system (MCS) as it moved from West Africa to the Atlantic Ocean on 31 August 2006. We document surface and atmospheric conditions preceding and following the MCS, particularly near the coast. These analyses are used to evaluate how thermodynamic and microphysical gradients influence storms as they move from continental to maritime environments. To achieve these goals, we employ observations from NASA African Monsoon Multidisciplinary Analyses (NAMMA) from the NASA S band polarimetric Doppler radar, a meteorological flux tower, upper-air soundings, and rain gauges. We show that the MCS maintained a convective leading edge and trailing stratiform region as it propagated from land to ocean. The initial strength and organization of the MCS were associated with favorable antecedent conditions in the continental lower atmosphere, including high specific humidity (18 g kg-1), temperatures (300 K), and wind shear. While transitioning, the convective and stratiform regions became weaker and disorganized. Such storm changes were linked to less favorable thermodynamic, dynamic, and microphysical conditions over ocean. To address whether storms in different life-cycle phases exhibited similar features, a composite analysis of major NAMMA events was performed. This analysis revealed an even stronger shift to lower reflectivity values over ocean. These findings support the hypothesis that favorable thermodynamic conditions over the coast are a prerequisite to ensuring that MCSs do not dissipate at the continental-maritime transition, particularly due to strong gradients that can weaken West African storms moving from land to ocean.

  6. The impact of soil moisture inhomogeneities on modification of a mesoscale convective system: a budget-based model analysis

    NASA Astrophysics Data System (ADS)

    Adler, Bianca; Gantner, Leonhard; Kalthoff, Norbert

    2010-05-01

    In order to investigate the sensitivity of a mesoscale convective system (MCS) to soil moisture inhomogeneities in West Africa cloud-resolving simulations with the COSMO-Model initialized with European Centre for Medium-range Weather Forecasts analyses data were performed. Three scenarios were investigated: homogeneous soil type and soil moisture (HOM) and homogeneous soil type with a north-south oriented band of two degrees width with reduced soil moisture (BANDT) and with increased soil moisture (BANDM). In all experiments an MCS developed east of the band in the late afternoon. Precipitation related to the MCS was continuously strong in HOM. When the MCS approached the band with reduced soil moisture in BANDT precipitation decreased because of higher convective inhibition (CIN) ahead of the band. Reaching the drier band precipitation increased again. The moist band in BANDM caused an increase of precipitation ahead of the band and a decrease in the area with higher soil moisture caused by very high CIN values. Soil moisture inhomogeneities induced thermal circulations which led to modified conditions in the lower troposphere and to changes in CIN and accounted for the modification of precipitation of an MCS. In BANDT, precipitating cells already developed in the western part of the dry band in the late afternoon, where convergence, generated by thermal circulations and supported by downward mixing of momentum from the African Easterly Jet, triggered convection.

  7. The impact of soil moisture inhomogeneities on the modification of a mesoscale convective system: An idealised model study

    NASA Astrophysics Data System (ADS)

    Adler, Bianca; Kalthoff, Norbert; Gantner, Leonhard

    2011-07-01

    In order to investigate the sensitivity of a mesoscale convective system (MCS) to soil moisture inhomogeneities in West Africa, convection-permitting simulations with the COSMO model are performed. Three scenarios are investigated in detail: a homogeneous soil texture and soil moisture distribution and a homogeneous soil texture field with a north-south oriented band of two degrees width with reduced and increased soil moisture, respectively. In all experiments an MCS develops in the late afternoon some hundred kilometres east of the band with modified soil moisture. About 100 km east of the band, significant differences in precipitation occur: when the MCS approaches the band with lower soil moisture, precipitation decreases because of higher convective inhibition (CIN) and higher saturation deficit above the lifting condensation level ahead of the band. Reaching the dry band, precipitation restarts. The moist band causes an increase of precipitation ahead of the band and a decrease over it due to very high CIN and saturation deficit values above the boundary layer. In both cases, the soil moisture patterns induce a secondary circulation which modifies the conditions in the lower troposphere. These altered conditions are responsible for the changes of the convection-related parameters and for the modification of the MCS. Additionally, the dry band causes the evolution of precipitating cells over its western part in the late afternoon. The cells are triggered by superimposed convergences, one generated by the thermally-forced circulation of the dry band and the other one caused by different boundary-layer depths over the dry band and its surroundings. The very deep boundary layer over the dry band is accompanied by downward mixing of momentum from the African Easterly Jet, resulting in a reduced westerly monsoon flow so that convergence and divergence zones develop at the transitions from the deeper to the lower boundary layers.

  8. Evolution of the total lightning activity in a leading-line and trailing stratiform mesoscale convective system over Beijing

    NASA Astrophysics Data System (ADS)

    Liu, Dongxia; Qie, Xiushu; Xiong, Yajun; Feng, Guili

    2011-07-01

    Data from the Beijing SAFIR 3000 lightning detection system and Doppler radar provided some insights into the three-dimensional lightning structure and evolution of a leading-line and trailing-stratiform (LLTS) mesoscale convective system (MCS) over Beijing on 31 July 2007. Most of the lightning in the LLTS-MCS was intracloud (IC) lightning, while the mean ratio of positive cloud-to-ground (+CG) lightning to -CG lightning was 1:4, which was higher than the average value from previous studies. The majority of CG lightning occurred in the convective region of the radar echo, particularly at the leading edge of the front. Little IC lightning and little +CG lightning occurred in the stratiform region. The distribution of the CG lightning indicated that the storm had a tilted dipole structure given the wind shear or the tripole charge structure. During the storm's development, most of the IC lightning occurred at an altitude of ˜9.5 km; the lightning rate reached its maximum at 10.5 km, the altitude of IC lightning in the mature stage of the storm. When the thunderstorm began to dissipate, the altitude of the IC lightning decreased gradually. The spatial distribution of lightning was well correlated with the rainfall on the ground, although the peak value of rainfall appeared 75 min later than the peak lightning rate.

  9. The effect of the United States Great Lakes on the maintenance of derecho-producing mesoscale convective systems.

    NASA Astrophysics Data System (ADS)

    Bentley, M.; Sparks, J.; Graham, R.

    2003-04-01

    The primary aim of this research is to investigate the influence of the United States Great Lakes on the intensity of mesoscale convective systems (MCSs). One of the greatest nowcast challenges during the warm season is anticipating the impact of the Great Lakes on severe convection, particularly MCSs capable of producing damaging widespread windstorms known as derechos. Since a major derecho activity corridor lies over the Great Lakes region, it is important to understand the effects of the Lakes on the intensity and propagation of severe wind producing MCSs. Specific objectives of the research include: 1) The development of a short-term climatology of MCS events that have impacted the Great Lakes region over the past seven years; 2) An analysis of radar, satellite, surface (including buoy and lighthouse observations), and lake surface temperature data to determine the environmental conditions impacting the evolution of MCSs passing over a Great Lake; 3) An examination of MCS initiation times and seasonal frequencies of occurrence to delineate temporal consistencies in MCS evolution due to changing lake surface temperatures; and 4) The development of conceptual and forecast models to help anticipate MCS intensity and morphology as these systems interact with the Great Lakes environment.

  10. A comparison of cloud radiation fields obtained by in-situ aircraft measurements and a numerical simulation of a tropical mesoscale convective system

    NASA Technical Reports Server (NTRS)

    Wong, Takmeng; Stackhouse, Paul; Stephens, Graeme; Valero, Francisco

    1990-01-01

    The radiation budget of a tropical mesoscale convective system (MCS) is investigated by comparing in situ aircraft measurements obtained in a tropical MCS during the Equatorial Mesoscale Experiment (EMEX), and coordinated aircraft radiation measurements, with radiation profiles calculated using cloud properties obtained from a cloud model simulation of a tropical MCS. Preliminary results indicate that the stratiform region of the tropical System B simulation represents the gross properties of the observed stratiform system between 4.5 to 15 km. The flux profiles predicted by the model are consistent with observed fluxes.

  11. Contribution of a mesoscale analysis to convection nowcasting

    NASA Astrophysics Data System (ADS)

    Calas, C.; Ducrocq, V.; Sénési, S.

    We study the contribution of surface data to convection nowcasting outside mountainous areas and under weak synoptic forcing. The CANARI optimal interpolation mesoscale analysis scheme is used, which combines guess-fields from the fine-mesh (10 km) ALADIN model with hourly routine observations arising from a mesonet of automated ground stations. A tuning of this scheme is realized in order to fit convective systems scales (meso-β scale) as well as the mesonet scale. Then, these grid point analyses allow the computation of diagnostic fields such as Convective Available Potential Energy (CAPE) and MOisture CONvergence (MOCON), which are relevant in convection nowcasting. These diagnostic fields are compared with radar reflectivities observed from 1 to 5 hours later, so as to estimate their skill in predicting convection triggering. First results on six case studies show that convection generally occurs over areas where high CAPE values and persisting convergence were analyzed 4 to 1 hour before.

  12. Sensitivity of summer ensembles of super-parameterized US mesoscale convective systems to cloud resolving model microphysics and resolution

    NASA Astrophysics Data System (ADS)

    Elliott, E.; Yu, S.; Kooperman, G. J.; Morrison, H.; Wang, M.; Pritchard, M. S.

    2014-12-01

    Microphysical and resolution sensitivities of explicitly resolved convection within mesoscale convective systems (MCSs) in the central United States are well documented in the context of single case studies simulated by cloud resolving models (CRMs) under tight boundary and initial condition constraints. While such an experimental design allows researchers to causatively isolate the effects of CRM microphysical and resolution parameterizations on modeled MCSs, it is still challenging to produce conclusions generalizable to multiple storms. The uncertainty associated with the results of such experiments comes both from the necessary physical constraints imposed by the limited CRM domain as well as the inability to evaluate or control model internal variability. A computationally practical method to minimize these uncertainties is the use of super-parameterized (SP) global climate models (GCMs), in which CRMs are embedded within GCMs to allow their free interaction with one another as orchestrated by large-scale global dynamics. This study uses NCAR's SP Community Atmosphere Model 5 (SP-CAM5) to evaluate microphysical and horizontal resolution sensitivities in summer ensembles of nocturnal MCSs in the central United States. Storm events within each run were identified using an objective empirical orthogonal function (EOF) algorithm, then further calibrated to harmonize individual storm signals and account for the temporal and spatial heterogeneity between them. Three summers of control data from a baseline simulation are used to assess model internal interannual variability to measure its magnitude relative to sensitivities in a number of distinct experimental runs with varying CRM parameters. Results comparing sensitivities of convective intensity to changes in fall speed assumptions about dense rimed species, one- vs. two-moment microphysics, and CRM horizontal resolution will be discussed.

  13. Mesoscale Convective Systems in SCSMEX: Simulated by a Regional Climate Model and a Cloud Resolving Model

    NASA Technical Reports Server (NTRS)

    Tao, W.-K.; Wang, Y.; Qian, I.; Lau, W.; Shie, C.-L.; Starr, David (Technical Monitor)

    2002-01-01

    A Regional Land-Atmosphere Climate Simulation (RELACS) System is being developed and implemented at NASA Goddard Space Flight Center. One of the major goals of RELACS is to use a regional scale model with improved physical processes, in particular land-related processes, to understand the role of the land surface and its interaction with convection and radiation as well as the water and energy cycles in Indo-China/ South China Sea (SCS)/China, N. America and S. America. The Penn State/NCAR MM5 atmospheric modeling system, a state of the art atmospheric numerical model designed to simulate regional weather and climate, has been successfully coupled to the Goddard Parameterization for Land-Atmosphere-C loud Exchange (PLACE) land surface model. PLACE allows for the effects of vegetation, and thus important physical processes such as evapotranspiration and interception are included. The PLACE model incorporates vegetation type and has been shown in international comparisons to accurately predict evapotranspiration and runoff over a wide variety of land surfaces. The coupling of MM5 and PLACE creates a numerical modeling system with the potential to more realistically simulate the atmosphere and land surface processes including land-sea interaction, regional circulations such as monsoons, and flash flood events. RELACS has been used to simulate the onset of the South China Sea Monsoon in 1986, 1997 and 1998. Sensitivity tests on various land surface models, cumulus parameterization schemes (CPSs), sea surface temperature (SST) variations and midlatitude influences have been performed. These tests have indicated that the land surface model has a major impact on the circulation over the S. China Sea. CPSs can effect the precipitation pattern while SST variation can effect the precipitation amounts over both land and ocean. RELACS has also been used to understand the soil-precipitation interaction and feedback associated with a flood event that occurred in and around China

  14. Mesoscale Convective Systems in SCSMEX: Simulated by a Regional Climate Model and a Cloud Resolving Model

    NASA Technical Reports Server (NTRS)

    Tao, W.-K.; Wang, Y.; Lau, W.; Jia, Y.; Johnson, D.; Shie, C.-L.; Einaudi, Franco (Technical Monitor)

    2001-01-01

    A Regional Land-Atmosphere Climate Simulation (RELACS) System is being developed and implemented at NASA Goddard Space Flight Center. One of the major goals of RELACS is to use a regional scale model with improved physical processes, in particular land-related processes, to understand the role of the land surface and its interaction with convection and radiation as well as the water and energy cycles in Indo-China/South China Sea (SCS)/China, North America and South America. The Penn State/NCAR MM5 atmospheric modeling system, a state of the art atmospheric numerical model designed to simulate regional weather and climate, has been successfully coupled to the Goddard Parameterization for Land-Atmosphere-Cloud Exchange (PLACE) land surface model, PLACE allows for the effect A vegetation, and thus important physical processes such as evapotranspiration and interception are included. The PLACE model incorporates vegetation type and has been shown in international comparisons to accurately predict evapotranspiration and runoff over a wide variety of land surfaces. The coupling of MM5 and PLACE creates a numerical modeling system with the potential to more realistically simulate the atmosphere and land surface processes including land-sea interaction, regional circulations such as monsoons, and flash flood events. RELACS has been used to simulate the onset of the South China Sea Monsoon in 1986, 1991 and 1998. Sensitivity tests on various land surface models, cumulus parameterization schemes (CPSs), sea surface temperature (SST) variations and midlatitude influences have been performed. These tests have indicated that the land surface model has a major impact on the circulation over the South China Sea. CPSs can effect the precipitation pattern while SST variation can effect the precipitation amounts over both land and ocean. RELACS has also been used to understand the soil-precipitation interaction and feedback associated with a flood event that occurred in and around

  15. Chemical composition in mesoscale convective systems during AMMA and its impact on the NOx and O3 budget

    NASA Astrophysics Data System (ADS)

    Huntrieser, H.; Schlager, H.; Lichtenstern, M.; Roiger, A.; Stock, P.; Höller, H.; Schmidt, K.; Betz, H.-D.

    2010-05-01

    Deep convection is responsible for a rapid redistribution of trace gases between the boundary layer (BL) and the upper troposphere (UT). Large convective systems as mesoscale convective systems (MCS) very effectively contribute to this redistribution and change the oxidizing capacity in the UT over a wide area. Especially ozone (O3) plays an essential role in determining the oxidizing capacity of the atmosphere and contributes largely to the global greenhouse effect. The production of ozone is driven by the oxidation of carbon monoxide (CO) and volatile organic compounds (VOC) in presence of nitrogen oxide (NO) and sunlight. During the African Monsoon Multidisciplinary Analysis (AMMA) Special Observation Period carried out in West Africa in July and August 2006, the DLR research aircraft Falcon probed several MCS originating over different vegetation types both north and south of the ITCZ. The outflow of the MCS was penetrated close to the convective core but also further away (~500 km). In the fresh outflow, mean NOx (=NO+NO2) mixing ratios between 0.3-0.4 nmol mol-1 were observed. A rapid entrainment of ambient air in the UT was observed and both CO and O3 mixing ratios soon reached ambient conditions. However, in the aged outflow NOx mixing ratios were still clearly enhanced above the background. The potential for ozone production in the UT was very different depending on the chemical composition in the BL and two different cases are presented. Mainly pollution from the BL (transported upward) but also some production by lightning contributed to enhance the NOx mixing ratios in the fresh outflow. The nitrogen mass flux in the MCS outflow was determined and combined with measurements from a smaller lightning location network (LINET) and with global lightning observations from LIS. A global contribution of ~1-2 Tg(N) a-1 was estimated to be produced by lightning if we assume that MCS over West Africa are typical global thunderstorms. Compared to results from

  16. Synoptic controls of outer mesoscale convective systems with high impact rainfall in western north pacific tropical cyclones

    NASA Astrophysics Data System (ADS)

    Chen, Buo-Fu; Elsberry, Russell L.; Lee, Cheng-Shang

    2016-02-01

    The generality of our conceptual model of Outer Mesoscale Convective System (OMCS) formation in western North Pacific Tropical Cyclones (TCs) that was based on a case study of Typhoon Fengshen (2008) is examined with a data base of 80 OMCSs during 1999-2009. Formations of 41 "Intersection type (Itype)" OMCSs are similar to our conceptual model in that the key feature is an elongated moisture band in the northerly TC circulation that interacts with the southwest monsoon flow. Two subtypes of these I-type OMCSs are defined based on different formation locations relative to the TC center, and relative to the monsoon flow, that lead to either outward or more cyclonic propagation of the OMCSs. Twenty-five "Upstream type (U-type)" OMCSs form in a similar moisture band, but upstream of the intersection of the outer TC circulation with the monsoon flow. Another 12 "Monsoon type (Mtype)" OMCSs are different from our conceptual model as the formation locations are within the monsoon flow south to the confluence region of TC northerly circulation with the monsoon flow. In all of these OMCSs, the monsoon flow is an important contributor to their climatology and synoptic environment. Expanded conceptual models of where the threat of heavy rainfall associated with the four types of OMCSs may be expected are provided based on different OMCS formation locations relative to the TC center and different propagation vectors in a storm-relative coordinate system.

  17. Interaction between moist physics, cumulus parameterization and GCM grid spacing in simulations of midlatitude mesoscale convective systems

    NASA Astrophysics Data System (ADS)

    Anderson, C. J.; Posselt, D. J.; Arritt, R. W.

    2011-12-01

    We have examined the representation of MCSs in the NASA GEOS-5 GCM via simulations of the 1993 Midwest flood period. The 1993 Midwest flood period is well suited for evaluating the ability of climate models to simulate aggregate characteristics of midlatitude mesoscale convective systems (MCSs). During June-July 1993, MCSs were unusually frequent and unusually coherent in space. As a consequence, time average quantities have MCS signatures, and composites of MCSs can be constructed from a relatively brief data record. A suite of numerical experiments is conducted for the purpose of examining the relative importance of interactions between cumulus and moist physical parameterizations at different model horizontal grid spacings. We examine composites of simulated MCSs, and find that it is necessary, particularly as grid spacing is reduced from 1.0 to 0.25-degree, to properly represent the heating profiles created by the interaction between cumulus and moist physics parameterization. Reconfiguration of the cumulus parameterization results in an increase in the availability of cloud material to the grid scale moist physics parameterization, resulting in increased grid scale precipitation and less precipitation generated in the cumulus parameterization. This modification leads to improvement in the precipitation spatial autocorrelation and more realistic treatment of the distribution of midlatitude MCSs.

  18. Convective cell development and propagation in a mesoscale convective complex

    NASA Technical Reports Server (NTRS)

    Ahn, Yoo-Shin; Brundidge, Kenneth C.

    1987-01-01

    A case study was made of the mesoscale convective complex (MCC) which occurred over southern Oklahoma and northern Texas on 27 May 1981. This storm moved in an eastsoutheasterly direction and during much of its lifetime was observable by radars at Oklahoma City, Ok. and Stephenville, Tx. It was found that the direction of cell (VIP level 3 or more reflectivity) propagation was somewhat erratic but approximately the same as the system (VIP level 1 reflectivity) movement and the ambient wind. New cells developed along and behind the gust front make it appear that once the MCC is initiated, a synergistic relationship exists between the gust front and the MCC. The relationship between rainfall patterns and amounts and the infrared (IR) temperature field in the satellite imagery were examined. The 210 K isotherm of GOES IR imagery was found to encompass the rain area of the storm. The heaviest rainfall was in the vicinity of the VIP level 3 cells and mostly contained within the 205 K isotherm of GOES IR imagery.

  19. The climatology of lightning producing large impulse charge moment changes with an emphasis on mesoscale convective systems

    NASA Astrophysics Data System (ADS)

    Beavis, Nicholas

    The use of both total charge moment change (CMC) and impulse charge moment change (iCMC) magnitudes to assess the potential of a cloud-to-ground (CG) lightning stroke to induce a mesospheric sprite has been well described in literature. However, this work has primarily been carried out on a case study basis. To complement these previous case studies, climatologies of regional, seasonal, and diurnal observations of large-iCMC discharges are presented. In this study, large-iCMC discharges for thresholds > 100 and > 300 C km in both positive and negative polarities are analyzed on a seasonal basis using density maps of 2o by 2o resolution across the conterminous U.S. using data from the Charge Moment Change Network (CMCN). Also produced were local solar time diurnal distributions in eight different regions covering the lower 48 states as well as the Atlantic Ocean, including the Gulf Stream. In addition, National Lightning Detection Network (NLDN) cloud-to-ground (CG) flash diurnal distributions were included. The seasonal maps show the predisposition of large positive iCMCs to dominate across the Northern Great Plains, with large negative iCMCs favored in the Southeastern U.S. year-round. During summer, the highest frequency of large positive iCMCs across the Upper Midwest aligns closely with the preferred tracks of nocturnal mesoscale convective systems (MCSs). As iCMC values increase above 300 C km, the maximum shifts eastward of the 100 C km maximum in the Central Plains. The Southwestern U.S. also experiences significant numbers of large-iCMC discharges in summer, presumably due to convection associated with the North American Monsoon (NAM). The Gulf Stream is active year round, with a bias towards more large positive iCMCs in winter. Diurnal distributions in the eight regions support these conclusions, with a nocturnal peak in large-iCMC discharges in the Northern Great Plains and Great Lakes, an early- to mid-afternoon peak in the Intermountain West and the

  20. Mesoscale analyses and diagnostic parameters for deep convection nowcasting

    NASA Astrophysics Data System (ADS)

    Calas, C.; Ducrocq, V.; Sénési, S.

    2000-06-01

    We study the contribution of surface data to convection nowcasting over regions of modest orography and under weak synoptic forcing. Hourly mesoscale analyses are performed using the CANARI optimal interpolation analysis scheme, which combines first-guess fields from the fine mesh (10 km) ALADIN model with hourly routine observations arising from a mesonet of automated ground stations. These analyses then allow the computation of diagnostic parameters that quantify convective instability, low-level lifting processes and moisture supply: these are the convective available potential energy (CAPE) and the moisture convergence (MOCON). A tuning of the analysis scheme is needed first for it to fit the meso-?-scale. Then, the skill of the computed diagnostics for convection nowcasting is evaluated by comparing their fields with radar reflectivities observed between one and four hours after the analysis time. This is done for four selected convective situations. With regard to thunderstorm triggering, results show that this usually happens over areas of persistently high values of CAPE which undergo convergence continuously from four to one hour before the event; on the other hand, areas of persistent divergence are never associated with convective developments. In addition, the proposed criteria allow a significant reduction in the areal extent of predicted thunderstorms (i.e. decreasing the false-alarm rate) compared with what can be currently done on an operational basis, while maintaining a low non-detection rate. As to convection monitoring, we find that the organization of convective systems into a reflectivity line is preceded by a similar organization in the MOCON field from one to three hours ahead.

  1. HAIC/HIWC field campaign - investigating ice microphysics in high ice water content regions of mesoscale convective systems

    NASA Astrophysics Data System (ADS)

    Leroy, Delphine; Fontaine, Emmanuel; Schwarzenboeck, Alfons; Strapp, J. Walter; Lilie, Lyle; Dezitter, Fabien; Grandin, Alice

    2015-04-01

    Despite existing research programs focusing on tropical convection, high ice water content (IWC) regions in Mesoscale Convective Systems (MCS) - potentially encountered by commercial aircraft and related to reported in-service events - remain poorly documented either because investigation of such high IWC regions was not of highest priority or because utilized instrumentation was not capable of providing accurate cloud microphysical measurements. To gather quantitative data in high IWC regions, a multi-year international HAIC/HIWC (High Altitude Ice Crystals / High Ice Water Content) field project has been designed including a first field campaign conducted out of Darwin (Australia) in 2014. The French Falcon 20 research aircraft had been equipped among others with a state-of-the-art in situ microphysics package including the IKP (isokinetic evaporator probe which provides a reference measurement of IWC and TWC), the CDP (cloud droplet spectrometer probe measuring particles in the range 2-50 µm), the 2D-S (2D-Stereo, 10-1280 µm) and PIP (precipitation imaging probe, 100-6400 µm) optical array probes. Microphysical data collection has been performed mainly at -40°C and -30°C levels, whereas little data could be sampled at -50°C and at -15C/-10°C. The study presented here focuses on ice crystal size properties, thereby analyzing in detail the 2D image data from 2D-S and PIP optical array imaging probes. 2D images recorded with 2D-S and PIP were processed in order to extract a large variety of geometrical parameters, such as maximum diameter (Dmax), 2D surface equivalent diameter (Deq), and the corresponding number particle size distribution (PSD). Using the PSD information from both probes, a composite size distribution was then built, with sizes ranging from few tens of µm to roughly 10 mm. Finally, mass-size relationships for ice crystals in tropical convection were established in terms of power laws in order to compute median mass diameters MMDmax and

  2. A mesoscale numerical forecast of an intense convective snowburst along the East Coast

    NASA Technical Reports Server (NTRS)

    Kocin, P. J.; Uccellini, L. W.; Zack, J. W.; Kaplan, M. L.

    1985-01-01

    Mesoscale numerical forecasts utilizing the Mesoscale Atmospheric Simulation System (MASS) are documented for a convective snowburst in the Washington, D.C.-Baltimore, Maryland, region on March 8, 1984 that was associated with secondary cyclogenesis along the East Coast. The forecasts are presented to demonstrate the ability of a mesoscale model to simulate dynamical interactions and diabatic process for a wintertime convective event that was inadequately predicted by local forecasters and to note some of the possible benefits of using mesoscale models for day-to-day forecasting. The results from this and other recent mesoscale modeling studies indicate that three-hourly output of key model fields, when combined with other data sources, can be a valuable aid to forecasters concerned with predicting weather events that are mesoscale in character.

  3. The formation and dust lifting processes associated with a large Saharan meso-scale convective system (MCS)

    NASA Astrophysics Data System (ADS)

    Roberts, Alex; Knippertz, Peter

    2013-04-01

    This work focusses on the meteorology that produced a large Mesoscale Convective System (MCS) and the dynamics of its associated cold pool. The case occurred between 8th-10th June 2010 and was initiated over the Hoggar and Aïr Mountains in southern Algeria and northern Niger respectively. The dust plume created covered parts of Algeria, Mali and Mauritania and was later deformed the by background flow and transported over the Atlantic and Mediterranean. This study is based on: standard surface observations (where available), ERA-Interim reanalysis, Meteosat imagery, MODIS imagery, Tropical Rainfall Measuring Mission (TRMM) rainfall estimates, Cloud Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO), CloudSat and a high resolution (3.3km) limited area simulation using the Weather Research and Forecasting (WRF) model. A variety of different processes appear to be important for the generation of this MCS and the spreading of the associated dusty cold pool. These include: the presence of a trough on the subtropical jet, the production of a tropical cloud plume, disruption to the structure of the Saharan heat low and the production of a Libyan high. These features produced moistening of the boundary layer and a convergence zone over the region of MCS initiation. Another important factor appears to have been the production of a smaller MCS and cold pool on the evening of the 7th June. This elevated low-level moisture and encouraged convective initiation the following day. Once triggered on the 8th June some cells grew and merged into a single large system that propagated south westward and produced a large cold pool that emanated from its northern edge. The cells on the northern edge of the system over the Hoggar grew and collapsed producing a haboob that spread over a large area. Cells further south continued to develop into the MCS and actively produce a cold pool over the system's lifetime. This undercut the dusty air from the earlier cold pool and

  4. A Climatology of Derecho-Producing Mesoscale Convective Systems in the Central and Eastern United States, 1986-95. Part I: Temporal and Spatial Distribution.

    NASA Astrophysics Data System (ADS)

    Bentley, Mace L.; Mote, Thomas L.

    1998-11-01

    In 1888, Iowa weather researcher Gustavus Hinrichs gave widespread convectively induced windstorms the name "derecho". Refinements to this definition have evolved after numerous investigations of these systems; however, to date, a derecho climatology has not been conducted.This investigation examines spatial and temporal aspects of derechos and their associated mesoscale convective systems that occurred from 1986 to 1995. The spatial distribution of derechos revealed four activity corridors during the summer, five during the spring, and two during the cool season. Evidence suggests that the primary warm season derecho corridor is located in the southern Great Plains. During the cool season, derecho activity was found to occur in the southeast states and along the Atlantic seaboard. Temporally, derechos are primarily late evening or overnight events during the warm season and are more evenly distributed throughout the day during the cool season.

  5. The radiative budgets of a tropical mesoscale convective system during the EMEX-STEP-AMEX experiment. I - Observations. II - Model results

    NASA Technical Reports Server (NTRS)

    Wong, Takmeng; Stephens, Graeme L.; Stackhouse, Paul W., Jr.; Valero, Francisco P. J.

    1993-01-01

    The spatial radiation heating budget associated with tropical mesoscale convective systems (MCSs) is studied and the change of this heating/budget throughout the life cycle of such a cloud system is investigated. The movements of an EMEX 9 cloud cluster are described. The vertical structure of the cluster contains two types of imbedded convection: an upright vertical structure and a pronounced rearward slope with vertical extent of 14.5 km or more and a horizontal scale of about 40 km. The cloud base and cloud top altitude in the stratiform region are of the order of 4.8 km and 15-16 km, respectively. The upward and downward solar flux profiles suggest very little solar heating in these regions. A tropical MCS that occurred during the EMEX Mission 9 is simulated, and the simulation is shown to broadly agree with the observations. The simulation results, which are reported in detail, show how tropical mesoscale cloud systems provide an effective radiative heat source for the tropical atmosphere.

  6. Investigation of the predictability and physical mechanisms of an extreme-rainfall-producing mesoscale convective system along the Meiyu front in East China: An ensemble approach

    NASA Astrophysics Data System (ADS)

    Luo, Yali; Chen, Yangruixue

    2015-10-01

    Forecast uncertainties and physical mechanisms of a quasi-linear extreme-rain-producing mesoscale convective system (MCS) along the Meiyu front in East China, during the midnight-to-morning hours on 8 July 2007, are studied using ensembles of 24 h convection-permitting simulations with a nested grid spacing of 1.11 km. The simulations reveal a strong sensitivity to uncertainties in the initial state despite the synoptic environment being favorable for heavy rainfall production. Linear changes of a less skillful member's initial state toward that of a skillful member lead to a monotonic improvement in the precipitation simulation, with the most significant contribution arising from changes in the moisture field. Sensitivity to physics parameterizations representing subgrid-scale processes fail to account for the larger simulation errors (missing the MCS) with the physics variation examined but could result in a large spread in the location and amount of accumulative rainfall. A robust feature of the best-performing members that reasonably simulate the MCS-associated heavy rainfall is the presence of a cold dome ahead of the Meiyu front generated by previous convection. The cold dome promotes nocturnal convective initiation by lifting high equivalent potential temperature air in the southwesterly flow to its level of free convection. The skillful members reproduce the convective backbuilding and echo-band training processes that are observed during this event and many other heavy rainfall events over China. In contrast, the less skillful members that miss the development of the MCS either do not simulate the previous convection or produce a cold dome that is too shallow to initiate the MCS.

  7. Structural Characteristics of Nocturnal Mesoscale Convective Systems in the U.S. Great Plains as Observed During the PECAN Field Campaign

    NASA Astrophysics Data System (ADS)

    Bodine, D. J.; Dougherty, E.; Rasmussen, K. L.; Torres, A. D.

    2015-12-01

    During the summer in the U.S. Great Plains, some of the heaviest precipitation falls from large thunderstorm complexes known as Mesoscale Convective Systems (MCSs). These frequently occurring MCSs are often nocturnal in nature, so the dynamics associated with these systems are more elusive than those in the daytime. The Plains Elevated Convection at Night (PECAN) field campaign was launched over a 7-week period as an endeavor to better understand nocturnal MCSs occurring in the Great Plains. PECAN featured a dense array of ground-based and airborne instruments to observe nocturnal MCS, including dual-polarization radars at multiple frequencies, mobile mesonets, and sounding units. Our role in PECAN involved deploying Ott Parsivel disdrometers to gain information on drop size distributions (DSDs) and fall speeds. Analysis of disdrometer data in conjunction with radar data presented using Contour Frequency by Altitude Diagrams (CFADs) and high-resolution radiosonde data allows for a structural comparison of PECAN MCS cases to previously identified MCS archetypes. Novel insights into the structural evolution of nocturnal MCSs in relation to their synoptic, mesoscale, and thermodynamic environments are presented, using data collected from dense and numerous observation platforms. Understanding the environmental conditions that result in different nocturnal MCS configurations is useful for gaining insight into precipitation distributions and potential severe weather and flooding hazards in the Great Plains.

  8. Modeling the impact of tropical mesoscale convective systems on Sahelian mineral dust budget: a case study during AMMA SOPs 1-2

    NASA Astrophysics Data System (ADS)

    Bouet, C.; Cautenet, G.; Marticorena, B.; Bergametti, G.; Chatenet, B.; Rajot, J.-L.; Descroix, L.

    2009-04-01

    Tropical mesoscale convective systems (MCSs) are a prominent feature of the African meteorology. A continuous monitoring of the aeolian activity in an experimental site located in Niger showed that such events are responsible for the major part of the annual local wind erosion, i.e. for most of the Sahelian dust emission [Rajot, 2001]. However, the net effect of these MCSs on mineral dust budget has to be estimated: on the one hand, these systems produce extremely high surface wind velocities leading to intense dust uptake, but on the other hand, rainfalls associated with these systems can efficiently remove the emitted dust from the atmosphere. High resolution modeling of MCSs appears as the most relevant approach to assess the budget between dust emission and deposition in such local meteorological systems. As a first step, in order to properly estimate dust emissions, it is necessary to accurately describe the surface wind fields at the local scale. Indeed, dust emission is a threshold phenomenon that depends on the third power of surface wind velocity. This study focuses on a case study of dust emission associated with the passage of a MCS observed during one of the intensive observation period of the international African Monsoon Multidisciplinary Analysis (AMMA - SOPs 1-2) program. The simulations were made using the Regional Atmospheric Modeling System (RAMS) coupled online with the dust production model (DPM) developed by Marticorena and Bergametti [1995] and recently improved by Laurent et al. [2008] for Africa. Two horizontal resolutions were tested (5 km and 2.5 km) as well as two microphysical schemes (a 1-moment scheme [Walko et al., 1995] and a 2-moment scheme [Meyers et al., 1997]). The use of the two convective parameterizations now available in the version 6 of RAMS (Kuo [1995] modified by Molinari [1985] and Molinari and Corsetti [1985], and Kain and Fritsch [1992; 1993]) to simulate cloud convection was also tested. Sensitivity tests have been

  9. An approach for parameterizing mesoscale precipitating systems

    SciTech Connect

    Weissbluth, M.J.; Cotton, W.R.

    1991-01-01

    A cumulus parameterization laboratory has been described which uses a reference numerical model to fabricate, calibrate and verify a cumulus parameterization scheme suitable for use in mesoscale models. Key features of this scheme include resolution independence and the ability to provide hydrometeor source functions to the host model. Thus far, only convective scale drafts have been parameterized, limiting the use of the scheme to those models which can resolve the mesoscale circulations. As it stands, the scheme could probably be incorporated into models having a grid resolution greater than 50 km with results comparable to the existing schemes for the large-scale models. We propose, however, to quantify the mesoscale circulations through the use of the cumulus parameterization laboratory. The inclusion of these mesoscale drafts in the existing scheme will hopefully allow the correct parameterization of the organized mesoscale precipitating systems.

  10. An approach for parameterizing mesoscale precipitating systems

    SciTech Connect

    Weissbluth, M.J.; Cotton, W.R.

    1991-12-31

    A cumulus parameterization laboratory has been described which uses a reference numerical model to fabricate, calibrate and verify a cumulus parameterization scheme suitable for use in mesoscale models. Key features of this scheme include resolution independence and the ability to provide hydrometeor source functions to the host model. Thus far, only convective scale drafts have been parameterized, limiting the use of the scheme to those models which can resolve the mesoscale circulations. As it stands, the scheme could probably be incorporated into models having a grid resolution greater than 50 km with results comparable to the existing schemes for the large-scale models. We propose, however, to quantify the mesoscale circulations through the use of the cumulus parameterization laboratory. The inclusion of these mesoscale drafts in the existing scheme will hopefully allow the correct parameterization of the organized mesoscale precipitating systems.

  11. Formation of African Easterly Waves and Mesoscale Convective Systems over Eastern Africa and its Implication to Tropical Cyclogenesis over Eastern Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Lin, Yuh-Lang

    2009-07-01

    The formation of African easterly waves and mesoscale convective systems in eastern North Africa and its impacts on the tropical cyclogenesis over the eastern Atlantic Ocean is studied. Based on numerical simulations, AEWs can be produced by vortex shedding from the EH. The lee vortex is generated mainly by the blocking of the EH and helped by the horizontal shear associated with the northeasterly wind and the jet passing through the Turkana channel. The MCS was originated from the moist convection over the EH triggered by diurnal sensible heating. When the MCS moved to the lee of the mountain, it merged with the lee vortex of the AEW train and formed the coupled AEW-MCS system. Numerical simulations of a regional climate model indicate that the simulated fields do possess the AEW characteristics and the convection was generated over the EH, and the pre-Alberto AEW-MCS system was generated near the lee of the EH. Finer-resolution numerical simulations demonstrate that the vortex generated on the lee and MCS over the mountain eventually merge and become an AEW-MCS system which might serve as a precursor of tropical cyclone.

  12. Formation and evolution of mesoscale convective systems that brought the heavy rainfall over Seoul on September 21, 2010

    NASA Astrophysics Data System (ADS)

    Jung, Woomi; Lee, Tae-Young

    2013-11-01

    An investigation has been carried out using observational data and a numerical model to explain the formation and development of heavy precipitation systems on September 21, 2010. These systems were responsible for heavy rainfall over the middle Korean peninsula, with a maximum 24-h rainfall amount greater than 290 mm in the Seoul metropolitan area. Both observational analysis and a numerical simulation indicate that an important starting condition for this heavy rainfall event is the presence of a pressure trough over the Shandong peninsula and the Yellow Sea. Convective cells formed in the early morning over this trough area, grew into larger systems as they moved eastward, and induced the formation of a meso low over the Yellow Sea around 0000 UTC on September 21, 2010. A stationary front with significant vertical circulation developed in response to the deformation of flow associated with the meso low. In the meantime, multicell-type convective systems continuously developed and moved along the front. These storms developed further and produced heavy rainfall over the middle Korean peninsula, which includes the Seoul metropolitan area. According to observations, the band structure appeared to change after 0700 UTC as a narrow convection band developed over the sea, upstream of the existing band of multicell storms. Numerical simulation showed a similar transition. However, it failed to reproduce the stationary behavior of the observed band.

  13. Tropical cyclogenesis in Eastern Atlantique: Impact of earlier passage of African Easterly Wave trough on the evolution of Mesoscale Convective Systems and air-sea interaction

    NASA Astrophysics Data System (ADS)

    Lahat Dieng, Abdou; Eymard, Laurence; Moustapha Sall, Saidou; Lazar, Alban; Leduc-Leballeur, Marion

    2014-05-01

    A large part of Atlantic tropical depressions is generated in the Eastern basin in relation with the African Easterly Waves and the Mesoscale Convective Systems coming from the African continent. But initial surface oceanic and atmosphere conditions favoring such evolution are largely unknown. This study analyzes the structures of strengthening and dissipating MCSs evolving near the West African coast and evaluates the role of the surface oceanic condition on their evolutions. Satellite brightness temperature from Meteosat Second Generation over the summer season of 2006 and radar data for the same season between 1993 and 1999 are used to subjectively select fourteen cases of strengthening (dissipating) MCSs when they cross the Senegalese coast. With these observed MCSs locations, a lagged composite analysis is then performed using Era interim and CFSR reanalyses. Results show that the strengthening MCS composite is preceded by prior passage of an AEW near the West African coast. This first trough wave was associated with a cyclonic circulation in the low and middle troposphere and has enhanced southwest wind flow behind him feeding humidly to the strengthening MCS composite which was located in the vicinity of the second AEW trough. The contraction of the wave length associated with the two troughs was probably facilitated this supply in humidity. The Sea Surface Temperature seem contribute to the MCS enhancement through surface evaporation flux but this contribution is less important than humidity advection by the fist system. These conditions were not found in the dissipating MCS case which dissipated in a drying environment air dominated by subsidence and anticyclonic circulation. Key words: Mesoscale Convective System, African Easterly Wave, Sea Surface Temperature, tropical depression.

  14. Mesoscale disturbances in the tropical stratosphere excited by convection - Observations and effects on the stratospheric momentum budget

    NASA Technical Reports Server (NTRS)

    Pfister, Leonhard; Scott, Stanley; Loewenstein, Max; Bowen, Stuart; Legg, Marion

    1993-01-01

    Aircraft temperature and pressure measurements as well as satellite imagery are used to establish the amplitudes and the space and time scale of potential temperature disturbances over convective systems. A conceptual model is proposed for the generation of mesoscale gravity waves by convection. The momentum forcing that a reasonable distribution of convection might exert on the tropical stratosphere through convectively excited mesoscale gravity waves of the observed amplitudes is estimated. Aircraft measurements show that presence of mesoscale disturbances in the lower stratospheric temperature, disturbances that appear to be associated with underlying convection. If the disturbances are convectively excited mesoscale gravity waves, their amplitude is sufficient that their breakdown in the upper stratosphere will exert a zonal force comparable to but probably smaller than the planetary-scale Kelvin waves.

  15. Mesoscale convective system surface pressure anomalies responsible for meteotsunamis along the U.S. East Coast on June 13th, 2013.

    PubMed

    Wertman, Christina A; Yablonsky, Richard M; Shen, Yang; Merrill, John; Kincaid, Christopher R; Pockalny, Robert A

    2014-01-01

    Two destructive high-frequency sea level oscillation events occurred on June 13th, 2013 along the U.S. East Coast. Seafloor processes can be dismissed as the sources, as no concurrent offshore earthquakes or landslides were detected. Here, we present evidence that these tsunami-like events were generated by atmospheric mesoscale convective systems (MCSs) propagating from inland to offshore. The USArray Transportable Array inland and NOAA tide gauges along the coast recorded the pressure anomalies associated with the MCSs. Once offshore, the pressure anomalies generated shallow water waves, which were amplified by the resonance between the water column and atmospheric forcing. Analysis of the tidal data reveals that these waves reflected off the continental shelf break and reached the coast, where bathymetry and coastal geometry contributed to their hazard potential. This study demonstrates that monitoring MCS pressure anomalies in the interior of the U.S. provides important observations for early warnings of MCS-generated tsunamis. PMID:25420958

  16. Mesoscale convective system surface pressure anomalies responsible for meteotsunamis along the U.S. East Coast on June 13th, 2013

    PubMed Central

    Wertman, Christina A.; Yablonsky, Richard M.; Shen, Yang; Merrill, John; Kincaid, Christopher R.; Pockalny, Robert A.

    2014-01-01

    Two destructive high-frequency sea level oscillation events occurred on June 13th, 2013 along the U.S. East Coast. Seafloor processes can be dismissed as the sources, as no concurrent offshore earthquakes or landslides were detected. Here, we present evidence that these tsunami-like events were generated by atmospheric mesoscale convective systems (MCSs) propagating from inland to offshore. The USArray Transportable Array inland and NOAA tide gauges along the coast recorded the pressure anomalies associated with the MCSs. Once offshore, the pressure anomalies generated shallow water waves, which were amplified by the resonance between the water column and atmospheric forcing. Analysis of the tidal data reveals that these waves reflected off the continental shelf break and reached the coast, where bathymetry and coastal geometry contributed to their hazard potential. This study demonstrates that monitoring MCS pressure anomalies in the interior of the U.S. provides important observations for early warnings of MCS-generated tsunamis. PMID:25420958

  17. Investigating an Automated Method to Explore Mesoscale Convective Complexes in West Africa

    NASA Astrophysics Data System (ADS)

    Whitehall, Kim Dionne

    Mesoscale convective complexes are convectively driven, high impact weather systems with durations of approximately 10-12 hours, and are large contributors to daily and monthly rainfall totals. In West Africa, approximately 40 mesoscale convective complexes contribute an estimated one-quarter of the total rainfall amounts between July and September annually. As such, an understanding of the lifecycle, characteristics, frequency, and seasonality of these weather features is important for climate studies, agricultural and hydrological studies, and disaster management. Identification criteria of mesoscale convective complexes exist for infrared satellite data, but the spatial expanse and the spatio-temporal variability of the convective characteristics of these mesoscale convective complexes make rainfall characterization difficult, even in dense networks of radars and / or surface gauges. Hence, fully automated methods are required to explore mesoscale convective complexes in long-term infrared satellite data, and to determine their characteristics from other datasets, such as precipitation rate satellite datasets. Automated identification methods of mesoscale convective complexes are based on forward- and / or backward-in-time spatial-temporal analyses of infrared satellite data, and usually incorporate a manual component to verify the features and / or characterize the associated precipitation. These existing identification and precipitation characterization methods are not readily transferable to voluminous data or other satellite-derived datasets, thus hindering comprehensive studies of these features, both at weather and climate timescales. In recognizing these limitations and the growing volume of satellite data, this study explores the applicability of graph theory to creating a fully automated method for identifying mesoscale convective systems in satellite datasets. The framework for such a method is provided in this work. The results indicate that applying

  18. Predictability and Mechanism of an Extreme-Rainfall-Producing Mesoscale Convective System along a Mei-Yu Front in East China

    NASA Astrophysics Data System (ADS)

    Luo, Yali; Ruixue Chen, Yang

    2015-04-01

    Forecast uncertainties of a quasi-linear extreme-rain-producing mesoscale convective system (MCS) along a mei-yu front in east China during the midnight-to-morning hours of 8 July 2007 are studied using several 24-h convection-permitting ensembles of simulation with the nested grid spacing of 1.11 km. There is considerable spread in the ensembles' precipitation forecast despite of the synoptic environment known conducive to heavy local rainfall. Forty simulations with perturbed initial condition reveal a very strong sensitivity to uncertainties in the initial fields. A robust feature of the best-performing members that reasonably simulated the MCS and associated heavy rainfall was the presence of a cold dome before the mei-yu front, which was generated by previous convection. The cold dome helped the nocturnal convective initiation (CI) by lifting the moist air in the low-level southwesterly flow to its level of free convection. In contrast, the bad members that missed the MCS' development could not simulate the previous convection or produced a cold dome that was not deep enough to initiate the MCS. At the initial time, the bad members had less atmospheric moisture over and upstream of the CI region than the good members. This resulted in the frontal-lifting-induced CI being delayed by about 4 hours and too weak convection to form the MCS in the bad members. Extra experiments were performed to test the sensitivity of precipitation simulation to the initial condition differences between a good and a bad member. Linear changing of the bad member's initial condition toward the good member's led to monotonic improvement of the precipitation simulation, with the most significant contribution from the moisture field. Sensitivity of the precipitation forecast to the model physical process parameterization schemes is examined by conducting three groups of experiment, each consisting of 9 members using different physics schemes and using the same initial condition as two

  19. Sensitivity of summer ensembles of fledgling superparameterized U.S. mesoscale convective systems to cloud resolving model microphysics and grid configuration

    DOE PAGESBeta

    Elliott, Elizabeth J.; Yu, Sungduk; Kooperman, Gabriel J.; Morrison, Hugh; Wang, Minghuai; Pritchard, Michael S.

    2016-05-01

    The sensitivities of simulated mesoscale convective systems (MCSs) in the central U.S. to microphysics and grid configuration are evaluated here in a global climate model (GCM) that also permits global-scale feedbacks and variability. Since conventional GCMs do not simulate MCSs, studying their sensitivities in a global framework useful for climate change simulations has not previously been possible. To date, MCS sensitivity experiments have relied on controlled cloud resolving model (CRM) studies with limited domains, which avoid internal variability and neglect feedbacks between local convection and larger-scale dynamics. However, recent work with superparameterized (SP) GCMs has shown that eastward propagating MCS-likemore » events are captured when embedded CRMs replace convective parameterizations. This study uses a SP version of the Community Atmosphere Model version 5 (SP-CAM5) to evaluate MCS sensitivities, applying an objective empirical orthogonal function algorithm to identify MCS-like events, and harmonizing composite storms to account for seasonal and spatial heterogeneity. A five-summer control simulation is used to assess the magnitude of internal and interannual variability relative to 10 sensitivity experiments with varied CRM parameters, including ice fall speed, one-moment and two-moment microphysics, and grid spacing. MCS sensitivities were found to be subtle with respect to internal variability, and indicate that ensembles of over 100 storms may be necessary to detect robust differences in SP-GCMs. Furthermore, these results emphasize that the properties of MCSs can vary widely across individual events, and improving their representation in global simulations with significant internal variability may require comparison to long (multidecadal) time series of observed events rather than single season field campaigns.« less

  20. The mesoscale forcing of a midlatitude upper-tropospheric jet streak by a simulated convective system. 1: Mass circulation and ageostrophic processes

    NASA Technical Reports Server (NTRS)

    Wolf, Bart J.; Johnson, D. R.

    1995-01-01

    The mutual forcing of a midlatitude upper-tropospheric jet streak by organized mesoscale adiabatic and diabatic processes within a simulated convective system (SCS) is investigated. Using isentropic diagnostics, results from a three-dimensional numerical simulation of an SCS are examined to study the isallobaric flow field, modes of dominant ageostrophic motion, and stability changes in relation to the mutual interdependence of adiabatic processes and latent heat release. Isentropic analysis affords an explicit isolation of a component of isallobaric flow associated with diabatic processes within the SCS. Prior to convective development within the simulations, atmospheric destabilization occurs through adiabatic ageostrophic mass adjustment and low-level convergence in association with the preexisting synoptic-scale upper-tropospheric jet streak. The SCS develops in a baroclinic zone and quickly initiates a vigorous mass circulation. By the mature stage, a pronounced vertical couplet of low-level convergence and upper-level mass divergence is established, linked by intense midtropospoheric diabatic heating. Significant divergence persists aloft for several hours subsequent to SCS decay. The dominant role of ageostrophic motion within which the low-level mass convergence develops is the adiabatic isallobaric component, while the mass divergence aloft develops principally through the diabatic isallobaric component. Both compnents are intrinsically linked to the convectively forced vertical mass transport. The inertial diabatic ageostrophic component is largest near the level of maximum heating and is responsible for the development of inertial instability to the north of SCS, resulting in this quadrant being preferred for outflow. The inertial advective component, the dominant term that produces the new downstream wind maximum, rapidly develops north of the SCS and through mutual adjustment creates the baroclinic support for the new jet streak.

  1. Analysis of Cloud-resolving Simulations of a Tropical Mesoscale Convective System Observed during TWP-ICE: Vertical Fluxes and Draft Properties in Convective and Stratiform Regions

    SciTech Connect

    Mrowiec, Agnieszka A.; Rio, Catherine; Fridlind, Ann; Ackerman, Andrew; Del Genio, Anthony D.; Pauluis, Olivier; Varble, Adam; Fan, Jiwen

    2012-10-02

    We analyze three cloud-resolving model simulations of a strong convective event observed during the TWP-ICE campaign, differing in dynamical core, microphysical scheme or both. Based on simulated and observed radar reflectivity, simulations roughly reproduce observed convective and stratiform precipitating areas. To identify the characteristics of convective and stratiform drafts that are difficult to observe but relevant to climate model parameterization, independent vertical wind speed thresholds are calculated to capture 90% of total convective and stratiform updraft and downdraft mass fluxes. Convective updrafts are fairly consistent across simulations (likely owing to fixed large-scale forcings and surface conditions), except that hydrometeor loadings differ substantially. Convective downdraft and stratiform updraft and downdraft mass fluxes vary notably below the melting level, but share similar vertically uniform draft velocities despite differing hydrometeor loadings. All identified convective and stratiform downdrafts contain precipitation below ~10 km and nearly all updrafts are cloudy above the melting level. Cold pool properties diverge substantially in a manner that is consistent with convective downdraft mass flux differences below the melting level. Despite differences in hydrometeor loadings and cold pool properties, convective updraft and downdraft mass fluxes are linearly correlated with convective area, the ratio of ice in downdrafts to that in updrafts is ~0.5 independent of species, and the ratio of downdraft to updraft mass flux is ~0.5-0.6, which may represent a minimum evaporation efficiency under moist conditions. Hydrometeor loading in stratiform regions is found to be a fraction of hydrometeor loading in convective regions that ranges from ~10% (graupel) to ~90% (cloud ice). These findings may lead to improved convection parameterizations.

  2. WRF forecast skill of the Great Plains low level jet and its correlation to forecast skill of mesoscale convective system precipitation

    NASA Astrophysics Data System (ADS)

    Squitieri, Brian Joseph

    One of the primary mechanisms for supporting summer nocturnal precipitation across the central United States is the Great Plains low-level Jet (LLJ). Mesoscale Convective Systems (MCSs) are organized storm complexes that can be supported from the upward vertical motion supplied at the terminus of the LLJ, which bring beneficial rains to farmers. As such, a need for forecasting these storm complexes exists. Correlating forecast skills of the LLJ and MCS precipitation in high spatial resolution modeling was the main goal of this research. STAGE IV data was used as observations for MCS precipitation and the 00-hr 13 km RUC analysis was employed for evaluation of the LLJ. The 4 km WRF was used for high resolution forecast simulations, with 2 microphysics and 3 planetary boundary layer schemes selected for a sensitivity study to see which model run best simulated reality. It was found that the forecast skill of the potential temperature and directional components of the geostrophic and ageostrophic winds within the LLJ correlated well with MCS precipitation, especially early during LLJ evolution. Since the 20 real cases sampled consisted of three LLJ types (synoptic, inertial oscillation and transition), forecast skill in other parameters such as deep layer and low level shear, convergence, frontogenesis and stability parameters were compared to MCS forecast skill to see if consistent signals outside of the LLJ influenced MCS evolution in forecasts. No correlations were found among these additional parameters. Given the variety of synoptic setups present, the lack of forecast skill correlations between several variables and MCSs resulted as different synoptic or mesoscale mechanisms played varying roles if importance in different cases.

  3. Mesoscale Convective Systems During SCSMEX: Simulations with a Regional Climate Model and a Cloud-Resolving Model

    NASA Technical Reports Server (NTRS)

    Tao, W. K.; Wang, Y.; Qian, J.; Shie, C. -L.; Lau, W. K. -M.; Kakar, R.; Starr, David O' C. (Technical Monitor)

    2002-01-01

    The South China Sea Monsoon Experiment (SCSMEX) was conducted in May-June 1998. One of its major objectives is to better understand the key physical processes for the onset and evolution of the summer monsoon over Southeast Asia and southern China (Lau et al. 2000). Multiple observation platforms (e.g., soundings, Doppler radar, ships, wind seafarers, radiometers, etc.) during SCSMEX provided a first attempt at investigating the detailed characteristics of convection and circulation changes, associated with monsoons over the South China Sea region. SCSMEX also provided precipitation derived from atmospheric budgets (Johnson and Ciesielski 2002) and comparison to those obtained from the Tropical Rainfall Measuring Mission (TRMM). In this paper, a regional climate model and a cloud-resolving model are used to perform multi-day integrations to understand the precipitation processes associated with the summer monsoon over Southeast Asia and southern China. The regional climate model is used to understand the soil - precipitation interaction and feedback associated with a flood event that occurred in and around China's Atlantic River during SCSMEX. Sensitivity tests on various land surface models, cumulus parameterization schemes (CASE), sea surface temperature (SST) variations and midlatitude influences are also performed to understand the processes associated with the onset of the monsoon over the S. China Sea during SCSMEX. Cloud-resolving models (CRMs) use more sophisticated and physically realistic parameterizations of cloud microphysical processes with very fine spatial and temporal resolution. One of the major characteristics of CRMs is an explicit interaction between clouds, radiation and the land/ocean surface. It is for this reason that GEWEX (Global Energy and Water Cycle Experiment) has formed the GCSS (GEWEX Cloud System Study) expressly for the purpose of improving the representation of the moist processes in large-scale models using CRMs. The Goddard

  4. The mesoscale forcing of a midlatitude upper-tropospheric jet streak by a simulated convective system. 2: Kinetic energy and resolution analysis

    NASA Technical Reports Server (NTRS)

    Wolf, Bart J.; Johnson, D. R.

    1995-01-01

    A kinetic energy (KE) analysis of the forcing of a mesoscale upper-tropospheric jet streak by organized diabatic processes within the simulated convective system (SCS) that was discussed in Part 1 is presented in this study. The relative contributions of the ageostrophic components of motion to the generation of KE of the convectively generated jet streak are compared, along with the KE generation by the rotational (nondivergent) and irrotational (divergent) mass transport. The sensitivity of the numerical simulations of SCS development to resolution is also briefly examined. Analysis within isentropic coordinates provides for an explicit determination of the influence of the diabatic processes on the generation of KE. The upper-level production of specific KE is due predominatly to the inertial advective ageostrophic component (IAD), and as such represents the primary process through which the KE of the convectively generated jet streak is realized. A secondary contribution by the inertial diabatic (IDI) term is observed. Partitioning the KE generation into its rotational and irrotational components reveals that the latter, which is directly linked to the diabatic heating within the SCS through isentropic continuity requirements, is the ultimate source of KE generation as the global area integral of generation by the rotational component vanishes. Comparison with an identical dry simulation reveals that the net generation of KE must be attributed to latent heating. Both the IAD and IDI ageostrophic components play important roles in this regard. Examination of results from simulations conducted at several resolutions supports the previous findings in that the effects of diabatic processes and ageostrophic motion on KE generation remain consistent. Resolution does impact the location and timing of SCS development, a result that has important implications in forecasting the onset of convection that develops from evolution of the large-scale flow and moisture

  5. The impact of reflectivity correction and conversion methods to improve precipitation estimation by weather radar for an extreme low-land Mesoscale Convective System

    NASA Astrophysics Data System (ADS)

    Hazenberg, Pieter; Leijnse, Hidde; Uijlenhoet, Remko

    2014-05-01

    Between 25 and 27 August 2010 a long-duration mesoscale convective system was observed above the Netherlands. For most of the country this led to over 15 hours of near-continuous precipitation, which resulted in total event accumulations exceeding 150 mm in the eastern part of the Netherlands. Such accumulations belong to the largest sums ever recorded in this country and gave rise to local flooding. Measuring precipitation by weather radar within such mesoscale convective systems is known to be a challenge, since measurements are affected by multiple sources of error. For the current event the operational weather radar rainfall product only estimated about 30% of the actual amount of precipitation as measured by rain gauges. In the current presentation we will try to identify what gave rise to such large underestimations. In general weather radar measurement errors can be subdivided into two different groups: 1) errors affecting the volumetric reflectivity measurements taken, and 2) errors related to the conversion of reflectivity values in rainfall intensity and attenuation estimates. To correct for the first group of errors, the quality of the weather radar reflectivity data was improved by successively correcting for 1) clutter and anomalous propagation, 2) radar calibration, 3) wet radome attenuation, 4) signal attenuation and 5) the vertical profile of reflectivity. Such consistent corrections are generally not performed by operational meteorological services. Results show a large improvement in the quality of the precipitation data, however still only ~65% of the actual observed accumulations was estimated. To further improve the quality of the precipitation estimates, the second group of errors are corrected for by making use of disdrometer measurements taken in close vicinity of the radar. Based on these data the parameters of a normalized drop size distribution are estimated for the total event as well as for each precipitation type separately (convective

  6. Cloud-scale simulation study on the evolution of latent heat processes of mesoscale convective system accompanying heavy rainfall: The Hainan case

    NASA Astrophysics Data System (ADS)

    Li, Jiangnan; Wu, Kailu; Li, Fangzhou; Chen, Youlong; Huang, Yanbin

    2016-03-01

    This paper investigates the structure of latent heat budgets and dynamical structure of mesoscale convective systems (MCS) accompanying heavy rain using a cloud-scale model WRF simulation for the Hainan case. Results show that: (1) according to the fractions skill score and HK scores, the WDM6 scheme is more suitable to predict the rainfall than other microphysical schemes. (2) During the lifetime of MCSs, the top two heating microphysical processes are water vapor condensed into cloud water and water vapor condensed into rainwater. The total latent heat is closely related to the top two heating processes. However, the change of latent heat released by some microphysical processes is not identical with the different rainfall processes. (3) The total latent heat of MCS1 increases during the short life, while the total latent heat of MCS2 and MCS3 reach maximum during the mature stage. The difference is mainly caused by the latent heat of water vapor condensed into cloud water and rainwater. The total latent heat released by cond and rcond of MCS1 is smallest during the mature stage, while it is largest during the mature stage of MCS2 and MCS3. (4) The vertical motions are different with different MCSs. The descending motion of the short-lived process (MCS1) is strongest during the mature stage. It caused the smallest latent heat released by water vapor condensed into cloud water and rainwater at the same period. Besides, there are some differences in the change of latent heat released by microphysical processes of MCS2 and MCS3, which are closely related to the drag force of the vertical motion.

  7. Systematic multiscale models for deep convection on mesoscales

    NASA Astrophysics Data System (ADS)

    Klein, Rupert; Majda, Andrew J.

    2006-11-01

    This paper builds on recent developments of a unified asymptotic approach to meteorological modeling [ZAMM, 80: 765 777, 2000, SIAM Proc. App. Math. 116, 227 289, 2004], which was used successfully in the development of Systematic multiscale models for the tropics in Majda and Klein [J. Atmosph. Sci. 60: 393 408, 2003] and Majda and Biello [PNAS, 101: 4736 4741, 2004]. Biello and Majda [J. Atmosph. Sci. 62: 1694 1720, 2005]. Here we account for typical bulk microphysics parameterizations of moist processes within this framework. The key steps are careful nondimensionalization of the bulk microphysics equations and the choice of appropriate distinguished limits for the various nondimensional small parameters that appear. We are then in a position to study scale interactions in the atmosphere involving moist physics. We demonstrate this by developing two systematic multiscale models that are motivated by our interest in mesoscale organized convection. The emphasis here is on multiple length scales but common time scales. The first of these models describes the short-time evolution of slender, deep convective hot towers with horizontal scale ~ 1 km interacting with the linearized momentum balance on length and time scales of (10 km/3 min). We expect this model to describe how convective inhibition may be overcome near the surface, how the onset of deep convection triggers convective-scale gravity waves, and that it will also yield new insight into how such local convective events may conspire to create larger-scale strong storms. The second model addresses the next larger range of length and time scales (10 km, 100 km, and 20 min) and exhibits mathematical features that are strongly reminiscent of mesoscale organized convection. In both cases, the asymptotic analysis reveals how the stiffness of condensation/evaporation processes induces highly nonlinear dynamics. Besides providing new theoretical insights, the derived models may also serve as a theoretical devices

  8. Mesoscale Convective Systems During SCSMEX: Simulations with a Regional Climate Model and a Cloud-Resolving Model

    NASA Technical Reports Server (NTRS)

    Tao, W.-K.; Wang, Y.; Qian, J.-H.; Shie, C.-L.; Lau, W. K.-M.; Kakar, R.; Starr, David (Technical Monitor)

    2002-01-01

    The South China Sea Monsoon Experiment (SCSMEX) was conducted in May-June 1998. One of its major objectives is to better understand the key physical processes for the onset and evolution of the summer monsoon over Southeast Asia and southern China. Multiple observation platforms (e.g., upper-air soundings, Doppler radar, ships, wind profilers, radiometers, etc.) during SCSMEX provided a first attempt at investigating the detailed characteristics of convection and circulation changes associated with monsoons over the South China Sea region. SCSMEX also provided precipitation derived from atmospheric budgets and comparison to those obtained from the Tropical Rainfall Measuring Mission (TRMM). In this paper, a regional scale model (with grid size of 20 km) and Goddard Cumulus Ensemble (GCE) model (with 1 km grid size) are used to perform multi-day integration to understand the precipitation processes associated with the summer monsoon over Southeast Asia and southern China. The regional climate model is used to understand the soil-precipitation interaction and feedback associated with a flood event that occurred in and around China's Yantz River during SCSMEX Sensitivity tests on various land surface models, sea surface temperature (SST) variations, and cloud processes are performed to understand the precipitation processes associated with the onset of the monsoon over the S. China Sea during SCSMEX. These tests have indicated that the land surface model has a major impact on the circulation over the S. China Sea. Cloud processes can effect the precipitation pattern while SST variation can effect the precipitation amounts over both land and ocean. The exact location (region) of the flooding can be effected by the soil-rainfall feedback. The GCE-model results captured many observed precipitation characteristics because it used a fine grid size. For example, the model simulated rainfall temporal variation compared quite well to the sounding-estimated rainfall. The

  9. A long-lived mesoscale convective complex. I - The mountain-generated component

    NASA Technical Reports Server (NTRS)

    Cotton, W. R.; George, R. L.; Wetzel, P. J.; Mcanelly, R. L.

    1983-01-01

    The South Park Area Cumulus Experiment (SPACE) was conducted during the summer of 1977, and takes into account meteorological developments in a broad, elevated basin called South Park, which is located northeast of Colorado Springs, Colorado. The experiment was designed to investigate the organization of the mesoscale and storm-scale systems in detail over South Park. Many of the convective storms which were observed in the developing stages over South Park participated in the genesis of mesoscale convective complexes (MCCs) on the meso-alpha-scale. The present investigation is concerned with the evolution of the second MCC of this episode, which matured on the evening of August 4, 1977. Attention is given to the events from the preconvective stage early on August 4 to the incipient MCC stage in the early evening.

  10. Impact of the ice phase on a mesoscale convective system: Implication of cloud parameterization and cloud radiative properties

    SciTech Connect

    Chin, H.N.S.; Bradley, M.M.; Molenkamp, C.R.; Grant, K.E.; Chuang, C.

    1991-08-01

    This study attempts to provide further understanding of the effect of the ice phase on cloud ensemble features which are useful for improving GCM cumulus parameterization. In addition, cloud model results are used to diagnose the radiative properties of anvils in order to assess cloud/radiation interaction and its feedback on the larger-scale climate for the future work. The heat, moisture and mass budget analyses of a simulated squall line system indicate that, at least for this type of system, the inclusion of the ice phase in the microphysics does not considerably change the net cloud heating and drying effects and the feedback on the large-scale motion. Nonetheless, its impact on the radiative properties of clouds significantly influences not only the squall line system itself, but also the larger-scale circulation due to the favorable stratification for long-lasting anvil clouds. The water budget suggests a simple methodology to parameterize the microphysical effect without considering it as a model physics module. Further application of the water budget might also be used to parameterize the cloud transport of condensates in the anvil cloud region, which allows the GCM columns to interact with each other. The findings of this study suggest that the ice phase could be ignored in the cloud parameterization in order to save significant amounts of computational resources and to simplify the model physics. More scientific effort should, however, be focused on the effect of the ice phase to further explore cloud feedback on the large-scale climate through the radiative process. The cloud/radiation interaction and its feedback on the larger-scale climate will be addressed in a companion study by coupling the radiative transfer model with the cloud model. 19 refs., 13 figs.

  11. Backscatter-to-Extinction Ratios in the Top Layers of Tropical Mesoscale Convective Systems and in Isolated Cirrus from LITE Observations

    NASA Technical Reports Server (NTRS)

    Platt, C. M. R.; Winker, D. M.; Vaughan, M. A.; Miller, S. D.

    1999-01-01

    Cloud-integrated attenuated backscatter from observations with the Lidar In-Space Technology Experiment (LITE) was studied over a range of cirrus clouds capping some extensive mesoscale convective systems (MCSS) in the Tropical West Pacific. The integrated backscatter when the cloud is completely attenuating, and when corrected for multiple scattering, is a measure of the cloud particle backscatter phase function. Four different cases of MCS were studied. The first was very large, very intense, and fully attenuating, with cloud tops extending to 17 km and a maximum lidar pulse penetration of about 3 km. It also exhibited the highest integrated attenuated isotropic backscatter, with values in the 532-nm channel of up to 2.5 near the center of the system, falling to 0.6 near the edges. The second MCS had cloud tops that extended to 14.8 km. Although MCS2 was almost fully attenuating, the pulse penetration into the cloud was up to 7 km and the MCS2 had a more diffuse appearance than MCS1. The integrated backscatter values were much lower in this system but with some systematic variations between 0.44 and 0.75. The third MCS was Typhoon Melissa. Values of integrated backscatter in tt-ds case varied from 1.64 near the eye of the typhoon to between 0.44 and 1.0 in the areas of typhoon outflow and in the 532-nm channel. Mean pulse penetration through the cloud top was 2-3 km, the lowest penetration of any of the systems. The fourth MCS consisted of a region of outflow from Typhoon Melissa. The cloud was semitransparent for more than half of the image time. During that time, maximum cloud depth was about 7 km. The integrated backscatter varied from about 0.38 to 0.63 in the 532-nm channel when the cloud was fully attenuating. In some isolated cirrus between the main systems, a plot of integrated backscatter against one minus the two-way transmittance gave a linear dependence with a maximum value of 0.35 when the clouds were fully attenuating. The effective backscatter

  12. Lightning-produced NOx over Brazil during TROCCINOX: airborne measurements in tropical and subtropical thunderstorms and the importance of mesoscale convective systems

    NASA Astrophysics Data System (ADS)

    Huntrieser, H.; Schlager, H.; Roiger, A.; Lichtenstern, M.; Schumann, U.; Kurz, C.; Brunner, D.; Schwierz, C.; Richter, A.; Stohl, A.

    2007-06-01

    During the TROCCINOX field experiments in February-March 2004 and February 2005, airborne in situ measurements of NO, NOy, CO, and O3 mixing ratios and the J(NO2) photolysis rate were carried out in the anvil outflow of thunderstorms over southern Brazil. Both tropical and subtropical thunderstorms were investigated, depending on the location of the South Atlantic convergence zone. Tropical air masses were discriminated from subtropical ones according to the higher equivalent potential temperature (Θe) in the lower and mid troposphere, the higher CO mixing ratio in the mid troposphere, and the lower wind velocity in the upper troposphere within the Bolivian High (north of the subtropical jet stream). During thunderstorm anvil penetrations, typically at 20-40 km horizontal scales, NOx mixing ratios were distinctly enhanced and the absolute mixing ratios varied between 0.2-1.6 nmol mol-1 on average. This enhancement was mainly attributed to NOx production by lightning and partly due to upward transport from the NOx-richer boundary layer. In addition, CO mixing ratios were occasionally enhanced, indicating upward transport from the boundary layer. For the first time, the composition of the anvil outflow from a large, long-lived mesoscale convective system (MCS) advected from northern Argentina and Uruguay was investigated in more detail. Over a horizontal scale of about 400 km, NOx, CO and O3 absolute mixing ratios were significantly enhanced in these air masses in the range of 0.6-1.1, 110-140 and 60-70 nmol mol-1, respectively. Analyses from trace gas correlations and a Lagrangian particle dispersion model indicate that polluted air masses, probably from the Buenos Aires urban area and from biomass burning regions, were uplifted by the MCS. Ozone was distinctly enhanced in the aged MCS outflow, due to photochemical production and entrainment of O3-rich air masses from the upper troposphere - lower stratosphere region. The aged MCS outflow was transported to the

  13. Lightning-produced NOx over Brazil during TROCCINOX: Airborne measurements in tropical and subtropical thunderstorms and the importance of mesoscale convective systems

    NASA Astrophysics Data System (ADS)

    Huntrieser, H.; Schlager, H.; Roiger, A.; Lichtenstern, M.; Schumann, U.; Kurz, C.; Brunner, D.; Schwierz, C.; Richter, A.; Stohl, A.

    2007-02-01

    During the TROCCINOX field experiments in February-March 2004 and February 2005, airborne in situ measurements of NO, NOy, CO, and O3 mixing ratios and the J(NO2) photolysis rate were carried out in the anvil outflow of thunderstorms over southern Brazil. Both tropical and subtropical thunderstorms were investigated, depending on the location of the South Atlantic convergence zone. Tropical air masses were discriminated from subtropical ones according to the higher equivalent potential temperature (Θe) in the lower and mid troposphere, the higher CO mixing ratio in the mid troposphere, and the lower wind velocity and proper wind direction in the upper troposphere. During thunderstorm anvil penetrations, typically at 20-40 km horizontal scales, NOx mixing ratios were on average enhanced by 0.2-1.6 nmol mol-1. This enhancement was mainly attributed to NOx production by lightning and partly due to upward transport from the NOx-richer boundary layer. In addition, CO mixing ratios were occasionally enhanced, indicating upward transport from the boundary layer. For the first time, the composition of the anvil outflow from a large, long-lived mesoscale convective system (MCS) advected from northern Argentina and Uruguay was investigated in more detail. Over a horizontal scale of about 400 km, NOx, CO and O3 mixing ratios were significantly enhanced in these air masses in the range of 0.6-1.1, 110-140 and 60-70 nmol mol-1, respectively. Analyses from trace gas correlations and a Lagrangian particle dispersion model indicate that polluted air masses, probably from the Buenos Aires urban area and from biomass burning regions, were uplifted by the MCS. Ozone was distinctly enhanced in the aged MCS outflow, due to photochemical production and entrainment of O3-rich air masses from the upper troposphere - lower stratosphere region. The aged MCS outflow was transported to the north, ascended and circulated, driven by the Bolivian High over the Amazon basin. In the observed

  14. Use of ARM observations and numerical models to determine radiative and latent heating profiles of mesoscale convective systems for general circulation models

    SciTech Connect

    Tao, Wei-Kuo; Houze, Robert, A., Jr.; Zeng, Xiping

    2013-03-14

    This three-year project, in cooperation with Professor Bob Houze at University of Washington, has been successfully finished as planned. Both ARM (the Atmospheric Radiation Measurement Program) data and cloud-resolving model (CRM) simulations were used to identify the water budgets of clouds observed in two international field campaigns. The research results achieved shed light on several key processes of clouds in climate change (or general circulation models), which are summarized below. 1. Revealed the effect of mineral dust on mesoscale convective systems (MCSs) Two international field campaigns near a desert and a tropical coast provided unique data to drive and evaluate CRM simulations, which are TWP-ICE (the Tropical Warm Pool International Cloud Experiment) and AMMA (the African Monsoon Multidisciplinary Analysis). Studies of the two campaign data were contrasted, revealing that much mineral dust can bring about large MCSs via ice nucleation and clouds. This result was reported as a PI presentation in the 3rd ASR Science Team meeting held in Arlington, Virginia in March 2012. A paper on the studies was published in the Journal of the Atmospheric Sciences (Zeng et al. 2013). 2. Identified the effect of convective downdrafts on ice crystal concentration Using the large-scale forcing data from TWP-ICE, ARM-SGP (the Southern Great Plains) and other field campaigns, Goddard CRM simulations were carried out in comparison with radar and satellite observations. The comparison between model and observations revealed that convective downdrafts could increase ice crystal concentration by up to three or four orders, which is a key to quantitatively represent the indirect effects of ice nuclei, a kind of aerosol, on clouds and radiation in the Tropics. This result was published in the Journal of the Atmospheric Sciences (Zeng et al. 2011) and summarized in the DOE/ASR Research Highlights Summaries (see http://www.arm.gov/science/highlights/RMjY5/view). 3. Used radar

  15. Automated Identification of Closed Mesoscale Cellular Convection and Impact of Resolution on Related Mesoscale Dynamics

    NASA Astrophysics Data System (ADS)

    Martini, M.; Gustafson, W. I.; Yang, Q.; Xiao, H.

    2013-12-01

    Organized mesoscale cellular convection (MCC) is a common feature of marine stratocumulus that forms in response to a balance between mesoscale dynamics and smaller scale processes such as cloud radiative cooling and microphysics. Cloud resolving models begin to resolve some, but not all, of these processes with less of the mesoscale dynamics resolved as one progresses from <1 km to 10 km grid spacing. While limited domain cloud resolving models can use high resolution to simulate MCC, global cloud resolving models must resort to using grid spacings closer to 5 to 10 km. This effectively truncates the scales through which the dynamics can act and impacts the MCC characteristics, potentially altering the climate impact of these clouds in climate models. To understand the impact of this truncation, we use the Weather Research and Forecasting model with chemistry (WRF-Chem) and fully coupled cloud-aerosol interactions to simulate marine low clouds during the VOCALS-REx campaign over the Southeast Pacific. A suite of experiments with 1-, 3- and 9-km grid spacing indicates resolution dependent behavior. The simulations with finer grid spacing have lower liquid water paths and cloud fractions, while cloud tops are higher. When compared to observed liquid water paths from GOES and MODIS, the 3-km simulation has better agreement over the coastal regions while the 9-km simulation better agrees over remote regions. The observed diurnal cycle is reasonably well simulated. To isolate organized MCC characteristics we developed a new automated method, which uses a variation of the watershed segmentation technique that combines the detection of cloud boundaries with a test for coincident vertical velocity characteristics. This has the advantage of ensuring that the detected cloud fields are dynamically consistent for closed MCC and helps minimize false detections from secondary circulations. We demonstrate that the 3-km simulation is able to reproduce the scaling between

  16. A shallow convection parameterization for the non-hydrostatic MM5 mesoscale model

    SciTech Connect

    Seaman, N.L.; Kain, J.S.; Deng, A.

    1996-04-01

    A shallow convection parameterization suitable for the Pennsylvannia State University (PSU)/National Center for Atmospheric Research nonhydrostatic mesoscale model (MM5) is being developed at PSU. The parameterization is based on parcel perturbation theory developed in conjunction with a 1-D Mellor Yamada 1.5-order planetary boundary layer scheme and the Kain-Fritsch deep convection model.

  17. The mesoscale convection life cycle: Building block or prototype for large-scale tropical waves?

    NASA Astrophysics Data System (ADS)

    Mapes, Brian; Tulich, Stefan; Lin, Jialin; Zuidema, Paquita

    2006-12-01

    A cumulonimbus cloud may ascend and spawn its anvil cloud, precipitation, and downdrafts within an hour or so. This paper inquires why a similar progression of events (life cycle) is observed for tropical weather fluctuations with time scales of hours, days, and even weeks. Regressions using point data illustrate the characteristic unit of rain production: the mesoscale convective system (MCS), covering tens of kilometers and lasting several hours, with embedded convective rain cells. Meanwhile, averages over larger spatial areas indicate a self-similar progression from shallow to deep convection to stratiform anvils on many time scales. Synthetic data exercises indicate that simple superpositions of fixed-structure MCS life cycles (the Building Block hypothesis) cannot explain why longer period life cycles are similar. Rather, it appears that an MCS may be a small analogue or prototype of larger scale waves. Multiscale structure is hypothesized to occur via a Stretched Building Block conceptual model, in which the widths (durations) of zones of shallow, deep, and stratiform anvil clouds in MCSs are modulated by larger scale waves. Temperature ( T) and humidity ( q) data are examined and fed into an entraining plume model, in an attempt to elucidate their relative roles in these large-scale convection zone variations. T profile variations, with wavelengths shorter than troposphere depth, appear important for high-frequency ( ˜ 2-5-day period) convectively coupled waves, as density directly links convection (via buoyancy) and large-scale wave dynamics (via restoring force). Still, the associated q anomalies are several times greater than adiabatic, suggesting a strong amplification by shallow convective feedbacks. For lower frequency (intraseasonal) variability, q anomalies are considerably larger compared to T, and may be dominant.

  18. Radar and satellite studies of the impact of mesoscale convective precipitation and wind systems on visibility, sulfates, and oxidants during persistent elevated pollution episodes

    SciTech Connect

    Lyons, W.A.; Calby, R.H.

    1983-06-01

    The results are consistent and supportive, but certainly not conclusive, of a hypothesis suggesting that PBL sulfate mass removal into the free troposphere are on the order of several times that deposited on the surface during convective rainfalls. Thus, given the highly episodic nature of wet deposition and the potential major contribution of a single event to a season's total, a need exists to better understand the contributions of the various MCPS types to visibility improvement and sulfate removal, both to the surface and especially into the free atmosphere. Few projects are cited in the literature in which the precipitation chemistry data were even crudely stratified into major storm types though Raynor and Hayes did find significantly higher surface deposition during frontal thunderstorms and squall lines. Hales and Dana suggest the importance of designing an experiment to achieve an accurate closure of species mass balance within the entire domain of a convective storm. In noting the extreme variability in species washout over a region, they speculate that the bulk of the variability within and between storms must occur by superposition of the effects of inhomogeneous storm features, as well as source characteristics. Grant stated that a definitive characterization of individual storm dynamics and trajectories must be performed before long-term trends can be established with certainty. From the viewpoint of a severe storms meteorologist, much of the effort ongoing to understand regional wet deposition, sulfate, ozone, and visibility patterns, is subject to large errors of interpretation unless an attempt is made to better understand the highly different ways in which various precipitation systems, convective and stratiform, impact the PBL.

  19. A Study of the Response of Deep Tropical Clouds to Mesoscale Processes. Part 1; Modeling Strategies and Simulations of TOGA-COARE Convective Systems

    NASA Technical Reports Server (NTRS)

    Johnson, Daniel E.; Tao, W.-K.; Simpson, J.; Sui, C.-H.; Einaudi, Franco (Technical Monitor)

    2001-01-01

    Interactions between deep tropical clouds over the western Pacific warm pool and the larger-scale environment are key to understanding climate change. Cloud models are an extremely useful tool in simulating and providing statistical information on heat and moisture transfer processes between cloud systems and the environment, and can therefore be utilized to substantially improve cloud parameterizations in climate models. In this paper, the Goddard Cumulus Ensemble (GCE) cloud-resolving model is used in multi-day simulations of deep tropical convective activity over the Tropical Ocean-Global Atmosphere Coupled Ocean-Atmosphere Response Experiment (TOGA COARE). Large-scale temperature and moisture advective tendencies, and horizontal momentum from the TOGA-COARE Intensive Flux Array (IFA) region, are applied to the GCE version which incorporates cyclical boundary conditions. Sensitivity experiments show that grid domain size produces the largest response to domain-mean temperature and moisture deviations, as well as cloudiness, when compared to grid horizontal or vertical resolution, and advection scheme. It is found that a minimum grid-domain size of 500 km is needed to adequately resolve the convective cloud features. The control experiment shows that the atmospheric heating and moistening is primarily a response to cloud latent processes of condensation/evaporation, and deposition/sublimation, and to a lesser extent, melting of ice particles. Air-sea exchange of heat and moisture is found to be significant, but of secondary importance, while the radiational response is small. The simulated rainfall and atmospheric heating and moistening, agrees well with observations, and performs favorably to other models simulating this case.

  20. Characteristics of Mesoscale Organization in WRF Simulations of Convection during TWP-ICE

    NASA Technical Reports Server (NTRS)

    Del Genio, Anthony D.; Wu, Jingbo; Chen, Yonghua

    2013-01-01

    Compared to satellite-derived heating profiles, the Goddard Institute for Space Studies general circulation model (GCM) convective heating is too deep and its stratiform upper-level heating is too weak. This deficiency highlights the need for GCMs to parameterize the mesoscale organization of convection. Cloud-resolving model simulations of convection near Darwin, Australia, in weak wind shear environments of different humidities are used to characterize mesoscale organization processes and to provide parameterization guidance. Downdraft cold pools appear to stimulate further deep convection both through their effect on eddy size and vertical velocity. Anomalously humid air surrounds updrafts, reducing the efficacy of entrainment. Recovery of cold pool properties to ambient conditions over 5-6 h proceeds differently over land and ocean. Over ocean increased surface fluxes restore the cold pool to prestorm conditions. Over land surface fluxes are suppressed in the cold pool region; temperature decreases and humidity increases, and both then remain nearly constant, while the undisturbed environment cools diurnally. The upper-troposphere stratiform rain region area lags convection by 5-6 h under humid active monsoon conditions but by only 1-2 h during drier break periods, suggesting that mesoscale organization is more readily sustained in a humid environment. Stratiform region hydrometeor mixing ratio lags convection by 0-2 h, suggesting that it is strongly influenced by detrainment from convective updrafts. Small stratiform region temperature anomalies suggest that a mesoscale updraft parameterization initialized with properties of buoyant detrained air and evolving to a balance between diabatic heating and adiabatic cooling might be a plausible approach for GCMs.

  1. Model studies on the role of moist convection as a mechanism for interaction between the mesoscales

    NASA Technical Reports Server (NTRS)

    Waight, Kenneth T., III; Song, J. Aaron; Zack, John W.; Price, Pamela E.

    1991-01-01

    A three year research effort is described which had as its goal the development of techniques to improve the numerical prediction of cumulus convection on the meso-beta and meso-gamma scales. Two MESO models are used, the MASS (mesoscale) and TASS (cloud scale) models. The primary meteorological situation studied is the 28-29 Jun. 1986 Cooperative Huntsville Meteorological Experiment (COHMEX) study area on a day with relatively weak large scale forcing. The problem of determining where and when convection should be initiated is considered to be a major problem of current approaches. Assimilation of moisture data from satellite, radar, and surface data is shown to significantly improve mesoscale simulations. The TASS model is shown to reproduce some observed mesoscale features when initialized with 3-D observational data. Convection evolution studies center on comparison of the Kuo and Fritsch-Chappell cumulus parameterization schemes to each other, and to cloud model results. The Fritsch-Chappell scheme is found to be superior at about 30 km resolution, while the Kuo scheme does surprisingly well in simulating convection down to 10 km in cases where convergence features are well-resolved by the model grid. Results from MASS-TASS interaction experiments are presented and discussed. A discussion of the future of convective simulation is given, with the conclusion that significant progress is possible on several fronts in the next few years.

  2. Sea breeze: Induced mesoscale systems and severe weather

    NASA Technical Reports Server (NTRS)

    Nicholls, M. E.; Pielke, R. A.; Cotton, W. R.

    1990-01-01

    Sea-breeze-deep convective interactions over the Florida peninsula were investigated using a cloud/mesoscale numerical model. The objective was to gain a better understanding of sea-breeze and deep convective interactions over the Florida peninsula using a high resolution convectively explicit model and to use these results to evaluate convective parameterization schemes. A 3-D numerical investigation of Florida convection was completed. The Kuo and Fritsch-Chappell parameterization schemes are summarized and evaluated.

  3. 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.

  4. Use of ARM observations and numerical models to determine radiative and latent heating profiles of mesoscale convective systems for general circulation models

    SciTech Connect

    Robert A. Houze, Jr.

    2013-11-13

    We examined cloud radar data in monsoon climates, using cloud radars at Darwin in the Australian monsoon, on a ship in the Bay of Bengal in the South Asian monsoon, and at Niamey in the West African monsoon. We followed on with a more in-depth study of the continental MCSs over West Africa. We investigated whether the West African anvil clouds connected with squall line MCSs passing over the Niamey ARM site could be simulated in a numerical model by comparing the observed anvil clouds to anvil structures generated by the Weather Research and Forecasting (WRF) mesoscale model at high resolution using six different ice-phase microphysical schemes. We carried out further simulations with a cloud-resolving model forced by sounding network budgets over the Niamey region and over the northern Australian region. We have devoted some of the effort of this project to examining how well satellite data can determine the global breadth of the anvil cloud measurements obtained at the ARM ground sites. We next considered whether satellite data could be objectively analyzed to so that their large global measurement sets can be systematically related to the ARM measurements. Further differences were detailed between the land and ocean MCS anvil clouds by examining the interior structure of the anvils with the satellite-detected the CloudSat Cloud Profiling Radar (CPR). The satellite survey of anvil clouds in the Indo-Pacific region was continued to determine the role of MCSs in producing the cloud pattern associated with the MJO.

  5. Overshooting convection during TRO-pico: mesoscale modelling of two cases hydrating the lower stratosphere

    NASA Astrophysics Data System (ADS)

    Rivière, Emmanuel; Marécal, Virginie; Khaykin, Sergey; Amarouche, Nadir; Ghysels, Mélanie; Mappe-Fogaing, Irène; Behera, Abhinna; Held, Gerhard; França, Hermes

    2016-04-01

    One of the main aims of the TRO-pico project (2010-2015) was to study the variability of overshooting convection at the local scale to try to deduce a typical impact on the TTL water at the global scale. In this study, we've identified local maximum in the water vapour profiles gathered by the balloon-borne hygrometers Pico-SDLA and Flash above Bauru, Brazil (22.3 S) during the TRO-pico campaign. We tried to link them to overshooting cells in the surrounding of Bauru with a trajectory analysis. In this study we select a couple of cases of overshooting convection both sampled by the Bauru S-Band radar and by one of the balloon-borne instruments of the TRO-pico campaign in 2012 and 2013. The selected cases are the case of March 13, 2012 (hereafter M12), sounded by both hygrometers Pico-SDLA and FLASH, and the case of January 26, 2013 (hereafter J13), sounded by Pico-SDLA. For the M12 case, local water vapour enhancements at two different altitudes due to two different cells were reported, with local enhancement of about 0.65 ppmv. For the J26 case, the water enhancement was about 1 ppmv. The corresponding mesoscale simulations with the Brazilian Regional Atmospheric Modelling System (BRAMS) using 3 nested grids with horizontal resolution down to 800 m were carried out. Simulation results are compared to Bauru's radar echo tops and and water vapour in situ measurements. As for the M12 simulation, the model is doing a rather good job in reproducing several overshooting cells, both in severity and timing. Associated stratospheric water budget are computed for each cases.

  6. An Automated Method to Identify Mesoscale Convective Complexes (MCCs) Implementing Graph Theory

    NASA Astrophysics Data System (ADS)

    Whitehall, K. D.; Mattmann, C. A.; Jenkins, G. S.; Waliser, D. E.; Rwebangira, R.; Demoz, B.; Kim, J.; Goodale, C. E.; Hart, A. F.; Ramirez, P.; Joyce, M. J.; Loikith, P.; Lee, H.; Khudikyan, S.; Boustani, M.; Goodman, A.; Zimdars, P. A.; Whittell, J.

    2013-12-01

    Mesoscale convective complexes (MCCs) are convectively-driven weather systems with a duration of ~10 - 12 hours and contributions of large amounts to the rainfall daily and monthly totals. More than 400 MCCs occur annually over various locations on the globe. In West Africa, ~170 MCCs occur annually during the 180 days representing the summer months (June - November), and contribute ~75% of the annual wet season rainfall. The main objective of this study is to improve automatic identification of MCC over West Africa. The spatial expanse of MCCs and the spatio-temporal variability in their convective characteristics make them difficult to characterize even in dense networks of radars and/or surface gauges. As such there exist criteria for identifying MCCs with satellite images - mostly using infrared (IR) data. Automated MCC identification methods are based on forward and/or backward in time spatial-temporal analysis of the IR satellite data and characteristically incorporate a manual component as these algorithms routinely falter with merging and splitting cloud systems between satellite images. However, these algorithms are not readily transferable to voluminous data or other satellite-derived datasets (e.g. TRMM), thus hindering comprehensive studies of these features both at weather and climate timescales. Recognizing the existing limitations of automated methods, this study explores the applicability of graph theory to creating a fully automated method for deriving a West African MCC dataset from hourly infrared satellite images between 2001- 2012. Graph theory, though not heavily implemented in the atmospheric sciences, has been used for the predicting (nowcasting) of thunderstorms from radar and satellite data by considering the relationship between atmospheric variables at a given time, or for the spatial-temporal analysis of cloud volumes. From these few studies, graph theory appears to be innately applicable to the complexity, non-linearity and inherent

  7. Regional analysis of convective systems during the West African monsoon

    NASA Astrophysics Data System (ADS)

    Guy, Bradley Nicholas

    The West African monsoon (WAM) occurs during the boreal summer and is responsible for a majority of precipitation in the northern portion of West Africa. A distinct shift of precipitation, often driven by large propagating mesoscale convective systems, is indicated from satellite observations. Excepting the coarser satellite observations, sparse data across the continent has prevented understanding of mesoscale variability of these important systems. The interaction between synoptic and mesoscale features appears to be an important part of the WAM system. Without an understanding of the mesoscale properties of precipitating systems, improved understanding of the feedback mechanism between spatial scales cannot be attained. Convective and microphysical characteristics of West African convective systems are explored using various observational data sets. Focus is directed toward meso -alpha and -beta scale convective systems to improve our understanding of characteristics at this spatial scale and contextualize their interaction with the larger-scale. Ground-based radar observations at three distinct geographical locations in West Africa along a common latitudinal band (Niamey, Niger [continental], Kawsara, Senegal [coastal], and Praia, Republic of Cape Verde [maritime]) are analyzed to determine convective system characteristics in each domain during a 29 day period in 2006. Ancillary datasets provided by the African Monsoon Multidisciplinary Analyses (AMMA) and NASA-AMMA (NAMMA) field campaigns are also used to place the radar observations in context. Results show that the total precipitation is dominated by propagating mesoscale convective systems. Convective characteristics vary according to environmental properties, such as vertical shear, CAPE, and the degree of synoptic forcing. Data are bifurcated based on the presence or absence of African easterly waves. In general, African easterly waves appear to enhance mesoscale convective system strength

  8. Convectively Generated Meso-Scale Gravity Waves in ER-2 Observations During CRYSTAL-FACE

    NASA Astrophysics Data System (ADS)

    Wang, L.; Alexander, M. J.

    2004-12-01

    The MMS and MTP data from ER-2 observations during the CRYSTAL-FACE campaign are analyzed to retrieve meso-scale gravity wave information at the aircraft flight level. For a given flight segment, the S-transform is used to locate small-scale (10-25 km) gravity wave events. The Stokes method and the MTP method are then used to determine the horizontal propagation directions, and the vertical scales of the wave events, respectively. Other wave parameters, such as horizontal scales, group velocities, can also be derived. From the estimated propagation directions, group velocities, and the ground-based radar reflectivity observations, some wave events are traced back to convectively active regions, suggesting convection as the source of the waves.

  9. Experiments with the Mesoscale Atmospheric Simulation System (MASS) using the synthetic relative humidity

    NASA Technical Reports Server (NTRS)

    Chang, Chia-Bo

    1994-01-01

    This study is intended to examine the impact of the synthetic relative humidity on the model simulation of mesoscale convective storm environment. The synthetic relative humidity is derived from the National Weather Services surface observations, and non-conventional sources including aircraft, radar, and satellite observations. The latter sources provide the mesoscale data of very high spatial and temporal resolution. The synthetic humidity data is used to complement the National Weather Services rawinsonde observations. It is believed that a realistic representation of initial moisture field in a mesoscale model is critical for the model simulation of thunderstorm development, and the formation of non-convective clouds as well as their effects on the surface energy budget. The impact will be investigated based on a real-data case study using the mesoscale atmospheric simulation system developed by Mesoscale Environmental Simulations Operations, Inc. The mesoscale atmospheric simulation system consists of objective analysis and initialization codes, and the coarse-mesh and fine-mesh dynamic prediction models. Both models are a three dimensional, primitive equation model containing the essential moist physics for simulating and forecasting mesoscale convective processes in the atmosphere. The modeling system is currently implemented at the Applied Meteorology Unit, Kennedy Space Center. Two procedures involving the synthetic relative humidity to define the model initial moisture fields are considered. It is proposed to perform several short-range (approximately 6 hours) comparative coarse-mesh simulation experiments with and without the synthetic data. They are aimed at revealing the model sensitivities should allow us both to refine the specification of the observational requirements, and to develop more accurate and efficient objective analysis schemes. The goal is to advance the MASS (Mesoscal Atmospheric Simulation System) modeling expertise so that the model

  10. Sensitivity and dependence of mesoscale downscaled prediction results on different parameterizations of convection and cloud microphysics

    NASA Astrophysics Data System (ADS)

    Remesan, R.; Bellerby, T.

    2012-04-01

    These days as operational real-time flood forecasting and warning systems rely more on high resolution mesoscale models employed with coupling system of hydrological models. So it is inevitable to assess prediction sensitivity or disparity in collection with selection of different cumulus and microphysical parameterization schemes, to assess the possible uncertainties associated with mesoscale downscaling. This study investigates the role of physical parameterization in mesoscale model simulations on simulation of unprecedented heavy rainfall over Yorkshire-Humberside in United Kingdom during 1-14th March, 1999. The study has used a popular mesoscale numerical weather prediction model named Advanced Research Weather Research Forecast model (version 3.3) which was developed at the National Center for Atmospheric Research (NCAR) in the USA. This study has performed a comprehensive evaluation of four cumulus parameterization schemes (CPSs) [Kian-Fritsch (KF), Betts-Miller-Janjic (BMJ) and Grell-Devenyi ensemble (GD)] and five microphysical schemes Lin et al scheme, older Thompson scheme, new Thompson scheme, WRF Single Moment - 6 class scheme, and WRF Single Moment - 5 class scheme] to identify how their inclusion influences the mesoscale model's meteorological parameter estimation capabilities and related uncertainties in prediction. The case study was carried out at the Upper River Derwent catchment in Northern Yorkshire, England using both the ERA-40 reanalysis data and the land based observation data.

  11. Impact of Resolution on Simulation of Closed Mesoscale Cellular Convection Identified by Dynamically Guided Watershed Segmentation

    SciTech Connect

    Martini, Matus N.; Gustafson, William I.; Yang, Qing; Xiao, Heng

    2014-11-18

    Organized mesoscale cellular convection (MCC) is a common feature of marine stratocumulus that forms in response to a balance between mesoscale dynamics and smaller scale processes such as cloud radiative cooling and microphysics. We use the Weather Research and Forecasting model with chemistry (WRF-Chem) and fully coupled cloud-aerosol interactions to simulate marine low clouds during the VOCALS-REx campaign over the southeast Pacific. A suite of experiments with 3- and 9-km grid spacing indicates resolution-dependent behavior. The simulations with finer grid spacing have smaller liquid water paths and cloud fractions, while cloud tops are higher. The observed diurnal cycle is reasonably well simulated. To isolate organized MCC characteristics we develop a new automated method, which uses a variation of the watershed segmentation technique that combines the detection of cloud boundaries with a test for coincident vertical velocity characteristics. This ensures that the detected cloud fields are dynamically consistent for closed MCC, the most common MCC type over the VOCALS-REx region. We demonstrate that the 3-km simulation is able to reproduce the scaling between horizontal cell size and boundary layer height seen in satellite observations. However, the 9-km simulation is unable to resolve smaller circulations corresponding to shallower boundary layers, instead producing invariant MCC horizontal scale for all simulated boundary layers depths. The results imply that climate models with grid spacing of roughly 3 km or smaller may be needed to properly simulate the MCC structure in the marine stratocumulus regions.

  12. Evaluation of the synoptic and mesoscale predictive capabilities of a mesoscale atmospheric simulation system

    NASA Technical Reports Server (NTRS)

    Koch, S. E.; Skillman, W. C.; Kocin, P. J.; Wetzel, P. J.; Brill, K.; Keyser, D. A.; Mccumber, M. C.

    1983-01-01

    The overall performance characteristics of a limited area, hydrostatic, fine (52 km) mesh, primitive equation, numerical weather prediction model are determined in anticipation of satellite data assimilations with the model. The synoptic and mesoscale predictive capabilities of version 2.0 of this model, the Mesoscale Atmospheric Simulation System (MASS 2.0), were evaluated. The two part study is based on a sample of approximately thirty 12h and 24h forecasts of atmospheric flow patterns during spring and early summer. The synoptic scale evaluation results benchmark the performance of MASS 2.0 against that of an operational, synoptic scale weather prediction model, the Limited area Fine Mesh (LFM). The large sample allows for the calculation of statistically significant measures of forecast accuracy and the determination of systematic model errors. The synoptic scale benchmark is required before unsmoothed mesoscale forecast fields can be seriously considered.

  13. a Mesoscale Atmospheric Dispersion Modeling System for Simulations of Topographically Induced Atmospheric Flow and Air Pollution Dispersion.

    NASA Astrophysics Data System (ADS)

    Boybeyi, Zafer

    A mesoscale atmospheric dispersion modeling system has been developed to investigate mesoscale circulations and associated air pollution dispersion, including effects of terrain topography, large water bodies and urban areas. The system is based on a three-dimensional mesoscale meteorological model coupled with two dispersion models (an Eulerian dispersion model and a Lagrangian particle dispersion model). The mesoscale model is hydrostatic and based on primitive equations formulated in a terrain-following coordinate system with a E-varepsilon turbulence closure scheme. The Eulerian dispersion model is based on numerical solution of the advection-diffusion equation to allow one to simulate releases of non-buoyant pollutants (especially from area and volume sources). The Lagrangian particle dispersion model allows one to simulate releases of buoyant pollutants from arbitrary sources (particularly from point and line sources). The air pollution dispersion models included in the system are driven by the meteorological information provided by the mesoscale model. Mesoscale atmospheric circulations associated with sea and lake breezes have been examined using the mesoscale model. A series of model sensitivity studies were performed to investigate the effects of different environmental parameters on these circulations. It was found that the spatial and temporal variation of the sea and lake breeze convergence zones and the associated convective activities depend to a large extent on the direction and the magnitude of the ambient wind. Dispersion of methyl isocyanate gas from the Bhopal accident was investigated using the mesoscale atmospheric dispersion modeling system. A series of numerical experiments were performed to investigate the possible role of the mesoscale circulations on this industrial gas episode. The temporal and spatial variations of the wind and turbulence fields were simulated with the mesoscale model. The dispersion characteristics of the accidental

  14. The structure and dynamics of mesoscale systems influencing severe thunderstorm development during AVE/SESAME 1

    NASA Technical Reports Server (NTRS)

    Wilson, G. S.

    1982-01-01

    Relationships between meso-beta scale systems and thunderstorm formation were examined as part of the NASA atmospheric variability experiment/severe environmental storms and mesoscale experiment 1979. The McIdas program was employed for meso-beta scale analyses of atmospheric structure and dynamics in kinematic computations of the Abilene Triangle on a grid mesh of 100 km for station spacing of 275 km. Mesoscale short wave systems were detected imbedded and propagating cyclonically around upper-level vortex circulation and creating environmental conditions conducive to thunderstorm development. TIROS-N and GOES satellite data served to connect the systems with two convective storms which developed. The necessity to use spaceborne instrumentation carried on the Shuttle or on free-flying satellites for enhancing the data-base on storm development is noted.

  15. Mesoscale modeling of lake effect snow over Lake Erie - sensitivity to convection, microphysics and the water temperature

    NASA Astrophysics Data System (ADS)

    Theeuwes, N. E.; Steeneveld, G. J.; Krikken, F.; Holtslag, A. A. M.

    2010-03-01

    Lake effect snow is a shallow convection phenomenon during cold air advection over a relatively warm lake. A severe case of lake effect snow over Lake Erie on 24 December 2001 was studied with the MM5 and WRF mesoscale models. This particular case provided over 200 cm of snow in Buffalo (NY), caused three casualties and 10 million of material damage. Hence, the need for a reliable forecast of the lake effect snow phenomenon is evident. MM5 and WRF simulate lake effect snow successfully, although the intensity of the snowbelt is underestimated. It appears that significant differences occur between using a simple and a complex microphysics scheme. In MM5, the use of the simple-ice microphysics scheme results in the triggering of the convection much earlier in time than with the more sophisticated Reisner-Graupel-scheme. Furthermore, we find a large difference in the maximum precipitation between the different nested domains: Reisner-Graupel produces larger differences in precipitation between the domains than "simple ice". In WRF, the sophisticated Thompson microphysics scheme simulates less precipitation than the simple WSM3 scheme. Increased temperature of Lake Erie results in an exponential growth in the 24-h precipitation. Regarding the convection scheme, the updated Kain-Fritsch scheme (especially designed for shallow convection during lake effect snow), gives only slight differences in precipitation between the updated and the original scheme.

  16. Mesoscale Coupled Ocean-Atmosphere Feedbacks in Boundary Current Systems

    NASA Astrophysics Data System (ADS)

    Putrasahan, Dian Ariyani

    The focus of this dissertation is on studying ocean-atmosphere (OA) interactions in the Humboldt Current System (HCS) and Kuroshio Extension (KE) region using satellite observations and the Scripps Coupled Ocean-Atmosphere Regional (SCOAR) model. Within SCOAR, a new technique is introduced by implementing an interactive 2-D spatial smoother within the SST-flux coupler to remove the mesoscale SST field felt by the atmosphere. This procedure allows large-scale SST coupling to be preserved while extinguishing the mesoscale eddy impacts on the atmospheric boundary layer (ABL). This technique provides insights to spatial-scale dependence of OA coupling, and the impact of mesoscale features on both the ABL and the surface ocean. For the HCS, the use of downscaled forcing from SCOAR, as compared to NCEP Reanalysis 2, proves to be more appropriate in quantifying wind-driven upwelling indices along the coast of Peru and Chile. The difference in their wind stress distribution has significant impact on the wind-driven upwelling processes and total upwelling transport along the coast. Although upwelling induced by coastal Ekman transport dominates the wind-driven upwelling along coastal areas, Ekman pumping can account for 30% of the wind-driven upwelling in several coastal locations. Control SCOAR shows significant SST-wind stress coupling during fall and winter, while Smoothed SCOAR shows insignificant coupling throughout, indicating the important role of ocean mesoscale eddies on air-sea coupling in HCS. The SST-wind stress coupling however, did not produce any rectified response on the ocean eddies. Coupling between SST, wind speed and latent heat flux is insignificant on large-scale coupling and full coupling mode. On the other hand, coupling between these three variables are significant on the mesoscale for most of the model run, which suggests that mesoscale SST affects latent heat through direct flux anomalies as well as indirectly through stability changes on the

  17. Telescoping views of planetary, synoptic, mesoscale and explicit-convection structure in a nonhydrostatic global GCM with 7km mesh

    NASA Astrophysics Data System (ADS)

    Mapes, B. E.; Putman, W.

    2014-12-01

    Visualizations and statistics from a 2-year 7km nonhydrostatic Nature Run of the NASA-Goddard GEOS-5 model will be shown, to illustrate how the crude but explicit convective cells and their mesoscale processes function as coherent entities withing the synoptic and planetary-scale general circulation. Comparisons with coarse-grained data and output from lower-resolution simulations illustrate how parameterizations can carry the same fluxes necessary for general circulation balances, but only as the mean state is distorted in order to cause the parameterizations to produce those fluxes. From these considerations, and from related considerations of outputds of a more homogeneous (cyclic) Giga-LES, we will attempt to draw conclusions about the geophysical importance of coherent cross-scale spatial organization vs. simply having a rich spectrum of scales.

  18. Sea breeze-induced mesoscale systems and severe weather

    NASA Technical Reports Server (NTRS)

    Pielke, R. A.

    1985-01-01

    The relationship between thunderstorm activity during the summer months along coastal regions of the Atlantic and Gulf coasts and the dry sea breeze circulation was investigated. Satellite composites of thunderstorm activity for synoptically undisturbed conditions have been obtained for south Florida for a series of days in the summer of 1983. These data were catalogued into different low level synoptic flow regimes. Five synoptic flow regimes were found from the data. A three-dimensional mesoscale numerical model was used for each sysnoptic flow regime to quantitatively predict the location of enhanced thunderstorm activity. This model includes a parameterization of vegetation and soil moisture feedbacks as well as a sophisticated planetary boundary layer representation. Using the results of the satellite image composites, spatial and temporal characteristics of deep convective cloud patterns and their variation with synoptic flow are described. The results from the numerical model have provided explanations for the observed patterns.

  19. Convection

    NASA Astrophysics Data System (ADS)

    Britz, Dieter

    Convection has long been coupled with electrochemistry, and the name hydrodynamic voltammetry has become standard. In electroanalytical chemistry we mainly seek reproducible conditions. These are almost always attained by systems in which a steady convective state is achieved, although not always. Thus, the once popular dropping mercury electrode (see texts such as [74, 257]) has convection around it, but is never in steady state; it might be called a reproducible periodic dynamic state.

  20. Transitional dispersive scenarios driven by mesoscale flows on complex terrain under strong dry convective conditions

    NASA Astrophysics Data System (ADS)

    Palau, J. L.; Pérez-Landa, G.; Millán, M. M.

    2009-01-01

    By experimentation and modelling, this paper analyses the atmospheric dispersion of the SO2 emissions from a power plant on complex terrain under strong convective conditions, describing the main dispersion features as an ensemble of "stationary dispersive scenarios" and reformulating some "classical" dispersive concepts to deal with the systematically monitored summer dispersive scenarios in inland Spain. The results and discussions presented arise from a statistically representative study of the physical processes associated with the multimodal distribution of pollutants aloft and around a 343-m-tall chimney under strong dry convective conditions in the Iberian Peninsula. This paper analyses the importance of the identification and physical implications of transitional periods for air quality applications. The indetermination of a transversal plume to the preferred transport direction during these transitional periods implies a small (or null) physical significance of the classical definition of horizontal standard deviation of the concentration distribution.

  1. Scaling Laws for Mesoscale and Microscale Systems

    SciTech Connect

    Spletzer, Barry

    1999-08-23

    The set of laws developed and presented here is by no means exhaustive. Techniques have been present to aid in the development of additional scaling laws and to combine these and other laws to produce additional useful relationships. Some of the relationships produced here have yielded perhaps surprising results. Examples include the fifth order scaling law for electromagnetic motor torque and the zero order scaling law for capacitive motor power. These laws demonstrate important facts about actuators in small-scale systems. The primary intent of this introduction into scaling law analysis is to provide needed tools to examine possible areas of the research in small-scale systems and direct research toward more fruitful areas. Numerous examples have been included to show the validity of developing scaling laws based on first principles and how real world systems tend to obey these laws even when many other variables may potentially come into play. Development of further laws may well serve to provide important high-level direction to the continued development of small-scale systems.

  2. Lightning characteristics related to radar morphology in linear convective systems over North China plain

    NASA Astrophysics Data System (ADS)

    Liu, D.; Qie, X.; Su, D.

    2015-12-01

    Based on SAFIR3000 Lightning Location Network and radar information, 89 linear mesoscale convective systems occurred in Beijing area are analyzed from the year of 2007 to 2011. All the linear convective systems are classified to six categories by radar morphologies, including leading convective lines with trailing stratiform region (TS), leading stratiform region trailing convective region (LS), leading convective lines with no stratiform region (NS), bow echo of leading line (BE), leading convective lines with parallel stratiform region (PS). The results show that linear convective systems occurred frequently in summer time over Beijing area, particularly the TS and LS mode, accounted for 61% of the linear MCSs. According to synoptic chart, the 89 linear convective systems are mainly influenced by cold vortex, wind shear, moving trough and western Pacific subtropical high. The lightning activities of linear MCSs including TS MCSs, LS MCSs and PS MCSs which are most frequent of three categories are discussed. On average, lightning mainly located in the linear convective region, and less or no lightning located in the trailing stratiform region. The lightning are mainly located in the strong radar echo of TS, LS and PS mode in the mature stage, but lightning activities present apparent different in the dissipating stage. At the dissipating stage, the lightning occurred gradually increased in the stratiform region of TS mode, whereas there is no lightning occurred in the stratiform region of LS mode, and +CG lightning take account for large percentage in PS MCSs.

  3. Debris Flows and Record Floods from Extreme Mesoscale Convective Thunderstorms over the Santa Catalina Mountains, Arizona

    USGS Publications Warehouse

    Magirl, Christopher S.; Shoemaker, Craig; Webb, Robert H.; Schaffner, Mike; Griffiths, Peter G.; Pytlak, Erik

    2007-01-01

    Ample geologic evidence indicates early Holocene and Pleistocene debris flows from the south side of the Santa Catalina Mountains north of Tucson, Arizona, but few records document historical events. On July 31, 2006, an unusual set of atmospheric conditions aligned to produce record floods and an unprecedented number of debris flows in the Santa Catalinas. During the week prior to the event, an upper-level area of low pressure centered near Albuquerque, New Mexico generated widespread heavy rainfall in southern Arizona. After midnight on July 31, a strong complex of thunderstorms developed over central Arizona in a deformation zone that formed on the back side of the upper-level low. High atmospheric moisture (2.00' of precipitable water) coupled with cooling aloft spawned a mesoscale thunderstorm complex that moved southeast into the Tucson basin. A 15-20 knot low-level southwesterly wind developed with a significant upslope component over the south face of the Santa Catalina Mountains advecting moist and unstable air into the merging storms. National Weather Service radar indicated that a swath of 3-6' of rainfall occurred over the lower and middle elevations of the southern Santa Catalina Mountains. This intense rain falling on saturated soil triggered over 250 hillslope failures and debris flows throughout the mountain range. Sabino Canyon, a heavily used recreation area administered by the U.S. Forest Service, was the epicenter of mass wasting, where at least 18 debris flows removed structures, destroyed the roadway in multiple locations, and closed public access for months. The debris flows were followed by streamflow floods which eclipsed the record discharge in the 75-year gaging record of Sabino Creek. In five canyons adjacent to Sabino Canyon, debris flows approached or excited the mountain front, compromising floow conveyance structures and flooding some homes.

  4. On the synoptic and mesoscale organization of mid-latitude, continental convective snow events

    NASA Astrophysics Data System (ADS)

    Melick, Christopher J.

    An ingredients-based methodology was pursued in order to evaluate the likelihood of thunderstorms occurring in the presence of snowfall (i.e. thundersnow; TSSN) by validating the collective presence of forcing, moisture, and instability in the atmosphere. Since the latter factor has been cited as crucial in distinguishing from typical snowstorms (i.e. non-TSSN), the detailed examination focused on stability characteristics of wintertime convection across the central United States immediately leading up to the onset of the event. Although results from several commonly employed techniques performed successfully, the research primarily analyzed the value of the seldom applied growth rate parameter through initial output fields of the 40-km Rapid Update Cycle model. The current work substantiated the premise that atmospheres were more unstable in episodes of convective snow. The analyses revealed pronounced forcing mechanisms and greater susceptibility to the produced upward vertical motions, thus, illustrating the positive feedback and strong, crucial connection between the two ingredients. The development of TSSN and any associated banding was correctly and most accurately predicted from trends in plots of the growth rate parameter analyzed at the level at which the highest significant growth rates occurred. An outlook for elevated, cold-season thunderstorms can be more accurately issued by identifying regions where reduced values of equivalent potential vorticity (i.e. small symmetric stability or instability) are collocated with estimates of high growth rates (i.e. where small-scale slantwise perturbations will grow). Given the overall success, it is hoped that some of the conclusions established will be implemented routinely in an operational environment and provide forecasters an additional, essential tool in dealing with nowcasting situations of hazardous winter weather events.

  5. Debris flows and Record Floods from Extreme Mesoscale Convective Thunderstorms over the Santa Catalina Mountains, Arizona

    NASA Astrophysics Data System (ADS)

    Magirl, C. S.; Shoemaker, C.; Webb, R. H.; Schaffner, M.; Griffiths, P. G.; Pytlak, E.

    2006-12-01

    Ample geologic evidence indicates early Holocene and Pleistocene debris flows from the south side of the Santa Catalina Mountains north of Tucson, Arizona, but few records document historical events. On July 31, 2006, an unusual set of atmospheric conditions aligned to produce record floods and an unprecedented number of debris flows in the Santa Catalinas. During the week prior to the event, an upper-level area of low pressure centered near Albuquerque, New Mexico generated widespread heavy rainfall in southern Arizona. After midnight on July 31, a strong and widespread complex of thunderstorms developed over the Mogollon Rim in central Arizona in a deformation zone that formed on the back side of the upper-level low. High atmospheric moisture (50 mm of precipitable water) coupled with cooling aloft spawned a mesoscale thunderstorm complex that moved southeast into the Tucson basin. These thunderstorms interacted with a low- to mid-level zone of atmospheric instability to create an initial wave of rainfall across the Tucson metropolitan area in the early morning hours. A second wave of thunderstorms and heavy rain developed over the Santa Catalina Mountain near dawn. A 15-20 knot low-level southwesterly wind developed with a significant upslope component over the south face of the Santa Catalina Mountains advecting moist and unstable air into the merging storms. NEXRAD radar indicates that a swath of 75-150 mm of rainfall occurred over the lower and middle elevations of the southern Santa Catalina Mountains in three increments: (1) from 2-6 AM, moderate intensity rainfall up to 65 mm; (2) from 6-7 AM, intensities up to 75 mm in 45 minutes; and (3) a final burst approaching 50 mm in 45 minutes from 8-9 AM. This intense rain falling on saturated soil triggered multiple debris flows in four adjacent canyons. Sabino Canyon, a heavily used recreation area administered by the U.S. Forest Service, was the epicenter of mass wasting where at least 18 debris flows removed

  6. Mesoscale Modeling of Impact Compaction of Primitive Solar System Solids

    NASA Astrophysics Data System (ADS)

    Davison, Thomas M.; Collins, Gareth S.; Bland, Philip A.

    2016-04-01

    We have developed a method for simulating the mesoscale compaction of early solar system solids in low-velocity impact events using the iSALE shock physics code. Chondrules are represented by non-porous disks, placed within a porous matrix. By simulating impacts into bimodal mixtures over a wide range of parameter space (including the chondrule-to-matrix ratio, the matrix porosity and composition, and the impact velocity), we have shown how each of these parameters influences the shock processing of heterogeneous materials. The temperature after shock processing shows a strong dichotomy: matrix temperatures are elevated much higher than the chondrules, which remain largely cold. Chondrules can protect some matrix from shock compaction, with shadow regions in the lee side of chondrules exhibiting higher porosity that elsewhere in the matrix. Using the results from this mesoscale modeling, we show how the ɛ - α porous-compaction model parameters depend on initial bulk porosity. We also show that the timescale for the temperature dichotomy to equilibrate is highly dependent on the porosity of the matrix after the shock, and will be on the order of seconds for matrix porosities of less than 0.1, and on the order of tens to hundreds of seconds for matrix porosities of ˜0.3-0.5. Finally, we have shown that the composition of the post-shock material is able to match the bulk porosity and chondrule-to-matrix ratios of meteorite groups such as carbonaceous chondrites and unequilibrated ordinary chondrites.

  7. Thin-walled compliant plastic structures for mesoscale fluidic systems

    NASA Astrophysics Data System (ADS)

    Miles, Robin R.; Schumann, Daniel L.

    1999-06-01

    Thin-walled, compliant plastic structures for meso-scale fluidic systems were fabricated, tested and used to demonstrate valving, pumping, metering and mixing. These structures permit the isolation of actuators and sensors form the working fluid, thereby reducing chemical compatibility issues. The thin-walled, compliant plastic structures can be used in either a permanent, reusable system or as an inexpensive disposable for single-use assay systems. The implementation of valving, pumping, mixing and metering operations involve only an elastic change in the mechanical shape of various portions of the structure. Advantages provided by the thin-walled plastic structures include reduced dead volume and rapid mixing. Five different methods for fabricating the thin-walled plastic structures discussed including laser welding, molding, vacuum forming, thermal heat staking and photolithographic patterning techniques.

  8. Surface mesoscale features associated with leading convective line-trailing stratiform squall lines over the Gangetic West Bengal

    NASA Astrophysics Data System (ADS)

    Dawn, S.; Mandal, M.

    2014-08-01

    In this paper an attempt is made to identify the mesoscale features in surface pressure pattern, if any, associated with thunderstorm over the Gangetic West Bengal region in India. The study was conducted over Kharagpur and the adjoining area in the Gangetic West Bengal, frequently affected by thunderstorms during the pre-monsoon seasons of April-May. Observations recorded at 50 m instrumented micro-meteorological tower and upper air sounding at Kharagpur under nationally coordinated Severe Thunderstorm Observations and Regional Modeling (STORM) Programme are used to study the variation in surface pressure, wind speed and direction, temperature and relative humidity associated with the squall lines with trailing stratiform precipitation region. In the surface pressure variation, pre-squall mesolow, mesohigh and wake low are identified with the passage of the squall line at Kharagpur. It is observed that in the squall line with trailing stratiform precipitation shield, the mesohigh is associated with convective line and wake low exists at the rear of the storms. The position of the mesohigh is typically found in the vicinity of the heavy rain directly beneath the downdraft. The mesohigh seems to be initiated by the cooling due to evaporation of precipitation in the downdraft and intensified due to the non-hydrostatic effect because of the rainfall directly beneath the downdraft. It is also observed that the passage of trailing edges of the stratiform precipitation coincided with the wake low. Upper air sounding shows mid-tropospheric cooling and lower tropospheric warming. It may be possible due to the dominance of evaporative cooling in the mid-levels and dynamically forced descending motion leading to adiabatic warming in the low levels which may lead to the formation of the wake low.

  9. Studying the impact of overshooting convection on the tropopause tropical layer (TTL) water vapor budget at the continental scale using a mesoscale model

    NASA Astrophysics Data System (ADS)

    Behera, Abhinna; Rivière, Emmanuel; Marécal, Virginie; Claud, Chantal; Rysman, Jean-François; Geneviève, Seze

    2016-04-01

    Water vapour budget is a key component in the earth climate system. In the tropical upper troposphere, lower stratosphere (UTLS), it plays a central role both on the radiative and the chemical budget. Its abundance is mostly driven by slow ascent above the net zero radiative heating level followed by ice crystals' formation and sedimentation, so called the cold trap. In contrast to this large scale temperature driven process, overshooting convection penetrating the stratosphere could be one piece of the puzzle. It has been proven to hydrate the lower stratosphere at the local scale. Satellite-borne H2O instruments can not measure with a fine enough resolution the water vapour enhancements caused by overshooting convection. The consequence is that it is difficult to estimate the role of overshooting deep convection at the global scale. Using a mesoscale model i.e., Brazilian Regional Atmospheric Modelling System (BRAMS), past atmospheric conditions have been simulated for the full wet season i.e., Nov 2012 to Mar 2013 having a single grid with horizontal resolution of 20 km × 20km over a large part of Brazil and South America. This resolution is too coarse to reproduce overshooting convection in the model, so that this simulation should be used as a reference (REF) simulation, without the impact of overshooting convection in the TTL water budget. For initialisation, as well as nudging the grid boundary in every 6 hours, European Centre for Medium-Range Weather Forecasts (ECMWF) analyses has been used. The size distribution of hydrometeors and number of cloud condensation nuclei (CCN) are fitted in order to best reproduce accumulated precipitations derived from Tropical Rainfall Measuring Mission (TRMM). Similarly, GOES and MSG IR mages have been thoroughly compared with model's outputs, using image correlation statistics for the position of the clouds. The model H2O variability during the wet season, is compared with the in situ balloon-borne measurements during

  10. Mesoscale Modeling of Impact Compaction of Primitive Solar System Solids

    NASA Astrophysics Data System (ADS)

    Davison, Thomas M.; Collins, Gareth S.; Bland, Philip A.

    2016-04-01

    We have developed a method for simulating the mesoscale compaction of early solar system solids in low-velocity impact events using the iSALE shock physics code. Chondrules are represented by non-porous disks, placed within a porous matrix. By simulating impacts into bimodal mixtures over a wide range of parameter space (including the chondrule-to-matrix ratio, the matrix porosity and composition, and the impact velocity), we have shown how each of these parameters influences the shock processing of heterogeneous materials. The temperature after shock processing shows a strong dichotomy: matrix temperatures are elevated much higher than the chondrules, which remain largely cold. Chondrules can protect some matrix from shock compaction, with shadow regions in the lee side of chondrules exhibiting higher porosity that elsewhere in the matrix. Using the results from this mesoscale modeling, we show how the ε ‑ α porous-compaction model parameters depend on initial bulk porosity. We also show that the timescale for the temperature dichotomy to equilibrate is highly dependent on the porosity of the matrix after the shock, and will be on the order of seconds for matrix porosities of less than 0.1, and on the order of tens to hundreds of seconds for matrix porosities of ∼0.3–0.5. Finally, we have shown that the composition of the post-shock material is able to match the bulk porosity and chondrule-to-matrix ratios of meteorite groups such as carbonaceous chondrites and unequilibrated ordinary chondrites.

  11. Entropy Production in Convective Hydrothermal Systems

    NASA Astrophysics Data System (ADS)

    Boersing, Nele; Wellmann, Florian; Niederau, Jan

    2016-04-01

    Exploring hydrothermal reservoirs requires reliable estimates of subsurface temperatures to delineate favorable locations of boreholes. It is therefore of fundamental and practical importance to understand the thermodynamic behavior of the system in order to predict its performance with numerical studies. To this end, the thermodynamic measure of entropy production is considered as a useful abstraction tool to characterize the convective state of a system since it accounts for dissipative heat processes and gives insight into the system's average behavior in a statistical sense. Solving the underlying conservation principles of a convective hydrothermal system is sensitive to initial conditions and boundary conditions which in turn are prone to uncertain knowledge in subsurface parameters. There exist multiple numerical solutions to the mathematical description of a convective system and the prediction becomes even more challenging as the vigor of convection increases. Thus, the variety of possible modes contained in such highly non-linear problems needs to be quantified. A synthetic study is carried out to simulate fluid flow and heat transfer in a finite porous layer heated from below. Various two-dimensional models are created such that their corresponding Rayleigh numbers lie in a range from the sub-critical linear to the supercritical non-linear regime, that is purely conductive to convection-dominated systems. Entropy production is found to describe the transient evolution of convective processes fairly well and can be used to identify thermodynamic equilibrium. Additionally, varying the aspect ratio for each Rayleigh number shows that the variety of realized convection modes increases with both larger aspect ratio and higher Rayleigh number. This phenomenon is also reflected by an enlarged spread of entropy production for the realized modes. Consequently, the Rayleigh number can be correlated to the magnitude of entropy production. In cases of moderate

  12. Analysis of mesoscale factors at the onset of deep convection on hailstorm days in Southern France and their relation to the synoptic patterns

    NASA Astrophysics Data System (ADS)

    Sanchez, Jose Luis; Wu, Xueke; Gascón, Estibaliz; López, Laura; Melcón, Pablo; García-Ortega, Eduardo; Berthet, Claude; Dessens, Jean; Merino, Andrés

    2013-04-01

    Storms and the weather phenomena associated to intense precipitation, lightning, strong winds or hail, are among the most common and dangerous weather risks in many European countries. To get a reliable forecast of their occurrence is remaining an open problem. The question is: how is possible to improve the reliability of forecast? Southwestern France is frequently affected by hailstorms, producing severe damages on crops and properties. Considerable efforts were made to improve the forecast of hailfall in this area. First of all, if we want to improve this type of forecast, it is necessary to have a good "ground truth" of the hail days and zones affected by hailfall. Fortunately, ANELFA has deployed thousands of hailpad stations in Southern France. The ANELFA processed the point hailfall data recorded during each hail season at these stations. The focus of this paper presents a methodology to improve the forecast of the occurrence of hailfall according to the synoptic environment and mesoscale factors in the study area. One hundred of hail days were selected, following spatial and severity criteria, occurred in the period 2000-2010. The mesoscale model WRF was applied for all cases to study the synoptic environment of mean geopotential and temperature fields at 500 hPa. Three nested domains have been defined following a two-way nesting strategy, with a horizontal spatial resolution of 36, 12 and 4 km, and 30 vertical terrains— following σ-levels. Then, using the Principal Component Analysis in T-Mode, 4 mesoscale configurations were defined for the fields of convective instability (CI), water vapor flux divergence and wind flow and humidity at low layer (850hPa), and several clusters were classified followed by using the K-means Clustering. Finally, we calculated several characteristic values of four hail forecast parameters: Convective Available Potential Energy (CAPE), Storm Relative Helicity between 0 and 3 km (SRH0-3), Energy-Helicity Index (EHI) and

  13. Geothermal reservoirs in hydrothermal convection systems

    SciTech Connect

    Sorey, M.L.

    1982-01-01

    Geothermal reservoirs commonly exist in hydrothermal convection systems involving fluid circulation downward in areas of recharge and upwards in areas of discharge. Because such reservoirs are not isolated from their surroundings, the nature of thermal and hydrologic connections with the rest of the system may have significant effects on the natural state of the reservoir and on its response to development. Conditions observed at numerous developed and undeveloped geothermal fields are discussed with respect to a basic model of the discharge portion of an active hydrothermal convection system. Effects of reservoir development on surficial discharge of thermal fluid are also delineated.

  14. Release of potential instability by mesoscale triggering - An objective model simulation. [in precipitation numerical weather forecasting

    NASA Technical Reports Server (NTRS)

    Matthews, D. A.

    1978-01-01

    The effects of mesoscale triggering on organized nonsevere convective cloud systems in the High Plains are considered. Two experiments were conducted to determine if a one-dimensional quasi-time dependent model could (1) detect soundings which were sensitive to mesoscale triggering, and (2) discriminate between cases which had mesoscale organized convection and those with no organized convection. The MESOCU model was used to analyze the available potential instability and thermodynamic potential for cloud growth. It is noted that lifting is a key factor in the release of available potential instability on the High Plains.

  15. How the Structure of Mesoscale Precipitation Systems Affects their Production of Transient Luminous Events

    NASA Astrophysics Data System (ADS)

    Lang, T. J.; Lyons, W.; Rutledge, S. A.; Cummer, S. A.; MacGorman, D. R.

    2011-12-01

    Recently, Lang et al. (2010) analyzed the parent lightning of transient luminous events (TLEs) in the context of the structure and evolution of two mesoscale convective systems (MCSs). These two MCSs were very different - one a giant symmetric leading-line/trailing stratiform storm, and one a small asymmetric MCS that contained a mesoscale convective vortex. These structural differences were associated with substantially different TLE-parent lightning structure as well as TLE production. The results suggested that TLE (especially sprite) production, and TLE-parent positive charge altitude, depend on MCS morphology. Current work is focused on analyzing the structure, evolution, lightning behavior, and TLE production of additional MCSs over various regions of the United States. Several additional TLE-producing MCS cases already have been identified for the years 2008-2010, featuring a variety of organizational modes (symmetric, asymmetric, and other more exotic varieties) in different meteorological regimes (including some cold-season cases). More cases will be incorporated as they occur and are observed. Data sources include geostationary satellite imagery, Doppler radar, three-dimensional lightning mapping networks, ground-strike detection networks, charge moment change measurements, and low-light video observations. The ultimate goal is to further test the hypothesis that MCS structure affects TLE production, and if so to quantify its impact. Research on two Oklahoma case studies, a multicellular system that occurred on 24 March 2009 and a classic bow-echo MCS that occurred on 19 August 2009, is ongoing. Over a 2.5-h period, the March case produced 23 observed TLEs (all sprites) whose parent flashes occurred within 175 km of the Oklahoma Lightning Mapping Array (OKLMA). The median altitude of LMA sources during the TLEs was 5.9 km above Mean Sea Level (MSL), or -19.2 °C. The August storm produced, in 2.5 hours, 34 TLEs (all sprites) with 32 of those having parent

  16. Quantifying the effects of resolution on convective organisation in cloud-system resolving simulations of West Africa.

    NASA Astrophysics Data System (ADS)

    White, Bethan; Stier, Philip; Birch, Cathryn

    2016-04-01

    Convection transports moisture, momentum, heat and aerosols through the troposphere, and so the variability of convection is a major driver of global weather and climate. Convection in the tropics is organised across a wide range of spatiotemporal scales, from the few kilometres and hours associated with individual cloud systems, through the mesoscale of squall lines and cloud clusters, to the synoptic scale of tropical cyclones. Global and limited area models often fail to represent many of these scales of organisation, and the interaction between the scales remains poorly understood. In this work we devise a new metric to quantify the degree of convective organisation. We apply this metric to data from simulations of the West African Monsoon region from the CASCADE project, where simulations were performed using the Met Office Unified Model at 12 km horizontal grid length with parameterised convection, and at 12, 4 and 1.5 km horizontal grid lengths with permitted convection. This allows us to perform quantitative analysis of convective organisation across model configurations that experience the same large-scale state and differ only in horizontal grid length and representation of deep convection. We show that our analysis technique can be usefully applied to high-resolution, cloud-system resolving, large-domain simulations of tropical convection. We use our technique to quantify the effects of horizontal grid length and of convective parameterisation on the degree of organisation in the simulated convection, and investigate the spatiotemporal variability of the convective organisation in the different model configurations. We then determine relationships between the degree of convective organisation and precipitation. Further, we compare our results against equivalent parameters derived from satellite data to identify how well each of the model configurations performs against observations. Through the use of this new metric, this work provides a quantitative

  17. Transitions to broad cells in a nonlinear thermal convection system

    NASA Astrophysics Data System (ADS)

    Fiedler, Brian H.

    This paper explores the properties of a two-dimensional, Boussinesq convection model with an ad hoc term in the buoyancy tendency equation that represents a positive external feedback process acting on the buoyancy fluctuations. Linear stability analyses and nonlinear integrations are presented for the case of constant heat flux boundary conditions. Although the large wavenumber modes grow the fastest from a state of rest, the nonlinear solutions progressively evolve to cells of small wavenumber. Applications to mesoscale cellular convection in the atmosphere are discussed.

  18. How does the Redi parameter for mesoscale mixing impact global climate in an Earth System Model?

    NASA Astrophysics Data System (ADS)

    Pradal, Marie-Aude; Gnanadesikan, Anand

    2014-09-01

    A coupled climate model is used to examine the impact of an increase in the mixing due to mesoscale eddies on the global climate system. A sixfold increase in the Redi mixing coefficient ARedi, which is within the admissible range of variation, has the overall effect of warming the global-mean surface air and sea surface temperatures by more than 1°C. Locally, sea surface temperatures increase by up to 7°C in the North Pacific and by up to 4°C in the Southern Ocean, with corresponding impacts on the ice concentration and ice extent in polar regions. However, it is not clear that the changes in heat transport from tropics to poles associated with changing this coefficient are primarily responsible for these changes. We found that the changes in the transport of heat are often much smaller than changes in long-wave trapping and short-wave absorption. Additionally, changes in the advective and diffusive transport of heat toward the poles often oppose each other. However, we note that the poleward transport of salt increases near the surface as ARedi increases. We suggest a causal chain in which enhanced eddy stirring leads to increased high-latitude surface salinity reducing salt stratification and water column stability and enhancing convection, triggering two feedback loops. In one, deeper convection prevents sea ice formation, which decreases albedo, which increases SW absorption, further increasing SST and decreasing sea ice formation. In the other, increased SST and reduced sea ice allow for more water vapor in the atmosphere, trapping long-wave radiation. Destratifying the polar regions is thus a potential way in which changes in ocean circulation might warm the planet.

  19. Investigation of mesoscale meteorological phenomena as observed by geostationary satellite

    NASA Technical Reports Server (NTRS)

    Brundidge, K. C.

    1982-01-01

    Satellite imagery plus conventional synoptic observations were used to examine three mesoscale systems recently observed by the GOES-EAST satellite. The three systems are an arc cloud complex (ACC), mountain lee wave clouds and cloud streets parallel to the wind shear. Possible gravity-wave activity is apparent in all three cases. Of particular interest is the ACC because of its ability to interact with other mesoscale phenomena to produce or enhance convection.

  20. Idealized Cloud-System Resolving Modeling for Tropical Convection Studies

    NASA Astrophysics Data System (ADS)

    Anber, Usama M.

    A three-dimensional limited-domain Cloud-Resolving Model (CRM) is used in idealized settings to study the interaction between tropical convection and the large scale dynamics. The model domain is doubly periodic and the large-scale circulation is parameterized using the Weak Temperature Gradient (WTG) Approximation and Damped Gravity Wave (DGW) methods. The model simulations fall into two main categories: simulations with a prescribed radiative cooling profile, and others in which radiative cooling profile interacts with clouds and water vapor. For experiments with a prescribed radiative cooling profile, radiative heating is taken constant in the vertical in the troposphere. First, the effect of turbulent surface fluxes and radiative cooling on tropical deep convection is studied. In the precipitating equilibria, an increment in surface fluxes produces a greater increase in precipitation than an equal increment in column-integrated radiative heating. The gross moist stability remains close to constant over a wide range of forcings. With dry initial conditions, the system exhibits hysteresis, and maintains a dry state with for a wide range of net energy inputs to the atmospheric column under WTG. However, for the same forcings the system admits a rainy state when initialized with moist conditions, and thus multiple equilibria exist under WTG. When the net forcing is increased enough that simulations, which begin dry, eventually develop precipitation. DGW, on the other hand, does not have the tendency to develop multiple equilibria under the same conditions. The effect of vertical wind shear on tropical deep convection is also studied. The strength and depth of the shear layer are varied as control parameters. Surface fluxes are prescribed. For weak wind shear, time-averaged rainfall decreases with shear and convection remains disorganized. For larger wind shear, rainfall increases with shear, as convection becomes organized into linear mesoscale systems. This non

  1. The Dependence on Grid Resolution of Numerically Simulated Convective Cloud Systems Using Ice Microphysics

    NASA Technical Reports Server (NTRS)

    Braun, Scott A.; Tao, Wei-Kuo; Lang, Stephen E.; Ferrier, Bradley S.

    1999-01-01

    Mesoscale research and forecast models are increasingly being used at horizontal resolutions of 1-8 km to simulate a variety of precipitating systems. When the model is used to simulate convective systems, it is uncertain to what extent the dynamics and microphysics of convective updrafts can be resolved with grids larger than 1 km. In this study, two- and three-dimensional versions of the Goddard Cumulus Ensemble model are used to determine the impact of horizontal grid resolution on the behavior of the simulated storms and on the characteristics of the cloud microphysical fields. It will be shown that as resolution decreases from about 1 km to greater than 3 km, there is a fairly rapid degradation of the storm structure in the form of reduced convective mass fluxes, updraft tilts, and cloud microphysics. A high-resolution simulation of hurricane outer rainbands using the MM5 mesoscale model shows also that there can be a substantial modification of the key microphysical processes that contribute to rainfall as a result of reducing the horizontal resolution.

  2. Analysis of Summertime Convective Initiation in Central Alabama Using the Land Information System

    NASA Technical Reports Server (NTRS)

    James, Robert S.; Case, Jonathan L.; Molthan, Andrew L.; Jedlovec, Gary J.

    2011-01-01

    During the summer months in the southeastern United States, convective initiation presents a frequent challenge to operational forecasters. Thunderstorm development has traditionally been referred to as random due to their disorganized, sporadic appearance and lack of atmospheric forcing. Horizontal variations in land surface characteristics such as soil moisture, soil type, land and vegetation cover could possibly be a focus mechanism for afternoon convection during the summer months. The NASA Land Information System (LIS) provides a stand-alone land surface modeling framework that incorporates these varying soil and vegetation properties, antecedent precipitation, and atmospheric forcing to represent the soil state at high resolution. The use of LIS as a diagnostic tool may help forecasters to identify boundaries in land surface characteristics that could correlate to favored regions of convection initiation. The NASA Shortterm Prediction Research and Transition (SPoRT) team has been collaborating with the National Weather Service Office in Birmingham, AL to help incorporate LIS products into their operational forecasting methods. This paper highlights selected convective case dates from summer 2009 when synoptic forcing was weak, and identifies any boundaries in land surface characteristics that may have contributed to convective initiation. The LIS output depicts the effects of increased sensible heat flux from urban areas on the development of convection, as well as convection along gradients in land surface characteristics and surface sensible and latent heat fluxes. These features may promote mesoscale circulations and/or feedback processes that can either enhance or inhibit convection. With this output previously unavailable to operational forecasters, LIS provides a new tool to forecasters in order to help eliminate the randomness of summertime convective initiation.

  3. The Spring 2014 Mesoscale Ensemble Prediction System "Dust Offensive"

    NASA Astrophysics Data System (ADS)

    Hunt, E. D.; Adams-Selin, R.; Sartan, J.; Creighton, G.; Kuchera, E.; Keane, J.; Jones, S.

    2014-12-01

    The Mesoscale Ensemble Prediction System (MEPS) at the Air Force Weather Agency (AFWA) is a 10-member ensemble run on a 20-km hemispheric domain and 4-km domains in regions of interest. In the Southwest Asia (SWA) regional domain, dust forecast products from MEPS are of particular interest. Over the past few years, subject matter experts at AFWA have acquired and implemented datasets and developed a soil moisture algorithm that have improved skill scores of dust forecasts in the AFWA GOddard Chemistry Aerosol Radiation and Transport (GOCART) module within the Weather Research and Forecast with Chemistry (WRF-Chem) model. The aforementioned datasets include, but are not limited to, the Desert Research Institute (DRI) dust source region and a dynamic 8-day Leaf Area Index (LAI) vegetation mask. We then tested these individual datasets as ensemble perturbations in all ten MEPS test members during a three-week "dust offensive" test over SWA in spring 2014. Remote sensing specialists at AFWA meticulously documented the locations, duration, and intensity of numerous dust events over the SWA domain during the three weeks. These data were then used for subjective verification of each individual MEPS member and of the individual perturbations within members. Results from the subjective verification showed that individual MEPS members with the DRI dust source region significantly outperformed members that used the standard Ginoux dust source region. The other individual perturbations tested were determined to have a neutral effect (i.e., neither degrading nor improving skill) on individual members during the three-week period. Thus, the DRI dust source region is now used in the majority of MEPS members in both the 4-km SWA domain and the 20-km hemispheric domain. The other individual perturbations are now utilized in a minority of MEPS members. However, additional testing is still needed over other domains to determine if the improved dust forecasting skill has spatial

  4. The Mesoscale Heavy Rainfall Observing System (MHROS) over the middle region of the Yangtze River in China

    NASA Astrophysics Data System (ADS)

    Cui, Chunguang; Wan, Rong; Wang, Bin; Dong, Xiquan; Li, Hongli; Wang, Xiaokang; Xu, Guirong; Wang, Xiaofang; Wang, Yehong; Xiao, Yanjiao; Zhou, Zhimin; Fu, Zhikang; Wan, Xia; Zhang, Wengang; Peng, Tao; Leng, Liang; Stenz, Ronald; Wang, Junchao

    2015-10-01

    The Mesoscale Heavy Rainfall Observing System (MHROS), supported by the Institute of Heavy Rain (IHR), Chinese Meteorology Administration, is one of the major systems to observe mesoscale convective systems (MCSs) over the middle region of the Yangtze River in China. The IHR MHROS consists of mobile C-POL and X-POL precipitation radars, millimeter wavelength cloud radar, fixed S-band precipitation radars, GPS network, microwave radiometers, radio soundings, wind profiler radars, and disdrometers. The atmospheric variables observed or retrieved by these instruments include the profiles of atmospheric temperature, moisture, wind speed and direction, vertical structures of MCS clouds and precipitation, atmospheric water vapor, and cloud liquid water. These quality-controlled observations and retrievals have been used in mesoscale numerical weather prediction to improve the accuracy of weather forecasting and MCS research since 2007. These long-term observations have provided the most comprehensive data sets for researchers to investigate the formation-dissipation processes of MCSs and for modelers to improve their simulations of MCSs. As the first paper of a series, we briefly introduce the IHR MHROS and describe the specifications of its major instruments. Then, we provide an integrative analysis of the IHR MHROS observations for a heavy rain case on 3-5 July 2014 as well as the application of IHR MHROS observations in improving the model simulations. In a series of papers, we will tentatively answer several key scientific questions related to the MCS and Meiyu frontal systems over the middle region of the Yangtze River using the IHR MHROS observations.

  5. Convective heat transport in geothermal systems

    SciTech Connect

    Lippmann, M.J.; Bodvarsson, G.S.

    1986-08-01

    Most geothermal systems under exploitation for direct use or electrical power production are of the hydrothermal type, where heat is transferred essentially by convection in the reservoir, conduction being secondary. In geothermal systems, buoyancy effects are generally important, but often the fluid and heat flow patterns are largely controlled by geologic features (e.g., faults, fractures, continuity of layers) and location of recharge and discharge zones. During exploitation, these flow patterns can drastically change in response to pressure and temperature declines, and changes in recharge/discharge patterns. Convective circulation models of several geothermal systems, before and after start of fluid production, are described, with emphasis on different characteristics of the systems and the effects of exploitation on their evolution. Convective heat transport in geothermal fields is discussed, taking into consideration (1) major geologic features; (2) temperature-dependent rock and fluid properties; (3) fracture- versus porous-medium characteristics; (4) single- versus two-phase reservoir systems; and (5) the presence of noncondensible gases.

  6. Chemistry on the mesoscale: Modeling and measurement issues

    NASA Technical Reports Server (NTRS)

    Thompson, Anne; Pleim, John; Walcek, Christopher; Ching, Jason; Binkowski, Frank; Tao, Wei-Kuo; Dickerson, Russell; Pickering, Kenneth

    1993-01-01

    The topics covered include the following: Regional Acid Deposition Model (RADM) -- a coupled chemistry/mesoscale model; convection in RADM; unresolved issues for mesoscale modeling with chemistry -- nonprecipitating clouds; unresolved issues for mesoscale modeling with chemistry -- aerosols; tracer studies with Goddard Cumulus Ensemble Model (GCEM); field observations of trace gas transport in convection; and photochemical consequences of convection.

  7. Evaluation of a Mesoscale Atmospheric Dispersion Modeling System with Observations from the 1980 Great Plains Mesoscale Tracer Field Experiment. Part I: Datasets and Meteorological Simulations.

    NASA Astrophysics Data System (ADS)

    Moran, Michael D.; Pielke, Roger A.

    1996-03-01

    The Colorado State University mesoscale atmospheric dispersion (MAD) numerical modeling system, which consists of a prognostic mesoscale meteorological model coupled to a mesoscale Lagrangian particle dispersion model, has been used to simulate the transport and diffusion of a perfluorocarbon tracer-gas cloud for one afternoon surface release during the July 1980 Great Plains mesoscale tracer field experiment. Ground-level concentration (GLC) measurements taken along arcs of samplers 100 and 600 km downwind of the release site at Norman, Oklahoma, up to three days after the tracer release were available for comparison. Quantitative measures of a number of significant dispersion characteristics obtained from analysis of the observed tracer cloud's moving GLC `footprint' have been used to evaluate the modeling system's skill in simulating this MAD case.MAD is more dependent upon the spatial and temporal structure of the transport wind field than is short-range atmospheric dispersion. For the Great Plains mesoscale tracer experiment, the observations suggest that the Great Plains nocturnal low-level jet played an important role in transporting and deforming the tracer cloud. A suite of ten two- and three-dimensional numerical meteorological experiments was devised to investigate the relative contributions of topography, other surface inhomogeneities, atmospheric baroclinicity, synoptic-scale flow evolution, and meteorological model initialization time to the structure and evolution of the low-level mesoscale flow field and thus to MAD. Results from the ten mesoscale meteorological simulations are compared in this part of the paper. The predicted wind fields display significant differences, which give rise in turn to significant differences in predicted low-level transport. The presence of an oscillatory ageostrophic component in the observed synoptic low-level winds for this case is shown to complicate initialization of the meteorological model considerably and is the

  8. Precipitation characteristics of CAM5 physics at mesoscale resolution during MC3E and the impact of convective timescale choice

    SciTech Connect

    Gustafson, William I.; Ma, Po-Lun; Singh, Balwinder

    2014-12-17

    The physics suite of the Community Atmosphere Model version 5 (CAM5) has recently been implemented in the Weather Research and Forecasting (WRF) model to explore the behavior of the parameterization suite at high resolution and in the more controlled setting of a limited area model. The initial paper documenting this capability characterized the behavior for northern high latitude conditions. This present paper characterizes the precipitation characteristics for continental, mid-latitude, springtime conditions during the Midlatitude Continental Convective Clouds Experiment (MC3E) over the central United States. This period exhibited a range of convective conditions from those driven strongly by large-scale synoptic regimes to more locally driven convection. The study focuses on the precipitation behavior at 32 km grid spacing to better anticipate how the physics will behave in the global model when used at similar grid spacing in the coming years. Importantly, one change to the Zhang-McFarlane deep convective parameterization when implemented in WRF was to make the convective timescale parameter an explicit function of grid spacing. This study examines the sensitivity of the precipitation to the default value of the convective timescale in WRF, which is 600 seconds for 32 km grid spacing, to the value of 3600 seconds used for 2 degree grid spacing in CAM5. For comparison, an infinite convective timescale is also used. The results show that the 600 second timescale gives the most accurate precipitation over the central United States in terms of rain amount. However, this setting has the worst precipitation diurnal cycle, with the convection too tightly linked to the daytime surface heating. Longer timescales greatly improve the diurnal cycle but result in less precipitation and produce a low bias. An analysis of rain rates shows the accurate precipitation amount with the shorter timescale is assembled from an over abundance of drizzle combined with too little heavy

  9. Precipitation characteristics of CAM5 physics at mesoscale resolution during MC3E and the impact of convective timescale choice

    DOE PAGESBeta

    Gustafson, William I.; Ma, Po-Lun; Singh, Balwinder

    2014-12-17

    The physics suite of the Community Atmosphere Model version 5 (CAM5) has recently been implemented in the Weather Research and Forecasting (WRF) model to explore the behavior of the parameterization suite at high resolution and in the more controlled setting of a limited area model. The initial paper documenting this capability characterized the behavior for northern high latitude conditions. This present paper characterizes the precipitation characteristics for continental, mid-latitude, springtime conditions during the Midlatitude Continental Convective Clouds Experiment (MC3E) over the central United States. This period exhibited a range of convective conditions from those driven strongly by large-scale synoptic regimesmore » to more locally driven convection. The study focuses on the precipitation behavior at 32 km grid spacing to better anticipate how the physics will behave in the global model when used at similar grid spacing in the coming years. Importantly, one change to the Zhang-McFarlane deep convective parameterization when implemented in WRF was to make the convective timescale parameter an explicit function of grid spacing. This study examines the sensitivity of the precipitation to the default value of the convective timescale in WRF, which is 600 seconds for 32 km grid spacing, to the value of 3600 seconds used for 2 degree grid spacing in CAM5. For comparison, an infinite convective timescale is also used. The results show that the 600 second timescale gives the most accurate precipitation over the central United States in terms of rain amount. However, this setting has the worst precipitation diurnal cycle, with the convection too tightly linked to the daytime surface heating. Longer timescales greatly improve the diurnal cycle but result in less precipitation and produce a low bias. An analysis of rain rates shows the accurate precipitation amount with the shorter timescale is assembled from an over abundance of drizzle combined with too

  10. A 7-km Non-Hydrostatic Global Mesoscale Simulation with the Goddard Earth Observing System Model (GEOS-5) for Observing System Simulation Experiments

    NASA Astrophysics Data System (ADS)

    Putman, W.; Suarez, M.; Gelaro, R.; daSilva, A.; Molod, A.; Ott, L. E.; Darmenov, A.

    2014-12-01

    The Global Modeling and Assimilation Office at NASA Goddard Space Flight Center has used the Goddard Earth Observing System model (GEOS-5) to produce a 2-year non-hydrostatic global mesoscale simulation for the period of June 2005-2007. This 7-km GEOS-5 Nature Run (7km-G5NR) product will provide synthetic observations for observing system simulation experiments (OSSE)s at NASA and NOAA through the Joint Center for Satellite Data Assimilation and the NASA Center for Climate Simulation. While GEOS-5 is regularly applied in seasonal-to-decadal climate simulations, and medium range weather prediction and data assimilation, GEOS-5 is also readily adaptable for application as a global mesoscale model in pursuit of global cloud resolving applications. Recent computing advances have permitted experimentation with global atmospheric models at these scales, although production applications like the 7km-G5NR have remained limited. By incorporating a non-hydrostatic finite-volume dynamical core with scale aware physics parameterizations, the 7km-G5NR produces organized convective systems and robust weather systems ideal for producing observations for existing and new remote sensing instruments. In addition to standard meteorological parameters, the 7km-G5NR includes 15 aerosol tracers (including dust, seasalt, sulfate, black and organic carbon), O3, CO and CO2. The 7km-G5NR is driven by prescribed sea-surface temperatures and sea-ice, daily volcanic and biomass burning emissions, as well as high-resolution inventories of anthropogenic sources. We will discuss the technical challenges of producing the 7km-G5NR including the nearly 5 petabytes of full resolution output at 30-minute intervals as required by the OSSE developers, and modifications to the standard GEOS-5 physics to permit convective organization at the 'grey-zone' resolution of 7km. Highlights of the 7km-G5NR validation will focus on the representation of clouds and organized convection including tropical cyclones

  11. A satellite-based perspective of convective systems over the Maritime Continent

    NASA Astrophysics Data System (ADS)

    Rowe, A.; Houze, R.; Virts, K.; Zuluaga, M. D.

    2014-12-01

    Data from TRMM, the A-Train satellites, and the Worldwide Lightning Location Network (WWLLN) have been used to study extreme weather throughout low latitudes, from deep convection over the Himalayas to oceanic mesoscale systems associated with the MJO. This study presents a more in-depth examination of convection over the Maritime Continent (Indonesia and Malaysia). During November to February, this area is the rainiest regional climate on Earth, thus constituting one of the atmosphere's primary heat sources. On multiple temporal and spatial scales, it is a complex region with clouds and precipitation having both oceanic and orographic influence. The November-February season encompasses both the eastward propagation of the MJO through this region and rainfall associated with the Asian-Australian monsoon. More specifically, the precipitation in this region is strongly modulated by MJO phases, pulsations of the monsoon, and the powerful diurnal effects of the islands and ocean. Through a feature-based analysis of convective and stratiform components of storms, the evolution of precipitating clouds in this region will be described using data from the November-February time period over multiple years. This analysis leads to an increased understanding of the characteristics of convection associated with the intraseasonal and diurnal variability during these months over the Maritime Continent. Previous work using A-Train data noted the prevalence of smaller separated MCSs over the region during the locally active phase of the MJO, and WWLLN data have shown a peak in lightning density as convection becomes deeper and more numerous leading up to this active period. By applying the analysis of the TRMM data in addition to the A-Train and WWLLN datasets, the relative roles of convective and stratiform components of MCSs to the behavior of convection can be determined during the MJO and monsoonal maxima of rainfall over the Maritime Continent.

  12. Soil Moisture and Mesoscale Convective Complex Development During the 1993 US Midwest Flood: Results from the MM5-PLACE Atmosphere/Land-Surface Model

    NASA Technical Reports Server (NTRS)

    Baker, R. David; Wang, Yansen; Tao, Wei-Kuo; Wetzel, Peter; Einaudi, Franco (Technical Monitor)

    2000-01-01

    The 1993 US Midwest Flood produced record levels of flooding, in the Mississippi River Basin. This flooding resulted from repeated frontal passages and mesoscale convective complexes (MCCs) during the months of June and July. A better understanding of processes that influenced MCC development during the 1993 Flood may lead to improved forecasts of heavy precipitation and flooding. Here, we consider the impact of soil moisture on MCC development during a two-day period (June 23-24) of the 1993 US Midwest Flood. The purpose of this study is to assess the importance of soil moisture distribution on the timing, intensity, and location of heavy precipitation. In this study, the MM5-PLACE Atmosphere/Land-Surface Model is utilized. The atmospheric component consists of the Penn State/NCAR MM5 mesoscale model, and the land-surface component consists of the Goddard Parameterization for Land Atmosphere-Cloud Exchange (PLACE). Initial soil moisture is provided from two sources: 1) NCEP reanalysis, and 2) Antecedent Precipitation Index (API) using NOAA rain gauge measurements as a proxy for soil moisture. NCEP reanalysis provides coarse resolution initial soil moisture (2.5 degree), while API provides high resolution initial soil moisture (10-200 km depending on NOAA rain gauge spacing). Initial results indicate that the distribution of soil moisture has a significant impact on the timing and location of heavy precipitation during this two-day flood event. Precipitation in simulations with high resolution initial soil moisture agrees more closely with observed precipitation. These results suggest that high resolution soil moisture observations are necessary to accurately predict severe storm development, heavy precipitation, and subsequent flooding.

  13. Accuracy of diagnostic heat and moisture budgets using SESAME-79 field data as revealed by observing system simulation experiments. [Severe Environmental Storm and Mesoscale Experiment

    NASA Technical Reports Server (NTRS)

    Kuo, Y.-H.; Anthes, R. A.

    1984-01-01

    Observing system simulation experiments are used to investigate the accuracy of diagnostic heat and moisture budgets which employ the AVE-SESAME 1979 data. The time-including, four-dimensional data set of a mesoscale model is used to simulate rawinsonde observations from AVE-SESAME 1979. The 5 C/day (heat budget) and 2 g/kg per day (moisture budget) magnitudes of error obtained indicate difficulties in the diagnosis of the heating rate in weak convective systems. The influences exerted by observational frequency, objective analysis, observational density, vertical interpolation, and observational errors on the budget are also studied, and it is found that the temporal and spatial resolution of the SESAME regional network is marginal for diagnosing convective effects on a horizontal time scale of 550 x 550 km.

  14. Initialization of a mesoscale model for April 10, 1979, using alternative data sources

    NASA Technical Reports Server (NTRS)

    Kalb, M. W.

    1984-01-01

    A 35 km grid limited area mesoscale model was initialized with high density SESAME radiosonde data and high density TIROS-N satellite temperature profiles for April 10, 1979. These data sources were used individually and with low level wind fields constructed from surface wind observations. The primary objective was to examine the use of satellite temperature data for initializing a mesoscale model by comparing the forecast results with similar experiments employing radiosonde data. The impact of observed low level winds on the model forecasts was also investigated with experiments varying the method of insertion. All forecasts were compared with each other and with mesoscale observations for precipitation, mass and wind structure. Several forecasts produced convective precipitation systems with characteristics satisfying criteria for a mesoscale convective complex. High density satellite temperature data and balanced winds can be used in a mesoscale model to produce forecasts which verify favorably with observations.

  15. Chemistry of rain events in West Africa: evidence of dust and biogenic influence in convective systems

    NASA Astrophysics Data System (ADS)

    Desboeufs, K.; Journet, E.; Rajot, J.-L.; Chevaillier, S.; Triquet, S.; Formenti, P.; Zakou, A.

    2010-10-01

    This paper documents the chemical composition of 7 rain events associated with mesoscale convective systems sampled at the supersite of Banizoumbou, Niger, during the first special observation periods (June-July 2006) of the African Monsoon Multidisciplinary Analyses (AMMA) experiment. Time-resolved rain sampling was performed in order to discriminate the local dust scavenged at the beginning of rain event from the aerosol particles incorporated in the cloud at the end of the rain. The total elemental composition is dominated by Al, Si, Fe and Ca, indicating a high influence of dust and limited marine or anthropogenic contribution. After the aerosol wash-out, the elemental concentrations normalized to Al and the microscopic observations of diatoms, a tracer of the Bodélé depression, both indicate that the total elemental composition of rainwater is controlled by dust originating from North-eastern Saharan sources and probably incorporated in the convective cloud from the Harmattan layer. The low variability of the rain composition over the measurement period indicates a regional and temporal homogeneity of dust composition in the Harmattan layer. In the dissolved phase, the dominant anions are nitrate (NO3-), sulphate (SO42-) and chloride (Cl-). However, between June and July we observe an increasing contribution of the organic anions (formate, acetate, oxalate) associated with biogenic emissions to the total ion composition. These results confirm the large influence of biogenic emissions on the rain composition over Sahel during the wet season. The paper concludes on the capacity of mesoscale convective systems to carry simultaneously dust and biogenic compounds originating from different locations and depose them jointly. It also discusses the potential biogeochemical impact of such a phenomenon.

  16. Microwave Brightness Temperatures of Tilted Convective Systems

    NASA Technical Reports Server (NTRS)

    Hong, Ye; Haferman, Jeffrey L.; Olson, William S.; Kummerow, Christian D.

    1998-01-01

    Aircraft and ground-based radar data from the Tropical Ocean and Global Atmosphere Coupled-Ocean Atmosphere Response Experiment (TOGA COARE) show that convective systems are not always vertical. Instead, many are tilted from vertical. Satellite passive microwave radiometers observe the atmosphere at a viewing angle. For example, the Special Sensor Microwave/Imager (SSM/I) on Defense Meteorological Satellite Program (DMSP) satellites and the Tropical Rainfall Measurement Mission (TRMM) Microwave Imager (TMI) on the TRMM satellite have an incident angle of about 50deg. Thus, the brightness temperature measured from one direction of tilt may be different than that viewed from the opposite direction due to the different optical depth. This paper presents the investigation of passive microwave brightness temperatures of tilted convective systems. To account for the effect of tilt, a 3-D backward Monte Carlo radiative transfer model has been applied to a simple tilted cloud model and a dynamically evolving cloud model to derive the brightness temperature. The radiative transfer results indicate that brightness temperature varies when the viewing angle changes because of the different optical depth. The tilt increases the displacements between high 19 GHz brightness temperature (Tb(sub 19)) due to liquid emission from lower level of cloud and the low 85 GHz brightness temperature (Tb(sub 85)) due to ice scattering from upper level of cloud. As the resolution degrades, the difference of brightness temperature due to the change of viewing angle decreases dramatically. The dislocation between Tb(sub 19) and Tb(sub 85), however, remains prominent.

  17. Evaluation of a Mesoscale Atmospheric Dispersion Modeling System with Observations from the 1980 Great Plains Mesoscale Tracer Field Experiment. Part II: Dispersion Simulations.

    NASA Astrophysics Data System (ADS)

    Moran, Michael D.; Piekle, Roger A.

    1996-03-01

    The Colorado State University mesoscale atmospheric dispersion (MAD) numerical modeling system, which consists of a prognostic mesoscale meteorological model coupled to a mesoscale Lagrangian particle dispersion model (MLPDM), has been used to simulate the emission, transport, and diffusion of a perfluorocarbon tracer-gas cloud for one afternoon surface release during the July 1980 Great Plains mesoscale tracer field experiment. The MLPDM was run for a baseline simulation and seven sensitivity experiments. The baseline simulation showed considerable skill in predicting such quantitative whole-could characteristics as peak ground-level concentration (GLC), maximum cloud width, cloud arrival and transit times, and crosswind integrated exposure at downwind distances of both 100 and 60 km. The baseline simulation also compared very favorably to simulations made by seven other MAD models for this same case in an earlier study. The sensitivity experiments explored the impact of various factors on MAD, especially the diurnal heating cycle and physiographic and atmospheric inhomogeneities, by including or excluding them in different combinations. The GLC `footprints' predicted in the sensitivity experiments were sensitive to differences in the simulated meteorological fields.The observations and the numerical simulations both suggest that the Great Plains nocturnal low-level jet played an important role in transporting and deforming the perfluorocarbon tracer cloud during this MAD experiment: the mean transport speed was supergeostrophic and both crosswind and alongwind cloud spreads were larger than can be explained by turbulent diffusion alone. The contributions of differential horizontal advection and mesoscale deformation to MAD dominate those of small-scale turbulent diffusion for this case, and Pasquill's delayed-shear enhancement mechanism for horizontal diffusion appears to have played a significant role during nighttime transport. These results demonstrate the

  18. Evaluation of a mesoscale atmospheric dispersion modeling system with observations from the 1980 Great Plains mesoscale tracer field experiment. Part I: Datasets and meterological simulations

    SciTech Connect

    Moran, M.D.; Pielke, R.A.

    1996-03-01

    A mesoscale atmospheric dispersion (MAD) numerical modeling system, consisting of a mesoscale meteorological model coupled to a mesoscale Lagrangian particle dispersion model, was used to simulate transport and diffusion of a perfluorocarbon tracer-gas cloud for a surface release during the July 1980 Great Plains mesoscale tracer field experiment. Ground-level concentration (GLC) measurements taken downwind of the release site up to three days after the tracer release were available for comparison. Quantitative measures of significant dispersion characteristics obtained from analysis of the tracer cloud`s moving GLC {open_quotes}footprint{close_quotes} were used to evaluate the simulation of the MAD case. MAD is more dependent on the spatial and temporal structure of the transport wind field than is short-range atmospheric dispersion. For the tracer experiment, the observations suggest that the nocturnal low-level jet played an important role in transporting and deforming the tracer cloud. Ten two- and three-dimensional numerical meteorological experiments were devised to investigate the relative contributions of topography, other surface inhomogeneities, atmospheric baroclinicity, synoptic-scale flow evolution, and meteorological model initialization time to the structure and evolution of the low-level mesoscale flow field and thus to MAD. Results from the meteorological simulations are compared in this paper. The predicted wind fields display significant differences, which give rise in turn to significant differences in predicted low-level transport. The presence of an oscillatory ageostrophic component in the observed synoptic low-level winds for this case is shown to complicate initialization of the meteorological model considerably and is the likely cause of directional errors in the predicted mean tracer transport. A companion paper describes the results from the associated dispersion simulations. 76 refs., 13 figs., 6 tabs.

  19. System enhancements of Mesoscale Analysis and Space Sensor (MASS) computer system

    NASA Technical Reports Server (NTRS)

    Hickey, J. S.; Karitani, S.

    1985-01-01

    The interactive information processing for the mesoscale analysis and space sensor (MASS) program is reported. The development and implementation of new spaceborne remote sensing technology to observe and measure atmospheric processes is described. The space measurements and conventional observational data are processed together to gain an improved understanding of the mesoscale structure and dynamical evolution of the atmosphere relative to cloud development and precipitation processes. A Research Computer System consisting of three primary computers was developed (HP-1000F, Perkin-Elmer 3250, and Harris/6) which provides a wide range of capabilities for processing and displaying interactively large volumes of remote sensing data. The development of a MASS data base management and analysis system on the HP-1000F computer and extending these capabilities by integration with the Perkin-Elmer and Harris/6 computers using the MSFC's Apple III microcomputer workstations is described. The objectives are: to design hardware enhancements for computer integration and to provide data conversion and transfer between machines.

  20. Impact of environmental conditions on the mesoscale characteristics of squall-line systems: Toward the development of anvil cirrus parameterization for GCMs

    SciTech Connect

    Chin, Hung-Neng S.; Bradley, M.M.

    1996-05-01

    Our earlier studies indicated that a strong coupling exists in the mesoscale convective systems (MCSs) between deep convection and its related anvil cloud through the interaction among dynamical, thermodynamical and radiative processes. They also showed that the tilting structure of MCSs makes an important contribution to the water budget of anvil clouds, particularly the tropical anvil due to the jetlike wind profile. However, most earlier GCMs did not include a direct and physically consistent representation of this coupling. To this end, Randall et al. suggested a more realistic anvil parameterization by adding prognostic cloud water (or ice) variables to account for the formation of anvil clouds from cumulus detrainment. In addition to this effort, our recent studies further suggest the need to parameterize the tilting structure of MCSs in GCMs. The objective of this work is to parameterize the large-scale effects of this tilting structure. Our primary interest focuses on MCSs in an environment with substantial wind shear, such as squall-line systems, since they have longer lifetimes and wider coverage to affect the earth-atmosphere radiation budget and climate. Using varied convective available potential energy (CAPE), wind shear intensity, shear depth, and the pattern of shear profile over a wide range of bulk Richardson number (Ri), a sensitivity study is performed in a cloud resolving model to link its resulting mesoscale ascent/descent with GCM-resolvable variables. The ultimate goal of this research is to develop an anvil cirrus parameterization (ACP), that will couple with cumulus parameterizations in GCMs to improve the cloud-radiation feedback on large-scale climate.

  1. AS sensitivity study of the mesoscale characteristics of squall-line systems to environmental conditions: Implication of anvil cirrus parameterization

    SciTech Connect

    Chin, H.-N.S.

    1996-04-01

    Cloud-radiation feedback has been identified as the single most important effect limiting general circulation models (GCMs) to further progress in climate change research, and regarded as major uncertainties in estimating the impact of increasing concentrations of green house gases on climate simulations. Therefore, it is crucially important to further understand the physical processes involved in order to improve the representation of cloud processes in GCMs. To this end, a cloud resolving model with enhanced model physics was used to study the impact of microphysics, long-and shortwave radiation on mediated and tropical mesoscale convective systems (MCSs). The objective of this work is to parameters the large- scale effects of an important sub-GCM-grid-scale process associated with the titling structure of MCSs. The objective of this work is to parameters the large-scale effects of an important sub- GCM-grid- scale process associated with the titling structure of MCSs. To this end, our primary interest focuses on MCSs in an environment with substantial wind shear, such as squall-line systems, since they have longer lifetimes and wider coverage to affect the earth- atmosphere radiation budget and climate.

  2. Evaluation of a mesoscale atmospheric dispersion modeling system with observations from the 1980 Great Plains mesoscale tracer field experiment. Part II: Dispersion simulations

    SciTech Connect

    Moran, M.D.; Pielke, R.A.

    1996-03-01

    A mesoscale atmospheric dispersion (MAD) numerical modeling system, consisting of a mesoscale meteorological model coupled to a mesoscale Lagrangian particle dispersion model (MLPDM), was used to simulate the emission, transport, and diffusion of a perfluorocarbon tracer-gas cloud for a surface release during a tracer field experiment. The MLPDM was run for a baseline simulation and seven sensitivity experiments. The baseline simulation showed considerable skill in predicting peak ground-level concentration (GLC), maximum cloud width, cloud arrival and transit times, and crosswind integrated exposure at downwind distances of 100 and 600 km. The baseline simulation also compared very well to simulations made by seven other MAD models for the same case in an earlier study. The sensitivity experiments explored the impact of various factors on MAD, especially the diurnal heating cycle and physiographic and atmospheric inhomogeneities, by including or excluding them in different combinations. The GLC footprints predicted in sensitivity experiments were sensitive to differences in simulated meteorological fields. The observations and numerical simulations suggest that the nocturnal low-level jet played an important role in transporting and deforming the tracer cloud during this MAD experiment: the mean transport speed was supergeostrophic and both crosswind and alongwind cloud spreads were larger than can be explained by turbulent diffusion alone. The contributions of differential horizontal advection and mesoscale deformation to MAD dominate those of small-scale turbulent diffusion for this case, and Pasquill`s delayed-shear enhancement mechanism for horizontal diffusion appears to have played a significant role during nighttime transport. These results demonstrate the need in some flow regimes for better temporal resolution of boundary layer vertical shear in MAD models than is available from the conventional twice-daily rawinsonde network. 34 refs., 14 figs., 4 tabs.

  3. On the episodic nature of derecho-producing convective systems in the United States

    NASA Astrophysics Data System (ADS)

    Ashley, Walker S.; Mote, Thomas L.; Bentley, Mace L.

    2005-11-01

    Convectively generated windstorms occur over broad temporal and spatial scales; however, one of the larger-scale and most intense of these windstorms has been given the name derecho. This study illustrates the tendency for derecho-producing mesoscale convective systems to group together across the United States - forming a derecho series. The derecho series is recognized as any succession of derechos that develop within a similar synoptic environment with no more than 72 h separating individual events. A derecho dataset for the period 1994-2003 was assembled to investigate the groupings of these extremely damaging convective wind events. Results indicate that over 62% of the derechos in the dataset were members of a derecho series. On average, nearly six series affected the United States annually. Most derecho series consisted of two or three events; though, 14 series during the period of record contained four or more events. Two separate series involved nine derechos within a period of nine days. Analyses reveal that derecho series largely frequent regions of the Midwest, Ohio Valley, and the south-central Great Plains during May, June, and July. Results suggest that once a derecho occurred during May, June, or July, there was a 58% chance that this event was the first of a series of two or more, and about a 46% chance that this was the first of a derecho series consisting of three or more events. The derecho series climatology reveals that forecasters in regions frequented by derechos should be prepared for the probable regeneration of a derecho-producing convective system after an initial event occurs. Copyright

  4. A System for Measurement of Convection Aboard Space Station

    NASA Technical Reports Server (NTRS)

    Bogatyrev, Gennady P.; Gorbunov, Aleksei V; Putin, Gennady F.; Ivanov, Alexander I.; Nikitin, Sergei A.; Polezhaev, Vadim I.

    1996-01-01

    A simple device for direct measurement of buoyancy driven fluid flows in a low-gravity environment is proposed. A system connecting spacecraft accelerometers data and results of thermal convection in enclosure measurements and numerical simulations is developed. This system will permit also to evaluate the low frequency microacceleration component. The goal of the paper is to present objectives and current results of ground-based experimental and numerical modeling of this convection detector.

  5. Walker-Type Mean Circulations and Convectively Coupled Tropical Waves as an Interacting System.

    NASA Astrophysics Data System (ADS)

    Yano, Jun-Ichi; Moncrieff, Mitchell W.; Grabowski, Wojciech W.

    2002-05-01

    Interactions between convectively coupled tropical waves and Walker-type mean circulations are examined using a two-dimensional analytic model wherein drying and cooling of the boundary layer by convective and mesoscale downdrafts are in equilibrium with the wind-induced perturbations of surface fluxes. The moist thermodynamic state directly affects the stability of the large-scale circulation by controlling the wind perturbation on surface fluxes and the strength of the convective downdrafts. Stability analyses yield two major conclusions.(i) The mean Walker circulation is linearly unstable, suggesting that it may only exist in a quasi-steady sense through the spontaneous generation of transient waves. The instability is a manifestation of positive feedback: enhanced low-level convergence increases the surface wind speed, which increases the surface flux. As a result, convective heating is increased, which further enhances the low-level convergence. The mean circulation is more unstable when its horizontal extent is small and its depth large. Hence, when the horizontal extent of the mean circulation is a few thousand kilometers, as in the authors' recent cloud-resolving simulations, the deep first-baroclinic mode circulation is too unstable to be maintained even in a quasi-steady sense, realizing a shallow double-cell structure.(ii) The convectively coupled large-scale wave differs from traditional tropical large-scale instabilities of a homogeneous mean state in an important way: the longest waves are the most unstable rather than the shortest. Linear coupling of the waves with the mean state, through wind-induced surface flux perturbations, induces monotonically growing instabilities when the ascent of the mean circulation occupies more than half of the total domain. These instabilities occur only with the odd-wavenumber modes, which have parity with the mean circulation. Otherwise, the system supports linear neutral waves that propagate slower than the dry

  6. Convection in a two-layer fluid system

    NASA Technical Reports Server (NTRS)

    Prakash, A.; Peltier, L. J.; Fujita, D.; Koster, J.; Biringen, S.

    1991-01-01

    Experimental results are presented, and preliminary computations are performed on a system of two immiscible liquid layers with a temperature gradient applied parallel to the interface. The experiments reflect the combined contribution of buoyancy and surface-tension-induced (Marangoni) convection. It is concluded that buoyancy effects appear to be dominant and mask any surface-tension-induced convection present. Numerical computations show significant modification of pure buoyant convection by surface-tension gradients. The results are of interest in connection with the liquid encapsulation of GaAs melts in a microgravity environment.

  7. Mesoscale simulations of two model systems in biophysics: from red blood cells to DNAs

    NASA Astrophysics Data System (ADS)

    Peng, Zhangli; Chen, Yeng-Long; Lu, Huijie; Pan, Zehao; Chang, Hsueh-Chia

    2015-12-01

    Computational modeling has become increasingly important in biophysics, but the great challenge in numerical simulations due to the multiscale feature of biological systems limits the capability of modeling in making discoveries in biology. Innovative multiscale modeling approaches are desired to bridge different scales from nucleic acids and proteins to cells and tissues. Although all-atom molecular dynamics has been successfully applied in many microscale biological processes such as protein folding, it is still prohibitively expensive for studying macroscale problems such as biophysics of cells and tissues. On the other hand, continuum-based modeling has become a mature procedure for analysis and design in many engineering fields, but new insights for biological systems in the microscale are limited when molecular details are missing in continuum-based modeling. In this context, mesoscale modeling approaches such as Langevin dynamics, lattice Boltzmann method, and dissipative particle dynamics have become popular by simultaneously incorporating molecular interactions and long-range hydrodynamic interactions, providing insights to properties on longer time and length scales than molecular dynamics. In this review, we summarized several mesoscale simulation approaches for studying two model systems in biophysics: red blood cells (RBCs) and deoxyribonucleic acids (DNAs). The RBC is a model system for cell mechanics and biological membranes, while the DNA represents a model system for biopolymers. We introduced the motivations of studying these problems and presented the key features of different mesoscale methods. Furthermore, we described the latest progresses in these methods and highlighted the major findings for modeling RBCs and DNAs. Finally, we also discussed the challenges and potential issues of different approaches.

  8. Environmental Characteristics of Convective Systems During TRMM-LBA

    NASA Technical Reports Server (NTRS)

    Halverson, Jeffrey B.; Rickenbach, Thomas; Roy, Biswadev; Pierce, Harold; Williams, Earle; Einaudi, Franco (Technical Monitor)

    2001-01-01

    In this paper, data collected from 51 days of continual upper atmospheric soundings and TOGA radar at ABRACOS Hill during the TRMM-LBA experiment are used to describe the mean thermodynamic and kinematic airmass properties of wet season convection over Rondonia, Brazil. Distinct multi-day easterly and westerly lower tropospheric wind regimes occurred during the campaign with contrasting airmass characteristics. Westerly wind periods featured modest CAPE (1000 J/kg), moist conditions (>90% RH) extending through 700 mb and shallow (900 mb) speed shear on the order of 10(exp -4)/s. This combination of characteristics promoted convective systems that featured a relatively large fraction of stratiform rainfall and weak convection nearly devoid of lightning. The environment is very similar to the general airmass conditions experienced during the Darwin, Australia monsoon convective regime. In contrast, easterly regime convective systems were more strongly electrified and featured larger convective rain rates and reduced stratiform rainfall fraction. These systems formed in an environment with significantly larger CAPE (1500 J/kg), drier lower and middle level humidities (< 80% RH) and a wind shear layer that was both stronger (10(exp -3)/s) and deeper (700 mb). The larger CAPE resulted from strong insolation under relatively cloud-free skies (owing to reduced column humidity) and was also weakly capped in the lowest 1-2 km, thus contributing to a more explosive growth of convection. The time series of low- and mid-level averaged humidity exhibited marked variability between westerly and easterly regimes and was characterized by low frequency (i.e., multi-day to weekly) oscillations. The synoptic scale origins of these moisture fluctuations are examined, which include the effects of variable low-level airmass trajectories and upper-level, westward migrating cyclonic vortices. The results reported herein provide an environmental context for ongoing dual Doppler analyses

  9. Convective Systems Over the Japan Sea: Cloud-Resolving Model Simulations

    NASA Technical Reports Server (NTRS)

    Tao, Wei-Kuo; Yoshizaki, Masanori; Shie, Chung-Lin; Kato, Teryuki

    2002-01-01

    Wintertime observations of MCSs (Mesoscale Convective Systems) over the Sea of Japan - 2001 (WMO-01) were collected from January 12 to February 1, 2001. One of the major objectives is to better understand and forecast snow systems and accompanying disturbances and the associated key physical processes involved in the formation and development of these disturbances. Multiple observation platforms (e.g., upper-air soundings, Doppler radar, wind profilers, radiometers, etc.) during WMO-01 provided a first attempt at investigating the detailed characteristics of convective storms and air pattern changes associated with winter storms over the Sea of Japan region. WMO-01 also provided estimates of the apparent heat source (Q1) and apparent moisture sink (Q2). The vertical integrals of Q1 and Q2 are equal to the surface precipitation rates. The horizontal and vertical adjective components of Q1 and Q2 can be used as large-scale forcing for the Cloud Resolving Models (CRMs). The Goddard Cumulus Ensemble (GCE) model is a CRM (typically run with a 1-km grid size). The GCE model has sophisticated microphysics and allows explicit interactions between clouds, radiation, and surface processes. It will be used to understand and quantify precipitation processes associated with wintertime convective systems over the Sea of Japan (using data collected during the WMO-01). This is the first cloud-resolving model used to simulate precipitation processes in this particular region. The GCE model-simulated WMO-01 results will also be compared to other GCE model-simulated weather systems that developed during other field campaigns (i.e., South China Sea, west Pacific warm pool region, eastern Atlantic region and central USA).

  10. Magnetosphere-Ionosphere Convection as a Compound System

    NASA Astrophysics Data System (ADS)

    Tanaka, T.

    2007-12-01

    Convection is the most fundamental process in understanding the structure of geospace and disturbances observed in the magnetosphere-ionosphere (M-I) system. In this paper, a self-consistent configuration of the global convection system is considered under the real topology as a compound system. Investigations are made based on the M-I coupling scheme by analyzing numerical results obtained from magnetohydrodynamic (MHD) simulations which guarantee the self-consistency in the whole system under the Bv (magnetic field and velocity) paradigm. It is emphasized in the M-I coupling scheme that convection and field-aligned current (FAC) are different aspects of same physical process characterizing the open magnetosphere. Special attention is given in this paper to the energy supplying (dynamo) process that drives the FAC system. In the convection system, the dynamo must be constructed from shear motion together with plasma population regimes to steadily drive the convection. Convection patterns observed in the ionosphere are also the manifestation of achievement in global self-consistency. A primary approach to apply these concepts to the study of geospace is to consider how the M-I system adjusts the relative motion between the compressible magnetosphere and the incompressible ionosphere when responding to given solar-wind conditions. The above principle is also applicable for the study of disturbance phenomena such as the substorm as well as for the study of apparently unique processes such as the flux transfer event (FTE), the sudden commencement (SC), and the theta aurora. Finally, an attempt is made to understand the substorm as the extension of enhanced convection under the southward interplanetary magnetic field (IMF) condition.

  11. Observation and numerical simulation of a convective initiation during COHMEX

    NASA Technical Reports Server (NTRS)

    Song, J. Aaron; Kaplan, Michael L.

    1991-01-01

    Under a synoptically undisturbed condition, a dual-peak convective lifecycle was observed with the COoperative Huntsville Meteorological EXperiment (COHMEX) observational network over a 24-hour period. The lifecycle included a multicell storm, which lasted about 6 hours, produced a peak rainrate exceeding 100 mm/hr, and initiated a downstream mesoscale convective system. The 24-hour accumulated rainfall of this event was the largest during the entire COHMEX. The downstream mesoscale convective system, unfortunately, was difficult to investigate quantitatively due to the lack of mesoscale observations. The dataset collected near the time of the multicell storm evolution, including its initiation, was one of the best datasets of COHMEX. In this study, the initiation of this multicell storm is chosen as the target of the numerical simulations.

  12. Radar Observations of Convective Systems from a High-Altitude Aircraft

    NASA Technical Reports Server (NTRS)

    Heymsfield, G.; Geerts, B.; Tian, L.

    1999-01-01

    Reflectivity data collected by the precipitation radar on board the tropical Rainfall Measuring Mission (TRMM) satellite, orbiting at 350 km altitude, are compared to reflectivity data collected nearly simultaneously by a doppler radar aboard the NASA ER-2 flying at 19-20 km altitude, i.e. above even the deepest convection. The TRMM precipitation radar is a scanning device with a ground swath width of 215 km, and has a resolution of about a4.4 km in the horizontal and 250 m in the vertical (125 m in the core swath 48 km wide). The TRMM radar has a wavelength of 217 cm (13.8 GHz) and the Nadir mirror echo below the surface is used to correct reflectivity for loss by attenuation. The ER-2 Doppler radar (EDOP) has two antennas, one pointing to the nadir, 34 degrees forward. The forward pointing beam receives both the normal and the cross-polarized echos, so the linear polarization ratio field can be monitored. EDOP has a wavelength of 3.12 cm (9.6 GHz), a vertical resolution of 37.5 m and a horizontal along-track resolution of about 100 m. The 2-D along track airflow field can be synthesized from the radial velocities of both beams, if a reflectivity-based hydrometer fall speed relation can be assumed. It is primarily the superb vertical resolution that distinguishes EDOP from other ground-based or airborne radars. Two experiments were conducted during 1998 into validate TRMM reflectivity data over convection and convectively-generated stratiform precipitation regions. The Teflun-A (TEXAS-Florida Underflight) experiment, was conducted in April and May and focused on mesoscale convective systems mainly in southeast Texas. TEFLUN-B was conducted in August-September in central Florida, in coordination with CAMEX-3 (Convection and Moisture Experiment). The latter was focused on hurricanes, especially during landfall, whereas TEFLUN-B concentrated on central; Florida convection, which is largely driven and organized by surface heating and ensuing sea breeze circulations

  13. Characterizing convection in geophysical dynamo systems

    NASA Astrophysics Data System (ADS)

    Cheng, Jonathan Shuo

    The Earth's magnetic field is produced by a fluid dynamo in the molten iron outer core. This geodynamo is driven by fluid motions induced by thermal and chemical convection and strongly influenced by rotational and magnetic field effects. While frequent observations are made of the morphology and time-dependent field behavior, flow dynamics in the core are all but inaccessible to direct measurement. Thus, forward models are essential for exploring the relationship between the geomagnetic field and its underlying fluid physics. The goal of my PhD is to further our understanding of the fluid physics driving the geodynamo. In order to do this, I have performed a suite of nonrotating and rotating convection laboratory experiments and developed a new experimental device that reaches more extreme values of the governing parameters than previously possible. In addition, I conduct a theoretical analysis of well-established results from a suite of dynamo simulations by Christensen and Aubert (2006). These studies are conducted at moderate values of the Ekman number (ratio between viscosity and Coriolis forces, ˜ 10-4), as opposed to the the extremely small Ekman numbers in planetary cores (˜ 10 -15). At such moderate Ekman values, flows tend to take the form of large-scale, quasi-laminar axial columns. These columnar structures give the induced magnetic field a dipolar morphology, similar to what is seen on planets. However, I find that some results derived from these simulations are fully dependent on the fluid viscosity, and therefore are unlikely to reflect the fluid physics driving dynamo action in the core. My findings reinforce the need to understand the turbulent processes that arise as the governing parameters approach planetary values. Indeed, my rotating convection experiments show that, as the Ekman number is decreased beyond ranges currently accessible to dynamo simulations, the regime characterized by laminar columns is found to dwindle. We instead find a

  14. Does mesoscale matters in decadal changes observed in the northern Canary upwelling system?

    NASA Astrophysics Data System (ADS)

    Relvas, P.; Luís, J.; Santos, A. M. P.

    2009-04-01

    The Western Iberia constitutes the northern limb of the Canary Current Upwelling System, one of the four Eastern Boundary Upwelling Systems of the world ocean. The strong dynamic link between the atmosphere and the ocean makes these systems highly sensitive to global change, ideal to monitor and investigate its effects. In order to investigate decadal changes of the mesoscale patterns in the Northern Canary upwelling system (off Western Iberia), the field of the satellite-derived sea surface temperature (SST) trends was built at the pixel scale (4x4 km) for the period 1985-2007, based on the monthly mean data from the Advanced Very High Resolution Radiometer (AVHRR) on board NOAA series satellites, provided by the NASA Physical Oceanography Distributed Active Archive Center (PO.DAAC) at the Jet Propulsion Laboratory. The time series were limited to the nighttime passes to avoid the solar heating effect and a suite of procedures were followed to guarantee that the temperature trends were not biased towards the seasonally more abundant summer data, when the sky is considerably clear. A robust linear fit was applied to each individual pixel, crossing along the time the same pixel in all the processed monthly mean AVHRR SST images from 1985 until 2007. The field of the SST trends was created upon the slopes of the linear fits applied to each pixel. Monthly mean SST time series from the one degree enhanced International Comprehensive Ocean-Atmosphere Data Set (ICOADS) and from near-shore measurements collected on a daily basis by the Portuguese Meteorological Office (IM) are also used to compare the results and extend the analysis back until 1960. A generalized warming trend is detected in the coastal waters off Western Iberia during the last decades, no matter which data set we analyse. However, significant spatial differences in the warming rates are observed in the satellite-derived SST trends. Remarkably, off the southern part of the Western Iberia the known

  15. Numerical simulations of mesoscale precipitation systems. Final progress report, 1 April-30 June 1981

    SciTech Connect

    Dingle, A.N.

    1982-05-12

    A numerical model designed for the study of mesoscale weather phenomena is presented. It is a three-dimensional, time-dependent model based upon a mesoscale primitive-equation system, and it includes parameterizations of cloud and precipitation processes, boundary-layer transfers, and ground surface energy and moisture budgets. This model was used to simulate the lake-effect convergence over and in the lee of Lake Michigan in late fall and early winter. The lake-effect convergence is created in advected cold air as it moves first from cold land to the warm constant-temperature lake surface, and then on to cold land. A numerical experiment with a prevailing northwesterly wind is conducted for a period of twelve hours. Two local maxima of the total precipitation are observed along the eastern shore of Lake Michigan. The results in this hypothetical case correspond quite well to the observed precipitation produced by a real event in which the hypothetical conditions are approximately fulfilled.

  16. Thin-walled compliant plastic structures for meso-scale fluidic systems

    SciTech Connect

    Miles, R R; Schumann, D L

    1998-12-29

    Thin-walled, compliant plastic structures for meso-scale fluidic systems were fabricated, tested and used to demonstrate valving, pumping, metering and mixing. These structures permit the isolation of actuators and sensors from the working fluid, thereby reducing chemical compatibility issues. The thin-walled, compliant plastic structures can be used in either a permanent, reusable system or as an inexpensive disposable for single-use assay systems. The implementation of valving, pumping, mixing and metering operations involve only an elastic change in the mechanical shape of various portions of the structure. Advantages provided by the thin-walled plastic structures include reduced dead volume and rapid mixing. Five different methods for fabricating the thin-walled plastic structures discussed including laser welding, molding, vacuum forming, thermal heat staking and photolithographic patterning techniques.

  17. Initial results from a mesoscale atmospheric simulation system and comparisons with the AVE-SESAME I data set. [Atmospheric Variability Experiment-Severe Environmental Storms And Mesoscale Experiment

    NASA Technical Reports Server (NTRS)

    Kaplan, M. L.; Zack, J. W.; Wong, V. C.; Tuccillo, J. J.

    1982-01-01

    The development of a comprehensive mesoscale atmospheric simulation system (MASS) is described in detail. The modeling system is designed for both research and real-time forecast applications. The 14-level numerical model, which has a 48 km grid mesh, can be run over most of North America and the adjacent oceanic regions. The model employs sixth-order accurate numerics, generalized similarity theory boundary-layer physics, a sophisticated cumulus parameterization scheme, and state of the art analysis and initialization techniques. Examples of model output on the synoptic and subsynoptic scales are presented for the AVE-SESAME I field experiment on 10-11 April 1979. The model output is subjectively compared to the observational analysis and the LFM II output on the synoptic scale. Subsynoptic model output is compared to analyses generated from the AVE-SESAME I data set.

  18. Chemical properties of rain events during the AMMA campaign: an evidence of dust and biogenic influence in the convective systems

    NASA Astrophysics Data System (ADS)

    Desboeufs, K.; Journet, E.; Rajot, J.-L.; Chevaillier, S.; Triquet, S.; Formenti, P.; Zakou, A.

    2010-06-01

    This paper documents the chemical composition of 7 rain events associated with mesoscale convective systems sampled at the supersite of Banizoumbou, Niger, during the first special observation periods (June-July 2006) of the African Monsoon Multidisciplinary Analyses (AMMA) experiment. Time-resolved rain sampling was performed in order to discriminate the local dust scavenged at the beginning of rain event from the aerosol particles incorporated in the cloud at the end of the rain. The total elemental composition is dominated by Al, Si, Fe and Ca, indicating a high influence of dust and limited marine or anthropogenic contribution. After the aerosol wash-out, the elemental concentrations normalized to Al and the microscopic observations of diatoms, a tracer of the Bodélé depression, both indicate that the total elemental composition of rainwater is controlled by dust originating from North-Eastern Saharan sources and probably incorporated in the convective cloud from the Harmattan layer. The low variability of the rain composition over the measurement period indicates a regional and temporal homogeneity of dust composition in the Harmattan layer. In the dissolved phase, the dominant anions are nitrate (NO3-), sulphate (SO42-) and chloride (Cl-). However, between June and July we observe an increasing contribution of the organic anions (formate, acetate, oxalate) associated with biogenic emissions to the total ion composition. These results confirm the large influence of biogenic emissions on the rain composition over Sahel during the wet season. The paper concludes on the capacity of mesoscale convective systems to carry simultaneously dust and biogenic compounds originating from different locations and depose them jointly. It also discusses the potential biogeochemical impact of such a phenomenon.

  19. Mesoscale Modeling of Heterogeneous Materials Systems: From Solid Oxide Fuel Cells to Bulk Metallic Glasses

    NASA Astrophysics Data System (ADS)

    Abdeljawad, Fadi F.

    Heterogeneous materials systems hold the key to the future development of a broad range of increasingly complex technological applications. For example, multi-phase and/or multi-component materials are at the forefront research on the development of efficient energy devices, and the future generation of structural materials with optimal mechanical properties. In this dissertation, we focus on two materials systems, namely, solid oxide fuel cells (SOFCs) and bulk metallic glasses (BMGs), where we investigate, through theoretical and mesoscale computational models, the role of microstructure on the properties of these heterogeneous systems. For the solid oxide fuel cell project, a computational framework is developed to investigate the topological evolution of Ni phase in SOFC porous anodes, and the accompanying changes to a wide range of microstructural attributes that affect electrochemical performance. Additionally, with the aid of this framework, we study the reduction-oxidation instability, mechanical deformation and damage accumulation in SOFC anodes. In particular, the SOFC project is focused on the role of anode microstructure, characterized by particle size and ratio, on the microstructural stability and mechanical durability of SOFC anodes. For the bulk metallic glass project, a mesoscale model is introduced that accounts for the structural heterogeneity of monolithic BMGs and BMG composites, and captures the fundamental aspects of plastic deformation in such systems. We examine the effect of internal structure, characterized by rigid/soft short range order (SRO), on the deformation behavior of monolithic BMGs, while for BMG composites, we study the role of ductile phase microstructure, particle size, morphology and area fraction, on the mechanical properties and overall ductility of these systems.

  20. Satellite contributions to convective scale weather analysis and forecasting

    NASA Technical Reports Server (NTRS)

    Purdom, James F. W.

    1986-01-01

    Severe weather phenomena which are amenable to remote sensing by satellite instruments and having resolution fine enough to discern mesoscale features are described. GOES satellites acquire imagery with 1 km resolution in the visible band and 8 km at IR wavelengths. Animation of the images allows tracking the evolution and motions of clouds, which are the prime indicators of convective activity. Sample satellite imagery of sea, lake and river breezes which reveal differential heating processes, the effect of early morning cloud cover, thunderstorm outflow processes, and mesoscale convective systems are provided. Techniques for analyzing the satellite data to predict the onset of severe weather are discussed.

  1. Intraseasonal variability of organized convective systems in the Central Andes: Relationship to Regional Dynamical Features

    NASA Astrophysics Data System (ADS)

    Mohr, K. I.; Slayback, D. A.; Nicholls, S.; Yager, K.

    2013-12-01

    The Andes extend from the west coast of Colombia (10N) to the southern tip of Chile (53S). In southern Peru and Bolivia, the Central Andes is split into separate eastern and western cordilleras, with a high plateau (≥ 3000 m), the Altiplano, between them. Because 90% of the Earth's tropical mountain glaciers are located in the Central Andes, our study focuses on this region, defining its zonal extent as 7S-21S and the meridional extent as the terrain 1000 m and greater. Although intense convection occurs during the wet season in the Altiplano, it is not included in the lists of regions with frequent or the most intense convection. The scarcity of in-situ observations with sufficient density and temporal resolution to resolve individual storms or even mesoscale-organized cloud systems and documented biases in microwave-based rainfall products in poorly gauged mountainous regions have impeded the development of an extensive literature on convection and convective systems in this region. With the tropical glaciers receding at unprecedented rates, leaving seasonal precipitation as an increasingly important input to the water balance in alpine valley ecosystems and streams, understanding the nature and characteristics of the seasonal precipitation becomes increasingly important for the rural economies in this region. Previous work in analyzing precipitation in the Central Andes has emphasized interannual variability with respect to ENSO, this is the first study to focus on shorter scale variability with respect to organized convection. The present study took advantage of the University of Utah's Precipitation Features database compiled from 14 years of TRMM observations (1998-2012), supplemented by field observations of rainfall and streamflow, historical gauge data, and long-term WRF-simulations, to analyze the intraseasonal variability of precipitating systems and their relationship regional dynamical features such as the Bolivian High. Through time series and

  2. Wall-Enhanced Convection in Vibrofluidized Granular Systems

    NASA Astrophysics Data System (ADS)

    Talbot, J.; Viot, P.

    2002-07-01

    An event-driven molecular dynamics simulation of inelastic hard spheres contained in a cylinder and subject to strong vibration reproduces accurately experimental results [R. D. Wildman et al., Phys. Rev. Lett. 86, 3304 (2001)] for a system of vibrofluidized glass beads. In particular, we are able to obtain the velocity field and the density and temperature profiles observed experimentally. In addition, we show that the appearance of convection rolls is strongly influenced by the value of the sidewall-particle restitution coefficient. Suggestions for observing more complex convection patterns are proposed.

  3. Use of observational and model-derived fields and regime model output statistics in mesoscale forecasting

    NASA Technical Reports Server (NTRS)

    Forbes, G. S.; Pielke, R. A.

    1985-01-01

    Various empirical and statistical weather-forecasting studies which utilize stratification by weather regime are described. Objective classification was used to determine weather regime in some studies. In other cases the weather pattern was determined on the basis of a parameter representing the physical and dynamical processes relevant to the anticipated mesoscale phenomena, such as low level moisture convergence and convective precipitation, or the Froude number and the occurrence of cold-air damming. For mesoscale phenomena already in existence, new forecasting techniques were developed. The use of cloud models in operational forecasting is discussed. Models to calculate the spatial scales of forcings and resultant response for mesoscale systems are presented. The use of these models to represent the climatologically most prevalent systems, and to perform case-by-case simulations is reviewed. Operational implementation of mesoscale data into weather forecasts, using both actual simulation output and method-output statistics is discussed.

  4. Impact of intensified Indian Ocean winds on mesoscale variability in the Agulhas system

    NASA Astrophysics Data System (ADS)

    Backeberg, Björn C.; Penven, Pierrick; Rouault, Mathieu

    2012-08-01

    South of Africa, the Agulhas Current retroflects and a portion of its waters flows into the South Atlantic Ocean, typically in the form of Agulhas rings. This flux of warm and salty water from the Indian to the Atlantic Ocean (the Agulhas leakage) is now recognized as a key element in global climate. An Agulhas leakage shutdown has been associated with extreme glacial periods, whereas a vigorous increase has preceded shifts towards interglacials. In the absence of a coherent observing system, studies of the Agulhas have relied heavily on ocean models, which have revealed a possible recent increase in Agulhas leakage. However, owing to the high levels of oceanic turbulence, model solutions of the region are highly sensitive to their numerical choices, stressing the need for observations to confirm these important model results. Here, using satellite altimetry observations from 1993 to 2009, we show that the mesoscale variability of the Agulhas system, in particular in the Mozambique Channel and south of Madagascar, has intensified. This seems to result from an increased South Equatorial Current driven by enhanced trade winds over the tropical Indian Ocean. Overall, the intensified mesoscale variability of the Agulhas system is reflected in accelerated eddy propagation, in its source regions as well as the retroflection from which eddies propagate into the South Atlantic Ocean. This suggests that the Agulhas leakage may have increased from 1993 to 2009, confirming previous modelling studies that have further implied an increased Agulhas leakage may compensate a deceleration of meridional overturning circulation associated with a freshening of the North Atlantic Ocean.

  5. Preliminary design of mesoscale turbocompressor and rotordynamics tests of rotor bearing system

    NASA Astrophysics Data System (ADS)

    Hossain, Md Saddam

    2011-12-01

    A mesoscale turbocompressor spinning above 500,000 RPM is evolutionary technology for micro turbochargers, turbo blowers, turbo compressors, micro-gas turbines, auxiliary power units, etc for automotive, aerospace, and fuel cell industries. Objectives of this work are: (1) to evaluate different air foil bearings designed for the intended applications, and (2) to design & perform CFD analysis of a micro-compressor. CFD analysis of shrouded 3-D micro compressor was conducted using Ansys Bladegen as blade generation tool, ICEM CFD as mesh generation tool, and CFX as main solver for different design and off design cases and also for different number of blades. Comprehensive experimental facilities for testing the turbocompressor system have been also designed and proposed for future work.

  6. Reactor with natural convection backup cooling system

    SciTech Connect

    Koutz, S.L.; Cavallaro, L.; Kapich, D.D.

    1988-07-26

    A nuclear reactor is described comprising: a closed vessel containing a pool of secondary coolant; a reactor core located within the pool; an inlet conduit system for directing primary coolant to the lower end of the core; pumping means for effecting flow of the primary coolant into the inlet conduit system; an outlet conduit system located above the core for receiving coolant from the upper end of the core and carrying it to an exterior outlet pipe; and pressure reduction means for reducing fluid pressure in the inlet conduit system adjacent all of the one or more opening therein by locally increasing fluid velocity adjacent all of the one or more openings.

  7. The hydrothermal-convection systems of kilauea: an historical perspective

    USGS Publications Warehouse

    Moore, R.B.; Kauahikaua, J.P.

    1993-01-01

    Kilauea is one of only two basaltic volcanoes in the world where geothermal power has been produced commercially. Little is known about the origin, size and longevity of its hydrothermal-convection systems. We review the history of scientific studies aimed at understanding these systems and describe their commercial development. Geothermal energy is a controversial issue in Hawai'i, partly because of hydrogen sulfide emissions and concerns about protection of rain forests. ?? 1993.

  8. Thermally-sustained structure in convectively unstable systems

    NASA Technical Reports Server (NTRS)

    Deissler, Robert J.

    1993-01-01

    The complex Ginzburg-Landau equation with a thermal noise term is studied under conditions when the system is convectively unstable. Under these conditions, the noise is selectively and spatially amplified giving rise to a noise-sustained structure. Analytical results, applicable to a wide range of physical systems, are derived for the variance, and the coefficients and thermal noise term are determined for Taylor-Couette flow with an axial through-flow. Comparison is made to recent experiments.

  9. The Prediction of Predominant Convection in Sedimentary Basin Systems

    NASA Astrophysics Data System (ADS)

    Musuuza, J. L.; Radu, F. A.; Attinger, S.

    2012-12-01

    We study a thermohaline system in which the density gradients arise from salinity and temperature differences. Such systems arise in practical applications e.g. geological waste storage and geothermal energy exploitation. A sedimentary-basin set-up is investigated where salinity and temperature increase with depth. In such systems, the buoyancy forces caused by salinity and temperature gradients give rise to counter-acting convection cells. The homogenization theory ideas from Held, Attinnger and Kinzelbach (2005) are applied to the solute and heat transport equations and the two resulting cell problems solved with the coupling between the heat and solute transport preserved. A dimensionless number whose sign changes to negative when thermal-convection is predominant is derived from the solutions to the cell problems in terms of physical variables. The number is tested against numerical simulations performed with the software package d3f on sufficiently refined grids that deliver stable numerical solutions without upwind techniques.

  10. Diagnosis of the secondary circulation of tropical storm Bilis (2006) and the effects of convective systems on its track

    NASA Astrophysics Data System (ADS)

    Yu, Jinhua; Fu, Hao; Tang, Sheng; Sheng, Siwei

    2014-02-01

    We diagnose characteristics of the quasi-balanced flow and secondary circulation (SC) of tropical storm Bilis (2006) using the potential vorticity (PV)- ω inversion method. We further analyze how secondary steering flows associated with mesoscale convective systems affected the track of tropical storm Bilis after it made landfall. The quasi-balanced asymmetric and axisymmetric circulation structures of tropical storm Bilis are represented well by the PV- ω inversion. The magnitude of the nonlinear quasi-balanced vertical velocity is approximately 75% of the magnitude simulated using the Weather Research and Forecasting (WRF) model. The SC of Bilis (2006) contained two strong regions of ascending motion, both of which were located in the southwest quadrant of the storm. The first (150-200 km southwest of the storm center) corresponded to the eyewall region, while the second (approximately 400 km southwest of the storm center) corresponded to latent heat release associated with strong precipitation in major spiral rainbands. The SC was very weak in the northeast quadrant (the upshear direction). Dynamical processes related to the environmental vertical wind shear produced an SC that partially offset the destructive effects of the environmental vertical wind shear (by 20%-25%). This SC consisted of upward motion in the southwest quadrant and subsidence in the northeast quadrant, with airflow oriented from southwest to northeast at high altitudes and from northeast to southwest at lower levels. The inverted secondary zonal and meridional steering flows associated with continuous asymmetric mesoscale convective systems were about -2.14 and -0.7 m s-1, respectively. These steering flows contributed substantially to the zonal (66.15%) and meridional (33.98%) motion of the storm at 0000 UTC 15 July 2006. The secondary steering flow had a significant influence on changing the track of Bilis from southward to northward. The direction of the large-scale meridional steering

  11. Chemically generated convective transport in microfluidic system

    NASA Astrophysics Data System (ADS)

    Shklyaev, Oleg; Das, Sambeeta; Altemose, Alicia; Shum, Henry; Balazs, Anna; Sen, Ayusman

    High precision manipulation of small volumes of fluid, containing suspended micron sized objects like cells, viruses, and large molecules, is one of the main goals in designing modern lab-on-a-chip devices which can find a variety of chemical and biological applications. To transport the cargo toward sensing elements, typical microfluidic devices often use pressure driven flows. Here, we propose to use enzymatic chemical reactions which decompose reagent into less dense products and generate flows that can transport particles. Density variations that lead to flow in the assigned direction are created between the place where reagent is fed into the solution and the location where it is decomposed by enzymes attached to the surface of the microchannel. When the reagent is depleted, the fluid motion stops and particles sediment to the bottom. We demonstrate how the choice of chemicals, leading to specific reaction rates, can affect the transport properties. In particular, we show that the intensity of the fluid flow, the final location of cargo, and the time for cargo delivery are controlled by the amount and type of reagent in the system.

  12. Role of upper-level wind shear on the structure and maintenance of derecho-producing convective systems

    NASA Astrophysics Data System (ADS)

    Coniglio, Michael Charles

    strong, linear mesoscale convective systems (MCSs) and may provide a conceptual model for the persistence of strong MCSs above a surface nocturnal inversion in situations that are not forced by a low-level jet.

  13. Equilibrium Structure of a Triblock Copolymer System Revealed by Mesoscale Simulation and Neutron Scattering

    SciTech Connect

    Do, Changwoo; Chen, Wei-Ren; Hong, Kunlun; Smith, Gregory Scott

    2013-01-01

    We have performed both mesoscale simulations and neutron scattering experiments on Pluronic L62, a poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) triblock copolymer system in aqueous solution. The influence of simulation variables such PEO/PPO block ratio, interaction parameters, and coarse-graining methods is extensively investigated by covering all permutations of parameters found in the literatures. Upon increasing the polymer weight fraction from 50 wt% to 90 wt%, the equilibrium structure of the isotropic, reverse micellar, bicontinuous, worm-like micelle network, and lamellar phases are respectively predicted from the simulation depending on the choices of simulation parameters. Small angle neutron scattering (SANS) measurements show that the same polymer systems exhibit the spherical micellar, lamellar, and reverse micellar phases with the increase of the copolymer concentration at room temperature. Detailed structural analysis and comparison with simulations suggest that one of the simulation parameter sets can provide reasonable agreement with the experimentally observed structures.

  14. Equilibrium structure of a triblock copolymer system revealed by mesoscale simulation and neutron scattering

    NASA Astrophysics Data System (ADS)

    Do, Changwoo; Chen, Wei-Ren; Hong, Kunlun; Smith, Gregory S.

    2013-12-01

    We have performed both mesoscale simulations and neutron scattering experiments on Pluronic L62, a poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) triblock copolymer system in aqueous solution. The influence of simulation variables such PEO/PPO block ratio, interaction parameters, and coarse-graining methods is extensively investigated by covering all permutations of parameters found in the literatures. Upon increasing the polymer weight fraction from 50 wt% to 90 wt%, the equilibrium structure of the isotropic, reverse micellar, bicontinuous, worm-like micelle network, and lamellar phases are respectively predicted from the simulation depending on the choices of simulation parameters. Small angle neutron scattering (SANS) measurements show that the same polymer systems exhibit the spherical micellar, lamellar, and reverse micellar phases with the increase of the copolymer concentration at room temperature. Detailed structural analysis and comparison with simulations suggest that one of the simulation parameter sets can provide reasonable agreement with the experimentally observed structures.

  15. Mesoscale Simulations of CRYSTAL-FACE 23 July 2002 Case

    NASA Technical Reports Server (NTRS)

    Starr, David; Lin, Ruei-Fong; Lare, Andrew; Demoz, Belay; Rickenbach, Thomas; Wang, Dong-Hai; Li, Li-Hua; Arnold, G. Thomas; Wang, Yan-Sen

    2004-01-01

    A key objective of the Cirrus Regional Study of Tropical Anvils and Cirrus Layers - Florida Area Cirrus Experiment (CRYSTAL-FACE) is to understand the relationships between properties of tropical convective cloud systems and the lifecycle of the extended cirrus anvils they produce. We report here on a case study of 23 July 2002 where a line of land-based convective storms was generated between Lake Okeechobee and the Florida east coast as a result of complex interactions between lake and sea breeze fronts and outflow boundaries. A central goal of this study is to develop a description of convective input to the anvil system and to quantify the ongoing dynamical forcing of anvil processes by mesoscale and large-scale dynamics. This information is then used to force high-resolution cloud simulations with a model that explicitly resolves cloud microphysical processes (bin model) for study of cirrus anvil microphysical development.

  16. Combined flatland ST radar and digital-barometer network observations of mesoscale processes

    NASA Technical Reports Server (NTRS)

    Clark, W. L.; Vanzandt, T. E.; Gage, K. S.; Einaudi, F. E.; Rottman, J. W.; Hollinger, S. E.

    1991-01-01

    The paper describes a six-station digital-barometer network centered on the Flatland ST radar to support observational studies of gravity waves and other mesoscale features at the Flatland Atmospheric Observatory in central Illinois. The network's current mode of operation is examined, and a preliminary example of an apparent group of waves evident throughout the network as well as throughout the troposphere is presented. Preliminary results demonstrate the capabilities of the current operational system to study wave convection, wave-front, and other coherent mesoscale interactions and processes throughout the troposphere. Unfiltered traces for the pressure and horizontal zonal wind, for days 351 to 353 UT, 1990, are illustrated.

  17. Convective Systems Observed and Simulated During TRMM Field Campaigns

    NASA Technical Reports Server (NTRS)

    Tao, Wei-Kuo; Einaudi, Franco (Technical Monitor)

    2001-01-01

    Recently completed TRMM field campaigns (TEFLUN1998, SCSMEX-1998, TRMM.LBA-1999, and KWAJEX 1999) have obtained direct measurements of microphysical data associated with convective systems from various geographical locations. These TRMM field experiments were designed to contribute to fundamental understanding of cloud dynamics and microphysics, as well as for validation,, testing assumptions and error estimates of cloud-resolving models, forward radiative transfer models, algorithms used to estimate rainfall statistics and vertical structure of precipitation and latent heating from both surface-based radar and satellites.

  18. Using Homogenization Theory to Study Convection in Thermohaline Systems

    NASA Astrophysics Data System (ADS)

    Musuuza, J. L.; Radu, F. A.; Attinger, S.

    2012-04-01

    We study a density-driven system in which the density gradients arise from salinity and temperature differences. Since the solute and heat diffuse at different rates, such systems are also called double-diffusive and arise in many practical applications like carbon dioxide sequestration, geothermal energy exploitation and the storage of nuclear and normal waste in geological formations. A typical sedimentary-basin set-up is adopted where both salinity and temperature increase with depth. In such systems, the buoyancy forces caused by salinity and temperature gradients give rise to counter-acting convection cells. The homogenization theory ideas originally developed in Held et al. (2005) are applied to the solute and heat transport equations and the two resulting cell problems solved coupled. A dimensionless number is derived from the solutions to the cell problems in terms of the physical variables temperature, viscosity and density contrasts; gravity-driven velocity, domain size and formation hydro-geological properties. The sign of the number changes to negative when the thermal-convection predominates over solutal-convection. The derived dimensionless number is tested against numerical simulations performed with the software package d3 f on sufficiently refined grids that deliver stable numerical solutions without upwind techniques (Frolkovic and De Schepper, 2001). We also investigate the possibility of groundwater intrusion into a geological formation by applying a horizontal drift at the top of the domain. The evolution of fingers in haline density-driven systems was studied e.g. in Musuuza et al. (2009) and such a velocity aligned orthogonal to the direction of finger propagation was found to retard finger growth. Frolkovic, P. and De Schepper, H. (2001), 'Numerical modelling of convection dominated transport coupled with density-driven flow in porous media', Ad. Wat. Resour. 24, 63-72. Held, R, S. Attinger and Kinzelbach, W. (2005), 'Homogenization and

  19. Capturing Nonlinearities with the Naval Research Laboratory's Global and Mesoscale 4DVar Data Assimilation Systems

    NASA Astrophysics Data System (ADS)

    Baker, N. L.; Xu, L.

    2015-12-01

    Numerical weather prediction models and observation (forward) operators are important components of modern data assimilation systems. They are inherently nonlinear or even highly nonlinear at times. These nonlinearities can be handled through an iterative procedure, often referred to as the "outer loop" / "inner loop" formulation in 3D/4DVar data assimilation. In the "inner loop", one typically minimizes a cost-function around a previous 3D/4D state that is already a good approximation of the true nonlinear state. Additional "outer loops" are then used to account for the missing nonlinearity in both the NWP model and the observation operator. There is no formal proof of convergence in the aforementioned iterative procedure in general. However, it can be formally shown that the procedure can converge under certain condition (e.g. the Gauss-Newton algorithm). In practice, the iterative procedure works quite well due to the fact that the NWP model and the observation operators are generally quite good in capturing majority of the nonlinearity in dynamical process. The NRL global and mesoscale 4DVar systems use the Accelerated Representer (AR) formulation to solve the analysis equations in observation space. The dual formulation has several strategic advantages, but also present additional challenges unique to this formulation. This presentation will describe various methods used within the NRL Accelerated Representer 4DVar formulations to extend the solution methods to weakly nonlinear problems. These include ocean surface wind speed assimilation, assimilation of water vapor sensitive radiances, the multiple outer loop formulation, and the inclusion of linearized physics in the tangent linear and adjoint models.

  20. Spatial and seasonal patterns of fine-scale to mesoscale upper ocean dynamics in an Eastern Boundary Current System

    NASA Astrophysics Data System (ADS)

    Grados, Daniel; Bertrand, Arnaud; Colas, François; Echevin, Vincent; Chaigneau, Alexis; Gutiérrez, Dimitri; Vargas, Gary; Fablet, Ronan

    2016-03-01

    The physical forcing of the ocean surface includes a variety of energetic processes, ranging from internal wave (IW) to submesoscale and mesoscale, associated with characteristic horizontal scales. While the description of mesoscale ocean dynamics has greatly benefited from the availability of satellite data, observations of finer scale patterns remain scarce. Recent studies showed that the vertical displacements of the oxycline depth, which separates the well-mixed oxygenated surface layer from the less oxygenated deeper ocean, estimated by acoustics, provide a robust proxy of isopycnal displacements over a wide range of horizontal scales. Using a high-resolution and wide-range acoustic data set in the Northern Humboldt Current System (NHCS) off Peru, the spatial and temporal patterns of fine-scale-to-mesoscale upper ocean dynamics are investigated. The spectral content of oxycline/pycnocline profiles presents patterns characteristic of turbulent flows, from the mesoscale to the fine scale, and an energization at the IW scale (2 km-200 m). On the basis of a typology performed on 35,000 structures we characterized six classes of physical structures according to their shape and scale range. The analysis reveals the existence of distinct features for the fine-scale range below ∼2-3 km, and clearly indicates the existence of intense IW and submesoscale activity over the entire NHCS region. Structures at scales smaller than ∼2 km were more numerous and energetic in spring than in summer. Their spatiotemporal variability supports the interpretation that these processes likely relate to IW generation by interactions between tidal flows, stratification and the continental slope. Given the impact of the physical forcing on the biogeochemical and ecological dynamics in EBUS, these processes should be further considered in future ecosystem studies based on observations and models. The intensification of upper ocean stratification resulting from climate change makes such

  1. Tracing troposphere-to-stratosphere transport above a mid-latitude deep convective system

    NASA Astrophysics Data System (ADS)

    Hegglin, M. I.; Brunner, D.; Wernli, H.; Schwierz, C.; Martius, O.; Hoor, P.; Fischer, H.; Parchatka, U.; Spelten, N.; Schiller, C.; Krebsbach, M.; Weers, U.; Staehelin, J.; Peter, Th.

    2004-05-01

    Within the project SPURT (trace gas measurements in the tropopause region) a variety of trace gases have been measured in situ in order to investigate the role of dynamical and chemical processes in the extra-tropical tropopause region. In this paper we report on a flight on 10 November 2001 leading from Hohn, Germany (52ºN) to Faro, Portugal (37ºN) through a strongly developed deep stratospheric intrusion. This streamer was associated with a large convective system over the western Mediterranean with potentially significant troposphere-to-stratosphere transport. Along major parts of the flight we measured unexpectedly high NOy mixing ratios. Also H2O mixing ratios were significantly higher than stratospheric background levels confirming the extraordinary chemical signature of the probed air masses in the interior of the streamer. Backward trajectories encompassing the streamer enable to analyze the origin and physical characteristics of the air masses and to trace troposphere-to-stratosphere transport. Near the western flank of the intrusion features caused by long range transport, such as tropospheric filaments characterized by sudden drops in the O3 and NOy mixing ratios and enhanced CO and H2O can be reconstructed in great detail using the reverse domain filling technique. These filaments indicate a high potential for subsequent mixing with the stratospheric air. At the south-western edge of the streamer a strong gradient in the NOy and the O3 mixing ratios coincides very well with a sharp gradient in potential vorticity in the ECMWF fields. In contrast, in the interior of the streamer the observed highly elevated NOy and H2O mixing ratios up to a potential temperature level of 365 K and potential vorticity values of maximum 10 PVU cannot be explained in terms of resolved troposphere-to-stratosphere transport along the backward trajectories. Also mesoscale simulations with a High Resolution Model reveal no direct evidence for convective H2O injection up to

  2. Tracing troposphere-to-stratosphere transport above a mid-latitude deep convective system

    NASA Astrophysics Data System (ADS)

    Hegglin, M. I.; Brunner, D.; Wernli, H.; Schwierz, C.; Martius, O.; Hoor, P.; Fischer, H.; Spelten, N.; Schiller, C.; Krebsbach, M.; Parchatka, U.; Weers, U.; Staehelin, J.; Peter, Th.

    2004-01-01

    Within the project SPURT (trace gas measurements in the tropopause region) a variety of trace gases have been measured in situ in order to investigate the role of dynamical and chemical processes in the extra-tropical tropopause region. In this paper we report on a flight on 10 November 2001 leading from Hohn, Germany (52° N) to Faro, Portugal (37° N) through a strongly developed deep stratospheric intrusion. This streamer was associated with a large convective system over the western Mediterranean with potentially significant troposphere-to-stratosphere transport. Along major parts of the flight we measured unexpectedly high NOy mixing ratios. Also H2O mixing ratios were significantly higher than stratospheric background levels confirming the extraordinary chemical signature of the probed air masses in the interior of the streamer. Backward trajectories encompassing the streamer enable to analyze the origin and physical characteristics of the air masses and to trace troposphere-to-stratosphere transport. Near the western flank of the intrusion features caused by long range transport, such as tropospheric filaments characterized by sudden drops in the O3 and NOy mixing ratios and enhanced CO and H2O can be reconstructed in great detail using the reverse domain filling technique. These filaments indicate a high potential for subsequent mixing with the stratospheric air. At the south-western edge of the streamer a strong gradient in the NOy and the O3 mixing ratios coincides very well with a sharp gradient in potential vorticity in the ECMWF fields. In contrast, in the interior of the streamer the observed highly elevated NOy and H2O mixing ratios up to a potential temperature level of 365 K and potential vorticity values of maximum 10 PVU cannot be explained in terms of resolved troposphere-to-stratosphere transport along the backward trajectories. Also mesoscale simulations with a High Resolution Model reveal no direct evidence for convective H2O injection up to

  3. The impact of polar mesoscale storms on northeast Atlantic ocean circulation (Invited)

    NASA Astrophysics Data System (ADS)

    Condron, A.; Renfrew, I.

    2013-12-01

    Every year thousands of mesoscale (<1000 km) storms cross the climatically sensitive sub-polar regions of the world's oceans. These storms are frequently too small, or short-lived, to be captured in meteorological reanalyses or numerical climate prediction models. As a result, the magnitude of the near-surface wind speeds and heat fluxes are considerably under-represented over the world's oceans where the atmosphere influences mixing, deep convection, upwelling, and deep water mass formation. Numerical models must, however, realistically simulate these processes in order to accurately predict future changes in the strength of the Atlantic Meridional Overturning Circulation (MOC) and the climate system. Implementing a parameterization to simulate mesoscale cyclones in the atmospheric fields driving an ocean model produced air-sea fluxes in remarkable agreement with observations. Over the Nordic Seas we found that mesoscale cyclones increased the depth, frequency and area of open ocean deep convection. At Denmark Strait we found a significant increase in the southward transport of Denmark Strait Overflow Water (DSOW); the deep water mass that plays a major role in driving the Atlantic MOC. Further south there was an increase in the cyclonic rotation of the sub-polar gyres and an increase in the northward transport of heat into the region. We conclude that polar mesoscale cyclones play an important role in driving the large-scale ocean circulation and so must be simulated globally in order to make accurate short-term climate predictions. An illustration of the effectiveness of our polar mesoscale parameterization. Panels show a 6-hourly snapshot of 10-m wind speed for (left) ECMWF ERA-40, (middle) ERA-40 with a polar mesoscale cyclone parameterized (right) satellite derived wind speed. The satellite data reveal a polar mesoscale cyclone over the Norwegian Sea with a diameter of ~400 km. The standard ERA-40 reanalysis (~1 deg.) does not capture this vortex

  4. A coarse grained stochastic particle interacting system for tropical convection

    NASA Astrophysics Data System (ADS)

    Khouider, B.

    2012-12-01

    Climate models (GCMs) fail to represent adequately the variability associated with organized convection in the tropics. This deficiency is believed to hinder medium and long range weather forecasts, over weeks to months. GCMs use very complex sub-grid models, known as cumulus parameterizations, to represent the effects of clouds and convection as well as other unresolved processes. Cumulus parameterizations are intrinsically deterministic and are typically based on the quasi-equilibrium theory, which assumes that convection instantaneously consumes the atmospheric instability produced by radiation. In this talk, I will discuss a stochastic model for organized tropical convection based on a particle interacting system defined on a microscopic lattice. An order parameter is assumed to take the values 0,1,2,3 at a any given lattice site according to whether it is a clear site or it is occupied by a cloud of a one of the three types: congestus, deep, or stratiform, following intuitive rules motivated by recent satellite observations and various field campaigns conducted over the Indian Ocean and Western Pacific. The microscopic Markov process is coarse-grained systematically to obtain a multidimensional birth-death process with immigration, following earlier work done by Katsoulakis, Majda, and Vlachos (JCP 2003) for the case of the Ising model where the order parameter takes the values 0 and 1. The coarse grained birth-death process is a stochastic model, intermediate between the microscopic lattice model and the deterministic mean field limit, that is used to represent the sub-grid scale variability of the underlying physical process (here the cloud cover) with a negligible computational overhead and yet permits both local interactions between lattice sites and two-way interactions between the cloud cover and the large-scale climate dynamics. The new systematic coarse-graining, developed here for the multivalued order parameter, provides a unifying framework

  5. Convective initiation in the vicinity of the subtropical Andes

    NASA Astrophysics Data System (ADS)

    Rasmussen, K. L.; Houze, R.

    2014-12-01

    Extreme convection tends to form in the vicinity of mountain ranges, and the Andes in subtropical South America help spawn some of the most intense convection in the world. An investigation of the most intense storms for 11 years of TRMM Precipitation Radar (PR) data shows a tendency for squall lines to initiate and develop in this region with the canonical leading convective line/trailing stratiform structure. The synoptic environment and structures of the extreme convection and MCSs in subtropical South America are similar to those found in other regions of the world, especially the United States. In subtropical South America, however, the topographical influence on the convective initiation and maintenance of the MCSs is unique. A capping inversion in the lee of the Andes is important in preventing premature triggering. The Andes and other mountainous terrain of Argentina focus deep convective initiation in a narrow region. Subsequent to initiation, the convection often evolves into propagating mesoscale convective systems similar to those seen over the Great Plains of the U. S. and produces damaging tornadoes, hail, and floods across a wide agricultural region. Numerical simulations conducted with the NCAR Weather Research and Forecasting (WRF) Model extend the observational analysis and provide an objective evaluation of storm initiation, terrain effects, and development mechanisms. The simulated mesoscale systems closely resemble the storm structures seen by the TRMM Precipitation Radar as well as the overall shape and character of the storms shown in GOES satellite data. A sensitivity experiment with different configurations of topography, including both decreasing and increasing the height of the Andes Mountains, provides insight into the significant influence of orography in focusing convective initiation in this region. Lee cyclogenesis and a strong low-level jet are modulated by the height of the Andes Mountains and directly affect the character

  6. Convection pattern and stress system under the African plate

    NASA Technical Reports Server (NTRS)

    Liu, H.-S.

    1977-01-01

    Studies on tectonic forces from satellite-derived gravity data have revealed a subcrustal stress system which provides a unifying mechanism for uplift, depression, rifting, plate motion and ore formation in Africa. The subcrustal stresses are due to mantle convection. Seismicity, volcanicity and kimberlite magmatism in Africa and the development of the African tectonic and magnetic features are explained in terms of this single stress system. The tensional stress fields in the crust exerted by the upwelling mantle flows are shown to be regions of structural kinship characterized by major concentration of mineral deposits. It is probable that the space techniques are capable of detecting and determining the tectonic forces in the crust of Africa.

  7. Mesoscale hybrid calibration artifact

    DOEpatents

    Tran, Hy D.; Claudet, Andre A.; Oliver, Andrew D.

    2010-09-07

    A mesoscale calibration artifact, also called a hybrid artifact, suitable for hybrid dimensional measurement and the method for make the artifact. The hybrid artifact has structural characteristics that make it suitable for dimensional measurement in both vision-based systems and touch-probe-based systems. The hybrid artifact employs the intersection of bulk-micromachined planes to fabricate edges that are sharp to the nanometer level and intersecting planes with crystal-lattice-defined angles.

  8. Mesoscale acid deposition modeling studies

    NASA Technical Reports Server (NTRS)

    Kaplan, Michael L.; Proctor, F. H.; Zack, John W.; Karyampudi, V. Mohan; Price, P. E.; Bousquet, M. D.; Coats, G. D.

    1989-01-01

    The work performed in support of the EPA/DOE MADS (Mesoscale Acid Deposition) Project included the development of meteorological data bases for the initialization of chemistry models, the testing and implementation of new planetary boundary layer parameterization schemes in the MASS model, the simulation of transport and precipitation for MADS case studies employing the MASS model, and the use of the TASS model in the simulation of cloud statistics and the complex transport of conservative tracers within simulated cumuloform clouds. The work performed in support of the NASA/FAA Wind Shear Program included the use of the TASS model in the simulation of the dynamical processes within convective cloud systems, the analyses of the sensitivity of microburst intensity and general characteristics as a function of the atmospheric environment within which they are formed, comparisons of TASS model microburst simulation results to observed data sets, and the generation of simulated wind shear data bases for use by the aviation meteorological community in the evaluation of flight hazards caused by microbursts.

  9. Vertical distribution of atmospheric constituents above complex terrain - Influence of a mesoscale system

    NASA Astrophysics Data System (ADS)

    Berkes, Florian; Hoor, Peter; Bozem, Heiko; Meixner, Franz; Weigel, Ralf; Sprenger, Michael; Lelieveld, Jos

    2014-05-01

    Measurements in and above the planetary boundary layer (PBL) are essential to fully understand the exchange and transport processes between the PBL and the free troposphere (FT). Here we discuss the impact of a mesoscale system on the local trace gas and particle distribution above the PBL over hilly terrain. During the field campaign PARADE (PArticles and RAdicals: Diel observations of the impact of urban and biogenic Emissions) in August and September 2011 measurements were conducted at the Taunus Observatory on Mount "Kleiner Feldberg (KF)" (825 m asl.), about 20 km northwest of Frankfurt am Main in Germany. For the vertical composition of the lowest 3000 m, high-resolution measurements were performed using 174 radio soundings. The measurements are complemented by continuous boundary layer observations of a ceilometer and a variety of reactive tracers (CO, NOx, O3, VOCs) on the mountain top. In addition, aircraft measurements of CO2, CO, O3, temperature, humidity and aerosol number concentration and size distribution were performed during the first week of September. The PBL height varied during the measurement campaign between 1 and 2.5 km. The variations are due to very changeable weather, synoptic fronts as well as local phenomena such as low clouds and fog. The analysis of the data from different instruments shows good agreement in determining the boundary layer height under windless high pressure conditions, as well as with certain restrictions on cloudy and windy days. Based on the PBL investigation, the aircraft-based trace gas measurements were used to identify transport and exchange processes between the free atmosphere and the boundary layer, additionally supported with high-resolution backward-trajectories initialized every 10 seconds along the flight track, based on the wind fields from the COSMO-EU model. On 2 September 2011 we observed an enhanced particle number concentration and low ozone in the free troposphere at two flights around KF. Local

  10. Equations for Nonlinear MHD Convection in Shearless Magnetic Systems

    SciTech Connect

    Pastukhov, V.P.

    2005-07-15

    A closed set of reduced dynamic equations is derived that describe nonlinear low-frequency flute MHD convection and resulting nondiffusive transport processes in weakly dissipative plasmas with closed or open magnetic field lines. The equations obtained make it possible to self-consistently simulate transport processes and the establishment of the self-consistent plasma temperature and density profiles for a large class of axisymmetric nonparaxial shearless magnetic devices: levitated dipole configurations, mirror systems, compact tori, etc. Reduced equations that are suitable for modeling the long-term evolution of the plasma on time scales comparable to the plasma lifetime are derived by the method of the adiabatic separation of fast and slow motions.

  11. Mesoscale ocean dynamics modeling

    SciTech Connect

    mHolm, D.; Alber, M.; Bayly, B.; Camassa, R.; Choi, W.; Cockburn, B.; Jones, D.; Lifschitz, A.; Margolin, L.; Marsden, L.; Nadiga, B.; Poje, A.; Smolarkiewicz, P.; Levermore, D.

    1996-05-01

    This is the final report of a three-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The ocean is a very complex nonlinear system that exhibits turbulence on essentially all scales, multiple equilibria, and significant intrinsic variability. Modeling the ocean`s dynamics at mesoscales is of fundamental importance for long-time-scale climate predictions. A major goal of this project has been to coordinate, strengthen, and focus the efforts of applied mathematicians, computer scientists, computational physicists and engineers (at LANL and a consortium of Universities) in a joint effort addressing the issues in mesoscale ocean dynamics. The project combines expertise in the core competencies of high performance computing and theory of complex systems in a new way that has great potential for improving ocean models now running on the Connection Machines CM-200 and CM-5 and on the Cray T3D.

  12. Using Satellite Observations to Infer the Relationship between Cold Pools and Subsequent Convection Development

    NASA Astrophysics Data System (ADS)

    Elsaesser, G.

    2015-12-01

    Cold pools are increasingly being recognized as important players in the evolution of both shallow and deep convection; hence, the incorporation of cold pool processes into a number of recently developed convective parameterizations. Unfortunately, observations serving to inform cold pool parameterization development are limited to select field programs and limited radar domains. However, a number of recent studies have noted that cold pools are often associated with arcs/lines of shallow clouds traversing 10 - 100 km in visible satellite imagery. Boundary layer thermodynamic perturbations are plausible at such scales, coincident with such mesoscale features. Atmospheric signatures of features at these spatial scales are potentially observable from satellites. In this presentation, we discuss recent work that uses multi-sensor, high-resolution satellite products for observing mesoscale wind vector fluctuations and boundary layer temperature depressions attributed to cold pools produced by antecedent convection. The relationship to subsequent convection as well as convective system longevity is discussed. As improvements in satellite technology occur and efforts to reduce noise in high-resolution orbital products progress, satellite pixel level (~10 km) thermodynamic and dynamic (e.g. mesoscale convergence) parameters can increasingly serve as useful benchmarks for constraining convective parameterization development, including for regimes where organized convection contributes substantially to the cloud and rainfall climatology.

  13. Using Satellite Observations to Infer the Relationship Between Cold Pools and Subsequent Convection Development

    NASA Technical Reports Server (NTRS)

    Elsaesser, Gregory

    2015-01-01

    Cold pools are increasingly being recognized as important players in the evolution of both shallow and deep convection; hence, the incorporation of cold pool processes into a number of recently developed convective parameterizations. Unfortunately, observations serving to inform cold pool parameterization development are limited to select field programs and limited radar domains. However, a number of recent studies have noted that cold pools are often associated with arcs-lines of shallow clouds traversing 10 100 km in visible satellite imagery. Boundary layer thermodynamic perturbations are plausible at such scales, coincident with such mesoscale features. Atmospheric signatures of features at these spatial scales are potentially observable from satellites. In this presentation, we discuss recent work that uses multi-sensor, high-resolution satellite products for observing mesoscale wind vector fluctuations and boundary layer temperature depressions attributed to cold pools produced by antecedent convection. The relationship to subsequent convection as well as convective system longevity is discussed. As improvements in satellite technology occur and efforts to reduce noise in high-resolution orbital products progress, satellite pixel level (10 km) thermodynamic and dynamic (e.g. mesoscale convergence) parameters can increasingly serve as useful benchmarks for constraining convective parameterization development, including for regimes where organized convection contributes substantially to the cloud and rainfall climatology.

  14. Observation of deep convection initiation from shallow convection environment

    NASA Astrophysics Data System (ADS)

    Lothon, Marie; Couvreux, Fleur; Guichard, Françoise; Campistron, Bernard; Chong, Michel; Rio, Catherine; Williams, Earle

    2010-05-01

    In the afternoon of 10 July 2006, deep convective cells initiated right in the field of view of the Massachusetts Institute Technology (MIT) C-band Doppler radar. This radar, with its 3D exploration at 10 min temporal resolution and 250 m radial resolution, allows us to track the deep convective cells and also provides clear air observations of the boundary layer structure prior to deep convection initiation. Several other observational platforms were operating then which allow us to thoroughly analyse this case: Vertically pointing aerosol lidar, W-band radar and ceilometer from the ARM Mobile Facility, along with radiosoundings and surface measurements enable us to describe the environment, from before their initiation to after the propagation of of one propagating cell that generated a circular gust front very nicely caught by the MIT radar. The systems considered here differ from the mesoscale convective systems which are often associated with African Easterly Waves, increasing CAPE and decreasing CIN. The former have smaller size, and initiate more locally, but there are numerous and still play a large role in the atmospheric circulation and scalar transport. Though, they remain a challenge to model. (See the presentation by Guichard et al. in the same session, for a model set up based on the same case, with joint single-column model and Large Eddy Simulation, which aims at better understanding and improving the parametrisation of deep convection initiation.) Based on the analysis of the observations mentioned above, we consider here the possible sources of deep convection initiation that day, which showed a typical boundary-layer growth in semi-arid environment, with isolated deep convective events.

  15. Optimization of convective fin systems: a holistic approach

    NASA Astrophysics Data System (ADS)

    Sasikumar, M.; Balaji, C.

    A numerical analysis of natural convection heat transfer and entropy generation from an array of vertical fins, standing on a horizontal duct, with turbulent fluid flow inside, has been carried out. The analysis takes into account the variation of base temperature along the duct, traditionally ignored by most studies on such problems. One-dimensional fin equation is solved using a second order finite difference scheme for each of the fins in the system and this, in conjunction with the use of turbulent flow correlations for duct, is used to obtain the temperature distribution along the duct. The influence of the geometric and thermal parameters, which are normally employed in the design of a thermal system, has been studied. Correlations are developed for (i) the total heat transfer rate per unit mass of the fin system (ii) total entropy generation rate and (iii) fin height, as a function of the geometric parameters of the fin system. Optimal dimensions of the fin system for (i) maximum heat transfer rate per unit mass and (ii) minimum total entropy generation rate are obtained using Genetic Algorithm. As expected, these optima do not match. An approach to a `holistic' design that takes into account both these criteria has also been presented.

  16. First satellite measurements of chemical changes in coincidence with sprite activity: characteristics of the TLE-producing convective system

    NASA Astrophysics Data System (ADS)

    Sao Sabbas, Fernanda; Arnone, Enrico; Soula, Serge; Azambuja, Rodrigo; Charion, Olivier; Castelli, Elisa; Carlotti, Massimo; Santiago, Jeison; Neubert, Torsten

    2010-05-01

    Sprites are some of the Transient Luminous Events (TLEs) that occur in the upper atmosphere above thunderstorms as a direct consequence of thunderstorm electrical activity. Sprites are formed by mesospheric streamer plasma channels, inside which chemical reactions take place altering the local composition of the atmosphere. Among the gases that may be produced by sprites are the nitric oxides that take part of the ozone destruction cycle, therefore understanding the characteristics and distribution of TLE-producing thunderstorms is necessary to quantify their overall impact on the upper atmosphere. On August 25th, 2003, 20 sprites were observed above a Mesoscale Convective System (MCS) over Corsica, the Mediterranean Sea and Northern Italy, by a camera located at Pic du Midi as part of the Eurosprite campaign. The MCS lasted for 16 h and reached a maximum extent of about 222,000 km2 about 6 h after it initiated. Sprite activity was only detected about 2 h later and, during this phase, MIPAS spectrometer onboard the Envisat satellite detected substantial enhancement of ambient NO2 directly above the sprite producing MCS (see companion paper by Arnone et al. for details on chemical changes). In this paper we present the characteristics of the convective system for which, for the first time, TLE-induced chemical changes were observed. The peculiarities of these systems are discussed in comparison with previously observed systems. On the basis of these observations, we present the prospects of adopting a similar strategy in Brazil and South America, as well as future observation scenarios in this continent.

  17. A review of major progresses in mesoscale dynamic research in China since 1999

    NASA Astrophysics Data System (ADS)

    Zhou, Xiaoping; Lu, Hancheng; Ni, Yunqi; Tan, Zhemin

    2004-06-01

    Mesoscale research conducted by Chinese meteorologists during the past four years is reviewed. Advances in theoretical studies include (a) mesoscale quasi-balanced and semi-balanced dynamics, derived through scale analysis and the perturbation method which are suitable for describing mesoscale vortices; (b) subcritical instability and vortex-sheet instability; (c) frontal adjustment mechanism and the effect of topography on frontgenesis; and (d) slantwise vorticity development theories, the slantwise vortex equation, and moist potential vorticity (MPV) anomalies with precipitation-related heat and mass sinks and MPV impermeability theorem. From the MPV conservation viewpoint, the transformation mechanism between different scale weather systems is analyzed. Based on the data analysis, a new dew-point front near the periphery of the West Pacific subtropical high is identified. In the light of MPV theory and Q-vector theory, some events associated with torrential rain systems and severe storms are analyzed and diagnosed. Progress in mesoscale numerical simulation has been made in the development of meso-α, meso-β vortices, meso-γ-scale downbursts and precipitation produced by deep convective systems with MM5 and other mesoscale models.

  18. A numerical study of a TOGA-COARE squall-line using a coupled mesoscale atmosphere-ocean model

    NASA Astrophysics Data System (ADS)

    Bao, Shaowu; Xie, Lian; Raman, Sethu

    2004-10-01

    An atmosphere-ocean coupled mesoscale modeling system is developed and used to investigate the interactions between a squall line and the upper ocean observed over the western Pacific warm pool during the Tropical Ocean/Global Atmosphere Coupled Ocean and Atmosphere Response Experiment (TOGA-COARE). The modeling system is developed by coupling the Advanced Regional Prediction System (ARPS) to the Princeton Ocean Model (POM) through precipitation and two-way exchanges of momentum, heat, and moisture across the air-sea interface. The results indicate that the interaction between the squall-line and the upper ocean produced noticeable differences in the sensible and latent heat fluxes, as compared to the uncoupled cases. Precipitation, which is often ignored in air-sea heat flux estimates, played a major role in the coupling between the mesoscale convective system and the ocean. Precipitation affected the air-sea interaction through both freshwater flux and sensible heat flux. The former led to the formation of a thin stable ocean layer underneath and behind the precipitating atmospheric convection. The presence of this stable layer resulted in a more significant convection-induced sea surface temperature (SST) change in and behind the precipitation zone. However, convection-induced SST changes do not seem to play an important role in the intsensification of the existing convective system that resulted in the SST change, as the convection quickly moved away from the region of original SST response.

  19. Mesoscale SST-wind stress coupling in the Peru-Chile current system: Which mechanisms drive its seasonal variability?

    NASA Astrophysics Data System (ADS)

    Oerder, Vera; Colas, François; Echevin, Vincent; Masson, Sebastien; Hourdin, Christophe; Jullien, Swen; Madec, Gurvan; Lemarié, Florian

    2016-01-01

    Satellite observations and a high-resolution regional ocean-atmosphere coupled model are used to study the air/sea interactions at the oceanic mesoscale in the Peru-Chile upwelling current system. Coupling between mesoscale sea surface temperature (SST) and wind stress (WS) intensity is evidenced and characterized by correlations and regression coefficients. Both the model and the observations display similar spatial and seasonal variability of the coupling characteristics that are stronger off Peru than off Northern Chile, in relation with stronger wind mean speed and steadiness. The coupling is also more intense during winter than during summer in both regions. It is shown that WS intensity anomalies due to SST anomalies are mainly forced by mixing coefficient anomalies and partially compensated by wind shear anomalies. A momentum balance analysis shows that wind speed anomalies are created by stress shear anomalies. Near-surface pressure gradient anomalies have a negligible contribution because of the back-pressure effect related to the air temperature inversion. As mixing coefficients are mainly unchanged between summer and winter, the stronger coupling in winter is due to the enhanced large-scale wind shear that enables a more efficient action of the turbulent stress perturbations. This mechanism is robust as it does not depend on the choice of planetary boundary layer parameterization.

  20. The Interannual Stability of Cumulative Frequency Distributions for Convective System Size and Intensity

    NASA Technical Reports Server (NTRS)

    Mohr, Karen I.; Molinari, John; Thorncroft, Chris D,

    2010-01-01

    The characteristics of convective system populations in West Africa and the western Pacific tropical cyclone basin were analyzed to investigate whether interannual variability in convective activity in tropical continental and oceanic environments is driven by variations in the number of events during the wet season or by favoring large and/or intense convective systems. Convective systems were defined from TRMM data as a cluster of pixels with an 85 GHz polarization-corrected brightness temperature below 255 K and with an area at least 64 km 2. The study database consisted of convective systems in West Africa from May Sep for 1998-2007 and in the western Pacific from May Nov 1998-2007. Annual cumulative frequency distributions for system minimum brightness temperature and system area were constructed for both regions. For both regions, there were no statistically significant differences among the annual curves for system minimum brightness temperature. There were two groups of system area curves, split by the TRMM altitude boost in 2001. Within each set, there was no statistically significant interannual variability. Sub-setting the database revealed some sensitivity in distribution shape to the size of the sampling area, length of sample period, and climate zone. From a regional perspective, the stability of the cumulative frequency distributions implied that the probability that a convective system would attain a particular size or intensity does not change interannually. Variability in the number of convective events appeared to be more important in determining whether a year is wetter or drier than normal.

  1. Effects of Moist Froude Number and CAPE on a Conditionally Unstable Flow over a Mesoscale Mountain Ridge.

    NASA Astrophysics Data System (ADS)

    Chen, Shu-Hua; Lin, Yuh-Lang

    2005-02-01

    In this study, idealized simulations are performed for a conditionally unstable flow over a two-dimensional mountain ridge in order to investigate the propagation and types of cloud precipitation systems controlled by the unsaturated moist Froude number (Fw) and the convective available potential energy (CAPE). A two-dimensional moist flow regime diagram, based on Fw and CAPE, is proposed for a conditionally unstable flow passing over a two-dimensional mesoscale mountain ridge. The characteristics of these flow regimes are 1) regime I: flow with an upstream-propagating convective system and an early, slowly moving convective system over the mountain; 2) regime II: flow with a long-lasting orographic convective system over the mountain peak, upslope, or lee slope; 3) regime III: flow with an orographic convective or mixed convective and stratiform precipitation system over the mountain and a downstream-propagating convective system; and 4) regime IV: flow with an orographic stratiform precipitation system over the mountain and possibly a downstream-propagating cloud system. Note that the fourth regime was not included in the flow regimes proposed by Chu and Lin and Chen and Lin. The propagation of the convective systems is explained by the orographic blocking and density current forcing associated with the cold-air outflow produced by evaporative cooling acting against the basic flow, which then determines the propagation and cloud types of the simulated precipitation systems.

  2. Convecting particle diffusion in a binary particle system under vertical vibration.

    PubMed

    Hu, Kaiwei; Xie, Zi-Ang; Wu, Ping; Sun, Jing; Li, Li; Jia, Chao; Zhang, Shiping; Liu, Chuanping; Wang, Li

    2014-06-28

    We studied the separation behaviour of binary granular particles in a vertically vibrated container. The final separation of the binary particle system exhibited the Brazil-Nut (BN) effect, though it was not complete. Particle convection occurred, and four different typical convection modes were observed when the frequency f changed from 20 Hz to 80 Hz at constant dimensionless acceleration Γ = 4πAf(2)/g. However, when Γ changed from 2 to 4 at constant f, the system's convection mode stayed almost the same. In our experiments, one type of particle generally moved much faster than the other, so the former was termed the 'convecting' particle, and the latter was termed the 'non-convecting' particle. To study the separation results qualitatively, we divided the system into vertical layers and calculated the mass distribution of the binary particles along the z axis. The results showed that when f increased at constant Γ or Γ decreased at constant f, the convecting particles, usually the smaller and lighter ones, distributed less to the top side and more to the bottom side of the container. Finally, to explain the experimental results, we derived a mass conservation equation for the convecting particles considering simultaneous convection and diffusion. The equation described the experimental results well. We also analysed the effects of f, Γ, diameter ratio, density ratio, etc., on the final separation results. PMID:24796705

  3. Comprehensive comparison of precipitation measurement systems for convective and non-convective events

    NASA Astrophysics Data System (ADS)

    Filipović, N.; Steinacker, R.; Dorninger, M.; Tüchler, L.

    2012-04-01

    During the field phase of Convective and Orographically-induced Precipitation Study (COPS) the supersite "S" was equipped with several collocated precipitation measuring devices including rainfall weighing gauge, tipping bucket gauge, optical disdrometer, and vertically pointing micro rain radar. Precipitation measurements from two scanning C-band radars covering the area of the eastern Black Forest were available for comparison with the surface-based measurements, as well as data of a wind-temperature radar collocated with above mentioned rainfall instruments at the supersite "S". In this study we present a comprehensive comparison of precipitation measurements for selected IOP-days during the COPS field phase. One issue of this study was to compare the rainfall amount estimated by several measurement devices during defined rainfall episodes under consideration of the differences in sampling strategy of the different instruments. Another goal was to test the rainfall sensors for their ability to catch the temporal variability of rainfall. We investigate time correlation of the rainfall and the autocorrelation of the measurements stratified after convective and non-convective events. Dependence of the observed measurement differences on the rainfall intensity was also investigated. Since the sampling characteristics (sample volume, sampling time) varies notably between the instruments used for comparison appropriate matching of the temporal and spatial scale of the different observations was done with a particular attention given to the differences in the height of the measurements. Due to the simultaneous observations of the two scanning C-band radars over the area of the supersite "S" it is possible to estimate the specific measurement error of the radars, relative to the precipitation amount observed on the ground. Using disdrometer and vertically pointing micro rain radar in conjunction with scanning radar data above, reflectivity factor of a scanned

  4. Deep convection in the Sahel : a focus on gust fronts

    NASA Astrophysics Data System (ADS)

    Dione, Cheikh; Lothon, Marie; Campistron, Bernard; Sall, Saidou M.; Guichard, Françoise; Badiane, Daouda; Couvreux, Fleur

    2014-05-01

    Convection in the Sahel presents a diurnal variability that is influenced by deep convection systems like the Mesoscale Convective Systems (MCSs) and isolated storms or smaller convective systems. These smaller systems have drew less attention than the MCSs, even though they also play a role in the water cycle of this region, contribute to the monsoon dynamics, and to set the scales of the surface heterogeneities. During the African Monsoon Multidisciplinary Analysis (AMMA) intensive observation period in 2006, many of these smaller systems have been observed with the Massachusetts Institute of Technology (MIT) radar that was installed in Niamey, Niger. A systematic study of daytime convection observed during the month of July 2006 is carried out based on the MIT radar data and on the complementary observations given by the ARM mobile facility, in order to analyse the processes and mechanisms involved of deep convection initiation. The results highlight a large frequency of occurrence of the density currents, and their importance in the initiation of new convective cells. Based on this observational analysis and on results from Large Eddy Simulation (LES), density currents are specifically studied, with the aim at : (1) evaluating their frequency of occurrence, (2) assessing their ability to trigger new convective cells, (3) analysing the sensitivity of density currents velocity to land surface contrasts, (4) testing a simple model for their parametrization, (5) evaluating the ability of the LES to represent density currents.

  5. Biogeochemical Response to Mesoscale Physical Forcing in the California Current System

    NASA Technical Reports Server (NTRS)

    Niiler, Pearn P.; Letelier, Ricardo; Moisan, John R.; Marra, John A. (Technical Monitor)

    2001-01-01

    In the first part of the project, we investigated the local response of the coastal ocean ecosystems (changes in chlorophyll, concentration and chlorophyll, fluorescence quantum yield) to physical forcing by developing and deploying Autonomous Drifting Ocean Stations (ADOS) within several mesoscale features along the U.S. west coast. Also, we compared the temporal and spatial variability registered by sensors mounted in the drifters to that registered by the sensors mounted in the satellites in order to assess the scales of variability that are not resolved by the ocean color satellite. The second part of the project used the existing WOCE SVP Surface Lagrangian drifters to track individual water parcels through time. The individual drifter tracks were used to generate multivariate time series by interpolating/extracting the biological and physical data fields retrieved by remote sensors (ocean color, SST, wind speed and direction, wind stress curl, and sea level topography). The individual time series of the physical data (AVHRR, TOPEX, NCEP) were analyzed against the ocean color (SeaWiFS) time-series to determine the time scale of biological response to the physical forcing. The results from this part of the research is being used to compare the decorrelation scales of chlorophyll from a Lagrangian and Eulerian framework. The results from both parts of this research augmented the necessary time series data needed to investigate the interactions between the ocean mesoscale features, wind, and the biogeochemical processes. Using the historical Lagrangian data sets, we have completed a comparison of the decorrelation scales in both the Eulerian and Lagrangian reference frame for the SeaWiFS data set. We are continuing to investigate how these results might be used in objective mapping efforts.

  6. Aerosols in the Convective Boundary Layer: Radiation Effects on the Coupled Land-Atmosphere System

    NASA Astrophysics Data System (ADS)

    Barbaro, E.; Vila-Guerau Arellano, J.; Ouwersloot, H. G.; Schroter, J.; Donovan, D. P.; Krol, M. C.

    2013-12-01

    We investigate the responses of the surface energy budget and the convective boundary-layer (CBL) dynamics to the presence of aerosols using a combination of observations and numerical simulations. A detailed observational dataset containing (thermo)dynamic variables observed at CESAR (Cabauw Experimental Site for Atmospheric Research) and aerosol information from the European Integrated Project on Aerosol, Cloud, Climate, and Air Quality Interactions (IMPACT/EUCAARI) campaign is employed to design numerical experiments reproducing two prototype clear-sky days characterized by: (i) a well-mixed residual layer above a ground inversion and (ii) a continuously growing CBL. A large-eddy simulation (LES) model and a mixed-layer (MXL) model, both coupled to a broadband radiative transfer code and a land-surface model, are used to study the impacts of aerosol scattering and absorption of shortwave radiation on the land-atmosphere system. We successfully validate our model results using the measurements of (thermo)dynamic variables and aerosol properties for the two different CBL prototypes studied here. Our findings indicate that in order to reproduce the observed surface energy budget and CBL dynamics, information of the vertical structure and temporal evolution of the aerosols is necessary. Given the good agreement between the LES and the MXL model results, we use the MXL model to explore the aerosol effect on the land-atmosphere system for a wide range of optical depths and single scattering albedos. Our results show that higher loads of aerosols decrease irradiance, imposing an energy restriction at the surface. Over the studied well-watered grassland, aerosols reduce the sensible heat flux more than the latent heat flux. As a result, aerosols increase the evaporative fraction. Moreover, aerosols also delay the CBL morning onset and anticipate its afternoon collapse. If also present above the CBL during the morning transition, aerosols maintain a persistent near

  7. Large Eddy Simulations of Severe Convection Induced Turbulence

    NASA Technical Reports Server (NTRS)

    Ahmad, Nash'at; Proctor, Fred

    2011-01-01

    Convective storms can pose a serious risk to aviation operations since they are often accompanied by turbulence, heavy rain, hail, icing, lightning, strong winds, and poor visibility. They can cause major delays in air traffic due to the re-routing of flights, and by disrupting operations at the airports in the vicinity of the storm system. In this study, the Terminal Area Simulation System is used to simulate five different convective events ranging from a mesoscale convective complex to isolated storms. The occurrence of convection induced turbulence is analyzed from these simulations. The validation of model results with the radar data and other observations is reported and an aircraft-centric turbulence hazard metric calculated for each case is discussed. The turbulence analysis showed that large pockets of significant turbulence hazard can be found in regions of low radar reflectivity. Moderate and severe turbulence was often found in building cumulus turrets and overshooting tops.

  8. Validation of mesoscale models

    NASA Technical Reports Server (NTRS)

    Kuo, Bill; Warner, Tom; Benjamin, Stan; Koch, Steve; Staniforth, Andrew

    1993-01-01

    The topics discussed include the following: verification of cloud prediction from the PSU/NCAR mesoscale model; results form MAPS/NGM verification comparisons and MAPS observation sensitivity tests to ACARS and profiler data; systematic errors and mesoscale verification for a mesoscale model; and the COMPARE Project and the CME.

  9. Parameterization of sub-grid scale convection

    NASA Technical Reports Server (NTRS)

    Frank, William; Molinari, John; Kain, Jack; Moncrieff, Mitch; Karyampudi, Mohan; Grell, Georg

    1993-01-01

    The following topics are discussed: an overview of the cumulus parameterization problem; interactions between explicit and implicit processes in mesoscale models; effects of model grid size on the cumulus parameterization problem; parameterizing convective effects on momentum fields in mesoscale models; differences between slantwise and vertical cumulus parameterization; experiments with different closure hypotheses; and coupling cumulus parameterizations to boundary layer, stable cloud, and radiation schemes.

  10. Acoustic Characterization of Mesoscale Objects

    SciTech Connect

    Chinn, D; Huber, R; Chambers, D; Cole, G; Balogun, O; Spicer, J; Murray, T

    2007-03-13

    This report describes the science and engineering performed to provide state-of-the-art acoustic capabilities for nondestructively characterizing mesoscale (millimeter-sized) objects--allowing micrometer resolution over the objects entire volume. Materials and structures used in mesoscale objects necessitate the use of (1) GHz acoustic frequencies and (2) non-contacting laser generation and detection of acoustic waves. This effort demonstrated that acoustic methods at gigahertz frequencies have the necessary penetration depth and spatial resolution to effectively detect density discontinuities, gaps, and delaminations. A prototype laser-based ultrasonic system was designed and built. The system uses a micro-chip laser for excitation of broadband ultrasonic waves with frequency components reaching 1.0 GHz, and a path-stabilized Michelson interferometer for detection. The proof-of-concept for mesoscale characterization is demonstrated by imaging a micro-fabricated etched pattern in a 70 {micro}m thick silicon wafer.