Ice nucleation in the upper troposphere: Sensitivity to aerosol number density, temperature, and cooling rate

NASA Technical Reports Server (NTRS)

Jensen, E. J.; Toon, O. B.

1994-01-01

We have investigated the processes that control ice crystal nucleation in the upper troposphere using a numerical model. Nucleation of ice resulting from cooling was simulated for a range of aerosol number densities, initial temperatures, and cooling rates. In contrast to observations of stratus clouds, we find that the number of ice crystals that nucleate in cirrus is relatively insensitive to the number of aerosols present. The ice crystal size distribution at the end of the nucleation process is unaffected by the assumed initial aerosol number density. Essentially, nucleation continues until enough ice crystals are present such that their deposition growth rapidly depletes the vapor and shuts off any further nucleation. However, the number of ice crystals nucleated increases rapidly with decreasing initial temperature and increasing cooling rate. This temperature dependence alone could explain the large ice crystal number density observed in very cold tropical cirrus.

Cirrus Cloud Seeding has Potential to Cool Climate

NASA Technical Reports Server (NTRS)

Storelvmo, T.; Kristjansson, J. E.; Muri, H.; Pfeffer, M.; Barahona, D.; Nenes, A.

2013-01-01

Cirrus clouds, thin ice clouds in the upper troposphere, have a net warming effect on Earth s climate. Consequently, a reduction in cirrus cloud amount or optical thickness would cool the climate. Recent research indicates that by seeding cirrus clouds with particles that promote ice nucleation, their lifetimes and coverage could be reduced. We have tested this hypothesis in a global climate model with a state-of-the-art representation of cirrus clouds and find that cirrus cloud seeding has the potential to cancel the entire warming caused by human activity from pre-industrial times to present day. However, the desired effect is only obtained for seeding particle concentrations that lie within an optimal range. With lower than optimal particle concentrations, a seeding exercise would have no effect. Moreover, a higher than optimal concentration results in an over-seeding that could have the deleterious effect of prolonging cirrus lifetime and contributing to global warming.

Midlatitude cirrus classification at Rome Tor Vergata through a multichannel Raman-Mie-Rayleigh lidar

NASA Astrophysics Data System (ADS)

Dionisi, D.; Keckhut, P.; Liberti, G. L.; Cardillo, F.; Congeduti, F.

2013-12-01

A methodology to identify and characterize cirrus clouds has been developed and applied to the multichannel-multiwavelength Rayleigh-Mie-Raman (RMR) lidar in Rome Tor Vergata (RTV). A set of 167 cirrus cases, defined on the basis of quasi-stationary temporal period conditions, has been selected in a data set consisting of about 500 h of nighttime lidar sessions acquired between February 2007 and April 2010. The derived lidar parameters (effective height, geometrical and optical thickness and mean back-scattering ratio) and the cirrus mid-height temperature (estimated from the radiosonde data of Pratica di Mare, WMO, World Meteorological Organization, site no. 16245) of this sample have been analyzed by the means of a clustering multivariate analysis. This approach identified four cirrus classes above the RTV site: two thin cirrus clusters in mid- and upper troposphere and two thick cirrus clusters in mid-upper troposphere. These results, which are very similar to those derived through the same approach at the lidar site of the Observatoire de Haute-Provence (OHP), allows characterization of cirrus clouds over the RTV site and attests to the robustness of such classification. To acquire some indications about the cirrus generation methods for the different classes, analyses of the extinction-to-backscatter ratio (lidar ratio, LReff, in terms of frequency distribution functions and dependencies on the mid-height cirrus temperature, have been performed. A preliminary study relating some meteorological parameters (e.g., relative humidity, wind components) to cirrus clusters has also been conducted. The RTV cirrus results, recomputed through the cirrus classification by Sassen and Cho (1992), show good agreement with other midlatitude lidar cirrus observations for the relative occurrence of subvisible (SVC), thin and opaque cirrus classes (10%, 49% and 41%, respectively). The overall mean value of cirrus optical depth is 0.37 ± 0.18, while most retrieved LReff values range between 10-60 sr, and the estimated mean value is 31 ± 15 sr, similar to LR values of lower latitude cirrus measurements. The obtained results are consistent with previous studies conducted with different systems and confirm that cirrus classification based on a statistical approach seems to be a good tool both to validate the height-resolved cirrus fields calculated by models and to investigate the key processes governing cirrus formation and evolution. However, the lidar ratio and optical depth analyses are affected by some uncertainties (e.g., lidar error noise, multiple scattering effects, supercooled water clouds) that reduce the confidence of the results. Future studies are needed to improve the characterization of the cirrus optical properties and, thus, the determination of their radiative impact.

Tropical Convection's Roles in Tropical Tropopause Cirrus

NASA Technical Reports Server (NTRS)

Boehm, Matthew T.; Starr, David OC.; Verlinde, Johannes; Lee, Sukyoung

2002-01-01

The results presented here show that tropical convection plays a role in each of the three primary processes involved in the in situ formation of tropopause cirrus. First, tropical convection transports moisture from the surface into the upper troposphere. Second, tropical convection excites Rossby waves that transport zonal momentum toward the ITCZ, thereby generating rising motion near the equator. This rising motion helps transport moisture from where it is detrained from convection to the cold-point tropopause. Finally, tropical convection excites vertically propagating tropical waves (e.g. Kelvin waves) that provide one source of large-scale cooling near the cold-point tropopause, leading to tropopause cirrus formation.

Aerosol Indirect Effects on Cirrus Clouds in Global Aerosol-Climate Models

NASA Astrophysics Data System (ADS)

Liu, X.; Zhang, K.; Wang, Y.; Neubauer, D.; Lohmann, U.; Ferrachat, S.; Zhou, C.; Penner, J.; Barahona, D.; Shi, X.

2015-12-01

Cirrus clouds play an important role in regulating the Earth's radiative budget and water vapor distribution in the upper troposphere. Aerosols can act as solution droplets or ice nuclei that promote ice nucleation in cirrus clouds. Anthropogenic emissions from fossil fuel and biomass burning activities have substantially perturbed and enhanced concentrations of aerosol particles in the atmosphere. Global aerosol-climate models (GCMs) have now been used to quantify the radiative forcing and effects of aerosols on cirrus clouds (IPCC AR5). However, the estimate uncertainty is very large due to the different representation of ice cloud formation and evolution processes in GCMs. In addition, large discrepancies have been found between model simulations in terms of the spatial distribution of ice-nucleating aerosols, relative humidity, and temperature fluctuations, which contribute to different estimates of the aerosol indirect effect through cirrus clouds. In this presentation, four GCMs with the start-of-the art representations of cloud microphysics and aerosol-cloud interactions are used to estimate the aerosol indirect effects on cirrus clouds and to identify the causes of the discrepancies. The estimated global and annual mean anthropogenic aerosol indirect effect through cirrus clouds ranges from 0.1 W m-2 to 0.3 W m-2 in terms of the top-of-the-atmosphere (TOA) net radiation flux, and 0.5-0.6 W m-2 for the TOA longwave flux. Despite the good agreement on global mean, large discrepancies are found at the regional scale. The physics behind the aerosol indirect effect is dramatically different. Our analysis suggests that burden of ice-nucleating aerosols in the upper troposphere, ice nucleation frequency, and relative role of ice formation processes (i.e., homogeneous versus heterogeneous nucleation) play key roles in determining the characteristics of the simulated aerosol indirect effects. In addition to the indirect effect estimate, we also use field campaign measurements and satellite retrievals to evaluate the simulated micro- and macro- physical properties of ice clouds in the four GCMs.

Cirrus Susceptibility to Changes in Ice Nuclei: Physical Processes, Model Uncertainties, and Measurement Needs

NASA Technical Reports Server (NTRS)

Jensen, Eric

2018-01-01

One of the proposed concepts for mitigating the warming effect of increasing greenhouse gases is seeding cirrus cloud with ice nuclei (IN) in order to reduce the lifetime and coverage of cold cirrus that have a net warming impact on the earth's surface. Global model simulations of the net impact of changing upper tropospheric IN have given widely disparate results, partly as a result of poor understanding of ice nucleation processes in the current atmosphere, and partly as a result of poor representation of these processes in global models. Here, we present detailed process-model simulations of tropical tropopause layer (TTL) transport and cirrus formation with ice nuclei properties based on recent laboratory nucleation experiments and field measurements of aerosol composition. The model is used to assess the sensitivity of TTL cirrus occurrence frequency and microphysical properties to the abundance and efficacy of ice nuclei. The simulated cloud properties compared with recent high-altitude aircraft measurements of TTL cirrus and ice supersaturation. We find that abundant effective IN (either from glassy organic aerosols or crystalline ammonium sulfate with concentrations greater than about 100/L) prevent the occurrences of large ice concentration and large ice supersaturations, both of which are clearly indicated by the in situ observations. We find that concentrations of effective ice nuclei larger than about 50/L can drive significant changes in cirrus microphysical properties and occurrence frequency. However, the cloud occurrence frequency can either increase or decrease, depending on the efficacy and abundance of IN added to the TTL. We suggest that our lack of information about ice nuclei properties in the current atmosphere, as well as uncertainties in ice nucleation processes and their representations in global models, preclude meaningful estimates of climate impacts associated with addition of ice nuclei in the upper troposphere. We will briefly discuss the key field measurements needed to constrain ice nucleation processes.

Optical and geometrical properties of cirrus clouds in Amazonia derived from 1 year of ground-based lidar measurements

NASA Astrophysics Data System (ADS)

Gouveia, Diego A.; Barja, Boris; Barbosa, Henrique M. J.; Seifert, Patric; Baars, Holger; Pauliquevis, Theotonio; Artaxo, Paulo

2017-03-01

Cirrus clouds cover a large fraction of tropical latitudes and play an important role in Earth's radiation budget. Their optical properties, altitude, vertical and horizontal coverage control their radiative forcing, and hence detailed cirrus measurements at different geographical locations are of utmost importance. Studies reporting cirrus properties over tropical rain forests like the Amazon, however, are scarce. Studies with satellite profilers do not give information on the diurnal cycle, and the satellite imagers do not report on the cloud vertical structure. At the same time, ground-based lidar studies are restricted to a few case studies. In this paper, we derive the first comprehensive statistics of optical and geometrical properties of upper-tropospheric cirrus clouds in Amazonia. We used 1 year (July 2011 to June 2012) of ground-based lidar atmospheric observations north of Manaus, Brazil. This dataset was processed by an automatic cloud detection and optical properties retrieval algorithm. Upper-tropospheric cirrus clouds were observed more frequently than reported previously for tropical regions. The frequency of occurrence was found to be as high as 88 % during the wet season and not lower than 50 % during the dry season. The diurnal cycle shows a minimum around local noon and maximum during late afternoon, associated with the diurnal cycle of precipitation. The mean values of cirrus cloud top and base heights, cloud thickness, and cloud optical depth were 14.3 ± 1.9 (SD) km, 12.9 ± 2.2 km, 1.4 ± 1.1 km, and 0.25 ± 0.46, respectively. Cirrus clouds were found at temperatures down to -90 °C. Frequently cirrus were observed within the tropical tropopause layer (TTL), which are likely associated to slow mesoscale uplifting or to the remnants of overshooting convection. The vertical distribution was not uniform, and thin and subvisible cirrus occurred more frequently closer to the tropopause. The mean lidar ratio was 23.3 ± 8.0 sr. However, for subvisible cirrus clouds a bimodal distribution with a secondary peak at about 44 sr was found suggesting a mixed composition. A dependence of the lidar ratio with cloud temperature (altitude) was not found, indicating that the clouds are vertically well mixed. The frequency of occurrence of cirrus clouds classified as subvisible (τ < 0. 03) were 41.6 %, whilst 37.8 % were thin cirrus (0. 03 < τ < 0. 3) and 20.5 % opaque cirrus (τ > 0. 3). Hence, in central Amazonia not only a high frequency of cirrus clouds occurs, but also a large fraction of subvisible cirrus clouds. This high frequency of subvisible cirrus clouds may contaminate aerosol optical depth measured by sun photometers and satellite sensors to an unknown extent.

Evaluation of Satellite-Based Upper Troposphere Cloud Top Height Retrievals in Multilayer Cloud Conditions During TC4

NASA Technical Reports Server (NTRS)

Chang, Fu-Lung; Minnis, Patrick; Ayers, J. Kirk; McGill, Matthew J.; Palikonda, Rabindra; Spangenberg, Douglas A.; Smith, William L., Jr.; Yost, Christopher R.

2010-01-01

Upper troposphere cloud top heights (CTHs), restricted to cloud top pressures (CTPs) less than 500 hPa, inferred using four satellite retrieval methods applied to Twelfth Geostationary Operational Environmental Satellite (GOES-12) data are evaluated using measurements during the July August 2007 Tropical Composition, Cloud and Climate Coupling Experiment (TC4). The four methods are the single-layer CO2-absorption technique (SCO2AT), a modified CO2-absorption technique (MCO2AT) developed for improving both single-layered and multilayered cloud retrievals, a standard version of the Visible Infrared Solar-infrared Split-window Technique (old VISST), and a new version of VISST (new VISST) recently developed to improve cloud property retrievals. They are evaluated by comparing with ER-2 aircraft-based Cloud Physics Lidar (CPL) data taken during 9 days having extensive upper troposphere cirrus, anvil, and convective clouds. Compared to the 89% coverage by upper tropospheric clouds detected by the CPL, the SCO2AT, MCO2AT, old VISST, and new VISST retrieved CTPs less than 500 hPa in 76, 76, 69, and 74% of the matched pixels, respectively. Most of the differences are due to subvisible and optically thin cirrus clouds occurring near the tropopause that were detected only by the CPL. The mean upper tropospheric CTHs for the 9 days are 14.2 (+/- 2.1) km from the CPL and 10.7 (+/- 2.1), 12.1 (+/- 1.6), 9.7 (+/- 2.9), and 11.4 (+/- 2.8) km from the SCO2AT, MCO2AT, old VISST, and new VISST, respectively. Compared to the CPL, the MCO2AT CTHs had the smallest mean biases for semitransparent high clouds in both single-layered and multilayered situations whereas the new VISST CTHs had the smallest mean biases when upper clouds were opaque and optically thick. The biases for all techniques increased with increasing numbers of cloud layers. The transparency of the upper layer clouds tends to increase with the numbers of cloud layers.

Cirrus cloud development in a mobile upper tropospheric trough: The November 26th FIRE cirrus case study

NASA Technical Reports Server (NTRS)

Mace, Gerald G.; Ackerman, Thomas P.

1993-01-01

The period from 18 UTC 26 Nov. 1991 to roughly 23 UTC 26 Nov. 1991 is one of the study periods of the FIRE (First International Satellite Cloud Climatology Regional Experiment) 2 field campaign. The middle and upper tropospheric cloud data that was collected during this time allowed FIRE scientists to learn a great deal about the detailed structure, microphysics, and radiative characteristics of the mid latitude cirrus that occurred during that time. Modeling studies that range from the microphysical to the mesoscale are now underway attempting to piece the detailed knowledge of this cloud system into a coherent picture of the atmospheric processes important to cirrus cloud development and maintenance. An important component of the modeling work, either as an input parameter in the case of cloud-scale models, or as output in the case of meso and larger scale models, is the large scale forcing of the cloud system. By forcing we mean the synoptic scale vertical motions and moisture budget that initially send air parcels ascending and supply the water vapor to allow condensation during ascent. Defining this forcing from the synoptic scale to the cloud scale is one of the stated scientific objectives of the FIRE program. From the standpoint of model validation, it is also necessary that the vertical motions and large scale moisture budget of the case studies be derived from observations. It is considered important that the models used to simulate the observed cloud fields begin with the correct dynamics and that the dynamics be in the right place for the right reasons.

Modification of cirrus clouds to reduce global warming

NASA Astrophysics Data System (ADS)

Mitchell, D. L.

2009-12-01

Since both greenhouse gases and cirrus clouds strongly affect outgoing longwave radiation (OLR) with no affect or less affect on solar radiation, respectively, an attempt to delay global warming to buy time for emission reduction strategies to work might naturally target cirrus clouds. Cirrus having optical depths < 3.6 cover 13% of the globe and have a net warming effect on climate, with the coldest cirrus having the strongest warming effect. Roughly 2/3 of predicted global warming is due to the feedback effect of water vapor and clouds from an initial greenhouse gas forcing, and a recent study indicates water vapor and clouds in the upper troposphere (UT) have the greatest impact on climate sensitivity (the equilibrium response of global-mean surface temperature to a CO2 doubling). Thus altering UT water vapor and cirrus may be a good strategy for climate engineering. Cirrus cloud coverage is predicted to be sensitive to the ice fall speed which depends on ice crystal size. The higher the cirrus, the greater their impact is on OLR. Thus by changing ice crystal size in the coldest cirrus, OLR and climate might be modified. Fortunately the coldest cirrus have the highest ice supersaturation due to the dominance of homogeneous freezing nucleation. Seeding such cirrus with very efficient heterogeneous ice nuclei should produce larger ice crystals due to vapor competition effects, thus increasing OLR and surface cooling. Preliminary estimates of this global net cloud forcing via GCM simulations are more negative than -2.8 W m-2 and could neutralize the radiative forcing due to a CO2 doubling (3.7 W m-2). This cirrus engineered net forcing is due to (1) reduced cirrus coverage and (2) reduced upper tropospheric water vapor, due to enhanced ice sedimentation. The implementation of this climate engineering could use the airline industry to disperse the seeding material. Commercial airliners typically fly at temperatures between -40 and -60 deg. C (where homogeneous freezing nucleation dominates). Weather modification research has developed ice nucleating substances that are extremely effective at these cold temperatures, are non-toxic and are relatively inexpensive. The seeding material could be released in both clear and cloudy conditions to build up a background concentration of efficient ice nuclei so that non-contrail cirrus will experience these nuclei and grow larger ice crystals. Flight corridors are denser in the high- and mid-latitudes where global warming is more severe. A risk with any geoengineering experiment is that it could affect climate in unforeseen ways, causing more harm than good. Since seeding aerosol residence times in the troposphere are 1-2 weeks, the climate might return back to its normal state within a few months after stopping the geoengineering. A drawback to this approach is that it would not stop ocean acidification. It may not have many of the draw-backs that stratospheric injection of sulfur species has, such as ozone destruction, decreased solar radiation possibly altering the hydrological cycle with more frequent droughts, greater expense, the creation of a white sky and less solar energy. In addition, modeling studies indicate it would take at least 3 years for the climate system to return to “normal” upon termination of stratospheric geoengineering.

Raman Lidar Measurements During the International H2O Project. 2; Instrument Comparisons and Case Studies

NASA Technical Reports Server (NTRS)

Whiteman, D. N.; Demoz, B.; DiGirolamo, P.; Corner, J.; Veselovskii, I.; Evans, K.; Wang, Z.; Sabatino, D.; Schwemmer, G.; Gentry, B.

2005-01-01

The NASA/GSFC Scanning Raman Lidar (SRL) participated in the International H2O Project (IHOP) that occurred in May and June, 2002 in the midwestern part of the U. S. The SRL system configuration and methods of data analysis were described in part I of this paper. In this second part, comparisons of SRL water vapor measurements and those of chilled mirror radiosonde and LASE airborne water vapor lidar are performed. Two case studies are presented; one for daytime and one for nighttime. The daytime case study is of a convectively driven boundary layer event and is used to characterize the SRL water vapor random error characteristics. The nighttime case study is of a thunderstorm-generated cirrus cloud case that is studied in it s meteorological context. Upper tropospheric humidification due to precipitation from the cirrus cloud is quantified as is the cirrus cloud ice water content and particle depolarization ratio. These detailed cirrus cloud measurements are being used in a cirrus cloud modeling study.

Dynamical States of Low Temperature Cirrus

NASA Technical Reports Server (NTRS)

Barahona, D.; Nenes, A.

2011-01-01

Low ice crystal concentration and sustained in-cloud supersaturation, commonly found in cloud observations at low temperature, challenge our understanding of cirrus formation. Heterogeneous freezing from effloresced ammonium sulfate, glassy aerosol, dust and black carbon are proposed to cause these phenomena; this requires low updrafts for cirrus characteristics to agree with observations and is at odds with the gravity wave spectrum in the upper troposphere. Background temperature fluctuations however can establish a dynamical equilibrium between ice production and sedimentation loss (as opposed to ice crystal formation during the first stages of cloud evolution and subsequent slow cloud decay) that explains low temperature cirrus properties. This newly-discovered state is favored at low temperatures and does not require heterogeneous nucleation to occur (the presence of ice nuclei can however facilitate its onset). Our understanding of cirrus clouds and their role in anthropogenic climate change is reshaped, as the type of dynamical forcing will set these clouds in one of two preferred microphysical regimes with very different susceptibility to aerosol.

Study of mesoscale phenomena, winter monsoon clouds and snow area based on LANDSAT data

NASA Technical Reports Server (NTRS)

Tsuchiya, K. (Principal Investigator)

1976-01-01

The author has identified the following significant results. Most longitudinal clouds which appear as continuous linear clouds are composed of small transversal clouds. There are mountain waves of different wavelength in a comparatively narrow area indicating complicated orographical effects on wind and temperature distribution or on both dynamical and static stability condition. There is a particular shape of cirrus cloud suggestive of turbulence in the vicinity of CAT in the upper troposphere near jet stream level and its cold air side. Thin cirrus of overcast condition can be distinguished by MSS; however, extremely thin cirrus of partly cloudy condition cannot be detected even in LANDSAT data. This presents a serious problem in the interpretation of satellite thermal infrared radiation data since they affect the value.

Sensitivity Studies of Dust Ice Nuclei Effect on Cirrus Clouds with the Community Atmosphere Model CAM5

NASA Technical Reports Server (NTRS)

Liu, Xiaohong; Zhang, Kai; Jensen, Eric J.; Gettelman, Andrew; Barahona, Donifan; Nenes, Athanasios; Lawson, Paul

2012-01-01

In this study the effect of dust aerosol on upper tropospheric cirrus clouds through heterogeneous ice nucleation is investigated in the Community Atmospheric Model version 5 (CAM5) with two ice nucleation parameterizations. Both parameterizations consider homogeneous and heterogeneous nucleation and the competition between the two mechanisms in cirrus clouds, but differ significantly in the number concentration of heterogeneous ice nuclei (IN) from dust. Heterogeneous nucleation on dust aerosol reduces the occurrence frequency of homogeneous nucleation and thus the ice crystal number concentration in the Northern Hemisphere (NH) cirrus clouds compared to simulations with pure homogeneous nucleation. Global and annual mean shortwave and longwave cloud forcing are reduced by up to 2.0+/-0.1Wm (sup-2) (1 uncertainty) and 2.4+/-0.1Wm (sup-2), respectively due to the presence of dust IN, with the net cloud forcing change of -0.40+/-0.20W m(sup-2). Comparison of model simulations with in situ aircraft data obtained in NH mid-latitudes suggests that homogeneous ice nucleation may play an important role in the ice nucleation at these regions with temperatures of 205-230 K. However, simulations overestimate observed ice crystal number concentrations in the tropical tropopause regions with temperatures of 190- 205 K, and overestimate the frequency of occurrence of high ice crystal number concentration (greater than 200 L(sup-1) and underestimate the frequency of low ice crystal number concentration (less than 30 L(sup-1) at NH mid-latitudes. These results highlight the importance of quantifying the number concentrations and properties of heterogeneous IN (including dust aerosol) in the upper troposphere from the global perspective.

The Correlation Between Tropical Convection and Upper Tropospheric Momentum Flux Convergence

NASA Technical Reports Server (NTRS)

O'CStarr, David; Boehm, Matthew T.

2003-01-01

In this study, the relationship between tropical convection and the meridional convergence of zonal momentum flux in the tropical upper troposphere is investigated using NOAA interpolated outgoing longwave radiation data and NCEP-NCAR reanalysis wind data. In particular, a variety of correlation coefficients are calculated between the data sets, both of which are filtered to isolate disturbances with frequencies and wavenumbers consistent with the Madden-Julian oscillation. The results show regions of significant correlation during each season, with the magnitude and area covered by significant correlation coefficients varying with season. Furthermore, it is found that the correlation structures look very similar to theoretical calculations of the atmospheric response to a region of tropical heating. This result suggests that tropical waves, in particular mixed Rossby-gravity waves, play an important role in the meridional transport zonal momentum into the deep tropical upper troposphere. Finally, these findings have implications to the generation of rising motion near the tropical tropopause, which in turn has ramifications for vertical moisture transport and tropopause cirrus formation.

Small-scale variability in tropical tropopause layer humidity

NASA Astrophysics Data System (ADS)

Jensen, E. J.; Ueyama, R.; Pfister, L.; Karcher, B.; Podglajen, A.; Diskin, G. S.; DiGangi, J. P.; Thornberry, T. D.; Rollins, A. W.; Bui, T. V.; Woods, S.; Lawson, P.

2016-12-01

Recent advances in statistical parameterizations of cirrus cloud processes for use in global models are highlighting the need for information about small-scale fluctuations in upper tropospheric humidity and the physical processes that control the humidity variability. To address these issues, we have analyzed high-resolution airborne water vapor measurements obtained in the Airborne Tropical TRopopause EXperiment over the tropical Pacific between 14 and 20 km. Using accurate and precise 1-Hz water vapor measurements along approximately-level aircraft flight legs, we calculate structure functions spanning horizontal scales ranging from about 0.2 to 50 km, and we compare the water vapor variability in the lower (about 14 km) and upper (16-19 km) Tropical Tropopause Layer (TTL). We also compare the magnitudes and scales of variability inside TTL cirrus versus in clear-sky regions. The measurements show that in the upper TTL, water vapor concentration variance is stronger inside cirrus than in clear-sky regions. Using simulations of TTL cirrus formation, we show that small variability in clear-sky humidity is amplified by the strong sensitivity of ice nucleation rate to supersaturation, which results in highly-structured clouds that subsequently drive variability in the water vapor field. In the lower TTL, humidity variability is correlated with recent detrainment from deep convection. The structure functions indicate approximately power-law scaling with spectral slopes ranging from about -5/3 to -2.

Modeled Impact of Cirrus Cloud Increases Along Aircraft Flight Paths

NASA Technical Reports Server (NTRS)

Rind, David; Lonergan, P.; Shah, K.

1999-01-01

The potential impact of contrails and alterations in the lifetime of background cirrus due to subsonic airplane water and aerosol emissions has been investigated in a set of experiments using the GISS GCM connected to a q-flux ocean. Cirrus clouds at a height of 12-15km, with an optical thickness of 0.33, were input to the model "x" percentage of clear-sky occasions along subsonic aircraft flight paths, where x is varied from .05% to 6%. Two types of experiments were performed: one with the percentage cirrus cloud increase independent of flight density, as long as a certain minimum density was exceeded; the other with the percentage related to the density of fuel expenditure. The overall climate impact was similar with the two approaches, due to the feedbacks of the climate system. Fifty years were run for eight such experiments, with the following conclusions based on the stable results from years 30-50 for each. The experiments show that adding cirrus to the upper troposphere results in a stabilization of the atmosphere, which leads to some decrease in cloud cover at levels below the insertion altitude. Considering then the total effect on upper level cloud cover (above 5 km altitude), the equilibrium global mean temperature response shows that altering high level clouds by 1% changes the global mean temperature by 0.43C. The response is highly linear (linear correlation coefficient of 0.996) for high cloud cover changes between 0. 1% and 5%. The effect is amplified in the Northern Hemisphere, more so with greater cloud cover change. The temperature effect maximizes around 10 km (at greater than 40C warming with a 4.8% increase in upper level clouds), again more so with greater warming. The high cloud cover change shows the flight path influence most clearly with the smallest warming magnitudes; with greater warming, the model feedbacks introduce a strong tropical response. Similarly, the surface temperature response is dominated by the feedbacks, and shows little geographical relationship to the high cloud input. Considering whether these effects would be observable, changing upper level cloud cover by as little as 0.4% produces warming greater than 2 standard deviations in the Microwave Sounding Unit (MSU) channels 4, 2 and 2r, in flight path regions and in the subtropics. Despite the simplified nature of these experiments, the results emphasize the sensitivity of the modeled climate to high level cloud cover changes, and thus the potential ability of aircraft to influence climate by altering clouds in the upper troposphere.

NASA Goddard Earth Sciences Graduate Student Program. [FIRE CIRRUS-II examination of coupling between an upper tropospheric cloud system and synoptic-scale dynamics

NASA Technical Reports Server (NTRS)

Ackerman, Thomas P.

1994-01-01

The evolution of synoptic-scale dynamics associated with a middle and upper tropospheric cloud event that occurred on 26 November 1991 is examined. The case under consideration occurred during the FIRE CIRRUS-II Intensive Field Observing Period held in Coffeyville, KS during Nov. and Dec., 1991. Using data from the wind profiler demonstration network and a temporally and spatially augmented radiosonde array, emphasis is given to explaining the evolution of the kinematically-derived ageostrophic vertical circulations and correlating the circulation with the forcing of an extensively sampled cloud field. This is facilitated by decomposing the horizontal divergence into its component parts through a natural coordinate representation of the flow. Ageostrophic vertical circulations are inferred and compared to the circulation forcing arising from geostrophic confluence and shearing deformation derived from the Sawyer-Eliassen Equation. It is found that a thermodynamically indirect vertical circulation existed in association with a jet streak exit region. The circulation was displaced to the cyclonic side of the jet axis due to the orientation of the jet exit between a deepening diffluent trough and building ridge. The cloud line formed in the ascending branch of the vertical circulation with the most concentrated cloud development occurring in conjunction with the maximum large-scale vertical motion. The relationship between the large scale dynamics and the parameterization of middle and upper tropospheric clouds in large-scale models is discussed and an example of ice water contents derived from a parameterization forced by the diagnosed vertical motions and observed water vapor contents is presented.

Water vapor measurements in- and outside cirrus with the novel water vapor mass spectrometer AIMS-H2O

NASA Astrophysics Data System (ADS)

Kaufmann, Stefan; Schlage, Romy; Voigt, Christiane; Jurkat, Tina; Krämer, Martina; Rolf, Christian; Zöger, Martin; Schäfler, Andreas; Dörnbrack, Andreas

2015-04-01

Water vapor plays a crucial role for the earth's climate both directly via its radiative properties and indirectly due to its ability to form clouds. However, accurate measurements of especially low water vapor concentrations prevalent in the upper troposphere and lower stratosphere are difficult and exhibit large discrepancies between different instruments and methods. In order to address this issue and to provide a comprehensive water vapor data set necessary to gather a complete picture of cloud formation processes, four state-of-the-art hygrometers including the novel water vapor mass spectrometer AIMS-H2O were deployed on the DLR research aircraft HALO during the ML-Cirrus campaign in March/April 2014 over Europe. Here, we present first water vapor measurements of AIMS-H2O on HALO. The instrument performance is validated by intercomparison with the fluorescence hygrometer FISH and the laser hygrometer SHARC, both also mounted in the aircraft. This intercomparison shows good agreement between the instruments from low stratospheric mixing ratios up to higher H2O concentrations at upper tropospheric conditions. Gathering data from over 24 flight hours, no significant offsets between the instruments were found (mean of relative deviation

Stratospheric ion and aerosol chemistry and possible links with cirrus cloud microphysics - A critical assessment

NASA Technical Reports Server (NTRS)

Mohnen, Volker A.

1990-01-01

Aspects of stratospheric ion chemistry and physics are assessed as they relate to aerosol formation and the transport of aerosols to upper tropospheric regions to create conditions favorable for cirrus cloud formation. It is found that ion-induced nucleation and other known phase transitions involving ions and sulfuric acid vapor are probably not efficient processes for stratospheric aerosol formation, and cannot compete with condensation of sulfuric acid on preexisting particles of volcanic or meteoritic origin which are larger than about 0.15 micron in radius. Thus, galactic cosmic rays cannot have a significant impact on stratospheric aerosol population. Changes in the stratospheric aerosol burden due to volcanos are up to two orders of magnitude larger than changes in ion densities. Thus, volcanic activity may modulate the radiative properties of cirrus clouds.

Two Years of Global Cirrus Cloud Statistics Using HIRS

NASA Technical Reports Server (NTRS)

Wylie, Donald; Menzel, W. Paul; Woolf, H. M.

1991-01-01

A climatology of upper tropospheric semi-transparent cirrus clouds has been compiled using HIRS multispectral infrared data, sensitive to CO2 absorption, from the NOAA polar orbiting satellites. This is a report on the two years of data analyzed (June 1989 - May 1991). Semi-transparent clouds were found in 36% of the observations. Large seasonal changes were found in these clouds in many geographical areas; large changes occur in areas dominated by the ITCZ, the sub-tropical high pressure systems, and the mid-latitude storm belts. Semi-transparent clouds associated with these features move latitudinally with the seasons. These clouds also are more frequent in the summer hemisphere than the winter hemisphere. They appear to be linked to convective cloud development and the mid-latitudinal frontal weather systems. However, very thin semi-transparent cirrus has less seasonal movement than other cloud forms.

CO Signatures in Subtropical Convective Clouds and Anvils During CRYSTAL-FACE: An Analysis of Convective Transport and Entertainment Using Observations and a Cloud-Resolving Model

NASA Technical Reports Server (NTRS)

Lopez, Jimena P.; Fridlind, Ann M.; Jost, Hans-Jurg; Loewenstein, Max; Ackerman, Andrew S.; Campos, Teresa L.; Weinstock, Elliot M.; Sayres, David S.; Smith, Jessica B.; Pittman, Jasna V.;

CO Signatures in Subtropical Convective Clouds and Anvils during CRYSTAL-FACE: An Analysis of Convective Transport and Entrainment using Observations and a Cloud-Resolving Model

NASA Technical Reports Server (NTRS)

Lopez, Jimena P.; Fridlind, Ann M.; Jost, Hans-Juerg; Loewenstein, Max; Ackerman, Andrew S.; Campos, Teresa L.; Weinstock, Elliot M.; Sayres, David S.; Smith, Jessica B.; Pittman, Jasna V.

2006-01-01

Convective systems are an important mechanism in the transport of boundary layer air into the upper troposphere. The Cirrus Regional Study of Tropical Anvils and Cirrus Layers-Florida Area Cirrus Experiment (CRYSTAL-FACE) campaign, in July 2002, was developed as a comprehensive atmospheric mission to improve knowledge of subtropical cirrus systems and their roles in regional and global climate. In situ measurements of carbon monoxide (CO), water vapor (H2Ov), and total water (H2Ot) aboard NASA's WB-57F aircraft and CO aboard the U.S. Navy's Twin Otter aircraft were obtained to study the role of convective transport. Three flights sampled convective outflow on 11, 16 and 29 July found varying degrees of CO enhancement relative to the free troposphere. A cloud-resolving model used the in situ observations and meteorological fields to study these three systems. Several methods of filtering the observations were devised here using ice water content, relative humidity with respect to ice, and particle number concentration as a means to statistically sample the model results to represent the flight tracks. A weighted histogram based on ice water content observations was then used to sample the simulations for the three flights. In addition, because the observations occurred in the convective outflow cirrus and not in the storm cores, the model was used to estimate the maximum CO within the convective systems. In general, anvil-level air parcels contained an estimated 20-40% boundary layer air in the analyzed storms.

Temperature structure and emergent flux of the Jovian planets

NASA Technical Reports Server (NTRS)

Silvaggio, P.; Sagan, C.

1978-01-01

Long path, low temperature, moderate resolution spectra of methane and ammonia, broadened by hydrogen and helium, are used to calculate non-gray model atmospheres for the four Jovian planets. The fundamental and first overtone of hydrogen contributes enough absorption to create a thermal inversion for each of the planets. The suite of emergent spectral fluxes and representative limb darkenings and brightenings are calculated for comparison with the Voyager infrared spectra. The temperature differences between Jovian belts and zones corresponds to a difference in the ammonia cirrus particle radii (1 to 3 micron in zones; 10 micron in belts). The Jovian tropopause is approximately at the 0.1 bar level. A thin ammonia cirrus haze should be distributed throughout the Saturnian troposphere; and NH3 gas must be slightly supersaturated or ammonia ice particles are carried upwards convectively in the upper troposphere of Saturn. Substantial methane clouds exist on both Uranus and Neptune. There is some evidence for almost isothermal structures in the deep atmospheres of these two planets.

Automatic Jet Contrail Detection and Segmentation

NASA Technical Reports Server (NTRS)

Weiss, J.; Christopher, S. A.; Welch, R. M.

1997-01-01

Jet contrails are an important subset of cirrus clouds in the atmosphere, and thin cirrus are thought to enhance the greenhouse effect due to their semi-transparent nature. They are nearly transparent to the solar energy reaching the surface, but they reduce the planetary emission to space due to their cold ambient temperatures. Having 'seeded' the environment, contrails often elongate and widen into cirrus-like features. However, there is great uncertainty regarding the impact of contrails on surface temperature and precipitation. With increasing numbers of subsonic aircraft operating in the upper troposphere, there is the possibility of increasing cloudiness which could lead to changes in the radiation balance. Automatic detection and seg- mentation of jet contrails in satellite imagery is important because (1) it is impractical to compile a contrail climatology by hand, and (2) with the segmented images it will be possible to retrieve contrail physical properties such as optical thickness, effective ice crystal diameter and emissivity.

Variability of cirrus clouds in a convective outflow during the Hibiscus campaign

NASA Astrophysics Data System (ADS)

Fierli, F.; di Donfrancesco, G.; Cairo, F.; Marécal, V.; Zampieri, M.; Orlandi, E.; Durry, G.

2008-08-01

Light-weight microlidar and water vapour measurements were taken on-board a stratospheric balloon during the HIBISCUS 2004 campaign, held in Bauru, Brazil (49° W, 22° S). Cirrus clouds were observed throughout the flight between 12 and 15 km height with a high mesoscale variability in optical and microphysical properties. It was found that the cirrus clouds were composed of different layers characterized by marked differences in height, thickness and optical properties. Simultaneous water vapour observations show that the different layers are characterized by different values of the saturation with respect to ice. A mesoscale simulation and a trajectory analysis clearly revealed that the clouds had formed in the outflow of a large and persistent convective region and that the observed variability of the optical properties and of the cloud structure is likely linked to the different residence times of the convectively-processed air in the upper troposphere.

Cirrus Simulations of CRYSTAL-FACE 23 July 2002 Case

NASA Technical Reports Server (NTRS)

Starr, David; Lin, Ruci-Fong; Demoz, Belay; Lare, Andrew

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 relationships between the properties of tropical convective cloud systems and the properties and lifecycle of the extended cirrus anvils they produce. We report here on a case study of 23 July 2002 where a sequence of convective storms over central Florida produced an extensive anvil outflow. Our approach is to use a suitably-initialized cloud-system simulation with MM5 to define initial conditions and time-dependent forcing for a simulation of anvil evolution using a two-dimensional fine-resolution (100 m) cirrus cloud model that explicitly accounts for details of cirrus microphysical development (bin or spectra model) and fully interactive radiative processes. The cirrus model follows Lin. Meteorological conditions and observations for the 23 July case are described in this volume. The goals of the present study are to evaluate how well we can simulate a cirrus anvil lifecycle, to evaluate the importance of various physical processes that operate within the anvil, and to evaluate the importance of environmental conditions in regulating anvil lifecycle. CRYSTAL-FACE produced a number of excellent case studies of anvil systems that will allow environmental factors, such as static stability or wind shear in the upper troposphere, to be examined. In the present study, we strive to assess the importance of propagating gravity waves, likely produced by the deep convection itself, and radiative processes, to anvil lifecycle and characteristics.

Impact of geoengineering on cirrus clouds

NASA Astrophysics Data System (ADS)

Cirisan, Ana; Spichtinger, Peter; Weisenstein, Debra; Lohmann, Ulrike; Wernli, Heini; Peter, Thomas

2010-05-01

Inspite of the framework convention agreement, climate warming is still an actual and very important issue society has to deal with. This has motivated some scientist to start thinking about implementation of artificial methods that could change the climate and weather patterns in order to stop or reverse the global warming effects. Nowadays, there is a consortium of politicians, scientists and engineers interested in evaluating different geoengineering schemes as a way to mitigate global warming, discount rates, and risk aversion (Polborn S. and Tintelnot F., 2009). The geoengineering proposal attracting the most attention and having considerably lower expected deployment costs than conventional emissions abatement approaches (Nordhaus, 2007) is stratospheric aerosol injection. This method, proposed by Budyko (1977) and Crutzen (2006), relies on the fact that large amounts of sulphur aerosols injected into the lower stratosphere enhance the Earth's albedo and lead to cooling of the globe. This proposal is currently discussed in the climate community and possible side effects are investigated. However, the investigations concentrate almost exclusively on the impact on chemistry and stratospheric circulation, whereas the impact on cirrus clouds in the underlying tropopause and upper troposphere region was not taken into account up to now. In this contribution we investigated the impact of artificially produced sulphate aerosol concentrations, modeled with the AER 2D aerosol model (Weisenstein et al., 2007), on the formation and evolution of cirrus clouds in the mid-latitudes. For large injections of SO2 some sulphate aerosol particles grow to large sizes that they can sediment to lower altitudes and eventually reach the troposphere, where they can influence ice crystal formation. Investigations are carried out using a bulk microphysical box model (Spichtinger and Gierens, 2009, Spichtinger and Cziczo, 2009), concentrating on moderate constant updrafts with different background aerosol mass and number concentrations in response to geoengineering measures. In order to obtain qualitative and quantitative estimations of troposphere-stratosphere air mixing (intrusions, tropopause folds etc.) trajectory studies are done using ECMWF data. The results of this conceptual study suggest that an enhancement of sulphuric acid in the tropopause and upper troposphere region may impact the ice crystal number concentrations in cirrus clouds formed via homogeneous nucleation. The global impact can not be estimated, but on the local level, this could lead to change of cloud lifetime and thickness. It would further influence the albedo and radiative properties of cirrus clouds, i.e. modifying the net warming impact of cirrus clouds. Budyko, M.I. (1977), Global Ecology. Mysl, Moscow, 327 pp. (in Russian). Crutzen, P.J. (2006), Albedo enhancement by stratospheric sulfur injections: A contribution to resolve a policy dilemma?, Climate Change, 77(3-4), 211-219. Nordhaus, W.D. (2007), A Question of Balance: Economic Modeling of Global Warming, Yale University Press, 2007. Polborn, S. and Tintelnot, F. (2009), How Geoengineering May Encourage Carbon Dioxide Abatement (June 2, 2009). Available at SSRN: http://ssrn.com/abstract=1413106 Spichtinger, P. and Gierens, K. (2009), Modelling of cirrus clouds - Part 1a: Model description and validation, Atmos. Chem. Phys., 9, 685-706. Spichtinger, P. and Cziczo, D. (2009), Impact of heterogeneous ice nuclei on homogeneous freezing events, J. Geophys. Res., in revision. Weisenstein, D.K., Penner, J.E., Herzog, M., and Liu, X., (2007), Global 2-D intercomparison of sectional and modal aerosol modules, Atmos. Chem. Phys., 7(9), 2339-2355.

Evaluation of cloud-resolving model simulations of midlatitude cirrus with ARM and A-train observations

DOE PAGES

Muhlbauer, A.; Ackerman, T. P.; Lawson, R. P.; ...

2015-07-14

Cirrus clouds are ubiquitous in the upper troposphere and still constitute one of the largest uncertainties in climate predictions. Our paper evaluates cloud-resolving model (CRM) and cloud system-resolving model (CSRM) simulations of a midlatitude cirrus case with comprehensive observations collected under the auspices of the Atmospheric Radiation Measurements (ARM) program and with spaceborne observations from the National Aeronautics and Space Administration A-train satellites. The CRM simulations are driven with periodic boundary conditions and ARM forcing data, whereas the CSRM simulations are driven by the ERA-Interim product. Vertical profiles of temperature, relative humidity, and wind speeds are reasonably well simulated bymore » the CSRM and CRM, but there are remaining biases in the temperature, wind speeds, and relative humidity, which can be mitigated through nudging the model simulations toward the observed radiosonde profiles. Simulated vertical velocities are underestimated in all simulations except in the CRM simulations with grid spacings of 500 m or finer, which suggests that turbulent vertical air motions in cirrus clouds need to be parameterized in general circulation models and in CSRM simulations with horizontal grid spacings on the order of 1 km. The simulated ice water content and ice number concentrations agree with the observations in the CSRM but are underestimated in the CRM simulations. The underestimation of ice number concentrations is consistent with the overestimation of radar reflectivity in the CRM simulations and suggests that the model produces too many large ice particles especially toward the cloud base. Simulated cloud profiles are rather insensitive to perturbations in the initial conditions or the dimensionality of the model domain, but the treatment of the forcing data has a considerable effect on the outcome of the model simulations. Despite considerable progress in observations and microphysical parameterizations, simulating the microphysical, macrophysical, and radiative properties of cirrus remains challenging. Comparing model simulations with observations from multiple instruments and observational platforms is important for revealing model deficiencies and for providing rigorous benchmarks. But, there still is considerable need for reducing observational uncertainties and providing better observations especially for relative humidity and for the size distribution and chemical composition of aerosols in the upper troposphere.« less

Chemistry and Transport in a Multi-Dimensional Model

NASA Technical Reports Server (NTRS)

Yung, Yuk L.

2004-01-01

Our work has two primary scientific goals, the interannual variability (IAV) of stratospheric ozone and the hydrological cycle of the upper troposphere and lower stratosphere. Our efforts are aimed at integrating new information obtained by spacecraft and aircraft measurements to achieve a better understanding of the chemical and dynamical processes that are needed for realistic evaluations of human impact on the global environment. A primary motivation for studying the ozone layer is to separate the anthropogenic perturbations of the ozone layer from natural variability. Using the recently available merged ozone data (MOD), we have carried out an empirical orthogonal function EOF) study of the temporal and spatial patterns of the IAV of total column ozone in the tropics. The outstanding problem about water in the stratosphere is its secular increase in the last few decades. The Caltech/PL multi-dimensional chemical transport model (CTM) photochemical model is used to simulate the processes that control the water vapor and its isotopic composition in the stratosphere. Datasets we will use for comparison with model results include those obtained by the Total Ozone Mapping Spectrometer (TOMS), the Solar Backscatter Ultraviolet (SBUV and SBUV/2), Stratosphere Aerosol and Gas Experiment (SAGE I and II), the Halogen Occultation Experiment (HALOE), the Atmospheric Trace Molecular Spectroscopy (ATMOS) and those soon to be obtained by the Cirrus Regional Study of Tropical Anvils and Cirrus Layers Florida Area Cirrus Experiment (CRYSTAL-FACE) mission. The focus of the investigations is the exchange between the stratosphere and the troposphere, and between the troposphere and the biosphere.

A Lidar at Clermont-Ferrand—France to describe the boundary layer dynamics, aerosols, cirrus and tropospheric water vapor

NASA Astrophysics Data System (ADS)

Baray, J. L.; Fréville, P.; Montoux, N.; Chauvigné, A.; Hadad, D.; Sellegri, K.

2018-04-01

A Rayleigh-Mie-Raman LIDAR provides vertical profiles of tropospheric variables at Clermont-Ferrand (France) since 2008, in order to describe the boundary layer dynamics, tropospheric aerosols, cirrus and water vapor. It is included in the EARLINET network. We performed hardware/software developments in order to upgrade the quality, calibration and improve automation. We present an overview of the system and some examples of measurements and a preliminary geophysical analysis of the data.

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

NASA Astrophysics Data System (ADS)

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

2014-01-01

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

Semitransparent cirrus clouds in the upper troposphere and their contribution to the particulate scattering in the tropical UTLS region

NASA Astrophysics Data System (ADS)

Thampi, Bijoy V.; Parameswaran, K.; Sunilkumar, S. V.

2012-01-01

Contribution of semitransparent cirrus (STC) to the scattering properties of particulates in the UTLS region is examined over the Indian region using the lidar data from Gadanki (13.5°N, 79.2°E) and SAGE-II measurements from 30°S to 30°N in the longitude region 70-90°E within the feasibility of these measurements. While the contribution of STC to particulate optical depth (τp) in UT is found to be quite significant in the equatorial and off-equatorial regions in both the hemispheres during summer, this is very small during winter in the off-equatorial regions. Dense STCs in UT also influences the aerosol scattering below the cloud-base and above the cloud-top (LS). This STC influence in LS is quite significant in the northern hemisphere and almost insignificant over the southern hemisphere, where the STC-cover as well as its optical depth is relatively low. This hemispheric difference is attributed to relatively strong tropospheric convection in the northern hemisphere.

Four years of global cirrus cloud statistics using HIRS

NASA Technical Reports Server (NTRS)

Wylie, Donald P.; Menzel, W. Paul; Woolf, Harold M.; Strabala, Kathleen I.

1994-01-01

Trends in global upper-tropospheric transmissive cirrus cloud cover are beginning to emerge from a four-year cloud climatology using NOAA polar-orbiting High-Resolution Infrared Radiation Sounder (HIRS) multispectral data. Cloud occurrence, height, and effective emissivity are determined with the CO2 slicing technique on the four years of data (June 1989-May 1993). There is a global preponderance of transmissive high clouds, 42% on the average; about three-fourths of these are above 500 hPa and presumed to be cirrus. In the Inter-tropical Convergence Zone (ITCZ), a high frequency of cirrus (greater than 50%) is found at all times; a modest seasonal movement tracks the sun. Large seasonal changes in cloud cover occur over the oceans in the storm belts at midlatitudes; the concentrations of these clouds migrate north and south with the seasons following the progressions of the subtropical highs (anticyclones). More cirrus is found in the summer than in the winter in each hemisphere. A significant change in cirrus cloud cover occurs in 1991, the third year of the study. Cirrus observations increase from 35% to 43% of the data, a change of eight percentage points. Other cloud forms, opaque to terrestrial radiation, decerase by nearly the same amount. Most of the increase is thinner cirrus with infrared optical depths below 0.7. The increase in cirrus happens at the same time as the 1991-92 El Nino/Southern Oscillation (ENSO) and the eruption of Mt. Pinatubo. The cirrus changes occur at the start of the ENSO and persist into 1993 in contrast to other climatic indicators that return to near pre-ENSO and volcanic levels in 1993.

The Prospect for Remote Sensing of Cirrus Clouds with a Submillimeter-Wave Spectrometer

NASA Technical Reports Server (NTRS)

Evans, K. Franklin; Evans, Aaron H.; Nolt, Ira G.; Marshall, B. Thomas

1999-01-01

Given the substantial radiative effects of cirrus clouds and the need to validate cirrus cloud mass in climate models, it is important to measure the global distribution of cirrus properties with satellite remote sensing. Existing cirrus remote sensing techniques, such as solar reflectance methods, measure cirrus ice water path (IWP) rather indirectly and with limited accuracy. Submillimeter/wave radiometry is an independent method of cirrus remote sensing based on ice particles scattering the upwelling radiance emitted by the lower atmosphere. A new aircraft instrument, the Far Infrared Sensor for Cirrus (FIRSC), is described. The FIRSC employs a Fourier Transform Spectrometer (FTS). which measures the upwelling radiance across the whole submillimeter region (0.1 1.0-mm wavelength). This wide spectral coverage gives high sensitivity to most cirrus particle sizes and allows accurate determination of the characteristic particle size. Radiative transfer modeling is performed to analyze the capabilities of the submillimeter FTS technique. A linear inversion analysis is done to show that cirrus IWP, particle size, and upper-tropospheric temperature and water vapor may be accurately measured, A nonlinear statistical algorithm is developed using a database of 20000 spectra simulated by randomly varying most relevant cirrus and atmospheric parameters. An empirical orthogonal function analysis reduces the 500-point spectrum (20 - 70/cm) to 15 "pseudo-channels" that are then input to a neural network to retrieve cirrus IWP and median particle diameter. A Monte Carlo accuracy study is performed with simulated spectra having realistic noise. The retrieval errors are low for IWP (rms less than a factor of 1.5) and for particle sizes (rins less than 30%) for IWP greater than 5 g/sq m and a wide range of median particle sizes. This detailed modeling indicates that there is good potential to accurately measure cirrus properties with a submillimeter FTS.

SUCCESS Evidence for Cirrus Cloud Ice Nucleation Mechanisms

NASA Technical Reports Server (NTRS)

Jensen, Eric; Gore, Warren J. Y. (Technical Monitor)

1997-01-01

During the SUCCESS mission, several measurements were made which should improve our understanding of ice nucleation processes in cirrus clouds. Temperature and water vapor concentration were made with a variety of instruments on the NASA DC-8. These observations should provide accurate upper tropospheric humidities. In particular, we will evaluate what humidities are required for ice nucleation. Preliminary results suggest that substantial supersaturations frequently exist in the upper troposphere. The leading-edge region of wave-clouds (where ice nucleation occurs) was sampled extensively at temperatures near -40 and -60C. These observations should give precise information about conditions required for ice nucleation. In addition, we will relate the observed aerosol composition and size distributions to the ice formation observed to evaluate the role of soot or mineral particles on ice nucleation. As an alternative technique for determining what particles act as ice nuclei, numerous samples of aerosols inside ice crystals were taken. In some cases, large numbers of aerosols were detected in each crystal, indicating that efficient scavenging occurred. Analysis of aerosols in ice crystals when only one particle per crystal was detected should help with the ice nucleation issue. Direct measurements of the ice nucleating activity of ambient aerosols drawn into airborne cloud chambers were also made. Finally, measurements of aerosols and ice crystals in contrails should indicate whether aircraft exhaust soot particles are effective ice nuclei.

Lidar observations of high altitude cirrus near the tropical tropopause

NASA Astrophysics Data System (ADS)

Parameswaran, K.; Kumar, S. Sunil; Krishna Murthy, B.

High altitude cirrus plays a significant role in atmospheric chemistry, radiation and troposphere-stratosphere exchanges. Studies on their global morphology using satellite data (SAGE) suggests that over the tropics these clouds occur quite frequently in the altitude region around 14 to 16 km with favoured locations centred over Southern Asia, India and Mexico. A monostatic Nd:YAG lidar (operating at 532 nm wavelength) located at National MST Radar Facility (NMRF), Gadanki (13.5°N, 79.2°E) provides an excellent opportunity to study the properties of these clouds. Lidar observations for ~120 nights during the period January 1999 to March 2000 are used to investigate the physical and optical properties of these clouds aswell as their spatial (altitude) and temporal variability. Based on optical depth ( c ) cirrus clouds are classified as Sub-visual Cirrus (SVC) with c 0.03, Thin Cirrus (TC) with 0.030.3. While SVCs are observed anywhere in the altitude region 12 to 18 km, with favoured altitude above 15 km, TCs and DCs usually occur around 14.5+/-1km. The altitude region 14 to 16km appears to be more conducive for cirrus formation. Even though the geometrical thickness (vertical extent) of these clouds varies from 0.3 to 3 km, they are mostly confined to altitudes below the level of tropopause temperature inversion. The cloud optical depth maximises around the post-mid-night period. These clouds also introduce significant depolarisation for the backscattered radiation indicating presence of abundant non-spherical particles presumably ice-crystals. Under favourable conditions these ice-crystals get aligned horizontally to enhance the co - polarized component of lidar backscatter signal through specular reflection, leading to a decrease in cloud depolarisation () below the ambient molecular depolarisation (m ). Such conditions are usually encountered in the case of optically dense clouds. Altitude profile of backscatter ratio within the cloud shows that the cloud is not optically symmetric with respect to the geometric centre. This asymmetry parameter () of the cloud shows significant temporal variability. For clouds with> m , as c increases, the optical centre descends in altitude and for clouds with< m the optical centre ascends as c increases. Occurrence of cirrus clouds and their optical properties are found to be closely associated with the characteristics of atmospheric turbulence in the upper troposphere.

Cirrus Simulations of CRYSTAL-FACE 23 July 2002 Case

NASA Technical Reports Server (NTRS)

Starr, David; Lin, Ruei-Fong; Demoz, Belay; Lare, Andrew

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 relationships between the properties of tropical convective cloud systems and the properties and lifecycle of the extended cirrus anvils they produce. We report here on a case study of 23 July 2002 where a sequence of convective storms over central Florida produced an extensive anvil outflow. Our approach is to use a suitably-initialized cloud- system simulation with MM5 (Starr et al., companion paper in this volume) to define initial conditions and time-dependent forcing for a simulation of anvil evolution using a two-dimensional fine-resolution (100 m) cirrus cloud model that explicitly accounts for details of cirrus microphysical development (bin or spectra model) and fully interactive radiative processes. The cirrus model follows Lin (1997). The microphysical components are described in Lin et al. (2004) - see Lin et a1 (this volume). Meteorological conditions and observations for the 23 July case are described in Starr et al. (this volume). The goals of the present study are to evaluate how well we can simulate a cirrus anvil lifecycle, to evaluate the importance of various physical processes that operate within the anvil, and to evaluate the importance of environmental conditions in regulating anvil lifecycle. CRYSTAL-FACE produced a number of excellent case studies of anvil systems that will allow environmental factors, such as static stability or wind shear in the upper troposphere, to be examined. In the present study, we strive to assess the importance of propagating gravity waves, likely produced by the deep convection itself, and radiative processes, to anvil lifecycle and characteristics.

Characterization of Individual Aerosol Particles Associated with Clouds (CRYSTAL-FACE)

NASA Technical Reports Server (NTRS)

Buseck, Peter R.

2004-01-01

The aim of our research was to obtain data on the chemical and physical properties of individual aerosol particles from near the bottoms and tops of the deep convective systems that lead to the generation of tropical cirrus clouds and to provide insights into the particles that serve as CCN or IN. We used analytical transmission electron microscopy (ATEM), including energy-dispersive X-ray spectrometry (EDS) and electron energy-loss spectroscopy (EELS), and field-emission electron microscopy (FESEM) to compare the compositions, concentrations, size distributions, shapes, surface coatings, and degrees of aggregation of individual particles from cloud bases and the anvils near the tropopause. Aggregates of sea salt and mineral dust, ammonium sulfate, and soot particles are abundant in in-cloud samples. Cirrus samples contain many H2SO4 droplets, but acidic sulfate particles are rare at the cloud bases. H2SO4 probably formed at higher altitudes through oxidation of SO2 in cloud droplets. The relatively high extent of ammoniation in the upper troposphere in-cloud samples appears to have resulted from vertical transport by strong convection. The morphology of H2SO4 droplets indicates that they had been at least yartiy ammoniated at the time of collection. They are internally mixed with organic materials, metal sulfates, and solid particles of various compositions. Ammoniation and internal mixing of result in freezing at higher temperature than in pure H2SO4 aerosols. K- and S-bearing organic particles and Si-Al-rich particles are common throughout. Sea salt and mineral dust were incorporated into the convective systems from the cloud bases and worked as ice nuclei while being vertically transported. The nonsulfate particles originated from the lower troposphere and were transported to the upper troposphere and lower stratosphere.

A numerical model characterizing the experimental performance of the Howard University Raman Lidar system

NASA Astrophysics Data System (ADS)

Connell, Rasheen M.

At the Howard University Atmospheric Observatory in Beltsville, MD, a Raman Lidar System was developed to provide both daytime and nighttime measurements of water vapor, aerosols, and cirrus clouds with 60 s temporal and 7.5 m spatial resolution in the lower and upper troposphere. This system analyzes signals at three wavelengths associated with Rayleigh/Mie scattering for aerosols and cirrus clouds at 354.7 nm, Raman scattering for nitrogen at 386.7 nm, and water vapor at 407.5 nm. The transmitter is a triple harmonic Nd: YAG solid state laser. The receiver is a 40 cm Cassegrain telescope. The detector system consists of a multi-channel wavelength separator unit and data acquisition system. This thesis develops a numerical model to provide a realistic representation of the system behavior. The variants of the lidar equation in the model use system parameters to solve and determine the return signals for the lidar system. This dissertation describes four case studies being investigated: clear sky, polluted, wet, and cirrus cloud atmospheric conditions. The first simulations are based on a standard atmosphere, which assumes an unpolluted (aerosol-free) dry-air atmosphere. The second and third sets of simulations are based on polluted and cirrus cloud atmospheric conditions, where aerosols and cirrus clouds are added to Case Study I. The last set of simulations is based on a wet atmosphere, where the troposphere is comprised of the same mixture of gases in Case Study II, with the addition of atmospheric water vapor. Lidar signals are simulated over the altitude range covered by our measurements (up to 14 km). Results of our simulations show that the measured and modeled signals agree within 10% over an extended period of time when the system (i.e., such as alignment, filter tuning, etc.) has not changed.

16-year Climatology of Cirrus cloud properties using ground-based Lidar over Gadanki (13.45˚N, 79.18˚E)

NASA Astrophysics Data System (ADS)

Pandit, Amit Kumar; Raghunath, Karnam; Jayaraman, Achuthan; Venkat Ratnam, Madineni; Gadhavi, Harish

Cirrus clouds are ubiquitous high level cold clouds predominantly consisting of ice-crystals. With their highest coverage over the tropics, these are one of the most vital and complex components of Tropical Tropopause Layer (TTL) due to their strong radiative feedback and dehydration in upper troposphere and lower stratosphere (UTLS) regions. The continuous changes in their coverage, position, thickness, and ice-crystal size and shape distributions bring uncertainties in the estimates of cirrus cloud radiative forcing. Long-term changes in the distribution of aerosols and water vapour in the TTL can influence cirrus properties. This necessitates long-term studies of tropical cirrus clouds, which are only few. The present study provides 16-year climatology of physical and optical properties of cirrus clouds observed using a ground-based Lidar located at Gadanki (13.45(°) N, 79.18(°) ˚E and 375 m amsl) in south-India. In general, cirrus clouds occurred for about 44% of the total Lidar observation time. Owing to the increased convective activities, the occurrence of cirrus clouds during the southwest-monsoon season is highest while it is lowest during the winter. Altitude distribution of cirrus clouds reveals that the peak occurrence was about 25% at 14.5 km. The most probable base and top height of cirrus clouds are 14 and 15.5 km, respectively. This is also reflected in the bulk extinction coefficient profile (at 532 nm) of cirrus clouds. These results are compared with the CALIPSO observations. Most of the time cirrus clouds are located within the TTL bounded by convective outflow level and cold-point tropopause. Cirrus clouds are thick during the monsoon season as compared to that during winter. An inverse relation between the thickness of cirrus clouds and TTL thickness is found. The occurrence of cirrus clouds at an altitude close to the tropopause (16 km) showed an increase of 8.4% in the last 16 years. Base and top heights of cirrus clouds also showed increase of 0.41 km and 0.56 km, respectively. These results are discussed in relation with the recent increase in the tropical tropopause altitude.

Midlatitude Cirrus Clouds Derived from Hurricane Nora: A Case Study with Implications for Ice Crystal Nucleation and Shape.

NASA Astrophysics Data System (ADS)

Sassen, Kenneth; Arnott, W. Patrick; O'C. Starr, David; Mace, Gerald G.; Wang, Zhien; Poellot, Michael R.

2003-04-01

Hurricane Nora traveled up the Baja Peninsula coast in the unusually warm El Niño waters of September 1997 until rapidly decaying as it approached southern California on 24 September. The anvil cirrus blowoff from the final surge of tropical convection became embedded in subtropical flow that advected the cirrus across the western United States, where it was studied from the Facility for Atmospheric Remote Sensing (FARS) in Salt Lake City, Utah, on 25 September. A day later, the cirrus shield remnants were redirected southward by midlatitude circulations into the southern Great Plains, providing a case study opportunity for the research aircraft and ground-based remote sensors assembled at the Clouds and Radiation Testbed (CART) site in northern Oklahoma. Using these comprehensive resources and new remote sensing cloud retrieval algorithms, the microphysical and radiative cloud properties of this unusual cirrus event are uniquely characterized.Importantly, at both the FARS and CART sites the cirrus generated spectacular halos and arcs, which acted as a tracer for the hurricane cirrus, despite the limited lifetimes of individual ice crystals. Lidar depolarization data indicate widespread regions of uniform ice plate orientations, and in situ particle replicator data show a preponderance of pristine, solid hexagonal plates and columns. It is suggested that these unusual aspects are the result of the mode of cirrus particle nucleation, presumably involving the lofting of sea salt nuclei in strong thunderstorm updrafts into the upper troposphere. This created a reservoir of haze particles that continued to produce halide-salt-contaminated ice crystals during the extended period of cirrus cloud maintenance. The inference that marine microbiota are embedded in the replicas of some ice crystals collected over the CART site points to the longevity of marine effects. Various nucleation scenarios proposed for cirrus clouds based on this and other studies, and the implications for understanding cirrus radiative properties on a global scale, are discussed.

Midlatitude Cirrus Clouds Derived from Hurricane Nora: A Case Study with Implications for Ice Crystal Nucleation and Shape

NASA Technical Reports Server (NTRS)

Sassen, Kenneth; Arnott, W. Patrick; OCStarr, David; Mace, Gerald G.; Wang, Zhien; Poellot, Michael R.

2002-01-01

Hurricane Nora traveled up the Bala Peninsula coast in the unusually warm El Nino waters of September 1997, until rapidly decaying as it approached Southern California on 24 September. The anvil cirrus blowoff from the final surge of tropical convection became embedded in subtropical flow that advected the cirrus across the western US, where it was studied from the Facility for Atmospheric Remote Sensing (FARS) in Salt Lake City, Utah. A day later, the cirrus shield remnants were redirected southward by midlatitude circulations into the Southern Great Plains, providing a case study opportunity for the research aircraft and ground-based remote sensors assembled at the Clouds and Radiation Testbed (CART) site in northern Oklahoma. Using these comprehensive resources and new remote sensing cloud retrieval algorithms, the microphysical and radiative cloud properties of this unusual cirrus event are uniquely characterized. Importantly, at both the FARS and CART sites the cirrus generated spectacular optical displays, which acted as a tracer for the hurricane cirrus, despite the limited lifetimes of individual ice crystals. Lidar polarization data indicate widespread regions of uniform ice plate orientations, and in situ particle masticator data show a preponderance of pristine, solid hexagonal plates and columns. It is suggested that these unusual aspects are the result of the mode of cirrus particle nucleation, presumably involving the lofting of sea-salt nuclei in thunderstorm updrafts into the upper troposphere. This created a reservoir of haze particles that continued to produce halide-saltcontaminated ice crystals during the extended period of cirrus cloud maintenance. The reference that marine microliters are embedded in the replicas of ice crystals collected over the CART site points to the longevity of marine effects. Various nucleation scenarios proposed for cirrus clouds based on this and other studies, and the implications for understanding cirrus radiative properties or a global scale, are discussed.

Optical scattering and microphysical properties of subvisual cirrus clouds, and climatic implications

NASA Technical Reports Server (NTRS)

Sassen, Kenneth; Griffin, Michael K.; Dodd, Gregory C.

1989-01-01

The optical and microphysical properties of subvisual cirrus clouds are derived from ground-based polarization lidar, shortwave radiation flux, and solar corona measurements of two approximately 0.75 km deep cirrus located near the tropopause. The first cloud produced no visual manifestations under excellent viewing conditions, and the second appeared to be a persistent aircraft contrail that was generally visible except in the zenith direction. Average lidar linear depolarization ratios and volume backscatter coefficients for the two clouds were 0.19 and 0.35, and 0.6 x 10 to the -3 and 1.4 x 10 to the -3 /km sr, respectively. It is estimated that the zenith-subvisual cirrus contained ice crystals of 25-micron effective diameter at a mean concentration of 25/1 and ice mass content of 0.2 mg/cu m. The threshold cloud optical thickness for visual-versus-invisible cirrus, derived from both broadband shortwave flux and 0.694 micrometer lidar data, is found to be tau sub c approx equal 0.03. Such tau values are comparable to those of 5 to 10 km deep stratospheric aerosol clouds of volcanic origin and polar stratospheric clouds, which are episodic in nature. Hence, we conclude that if these clouds are a fairly common feature of the upper troposphere, as recent SAGE satellite measurements would suggest, then the impact of natural and contrail subvisual cirrus on the planet's radiation balance may be relatively significant.

Optical scattering and microphysical properties of subvisual cirrus clouds, and climatic implications

NASA Technical Reports Server (NTRS)

Sassen, Kenneth; Griffin, Michael K.; Dodd, Gregory C.

1988-01-01

The optical and microphysical properties of subvisual cirrus clouds are derived from ground-based polarization lidar, shortwave radiation flux, and solar corona measurements of two approximately 0.75 km deep cirrus located near the tropopause. The first cloud produced no visual manifestations under excellent viewing conditions, and the second appeared to be a persistent aircraft contrail that was generally visible except in the zenith direction. Average lidar linear depolarization ratios and volume backscatter coefficients for the two clouds were 0.19 and 0.35, and 0.6x10 to the -3 and 1.4x10 to the -3 /km sr, respectively. It is estimated that the zenith-subvisual cirrus contained ice crystals of 25 micron effective diameter at a mean concentration of 25/l and ice mass content of 0.2 mg/cu m. The threshold cloud optical thickness for visual-versus-invisible cirrus, derived from both broadband shortwave flux and 0.694 micrometer lidar data, is found to be tau sub c approx equal 0.03. Such tau values are comparable to those of 5 to 10 km deep stratospheric aerosol clouds of volcanic origin and polar stratospheric clouds, which are episodic in nature. Hence, we conclude that if these clouds are a fairly common feature of the upper troposphere, as recent SAGE satellite measurements would suggest, then the impact of natural and contrail subvisual cirrus on the planet's radiation balance may be relatively significant.

Clouds and Water Vapor in the Climate System and Radiative Transfer in Clear Air and Cirrus Clouds in the Tropics

NASA Technical Reports Server (NTRS)

Anderson, James G.; DeSouza-Machado, Sergio; Strow, L. Larrabee

2002-01-01

Research supported under this grant was aimed at attacking unanswered scientific questions that lie at the intersection of radiation, dynamics, chemistry, and climate. Considerable emphasis was placed on scientific collaboration and the innovative development of instruments required to address these issues. Specific questions include water vapor distribution in the tropical troposphere, atmospheric radiation, thin cirrus clouds, stratosphere-troposphere exchange, and correlative science with satellite observations.

Submillimeter-Wave Cloud Ice Radiometry

NASA Technical Reports Server (NTRS)

Walter, Steven J.

1999-01-01

Submillimeter-wave cloud ice radiometry is a new and innovative technique for characterizing cirrus ice clouds. Cirrus clouds affect Earth's climate and hydrological cycle by reflecting incoming solar energy, trapping outgoing IR radiation, sublimating into vapor, and influencing atmospheric circulation. Since uncertainties in the global distribution of cloud ice restrict the accuracy of both climate and weather models, successful development of this technique could provide a valuable tool for investigating how clouds affect climate and weather. Cloud ice radiometry could fill an important gap in the observational capabilities of existing and planned Earth-observing systems. Using submillimeter-wave radiometry to retrieve properties of ice clouds can be understood with a simple model. There are a number of submillimeter-wavelength spectral regions where the upper troposphere is transparent. At lower tropospheric altitudes water vapor emits a relatively uniform flux of thermal radiation. When cirrus clouds are present, they scatter a portion of the upwelling flux of submillimeter-wavelength radiation back towards the Earth as shown in the diagram, thus reducing the upward flux o f energy. Hence, the power received by a down-looking radiometer decreases when a cirrus cloud passes through the field of view causing the cirrus cloud to appear radiatively cool against the warm lower atmospheric thermal emissions. The reduction in upwelling thermal flux is a function of both the total cloud ice content and mean crystal size. Radiometric measurements made at multiple widely spaced frequencies permit flux variations caused by changes in crystal size to be distinguished from changes in ice content, and polarized measurements can be used to constrain mean crystal shape. The goal of the cloud ice radiometry program is to further develop and validate this technique of characterizing cirrus. A multi-frequency radiometer is being designed to support airborne science and spacecraft validation missions. This program has already extended the initial millimeter-wave modeling studies to submillimeter-wavelengths and has improved the realism of the cloud scattering models. Additionally a proof-of-concept airborne submillimeter-wave radiometer was constructed and fielded. It measured a radiometric signal from cirrus confirming the basic technical feasibility of this technique. This program is a cooperative effort of the University of Colorado, Colorado State University, Swales Aerospace, and Jet Propulsion Laboratory. Additional information is contained in the original.

Quantifying the Amount of Ice in Cold Tropical Cirrus Clouds

NASA Technical Reports Server (NTRS)

Avery, Melody A.; Winker, David M.; Garnier, Anne; Lawson, R. Paul; Heymsfield, Andrew J.; Mo, Qixu; Schoeberl, Mark R.; Woods, Sarah; Lance, Sara; Young, Stuart A.;

Far-infrared Spectral Radiance Observations and Modeling of Arctic Cirrus: Preliminary Results From RHUBC

NASA Astrophysics Data System (ADS)

Humpage, Neil; Green, Paul D.; Harries, John E.

2009-03-01

Recent studies have highlighted the important contribution of the far-infrared (electromagnetic radiation with wavelengths greater than 12 μm) to the Earth's radiative energy budget. In a cloud-free atmosphere, a significant fraction of the Earth's cooling to space from the mid- and upper troposphere takes place via the water vapor pure rotational band between 17 and 33 μm. Cirrus clouds also play an important role in the Earth's outgoing longwave radiation. The effect of cirrus on far-infrared radiation is of particular interest, since the refractive index of ice depends strongly on wavelength in this spectral region. The scattering properties of ice crystals are directly related to the refractive index, so consequently the spectral signature of cirrus measured in the FIR is sensitive to the cloud microphysical properties [1, 2]. By examining radiances measured at wavelengths between the strong water vapor absorption lines in the FIR, the understanding of the relationship between cirrus microphysics and the radiative transfer of thermal energy through cirrus may be improved. Until recently, very few observations of FIR spectral radiances had been made. The Tropospheric Airborne Fourier Transform Spectrometer (TAFTS) was developed by Imperial College to address this lack of observational data. TAFTS observes both zenith and nadir radiances at 0.1 cm-1 resolution, between 80 and 600 cm-1. During February and March 2007, TAFTS was involved in RHUBC (the Radiative Heating in Under-explored Bands Campaign), an ARM funded field campaign based at the ACRF-North Slope of Alaska site near Barrow, situated at 71° latitude. Infrared zenith spectral observations were taken by both TAFTS and the AERI-ER (spectral range 400-3300 cm-1) from the ground during both cloud-free and cirrus conditions. A wide range of other instrumentation was also available at the site, including a micropulse lidar, 35 GHz radar and the University of Colorado/NOAA Ground-based Scanning Radiometer (GSR). Data from these instruments, as well as from frequently launched radiosondes, were used to characterize the atmospheric state needed as input for line-by-line radiative transfer calculations. By comparing these calculations with the TAFTS and AERI-ER observations, it is possible to test the effectiveness of ice crystal size distribution parameterizations (which are generally derived from mid-latitude and tropical in-situ observations) when applied to Arctic cirrus. The influence of the assumed single scattering properties (here calculated for ice aggregates by A. Baran of the UK Met Office) on the calculated spectra is also considered in this work.

Balloon-borne match measurements of mid-latitude cirrus clouds

NASA Astrophysics Data System (ADS)

Cirisan, A.; Luo, B. P.; Engel, I.; Wienhold, F. G.; Krieger, U. K.; Weers, U.; Romanens, G.; Levrat, G.; Jeannet, P.; Ruffieux, D.; Philipona, R.; Calpini, B.; Spichtinger, P.; Peter, T.

2013-10-01

Observations of persistent high supersaturations with respect to ice inside cirrus clouds are challenging our understanding of cloud microphysics and of climate feedback processes in the upper troposphere. Single measurements of a cloudy air mass provide only a snapshot from which the persistence of ice supersaturation cannot be judged. We introduce here the "cirrus match technique" to obtain information of the evolution of clouds and their saturation ratio. The aim of these coordinated balloon soundings is to analyze the same air mass twice. To this end the standard radiosonde equipment is complemented by a frost point hygrometer "SnowWhite" and a particle backscatter detector "COBALD" (Compact Optical Backscatter Aerosol Detector). Extensive trajectory calculations based on regional weather model COSMO forecasts are performed for flight planning and COSMO analyses are used as basis for comprehensive microphysical box modeling (with grid scale 2 km and 7 km, respectively). Here we present the results of matching a cirrus cloud to within 2-15 km, realized on 8 June 2010 over Payerne, Switzerland, and a location 120 km downstream close to Zurich. A thick cirrus was detected over both measurement sites. We show that in order to quantitatively reproduce the measured particle backscatter ratios, the small-scale temperature fluctuations not resolved by COSMO must be superimposed on the trajectories. The stochastic nature of the fluctuations is captured by ensemble calculations. Possibilities for further improvements in the agreement with the measured backscatter data are investigated by assuming a very slow mass accommodation of water on ice, the presence of heterogeneous ice nuclei, or a wide span of (spheroidal) particle shapes. However, the resulting improvements from microphysical refinements are moderate and comparable in magnitude with changes caused by assuming different regimes of temperature fluctuations for clear sky or cloudy sky conditions, highlighting the importance of a proper treatment of subscale fluctuations. The model yields good agreement with the measured backscatter over both sites and reproduces the measured saturation ratios with respect to ice over Payerne. Conversely, the 30% in-cloud supersaturation measured in a massive, 4-km thick cloud layer over Zurich cannot be reproduced, irrespective of the choice of meteorological or microphysical model parameters. The measured supersaturation can only be explained by either resorting to an unknown physical process, which prevents the ice particles from consuming the excess humidity, or - much more likely - by a measurement error, such as a contamination of the sensor housing of the SnowWhite hygrometer by a precipitation drop from a mixed phase cloud just below the cirrus layer or from some very slight rain in the boundary layer. This uncertainty calls for in-flight checks or calibrations of hygrometers under the extreme humidity conditions in the upper troposphere.

Isentropic modeling of a cirrus cloud event observed in the midlatitude upper troposphere and lower stratosphere

NASA Astrophysics Data System (ADS)

Montoux, N.; Keckhut, P.; Hauchecorne, A.; Jumelet, J.; Brogniez, H.; David, C.

2010-01-01

This publication provides a detailed study of one cirrus cloud observed by lidar at the Observatory of Haute-Provence (˜44°N) in January 2006 in the vicinity of the tropopause (12-14 km/˜136-190 hPa/328-355 K). The higher part of the air mass observed comes from the wet subtropics while the lower part comes from the midlatitudes. Both are advected by the Azores anticyclone, encounter cold temperatures (˜205 K) above the North Atlantic Ocean, and flow eastward along the anticyclonic flank of the polar jet stream. A simulation of this cloud by an isentropic model is tested to see if synoptic-scale atmospheric structures could explain by itself the presence of such clouds. The developments made in the Modélisation Isentrope du transport Méso-échelle de l'Ozone Stratosphérique par Advection (MIMOSA) model to take into account the three phases of water and their interactions allow reproduction of the occurrence of the cirrus and its temporal evolution. MIMOSA-H2O reproduces the atmospheric water vapor structures observed with Atmospheric Infrared Sounder (AIRS) with, however, an apparent wet bias of around 50%. Reliable water vapor fields appear to be the main condition to correctly simulate such cirrus clouds. The model reproduces the cirrus cloud altitude for fall speeds around 1 cm/s and gives ice water content around 3-4 mg/m3. Fall speed is also a critical parameter, and a better parameterization with altitude or other atmospheric conditions in the modeling of such cirrus clouds is required. This study also shows that supersaturation threshold impacts strongly the vertical and horizontal extension of the cirrus cloud but more slightly the ice water path.

What is the role of laminar cirrus cloud on regulating the cross-tropopause water vapor transport?

NASA Astrophysics Data System (ADS)

Wu, D. L.; Gong, J.; Tsai, V.

2016-12-01

Laminar cirrus is an extremely thin ice cloud found persistently inhabit in the tropical and subtropical tropopause. Due to its sub-visible optical depth and high formation altitude, knowledge about the characteristics of this special type of cloud is very limited, and debates are ongoing about its role on regulating the cross-tropopause transport of water vapor. The Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) onboard the CALIPSO satellite has been continuously providing us with unprecedented details of the laminar cirrus since its launch in 2006. In this research, we adapted Winker and Trepte (1998)'s eyeball detection method. A JAVA-based applet and graphical user interface (GUI) is developed to manually select the laminar, which then automatically record the cloud properties, such as spatial location, shape, thickness, tilt angle, and whether its isolated or directly above a deep convective cloud. Monthly statistics of the laminar cirrus are then separately analyzed according to the orbit node, isolated/convective, banded/non-banded, etc. Monthly statistics support a diurnal difference in the occurring frequency and formation height of the laminar cirrus. Also, isolated and convective laminars show diverse behaviors (height, location, distribution, etc.), which strongly implies that their formation mechanisms and their roles on depleting the upper troposphere water vapor are distinct. We further study the relationship between laminar characteristics and collocated and coincident water vapor gradient measurements from Aura Microwave Limb Sounder (MLS) observations below and above the laminars. The identified relationship provides a quantitative answer to the role laminar cirrus plays on regulating the water vapor entering the stratosphere.

Monitoring Cirrus Clouds Using Lamp Observations in Association with Balloon-Borne Radiosonde Over Nainital: Few Case Studies

NASA Astrophysics Data System (ADS)

Solanki, R.; Singh, N.

2012-12-01

Upper tropospheric clouds such as cirrus have been identified as one of the important regulator of the radiation balance of the earth atmospheric-system. Though the satellite observation provide valuable information on cirrus clouds, they have limitations on spectral, temporal and spatial coverage, hence the need for local remote sensing, such as LiDAR a leading technique for studying the characteristics and properties of cirrus clouds. The upgraded version of a micro pulse LiDAR popularly known as LiDAR for Atmospheric Measurements and Probing (LAMP) developed by National Atmospheric Research Laboratory (NARL) is operational since October 2011, at ARIES Nainital (29.4oN, 79.5oE, ~2 km above the mean sea level) a high altitude location in the central Himalayas. Regular observations are being carried out in order to study the vertical distribution of aerosols, clouds and boundary layer structure etc. Altitude profiles of range corrected photon count and derived aerosol back scatter coefficients have depicted the occurrence of high altitude cirrus clouds/ ice clouds in an altitude range of 7 to 11 Km. Among the total observations in 27% of the cases the occurrence of cirrus clouds were detected. The corresponding cloud parameters such as temperature (-59 0C), horizontal wind speed (26 m/s), vertical wind speed (24 m/s), Relative Humidity (61%), at a height (~9 Km) were measured with Radiosonde observations. The prevailing region for cirrus cloud is found to be highly turbulent, indicating the region of divergence followed by a convergence, showing the favorable conditions for cirrus cloud formation. Optical and geometrical characteristics of Cirrus clouds have been analyzed using LiDAR and radiosonde measurements. The temperature and thickness dependence of optical properties have also been studied. The results will be further substantiated with CALIPSO satellite and details will be discussed during the presentation.

Aircraft Observation of Gravity Wave Breaking at the Storm Top and Comparison with High Resolution Cloud Model Simulations and Satellite Images

NASA Astrophysics Data System (ADS)

Wang, P. K.; Cheng, K. Y.; Lindsey, D. T.

2017-12-01

Deep convective clouds play an important role in the transport of momentum, energy, and chemical species from the surface to upper troposphere and lower stratosphere (UT/LS), but exactly how these processes occur and how important they are as compared to other processes are still up to debate. The main hurdle to the complete understanding of these transport processes is the difficulty in observing storm systems directly. Remote sensing data such as those obtained by radars and satellites are very valuable but they need correct interpretation before we can use them profitably. We have performed numerical simulations of thunderstorms using a physics-based cloud resolving model and compared model results with satellite observations. Many major features of observed satellite storm top images, such as cold-V, close in warm area, above anvil cirrus plumes, are successfully simulated and can be interpreted by the model physics. However, due to the limitation of resolution and other ambiguities, we have been unable to determine the real cause of some features such as the conversion of jumping cirrus to long trail plumes and whether or no small scale ( < 1 km) wave breaking occur. We are fortunate to have encountered a line of sea breeze storms along the coast of China during a flight from Beijing to Taipei in July 2106. The flight was at an altitude such that storm tops could be clearly observed. Nearly all of the mature storm cells that can be identified had very vigorous storm top activities, indicating very strong stratosphere/troposphere exchange (STE). There is no doubt that the signatures of wave breaking, i.e., jumping cirrus, occurs from very small scale (< 1 km) to tens of km. this matches our previous model results very well. Furthermore, one storm cell shows very clearly the process whereby a jumping cirrus is being transformed into a long trail cirrus plume which was often observed in satellite images. We have also obtained the corresponding Himawari-8 satellite images for this line of storms. Aircraft observation, satellite images and model results will be compared and the implications to STE discussed.

Observing Ice in Clouds from Space

NASA Technical Reports Server (NTRS)

Ackerman, S.; Star, D. O'C.; Skofronick-Jackson, G.; Evans, F.; Wang, J. R.; Norris, P.; daSilva, A.; Soden, B.

2006-01-01

There are many satellite observations of cloud top properties and the liquid and rain content of clouds, however, we do not yet quantitatively understand the processes that control the water budget of the upper troposphere where ice is the predominant phase, and how these processes are linked to precipitation processes and the radiative energy budget. The ice in clouds in the upper troposphere either melts into rain or is detrained, and persists, as cirrus clouds affecting the hydrological and energy cycle, respectively. Fully modeling the Earth's climate and improving weather and climate forecasts requires accurate satellite measurements of various cloud properties at the temporal and spatial scales of cloud processes. These properties include cloud horizontal and vertical structure, cloud water content and some measure of particle sizes and shapes. The uncertainty in knowledge of these ice characteristics is reflected in the large discrepancies in model simulations of the upper tropospheric water budget. Model simulations are sensitive to the partition of ice between precipitation and outflow processes, i.e., to the parameterization of ice clouds and ice processes. One barrier to achieving accurate global ice cloud properties is the lack of adequate observations at millimeter and submillimeter wavelengths (183-874 GHz). Recent advances in instrumentation have allowed for the development and implementation of an airborne submillimeter-wave radiometer. The brightness temperatures at these frequencies are especially sensitive to cirrus ice particle sizes (because they are comparable to the wavelength). This allows for more accurate ice water path estimates when multiple channels are used to probe into the cloud layers. Further, submillimeter wavelengths offer simplicity in the retrieval algorithms because they do not probe into the liquid and near surface portions of clouds, thus requiring only one term of the radiative transfer equation (ice scattering) to relate brightness temperatures to ice. The next step is a satellite mission designed to acquire global Earth radiance measurements in the submillimeter-wave region, thus bridging the measurement gap between microwave sounders and shorter-wavelength infrared and visible sensors. This presentation provides scientific justification and an approach to measuring ice water path and particle size from a satellite platform that spans a range encompassing both the hydrologically active and radiatively active components of cloud systems.

Extended field observations of cirrus clouds using a ground-based cloud observing system

NASA Technical Reports Server (NTRS)

Ackerman, Thomas P.

1994-01-01

The evolution of synoptic-scale dynamics associated with a middle and upper tropospheric cloud event that occurred on 26 November 1991 is examined. The case under consideration occurred during the FIRE CIRRUS-II Intensive Field Observing Period held in Coffeyville, KS during Nov. and Dec., 1991. Using data from the wind profiler demonstration network and a temporally and spatially augmented radiosonde array, emphasis is given to explaining the evolution of the kinematically-derived ageostrophic vertical circulations and correlating the circulation with the forcing of an extensively sampled cloud field. This is facilitated by decomposing the horizontal divergence into its component parts through a natural coordinate representation of the flow. Ageostrophic vertical circulations are inferred and compared to the circulation forcing arising from geostrophic confluence and shearing deformation derived from the Sawyer-Eliassen Equation. It is found that a thermodynamically indirect vertical circulation existed in association with a jet streak exit region. The circulation was displaced to the cyclonic side of the jet axis due to the orientation of the jet exit between a deepening diffluent trough and building ridge. The cloud line formed in the ascending branch of the vertical circulation with the most concentrated cloud development occurring in conjunction with the maximum large-scale vertical motion. The relationship between the large scale dynamics and the parameterization of middle and upper tropospheric clouds in large-scale models is discussed and an example of ice water contents derived from a parameterization forced by the diagnosed vertical motions and observed water vapor contents is presented.

New Particle Formation in the Mid-Latitude Upper Troposphere

NASA Astrophysics Data System (ADS)

Axisa, Duncan

Primary aerosol production due to new particle formation (NPF) in the upper troposphere and the impact that this might have on cloud condensation nuclei (CCN) concentration can be of sufficient magnitude to contribute to the uncertainty in radiative forcing. This uncertainty affects our ability to estimate how sensitive the climate is to greenhouse gas emissions. Therefore, new particle formation must be accurately defined, parametrized and accounted for in models. This research involved the deployment of instruments, data analysis and interpretation of particle formation events during the Mid-latitude Airborne Cirrus Properties Experiment (MACPEX) campaign. The approach combined field measurements and observations with extensive data analysis and modeling to study the process of new particle formation and growth to CCN active sizes. Simultaneous measurements of O3, CO, ultrafine aerosol particles and surface area from a high-altitude research aircraft were used to study tropospheric-stratospheric mixing as well as the frequency and location of NPF. It was found that the upper troposphere was an active region in the production of new particles by gas-to-particle conversion, that nucleation was triggered by convective clouds and mixing processes, and that NPF occurred in regions with high relative humidity and low surface area. In certain cases, mesoscale and synoptic features enhanced mixing and facilitated the formation of new particles in the northern mid-latitudes. A modeling study of particle growth and CCN formation was done based on measured aerosol size distributions and modeled growth. The results indicate that when SO2 is of sufficient concentration NPF is a significant source of potential CCN in the upper troposphere. In conditions where convective cloud outflow eject high concentrations of SO2, a large number of new particles can form especially in the instance when the preexisting surface area is low. The fast growth of nucleated clusters produces a particle mode that becomes CCN active within 24-hours.

LOSA-M3: multi-wave polarization scanning lidar for research of the troposphere and cirrus clouds

NASA Astrophysics Data System (ADS)

Kokhanenko, G. P.; Balin, Yu. S.; Klemasheva, M. G.; Penner, I. E.; Nasonov, S. V.; Samoilova, S. V.

2017-11-01

Lidar is designed to study the aerosol fields of the troposphere and the polarization characteristics of crystal clouds. Two laser wavelengths are used - 1064 and 532 nm, elastic scattering signals and spontaneous Raman scattering of nitrogen (607 nm) are recorded. Lidar is made in a mobile version, allowing its transportation by road and working under expeditionary conditions. The lidar transceiver is placed on a scanning column, which allows to change the direction of sounding within the upper hemisphere at a speed of 1 degree per second. The polarization characteristics of the transmitter and receiver can be changed by rotating the phase plates synchronously with the the laser pulses. In combination with conical scanning of the lidar, this makes it possible to detect the anisotropy of scattering and the possible azimuthal orientation of the crystal particles.

Analysis of in situ measurements of cirrus anvil outflow dynamics

NASA Astrophysics Data System (ADS)

Lederman, J. I.; Whiteway, J. A.

2012-12-01

The airborne campaign, EMERALD 2 (Egrett Microphysics Experiment with Radiation, Lidar, and Dynamics,) was conducted out of Darwin, Australia in 2002. Objectives included characterization of the dynamics in the cirrus anvil outflow from tropical deep convection. Two aircraft, the Egrett and King Air, were flown in tandem in the upper troposphere (7 km - 15 km) to collect in situ measurements in the anvil outflow from a storm named "Hector" that occurs on a regular basis over the Tiwi Islands north of Darwin during November and December. Turbulence probes mounted on the wings of the Egrett aircraft were used to measure the wind fluctuations across the anvil and along its length with a spatial resolution of 2 meters. The in situ measurements from the Egrett were coincident with lidar measurements of the cloud structure from the King Air aircraft flying directly below. The presentation will show results of the analysis of the measurements with an emphasis on the turbulence, gravity waves, and coherent structures that are particular to the cirrus anvil outflow environment. Emphasis is placed on the dynamics associated with the generation of mammatus formations at the base of the anvil clouds.

Impact of Tropopause Structures on Deep Convective Transport Observed during MACPEX

NASA Astrophysics Data System (ADS)

Mullendore, G. L.; Bigelbach, B. C.; Christensen, L. E.; Maddox, E.; Pinkney, K.; Wagner, S.

2016-12-01

Deep convection is the most efficient method of transporting boundary layer mass to the upper troposphere and stratosphere (UTLS). The Mid-latitude Airborne Cirrus Properties Experiment (MACPEX) was conducted during April of 2011 over the central U.S. With a focus on cirrus clouds, the campaign flights often sampled large cirrus anvils downstream from deep convection and included an extensive observational suite of chemical measurements on a high altitude aircraft. As double-tropopause structures are a common feature in the central U.S. during the springtime, the MACPEX campaign provides a good opportunity to gather cases of deep convective transport in the context of both single and double tropopause structures. Sampling of chemical plumes well downstream from convection allows for sampling in relatively quiescent conditions and analysis of irreversible transport. The analysis presented includes multiple methods to assess air mass source and possible convective processing, including back trajectories and ratios of chemical concentrations. Although missions were flown downstream of deep convection, recent processing by convection does not seem likely in all cases that high altitude carbon monoxide plumes were observed. Additionally, the impact of single and double tropopause structures on deep convective transport is shown to be strongly dependent on high stability layers.

Balloon-borne match measurements of midlatitude cirrus clouds

NASA Astrophysics Data System (ADS)

Cirisan, A.; Luo, B. P.; Engel, I.; Wienhold, F. G.; Sprenger, M.; Krieger, U. K.; Weers, U.; Romanens, G.; Levrat, G.; Jeannet, P.; Ruffieux, D.; Philipona, R.; Calpini, B.; Spichtinger, P.; Peter, T.

2014-07-01

Observations of high supersaturations with respect to ice inside cirrus clouds with high ice water content (> 0.01 g kg-1) and high crystal number densities (> 1 cm-3) are challenging our understanding of cloud microphysics and of climate feedback processes in the upper troposphere. However, single measurements of a cloudy air mass provide only a snapshot from which the persistence of ice supersaturation cannot be judged. We introduce here the "cirrus match technique" to obtain information about the evolution of clouds and their saturation ratio. The aim of these coordinated balloon soundings is to analyze the same air mass twice. To this end the standard radiosonde equipment is complemented by a frost point hygrometer, "SnowWhite", and a particle backscatter detector, "COBALD" (Compact Optical Backscatter AerosoL Detector). Extensive trajectory calculations based on regional weather model COSMO (Consortium for Small-Scale Modeling) forecasts are performed for flight planning, and COSMO analyses are used as a basis for comprehensive microphysical box modeling (with grid scale of 2 and 7 km, respectively). Here we present the results of matching a cirrus cloud to within 2-15 km, realized on 8 June 2010 over Payerne, Switzerland, and a location 120 km downstream close to Zurich. A thick cirrus cloud was detected over both measurement sites. We show that in order to quantitatively reproduce the measured particle backscatter ratios, the small-scale temperature fluctuations not resolved by COSMO must be superimposed on the trajectories. The stochastic nature of the fluctuations is captured by ensemble calculations. Possibilities for further improvements in the agreement with the measured backscatter data are investigated by assuming a very slow mass accommodation of water on ice, the presence of heterogeneous ice nuclei, or a wide span of (spheroidal) particle shapes. However, the resulting improvements from these microphysical refinements are moderate and comparable in magnitude with changes caused by assuming different regimes of temperature fluctuations for clear-sky or cloudy-sky conditions, highlighting the importance of proper treatment of subscale fluctuations. The model yields good agreement with the measured backscatter over both sites and reproduces the measured saturation ratios with respect to ice over Payerne. Conversely, the 30% in-cloud supersaturation measured in a massive 4 km thick cloud layer over Zurich cannot be reproduced, irrespective of the choice of meteorological or microphysical model parameters. The measured supersaturation can only be explained by either resorting to an unknown physical process, which prevents the ice particles from consuming the excess humidity, or - much more likely - by a measurement error, such as a contamination of the sensor housing of the SnowWhite hygrometer by a precipitation drop from a mixed-phase cloud just below the cirrus layer or from some very slight rain in the boundary layer. This uncertainty calls for in-flight checks or calibrations of hygrometers under the special humidity conditions in the upper troposphere.

A potential regulation of jet stream behavior by changes in Arctic cirrus cloud formation mechanism and coverage

NASA Astrophysics Data System (ADS)

Mejia, J.; Mitchell, D. L.; Garnier, A.; Hosseinpour, F.; Avery, M. A.

2017-12-01

Global retrievals of cirrus cloud effective diameter De and mid-cloud temperature T were used to make the cirrus clouds simulated in CAM5 conform with the retrieved De, with the ice fall speeds in CAM5 calculated from the retrieved De. This was done by developing De-T relationships for six latitude zones. Within each latitude zone, seasonal De-T relationships were developed for cirrus over land and for cirrus over ocean (making 48 De-T relationships in total). The recently developed CALIPSO retrieval algorithm is sensitive to the ice crystal number concentration N, which is also retrieved, and it utilizes radiances from the infrared imaging radiometer and backscatter from the CALIPSO lidar. Retrieved De (N) is largest (lowest) between 30S and 30N latitude; a region dominated by anvil cirrus where pre-existing ice strongly favors heterogeneous ice nucleation (henceforth het). Therefore, the De-T relations for this region are considered representative for cirrus formed via het. Outside this region, retrieved De (N) tended to be considerably smaller (higher), presumably due to homogeneous ice nucleation (henceforth hom). Two CAM5 simulations were performed; one where cirrus cloud De is based on the CALIPSO retrievals and one where De-T for het cirrus is applied globally. Differences in net cloud radiative forcing between runs are believed due to differences in cirrus formation mechanism (hom vs. het). Such differences are typically 1.3 W m-2 in the mid-to-high latitudes in the N. Hemisphere excepting summer. These differences imply differences in cirrus cloud heating rates that affect temperatures in the underlying troposphere, which in turn affect the wind fields. The natural cirrus (mixture of hom and het) tend to trap more heat than the het cirrus. Changes in zonal wind fields between simulations suggest that heating by polar cirrus clouds have modifed meridional temperature gradients and thus zonal winds through the thermal wind balance. These changes in heating by polar cirrus clouds can modify the amplitude and meridional position of the midlatitude jet streams, which can lead to more extreme weather. Moreover, the retrievals indicate a doubling of Arctic cirrus coverage during winter, which will also result in increased heating of the underlying troposphere, likely contributing to this same phenomenon.

Cirrus clouds as seen by the CALIPSO satellite and ECHAM-HAM global climate model

NASA Astrophysics Data System (ADS)

Gasparini, Blaz; Meyer, Angela; Neubauer, David; Münch, Steffen; Lohmann, Ulrike

2017-04-01

Ice clouds impact the planetary energy balance and upper tropospheric water vapour transport and are therefore relevant for climate. In this study ice clouds at temperatures below -40°C simulated by the ECHAM-HAM global climate model are compared to CALIPSO/CALIOP satellite data. The model reproduces well the mean occurrence of ice clouds, while the ice water path, ice crystal radius, cloud optical depth and extinction are overestimated in terms of annual means and temperature dependent frequency histograms. Two distinct types of cirrus clouds are found: in-situ formed cirrus dominating at temperatures below -60°C and liquid-origin cirrus, dominating at temperatures warmer than -55°C. The latter form in anvils of deep convective clouds or by glaciation of mixed-phase clouds. They are associated with ice water contents of up to 0.1 g m-3 and extinctions of up to 0.1 km-1, while the in-situ formed cirrus are optically thinner and contain at least an order of magnitude less ice. The ice cloud properties do not differ significantly between the southern and the northern hemisphere. In-situ formed ice clouds are further divided into homogeneously and heterogeneously nucleated ones. The simulated liquid-origin ice crystals mainly form in convective outflow in large number concentrations, similar to in-situ homogeneously nucleated ice crystals. On the contrary, heterogeneously nucleated ice crystals are associated with smaller number concentrations. However, ice crystal aggregation and depositional growth smooth the differences between several formation mechanisms making the attribution to a specific ice nucleation mechanism challenging.

Combining laboratory results, numerical modeling, and in situ measurements to investigate the relative contributions of homogeneous and heterogeneous nucleation to ice formation in the tropical tropopause layer

NASA Astrophysics Data System (ADS)

Jensen, E. J.; Karcher, B.; Ueyama, R.; Pfister, L.; Bui, T. V.; Diskin, G. S.; DiGangi, J. P.; Woods, S.; Lawson, P.; Froyd, K. D.; Murphy, D. M.

2017-12-01

Laboratory experiments over the past decade have advanced our understanding of the physical state and ice nucleation efficacy of aerosols with atmospherically-relevant compositions at low temperatures. We use these laboratory results along with measurements of upper-tropospheric aerosol composition to develop a parameterization if the ice nuclei number, and activity dependence on ice supersaturation and temperature in the cold tropical tropopause layer (TTL, 13-18 km). We show that leading candidates for aerosol types serving as effective ice nuclei are glassy organic-containing aerosols, crystalline ammonium sulfate, and mineral dust. We apply the low-temperature heterogeneous ice nucleation parameterization in a detailed model of TTL transport and cirrus formation. The model treats heterogeneous ice nucleation and homogeneous freezing of aqueous aerosols, deposition growth and sublimation of ice crystals, and sedimentation of ice crystals. The model is driven by meteorological fields with high-frequency waves superimposed, and simulated cirrus microphysical properties are statistically compared with recent measurements of TTL cirrus microphysical properties and ice supersaturation from recent high-altitude aircraft campaigns. We show that effective ice nuclei concentrations on the order of 50-100/L can dominate over homogeneous freezing production of TTL cirrus ice crystals. Glassy organic-containing aerosols or crystalline ammonium sulfate could conceivably provide more abundant sources of ice nuclei, but the simulations indicate that high concentrations of effective IN would prevent observed occurrence of large supersaturations and high ice concentrations. We will also show the impact of heterogeneous ice nuclei on TTL cirrus microphysical properties and occurrence frequencies.

Lidar Measurements of Relative Humidity and Ice Supersaturation in the Upper Troposphere

NASA Technical Reports Server (NTRS)

Ferrare, Richard A.; Browell, Edward V.; Ismail, Syed; Brackett, Vincent G.; Clayton, Marian B.; Fenn, Marta; Heilman, Lorraine; Kooi, Susan A.; Turner, David D.; Mahoney, Michael J.

2000-01-01

We compute upper tropospheric relative humidity profiles using water vapor profiles measured by an airborne DIAL and a ground-based Raman lidar. LASE water vapor and MTP temperature profiles acquired from the NASA DC-8 aircraft during the recent Pacific Exploratory Mission Tropics B (PEM Tropics B) field mission in the tropical Pacific and the SAGE-III Ozone Loss and Validation Experiment (SOLVE) in the Arctic as well as water vapor profiles derived from the ground-based DOE ARM Southern Great Plains (SGP) CART Raman lidar are used. Comparisons of the lidar water vapor measurements with available in situ measurements show reasonable agreement for water vapor mixing ratios above 0.05 g/kg. Relative humidity frequency distributions computed using LASE data indicate that ice supersaturation occurred about 5-11% of the time when temperatures were below -35 C. While a higher frequency of ice supersaturation was observed during SOLVE, higher peak values of relative humidity were observed during PEM Tropics B. The relative humidity fields associated with cirrus clouds are also examined.

Radiatively driven stratosphere-troposphere interactions near the tops of tropical cloud clusters

NASA Technical Reports Server (NTRS)

Churchill, Dean D.; Houze, Robert A., Jr.

1990-01-01

Results are presented of two numerical simulations of the mechanism involved in the dehydration of air, using the model of Churchill (1988) and Churchill and Houze (1990) which combines the water and ice physics parameterizations and IR and solar-radiation parameterization with a convective adjustment scheme in a kinematic nondynamic framework. One simulation, a cirrus cloud simulation, was to test the Danielsen (1982) hypothesis of a dehydration mechanism for the stratosphere; the other was to simulate the mesoscale updraft in order to test an alternative mechanism for 'freeze-drying' the air. The results show that the physical processes simulated in the mesoscale updraft differ from those in the thin-cirrus simulation. While in the thin-cirrus case, eddy fluxes occur in response to IR radiative destabilization, and, hence, no net transfer occurs between troposphere and stratosphere, the mesosphere updraft case has net upward mass transport into the lower stratosphere.

Radon measurements in the lower tropical stratosphere - Evidence for rapid vertical transport and dehydration of tropospheric air

NASA Technical Reports Server (NTRS)

Kritz, Mark A.; Rosner, Stefan W.; Kelly, Kenneth K.; Loewenstein, Max; Chan, K. R.

1993-01-01

During the tropical experiment of NASA's Stratosphere-Troposphere Exchange Program (STEP), in situ radon and other trace constituent measurements were made aboard a NASA ER-2 high-altitude research aircraft to investigate the mechanisms of irreversible transfers from the troposphere into the tropical stratosphere. Observations made in and downwind of the cirrus shields of three large tropical cyclones and downwind of the cirrus anvil of a large cumulonimbus cloud cluster showed several clear instances of elevated radon activity occurring simultaneously with low total water mixing ratios. These observations are unambiguous evidence of an effective dehydration process, capable of reducing total water vapor mixing ratios to less than 2.5 ppmv, occurring in conjunction with troposphere-to-stratosphere transport and indicate that rapid localized convection, rather than slow regional mean motions, was responsible for the observed transports and associated with the accompanying dehydration. Radon activities measured in regions of active or recent troposphere-to-stratosphere transport were consistent with the 17 pCi/scm mean value needed to support the observed abundance of stratospheric 210 Pb.

Stratospheric Tracers of Atmospheric Transport (STRAT) Campaign: ER-2 Participation

NASA Technical Reports Server (NTRS)

Anderson, James G.

1999-01-01

The NASA Stratospheric Tracers of Atmospheric Transport (STRAT) mission was initiated to advance knowledge of the major transport mechanisms of the upper troposphere-lower stratosphere. This is the region of the atmosphere within which exchange processes take place that critically determine the response of the climate system and ozone distribution to changing conditions triggered by the release of chemicals at the surface. The mission series that extended from October 1995 to November 1997 was extremely successful. The scientific advances that emerged from that mission include analyses of- troposphere-to-stratosphere transport in the lowermost stratosphere from measurements of H2O, CO2, N2O, and O3; the effects of tropical cirrus clouds on the abundance of lower stratospheric ozone; the role of HO, in super- and subsonic aircraft exhaust plumes; and dehydration and denitrification in the arctic polar vortex during the 1995-96 winter.

Stratospheric Tracers of Atmospheric Transport (STRAT) Campaign: ER-2 Participation

NASA Technical Reports Server (NTRS)

Anderson, James G.

1995-01-01

The NASA Stratospheric Tracers of Atmospheric Transport (STRAT) mission was initiated to advance knowledge of the major transport mechanisms of the upper troposphere-lower stratosphere. This is the region of the atmosphere within which exchange processes take place that critically determine the response of the climate system and ozone distribution to changing conditions triggered by the release of chemicals at the surface. The mission series that extended from October 1995 to November 1997 was extremely successful. The scientific advances that emerged from that mission include analyses of: (1)troposphere-to-stratosphere transport in the lowermost stratosphere from measurements of H2O, CO2, N2O, and O3; (2) the effects of tropical cirrus clouds on the abundance of lower stratospheric ozone; and (3) the role of HO(x) in super- and subsonic aircraft exhaust plumes; and dehydration and denitrification in the arctic polar vortex during the 1995-96 winter.

A Study of Global Cirrus Cloud Morphology with AIRS Cloud-clear Radiances (CCRs)

NASA Technical Reports Server (NTRS)

Wu, Dong L.; Gong, Jie

2012-01-01

Version 6 (V6) AIRS cloud-clear radiances (CCR) are used to derive cloud-induced radiance (Tcir=Tb-CCR) at the infrared frequencies of weighting functions peaked in the middle troposphere. The significantly improved V 6 CCR product allows a more accurate estimation of the expected clear-sky radiance as if clouds are absent. In the case where strong cloud scattering is present, the CCR becomes unreliable, which is reflected by its estimated uncertainty, and interpolation is employed to replace this CCR value. We find that Tcir derived from this CCR method are much better than other methods and detect more clouds in the upper and lower troposphere as well as in the polar regions where cloud detection is particularly challenging. The cloud morphology derived from the V6 test month, as well as some artifacts, will be shown.

NASA/GSFC Scanning Raman Lidar Measurements of Water Vapor and Cirrus Clouds during WVIOP2000 and AFWEX

NASA Technical Reports Server (NTRS)

Whiteman, D. N.; Evans, K. D.; DiGirolamo, P.; Demoz, B. B.; Turner, D.; Comstock, J.; Ismail, S.; Ferrare, R. A.; Browell, E. V.; Goldsmith, J. E. M.;

First Light from the Far-Infrared Spectroscopy of the Troposphere (FIRST) Instrument

NASA Technical Reports Server (NTRS)

Mlynczak, Martin G.; Johnson, David G.; Latvakoski, Harri; Jucks, Kenneth; Watson, Mike; Bingham, Gail; Kratz, David P.; Traub, Wesley A.; Wellard, Stanley J.; Hyde, Charles R.;

CO2 lidar observations of Mount Pinatubo debris: FIRE 2 and longer-term measurements

NASA Technical Reports Server (NTRS)

Levinson, David H.; Post, Madison J.; Grund, Christian J.

1993-01-01

The volcanic debris in the stratosphere from the June 1991 eruption of Mt. Pinatubo first appeared over the NOAA Wave Propagation Laboratory (WPL) field site near Boulder, Colorado (40.15 N, 105.23 W), in July of 1991. The presence of the Pinatubo cloud has allowed us to characterize both the tropospheric and stratospheric aerosol backscatter using the NOAA/WPL CO2 Doppler lidar. The lidar has measured vertical backscatter profiles at lambda = 10.59 mu m for over a decade. Analysis of this dense set of profiles reveals the effects of atmospheric and microphysical processes during the buildup and decay of Mt. Pinatubo's clouds. Further information on the NOAA lidar, specifically calibrations using a hard target, can be found in Post and Cupp (1990). We present results of those measurements for June 15, 1991, through December 31, 1992. During that period of longer-term measurements, WPL took part in FIRE II (First ISCCP (International Satellite Cloud Climatology Project) Regional Experiment II), from November 12 through December 8, 1991, measuring vertical backscatter profiles almost daily. One of the mechanisms for purging stratospheric aerosols is tropopause folding, which occurs in cold-core extratropical cyclones. Tropospheric mass loading occurs during folding events which can substantially increase the amount of ice nuclei in the upper troposphere, and may affect the formation of cirrus in that region. Spring and fall are prominent times for tropopause folding events because of the migration of the subtropical and polar jet streams during the transition seasons. Sassen has suggested that the volcanic aerosols from Pinatubo played a role in the formation of cirrus during FIRE II, particularly during a period of moist subtropical flow on December 5-6, 1991.

Dehydration of the Upper Troposphere and Lower Stratosphere by Subvisible Cirrus Clouds Near the Tropical Tropopause

NASA Technical Reports Server (NTRS)

Jensen, Eric J.; Toon, Owen B.; Pfister, Leonhard; Selkirk, Henry B.

1996-01-01

The extreme dryness of the lower stratosphere is believed to be caused by freeze-drying of air as it enters the stratosphere through the cold tropical tropopause. Previous investigations have been focused on dehydration occurring at the tops of deep convective cloud systems, However, recent observations of a ubiquitous stratiform cirrus cloud layer near the tropical tropopause suggest the possibility of dehydration as air is slowly lifted by large-scale motions, In this study, we have evaluated this possibility using a detailed ice cloud model. Simulations of ice cloud formation in the temperature minima of gravity waves (wave periods of 1 - 2 hours) indicate that large numbers of ice crystals will likely form due to the low temperatures and rapid cooling. As a result, the crystals do not grow larger than about 10 microns, fallspeeds are no greater than a few cm/s, and little or no precipitation or dehydration occurs. However, ice cloud's formed by large-scale vertical motions (with lifetimes of a day or more) should have,fever crystals and more time for crystal sedimentation to occur, resulting in water vapor depletions as large as 1 ppmv near the tropopause. We suggest that gradual lifting near the tropical tropopause, accompanied by formation of thin cirrus, may account for the dehydration.

Lidar cirrus cloud retrieval - methodology and applications

NASA Astrophysics Data System (ADS)

Larroza, Eliane; Keckhut, Philippe; Nakaema, Walter; Brogniez, Gérard; Dubuisson, Philippe; Pelon, Jacques; Duflot, Valentin; Marquestaut, Nicolas; Payen, Guillaume

2016-04-01

In the last decades numerical modeling has experimented sensitive improvements on accuracy and capability for climate predictions. In the same time it has demanded the reduction of uncertainties related with the respective input parameters. In this context, high altitude clouds (cirrus) have attracted special attention for their role as radiative forcing. Also such clouds are associated with the vertical transport of water vapor from the surface to upper troposphere/lower stratosphere (URLS) in form of ice crystals with variability of concentration and morphology. Still cirrus formation can occur spatially and temporally in great part of the globe due to horizontal motion of air masses and circulations. Determining accurately the physical properties of cirrus clouds still represents a challenge. Especially the so-called subvisible cirrus clouds (optical depth inferior to 0.03) are invisible for space-based passive observations. On the other hand, ground based active remote sensing as lidar can be used to suppress such deficiency. Lidar signal can provide spatial and temporal high resolution to characterize physically (height, geometric thickness, mean temperature) and optically (optical depth, extinction-to-scattering ratio or lidar ratio, depolarization ratio) the cirrus clouds. This report describes the evolution of the methodology initially adopted to retrieval systematically the lidar ratio and the subsequent application on case studies and climatology on the tropical sites of the globe - São Paulo, Brazil (23.33 S, 46.44 W) and OPAR observatory at Ille de La Réunion (21.07 S, 55.38 W). Also is attempting a synergy between different instrumentations and lidar measurements: a infrared radiometer to estimate the kind of ice crystals compounding the clouds; CALIPSO satellite observations and trajectory model (HYSPLIT) for tracking air masses potentially responsible for the horizontal displacement of cirrus. This last approach is particularly interesting to understand the history of the cirrus clouds - time of residence in different altitudes, ageing process and possible phase changes. Finally the radiative transfer code FASDOM fed by ancillary meteorological and surface data is used to simulate brightness temperatures as measured by the infrared radiometer locate at the ground level in the OPAR laboratory.

Correlated k-distribution method for radiative transfer in climate models: Application to effect of cirrus clouds on climate

NASA Technical Reports Server (NTRS)

Lacis, A. A.; Wang, W. C.; Hansen, J. E.

1979-01-01

A radiative transfer method appropriate for use in simple climate models and three dimensional global climate models was developed. It is fully interactive with climate changes, such as in the temperature-pressure profile, cloud distribution, and atmospheric composition, and it is accurate throughout the troposphere and stratosphere. The vertical inhomogeneity of the atmosphere is accounted for by assuming a correlation of gaseous k-distributions of different pressures and temperatures. Line-by-line calculations are made to demonstrate that The method is remarkably accurate. The method is then used in a one-dimensional radiative-convective climate model to study the effect of cirrus clouds on surface temperature. It is shown that an increase in cirrus cloud cover can cause a significant warming of the troposphere and the Earth's surface, by the mechanism of an enhanced green-house effect. The dependence of this phenomenon on cloud optical thickness, altitude, and latitude is investigated.

Scanning Raman Lidar Measurements During the WVIOP2000 and AFWEX Field Experiments

NASA Technical Reports Server (NTRS)

Whiteman, David N.; Evans, K. D.; Berkoff, T. B.; Demoz, B. D.; DiGirolamo, P.; Smith, David E. (Technical Monitor)

2001-01-01

The NASA/Goddard Space Flight Center Scanning Raman Lidar (SRL) participated in the Water Vapor IOP 2000 (WVIOP2000) and ARM FIRE Water Vapor Experiment (AFWEX) at the DOE SGP CART site in northern Oklahoma. These experiments occurred during the period of September and December, 2000. The goals of both the WVIOP2000 and AFWEX were to better characterize the water vapor measurement capability of numerous sensors in the lower atmosphere and upper troposphere, respectively. The SRL received several hardware upgrades in anticipation of these experiments that permitted improved measurements of water vapor during the daytime and in the upper troposphere (UT). The daytime SRL water vapor error statistics were demonstrated a factor of 2-3 improvement compared to the permanently stationed CART Raman lidar (CARL). The performance of the SRL in the UT showed improvements as well. The technological upgrades that permitted these improved SRL measurements could also be implemented in the CARL system. Data examples demonstrating the new daytime and upper tropospheric measurement capability of the SRL will be shown at the meeting. In addition, preliminary analysis will be presented on several topics: 1) inter comparison of the water vapor measurements for several water vapor sensors including SRL, CARL, the NASA/Langley Lidar Atmospheric Sensing Experiment (LASE) flown onboard the NASA DC-8, in-situ sensors flown on the DC-8, and the Max Planck Institute Differential Absorption Lidar 2) comparison of cirrus cloud measurements using SRL and CARL and 3) case studies of meteorological events that occurred during the IOPs such as a cold frontal passage on the night of September 23.

Airborne In Situ and Ground-based Polarimetric Radar Measurements of Tropical Convection in Support of CRYSTAL-FACE

NASA Technical Reports Server (NTRS)

Poellot, Michael R.; Kucera, Paul A.

2004-01-01

This report describes the work performed by the University of North Dakota (UND) under NASA Grant NAG5-11509, titled Airborne In Situ and Ground-based Polarimetric Radar Measurements of Tropical Convection in Support of CRYSTAL-FACE. This work focused on the collection of data by two key platforms: the UND Citation II research aircraft and the NASA NPOL radar system. The CRYSTAL-FACE (C-F) mission addresses several key issues from the NASA Earth System Enterprise, including the variability of water in the atmosphere, the forcing provided by tropical cirrus and the response of the Earth system to this forcing. In situ measurements and radar observations of tropical convection, cirrus clouds and their environment are core elements of C-F. One of the primary issues that C-F is addressing is the relationship of tropical cirrus anvils to precipitating deep convection. The in situ measurements from C-F are being used to validate remote sensing of Earth-Atmosphere properties, increase our knowledge of upper tropospheric water vapor and its distribution, and increase our knowledge of tropical cirrus cloud morphology and composition. Radar measurements, especially polarimetric diversity observations available fiom the NASA NPOL radar, are providing essential information about the initiation, modulation, and dissipation of convective cores and the generation of associated anvils in tropical convection. Specifically, NPOL radar measurements contain information about convective intensity and its vertical structure for comparison with thermodynamic and kinematic environmental measurements observed from soundings. Because of the polarimetric diversity of MOL, statistics on bulk microphysical properties can be retrieved and compared to the other characteristics of convection and associated cirrus anvils. In summary, the central objectives of this proposal were to deploy the UND Citation research aircraft as an in situ sensing platform for this mission and to provide collaborative analyses of the recorded data and to deploy the NPOL radar to observe the characteristics of cirrus and parent convection.

Performance of operational radiosonde humidity sensors in direct comparison with a chilled mirror dew-point hygrometer and its climate implication

NASA Astrophysics Data System (ADS)

Wang, Junhong; Carlson, David J.; Parsons, David B.; Hock, Terrence F.; Lauritsen, Dean; Cole, Harold L.; Beierle, Kathryn; Chamberlain, Edward

2003-08-01

This study evaluates performance of humidity sensors in two widely used operational radiosondes, Vaisala and Sippican (formally VIZ), in comparison with a research quality, and potentially more accurate, chilled mirror dew-point hygrometer named ``Snow White''. A research radiosonde system carrying the Snow White (SW) hygrometer was deployed in the Oklahoma panhandle and at Dodge City, KS during the International H2O Project (IHOP_2002). A total of sixteen sondes were launched with either Vaisala RS80 or Sippican VIZ-B2 radiosondes on the same balloons. Comparisons of humidity data from the SW with Vaisala and Sippican data show that (a) Vaisala RS80-H agrees with the SW very well in the middle and lower troposphere, but has dry biases in the upper troposphere (UT), (b) Sippican carbon hygristor (CH) has time-lag errors throughout the troposphere and fails to respond to humidity changes in the UT, sometimes even in the middle troposphere, and (c) the SW can detect cirrus clouds near the tropopause and possibly estimate their ice water content (IWC). The failure of CH in the UT results in significant and artificial humidity shifts in radiosonde climate records at stations where a transition from VIZ to Vaisala radiosondes has occurred.

Raman scattering investigation of VOCs in interaction with ice particles

NASA Astrophysics Data System (ADS)

Facq, Sébastien; Oancea, Adriana; Focsa, Cristian; Chazallon, Bertrand

2010-05-01

Cirrus clouds that form in the Earth's upper troposphere (UT) are known to play a significant role in the radiation budget and climate [1]. These clouds that cover about 35% of the Earth's surface [2] are mainly composed of small ice particles that can provide surfaces for trace gas interactions [3]. Volatile Organic Compounds (VOCs) are present in relative high abundance in the UT [4][5]. They promote substantial sources of free OH radicals that are responsible for driving photochemical cycles in the atmosphere. Their presence can both influence the oxidizing capacity and the ozone budget of the atmosphere. VOCs can interact with ice particles via different trapping processes (adsorption, diffusion, freezing, and co-deposition, i.e., incorporation of trace gases during growing ice conditions) which can result in the perturbation of the chemistry and photochemistry of the UT. Knowledge of the incorporation processes of VOCs in ice particles is important in order to understand and predict their impact on the ice particles structure and reactivity and more generally on the cirrus cloud formation. This proceeds via the in-situ characterization of the ice condensed phase in a pressure and temperature range of the UT. An important mechanism of UT cirrus cloud formation is the heterogeneous ice freezing process. In this study, we examine and characterize the interaction of a VOC, i.e., ethanol (EtOH) with ice particles during freezing. Vibrational spectra of water O-H and EtOH C-H spectral regions are analysed using confocal micro-Raman spectroscopy. Information at the molecular level on the surface structure can be derived from accompanying changes observed in band shapes and vibrational mode frequencies. Depending of the EtOH content, different crystalline phases have been identified and compared to hydrates previously reported for the EtOH-water system. Particular attention is paid on the effect of EtOH aqueous solutions cooling rate and droplet sizes on the phases formed. These results are finally compared with those obtained by co-deposition trapping process. [1] K. Liou, "Influence of Cirrus Clouds on Weather and Climate Processes: A Global Perspective," Monthly Weather Review, vol. 114, Juin. 1986, pp. 1167-1199. [2] A. Heymsfield and R. Sabin, "Cirrus crystal nucleation by homogeneous freezing of solution droplets," Journal of the Atmospheric Sciences, vol. 46, 1989, pp. 2252-2264. [3] J.P.D. Abbatt, "Interactions of Atmospheric Trace Gases with Ice Surfaces: Adsorption and Reaction," Chemical Reviews, vol. 103, Déc. 2003, pp. 4783-4800. [4] H. Singh, Y. Chen, A. Staudt, D. Jacob, D. Blake, B. Heikes, et J. Snow, "Evidence from the Pacific troposphere for large global sources of oxygenated organic compounds," Nature, vol. 410, Avr. 2001, pp. 1078-1081. [5] H.B. Singh, M. Kanakidou, P.J. Crutzen, and D.J. Jacob, "High concentrations and photochemical fate of oxygenated hydrocarbons in the global troposphere," Nature, vol. 378, Nov. 1995, pp. 50-54.

On the Importance of High Frequency Gravity Waves for Ice Nucleation in the Tropical Tropopause Layer

NASA Technical Reports Server (NTRS)

Jensen, Eric J.

2016-01-01

Recent investigations of the influence of atmospheric waves on ice nucleation in cirrus have identified a number of key processes and sensitivities: (1) ice concentrations produced by homogeneous freezing are strongly dependent on cooling rates, with gravity waves dominating upper tropospheric cooling rates; (2) rapid cooling driven by high-frequency waves are likely responsible for the rare occurrences of very high ice concentrations in cirrus; (3) sedimentation and entrainment tend to decrease ice concentrations as cirrus age; and (4) in some situations, changes in temperature tendency driven by high-frequency waves can quench ice nucleation events and limit ice concentrations. Here we use parcel-model simulations of ice nucleation driven by long-duration, constant-pressure balloon temperature time series, along with an extensive dataset of cold cirrus microphysical properties from the recent ATTREX high-altitude aircraft campaign, to statistically examine the importance of high-frequency waves as well as the consistency between our theoretical understanding of ice nucleation and observed ice concentrations. The parcel-model simulations indicate common occurrence of peak ice concentrations exceeding several hundred per liter. Sedimentation and entrainment would reduce ice concentrations as clouds age, but 1-D simulations using a wave parameterization (which underestimates rapid cooling events) still produce ice concentrations higher than indicated by observations. We find that quenching of nucleation events by high-frequency waves occurs infrequently and does not prevent occurrences of large ice concentrations in parcel simulations of homogeneous freezing. In fact, the high-frequency variability in the balloon temperature data is entirely responsible for production of these high ice concentrations in the simulations.

Climate impact of anthropogenic aerosols on cirrus clouds

NASA Astrophysics Data System (ADS)

Penner, J.; Zhou, C.

2017-12-01

Cirrus clouds have a net warming effect on the atmosphere and cover about 30% of the Earth's area. Aerosol particles initiate ice formation in the upper troposphere through modes of action that include homogeneous freezing of solution droplets, heterogeneous nucleation on solid particles immersed in a solution, and deposition nucleation of vapor onto solid particles. However, the efficacy with which particles act to form cirrus particles in a model depends on the representation of updrafts. Here, we use a representation of updrafts based on observations of gravity waves, and follow ice formation/evaporation during both updrafts and downdrafts. We examine the possible change in ice number concentration from anthropogenic soot originating from surface sources of fossil fuel and biomass burning and from aircraft particles that have previously formed ice in contrails. Results show that fossil fuel and biomass burning soot aerosols with this version exert a radiative forcing of -0.15±0.02 Wm-2 while aircraft aerosols that have been pre-activated within contrails exert a forcing of -0.20±0.06 Wm-2, but it is possible to decrease these estimates of forcing if a larger fraction of dust particles act as heterogeneous ice nuclei. In addition aircraft aerosols may warm the climate if a large fraction of these particles act as ice nuclei. The magnitude of the forcing in cirrus clouds can be comparable to the forcing exerted by anthropogenic aerosols on warm clouds. This assessment could therefore support climate models with high sensitivity to greenhouse gas forcing, while still allowing the models to fit the overall historical temperature change.

Mie lidar and radiosonde observations at Gadanki (13.5°N, 79.2°E) during sudden stratospheric warming of 2009

NASA Astrophysics Data System (ADS)

Sridharan, S.; Raghunath, K.; Sathishkumar, S.; Nath, D.

2011-03-01

During a major sudden stratospheric warming event (21-27 January 2009), Mie-lidar observations at Gadanki (13.5°N, 79.2°E) show persistent occurrence of cirrus clouds. Outgoing long-wave radiation averaged for 70°E-90°E, decreases to a low value (170 W/m2) on 27 January 2009 over equator indicating deep convection. The zonal mean ERA-Interim data reveal large northward and upward circulation over equatorial upper troposphere. The latitude-longitude map of ERA-Interim zonal mean potential vorticity (PV) indicates two tongues of high PV emanating from polar latitudes and extending further down to equator. Radiosonde observations at Gadanki show the presence of ∼40% relative humidity at 11-13 km and lower tropopause temperature. It is inferred that the tropical circulation change due to PV intrusion leads to deep convection, which along with high humidity and low tropopause temperature leading to the formation of persistent cirrus clouds, the occurrence frequency of which is normally less during winter season over Gadanki.

LASE validation experiment: preliminary processing of relative humidity from LASE derived water vapor in the middle to upper troposphere

NASA Technical Reports Server (NTRS)

Brackett, Vincent G.; Ismail, Syed; Browell, Edward V.; Kooi, Susan A.; Clayton, Marian B.; Ferrare, Richard A.; Minnis, Patrick; Getzewich, Brian J.; Staszel, Jennifer

1998-01-01

Lidar Atmospheric Sensing Experiment (LASE) is the first fully engineered, autonomous airborne DIAL (Differentials Absorption Lidar) system to measure water vapor, aerosols, and clouds throughout the troposphere. This system uses a double-pulsed Ti:sapphire laser, which is pumped by a frequency-doubled flashlamp-pumped Nd: YAG laser, to transmit light in the 815 mn absorption band of water vapor. LASE operates by locking to a strong water vapor line and electronically tuning to any spectral position on the absorption line to choose the suitable absorption cross-section for optimum measurements over a range of concentrations in the atmosphere. During the LASE Validation Experiment, which was conducted over Wallops Island during September, 1995, LASE operated on either the strong water line for measurements in middle to upper troposphere, or on the weak water line for measurements made in the middle to lower troposphere including the boundary layer. Comparisons with water vapor measurements made by airborne dew point and frost point hygrometers, NASA/GSFC (Goddard Space Flight Center) Raman Lidar, and radiosondes showed the LASE water vapor mixing ratio measurements to have an accuracy of better than 6% or 0.01 g/kg, whichever is larger, throughout the troposphere. In addition to measuring water vapor mixing ratio profiles, LASE simultaneously measures aerosol backscattering profiles at the off-line wavelength near 815 nm from which atmospheric scattering ratio (ASR) profiles are calculated. ASR is defined as the ratio of total (aerosol + molecular) atmospheric scattering to molecular scattering. Assuming a region with very low aerosol loading can be identified, such as that typically found just below the tropopause, then the ASR can be determined. The ASR profiles are calculated by normalizing the scattering in the region containing enhanced aerosols to the expected scattering by the "clean" atmosphere at that altitude. Images of the total ASR clearly depict cloud regions, including multiple cloud layers, thin upper level cirrus, etc., throughout the troposphere. New data products that are being derived from the LASE aerosol and water measurements include: 1) aerosol extinction coefficient, 2) aerosol optical thickness, 3) precipitable water vapor, and 4) relative humidity (RH). These products can be compared with airborne in-situ, and ground and satellite remote sensing measurements,. This paper presents a preliminary examination of RH profiles in the middle to upper troposphere that are generated from LASE measured water vapor mixing ratio profiles coupled with rawinsonde profiles of temperature and pressure.

Stratospheric Tracers of Atmospheric Transport (STRAT) Campaign: ER-2 Participation

NASA Technical Reports Server (NTRS)

Anderson, James G.

1999-01-01

The NASA Stratospheric Tracers of Atmospheric Transport (STRAT) mission was initiated to advance knowledge of the major transport mechanisms of the upper troposphere-lower stratosphere. This is the region of the atmosphere within which exchange processes take place that critically determine the response of the climate system and ozone distribution to changing conditions triggered by the release of chemicals at the surface. The mission series that extended from October 1995 to November 1997 was extremely successful. The scientific advances that emerged from that mission include analyses of: (1) troposphere-to-stratosphere transport in the lowermost stratosphere from measurements of H2O, CO2, N2O, and O3; (2) the effects of tropical cirrus clouds on the abundance of lower stratospheric ozone; (3) the role of HO(sub x) in super- and subsonic aircraft exhaust plumes; and (4) dehydration and denitrification in the arctic polar vortex during the 1995-96 winter. The abstracts from published papers are included.

Convective Distribution of Tropospheric Ozone and Tracers in the Central American ITCZ Region: Evidence from Observations During TC4

NASA Technical Reports Server (NTRS)

Avery, Melody; Twohy, Cynthia; MCabe, David; Joiner, Joanna; Severance, Kurt; Atlas, Eliot; Blake, Donald; Bui, T. P.; Crounse, John; Dibb, Jack;

Assurance of MOZAIC/IAGOS relative humidity data quality by evaluating the Capacitive Hygrometer during airborne field studies

NASA Astrophysics Data System (ADS)

Neis, Patrick; Smit, Herman G. J.; Rohs, Susanne; Rolf, Christian; Krämer, Martina; Ebert, Volker; Buchholz, Bernhard; Bundke, Ulrich; Finger, Fanny; Klingebiel, Marcus; Petzold, Andreas

2015-04-01

Water vapour is a major parameter in weather prediction and climate research but the interaction between the water vapour in the upper troposphere and lowermost stratosphere (UT/LS) and tropopause dynamics are not well understood. A continuous measurement of upper tropospheric humidity (UTH) is difficult because the abundance of UTH is highly variable on spatial and temporal scales that cannot be resolved, neither by the global radiosondes network nor by satellites. Since 1994, data with high spatial and temporal resolution for relative humidity are provided by the in-situ measurements aboard civil passenger aircraft from the MOZAIC/IAGOS-programme (www.iagos.org). The data set emerging from this long-term observation effort builds the backbone of the ongoing in-situ UTH climatology and trend analyses. In order to assess the validity of the long-term water vapour data and its limitations, an analysis of the humidity data sets of two field campaigns is presented. The validation of applied measurement methods, i.e. the MOZAIC/IAGOS Capacitive Hygrometer, is valued on the basis of the aircraft campaigns CIRRUS-III (2006) and AIRTOSS-ICE (2013), where research-grade water vapour instruments were operated simultaneously to the MOZAIC/IAGOS Capacitive Hygrometers. The performance of the MOZAIC Capacitive Hygrometer (MCH; operated from 1994 to 2014 on MOZAIC aircraft) and the advanced IAGOS Capacitive Hygrometer (ICH; operated since 2011 on IAGOS aircraft) are explored in clear sky, in the vicinity of and inside cirrus clouds as a blind intercomparison to the research-grade water vapour instruments. From these intercomparisons the qualification of the Capacitive Hygrometer for the use in long-term observation programmes is successfully demonstrated and the continuation of high data quality is confirmed for the transition from MCH to ICH. In particular the Capacitive Hygrometer response time to changes in relative humidity could be determined for the full range of temperatures in the comparison against the research-grade instruments.

Contrail Coverage Over the USA Derived from NOAA and EOS Satellite Data

NASA Technical Reports Server (NTRS)

Palikonda, Rabindra; Minnis, Patrick; Duda, David P.

2004-01-01

Contrails, like natural cirrus clouds, can cause a warming of the Earth-atmospheric system by absorbing longwave radiation from the surface and lower troposphere and radiating additional radiation back to the surface. They can also produce some cooling of the surface during the daytime by reflecting some sunlight back to space. Recently, Minnis et al. (2004) determined from surface observations of cirrus cloud cover that the overall impact appears to be a warming that is consistent with theoretical calculations, at least over the United States of America (USA) and surrounding areas. This finding highlights the need to better understand the formation and persistence of contrails and their radiative properties. To better assess the climatic impact of contrails, it is essential to determine the variability of the contrail microphysical properties, their impact on the atmospheric radiation budget, and their relationship to the atmospheric state. To that end, this paper continues the analyses of Advanced Very High Resolution Radiometer (AVHRR) data from the NOAA-15 (N15), NOAA-16 (N16), and NOAA-17 (N17) satellites, Moderate Resolution Imaging Spectroradiometer (MODIS) data from the Terra and Aqua satellites. The combination of these satellites provides a relatively comprehensive coverage of the daily cycle of air traffic. Thus, it should be possible to use these data to help understand the impact of air traffic on the upper tropospheric humidity during the day as well as determine the local-time variability of contrail coverage. The results will be valuable for developing models of contrail effects and methods for mitigating the impact of aviation on climate.

Modification of cirrus clouds to reduce global warming

NASA Astrophysics Data System (ADS)

Mitchell, David L.; Finnegan, William

2009-10-01

Greenhouse gases and cirrus clouds regulate outgoing longwave radiation (OLR) and cirrus cloud coverage is predicted to be sensitive to the ice fall speed which depends on ice crystal size. The higher the cirrus, the greater their impact is on OLR. Thus by changing ice crystal size in the coldest cirrus, OLR and climate might be modified. Fortunately the coldest cirrus have the highest ice supersaturation due to the dominance of homogeneous freezing nucleation. Seeding such cirrus with very efficient heterogeneous ice nuclei should produce larger ice crystals due to vapor competition effects, thus increasing OLR and surface cooling. Preliminary estimates of this global net cloud forcing are more negative than -2.8 W m-2 and could neutralize the radiative forcing due to a CO2 doubling (3.7 W m-2). A potential delivery mechanism for the seeding material is already in place: the airline industry. Since seeding aerosol residence times in the troposphere are relatively short, the climate might return to its normal state within months after stopping the geoengineering experiment. The main known drawback to this approach is that it would not stop ocean acidification. It does not have many of the drawbacks that stratospheric injection of sulfur species has.

Effects of pre-existing ice crystals on cirrus clouds and comparison between different ice nucleation parameterizations with the Community Atmosphere Model (CAM5)

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

Shi, Xiangjun; Liu, Xiaohong; Zhang, Kai

In order to improve the treatment of ice nucleation in a more realistic manner in the Community Atmosphere Model version 5.3 (CAM5.3), the effects of pre-existing ice crystals on ice nucleation in cirrus clouds are considered. In addition, by considering the in-cloud variability in ice saturation ratio, homogeneous nucleation takes place spatially only in a portion of the cirrus cloud rather than in the whole area of the cirrus cloud. Compared to observations, the ice number concentrations and the probability distributions of ice number concentration are both improved with the updated treatment. The pre-existing ice crystals significantly reduce ice numbermore » concentrations in cirrus clouds, especially at mid- to high latitudes in the upper troposphere (by a factor of ~10). Furthermore, the contribution of heterogeneous ice nucleation to cirrus ice crystal number increases considerably. Besides the default ice nucleation parameterization of Liu and Penner (2005, hereafter LP) in CAM5.3, two other ice nucleation parameterizations of Barahona and Nenes (2009, hereafter BN) and Kärcher et al. (2006, hereafter KL) are implemented in CAM5.3 for the comparison. In-cloud ice crystal number concentration, percentage contribution from heterogeneous ice nucleation to total ice crystal number, and pre-existing ice effects simulated by the three ice nucleation parameterizations have similar patterns in the simulations with present-day aerosol emissions. However, the change (present-day minus pre-industrial times) in global annual mean column ice number concentration from the KL parameterization (3.24 × 10 6 m -2) is less than that from the LP (8.46 × 10 6 m -2) and BN (5.62 × 10 6 m -2) parameterizations. As a result, the experiment using the KL parameterization predicts a much smaller anthropogenic aerosol long-wave indirect forcing (0.24 W m -2) than that using the LP (0.46 W m −2) and BN (0.39 W m -2) parameterizations.« less

Effects of pre-existing ice crystals on cirrus clouds and comparison between different ice nucleation parameterizations with the Community Atmosphere Model (CAM5)

DOE PAGES

Shi, Xiangjun; Liu, Xiaohong; Zhang, Kai

2015-02-11

In order to improve the treatment of ice nucleation in a more realistic manner in the Community Atmosphere Model version 5.3 (CAM5.3), the effects of pre-existing ice crystals on ice nucleation in cirrus clouds are considered. In addition, by considering the in-cloud variability in ice saturation ratio, homogeneous nucleation takes place spatially only in a portion of the cirrus cloud rather than in the whole area of the cirrus cloud. Compared to observations, the ice number concentrations and the probability distributions of ice number concentration are both improved with the updated treatment. The pre-existing ice crystals significantly reduce ice numbermore » concentrations in cirrus clouds, especially at mid- to high latitudes in the upper troposphere (by a factor of ~10). Furthermore, the contribution of heterogeneous ice nucleation to cirrus ice crystal number increases considerably. Besides the default ice nucleation parameterization of Liu and Penner (2005, hereafter LP) in CAM5.3, two other ice nucleation parameterizations of Barahona and Nenes (2009, hereafter BN) and Kärcher et al. (2006, hereafter KL) are implemented in CAM5.3 for the comparison. In-cloud ice crystal number concentration, percentage contribution from heterogeneous ice nucleation to total ice crystal number, and pre-existing ice effects simulated by the three ice nucleation parameterizations have similar patterns in the simulations with present-day aerosol emissions. However, the change (present-day minus pre-industrial times) in global annual mean column ice number concentration from the KL parameterization (3.24 × 10 6 m -2) is less than that from the LP (8.46 × 10 6 m -2) and BN (5.62 × 10 6 m -2) parameterizations. As a result, the experiment using the KL parameterization predicts a much smaller anthropogenic aerosol long-wave indirect forcing (0.24 W m -2) than that using the LP (0.46 W m −2) and BN (0.39 W m -2) parameterizations.« less

The Response of a Spectral General Circulation Model to Refinements in Radiative Processes.

NASA Astrophysics Data System (ADS)

Ramanathan, V.; Pitcher, Eric J.; Malone, Robert C.; Blackmon, Maurice L.

1983-03-01

We present here results and analyses of a series of numerical experiments performed with a spectral general circulation model (GCM). The purpose of the GCM experiments is to examine the role of radiation/cloud processes in the general circulation of the troposphere and stratosphere. The experiments were primarily motivated by the significant improvements in the GCM zonal mean simulation as refinements were made in the model treatment of clear-sky radiation and cloud-radiative interactions. The GCM with the improved cloud/radiation model is able to reproduce many observed features, such as: a clear separation between the wintertime tropospheric jet and the polar night jet; winter polar stratospheric temperatures of about 200 K; interhemispheric and seasonal asymmetries in the zonal winds.In a set of sensitivity experiments, we have stripped the cloud/radiation model of its improvements, the result being a significant degradation of the zonal mean simulations by the GCM. Through these experiments we have been able to identify the processes that are responsible for the improved GCM simulations: (i) careful treatment of the upper boundary condition for O3 solar heating; (ii) temperature dependence of longwave cooling by CO2 15 m bands., (iii) vertical distribution of H2O that minimizes the lower stratospheric H2O longwave cooling; (iv) dependence of cirrus emissivity on cloud liquid water content.Comparison of the GCM simulations, with and without the cloud/radiation improvements, reveals the nature and magnitude of the following radiative-dynamical interactions: (i) the temperature decrease (due to errors in radiative heating) within the winter polar stratosphere is much larger than can be accounted for by purely radiative adjustment; (ii) the role of dynamics in maintaining the winter polar stratosphere thermal structure is greatly diminished in the GCM with the degraded treatment of radiation; (iii) the radiative and radiative-dynamical response times of the atmosphere vary from periods of less than two weeks in the lower troposphere to roughly three months in the polar lower stratosphere; (iv) within the stratosphere, the radiative response times vary significantly with temperature, with the winter polar values larger than the summer polar values by as much as a factor of 2.5.Cirrus clouds, if their emissivities are arbitrarily prescribed to be black, unrealistically enhance the radiative cooling of the polar troposphere above 8 km. This results in a meridional temperature gradient much stronger than that which is observed. We employ a more realistic parameterization that accounts for the non-blackness of cirrus, and we describe the resulting improvements in the model simulation of zonal winds, temperatures, and radiation budget.

Overview of MPLNET Version 3 Cloud Detection

NASA Technical Reports Server (NTRS)

Lewis, Jasper R.; Campbell, James; Welton, Ellsworth J.; Stewart, Sebastian A.; Haftings, Phillip

2016-01-01

The National Aeronautics and Space Administration Micro Pulse Lidar Network, version 3, cloud detection algorithm is described and differences relative to the previous version are highlighted. Clouds are identified from normalized level 1 signal profiles using two complementary methods. The first method considers vertical signal derivatives for detecting low-level clouds. The second method, which detects high-level clouds like cirrus, is based on signal uncertainties necessitated by the relatively low signal-to-noise ratio exhibited in the upper troposphere by eye-safe network instruments, especially during daytime. Furthermore, a multitemporal averaging scheme is used to improve cloud detection under conditions of a weak signal-to-noise ratio. Diurnal and seasonal cycles of cloud occurrence frequency based on one year of measurements at the Goddard Space Flight Center (Greenbelt, Maryland) site are compared for the new and previous versions. The largest differences, and perceived improvement, in detection occurs for high clouds (above 5 km, above MSL), which increase in occurrence by over 5%. There is also an increase in the detection of multilayered cloud profiles from 9% to 19%. Macrophysical properties and estimates of cloud optical depth are presented for a transparent cirrus dataset. However, the limit to which the cirrus cloud optical depth could be reliably estimated occurs between 0.5 and 0.8. A comparison using collocated CALIPSO measurements at the Goddard Space Flight Center and Singapore Micro Pulse Lidar Network (MPLNET) sites indicates improvements in cloud occurrence frequencies and layer heights.

Internally mixed sulfate and organic particles as potential ice nuclei in the tropical tropopause region

PubMed Central

Tolbert, Margaret A.

2010-01-01

Cirrus clouds are ubiquitous in the tropical tropopause region and play a major role in the Earth’s climate. Any changes to cirrus abundance due to natural or anthropogenic influences must be considered to evaluate future climate change. The detailed impact of cirrus clouds on climate depends on ice particle number, size, morphology, and composition. These properties depend in turn on the nucleation mechanism of the ice particles. Although it is often assumed that ice nucleates via a homogeneous mechanism, recent work points to the possibility that heterogeneous ice nucleation is important in the tropical tropopause region. However, there are very few studies of depositional ice nucleation on the complex types of particles likely to be found in this region of the atmosphere. Here, we use a unique method to probe depositional ice nucleation on internally mixed ammonium sulfate/palmitic acid particles, namely optical microscopy coupled with Raman microscopy. The deliquescence and efflorescence phase transitions of the mixed particles were first studied to gain insight into whether the particles are likely to be liquid or solid in the tropical tropopause region. The ice nucleating ability of the particles was then measured under typical upper tropospheric conditions. It was found that coating the particles with insoluble palmitic acid had little effect on the deliquescence, efflorescence, or ice nucleating ability of ammonium sulfate. Additional experiments involving Raman mapping provide new insights into how the composition and morphology of mixed particles impact their ability to nucleate ice. PMID:20388912

Coincident Occurrences of Tropical Individual Cirrus Clouds and Deep Convective Systems Derived from TRMM Observations

NASA Technical Reports Server (NTRS)

Lin, Bing; Xu, Kuan-Man; Minnis, Patrick; Wielicki, Bruce A.; Hu, Yongxiang; Chambers, Lin; Fan, Alice; Sun, Wenbo

2007-01-01

Measurements of cloud properties and atmospheric radiation taken between January and August 1998 by the Tropical Rainfall Measuring Mission (TRMM) satellite were used to investigate the effect of spatial and temporal scales on the coincident occurrences of tropical individual cirrus clouds (ICCs) and deep convective systems (DCSs). It is found that there is little or even negative correlation between instantaneous occurrences of ICC and DCS in small areas, in which both types of clouds cannot grow and expand simultaneously. When spatial and temporal domains are increased, ICCs become more dependent on DCSs due to the origination of many ICCs from DCSs and moisture supply from the DCS in the upper troposphere for the ICCs to grow, resulting in significant positive correlation between the two types of tropical high clouds in large spatial and long temporal scales. This result may suggest that the decrease of tropical high clouds with SST from model simulations is likely caused by restricted spatial domains and limited temporal periods. Finally, the radiative feedback due to the change in tropical high cloud area coverage with sea surface temperature appears small and about -0.14 W/sq m per degree Kelvin.

3D reconstruction of tropospheric cirrus clouds by stereovision system

NASA Astrophysics Data System (ADS)

Nadjib Kouahla, Mohamed; Moreels, Guy; Seridi, Hamid

2016-07-01

A stereo imaging method is applied to measure the altitude of cirrus clouds and provide a 3D map of the altitude of the layer centroid. They are located in the high troposphere and, sometimes in the lower stratosphere, between 6 and 10 km high. Two simultaneous images of the same scene are taken with Canon cameras (400D) in two sites distant of 37 Km. Each image processed in order to invert the perspective effect and provide a satellite-type view of the layer. Pairs of matched points that correspond to a physical emissive point in the common area are identified in calculating a correlation coefficient (ZNCC: Zero mean Normalized Cross-correlation or ZSSD: as Zero mean Sum of Squared Differences). This method is suitable for obtaining 3D representations in the case of low-contrast objects. An observational campaign was conducted in June 2014 in France. The images were taken simultaneously at Marnay (47°17'31.5" N, 5°44'58.8" E; altitude 275 m) 25 km northwest of Besancon and in Mont poupet (46°58'31.5" N, 5°52'22.7" E; altitude 600 m) southwest of Besancon at 43 km. 3D maps of the Natural cirrus clouds and artificial like "aircraft trails" are retrieved. They are compared with pseudo-relief intensity maps of the same region. The mean altitude of the cirrus barycenter is located at 8.5 ± 1km on June 11.

3D reconstruction of tropospheric cirrus clouds

NASA Astrophysics Data System (ADS)

Kouahla, M. N.; Faivre, M.; Moreels, G.; Seridi, H.

2016-10-01

In this paper, we present a series of results from stereo-imagery of cirrus clouds in the troposphere. These clouds are either of natural origin or are created by aircraft exhausts. They are presently considered to be a major cause for the climate change. Two observation campaigns were conducted in France in 2013 and 2014. The observing sites were located in Marnay (47°17‧31.5″ N, 5°44‧58.8″ E; altitude 275 m) and in Mont Poupet (46°58‧31.5″ N, 5°52‧22.7″ E; altitude 600 m). The distance between both sites was 36 km. We used numeric CMOS photographic cameras. The image processing sequence included a contrast enhancement and a perspective inversion to obtain a satellite-type view. Finally, the triangulation procedure was used in an area that is a common part of both fields of view.

Mineral dust: observations of emission events and modeling of transport to the upper troposphere

NASA Astrophysics Data System (ADS)

Peter, T.; Wiacek, A.; Taddeo, M.

2009-04-01

The present study explores differences between mineral dust emission events in West African and Asian (Taklimakan) deserts, focusing on the availability of bare mineral dust ice nuclei for interactions with cirrus clouds without previous processing or washout by liquid water clouds. One-week trajectory calculations with high-resolution ECMWF fields are used to track transported (Lagrangian) relative humidities with respect to liquid water and ice, allowing to estimate the formation of liquid, mixed-phase and ice clouds. Transport trajectories can reasonably be assumed to carry dust with them throughout the year, except for the months of December-February, which are quiescent with respect to dust emission in both regions. Practically none of the simulated air parcels reach regions where homogeneous nucleation can take place (T < -35°C) along trajectories that have not experienced water saturation first, i.e. it is very unlikely that mineral dust particles could be a serious competitor for homogeneous nucleation during the formation of high, cold cirrus clouds. For the temperature region between -35°C < T < 0°C, i.e. in air parcels exhibiting necessary conditions for warmer ice clouds at lower altitudes, a small but significant number of air parcels are found to follow trajectories where RHw < 100% and RHi > 100% are simultaneously maintained. However, the potential for such low ice clouds originating from the Taklimakan desert is greater than that of the Sahara by a factor of 4-6. The implication is that although the Sahara is by far the biggest source of dust in the world, the much smaller Taklimakan desert in China's Tarim Basin may be of greater importance as a source of ice nuclei affecting cirrus cloud formation. This is likely the result of several meteorological factors, including the complex regional topography combined with the higher altitude of Taklimakan dust emissions and, on the synoptic scale, the higher altitude of potential temperature levels in the free troposphere at mid-latitudes than in the tropics. Finally, the very active Bodélé source region in Africa and the Gobi Desert in Asia will also be addressed.

Real-Time Prediction of Tropical Cyclone Intensity Using COAMPS-TC

DTIC Science & Technology

2012-01-01

tropospheric (UT) cloud fields (i.e., cirrus clouds) long after the initial eruption cycle from gradual particle settling and re-entrainment back into the... troposphere . Volcanic sul- fur dioxide and hydrogen sulfide vapor molecules are photo-oxidized in the LS, forming gaseous sulphuric acid, which in...concentration over the eastern United States at 1815 UTC on the 17th shown in Fig. 5(a), derived from NASA Ozone Monitoring Instrument (OMI) measurements

Constraints Pb-210 and Be-7 on Wet Deposition and Transport in a Global Three-Dimensional Chemical Tracer Model Driven by Assimilated Meteorological Fields

NASA Technical Reports Server (NTRS)

Liu, Hong-Yu; Jacob, Daniel J.; Bey, Isabelle; Yantosca, Robert M.

2001-01-01

The atmospheric distributions of the aerosol tracers Pb-210 and Be-7 are simulated with a global three-dimensional model driven by assimilated meteorological observations for 1991-1996 from the NASA Goddard Earth Observing System (GEOSl). The combination of terrigenic Pb-210 and cosmogenic Be-7 provides a sensitive test of wet deposition and vertical transport in the model. Our simulation of moist transport and removal includes scavenging in wet convective updrafts (40% scavenging efficiency per kilometer of updraft), midlevel entrainment and detrainment, first-order rainout and washout from both convective anvils and large-scale precipitation, and cirrus precipitation. Observations from surface sites in specific years are compared to model results for the corresponding meteorological years, and observations from aircraft missions over the Pacific are compared to model results for the days of the flights. Initial simulation of Be-7 showed that cross-tropopause transport in the GEOSl meteorological fields is too fast by a factor of 3-4. We adjusted the stratospheric Be-7 source to correct the tropospheric simulation. Including this correction, we find that the model gives a good simulation of observed Pb-210 and Be-7 concentrations and deposition fluxes at surface sites worldwide, with no significant global bias and with significant success in reproducing the observed latitudinal and seasonal distributions. We achieve several improvements over previous models; in particular, we reproduce the observed Be-7 minimum in the tropics and show that its simulation is sensitive to rainout from convective anvils. Comparisons with aircraft observations up to 12-km altitude suggest that cirrus precipitation could be important for explaining the low concentrations in the middle and upper troposphere.

Aqueous aerosol may build up large upper tropospheric ice supersaturation

NASA Astrophysics Data System (ADS)

Bogdan, Anatoli; Molina, Mario J.

2010-05-01

Keywords: ice supersaturation, upper tropospheric cirrus clouds, freezing of aqueous aerosol. Observations often reveal enhanced and persistent upper tropospheric (UT) ice supersaturation, Si up to 100%, independently of whether cirrus ice clouds are present or not (Krämer et al., 2009; Lawson et al., 2008). However, a water activity criterion (WAC) (Koop et al., 2000) does not allow the formation of Si > ~67% by the homogeneous freezing of aqueous droplets even at the lowest atmospheric temperature of ~185 K. For aqueous aerosol the WAC predicts the existence of a so called homogeneous ice nucleation threshold which, being expressed as Si, is between ~52 and 67% in the temperature range of ~220 - 185 K. The nature of the formation of large Si remains unclear. Since water vapor is the dominant greenhouse gas it is important to know the nature of the accumulation and persistence of water vapor in the UT. We studied the freezing behavior of micrometer-scaled 3-, 4-, and 5-component droplets, which contain different weight fractions of H2O, H2SO4, HNO3, (NH4)2SO4, (NH4)HSO4, NH4NO3, and (NH4)3H(SO4)2. The study was performed between 133 and 278 K at cooling rates of 3, 0.1, and 0.05 K/min using differential scanning calorimetry (DSC) (Bogdan and Molina, 2010). The cooling rates of 0.1 and 0.05 K/min (6 and 3 K/h) are similar to the smallest reported synoptic temperature change of ~2 K/h (Carslaw et al., 1998). Using the measured freezing temperature of ice, Ti, and the thermodynamic E-AIM model of the system of H+ - NH4+ - SO42-- NO3-- H2O (Clegg et al., 1998), we calculated the corresponding clear-sky Si which would be built up immediately prior to the formation of ice cirrus clouds by the homogeneous freezing of aqueous aerosol of similar composition. We found that our calculated values of Si are both larger and smaller than the homogeneous ice nucleation threshold. For example, for the droplets of compositions of 15/10 and 20/10 wt % (NH4)3H(SO4)2/H2SO4, which freeze at 194 and 186 K, respectively, the calculated clear-sky Si can exceed 80%. Although our Si values are smaller than the largest observed value of Si ≈ 100%, they are nevertheless larger than the Si ≈ 67% predicted by the WAC at 185 K. Our results can give an impetus for the study of whether multi-component aqueous aerosol, which besides inorganic components also contains organics, may produce the observed Si ≈ 100%. Krämer, M., Schiller, C., Afchine, A., Bauer, R., Gensch, I., Mangold, A.., Schlicht, S., Spelten, N., Sitnikov, N., Borrmann, S., de Reus, M., Spichtinger, P. (2009), Atmos. Chem. Phys. 9, 3505. Lawson, R. P., Pilson, B., Baker, B., Mo, Q., Jensen, E., Pfister, L., Bui, P. (2008), Atmos. Chem. Phys. 8, 1609. Koop, T., Luo, B., Tsias, A., Peter, T. (2000), Nature, 406, 611. Bogdan, A. and Moilna, M. J. (2010), J. Phys. Chem. A (Published online: 5 February). Carslaw, K. S., Wirth, M., Tsias, A., Luo, B. P., Dörnbrack, A., Leutbecher, M., Volkert, H., Renger, W., Bacmeister, J. T., Peter, T. (1998), J. Geophys. Res. 103, 5785. Clegg, S. L., Brimblecombe, P., Wexler, A. S. (1998), J. Phys. Chem. A 102, 2137.

A Mission to Observe Ice in Clouds from Space

NASA Technical Reports Server (NTRS)

Ackerman, S.; O'CStarr, D.; Skofronick-Jackson, G.; Evans, F.; Wang, J. R.; Racette, P.; Norris, P.; daSilva, A.; Soden, B.

2006-01-01

To date there have been multiple satellite missions to observe and retrieve cloud top properties and the liquid in, and precipitation from, clouds. There are currently a few missions that attempt to measure cloud ice properties as a byproduct of other observations. However, we do not yet quantitatively understand the processes that control the water budget of the upper troposphere where ice is the predominant phase, and how these processes are linked to precipitation processes and the radiative energy budget. The ice in clouds either melts into rain or is detrained, and persists, as cirrus clouds affecting the hydrological and energy cycle, respectively. Fully modeling the Earth's climate and improving weather and climate forecasts requires accurate satellite measurements of various cloud properties at the temporal and spatial scales of cloud processes. The uncertainty in knowledge of these ice characteristics is reflected in the large discrepancies in model simulations of the upper tropospheric water budget. Model simulations are sensitive to the partition of ice between precipitation and outflow processes, i.e., to the parameterization of ice clouds and ice processes. This presentation will describe the Submillimeter-wave InfraRed Ice Cloud Experiment (SIRICE) concept, a satellite mission designed to acquire global Earth radiance measurements in the infrared and submillimeter-wave region (183-874 GHz). If successful, this mission will bridge the measurement gap between microwave sounders and shorter-wavelength infrared and visible sensors. The brightness temperatures at submillimeter-wave frequencies are especially sensitive to cirrus ice particle sizes (because they are comparable to the wavelength). This allows for more accurate ice water path estimates when multiple channels are used to probe into the cloud layers. Further, submillimeter wavelengths offer simplicity in the retrieval algorithms because they do not probe into the liquid and near surface portions of clouds, thus requiring only one term of the radiative transfer equation (ice scattering) to relate brightness temperatures to ice. Scientific justification and the SIRICE approach to measuring ice water path and particle size that span a range encompassing both the hydrologically active and radiatively active components of cloud systems will be presented.

Sensitivity of Homogeneous Ice Nucleation to Aerosol Perturbations and Its Implications for Aerosol Indirect Effects Through Cirrus Clouds

NASA Astrophysics Data System (ADS)

Liu, X.; Shi, X.

2018-02-01

The magnitude and sign of anthropogenic aerosol impacts on cirrus clouds through ice nucleation are still very uncertain. In this study, aerosol sensitivity (ηα), defined as the sensitivity of the number concentration (Ni) of ice crystals formed from homogeneous ice nucleation to aerosol number concentration (Na), is examined based on simulations from a cloud parcel model. The model represents the fundamental process of ice crystal formation that results from homogeneous nucleation. We find that the geometric dispersion (σ) of the aerosol size distribution used in the model is a key factor for ηα. For a monodisperse size distribution, ηα is close to zero in vertical updrafts (V < 50 cm s-1) typical of cirrus clouds. However, ηα increases to 0.1-0.3 (i.e., Ni increases by a factor of 1.3-2.0 for a tenfold increase in Na) if aerosol particles follow lognormal size distributions with a σ of 1.6-2.3 in the upper troposphere. By varying the input aerosol and environmental parameters, our model reproduces a large range of ηα values derived from homogeneous ice nucleation parameterizations widely used in global climate models (GCMs). The differences in ηα from these parameterizations can translate into a range of anthropogenic aerosol longwave indirect forcings through cirrus clouds from 0.05 to 0.36 W m-2 with a GCM. Our study suggests that a larger ηα (0.1-0.3) is more plausible and the homogeneous nucleation parameterizations should include a realistic aerosol size distribution to accurately quantify anthropogenic aerosol indirect effects.

Do detailed simulations with size-resolved microphysics reproduce basic features of observed cirrus ice size distributions?

NASA Astrophysics Data System (ADS)

Fridlind, A. M.; Atlas, R.; van Diedenhoven, B.; Ackerman, A. S.; Rind, D. H.; Harrington, J. Y.; McFarquhar, G. M.; Um, J.; Jackson, R.; Lawson, P.

2017-12-01

It has recently been suggested that seeding synoptic cirrus could have desirable characteristics as a geoengineering approach, but surprisingly large uncertainties remain in the fundamental parameters that govern cirrus properties, such as mass accommodation coefficient, ice crystal physical properties, aggregation efficiency, and ice nucleation rate from typical upper tropospheric aerosol. Only one synoptic cirrus model intercomparison study has been published to date, and studies that compare the shapes of observed and simulated ice size distributions remain sparse. Here we amend a recent model intercomparison setup using observations during two 2010 SPARTICUS campaign flights. We take a quasi-Lagrangian column approach and introduce an ensemble of gravity wave scenarios derived from collocated Doppler cloud radar retrievals of vertical wind speed. We use ice crystal properties derived from in situ cloud particle images, for the first time allowing smoothly varying and internally consistent treatments of nonspherical ice capacitance, fall speed, gravitational collection, and optical properties over all particle sizes in our model. We test two new parameterizations for mass accommodation coefficient as a function of size, temperature and water vapor supersaturation, and several ice nucleation scenarios. Comparison of results with in situ ice particle size distribution data, corrected using state-of-the-art algorithms to remove shattering artifacts, indicate that poorly constrained uncertainties in the number concentration of crystals smaller than 100 µm in maximum dimension still prohibit distinguishing which parameter combinations are more realistic. When projected area is concentrated at such sizes, the only parameter combination that reproduces observed size distribution properties uses a fixed mass accommodation coefficient of 0.01, on the low end of recently reported values. No simulations reproduce the observed abundance of such small crystals when the projected area is concentrated at larger sizes. Simulations across the parameter space are also compared with MODIS collection 6 retrievals and forward simulations of cloud radar reflectivity and mean Doppler velocity. Results motivate further in situ and laboratory measurements to narrow parameter uncertainties in models.

Laser-induced plasma cloud interaction and ice multiplication under cirrus cloud conditions

PubMed Central

Leisner, Thomas; Duft, Denis; Möhler, Ottmar; Saathoff, Harald; Schnaiter, Martin; Henin, Stefano; Stelmaszczyk, Kamil; Petrarca, Massimo; Delagrange, Raphaëlle; Hao, Zuoqiang; Lüder, Johannes; Petit, Yannick; Rohwetter, Philipp; Kasparian, Jérôme; Wolf, Jean-Pierre; Wöste, Ludger

2013-01-01

Potential impacts of lightning-induced plasma on cloud ice formation and precipitation have been a subject of debate for decades. Here, we report on the interaction of laser-generated plasma channels with water and ice clouds observed in a large cloud simulation chamber. Under the conditions of a typical storm cloud, in which ice and supercooled water coexist, no direct influence of the plasma channels on ice formation or precipitation processes could be detected. Under conditions typical for thin cirrus ice clouds, however, the plasma channels induced a surprisingly strong effect of ice multiplication. Within a few minutes, the laser action led to a strong enhancement of the total ice particle number density in the chamber by up to a factor of 100, even though only a 10−9 fraction of the chamber volume was exposed to the plasma channels. The newly formed ice particles quickly reduced the water vapor pressure to ice saturation, thereby increasing the cloud optical thickness by up to three orders of magnitude. A model relying on the complete vaporization of ice particles in the laser filament and the condensation of the resulting water vapor on plasma ions reproduces our experimental findings. This surprising effect might open new perspectives for remote sensing of water vapor and ice in the upper troposphere. PMID:23733936

Evaluation of UT/LS hygrometer accuracy by intercomparison during the NASA MACPEX mission.

PubMed

Rollins, A W; Thornberry, T D; Gao, R S; Smith, J B; Sayres, D S; Sargent, M R; Schiller, C; Krämer, M; Spelten, N; Hurst, D F; Jordan, A F; Hall, E G; Vömel, H; Diskin, G S; Podolske, J R; Christensen, L E; Rosenlof, K H; Jensen, E J; Fahey, D W

2014-02-27

Acquiring accurate measurements of water vapor at the low mixing ratios (< 10 ppm) encountered in the upper troposphere and lower stratosphere (UT/LS) has proven to be a significant analytical challenge evidenced by persistent disagreements between high-precision hygrometers. These disagreements have caused uncertainties in the description of the physical processes controlling dehydration of air in the tropical tropopause layer and entry of water into the stratosphere and have hindered validation of satellite water vapor retrievals. A 2011 airborne intercomparison of a large group of in situ hygrometers onboard the NASA WB-57F high-altitude research aircraft and balloons has provided an excellent opportunity to evaluate progress in the scientific community toward improved measurement agreement. In this work we intercompare the measurements from the Midlatitude Airborne Cirrus Properties Experiment (MACPEX) and discuss the quality of agreement. Differences between values reported by the instruments were reduced in comparison to some prior campaigns but were nonnegligible and on the order of 20% (0.8 ppm). Our analysis suggests that unrecognized errors in the quantification of instrumental background for some or all of the hygrometers are a likely cause. Until these errors are understood, differences at this level will continue to somewhat limit our understanding of cirrus microphysical processes and dehydration in the tropical tropopause layer.

Evaluation of UT/LS hygrometer accuracy by intercomparison during the NASA MACPEX mission

PubMed Central

Rollins, A. W.; Thornberry, T. D.; Gao, R. S.; Smith, J. B.; Sayres, D. S.; Sargent, M. R.; Schiller, C.; Krämer, M.; Spelten, N.; Hurst, D. F.; Jordan, A. F.; Hall, E. G.; Vömel, H.; Diskin, G. S.; Podolske, J. R.; Christensen, L. E.; Rosenlof, K. H.; Jensen, E. J.; Fahey, D. W.

2017-01-01

Acquiring accurate measurements of water vapor at the low mixing ratios (< 10 ppm) encountered in the upper troposphere and lower stratosphere (UT/LS) has proven to be a significant analytical challenge evidenced by persistent disagreements between high-precision hygrometers. These disagreements have caused uncertainties in the description of the physical processes controlling dehydration of air in the tropical tropopause layer and entry of water into the stratosphere and have hindered validation of satellite water vapor retrievals. A 2011 airborne intercomparison of a large group of in situ hygrometers onboard the NASA WB-57F high-altitude research aircraft and balloons has provided an excellent opportunity to evaluate progress in the scientific community toward improved measurement agreement. In this work we intercompare the measurements from the Midlatitude Airborne Cirrus Properties Experiment (MACPEX) and discuss the quality of agreement. Differences between values reported by the instruments were reduced in comparison to some prior campaigns but were nonnegligible and on the order of 20% (0.8 ppm). Our analysis suggests that unrecognized errors in the quantification of instrumental background for some or all of the hygrometers are a likely cause. Until these errors are understood, differences at this level will continue to somewhat limit our understanding of cirrus microphysical processes and dehydration in the tropical tropopause layer. PMID:28845379

Laser-induced plasma cloud interaction and ice multiplication under cirrus cloud conditions.

PubMed

Leisner, Thomas; Duft, Denis; Möhler, Ottmar; Saathoff, Harald; Schnaiter, Martin; Henin, Stefano; Stelmaszczyk, Kamil; Petrarca, Massimo; Delagrange, Raphaëlle; Hao, Zuoqiang; Lüder, Johannes; Petit, Yannick; Rohwetter, Philipp; Kasparian, Jérôme; Wolf, Jean-Pierre; Wöste, Ludger

2013-06-18

Potential impacts of lightning-induced plasma on cloud ice formation and precipitation have been a subject of debate for decades. Here, we report on the interaction of laser-generated plasma channels with water and ice clouds observed in a large cloud simulation chamber. Under the conditions of a typical storm cloud, in which ice and supercooled water coexist, no direct influence of the plasma channels on ice formation or precipitation processes could be detected. Under conditions typical for thin cirrus ice clouds, however, the plasma channels induced a surprisingly strong effect of ice multiplication. Within a few minutes, the laser action led to a strong enhancement of the total ice particle number density in the chamber by up to a factor of 100, even though only a 10(-9) fraction of the chamber volume was exposed to the plasma channels. The newly formed ice particles quickly reduced the water vapor pressure to ice saturation, thereby increasing the cloud optical thickness by up to three orders of magnitude. A model relying on the complete vaporization of ice particles in the laser filament and the condensation of the resulting water vapor on plasma ions reproduces our experimental findings. This surprising effect might open new perspectives for remote sensing of water vapor and ice in the upper troposphere.

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

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

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

2014-04-16

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

Homogeneous Aerosol Freezing in the Tops of High-Altitude Tropical Cumulonimbus Clouds

NASA Technical Reports Server (NTRS)

Jensen, E. J.; Ackerman, A. S.

2006-01-01

Numerical simulations of deep, intense continental tropical convection indicate that when the cloud tops extend more than a few kilometers above the liquid water homogeneous freezing level, ice nucleation due to freezing of entrained aqueous sulfate aerosols generates large concentrations of small crystals (diameters less than approx. equal to 20 micrometers). The small crystals produced by aerosol freezing have the largest impact on cloud-top ice concentration for convective clouds with strong updrafts but relatively low aerosol concentrations. An implication of this result is that cloud-top ice concentrations in high anvil cirrus can be controlled primarily by updraft speeds in the tops of convective plumes and to a lesser extent by aerosol concentrations in the uppermost troposphere. While larger crystals precipitate out and sublimate in subsaturated air below, the population of small crystals can persist in the saturated uppermost troposphere for many hours, thereby prolonging the lifetime of remnants from anvil cirrus in the tropical tropopause layer.

Ubiquity and impact of thin mid-level clouds in the tropics

PubMed Central

Bourgeois, Quentin; Ekman, Annica M. L.; Igel, Matthew R.; Krejci, Radovan

2016-01-01

Clouds are crucial for Earth's climate and radiation budget. Great attention has been paid to low, high and vertically thick tropospheric clouds such as stratus, cirrus and deep convective clouds. However, much less is known about tropospheric mid-level clouds as these clouds are challenging to observe in situ and difficult to detect by remote sensing techniques. Here we use Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) satellite observations to show that thin mid-level clouds (TMLCs) are ubiquitous in the tropics. Supported by high-resolution regional model simulations, we find that TMLCs are formed by detrainment from convective clouds near the zero-degree isotherm. Calculations using a radiative transfer model indicate that tropical TMLCs have a cooling effect on climate that could be as large in magnitude as the warming effect of cirrus. We conclude that more effort has to be made to understand TMLCs, as their influence on cloud feedbacks, heat and moisture transport, and climate sensitivity could be substantial. PMID:27530236

Ubiquity and impact of thin mid-level clouds in the tropics.

PubMed

Bourgeois, Quentin; Ekman, Annica M L; Igel, Matthew R; Krejci, Radovan

2016-08-17

Clouds are crucial for Earth's climate and radiation budget. Great attention has been paid to low, high and vertically thick tropospheric clouds such as stratus, cirrus and deep convective clouds. However, much less is known about tropospheric mid-level clouds as these clouds are challenging to observe in situ and difficult to detect by remote sensing techniques. Here we use Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) satellite observations to show that thin mid-level clouds (TMLCs) are ubiquitous in the tropics. Supported by high-resolution regional model simulations, we find that TMLCs are formed by detrainment from convective clouds near the zero-degree isotherm. Calculations using a radiative transfer model indicate that tropical TMLCs have a cooling effect on climate that could be as large in magnitude as the warming effect of cirrus. We conclude that more effort has to be made to understand TMLCs, as their influence on cloud feedbacks, heat and moisture transport, and climate sensitivity could be substantial.

Total Water Measurements Using In Situ UV Fragment Fluorescence Spectroscopy in Support of CRYSTAL-FACE

NASA Technical Reports Server (NTRS)

Anderson, James G.

2004-01-01

Given both the powerful diagnostic importance of the condensed phases of water for dynamics and the impact of phase changes in water on the radiation field, the accurate, in situ observation of total water is of central importance to CRYSTAL-FACE. This is clear both from the defined scientific objectives of the NRA and from developments in the coupled fields of stratosphere/troposphere exchange, cirrus cloud formation/removal and mechanisms for the distribution of water vapor in the middle/upper troposphere. Accordingly, we were funded under NASA Grant NAG5-115487 to perform the following tasks for the CRYSTAL-FACE mission that took place in Key West, Florida, during July 2001: 1) Prepare the Total Water instrument for integration into the WB57F and test flights scheduled for Spring 2002. 2) Calibrate and prepare the Total Water instrument for the Summer 2002 CRYSTAL-FACE science flights based in Jacksonville, Florida. 3) Provide both science and engineering support for the above-mentioned efforts. 4) Analyze and interpret the CRYSTAL-FACE data in collaboration with the other mission scientists. 5) Attend the proposed science workshop in Spring 2003. 6) Publish the data and analysis in peer-reviewed journals.

Single particle measurements of the chemical composition of cirrus ice residue during CRYSTAL-FACE

NASA Astrophysics Data System (ADS)

Cziczo, D. J.; Murphy, D. M.; Hudson, P. K.; Thomson, D. S.

2004-02-01

The first real-time, in situ, investigation of the chemical composition of the residue of cirrus ice crystals was performed during July 2002. This study was undertaken on a NASA WB-57F high-altitude research aircraft as part of CRYSTAL-FACE, a field campaign which sought to further our understanding of the relation of clouds, water vapor, and climate by characterizing, among other parameters, anvil cirrus formed about the Florida peninsula. A counter flow virtual impactor (CVI) was used to separate cirrus ice from the unactivated interstitial aerosol particles and evaporate condensed-phase water. Residual material, on a crystal-by-crystal basis, was subsequently analyzed using the NOAA Aeronomy Laboratory's Particle Analysis by Laser Mass Spectrometry (PALMS) instrument. Sampling was performed from 5 to 15 km altitude and from 12° to 28° north latitude within cirrus originating over land and ocean. Chemical composition measurements provided several important results. Sea salt was often incorporated into cirrus, consistent with homogeneous ice formation by aerosol particles from the marine boundary layer. Size measurements showed that large particles preferentially froze over smaller ones. Meteoritic material was found within ice crystals, indicative of a relation between stratospheric aerosol particles and tropospheric clouds. Mineral dust was the dominant residue observed in clouds formed during a dust transport event from the Sahara, consistent with a heterogeneous freezing mechanism. These results show that chemical composition and size are important determinants of which aerosol particles form cirrus ice crystals.

Heterogeneous ice nucleation on phase-separated organic-sulfate particles: effect of liquid vs. glassy coatings

NASA Astrophysics Data System (ADS)

Schill, G. P.; Tolbert, M. A.

2013-05-01

Atmospheric ice nucleation on aerosol particles relevant to cirrus clouds remains one of the least understood processes in the atmosphere. Upper tropospheric aerosols as well as sub-visible cirrus residues are known to be enhanced in both sulfates and organics. The hygroscopic phase transitions of organic-sulfate particles can have an impact on both the cirrus cloud formation mechanism and resulting cloud microphysical properties. In addition to deliquescence and efflorescence, organic-sulfate particles are known to undergo another phase transition known as liquid-liquid phase separation. The ice nucleation properties of particles that have undergone liquid-liquid phase separation are unknown. Here, Raman microscopy coupled with an environmental cell was used to study the low temperature deliquescence, efflorescence, and liquid-liquid phase separation behavior of 2 : 1 mixtures of organic polyols (1,2,6-hexanetriol and 1 : 1 1,2,6-hexanetriol + 2,2,6,6-tetrakis(hydroxymethyl)cyclohexanol) and ammonium sulfate from 240-265 K. Further, the ice nucleation efficiency of these organic-sulfate systems after liquid-liquid phase separation and efflorescence was investigated from 210-235 K. Raman mapping and volume-geometry analysis indicate that these particles contain solid ammonium sulfate cores fully engulfed in organic shells. For the ice nucleation experiments, we find that if the organic coatings are liquid, water vapor diffuses through the shell and ice nucleates on the ammonium sulfate core. In this case, the coatings minimally affect the ice nucleation efficiency of ammonium sulfate. In contrast, if the coatings become semi-solid or glassy, ice instead nucleates on the organic shell. Consistent with recent findings that glasses can be efficient ice nuclei, the phase-separated particles are nearly as efficient at ice nucleation as pure crystalline ammonium sulfate.

Heterogeneous ice nucleation on phase-separated organic-sulfate particles: effect of liquid vs. glassy coatings

NASA Astrophysics Data System (ADS)

Schill, G. P.; Tolbert, M. A.

2012-12-01

Atmospheric ice nucleation on aerosol particles relevant to cirrus clouds remains one of the least understood processes in the atmosphere. Upper tropospheric aerosols as well as sub-visible cirrus residues are known to be enhanced in both sulfates and organics. The hygroscopic phase transitions of organic-sulfate particles can have an impact on both the cirrus cloud formation mechanism and resulting cloud microphysical properties. In addition to deliquescence and efflorescence, organic-sulfate particles are known to undergo another phase transition known as liquid-liquid phase separation. The ice nucleation properties of particles that have undergone liquid-liquid phase separation are unknown. Here, Raman microscopy coupled with an environmental cell was used to study the low temperature deliquescence, efflorescence, and liquid-liquid phase separation behavior of 2:1 mixtures of organic polyols (1,2,6-hexanetriol, and 1:1 1,2,6-hexanetriol +2,2,6,6-tetrakis(hydroxymethyl)cycohexanol) and ammonium sulfate from 240-265 K. Further, the ice nucleation efficiency of these organic-sulfate systems after liquid-liquid phase separation and efflorescence was investigated from 210-235 K. Raman mapping and volume-geometry analysis indicates that these particles contain solid ammonium sulfate cores fully engulfed in organic shells. For the ice nucleation experiments, we find that if the organic coatings are liquid, water vapor diffuses through the shell and ice nucleates on the ammonium sulfate core. In this case, the coatings minimally affect the ice nucleation efficiency of ammonium sulfate. In contrast, if the coatings become semi-solid or glassy, ice instead nucleates on the organic shell. Consistent with recent findings that glasses can be efficient ice nuclei, the phase separated particles are nearly as efficient at ice nucleation as pure crystalline ammonium sulfate.

Observation of Upper and Middle Tropospheric Clouds

NASA Technical Reports Server (NTRS)

Cox, Stephen K.

1996-01-01

The goal of this research has been to identify and describe the properties of climatically important cloud systems critically important to understanding their effects upon satellite remote sensing and the global climate. These goals have been pursued along several different but complementary lines of investigation: the design, construction, testing and application of instrumentation; the collection of data sets during Intensive Field Observation periods; the reduction and analysis of data collected during IFO's; and completion of research projects specifically designed to address important and timely research objectives. In the first year covered by this research proposal, three papers were authored in the refereed literature which reported completed analyses of FIRE 1 IFO studies initiated under the previous NASA funding of this topic area. microphysical and radiative properties of marine stratocumulus cloud systems deduced from tethered balloon observations were reported from the San Nicolas Island site of the first FIRE marine stratocumulus experiment. Likewise, in situ observations of radiation and dynamic properties of a cirrus cloud layer were reported from first FIRE cirrus IFO based from Madison, Wisconsin. In addition, application techniques were under development for monitoring cirrus cloud systems using a 403 MHz Doppler wind profiler system adapted with a RASS (Radio Acoustic Sounding System) and an infrared interferometer system; these instrument systems were used in subsequent deployments for the FIRE 2 Parsons, Kansas and FIRE 2 Porto Santo, ASTEX expeditions. In November 1991 and in June 1992, these two systems along with a complete complement of surface radiation and meteorology measurements were deployed to the two sites noted above as anchor points for the respective IFO'S. Subsequent research activity concentrated on the interpretation and integration of the IFO analyses in the context of the radiative properties of cloud systems and our ability to remotely observe radiative, thermodynamic and dynamic properties of these cloud systems.

The UARS and EOS Microwave Limb Sounder (MLS) Experiments.

NASA Astrophysics Data System (ADS)

Waters, J. W.; Read, W. G.; Froidevaux, L.; Jarnot, R. F.; Cofield, R. E.; Flower, D. A.; Lau, G. K.; Pickett, H. M.; Santee, M. L.; Wu, D. L.; Boyles, M. A.; Burke, J. R.; Lay, R. R.; Loo, M. S.; Livesey, N. J.; Lungu, T. A.; Manney, G. L.; Nakamura, L. L.;  Perun, V. S.;  Ridenoure, B. P.;  Shippony, Z.;  Siegel, P. H.;  Thurstans, R. P.;  Harwood, R. S.;  Pumphrey, H. C.;  Filipiak, M. J.

1999-01-01

The Microwave Limb Sounder (MLS) experiments obtain measurements of atmospheric composition, temperature, and pressure by observations of millimeter- and submillimeter-wavelength thermal emission as the instrument field of view is scanned through the atmospheric limb. Features of the measurement technique include the ability to measure many atmospheric gases as well as temperature and pressure, to obtain measurements even in the presence of dense aerosol and cirrus, and to provide near-global coverage on a daily basis at all times of day and night from an orbiting platform. The composition measurements are relatively insensitive to uncertainties in atmospheric temperature. An accurate spectroscopic database is available, and the instrument calibration is also very accurate and stable. The first MLS experiment in space, launched on the (NASA) Upper Atmosphere Research Satellite (UARS) in September 1991, was designed primarily to measure stratospheric profiles of ClO, O3, H2O, and atmospheric pressure as a vertical reference. Global measurement of ClO, the predominant radical in chlorine destruction of ozone, was an especially important objective of UARS MLS. All objectives of UARS MLS have been accomplished and additional geophysical products beyond those for which the experiment was designed have been obtained, including measurement of upper-tropospheric water vapor, which is important for climate change studies. A follow-on MLS experiment is being developed for NASA's Earth Observing System (EOS) and is scheduled to be launched on the EOS CHEMISTRY platform in late 2002. EOS MLS is designed for many stratospheric measurements, including HOx radicals, which could not be measured by UARS because adequate technology was not available, and better and more extensive upper-tropospheric and lower-stratospheric measurements.

The Impact of Upper Tropospheric Humidity from Microwave Limb Sounder on the Midlatitude Greenhouse Effect

NASA Technical Reports Server (NTRS)

Hu, Hua; Liu, W. Timothy

1998-01-01

This paper presents an analysis of upper tropospheric humidity, as measured by the Microwave Limb Sounder, and the impact of the humidity on the greenhouse effect in the midlatitudes. Enhanced upper tropospheric humidity and an enhanced greenhouse effect occur over the storm tracks in the North Pacific and North Atlantic. In these areas, strong baroclinic activity and the large number of deep convective clouds transport more water vapor to the upper troposphere, and hence increase greenhouse trapping. The greenhouse effect increases with upper tropospheric humidity in areas with a moist upper troposphere (such as areas over storm tracks), but it is not sensitive to changes in upper tropospheric humidity in regions with a dry upper troposphere, clearly demonstrating that there are different mechanisms controlling the geographical distribution of the greenhouse effect in the midlatitudes.

A Study of Tropical thin Cirrus Clouds with Supervised Learning

NASA Astrophysics Data System (ADS)

Rodier, S. D.; Hu, Y.; Vaughan, M. A.

2007-12-01

ABSTRACT Accurate knowledge of the temporal frequency and spatial extent of optically thin cirrus is crucial to climate feedback analysis. Current global warming theory asserts that when the atmospheric concentration of CO2 increases, the outgoing longwave radiation at non-window wavelengths is reduced. If the Earth's net radiative balance is to remain stable, ground temperatures must rise in response, thereby increasing thermal emission to space. Current models do not account for subsequent changes in cloud cover, because this aspect of the climate feedback system is so poorly understood. One possible response of the cloud-climate feedback process is an increase in the global occurrence of thin cirrus clouds, driven by the increase in longwave cooling in the upper troposphere that results from higher CO2 concentrations. Exacerbating the difficulty of assessing the situation is the fact that passive remote sensing instruments cannot reliably detect cirrus clouds with optical depths less than ~0.3, because these clouds do not reflect enough sunlight to create a sufficient contrast with the Earth's surface. Now, however, the presence of thin cirrus can for the first time be accurately detected and systematically monitored by the combination of active and passive sensors onboard the CALIPSO satellite. Nevertheless, the data record is still quite limited, as CALIPSO has been in orbit for only 16 months. We have therefore initiated a multi-platform data fusion study to establish a methodology for extending the limited set of CALIPSO measurements to the existing 30-year record of passive remote sensing data, and thus improve our understanding of cloud feedback mechanisms. Using nighttime data from the first 10 days in April 2007 as a training set, we applied a general regression neural network (GRNN) to collocated samples of sea surface temperature (SST) reported by AMSR, brightness temperatures (BT) from the CALIPSO imaging infrared radiometer (IIR), and optical depths (OD) derived from the CALIPSO lidar measurements. The result is an accurate mapping of the optical depths derived from the active sensors to the brightness temperatures computed from the passive sensor measurements. Applying the trained network to this combination of passive sensor parameters, optical depths as small as 0.1 can be reliably retrieved. The relative uncertainties in the retrieval are reasonable, and can be improved significantly by use of a much larger training set.

Raman scattering investigations of the interaction of a COV with pure and acid doped ice particles

NASA Astrophysics Data System (ADS)

Facq, S.; Oancea, A.; Focsa, C.; Chazallon, B.

2009-04-01

Ice present in polar stratosphere is as well a common component of the troposphere, particularly in cirrus clouds widespread in tropopause and upper troposphere region. With water droplets, ice constitutes the condensed matter that can interact with atmospheric trace gases via many different trapping processes (co-deposition i.e; incorporation during growing ice conditions, adsorption, freezing etc). The incorporation of trace gases in ice surface/volume can both affect the atmospheric chemistry and the ice structure and reactivity. This can therefore modify the nature and composition of the incorporated species in ice, or in the gas phase. Recently, field measurements have demonstrated the presence of nitric acid in ice particles from cirrus clouds(1,2) (concentration between 0.63 wt% and 2.5 wt %). Moreover, laboratory experiments have shown that the uptake of atmospheric trace gases can be enhanced up to 1 or 2 orders of magnitude in these doped ice particles. Among trace gases capable to interact with atmospheric condensed matter figure volatile organic compounds such as aldehydes, ketones and alcohols (ex: ethanol and methanol). They play an important role in the upper troposphere (3,4) and snowpack chemistry (5) as they can be easily photolysed, producing free radicals and so influence the oxidizing capacity and the ozone-budget of the atmosphere (3,4). The temperature range at which these physico-chemical processes occur extents between ~ 190 K and 273K. Interaction between ice and trace gases are therefore largely dependent on the ice surface properties as well as on the phase formation dynamic (crystalline or not). This study aims to examine and characterize the incorporation of a COV (ex: ethanol), at the surface or in the volume of ice formed by different growth mechanisms (vapour deposition or droplets freezing). Vibrational spectra of water OH and ethanol CH-spectral regions are analysed using confocal micro-Raman spectroscopy at different temperatures (183 K to 273 K). Information at the molecular level on the surface structure can be derived from accompanying changes observed in band shapes and vibrational mode frequencies. The influence of the presence of nitric acid on the molecular interactions with the trapped organic species in ice particles can be also spectroscopically characterized. (1) Gao et al., Science, 2004, 303, 516. (2) Journet et al., J. Phys. Chem. B, 2005, 109, 14112. (3)H. Singh, M. Kanakidou, P.J Crutzen & D.J Jacob, Nature, 1995, 378, 50. (4)H. Singh, Y. Chen, A. Staudt, D. Jacob, D. Blake, B. Heikes & J. Snow, Nature, 2001, 410, 1078. (5)F. Dominé & P.B Shepson, Science, 2002, 297, 1506

What Controls the Low Ice Number Concentration in the Upper Tropical Troposphere?

NASA Astrophysics Data System (ADS)

Penner, J.; Zhou, C.; Lin, G.; Liu, X.; Wang, M.

2015-12-01

Cirrus clouds in the tropical tropopause play a key role in regulating the moisture entering the stratosphere through their dehydrating effect. Low ice number concentrations and high supersaturations were frequently were observed in these clouds. However, low ice number concentrations are inconsistent with cirrus cloud formation based on homogeneous freezing. Different mechanisms have been proposed to explain this discrepancy, including the inhibition of homogeneous freezing by pre-existing ice crystals and/or glassy organic aerosol heterogeneous ice nuclei (IN) and limiting the formation of ice number from high frequency gravity waves. In this study, we examined the effect from three different parameterizations of in-cloud updraft velocities, the effect from pre-existing ice crystals, the effect from different water vapor deposition coefficients (α=0.1 or 1), and the effect from 0.1% of secondary organic aerosol (SOA) acting as glassy heterogeneous ice nuclei (IN) in CAM5. Model simulated ice crystal numbers are compared against an aircraft observational dataset. Using grid resolved large-scale updraft velocity in the ice nucleation parameterization generates ice number concentrations in better agreement with observations for temperatures below 205K while using updraft velocities based on the model-generated turbulence kinetic energy generates ice number concentrations in better agreement with observations for temperatures above 205K. A larger water vapor deposition coefficient (α=1) can efficiently reduce the ice number at temperatures below 205K but less so at higher temperatures. Glassy SOA IN are most effective at reducing the ice number concentrations when the effective in-cloud updraft velocities are moderate (~0.05-0.2 m s-1). Including the removal of water vapor on pre-existing ice can also effectively reduce the ice number and diminish the effects from the additional glassy SOA heterogeneous IN. We also re-evaluate whether IN seeding in cirrus cloud is a viable mechanism for cooling. A significant amount of negative climate forcing can only be achieved if we restrict the updraft velocity in regions of background cirrus formation to moderate values (~0.05-0.2 m s-1).

A Meteorological Overview of the TC4 Mission

NASA Technical Reports Server (NTRS)

Pfister, L.; Selkirk, H. B.; Starr, D. O.; Rosenlof, K.; Newman, P. F.

2010-01-01

The TC4 mission in Central America during summer 2007 examined convective transport into the tropical Upper Troposphere/Lower Stratosphere (UTLS) and the evolution of cirrus clouds. The tropical tropopause layer (TTL) circulation is dominated by the Asian monsoon anticyclone and westward winds that stretch from the western Pacific into the Atlantic. During TC4, TTL westward flow over Central America was stronger than normal. Incidence of cold clouds over the Central American region was the third lowest out of 34 years sampled. The major factor was an incipient La Nina, specifically anomalously cold temperatures off the Pacific Coast of South America. Weakness in the low level Caribbean jet caused a shift in the coldest clouds from the Caribbean to the Pacific side of Central America. The character of tropopause temperature variability was that of upward propagating waves generated by local and nonlocal convection. These waves produced tropopause temperature variations of 3 K, with peak-to-peak variations of 8 K. At low levels in Central America, flow from the Sahara desert predominated; further south, the air came from the Amazon region. Convectively influenced air in the upper troposphere came from Central America, the northern Amazon region, the Atlantic ITCZ, and the North American monsoon. In the TTL, Asian and African convection affected the observed air masses. North of 10N in the Central American TTL, African and Asian convection may have contributed as much to the air masses as Central and South American convection. South of 8N, Asian and African convection had far less impact.

LIDAR Developments at Clermont-Ferrand—France for Atmospheric Observation

PubMed Central

Fréville, Patrick; Montoux, Nadège; Baray, Jean-Luc; Chauvigné, Aurélien; Réveret, François; Hervo, Maxime; Dionisi, Davide; Payen, Guillaume; Sellegri, Karine

2015-01-01

We present a Rayleigh-Mie-Raman LIDAR system in operation at Clermont-Ferrand (France) since 2008. The system provides continuous vertical tropospheric profiles of aerosols, cirrus optical properties and water vapour mixing ratio. Located in proximity to the high altitude Puy de Dôme station, labelled as the GAW global station PUY since August 2014, it is a useful tool to describe the boundary layer dynamics and hence interpret in situ measurements. This LIDAR has been upgraded with specific hardware/software developments and laboratory calibrations in order to improve the quality of the profiles, calibrate the depolarization ratio, and increase the automation of operation. As a result, we provide a climatological water vapour profile analysis for the 2009–2013 period, showing an annual cycle with a winter minimum and a summer maximum, consistent with in-situ observations at the PUY station. An overview of a preliminary climatology of cirrus clouds frequency shows that in 2014, more than 30% of days present cirrus events. Finally, the backscatter coefficient profile observed on 27 September 2014 shows the capacity of the system to detect cirrus clouds at 13 km altitude, in presence of aerosols below the 5 km altitude. PMID:25643059

Correlations and linkages between the sun and the earth's atmosphere: Needed measurements and observations

NASA Technical Reports Server (NTRS)

Kellogg, W. W.

1975-01-01

A study was conducted to identify the sequence of processes that lead from some change in solar input to the earth to a change in tropospheric circulation and weather. Topics discussed include: inputs from the sun, the solar wind, and the magnetosphere; bremsstrahlung, ionizing radiation, cirrus clouds, thunderstorms, wave propagation, and gravity waves.

Coupling of Clouds and Moisture Transport in Extratropical Cyclonic Systems and the Associated Atmospheric Heating (Q1) and Moisture Sink (Q2)

NASA Astrophysics Data System (ADS)

Wong, S.; Naud, C. M.; Kahn, B. H.; Wu, L.; Fetzer, E. J.

2017-12-01

Different sectors in extratropical cyclonic systems (ETCs) exhibit various patterns in atmospheric moisture transport and provide an excellent test bed for studying coupling between cloud processes and large-scale circulation. Large-scale atmospheric moisture transport diagnosed from the Modern-Era Retrospective analysis for Research and Applications Version 2 and cloud properties (cloud top pressure and optical depth, cloud effective radii and thermodynamic phase) from both the Moderate Resolution Imaging Spectroradiometer (MODIS) and Atmospheric Infrared Sounder (AIRS) will be composited around Northern Hemispheric ETCs over ocean according to their stages of development. Atmospheric diabatic heating rates (Q1) and moisture sinks (Q2) are also inferred from the reanalysis winds, temperature, and specific humidity. Across the warm fronts, elevated convection in the pre-warm front regime is associated with frequent stratiform clouds with middle-to-upper tropospheric heating and lower tropospheric cooling, while upright convection in the warm front regime has frequent deep convective clouds with free-tropospheric heating and strong boundary layer cooling. Thinner stratiform and cirrus clouds are evident in the warm sector with top-heavy profiles of rising motion and diabatic heating. Moisture advection exhibits a sharp gradient across the cold fronts, with convection in the pre-cold front regime highly dependent on the stage of the ETC development. Heating in the boundary layers of the cold sector, polar-air intrusion, and pre-warm sector regimes depends on the amount of low-level clouds, which is again modulated by the stage of the ETC development.

Cloud-Radiative Driving of the Madden-Julian Oscillation as Seen by the A-Train

NASA Technical Reports Server (NTRS)

Del Genio, Anthony; Chen, Yonghua

2015-01-01

Cloud and water vapor radiative heating anomalies associated with convection may be an effective source of moist static energy driving the Madden-Julian Oscillation (MJO). In this paper five years of radiative heating profiles derived from CloudSat radar and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation data are analyzed to document radiative heating anomalies during the MJO. Atmospheric shortwave absorption and surface longwave radiation anomalies are of opposite sign and 10-20% as large as top-of-atmosphere outgoing longwave radiation (OLR) anomalies, confirming that OLR provides a useful estimate of the total column radiative heating anomaly. Positive anomalies generally peak about one week before the MJO peak and are smallest over the Indian Ocean. Anomalies over the Maritime Continent are strongest, and coincident with the MJO peak. Shortwave heating profile anomalies are about half as large as longwave anomalies in the active region of the MJO but generally of opposite sign; thus shortwave heating damps the longwave destabilization of the lower troposphere. The exception is the onset phase of the MJO, where shortwave and longwave heating anomalies due to thin cirrus are both positive in the upper troposphere and exert a stabilizing influence. Specific humidity anomalies in the middle troposphere reach 0.5 g kg(exp. -1), but the associated clear sky heating anomaly is very small. Radiative enhancement of column moist static energy becomes significant about 10 days before the MJO peak, when precipitation anomalies are still increasing, and then remains high after the MJO peak after precipitation has begun to decline.

The 1980 stratospheric-tropospheric exchange experiment

NASA Technical Reports Server (NTRS)

Margozzi, A. P. (Editor)

1983-01-01

Data are presented from the Stratospheric-Tropospheric Water Vapor Exchange Experiment. Measurements were made during 11 flights of the NASA U-2 aircraft which provided data from horizontal traverser and samplings in and about the tops of extensive cirrus-anvil clouds produced by overshooting cumulus turrets. Aircraft measurements were made of water vapor, ozone, ambient and cloud top temperature, fluorocarbons, nitrous oxide, nitric acid, aerosols, and ice crystal populations. Balloonsondes were flown about twice daily providing data on ozone, wind fields, pressure and temperature to altitudes near 30 km. Satellite photography provided detailed cloud and cloud top temperature information. Descriptions of individual experiments and detailed compilations of all results are provided.

78 FR 35747 - Special Conditions: Cirrus Design Corporation, Model SF50; Fire Extinguishing for Upper Aft...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-06-14

... DEPARTMENT OF TRANSPORTATION Federal Aviation Administration 14 CFR Part 23 [Docket No. CE305; Special Conditions No. 23-245-SC] Special Conditions: Cirrus Design Corporation, Model SF50; Fire... from fires, were not envisioned in the development of the part 23 normal category regulations. The...

Investigating ice nucleation in cirrus clouds with an aerosol-enabled Multiscale Modeling Framework

DOE PAGES

Zhang, Chengzhu; Wang, Minghuai; Morrison, H.; ...

2014-11-06

In this study, an aerosol-dependent ice nucleation scheme [Liu and Penner, 2005] has been implemented in an aerosol-enabled multi-scale modeling framework (PNNL MMF) to study ice formation in upper troposphere cirrus clouds through both homogeneous and heterogeneous nucleation. The MMF model represents cloud scale processes by embedding a cloud-resolving model (CRM) within each vertical column of a GCM grid. By explicitly linking ice nucleation to aerosol number concentration, CRM-scale temperature, relative humidity and vertical velocity, the new MMF model simulates the persistent high ice supersaturation and low ice number concentration (10 to 100/L) at cirrus temperatures. The low ice numbermore » is attributed to the dominance of heterogeneous nucleation in ice formation. The new model simulates the observed shift of the ice supersaturation PDF towards higher values at low temperatures following homogeneous nucleation threshold. The MMF models predict a higher frequency of midlatitude supersaturation in the Southern hemisphere and winter hemisphere, which is consistent with previous satellite and in-situ observations. It is shown that compared to a conventional GCM, the MMF is a more powerful model to emulate parameters that evolve over short time scales such as supersaturation. Sensitivity tests suggest that the simulated global distribution of ice clouds is sensitive to the ice nucleation schemes and the distribution of sulfate and dust aerosols. Simulations are also performed to test empirical parameters related to auto-conversion of ice crystals to snow. Results show that with a value of 250 μm for the critical diameter, Dcs, that distinguishes ice crystals from snow, the model can produce good agreement to the satellite retrieved products in terms of cloud ice water path and ice water content, while the total ice water is not sensitive to the specification of Dcs value.« less

Anvil Glaciation in a Deep Cumulus Updraught over Florida Simulated with the Explicit Microphysics Model. I: Impact of Various Nucleation Processes

NASA Technical Reports Server (NTRS)

Phillips, Vaughan T. J.; Andronache, Constantin; Sherwood, Steven C.; Bansemer, Aaron; Conant, William C.; Demott, Paul J.; Flagan, Richard C.; Heymsfield, Andy; Jonsson, Haflidi; Poellot, Micheal;

The DC-8 Submillimeter-Wave Cloud Ice Radiometer

NASA Technical Reports Server (NTRS)

Walter, Steven J.; Batelaan, Paul; Siegel, Peter; Evans, K. Franklin; Evans, Aaron; Balachandra, Balu; Gannon, Jade; Guldalian, John; Raz, Guy; Shea, James

2000-01-01

An airborne radiometer is being developed to demonstrate the capability of radiometry at submillimeter-wavelengths to characterize cirrus clouds. At these wavelengths, cirrus clouds scatter upwelling radiation from water vapor in the lower troposphere. Radiometric measurements made at multiple widely spaced frequencies permit flux variations caused by changes in scattering due to crystal size to be distinguished from changes in cloud ice content. Measurements at dual polarizations can also be used to constrain the mean crystal shape. An airborne radiometer measuring the upwelling submillimeter-wave flux should then able to retrieve both bulk and microphysical cloud properties. The radiometer is being designed to make measurements at four frequencies (183 GHz, 325 GHz, 448 GHz, and 643 GHz) with dual-polarization capability at 643 GHz. The instrument is being developed for flight on NASA's DC-8 and will scan cross-track through an aircraft window. Measurements with this radiometer in combination with independent ground-based and airborne measurements will validate the submillimeter-wave radiometer retrieval techniques. The goal of this effort is to develop a technique to enable spaceborne characterization of cirrus, which will meet a key climate measurement need. The development of an airborne radiometer to validate cirrus retrieval techniques is a critical step toward development of spaced-based radiometers to investigate and monitor cirrus on a global scale. The radiometer development is a cooperative effort of the University of Colorado, Colorado State University, Swales Aerospace, and Jet Propulsion Laboratory and is funded by the NASA Instrument Incubator Program.

Sunrise, Earth Limb, SW Pacific Ocean

NASA Image and Video Library

1992-09-20

STS047-54-018 (12-20 Sept. 1992) --- The colors in this photograph provide insight into the relative density of the atmosphere. The crew members had many opportunities to witness sunrises and sunsets, considering they orbit the Earth every 90 minutes, but few, they said, compared to this scene. It captures the silhouette of several mature thunderstorms with their cirrus anvil tops spreading out against the tropopause (the top of the lowest layer of Earth's atmosphere) at sunset. The lowest layer (troposphere) is the densest and refracts light at the red end of the visible spectrum (7,400 Angstroms), while the blues (4,000 Angstroms) are separated in the least dense portion of the atmosphere (middle and upper atmosphere, or stratosphere and mesosphere). Several layers of blue can be seen. NASA scientists studying the photos believe this stratification to be caused by the scattering of light by particulate trapped in the stratosphere and mesosphere particulate that generally originate from volcanic eruptions, such as those of Mt. Pinatubo in the Philippines and, most recently, Mt. Spurr in Alaska.

Upper Tropospheric Ozone Between Latitudes 60S and 60N Derived from Nimbus 7 TOMS/THIR Cloud Slicing

NASA Technical Reports Server (NTRS)

Ziemke, Jerald R.; Chandra, Sushil; Bhartia, P. K.

2002-01-01

This study evaluates the spatial distributions and seasonal cycles in upper tropospheric ozone (pressure range 200-500 hPa) from low to high latitudes (60S to 60N) derived from the satellite retrieval method called "Cloud Slicing." Cloud Slicing is a unique technique for determining ozone profile information in the troposphere by combining co-located measurements of cloud-top, pressure and above-cloud column ozone. For upper tropospheric ozone, co-located measurements of Nimbus 7 Total Ozone Mapping Spectrometer (TOMS) above-cloud column ozone, and Nimbus 7 Temperature Humidity Infrared Radiometer (THIR) cloud-top pressure during 1979-1984 were incorporated. In the tropics, upper tropospheric ozone shows year-round enhancement in the Atlantic region and evidence of a possible semiannual variability. Upper tropospheric ozone outside the tropics shows greatest abundance in winter and spring seasons in both hemispheres with largest seasonal and largest amounts in the NH. These characteristics are similar to lower stratospheric ozone. Comparisons of upper tropospheric column ozone with both stratospheric ozone and a proxy of lower stratospheric air mass (i.e., tropopause pressure) from National Centers for Environmental Prediction (NCEP) suggest that stratosphere-troposphere exchange (STE) may be a significant source for the seasonal variability of upper tropospheric ozone almost everywhere between 60S and 60N except in low latitudes around 10S to 25N where other sources (e.g., tropospheric transport, biomass burning, aerosol effects, lightning, etc.) may have a greater role.

In Situ Water Vapor Measurements Using Coupled UV Fragment Fluorescence/Absorption Spectroscopy in Support of CRYSTAL-FACE

NASA Technical Reports Server (NTRS)

Anderson, James G.

2004-01-01

Understanding the coupling of dynamics, chemistry, and radiation within the context of the NASA Earth Science Enterprise (ESE) and the national Climate Change Science Program (CCSP) requires, as a first-order priority, high spatial resolution, high-accuracy observations of water in its various phases. Given the powerful diagnostic importance of the condensed phases of water for dynamics and the impact of phase changes in water on the radiation field, the accurate, in situ observation of water vapor is of central importance to CRYSTAL FACE (CF). This is clear both from the defined scientific objectives of the NRA and from developments in the coupled fields of stratosphere/troposphere exchange, cirrus cloud formation/removal and mechanisms for the distribution of water vapor in the middle/upper troposphere. Accordingly, we were funded under NASA Grant NAG5-11548 to perform the following tasks for the CF mission: 1. Prepare the water vapor instrument for integration into the WB57F and test flights scheduled for Spring 2002. 2. Calibrate and prepare the water vapor instrument for the Summer 2002 CF science flights based in Jacksonville, Florida. 3. Provide both science and engineering support for the above-mentioned efforts. 4. Analyze and interpret the CF data in collaboration with other mission scientists. 5. Attend the science workshop in Spring 2003. 6. Publish the data and analysis in peer-reviewed journals.

Study Pollution Impacts on Upper-Tropospheric Clouds with Aura, CloudSat, and CALIPSO Data

NASA Technical Reports Server (NTRS)

Wu, Dong

2007-01-01

This viewgraph presentation reviews the impact of pollution on clouds in the Upper Troposphere. Using the data from the Aura Microwave Limb Sounder (MLS), CloudSat, CALIPSO the presentation shows signatures of pollution impacts on clouds in the upper troposphere. The presentation demonstrates the complementary sensitivities of MLS , CloudSat and CALIPSO to upper tropospheric clouds. It also calls for careful analysis required to sort out microphysical changes from dynamical changes.

75 FR 20516 - Special Conditions: Cirrus Design Corporation, Model SF50; Fire Extinguishing for Upper Aft...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-04-20

...; Special Conditions No. 23-245-SC] Special Conditions: Cirrus Design Corporation, Model SF50; Fire... protect such installed engines from fires, were not envisioned in the development of the part 23 normal... condition for the fire extinguishing system for the engine on the model SF50 is required. Regulations...

A new direct absorption tunable diode laser spectrometer for high precision measurement of water vapor in the upper troposphere and lower stratosphere.

PubMed

Sargent, M R; Sayres, D S; Smith, J B; Witinski, M; Allen, N T; Demusz, J N; Rivero, M; Tuozzolo, C; Anderson, J G

2013-07-01

We present a new instrument for the measurement of water vapor in the upper troposphere and lower stratosphere (UT∕LS), the Harvard Herriott Hygrometer (HHH). HHH employs a tunable diode near-IR laser to measure water vapor via direct absorption in a Herriott cell. The direct absorption technique provides a direct link between the depth of the observed absorption line and the measured water vapor concentration, which is calculated based on spectroscopic parameters in the HITRAN database. While several other tunable diode laser (TDL) instruments have been used to measure water vapor in the UT∕LS, HHH is set apart by its use of an optical cell an order of magnitude smaller than those of other direct absorption TDLs in operation, allowing for a more compact, lightweight instrument. HHH is also unique in its integration into a common duct with the Harvard Lyman-α hygrometer, an independent photo-fragment fluorescence instrument which has been thoroughly validated over 19 years of flight measurements. The instrument was flown for the first time in the Mid-latitude Airborne Cirrus Properties Experiment (MACPEX) on NASA's WB-57 aircraft in spring, 2011, during which it demonstrated in-flight precision of 0.1 ppmv (1 s) with 1-sigma uncertainty of 5% ± 0.7 ppmv. Since the campaign, changes to the instrument have lead to improved accuracy of 5% ± 0.2 ppmv as demonstrated in the laboratory. During MACPEX, HHH successfully measured water vapor at concentrations from 3.5 to 600 ppmv in the upper troposphere and lower stratosphere. HHH and Lyman-α, measuring independently but under the same sampling conditions, agreed on average to within 1% at water vapor mixing ratios above 20 ppmv and to within 0.3 ppmv at lower mixing ratios. HHH also agreed with a number of other in situ water vapor instruments on the WB-57 to within their stated uncertainties, and to within 0.7 ppmv at low water. This agreement constitutes a significant improvement over past in situ comparisons, in which differences of 1.5-2 ppmv were routinely observed, and demonstrates that the accuracy of HHH is consistent with other instruments which use a range of detection methods and sampling techniques.

Synopsis of TC4 Missions and Meteorology

NASA Astrophysics Data System (ADS)

Starr, D.; Pfister, L.; Selkirk, H.; Nguyen, L.

2007-12-01

The TC4 (Tropical Composition, Clouds and Climate Coupling) Experiment conducted 26 aircraft sorties on 13 flight days from July 17 to August 8, 2007 (23 days). Quality science observations were also obtained during the transit flights to/from from San Jose, Costa Rica, where the mission was based. On 9 days, coordinated aircraft missions were flown with the NASA ER-2 and DC-8, and with the NASA WB-57 on 3 occasions (and transit flights). The ER-2 served as an A-Train simulator (MODIS, CloudSat, CALIPSO, AIRS/TES, partial AMSR-E) while the WB-57 provided in-situ measurements of upper tropospheric cloud particles, aerosols and trace gases. The DC-8 provided both in-situ and remote sensing measurements, where the latter were focused on Aura validation, and also including a down-looking scanning precipitation radar (TRMM PR simulator). This paper will provide a synopsis of the science observations that were obtained, as regards the clouds and cloud systems sampled, from a meteorological perspective. A diversity of clouds were sampled and the meteorology proved more interesting than expected, at least to this author. Upper tropospheric cirrus outflows were sampled from a number of convective cloud systems including ITCZ-type systems as well as systems close to and affected by land. The low level inflows to these systems were also sampled in some cases (DC-8) and missions were flown to sample stratocumulus clouds over the Pacific Ocean exploiting the unique instrumentation on the DC-8 to add to the knowledge of these clouds which are so important to the Earth radiation budget. Measurements were made in the tropical Tropopause Transition Layer (TTL) by the WB-57. Upper tropospheric clouds and TTL properties and processes were central TC4 objectives. Excellent data were also obtained on the fate of the Saharan Air Layer and its aerosols over the Caribbean and Central America, as well as samples of plumes from volcanoes in Ecuador and Columbia and biogenic emissions over Columbia and the Pacific Ocean. Satellite observations, including those from various A-Train sensors, were used in planning the missions which were, in many cases, coordinated, at least in part, with satellite overpasses, especially Aura and other A-Train sensors (DC-8) and Terra.

Extratropical Influence of Upper Tropospheric Water Vapor on Greenhouse Warming

NASA Technical Reports Server (NTRS)

Hu, H.; Liu, W.

1998-01-01

The purpose of this paper is to re-examine the impact of upper tropospheric water vapor on greenhouse warming in midlatitudes by analyzing the recent observations of the upper tropospheric water vapor from the Microwave Limb Sounder (MLS) on the Upper Atmosphere Research Satellite (UARS), in conjuction with other space-based measurement and model simulation products.

Direct Comparisons of Ice Cloud Microphysical Properties Simulated by the Community Atmosphere Model CAM5 with ARM SPartICus Observations

NASA Astrophysics Data System (ADS)

Wu, C.; Liu, X.; Zhang, K.; Diao, M.; Gettelman, A.

2016-12-01

Cirrus clouds in the upper troposphere play a key role in the Earth radiation budget, and their radiative forcing depends strongly on number concentration and size distribution of ice particles. In this study we evaluate the cloud microphysical properties simulated by the Community Atmosphere Model version 5.4 (CAM5) against the Small Particles in Cirrus (SPartICus) observations over the ARM South Great Plain (SGP) site between January and June 2010. Model simulation is performed using specific dynamics to preserve prognostic meteorology (U, V, and T) close to GEOS-5 analysis. Model results collocated with SPartICus flight tracks spatially and temporally are directly compared with the observations. We compare CAM5 simulated ice crystal number concentration (Ni), ice particle size distribution, ice water content (IWC), and Ni co-variances with temperature and vertical velocity with the statistics from SPartICus observations. All analyses are restricted to T ≤ -40°C and in a 6°×6° area centered at SGP. Model sensitivity tests are performed with different ice nucleation mechanisms and with the effects of pre-existing ice crystals to reflect the uncertainties in cirrus parameterizations. In addition, different threshold size for autoconversion of cloud ice to snow (Dcs) is also tested. We find that (1) a distinctly high Ni (100-1000 L-1) often occurred in the observations but is significantly underestimated in the model, which may be due to the smaller relative humidity with respect to ice (RHi) in the simulation that could suppress the homogeneous nucleation, (2) a positive correlation exists between Ni and vertical velocity variance (σw) at horizontal scales up to 50 km in the observation, and the model can reproduce this relationship but tends to underestimate Ni when σw is relatively small, (3) simulated Ni differs greatly among the sensitive experiments, and simulated IWC is also sensitive to the cirrus parameterizations but to a lesser extent. Moreover, the model produces much better ice particle sizes in terms of number-mean diameter (Dnm) but significantly underestimate Ni and IWC for all the designed sensitive experiments. Our results suggest that better representation of environmental conditions (e.g., RHi and water vapor) is needed to improve the formation and evolution of ice clouds in the model.

A scheme for parameterizing cirrus cloud ice water content in general circulation models

NASA Technical Reports Server (NTRS)

Heymsfield, Andrew J.; Donner, Leo J.

1990-01-01

Clouds strongly influence th earth's energy budget. They control th amount of solar radiative energy absorbed by the climate system, partitioning the energy between the atmosphere and the earth's surface. They also control the loss of energy to space by their effect on thermal emission. Cirrus and altostratus are the most frequent cloud types, having an annual average global coverage of 35 and 40 percent, respectively. Cirrus is composed almost entirely of ice crystals and the same is frequently true of the upper portions of altostratus since they are often formed by the thickening of cirrostratus and by the spreading of the middle or upper portions of thunderstorms. Thus, since ice clouds cover such a large portion of the earth's surface, they almost certainly have an important effect on climate. With this recognition, researchers developing climate models are seeking largely unavailable methods for specifying the conditions for ice cloud formation, and quantifying the spatial distribution of ice water content, IWC, a necessary step in deriving their radiative characteristics since radiative properties are apparently related to IWC. A method is developed for specifying IWC in climate models, based on theory and measurements in cirrus during FIRE and other experiments.

Upper-Tropospheric Synoptic-Scale Waves. Part II: Maintenance and Excitation of Quasi Modes.

NASA Astrophysics Data System (ADS)

Rivest, Chantal; Farrell, Brian F.

1992-11-01

In a preceding paper a simple dynamical model for the maintenance of upper-tropospheric waves was proposed: the upper-level Eady normal modes. In this paper it is shown that these modes have counterparts in basic states with positive tropospheric gradients of potential vorticity, and that these counterparts can be maintained and excited on time scales consistent with observations.In the presence of infinitesimal positive tropospheric gradients of potential vorticity, the upper-level normal-mode solutions no longer exist. That the normal-mode solution disappears when gradients are infinitesimal represents an apparent singularity and challenges the interpretation of upper-level synoptic-scale waves as related to the upper-level Eady normal modes. What happens to the upper-level modal solution in the presence of tropospheric gradients of potential vorticity is examined in a series of initial-value experiments. Our results show that they become slowly decaying quasi modes. Mathematically the quasi modes consist of a superposition of singular modes sharply peaked in the phase speed domain, and their decay proceeds as the modes interfere with one another. We repeat these experiments in basic states with a smooth tropopause in the presence of tropospheric and stratospheric gradients, and similar results are obtained.Following a previous study by Farrell, a class of near-optimal initial conditions for the excitation of upper-level waves is identified. The initial conditions consist of upper-tropospheric disturbances that lean against the shear. They strongly excite upper-level waves not only in the absence of tropospheric potential vorticity gradients, but also in their presence. This result is important mathematically since it suggests that quasi modes are as likely to emerge from favorably configured initial disturbances as true normal modes, although the excitation is followed by a slow decay.

A molecular perspective for global modeling of upper atmospheric NH3 from freezing clouds.

PubMed

Ge, Cui; Zhu, Chongqin; Francisco, Joseph S; Zeng, Xiao Cheng; Wang, Jun

2018-05-30

Ammonia plays a key role in the neutralization of atmospheric acids such as sulfate and nitrates. A few in situ observations have supported the theory that gas-phase NH 3 concentrations should decrease sharply with altitude and be extremely low in the upper troposphere and lower stratosphere (UTLS). This theory, however, seems inconsistent with recent satellite measurements and is also not supported by the aircraft data showing highly or fully neutralized sulfate aerosol particles by ammonium in the UTLS in many parts of the world. Here we reveal the contributions of deep convective clouds to NH 3 in the UTLS by using integrated cross-scale modeling, which includes molecular dynamic simulations, a global chemistry transport model, and satellite and aircraft measurements. We show that the NH 3 dissolved in liquid cloud droplets is prone to being released into the UTLS upon freezing during deep convection. Because NH 3 emission is not regulated in most countries and its future increase is likely persistent from agricultural growth and the warmer climate, the effect of NH 3 on composition and phase of aerosol particles in the UTLS can be significant, which in turn can affect cirrus cloud formation, radiation, and the budgets of NOx and O 3 .

Radiative Heating of the ISCCP Upper Level Cloud Regimes and its Impact on the Large-scale Tropical Circulation

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

Li, Wei; Schumacher, Courtney; McFarlane, Sally A.

2013-01-31

Radiative heating profiles of the International Satellite Cloud Climatology Project (ISCCP) cloud regimes (or weather states) were estimated by matching ISCCP observations with radiative properties derived from cloud radar and lidar measurements from the Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) sites at Manus, Papua New Guinea, and Darwin, Australia. Focus was placed on the ISCCP cloud regimes containing the majority of upper level clouds in the tropics, i.e., mesoscale convective systems (MCSs), deep cumulonimbus with cirrus, mixed shallow and deep convection, and thin cirrus. At upper levels, these regimes have average maximum cloud occurrences ranging from 30% tomore » 55% near 12 km with variations depending on the location and cloud regime. The resulting radiative heating profiles have maxima of approximately 1 K/day near 12 km, with equal heating contributions from the longwave and shortwave components. Upper level minima occur near 15 km, with the MCS regime showing the strongest cooling of 0.2 K/day and the thin cirrus showing no cooling. The gradient of upper level heating ranges from 0.2 to 0.4 K/(day∙km), with the most convectively active regimes (i.e., MCSs and deep cumulonimbus with cirrus) having the largest gradient. When the above heating profiles were applied to the 25-year ISCCP data set, the tropics-wide average profile has a radiative heating maximum of 0.45Kday-1 near 250 hPa. Column-integrated radiative heating of upper level cloud accounts for about 20% of the latent heating estimated by the Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR). The ISCCP radiative heating of tropical upper level cloud only slightly modifies the response of an idealized primitive equation model forced with the tropics-wide TRMM PR latent heating, which suggests that the impact of upper level cloud is more important to large-scale tropical circulation variations because of convective feedbacks rather than direct forcing by the cloud radiative heating profiles. However, the height of the radiative heating maxima and gradient of the heating profiles are important to determine the sign and patterns of the horizontal circulation anomaly driven by radiative heating at upper levels.« less

Observational evidence for the convective transport of dust over the Central United States

NASA Astrophysics Data System (ADS)

Corr, C. A.; Ziemba, L. D.; Scheuer, E.; Anderson, B. E.; Beyersdorf, A. J.; Chen, G.; Crosbie, E.; Moore, R. H.; Shook, M.; Thornhill, K. L.; Winstead, E.; Lawson, R. P.; Barth, M. C.; Schroeder, J. R.; Blake, D. R.; Dibb, J. E.

2016-02-01

Bulk aerosol composition and aerosol size distributions measured aboard the DC-8 aircraft during the Deep Convective Clouds and Chemistry Experiment mission in May/June 2012 were used to investigate the transport of mineral dust through nine storms encountered over Colorado and Oklahoma. Measurements made at low altitudes (<5 km mean sea level (MSL)) in the storm inflow region were compared to those made in cirrus anvils (altitude > 9 km MSL). Storm mean outflow Ca2+ mass concentrations and total coarse (1 µm < diameter < 5 µm) aerosol volume (Vc) were comparable to mean inflow values as demonstrated by average outflow/inflow ratios greater than 0.5. A positive relationship between Ca2+, Vc, ice water content, and large (diameter > 50 µm) ice particle number concentrations was not evident; thus, the influence of ice shatter on these measurements was assumed small. Mean inflow aerosol number concentrations calculated over a diameter range (0.5 µm < diameter < 5.0 µm) relevant for proxy ice nuclei (NPIN) were ~15-300 times higher than ice particle concentrations for all storms. Ratios of predicted interstitial NPIN (calculated as the difference between inflow NPIN and ice particle concentrations) and inflow NPIN were consistent with those calculated for Ca2+ and Vc and indicated that on average less than 10% of the ingested NPIN were activated as ice nuclei during anvil formation. Deep convection may therefore represent an efficient transport mechanism for dust to the upper troposphere where these particles can function as ice nuclei cirrus forming in situ.

Assessing the quality of humidity measurements from global operational radiosonde sensors

NASA Astrophysics Data System (ADS)

Moradi, Isaac; Soden, Brian; Ferraro, Ralph; Arkin, Phillip; Vömel, Holger

2013-07-01

The quality of humidity measurements from global operational radiosonde sensors in upper, middle, and lower troposphere for the period 2000-2011 were investigated using satellite observations from three microwave water vapor channels operating at 183.31±1, 183.31±3, and 183.31±7 GHz. The radiosonde data were partitioned based on sensor type into 19 classes. The satellite brightness temperatures (Tb) were simulated using radiosonde profiles and a radiative transfer model, then the radiosonde simulated Tb's were compared with the observed Tb's from the satellites. The surface affected Tb's were excluded from the comparison due to the lack of reliable surface emissivity data at the microwave frequencies. Daytime and nighttime data were examined separately to see the possible effect of daytime radiation bias on the sonde data. The error characteristics among different radiosondes vary significantly, which largely reflects the differences in sensor type. These differences are more evident in the mid-upper troposphere than in the lower troposphere, mainly because some of the sensors stop responding to tropospheric humidity somewhere in the upper or even in the middle troposphere. In the upper troposphere, most sensors have a dry bias but Russian sensors and a few other sensors including GZZ2, VZB2, and RS80H have a wet bias. In middle troposphere, Russian sensors still have a wet bias but all other sensors have a dry bias. All sensors, including Russian sensors, have a dry bias in lower troposphere. The systematic and random errors generally decrease from upper to lower troposphere. Sensors from China, India, Russia, and the U.S. have a large random error in upper troposphere, which indicates that these sensors are not suitable for upper tropospheric studies as they fail to respond to humidity changes in the upper and even middle troposphere. Overall, Vaisala sensors perform better than other sensors throughout the troposphere exhibiting the smallest systematic and random errors. Because of the large differences between different radiosonde humidity sensors, it is important for long-term trend studies to only use data measured using a single type of sensor at any given station. If multiple sensor types are used then it is necessary to consider the bias between sensor types and its possible dependence on humidity and temperature.

Sunrise, Earth Limb, SW Pacific Ocean

NASA Technical Reports Server (NTRS)

1992-01-01

The colors of this sunrise/sunset scene provide insights into the relative density of the Earth's atmosphere (15.5S, 158.5E). This scene captures the silhouette of several thunderstorms with their cirrus anvil tops spreading out against the tropopause - the top of the lowest layer of atmosphere, the troposphere which is also the most dense and refracts light at the red end of the spectrum while the blues refract in the stratosphere, the highest layer.

Scale Invariance of High Altitude Aircraft Observations in the Upper Troposphere and Lower Stratosphere at Tropical and Subtropical Latitudes

NASA Technical Reports Server (NTRS)

Mahoney, M.; Hovde, S.; Kelly, K.; Proffitt, M.; Richard, E.; Thompson, T.; Tuck, A.

2000-01-01

Exchange between the upper tropical troposphere and the lower troposphere is considered by examining high altitude aircraft observations of water, ozone, methane, wind and temperature for scale invariance.

Changes in Cirrus Cloudiness and their Relationship to Contrails

NASA Technical Reports Server (NTRS)

Minnis, Patrick; Ayers, J. Kirk; Palikonda, Rabindra; Doelling, David R.; Schumann, Ulrich; Gierens, Klaus

2001-01-01

Condensation trails, or contrails, formed in the wake of high-altitude aircraft have long been suspected of causing the formation of additional cirrus cloud cover. More cirrus is possible because 10 - 20% of the atmosphere at typical commercial flight altitudes is clear but ice-saturated. Since they can affect the radiation budget like natural cirrus clouds of equivalent optical depth and microphysical properties, contrail -generated cirrus clouds are another potential source of anthropogenic influence on climate. Initial estimates of contrail radiative forcing (CRF) were based on linear contrail coverage and optical depths derived from a limited number of satellite observations. Assuming that such estimates are accurate, they can be considered as the minimum possible CRF because contrails often develop into cirrus clouds unrecognizable as contrails. These anthropogenic cirrus are not likely to be identified as contrails from satellites and would, therefore, not contribute to estimates of contrail coverage. The mean lifetime and coverage of spreading contrails relative to linear contrails are needed to fully assess the climatic effect of contrails, but are difficult to measure directly. However, the maximum possible impact can be estimated using the relative trends in cirrus coverage over regions with and without air traffic. In this paper, the upper bound of CRF is derived by first computing the change in cirrus coverage over areas with heavy air traffic relative to that over the remainder of the globe assuming that the difference between the two trends is due solely to contrails. This difference is normalized to the corresponding linear contrail coverage for the same regions to obtain an average spreading factor. The maximum contrail-cirrus coverage, estimated as the product of the spreading factor and the linear contrail coverage, is then used in the radiative model to estimate the maximum potential CRF for current air traffic.

Monitoring tropical cyclone intensity using wind fields derived from short-interval satellite images

NASA Technical Reports Server (NTRS)

Rodgers, E. B.; Gentry, R. C.

1981-01-01

Rapid scan visible images from the Visible Infrared Spin Scan Radiometer sensor on board SMS-2 and GOES-1 were used to derive high resolution upper and lower tropospheric environmental wind fields around three western Atlantic tropical cyclones (1975-78). These wind fields were used to derive upper and lower tropospheric areal mean relative vorticity and their differences, the net relative angular momentum balance and upper tropospheric mass outflow. These kinematic parameters were shown by studies using composite rawinsonde data to be strongly related to tropical cyclone formation and intensity changes. Also, the role of forced synoptic scale subsidence in tropical cyclone formation was examined. The studies showed that satellite-derived lower and upper tropospheric wind fields can be used to monitor and possibly predict tropical cyclone formation and intensity changes. These kinematic analyses showed that future changes in tropical cyclone intensity are mainly related to the "spin-up" of the storms by the net horizontal transport of relative angular momentum caused by convergence of cyclonic vorticity in the lower troposphere and to a lesser extent the divergence of anticyclone vorticity in the upper troposphere.

Earth views and an illuminated earth limb

NASA Image and Video Library

1998-11-20

STS047-54-016 (12 - 20 Sept 1992) --- The colors in this photograph provide insight into the relative density of the atmosphere. The crew members had many opportunities to witness sunrises and sunsets, considering they orbit the Earth every 90 minutes, but few, they said, compared to this scene. It captures the silhouette of several mature thunderstorms with their cirrus anvil tops spreading out against the tropopause (the top of the lowest layer of Earth's atmosphere) at sunset. The lowest layer (troposphere) is the densest and refracts light at the red end of the visible spectrum (7,400 Angstroms), while the blues (4,000 Angstroms) are separated in the least dense portion of the atmosphere (middle and upper atmosphere, or stratosphere and mesosphere). Several layers of blue can be seen. NASA scientists studying the photos believe this stratification to be caused by the scattering of light by particulate trapped in the stratosphere and mesosphere particulate that generally originate from volcanic eruptions, such as those of Mt. Pinatubo in the Philippines and, most recently, Mt. Spurr in Alaska.

Origins of tropospheric ozone interannual variation over Réunion: A model investigation

NASA Astrophysics Data System (ADS)

Liu, Junhua; Rodriguez, Jose M.; Thompson, Anne M.; Logan, Jennifer A.; Douglass, Anne R.; Olsen, Mark A.; Steenrod, Stephen D.; Posny, Françoise

2016-01-01

Observations from long-term ozonesonde measurements show robust variations and trends in the evolution of ozone in the middle and upper troposphere over Réunion Island (21.1°S, 55.5°E) in June-August. Here we examine possible causes of the observed ozone variation at Réunion Island using hindcast simulations by the stratosphere-troposphere Global Modeling Initiative chemical transport model for 1992-2014, driven by assimilated Modern-Era Retrospective Analysis for Research and Applications meteorological fields. Réunion Island is at the edge of the subtropical jet, a region of strong stratospheric-tropospheric exchange. Our analysis implies that the large interannual variation (IAV) of upper tropospheric ozone over Réunion is driven by the large IAV of the stratospheric influence. The IAV of the large-scale, quasi-horizontal wind patterns also contributes to the IAV of ozone in the upper troposphere. Comparison to a simulation with constant emissions indicates that increasing emissions do not lead to the maximum trend in the middle and upper troposphere over Réunion during austral winter implied by the sonde data. The effects of increasing emission over southern Africa are limited to the lower troposphere near the surface in August-September.

Origins of Tropospheric Ozone Interannual Variation (IAV) over Reunion: A Model Investigation

NASA Technical Reports Server (NTRS)

Liu, Junhua; Rodriguez, Jose M.; Thompson, Anne M.; Logan, Jennifer A.; Douglass, Anne R.; Olsen, Mark A.; Steenrod, Stephen D.; Posny, Francoise

2016-01-01

Observations from long-term ozonesonde measurements show robust variations and trends in the evolution of ozone in the middle and upper troposphere over Reunion Island (21.1 degrees South Latitude, 55.5 degrees East Longitude) in June-August. Here we examine possible causes of the observed ozone variation at Reunion Island using hindcast simulations by the stratosphere-troposphere Global Modeling Initiative chemical transport model for 1992-2014, driven by assimilated Modern-Era Retrospective Analysis for Research and Applications (MERRA) meteorological fields. Reunion Island is at the edge of the subtropical jet, a region of strong stratospheric-tropospheric exchange. Our analysis implies that the large interannual variation (IAV) of upper tropospheric ozone over Reunion is driven by the large IAV of the stratospheric influence. The IAV of the large-scale, quasi-horizontal wind patterns also contributes to the IAV of ozone in the upper troposphere. Comparison to a simulation with constant emissions indicates that increasing emissions do not lead to the maximum trend in the middle and upper troposphere over Reunion during austral winter implied by the sonde data. The effects of increasing emission over southern Africa are limited tothe lower troposphere near the surface in August-September.

Improvements in Raman Lidar Measurements Using New Interference Filter Technology

NASA Technical Reports Server (NTRS)

Whiteman, David N.; Potter, John R.; Tola, Rebecca; Veselovskii, Igor; Cadirola, Martin; Rush, Kurt; Comer, Joseph

2006-01-01

Narrow-band interference filters with improved transmission in the ultra-violet have been developed under NASA-funded research and used in the Raman Airborne Spectroscopic Lidar (RASL) in ground-based, upward-looking tests. Measurements were made of atmospheric water vapor, cirrus cloud optical properties and carbon dioxide that improve upon any previously demonstrated using Raman lidar. Daytime boundary and mixed layer profiling of water vapor mixing ratio up to an altitude of approximately 4 h is performed with less than 5% random error using temporal and spatial resolution of 2-minutes and 60 - 210, respectively. Daytime cirrus cloud optical depth and extinction-to-backscatter ratio measurements are made using 1 -minute average. Sufficient signal strength is demonstrated to permit the simultaneous profiling of carbon dioxide and water vapor mixing ratio into the free troposphere during the nighttime. A description of the filter technology developments is provided followed by examples of the improved Raman lidar measurements.

The hydrological cycle response to cirrus cloud thinning

NASA Astrophysics Data System (ADS)

Kristjánsson, Jón Egill; Muri, Helene; Schmidt, Hauke

2015-12-01

Recent multimodel studies have shown that if one attempts to cancel increasing CO2 concentrations by reducing absorbed solar radiation, the hydrological cycle will weaken if global temperature is kept unchanged. Using a global climate model, we investigate the hydrological cycle response to "cirrus cloud thinning (CCT)," which is a proposed climate engineering technique that seeks to enhance outgoing longwave radiation. Investigations of the "fast response" in experiments with fixed sea surface temperatures reveal that CCT causes a significant enhancement of the latent heat flux and precipitation. This is due to enhanced radiative cooling of the troposphere, which is opposite to the effect of increased CO2 concentrations. By combining CCT with CO2 increase in multidecadal simulations with a slab ocean, we demonstrate a systematic enhancement of the hydrological cycle due to CCT. This leads to enhanced moisture availability in low-latitude land regions and a strengthening of the Indian monsoon.

A Numerical Model of the Performance of the Howard University Raman Lidar System

NASA Astrophysics Data System (ADS)

Connell, Rasheen M.; Adam, Mariana; Venable, Demetrius

2009-07-01

At the Howard University Atmospheric Observatory in Beltsville, MD, a Raman Lidar system was developed to provide both daytime and nighttime measurements of water vapor, aerosols, and cirrus clouds with 1 min temporal and 7.5 m spatial resolution in the lower troposphere. Signals at three wavelengths associated with Rayleigh/Mie scattering for aerosols and cirrus clouds at 354.7 nm, Raman scattering for nitrogen at 386.7 nm, and water vapor at 407.5 nm are analyzed. The transmitter is a triple harmonic Nd: YAG solid state laser. The receiver is a 40 cm Cassegrain telescope. Our detector system consists of a multi-channel wavelength separator unit and data acquisition system. We are developing a numerical model to provide a realistic representation of the system behavior. The variants of the lidar equation in the model use system parameters and are solved to determine the return signals for our lidar system. In this paper, we report on two of the five case studies being investigated: clear sky and cirrus cloud covered molecular atmosphere. The first simulations are based on a standard atmosphere, which assumes an unpolluted (aerosol-free) dry air atmosphere. The second set of simulations is based on a cloudy atmosphere, where cirrus clouds are added to the conditions in case study I. Lidar signals are simulated over the altitude range covered by our measurements (up to 14 km). Results will show comparisons between the simulated and actual measurements when varying lidar and atmospheric optical parameters in the model.

Florida Thunderstorms: A Faucet of Reactive Nitrogen to the Upper Troposphere

NASA Technical Reports Server (NTRS)

Ridley, B.; Ott, L.; Emmons, L.; Montzka, D.; Weinheimer, A.; Knapp, D.; Grahek, F.; Li, L.; Heymsfield, G.; McGill, M.

2004-01-01

During the NASA Cirrus Regional Study of Tropical Anvils and Cirrus Layers-Florida Area Cirrus Experiment (CRYSTAL-FACE) enhanced mixing ratios of nitric oxide were measured in the anvils of thunderstorms and in clear air downwind of storm systems on flights of a Wl3-57F high-altitude aircraft. Mixing ratios greater than l0 - 20 times background were readily observed over distances of 25-120 km due to lightning activity. In many of the Florida storms deposition of NO occurred up to near the tropopause but major deposition usually occurred 1 - 2 km below the tropopause, or mostly within the visible anvil volume formed prior to storm decay. Observations from two storms of very different anvil size and electrical activity allowed estimates of the total mass of NO, vented to the middle and upper troposphere. Using the cloud-to ground (CG) flash accumulations from the National Lightning Detection Network, climatological intra-cloud (IC) to CG ratios, and assuming that CG and IC flashes were of equivalent efficiency for NO production, the ranges of production per flash for a moderate-sized and a large storm were (0.51 - 1.0) x l0(exp 26) and (2.3 - 3.1) x 10(exp 26) molecules NO/flash, respectively. Using the recently determined average global flash rate of 44 8, a gross extrapolation of these two storms to represent possible global annual production rates yield 1.6 - 3.2 and 7.3 - 9.9 Tg(N)/yr, respectively. If the more usual assumption is made that IC efficiency is l/l0th that of CG activity, the ranges of production for the moderate-sized and large storm were (1.3 - 2.7) x l0(exp 26) and (6.0 - 8.1) x l0(exp 26) molecules NO/CG flash, respectively. The estimates from the large storm may be high because there is indirect evidence that the IC/CG ratio was larger than would be derived from climatology. These two storms and others studied did not have flash rates that scaled as approx. H(sup 5) where H is the cloud top altitude. The observed CG flash accumulations and NO(x) mass production estimate for the month of July over the Florida area were compared with a representative 3D global Chemistry-Transport Model (CTMJ that uses the Price et al. lightning parameterization. For two land grid points representing the Florida peninsula the model compared well with the observations: CG flash rates were low by only a factor of approx. 2. When the model grid points included the coastal regions of Florida the flash accumulations were lower than observed by a factor of 3.4 - 4.6. It is recommended that models using the Price et al. parameterization allow any global coastal grid point to maintain the land rather than the marine flash rate parameterization. The convection in this CTM underestimated the actual cloud top heights over Florida by 1 - 2 km and thus the total lightning flash rates and the altitude range of reactive nitrogen deposition. Broad scale (20 - 120 km) median mixing ratios of NO within anvils over Florida were significantly larger than in storms previously investigated over Colorado and New Mexico.

"Cloud Slicing" : A New Technique to Derive Tropospheric Ozone Profile Information from Satellite Measurements

NASA Technical Reports Server (NTRS)

Ziemke, J. R.; Chandra, S.; Bhartia, P. K.; Einaudi, Franco (Technical Monitor)

2000-01-01

A new technique denoted cloud slicing has been developed for estimating tropospheric ozone profile information. All previous methods using satellite data were only capable of estimating the total column of ozone in the troposphere. Cloud slicing takes advantage of the opaque property of water vapor clouds to ultraviolet wavelength radiation. Measurements of above-cloud column ozone from the Nimbus 7 total ozone mapping spectrometer (TOMS) instrument are combined together with Nimbus 7 temperature humidity and infrared radiometer (THIR) cloud-top pressure data to derive ozone column amounts in the upper troposphere. In this study tropical TOMS and THIR data for the period 1979-1984 are analyzed. By combining total tropospheric column ozone (denoted TCO) measurements from the convective cloud differential (CCD) method with 100-400 hPa upper tropospheric column ozone amounts from cloud slicing, it is possible to estimate 400-1000 hPa lower tropospheric column ozone and evaluate its spatial and temporal variability. Results for both the upper and lower tropical troposphere show a year-round zonal wavenumber 1 pattern in column ozone with largest amounts in the Atlantic region (up to approx. 15 DU in the 100-400 hPa pressure band and approx. 25-30 DU in the 400-1000 hPa pressure band). Upper tropospheric ozone derived from cloud slicing shows maximum column amounts in the Atlantic region in the June-August and September-November seasons which is similar to the seasonal variability of CCD derived TCO in the region. For the lower troposphere, largest column amounts occur in the September-November season over Brazil in South America and also southern Africa. Localized increases in the tropics in lower tropospheric ozone are found over the northern region of South America around August and off the west coast of equatorial Africa in the March-May season. Time series analysis for several regions in South America and Africa show an anomalous increase in ozone in the lower troposphere around the month of March which is not observed in the upper troposphere. The eastern Pacific indicates weak seasonal variability of upper, lower, and total tropospheric ozone compared to the western Pacific which shows largest TCO amounts in both hemispheres around spring months. Ozone variability in the western Pacific is expected to have greater variability caused by strong convection, pollution and biomass burning, land/sea contrast and monsoon developments.

Enhancement in the upper tropospheric humidity associated with aerosol loading over tropical Pacific

NASA Astrophysics Data System (ADS)

Kottayil, Ajil; Satheesan, K.

2015-12-01

Many modeling studies have indicated that aerosol interactions with clouds increase the upper tropospheric humidity (UTH), but observational evidences are sparse. Using satellite datasets of upper tropospheric humidity and aerosols, this study shows that aerosols increase the upper tropospheric humidity over the tropical North West Pacific (NWP) and North East Pacific (NEP). The observations show an increase in the UTH by 2.8%RH over NEP for an increment of 0.12 in aerosol optical depth (AOD) and 2%RH increase in UTH over NWP for an increment of 0.19 in AOD. The study also quantifies the change in longwave cloud radiative forcing (LWCRF) as a consequence of the increase in UTH due to aerosols. The LWCRF increases by 3.38 W m-2 over NEP and by 4.46 W m-2 over NWP. The result that aerosols increase the upper tropospheric humidity is significant since the latter plays a crucial role in regulating the Earth's radiation budget and water vapor feedback.

Physical Mechanisms Controlling Upper Tropospheric Water Vapor as Revealed by MLS Data from UARS

NASA Technical Reports Server (NTRS)

Newell, Reginald E.; Douglass, Anne (Technical Monitor)

2002-01-01

The third year and final report on the physical mechanisms controlling upper tropospheric water vapor revealed by the Microwave Limb Sounder (MLS) on the Upper Atmosphere Research Satellite (UARS) is presented.

Resolving ice cloud optical thickness biases between CALIOP and MODIS using infrared retrievals

NASA Astrophysics Data System (ADS)

Holz, R. E.; Platnick, S.; Meyer, K.; Vaughan, M.; Heidinger, A.; Yang, P.; Wind, G.; Dutcher, S.; Ackerman, S.; Amarasinghe, N.; Nagle, F.; Wang, C.

2015-10-01

Despite its importance as one of the key radiative properties that determines the impact of upper tropospheric clouds on the radiation balance, ice cloud optical thickness (IOT) has proven to be one of the more challenging properties to retrieve from space-based remote sensing measurements. In particular, optically thin upper tropospheric ice clouds (cirrus) have been especially challenging due to their tenuous nature, extensive spatial scales, and complex particle shapes and light scattering characteristics. The lack of independent validation motivates the investigation presented in this paper, wherein systematic biases between MODIS Collection 5 (C5) and CALIOP Version 3 (V3) unconstrained retrievals of tenuous IOT (< 3) are examined using a month of collocated A-Train observations. An initial comparison revealed a factor of two bias between the MODIS and CALIOP IOT retrievals. This bias is investigated using an infrared (IR) radiative closure approach that compares both products with MODIS IR cirrus retrievals developed for this assessment. The analysis finds that both the MODIS C5 and the unconstrained CALIOP V3 retrievals are biased (high and low, respectively) relative to the IR IOT retrievals. Based on this finding, the MODIS and CALIOP algorithms are investigated with the goal of explaining and minimizing the biases relative to the IR. For MODIS we find that the assumed ice single scattering properties used for the C5 retrievals are not consistent with the mean IR COT distribution. The C5 ice scattering database results in the asymmetry parameter (g) varying as a function of effective radius with mean values that are too large. The MODIS retrievals have been brought into agreement with the IR by adopting a new ice scattering model for Collection 6 (C6) consisting of a modified gamma distribution comprised of a single habit (severely roughened aggregated columns); the C6 ice cloud optical property models have a constant g ~ 0.75 in the mid-visible spectrum, 5-15 % smaller than C5. For CALIOP, the assumed lidar ratio for unconstrained retrievals is fixed at 25 sr for the V3 data products. This value is found to be inconsistent with the constrained (predominantly nighttime) CALIOP retrievals. An experimental data set was produced using a modified lidar ratio of 32 sr for the unconstrained retrievals (an increase of 28 %), selected to provide consistency with the constrained V3 results. These modifications greatly improve the agreement with the IR and provide consistency between the MODIS and CALIOP products. Based on these results the recently released MODIS C6 optical products use the single habit distribution given above, while the upcoming CALIOP V4 unconstrained algorithm will use higher lidar ratios for unconstrained retrievals.

Resolving Ice Cloud Optical Thickness Biases Between CALIOP and MODIS Using Infrared Retrievals

NASA Technical Reports Server (NTRS)

Holz, R. E.; Platnick, S.; Meyer, K.; Vaughan, M.; Heidinger, A.; Yang, P.; Wind, G.; Dutcher, S.; Ackerman, S.; Amarasinghe, N.;

Resolving ice cloud optical thickness biases between CALIOP and MODIS using infrared retrievals

NASA Astrophysics Data System (ADS)

Holz, Robert E.; Platnick, Steven; Meyer, Kerry; Vaughan, Mark; Heidinger, Andrew; Yang, Ping; Wind, Gala; Dutcher, Steven; Ackerman, Steven; Amarasinghe, Nandana; Nagle, Fredrick; Wang, Chenxi

2016-04-01

Despite its importance as one of the key radiative properties that determines the impact of upper tropospheric clouds on the radiation balance, ice cloud optical thickness (IOT) has proven to be one of the more challenging properties to retrieve from space-based remote sensing measurements. In particular, optically thin upper tropospheric ice clouds (cirrus) have been especially challenging due to their tenuous nature, extensive spatial scales, and complex particle shapes and light-scattering characteristics. The lack of independent validation motivates the investigation presented in this paper, wherein systematic biases between MODIS Collection 5 (C5) and CALIOP Version 3 (V3) unconstrained retrievals of tenuous IOT (< 3) are examined using a month of collocated A-Train observations. An initial comparison revealed a factor of 2 bias between the MODIS and CALIOP IOT retrievals. This bias is investigated using an infrared (IR) radiative closure approach that compares both products with MODIS IR cirrus retrievals developed for this assessment. The analysis finds that both the MODIS C5 and the unconstrained CALIOP V3 retrievals are biased (high and low, respectively) relative to the IR IOT retrievals. Based on this finding, the MODIS and CALIOP algorithms are investigated with the goal of explaining and minimizing the biases relative to the IR. For MODIS we find that the assumed ice single-scattering properties used for the C5 retrievals are not consistent with the mean IR COT distribution. The C5 ice scattering database results in the asymmetry parameter (g) varying as a function of effective radius with mean values that are too large. The MODIS retrievals have been brought into agreement with the IR by adopting a new ice scattering model for Collection 6 (C6) consisting of a modified gamma distribution comprised of a single habit (severely roughened aggregated columns); the C6 ice cloud optical property models have a constant g ≈ 0.75 in the mid-visible spectrum, 5-15 % smaller than C5. For CALIOP, the assumed lidar ratio for unconstrained retrievals is fixed at 25 sr for the V3 data products. This value is found to be inconsistent with the constrained (predominantly nighttime) CALIOP retrievals. An experimental data set was produced using a modified lidar ratio of 32 sr for the unconstrained retrievals (an increase of 28 %), selected to provide consistency with the constrained V3 results. These modifications greatly improve the agreement with the IR and provide consistency between the MODIS and CALIOP products. Based on these results the recently released MODIS C6 optical products use the single-habit distribution given above, while the upcoming CALIOP V4 unconstrained algorithm will use higher lidar ratios for unconstrained retrievals.

Cirrus cloud mimic surfaces in the laboratory: organic acids, bases and NOx heterogeneous reactions

NASA Astrophysics Data System (ADS)

Sodeau, J.; Oriordan, B.

2003-04-01

CIRRUS CLOUD MIMIC SURFACES IN THE LABORATORY:ORGANIC ACIDS, BASES AND NOX HETEROGENEOUS REACTIONS. B. ORiordan, J. Sodeau Department of Chemistry and Environment Research Institute, University College Cork, Ireland j.sodeau@ucc.ie /Fax: +353-21-4902680 There are a variety of biogenic and anthropogenic sources for the simple carboxylic acids to be found in the troposphere giving rise to levels as high as 45 ppb in certain urban areas. In this regard it is of note that ants of genus Formica produce some 10Tg of formic acid each year; some ten times that produced by industry. The expected sinks are those generally associated with tropospheric chemistry: the major routes studied, to date, being wet and dry deposition. No studies have been carried out hitherto on the role of water-ice surfaces in the atmospheric chemistry of carboxylic acids and the purpose of this paper is to indicate their potential function in the heterogeneous release of atmospheric species such as HONO. The deposition of formic acid on a water-ice surface was studied using FT-RAIR spectroscopy over a range of temperatures between 100 and 165K. In all cases ionization to the formate (and oxonium) ions was observed. The results were confirmed by TPD (Temperature Programmed Desorption) measurements, which indicated that two distinct surface species adsorb to the ice. Potential reactions between the formic acid/formate ion surface and nitrogen dioxide were subsequently investigated by FT-RAIRS. Co-deposition experiments showed that N2O3 and the NO+ ion (associated with water) were formed as products. A mechanism is proposed to explain these results, which involves direct reaction between the organic acid and nitrogen dioxide. Similar experiments involving acetic acid also indicate ionization on a water-ice surface. The results are put into the context of atmospheric chemistry potentially occuring on cirrus cloud surfaces.

Origins of tropospheric ozone interannual variation (IAV) over Réunion: A model investigation.

PubMed

Liu, Junhua; Rodriguez, Jose M; Thompson, Anne M; Logan, Jennifer A; Douglass, Anne R; Olsen, Mark A; Steenrod, Stephen D; Posny, Francoise

2016-01-16

Observations from long-term ozonesonde measurements show robust variations and trends in the evolution of ozone in the middle and upper troposphere over Réunion Island (21.1°S, 55.5°E) in June-August. Here we examine possible causes of the observed ozone variation at Réunion Island using hindcast simulations by the stratosphere-troposphere Global Modeling Initiative chemical transport model (GMI-CTM) for 1992-2014, driven by assimilated Modern-Era Retrospective Analysis for Research and Applications (MERRA) meteorological fields. Réunion Island is at the edge of the subtropical jet, a region of strong stratospheric-tropospheric exchange (STE). Our analysis implies that the large interannual variation (IAV) of upper tropospheric ozone over Réunion is driven by the large IAV of the stratospheric influence. The IAV of the large-scale, quasi-horizontal wind patterns also contributes to the IAV of ozone in the upper troposphere. Comparison to a simulation with constant emissions indicates that increasing emissions do not lead to the maximum trend in the middle and upper troposphere over Réunion during austral winter implied by the sonde data. The effects of increasing emission over southern Africa are limited to the lower troposphere near the surface in August - September.

Origins of tropospheric ozone interannual variation (IAV) over Réunion: A model investigation

PubMed Central

Liu, Junhua; Rodriguez, Jose M.; Thompson, Anne M.; Logan, Jennifer A.; Douglass, Anne R.; Olsen, Mark A.; Steenrod, Stephen D.; Posny, Francoise

2018-01-01

Observations from long-term ozonesonde measurements show robust variations and trends in the evolution of ozone in the middle and upper troposphere over Réunion Island (21.1°S, 55.5°E) in June-August. Here we examine possible causes of the observed ozone variation at Réunion Island using hindcast simulations by the stratosphere-troposphere Global Modeling Initiative chemical transport model (GMI-CTM) for 1992–2014, driven by assimilated Modern-Era Retrospective Analysis for Research and Applications (MERRA) meteorological fields. Réunion Island is at the edge of the subtropical jet, a region of strong stratospheric-tropospheric exchange (STE). Our analysis implies that the large interannual variation (IAV) of upper tropospheric ozone over Réunion is driven by the large IAV of the stratospheric influence. The IAV of the large-scale, quasi-horizontal wind patterns also contributes to the IAV of ozone in the upper troposphere. Comparison to a simulation with constant emissions indicates that increasing emissions do not lead to the maximum trend in the middle and upper troposphere over Réunion during austral winter implied by the sonde data. The effects of increasing emission over southern Africa are limited to the lower troposphere near the surface in August – September. PMID:29657911

Variations in Upper-Tropospheric Humidity and Convective Processes as Seen from SSM/T-2

NASA Technical Reports Server (NTRS)

Robertson, Franklin R.; Fitzjarrald, Dan E.

2007-01-01

Water vapor feedback, particularly involving water vapor in the upper troposphere (UTH), is widely regarded as the process with the most potential to amplify anthropogenic greenhouse forcing. Yet, our ability to quantify observationally water vapor variations in the current climate and the relationships to convective processes remains rather crude. Remote sensing from polar orbiting instruments has played a major role in documenting UTH variability, supplementing highly undersampled and poorly calibrated rawinsonde measurements. Most of our observational understanding of UTH has come from the 6.7 micrometer channel measurements which are subject to cloud contamination uncertainties. In this work we examine UTH variations present in the Special Sensor Microwave Temperature Sounder 2 (SSM/T-2) sensors flying aboard Defense Military Satellite Program (DMSP) polar orbiting satellites during the period 1993 through 2001. We employ data from the the 183.3 +/- 1 GHz channel which is far less sensitive to cirrus than IR methods. Our primary focus is on obtaining more reliable statistics of interannual behavior; i.e. How close to constant RH are interannual variations in T2 UTH over the tropics? How do temperature and moisture variations contribute regionally? The 1997/1998 strong ENS0 warming event and adjacent cool periods provide a strong signal to study, albeit a perturbation of natural climate variability. Modeling the 183.3 GHz channel using reanalysis temperature data, but with climatological water vapor, allows us to infer the separate contribution by water vapor in the observations. In addition, frozen hydrometeors produced by deep convection are also captured in the 150 GHz oxygen channel, providing an opportUnity to relate the incidence of deep convection to water vapor variability. Our results indicate a much larger variation of 183.3 GHz brightness temperatures would be observed were it not for water vapor variations positively correlated with tropical SSTs. Comparisons are made with previous studies using both IR and microwave observations to characterize UTH response to tropical SSTs.

Cloud and aerosol occurrences in the UTLS region across Pakistan during summer monsoon seasons using CALIPSO and CloudSat observations

NASA Astrophysics Data System (ADS)

Chishtie, Farrukh

2016-04-01

As part of the A-train NASA constellation, Coudsat and CALIPSO provide an unprecedented vertical observation of clouds and aerosols. Using observational data from both of these satellites, we conduct a multi-year analysis from 2006-2014, of the UTLS (Upper Troposphere and the Lower Stratosphere) region. We map out cloud and aerosol occurrences in this region across Pakistan, specifically around the summer monsoon season. Over the past five years, Pakistan has faced tremendous challenges due to massive flooding as well as earlier brief monsoon seasons of low precipitation and short drought periods. Hence, this motivates the present study towards understanding the deep convective and related dynamics in this season which can possibly influence cloud and aerosol transport in the region. Further, while global studies are conducted, the goal of this study is to conduct a detailed study of cloud, aerosols and their interplay, across Pakistan. Due to a dearth of ground observations, this study provides a dedicated focus on the UTLS domain. Vertical profiling satellites in this region are deemed important as there are no ground observations being done. This is important as both the properties and dynamics of clouds and aerosols have to be studied in a wider context in order to better understand the monsoon season and its onset in this region. With the CALIPSO Vertical Feature Mask (VFM), Total Attenuated Backscatter (TAB) and Depolarization Ratio (DR) as well as the combined CloudSat's 2B-GEOPROF-LIDAR (Radar-Lidar Cloud Geometrical Profile) and 2B-CLDCLASS-LIDAR (Radar-Lidar Cloud Classification) products, we find the presence of thin cirrus clouds in the UTLS region in the periods of June-September from the 2006-2014 period. There are marked differences in day observations as compared to night in both of these satellite retrievals, with the latter period finding more occurrences of clouds in the UTLS region. Dedicated CloudSat products 2B-CLDCLASS (cloud classification) and 2C-TAU (Cloud Optical Depth) further confirm the presence of sub-visual and thin cirrus clouds in the UTLS region, during the summer monsoon season. From CALIPSO observations, there is significant presence of aerosol layers before the onset of precipitation in the troposphere. This thickness ranges from 1-4 km, with increasing thickness observed the 2009-2014 period. Implications of these findings are detailed in this presentation.

Monthly mean large-scale analyses of upper-tropospheric humidity and wind field divergence derived from three geostationary satellites

NASA Technical Reports Server (NTRS)

Schmetz, Johannes; Menzel, W. Paul; Velden, Christopher; Wu, Xiangqian; Vandeberg, Leo; Nieman, Steve; Hayden, Christopher; Holmlund, Kenneth; Geijo, Carlos

1995-01-01

This paper describes the results from a collaborative study between the European Space Operations Center, the European Organization for the Exploitation of Meteorological Satellites, the National Oceanic and Atmospheric Administration, and the Cooperative Institute for Meteorological Satellite Studies investigating the relationship between satellite-derived monthly mean fields of wind and humidity in the upper troposphere for March 1994. Three geostationary meteorological satellites GOES-7, Meteosat-3, and Meteosat-5 are used to cover an area from roughly 160 deg W to 50 deg E. The wind fields are derived from tracking features in successive images of upper-tropospheric water vapor (WV) as depicted in the 6.5-micron absorption band. The upper-tropospheric relative humidity (UTH) is inferred from measured water vapor radiances with a physical retrieval scheme based on radiative forward calculations. Quantitative information on large-scale circulation patterns in the upper-troposphere is possible with the dense spatial coverage of the WV wind vectors. The monthly mean wind field is used to estimate the large-scale divergence; values range between about-5 x 10(exp -6) and 5 x 10(exp 6)/s when averaged over a scale length of about 1000-2000 km. The spatial patterns of the UTH field and the divergence of the wind field closely resemble one another, suggesting that UTH patterns are principally determined by the large-scale circulation. Since the upper-tropospheric humidity absorbs upwelling radiation from lower-tropospheric levels and therefore contributes significantly to the atmospheric greenhouse effect, this work implies that studies on the climate relevance of water vapor should include three-dimensional modeling of the atmospheric dynamics. The fields of UTH and WV winds are useful parameters for a climate-monitoring system based on satellite data. The results from this 1-month analysis suggest the desirability of further GOES and Meteosat studies to characterize the changes in the upper-tropospheric moisture sources and sinks over the past decade.

The Development Of Enabling Technologies For Submillimeter-Wave Remote Sensing of Ice Clouds From Space

NASA Technical Reports Server (NTRS)

Racette, Paul; Wang, James R.; Ackerman, Steven; Skofronick-Jackson, Gail; Evans, K. Frank; O'CStarr, David

2006-01-01

This paper presents the chronological development of technologies and techniques that have led to a satellite mission concept aimed at quantifying the temporal and spatial distributions of upper tropospheric ice clouds. The Submillimeter-wave and Infrared Ice Cloud Experiment (SIRICE) is an Earth System Science Pathfinder mission concept designed to improve our understanding of the upper tropospheric water cycle and its coupling to the Earth s radiation budget. Ice outflow from convective storm systems is known to play an important role in regional energy budgets; however, ice generation and subsequent precipitation and sublimation are poorly quantified. SIRICE will provide measurements of ice cloud distributions and microphysical properties which are needed for understanding the crucial link between the hydrologic and energy cycles. The SIRICE measurement platform is comprised of two integrated instruments, the Submillimeter/millimeter-wave radiometer (SM4) and the Infrared Cloud Ice Radiometer (IRCIR). The primary instrument is the SM4, a conical scanner that provides a 1600 km swath of the Earth's surface at 53 degree incidence. The SM4 has 6 linearly polarized receivers measuring 12 spectral bands centered at 183 GHz, 325 GHz, 448 GHz, 643 GHz and 874 GHz; two receivers at 643 GHz measure horizontal and vertical polarizations. Submillimeter-wavelengths are well suited to the remote sensing of ice clouds due to the relative size of the wavelengths to particle sizes. Upwelling emission from lower tropospheric water vapor is scattered by the ice clouds thus causing a brightness temperature depression at submillimeter wavelengths. The IRCIR is a push broom imager with approximately 1500 km swath and spectral channels at 11 and 12 micrometers. This combination of coincident infrared and submillimeter-wavelength measurements were chosen because of its ability to provide retrieval of ice water path and median particle size for a wide range of ice clouds from thin cirrus to thick anvil structures. Over the past decade there has been a parallel development of submillimeter-wave technologies, demonstration instruments, and remote sensing techniques that have led to the present SIRICE mission concept. Mapping of these developmental paths reveals the origins, rational and maturity of features of the SIRICE payload such as its channel selection, compact design, and multipoint calibration. This presentation traces the evolution of the SIRICE mission concept from the early 1990's to its present status.

Cirrus Cloud Retrieval Using Infrared Sounding Data: Multilevel Cloud Errors.

NASA Astrophysics Data System (ADS)

Baum, Bryan A.; Wielicki, Bruce A.

1994-01-01

In this study we perform an error analysis for cloud-top pressure retrieval using the High-Resolution Infrared Radiometric Sounder (HIRS/2) 15-µm CO2 channels for the two-layer case of transmissive cirrus overlying an overcast, opaque stratiform cloud. This analysis includes standard deviation and bias error due to instrument noise and the presence of two cloud layers, the lower of which is opaque. Instantaneous cloud pressure retrieval errors are determined for a range of cloud amounts (0.1 1.0) and cloud-top pressures (850250 mb). Large cloud-top pressure retrieval errors are found to occur when a lower opaque layer is present underneath an upper transmissive cloud layer in the satellite field of view (FOV). Errors tend to increase with decreasing upper-cloud elective cloud amount and with decreasing cloud height (increasing pressure). Errors in retrieved upper-cloud pressure result in corresponding errors in derived effective cloud amount. For the case in which a HIRS FOV has two distinct cloud layers, the difference between the retrieved and actual cloud-top pressure is positive in all casts, meaning that the retrieved upper-cloud height is lower than the actual upper-cloud height. In addition, errors in retrieved cloud pressure are found to depend upon the lapse rate between the low-level cloud top and the surface. We examined which sounder channel combinations would minimize the total errors in derived cirrus cloud height caused by instrument noise and by the presence of a lower-level cloud. We find that while the sounding channels that peak between 700 and 1000 mb minimize random errors, the sounding channels that peak at 300—500 mb minimize bias errors. For a cloud climatology, the bias errors are most critical.

Hydrogen Radicals, Nitrogen Radicals, and the Production of O3 in the Upper Troposphere

NASA Technical Reports Server (NTRS)

Wennberg, P. O.; Hanisco, T. F.; Jaegle, L.; Jacob, D. J.; Hintsa, E. J.; Lanzendorf, E. J.; Anderson, J. G.; Gao, R.-S.; Keim, E. R.; Donnelly, S. G.;

Hydrogen Radicals, Nitrogen Radicals, and the Production of O3 in the Upper Troposphere

NASA Technical Reports Server (NTRS)

Wennberg, P. O.; Hanisco, T. F.; Jaegle, L.; Jacob, D. J.; Hintsa, E. J.; Lanzendorf, E. J.; Anderson, J. G.; Gao, R.-S.; Keim, E. R.; Donnelly, S. G.;

Cloud and radiative heating profiles associated with the boreal summer intraseasonal oscillation

NASA Astrophysics Data System (ADS)

Kim, Jinwon; Waliser, Duane E.; Cesana, Gregory V.; Jiang, Xianan; L'Ecuyer, Tristan; Neena, J. M.

2018-03-01

The cloud water content (CW) and radiative heating rate (QR) structures related to northward propagating boreal summer intraseasonal oscillations (BSISOs) are analyzed using data from A-train satellites in conjunction with the ERA-Interim reanalysis. It is found that the northward movement of CW- and QR anomalies are closely synchronized with the northward movement of BSISO precipitation maxima. Commensurate with the northward propagating BSISO precipitation maxima, the CW anomalies exhibit positive ice (liquid) CW maxima in the upper (middle/low) troposphere with a prominent tilting structure in which the low-tropospheric (upper-tropospheric) liquid (ice) CW maximum leads (lags) the BSISO precipitation maximum. The BSISO-related shortwave heating (QSW) heats (cools) the upper (low) troposphere; the longwave heating (QLW) cools (heats) the upper (middle/low) troposphere. The resulting net radiative heating (QRN), being dominated by QLW, cools (heats) the atmosphere most prominently above the 200 hPa level (below the 600 hPa level). Enhanced clouds in the upper and middle troposphere appears to play a critical role in increasing low-level QLW and QRN. The vertically-integrated QSW, QLW and QRN are positive in the region of enhanced CW with the maximum QRN near the latitude of the BSISO precipitation maximum. The bottom-heavy radiative heating anomaly resulting from the cloud-radiation interaction may act to strengthen convection.

Comparisons of cirrus cloud microphysical properties between polluted and pristine air

NASA Astrophysics Data System (ADS)

Diao, Minghui; Schumann, Ulrich; Minikin, Andreas; Jensen, Jorgen

2015-04-01

Cirrus clouds occur in the upper troposphere at altitudes where atmospheric radiative forcing is most sensitive to perturbations of water vapor concentration and water phase. The formation of cirrus clouds influences the distributions of water in both vapor and ice forms. The radiative properties of cirrus depend strongly on particle sizes. Currently it is still unclear how the formation of cirrus clouds and their microphysical properties are influenced by anthropogenic emissions (e.g., industrial emission and biomass burning). If anthropogenic emissions influence cirrus formation in a significant manner, then one should expect a systematic difference in cirrus properties between pristine (clean) air and polluted air. Because of the pollution contrasts between the Southern (SH) and Northern Hemispheres (NH), cirrus properties could have hemispheric differences as well. Therefore, we study high-resolution (~200 m), in-situ observations from two global flight campaigns: 1) the HIAPER Pole-to-Pole Observations (HIPPO) global campaign in 2009-2011 funded by the US National Science Foundation (NSF), and 2) the Interhemispheric Differences In Cirrus Properties from Anthropogenic Emissions (INCA) campaign in 2000 funded by the European Union and participating research institutions. To investigate the changes of cirrus clouds by anthropogenic emissions, we compare ice crystal distributions in polluted and pristine air, in terms of their frequency occurrence, number concentration (Nc) and mean diameter (i.e., effective-mean Deff and volume-mean Dc). Total aerosol concentration is used to represent the combined influence of natural and anthropogenic aerosols. In addition, measured carbon monoxide (CO) mixing ratio is used to discriminate between polluted and pristine air masses. All analyses are restricted to temperatures ≤ -40°C to exclude mixed-phased clouds. The HIPPO campaign observations were obtained over the North America continent and the central Pacific Ocean from 87°N to 67°S. Ice crystals are measured by a Fast-2DC probe, and the analyses are restricted to particles ≥ 87.5 µm to minimize the shattering effects and optical uncertainties. When analyzing ice crystals distribution in the HIPPO campaign, the occurrence frequency of in-cloud conditions increases with both total aerosol and CO concentrations. On the other hand, the changes of ice crystal sizes are not the same for increases of total aerosol and CO concentrations, that is, Dc increases with higher total aerosol concentration but decreases with higher CO concentration. These results suggest that ice crystal formation is likely facilitated when the air parcel is under influence of both natural and anthropogenic emissions, but the anthropogenic emission is likely to decrease the sizes of ice crystals. During the INCA campaign, cirrus clouds were sampled with optical particle counters in the size range of about 1 to 800 μm at midlatitudes, mainly over the Pacific west of Punta Arenas and over the North Atlantic west of Great Britain. Simultaneous measurements of trace gases (CO, NOx and O3) and a suite of aerosols properties show that the INCA measurements in the SH occurred in air masses which were far cleaner than those measured in the NH. Previous INCA data analysis revealed differences between SH and NH cirrus: a lower Nc, a larger Deff, and a larger extinction in the cirrus in the SH compared to the NH (Gayet et al., JGR, 2004). We now recompiled the INCA data and performed a further analysis of the cirrus properties in correlation with simultaneous CO measurements. Based on in-situ sampling of ice crystals of different lower cut-off sizes ( ≥1, 3 and 6 µm) from the INCA campaign, Nc is found to have weak positive correlation with CO concentration (r2 within a range of 0.2 to 0.6). The correlation appears to be significant (95% level) based on a limited set of tests with different data subsets. The correlation is strongest for the smallest ice particles. The correlation persists when restricting the data to temperatures below -45°C. The data also reveal higher ice supersaturation in air masses with low CO concentration. The correlations suggest stronger ice nucleation in polluted air masses. Still, further measurements are desirably to exclude possible artifacts and to confirm these results. Possibly due to the larger cutoff size (≥ 87.5 µm), such correlations between Nc and CO are not captured in the HIPPO data. But the increasing Nc observed from INCA campaign is consistent with the decreasing Dc from the HIPPO campaign, since Nc and Dc are generally anti-correlated during ice crystal formation. The influence of dynamical conditions (e.g. nearby convection) and aerosol contents on the observed cirrus cloud perturbations has still to be investigated. The comparison between data from SH and NH or from different pollution regions may be affected by sampling biases over different cirrus evolution phases. Diao et al. (GRL, 2013) suggested a method to identify the occurrence frequencies of five different phases of ice crystal evolution: (1) Clear-sky ice supersaturated region, (2) Nucleation, (3) Early growth of ice crystals, (4) Late growth of ice crystals, (5) Sedimentation/sublimation. "Nucleation" events in this analysis are partially cloudy segments in ice supersaturated air masses. The HIPPO and INCA data show different frequencies for these evolution phases. The full analysis of the data is still ongoing, but the INCA FSSP data (> 1 µm) seem to show more "clear-sky ice supersaturated region" and "nucleation" events to occur in the SH than in the NH.

Dynamic-Chemical Coupling of the Upper Troposphere and Lower Stratosphere Region

NASA Technical Reports Server (NTRS)

Grewe, Volker; Shindell, Drew T.; Reithmeier, Christian

2000-01-01

The importance of the interaction of chemistry and dynamics in the upper troposphere and lower stratosphere for chemical species like ozone is investigated using two chemistry-climate models. Species emitted in the upper troposphere, like NOx (=NO+NO2) by lightning or aircraft, have the chance to be transported into the lowermost stratosphere. Trajectory calculations suggest that the main transport pathway runs via the Inter Tropical Convergence Zone, across the tropical tropopause and then to higher latitudes, i.e. into the lowermost stratosphere. Longer lifetimes of NOx in the lower stratosphere yield an accumulation of NO. there, which feeds back on upper troposphere chemistry. This effect has been estimated for lightning NO. emissions and reveals a contribution of at least 25% to 40% to the total northern hemisphere mid-latitude lightning increase of either NOx and ozone.

Understanding tropical upper tropospheric warming: The role of SSTs, convective parameterizations, and observational uncertainties

NASA Astrophysics Data System (ADS)

Po-Chedley, S.; Thorsen, T. J.; Fu, Q.

2015-12-01

Recent research has compared CMIP5 general circulation model (GCM) simulations with satellite observations of warming in the tropical upper troposphere relative to the lower-middle troposphere. Although the pattern of SST warming is important, this research demonstrated that models overestimate increases in static stability between the mid- to upper- tropical troposphere, even when they are forced with historical sea surface temperatures. This discrepancy between satellite-borne microwave sounding unit measurements (MSU) and GCMs is important because it has implications for the strength of the lapse rate and water vapor feedback. The apparent model-observational difference for changes in static stability in the tropical upper troposphere represents an important problem, but it is not clear whether the difference is a result of common biases in GCMs, biases in observational datasets, or both. In this work, we will use GCM simulations to examine the importance of the spatial pattern of SST warming and different convective parameterizations in determining the lapse rate changes in tropical troposphere. We will also consider uncertainties in MSU satellite observations, including changes in the diurnal sampling of temperature and instrument calibration biases when comparing GCMs with the observed record.

The Sources and Significance of Stratospheric Water Vapor: Mechanistic Studies from Equator to Pole

NASA Astrophysics Data System (ADS)

Smith, Jessica Birte

It is the future of the stratospheric ozone layer, which protects life at Earth's surface from harmful ultraviolet (UV) radiation, that is the focus of the present work. Fundamental changes in the composition and structure of the stratosphere in response to anthropogenic climate forcing may lead to catastrophic ozone loss under current, and even reduced, stratospheric halogen loading. In particular, the evolution toward a colder, wetter stratosphere, threatens to enhance the heterogeneous conversion of inorganic halogen from its reservoir species to its catalytically active forms, and thus promote in situ ozone loss. Water vapor concentrations control the availability of reactive surface area, which facilitates heterogeneous chemistry. Furthermore, the rates of the key heterogeneous processes are tightly controlled by the ambient humidity. Thus, credible predictions of UV dosage require a quantitative understanding of both the sensitivity of these chemical mechanisms to water vapor concentrations, and an elucidation of the processes controlling stratospheric water vapor concentrations. Toward this end, we present a set of four case studies utilizing high resolution in situ data acquired aboard NASA aircraft during upper atmospheric research missions over the past two decades. 1) We examine the broad scale humidity structure of the upper troposphere and lower stratosphere from the midlatitudes to the tropics, focusing on cirrus formation and dehydration at the cold-point tropical tropopause. The data show evidence for frequent supersaturation in clear air, and sustained supersaturation in the presence of cirrus. These results challenge the strict thermal control of the tropical tropopause. 2) We investigate the likelihood of cirrus-initiated activation of chlorine in the midlatitude lower stratosphere. At midlatitudes the transition from conditions near saturation below the local tropopause to undersaturated air above greatly reduces the probability of heterogeneous activation and in situ ozone loss in this region. 3) We probe the details of heterogeneous processing in the wintertime Arctic vortex, and find that in situ measurements of OH provide incontrovertible evidence for the heterogeneous reaction of HOCl with HCl. This reaction is critical to sustaining catalytically active chlorine and prolonging ozone loss in the springtime vortex. 4) We revisit the topic of midlatitude ozone loss with an emphasis upon the response of ozone in this region to changes in the chemical composition and thermal structure of the lower stratosphere induced by anthropogenic climate change. Specifically, we show evidence for episodic moisture plumes in the overworld stratosphere generated by the rapid evaporation of ice injected into this region by deep convection, and find that these high water vapor plumes have the potential to alter the humidity of the lower stratosphere, and drastically increase the rate of heterogeneous chemistry and in situ ozone loss, given sufficient reactive surface.

Hydrogen Radicals, Nitrogen Radicals, and the Production of O3 in the Upper Troposphere

NASA Technical Reports Server (NTRS)

Wennberg, P. O.; Hanisco, T. F.; Jaegle, L.; Jacob, D. J.; Hintsa, E. J.; Lanzendorf, E. J.; Anderson, J. G.; Gao, R.-S.; Keim, E. R.; Donnelly, S. G.;

Lidar investigations of ozone in the upper troposphere - lower stratosphere: technique and results of measurements

NASA Astrophysics Data System (ADS)

Romanovskii, Oleg A.; Nevzorov, Alexey A.; Nevzorov, Alexey V.; Kharchenko, Olga V.

2018-04-01

The main aim of the research is to develop the technique for laser remote ozone sensing in the upper troposphere - lower stratosphere by differential absorption method for temperature and aerosol correction and analysis of measurement results. The authors have determined wavelengths, promising to measure ozone profiles in the upper troposphere - lower stratosphere. We present the results of DIAL measurements of the vertical ozone distribution at the Siberian lidar station in Tomsk. The recovered ozone profiles were compared with IASI satellite data and Kruger model.

Neutron diffraction study of water freezing on aircraft engine combustor soot.

PubMed

Tishkova, V; Demirdjian, B; Ferry, D; Johnson, M

2011-12-14

The study of the formation of condensation trails and cirrus clouds on aircraft emitted soot particles is important because of its possible effects on climate. In the present work we studied the freezing of water on aircraft engine combustor (AEC) soot particles under conditions of pressure and temperature similar to the upper troposphere. The microstructure of the AEC soot was found to be heterogeneous containing both primary particles of soot and metallic impurities (Fe, Cu, and Al). We also observed various surface functional groups such as oxygen-containing groups, including sulfate ions, that can act as active sites for water adsorption. Here we studied the formation of ice on the AEC soot particles by using neutron diffraction. We found that for low amount of adsorbed water, cooling even up to 215 K did not lead to the formation of hexagonal ice. Whereas, larger amount of adsorbed water led to the coexistence of liquid water (or amorphous ice) and hexagonal ice (I(h)); 60% of the adsorbed water was in the form of ice I(h) at 255 K. Annealing of the system led to the improvement of the crystal quality of hexagonal ice crystals as demonstrated from neutron diffraction.

Relationship between changes in the upper and lower tropospheric water vapor: A revisit

NASA Astrophysics Data System (ADS)

Yang, M.; Sun, D. Z.; Zhang, G. J.

2017-12-01

Upper tropospheric water vapor response to enhanced greenhouse gas forcing is as important as the lower tropospheric water vapor response in determining climate sensitivity. Early studies using older versions of climate models have suggested that the upper- and lower-troposphere water vapor changes are more strongly coupled in the climate models than in the observations. Here we reexamine this issue using a state-of-the-art climate model—the NCAR community model CAM5. Specifically, we have calculated the correlations between interannual variations of specific humidity in all levels of the troposphere with that at the surface in CAM5 and in the observations (as represented by the updated ERA-Interim and NCEP reanalysis). It is found that the previously noted biases in how strongly upper tropospheric water vapor and lower troposphere water vapor are linked still exist in CAM5—the change in the tropical averaged upper tropospheric water vapor is more strongly correlated with the change in the surface. However, this bias disappears in the averaged correlation obtained by averaging the point-by-point correlations over the tropics. The spatial pattern of the point-by-point correlations reveals that the better agreement between the model and the observations is related to the opposite model biases in different regions: the correlation is weaker in the model in the western Pacific, but stronger in the central and eastern Pacific. Further analysis of precipitation fields suggests that the weaker (stronger) coupling between tropospheric water vapor and surface moisture over western (central-eastern) Pacific in model is related to weaker (stronger) simulated convective activities in these regions. More specifically, during El Nino, the model has excessive deep convection in the central Pacific, but too littler deep convection in western Pacific. Implications of the results are discussed in the context of climate change as well as in the context of how to improve the model in this regard.

Concentrations of ethane (C2H6) in the lower stratosphere and upper troposphere and acetylene (C2H2) in the upper troposphere deduced from Atmospheric Trace Molecule Spectroscopy/Spacelab 3 spectra

NASA Technical Reports Server (NTRS)

Rinsland, C. P.; Russell, J. M., III; Zander, R.; Farmer, C. B.; Norton, R. H.

1987-01-01

This paper reports the results of the spectroscopic analysis of C2H6 and C2H2 absorption spectra obtained by the Atmospheric Trace Molecule Spectroscopy (ATMOS) instrument flown on the Shuttle as part of the Spacelab 3 mission. The spectra were recorded during sunset occultations occurring between 25 deg N and 31 deg N latitudes, yielding volume-mixing ratio profiles of C2H6 in the lower stratosphere and the upper troposphere, and an upper tropospheric profile of C2H2. These results compare well with previous in situ and remote sounding data obtained at similar latitudes and with model calculations. The results demonstrate the feasibility of the ATMOS instrument to sound the lower atmosphere from space.

HALOE Algorithm Improvements for Upper Tropospheric Sounding

NASA Technical Reports Server (NTRS)

Thompson, Robert Earl; McHugh, Martin J.; Gordley, Larry L.; Hervig, Mark E.; Russell, James M., III; Douglass, Anne (Technical Monitor)

2001-01-01

This report details the ongoing efforts by GATS, Inc., in conjunction with Hampton University and University of Wyoming, in NASA's Mission to Planet Earth Upper Atmospheric Research Satellite (UARS) Science Investigator Program entitled 'HALOE Algorithm Improvements for Upper Tropospheric Sounding.' The goal of this effort is to develop and implement major inversion and processing improvements that will extend Halogen Occultation Experiment (HALOE) measurements further into the troposphere. In particular, O3, H2O, and CH4 retrievals may be extended into the middle troposphere, and NO, HCl and possibly HF into the upper troposphere. Key areas of research being carried out to accomplish this include: pointing/tracking analysis; cloud identification and modeling; simultaneous multichannel retrieval capability; forward model improvements; high vertical-resolution gas filter channel retrievals; a refined temperature retrieval; robust error analyses; long-term trend reliability studies; and data validation. The current (first year) effort concentrates on the pointer/tracker correction algorithms, cloud filtering and validation, and multichannel retrieval development. However, these areas are all highly coupled, so progress in one area benefits from and sometimes depends on work in others.

Quasi-biweekly oscillations of the South Asian monsoon and its co-evolution in the upper and lower troposphere

NASA Astrophysics Data System (ADS)

Ortega, Sebastián; Webster, Peter J.; Toma, Violeta; Chang, Hai-Ru

2017-11-01

The Upper Tropospheric Quasi-Biweekly Oscillation (UQBW) of the South Asian monsoon is studied using the potential vorticity field on the 370 K isentrope. The UQBW is shown to be a common occurrence in the upper troposphere during the monsoon, and its typical evolution is described. We suggest that the UQBW is a phenomenon of both the middle and tropical latitudes, owing its existence to the presence of the planetary-scale upper-tropospheric monsoon anticyclone. The UQBW is first identified as Rossby waves originating in the northern flank of the monsoon anticyclone. These Rossby waves break when reaching the Pacific Ocean, and their associated cyclonic PV anomalies move southward to the east of Asia and then westward across the Indian Ocean and Africa advected by the monsoon anticyclone. A strong correlation, or co-evolution, between the UQBW and quasi-biweekly oscillations in the lower troposphere (QBW) is also found. In particular, analysis of vertically-integrated horizontal moisture transport, 850 hPa geopotential, and outgoing long-wave radiation show that the UQBW is usually observed at the same time as, and co-evolves with, the lower tropospheric QBW over South Asia. We discuss the nature of the UQBW, and its possible physical link with the QBW.

Advances in Raman Lidar Measurements of Water Vapor, Cirrus Clouds and Carbon Dioxide

NASA Technical Reports Server (NTRS)

Whiteman, David N.; Potter, John R.; Tola, Rebecca; Rush, Kurt; Veselovskii, Igor; Cadirola, Martin; Comer, Joseph

2006-01-01

Narrow-band interference filters with improved transmission in the ultraviolet have been developed under NASA-funded research and used in the Raman Airborne Spectroscopic Lidar (RASL) in ground- based, upward-looking tests. RASL is an airborne Raman Lidar system designed to measure water vapor mixing ratio, and aerosol backscatter/extinction/depolarization. It also possesses the capability to make experimental measurements of cloud liquid water and carbon dioxide. It is being prepared for first flight tests during the summer of 2006. With the newly developed filters installed in RASL, measurements were made of atmospheric water vapor, cirrus cloud optical properties and carbon dioxide that improve upon any previously demonstrated using Raman lidar. Daytime boundary layer profiling of water vapor mixing ratio is performed with less than 5% random error using temporal and spatial resolution of 2-minutes and 60 - 210, respectively. Daytime cirrus cloud optical depth and extinction- to-backscatter ratio measurements are made using 1-minute average. Sufficient signal strength is demonstrated to permit the simultaneous profiling of carbon dioxide and water vapor mixing ratio into the free troposphere during the nighttime. Downward-looking from an airborne RASL should possess the same measurement statistics with approximately a factor of 5 - 10 decrease in averaging time. A description of the technology improvements are provided followed by examples of the improved Raman lidar measurements.

Stratospheric Aerosol and Gas Experiment (SAGE) II and III Aerosol Extinction Measurements in the Arctic Middle and Upper Troposphere

NASA Technical Reports Server (NTRS)

Treffeisen, R. E.; Thomason, L. W.; Strom, J.; Herber, A. B.; Burton, S. P.; Yamanouchi, T.

2006-01-01

In recent years, substantial effort has been expended toward understanding the impact of tropospheric aerosols on Arctic climate and chemistry. A significant part of this effort has been the collection and documentation of extensive aerosol physical and optical property data sets. However, the data sets present significant interpretive challenges because of the diverse nature of these measurements. Among the longest continuous records is that by the spaceborne Stratospheric Aerosol and Gas Experiment (SAGE) II. Although SAGE tropospheric measurements are restricted to the middle and upper troposphere, they may be able to provide significant insight into the nature and variability of tropospheric aerosol, particularly when combined with ground and airborne observations. This paper demonstrates the capacity of aerosol products from SAGE II and its follow-on experiment SAGE III to describe the temporal and vertical variations of Arctic aerosol characteristics. We find that the measurements from both instruments are consistent enough to be combined. Using this combined data set, we detect a clear annual cycle in the aerosol extinction for the middle and upper Arctic troposphere.

Global cloud top height retrieval using SCIAMACHY limb spectra: model studies and first results

NASA Astrophysics Data System (ADS)

Eichmann, Kai-Uwe; Lelli, Luca; von Savigny, Christian; Sembhi, Harjinder; Burrows, John P.

2016-03-01

Cloud top heights (CTHs) are retrieved for the period 1 January 2003 to 7 April 2012 using height-resolved limb spectra measured with the SCanning Imaging Absorption SpectroMeter for Atmospheric CHartographY (SCIAMACHY) on board ENVISAT (ENVIronmental SATellite). In this study, we present the retrieval code SCODA (SCIAMACHY cloud detection algorithm) based on a colour index method and test the accuracy of the retrieved CTHs in comparison to other methods. Sensitivity studies using the radiative transfer model SCIATRAN show that the method is capable of detecting cloud tops down to about 5 km and very thin cirrus clouds up to the tropopause. Volcanic particles can be detected that occasionally reach the lower stratosphere. Upper tropospheric ice clouds are observable for a nadir cloud optical thickness (COT) ≥ 0.01, which is in the subvisual range. This detection sensitivity decreases towards the lowermost troposphere. The COT detection limit for a water cloud top height of 5 km is roughly 0.1. This value is much lower than thresholds reported for passive cloud detection methods in nadir-viewing direction. Low clouds at 2 to 3 km can only be retrieved under very clean atmospheric conditions, as light scattering of aerosol particles interferes with the cloud particle scattering. We compare co-located SCIAMACHY limb and nadir cloud parameters that are retrieved with the Semi-Analytical CloUd Retrieval Algorithm (SACURA). Only opaque clouds (τN,c > 5) are detected with the nadir passive retrieval technique in the UV-visible and infrared wavelength ranges. Thus, due to the frequent occurrence of thin clouds and subvisual cirrus clouds in the tropics, larger CTH deviations are detected between both viewing geometries. Zonal mean CTH differences can be as high as 4 km in the tropics. The agreement in global cloud fields is sufficiently good. However, the land-sea contrast, as seen in nadir cloud occurrence frequency distributions, is not observed in limb geometry. Co-located cloud top height measurements of the limb-viewing Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on ENVISAT are compared for the period from January 2008 to March 2012. The global CTH agreement of about 1 km is observed, which is smaller than the vertical field of view of both instruments. Lower stratospheric aerosols from volcanic eruptions occasionally interfere with the cloud retrieval and inhibit the detection of tropospheric clouds. The aerosol impact on cloud retrievals was studied for the volcanoes Kasatochi (August 2008), Sarychev Peak (June 2009), and Nabro (June 2011). Long-lasting aerosol scattering is detected after these events in the Northern Hemisphere for heights above 12.5 km in tropical and polar latitudes. Aerosol top heights up to about 22 km are found in 2009 and the enhanced lower stratospheric aerosol layer persisted for about 7 months. In August 2009 about 82 % of the lower stratosphere between 30 and 70° N was filled with scattering particles and nearly 50 % in October 2008.

The MJO Transition from Shallow to Deep Convection in CloudSat/CALIPSO Data and GISS GCM Simulations

NASA Technical Reports Server (NTRS)

DelGenio, Anthony G.; Chen, Yonghua; Kim, Daehyun; Yao, Mao-Sung

2013-01-01

The relationship between convective penetration depth and tropospheric humidity is central to recent theories of the Madden-Julian oscillation (MJO). It has been suggested that general circulation models (GCMs) poorly simulate the MJO because they fail to gradually moisten the troposphere by shallow convection and simulate a slow transition to deep convection. CloudSat and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) data are analyzed to document the variability of convection depth and its relation to water vapor during the MJO transition from shallow to deep convection and to constrain GCM cumulus parameterizations. Composites of cloud occurrence for 10MJO events show the following anticipatedMJO cloud structure: shallow and congestus clouds in advance of the peak, deep clouds near the peak, and upper-level anvils after the peak. Cirrus clouds are also frequent in advance of the peak. The Advanced Microwave Scanning Radiometer for EarthObserving System (EOS) (AMSR-E) columnwater vapor (CWV) increases by;5 mmduring the shallow- deep transition phase, consistent with the idea of moisture preconditioning. Echo-top height of clouds rooted in the boundary layer increases sharply with CWV, with large variability in depth when CWV is between;46 and 68 mm. International Satellite Cloud Climatology Project cloud classifications reproduce these climatological relationships but correctly identify congestus-dominated scenes only about half the time. A version of the Goddard Institute for Space Studies Model E2 (GISS-E2) GCM with strengthened entrainment and rain evaporation that produces MJO-like variability also reproduces the shallow-deep convection transition, including the large variability of cloud-top height at intermediate CWV values. The variability is due to small grid-scale relative humidity and lapse rate anomalies for similar values of CWV. 1.

A reference radiosonde system for climate and weather research: IHOP experience

NASA Astrophysics Data System (ADS)

Wang, Junhong; Hock, Terry F.; Lauritsen, Dean; Cole, Harold L.; Beierle, Kathryn; Chamberlain, Ned; Parsons, David B.; Carlson, David J.

2003-04-01

Global radiosonde data are required by meteorological analysis centers for initializing numerical prediction models for weather forecasting, and represent an increasingly valuable resource for studies of climate change and in the development, calibration and validation of retrieval techniques for atmospheric temperature and water vapor profiles from satellite. Unfortunately, the usefulness of radiosonde data is limited by sensor accuracy, by data reporting practices, and by the fact that sonde and sensor types vary by location and with time. Numerous studies and reports have called for a reference sonde to serve as a transfer standard to compare and connect data from past, present and future sonde systems. We are working on developing a reference radiosonde system at the Atmospheric Technology Division (ATD) at NCAR. The reference radiosonde system will carry the best sensors, have a flexible infrastructure to host multiple and different user-provided sensors and will be recoverable to reduce costs. The first version of the reference radiosonde system was deployed in the Oklahoma panhandle and Dodge City, KS (NWS radiosonde site) during the International H2O Project (IHOP_2002). A total of sixteen reference sondes were launched during IHOP either with Vaisala RS80 or Sippican (VIZ) radiosondes. The humidity data from the reference humidity sensor (Snow White, SW) are compared with Vaisala and VIZ data. The comparisons show that (a) VIZ carbon hygristor fails to respond to humidity changes in the upper troposphere, (b) the carbon hygristor inside the reference sonde has slower response than that inside NWS VIZ sonde, (c) Vaisala RS80-H agrees with SW very well in the middle and lower troposphere, and (d) SW can detect cirrus clouds near the tropopause and possibly estimate their ice water content (IWC). The climate impacts of these results are also discussed.

Upper-Tropospheric Winds Derived from Geostationary Satellite Water Vapor Observations

NASA Technical Reports Server (NTRS)

Velden, Christopher S.; Hayden, Christopher M.; Nieman, Steven J.; Menzel, W. Paul; Wanzong, Steven; Goerss, James S.

1997-01-01

The coverage and quality of remotely sensed upper-tropospheric moisture parameters have improved considerably with the deployment of a new generation of operational geostationary meteorological satellites: GOES-8/9 and GMS-5. The GOES-8/9 water vapor imaging capabilities have increased as a result of improved radiometric sensitivity and higher spatial resolution. The addition of a water vapor sensing channel on the latest GMS permits nearly global viewing of upper-tropospheric water vapor (when joined with GOES and Meteosat) and enhances the commonality of geostationary meteorological satellite observing capabilities. Upper-tropospheric motions derived from sequential water vapor imagery provided by these satellites can be objectively extracted by automated techniques. Wind fields can be deduced in both cloudy and cloud-free environments. In addition to the spatially coherent nature of these vector fields, the GOES-8/9 multispectral water vapor sensing capabilities allow for determination of wind fields over multiple tropospheric layers in cloud-free environments. This article provides an update on the latest efforts to extract water vapor motion displacements over meteorological scales ranging from subsynoptic to global. The potential applications of these data to impact operations, numerical assimilation and prediction, and research studies are discussed.

Investigation of shortcomings in simulated aerosol vertical profiles

NASA Astrophysics Data System (ADS)

Park, S.; Allen, R.

2017-12-01

The vertical distribution of aerosols is one important factor for aerosol radiative forcing. Previous studies show that climate models poorly reproduce the aerosol vertical profile, with too much aerosol aloft in the upper troposphere. This bias may be related to several factors, including excessive convective mass flux and wet removal. In this study, we evaluate the aerosol vertical profile from several Coupled Model Intercomparison Project 5 (CMIP5) models, as well as the Community Atmosphere Model 5 (CAM5), relative to the Cloud-Aerosol Lidar Infrared Pathfinder Satellite Observation (CALIPSO). The results show that all models significantly underestimate extinction coefficient in the lower troposphere, while overestimating extinction coefficient in the upper troposphere. In addition, the majority of models indicate a land-ocean dependence in the relationship between aerosol extinction coefficient in the upper troposphere and convective mass flux. Over the continents, more convective mass flux is related to more aerosol aloft; over the ocean, more convective mass flux is associated with less aerosol in upper troposphere. Sensitivity experiments are conducted to investigate the role that convection and wet deposition have in contributing to the deficient simulation of the vertical aerosol profile, including the land-ocean dependence.

Cirrus and Polar Stratospheric Cloud Studies using CLAES Data

NASA Technical Reports Server (NTRS)

Mergenthaler, John L.; Douglass, A. (Technical Monitor)

2001-01-01

We've concluded a 3 year (Period of Performance- January 21, 1998 to February 28, 2001) study of cirrus and polar stratospheric clouds using CLAES (Cryogenic Limb Array Etalon Spectrometer) data. We have described the progress of this study in monthly reports, UARS (Upper Atmosphere Research Satellite) science team meetings, American Geophysical Society Meetings, refereed publications and collaborative publications. Work undertaken includes the establishment of CLAES cloud detection criteria, the refinement of CLAES temperature retrieval techniques, compare the findings of CLAES with those of other instruments, and present findings to the larger community. This report describes the progress made in these areas.

Reanalysis comparisons of upper tropospheric-lower stratospheric jets and multiple tropopauses

NASA Astrophysics Data System (ADS)

Manney, Gloria L.; Hegglin, Michaela I.; Lawrence, Zachary D.; Wargan, Krzysztof; Millán, Luis F.; Schwartz, Michael J.; Santee, Michelle L.; Lambert, Alyn; Pawson, Steven; Knosp, Brian W.; Fuller, Ryan A.; Daffer, William H.

2017-09-01

The representation of upper tropospheric-lower stratospheric (UTLS) jet and tropopause characteristics is compared in five modern high-resolution reanalyses for 1980 through 2014. Climatologies of upper tropospheric jet, subvortex jet (the lowermost part of the stratospheric vortex), and multiple tropopause frequency distributions in MERRA (Modern-Era Retrospective analysis for Research and Applications), ERA-I (ERA-Interim; the European Centre for Medium-Range Weather Forecasts, ECMWF, interim reanalysis), JRA-55 (the Japanese 55-year Reanalysis), and CFSR (the Climate Forecast System Reanalysis) are compared with those in MERRA-2. Differences between alternate products from individual reanalysis systems are assessed; in particular, a comparison of CFSR data on model and pressure levels highlights the importance of vertical grid spacing. Most of the differences in distributions of UTLS jets and multiple tropopauses are consistent with the differences in assimilation model grids and resolution - for example, ERA-I (with coarsest native horizontal resolution) typically shows a significant low bias in upper tropospheric jets with respect to MERRA-2, and JRA-55 (the Japanese 55-year Reanalysis) a more modest one, while CFSR (with finest native horizontal resolution) shows a high bias with respect to MERRA-2 in both upper tropospheric jets and multiple tropopauses. Vertical temperature structure and grid spacing are especially important for multiple tropopause characterizations. Substantial differences between MERRA and MERRA-2 are seen in mid- to high-latitude Southern Hemisphere (SH) winter upper tropospheric jets and multiple tropopauses as well as in the upper tropospheric jets associated with tropical circulations during the solstice seasons; some of the largest differences from the other reanalyses are seen in the same times and places. Very good qualitative agreement among the reanalyses is seen between the large-scale climatological features in UTLS jet and multiple tropopause distributions. Quantitative differences may, however, have important consequences for transport and variability studies. Our results highlight the importance of considering reanalyses differences in UTLS studies, especially in relation to resolution and model grids; this is particularly critical when using high-resolution reanalyses as an observational reference for evaluating global chemistry-climate models.

Hydrogen Radicals, Nitrogen Radicals, and the Production of Ozone in the Middle and Upper Troposphere

NASA Technical Reports Server (NTRS)

Bui, T. P.

1997-01-01

The concentrations of hydrogen radicals, OH and HO2, in the middle and upper troposphere were measured simultaneously with those of NO, O3,CO, H20, CH4, non-methane hydrocarbons, and with the ultraviolet and visible radiation field.

An aerosol chamber investigation of the heterogeneous ice nucleating potential of refractory nanoparticles

NASA Astrophysics Data System (ADS)

Saunders, R. W.; Möhler, O.; Schnaiter, M.; Benz, S.; Wagner, R.; Saathoff, H.; Connolly, P. J.; Burgess, R.; Gallagher, M.; Wills, R.; Murray, B. J.; Plane, J. M. C.

2009-11-01

Nanoparticles of iron oxide (crystalline and amorphous), silicon oxide and magnesium oxide were investigated for their propensity to nucleate ice over the temperature range 180-250 K, using the AIDA chamber in Karlsruhe, Germany. All samples were observed to initiate ice formation via the deposition mode at threshold ice super-saturations (RHi thresh) ranging from 105% to 140% for temperatures below 220 K. Approximately 10% of amorphous Fe2O3 particles (modal diameter = 30 nm) generated in situ from a photochemical aerosol reactor, led to ice nucleation at RHi thresh = 140% at an initial chamber temperature of 182 K. Quantitative analysis using a singular hypothesis treatment provided a fitted function [ns (190 K) = 10(3.33×sice)+8.16] for the variation in ice-active surface site density (ns: m-2) with ice saturation (sice) for Fe2O3 nanoparticles. This was implemented in an aerosol-cloud model to determine a predicted deposition (mass accommodation) coefficient for water vapour on ice of 0.1 at temperatures appropriate for the upper atmosphere. Classical nucleation theory was used to determine representative contact angles (θ) for the different particle compositions. For the in situ generated Fe2O3 particles, a slight inverse temperature dependence was observed with θ = 10.5° at 182 K, decreasing to 9.0° at 200 K (compared with 10.2° and 11.4°, respectively for the SiO2 and MgO particle samples at the higher temperature). These observations indicate that such refractory nanoparticles are relatively efficient materials for the nucleation of ice under the conditions studied in the chamber which correspond to cirrus cloud formation in the upper troposphere. The results also show that Fe2O3 particles do not act as ice nuclei under conditions pertinent for tropospheric mixed phase clouds, which necessarily form above ~233 K. At the lower temperatures (<150 K) where noctilucent clouds form during summer months in the high latitude mesosphere, higher contact angles would be expected, which may reduce the effectiveness of these particles as ice nuclei in this part of the atmosphere.

An aerosol chamber investigation of the heterogeneous ice nucleating potential of refractory nanoparticles

NASA Astrophysics Data System (ADS)

Saunders, R. W.; Möhler, O.; Schnaiter, M.; Benz, S.; Wagner, R.; Saathoff, H.; Connolly, P. J.; Burgess, R.; Murray, B. J.; Gallagher, M.; Wills, R.; Plane, J. M. C.

2010-02-01

Nanoparticles of iron oxide (crystalline and amorphous), silicon oxide and magnesium oxide were investigated for their propensity to nucleate ice over the temperature range 180-250 K, using the AIDA chamber in Karlsruhe, Germany. All samples were observed to initiate ice formation via the deposition mode at threshold ice super-saturations (RHithresh) ranging from 105% to 140% for temperatures below 220 K. Approximately 10% of amorphous Fe2O3 particles (modal diameter = 30 nm) generated in situ from a photochemical aerosol reactor, led to ice nucleation at RHithresh = 140% at an initial chamber temperature of 182 K. Quantitative analysis using a singular hypothesis treatment provided a fitted function [ns(190 K)=10(3.33×sice)+8.16] for the variation in ice-active surface site density (ns:m-2) with ice saturation (sice) for Fe2O3 nanoparticles. This was implemented in an aerosol-cloud model to determine a predicted deposition (mass accommodation) coefficient for water vapour on ice of 0.1 at temperatures appropriate for the upper atmosphere. Classical nucleation theory was used to determine representative contact angles (θ) for the different particle compositions. For the in situ generated Fe2O3 particles, a slight inverse temperature dependence was observed with θ = 10.5° at 182 K, decreasing to 9.0° at 200 K (compared with 10.2° and 11.4° respectively for the SiO2 and MgO particle samples at the higher temperature). These observations indicate that such refractory nanoparticles are relatively efficient materials for the nucleation of ice under the conditions studied in the chamber which correspond to cirrus cloud formation in the upper troposphere. The results also show that Fe2O3 particles do not act as ice nuclei under conditions pertinent for tropospheric mixed phase clouds, which necessarily form above ~233 K. At the lower temperatures (<150 K) where noctilucent clouds form during summer months in the high latitude mesosphere, higher contact angles would be expected, which may reduce the effectiveness of these particles as ice nuclei in this part of the atmosphere.

GPS radio occultation simulation experiments for the upcoming Strateole-2 superpressure balloon campaign investigating equatorial waves

NASA Astrophysics Data System (ADS)

Haase, J. S.; Cao, B.; Alexander, M. J.; Zhang, W.

2017-12-01

Deep tropical convection influences the transport of mass and momentum from the equatorial upper troposphere into the lower stratosphere through the generation and interaction of waves at a broad range of scales. The France-US collaborative Stratéole-2 project will explore equatorial waves in the tropopause region with super-pressure balloons, designed to drift on quasi-Lagrangian trajectories in the lower stratosphere. The Stratéole-2 program will launch 5 balloons from the Seychelles in the Indian Ocean in 2018-2019, and 20 balloons in 2020-2021, each with a flight duration of about 80 days. Five balloons will carry the Radio OCcultation (ROC2) instrument at 20 km altitude to execute a continuous sequence of temperature profiles on either side of the balloon trajectory to sample the equatorial wave field in three dimensions. It will also carry a micro-lidar for detecting cirrus and convective cloud tops. The goals are to describe the horizontal and vertical structure of tropical waves and their impact on cirrus formation and to investigate the relationships of waves to convective clouds. The GPS measurements quantify wave activity by providing precise estimates of balloon velocity and height perturbations due to waves and by providing refractivity profiles that are sensitive to vertical temperature fluctuations caused by waves. We present ray-tracing simulations of the propagation of GPS signals through the Earth's atmosphere, where they will be bent and delayed due to the gradient of atmospheric refractive index. European Centre for Medium-Range Weather Forecasts (ECMWF) analyses are used to construct the refractive index of the equatorial atmosphere, in which abundant atmospheric waves are present. With the known GPS signal geometry, the excess phase/Doppler are simulated that reflect the wave signatures. The resulting refractivity retrievals provide guidance for interpreting the spectral range of waves that the ROC2 instruments are most likely to reveal.

Modeled Full-Flight Aircraft Emissions Impacts on Air Quality and Their Sensitivity to Grid Resolution

EPA Science Inventory

Aviation is a unique anthropogenic source with four-dimensional varying emissions, peaking at cruise altitudes (9–12 km). Aircraft emission budgets in the upper troposphere lower stratosphere region and their potential impacts on upper troposphere and surface air quality ar...

Internal gravity waves in the upper atmosphere, generated by tropospheric jet streams

NASA Technical Reports Server (NTRS)

Chunchuzov, Y. P.; Torgashin, Y. M.

1979-01-01

A mechanism of internal gravity wave generation by jet streams in the troposphere is considered. Evaluations of the energy and pulse of internal gravity waves emitted into the upper atmosphere are given. The obtained values of flows can influence the thermal and dynamic regime of these layers.

Methane from the Tropospheric Emission Spectrometer (TES)

NASA Technical Reports Server (NTRS)

Payne, Vivienne; Worden, John; Kulawik, Susan; Frankenberg, Christian; Bowman, Kevin; Wecht, Kevin

2012-01-01

TES V5 CH4 captures latitudinal gradients, regional variability and interannual variation in the free troposphere. V5 joint retrievals offer improved sensitivity to lower troposphere. Time series extends from 2004 to present. V5 reprocessing in progress. Upper tropospheric bias. Mitigated by N2O correction. Appears largely spatially uniform, so can be corrected. How to relate free-tropospheric values to surface emissions.

Upper-Level Waves of Synoptic Scale at Midlatitudes

NASA Astrophysics Data System (ADS)

Rivest, Chantal

1990-01-01

Upper-level waves of synoptic scale are important dynamical entities at midlatitudes. They often induce surface cyclogenesis (cf. Peterssen and Smebye, 1971), and their life duration is typically longer than time scales for disruption by the ambient shear (Sanders, 1988). The objectives of the present thesis are to explain the maintenance and genesis of upper-level synoptic-scale waves in the midlatitude flow. We develop an analytical model of waves on generalized Eady basic states that have uniform tropospheric and stratospheric potential vorticity, but allow for the decay of density with height. The Eady basic state represents the limiting case of infinite stratospheric stability and constant density. We find that the Eady normal mode characteristics hold in the presence of realistic tropopause and stratosphere. In particular, the basic states studied support at the synoptic scale upper-level normal modes. These modes provide simple models for the dynamics of upper-level synoptic-scale waves, as waves supported by the large latitudinal gradients of potential vorticity at the tropopause. In the presence of infinitesimal positive tropospheric gradients of potential vorticity, the upper-level normal mode solutions no longer exist, as was demonstrated in Green (1960). Disappearance of the normal mode solution when a parameter changes slightly represents a dilemma that we seek to understand. We examine what happens to the upper-level normal modes in the presence of tropospheric gradients of potential vorticity in a series of initial -value experiments. Our results show that the normal modes become slowly decaying quasi-modes. Mathematically the quasi-modes consist of a superposition of singular modes sharply peaked in the phase speed domain, and their decay proceeds as the modes interfere with one another. We repeat these experiments in basic states with a smooth tropopause in the presence of tropospheric and stratospheric gradients, and similar results are obtained. Basic states with positive tropospheric and stratospheric gradients of potential vorticity are found to support upper-level synoptic-scale waves for time scales consistent with observations. Following Farrell (1989), we then identify a class of near optimal initial conditions for the excitation of upper-level waves. The initial conditions consist of upper -tropospheric disturbances that lean against the shear. They strongly excite upper-level waves not only in the absence of tropospheric potential vorticity gradients, but also in their presence. This result demonstrates that quasi -modes are as likely to emerge from favorably configured initial conditions as real normal modes, although their excitation is followed by a slow decay. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617-253-5668; Fax 617-253-1690.).

Space-Time Variations in Water Vapor as Observed by the UARS Microwave Limb Sounder

NASA Technical Reports Server (NTRS)

Elson, Lee S.; Read, William G.; Waters, Joe W.; Mote, Philip W.; Kinnersley, Jonathan S.; Harwood, Robert S.

1996-01-01

Water vapor in the upper troposphere has a significant impact on the climate system. Difficulties in making accurate global measurements have led to uncertainty in understanding water vapor's coupling to the hydrologic cycle in the lower troposphere and its role in radiative energy balance. The Microwave Limb Sounder (MLS) on the Upper Atmosphere Research Satellite is able to retrieve water vapor concentration in the upper troposphere with good sensitivity and nearly global coverage. An analysis of these preliminary retrievals based on 3 years of observations shows the water vapor distribution to be similar to that measured by other techniques and to model results. The primary MLS water vapor measurements were made in the stratosphere, where this species acts as a conserved tracer under certain conditions. As is the case for the upper troposphere, most of the stratospheric discussion focuses on the time evolution of the zonal mean and zonally varying water vapor. Stratospheric results span a 19-month period and tropospheric results a 36-month period, both beginning in October of 1991. Comparisons with stratospheric model calculations show general agreement, with some differences in the amplitude and phase of long-term variations. At certain times and places, the evolution of water vapor distributions in the lower stratosphere suggests the presence of meridional transport.

Impact of diabatic processes on the tropopause inversion layer formation in baroclinic life cycles

NASA Astrophysics Data System (ADS)

Kunkel, Daniel; Hoor, Peter; Wirth, Volkmar

2015-04-01

Observations of temperature profiles in the extratropical upper troposphere/lower stratosphere (UTLS) show the presence of an inversion layer just above the thermal tropopause, i.e., the tropopause inversion layer (TIL). In recent studies both diabatic and adiabatic processes have been identified to contribute to the formation of this layer. In particular, adiabatic simulations indicate a TIL formation without the explicit simulation of diabatic, i.e. radiative or humidity related, processes after wave breaking during baroclinic life cycles. One goal of this study is to assess the additional contribution of diabatic processes to the formation and strength of the TIL in such life cycles. Moreover, since irreversible stratosphere-troposphere exchange (STE) is another inherent feature of baroclinic life cycles and a consequence of diabatic processes, we study whether there is a relationship between STE and TIL. We use the non-hydrostatic model COSMO in an idealized mid-latitude channel configuration to simulate baroclinic life cycles. In a first step contributions of individual diabatic processes from turbulence, radiation, and cloud microphysics to the formation of the TIL are analyzed. These results are compared to those from adiabatic simulations of baroclinic life cycles in which the TIL forms during the life cycle with the limitation of being less sharp than in observations. In a second step the combined effects of several diabatic processes are studied to further include interactions between these processes as well as to advance towards a more realistic model setup. The results suggest a much more vigorous development of the TIL due to microphysics and the release of latent heat. Moreover, radiative effects can foster an increase in static stability above the thermal tropopause when large gradients of either water vapor or cloud ice are present at the level of the tropopause. By additionally adding sub-grid scale turbulence, a co-location of high static stability and increased turbulent kinetic energy is found in the vicinity of cirrus clouds at the tropopause level. The potential relation between STE and high static stability is further discussed based on results from trajectory calculations and the distribution of passive tracers of tropospheric and stratospheric origin.

Ground-based remote sensing of HDO/H2O ratio profiles: introduction and validation of an innovative retrieval approach

NASA Astrophysics Data System (ADS)

Schneider, M.; Hase, F.; Blumenstock, T.

2006-10-01

We propose an innovative approach for analysing ground-based FTIR spectra which allows us to detect variabilities of lower and middle/upper tropospheric HDO/H2O ratios. We show that the proposed method is superior to common approaches. We estimate that lower tropospheric HDO/H2O ratios can be detected with a noise to signal ratio of 15% and middle/upper tropospheric ratios with a noise to signal ratio of 50%. The method requires the inversion to be performed on a logarithmic scale and to introduce an inter-species constraint. While common methods calculate the isotope ratio posterior to an independent, optimal estimation of the HDO and H2O profile, the proposed approach is an optimal estimator for the ratio itself. We apply the innovative approach to spectra measured continuously during 15 months and present, for the first time, an annual cycle of tropospheric HDO/H2O ratio profiles as detected by ground-based measurements. Outliers in the detected middle/upper tropospheric ratios are interpreted by backward trajectories.

Ground-based remote sensing of HDO/H2O ratio profiles: introduction and validation of an innovative retrieval approach

NASA Astrophysics Data System (ADS)

Schneider, M.; Hase, F.; Blumenstock, T.

2006-06-01

We propose an innovative approach for analysing ground-based FTIR spectra which allows us to detect variabilities of lower and middle/upper tropospheric HDO/H2O ratios. We show that the proposed method is superior to common approaches. We estimate that lower tropospheric HDO/H2O ratios can be detected with a noise to signal ratio of 15% and middle/upper tropospheric ratios with a noise to signal ratio of 50%. The method requires the inversion to be performed on a logarithmic scale and to introduce an inter-species constraint. While common methods calculate the isotope ratio posterior to an independent, optimal estimation of the HDO and H2O profile, the proposed approach is an optimal estimator for the ratio itself. We apply the innovative approach to spectra measured continuously during 15 months and present, for the first time, an annual cycle of tropospheric HDO/H2O ratio profiles as detected by ground-based measurements. Outliers in the detected middle/upper tropospheric ratios are interpreted by backward trajectories.

HALOE Algorithm Improvements for Upper Tropospheric Sounding

NASA Technical Reports Server (NTRS)

McHugh, Martin J.; Gordley, Larry L.; Russell, James M., III; Hervig, Mark E.

1999-01-01

This report details the ongoing efforts by GATS, Inc., in conjunction with Hampton University and University of Wyoming, in NASA's Mission to Planet Earth UARS Science Investigator Program entitled "HALOE Algorithm Improvements for Upper Tropospheric Soundings." The goal of this effort is to develop and implement major inversion and processing improvements that will extend HALOE measurements further into the troposphere. In particular, O3, H2O, and CH4 retrievals may be extended into the middle troposphere, and NO, HCl and possibly HF into the upper troposphere. Key areas of research being carried out to accomplish this include: pointing/tracking analysis; cloud identification and modeling; simultaneous multichannel retrieval capability; forward model improvements; high vertical-resolution gas filter channel retrievals; a refined temperature retrieval; robust error analyses; long-term trend reliability studies; and data validation. The current (first-year) effort concentrates on the pointer/tracker correction algorithms, cloud filtering and validation, and multi-channel retrieval development. However, these areas are all highly coupled, so progress in one area benefits from and sometimes depends on work in others.

Aircraft measurements of NO and NOy at 12 km over the Pacific Ocean

NASA Technical Reports Server (NTRS)

Koike, M.; Kondo, Y.; Makino, Y.; Sugimura, Y.

1994-01-01

Measurements of nitric oxide (NO) and total reactive nitrogen (NOy) at altitudes about 12 km were made from two aircraft missions over the central and western Pacific Ocean at latitudes between 65 deg N and 65 deg S during the International Strato-Tropospheric Air Chemistry (INSTAC) program. NO measurements were performed during the first mission in late February and early march 1990, while NOy measurements were performed during the second mission in October 1990. Lowest NO and NOy mixing ratios in the upper troposphere were observed near the equator to be about 30 to approximately 70pptv and 150 to approximately 220pptv, respectively. NOy mixing ratios in the upper troposphere were higher in the northern middle latitude than in the southern middle latitude; 300 to approximately 900pptv in 30 deg N to approximately 50 deg N and 250 to approximately 400pptv around 25 deg S and 50 deg S possibly due to the transport of the polluted air from the boundary layer and the emissions from the commercial aircraft in the northern middle latitudes. Near the equator up to 40 deg S, the NO values showed very high variability and reached between 200 and 2000 pptv. NOy(pptv)/ozone(ppbv) ratios in the upper troposphere were between about 3 and 20 and these values seem to be higher in the lower latitude except for the polluted air in the northern middle latitude. These NOy/ozone ratios in the equatorial upper troposphere are higher than those in the lower stratosphere observed by others. These features of NO and NOy in the equatorial upper troposphere suggest that NOx is produced possibly by the lightning.

Evidence of Convective Redistribution of Carbon Monoxide in Aura Tropospheric Emission Sounder (TES) and Microwave Limb Sounder (MLS) Observations

NASA Technical Reports Server (NTRS)

Manyin, Michael; Douglass, Anne; Schoeberl, Mark

2010-01-01

Vertical convective transport is a key element of the tropospheric circulation. Convection lofts air from the boundary layer into the free troposphere, allowing surface emissions to travel much further, and altering the rate of chemical processes such as ozone production. This study uses satellite observations to focus on the convective transport of CO from the boundary layer to the mid and upper troposphere. Our hypothesis is that strong convection associated with high rain rate regions leads to a correlation between mid level and upper level CO amounts. We first test this hypothesis using the Global Modeling Initiative (GMI) chemistry and transport model. We find the correlation is robust and increases as the precipitation rate (the strength of convection) increases. We next examine three years of CO profiles from the Tropospheric Emission Sounder (TES) and Microwave Limb Sounder (MLS) instruments aboard EOS Aura. Rain rates are taken from the Tropical Rainfall Measuring Mission (TRMM) 3B-42 multi-satellite product. Again we find a correlation between mid-level and upper tropospheric CO, which increases with rain rate. Our result shows the critical importance of tropical convection in coupling vertical levels of the troposphere in the transport of trace gases. The effect is seen most clearly in strong convective regions such as the Inter-tropical Convergence Zone.

Climatology of water vapor in the upper troposphere and lower stratosphere determined from Sage 2 observations

NASA Technical Reports Server (NTRS)

Chiou, Er-Woon; McCormick, M. P.

1994-01-01

The purpose of this paper is to present a vertically-resolved global climatology of water vapor in the upper troposphere and lower stratosphere based on multi-year SAGE 2 observations. Seasonally averaged zonal mean profiles are illustrated in terms of both mixing ration and relative humidity.

Evaluation of Simulated Photochemical Partitioning of Oxidized Nitrogen in the Upper Troposphere

EPA Science Inventory

Regional and global chemical transport models underpredict NO_x (NO +NO₂) in the upper troposphere where it is a precursor to the greenhouse gas ozone. The NO_x bias has been shown in model evaluations using aircraft data (Singh et al., 2007) and to...

The China Clipper - Fast advective transport of radon-rich air from the Asian boundary layer to the upper troposphere near California

NASA Technical Reports Server (NTRS)

Kritz, Mark A.; Le Roulley, Jean-Claude; Danielsen, Edwin F.

1990-01-01

A series of upper tropospheric radon concentration measurements made over the eastern Pacific and west coast of the U.S. during the summers of 1983 and 1984 has revealed the occurrence of unexpectedly high radon concentrations for 9 of the 61 measurements. A frequency distribution plot of the set of 61 observations shows a distinct bimodal distribution, with approximately 2/5 of the observations falling close to 1 pCi/SCM, and 3/5 falling in a high concentration mode centered at about 11 pCi/SCM. Trajectory and synoptic analyses for two of the flights on which such high radon concentrations were observed indicate that this radon-rich air originated in the Asian boundary layer, ascended in cumulus updrafts, and was carried eastward in the fast moving air on the anticyclonic side of the upper tropospheric jet. The results suggest that the combination of rapid vertical transport from the surface boundary layer to the upper troposphere, followed by rapid horizontal transport eastward represents an efficient mode of long-transport for other, chemically reactive atmospheric trace constituents.

The China Clipper - Fast advective transport of radon-rich air from the Asian boundary layer to the upper troposphere near California

NASA Astrophysics Data System (ADS)

Kritz, Mark A.; Le Roulley, Jean-Claude; Danielsen, Edwin F.

1990-02-01

A series of upper tropospheric radon concentration measurements made over the eastern Pacific and west coast of the U.S. during the summers of 1983 and 1984 has revealed the occurrence of unexpectedly high radon concentrations for 9 of the 61 measurements. A frequency distribution plot of the set of 61 observations shows a distinct bimodal distribution, with approximately 2/5 of the observations falling close to 1 pCi/SCM, and 3/5 falling in a high concentration mode centered at about 11 pCi/SCM. Trajectory and synoptic analyses for two of the flights on which such high radon concentrations were observed indicate that this radon-rich air originated in the Asian boundary layer, ascended in cumulus updrafts, and was carried eastward in the fast moving air on the anticyclonic side of the upper tropospheric jet. The results suggest that the combination of rapid vertical transport from the surface boundary layer to the upper troposphere, followed by rapid horizontal transport eastward represents an efficient mode of long-transport for other, chemically reactive atmospheric trace constituents.

Trace gas transport out of the Indian Summer Monsoon

NASA Astrophysics Data System (ADS)

Tomsche, Laura; Pozzer, Andrea; Zimmermann, Peter; Parchatka, Uwe; Fischer, Horst

2016-04-01

The trace gas transport out of the Indian summer monsoon was investigated during the aircraft campaign OMO (Oxidation Mechanism Observations) with the German research aircraft HALO (High Altitude and Long Range Research Aircraft) in July/August 2015. HALO was based at Paphos/Cyprus and also on Gan/Maledives. Flights took place over the Mediterranean Sea, the Arabian Peninsula and the Arabian Sea. In this work the focus is on the distribution of carbon monoxide (CO) and methane (CH4) in the upper troposphere. They were measured with the laser absorption spectrometer TRISTAR on board of HALO. During the Indian summer monsoon strong convection takes place over India and the Bay of Bengal. In this area the population is high accompanied by many emission sources e.g. wetlands and cultivation of rice. Consequently the boundary layer is polluted containing high concentrations of trace gases like methane and carbon monoxide. Due to vertical transport these polluted air masses are lifted to the upper troposphere. Here they circulate with the so called Asian monsoon anticyclone. In the upper troposphere polluted air masses lead to a change in the chemical composition thus influence the chemical processes. Furthermore the anticyclone spreads the polluted air masses over a larger area. Thus the outflow of the anticyclone in the upper troposphere leads to higher concentrations of trace gases over the Arabian Sea, the Arabian Peninsula and also over the eastern part of North Africa and the eastern part of the Mediterranean Sea. During OMO higher concentrations of methane and carbon monoxide were detected at altitudes between 11km and 15km. The highest measured concentrations of carbon monoxide and methane were observed over Oman. The CO concentration in the outflow of the monsoon exceeds background levels by 10-15ppb. However the enhancement in the concentration is not obviously connected to the monsoon due to the natural variability in the troposphere. The enhancement in the methane concentration (30-40ppb) is more obviously connected to the monsoon because it is much higher than the natural variability. Consequently methane is a very good tracer for the monsoon influenced air masses. Beside flights into the outflow of the Indian summer monsoon, there were also measurements of background concentrations in the upper troposphere in air not influenced by the monsoon. Profiles have shown that the high concentrations of trace gases are only observed in the upper troposphere. The high concentrations in the upper troposphere cannot be explained by vertical transport form local ground sources.

Three-dimensional circulation structures leading to heavy summer rainfall over central North China

NASA Astrophysics Data System (ADS)

Sun, Wei; Yu, Rucong; Li, Jian; Yuan, Weihua

2016-04-01

Using daily and hourly rain gauge records and Japanese 25 year reanalysis data over 30 years, this work reveals two major circulation structures leading to heavy summer rainfall events in central North China (CNC), and further analyzes the effects of the circulations on these rainfall events. One circulation structure has an extensive upper tropospheric warm anomaly (UTWA) covering North China (NC). By strengthening the upper anticyclonic anomaly and lower southerly flows around NC, the UTWA plays a positive role in forming upper level divergence and lower level moisture convergence. As a result, the warm anomalous circulation has a solid relationship with large-scale, long-duration rainfall events with a diurnal peak around midnight to early morning. The other circulation structure has an upper tropospheric cold anomaly (UTCA) located in the upper stream of NC. Contributed to by the UTCA, a cold trough appears in the upper stream of NC and an unstable configuration with upper (lower) cold (warm) anomalies forms around CNC. Consequently, CNC is covered by strong instability and high convective energy, and the cold anomalous circulation is closely connected with local, short-duration rainfall events concentrated from late afternoon to early nighttime. The close connections between circulation structures and typical rainfall events are confirmed by two independent converse analysis processes: from circulations to rainfall characteristics, and from typical rainfall events to circulations. The results presented in this work indicate that the upper tropospheric temperature has significant influences on heavy rainfall, and thus more attention should be paid to the upper tropospheric temperature in future analyses.

A High-Altitude Site Survey for SOFIA

NASA Astrophysics Data System (ADS)

Haas, Michael R.; Pfister, Leonhard

1998-03-01

The Stratospheric Observatory for Infrared Astronomy (SOFIA) is a modified Boeing 747-SP equipped with a 2.5 m telescope dedicated to astronomical research. Currently under joint development by the US (NASA) and Germany (DLR), it is scheduled to begin operations in late 2001. The ability of SOFIA to carry out its mission will depend strongly on the meteorological conditions at and above flight altitudes in the vicinity of its home base. The most important meteorological factors are the frequency of high-altitude clouds and the magnitude of the water vapor overburdens. This paper performs a high-altitude site survey by gathering together the best available meteorological data, defining metrics, and evaluating them for a variety of sites. These metrics are found to corroborate past airborne experience and to be consistent with well-known global circulation patterns, convection, and upper tropospheric dynamics. They indicate that there are significant variations in the weather at SOFIA flight altitudes. Particularly in summer, some continental US sites are shown to be worse than Hawaii, where high-altitude cirrus clouds and the associated moisture have historically caused significant losses in the amount and quality of the astronomical data collected by NASA's Kuiper Airborne Observatory. SOFIA's planned home base, Moffett Field, CA, is found to have excellent high-altitude weather and to be one of the best continental US sites.

Dependence of Cumulus Anvil Radiative Properties on Environmental Conditions in the Tropical West Pacific

NASA Technical Reports Server (NTRS)

Ye, B.; DelGenio, A. D.

1999-01-01

Areally extensive, optically thick anvil clouds associated with mesoscale convective clusters dominate the shortwave cloud forcing in the tropics and provide longwave forcing comparable to that of thin cirrus. Changes in the cover and optical thickness of tropical anvils as climate warms can regulate the sign of cloud feedback. As a prelude to the study of MMCR data from the ARM TWP sites, we analyze ISCCP-derived radiative characteristics of anvils observed in the tropical west Pacific during the TOGA-COARE IOP. Anvils with radius greater than 100 km were identified and tracked from inception to decay using the Machado-Rossow algorithm. Corresponding environmental conditions just prior to the start of the convectove event were diagnosed using the Lin-Johnson objective analysis product. Small clusters (100-200 km radius) are observed to have a broad range of optical thicknesses (10-50), while intermediate optical thickness clusters are observed to range in size from 100 km to almost 1000 km. Large-size clusters appear to be favored by strong pre-storm large scale upward motion throughout the troposphere, moist low-to-midlevel relative humidities, environments with slightly higher CAPE than those for smaller clusters, and strong front-to-rear flow. Optically thick anvils are favored in situations of strong low-level moisture convergence and strong upper-level shear.

Atmospheric chemistry and transport modeling in the outer solar system

NASA Astrophysics Data System (ADS)

Lee, Yuan-Tai (Anthony)

2001-11-01

This thesis consists of 1-D and 2-D photochemical- dynamical modeling in the upper atmospheres of outer planets. For 1-D modeling, a unified hydrocarbon photochemical model has been studied in Jupiter, Saturn, Uranus, Neptune, and Titan, by comparing with the Voyager observations, and the recent measurements of methyl radicals by ISO in Saturn and Neptune. The CH3 observation implies a kinetically sensitive test to the measured and estimated hydrocarbon rate constants at low temperatures. We identify the key reactions that control the concentrations of CH3 in the model, such as the three-body recombination reaction, CH3 + CH3 + M --> C 2H6 + M, and the recycling reaction H + CH3 + M --> CH4 + M. The results show reasonable agreement with ISO values. In Chapter 4, the detection of PH3 in the lower stratosphere and upper troposphere of Jupiter has provided a photochemical- dynamical coupling model to derive the eddy diffusion coefficient in the upper troposphere of Jupiter. Using a two-layers photochemical model with updated photodissociation cross-sections and chemical rate constants for NH3 and PH 3, we find that the upper tropospheric eddy diffusion coefficient <10 5 cm2 sec-1, and the deeper tropospheric value >106 cm2 sec-1, are required to match the derived PH3 vertical profile by the observation. The best-fit functional form derivation of eddy diffusion coefficient in the upper troposphere of Jupiter above 400 mbar is K = 2.0 × 104 (n/2.2 × 1019)-0.5 cm 2 sec-1. On the other hand, Chapter 5 demonstrates a dynamical-only 2-D model of C2H6 providing a complete test for the current 2-D transport models in Jovian lower stratosphere and upper troposphere (270 to 0.1 mbar pressure levels). Different combinations of residual advection, horizontal eddy dispersion, and vertical eddy mixing are examined at different latitudes.

Physical Mechanisms for the Maintenance of GCM-Simulated Madden-Julian Oscillation over the Indian Ocean and Pacific

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

Deng, Liping; Wu, Xiaoqing

2011-05-05

The kinetic energy budget is conducted to analyze the physical processes responsible for the improved Madden-Julian Oscillation (MJO) simulated by the Iowa State University general circulation models (ISUGCM). The modified deep convection scheme that includes the revised convection closure, convection trigger condition and convective momentum transport (CMT) enhances the equatorial (10oS-10oN) MJO-related perturbation kinetic energy (PKE) in the upper troposphere and leads to more robust and coherent eastward propagating MJO signal. In the MJO source region-the Indian Ocean (45oE-120oE), the upper-tropospheric MJO PKE is maintained by the vertical convergence of wave energy flux and the barotropic conversion through the horizontalmore » shear of mean flow. In the convectively active region-the western Pacific (120oE-180o), the upper-tropospheric MJO PKE is supported by the convergence of horizontal and vertical wave energy fluxes. Over the central-eastern Pacific (180o-120oW), where convection is suppressed, the upper-tropospheric MJO PKE is mainly due to the horizontal convergence of wave energy flux. The deep convection trigger condition produces stronger convective heating which enhances the perturbation available potential energy (PAPE) production and the upward wave energy fluxes, and leads to the increased MJO PKE over the Indian Ocean and western Pacific. The trigger condition also enhances the MJO PKE over the central-eastern Pacific through the increased convergence of meridional wave energy flux from the subtropical latitudes of both hemispheres. The revised convection closure affects the response of mean zonal wind shear to the convective heating over the Indian Ocean and leads to the enhanced upper-tropospheric MJO PKE through the barotropic conversion. The stronger eastward wave energy flux due to the increase of convective heating over the Indian Ocean and western Pacific by the revised closure is favorable to the eastward propagation of MJO and the convergence of horizontal wave energy flux over the central-eastern Pacific. The convection-induced momentum tendency tends to decelerate the upper-tropospheric wind which results in a negative work to the PKE budget in the upper troposphere. However, the convection momentum tendency accelerates the westerly wind below 800 hPa over the western Pacific, which is partially responsible for the improved MJO simulation.« less

Aerosols increase upper tropospheric humidity over the North Western Pacific

NASA Astrophysics Data System (ADS)

Riuttanen, Laura; Bister, Marja; John, Viju; Sundström, Anu-Maija; Dal Maso, Miikka; Räisänen, Jouni; de Leeuw, Gerrit; Kulmala, Markku

2014-05-01

Water vapour in the upper troposphere is highly important for the global radiative transfer. The source of upper tropospheric humidity is deep convection, and aerosol effects on them have got attention only recently. E.g., aerosol effects on deep convective clouds have been missing in general circulation models (Quaas et al., 2009). In deep convection, aerosol effect on cloud microphysics may lead to more ice precipitation and less warm rain (Khain et al., 2005), and thus more water vapour in upper troposphere (Bister & Kulmala, 2011). China outflow region over the Pacific Ocean was chosen as a region for a more detailed study, with latitudes 25-45 N and three longitude slots: 120-149 E, 150-179 E and 150-179 W. In this study, we used satellite measurements of aerosol optical depth (AOD) and upper tropospheric humidity (UTH). AOD was obtained from the MODIS instrument onboard Terra satellite, that crosses the equator southward at 10:30 AM local solar time (Remer et al., 2005). UTH was obtained from a microwave humidity sounder (MHS) onboard MetOp-A satellite, with passing time at 9:30 PM local solar time. It measures relative humidity of a layer extending approximately from 500 to 200 hPa. We binned the AOD and UTH data according to daily rainfall product 3B42 from Tropical Rainfall Measuring Mission (TRMM) satellite. Binning the data according to the amount of precipitation gives us a new way to account for the possible aerosol invigoration effect on convection and to alleviate the contamination and causality problems in aerosol indirect effect studies. In this study, we show for the first time, based on satellite data, that there is a connection between upper tropospheric humidity and aerosols. Anthropogenic aerosols from China increase upper tropospheric humidity, which causes a significant positive local radiative forcing in libRadtran radiative transfer model (Mayer & Kylling, 2005). References: Bister, M. & Kulmala, M. (2011). Atmos. Chem. Phys., 11, 4577-4586. Khain, A., Rosenfeld, D. & Pokrovsky, A. (2005). Q. J. R. Meteorol. Soc., 131, 2639-2663. Mayer, B. & Kylling, A. (2005). Atmos. Chem. Phys., 5, 1855-1877. Remer, L. A. et al. (2005). J. Atmos. Sci., 62, 947-973. Quaas, J. et al. (2009). Atmos. Chem. Phys., 9, 8697-8717.

On the Tropospheric Measurements of Ozone by the Stratospheric Aerosol and Gas Experiment II (SAGE II, version 6.1) in the Tropics

NASA Technical Reports Server (NTRS)

Kar, J.; Trepte, C. R.; Thomason, L. W.; Zawodny, J. M.; Cunnold, D. M.; Wang, H. J.

2002-01-01

Tropospheric measurements of ozone from SAGE II (version 6.1) in the tropics have been analyzed using 12 years of data (1985-1990, 1994-1999). The seasonally averaged vertical profiles of the ozone mixing ratio in the upper troposphere have been presented for the first time from satellite measurements. These profiles show qualitative similarities with corresponding seasonal mean ozonesonde profiles at northern and southern tropical stations and are about 40-50% less than the sonde values. Despite this systematic offset, the measurements appear to be consistent with a zonal wave one pattern in the upper tropospheric column ozone and with the recently predicted summertime ozone enhancement over the Middle East. These results thus affirm the usefulness of the occultation method in studying tropospheric ozone.

Subtropical subsidence and surface deposition of oxidized mercury produced in the free troposphere

NASA Astrophysics Data System (ADS)

Shah, Viral; Jaeglé, Lyatt

2017-07-01

Oxidized mercury (Hg(II)) is chemically produced in the atmosphere by oxidation of elemental mercury and is directly emitted by anthropogenic activities. We use the GEOS-Chem global chemical transport model with gaseous oxidation driven by Br atoms to quantify how surface deposition of Hg(II) is influenced by Hg(II) production at different atmospheric heights. We tag Hg(II) chemically produced in the lower (surface-750 hPa), middle (750-400 hPa), and upper troposphere (400 hPa-tropopause), in the stratosphere, as well as directly emitted Hg(II). We evaluate our 2-year simulation (2013-2014) against observations of Hg(II) wet deposition as well as surface and free-tropospheric observations of Hg(II), finding reasonable agreement. We find that Hg(II) produced in the upper and middle troposphere constitutes 91 % of the tropospheric mass of Hg(II) and 91 % of the annual Hg(II) wet deposition flux. This large global influence from the upper and middle troposphere is the result of strong chemical production coupled with a long lifetime of Hg(II) in these regions. Annually, 77-84 % of surface-level Hg(II) over the western US, South America, South Africa, and Australia is produced in the upper and middle troposphere, whereas 26-66 % of surface Hg(II) over the eastern US, Europe, and East Asia, and South Asia is directly emitted. The influence of directly emitted Hg(II) near emission sources is likely higher but cannot be quantified by our coarse-resolution global model (2° latitude × 2.5° longitude). Over the oceans, 72 % of surface Hg(II) is produced in the lower troposphere because of higher Br concentrations in the marine boundary layer. The global contribution of the upper and middle troposphere to the Hg(II) dry deposition flux is 52 %. It is lower compared to the contribution to wet deposition because dry deposition of Hg(II) produced aloft requires its entrainment into the boundary layer, while rain can scavenge Hg(II) from higher altitudes more readily. We find that 55 % of the spatial variation of Hg wet deposition flux observed at the Mercury Deposition Network sites is explained by the combined variation of precipitation and Hg(II) produced in the upper and middle troposphere. Our simulation points to a large role of the dry subtropical subsidence regions. Hg(II) present in these regions accounts for 74 % of Hg(II) at 500 hPa over the continental US and more than 60 % of the surface Hg(II) over high-altitude areas of the western US. Globally, it accounts for 78 % of the tropospheric Hg(II) mass and 61 % of the total Hg(II) deposition. During the Nitrogen, Oxidants, Mercury, and Aerosol Distributions, Sources, and Sinks (NOMADSS) aircraft campaign, the contribution of Hg(II) from the dry subtropical regions was found to be 75 % when measured Hg(II) exceeded 250 pg m-3. Hg(II) produced in the upper and middle troposphere subsides in the anticyclones, where the dry conditions inhibit the loss of Hg(II). Our results highlight the importance the subtropical anticyclones as the primary conduits for the production and export of Hg(II) to the global atmosphere.

Spatial and Temporal Variability of Surface Energy Fluxes During Autumn Ice Advance: Observations and Model Validation

NASA Astrophysics Data System (ADS)

Persson, O. P. G.; Blomquist, B.; Grachev, A. A.; Guest, P. S.; Stammerjohn, S. E.; Solomon, A.; Cox, C. J.; Capotondi, A.; Fairall, C. W.; Intrieri, J. M.

2016-12-01

From Oct 4 to Nov 5, 2015, the Office of Naval Research - sponsored Sea State cruise in the Beaufort Sea with the new National Science Foundation R/V Sikuliaq obtained extensive in-situ and remote sensing observations of the lower troposphere, the advancing sea ice, wave state, and upper ocean conditions. In addition, a coupled atmosphere, sea ice, upper-ocean model, based on the RASM model, was run at NOAA/PSD in a hindcast mode for this same time period, providing a 10-day simulation of the atmosphere/ice/ocean evolution. Surface energy fluxes quantitatively represent the air-ice, air-ocean, and ice-ocean interaction processes, determining the cooling (warming) rate of the upper ocean and the growth (melting) rate of sea ice. These fluxes also impact the stratification of the lower troposphere and the upper ocean. In this presentation, both direct and indirect measurements of the energy fluxes during Sea State will be used to explore the spatial and temporal variability of these fluxes and the impacts of this variability on the upper ocean, ice, and lower atmosphere during the autumn ice advance. Analyses have suggested that these fluxes are impacted by atmospheric synoptic evolution, proximity to existing ice, ice-relative wind direction, ice thickness and snow depth. In turn, these fluxes impact upper-ocean heat loss and timing of ice formation, as well as stability in the lower troposphere and upper ocean, and hence heat transport to the free troposphere and ocean mixed-layer. Therefore, the atmospheric structure over the advancing first-year ice differs from that over the nearby open water. Finally, these observational analyses will be used to provide a preliminary validation of the spatial and temporal variability of the surface energy fluxes and the associated lower-tropospheric and upper-ocean structures in the simulations.

Long-range transport of Asian pollution to the northeast Pacific: Seasonal variations and transport pathways of carbon monoxide

NASA Astrophysics Data System (ADS)

Liang, Qing; Jaeglé, Lyatt; Jaffe, Daniel A.; Weiss-Penzias, Peter; Heckman, Anna; Snow, Julie A.

2004-12-01

Continuous CO measurements were obtained at Cheeka Peak Observatory (CPO, 48.3°N, 124.6°W, 480 m), a coastal site in Washington state, between 9 March 2001 and 31 May 2002. We analyze these observations as well as CO observations at ground sites throughout the North Pacific using the GEOS-CHEM global tropospheric chemistry model to examine the seasonal variations of Asian long-range transport. The model reproduces the observed CO levels, their seasonal cycle and day-to-day variability, with a 5-20 ppbv negative bias in winter/spring and 5-10 ppbv positive bias during summer. Asian influence on CO levels in the North Pacific troposphere maximizes during spring and minimizes during summer, ranging from 91 ppbv (44% of total CO) to 52 ppbv (39%) along the Asian Pacific Rim and from 44 ppbv (30%) to 24 ppbv (23%) at CPO. Maximum export of Asian pollution to the western Pacific occurs at 20°-50°N during spring throughout the tropospheric column, shifting to 30°-60°N during summer, mostly in the upper troposphere. The model captures five particularly strong transpacific transport events reaching CPO (four in spring, one in winter) resulting in 20-40 ppbv increases in observed CO levels. Episodic long-range transport of pollutants from Asia to the NE Pacific occurs throughout the year every 10, 15, and 30 days in the upper, middle, and lower troposphere, respectively. Lifting ahead of cold fronts followed by transport in midlatitude westerlies accounts for 78% of long-range transport events reaching the NE Pacific middle and upper troposphere. During summer, convective injection into the upper troposphere competes with frontal mechanisms in this export. Most events reaching the NE Pacific lower troposphere below 2 km altitude result from boundary layer outflow behind cold fronts (for spring) or ahead of cold fronts (for other seasons) followed by low-level transpacific transport.

Impact of varying lidar measurement and data processing techniques in evaluating cirrus cloud and aerosol direct radiative effects

NASA Astrophysics Data System (ADS)

Lolli, Simone; Madonna, Fabio; Rosoldi, Marco; Campbell, James R.; Welton, Ellsworth J.; Lewis, Jasper R.; Gu, Yu; Pappalardo, Gelsomina

2018-03-01

In the past 2 decades, ground-based lidar networks have drastically increased in scope and relevance, thanks primarily to the advent of lidar observations from space and their need for validation. Lidar observations of aerosol and cloud geometrical, optical and microphysical atmospheric properties are subsequently used to evaluate their direct radiative effects on climate. However, the retrievals are strongly dependent on the lidar instrument measurement technique and subsequent data processing methodologies. In this paper, we evaluate the discrepancies between the use of Raman and elastic lidar measurement techniques and corresponding data processing methods for two aerosol layers in the free troposphere and for two cirrus clouds with different optical depths. Results show that the different lidar techniques are responsible for discrepancies in the model-derived direct radiative effects for biomass burning (0.05 W m-2 at surface and 0.007 W m-2 at top of the atmosphere) and dust aerosol layers (0.7 W m-2 at surface and 0.85 W m-2 at top of the atmosphere). Data processing is further responsible for discrepancies in both thin (0.55 W m-2 at surface and 2.7 W m-2 at top of the atmosphere) and opaque (7.7 W m-2 at surface and 11.8 W m-2 at top of the atmosphere) cirrus clouds. Direct radiative effect discrepancies can be attributed to the larger variability of the lidar ratio for aerosols (20-150 sr) than for clouds (20-35 sr). For this reason, the influence of the applied lidar technique plays a more fundamental role in aerosol monitoring because the lidar ratio must be retrieved with relatively high accuracy. In contrast, for cirrus clouds, with the lidar ratio being much less variable, the data processing is critical because smoothing it modifies the aerosol and cloud vertically resolved extinction profile that is used as input to compute direct radiative effect calculations.

On the existence of tropical anvil clouds

NASA Astrophysics Data System (ADS)

Seeley, J.; Jeevanjee, N.; Langhans, W.; Romps, D.

2017-12-01

In the deep tropics, extensive anvil clouds produce a peak in cloud cover below the tropopause. The dominant paradigm for cloud cover attributes this anvil peak to a layer of enhanced mass convergence in the clear-sky upper-troposphere, which is presumed to force frequent detrainment of convective anvils. However, cloud cover also depends on the lifetime of cloudy air after it detrains, which raises the possibility that anvil clouds may be the signature of slow cloud decay rather than enhanced detrainment. Here we measure the cloud decay timescale in cloud-resolving simulations, and find that cloudy updrafts that detrain in the upper troposphere take much longer to dissipate than their shallower counterparts. We show that cloud lifetimes are long in the upper troposphere because the saturation specific humidity becomes orders of magnitude smaller than the typical condensed water loading of cloudy updrafts. This causes evaporative cloud decay to act extremely slowly, thereby prolonging cloud lifetimes in the upper troposphere. As a consequence, extensive anvil clouds still occur in a convecting atmosphere that is forced to have no preferential clear-sky convergence layer. On the other hand, when cloud lifetimes are fixed at a characteristic lower-tropospheric value, extensive anvil clouds do not form. Our results support a revised understanding of tropical anvil clouds, which attributes their existence to the microphysics of slow cloud decay rather than a peak in clear-sky convergence.

Evaluating Lightning-generated NOx (LNOx) Parameterization based on Cloud Top Height at Resolutions with Partially-resolved Convection for Upper Tropospheric Chemistry Studies

NASA Astrophysics Data System (ADS)

Wong, J.; Barth, M. C.; Noone, D. C.

2012-12-01

Lightning-generated nitrogen oxides (LNOx) is an important precursor to tropospheric ozone production. With a meteorological time-scale variability similar to that of the ozone chemical lifetime, it can nonlinearly perturb tropospheric ozone concentration. Coupled with upper-air circulation patterns, LNOx can accumulate in significant amount in the upper troposphere with other precursors, thus enhancing ozone production (see attached figure). While LNOx emission has been included and tuned extensively in global climate models, its inclusions in regional chemistry models are seldom tested. Here we present a study that evaluates the frequently used Price and Rind parameterization based on cloud-top height at resolutions that partially resolve deep convection using the Weather Research and Forecasting model with Chemistry (WRF-Chem) over the contiguous United States. With minor modifications, the parameterization is shown to generate integrated flash counts close to those observed. However, the modeled frequency distribution of cloud-to-ground flashes do not represent well for storms with high flash rates, bringing into question the applicability of the intra-cloud/ground partitioning (IC:CG) formulation of Price and Rind in some studies. Resolution dependency also requires attention when sub-grid cloud-tops are used instead of the originally intended grid-averaged cloud-top. LNOx passive tracers being gathered by monsoonal upper tropospheric anticyclone.

The Tropical Upper Troposphere and Lower Stratosphere in the GEOS-2 GCM

NASA Technical Reports Server (NTRS)

Pawson, S.; Takacs, L.; Molod, A.; Nebuda, S.; Chen, M.; Rood, R.; Read, W. L.; Fiorino, M.

1999-01-01

The structure of the tropical upper troposphere and lower stratosphere in the GEOS-2 General Circulation Model (GCM) is discussed. The emphasis of this study is on the reality of monthly-mean temperature and water vapor distributions in the model, compared to reasonable observational estimates. It is shown that although the zonal-mean temperature is in good agreement with observations, the GCM supports an excessive zonal asymmetry near the tropopause compared to the ECMWF Reanalyses. In reality there is a QBO-related variability in the zonally averaged lower stratospheric temperature which is not captured by the model. The observed upper tropospheric temperature and humidity fields show variations related to those in the sea surface temperature, which are not incorporated in the GCM; nevertheless, there is some interannual variability in the GCM, indicating a component arising from internal processes. The model is too moist in the middle troposphere (500 hPa) but too dry in the upper troposphere, suggesting that there is too little vertical transport or too much drying in the GCM. Transport into the stratosphere shows a pronounced annual cycle, with drier air entering the tropical stratosphere when the tropopause is coldest in northern winter; while the alternating dry and moist air masses can be traced ascending through the tropical lower stratosphere, the progression of the anomalies is too rapid.

Oxidation of mercury by bromine in the subtropical Pacific free troposphere

NASA Astrophysics Data System (ADS)

Gratz, L. E.; Ambrose, J. L.; Jaffe, D. A.; Shah, V.; Jaeglé, L.; Stutz, J.; Festa, J.; Spolaor, M.; Tsai, C.; Selin, N. E.; Song, S.; Zhou, X.; Weinheimer, A. J.; Knapp, D. J.; Montzka, D. D.; Flocke, F. M.; Campos, T. L.; Apel, E.; Hornbrook, R.; Blake, N. J.; Hall, S.; Tyndall, G. S.; Reeves, M.; Stechman, D.; Stell, M.

2015-12-01

Mercury is a global toxin that can be introduced to ecosystems through atmospheric deposition. Mercury oxidation is thought to occur in the free troposphere by bromine radicals, but direct observational evidence for this process is currently unavailable. During the 2013 Nitrogen, Oxidants, Mercury and Aerosol Distributions, Sources and Sinks campaign, we measured enhanced oxidized mercury and bromine monoxide in a free tropospheric air mass over Texas. We use trace gas measurements, air mass back trajectories, and a chemical box model to confirm the origin and chemical history of the sampled air mass. We find the presence of elevated oxidized mercury to be consistent with oxidation of elemental mercury by bromine atoms in this subsiding upper tropospheric air mass within the subtropical Pacific High, where dry atmospheric conditions are conducive to oxidized mercury accumulation. Our results support the role of bromine as the dominant oxidant of mercury in the upper troposphere.

Large-Eddy Simulations of Tropical Convective Systems, the Boundary Layer, and Upper Ocean Coupling

DTIC Science & Technology

2014-09-30

warmer profile through greater latent heat release. Resulting temperature profiles all follow essentially moist adiabats in the upper troposphere ...default RRTM ozone concentration profile). Greater convective mixing deepens the tropopause for cases with stronger moisture flux convergence. Case...with tropospheric temperatures about 4 degrees cooler than the original temperature profile. This case represents conditions during the suppressed

Nitric Acid Particles in Cold Thick Ice Clouds Observed at Global Scale: Link with Lightning, Temperature, and Upper Tropospheric Water Vapor

NASA Technical Reports Server (NTRS)

Chepfer, H.; Minnis, P.; Dubuisson, P.; Chiriaco, M.; Sun-Mack, S.; Riviere, E. D.

2007-01-01

Signatures of nitric acid particles (NAP) in cold thick ice clouds have been derived from satellite observations. Most NAP are detected in the Tropics (9 to 20% of clouds with T less than 202.5 K). Higher occurrences were found in the rare mid-latitudes very cold clouds. NAP occurrence increases as cloud temperature decreases and NAP are more numerous in January than July. Comparisons of NAP and lightning distributions show that lightning is the main source of the NOx, which forms NAP in cold clouds. Qualitative comparisons of NAP with upper tropospheric humidity distributions suggest that NAP play a role in the dehydration of the upper troposphere when the tropopause is colder than 195K.

Nitric acid particles in cold thick ice clouds observed at global scale: Link with lightning, temperature, and upper tropospheric water vapor

NASA Astrophysics Data System (ADS)

Chepfer, H.; Minnis, P.; Dubuisson, P.; Chiriaco, M.; Sun-Mack, S.; RivièRe, E. D.

2007-03-01

Signatures of nitric acid particles (NAP) in cold thick ice clouds have been derived from satellite observations. Most NAP are detected in the tropics (9 to 20% of clouds with T < 202.5 K). Higher occurrences were found in the rare midlatitudes very cold clouds. NAP occurrence increases as cloud temperature decreases, and NAP are more numerous in January than July. Comparisons of NAP and lightning distributions show that lightning seems to be the main source of the NOx, which forms NAP in cold clouds over continents. Qualitative comparisons of NAP with upper tropospheric humidity distributions suggest that NAP may play a role in the dehydration of the upper troposphere when the tropopause is colder than 195 K.

The role of chemistry in under-predictions of NO2 in the upper troposphere

NASA Astrophysics Data System (ADS)

Henderson, B. H.; Pinder, R. W.; Goliff, W. S.; Stockwell, W. R.; Fahr, A.; Sarwar, G.; Hutzell, W. T.; Mathur, R.; Vizuete, W.; Cohen, R. C.

2009-12-01

Global and regional atmospheric models under-predict upper troposphere NO2 compared to satellite and aircraft observations. The upper tropospheric under-prediction of NO2 could be a function of emissions, transport, chemistry or some combination. Previous researchers have linked poor performance in the model to over-prediction of the OH and under-prediction of the HO2 by chemistry (Olson et al. 2006, Bertram et al. 2007). This study isolates upper tropospheric chemistry to evaluate the chemical contribution to NO2 under-predictions and to diagnose OH and HO2 discrepancies.

We use a 0-dimensional time dependent model to evaluate seven chemical mechanisms. Because chamber data representing upper tropospheric conditions does not exist, we evaluate the predictions based against an observation-based aging model. Following Bertram et al (2007), we use the NOx:HNO3 ratio to categorize the chemical age of thousands of 10 second average observations between 8 and 10km. Measurements of 10 inorganics and 32 hydrocarbons are translated to model species for each of seven chemical mechanisms. We chose mechanisms ranging from condensed to semi-explicit. The seven mechanisms' design scopes range from urban to global scale. Results include simulations from Model for OZone And Related chemical Tracers (MOZART), Carbon Bond 05 (CB05), State Air Pollution Research Center (SAPRC) 99, SAPRC 07, GEOS-Chem, Regional Atmospheric Chemical Mechanism version 2, and the LEEDS Master Chemical Mechanism.

Results from each chemical mechanism are compared to aircraft observations and to those obtained with other chemical mechanisms. Each mechanism is then further evaluated using integrated reaction rate analysis to identify sources of NO2 bias. We find that the largest contributors to the NO2 bias are over-predictions of PAN and HNO3. The formation of PAN is sensitive to the acetone photolysis rate. The conversion of NOx to HNO3 is most sensitive to hydroxyl radical concentrations. Hydroxyl radical sources and sinks have been quantified for each chemical mechanism using IRR analysis. Based on our modeling experience and results, we make recommendations for better simulating upper tropospheric photochemistry and we identify future research needs.

Bertram et al. Direct Measurements of the Convective Recycling of the Upper Troposphere. Science (2007)
Olson et al. A reevaluation of airborne HOx observations from NASA field campaigns. J Geophys Res-Atmos (2006) vol. 111 pp. D10301

Observations of Subvisible Cirrus Clouds and Gravity Waves at the Tropical Tropopause

NASA Technical Reports Server (NTRS)

Pfister, Leonhard; Browell, E. V.; Hipskind, R. Stephen (Technical Monitor)

1998-01-01

Thin, subvisible cirrus (SVC) clouds at the tropical tropopause have been observed by a number of methods in a variety of observational programs, including in situ sampling and aircraft and space-based lidar. Modeling studies suggest that these clouds play an important role in dehydrating tropospheric air as it enters the stratosphere. This is because particles large enough to have significant fall speeds can form under the conditions of slow cooling that are implied by the large horizontal extent of the SVC sheets. The IR radiation that these clouds absorb, and the upward vertical motion this implies, also makes them candidates for a tropical troposphere-to-stratosphere mass transfer mechanism. They may also play a role in the earth's radiation budget. These sheets were observed on five flights during the Tropical Ozone Transport Experiment (TOTE) by the NASA Langley DIAL lidar aboard NASA's DC-8 research aircraft operating during December 1995 and February 1996 south of Hawaii. The relationship of the SVC's observed during TOTE to convection was not a simple one. One class of SVC's are within 1000 km of the persistent strong convection near 15S (the SPCZ). Trajectory analyses indicated that the SVC air masses have in fact passed through the SPCZ within a few days of observation. These clouds are very close to the tropopause, with maximum potential temperatures not much higher than 370K, consistent with in situ water and total water measurements near the tropopause made during the Stratosphere Troposphere Exchange Project in January 1987 at Darwin, Australia. A second class of SVC's are not immediately downstream of convection. These clouds tend to be higher, reaching potential temperatures of 390K or more. Trajectory analyses indicate that the air in these SVC's originates either in the equatorial western Pacific or along the subtropical jet. In any case, the warm temperatures the SVC air masses encounter just prior to the observation time along the back trajectory imply that the clouds cannot be residual particles from cirrus blowoff, but must form locally as the air move upward and equatorward south of Hawaii. Since all the parcels have encountered colder temperatures than those at the time of observation early in their history, subsynoptic scale temperatures colder than the analysis temperatures appear to be required to explain the formation of ice particles. In fact, the sloping shapes of the SVC's do suggest that they are gravity or inertia-gravity waves. In situ meteorological measurements made by the ER-2 within a day of the DC-8 remote lidar observations show a gravity wave structure near the equator with an estimated period of about 30 hours. This is sufficiently long to allow large particles to form and fall out (thus allowing dehydration). Other ER-2 flights south of Hawaii at other times of year show gravity and inertia-gravity waves with a poleward wavenumber component and significant (5 degrees peak to peak) temperature perturbation.

Cubic ice and large humidity with respect to ice in cold cirrus clouds

NASA Astrophysics Data System (ADS)

Bogdan, A.; Loerting, T.

2009-04-01

Recently several studies have reported about the possible formation of cubic ice in upper-tropospheric cirrus ice clouds and its role in the observed elevated relative humidity with respect to hexagonal ice, RHi, within the clouds. Since cubic ice is metastable with respect to stable hexagonal ice, its vapour pressure is higher. A key issue in determining the ratio of vapour pressures of cubic ice Pc and hexagonal ice Ph is the enthalpy of transformation from cubic to hexagonal ice Hc→h. By dividing the two integrated forms of the Clausius-Clapeyron equation for cubic ice and hexagonal ice, one obtains the relationship (1): ln Pc-- ln P*c-=--(Hc→h--) Ph P*h R 1T-- 1T* (1) from which the importance of Hc→h is evident. In many literature studies the approximation (2) is used: ln Pc-= Hc-→h. Ph RT (2) Using this approximated form one can predict the ratio of vapour pressures by measuring Hc→h. Unfortunately, the measurement of Hc→h is difficult. First, the enthalpy difference is very small, and the transition takes place over a broad temperature range, e.g., between 230 K and 260 K in some of our calorimetry experiments. Second, cubic ice (by contrast to hexagonal ice) can not be produced as a pure crystal. It always contains hexagonal stacking faults, which are evidenced by the (111)-hexagonal Bragg peak in the powder diffractogram. If the number of hexagonal stacking faults in cubic ice is high, then one could even consider this material as hexagonal ice with cubic stacking faults. Using the largest literature value of the change of enthalpy of transformation from cubic to hexagonal ice, Hc→h ? 160 J/mol, Murphy and Koop (2005) calculated that Pc would be ~10% higher than that of hexagonal ice Phat 180 K - 190 K, which agrees with the measurements obtained later by Shilling et al. (2006). Based on this result Shilling et al. concluded that "the formation of cubic ice at T < 202 K may significantly contribute to the persistent in-cloud water supersaturations" in the upper-tropospheric cold cirrus clouds. Using instead the value of Hc→h ? 50 J/mol (Handa et al., 1986; Mayer and Hallbrucker, 1987) the calculation gives that Pc is only ~3% larger than that of Ph. Recently it has been reported that emulsified water droplets freeze to cubic ice when being cooled at a rate of 10 K/min (Murray and Bertram, 2006,). We prepared emulsified droplets using the same emulsification technique and studied them with a differential scanning calorimeter (DSC) between 278 and 180 K using a scanning rate of 10 K/min. During the warming of the samples we observed a very broad, tiny exothermal peak approximately between 230 and 260 K. Kohl et al. (2000) observed exothermal peak at ~230 K during the warming at 30 K/min of several samples of hyperquenched glassy water (HGW) prepared at temperature between 130 and 190 K. They attributed this peak to the cubic-to-hexagonal ice transition and estimated Hc→h to be between ~33 and 75 J/mol. Johari (2005) used the value of Hc→h ? 37 J/mol. Assuming that in our case the broad peak between 230 and 260 K is also due to the cubic-to-hexagonal ice transition we obtained approximately between 10 and 25 J/mol for Hc→h. This low enthalpy of transformation suggests that cubic ice in the atmosphere contains many hexagonal stacking faults. Using these values of Hc→h for cubic ice as produced at atmospheric cooling rates, the above mentioned formula gives that Pc is larger than that of Ph only by ~1%. We, therefore, suggest that the difference in the water vapor pressures between ice Ic and ice Ih is small and does not play a significant role in the elevation of RHi in cold cirrus clouds. Murphy, D. M., and T. Koop (2005), Q. J. R. Meteorol. Soc. 131, 1539-1565. Shilling, J. E. et al. (2006). Geophys. Res. Lett. 33, L17801, doi:1029/2006GL026671. Handa, P. Y., D. D. Klug, and E. Whalley (1986). J. Chem. Phys. 84, 7009-7010. Mayer, E., and A. Hallbrucker (1987), Nature, 325, 601-602. Murray, B. J. and A. K. Bertram (2006), Phys. Chem. Chem. Phys. 8, 186-192. Kohl, I., E. Mayer, and A. Hallbrucker (2000), Phys. Chem. Chem. Phys. 2, 1579-1586. G. P. Johari, (2005), J. Chem. Phys. 122, 194504.

Extratropical influence of upper tropospheric water vapor on Greenhouse warming

NASA Technical Reports Server (NTRS)

Liu, W. Timothy; Hu, Hua

1997-01-01

Despite its small quantity, the importance of upper tropospheric water vapor is its ability to trap the longwave radiation emitted from the Earth's surface, namely the greenhouse effect. The greenhouse effect is defined quantitatively as the difference between the longwave flux emitted by the Earth's surface and the outgoing longwave radiation (OLR) flux emitted from the top of the atmosphere (TOA) (Raval and Ramanathan 1989).

Global Distribution and Sources of Volatile and Nonvolatile Aerosol In the Remote Troposphere

NASA Technical Reports Server (NTRS)

Singh, Hanwant B.; Avery, M.; Viezee, W.; Che, Y.; Tabazadeh, A.; Hamill, P.; Pueschel, R.; Hannan, J. R.; Anderson, B.; Fuelberg, H. E.;

Long-term tropospheric and lower stratospheric ozone variations from ozonesonde observations

NASA Technical Reports Server (NTRS)

London, J.; Liu, S. C.

1992-01-01

An analysis is presented of the long-term mean pressure-latitude seasonal distribution of tropospheric and lower stratospheric ozone for the four seasons covering, in part, over 20 years of ozonesonde data. The observed patterns show minimum ozone mixing ratios in the equatorial and tropical troposphere except in regions where net photochemical production is dominant. In the middle and upper troposphere, and low stratosphere to 50 mb, ozone increases from the tropics to subpolar latitudes of both hemispheres. In mid stratosphere, the ozone mixing ratio is a maximum over the tropics. The observed vertical ozone gradient is small in the troposphere but increases rapidly above the tropopause. The amplitude of the annual variation increases from a minimum in the tropics to a maximum in polar regions. Also, the amplitude increases with height at all latitudes up to about 30 mb where the phase of the annual variation changes abruptly. The phase of the annual variation is during spring in the boundary layer, summer in mid troposphere, and spring in the upper troposhere and lower stratosphere.

Characteristics of intercontinental transport of tropospheric ozone from Africa to Asia

NASA Astrophysics Data System (ADS)

Han, Han; Liu, Jane; Yuan, Huiling; Zhuang, Bingliang; Zhu, Ye; Wu, Yue; Yan, Yuhan; Ding, Aijun

2018-03-01

In this study, we characterize the transport of ozone from Africa to Asia through the analysis of the simulations of a global chemical transport model, GEOS-Chem, from 1987 to 2006. The receptor region Asia is defined within 5-60° N and 60-145° E, while the source region Africa is within 35° S-15° N and 20° W-55° E and within 15-35° N and 20° W-30° E. The ozone generated in the African troposphere from both natural and anthropogenic sources is tracked through tagged ozone simulation. Combining this with analysis of trajectory simulations using the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model, we find that the upper branch of the Hadley cell connects with the subtropical westerlies in the Northern Hemisphere (NH) to form a primary transport pathway from Africa to Asia in the middle and upper troposphere throughout the year. The Somali jet that runs from eastern Africa near the equator to the Indian subcontinent in the lower troposphere is the second pathway that appears only in NH summer. The influence of African ozone mainly appears over Asia south of 40° N. The influence shows strong seasonality, varying with latitude, longitude, and altitude. In the Asian upper troposphere, imported African ozone is largest from March to May around 30° N (12-16 ppbv) and lowest during July-October around 10° N ( ˜ 2 ppbv). In the Asian middle and lower troposphere, imported African ozone peaks in NH winter between 20 and 25° N. Over 5-40° N, the mean fractional contribution of imported African ozone to the overall ozone concentrations in Asia is largest during NH winter in the middle troposphere ( ˜ 18 %) and lowest in NH summer throughout the tropospheric column ( ˜ 6 %). This seasonality mainly results from the collective effects of the ozone precursor emissions in Africa and meteorology and chemistry in Africa, in Asia and along the transport pathways. The seasonal swing of the Hadley circulation and subtropical westerlies along the primary transport pathway plays a dominant role in modulating the seasonality. There is more imported African ozone in the Asian upper troposphere in NH spring than in winter. This is likely due to more ozone in the NH African upper troposphere generated from biogenic and lightning NOx emissions in NH spring. The influence of African ozone on Asia appears larger in NH spring than in autumn. This can be attributed to both higher altitudes of the elevated ozone in Africa and stronger subtropical westerlies in NH spring. In NH summer, African ozone hardly reaches Asia because of the blocking by the Saharan High, Arabian High, and Tibetan High on the transport pathway in the middle and upper troposphere, in addition to the northward swing of the subtropical westerlies. The seasonal swings of the intertropical convergence zone (ITCZ) in Africa, coinciding with the geographic variations of the ozone precursor emissions, can further modulate the seasonality of the transport of African ozone, owing to the functions of the ITCZ in enhancing lightning NOx generation and uplifting ozone and ozone precursors to upper layers. The strength of the ITCZ in Africa is also found to be positively correlated with the interannual variation of the transport of African ozone to Asia in NH winter. Ozone from NH Africa makes up over 80 % of the total imported African ozone over Asia in most altitudes and seasons. The interhemispheric transport of ozone from southern hemispheric Africa (SHAF) is most evident in NH winter over the Asian upper troposphere and in NH summer over the Asian lower troposphere. The former case is associated with the primary transport pathway in NH winter, while the latter case is associated with the second transport pathway. The intensities of the ITCZ in Africa and the Somali jet can each explain ˜ 30 % of the interannual variations in the transport of ozone from SHAF to Asia in the two cases.

On the Roles of Upper- versus Lower-level Thermal Forcing in Shifting the Eddy-Driven Jet

NASA Astrophysics Data System (ADS)

Zhang, Y.; Nie, Y.; Chen, G.; Yang, X. Q.

2017-12-01

One most drastic atmospheric change in the global warming scenario is the increase in temperature over tropical upper-troposphere and polar surface. The strong warming over those two area alters the spacial distributions of the baroclinicity in the upper-troposphere of subtropics and in the lower-level of subpolar region, with competing effects on the mid-latitude atmospheric circulation. The final destination of the eddy-driven jet in future climate could be "a tug of war" between the impacts of such upper- versus lower-level thermal forcing. In this study, the roles of upper- versus lower-level thermal forcing in shifting the eddy-driven jet are investigated using a nonlinear multi-level quasi-geostrophic channel model. All of our sensitivity experiments show that the latitudinal position of the eddy-driven jet is more sensitive to the upper-level thermal forcing. Such upper-level dominance over the lower-level forcing can be attributed to the different mechanisms through which eddy-driven jet responses to them. The upper-level thermal forcing induces a jet shift mainly by affecting the baroclinic generation of eddies, which supports the latitudinal shift of the eddy momentum flux convergence. The jet response to the lower-level thermal forcing, however, is strongly "eddy dissipation control". The lower-level forcing, by changing the baroclinicity in the lower troposphere, induces a direct thermal zonal wind response in the upper level thus modifies the nonlinear wave breaking and the resultant irreversible eddy mixing, which amplifies the latitudinal shift of the eddy-driven jet. Whether the eddy response is "generation control" or "dissipation control" may strongly depend on the eddy behavior in its baroclinic processes. Only the anomalous eddy generation that penetrates into the upper troposphere can have a striking impact on the eddy momentum flux, which pushes the jet shift more efficiently and dominates the eddy response.

Long-lived contrails and convective cirrus above the tropical tropopause

NASA Astrophysics Data System (ADS)

Schumann, Ulrich; Kiemle, Christoph; Schlager, Hans; Weigel, Ralf; Borrmann, Stephan; D'Amato, Francesco; Krämer, Martina; Matthey, Renaud; Protat, Alain; Voigt, Christiane; Volk, C. Michael

2017-02-01

This study has two objectives: (1) it characterizes contrails at very low temperatures and (2) it discusses convective cirrus in which the contrails occurred. (1) Long-lived contrails and cirrus from overshooting convection are investigated above the tropical tropopause at low temperatures down to -88 °C from measurements with the Russian high-altitude research aircraft M-55 Geophysica, as well as related observations during the SCOUT-O3 field experiment near Darwin, Australia, in 2005. A contrail was observed to persist below ice saturation at low temperatures and low turbulence in the stratosphere for nearly 1 h. The contrail occurred downwind of the decaying convective system Hector of 16 November 2005. The upper part of the contrail formed at 19 km altitude in the tropical lower stratosphere at ˜ 60 % relative humidity over ice at -82 °C. The ˜ 1 h lifetime is explained by engine water emissions, slightly enhanced humidity from Hector, low temperature, low turbulence, and possibly nitric acid hydrate formation. The long persistence suggests large contrail coverage in case of a potential future increase of air traffic in the lower stratosphere. (2) Cirrus observed above the strongly convective Hector cloud on 30 November 2005 was previously interpreted as cirrus from overshooting convection. Here we show that parts of the cirrus were caused by contrails or are mixtures of convective and contrail cirrus. The in situ data together with data from an upward-looking lidar on the German research aircraft Falcon, the CPOL radar near Darwin, and NOAA-AVHRR satellites provide a sufficiently complete picture to distinguish between contrail and convective cirrus parts. Plume positions are estimated based on measured or analyzed wind and parameterized wake vortex descent. Most of the non-volatile aerosol measured over Hector is traceable to aircraft emissions. Exhaust emission indices are derived from a self-match experiment of the Geophysica in the polar stratosphere in 2010. The number of ice particles in the contrails is less than 1 % of the number of non-volatile aerosol particles, possibly because of sublimation losses and undetected very small ice particles. The radar data show that the ice water content in convective overshoots is far higher than measured along the flight path. These findings add insight into overshooting convection and are of relevance with respect to hydration of the lower stratosphere.

Potential Nighttime Contamination of CERES Clear-sky Field of View by Optically Thin Cirrus during the CRYSTAL-FACE Campaign

NASA Technical Reports Server (NTRS)

Lee, Yong-Keun; Yang, Ping; Hu, Yongxiang; Baum, Bryan A.; Loeb, Norman G.; Gao, Bo-Cai

2006-01-01

We investigate the outgoing broadband longwave (LW, 5 to approx. 200 microns) and window (WIN, 8 to approx. 12 microns) channel radiances at the top of atmosphere (TOA) under clear-sky conditions, using data acquired by the Cloud and the Earth s Radiant Energy System (CERES) and Moderate-Resolution Imaging Spectroradiometer (MODIS) instruments onboard the NASA Terra satellite platform. In this study, detailed analyses are performed on the CERES Single Scanner Footprint TOA/Surface Fluxes and Clouds product to understand the radiative effect of thin cirrus. The data are acquired over the Florida area during the Cirrus Regional Study of Tropical Anvils and Cirrus Layers Florida Area Cirrus Experiment (CRYSTAL-FACE) field program. Of particular interest is the anisotropy associated with the radiation field. Measured CERES broadband radiances are compared to those obtained from rigorous radiative transfer simulations. Analysis of results from this comparison indicates that the simulated radiances tend to be larger than their measured counterparts, with differences ranging from 2.1% to 8.3% for the LW band and from 1.7% to 10.6% for the WIN band. The averaged difference in radiance is approximately 4% for both the LW and WIN channels. A potential cause for the differences could be the presence of thin cirrus (i.e., optically thin ice clouds with visible optical thicknesses smaller than approximately 0.3). The detection and quantitative analysis of these thin cirrus clouds are challenging even with sophisticated multispectral instruments. While large differences in radiance between the CERES observations and the theoretical calculations are found, the corresponding difference in the anisotropic factors is very small (0.2%). Furthermore, sensitivity studies show that the influence due to a 1 K bias of the surface temperature on the errors of the LW and WIN channel radiances is of the same order as that associated with a 2% bias of the surface emissivity. The LW and WIN errors associated with a 5% bias of water vapor amount in the lower atmosphere in conjunction with a 50% bias of water vapor amount in the upper atmosphere is similar to that of a 1 K bias of the vertical temperature profile. Even with the uncertainties considered for these various factors, the simulated LW and WIN radiances are still larger than the observed radiances if thin cirrus clouds are excluded.

Physical Mechanisms Controlling Upper Tropospheric Water Vapor as Revealed by MLS Data from UARS

NASA Technical Reports Server (NTRS)

Newell, Reginald E.

1998-01-01

The seasonal changes of the upper tropospheric humidity are studied with the water vapor data from the Microwave Limb Sounder on the NASA Upper Atmosphere Research Satellite, and the winds and vertical velocity data obtained from the European Centre for Medium-Range Weather Forecasts. Using the same algorithm for vertical transport as that used for horizontal transport (Zhu and Newell, 1998), we find that the moisture in the tropical upper troposphere may be increased mainly by intensified local convection in a small portion, less than 10%, of the whole area between 40 deg S to 40 deg N. The contribution of large scale background circulations and divergence of horizontal transport is relatively small in these regions. These dynamic processes cannot be revealed by the traditional analyses of moisture fluxes. The negative feedback suggested by Lindzen (1990) also exists, if enhanced convection is concentrated in the tropics, but is apparently not the dominant process in the moisture budget.

Subtropical Potential Vorticity Intrusion Drives Increasing Tropospheric Ozone over the Tropical Central Pacific.

PubMed

Nath, Debashis; Chen, Wen; Graf, Hans-F; Lan, Xiaoqing; Gong, Hainan; Nath, Reshmita; Hu, Kaiming; Wang, Lin

2016-02-12

Drawn from multiple reanalysis datasets, an increasing trend and westward shift in the number of Potential Vorticity intrusion events over the Pacific are evident. The increased frequency can be linked to a long-term trend in upper tropospheric equatorial westerly wind and subtropical jets during boreal winter to spring. These may be resulting from anomalous warming and cooling over the western Pacific warm pool and the tropical eastern Pacific, respectively. The intrusions brought dry and ozone rich air of stratospheric origin deep into the tropics. In the tropical upper troposphere, interannual ozone variability is mainly related to convection associated with El Niño/Southern Oscillation. Zonal mean stratospheric overturning circulation organizes the transport of ozone rich air poleward and downward to the high and midlatitudes leading there to higher ozone concentration. In addition to these well described mechanisms, we observe a long-term increasing trend in ozone flux over the northern hemispheric outer tropical (10-25°N) central Pacific that results from equatorward transport and downward mixing from the midlatitude upper troposphere and lower stratosphere during PV intrusions. This increase in tropospheric ozone flux over the Pacific Ocean may affect the radiative processes and changes the budget of atmospheric hydroxyl radicals.

Evidence of Seasonally Dependent Stratosphere-Troposphere Exchange and Purging of Lower Stratospheric Aeroso from a Multi-Year Lidar Dataset

NASA Technical Reports Server (NTRS)

Menzies, R. T.; Tratt, D. M.

1994-01-01

Tropospheric and lower stratospheric aerosol backscatter data obtained from a calibrated backscatter lidar at Pasadena, California (34 deg N latitude)over the 1984-1993 period clearly indicate tightly coupled aerosol optical properties in the upper troposphere and lower stratosphere in the winter and early spring, due to the active mid-latitude stratospheric-tropospheric (ST) exchange processes occurring at this time of year.

Surface measurements of upper tropospheric water vapor isotopic composition on the Chajnantor Plateau, Chile

NASA Astrophysics Data System (ADS)

Galewsky, Joseph; Rella, Christopher; Sharp, Zachary; Samuels, Kimberly; Ward, Dylan

2011-09-01

Simultaneous, real-time measurements of atmospheric water vapor mixing ratio and isotopic composition (δD and δ18O) were obtained using cavity ringdown spectroscopy on the arid Chajnantor Plateau in the subtropical Chilean Andes (elevation 5080 m or 550 hPa; latitude 23°S) during July and August 2010. The measurements show surface water vapor mixing ratio as low as 215 ppmv, δD values as low as -540‰, and δ18O values as low as -68‰, which are the lowest atmospheric water vapor δ values reported from Earth's surface. The results are consistent with previous measurements from the base of the tropical tropopause layer (TTL) and suggest large-scale subsidence of air masses from the upper troposphere to the Earth's surface. The range of measurements is consistent with condensation under conditions of ice supersaturation and mixing with moister air from the lower troposphere that has been processed through shallow convection. Diagnostics using reanalysis data show that the extreme aridity of the Chajnantor Plateau is controlled by condensation in the upper tropical troposphere.

Tropospheric ozone over the North Pacific from ozonesonde observations

NASA Astrophysics Data System (ADS)

Oltmans, S. J.; Johnson, B. J.; Harris, J. M.; Thompson, A. M.; Liu, H. Y.; Chan, C. Y.; VöMel, H.; Fujimoto, T.; Brackett, V. G.; Chang, W. L.; Chen, J.-P.; Kim, J. H.; Chan, L. Y.; Chang, H.-W.

2004-08-01

As part of the Transport and Chemical Evolution over the Pacific (TRACE-P) mission, ozonesondes were used to make ozone vertical profile measurements at nine locations in the North Pacific. At most of the sites there is a multiyear record of observations. From locations in the western Pacific (Hong Kong; Taipei; Jeju Island, Korea; and Naha, Kagoshima, Tsukuba, and Sapporo, Japan), a site in the central Pacific (Hilo, Hawaii), and a site on the west coast of the United States (Trinidad Head, California) both a seasonal and event specific picture of tropospheric ozone over the North Pacific emerges. Ozone profiles over the North Pacific generally show a prominent spring maximum throughout the troposphere. This maximum is tied to the location of the jet stream and its influence on stratosphere-troposphere exchange and the increase in photochemical ozone production through the spring. Prominent layers of enhanced ozone in the middle and upper troposphere north of about 30°N seem to be more closely tied to stratospheric intrusions while biomass burning leads to layers of enhanced ozone in the lower and upper troposphere at Hong Kong (22°N) and Taipei (25°N). The lower free tropospheric layers at Hong Kong are associated with burning in SE Asia, but the upper layer may be associated with either equatorial Northern Hemisphere burning in Africa or SE Asian biomass burning. In the boundary layer at Taipei very high mixing ratios of ozone were observed that result from pollution transport from China in the spring and local urban pollution during the summer. At the ozonesonde site near Tokyo (Tsukuba, 36°N) very large enhancements of ozone are seen in the boundary layer in the summer that are characteristic of urban air pollution. At sites in the mid and eastern Pacific the signature of transport of polluted air from Asia is not readily identifiable from the ozonesonde profile. This is likely due to the more subtle signal and the fact that from the ozone profile and meteorological data by themselves it is difficult to identify such a signal. During the TRACE-P intensive campaign period (February-April 2001), tropospheric ozone amounts were generally typical of those seen in the long-term records of the stations with multiyear soundings. The exception was the upper troposphere over Hong Kong and Taipei where ozone amounts were lower in 2001.

Observations of the upper troposphere and lower stratosphere using the urbana coherent-scatter radar

NASA Technical Reports Server (NTRS)

Goss, L. D.; Bowhill, S. A.

1983-01-01

The Urbana coherent-scatter radar was used to observe the upper troposphere and lower stratosphere, and 134 hours of data were collected. Horizontal wind measurements show good agreement with balloon-measured winds. Gravity waves were frequently observed, and were enhanced during convective activity. Updrafts and downdrafts were observed within thunderstorms. Power returns are related to hydrostatic stability, and changes in echo specularity are shown.

Measurements of selected C2-C5 hydrocarbons in the troposphere - Latitudinal, vertical, and temporal variations

NASA Technical Reports Server (NTRS)

Singh, Hanwant B.; Viezee, William; Salas, Louis J.

1988-01-01

The tropospheric distribution of 1077 C2-C5 hydrocarbon samples was determined. Shipboard measurements obtained over the eastern Pacific Ocean reveal large north-to-south gradients for most nonmethane hydrocarbons (NMHCs). The results show that NMHC concentrations can decrease by a factor of two or more during the passage of cold fronts in winter and spring, and that upper tropospheric concentrations were lower than those in the lower troposphere.

Atmospheric influences on infrared-laser signals used for occultation measurements between Low Earth Orbit satellites

NASA Astrophysics Data System (ADS)

Schweitzer, S.; Kirchengast, G.; Proschek, V.

2011-10-01

LEO-LEO infrared-laser occultation (LIO) is a new occultation technique between Low Earth Orbit (LEO) satellites, which applies signals in the short wave infrared spectral range (SWIR) within 2 μm to 2.5 μm. It is part of the LEO-LEO microwave and infrared-laser occultation (LMIO) method that enables to retrieve thermodynamic profiles (pressure, temperature, humidity) and altitude levels from microwave signals and profiles of greenhouse gases and further variables such as line-of-sight wind speed from simultaneously measured LIO signals. Due to the novelty of the LMIO method, detailed knowledge of atmospheric influences on LIO signals and of their suitability for accurate trace species retrieval did not yet exist. Here we discuss these influences, assessing effects from refraction, trace species absorption, aerosol extinction and Rayleigh scattering in detail, and addressing clouds, turbulence, wind, scattered solar radiation and terrestrial thermal radiation as well. We show that the influence of refractive defocusing, foreign species absorption, aerosols and turbulence is observable, but can be rendered small to negligible by use of the differential transmission principle with a close frequency spacing of LIO absorption and reference signals within 0.5%. The influences of Rayleigh scattering and terrestrial thermal radiation are found negligible. Cloud-scattered solar radiation can be observable under bright-day conditions, but this influence can be made negligible by a close time spacing (within 5 ms) of interleaved laser-pulse and background signals. Cloud extinction loss generally blocks SWIR signals, except very thin or sub-visible cirrus clouds, which can be addressed by retrieving a cloud layering profile and exploiting it in the trace species retrieval. Wind can have a small influence on the trace species absorption, which can be made negligible by using a simultaneously retrieved or a moderately accurate background wind speed profile. We conclude that the set of SWIR channels proposed for implementing the LMIO method (Kirchengast and Schweitzer, 2011) provides adequate sensitivity to accurately retrieve eight trace species of key importance to climate and atmospheric chemistry (H2O, CO2, 13CO2, C18OO, CH4, N2O, O3, CO) in the upper troposphere/lower stratosphere region outside clouds under all atmospheric conditions. Two further species (HDO, H218O) can be retrieved in the upper troposphere.

Airborne LIDAR Measurements of Water Vapor, Ozone, Clouds, and Aerosols in the Tropics Near Central America During the TC4 Experiment

NASA Technical Reports Server (NTRS)

Kooi, Susan; Fenn, Marta; Ismail, Syed; Ferrare, Richard; Hair, John; Browell, Edward; Notari, Anthony; Butler, Carolyn; Burton, Sharon; Simpson, Steven

2008-01-01

Large scale distributions of ozone, water vapor, aerosols, and clouds were measured throughout the troposphere by two NASA Langley lidar systems on board the NASA DC-8 aircraft as part of the Tropical Composition, Cloud, and Climate Coupling Experiment (TC4) over Central and South America and adjacent oceans in the summer of 2007. Special emphasis was placed on the sampling of convective outflow and transport, sub-visible cirrus clouds, boundary layer aerosols, Saharan dust, volcanic emissions, and urban and biomass burning plumes. This paper presents preliminary results from this campaign, and demonstrates the value of coordinated measurements by the two lidar systems.

Lidar determination of the composition of atmosphere aerosols

NASA Technical Reports Server (NTRS)

Wright, M. L.

1980-01-01

Theoretical and experimental studies of the feasibility of using DIfferential SCatter (DISC) lidar to measure the composition of atmospheric aerosols are described. This technique involves multiwavelength measurements of the backscatter cross section of aerosols in the middle infrared, where a number of materials display strong restrahlen features that significantly modulate the backscatter spectrum. The theoretical work indicates that a number of materials of interest, including sulfuric acid, ammonium sulfate, and silicates, can be discriminated among with a CO2 lidar. An initial evaluation of this procedure was performed in which cirrus clouds and lower altitude tropospheric aerosols were developed. The observed ratio spectrum of the two types of aerosol displays structure that is in crude accord with theoretical expectations.

Observations of O3, NO2 and BrO and in the tropical UT/LS during the 2013/2014 NASA ATTREX experiment

NASA Astrophysics Data System (ADS)

Werner, Bodo; Stutz, Jochen; Spolaor, Max; Tsai, Catalina; Colosimo, Fedele; Cheung, Ross; Deutschmann, Tim; Raecke, Rasmus; Tricoli, Ugo; Scalone, Lisa; Pfeilsticker, Klaus

2014-05-01

Reactive bromine plays an important role for the chemistry of ozone in the stratosphere and likely also in the upper troposphere. It is thus crucial to understand the sources and sinks of inorganic bromine species as well as their transport and that of their organic precursors into the stratosphere. Much progress has been made in recent years in understanding the budget of inorganic bromine through field observations of very short-lived organic bromine precursors, such as CHBr3 und CH2Br2 and inorganic product gases at stratospheric entry level. Nevertheless a number of processes influencing bromine chemistry require better quantification, including the transport of organic and inorganic bromine through the tropical TTL region and the interaction of inorganic bromine species with ice particles in cirrus clouds. Here we report on BrO, NO2, and O3 profile measurements performed within the TTL from aboard the NASA's unmanned high-altitude Global Hawk aircraft during the Airborne Tropical TRopopause EXperiment (ATTREX) deployments in 2011 - 2014. The technique involves limb scanning of UV/vis skylight spectra, spectral retrieval via Differential Optical Absorption Spectroscopy (DOAS), forward modelling of the radiative transfer for each observation and a non-linear optimal estimation of the targeted atmospheric parameters. Key features of the technique are reported and first retrieval results are discussed.

Biofuel blending reduces particle emissions from aircraft engines at cruise conditions

NASA Astrophysics Data System (ADS)

Moore, Richard H.; Thornhill, Kenneth L.; Weinzierl, Bernadett; Sauer, Daniel; D'Ascoli, Eugenio; Kim, Jin; Lichtenstern, Michael; Scheibe, Monika; Beaton, Brian; Beyersdorf, Andreas J.; Barrick, John; Bulzan, Dan; Corr, Chelsea A.; Crosbie, Ewan; Jurkat, Tina; Martin, Robert; Riddick, Dean; Shook, Michael; Slover, Gregory; Voigt, Christiane; White, Robert; Winstead, Edward; Yasky, Richard; Ziemba, Luke D.; Brown, Anthony; Schlager, Hans; Anderson, Bruce E.

2017-03-01

Aviation-related aerosol emissions contribute to the formation of contrail cirrus clouds that can alter upper tropospheric radiation and water budgets, and therefore climate. The magnitude of air-traffic-related aerosol-cloud interactions and the ways in which these interactions might change in the future remain uncertain. Modelling studies of the present and future effects of aviation on climate require detailed information about the number of aerosol particles emitted per kilogram of fuel burned and the microphysical properties of those aerosols that are relevant for cloud formation. However, previous observational data at cruise altitudes are sparse for engines burning conventional fuels, and no data have previously been reported for biofuel use in-flight. Here we report observations from research aircraft that sampled the exhaust of engines onboard a NASA DC-8 aircraft as they burned conventional Jet A fuel and a 50:50 (by volume) blend of Jet A fuel and a biofuel derived from Camelina oil. We show that, compared to using conventional fuels, biofuel blending reduces particle number and mass emissions immediately behind the aircraft by 50 to 70 per cent. Our observations quantify the impact of biofuel blending on aerosol emissions at cruise conditions and provide key microphysical parameters, which will be useful to assess the potential of biofuel use in aviation as a viable strategy to mitigate climate change.

Biofuel blending reduces particle emissions from aircraft engines at cruise conditions.

PubMed

Moore, Richard H; Thornhill, Kenneth L; Weinzierl, Bernadett; Sauer, Daniel; D'Ascoli, Eugenio; Kim, Jin; Lichtenstern, Michael; Scheibe, Monika; Beaton, Brian; Beyersdorf, Andreas J; Barrick, John; Bulzan, Dan; Corr, Chelsea A; Crosbie, Ewan; Jurkat, Tina; Martin, Robert; Riddick, Dean; Shook, Michael; Slover, Gregory; Voigt, Christiane; White, Robert; Winstead, Edward; Yasky, Richard; Ziemba, Luke D; Brown, Anthony; Schlager, Hans; Anderson, Bruce E

2017-03-15

Aviation-related aerosol emissions contribute to the formation of contrail cirrus clouds that can alter upper tropospheric radiation and water budgets, and therefore climate. The magnitude of air-traffic-related aerosol-cloud interactions and the ways in which these interactions might change in the future remain uncertain. Modelling studies of the present and future effects of aviation on climate require detailed information about the number of aerosol particles emitted per kilogram of fuel burned and the microphysical properties of those aerosols that are relevant for cloud formation. However, previous observational data at cruise altitudes are sparse for engines burning conventional fuels, and no data have previously been reported for biofuel use in-flight. Here we report observations from research aircraft that sampled the exhaust of engines onboard a NASA DC-8 aircraft as they burned conventional Jet A fuel and a 50:50 (by volume) blend of Jet A fuel and a biofuel derived from Camelina oil. We show that, compared to using conventional fuels, biofuel blending reduces particle number and mass emissions immediately behind the aircraft by 50 to 70 per cent. Our observations quantify the impact of biofuel blending on aerosol emissions at cruise conditions and provide key microphysical parameters, which will be useful to assess the potential of biofuel use in aviation as a viable strategy to mitigate climate change.

Added Value of Far-Infrared Radiometry for Ice Cloud Remote Sensing

NASA Astrophysics Data System (ADS)

Libois, Q.; Blanchet, J. P.; Ivanescu, L.; S Pelletier, L.; Laurence, C.

2017-12-01

Several cloud retrieval algorithms based on satellite observations in the infrared have been developed in the last decades. However, most of these observations only cover the midinfrared (MIR, λ < 15 μm) part of the spectrum, and none are available in the far-infrared (FIR, λ ≥ 15 μm). Recent developments in FIR sensors technology, though, now make it possible to consider spaceborne remote sensing in the FIR. Here we show that adding a few FIR channels with realistic radiometric performances to existing spaceborne narrowband radiometers would significantly improve their ability to retrieve ice cloud radiative properties. For clouds encountered in the polar regions and the upper troposphere, where the atmosphere above clouds is sufficiently transparent in the FIR, using FIR channels would reduce by more than 50% the uncertainties on retrieved values of optical thickness, effective particle diameter, and cloud top altitude. This would somehow extend the range of applicability of current infrared retrieval methods to the polar regions and to clouds with large optical thickness, where MIR algorithms perform poorly. The high performance of solar reflection-based algorithms would thus be reached in nighttime conditions. Using FIR observations is a promising venue for studying ice cloud microphysics and precipitation processes, which is highly relevant for cirrus clouds and convective towers, and for investigating the water cycle in the driest regions of the atmosphere.

Saharan dust, convective lofting, aerosol enhancement zones, and potential impacts on ice nucleation in the tropical upper troposphere

NASA Astrophysics Data System (ADS)

Twohy, C. H.; Anderson, B. E.; Ferrare, R. A.; Sauter, K. E.; L'Ecuyer, T. S.; van den Heever, S. C.; Heymsfield, A. J.; Ismail, S.; Diskin, G. S.

2017-08-01

Dry aerosol size distributions and scattering coefficients were measured on 10 flights in 32 clear-air regions adjacent to tropical storm anvils over the eastern Atlantic Ocean. Aerosol properties in these regions were compared with those from background air in the upper troposphere at least 40 km from clouds. Median values for aerosol scattering coefficient and particle number concentration >0.3 μm diameter were higher at the anvil edges than in background air, showing that convective clouds loft particles from the lower troposphere to the upper troposphere. These differences are statistically significant. The aerosol enhancement zones extended 10-15 km horizontally and 0.25 km vertically below anvil cloud edges but were not due to hygroscopic growth since particles were measured under dry conditions. Number concentrations of particles >0.3 μm diameter were enhanced more for the cases where Saharan dust layers were identified below the clouds with airborne lidar. Median number concentrations in this size range increased from 100 l-1 in background air to 400 l-1 adjacent to cloud edges with dust below, with larger enhancements for stronger storm systems. Integration with satellite cloud frequency data indicates that this transfer of large particles from low to high altitudes by convection has little impact on dust concentrations within the Saharan Air Layer itself. However, it can lead to substantial enhancement in large dust particles and, therefore, heterogeneous ice nuclei in the upper troposphere over the Atlantic. This may induce a cloud/aerosol feedback effect that could impact cloud properties in the region and downwind.

Global distribution and sources of volatile and nonvolatile aerosol in the remote troposphere

NASA Astrophysics Data System (ADS)

Singh, Hanwant B.; Anderson, B. E.; Avery, M. A.; Viezee, W.; Chen, Y.; Tabazadeh, A.; Hamill, P.; Pueschel, R.; Fuelberg, H. E.; Hannan, J. R.

2002-06-01

Airborne measurements of aerosol (condensation nuclei, CN) and selected trace gases made over areas of the North Atlantic Ocean during Subsonic Assessment (SASS) Ozone and Nitrogen Oxide Experiment (SONEX) (October/November 1997), the south tropical Pacific Ocean during Pacific Exploratory Mission (PEM)-Tropics A (September/October 1996), and PEM-Tropics B (March/April 1999) have been analyzed. The emphasis is on interpreting variations in the number densities of fine (>17 nm) and ultrafine (>8 nm) aerosol in the upper troposphere (8-12 km). These data suggest that large number densities of highly volatile CN (104 - 105 cm-3) are present in the upper troposphere and particularly over the tropical/subtropical region. CN number densities in all regions are largest when the atmosphere is devoid of nonvolatile particles. Through marine convection and long-distance horizontal transport, volatile CN originating from the tropical/subtropical regions can frequently impact the abundance of aerosol in the middle and upper troposphere at mid to high latitudes. Nonvolatile aerosols behave in a manner similar to tracers of combustion (CO) and photochemical pollution (peroxyacetylnitrate (PAN)), implying a continental pollution source from industrial emissions or biomass burning. In the upper troposphere we find that volatile and nonvolatile aerosol number densities are inversely correlated. Results from an aerosol microphysical model suggest that the coagulation of fine volatile particles with fewer but larger nonvolatile particles, of principally anthropogenic origin, is one possible explanation for this relationship. In some instances the larger nonvolatile particles may also directly remove precursors (e.g., H2SO4) and effectively stop nucleation.

Tropical storm redistribution of Saharan dust to the upper troposphere and ocean surface

NASA Astrophysics Data System (ADS)

Herbener, Stephen R.; Saleeby, Stephen M.; Heever, Susan C.; Twohy, Cynthia H.

2016-10-01

As a tropical cyclone traverses the Saharan Air Layer (SAL), the storm will spatially redistribute the dust from the SAL. Dust deposited on the surface may affect ocean fertilization, and dust transported to the upper levels of the troposphere may impact radiative forcing. This study explores the relative amounts of dust that are vertically redistributed when a tropical cyclone crosses the SAL. The Regional Atmospheric Modeling System (RAMS) was configured to simulate the passage of Tropical Storm Debby (2006) through the SAL. A dust mass budget approach has been applied, enabled by a novel dust mass tracking capability of the model, to determine the amounts of dust deposited on the ocean surface and transferred aloft. The mass of dust removed to the ocean surface was predicted to be nearly 2 orders of magnitude greater than the amount of dust transported to the upper troposphere.

Solubility of methanol in low-temperature aqueous sulfuric acid and implications for atmospheric particle composition

NASA Technical Reports Server (NTRS)

Iraci, Laura T.; Essin, Andrew M.; Golden, David M.; Hipskind, R. Stephen (Technical Monitor)

2001-01-01

Using traditional Knudsen cell techniques, we find well-behaved Henry's law uptake of methanol in aqueous 45 - 70 wt% H2SO4 solutions at temperatures between 197 and 231 K. Solubility of methanol increases with decreasing temperature and increasing acidity, with an effective Henry's law coefficient ranging from 10(exp 5) - 10(exp 8) M/atm. Equilibrium uptake of methanol into sulfuric acid aerosol particles in the upper troposphere and lower stratosphere will not appreciably alter gas-phase concentrations of methanol. The observed room temperature reaction between methanol and sulfuric acid is too slow to provide a sink for gaseous methanol at the temperatures of the upper troposphere and lower stratosphere. It is also too slow to produce sufficient quantities of soluble reaction products to explain the large amount of unidentified organic material seen in particles of the upper troposphere.

The Use of Sage Water Vapor Data for Investigating Climate Change Issues

NASA Technical Reports Server (NTRS)

Rind, D.

2003-01-01

SAGE water vapor data has proven valuable for addressing several of the important issues in climate change research. It has been used to investigate how the upper troposphere water vapor responds to warming and convection, a key question in understanding the water vapor feedback to anthropogenic global warming. In the case of summer versus winter differences, SAGE results showed that the upper tropospheric relative humidity remained approximately constant; this result was in general agreement with how a GCM handled the seasonal difference, and gave credence to the argument that the GCM was not overestimating the water vapor feedback associated with convection. In addition, the convection-water vapor relationship was investigated further using SAGE water vapor and ISCCP cloud data. The results showed that upper tropospheric drying did appear to occur simultaneously with deep convective events in the tropics, only to be replaced by moistening a few hours later, associated (most likely) with the reevaporation of moisture from anvil clouds. The total effect was, again, a moistening of the upper troposphere associated with convection. Calculation of the actual trends in upper tropospheric moisture is a potential goal for SAGE data usage; trends calculated with radiosonde data, or instruments calibrated with radiosonde data have the problem of the effect of changing radiosonde instruments. SAGE data have in effect been used to compare different radiosondes through comparisons, and could continue to do so. SAGE 3 should also help clarify the absolute accuracy of SAGE retrievals in the troposphere. and its consequences. Model results show that water vapor increases can help explain the observations of stratospheric cooling, along with increasing C02 and ozone reduction. SAGE has been shown to provide trends similar to those of some other satellite and in situ retrievals, with increasing water vapor over time. However, SAGE is impacted by aerosol contamination which must be removed from the data; approaches used in the past will be reviewed. The SAGE water vapor errors, if taken literally, would make it hard to justify using SAGE data for such trends, and the error bars must be investigated. Stratospheric water vapor increases, like tropospheric increases, would lead to noticeable warming at the surface, and their changes must be quantified.

Laboratory Studies of Homogeneous and Heterogeneous Chemical Processes of Importance in the Upper Atmosphere

NASA Technical Reports Server (NTRS)

Molina, Mario J.

2003-01-01

The objective of this study was to conduct measurements of chemical kinetics parameters for reactions of importance in the stratosphere and upper troposphere, and to study the interaction of trace gases with ice surfaces in order to elucidate the mechanism of heterogeneous chlorine activation processes, using both a theoretical and an experimental approach. The measurements were carried out under temperature and pressure conditions covering those applicable to the stratosphere and upper troposphere. The main experimental technique employed was turbulent flow-chemical ionization mass spectrometry, which is particularly well suited for investigations of radical-radical reactions.

Ice crystal characterization in cirrus clouds: a sun-tracking camera system and automated detection algorithm for halo displays

NASA Astrophysics Data System (ADS)

Forster, Linda; Seefeldner, Meinhard; Wiegner, Matthias; Mayer, Bernhard

2017-07-01

Halo displays in the sky contain valuable information about ice crystal shape and orientation: e.g., the 22° halo is produced by randomly oriented hexagonal prisms while parhelia (sundogs) indicate oriented plates. HaloCam, a novel sun-tracking camera system for the automated observation of halo displays is presented. An initial visual evaluation of the frequency of halo displays for the ACCEPT (Analysis of the Composition of Clouds with Extended Polarization Techniques) field campaign from October to mid-November 2014 showed that sundogs were observed more often than 22° halos. Thus, the majority of halo displays was produced by oriented ice crystals. During the campaign about 27 % of the cirrus clouds produced 22° halos, sundogs or upper tangent arcs. To evaluate the HaloCam observations collected from regular measurements in Munich between January 2014 and June 2016, an automated detection algorithm for 22° halos was developed, which can be extended to other halo types as well. This algorithm detected 22° halos about 2 % of the time for this dataset. The frequency of cirrus clouds during this time period was estimated by co-located ceilometer measurements using temperature thresholds of the cloud base. About 25 % of the detected cirrus clouds occurred together with a 22° halo, which implies that these clouds contained a certain fraction of smooth, hexagonal ice crystals. HaloCam observations complemented by radiative transfer simulations and measurements of aerosol and cirrus cloud optical thickness (AOT and COT) provide a possibility to retrieve more detailed information about ice crystal roughness. This paper demonstrates the feasibility of a completely automated method to collect and evaluate a long-term database of halo observations and shows the potential to characterize ice crystal properties.

A comparison of the structure and flow characteristics of the upper troposphere and stratosphere of the Northern and Southern Hemispheres

NASA Technical Reports Server (NTRS)

Adler, R. F.

1974-01-01

The general circulations of the Northern and Southern Hemispheres are compared with regard to the upper troposphere and stratosphere using atmospheric structure obtained from satellite, multi-channel radiance data. Specifically, the data are from the Satellite Infrared Spectrometer (SIRS) instrument aboard the Nimbus 3 spacecraft. The inter-hemispheric comparisons are based on two months of data (one summer month and one winter month) in each hemisphere. Topics studied include: mean meridional circulation in the Southern Hemisphere stratosphere; magnitude and distribution of tropospheric eddy heat flux; magnitudes of energy cycle components; and the relation of vortex structure to the breakdown climatology of the Antarctic stratospheric polar vortex.

Western Pacific Tropospheric Ozone and Potential Vorticity: Implications for Asian Pollution

NASA Technical Reports Server (NTRS)

Browell, Edward V.; Newell, Reginald E.; Davis, Douglas D.; Liu, Shaw C.

1997-01-01

Tropospheric ozone (03) cross sections measured with lidar from a DC-8 aircraft over the western Pacific correspond closely with potential vorticity (PV). Both are transported from the middle latitude stratosphere, although this is not the only source of 03, and both have sinks in the tropical boundary layer. 03 and PV are good indicators of photochemical and transport process interactions. In summer, some Asian pollution, raised by convection to the upper troposphere, passes southward into the tropics and to the Southern Hemisphere. In winter, subsidence keeps the pollution at low altitudes where it moves over the ocean towards the Inter-Tropical Convergence Zone (ITCZ), with photochemical destruction and secondary pollutant generation occurring en route. Convection raises this modified air to the upper troposphere, where some re may enter the stratosphere. Thus winter Asian pollution may at have a smaller direct influence on the global atmosphere than it would if injected at other longitudes and seasons.

The Response of Tropical Tropospheric Ozone to ENSO

NASA Technical Reports Server (NTRS)

Oman, L. D.; Ziemke, J. R.; Douglass, A. R.; Waugh, D. W.; Lang, C.; Rodriguez, J. M.; Nielsen, J. E.

2011-01-01

We have successfully reproduced the Ozone ENSO Index (OEI) in the Goddard Earth Observing System (GEOS) chemistry-climate model (CCM) forced by observed sea surface temperatures over a 25-year period. The vertical ozone response to ENSO is consistent with changes in the Walker circulation. We derive the sensitivity of simulated ozone to ENSO variations using linear regression analysis. The western Pacific and Indian Ocean region shows similar positive ozone sensitivities from the surface to the upper troposphere, in response to positive anomalies in the Nino 3.4 Index. The eastern and central Pacific region shows negative sensitivities with the largest sensitivity in the upper troposphere. This vertical response compares well with that derived from SHADOZ ozonesondes in each region. The OEI reveals a response of tropospheric ozone to circulation change that is nearly independent of changes in emissions and thus it is potentially useful in chemistry-climate model evaluation.

Vertical transport of ozone and CO during super cyclones in the Bay of Bengal as detected by Tropospheric Emission Spectrometer.

PubMed

Fadnavis, S; Beig, G; Buchunde, P; Ghude, Sachin D; Krishnamurti, T N

2011-02-01

Vertical profiles of carbon monoxide (CO) and ozone retrieved from Tropospheric Emission Spectrometer have been analyzed during two super cyclone systems Mala and Sidr. Super cyclones Mala and Sidr traversed the Bay of Bengal (BOB) region on April 24-29, 2006 and November 12-16, 2007 respectively. The CO and ozone plume is observed as a strong enhancement of these pollutants in the upper troposphere over the BOB, indicating deep convective transport. Longitude-height cross-section of these pollutants shows vertical transport to the upper troposphere. CO mixing ratio ~90 ppb is observed near the 146-mb level during the cyclone Mala and near 316 mb during the cyclone Sidr. Ozone mixing ratio ~60-100 ppb is observed near the 316-mb level during both the cyclones. Analysis of National Centers for Environmental Prediction (NCEP) reanalysis vertical winds (omega) confirms vertical transport in the BOB.

Deep Convective Cloud Top Heights and Their Thermodynamic Control During CRYSTAL-FACE

NASA Technical Reports Server (NTRS)

Sherwood, Steven C.; Minnis, Patrick; McGill, Matthew

2004-01-01

Infrared (11 micron) radiances from GOES-8 and local radiosonde profiles, collected during the Cirrus Regional Study of Tropical Anvils and Cirrus Layers-Florida Area Cirrus Experiment (CRYSTAL-FACE) in July 2002, are used to assess the vertical distribution of Florida-area deep convective cloud top height and test predictions as to its variation based on parcel theory. The highest infrared tops (Z(sub 11)) reached approximately to the cold point, though there is at least a 1-km uncertainty due to unknown cloud-environment temperature differences. Since lidar shows that visible 'tops' are 1 km or more above Z(sub 11), visible cloud tops frequently penetrated the lapse-rate tropopause (approx. 15 km). Further, since lofted ice content may be present up to approx. 1 km above the visible tops, lofting of moisture through the mean cold point (15.4 km) was probably common. Morning clouds, and those near Key West, rarely penetrated the tropopause. Non-entraining parcel theory (i.e., CAPE) does not successfully explain either of these results, but can explain some of the day-to-day variations in cloud top height over the peninsula. Further, moisture variations above the boundary layer account for most of the day-today variability not explained by CAPE, especially over the oceans. In all locations, a 20% increase in mean mixing ratio between 750 and 500 hPa was associated with about 1 km deeper maximum cloud penetration relative to the neutral level. These results suggest that parcel theory may be useful for predicting changes in cumulus cloud height over time, but that parcel entrainment must be taken into account even for the tallest clouds. Accordingly, relative humidity above the boundary layer may exert some control on the height of the tropical troposphere.

Differences in ice nucleation behavior of arable and desert soil dust in deposition nucleation regime

NASA Astrophysics Data System (ADS)

Ullrich, Romy; Vogel, Franziska; Möhler, Ottmar; Höhler, Kristina; Schiebel, Thea

2017-04-01

Soil dust from arid and semi-arid regions is one of the most abundant aerosol types in the atmosphere with emission rates of about 1600 Tg per year (Andreae et al. (2009)). Therewith, soil dust plays an important role for the atmospheric radiative transfer and also for the formation of clouds. Soil dust refers to dust sampled from agricultural used areas, to dust from bare soil as well as to dust from desert regions. By mass-spectrometric measurements of the chemical composition of ice residuals, mineral dust as component of soil dust was found to be the major heterogeneous ice nucleating particle (INP) type (e.g. Cziczo et al. (2013)), in particular in the upper troposphere. Also in laboratory studies the ice nucleation efficiency of the different soil dusts was investigated. It was shown that desert dusts (Ullrich et al. (2017)) as well as soil dusts from arable regions (O'Sullivan et al. (2014), Tobo et al. (2014)) are efficient INP. However, there is still a lack of data for ice nucleation on soil dusts for temperatures below about 220 K. With the AIDA (Aerosol Interactions and Dynamics in the Atmosphere) cloud chamber, we are able to characterize the ice nucleation efficiency for different aerosol types to temperatures down to 180 K and high ice supersaturations. In order to extend the already existing AIDA data base for deposition nucleation on desert dusts and agricultural soil dusts, new experiments were done in the upper tropospheric temperature regime. This contribution will show the results of the new experiments with desert dust in comparison to existing data for higher temperatures. The first data analysis confirms the temperature dependent trend of the ice nucleation activity as discussed and parameterized in a recent paper by Ullrich et al. (2017). Furthermore, the update and extension of the recently published parameterization of deposition nucleation for desert dust to lower temperatures will be discussed. The experiments with agricultural soil dust will be compared to existing AIDA experiments at higher temperatures published by Steinke et al. (2016). Finally, the ice nucleation activity of both desert dust and agricultural soil dust will be compared for the upper tropospheric temperature regime. Andreae et al. (2009), Sources and Nature of Atmospheric Aerosols, in Aerosol Pollution Impact on Precipitation - A Scientific Review, Ch.3, Springer Netherlands, 45-89 Cziczo et al. (2013), Clarifying the Dominant Sources and Mechanisms of Cirrus Cloud Formation, Science, 340, 1320-1324 O'Sullivan et al. (2014), Ice nucleation by fertile soil dusts: relative importance of mineral and biogenic components, Atmos. Chem. Phys., 14, 1853-1867 Steinke et al. (2016), Ice nucleation activity of agricultural soil dust aerosols from Mongolia, Argentina and Germany, J. Geophys. Res., 121 Tobo et al. (2014), Organic matter matters for ice nuclei of agricultural soil origin, Atmos. Chem. Phys., 14, 8521-8531 Ullrich et al. (2017), A new ice nucleation active site parametrization for desert dust and soot, J. Atmos. Sci., in press

The Origins of Air Parcels Uplifted in a Two Dimensional Gravity Wave in the Tropical Upper Troposphere During the NASA Stratosphere Troposphere Exchange Project (STEP)

NASA Technical Reports Server (NTRS)

Selkirk, Henry B.; Pfister, Leonhard; Chan, K. Roland; Kritz, Mark; Kelly, Ken

1989-01-01

During January and February 1987, as part of the Stratosphere-Troposphere Exchange Project, the NASA ER-2 made 11 flights from Darwin, Australia to investigate dehydration mechanisms in the vicinity of the tropical tropopause. After the monsoon onset in the second week of January, steady easterly flow of 15-25 ms (exp -1) was established in the upper troposphere and lower stratosphere over northern Australia and adjacent seas. Penetrating into this regime were elements of the monsoon convection such as overshooting convective turrets and extensive anvils including cyclone cloud shields. In cases of the latter, the resulting flow obstructions tended to produce mesoscale gravity waves. In several instances the ER- 2 meteorological and trace constituent measurements provide a detailed description of the structure of these gravity waves. Among these was STEP Flight 6, 22-23 January. It is of particular interest to STEP because of the close proximity of ice-laden and dehydrated air on the same isentropic surfaces. Convective events inject large amounts of ice into the upper troposphere and lower stratosphere which may not be completely removed by local precipitation processes. In the present instance, a gravity wave for removed from the source region appears to induce relativity rapid upward motion in the ice-laden air and subsequent dessication. Potential mechanisms for such a localized removal process are under investigation.

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

Mitchell, David; Erfani, Ehsan; Garnier, Anne

This project has evolved during its execution, and what follows are the key project findings. This project has arguably provided the first global view of how cirrus cloud (defined as having cloud base temperature T < 235 K) nucleation physics (evaluated through satellite retrievals of ice particle number concentration Ni, effective diameter De and ice water content IWC) evolves with the seasons for a given temperature, latitude zone and surface type (e.g. ocean vs. land), based on a new satellite remote sensing method developed for this project. The retrieval method is unique in that it is very sensitive to themore » small ice crystals that govern the number concentration Ni, allowing Ni to be retrieved. The method currently samples single-layer cirrus clouds having visible optical depth ranging from about 0.3 to 3.0, using co-located observations from the Infrared Imaging Radiometer (IIR) and from the CALIOP (Cloud and Aerosol Lidar with Orthogonal Polarization) lidar aboard the CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation) polar orbiting satellite, employing IIR channels at 10.6 μm and 12.05 μm. Retrievals of Ni are primarily used to estimate the cirrus cloud formation mechanism; that is, either homo- or heterogeneous ice nucleation (henceforth hom and het). This is possible since, in general, hom produces more than an order of magnitude more ice crystals than does het. Thus the retrievals provide insight on how these mechanisms change with the seasons for a given latitude zone or region, based on the years 2008 and 2013. Using a conservative criterion for hom cirrus, on average, the sampled cirrus clouds formed through hom occur about 43% of the time in the Arctic and 50% of the time in the Antarctic, and during winter at mid-latitudes in the Northern Hemisphere, hom cirrus occur 37% of the time. Elsewhere (and during other seasons in the Northern Hemisphere mid-latitudes), this hom cirrus fraction is lower, and it is lowest in the tropics. Thus, the microphysical properties of cirrus clouds in the Polar Regions are much different than they are in the tropics; something unknown prior to this study. Moreover, the frequency of cirrus cloud occurrence in the Polar Regions varies strongly with season, peaking during winter in the Arctic and during spring in the Antarctic. Considering these seasonal changes in microphysics and inferred cloud coverage, this leads us to speculate that the buildup of Arctic cirrus during winter may significantly contribute to tropospheric heating in that region, possibly affecting winter jet-stream dynamics and mid-latitude weather patterns through the thermal-wind balance relationship. This cirrus cloud research provides essential guidance for realistically representing cirrus clouds in climate models; guidance previously unavailable. For example, mid-latitude hom cirrus were widespread during winter over or nearby mountainous terrain, evidently due to mountain-induced waves that produce strong updrafts at cirrus cloud levels. The treatment of turbulent mountain stress and gravity waves will likely need to be improved in climate models in order to adequately represent cirrus clouds outside the tropics. Another goal of this project was to develop a ground-based 94-GHz radar retrieval for winter snowstorms, based on (1) an improved analytical framework describing the interaction of radiation from radar with snowfall and (2) the development of a steady-state snow growth model that predicts the height-evolution of the ice particle size distribution through ice particle growth by vapor diffusion, aggregation and riming (i.e. the growth of snow through collisions with supercooled cloud droplets). Although activities (1) and (2) were completed, there was insufficient time to test and finalize the radar retrieval scheme. However, activity (2) provided a new method for relating ice particle mass “m” and projected area “A” to the ice particle maximum dimension “D”. The ice cloud microphysical processes (which determine ice cloud radiative properties) in climate models are parameterized in terms of these m-D and A-D relationships. By improving these relationships, the ice cloud radiative properties in Community Atmosphere Model version 5, or CAM5 (an atmosphere global climate model, or GCM) were improved. Student funding from the University of Nevada, Reno, was combined with funds from this project to conduct some basic research on the mechanism of the North American monsoon, or NAM. Federal research on the NAM has dwindled since 2006, but atmospheric soundings taken during research vessel cruises in the Gulf of California (GC) during the North American Monsoon Experiment (NAME) were used to reveal a likely mechanism that explains the relationship between an intrusion of tropical warm water into the GC during late spring-early summer and the onset of relatively heavy NAM rainfall in northwest Mexico and the southwestern United States. These soundings, combined with reanalysis data, satellite sea surface temperatures and satellite measurements of outgoing longwave radiation were used to develop and provide evidence for a planetary-scale NAM mechanism. As far as we know, no other physical explanation has been offered for the spring-summer evolution of the NAM system.« less

The Radiative Role of Free Tropospheric Aerosols and Marine Clouds over the Central North Atlantic

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

Mazzoleni, Claudio; Kumar, Sumit; Wright, Kendra

The scientific scope of the project was to exploit the unique location of the Pico Mountain Observatory (PMO) located in the summit caldera of the Pico Volcano in Pico Island in the Azores, for atmospheric studies. The observatory, located at 2225m a.s.l., typically samples free tropospheric aerosols laying above the marine low-level clouds and long-range transported from North America. The broad purpose of this research was to provide the scientific community with a better understanding of fundamental physical processes governing the effects of aerosols on radiative forcing and climate; with the ultimate goal of improving our abilities to understand pastmore » climate and to predict future changes through numerical models. The project was 'exploratory' in nature, with the plan to demonstrate the feasibility of deploying for the first time, an extensive aerosol research package at PMO. One of the primary activities was to test the deployment of these instruments at the site, to collect data during the 2012 summer season, and to further develop the infrastructure and the knowledge for performing novel research at PMO in follow-up longer-term aerosol-cloud studies. In the future, PMO could provide an elevated research outpost to support the renewed DOE effort in the Azores that was intensified in 2013 with the opening of the new sea-level ARM-DOE Eastern North Atlantic permanent facility at Graciosa Island. During the project period, extensive new data sets were collected for the planned 2012 season. Thanks to other synergistic activities and opportunities, data collection was then successfully extended to 2013 and 2014. Highlights of the scientific findings during this project include: a) biomass burning contribute significantly to the aerosol loading in the North Atlantic free troposphere; however, long-range transported black carbon concentrations decreased substantially in the last decade. b) Single black carbon particles – analyzed off-line at the electron microscope – were often very compacted, suggesting cloud processing and exhibiting different optical properties from fresh emissions. In addition, black carbon was found to be sometimes mixed with mineral dust, affecting its optical properties and potential forcing. c) Some aerosols collected at PMO acted as ice nuclei, potentially contributing to cirrus cloud formation during their transport in the upper free troposphere. Identified good ice nuclei were often mineral dust particles. d) The free tropospheric aerosols studied at PMO have relevance to low level marine clouds due, for example, to synoptic subsidence entraining free tropospheric aerosols into the marine boundary layer. This has potentially large consequences on cloud condensation nuclei concentrations and compositions in the marine boundary layer; therefore, having an effect on the marine stratus clouds, with potentially important repercussions on the radiative forcing. The scientific products of this project currently include contributions to two papers published in the Nature Publishing group (Nature Communications and Scientific Reports), one paper under revision for Atmospheric Chemistry and Physics, one in review in Geophysical Research Letters and one recently submitted to Atmospheric Chemistry and Physics Discussion. In addition, four manuscripts are in advanced state of preparation. Finally, twenty-eight presentations were given at international conferences, workshops and seminars.« less

NO(x) Concentrations in the Upper Troposphere as a Result of Lightning

NASA Technical Reports Server (NTRS)

Penner, Joyce E.

1998-01-01

Upper tropospheric NO(x) controls, in part, the distribution of ozone in this greenhouse-sensitive region of the atmosphere. Many factors control NO(x) in this region. As a result it is difficult to assess uncertainties in anthropogenic perturbations to NO from aircraft, for example, without understanding the role of the other major NO(x) sources in the upper troposphere. These include in situ sources (lightning, aircraft), convection from the surface (biomass burning, fossil fuels, soils), stratospheric intrusions, and photochemical recycling from HNO3. This work examines the separate contribution to upper tropospheric "primary" NO(x) from each source category and uses two different chemical transport models (CTMS) to represent a range of possible atmospheric transport. Because aircraft emissions are tied to particular pressure altitudes, it is important to understand whether those emissions are placed in the model stratosphere or troposphere and to assess whether the models can adequately differentiate stratospheric air from tropospheric air. We examine these issues by defining a point-by-point "tracer tropopause" in order to differentiate stratosphere from troposphere in terms of NO(x) perturbations. Both models predict similar zonal average peak enhancements of primary NO(x) due to aircraft (approx. = 10-20 parts per trillion by volume (pptv) in both January and July); however, the placement of this peak is primarily in a region of large stratospheric influence in one model and centered near the level evaluated as the tracer tropopause in the second. Below the tracer tropopause, both models show negligible NO(x) derived directly from the stratospheric source. Also, they predict a typically low background of 1 - 20 pptv NO(x) when tropospheric HNO3 is constrained to be 100 pptv of HNO3. The two models calculate large differences in the total background NO(x) (defined as the source of NO(x) from lightning + stratosphere + surface + HNO3) when using identical loss frequencies for NO(x). This difference is primarily due to differing treatments of vertical transport. An improved diagnosis of this transport that is relevant to NO(x) requires either measurements of a surface-based tracer with a substantially shorter lifetime than Rn-222 or diagnosis and mapping of tracer correlations with different source signatures. Because of differences in transport by the two models we cannot constrain the source of NO(x) from lightning through comparison of average model concentrations with observations of NO(x).

Poleward upgliding Siberian atmospheric rivers over sea ice heat up Arctic upper air.

PubMed

Komatsu, Kensuke K; Alexeev, Vladimir A; Repina, Irina A; Tachibana, Yoshihiro

2018-02-13

We carried out upper air measurements with radiosondes during the summer over the Arctic Ocean from an icebreaker moving poleward from an ice-free region, through the ice edge, and into a region of thick ice. Rapid warming of the Arctic is a significant environmental issue that occurs not only at the surface but also throughout the troposphere. In addition to the widely accepted mechanisms responsible for the increase of tropospheric warming during the summer over the Arctic, we showed a new potential contributing process to the increase, based on our direct observations and supporting numerical simulations and statistical analyses using a long-term reanalysis dataset. We refer to this new process as "Siberian Atmospheric Rivers (SARs)". Poleward upglides of SARs over cold air domes overlying sea ice provide the upper atmosphere with extra heat via condensation of water vapour. This heating drives increased buoyancy and further strengthens the ascent and heating of the mid-troposphere. This process requires the combination of SARs and sea ice as a land-ocean-atmosphere system, the implication being that large-scale heat and moisture transport from the lower latitudes can remotely amplify the warming of the Arctic troposphere in the summer.

Space Shuttle ice nuclei

NASA Astrophysics Data System (ADS)

Turco, R. P.; Toon, O. B.; Whitten, R. C.; Cicerone, R. J.

1982-08-01

Estimates are made showing that, as a consequence of rocket activity in the earth's upper atmosphere in the Shuttle era, average ice nuclei concentrations in the upper atmosphere could increase by a factor of two, and that an aluminum dust layer weighing up to 1000 tons might eventually form in the lower atmosphere. The concentrations of Space Shuttle ice nuclei (SSIN) in the upper troposphere and lower stratosphere were estimated by taking into account the composition of the particles, the extent of surface poisoning, and the size of the particles. Calculated stratospheric size distributions at 20 km with Space Shuttle particulate injection, calculated SSIN concentrations at 10 and 20 km altitude corresponding to different water vapor/ice supersaturations, and predicted SSIN concentrations in the lower stratosphere and upper troposphere are shown.

The effects of deep convection on the concentration and size distribution of aerosol particles within the upper troposphere: A case study

NASA Astrophysics Data System (ADS)

Yin, Yan; Chen, Qian; Jin, Lianji; Chen, Baojun; Zhu, Shichao; Zhang, Xiaopei

2012-11-01

A cloud resolving model coupled with a spectral bin microphysical scheme was used to investigate the effects of deep convection on the concentration and size distribution of aerosol particles within the upper troposphere. A deep convective storm that occurred on 1 December, 2005 in Darwin, Australia was simulated, and was compared with available radar observations. The results showed that the radar echo of the storm in the developing stage was well reproduced by the model. Sensitivity tests for aerosol layers at different altitudes were conducted in order to understand how the concentration and size distribution of aerosol particles within the upper troposphere can be influenced by the vertical transport of aerosols as a result of deep convection. The results indicated that aerosols originating from the boundary layer can be more efficiently transported upward, as compared to those from the mid-troposphere, due to significantly increased vertical velocity through the reinforced homogeneous freezing of droplets. Precipitation increased when aerosol layers were lofted at different altitudes, except for the case where an aerosol layer appeared at 5.4-8.0 km, in which relatively more efficient heterogeneous ice nucleation and subsequent Wegener-Bergeron-Findeisen process resulted in more pronounced production of ice crystals, and prohibited the formation of graupel particles via accretion. Sensitivity tests revealed, at least for the cases considered, that the concentration of aerosol particles within the upper troposphere increased by a factor of 7.71, 5.36, and 5.16, respectively, when enhanced aerosol layers existed at 0-2.2 km, 2.2-5.4 km, and 5.4-8.0 km, with Aitken mode and a portion of accumulation mode (0.1-0.2μm) particles being the most susceptible to upward transport.

Initial studies of middle and upper tropospheric stratiform clouds

NASA Technical Reports Server (NTRS)

Cox, S. K.

1982-01-01

The spatial and temporal occurrence of cloud layers, the development of a physical-numerical model to simulate the life cycles of tropospheric cloud layers, and the design of an observational program to study the properties of these layers are described.

Thermosphere Extension of the Whole Atmosphere Community Climate Model

DTIC Science & Technology

2010-12-04

tropospheric ozone and related tracers: Description and evaluation of MOZART, version 2, J. Geophys. Res., 108(D24), 4784, doi:10.1029/2002JD002853. Immel, T... troposphere to the upper thermosphere and their variability on interannual, seasonal, and daily scales. These quantities are compared with observational and...gravity waves are excited by tropospheric processes. As their amplitudes grow exponen- tially with altitude, they will cause larger variability

Laser Atmospheric Wind Sounder (LAWS) phase 1. Volume 1: Executive summary

NASA Technical Reports Server (NTRS)

1990-01-01

The laser atmospheric wind sounder (LAWS) will provide a new space based capability for the direct measurement of atmospheric winds in the troposphere. LAWS will make a major contribution toward advancing the understanding and prediction of the total Earth system and NASA's Earth Observing System (EOS) Program. LAWS is designed to measure a fundamental atmospheric parameter required to advance weather forecasting accuracies and investigate global climatic change. LAWS has a potential added benefit of providing (global) concentration profiles of large aerosols including visible and subvisible cirrus clouds, volcanic dust, smoke, and other pollutants. The objective of this Phase One study was to develop a LAWS concept and configuration. The instrument design is outlined in this first volume of three.

Effects of latent heat in various cloud microphysics processes on autumn rainstorms with different intensities on Hainan Island, China

NASA Astrophysics Data System (ADS)

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

2017-06-01

In this study, we used the Weather Research and Forecasting (WRF) and WRF-3DVAR models to perform a series of simulations of two autumn rainstorms on Hainan Island. The results of neighborhood fractions and Hanssen skill scoring (FSS, HSS) methods show that the control experiments reproduced well two heavy rainfall episodes. Effects of latent heat in various cloud microphysical processes are different at distinct intensities or stages of precipitation. In the absence of any heating effect of deposition, precipitation weakened. The greater was the precipitation, the more significant was the weakening effect. Ascending movement at upper troposphere could be weakened or descending movement at lower troposphere enhanced. With decreases in the strength of precipitation, cloud ice, snow, graupel, and rainwater, increases in latent heat lessened. With weak precipitation, at upper troposphere the rainwater content increased and snow and ice content decreased, whereas at middle troposphere, the ice, snow, and graupel contents increased. Latent heating increased at middle and lower troposphere and decreased at upper troposphere. The absence of any heating effect of freezing had little effect on precipitation. By removing the evaporative cooling of cloud water, the interactions between vertical movement and cloud microphysical processes resulted in a weakening of strong precipitation and an intensification of weak precipitation. However, in the preliminary stages of these two precipitation events, snow, graupel, cloud ice, and rainwater all increased, and precipitation was enhanced in both. In the later stages, strong precipitation systems weakened and weak precipitation systems strengthened. Latent heating first increased and then dropped in strong precipitation systems, whereas they continuously increased in weak precipitation systems.

Evidence of Convection as a Dominant Source of Condensation Nuclei in the Northern Midlatitude Upper Troposphere

NASA Technical Reports Server (NTRS)

Wang, Y.; Liu, S. C.; Anderson, B. E.; Kondo, Y.; Gregory, G. L.; Sachse, G. W.; Vay, S. A.; Blake, D.; Singh, H. B.; Thompson, A. M.

1999-01-01

We examine concurrent upper tropospheric measurements of CN (diameter greater than 4 nm). NO, and NO(Y) during the SONEX Experiment over the North Atlantic (Oct.-Nov., 1997). Elevated CN and NO(Y) concentrations observed in the upper troposphere are attributed largely to enhancements in convective outflows. We estimate that less than 7% of observed high-CN plumes (greater than 10000 /cc) may be attributed to aircraft emissions. Dilution of high-CN convective and aircraft plumes appears to be much more rapid than losses of NO(X) and CN by oxidation and coagulation, respectively, and accounts for much of observed CN concentrations. When taking into account of different time scales against dilution for observable aircraft and convective high-CN plumes (estimated to be 1:4), the contribution by aircraft emissions to CN concentrations is significant, about 20% of the convective source. We find no evidence that particle formation in convective plumes is limited by OH oxidation of SO2.

Analysis of TRMM Microphysical Measurements: Tropical Rainfall Measuring Mission (TRMM)

NASA Technical Reports Server (NTRS)

2004-01-01

SPEC Incorporated participated in three of the four TRMM field campaigns (TEFLUN-A, TEFLUN-B and KWAJEX), installing and operating a cloud particle imager (CPI) and a high volume precipitation spectrometer (HVPS) on the SPEC Learjet in TEFLUN-A, the University of North Dakota Citation in TEFLUN-B and KWAJEX, and a CPI on the NASA DC-8 in KWAJEX. This report presents and discusses new software tools and algorithms that were developed to analyze microphysical data collected during these field campaigns, as well as scientific interpretations of the data themselves. Software algorithms were developed to improve the analysis of microphysical measurements collected by the TRMM aircraft during the field campaigns. Particular attention was paid to developing and/or improving algorithms used to compute particle size distributions and ice water content. Software was also developed in support of production of the TRMM Common Microphysical Product (CMP) data files. CMP data files for TEFLUN-A field campaign were produced and submitted to the DAAC. Typical microphysical properties of convective and stratiform regions from TEFLUN-A and KWAJEX clouds were produced. In general, it was found that in the upper cloud region near -20 to -25 C, stratiform clouds contain very high (greater than 1 per cubic centimeter) concentrations of small ice particles, which are suspected to be a residual from homogeneous freezing and sedimentation of small drops in a convective updraft. In the upper cloud region near -20 to -25 C, convective clouds contain aggregates, which are not found lower in the cloud. Stratiform clouds contain aggregates at all levels, with the majority in the lowest levels. Convective cloud regions contain much higher LWC and drop concentrations than stratiform regions at all levels, and higher LWC in the middle and upper regions. Stratiform clouds contain higher IWC than convective clouds only at the lowest level. Irregular shaped ice particles are found in very high concentrations throughout both convective and stratiform cloud regions. A striking difference in particle shape in cirrus formed in situ, cirrus formed from maritime anvils and cirrus formed from continental anvils. Over 50% of the mass of in situ cirrus ice particles is composed of bullet rosettes, while bullet rosettes are virtually non-existent in maritime and tropical anvils. Tropical anvils are composed of mostly singular, plates, capped columns, and blocky irregular shapes, while continental anvils have a much higher percentage of aggregates, some of which are chains of small spheroidal particles that appear to result from homogeneous freezing of drops. A correlation between high electric fields in continental anvils and the formation of aggregates is hypothesized.

Variations of GHGs from the lower-troposphere to the UT/LS revealed by two Japanese regular aircraft observation programs

NASA Astrophysics Data System (ADS)

Niwa, Yosuke; Machida, Toshinobu; Sawa, Yousuke; Tsuboi, Kazuhiro; Matsueda, Hidekazu; Imasu, Ryoichi

2014-05-01

A Japan-centered observation network consisting of two regular aircraft programs have revealed the greenhouse gases variations from the lower-troposphere to the upper-troposphere/lower-stratosphere (UT/LS) regions. In the Comprehensive Observation Network for Trace gases by Airliner (CONTRAIL) project, in-situ continuous measurement equipment (CME) onboard commercial passenger aircraft world-widely observes CO2 profiles in vertical over tens of airports and in horizontal in the UT/LS regions. The CONTRAIL-CME has revealed three-dimensional structure of the global CO2 distribution and has exposed significant inter-hemispheric transport of CO2 through the upper-troposphere. In inverse modeling, the CME data have provided strong constraints on CO2 flux estimation especially for the Asian tropics. Automatic flask air sampling equipment (ASE) is also onboard the CONTRAIL aircraft and has been observing CO2 mixing ratios as well as those of methane, carbon monoxide, nitrous oxide and other trace species in the upper-troposphere between Japan and Australia. The observation period of the ASE has reached 20 years. In recent years, the ASE program has extended to the northern subarctic UT/LS region and has given an insight of transport mechanisms in the UT/LS by observing seasonal GHGs variations. In the other aircraft observation program by Japan Meteorological Agency, variations of GHGs have been observed by flask-sampling onboard a C-130H aircraft horizontally in the mid-troposphere over the western North Pacific as well as vertically over Minamitorishima-Island. The C-130H aircraft has persistently observed high mixing ratios of CH4 in the mid-troposphere, which seems to be originated from fossil fuel combustion throughout the year as well as from biogenic sources during summer in the Asian regions. Those above aircraft observation programs have a significant role for constraining GHGs flux estimates by filling the data gap of the existing surface measurement network specifically in the regions of Asia and the western North Pacific.

Surface and Lightning Sources of Nitrogen Oxides over the United States: Magnitudes, Chemical Evolution, and Outflow

NASA Technical Reports Server (NTRS)

Hudman, Rynda C.; Jacob, Daniel J.; Turquety, Solene; Leinbensperger, E. M.; Murray, L. T.; Wu, Samuel; Gilliland, A. B.; Avery, Melody A.; Bertram, Timothy H.; Brune, W. H.;

Comparisons of Upper Tropospheric Humidity Retrievals from TOVS and METEOSAT

NASA Technical Reports Server (NTRS)

Escoffier, C.; Bates, J.; Chedin, A.; Rossow, W. B.; Schmetz, J.

1999-01-01

Two different methods for retrieving Upper Tropospheric Humidities (UTH) from the TOVS (TIROS Operational Vertical Sounder) instruments aboard NOAA polar orbiting satellites are presented and compared. The first one, from the Environmental Technology Laboratory, computed by J. Bates and D. Jackson (hereafter BJ method), estimates UTH from a simplified radiative transfer analysis of the upper tropospheric infrared water vapor channel at wavelength measured by HIRS (6.3 micrometer). The second one results from a neural network analysis of the TOVS (HIRS and MSU) data developed at, the Laboratoire de Meteorologie Dynamique (hereafter the 3I (Improved Initialization Inversion) method). Although the two methods give very similar retrievals in temperate regions (30-60 N and S), an absolute bias up to 16% appears in the convective zone of the tropics. The two datasets have also been compared with UTH retrievals from infrared radiance measurements in the 6.3 micrometer channel from the geostationary satellite METEOSAT (hereafter MET method). The METEOSAT retrievals are systematically drier than the TOVS-based results by an absolute bias between 5 and 25%. Despite the biases, the spatial and temporal correlations are very good. The purpose of this study is to explain the deviations observed between the three datasets. The sensitivity of UTH to air temperature and humidity profiles is analysed as are the clouds effects. Overall, the comparison of the three retrievals gives an assessment of the current uncertainties in water vapor amounts in the upper troposphere as determined from NOAA and METEOSAT satellites.

Modeling the effects of UV variability and the QBO on the troposphere-stratosphere system. Part II: The troposphere

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

Rind, D.; Balachandran, N.K.

1995-08-01

Results of experiments with a GCM involving changes in UV input ({plus_minus} 25%, {plus_minus}5% at wavelengths below 0.3 {mu}) and simulated equatorial QBO are presented, with emphasis on the tropospheric response. The QBO and UV changes alter the temperature in the lower stratosphere/upper troposphere warms, tropospheric eddy energy is reduced, leading to extratropical tropospheric cooling of some 0.5{degrees}C on the zonal average, and surface temperature changes up to {plus_minus}5{degrees}C locally. Opposite effects occur when the extratropical lower stratosphere/upper troposphere cools. Cooling or warming of the comparable region in the Tropics decreases/increases static stability, accelerating/decelerating the Hadley circulation. Tropospheric dynamical changesmore » are on the order of 5%. The combined UV/QBO effect in the troposphere results from its impact on the middle atmosphere; in the QBO east phase, more energy is refracted to higher latitudes, due to the increased horizontal shear of the zonal wind, but with increased UV, this energy propagates preferentially out of the polar lower stratosphere, in response to the increased vertical shear of the zonal winds; therefore, it is less effective in warming the polar lower stratosphere. Due to their impacts on planetary wave generation and propagation, all combinations of UV and QBO phases affect the longitudinal patterns of tropospheric temperatures and geopotential heights. The modeled perturbations often agree qualitatively with observations and are of generally similar orders of magnitude. The results are sensitive to the forcing employed. In particular, the nature of the tropospheric response depends upon the magnitude (and presumably wavelength) of the solar irradiance perturbation. The results of the smaller UV variations ({plus_minus}5%) are more in agreement with observations, showing clear differences between the UV impact in the east and west QBO phase. 34 refs., 15 figs., 3 tabs.« less

Characterization of residuals from ice particles and droplets sampled in mid-latitude natural and aviation-influenced cirrus and in tropical deep convective cloud systems during ML-CIRRUS and ACRIDICON

NASA Astrophysics Data System (ADS)

Mertes, Stephan; Kästner, Udo; Schulz, Christiane; Klimach, Thomas; Krüger, Mira; Schneider, Johannes

2015-04-01

Airborne sampling of cloud particles inside different cirrus cloud types and inside deep convective clouds was conducted during the HALO missions ML-CIRRUS over Europe in March/April 2014 and ACRIDICON over Amazonia in September 2014. ML-CIRRUS aims at the investigation of the for-mation, evolution, microphysical state and radiative effects of different natural and aviation-induced cirrus clouds in the mid-latitudes. The main objectives of ACRIDICON are the microphysical vertical profiling, vertical aerosol transport and the cloud processing of aerosol particles (compari-son in- and outflow) of tropical deep convective cloud systems in clean and polluted air masses and over forested and deforested regions. The hydrometeors (drops and ice particles) are sampled by a counterflow virtual impactor (CVI) which has to be installed in the front part of the upper fuselage of the HALO aircraft. Such an intake position implies a size dependent abundance of cloud particles with respect to ambient conditions that was studied by particle trajectory simulations (Katrin Witte, HALO Technical Note 2008-003-A). On the other hand, this sampling location avoids that large ice crystals which could potentially bias the cloud particle sampling by shattering and break-up at the inlet shroud and tip enter the inlet. Both aspects as well as the flight conditions of HALO were taken into account for an optimized CVI design for HALO (HALO-CVI). Interstitial particles are pre-segregated and the condensed phase is evaporated/sublimated by the CVI, such that the residuals from cloud droplets and ice particles (CDR and IPR) can be microphysically and chemically analyzed by respective aerosol sensors located in the cabin. Although an even more comprehensive characterization of CDR and IPR was carried out, we like to report on the following measurements of certain aerosol properties. Particle number concentra-tion and size distribution are measured by a condensation particle counter (CPC) and an ultra-high sensitivity aerosol spectrometer (UHSAS). The absorption coefficient and thus a measure for the black carbon mass concentration is derived from the particle soot absorption photometer (PSAP). In the lower warm parts of the probed convective clouds during the ACRIDICON mission the mean charge of droplets was inferred by means of electrometer measurements. For the determination of the chemical properties of CDR and IPR, the Aircraft-based Laser Ablation Aerosol Mass Spec-trometer (ALABAMA) and a Compact-Time-of-Flight-Aerosol-Mass-Spectrometer (C-ToF-AMS) was operated during ML-CIRRUS and ACRIDICON, respectively, to obtain the mixing state and chemical composition of the cloud particle residues. During ML-CIRRUS, differences in IPR concentration, size distribution, and chemical composition between natural and aviation influenced cirrus clouds could be observed as well as between dif-ferent natural cirrus types and between young and aged contrail cirrus. During ACRIDICON, CDR concentration, size distribution, and chemical composition are found to be different for convective cloud systems evolving from more clean air masses compared to systems evolving from more polluted air masses. Droplet charges change from negative to positive values with height in all vertical cloud profiles. The measured IPR concentration strongly vary in the anvil outflow regions.

Hydrogen Cyanide in the Upper Troposphere: GEM-AQ Simulation and Comparison with ACE-FTS Observations

NASA Technical Reports Server (NTRS)

Lupu, A.; Kaminski, J. W.; Neary, L.; McConnell, J. C.; Toyota, K.; Rinsland, C. P.; Bernath, P. F.; Walker, K. A.; Boone, C. D.; Nagahama, Y.;

Influence of isentropic transport on seasonal ozone variations in the lower stratosphere and subtropical upper troposphere

NASA Technical Reports Server (NTRS)

Jing, P.; Cunnold, D. M.; Yang, E.-S.; Wang, H.-J.

2005-01-01

The isentropic cross-tropopause ozone transport has been estimated in both hemispheres in 1999 based on the potential vorticity mapping of Stratospheric Aerosol and Gas Experiment 11 ozone measurements and contour advection calculations using the NASA Goddard Space Flight Center Global and Modeling Assimilation Office analysis. The estimated net isentropic stratosphere-to-troposphere ozone flux is approx.118 +/- 61 x 10(exp9)kg/yr globally within the layer between 330 and 370 K in 1999; 60% of it is found in the Northern Hemisphere, and 40% is found in the Southern Hemisphere. The monthly average ozone fluxes are strongest in summer and weakest in winter in both hemispheres. The seasonal variations of ozone in the lower stratosphere (LS) and upper troposphere (UT) have been analyzed using ozonesonde observations from ozonesonde stations in the extratropics and subtropics, respectively. It is shown that observed ozone levels increase in the UT over subtropical ozonesonde stations and decrease in the LS over extratropical stations in late spring/early summer and that the ozone increases in the summertime subtropical UT are unlikely to be explained by photochemical ozone production and diabatic transport alone. We conclude that isentropic transport is a significant contributor to ozone levels in the subtropical upper troposphere, especially in summer.

Regional Impact on Pollution Event in the Upper Troposphere during CARIBIC Flights between South China and the Philippines

NASA Astrophysics Data System (ADS)

Lai, S. C.; Baker, A. R.; Schuck, T. J.; van Velthoven, P.; Oram, D. E.; Zahn, A.; Hermann, M.; Weigelt, A.; Slemr, S.; Brenninkmeijer, C. A. M.

2010-05-01

The research project CARIBIC (Civil Aircraft for the Regular Investigation of the atmosphere Based on an Instrumented Container, phase II) is designed to conduct regular, long-term and detailed observations of the free troposphere and UT/LS regions where passenger aircraft happen to cruise. A fully-automated measurement container (1.5 tons) was equipped onboard an Airbus 340-600 operated by Lufthansa Airlines during regular passenger flights to conduct real time trace gas and aerosol measurements and to collect aerosol and air samples on a near monthly basis. During May 2005 - March 2008, CARIBIC observations have been performed along the flight tracks of Frankfurt-Guangzhou-Manila. Data have been collected in the upper troposphere during a total of 81 flights over the region between South China and the Philippines. Carbon monoxide was used an indicator to identify the pollution events and to access the regional impacts of fossil fuel burning and biomass/biofuel burning on upper tropospheric air. Five regions, i.e. Northeast Asia, South China, Indochina Peninsula, India and Indonesia/Philippines, are identified as the major source regions to be related to the observed pollution events. The characteristics of the events from these regions are investigated. The contributions of different source categories are also estimated.

Quantifying Sulfate, Organics, and Lubrication Oil in Particles Emitted from Military Aircraft Engines

DTIC Science & Technology

2012-10-01

Measurements. Part 1: Theory. Aerosol Sci. Tech., 38, 1185-1205 Finlayson-Pitts, B. J. and Pitts, J. N. 1997. Tropospheric air pollution: Ozone ...2004). Wetting and Hydration of Insoluble Soot Particles in the Upper Troposphere . J. Environ. Monitoring, 6:939-945. Petzold, A., Gysel, M...nanoparticles: role of ambient ionization in tropospheric aerosol formation. Journal of Geophysical Research, 106(5): 4797–4814. Yu, F. (2005). Quasi

Reactive Nitrogen Distribution and Partitioning in the North American Troposphere and Lowermost Stratosphere

NASA Technical Reports Server (NTRS)

Singh, H. B.; Salas, L.; Herlth, D.; Kolyer, R.; Czech, E.; Avery, M.; Crawford, J. H.; Pierce, B.; Sachse, G. W.; Blake, D. R.;

Variability of Upper-Tropospheric Precipitable from Satellite and Model Reanalysis Datasets

NASA Technical Reports Server (NTRS)

Jedlovec, Gary J.; Iwai, Hisaki

1999-01-01

Numerous datasets have been used to quantify water vapor and its variability in the upper-troposphere from satellite and model reanalysis data. These investigations have shown some usefulness in monitoring seasonal and inter-annual variations in moisture either globally, with polar orbiting satellite data or global model output analysis, or regionally, with the higher spatial and temporal resolution geostationary measurements. The datasets are not without limitations, however, due to coverage or limited temporal sampling, and may also contain bias in their representation of moisture processes. The research presented in this conference paper inter-compares the NVAP, NCEP/NCAR and DAO reanalysis models, and GOES satellite measurements of upper-tropospheric,precipitable water for the period from 1988-1994. This period captures several dramatic swings in climate events associated with ENSO events. The data are evaluated for temporal and spatial continuity, inter-compared to assess reliability and potential bias, and analyzed in light of expected trends due to changes in precipitation and synoptic-scale weather features. This work is the follow-on to previous research which evaluated total precipitable water over the same period. The relationship between total and upper-level precipitable water in the datasets will be discussed as well.

Comparisons of Satellite-Deduced Overlapping Cloud Properties and CALIPSO CloudSat Data

NASA Technical Reports Server (NTRS)

Chang, Fu-Lung; Minnis, Patrick; Lin, Bing; Sun-Mack, Sunny

2010-01-01

Introduction to the overlapped cloud properties derived from polar-orbiting (MODIS) and geostationary (GOES-12, -13, Meteosat-8, -9, etc.) meteorological satellites, which are produced at the NASA Langley Research Center (LaRC) cloud research & development team (NASA lead scientist: Dr. Patrick Minnis). Comparison of the LaRC CERES MODIS Edition-3 overlapped cloud properties to the CALIPSO and the CloudSat active sensing data. High clouds and overlapped clouds occur frequently as deduced by CALIPSO (44 & 25%), CloudSat (25 & 4%), and MODIS (37 & 6%). Large fractions of optically-thin cirrus and overlapped clouds are deduced from CALIPSO, but much smaller fractions are from CloudSat and MODIS. For overlapped clouds, the averaged upper-layer CTHs are about 12.8 (CALIPSO), 10.9 (CloudSat) and 10 km (MODIS), and the averaged lower-layer CTHs are about 3.6 (CALIPSO), 3.2 (CloudSat) and 3.9 km (MODIS). Based on comparisons of upper and lower-layer cloud properties as deduced from the MODIS, CALIPSO and CloudSat data, more enhanced passive satellite methods for retrieving thin cirrus and overlapped cloud properties are needed and are under development.

Introducing and Validating the New Aura CO Product Derived from Joined TES and MLS Measurements

NASA Astrophysics Data System (ADS)

Luo, M.; Schwartz, M. J.; Read, W. G.; Herman, R. L.; Kulawik, S. S.; Worden, J.; Livesey, N. J.; Bowman, K. W.; Sweeney, C.

2014-12-01

The new Aura CO product consists of CO vertical profiles derived from TES and MLS measurements. This product has been released to the public. We describe the algorithms for generating the product and the evaluations of it using in-situ measurements. TES and MLS standalone CO profile retrievals are sensitive respectively to lower-mid troposphere and upper troposphere and above. We pair TES nadir and MLS limb tangent locations within 6-8 min and less than 220 km. The paired radiance measurements of the two instruments per location are optimally combined to retrieve a single CO profile along with other interfering species. This combined CO profile has improved vertical resolution and vertical range over the two standalone products, especially in the upper-troposphere/lower-stratosphere. For example, the degree of freedom for signal (DOFS) between surface and 50hPa for TES alone is < 2, and for the combined CO profiles is 2-4. We will present the comparison results between the Aura CO and AirCore, HIPPO, and MOZAIC observations. The new Aura CO product provides a unique data set to studies on tropospheric transport of air pollutants and troposphere-stratospheric exchange processes.

Investigation of Dynamic and Physical Processes in the Upper Troposphere and Lower Stratosphere

NASA Technical Reports Server (NTRS)

Selkirk, Henry B.; Pfister, Leonhard (Technical Monitor)

2002-01-01

Research under this Cooperative Agreement has been funded by several NASA Earth Science programs: the Atmospheric Effects of Radiation Program (AEAP), the Upper Atmospheric Research Program (UARP), and most recently the Atmospheric Chemistry and Modeling Assessment Program (ACMAP). The purpose of the AEAP was to understand the impact of the present and future fleets of conventional jet traffic on the upper troposphere and lower stratosphere, while complementary airborne observations under UARP seek to understand the complex interactions of dynamical and chemical processes that affect the ozone layer. The ACMAP is a more general program of modeling and data analysis in the general area of atmospheric chemistry and dynamics, and the Radiation Sciences program.

View of portion of the northeastern United States as seen from Skylab

NASA Technical Reports Server (NTRS)

1974-01-01

An oblique view of a portion of the northeastern United States (41.5N, 91.0W), as photographed from the Skylab space station in Earth orbit by one of the Skylab 4 crewmen. The entire area of New Jersey, eastern Pennsylvania, southeastern New York, and southern New England can be examined in one view. Long Island, New York City, and the lower Hudson River Valley are readily seen in their regional framework. The Boston area, although blurred by clouds, is also included. The snow enhances the contrast, especially of terrain and cultural features. Different levels of clouds can be studied, especially the crossing layers of cirrus in the center of the photograph, with the lower cirrus trending north-south and the upper (probably associated with a jet steam) trending east-west.

Atmospheric mercury speciation dynamics at the high-altitude Pic du Midi Observatory, southern France

NASA Astrophysics Data System (ADS)

Fu, Xuewu; Marusczak, Nicolas; Heimbürger, Lars-Eric; Sauvage, Bastien; Gheusi, François; Prestbo, Eric M.; Sonke, Jeroen E.

2016-05-01

Continuous measurements of atmospheric gaseous elemental mercury (GEM), particulate bound mercury (PBM) and gaseous oxidized mercury (GOM) at the high-altitude Pic du Midi Observatory (PDM Observatory, 2877 m a.s.l.) in southern France were made from November 2011 to November 2012. The mean GEM, PBM and GOM concentrations were 1.86 ng m-3, 14 pg m-3 and 27 pg m-3, respectively and we observed 44 high PBM (peak PBM values of 33-98 pg m-3) and 61 high GOM (peak GOM values of 91-295 pg m-3) events. The high PBM events occurred mainly in cold seasons (winter and spring) whereas high GOM events were mainly observed in the warm seasons (summer and autumn). In cold seasons the maximum air mass residence times (ARTs) associated with high PBM events were observed in the upper troposphere over North America. The ratios of high PBM ARTs to total ARTs over North America, Europe, the Arctic region and Atlantic Ocean were all elevated in the cold season compared to the warm season, indicating that the middle and upper free troposphere of the Northern Hemisphere may be more enriched in PBM in cold seasons. PBM concentrations and PBM / GOM ratios during the high PBM events were significantly anti-correlated with atmospheric aerosol concentrations, air temperature and solar radiation, suggesting in situ formation of PBM in the middle and upper troposphere. We identified two distinct types of high GOM events with the GOM concentrations positively and negatively correlated with atmospheric ozone concentrations, respectively. High GOM events positively correlated with ozone were mainly related to air masses from the upper troposphere over the Arctic region and middle troposphere over the temperate North Atlantic Ocean, whereas high GOM events anti-correlated with ozone were mainly related to air masses from the lower free troposphere over the subtropical North Atlantic Ocean. The ARTs analysis demonstrates that the lower and middle free troposphere over the North Atlantic Ocean was the largest source region of atmospheric GOM at the PDM Observatory. The ratios of high GOM ARTs to total ARTs over the subtropical North Atlantic Ocean in summer were significantly higher than those over the temperate and sub-arctic North Atlantic Ocean as well as that over the North Atlantic Ocean in other seasons, indicating abundant in situ oxidation of GEM to GOM in the lower free troposphere over the subtropical North Atlantic Ocean in summer.

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

NASA Astrophysics Data System (ADS)

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

2016-03-01

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

Direct Measurements of the Convective Recycling of the Upper Troposphere

NASA Technical Reports Server (NTRS)

Bertram, Timothy H.; Perring, Anne E.; Wooldridge, Paul J.; Crounse, John D.; Kwan, Alan J.; Wennberg, Paul O.; Scheuer, Eric; Dibb, Jack; Avery, Melody; Sachse, Glen;

Level of Neutral Buoyancy, Deep Convective Outflow, and Hot Tower: New Perspectives Based on the A-Train Observations

NASA Astrophysics Data System (ADS)

Takahashi, H.; Luo, J.; Stephens, G. L.

2016-12-01

Deep convective cores, or "hot towers (HTs)", play a significant role in controlling the energy budgets and hydrological cycles. The vertical convective transport by HTs is like an express elevator transporting the near-surface air directly into the upper troposphere or lower stratosphere (e.g., Riehl and Malkus, 1958; Sun and Lindzen, 1993; Soden and Fu, 1995). The vertical convective transport will eventually make a transition to horizontal outflows where widespread cirrus anvils develop, which also play an important role in radiative-convective feedbacks (e.g., Stephens et al. 2008). In this study, we introduce two proxies to evaluate the strength of vertical and horizontal convective mass transport by hot towers. Result shows that HTs tend to have wider horizontal mass transport over land than ocean. In addition, an important aspect of the deep convection-to-outflow transition is the altitude where the outflow occurs, which can be conveniently summarized into a single parameter called level of neutral buoyancy (LNB). LNB is a critical parameter for understanding convection because it sets the potential vertical extent for convective development. This study develops a deeper and more comprehensive understanding of the relationship between LNB and deep convective outflow, including regional variations. To this end, a useful proxy to estimate convective dilution is introduced. Results show that active convective dilution can be seen over the Warm Pool throughout the year, while deep convection over tropical Africa and Amazonia tends to be less diluted.

Nitric Acid Uptake and Decomposition on Black Carbon (Soot) Surfaces: Its Implications for the Upper Troposphere and Lower Stratosphere

NASA Technical Reports Server (NTRS)

Choi, W.; Leu, M. T.

1998-01-01

Black carbon particles (soot) are formed as a result of incomplete combustion processes and are ubiquitous in the atmosphere. The lower troposphere contains plenty of soot particles whose principal sources are fossil fuel and biomass combustion at the ground level.

Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) Observations of Polar Winter Conditions in 2009; Comparisons with Years 2002-2008

DTIC Science & Technology

2011-02-03

focused upon the tropospheric forcing, for example the role of blocking systems (large-scale, quasi-stationary, high-pressure systems that may steer...disruptions of the stratosphere may in turn perturb the troposphere and even affect surface weather. In early February 2009, London received heavy snowfall...global measurements from twelve SSW periods, found cooling in the equatorial lower stratosphere and upper troposphere that is associated with increased

Understanding Wave-mean Flow Feedbacks and Tropospheric Annular Variability

NASA Astrophysics Data System (ADS)

Lorenz, D. J.

2016-12-01

The structure of internal tropospheric variability is important for determining the impact of the stratosphere on the troposphere. This study aims to better understand the fundamental dynamical mechanisms that control the feedbacks between the eddies and the mean flow, which in turn select the tropospheric annular mode. Recent work using Rossby Wave Chromatography suggests that "barotropic processes", which directly impact the meridional propagation of wave activity (specifically the reflectivity of the poleward flank of the mid-latitude jet), are more important for the positive feedback between the annular mode and the eddies than "baroclinic processes", which involve changes in the generation of wave activity by baroclinic instability. In this study, experiments with a fully nonlinear quasi-geostrophic model are discussed which provide independent confirmation of the importance of barotropic versus baroclinic processes. The experiments take advantage of the steady-state balance at upper-levels between the meridional gradient in diabatic heating and the second derivative of the upper-level EP flux divergence. Simulations with standard Newtonian heating are compared to simulations with constant-in-time heating taken from the climatology of the standard run and it is found that the forced annular mode response to changes in surface friction is very similar. Moreover, as expected from the annular mode response, the eddy momentum fluxes are also very similar. This is despite the fact that the upper-level EP flux divergence is very different between the two simulations (upper-level EP flux divergence must remain constant in the constant heating simulation while in the standard simulation there is no such constraint). The upper-level balances are maintained by a large change in the baroclinic wave source (i.e. vertical EP flux), which is accompanied by little momentum flux change. Therefore the eddy momentum fluxes appear to be relatively insensitive to the wave activity source. A more detailed comparison suggests a helpful rule-of-thumb relating the amplitude of the baroclinic wave source to the upper-level vorticity flux forced by this wave source.

In Situ Balloon-Borne Ice Particle Imaging in High-Latitude Cirrus

NASA Astrophysics Data System (ADS)

Kuhn, Thomas; Heymsfield, Andrew J.

2016-09-01

Cirrus clouds reflect incoming solar radiation, creating a cooling effect. At the same time, these clouds absorb the infrared radiation from the Earth, creating a greenhouse effect. The net effect, crucial for radiative transfer, depends on the cirrus microphysical properties, such as particle size distributions and particle shapes. Knowledge of these cloud properties is also needed for calibrating and validating passive and active remote sensors. Ice particles of sizes below 100 µm are inherently difficult to measure with aircraft-mounted probes due to issues with resolution, sizing, and size-dependent sampling volume. Furthermore, artefacts are produced by shattering of particles on the leading surfaces of the aircraft probes when particles several hundred microns or larger are present. Here, we report on a series of balloon-borne in situ measurements that were carried out at a high-latitude location, Kiruna in northern Sweden (68N 21E). The method used here avoids these issues experienced with the aircraft probes. Furthermore, with a balloon-borne instrument, data are collected as vertical profiles, more useful for calibrating or evaluating remote sensing measurements than data collected along horizontal traverses. Particles are collected on an oil-coated film at a sampling speed given directly by the ascending rate of the balloon, 4 m s-1. The collecting film is advanced uniformly inside the instrument so that an always unused section of the film is exposed to ice particles, which are measured by imaging shortly after sampling. The high optical resolution of about 4 µm together with a pixel resolution of 1.65 µm allows particle detection at sizes of 10 µm and larger. For particles that are 20 µm (12 pixel) in size or larger, the shape can be recognized. The sampling volume, 130 cm3 s-1, is well defined and independent of particle size. With the encountered number concentrations of between 4 and 400 L-1, this required about 90- to 4-s sampling times to determine particle size distributions of cloud layers. Depending on how ice particles vary through the cloud, several layers per cloud with relatively uniform properties have been analysed. Preliminary results of the balloon campaign, targeting upper tropospheric, cold cirrus clouds, are presented here. Ice particles in these clouds were predominantly very small, with a median size of measured particles of around 50 µm and about 80 % of all particles below 100 µm in size. The properties of the particle size distributions at temperatures between -36 and -67 °C have been studied, as well as particle areas, extinction coefficients, and their shapes (area ratios). Gamma and log-normal distribution functions could be fitted to all measured particle size distributions achieving very good correlation with coefficients R of up to 0.95. Each distribution features one distinct mode. With decreasing temperature, the mode diameter decreases exponentially, whereas the total number concentration increases by two orders of magnitude with decreasing temperature in the same range. The high concentrations at cold temperatures also caused larger extinction coefficients, directly determined from cross-sectional areas of single ice particles, than at warmer temperatures. The mass of particles has been estimated from area and size. Ice water content (IWC) and effective diameters are then determined from the data. IWC did vary only between 1 × 10-3 and 5 × 10-3 g m-3 at temperatures below -40 °C and did not show a clear temperature trend. These measurements are part of an ongoing study.

Chemical processes related to net ozone tendencies in the free troposphere

NASA Astrophysics Data System (ADS)

Bozem, Heiko; Butler, Tim M.; Lawrence, Mark G.; Harder, Hartwig; Martinez, Monica; Kubistin, Dagmar; Lelieveld, Jos; Fischer, Horst

2017-09-01

Ozone (O3) is an important atmospheric oxidant, a greenhouse gas, and a hazard to human health and agriculture. Here we describe airborne in situ measurements and model simulations of O3 and its precursors during tropical and extratropical field campaigns over South America and Europe, respectively. Using the measurements, net ozone formation/destruction tendencies are calculated and compared to 3-D chemistry-transport model simulations. In general, observation-based net ozone tendencies are positive in the continental boundary layer and the upper troposphere at altitudes above ˜ 6 km in both environments. On the other hand, in the marine boundary layer and the middle troposphere, from the top of the boundary layer to about 6-8 km altitude, net O3 destruction prevails. The ozone tendencies are controlled by ambient concentrations of nitrogen oxides (NOx). In regions with net ozone destruction the available NOx is below the threshold value at which production and destruction of O3 balance. While threshold NO values increase with altitude, in the upper troposphere NOx concentrations are generally higher due to the integral effect of convective precursor transport from the boundary layer, downward transport from the stratosphere and NOx produced by lightning. Two case studies indicate that in fresh convective outflow of electrified thunderstorms net ozone production is enhanced by a factor 5-6 compared to the undisturbed upper tropospheric background. The chemistry-transport model MATCH-MPIC generally reproduces the pattern of observation-based net ozone tendencies but mostly underestimates the magnitude of the net tendency (for both net ozone production and destruction).

The Evolution of Tropospheric Temperature Field and its Relationship With The Onset of Asian Summer Monsoon

NASA Technical Reports Server (NTRS)

He, H.; Sui, C-H.; Jian, M.; Wen, Z.

2000-01-01

The mean state and year-to-year variations of the tropospheric temperature fields and their relationship with the establishment of the summertime East Asian monsoon (EAM) and the Indian monsoon (INM) are studied using the NCEP reanalysis data of 15 years (1982-1996). The results show that the seasonal shift of the South Asian High in the upper troposphere and the establishment of the EAM and the INM are closely related to the seasonal warming which causes a reversal of the meridional gradient of upper tropospheric mean temperature over the monsoon regions. On the average of 15 years, the reversal time of the temperature gradient in the EAM region (INM region) is concurrent with (one pentad earlier than) the onset time of the summer monsoon. In most years of the 15-year period, the reversal of temperature gradient coincides or precedes the onset time of the summer monsoon in both the EAM region and the INM region. The results suggest an important role of thermal processes on the establishment of the Asian monsoon. The contributors to the upper tropospheric warming over the EAM region are the strong horizontal warm advection and the diabetic heating against the adiabatic cooling due to upward motion. In the INM region, strong adiabatic heating by subsidence and the diabetic heating are major warming processes against the strong horizontal cold advection related to the persistent northwestlies to the southwestern periphery of the Tibetan Plateau. It appears that the early or late establishment of the Asian summer monsoon is not directly related to the differential warming near the surface.

Laboratory Studies of Homogeneous and Heterogeneous Chemical Processes of Importance in the Upper Atmosphere

NASA Technical Reports Server (NTRS)

Molina, Mario J.

2001-01-01

The objective of this study is to conduct measurements of chemical kinetics parameters for reactions of importance in the stratosphere and upper troposphere, and to study the interaction of trace gases such as HCl with ice surfaces in order to elucidate the mechanism of heterogeneous chlorine activation processes, using both a theoretical and an experimental approach. The measurements will be carried out under temperature and pressure conditions covering those applicable to the stratosphere and upper troposphere. The techniques to be employed include turbulent flow - chemical ionization mass spectrometry, and optical ellipsometry. The next section summarizes our research activities during the second year of the project, and the section that follows consists of the statement of work for the third year.

Subtropical westerly jet waveguide and winter persistent heavy rainfall in south China

NASA Astrophysics Data System (ADS)

Ding, Feng; Li, Chun

2017-07-01

Using observed daily precipitation and National Centers for Environmental Prediction-National Center for Atmospheric Research reanalysis data, what induced winter large spatial persistent heavy rainfall (PHR) events in south China was examined, based on composite analyses of 30 large spatial PHR events during 1951-2015. The results showed that wave trains within North Africa-Asia (NAA) westerly jet existed in upper troposphere during these PHR processes. The wave trains shared the characteristic of a Rossby wave. The Rossby wave originated from northwest Europe, entered into the NAA jet through strong cold air advection to form convergence over the Mediterranean, and then propagated eastward along subtropical NAA jet. The Rossby wave propagated toward Southeast Asia and caused strong divergence in the upper troposphere. The strong divergence in the upper troposphere induced vertical convection and favored large spatial PHR events in south China. In addition, the enhanced India-Burma trough and subtropical high in the northwestern Pacific supplied enough water vapor transportation. This mechanism would be useful to the medium-range forecast of such winter rainfall processes over south China.

Atmos/Atlas 3 Infrared Profile Measurements of Trace Gases in The November 1994 Tropical and Subtropical Upper Troposphere

NASA Technical Reports Server (NTRS)

Rinsland, C. P.; Gunson, M. R.; Wang, P.-H.; Arduini, R. F.; Baum, B. A.; Minnis, P.; Minnis, P.; Goldman, A.; Abrams, M. C.; Zander, R.;

Reactive Nitrogen, Ozone and Ozone Production in the Arctic Troposphere and the Impact of Stratosphere-Troposphere Exchange

NASA Technical Reports Server (NTRS)

Liang, Q.; Rodriquez, J. M.; Douglass, A. R.; Crawford, J. H.; Apel, E.; Bian, H.; Blake, D. R.; Brune, W.; Chin, M.; Colarco, P. R.;

Five blind men and the elephant: what can the NASA Aura ozone measurements tell us about stratosphere-troposphere exchange?

NASA Astrophysics Data System (ADS)

Tang, Q.; Prather, M. J.

2012-03-01

We examine whether the individual ozone (O3) measurements from the four Aura instruments can quantify the stratosphere-troposphere exchange (STE) flux of O3, an important term of the tropospheric O3 budget. The level 2 (L2) Aura swath data and the nearly coincident ozone sondes for the years 2005-2006 are compared with the 4-D, high-resolution (1° × 1° × 40-layer × 0.5 h) model simulation of atmospheric ozone for the same period from the University of California, Irvine chemistry transport model (CTM). The CTM becomes a transfer standard for comparing individual profiles from these five, not-quite-coincident measurements of atmospheric ozone. Even with obvious model discrepancies identified here, the CTM can readily quantify instrument-instrument biases in the tropical upper troposphere and mid-latitude lower stratosphere. In terms of STE processes, all four Aura datasets have some skill in identifying stratosphere-troposphere folds, and we find several cases where both model and measurements see evidence of high-O3 stratospheric air entering the troposphere. In many cases identified in the model, however, the individual Aura profile retrievals in the upper troposphere and lower stratosphere show too much noise, as expected from their low sensitivity and coarse vertical resolution at and below the tropopause. These model-measurement comparisons of individual profiles do provide some level of confidence in the model-derived STE O3 flux, but it will be difficult to integrate this flux from the satellite data alone.

Mie Lidar for Aerosols and Clouds Monitoring at Otlica Observatory

NASA Astrophysics Data System (ADS)

Gao, F.; Stanič, S.; Bergant, K.; Filipčič, A.; Veberič, D.; Forte, B.

2009-04-01

Aerosol and cloud densities are the most important atmospheric parameters, which significantly influence the atmospheric conditions. The study of their spatial and temporal properties can provide detailed information about the transport processes of the air masses. In recent years, lidar techniques for remote sensing of the atmospheric parameters have been greatly improved. Like the lidar systems of the Pierre Auger Observatory in Argentina (35.2S, 69.1W, 1400 m a.s.l.), the Mie lidar built at Otlica Observatory (45.93N, 13.91E, 945 m a.s.l.) in Slovenia employs the same hardware, including the transmitter, the receiver, and the DAQ system. Due to its high-power laser, large-diameter telescope, and photon-counting data-acquisition technique, the Mie lidar has the potential ability to measure the tropospheric and stratospheric atmospheric conditions, and is suitable for monitoring the changes of the cirrus clouds and atmospheric boundary layer. We have been performing routine atmospheric monitoring experiments with the Otlica Mie lidar since September 2008. Using the techniques of event-averaging, noise-elimination, and data-gluing, the far end of lidar probing range is extended from 30 km up to 40 km. The extinction profiles are calculated using the Klett method and the time-height-intensity plots were made. They clearly show the evolution of atmospheric conditions, especially the motion of the cirrus clouds above Otlica.

Lightning NOx Production in CMAQ Part I – Using Hourly NLDN Lightning Strike Data

EPA Science Inventory

Lightning-produced nitrogen oxides (NOX=NO+NO2) in the middle and upper troposphere play an essential role in the production of ozone (O3) and influence the oxidizing capacity of the troposphere. Despite much effort in both observing and modeling lightning NOX during the past dec...

Tropospheric Waves, Jet Streams, and United States Weather Patterns. Resource Paper No. 11.

ERIC Educational Resources Information Center

Harman, Jay R.

Intended as a supplement to undergraduate college geography courses, this resource paper reviews the mechanism by which surface weather features are linked with the mid-atmospheric circulation within the westerly wind belt. Specifically, vertical atmospheric motions associated with certain aspects of the upper tropospheric flow, including jet…

Air motion determination by tracking humidity patterns in isentropic layers

NASA Technical Reports Server (NTRS)

Mancuso, R. L.; Hall, D. J.

1975-01-01

Determining air motions by tracking humidity patterns in isentropic layers was investigated. Upper-air rawinsonde data from the NSSL network and from the AVE-II pilot experiment were used to simulate temperature and humidity profile data that will eventually be available from geosynchronous satellites. Polynomial surfaces that move with time were fitted to the mixing-ratio values of the different isentropic layers. The velocity components of the polynomial surfaces are part of the coefficients that are determined in order to give an optimum fitting of the data. In the mid-troposphere, the derived humidity motions were in good agreement with the winds measured by rawinsondes so long as there were few or no clouds and the lapse rate was relatively stable. In the lower troposphere, the humidity motions were unreliable primarily because of nonadiabatic processes and unstable lapse rates. In the upper troposphere, the humidity amounts were too low to be measured with sufficient accuracy to give reliable results. However, it appears that humidity motions could be used to provide mid-tropospheric wind data over large regions of the globe.

Improvement of OMI Ozone Profile Retrievals in the Troposphere and Lower Troposphere by the Use of the Tropopause-Based Ozone Profile Climatology

NASA Technical Reports Server (NTRS)

Bak, Juseon; Liu, X.; Wei, J.; Kim, J. H.; Chance, K.; Barnet, C.

2011-01-01

An advance algorithm based on the optimal estimation technique has beeen developed to derive ozone profile from GOME UV radiances and have adapted it to OMI UV radiances. OMI vertical resolution : 7-11 km in the troposphere and 10-14 km in the stratosphere. Satellite ultraviolet measurements (GOME, OMI) contain little vertical information for the small scale of ozone, especially in the upper troposphere (UT) and lower stratosphere (LS) where the sharp O3 gradient across the tropopause and large ozone variability are observed. Therefore, retrievals depend greatly on the a-priori knowledge in the UTLS

Carbon monoxide measurements in the troposphere

NASA Technical Reports Server (NTRS)

Reichle, H. G., Jr.; Beck, S. M.; Haynes, R. E.; Hesketh, W. D.; Holland, J. A.; Hypes, W. D.; Orr, H. D., III; Sherrill, R. T.; Wallio, H. A.; Casas, J. C.

1982-01-01

Approximately 35 hours of radiometric measurements were obtained of the CO mixing ratio in the middle troposphere, upper troposphere, and lower stratosphere, by means of the Measurement of Air Pollution from Satellites (MAPS) experiment carried in the OSTA-1 payload of the second Space Shuttle flight. In view of gas filter radiometer data in the 4.67-micron band, gathered over the 38 N-38 S latitude region during both daytime and nighttime, the performance of MAPS was excellent. Significant gradients have been found in the middle tropospheric CO mixing ratio with both latitude and longitude over the North Atlantic, the Mediterranean Sea, and the Middle East.

A new monozoic tapeworm, Parabreviscolex niepini n. g., n. sp. (Cestoda: Caryophyllidea), from schizothoracine fishes (Cyprinidae: Schizothoracinae) in Tibet, China.

PubMed

Xi, Bing-Wen; Oros, Mikuláš; Chen, Kai; Xie, Jun

2018-02-01

A new monozoic cestode, Parabreviscolex niepini n. gen. and n. sp. (Cestoda: Caryophyllidea), is described from the type-host Schizopygopsis younghusbandi Regan, 1905 (Cyprinidae: Schizothoracinae) and Schizothorax waltoni Regan, 1905 (Cyprinidae: Schizothoracinae) in the Yarlung Tsangpo River, the upper tributary of the Brahmaputra River on the Tibetan Plateau. The new genus is placed in the Capingentidae because the vitellarium is situated partly in the medullary and cortical parenchyma, i.e., neither completely external nor internal to inner longitudinal muscles. Parabreviscolex n. gen. is characterized by possessing an afossate and cuneiform scolex; numerous vitelline follicles and testes present immediately after the scolex, and spread backward near the cirrus sac; the uterus does not loop anterior to the cirrus sac; genital pores separate, opening to the common genital atrium; the pre-ovarian vitelline follicles lateral and median, post-ovarian vitelline follicles present; ovary H-shaped, compact, and ovarian arms long, anteriorly reaching the cirrus sac. Homology search by the basic local alignment search tool (BLAST) showed that the partial 18S rDNA and complete mtDNA cox-1 sequences obtained in this report were not consistent with any sequences available in GenBank, and molecular phylogenetic analyses revealed Parabreviscolex formed a separated long branch within the caryophyllideans from cyprinids.

The use of satellite data to determine the distribution of ozone in the troposphere

NASA Technical Reports Server (NTRS)

Fishman, Jack; Watson, Catherine E.; Brackett, Vincent G.; Fakhruzzaman, Khan; Veiga, Robert E.

1991-01-01

Measurements from two independent satellite data sets have been used to derive the climatology of the integrated amount of ozone in the troposphere. These data have led to the finding that large amounts of ozone pollution are generated by anthropogenic activity originating from both the industrialized regions of the Northern Hemisphere and from the southern tropical regions of Africa. To verify the existence of this ozone anomaly at low latitudes, an ozonesonde capability has been established at Ascension Island (8 deg S, 15 deg W) since July 1990. According to the satellite analyses, Ascension Island is located downwind of the primary source region of this ozone pollution, which likely results from the photochemical oxidation of emissions emanating from the widespread burning of savannas and other biomass. These in situ measurements confirm the existence of large amounts of ozone in the lower atmosphere. A summary of these ozonesonde data to date will be presented. In addition, we will present some ozone profile measurements from SAGE II which can be used to provide upper tropospheric ozone measurements directly in the tropical troposphere. A preliminary comparison between the satellite observations and the ozonesonde profiles in the upper troposphere and lower stratosphere will also be presented.

Chemical Composition and Dynamics of the Upper Troposphere and the Lower Stratosphere: Overview of the Project

NASA Astrophysics Data System (ADS)

Sofieva, V. F.; Liu, C.; Huang, F.; Kyrola, E.; Liu, Y.; Ialongo, I.; Hakkarainen, J.; Zhang, Y.

2016-08-01

The DRAGON-3 cooperation study on the upper troposphere and the lower stratosphere (UTLS) is based on new satellite data and modern atmospheric models. The objectives of the project are: (i) assessment of satellite data on chemical composition in UTLS, (ii) dynamical and chemical structures of the UTLS and its variability, (iii) multi-scale variability of stratospheric ozone, (iv) climatology of the stratospheric aerosol layer and its variability, and (v) updated ozone climatology and its relation to tropopause/multiple tropopauses.In this paper, we present the main results of the project.

Interpretation of Aura satellite observations of CO and aerosol index related to the December 2006 Australia fires

NASA Astrophysics Data System (ADS)

Luo, M.; Boxe, C.; Jiang, J.; Nassar, R.; Livesey, N.

2009-11-01

Enhanced Carbon Monoxide (CO) in the upper troposphere (UT) is shown by collocated Tropospheric Emission Spectrometer (TES) and Microwave Limb Sounder (MLS) measurements near and down-wind from the known wildfire region of SE Australia from 12-19 December 2006. Enhanced UV aerosol index (AI) derived from Ozone Monitoring Instrument (OMI) measurements correlate with these high CO concentrations. HYSPLIT model back trajectories trace selected air parcels to the SE Australia fire region as their initial location, where TES observes enhanced CO in the upper and lower troposphere. Simultaneously, they show a lack of vertical advection along their tracks. TES retrieved CO vertical profiles in the higher and lower southern latitudes are examined together with the averaging kernels and show that TES CO retrievals are most sensitive at approximately 300-400 hPa. The enhanced CO observed by TES at the upper (215 hPa) and lower (681 hPa) troposphere are, therefore, influenced by mid-tropospheric CO. GEOS-Chem model simulations with an 8-day emission inventory, as the wildfire source over Australia, are sampled to the TES/MLS observation times and locations. These simulations only show CO enhancements in the lower troposphere near and down-wind from the wildfire region of SE Australia with drastic underestimates of UT CO. Although CloudSat along-track ice-water content curtains are examined to see whether possible vertical convection events can explain the high UT CO values, sparse observations of collocated Aura CO and CloudSat along-track ice-water content measurements for the single event precludes any conclusive correlation. Vertical convection that uplift fire-induced CO (i.e. most notably referred to as pyro-cumulonimbus, pyroCb) may provide an explanation for the incongruence between these simulations and the TES/MLS observations of enhanced CO in the UT. Future GEOS-Chem simulations are needed to validate this conjecture as the the PyroCb mechanism is currently not incorporated in GEOS-Chem.

Physical and Optical/Radiative Characteristics of Aerosol and Cloud Particles in Tropical Cirrus: Importance in Radiation Balance

NASA Technical Reports Server (NTRS)

Pueschel, R. F.; Howard, S. D.; Foster, T. C.; Hallett, J.; Arnott, W. P.; Condon, Estelle P. (Technical Monitor)

1996-01-01

Whether cirrus clouds heat or cool the Earth-atmosphere system depends on the relative importance of the cloud shortwave albedo effect and the cloud thermal greenhouse effect. Both are determined by the distribution of ice condensate with cloud particle size. The microphysics instrument package flown aboard the NASA DC-8 in TOGA/COARE included an ice crystal replicator, a 2D Greyscale Cloud Particle Probe and a Forward Scattering Spectrometer Aerosol Probe. In combination, the electro-optical instruments permitted particle size measurements between 0.5 micrometer and 2.6 millimeter diameter. Ice crystal replicas were used to validate signals from the electrooptical instruments. Both optical and scanning electron microscopy were utilized to analyze aerosol and ice particle replicas between 0.1 micrometer and several 100 micrometer diameter. In first approximation, the combined aerosol-cloud particle spectrum in several clouds followed a power law N alpha D(sup -2.5). Thus, large cloud particles carried most of the condensate mass, while small cloud and aerosol particles determined the surface area. The mechanism of formation of small particles is growth of (hygroscopic, possibly ocean-derived) aerosol particles along the Kohler curves. The concentration of small particles is higher and less variable in space and time, and their tropospheric residence time is longer, than those of large cloud particles because of lower sedimentation velocities. Small particles shift effective cloud particle radii to sizes much smaller than the mean diameter of the cloud particles. This causes an increase in shortwave reflectivity and IR emissivity, and a decrease in transmissivity. Occasionally, the cloud reflectivity increased with altitude (decreasing temperature) stronger than did cloud emissivity, yielding enhanced radiative cooling at higher altitudes. Thus, cirrus produced by deep convection in the tropics may be critical in controlling processes whereby energy from warm tropical oceans is injected to different levels in the atmosphere to subsequently influence not only tropical but mid-latitude climate.

Reactive nitrogen, ozone and ozone production in the Arctic troposphere and the impact of stratosphere-troposphere exchange

NASA Astrophysics Data System (ADS)

Liang, Q.; Rodriguez, J. M.; Douglass, A. R.; Crawford, J. H.; Olson, J. R.; Apel, E.; Bian, H.; Blake, D. R.; Brune, W.; Chin, M.; Colarco, P. R.; da Silva, A.; Diskin, G. S.; Duncan, B. N.; Huey, L. G.; Knapp, D. J.; Montzka, D. D.; Nielsen, J. E.; Pawson, S.; Riemer, D. D.; Weinheimer, A. J.; Wisthaler, A.

2011-12-01

We use aircraft observations obtained during the Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) mission to examine the distributions and source attributions of O3 and NOy in the Arctic and sub-Arctic region. Using a number of marker tracers, we distinguish various air masses from the background troposphere and examine their contributions to NOx, O3, and O3 production in the Arctic troposphere. The background Arctic troposphere has a mean O3 of ~60 ppbv and NOx of ~25 pptv throughout spring and summer with CO decreasing from ~145 ppbv in spring to ~100 ppbv in summer. These observed mixing ratios are not notably different from the values measured during the 1988 ABLE-3A and the 2002 TOPSE field campaigns despite the significant changes in emissions and stratospheric ozone layer in the past two decades that influence Arctic tropospheric composition. Air masses associated with stratosphere-troposphere exchange are present throughout the mid and upper troposphere during spring and summer. These air masses, with mean O3 concentrations of 140-160 ppbv, are significant direct sources of O3 in the Arctic troposphere. In addition, air of stratospheric origin displays net O3 formation in the Arctic due to its sustainable, high NOx (75 pptv in spring and 110 pptv in summer) and NOy (~800 pptv in spring and ~1100 pptv in summer). The air masses influenced by the stratosphere sampled during ARCTAS-B also show conversion of HNO3 to PAN. This active production of PAN is the result of increased degradation of ethane in the stratosphere-troposphere mixed air mass to form CH3CHO, followed by subsequent formation of PAN under high NOx conditions. These findings imply that an adequate representation of stratospheric NOy input, in addition to stratospheric O3 influx, is essential to accurately simulate tropospheric Arctic O3, NOx and PAN in chemistry transport models. Plumes influenced by recent anthropogenic and biomass burning emissions observed during ARCTAS show highly elevated levels of hydrocarbons and NOy (mostly in the form of NOx and PAN), but do not contain O3 higher than that in the Arctic tropospheric background except some aged biomass burning plumes sampled during spring. Convection and/or lightning influences are negligible sources of O3 in the Arctic troposphere but can have significant impacts in the upper troposphere in the continental sub-Arctic during summer.

Introduction to the SONEX (Subsonic Assessment Ozone and Nitrogen Oxides Experiment) and POLINAT-2 (Pollution from Aircraft Emissions in the North Atlantic Flight Corridor) Special Issue

NASA Technical Reports Server (NTRS)

Thompson, Anne M.; Singh, Hanwant B.; Schlager, Hans; Einaudi, Franco (Technical Monitor)

2000-01-01

Emissions of atmospheric species from the engines of subsonic aircraft at cruise altitude (roughly, above seven kilometers) are of concern to scientists, the aviation industry and policymakers for two reasons. First, water vapor, soot and sulfur oxides, and related heterogeneous processes, may modify clouds and aerosols enough to perturb radiative forcing in the UT/LS (upper troposphere/lower stratosphere). A discussion of these phenomena appears in Chapter 3 of the IPCC Aviation Assessment (1999). An airborne campaign conducted to evaluate aviation effects on contrail, cirrus and cloud formation, is described in Geophysical Research Letters. The second concern arises from subsonic aircraft emissions of nitrogen oxides (NO + NO2 = NO(sub x)), CO, and hydrocarbons. These species may add to the background mixture of photochemically reactive species that form ozone. In the UT/LS, ozone is a highly effective greenhouse gas. The impacts of subsonic aircraft emissions on tropospheric NO(sub x) and ozone budgets have been studied with models that focus on UT chemistry [e.g. see discussions of individual models in Brasseur et al., 1998; Friedl et al., 1997; IPCC, 1999]. Depending on the model used, projected increases in the global subsonic aircraft fleet from 1992 to 2015 will lead to a 50-100 pptv increase in UT/LS NO. at 12 km (compared to 50-150 pptv background) in northern hemisphere midlatitudes. The corresponding 12-km ozone increase is 7-11 ppbv, or 5-10% (Chapter 4 in IPCC, 1999). Two major sources of uncertainties in model estimates of aviation effects are: (1) the often limited degree to which global models - the scale required to evaluate aircraft emissions - realistically simulate atmospheric transport and other physical processes; (2) limited UT/LS observations of trace gases with which to evaluate model performance. In response to the latter deficiency, a number of airborne campaigns aimed at elucidating the effect of aircraft on atmospheric nitrogen oxides and ozone were performed between 1990 and 1996 (see descriptions in Friedl et al., 1997; Brasseur et al., 1998).

Tropospheric Ozone as a Short-lived Chemical Climate Forcer

NASA Technical Reports Server (NTRS)

Pickering, Kenneth E.

2012-01-01

Tropospheric ozone is the third most important greenhouse gas according to the most recent IPCC assessment. However, tropospheric ozone is highly variable in both space and time. Ozone that is located in the vicinity of the tropopause has the greatest effect on climate forcing. Nitrogen oxides (NOx) are the most important precursors for ozone In most of the troposphere. Therefore, pollution that is lofted upward in thunderstorm updrafts or NOx produced by lightning leads to efficient ozone production in the upper troposphere, where ozone is most important climatically. Global and regional model estimates of the impact of North American pollution and lightning on ozone radiative forcing will be presented. It will be shown that in the Northern Hemisphere summer, the lightning effect on ozone radiative forcing can dominate over that of pollution, and that the radiative forcing signal from North America extends well into Europe and North Africa. An algorithm for predicting lightning flash rates and estimating lightning NOx emissions is being incorporated into the NASA GEOS-5 Chemistry and Climate Model. Changes in flash rates and emissions over an ENSO cycle and in future climates will be assessed, along with the resulting changes in upper tropospheric ozone. Other research on the production of NOx per lightning flash and its distribution in the vertical based on cloud-resolving modeling and satellite observations will be presented. Distributions of NO2 and O3 over the Middle East from the OMI instrument on NASA's Aura satellite will also be shown.

Evaluations of Thin Cirrus Contamination and Screening in Ground Aerosol Observations Using Collocated Lidar Systems

NASA Technical Reports Server (NTRS)

Huang, Jingfeng; Hsu, N. Christina; Tsay, Si-Chee; Holben, Brent N.; Welton, Ellsworth J.; Smirnov, Alexander; Jeong, Myeong-Jae; Hansell, Richard A.; Berkoff, Timothy A.

2012-01-01

Cirrus clouds, particularly sub visual high thin cirrus with low optical thickness, are difficult to be screened in operational aerosol retrieval algorithms. Collocated aerosol and cirrus observations from ground measurements, such as the Aerosol Robotic Network (AERONET) and the Micro-Pulse Lidar Network (MPLNET), provide us with an unprecedented opportunity to examine the susceptibility of operational aerosol products to thin cirrus contamination. Quality assured aerosol optical thickness (AOT) measurements were also tested against the CALIPSO vertical feature mask (VFM) and the MODIS-derived thin cirrus screening parameters for the purpose of evaluating thin cirrus contamination. Key results of this study include: (1) Quantitative evaluations of data uncertainties in AERONET AOT retrievals are conducted. Although AERONET cirrus screening schemes are successful in removing most cirrus contamination, strong residuals displaying strong spatial and seasonal variability still exist, particularly over thin cirrus prevalent regions during cirrus peak seasons, (2) Challenges in matching up different data for analysis are highlighted and corresponding solutions proposed, and (3) Estimation of the relative contributions from cirrus contamination to aerosol retrievals are discussed. The results are valuable for better understanding and further improving ground aerosol measurements that are critical for aerosol-related climate research.

Vertical structure of tropospheric winds on gas giants

NASA Astrophysics Data System (ADS)

Scott, R. K.; Dunkerton, T. J.

2017-04-01

Zonal mean zonal velocity profiles from cloud-tracking observations on Jupiter and Saturn are used to infer latitudinal variations of potential temperature consistent with a shear stable potential vorticity distribution. Immediately below the cloud tops, density stratification is weaker on the poleward and stronger on the equatorward flanks of midlatitude jets, while at greater depth the opposite relation holds. Thermal wind balance then yields the associated vertical shears of midlatitude jets in an altitude range bounded above by the cloud tops and bounded below by the level where the latitudinal gradient of static stability changes sign. The inferred vertical shear below the cloud tops is consistent with existing thermal profiling of the upper troposphere. The sense of the associated mean meridional circulation in the upper troposphere is discussed, and expected magnitudes are given based on existing estimates of the radiative timescale on each planet.

Interhemispheric comparison of atmospheric circulation features as evaluated from Nimbus satellite data. A comparison of the structure and flow characteristics of the upper troposphere and stratosphere of the Northern and Southern Hemispheres. Ph.D. Thesis. Annual Report, 1 Nov. 1973 - 31 Oct. 1974

NASA Technical Reports Server (NTRS)

Reiter, E. R.; Adler, R.; Fields, A.

1974-01-01

The general circulations of the Northern and Southern Hemispheres are compared with regard to the upper troposphere and stratosphere, using atmospheric structure obtained from multi-channel radiance data from the satellite infrared spectrometer instrument aboard the Nimbus 3 spacecraft. The inter-hemispheric comparisons are based on two months of data (one summer month and one winter month) in each hemisphere. Topics studied include: (1) mean meridional circulation in the Southern Hemisphere stratosphere; (2) magnitude and distribution of tropospheric eddy heat flux; (3) relative importance of standing and transient eddies in the two hemispheres; (4) magnitudes of energy cycle components; and (5) the relation of vortex structure to the breakdown climatology of the Antarctic stratospheric polar vortex.

The synoptic setting and possible energy sources for mesoscale wave disturbances

NASA Technical Reports Server (NTRS)

Uccellini, Louis W.; Koch, Steven E.

1987-01-01

Published data on 13 cases of mesoscale wave disturbances and their environment were examined to isolate common features for these cases and to determine possible energy sources for the waves. These events are characterized by either a singular wave of depression or wave packets with periods of 1-4 h, horizontal wavelengths of 50-500 km, and surface-pressure perturbation amplitudes of 0.2-7.0 mb. These wave events are shown to be associated with a distinct synoptic pattern (including the existence of a strong inversion in the lower troposphere and the propagation of a jet streak toward a ridge axis in the upper troposphere) while displaying little correlation with the presence of convective storm cells. The observed development of the waves is consistent with the hypothesis that the energy source needed to initiate and sustain the wave disturbances may be related to a geostrophic adjustment process associated with upper-tropospheric jet streaks.

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

Bony, Sandrine; Stevens, Bjorn; Coppin, David

General circulation models show that as the surface temperature increases, the convective anvil clouds shrink. By analyzing radiative–convective equilibrium simulations, our work shows that this behavior is rooted in basic energetic and thermodynamic properties of the atmosphere: As the climate warms, the clouds rise and remain at nearly the same temperature, but find themselves in a more stable atmosphere; this enhanced stability reduces the convective outflow in the upper troposphere and decreases the anvil cloud fraction. By warming the troposphere and increasing the upper-tropospheric stability, the clustering of deep convection also reduces the convective outflow and the anvil cloud fraction.more » When clouds are radiatively active, this robust coupling between temperature, high clouds, and circulation exerts a positive feedback on convective aggregation and favors the maintenance of strongly aggregated atmospheric states at high temperatures. This stability iris mechanism likely contributes to the narrowing of rainy areas as the climate warms. Whether or not it influences climate sensitivity requires further investigation.« less

The possible influences of the increasing anthropogenic emissions in India on tropospheric ozone and OH

NASA Astrophysics Data System (ADS)

Liu, Yu; Li, Weiliang; Zhou, Xiuji; Isaksen, I. S. A.; Sundet, J. K.; He, Jinhai

2003-11-01

A 3-D chemical transport model (OSLO CTM2) is used to investigate the influences of the increasing anthropogenic emission in India. The model is capable of reproducing the observational results of the INDOEX experiment and the measurements in summer over India well. The model results show that when NO x and CO emissions in India are doubled, ozone concentration increases, and global average OH decreases a little. Under the effects of the Indian summer monsoon, NO x and CO in India are efficiently transported into the middle and upper troposphere by the upward current and the convective activities so that the NO x , CO, and ozone in the middle and upper troposphere significantly increase with the increasing NO x and CO emissions. These increases extensively influence a part of Asia, Africa, and Europe, and persist from June to September.

Investigation of tropical cirrus cloud properties using ground based lidar measurements

NASA Astrophysics Data System (ADS)

Dhaman, Reji K.; Satyanarayana, Malladi; Krishnakumar, V.; Mahadevan Pillai, V. P.; Jayeshlal, G. S.; Raghunath, K.; Venkat Ratnam, M.

2016-05-01

Cirrus clouds play a significant role in the Earths radiation budget. Therefore, knowledge of geometrical and optical properties of cirrus cloud is essential for the climate modeling. In this paper, the cirrus clouds microphysical and optical properties are made by using a ground based lidar measurements over an inland tropical station Gadanki (13.5°N, 79.2°E), Andhra Pradesh, India. The variation of cirrus microphysical and optical properties with mid cloud temperature is also studied. The cirrus clouds mean height is generally observed in the range of 9-17km with a peak occurrence at 13- 14km. The cirrus mid cloud temperature ranges from -81°C to -46°C. The cirrus geometrical thickness ranges from 0.9- 4.5km. During the cirrus occurrence days sub-visual, thin and dense cirrus were at 37.5%, 50% and 12.5% respectively. The monthly cirrus optical depth ranges from 0.01-0.47, but most (<80%) of the cirrus have values less than 0.1. Optical depth shows a strong dependence with cirrus geometrical thickness and mid-cloud height. The monthly mean cirrus extinction ranges from 2.8E-06 to 8E-05 and depolarization ratio and lidar ratio varies from 0.13 to 0.77 and 2 to 52 sr respectively. A positive correlation exists for both optical depth and extinction with the mid-cloud temperature. The lidar ratio shows a scattered behavior with mid-cloud temperature.

Effects of the 2004 El Nino on Tropospheric Ozone and Water Vapor

NASA Technical Reports Server (NTRS)

Chandra, S.; Ziemke, J. R.; Schoeberl, M. R.; Froidevaux, L.; Read, W. G.; Levelt, P. F.; Bhartia, P. K.

2007-01-01

The global effects of the 2004 El Nino on tropospheric ozone and H2O based on Aura OM1 and MLS measurements are analyzed. Although it was a weak El Nino from a historical perspective, it produced significant changes in these parameters in tropical latitudes. Tropospheric ozone increased by 10-20% over most of the western Pacific region and decreased by about the same amount over the eastern Pacific region. H2O in the upper troposphere showed similar changes but with opposite sign. These zonal changes in tropospheric ozone and H2O are caused by the eastward shift in the Walker circulation in the tropical pacific region during El Nino. For the 2004 El Nino, biomass burning did not have a significant effect on the ozone budget in the troposphere unlike the 1997 El Nino. Zonally averaged tropospheric column ozone did not change significantly either globally or over the tropical and subtropical latitudes.

Future local and remote influences on Mediterranean ozone air quality and climate forcing

NASA Astrophysics Data System (ADS)

Arnold, Steve; Martin, Maria Val; Emmons, Louisa; Rap, Alex; Heald, Colette; Lamarque, Jean-Francois; Tilmes, Simone

2013-04-01

The Mediterranean region is expected to display large increases in population over the coming decades, and to exhibit strong sensitivity to projected climate change, with increasing frequency of extreme summer temperatures and decreases in precipitation. Understanding of how these changes will affect atmospheric composition in the region is limited. The eastern Mediterranean basin has been shown to exhibit a pronounced summertime local maximum in tropospheric ozone, which impacts both local air quality and the atmospheric radiation balance. In summer, the region is subject to import of pollution from Northern Europe in the boundary layer and lower troposphere, from North American sources in the large-scale westerly flow of the free mid and upper-troposphere, as well as import of pollution lofted in the Asian monsoon and carried west to the eastern Mediterranean in anticyclonic flow in the upper troposphere over north Africa. In addition, interactions with the land-surface through biogenic emission sources and dry deposition play important roles in the Mediterranean ozone budget. Here we use the NCAR Community Earth System Model (CESM) to investigate how tropospheric ozone in the Mediterranean region responds to climate, land surface and global emissions changes between present day and 2050. We simulate climate and atmospheric composition for the year 2050, based on greenhouse gas abundances, trace gas and aerosol emissions and land cover and use from two representative concentration pathway (RCP) scenarios (RCP4.5 & RCP8.5), designed for use by the Coupled Model Intercomparison Project Phase 5(CMIP5) experiments in support of the IPCC. By comparing these simulations with a present-day scenario, we investigate the effects of predicted changes in climate and emissions on air quality and climate forcing over the Mediterranean region. The simulations suggest decreases in boundary layer ozone and sulfate aerosol throughout the tropospheric column over the Mediterranean under both RCP scenarios, and a significant increase in ozone between 5-10km. Using tagged regional NOy and tropospheric ozone tracers, we show that this ozone increase is coincident with an increase in easterly import of ozone and precursors in upper tropospheric outflow from Asian monsoon convection in 2050. We present a breakdown of the projected Mediterranean ozone changes by precursor source (anthropogenic and biogenic), and contributions due to changes in climate. Finally, we estimate the implications of the predicted changes in tropospheric composition for Mediterranean air quality and climate in 2050, and the consequences for the effectiveness of European policies aimed at protecting the region's climate and public health.

Microwave Limb Sounder/El Niño Watch - Water Vapor Measurement, October, 1997

NASA Image and Video Library

1997-10-30

This image shows atmospheric water vapor in Earth upper troposphere, about 10 kilometers 6 miles above the surface, as measured by NASA Microwave Limb Sounder MLS instrument flying aboard the Upper Atmosphere Research Satellite.

On the Relationship between Observed NLDN Lightning Strikes and Modeled Convective Precipitation Rates Parameterization of Lightning NOx Production in CMAQ

EPA Science Inventory

Lightning-produced nitrogen oxides (NOX=NO+NO2) in the middle and upper troposphere play an essential role in the production of ozone (O3) and influence the oxidizing capacity of the troposphere. Despite much effort in both observing and modeling lightning NOX during the past dec...

Changes in growth, leaf abscission, and biomass associated with seasonal tropospheric ozone exposures of Populus tremuloides clones and seedlings

Treesearch

D.F. Karnosky; Z.E. Gagnon; R.E. Dickson; M.D. Coleman; E.H. Lee; J.G. Isebrands

1996-01-01

The effects of single-season tropospheric ozone (03) exposures on growth, leaf abscission, and biomass of trembling aspen (Populus tremuloides Michx.) rooted cuttings and seedlings were studied. Plants were grown in the Upper Peninsula of Michigan in open-top chambers with 03 exposures that ranged from...

A Three-Dimensional Total Odd Nitrogen (NO(y)) Simulation During SONEX using a Stretched-Grid Chemical Transport Model

NASA Technical Reports Server (NTRS)

Allen, Dale; Pickering, Kenneth; Stenchikov, Georgiy; Thompson, Anne M.; Kondo, Yutaka

1999-01-01

The relative importance of various odd nitrogen (NOy) sources including lightning, aircraft, and surface emissions on upper tropospheric total odd nitrogen is illustrated as a first application of the three-dimensional Stretched-Grid University of Maryland/Goddard Chemical-Transport Model (SG-GCTM). The SG-GCTM has been developed to look at the effect of localized sources and/or small scale mixing processes on the large-scale or global chemical balance. For this simulation, the stretched-arid was chosen so that its maximum resolution is located over eastern North America and the North Atlantic; a region that includes most of the SONEX (the SASS (Subsonic Assessment) Ozone and Nitrogen Oxides Experiment) flight paths. The SONEX period (October-November 1997) is simulated by driving the SG-GCTM with assimilated data from the GEOS-STRAT DAS (Goddard Earth Observing System-STRAT Data Assimilation System). A new algorithm is used to parameterize the lightning, flash rates that are needed to calculate emissions of NOy by lightning. Model-calculated upper tropospheric NOy and NOy measurements from the NASA DC-8 aircraft are compared. Spatial variations in NOy were well captured especially with the stretched-grid run; however, model-calculated concentrations were often too high in the upper troposphere, particularly during the first several flights. The lightning algorithm does a reasonably good job; however, the use of emissions from observed lightning, flashes significantly improves the simulation on a few occasions, especially November 3, 1997, indicating that significant uncertainty remains in parameterizing lightning in CTMS. Aircraft emissions play a relatively minor role (about 12%) in the upper tropospheric NOY budget averaged along SONEX flight paths; however, the contribution of such emmissions is as large as about 30% during portions of some flights.

The Use of a Satellite Climatological Data Set to Infer Large Scale Three Dimensional Flow Characteristics

NASA Technical Reports Server (NTRS)

Lerner, Jeffrey A.; Jedlovec, Gary J.; Atkinson, Robert J.

1998-01-01

Ever since the first satellite image loops from the 6.3 micron water vapor channel on the METEOSAT-1 in 1978, there have been numerous efforts (many to a great degree of success) to relate the water vapor radiance patterns to familiar atmospheric dynamic quantities. The realization of these efforts is becoming evident with the merging of satellite derived winds into predictive models (Velden et al., 1997; Swadley and Goerss, 1989). Another parameter that has been quantified from satellite water vapor channel measurements is upper tropospheric relative humidity (UTH) (e.g., Soden and Bretherton, 1996; Schmetz and Turpeinen, 1988). These humidity measurements, in turn, can be used to quantify upper tropospheric water vapor and its transport to more accurately diagnose climate changes (Lerner et al., 1998; Schmetz et al. 1995a) and quantify radiative processes in the upper troposphere. Also apparent in water vapor imagery animations are regions of subsiding and ascending air flow. Indeed, a component of the translated motions we observe are due to vertical velocities. The few attempts at exploiting this information have been met with a fair degree of success. Picon and Desbois (1990) statistically related Meteosat monthly mean water vapor radiances to six standard pressure levels of the European Centre for Medium Range Weather Forecast (ECMWF) model vertical velocities and found correlation coefficients of about 0.50 or less. This paper presents some preliminary results of viewing climatological satellite water vapor data in a different fashion. Specifically, we attempt to infer the three dimensional flow characteristics of the mid- to upper troposphere as portrayed by GOES VAS during the warm ENSO event (1987) and a subsequent cold period in 1998.

Temperature Trends in the Tropical Upper Troposphere and Lower Stratosphere: Connections with Sea Surface Temperatures and Implications for Water Vapor and Ozone

NASA Technical Reports Server (NTRS)

Garfinkel, C. I.; Waugh, D. W.; Oman, L. D.; Wang, L.; Hurwitz, M. M.

2013-01-01

Satellite observations and chemistry-climate model experiments are used to understand the zonal structure of tropical lower stratospheric temperature, water vapor, and ozone trends. The warming in the tropical upper troposphere over the past 30 years is strongest near the Indo-Pacific warm pool, while the warming trend in the western and central Pacific is much weaker. In the lower stratosphere, these trends are reversed: the historical cooling trend is strongest over the Indo-Pacific warm pool and is weakest in the western and central Pacific. These zonal variations are stronger than the zonal-mean response in boreal winter. Targeted experiments with a chemistry-climate model are used to demonstrate that sea surface temperature (hereafter SST) trends are driving the zonal asymmetry in upper tropospheric and lower stratospheric tropical temperature trends. Warming SSTs in the Indian Ocean and in the warm pool region have led to enhanced moist heating in the upper troposphere, and in turn to a Gill-like response that extends into the lower stratosphere. The anomalous circulation has led to zonal structure in the ozone and water vapor trends near the tropopause, and subsequently to less water vapor entering the stratosphere. The radiative impact of these changes in trace gases is smaller than the direct impact of the moist heating. Projected future SSTs appear to drive a temperature and water vapor response whose zonal structure is similar to the historical response. In the lower stratosphere, the changes in water vapor and temperature due to projected future SSTs are of similar strength to, though slightly weaker than, that due directly to projected future CO2, ozone, and methane.

Increase in upper tropospheric and lower stratospheric aerosol levels and its potential connection with Asian pollution.

PubMed

Vernier, J-P; Fairlie, T D; Natarajan, M; Wienhold, F G; Bian, J; Martinsson, B G; Crumeyrolle, S; Thomason, L W; Bedka, K M

2015-02-27

Satellite observations have shown that the Asian Summer Monsoon strongly influences the upper troposphere and lower stratosphere (UTLS) aerosol morphology through its role in the formation of the Asian Tropopause Aerosol Layer (ATAL). Stratospheric Aerosol and Gas Experiment II solar occultation and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) lidar observations show that summertime UTLS Aerosol Optical Depth (AOD) between 13 and 18 km over Asia has increased by three times since the late 1990s. Here we present the first in situ balloon measurements of aerosol backscatter in the UTLS from Western China, which confirm high aerosol levels observed by CALIPSO since 2006. Aircraft in situ measurements suggest that aerosols at lower altitudes of the ATAL are largely composed of carbonaceous and sulfate materials (carbon/sulfur elemental ratio ranging from 2 to 10). Back trajectory analysis from Cloud-Aerosol Lidar with Orthogonal Polarization observations indicates that deep convection over the Indian subcontinent supplies the ATAL through the transport of pollution into the UTLS. Time series of deep convection occurrence, carbon monoxide, aerosol, temperature, and relative humidity suggest that secondary aerosol formation and growth in a cold, moist convective environment could play an important role in the formation of ATAL. Finally, radiative calculations show that the ATAL layer has exerted a short-term regional forcing at the top of the atmosphere of -0.1 W/m 2 in the past 18 years. Increase of summertime upper tropospheric aerosol levels over Asia since the 1990s Upper tropospheric enhancement also observed by in situ backscatter measurements Significant regional radiative forcing of -0.1 W/m 2 .

Decomposing variations of geopotential height in the troposphere and stratosphere into stationary and travelling waves

NASA Astrophysics Data System (ADS)

Guryanov, Vladimir; Eliseev, Alexey

2016-07-01

The ERA-Interim geopotential height in the Northern Hemisphere from November to March, 1992-2015 in the layer from between pressure levels 1000 mb and 1 mb is expanded into stationary and travelling zonal waves with zonal wavenumbers, k, from 1 to 10, and with periods, T, from 2 to 156 days (the so called Hayashi spectra). Among the studied waves, the largest amplitude is attained by the stationary and travelling waves with zonal wavenumber k=1 and with periods from 3 to 4 weeks in the upper stratosphere over the latitudinal belt 60-70oN. The stationary waves with k from 1 to 3 and with T from 2 to 3 weeks are most pronounced in the stratosphere. In turn, the largest amplitudes of the travelling waves with zonal wavenumbers k ≥ 5 are found in the troposphere. The dominant periods of the latter waves are about 1 week or slightly higher, and this dominant period basically decrease with increasing wavenumber. In the upper stratosphere, the eastward travelling waves generally dominate over westward ones. The only exception is the longest zonal mode with k=1, for which the amplitude of the westward travelling wave is larger than that for the eastward one. The period of the travelling waves dominating in the upper stratosphere is close to 3 weeks. In the upper troposphere, the amplitudes of the eastward waves with k from 4 to 10 is several-fold larger than those for their westward counterparts. The latter is reflected in the larger average wavenumber of the eastward travelling wave in comparison to that of the westarward one. The period of the gravest of the dominant travelling waves in the upper troposphere is close to one week, and it decreases to 2-4 days for the dominant travelling waves with k=8-10.

A Ring-‘Rain’ influence for Saturn’s Cloud Albedo and Temperatures? Evidence Pro or Con from Voyager, HST, and Cassini

NASA Astrophysics Data System (ADS)

West, Robert A.; Li, Liming

2015-11-01

J. E. P. Connerney [Geophys. Res. Lett, 13, 773-776, 1986] pointed out that ‘latitudinal variations in images of Saturn’s disk, upper atmospheric temperatures, and ionospheric electron densities are found in magnetic conjugacy with features in Saturn’s ring plane’, and proposed ‘that these latitudinal variations are the result of a variable influx of water, transported along magnetic field lines from sources in Saturn’s ring plane’. Observations of H3+ support a ring-ionosphere connection [O'Donoghue et al., Nature 496, 7444, 2013]. What about cloud albedo and temperature? Connerney attributed a hemispheric asymmetry in haze and temperature to an asymmetry in water flux and predicted that ‘the presently-observed north-south asymmetry (upper tropospheric temperatures, aerosols) will persist throughout the Saturn year’. We can now test these ideas with data from the Cassini mission, from the Hubble Space Telescope, and from ground-based observations. Analyses of ground-based images and especially Hubble data established that the hemispheric asymmetry of the aerosol population does change, and seasonal effects are dominant, although non-seasonal variations are also observed [Karkoschka and Tomasko, Icarus 179, 195-221, 2005]. Upper tropospheric temperatures also vary as expected in response to seasonal forcing [Fletcher et al., Icarus 208, 337-352, 2009]. Connerney also identified dark bands in Voyager Green-filter images on magnetic conjugacy with the E ring and edges of the A and B rings. In Cassini Green-filter images there is some correspondence between dark bands and ring features in magnetic conjugacy, but collectively the correlation is not strong. Cassini 727-nm methane band images do not suggest depletion of aerosols in the upper troposphere at ring edge magnetic conjugacy latitudes as proposed by Connerney. We conclude that ring rain does not have a significant influence on upper tropospheric aerosols and temperatures on Saturn. Part of this work was performed by the Jet Propulsion Lab, Calif. Institute of Technology.

Tropospheric Ozone Over North America

NASA Astrophysics Data System (ADS)

Oltmans, S. J.; Thompson, A. M.; Cooper, O. R.; Merrill, J. T.; Tarasick, D. W.; Newchurch, M. J.

2007-05-01

Ozone in the troposphere plays a significant role as an absorber of infrared radiation (greenhouse gas), in the cleansing capacity of the atmosphere as a precursor of hydroxol radical formation, and a regulated air pollutant capable of deleterious health and ecosystem effects. Knowledge of the ozone budget in the troposphere over North America (NA) is required to properly understand the various mechanisms that contribute to the measured distribution and to develop and test models capable of simulating and predicting this key player in atmospheric chemical and physical processes. Recent field campaigns including the 2004 and 2006 INTEX Ozone Network Studies (IONS) http:croc.gsfc.nasa.gov/intexb/ions06.html that have included intensive ozone profile measurements from ozonesondes provide a unique data set for describing tropospheric ozone over a significant portion of the North American continent. These campaigns have focused on the spring and summer seasons when tropospheric ozone over NA is particularly influenced by long-range transport processes, significant photochemical ozone production resulting from both anthropogenic and natural (lightning) precursor emissions, and exchange with the stratosphere. This study uses ozone profiles measured over NA in the latitude band from approximately 12-60N, extending from the tropics to the high mid latitudes, to describe the seasonal behavior of tropospheric ozone over NA with an emphasis on the spring and summer. This includes the variability within seasons at a particular site as well as the contrasts between the seasons. Emphasis is placed on the variations among the sites including latitudinal and longitudinal gradients and how these differ through the seasons and with altitude in the troposphere. Regional differences are most pronounced during the summer season likely reflecting the influence of a wider variation in processes influencing the tropospheric ozone distribution including lightning NOX production in the upper troposphere and active photochemistry from human emitted precursors in the lower troposphere. In all seasons, including the summer, transfer from the stratosphere significantly influences the upper tropospheric distribution at mid latitude (35-55N) locations. Although the seasonal maximum is found in spring in most locations and throughout much of the troposphere, this season tends to show less geographic variability compared to the summer. The FLEXPART Lagrangian tracer model is used to help identify processes associated with distinctive profile characteristics in the ozonesonde measurements.

Impact of Surface Emissions to the Zonal Variability of Tropical Tropospheric Ozone and Carbon Monoxide for November 2004

NASA Technical Reports Server (NTRS)

Bowman, K. W.; Jones, D.; Logan, J.; Worden, H.; Boersma, F.; Chang, R.; Kulawik, S.; Osterman, G.; Worden, J.

2008-01-01

The chemical and dynamical processes governing the zonal variability of tropical tropospheric ozone and carbon monoxide are investigated for November 2004 using satellite observations, in-situ measurements, and chemical transport models in conjunction with inverse-estimated surface emissions. Vertical ozone profile estimates from the Tropospheric Emission Spectrometer (TES) and ozone sonde measurements from the Southern Hemisphere Additional Ozonesondes (SHADOZ) network show the so called zonal 'wave-one' pattern, which is characterized by peak ozone concentrations (70-80 ppb) centered over the Atlantic, as well as elevated concentrations of ozone over Indonesia and Australia (60-70 ppb) in the lower troposphere. Observational evidence from TES CO vertical profiles and Ozone Monitoring Instrument (OMI) NO2 columns point to regional surface emissions as an important contributor to the elevated ozone over Indonesia. This contribution is investigated with the GEOS-Chem chemistry and transport model using surface emission estimates derived from an optimal inverse model, which was constrained by TES and Measurements Of Pollution In The Troposphere (MOPITT) CO profiles (Jones et al., 2007). These a posteriori estimates, which were over a factor of 2 greater than climatological emissions, reduced differences between GEOS-Chem and TES ozone observations by 30-40% and led to changes in GEOS-Chem upper tropospheric ozone of up to 40% over Indonesia. The remaining residual differences can be explained in part by upper tropospheric ozone produced from lightning NOx in the South Atlantic. Furthermore, model simulations from GEOS-Chem indicate that ozone over Indonesian/Australian is more sensitive to changes in surface emissions of NOx than ozone over the tropical Atlantic.

Dynamics and Composition of the Asian Summer Monsoon Anticyclone

NASA Astrophysics Data System (ADS)

Gottschaldt, K. D.; Schlager, H.; Baumann, R.; Bozem, H.; Cai, D. S.; Eyring, V.; Hoor, P. M.; Graf, P.; Joeckel, P.; Jurkat, T.; Voigt, C.; Grewe, V.; Zahn, A.; Ziereis, H.

2017-12-01

This study places trace gas observations in the upper-tropospheric Asian summer monsoon anticyclone (ASMA) obtained with the HALO research aircraft during the ESMVal campaign into the context of regional, intra-annual variability by hindcasts with the EMAC model. The simulations demonstrate that tropospheric trace gas profiles in the monsoon season are distinct from the rest of the year. Air uplifted from the lower troposphere to the tropopause layer dominates the eastern part of the ASMA's interior, while the western part is characterized by subsidence down to the mid-troposphere. Soluble compounds are being washed out when uplifted by convection in the eastern part, where lightning simultaneously replenishes reactive nitrogen in the upper troposphere. Net photochemical ozone production is significantly enhanced in the ASMA, contrasted by an ozone depleting regime in the mid-troposphere and more neutral conditions in autumn and winter. An analysis of multiple monsoon seasons in the simulation shows that stratospherically influenced tropopause layer air is regularly entrained at the eastern ASMA flank, and then transported in the southern fringe around the interior region. Observed and simulated tracer-tracer relations reflect photochemical O3 production, as well as in-mixing from the lower troposphere and the tropopause layer. The simulation additionally shows entrainment of clean air from the equatorial region by northerly winds at the western ASMA flank. Although the in situ measurements were performed towards the end of summer, the main ingredients needed for their interpretation are present throughout the monsoon season.Subseasonal dynamical instabilities of the ASMA effectively overcome horizontal transport barriers, occur quite frequently, and are of paramount importance for the trace gas composition of the ASMA and its outflow into regions around the world.

Sulfate geoengineering impact on methane transport and lifetime: results from the Geoengineering Model Intercomparison Project (GeoMIP)

NASA Astrophysics Data System (ADS)

Visioni, Daniele; Pitari, Giovanni; Aquila, Valentina; Tilmes, Simone; Cionni, Irene; Di Genova, Glauco; Mancini, Eva

2017-09-01

Sulfate geoengineering (SG), made by sustained injection of SO2 in the tropical lower stratosphere, may impact the CH4 abundance through several photochemical mechanisms affecting tropospheric OH and hence the methane lifetime. (a) The reflection of incoming solar radiation increases the planetary albedo and cools the surface, with a tropospheric H2O decrease. (b) The tropospheric UV budget is upset by the additional aerosol scattering and stratospheric ozone changes: the net effect is meridionally not uniform, with a net decrease in the tropics, thus producing less tropospheric O(1D). (c) The extratropical downwelling motion from the lower stratosphere tends to increase the sulfate aerosol surface area density available for heterogeneous chemical reactions in the mid-to-upper troposphere, thus reducing the amount of NOx and O3 production. (d) The tropical lower stratosphere is warmed by solar and planetary radiation absorption by the aerosols. The heating rate perturbation is highly latitude dependent, producing a stronger meridional component of the Brewer-Dobson circulation. The net effect on tropospheric OH due to the enhanced stratosphere-troposphere exchange may be positive or negative depending on the net result of different superimposed species perturbations (CH4, NOy, O3, SO4) in the extratropical upper troposphere and lower stratosphere (UTLS). In addition, the atmospheric stabilization resulting from the tropospheric cooling and lower stratospheric warming favors an additional decrease of the UTLS extratropical CH4 by lowering the horizontal eddy mixing. Two climate-chemistry coupled models are used to explore the above radiative, chemical and dynamical mechanisms affecting CH4 transport and lifetime (ULAQ-CCM and GEOSCCM). The CH4 lifetime may become significantly longer (by approximately 16 %) with a sustained injection of 8 Tg-SO2 yr-1 starting in the year 2020, which implies an increase of tropospheric CH4 (200 ppbv) and a positive indirect radiative forcing of sulfate geoengineering due to CH4 changes (+0.10 W m-2 in the 2040-2049 decade and +0.15 W m-2 in the 2060-2069 decade).

Sources of Springtime Tropospheric Ozone Over North China: A Modeling Analysis of Ozonesonde and Satellite Observations

NASA Astrophysics Data System (ADS)

Liu, H.; Chan, C.; Huang, J.; Zhang, Y.; Choi, H.; Crawford, J. H.; Considine, D. B.; Zheng, X.; Oltmans, S. J.; Liu, S. C.; Zhang, L.; Liu, X.; Thouret, V.

2012-12-01

Tropospheric ozone concentrations and emissions of NOx have both increased significantly over China as a result of rapid industrialization during the past decade. These trends degrade local and regional air quality and have important effects on background tropospheric ozone and surface ozone over downwind North Pacific and North America. In-situ observations of tropospheric ozone over China are therefore essential to testing and improving our understanding of the impact of Asian anthropogenic (versus natural) emissions and various chemical, physical, and dynamical processes on both regional and global tropospheric ozone. Despite their critical importance, in-situ observations of tropospheric ozone profiles over China have been few and far between in most of the country. To investigate the ensemble of processes that control the distribution, variability, and sources of springtime tropospheric ozone over China and its surrounding regions, an intensive ozonesonde sounding campaign, called Transport of Air Pollutants and Tropospheric Ozone over China (TAPTO-China), was conducted at nine locations across China in the springs of 2004 (South China) and 2005 (North China). In this paper, we use a global 3-D model of tropospheric chemistry (GEOS-Chem) to examine the characteristics of distribution and variability and quantify various sources of tropospheric ozone over North China by analysis of intensive ozonesonde data obtained at four stations in North / Northwest China during the second phase of TAPTO-China (April-May 2005). These four stations include Xining (36.43N, 101.45E), Beijing (39.80N, 116.18E), Longfengshan (44.44N, 127.36E), and Aletai (47.73N, 88.08E). We drive GEOS-Chem with two sets of assimilated meteorological observations (GEOS-4 and GEOS-5) from the Goddard Earth Observing System (GEOS) of the NASA Global Modeling and Assimilation Office (GAMO), allowing us to examine the impacts of variability in meteorology. We show that the observed tropospheric ozone mixing ratios exhibit strong spatio-temporal variability. The model generally simulates well the ozonesonde observations but tends to underestimate ozone in the upper troposphere over Beijing and Longfengshan. We find that Asian fossil fuel emissions, stratospheric ozone, African lightning NOx emissions, as well as intercontinental transport are the main contributors to tropospheric ozone over North China in spring. While the lower-tropospheric ozone is largely influenced by Asian fossil fuel emissions (except over Aletai, Northwest China), lightning NOx emissions have a larger impact on the upper-tropospheric ozone than Asian fossil fuel emissions (except over Longfengshan, Northeast China). Model simulations suggest that the European fossil fuel emissions contribute more to the lower-tropospheric ozone over Aletai than the Asian fossil fuel emissions. We will also show that tropospheric ozone measurements by Tropospheric Emission Spectrometer (TES) aboard the NASA EOS Aura satellite can be used to study tropospheric ozone variability at Xining.

Enhancement of free tropospheric ozone production by deep convection

NASA Technical Reports Server (NTRS)

Pickering, Kenneth E.; Thompson, Anne M.; Scala, John R.; Tao, Wei-Kuo; Simpson, Joanne

1994-01-01

It is found from model simulations of trace gas and meteorological data from aircraft campaigns that deep convection may enhance the potential for photochemical ozone production in the middle and upper troposphere by up to a factor of 60. Examination of half a dozen individual convective episodes show that the degree of enhancement is highly variable. Factors affecting enhancement include boundary layer NO(x) mixing ratios, differences in the strength and structure of convective cells, as well as variation in the amount of background pollution already in the free troposphere.

Cirrus microphysics and radiative transfer: Cloud field study on October 28, 1986

NASA Technical Reports Server (NTRS)

Kinne, Stefan; Ackerman, Thomas P.; Heymsfield, Andrew J.; Valero, Francisco P. J.; Sassen, Kenneth; Spinhirne, James D.

1990-01-01

The radiative properties of cirrus clouds present one of the unresolved problems in weather and climate research. Uncertainties in ice particle amount and size and, also, the general inability to model the single scattering properties of their usually complex particle shapes, prevent accurate model predictions. For an improved understanding of cirrus radiative effects, field experiments, as those of the Cirrus IFO of FIRE, are necessary. Simultaneous measurements of radiative fluxes and cirrus microphysics at multiple cirrus cloud altitudes allows the pitting of calculated versus measured vertical flux profiles; with the potential to judge current cirrus cloud modeling. Most of the problems in this study are linked to the inhomogeneity of the cloud field. Thus, only studies on more homogeneous cirrus cloud cases promises a possibility to improve current cirrus parameterizations. Still, the current inability to detect small ice particles will remain as a considerable handicap.

Investigation of the radiative forcings of thin cirrus in the tropical atmosphere using remote sensing data

NASA Astrophysics Data System (ADS)

Yue, Qing

Cirrus clouds have a unique influence on the climate system through their effects on the radiation budget of the earth and the atmosphere. To better understand the radiative effect of cirrus clouds, the microphysical and radiative properties of these clouds, especially tropical thin cirrus clouds, are studied based on both insitu cirrus measurements and satellite remote sensing observations. We perform a correlation analysis involving ice water content (IWC) and mean effective diameter (De) for applications to radiative transfer calculations and climate models using insitu measurements obtained from numerous field campaigns in the tropics, midlatitude, and Arctic regions. In conjunction with the study of cirrus clouds, we develop a high-resolution spectral infrared radiative transfer model for thin cirrus cloudy atmosphere, which is employed to retrieve De and cirrus optical depth from the Atmospheric Infrared Sounder (AIRS) infrared spectra. Numerical simulations show that cirrus cloudy radiances in the 800-1130 cm-1 thermal infrared window are sufficiently sensitive to variations in cirrus optical depth, and ice crystal size and habit. A number of nighttime thin cirrus scenes over the Atmospheric Radiation Measurement (ARM) program's Tropical Western Pacific sites have been selected from AIRS datasets for this study. The radiative transfer model is applied to these selected cases to determine cirrus optical depth, De and habit factors. Solar and infrared radiative forcings and heating rates produced by thin cirrus in the tropical atmosphere have been calculated using the retrieved cirrus optical and microphysical properties along with a modified Fu and Liou broadband radiative transfer scheme to analyze their dependence on cirrus cloud properties. Generally, larger TOA warming and smaller surface warming are associated with higher cirrus clouds. To cross-check the validity of our model, the collocated and coincident surface radiation measurements taken by ARM pyrgeometers have been compared with the calculated surface fluxes. Using the method developed in this study, regional radiation budget analyses can be carried out in the future study to quantitatively understand the role of thin cirrus clouds on solar and thermal infrared radiative forcings at the top of the atmosphere, the tropopause, and the surface.

AO/NAO Response to Climate Change. 1; Respective Influences of Stratospheric and Tropospheric Climate Changes

NASA Technical Reports Server (NTRS)

Rind, D.; Perlwitz, J.; Lonergan, P.

2005-01-01

We utilize the GISS Global Climate Middle Atmosphere Model and 8 different climate change experiments, many of them focused on stratospheric climate forcings, to assess the relative influence of tropospheric and stratospheric climate change on the extratropical circulation indices (Arctic Oscillation, AO; North Atlantic Oscillation, NAO). The experiments are run in two different ways: with variable sea surface temperatures (SSTs) to allow for a full tropospheric climate response, and with specified SSTs to minimize the tropospheric change. The results show that tropospheric warming (cooling) experiments and stratospheric cooling (warming) experiments produce more positive (negative) AO/NAO indices. For the typical magnitudes of tropospheric and stratospheric climate changes, the tropospheric response dominates; results are strongest when the tropospheric and stratospheric influences are producing similar phase changes. Both regions produce their effect primarily by altering wave propagation and angular momentum transports, but planetary wave energy changes accompanying tropospheric climate change are also important. Stratospheric forcing has a larger impact on the NAO than on the AO, and the angular momentum transport changes associated with it peak in the upper troposphere, affecting all wavenumbers. Tropospheric climate changes influence both the A0 and NAO with effects that extend throughout the troposphere. For both forcings there is often vertical consistency in the sign of the momentum transport changes, obscuring the difference between direct and indirect mechanisms for influencing the surface circulation.

The effects of aircraft on climate and pollution. Part II: 20-year impacts of exhaust from all commercial aircraft worldwide treated individually at the subgrid scale.

PubMed

Jacobson, M Z; Wilkerson, J T; Naiman, A D; Lele, S K

2013-01-01

This study examines the 20-year impacts of emissions from all commercial aircraft flights worldwide on climate, cloudiness, and atmospheric composition. Aircraft emissions from each individual flight worldwide were modeled to evolve from the subgrid to grid scale with the global model described and evaluated in Part I of this study. Simulations with and without aircraft emissions were run for 20 years. Aircraft emissions were found to be responsible for -6% of Arctic surface global warming to date, -1.3% of total surface global warming, and -4% of global upper tropospheric warming. Arctic warming due to aircraft slightly decreased Arctic sea ice area. Longer simulations should result in more warming due to the further increase in CO2. Aircraft increased atmospheric stability below cruise altitude and decreased it above cruise altitude. The increase in stability decreased cumulus convection in favor of increased stratiform cloudiness. Aircraft increased total cloud fraction on average. Aircraft increased surface and upper tropospheric ozone by -0.4% and -2.5%, respectively and surface and upper-tropospheric peroxyacetyl nitrate (PAN) by -0.1% and -5%, respectively. Aircraft emissions increased tropospheric OH, decreasing column CO and CH4 by -1.7% and -0.9%, respectively. Aircraft emissions increased human mortality worldwide by -620 (-240 to 4770) deaths per year, with half due to ozone and the rest to particulate matter less than 2.5 micrometers in diameter (PM2.5).

A growing threat to the ozone layer from short-lived anthropogenic chlorocarbons

NASA Astrophysics Data System (ADS)

Oram, David E.; Ashfold, Matthew J.; Laube, Johannes C.; Gooch, Lauren J.; Humphrey, Stephen; Sturges, William T.; Leedham-Elvidge, Emma; Forster, Grant L.; Harris, Neil R. P.; Mead, Mohammed Iqbal; Abu Samah, Azizan; Moi Phang, Siew; Ou-Yang, Chang-Feng; Lin, Neng-Huei; Wang, Jia-Lin; Baker, Angela K.; Brenninkmeijer, Carl A. M.; Sherry, David

2017-10-01

Large and effective reductions in emissions of long-lived ozone-depleting substance (ODS) are being achieved through the Montreal Protocol, the effectiveness of which can be seen in the declining atmospheric abundances of many ODSs. An important remaining uncertainty concerns the role of very short-lived substances (VSLSs) which, owing to their relatively short atmospheric lifetimes (less than 6 months), are not regulated under the Montreal Protocol. Recent studies have found an unexplained increase in the global tropospheric abundance of one VSLS, dichloromethane (CH2Cl2), which has increased by around 60 % over the past decade. Here we report dramatic enhancements of several chlorine-containing VSLSs (Cl-VSLSs), including CH2Cl2 and CH2ClCH2Cl (1,2-dichloroethane), observed in surface and upper-tropospheric air in East and South East Asia. Surface observations were, on occasion, an order of magnitude higher than previously reported in the marine boundary layer, whilst upper-tropospheric data were up to 3 times higher than expected. In addition, we provide further evidence of an atmospheric transport mechanism whereby substantial amounts of industrial pollution from East Asia, including these chlorinated VSLSs, can rapidly, and regularly, be transported to tropical regions of the western Pacific and subsequently uplifted to the tropical upper troposphere. This latter region is a major provider of air entering the stratosphere, and so this mechanism, in conjunction with increasing emissions of Cl-VSLSs from East Asia, could potentially slow the expected recovery of stratospheric ozone.

Annual variations of water vapor in the stratosphere and upper troposphere observed by the Stratospheric Aerosol and Gas Experiment II

NASA Technical Reports Server (NTRS)

Mccormick, M. P.; Chiou, E. W.; Mcmaster, L. R.; Chu, W. P.; Larsen, J. C.; Rind, D.; Oltmans, S.

1993-01-01

Data collected by the Stratospheric Aerosol and Gas Experiment II are presented, showing annual variations of water vapor in the stratosphere and the upper troposphere. The altitude-time cross sections of water vapor were found to exhibit annually repeatable patterns in both hemispheres, with a yearly minimum in water vapor appearing in both hemispheres at about the same time, supporting the concept of a common source for stratospheric dry air. A linear regression analysis was applied to the three-year data set to elucidate global values and variations of water vapor ratio.

A search for formic acid in the upper troposphere - A tentative identification of the 1105-per cm nu-6 band Q branch in high-resolution balloon-borne solar absorption spectra

NASA Technical Reports Server (NTRS)

Goldman, A.; Murcray, F. H.; Murcray, D. G.; Rinsland, C. P.

1984-01-01

Infrared solar absorption spectra recorded at 0.02-per cm resolution during a balloon flight from Alamogordo, NM (33 deg N), on March 23, 1981, have been analyzed for the possible presence of absorption by formic acid (HCOOH). An absorption feature at 1105 per cm has been tentatively identified in upper tropospheric spectra as due to the nu-6 band Q branch. A preliminary analysis indicates a concentration of about 0.6 ppbv and 0.4 ppbv near 8 and 10 km, respectively.

The nature of large-scale turbulence in the Jovian atmosphere

NASA Technical Reports Server (NTRS)

Mitchell, J. L.

1982-01-01

The energetics and spectral characteristis of quasi-geostrophic turbulence in Jupiter's atmosphere are examined using sequences of Voyager images and infrared temperature soundings. Using global wind measurements momentum transports associated with zonally symmetric stresses and turbulent stresses are quantified. Though a strong up-gradient flux of momentum by eddies was observed, measurements do not preclude the possibility that symmetric stresses play a critical role in maintaining the mean zonal circulation. Strong correlation between the observed meridional distribution of eddy-scale kinetic energy and available potential energy suggests coupling between the observed cloudtop turbulent motions and the upper tropospheric thermodynamics. An Oort energy budget for Jupiter's upper troposphere is formulated.

Impact of convection on stratospheric humidity and upper tropospheric clouds

NASA Astrophysics Data System (ADS)

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

2017-12-01

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

Estimation of the global climate effect of brown carbon

NASA Astrophysics Data System (ADS)

Zhang, A.; Wang, Y.; Zhang, Y.; Weber, R. J.; Song, Y.

2017-12-01

Carbonaceous aerosols significantly affect global radiative forcing and climate through absorption and scattering of sunlight. Black carbon (BC) and brown carbon (BrC) are light-absorbing carbonaceous aerosols. The global distribution and climate effect of BrC is uncertain. A recent study suggests that BrC absorption is comparable to BC in the upper troposphere over biomass burning region and that the resulting heating tends to stabilize the atmosphere. Yet current climate models do not include proper treatments of BrC. In this study, we derived a BrC global biomass burning emission inventory from Global Fire Emissions Database 4 (GFED4) and developed a BrC module in the Community Atmosphere Model version 5 (CAM5) of Community Earth System Model (CESM) model. The model simulations compared well to BrC observations of the Studies of Emissions, Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys (SEAC4RS) and Deep Convective Clouds and Chemistry Project (DC-3) campaigns and includes BrC bleaching. Model results suggested that BrC in the upper troposphere due to convective transport is as important an absorber as BC globally. Upper tropospheric BrC radiative forcing is particularly significant over the tropics, affecting the atmosphere stability and Hadley circulation.

Comparing upper tropospheric humidity data from microwave satellite instruments and tropical radiosondes

NASA Astrophysics Data System (ADS)

Moradi, Isaac; Buehler, Stefan A.; John, Viju O.; Eliasson, Salomon

2010-12-01

Atmospheric humidity plays an important role in the Earth's climate. Microwave satellite data provide valuable humidity observations in the upper troposphere with global coverage. In this study, we compare upper tropospheric humidity (UTH) retrieved from the Advanced Microwave Sounding Unit and the Microwave Humidity Sounder against radiosonde data measured at four of the central facilities of the Atmospheric Radiation Measurement program. The Atmospheric Radiative Transfer Simulator (ARTS) was used to simulate satellite brightness temperatures from the radiosonde profiles. Strong ice clouds were filtered out, as their influence on microwave measurements leads to incorrect UTH values. Day and night radiosonde profiles were analyzed separately to take into account the radiosonde radiation bias. The comparison between radiosonde and satellite is most meaningful for data in cloud-free, nighttime conditions and with a time difference of less than 2 hr. We found good agreement between the two data sets. The satellite data were slightly moister than the radiosonde data, with a mean difference of 1%-2.3% relative humidity (RH), depending on the radiosonde site. Monthly gridded data were also compared and showed a slightly larger mean difference of up to 3.3% RH, which can be explained by sampling issues.

Correction Technique for Raman Water Vapor Lidar Signal-Dependent Bias and Suitability for Water Wapor Trend Monitoring in the Upper Troposphere

NASA Technical Reports Server (NTRS)

Whiteman, D. N.; Cadirola, M.; Venable, D.; Calhoun, M.; Miloshevich, L; Vermeesch, K.; Twigg, L.; Dirisu, A.; Hurst, D.; Hall, E.;

Characterization of Upper-Troposphere Water Vapor Measurements during AFWEX Using LASE

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

Ferrare, Richard; Browell, E. V.; Ismail, S.

Water vapor profiles from NASA's Lidar Atmospheric Sensing Experiment (LASE) system acquired during the ARM/FIRE Water Vapor Experiment (AFWEX) are used to characterize upper troposphere water vapor (UTWV) measured by ground-based Raman lidars, radiosondes, and in situ aircraft sensors over the Department of Energy Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) site in northern Oklahoma. LASE was deployed from the NASA DC-8 aircraft and measured water vapor over the ARM SGP Central Facility (CF) site during seven flights between November 27 and December 10, 2000. Initially, the DOE ARM SGP Cloud and Radiation Testbed (CART) Raman lidar (CARL) UTWVmore » profiles were about 5-7% wetter than LASE in the upper troposphere, and the Vaisala RS80-H radiosonde profiles were about 10% drier than LASE between 8-12 km. Scaling the Vaisala water vapor profiles to match the precipitable water vapor (PWV) measured by the ARM SGP microwave radiometer (MWR) did not change these results significantly. By accounting for an overlap correction of the CARL water vapor profiles and by employing schemes designed to correct the Vaisala RS80-H calibration method and account for the time response of the Vaisala RS80H water vapor sensor, the average differences between the CARL and Vaisala radiosonde upper troposphere water vapor profiles are reduced to about 5%, which is within the ARM goal of mean differences of less than 10%. The LASE and DC-8 in situ Diode Laser Hygrometer (DLH) UTWV measurements generally agreed to within about 3 to 4%. The DC-8 in situ frost point cryogenic hygrometer and Snow White chilled mirror measurements were drier than the LASE, Raman lidars, and corrected Vaisala RS80H measurements by about 10-25% and 10-15%, respectively. Sippican (formerly VIZ manufacturing) carbon hygristor radiosondes exhibited large variabilities and poor agreement with the other measurements. PWV derived from the LASE profiles agreed to within about 3% on average with PWV derived from the ARM SGP microwave radiometer. The agreement between the LASE and MWR PWV and the LASE and CARL UTWV measurements supports the hypotheses that MWR measurements of the 22 GHz water vapor line can accurately constrain the total water vapor amount and that the CART Raman lidar, when calibrated using the MWR PWV, can provide an accurate, stable reference for characterizing upper troposphere water vapor.« less

The life-cycle of upper-tropospheric jet streams identified with a novel data segmentation algorithm

NASA Astrophysics Data System (ADS)

Limbach, S.; Schömer, E.; Wernli, H.

2010-09-01

Jet streams are prominent features of the upper-tropospheric atmospheric flow. Through the thermal wind relationship these regions with intense horizontal wind speed (typically larger than 30 m/s) are associated with pronounced baroclinicity, i.e., with regions where extratropical cyclones develop due to baroclinic instability processes. Individual jet streams are non-stationary elongated features that can extend over more than 2000 km in the along-flow and 200-500 km in the across-flow direction, respectively. Their lifetime can vary between a few days and several weeks. In recent years, feature-based algorithms have been developed that allow compiling synoptic climatologies and typologies of upper-tropospheric jet streams based upon objective selection criteria and climatological reanalysis datasets. In this study a novel algorithm to efficiently identify jet streams using an extended region-growing segmentation approach is introduced. This algorithm iterates over a 4-dimensional field of horizontal wind speed from ECMWF analyses and decides at each grid point whether all prerequisites for a jet stream are met. In a single pass the algorithm keeps track of all adjacencies of these grid points and creates the 4-dimensional connected segments associated with each jet stream. In addition to the detection of these sets of connected grid points, the algorithm analyzes the development over time of the distinct 3-dimensional features each segment consists of. Important events in the development of these features, for example mergings and splittings, are detected and analyzed on a per-grid-point and per-feature basis. The output of the algorithm consists of the actual sets of grid-points augmented with information about the particular events, and of the so-called event graphs, which are an abstract representation of the distinct 3-dimensional features and events of each segment. This technique provides comprehensive information about the frequency of upper-tropospheric jet streams, their preferred regions of genesis, merging, splitting, and lysis, and statistical information about their size, amplitude and lifetime. The presentation will introduce the technique, provide example visualizations of the time evolution of the identified 3-dimensional jet stream features, and present results from a first multi-month "climatology" of upper-tropospheric jets. In the future, the technique can be applied to longer datasets, for instance reanalyses and output from global climate model simulations - and provide detailed information about key characteristics of jet stream life cycles.

Possibility of weather and climate change by active experiments

NASA Astrophysics Data System (ADS)

Avakyan, Sergey; Voronin, Nikolai; Troitsky, Arkadil; Chernouss, Sergey

The anonymous remote impact on weather and climatic characteristics permanently discussed in last decade despite the fact that the UN Convention forbid to use the weather as a weapon since the 1970's. For example, Ross N. Hoffman proposed to operate weather conditions by direct flux of microwave radiation from space. This flux could affects on water vapor in the troposphere. The development of an optically thin cirrus cloud is especially promising situation because even the formation of the aeroplane cirrus-track can stimulate disturbance, which is necessary to development of an initial cyclone stage. Our studies confirmed the results of experiments of NIRFI on sporadic appearance of the microwave radiation of ionospheric nature during periods of solar flares and geomagnetic storms, and also during work of the "Sura” ionospheric heating facility. Such microwave radiation also occurs, when precipitation of particles from radiation belts stimulated by work of powerful (˜ 1 MW) navigation transmitters at frequencies ˜ 5 - 22 kHz. This effect was discovered by measurements at the Intercosmos satellite Bulgaria-1300 in 1982, and recently was confirmed by the spacecraft DEMETER measurements Leningrad State University measurements 1990-1991 at altitude about 2100 m proved the impact of microwave radiation from solar radiobursts on the amount of water vapor in the upper troposphere column. 25 - 40% of the vapour are involved into the formation of clusters decreased an atmospheric transparency. Papers of State Optical Institute (2008) proposed to account the electron-stimulated precipitation from the radiation belts over powerful radio transmitters (registered on the spacecraft DEMETER) as an additional source of microwave radiation of the ionosphere. This source can participate in the condensation-cluster mechanism changes of atmospheric transparency by the same way as natural geomagnetic storm. (Grach et al) also recorded stream microwave ionospheric disturbance stimulated by HF heating in an experiment at the "Sura" even earlier (2002) This led to the appearance of Rydberg states exited by the accelerated electrons impact (Troitskii et al.) found that at the threshold of sensitivity of radiometric measurements in 0.006 g/cm(2) observed a decrease in the water vapor content in the troposphere at 0.05 g/cm(2) at a total natural content 1.8-2.1 g/cm(2) in a special experiment on the basis of "Sura" facility to study the cluster-condensation mechanism. These reductions were observed almost simultaneously with the work of facility and time delay was about 1 minute. It should be noted that the heating power was 20 times less than the maximal reached power in such facilities. The extending of the experimental possibilities on the clustering in the troposphere by ionospheric microwave radiation (SPbSU) supposedly can give us the same result as an active impact on the ionosphere by heating facilities and power transmitters. We believe that manifestation of the described effects give a contribution to change of climatic characteristics: cloud formation, cyclogenesis, temperature anomalies and precipitation. This follows from the results of the analysis of correlation between cloud cover, temperature and precipitation and solar-geomagnetic activity over secular and annual (2 - 5 years) scales. Authors propose to use an optical method for detecting emissions of atomic oxygen in those electronic transitions between Rydberg states, which wavelengths are located in the atmospheric spectral windows in the visible and IR ranges. It will be the test for contribution of the Rydberg excitation processes in the formation of the flux of microwave active effects of the ionosphere. Corresponding lines for the visible region of the spectrum in low-lying Rydberg levels (with principal quantum number n of about 10) are in the blue region of the spectrum: 448.4 nm (the electronic transition is 11d - 3p), 452,3 nm (10d - 3p), and 457.7 nm (9d - 3p). Application of the optical recording channel in active experiments (i.e., at a fixed space-time artificial ionospheric disturbances) allow: - to confirm experimentally the Rydberg channel of generating microwave fluxes from the ionosphere at its perturbations; - to offer remote monitoring as international control of sources of artificial influence on weather and climatic characteristics.

Retrieval of Aerosol Optical Depth Under Thin Cirrus from MODIS: Application to an Ocean Algorithm

NASA Technical Reports Server (NTRS)

Lee, Jaehwa; Hsu, Nai-Yung Christina; Sayer, Andrew Mark; Bettenhausen, Corey

2013-01-01

A strategy for retrieving aerosol optical depth (AOD) under conditions of thin cirrus coverage from the Moderate Resolution Imaging Spectroradiometer (MODIS) is presented. We adopt an empirical method that derives the cirrus contribution to measured reflectance in seven bands from the visible to shortwave infrared (0.47, 0.55, 0.65, 0.86, 1.24, 1.63, and 2.12 µm, commonly used for AOD retrievals) by using the correlations between the top-of-atmosphere (TOA) reflectance at 1.38 micron and these bands. The 1.38 micron band is used due to its strong absorption by water vapor and allows us to extract the contribution of cirrus clouds to TOA reflectance and create cirrus-corrected TOA reflectances in the seven bands of interest. These cirrus-corrected TOA reflectances are then used in the aerosol retrieval algorithm to determine cirrus-corrected AOD. The cirrus correction algorithm reduces the cirrus contamination in the AOD data as shown by a decrease in both magnitude and spatial variability of AOD over areas contaminated by thin cirrus. Comparisons of retrieved AOD against Aerosol Robotic Network observations at Nauru in the equatorial Pacific reveal that the cirrus correction procedure improves the data quality: the percentage of data within the expected error +/-(0.03 + 0.05 ×AOD) increases from 40% to 80% for cirrus-corrected points only and from 80% to 86% for all points (i.e., both corrected and uncorrected retrievals). Statistical comparisons with Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) retrievals are also carried out. A high correlation (R = 0.89) between the CALIOP cirrus optical depth and AOD correction magnitude suggests potential applicability of the cirrus correction procedure to other MODIS-like sensors.

Role of atmospheric heating over the South China Sea and western Pacific regions in modulating Asian summer climate under the global warming background

NASA Astrophysics Data System (ADS)

He, Bian; Yang, Song; Li, Zhenning

2016-05-01

The response of monsoon precipitation to global warming, which is one of the most significant climate change signals at the earth's surface, exhibits very distinct regional features, especially over the South China Sea (SCS) and adjacent regions in boreal summer. To understand the possible atmospheric dynamics in these specific regions under the global warming background, changes in atmospheric heating and their possible influences on Asian summer climate are investigated by both observational diagnosis and numerical simulations. Results indicate that heating in the middle troposphere has intensified in the SCS and western Pacific regions in boreal summer, accompanied by increased precipitation, cloud cover, and lower-tropospheric convergence and decreased sea level pressure. Sensitivity experiments show that middle and upper tropospheric heating causes an east-west feedback pattern between SCS and western Pacific and continental South Asia, which strengthens the South Asian High in the upper troposphere and moist convergence in the lower troposphere, consequently forcing a descending motion and adiabatic warming over continental South Asia. When air-sea interaction is considered, the simulation results are overall more similar to observations, and in particular the bias of precipitation over the Indian Ocean simulated by AGCMs has been reduced. The result highlights the important role of air-sea interaction in understanding the changes in Asian climate.

Coordinated profiling of stratospheric intrusions and transported pollution by the Tropospheric Ozone Lidar Network (TOLNet) and NASA Alpha Jet experiment (AJAX): Observations and comparison to HYSPLIT, RAQMS, and FLEXPART

NASA Astrophysics Data System (ADS)

Langford, A. O.; Alvarez, R. J.; Brioude, J.; Evan, S.; Iraci, L. T.; Kirgis, G.; Kuang, S.; Leblanc, T.; Newchurch, M. J.; Pierce, R. B.; Senff, C. J.; Yates, E. L.

2018-02-01

Ground-based lidars and ozonesondes belonging to the NASA-supported Tropospheric Ozone Lidar Network (TOLNet) are used in conjunction with the NASA Alpha Jet Atmospheric eXperiment (AJAX) to investigate the transport of stratospheric ozone and entrained pollution into the lower troposphere above the United States on May 24-25, 2013. TOLNet and AJAX measurements made in California, Nevada, and Alabama are compared to tropospheric ozone retrievals from the Atmospheric Infrared Sounder (AIRS), to back trajectories from the NOAA Air Resources Laboratory (ARL) Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model, and to analyses from the NOAA/NESDIS Real-time Air Quality Modeling System (RAQMS) and FLEXPART particle dispersion model. The measurements and model analyses show much deeper descent of ozone-rich upper tropospheric/lower stratospheric air above the Desert Southwest than above the Southeast, and comparisons to surface measurements from regulatory monitors reporting to the U.S. EPA Air Quality System (AQS) suggest that there was a much greater surface impact in the Southwest including exceedances of the 2008 National Ambient Air Quality Standard (NAAQS) of 0.075 ppm in both Southern California and Nevada. Our analysis demonstrates the potential benefits to be gained by supplementing the existing surface ozone network with coordinated upper air observations by TOLNet.

The Relative Importance of Random Error and Observation Frequency in Detecting Trends in Upper Tropospheric Water Vapor

NASA Technical Reports Server (NTRS)

Whiteman, David N.; Vermeesch, Kevin C.; Oman, Luke D.; Weatherhead, Elizabeth C.

2011-01-01

Recent published work assessed the amount of time to detect trends in atmospheric water vapor over the coming century. We address the same question and conclude that under the most optimistic scenarios and assuming perfect data (i.e., observations with no measurement uncertainty) the time to detect trends will be at least 12 years at approximately 200 hPa in the upper troposphere. Our times to detect trends are therefore shorter than those recently reported and this difference is affected by data sources used, method of processing the data, geographic location and pressure level in the atmosphere where the analyses were performed. We then consider the question of how instrumental uncertainty plays into the assessment of time to detect trends. We conclude that due to the high natural variability in atmospheric water vapor, the amount of time to detect trends in the upper troposphere is relatively insensitive to instrumental random uncertainty and that it is much more important to increase the frequency of measurement than to decrease the random error in the measurement. This is put in the context of international networks such as the Global Climate Observing System (GCOS) Reference Upper-Air Network (GRUAN) and the Network for the Detection of Atmospheric Composition Change (NDACC) that are tasked with developing time series of climate quality water vapor data.

The relative importance of random error and observation frequency in detecting trends in upper tropospheric water vapor

NASA Astrophysics Data System (ADS)

Whiteman, David N.; Vermeesch, Kevin C.; Oman, Luke D.; Weatherhead, Elizabeth C.

2011-11-01

Recent published work assessed the amount of time to detect trends in atmospheric water vapor over the coming century. We address the same question and conclude that under the most optimistic scenarios and assuming perfect data (i.e., observations with no measurement uncertainty) the time to detect trends will be at least 12 years at approximately 200 hPa in the upper troposphere. Our times to detect trends are therefore shorter than those recently reported and this difference is affected by data sources used, method of processing the data, geographic location and pressure level in the atmosphere where the analyses were performed. We then consider the question of how instrumental uncertainty plays into the assessment of time to detect trends. We conclude that due to the high natural variability in atmospheric water vapor, the amount of time to detect trends in the upper troposphere is relatively insensitive to instrumental random uncertainty and that it is much more important to increase the frequency of measurement than to decrease the random error in the measurement. This is put in the context of international networks such as the Global Climate Observing System (GCOS) Reference Upper-Air Network (GRUAN) and the Network for the Detection of Atmospheric Composition Change (NDACC) that are tasked with developing time series of climate quality water vapor data.

Characterizing relative humidity with respect to ice in midlatitude cirrus clouds as a function of atmospheric state

NASA Astrophysics Data System (ADS)

Dzambo, Andrew M.; Turner, David D.

2016-10-01

Midlatitude cirrus cloud macrophysical and microphysical properties have been shown in previous studies to vary seasonally and in various large-scale dynamical regimes, but relative humidity with respect to ice (RHI) within cirrus clouds has not been studied extensively in this context. Using a combination of radiosonde and millimeter-wavelength cloud radar data, we identify 1076 cirrus clouds spanning a 7 year period from 2004 to 2011. These data are separated into five classes using a previously published algorithm that is based largely on synoptic conditions. Using these data and classification scheme, we find that RHI in cirrus clouds varies seasonally. Variations in cirrus cloud RHI exist within the prescribed classifications; however, most of the variations are within the measurement uncertainty. Additionally, with the exception of nonsummer class cirrus, these variations are not statistically significant. We also find that cirrus cloud occurrence is not necessarily correlated with higher observed values of RHI. The structure of RHI in cirrus clouds varies more in thicker clouds, which follows previous studies showing that macrophysical and microphysical variability increases in thicker cirrus clouds.

The EOS Aura Mission

NASA Technical Reports Server (NTRS)

Schoeberl, Mark R.; Douglass, A. R.; Hilsenrath, E.; Luce, M.; Barnett, J.; Beer, R.; Waters, J.; Gille, J.; Levelt, P. F.; DeCola, P.;

On the Relationship Between Observed NLDN Lightning Strikes and Modeled Convective Precipitation Rates: Parameterization of Lightning NOx Production in CMAQ

EPA Science Inventory

In the middle and upper troposphere, lightning is the most important source of nitrogen oxides (NO X = NO + NO 2), which play an essential role in the production of ozone (O 3) and influence the oxidizing capacity of the troposphere (Murray 2016). Despite much effort in both obse...

Lightning NOx Production in CMAQ: Part II - Parameterization Based on Relationship between Observed NLDN Lightning Strikes and Modeled Convective Precipitation Rates

EPA Science Inventory

Lightning-produced nitrogen oxides (NOX=NO+NO2) in the middle and upper troposphere play an essential role in the production of ozone (O3) and influence the oxidizing capacity of the troposphere. Despite much effort in both observing and modeling lightning NOX during the past dec...

Observed NO/NO2 Ratios in the Upper Troposphere Imply Errors in NO-NO2-O3 Cycling Kinetics or an Unaccounted NOx Reservoir

NASA Astrophysics Data System (ADS)

Silvern, R. F.; Jacob, D. J.; Travis, K. R.; Sherwen, T.; Evans, M. J.; Cohen, R. C.; Laughner, J. L.; Hall, S. R.; Ullmann, K.; Crounse, J. D.; Wennberg, P. O.; Peischl, J.; Pollack, I. B.

2018-05-01

Observations from the SEAC4RS aircraft campaign over the southeast United States in August-September 2013 show NO/NO2 concentration ratios in the upper troposphere that are approximately half of photochemical equilibrium values computed from Jet Propulsion Laboratory (JPL) kinetic data. One possible explanation is the presence of labile NOx reservoir species, presumably organic, decomposing thermally to NO2 in the instrument. The NO2 instrument corrects for this artifact from known labile HNO4 and CH3O2NO2 NOx reservoirs. To bridge the gap between measured and simulated NO2, additional unaccounted labile NOx reservoir species would have to be present at a mean concentration of 40 ppt for the SEAC4RS conditions (compared with 197 ppt for NOx). An alternative explanation is error in the low-temperature rate constant for the NO + O3 reaction (30% 1-σ uncertainty in JPL at 240 K) and/or in the spectroscopic data for NO2 photolysis (20% 1-σ uncertainty). Resolving this discrepancy is important for understanding global budgets of tropospheric oxidants and for interpreting satellite observations of tropospheric NO2 columns.

The Plunger Hypothesis: an overview of a new theory of stratosphere-troposphere dynamic coupling

NASA Astrophysics Data System (ADS)

Clark, S.; Baldwin, M. P.; Stephenson, D.

2015-12-01

I will demonstrate the advantages of a new method of quantifying polar stratosphere-troposphere coupling by considering large-scale movements of mass into and out of the polar stratosphere. This project aims to use these mass movements to explain pressure and temperature anomalies throughout the polar troposphere and lower stratosphere in the aftermath of extreme stratospheric events. We hypothesise that these mass movements are induced by deposition of momentum by breaking waves in the stratosphere, slowing the wintertime polar vortex, and so are associated with sudden stratospheric warmings (SSWs). Such a mass movement in the upper stratosphere acts to compress the polar atmosphere below it in the manner of a plunger. In this way the pressure anomaly in the upper polar stratosphere 'controls' the pressure and temperature anomalies below by adiabatic compression of the polar atmospheric column. Better understanding this method of control will allow us to use stratospheric data to improve medium-range forecasting ability in the troposphere. One of the key innovations featured in this project is considering pressure and temperature fields at fixed geopotential surfaces, allowing for the easy observation of mass movement into and out of a polar cap region (which we have defined as north of 65N) as a function of altitude. Reanalysis data considered in this manner demonstrates a relationship between tropospheric pressure anomalies and stratospheric anomalies in the polar cap, and so a way to predict tropospheric variability given stratospheric information. This work forms part of a three and a half year PhD project.

Sensitivity of Methane Lifetime and Transport to Sulfate Geoengineering

NASA Astrophysics Data System (ADS)

Aquila, V.; Pitari, G.; Tilmes, S.; Cionni, I.; de Luca, N.; Di Genova, G.; Iachetti, D.

2014-12-01

Sulfate geoengineering, made by sustained injection of SO2 in the tropical lower stratosphere, may impact the abundance of tropospheric methane through several photochemical mechanisms affecting the tropospheric OH abundance and hence the methane lifetime. Changes of the stratospheric Brewer-Dobson circulation also play a role in the upper tropospheric CH4 transport. Three mechanisms lead to lower OH concentrations and a longer CH4 lifetime: (a) solar radiation scattering increases the planetary albedo and cools the surface, with a tropospheric water vapor decrease as a response to this cooling. (b) The tropospheric UV budget is upset by the additional aerosol scattering and stratospheric ozone changes: the net effect is meridionally not uniform, with a net decrease in the tropics, thus producing less tropospheric O(1D). (c) The extra-tropical downwelling motion from the lower stratosphere tends to increase the sulfate aerosol surface area density available for heterogeneous chemical reactions in the mid-upper troposphere, thus reducing the amount of NOx and tropospheric O3 production. On the other hand, the tropical lower stratosphere is warmed by solar and planetary radiation absorption by the aerosols. The heating rates perturbation are strongly latitude dependent, producing a significant change of the pole-to-equator temperature gradient and mean zonal wind distribution, with a net increase of tropical upwelling. A stronger meridional component of the Brewer-Dobson circulation increases the extra-tropical stratosphere to troposphere transport of CH4 poorer air, resulting in less CH4 transported in the UTLS. The net effect on tropospheric OH may be positive or negative depending on the net result of different superimposed species perturbations in the UTLS, i.e. CH4 (negative), NOy and O3 (positive). Three climate-chemistry coupled models are used here to explore the above radiative, chemical and dynamical mechanisms affecting the methane lifetime (ULAQ-CCM, GEOSCCM, CCSM-CAM4). First results show that the CH4 lifetime may become significantly longer (by about 10%) with a sustained injection of 2.5 Tg-S/yr started in year 2020, which implies an increase of tropospheric CH4 (200 ppbv) and a positive indirect radiative forcing of sulfate geoengineering due to CH4 changes (+0.1 W/m2 in the 2045).

Simulations of the effect of a warmer climate on atmospheric humidity

NASA Technical Reports Server (NTRS)

Del Genio, Anthony D.; Lacis, Andrew A.; Ruedy, Reto A.

1991-01-01

Increases in the concentration of water vapor constitute the single largest positive feedback in models of global climate warming caused by greenhouse gases. It has been suggested that sinking air in the regions surrounding deep cumulus clouds will dry the upper troposphere and eliminate or reverse the direction of water vapor feedback. This hypothesis has been tested by performing an idealized simulation of climate change with two different versions of a climate model which both incorporate drying due to subsidence of clear air but differ in their parameterization of moist convection and stratiform clouds. Despite increased drying of the upper troposphere by cumulus clouds, upper-level humidity increases in the warmer climate because of enhanced upward moisture transport by the general circulation and increased accumulation of water vapor and ice at cumulus cloud tops.

Effects of Subsonic Aircraft on Aerosols and Cloudiness in the Upper Troposphere and Lower Stratosphere

NASA Technical Reports Server (NTRS)

Detwiler, Andrew G.

1997-01-01

This work was accomplished primarily by Allison G. Wozniak, a graduate research assistant who has completed the Master of Science in Meteorology program at the South Dakota School of Mines and Technology. Ms. Wozniak was guided and assisted in her work by L. R. Johnson and the principal investigator. Invaluable guidance was supplied by Dr. James Holdeman, NASA Lewis, the manager of the Global Atmospheric Sampling Program (GASP). Dr. Gregory Nastrom, St. Cloud (Minnesota) State University, who has used the GASP data set to provide unique views of the distribution of ozone, clouds, and atmospheric waves and turbulence, in the upper troposphere/lower stratosphere region, was also extremely helpful. Finally, Dr. Terry Deshler, University of Wyoming, supplied observations from the university's upper atmospheric monitoring program for comparison to GASP data.

Added value of far-infrared radiometry for remote sensing of ice clouds

NASA Astrophysics Data System (ADS)

Libois, Quentin; Blanchet, Jean-Pierre

2017-06-01

Several cloud retrieval algorithms based on satellite observations in the infrared have been developed in the last decades. However, these observations only cover the midinfrared (MIR, λ < 15 μm) part of the spectrum, and none are available in the far-infrared (FIR, λ≥ 15 μm). Using the optimal estimation method, we show that adding a few FIR channels to existing spaceborne radiometers would significantly improve their ability to retrieve ice cloud radiative properties. For clouds encountered in the polar regions and the upper troposphere, where the atmosphere is sufficiently transparent in the FIR, using FIR channels would reduce by more than 50% the uncertainties on retrieved values of optical thickness, effective particle diameter, and cloud top altitude. Notably, this would extend the range of applicability of current retrieval methods to the polar regions and to clouds with large optical thickness, where MIR algorithms perform poorly. The high performance of solar reflection-based algorithms would thus be reached in nighttime conditions. Since the sensitivity of ice cloud thermal emission to effective particle diameter is approximately 5 times larger in the FIR than in the MIR, using FIR observations is a promising venue for studying ice cloud microphysics and precipitation processes. This is highly relevant for cirrus clouds and convective towers. This is also essential to study precipitation in the driest regions of the atmosphere, where strong feedbacks are at play between clouds and water vapor. The deployment in the near future of a FIR spaceborne radiometer is technologically feasible and should be strongly supported.

Insights on the Feasibility, Modeling and Field Testing of Cirrus Cloud Thinning from Satellite Remote Sensing

NASA Astrophysics Data System (ADS)

Mitchell, D. L.; Garnier, A.; Mejia, J.; Avery, M. A.; Erfani, E.

2016-12-01

To date, it is not clear whether the climate intervention method known as cirrus cloud thinning (CCT) can be viable since it requires cirrus clouds to form through homogeneous ice nucleation (henceforth hom) and some recent GCM studies predict cirrus are formed primarily through heterogeneous ice nucleation (henceforth het). A new CALIPSO infrared retrieval method has been developed for single-layer cirrus cloud that measures the temperature dependence of their layer-averaged number concentration N, effective diameter De and ice water content for optical depths (OD) between 0.3 and 3.0. Based on N, the prevailing ice nucleation mechanism (hom or het) can be estimated as a function of temperature, season, latitude and surface type. These satellite results indicate that seeding cirrus clouds at high latitudes during winter may produce significant global surface cooling. This is because hom often appears to dominate over land during winter north of 30°N latitude while the same appears true for most of the Southern Hemisphere (south of 30°S) during all seasons. Moreover, the sampled cirrus cloud frequency of occurrence in the Arctic is at least twice as large during winter relative to other seasons, while frequency of occurrence in the Antarctic peaks in the spring and is second-highest during winter. During Arctic winter, a combination of frequent hom cirrus, maximum cirrus coverage and an extreme or absent sun angle produces the maximum seasonal cirrus net radiative forcing (warming). Thus a reduction in OD and coverage (via CCT) for these cirrus clouds could yield a significant net cooling effect. From these CALIPSO retrievals, De-T relationships are generated as a function of season, latitude and surface type (land vs. ocean). These will be used in CAM5 to estimate De and the ice fall speed, from which the cirrus radiative forcing will be estimated during winter north of 30°latitude, where hom cirrus are common. Another CAM5 simulation will replace the hom cirrus De-T relationships with those corresponding to het cirrus (at similar latitudes). In this way the potential cooling from CCT in the Northern Hemisphere will be estimated. If a field campaign was ever conducted for testing the efficacy of CCT, this CALIPSO retrieval could be used to help determine whether the seeded hom cirrus were transformed into het cirrus.

Susceptibility of Aerosol Retrievals to Cirrus Contamination during the BASE-ASIA Campaign and at Global View

NASA Astrophysics Data System (ADS)

Huang, J.; Hsu, C.; Tsay, S.; Jeong, M.; Holben, B.; Berkoff, T.; Welton, E. J.

2010-12-01

Cirrus clouds, particularly subvisual high thin cirrus with low optical thickness, are difficult to be screened out in the operational aerosol retrieval algorithms. In this study, we jointly used ground measurements (AERONET, aerosol robotic network; MPLNET, micro-pulse lidar network) and satellite data (MODIS, moderate resolution imaging spectroradiometer; CALIPSO, cloud-aerosol lidar and infrared pathfinder satellite observations) to closely examine the susceptibility of satellite retrieved and ground measured aerosol optical thickness (AOT) to cirrus contamination. Special cases were selected at Phimai (102.56°E, 15.18°N, also known as Pimai), Thailand, during the Biomass-burning Aerosols in South East-Asia: Smoke Impact Assessment (BASE-ASIA) campaign (February-May 2006). By taking advantage of space-borne and ground lidars in detecting cirrus clouds, we conducted the statistical analysis by matching up concurrent cirrus and aerosol observations at four levels: MPLNET vs AERONET, MPLNET vs MODIS, CALIPSO vs AERONET, and CALIPSO vs MODIS. Results suggest that the susceptibility of current operational AERONET and MODIS AOT products to cirrus features strong regional and seasonal variability, particularly in cirrus prevailing regions. The values of AOT and aerosol particle size appear to be larger for cirrus-susceptible cases than those for confidently non-cirrus cases, a possible signature of cirrus contamination. To further assess cirrus-screening algorithms, we tested 8 MODIS-derived cirrus screening parameters against lidar observations for their performance and robustness on cirrus screening: apparent reflectance at 1.38μm (R1.38), cirrus reflectance at 0.66μm (CR0.66), CR0.66 cirrus flag, reflectance ratio between 1.38μm and 0.66μm (RR1.38/0.66), reflectance ratio between 1.38μm and 1.24μm (RR1.38/1.24), brightness temperature difference between 8.6μm and 11μm (BTD8.6-11), brightness temperature difference between 11μm and 12μm (BTD11-12), and cloud phase infrared approach (CPIR). The quantitative findings from the study suggest that particular caution and careful evaluations on cirrus contamination in the satellite and ground AOT measurements should be exercised before they are used for aerosol related climatic forcing studies.

On the structure of climate variability near the tropopause and its relationship to equatorial planetary waves

NASA Astrophysics Data System (ADS)

Grise, Kevin M.

The tropopause is an important interface in the climate system, separating the unique dynamical, chemical, and radiative regimes of the troposphere and stratosphere. Previous studies have demonstrated that the long-term mean structure and variability of the tropopause results from a complex interaction of stratospheric and tropospheric processes. This project provides new insight into the processes involved in the global tropopause region through two perspectives: (1) a high vertical resolution climatology of static stability and (2) an observational analysis of equatorial planetary waves. High vertical resolution global positioning system radio occultation profiles are used to document fine-scale features of the global static stability field near the tropopause. Consistent with previous studies, a region of enhanced static stability, known as the tropopause inversion layer (TIL), exists in a narrow layer above the extratropical tropopause and is strongest over polar regions during summer. However, in the tropics, the TIL possesses a unique horizontally and vertically varying structure with maxima located at ˜17 and ˜19 km. The upper feature peaks during boreal winter and has its largest magnitude between 10º and 15º latitude in both hemispheres; the lower feature exhibits a weaker seasonal cycle and is centered at the Equator. The spatial structure of both features resembles the equatorial planetary wave response to the climatological distribution of deep convection. Equatorial planetary waves not only dominate the climatological-mean general circulation near the tropical tropopause but also play an important role in its intraseasonal and interannual variability. The structure of the equatorial planetary waves emerges as the leading pattern of variability of the zonally asymmetric tropical atmospheric circulation. Regressions on an index of the equatorial planetary waves reveal that they are associated with a distinct pattern of equatorially symmetric climate variability characterized by variations in: (1) the distribution of convection in the deep tropics; (2) the eddy momentum flux convergence and the zonal-mean zonal wind in the tropical upper troposphere; (3) the mean meridional circulation of the tropical and subtropical troposphere; (4) temperatures in the tropical upper troposphere, the tropical lower stratosphere, and the subtropical troposphere of both hemispheres; and (5) the amplitude of the upper tropospheric anticyclones that straddle the Equator over the western tropical Pacific Ocean. The pulsation of the equatorial planetary waves in time provides a framework for interpreting a broad range of climate phenomena. Variability in the equatorial planetary waves is associated with variability in the tropical TIL and is linked to both the El Nino-Southern Oscillation and the Madden-Julian Oscillation (MJO). Evidence is presented that suggests that the MJO can be viewed as the linear superposition of: (1) the pulsation of the equatorial planetary waves at a fixed location and (2) a propagating component. Variability in the equatorial planetary waves may also contribute to variability in troposphere/stratosphere exchange and the width of the tropical belt.

Characteristics of cirrus clouds and tropical tropopause layer: Seasonal variation and long-term trends

NASA Astrophysics Data System (ADS)

Pandit, Amit Kumar; Gadhavi, Harish; Ratnam, M. Venkat; Jayaraman, A.; Raghunath, K.; Rao, S. Vijaya Bhaskara

2014-12-01

In the present study, characteristics of tropical cirrus clouds observed during 1998-2013 using a ground-based lidar located at Gadanki (13.5°N, 79.2°E), India, are presented. Altitude occurrences of cirrus clouds as well as its top and base heights are estimated using the advanced mathematical tool, wavelet covariance transform (WCT). The association of observed cirrus cloud properties with the characteristics of tropical tropopause layer (TTL) is investigated using co-located radiosonde measurements available since 2006. In general, cirrus clouds occurred for about 44% of the total lidar observation time (6246 h). The most probable altitude at which cirrus clouds occurr is 14.5 km. The occurrence of cirrus clouds exhibited a strong seasonal dependence with maximum occurrence during monsoon season (76%) and minimum occurrence during winter season (33%) which is consistent with the results reported recently using space-based lidar measurements. Most of the time, cirrus top was located within the TTL (between cold point and convective outflow level) while cirrus base occurred near the convective outflow level. The geometrical thickness of the cirrus cloud is found to be higher during monsoon season compared to winter and there exists a weak inverse relation with TTL thickness. During the observation period the percentage occurrence of cirrus clouds near the tropopause showed an 8.4% increase at 70% confidence level. In the last 16 years, top and base heights of cirrus cloud increased by 0.56 km and 0.41 km, respectively.

Detecting Thin Cirrus in Multiangle Imaging Spectroradiometer Aerosol Retrievals

NASA Technical Reports Server (NTRS)

Pierce, Jeffrey R.; Kahn, Ralph A.; Davis, Matt R.; Comstock, Jennifer M.

2010-01-01

Thin cirrus clouds (optical depth (OD) < 03) are often undetected by standard cloud masking in satellite aerosol retrieval algorithms. However, the Mu]tiangle Imaging Spectroradiometer (MISR) aerosol retrieval has the potential to discriminate between the scattering phase functions of cirrus and aerosols, thus separating these components. Theoretical tests show that MISR is sensitive to cirrus OD within Max{0.05 1 20%l, similar to MISR's sensitivity to aerosol OD, and MISR can distinguish between small and large crystals, even at low latitudes, where the range of scattering angles observed by MISR is smallest. Including just two cirrus components in the aerosol retrieval algorithm would capture typical MISR sensitivity to the natural range of cinus properties; in situations where cirrus is present but the retrieval comparison space lacks these components, the retrieval tends to underestimate OD. Generally, MISR can also distinguish between cirrus and common aerosol types when the proper cirrus and aerosol optical models are included in the retrieval comparison space and total column OD is >-0.2. However, in some cases, especially at low latitudes, cirrus can be mistaken for some combinations of dust and large nonabsorbing spherical aerosols, raising a caution about retrievals in dusty marine regions when cirrus is present. Comparisons of MISR with lidar and Aerosol Robotic Network show good agreement in a majority of the cases, but situations where cirrus clouds have optical depths >0.15 and are horizontally inhomogeneous on spatial scales shorter than 50 km pose difficulties for cirrus retrieval using the MISR standard aerosol algorithm..

Thermodynamic constraint on the depth of the global tropospheric circulation.

PubMed

Thompson, David W J; Bony, Sandrine; Li, Ying

2017-08-01

The troposphere is the region of the atmosphere characterized by low static stability, vigorous diabatic mixing, and widespread condensational heating in clouds. Previous research has argued that in the tropics, the upper bound on tropospheric mixing and clouds is constrained by the rapid decrease with height of the saturation water vapor pressure and hence radiative cooling by water vapor in clear-sky regions. Here the authors contend that the same basic physics play a key role in constraining the vertical structure of tropospheric mixing, tropopause temperature, and cloud-top temperature throughout the globe. It is argued that radiative cooling by water vapor plays an important role in governing the depth and amplitude of large-scale dynamics at extratropical latitudes.

Simulated forecast error and climate drift resulting from the omission of the upper stratosphere in numerical models

NASA Technical Reports Server (NTRS)

Boville, Byron A.; Baumhefner, David P.

1990-01-01

Using an NCAR community climate model, Version I, the forecast error growth and the climate drift resulting from the omission of the upper stratosphere are investigated. In the experiment, the control simulation is a seasonal integration of a medium horizontal general circulation model with 30 levels extending from the surface to the upper mesosphere, while the main experiment uses an identical model, except that only the bottom 15 levels (below 10 mb) are retained. It is shown that both random and systematic errors develop rapidly in the lower stratosphere with some local propagation into the troposphere in the 10-30-day time range. The random growth rate in the troposphere in the case of the altered upper boundary was found to be slightly faster than that for the initial-condition uncertainty alone. However, this is not likely to make a significant impact in operational forecast models, because the initial-condition uncertainty is very large.

Future local and remote influences on Mediterranean ozone air quality and climate forcing

NASA Astrophysics Data System (ADS)

Arnold, S.; Val Martin, M.; Heald, C. L.; Lamarque, J.; Tilmes, S.; Emmons, L. K.

2012-12-01

The Mediterranean region is expected to display large increases in population over the coming decades, and to exhibit strong sensitivity to projected climate change, with increasing frequency of extreme summer temperatures and decreases in precipitation. Understanding of how these changes will affect atmospheric composition in the region is limited. The eastern Mediterranean basin has been shown to exhibit a pronounced summertime local maximum in tropospheric ozone, which impacts both local air quality and the atmospheric radiation balance. The Mediterranean troposphere is influenced by a diverse range of sources, including contributions from inter-continental import, in addition to local anthropogenic and biogenic sources. In summer, the region is subject to import of pollution from Northern Europe in the boundary layer and lower troposphere, from North American sources in the large-scale westerly flow of the free mid and upper-troposphere, as well as import of pollution lofted in the Asian monsoon and carried west to the eastern Mediterranean in anticyclonic flow in the upper troposphere over north Africa. Future atmospheric composition in the Mediterranean is likely to be sensitive to projected changes in emissions from these different sources, as well as changes in transport patterns and dry deposition fluxes under future climate conditions. We use the NCAR Community Earth System Model (CESM) to simulate climate and atmospheric composition for the 2050s, based on greenhouse gas abundances, trace gas and aerosol emissions and land cover and use from two representative concentration pathway (RCP) scenarios (RCP4.5 & RCP8.5), designed for use by the IPCC Coupled Model Intercomparison Project Phase 5 (CMIP5) experiments. By comparing these simulations with a present-day scenario, we investigate the effects of predicted changes in climate and emissions on air quality and climate forcing over the Mediterranean region. The simulations suggest decreases in boundary layer ozone and sulfate aerosol throughout the tropospheric column over the Mediterranean under both RCP scenarios, and an increase in ozone of up to 14 ppbv between 5-10km. This ozone increase is coincident with an increase in easterly import of ozone precursors in upper tropospheric outflow from Asian monsoon convection. We present a breakdown of contributions to the projected ozone changes from changes in emissions and from climate-driven changes. We estimate the implications of the predicted changes in tropospheric composition for Mediterranean air quality and climate in 2050, and the consequences for the effectiveness of European policies aimed at protecting the region's climate and public health.

Characterization of Transport Errors in Chemical Forecasts from a Global Tropospheric Chemical Transport Model

NASA Technical Reports Server (NTRS)

Bey, I.; Jacob, D. J.; Liu, H.; Yantosca, R. M.; Sachse, G. W.

2004-01-01

We propose a new methodology to characterize errors in the representation of transport processes in chemical transport models. We constrain the evaluation of a global three-dimensional chemical transport model (GEOS-CHEM) with an extended dataset of carbon monoxide (CO) concentrations obtained during the Transport and Chemical Evolution over the Pacific (TRACE-P) aircraft campaign. The TRACEP mission took place over the western Pacific, a region frequently impacted by continental outflow associated with different synoptic-scale weather systems (such as cold fronts) and deep convection, and thus provides a valuable dataset. for our analysis. Model simulations using both forecast and assimilated meteorology are examined. Background CO concentrations are computed as a function of latitude and altitude and subsequently subtracted from both the observed and the model datasets to focus on the ability of the model to simulate variability on a synoptic scale. Different sampling strategies (i.e., spatial displacement and smoothing) are applied along the flight tracks to search for systematic model biases. Statistical quantities such as correlation coefficient and centered root-mean-square difference are computed between the simulated and the observed fields and are further inter-compared using Taylor diagrams. We find no systematic bias in the model for the TRACE-P region when we consider the entire dataset (i.e., from the surface to 12 km ). This result indicates that the transport error in our model is globally unbiased, which has important implications for using the model to conduct inverse modeling studies. Using the First-Look assimilated meteorology only provides little improvement of the correlation, in comparison with the forecast meteorology. These general statements can be refined when the entire dataset is divided into different vertical domains, i.e., the lower troposphere (less than 2 km), the middle troposphere (2-6 km), and the upper troposphere (greater than 6 km). The best agreement between the observations and the model is found in the lower and middle troposphere. Downward displacements in the lower troposphere provide a better fit with the observed value, which could indicate a problem in the representation of boundary layer height in the model. Significant improvement is also found for downward and southward displacements in the upper troposphere. There are several potential sources of errors in our simulation of the continental outflow in the upper troposphere which could lead to such biases, including the location and/or the strength of deep convective cells as well as that of wildfires in Southeast Asia.

(abstract) Infrared Cirrus and Future Space Based Astronomy

NASA Technical Reports Server (NTRS)

Gautier, T. N.

1993-01-01

A review of the known properties of the distribution of infrared cirrus is followed by a discussion of the implications of cirrus on observations from space. Probable limitations on space observations due to IR cirrus.

High levels of reactive gaseous mercury observed at a high elevation research laboratory in the Rocky Mountains

NASA Astrophysics Data System (ADS)

Faïn, X.; Obrist, D.; Hallar, A. G.; McCubbin, I.; Rahn, T.

2009-10-01

The chemical cycling and spatiotemporal distribution of mercury in the troposphere is poorly understood. We measured gaseous elemental mercury (GEM), reactive gaseous mercury (RGM) and particulate mercury (HgP) along with carbon monoxide (CO), ozone (O3), aerosols, and meteorological variables at Storm Peak Laboratory at an elevation of 3200 m a.s.l., in Colorado, from 28 April to 1 July 2008. The mean mercury concentrations were 1.6 ng m-3 (GEM), 20 pg m-3 (RGM) and 9 pg m-3 (HgP). We observed eight events of strongly enhanced atmospheric RGM levels with maximum concentrations up to 137 pg m-3. RGM enhancement events lasted for long time periods of 2 to 6 days showing both enriched level during daytime and nighttime when other tracers (e.g., aerosols) showed different representations of boundary layer air and free tropospheric air. During seven of these events, RGM was inversely correlated to GEM (RGM/GEM regression slope ~-0.1), but did not exhibit correlations with ozone, carbon monoxide, or aerosol concentrations. Relative humidity was the dominant factor affecting RGM levels with high RGM levels always present whenever relative humidity was below 40 to 50%. We conclude that RGM enhancements observed at Storm Peak Laboratory were not induced by pollution events and were related to oxidation of tropospheric GEM. High RGM levels were not limited to upper tropospheric or stratospherically influenced air masses, indicating that entrainment processes and deep vertical mixing of free tropospheric air enriched in RGM may lead to high RGM levels throughout the troposphere and into the boundary layer over the Western United States. Based on backtrajectory analysis and a lack of mass balance between RGM and GEM, atmospheric production of RGM may also have occurred in some distance allowing for scavenging and/or deposition of RGM prior to reaching the laboratory. Our observations provide evidence that the tropospheric pool of mercury is frequently enriched in divalent mercury, that high RGM levels are not limited to upper tropospheric air masses, but that the build-up of high RGM in the troposphere is limited to the presence of dry air.

The role of isoprene oxidation in the tropospheric ozone budget in the tropics

NASA Technical Reports Server (NTRS)

Brewer, D. A.; Levine, J. S.

1985-01-01

A comprehensive chemical mechanism for the oxidation of isoprene (a hydrocarbon, C5H8 emitted primarily by vegetation) by OH and O3 in the troposphere was developed and incorporated into a one-dimensional steady-state photochemical model of the troposphere. Flux boundary conditions for NOx (NO + NO2), HNO3, O3, and CO were used to investigate the changes produced in the tropospheric concentrations and integrated column of ozone from including isoprene chemistry in the model. Two calculations were performed at 15 deg N latitude for annual conditions using identical flux boundary conditions for NOx, HNO3, O3, and CO; in one calculation, the chemistry describing isoprene oxidation was included while in the other it was not. Both sets of calculations included reactions describing the chemistry of anthropogenic nonmethane hydrocarbons. The calculations showed decreases in concentrations of ozone throughout the troposphere when isoprene chemistry was included. Concentrations of NOx and HNO3 increased in the lower troposphere and decreased in the upper troposphere while concentrations of CO and PAN increased throughout the troposphere when isoprene chemistry was included. Implications of this study to the budgets of these species in the tropics is discussed.

Dynamical Meteorology of the Equatorial and Extratropical Stratosphere

NASA Technical Reports Server (NTRS)

Dunkerton, Tomothy

1999-01-01

Observational studies were performed of westward propagating synoptic scale waves in the tropical troposphere, the structure of monsoon circulations in the upper troposphere and lower stratosphere, and zonally propagating features in deep tropical convection. The effect of the quasi-biennial oscillation (QBO) were investigated, and a numerical study of the QBO was performed using a two-dimensional model, highlighting the role of gravity waves in the momentum balance of the QBO. Vertical coupling of the troposphere and stratosphere was examined in polar regions on intraseasonal and interannual timescales. A deep circumpolar mode was discovered, now known as the Arctic Oscillation.

What controls the seasonal cycle of columnar methane observed by GOSAT over different regions in India?

NASA Astrophysics Data System (ADS)

Chandra, Naveen; Hayashida, Sachiko; Saeki, Tazu; Patra, Prabir K.

2017-10-01

Methane (CH4) is one of the most important short-lived climate forcers for its critical roles in greenhouse warming and air pollution chemistry in the troposphere, and the water vapor budget in the stratosphere. It is estimated that up to about 8 % of global CH4 emissions occur from South Asia, covering less than 1 % of the global land. With the availability of satellite observations from space, variability in CH4 has been captured for most parts of the global land with major emissions, which were otherwise not covered by the surface observation network. The satellite observation of the columnar dry-air mole fractions of methane (XCH4) is an integrated measure of CH4 densities at all altitudes from the surface to the top of the atmosphere. Here, we present an analysis of XCH4 variability over different parts of India and the surrounding cleaner oceanic regions as measured by the Greenhouse gases Observation SATellite (GOSAT) and simulated by an atmospheric chemistry-transport model (ACTM). Distinct seasonal variations of XCH4 have been observed over the northern (north of 15° N) and southern (south of 15° N) parts of India, corresponding to the peak during the southwestern monsoon (July-September) and early autumn (October-December) seasons, respectively. Analysis of the transport, emission, and chemistry contributions to XCH4 using ACTM suggests that a distinct XCH4 seasonal cycle over northern and southern regions of India is governed by both the heterogeneous distributions of surface emissions and a contribution of the partial CH4 column in the upper troposphere. Over most of the northern Indian Gangetic Plain regions, up to 40 % of the peak-to-trough amplitude during the southwestern (SW) monsoon season is attributed to the lower troposphere ( ˜ 1000-600 hPa), and ˜ 40 % to uplifted high-CH4 air masses in the upper troposphere ( ˜ 600-200 hPa). In contrast, the XCH4 seasonal enhancement over semi-arid western India is attributed mainly ( ˜ 70 %) to the upper troposphere. The lower tropospheric region contributes up to 60 % in the XCH4 seasonal enhancement over the Southern Peninsula and oceanic region. These differences arise due to the complex atmospheric transport mechanisms caused by the seasonally varying monsoon. The CH4 enriched air mass is uplifted from a high-emission region of the Gangetic Plain by the SW monsoon circulation and deep cumulus convection and then confined by anticyclonic wind in the upper tropospheric heights ( ˜ 200 hPa). The anticyclonic confinement of surface emission over a wider South Asia region leads to a strong contribution of the upper troposphere in the formation of the XCH4 peak over northern India, including the semi-arid regions with extremely low CH4 emissions. Based on this analysis, we suggest that a link between surface emissions and higher levels of XCH4 is not always valid over Asian monsoon regions, although there is often a fair correlation between surface emissions and XCH4. The overall validity of ACTM simulation for capturing GOSAT observed seasonal and spatial XCH4 variability will allow us to perform inverse modeling of XCH4 emissions in the future using XCH4 data.

Seasonal Variability in Tropospheric Ozone Distribution Over Qatar

NASA Astrophysics Data System (ADS)

Ayoub, Mohammed; Ackermann, Luis

2015-04-01

We report on the vertical distribution and seasonal variability in tropospheric ozone over the Middle East through one year of weekly ozonesondes launched from Doha, Qatar during 2014. A total of 49 2Z-V7 DMT/EN-SCI Electrochemical Concentration Cell (ECC) ozonesondes employing a 1% buffered potassium iodide solution (KI), coupled with iMet-1-RS GPS radiosondes were launched around 1300 local time. The authors used the SkySonde telemetry software (developed by CIRES and NOAA/ESRL) and developed robust in-house data quality assurance and validation methodologies. The average height of the thermal tropopause is between 15-17.5 km (125-85 hPa). Monthly average relative humidity around the tropopause shows an enhancement during the months of June through the beginning of October. Monthly average temperature profiles show the development of the subtropical subsidence inversion around 5-6 km (450-520 hPa) between the months of April through October. The subsidence inversion is strongest during the months of June and July and is accompanied by a sharp drop in relative humidity over a 100-300 m in the vertical. The monthly average ozone background concentration between the Planetary Boundary Layer (PBL) height and the subsidence inversion increases from 50 ppb in the winter to almost 80 ppb in the summer months. An enhancement of up to 50% in the average ozone in the mid-to-upper troposphere (above the subsidence inversion) is strongest during the summer months (June through September) and results in average concentrations between 80-100 ppb. In the upper troposphere (above 13 km/200 hPa) ozone concentrations are highest during the spring and summer months. This is coupled with a drop in the average height of the tropopause. HYSPLIT back-trajectory analysis shows the enhancement in mid-to-upper tropospheric ozone in the summer is due to persistent high pressure over the Middle East between the months of June through September. Evidence of Stratosphere-Troposphere Exchange (STE) in the winter and spring months and Monsoonal outflow observed in late summer are also reflected in the ozone profiles and HYSPLIT back-trajectories.

Evaluation of Near-Tropopause Ozone Distributions in the Global Modeling Initiative Combined Stratosphere/Troposphere Model with Ozonesonde Data

NASA Technical Reports Server (NTRS)

Considine, David B.; Logan, Jennifer A.; Olsen, Mark A.

2008-01-01

The NASA Global Modeling Initiative has developed a combined stratosphere/troposphere chemistry and transport model which fully represents the processes governing atmospheric composition near the tropopause. We evaluate model ozone distributions near the tropopause, using two high vertical resolution monthly mean ozone profile climatologies constructed with ozonesonde data, one by averaging on pressure levels and the other relative to the thermal tropopause. Model ozone is high biased at the SH tropical and NH midlatitude tropopause by approx. 45% in a 4 deg. latitude x 5 deg. longitude model simulation. Increasing the resolution to 2 deg. x 2.5 deg. increases the NH tropopause high bias to approx. 60%, but decreases the tropical tropopause bias to approx. 30%, an effect of a better-resolved residual circulation. The tropopause ozone biases appear not to be due to an overly vigorous residual circulation or excessive stratosphere/troposphere exchange, but are more likely due to insufficient vertical resolution or excessive vertical diffusion near the tropopause. In the upper troposphere and lower stratosphere, model/measurement intercomparisons are strongly affected by the averaging technique. NH and tropical mean model lower stratospheric biases are less than 20%. In the upper troposphere, the 2 deg. x 2.5 deg. simulation exhibits mean high biases of approx. 20% and approx. 35% during April in the tropics and NH midlatitudes, respectively, compared to the pressure averaged climatology. However, relative-to-tropopause averaging produces upper troposphere high biases of approx. 30% and 70% in the tropics and NH midlatitudes. This is because relative-to-tropopause averaging better preserves large cross-tropopause O3 gradients, which are seen in the daily sonde data, but not in daily model profiles. The relative annual cycle of ozone near the tropopause is reproduced very well in the model Northern Hemisphere midlatitudes. In the tropics, the model amplitude of the near tropopause annual cycle is weak. This is likely due to the annual amplitude of mean vertical upwelling near the tropopause, which analysis suggests is approx. 30% weaker than in the real atmosphere.

The Tropospheric cooling and the Stratospheric warming at Tirunelveli during the Annular Solar Eclipse of 15 January, 2010

NASA Astrophysics Data System (ADS)

Nelli, Narendra Reddy; Choudhary, Raj Kumar; Rao, Kusuma

The UTLS region, a transition region between the troposphere and the stratosphere is of concern to climate scientists as its temperature variations are crucial in determining the water vapour and the other trace gases transport between the two regions, which inturn determine the radiative warming and cooling of the troposphere and the stratosphere. To examine, the temperature variations from surface to lower stratosphere,a major experiment facility was set up for upper air and surface measurements during the Annular Solar Eclipse (ASE) of January 15, 2010 at Tirunelveli (8.72 N, 77.81 E) located in 94% eclipse path in the southern peninsular India. The instruments,namely, 1. high resolution GPS radiosonde system, 2. an instrumented 15 m high Mini Boundary Layer Mast, 3. an instrumented 1 m high Near Surface Mast (NSM), radiation and other ground sensors were operated during the period 14-19 Jan, 2010. The ASE of January 15, 2010 was unique being the longest in duration (9 min, 15.3 sec) among the similar ones that occurred in the past. The major inference from an analysis of surface and upper air measurements is the occurrence of troposphere cooling during the eclipse with the peak cooling of 5 K at 15 km height with respect to no-eclispe conditions. Also, intense warming in the stratosphere is observed with the peak warming of 7 K at 19 km height.Cooling of the Troposphere as the eclipse advanced and the revival to its normal temperature is clearly captured in upper air measurements. The downward vertical velocities observed at 100 hPa in NCEP Re-analyses, consistent with the tropospheric cooling during the ASE window, may be causing the stratospheric warming. Partly, these vertical velocities could be induced by the mesoscale circulation associated with the mesoscale convective system that prevailed parallel to the eclipse path as described in METEOSAT imageries of brightness temperatures from IR channel. Further analysis is being carried out to quantify the variations in turbulent parameters during ASE window using the high resolution GPS Radiosonde data.

Tropospheric Vertical Distribution of Tropical Atlantic Ozone Observed by TES during the Northern African Biomass Burning Season

NASA Technical Reports Server (NTRS)

Jourdain, L.; Worden, H. M.; Worden, J. R.; Bowman, K.; Li, Q.; Eldering, A.; Kulawik, S. S.; Osterman, G.; Boersma, K. F.; Fisher, B.;

Balloon Borne Soundings of Water Vapor, Ozone and Temperature in the Upper Tropospheric and Lower Stratosphere as Part of the Second SAGE III Ozone Loss and Validation Experiment (SOLVE-2)

NASA Technical Reports Server (NTRS)

Voemel, Holger

2004-01-01

The main goal of our work was to provide in situ water vapor and ozone profiles in the upper troposphere and lower stratosphere as reference measurements for the validation of SAGE III water vapor and ozone retrievals. We used the NOAA/CMDL frost point hygrometer and ECC ozone sondes on small research balloons to provide continuous profiles between the surface and the mid stratosphere. The NOAA/CMDL frost point hygrometer is currently the only lightweight balloon borne instrument capable of measuring water vapor between the lower troposphere and middle stratosphere. The validation measurements were based in the arctic region of Scandinavia for northern hemisphere observations and in New Zealand for southern hemisphere observations and timed to coincide with overpasses of the SAGE III instrument. In addition to SAGE III validation we also tried to coordinate launches with other instruments and studied dehydration and transport processes in the Arctic stratospheric vortex.

Stratospheric Aerosol and Gas Experiment (SAGE 3)

NASA Technical Reports Server (NTRS)

Mccormick, M. P.

1993-01-01

The proposed SAGE III instrument would be the principal source of data for global changes of stratospheric aerosols, stratospheric water vapor, and ozone profiles, and a contributing source of data for upper tropospheric water vapor, aerosols, and clouds. The ability to obtain such data has been demonstrated by the predecessor instrument, SAGE II, but SAGE III will be substantially more capable, as discussed below. The capabilities for monitoring the profiles of atmospheric constituents have been verified in detail, including ground-based validations, for aerosol, ozone, and water vapor. Indeed, because of its self-calibrating characteristics, SAGE II was an essential component of the international ozone trend assessments, and SAGE II is now proving to be invaluable in tracking the aerosols from Mt. Pinatubo. Although SAGE profiles generally terminate at the height of the first tropospheric cloud layer, it has been found that the measurements extend down to 3 km altitude more than 40 percent of the time at most latitudes. Thus, useful information can also be obtained on upper tropospheric aerosols, water vapor, and ozone.

Thermodynamic control of anvil cloud amount

PubMed Central

Bony, Sandrine; Stevens, Bjorn; Coppin, David; Becker, Tobias; Reed, Kevin A.; Voigt, Aiko

2016-01-01

General circulation models show that as the surface temperature increases, the convective anvil clouds shrink. By analyzing radiative–convective equilibrium simulations, we show that this behavior is rooted in basic energetic and thermodynamic properties of the atmosphere: As the climate warms, the clouds rise and remain at nearly the same temperature, but find themselves in a more stable atmosphere; this enhanced stability reduces the convective outflow in the upper troposphere and decreases the anvil cloud fraction. By warming the troposphere and increasing the upper-tropospheric stability, the clustering of deep convection also reduces the convective outflow and the anvil cloud fraction. When clouds are radiatively active, this robust coupling between temperature, high clouds, and circulation exerts a positive feedback on convective aggregation and favors the maintenance of strongly aggregated atmospheric states at high temperatures. This stability iris mechanism likely contributes to the narrowing of rainy areas as the climate warms. Whether or not it influences climate sensitivity requires further investigation. PMID:27412863

On the role of ozone feedback in the ENSO amplitude response under global warming.

PubMed

Nowack, Peer J; Braesicke, Peter; Luke Abraham, N; Pyle, John A

2017-04-28

The El Niño-Southern Oscillation (ENSO) in the tropical Pacific Ocean is of key importance to global climate and weather. However, state-of-the-art climate models still disagree on the ENSO's response under climate change. The potential role of atmospheric ozone changes in this context has not been explored before. Here we show that differences between typical model representations of ozone can have a first-order impact on ENSO amplitude projections in climate sensitivity simulations. The vertical temperature gradient of the tropical middle-to-upper troposphere adjusts to ozone changes in the upper troposphere and lower stratosphere, modifying the Walker circulation and consequently tropical Pacific surface temperature gradients. We show that neglecting ozone changes thus results in a significant increase in the number of extreme ENSO events in our model. Climate modeling studies of the ENSO often neglect changes in ozone. We therefore highlight the need to understand better the coupling between ozone, the tropospheric circulation, and climate variability.

Thermodynamic control of anvil cloud amount

DOE PAGES

Bony, Sandrine; Stevens, Bjorn; Coppin, David; ...

2016-07-13

General circulation models show that as the surface temperature increases, the convective anvil clouds shrink. By analyzing radiative–convective equilibrium simulations, our work shows that this behavior is rooted in basic energetic and thermodynamic properties of the atmosphere: As the climate warms, the clouds rise and remain at nearly the same temperature, but find themselves in a more stable atmosphere; this enhanced stability reduces the convective outflow in the upper troposphere and decreases the anvil cloud fraction. By warming the troposphere and increasing the upper-tropospheric stability, the clustering of deep convection also reduces the convective outflow and the anvil cloud fraction.more » When clouds are radiatively active, this robust coupling between temperature, high clouds, and circulation exerts a positive feedback on convective aggregation and favors the maintenance of strongly aggregated atmospheric states at high temperatures. This stability iris mechanism likely contributes to the narrowing of rainy areas as the climate warms. Whether or not it influences climate sensitivity requires further investigation.« less

Reactive Nitrogen and its Correlation with O3 and CO Over the Pacific in Winter and Early Spring

NASA Technical Reports Server (NTRS)

Koike, M.; Kondo,Y.; Kawakami, S.; Nakajima, H.; Sachse, G. W.; Singh, H. B.; Browell, E. V.; Merrill, J. T.; Newell, R. E.

1997-01-01

Measurements of NO, NO(y), O3, and CO were made during NASA's Global Tropospheric Experiment/Pacific Exploratory Mission-West B (GTE/PEM-West B) carried out over the western Pacific in February and March 1994. NO(x) was calculated from NO using a photostationary state model ((NO(x)(sub mc)). Correlations between these species are presented, and some insights into the sources of NO(x) and NO(y) are described. The boundaries between the lower, middle, and upper troposphere have been defined at potential temperatures of 311 K and 328 K, which correspond to the geometric altitudes of about 5 and 9 km at 30degN. Enhancements in the mixing ratios of NO(y) and CO were observed in the lower and middle troposphere. A positive correlation was found between these two species suggesting that the high NO(y) values were due to anthropogenic emissions over the continental surface. On the other hand, O3 increased little with increase in CO. As a result, NO(y)/O3 ratios were higher in air more influenced by pollution. NO(y), values in 55 and 28% of the air masses sampled in the lower and middle troposphere, respectively, were higher than the clean free tropospheric NO(y)-O3 range when O3 values simultaneously observed were used. High (NOx)mc/NOy ratios between 0.15 and 0.3 were found in the boundary layer with relatively low mixing ratios of CO and NOy during the three flights. These air masses were transported from a higher altitude (approximately 5 km) and a higher latitude (approximately 50degN) within a few days. The peroxyacetyl nitrate (PAN)/NO(y) ratios were generally high (approximately 0.4) in these air masses, and the thermal decomposition of PAN was a probable source of NO(x). In the middle troposphere the (NO(x))mc mixing ratio did not generally increase with NO(y) or CO, suggesting that the transport of air masses affected by anthropogenic emissions did not increase the NO(x) level significantly. In the upper troposphere, very minor effects from the continental surface sources were seen in the CO mixing ratio. By contrast, NO(y) values in 33% of the air masses were higher than those expected when stratospheric air intrusion is assumed to be a single source of NO(y) based on NO(y)-O3 correlation analyses. This result suggests significant free tropospheric NO(y) sources, namely exhaust from the aircraft and NO production by lightning activity. In fact, spikes in the (NO(x))(sub m)c mixing ratios were observed near the aircraft corridor south of Tokyo at an altitude of 10 km. These two free tropospheric NO(x) sources were considered to be important in determining the levels of the upper tropospheric NO(x) and NO(y) during PEM-West B.

Measurements of upper troposheric humidity at low temperatures during CRYSTAL-FACE

NASA Technical Reports Server (NTRS)

Herman, Robert L.; Heymsfield, Andrew J.; Ridley, Brian A.; Bui, Paul T.

2003-01-01

Aircraft condensation trails (contrails) and thin cirrus were studied by instruments on the NASA WB-57F high-altitude aircraft during contrails and optically thing cirrus are contrasted by different levels of supersaturation with respect to ice. During the July 13, 2002, flight of the WB-57F aircraft intercepted visible contrails produced by both the WB-57F and ER-2 aircraft. These contrails were located immediately below the local tropopause, where ambient temperatures were very low (-76 degree C). The contrails were clearly indicated by an abrupt increase in NO and a simultaneous, abrupt decrease in ice supersaturation. With in the contrail, the relative humidity was close to 130% with respect to ice, higher than expected from theory. Outside the contrails was a persistent layer of subvisible currus extending from approximately 13 to 15 km altitude. This layer was characterized y significant supersaturations because the ambient concentrations of ice particles were insufficient to significantly deplete the ice supersaturation. We will discuss in situ measurements and models simulations of humidity.

Cirrus cloud retrieval from MSG/SEVIRI during day and night using artificial neural networks

NASA Astrophysics Data System (ADS)

Strandgren, Johan; Bugliaro, Luca

2017-04-01

By covering a large part of the Earth, cirrus clouds play an important role in climate as they reflect incoming solar radiation and absorb outgoing thermal radiation. Nevertheless, the cirrus clouds remain one of the largest uncertainties in atmospheric research and the understanding of the physical processes that govern their life cycle is still poorly understood, as is their representation in climate models. To monitor and better understand the properties and physical processes of cirrus clouds, it's essential that those tenuous clouds can be observed from geostationary spaceborne imagers like SEVIRI (Spinning Enhanced Visible and InfraRed Imager), that possess a high temporal resolution together with a large field of view and play an important role besides in-situ observations for the investigation of cirrus cloud processes. CiPS (Cirrus Properties from Seviri) is a new algorithm targeting thin cirrus clouds. CiPS is an artificial neural network trained with coincident SEVIRI and CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) observations in order to retrieve a cirrus cloud mask along with the cloud top height (CTH), ice optical thickness (IOT) and ice water path (IWP) from SEVIRI. By utilizing only the thermal/IR channels of SEVIRI, CiPS can be used during day and night making it a powerful tool for the cirrus life cycle analysis. Despite the great challenge of detecting thin cirrus clouds and retrieving their properties from a geostationary imager using only the thermal/IR wavelengths, CiPS performs well. Among the cirrus clouds detected by CALIOP, CiPS detects 70 and 95 % of the clouds with an optical thickness of 0.1 and 1.0 respectively. Among the cirrus free pixels, CiPS classify 96 % correctly. For the CTH retrieval, CiPS has a mean absolute percentage error of 10 % or less with respect to CALIOP for cirrus clouds with a CTH greater than 8 km. For the IOT retrieval, CiPS has a mean absolute percentage error of 100 % or less with respect to CALIOP for cirrus clouds with an optical thickness down to 0.07. For such thin cirrus clouds an error of 100 % should be regarded as low from a geostationary imager like SEVIRI. The IWP retrieved by CiPS shows a similar performance, but has larger deviations for the thinner cirrus clouds.

Mesoscale aspects of jet streak coupling and implications for the short term forecasting of severe convective storms. [severe environmental storms and mesoscale experiment (SESAME)

NASA Technical Reports Server (NTRS)

Uccellini, L. W.; Kocin, P. J.

1981-01-01

An analysis of a tornado outbreak in Wichita Falls, Texas was analyzed. The coupling of upper and lower tropospheric jet streaks, leading to severe storm outbreaks is illustrated. The high resolution SESAME data sets indicate that mass and momentum adjustments which couple upper and lower tropospheric jets occur within a 3 to 6 hr time frame over a 100 to 500 km domain, and establish the role of isallobaric forcing in the storm development. It is suggested that the output rate of data from the existing 12 hr network be increased to provide better temporal resolution of wind, mass and moisture data.

Theoretical Investigations of Clouds and Aerosols in the Stratosphere and Upper Troposphere

NASA Technical Reports Server (NTRS)

Toon, Owen B.

2005-01-01

support of the Atmospheric Chemistry Modeling and Data Analysis Program. We investigated a wide variety of issues involving ambient stratospheric aerosols, polar stratospheric clouds or heterogeneous chemistry, analysis of laboratory data, and particles in the upper troposphere. The papers resulting from these studies are listed below. In addition, I participated in the 1999-2000 SOLVE mission as one of the project scientists and in the 2002 CRYSTAL field mission as one of the project scientists. Several CU graduate students and research associates also participated in these mission, under support from the ACMAP program, and worked to interpret data. During the past few years my group has completed a number of projects under the

Concentrations of carbonyl sulfide and hydrogen cyanide in the free upper troposphere and lower stratosphere deduced from ATMOS/Spacelab 3 infrared solar occultation spectra

NASA Technical Reports Server (NTRS)

Zander, R.; Rinsland, C. P.; Russell, J. M., III; Farmer, C. B.; Norton, R. H.

1988-01-01

This paper presents the results on the volume mixing ratio profiles of carbonyl sulfide and hydrogen cyanide, deduced from the spectroscopic analysis of IR solar absorption spectra obtained in the occultation mode with the Atmospheric Trace Molecule Spectroscopy (ATMOS) instrument during its mission aboard Spacelab 3. A comparison of the ATMOS measurements for both northern and southern latitudes with previous field investigations at low midlatitudes shows a relatively good agreement. Southern Hemisphere volume mixing ratio profiles for both molecules were obtained for the first time, as were the profiles for the Northern Hemisphere covering the upper troposphere and the lower stratosphere simultaneously.

Investigation of the effects of the macrophysical and microphysical properties of cirrus clouds on the retrieval of optical properties: Results for FIRE 2

NASA Technical Reports Server (NTRS)

Stackhouse, Paul W., Jr.; Stephens, Graeme L.

1993-01-01

Due to the prevalence and persistence of cirrus cloudiness across the globe, cirrus clouds are believed to have an important effect on the climate. Stephens et al., (1990) among others have shown that the important factor determining how cirrus clouds modulate the climate is the balance between the albedo and emittance effect of the cloud systems. This factor was shown to depend in part upon the effective sizes of the cirrus cloud particles. Since effective sizes of cirrus cloud microphysical distributions are used as a basis of parameterizations in climate models, it is crucial that the relationships between effective sizes and radiative properties be clearly established. In this preliminary study, the retrieval of cirrus cloud effective sizes are examined using a two dimensional radiative transfer model for a cirrus cloud case sampled during FIRE Cirrus 11. The purpose of this paper is to present preliminary results from the SHSG model demonstrating the sensitivity of the bispectral relationships of reflected radiances and thus the retrieval of effective sizes to phase function and dimensionality.

Microbiome of the upper troposphere: species composition and prevalence, effects of tropical storms, and atmospheric implications.

PubMed

DeLeon-Rodriguez, Natasha; Lathem, Terry L; Rodriguez-R, Luis M; Barazesh, James M; Anderson, Bruce E; Beyersdorf, Andreas J; Ziemba, Luke D; Bergin, Michael; Nenes, Athanasios; Konstantinidis, Konstantinos T

2013-02-12

The composition and prevalence of microorganisms in the middle-to-upper troposphere (8-15 km altitude) and their role in aerosol-cloud-precipitation interactions represent important, unresolved questions for biological and atmospheric science. In particular, airborne microorganisms above the oceans remain essentially uncharacterized, as most work to date is restricted to samples taken near the Earth's surface. Here we report on the microbiome of low- and high-altitude air masses sampled onboard the National Aeronautics and Space Administration DC-8 platform during the 2010 Genesis and Rapid Intensification Processes campaign in the Caribbean Sea. The samples were collected in cloudy and cloud-free air masses before, during, and after two major tropical hurricanes, Earl and Karl. Quantitative PCR and microscopy revealed that viable bacterial cells represented on average around 20% of the total particles in the 0.25- to 1-μm diameter range and were at least an order of magnitude more abundant than fungal cells, suggesting that bacteria represent an important and underestimated fraction of micrometer-sized atmospheric aerosols. The samples from the two hurricanes were characterized by significantly different bacterial communities, revealing that hurricanes aerosolize a large amount of new cells. Nonetheless, 17 bacterial taxa, including taxa that are known to use C1-C4 carbon compounds present in the atmosphere, were found in all samples, indicating that these organisms possess traits that allow survival in the troposphere. The findings presented here suggest that the microbiome is a dynamic and underappreciated aspect of the upper troposphere with potentially important impacts on the hydrological cycle, clouds, and climate.

Water vapor changes under global warming and the linkage to present-day interannual variabilities in CMIP5 models

NASA Astrophysics Data System (ADS)

Takahashi, Hanii; Su, Hui; Jiang, Jonathan H.

2016-12-01

The fractional water vapor changes under global warming across 14 Coupled Model Intercomparison Project Phase 5 simulations are analyzed. We show that the mean fractional water vapor changes under global warming in the tropical upper troposphere between 300 and 100 hPa range from 12.4 to 28.0 %/K across all models while the fractional water vapor changes are about 5-8 %/K in other regions and at lower altitudes. The "upper-tropospheric amplification" of the water vapor change is primarily driven by a larger temperature increase in the upper troposphere than in the lower troposphere per degree of surface warming. The relative contributions of atmospheric temperature and relative humidity changes to the water vapor change in each model vary between 71.5 to 131.8 % and 24.8 to -20.1 %, respectively. The inter-model differences in the water vapor change is primarily caused by differences in temperature change, except over the inter-tropical convergence zone within 10°S-10°N where the model differences due to the relative humidity change are significant. Furthermore, we find that there is generally a positive correlation between the rates of water vapor change for long-tem surface warming and those on the interannual time scales. However, the rates of water vapor change under long-term warming have a systematic offset from those on the inter-annual time scales and the dominant contributor to the differences also differs for the two time scales, suggesting caution needs to be taken when inferring long-term water vapor changes from the observed interannual variations.

Effects of diabatic heating on the ageostrophic circulation of an upper tropospheric jet streak

NASA Technical Reports Server (NTRS)

Keyser, D. A.; Johnson, D. R.

1982-01-01

Interaction between the mass circulation within a mesoscale convective complex (MCC) and a direct mass circulation in the entrance region of an upper tropospheric polar jet streak was examined within the isentropic structure to investigate mechanisms responsible for linking these two scales of motion. The results establish that latent heating in the MCC modifies the direct mass circulation in the jet streak entrance region through the diabatically induced components of ageostrophic motion analyzed within isentropic coordinates. Within the strong mesoscale mass circulation of each MCC, strong horizontal mass flux convergence into the MCC at low levels is balanced by strong horizontal mass flux divergence away from the convergence at upper levels. Locations of large diabatic heating rates correspond well to the MCC position for each case; diabatic heating forces the upward vertical branch for the mesoscale mass circulation.

Global view of the upper level outflow patterns associated with tropical cyclone intensity changes during FGGE

NASA Technical Reports Server (NTRS)

Chen, L.; Gray, W. M.

1985-01-01

The characteristics of the upper tropospheric outflow patterns which occur with tropical cyclone intensification and weakening over all of the global tropical cyclone basins during the year long period of the First GARP Global Experiment (FGGE) are discussed. By intensification is meant the change in the tropical cyclone's maximum wind or central pressure, not the change of the cyclone's outer 1 to 3 deg radius mean wind which we classify as cyclone strength. All the 80 tropical cyclones which existed during the FGGE year are studied. Two-hundred mb wind fields are derived from the analysis of the European Center for Medium Range Weather Forecasting (ECMWF) which makes extensive use of upper tropospheric satellite and aircraft winds. Corresponding satellite cloud pictures from the polar orbiting U.S. Defense Meteorological Satellite Program (DMSP) and other supplementary polar and geostationary satellite data are also used.

Tropospheric temperature climatology and trends observed over the Middle East

NASA Astrophysics Data System (ADS)

Basha, Ghouse; Marpu, P. R.; Ouarda, T. B. M. J.

2015-10-01

In this study, we report for the first time, the upper air temperature climatology, and trends over the Middle East, which seem to be significantly affected by the changes associated with hot summer and low precipitation. Long term (1985-2012) radiosonde data from 12 stations are used to derive the mean temperature climatology and vertical trends. The study was performed by analyzing the data at different latitudes. The vertical profiles of air temperature show distinct behavior in terms of vertical and seasonal variability at different latitudes. The seasonal cycle of temperature at the 100 hPa, however, shows an opposite pattern compared to the 200 hPa levels. The temperature at 100 hPa shows a maximum during winter and minimum in summer. Spectral analysis shows that the annual cycle is dominant in comparison with the semiannual cycle. The time-series of temperature data was analyzed using the Bayesian change point analysis and cumulative sum method to investigate the changes in temperature trends. Temperature shows a clear change point during the year 1999 at all stations. Further, Modified Mann-Kendall test was applied to study the vertical trend, and analysis shows statistically significant lower tropospheric warming and cooling in upper troposphere after the year 1999. In general, the magnitude of the trend decreases with altitude in the troposphere. In all the latitude bands in lower troposphere, significant warming is observed, whereas at higher altitudes cooling is noticed based on 28 years temperature observations over the Middle East.

Upper-tropospheric inversion and easterly jet in the tropics

NASA Astrophysics Data System (ADS)

Fujiwara, M.; Xie, S.-P.; Shiotani, M.; Hashizume, H.; Hasebe, F.; VöMel, H.; Oltmans, S. J.; Watanabe, T.

2003-12-01

Shipboard radiosonde measurements revealed a persistent temperature inversion layer with a thickness of ˜200 m at 12-13 km in a nonconvective region over the tropical eastern Pacific, along 2°N, in September 1999. Simultaneous relative humidity measurements indicated that the thin inversion layer was located at the top of a very wet layer with a thickness of 3-4 km, which was found to originate from the intertropical convergence zone (ITCZ) to the north. Radiative transfer calculations suggested that this upper tropospheric inversion (UTI) was produced and maintained by strong longwave cooling in this wet layer. A strong easterly jet stream was also observed at 12-13 km, centered around 4°-5°N. This easterly jet was in the thermal wind balance, with meridional temperature gradients produced by the cloud and radiative processes in the ITCZ and the wet outflow. Furthermore, the jet, in turn, acted to spread inversions further downstream through the transport of radiatively active water vapor. This feedback mechanism may explain the omnipresence of temperature inversions and layering structures in trace gases in the tropical troposphere. Examination of high-resolution radiosonde data at other sites in the tropical Pacific indicates that similar UTIs often appear around 12-15 km. The UTI around 12-15 km may thus be characterized as one of the "climatological" inversions in the tropical troposphere, forming the lower boundary of the so-called tropical tropopause layer, where the tropospheric air is processed photochemically and microphysically before entering the stratosphere.

Tropical Convective Responses to Microphysical and Radiative Processes: A Sensitivity Study With a 2D Cloud Resolving Model

NASA Technical Reports Server (NTRS)

Li, Xiao-Fan; Sui, C.-H.; Lau, K.-M.; Tao, W.-K.

2004-01-01

Prognostic cloud schemes are increasingly used in weather and climate models in order to better treat cloud-radiation processes. Simplifications are often made in such schemes for computational efficiency, like the scheme being used in the National Centers for Environment Prediction models that excludes some microphysical processes and precipitation-radiation interaction. In this study, sensitivity tests with a 2D cloud resolving model are carried out to examine effects of the excluded microphysical processes and precipitation-radiation interaction on tropical thermodynamics and cloud properties. The model is integrated for 10 days with the imposed vertical velocity derived from the Tropical Ocean Global Atmosphere Coupled Ocean-Atmosphere Response Experiment. The experiment excluding the depositional growth of snow from cloud ice shows anomalous growth of cloud ice and more than 20% increase of fractional cloud cover, indicating that the lack of the depositional snow growth causes unrealistically large mixing ratio of cloud ice. The experiment excluding the precipitation-radiation interaction displays a significant cooling and drying bias. The analysis of heat and moisture budgets shows that the simulation without the interaction produces more stable upper troposphere and more unstable mid and lower troposphere than does the simulation with the interaction. Thus, the suppressed growth of ice clouds in upper troposphere and stronger radiative cooling in mid and lower troposphere are responsible for the cooling bias, and less evaporation of rain associated with the large-scale subsidence induces the drying in mid and lower troposphere.

Signals of El Niño Modoki in the tropical tropopause layer and stratosphere

NASA Astrophysics Data System (ADS)

Xie, F.; Li, J.; Tian, W.; Feng, J.; Huo, Y.

2012-06-01

The effects of El Niño Modoki events on the tropical tropopause layer (TTL) and on the stratosphere were investigated using European Center for Medium Range Weather Forecasting (ECMWF) reanalysis data, oceanic El Niño indices, and general climate model outputs. El Niño Modoki events tend to depress convective activities in the western and eastern Pacific but enhance convective activities in the central and northern Pacific. Consequently, during El Niño Modoki events, negative water vapor anomalies occur in the western and eastern Pacific upper troposphere, whereas there are positive anomalies in the central and northern Pacific upper troposphere. The spatial patterns of the outgoing longwave radiation (OLR) and upper tropospheric water vapor anomalies exhibit a tripolar form. The empirical orthogonal function (EOF) analysis of the OLR and upper tropospheric water vapor anomalies reveals that canonical El Niño events are associated with the leading mode of the EOF, while El Niño Modoki events correspond to the second mode. The composite analysis based on ERA-interim data indicate that El Niño Modoki events have a reverse effect on middle-high latitudes stratosphere, as compared with the effect of typical El Niño events, i.e., the northern polar vortex is stronger and colder but the southern polar vortex is weaker and warmer during El Niño Modoki events. According to the simulation' results, we found that the reverse effect on the middle-high latitudes stratosphere is resulted from a complicated interaction between quasi-biennial oscillation (QBO) signal of east phase and El Niño Modoki signal. This interaction is not a simply linear overlay of QBO signal and El Niño Modoki signal in the stratosphere, it is El Niño Modoki that leads to different tropospheric zonal wind anomalies with QBO forcing from that caused by typical El Niño, thus, the planetary wave propagation from troposphere to the stratosphere during El Niño Modoki events is different from that during canonical El Niño events. However, when QBO is in its west phase, El Niño Modoki events have the same effect on middle-high latitudes stratosphere as the typical El Niño events. Our simulations also suggest that canonical El Niño and El Niño Modoki activities actually have the same influence on the middle-high latitudes stratosphere when in the absence of QBO forcing.

The Ozone Budget in the Upper Troposphere from Global Modeling Initiative (GMI)Simulations

NASA Technical Reports Server (NTRS)

Rodriquez, J.; Duncan, Bryan N.; Logan, Jennifer A.

2006-01-01

Ozone concentrations in the upper troposphere are influenced by in-situ production, long-range tropospheric transport, and influx of stratospheric ozone, as well as by photochemical removal. Since ozone is an important greenhouse gas in this region, it is particularly important to understand how it will respond to changes in anthropogenic emissions and changes in stratospheric ozone fluxes.. This response will be determined by the relative balance of the different production, loss and transport processes. Ozone concentrations calculated by models will differ depending on the adopted meteorological fields, their chemical scheme, anthropogenic emissions, and treatment of the stratospheric influx. We performed simulations using the chemical-transport model from the Global Modeling Initiative (GMI) with meteorological fields from (It)h e NASA Goddard Institute for Space Studies (GISS) general circulation model (GCM), (2) the atmospheric GCM from NASA's Global Modeling and Assimilation Office(GMAO), and (3) assimilated winds from GMAO . These simulations adopt the same chemical mechanism and emissions, and adopt the Synthetic Ozone (SYNOZ) approach for treating the influx of stratospheric ozone -. In addition, we also performed simulations for a coupled troposphere-stratosphere model with a subset of the same winds. Simulations were done for both 4degx5deg and 2degx2.5deg resolution. Model results are being tested through comparison with a suite of atmospheric observations. In this presentation, we diagnose the ozone budget in the upper troposphere utilizing the suite of GMI simulations, to address the sensitivity of this budget to: a) the different meteorological fields used; b) the adoption of the SYNOZ boundary condition versus inclusion of a full stratosphere; c) model horizontal resolution. Model results are compared to observations to determine biases in particular simulations; by examining these comparisons in conjunction with the derived budgets, we may pinpoint deficiencies in the representation of chemical/dynamical processes.

High resolution modeling of the upper troposphere and lower stratosphere region over the Arctic - GEM-AC simulations for the future climate with and without aviation emissions.

NASA Astrophysics Data System (ADS)

Porebska, Magdalena; Struzewska, Joanna; Kaminski, Jacek W.

2016-04-01

Upper troposphere and lower stratosphere (UTLS) region is a layer around the tropopause. Perturbation of the chemical composition in the UTLS region can impact physical and dynamical processes that can lead to changes in cloudiness, precipitation, radiative forcing, stratosphere-troposphere exchange and zonal flow. The objective of this study is to investigate the potential impacts of aviation emissions on the upper troposphere and lower stratosphere. In order to assess the impact of the aviation emissions we will focus on changes in atmospheric dynamic due to changes in chemical composition in the UTLS over the Arctic. Specifically, we will assess perturbations in the distribution of the wind, temperature and pressure fields in the UTLS region. Our study will be based on simulations using a high resolution chemical weather model for four scenarios of current (2006) and future (2050) climate: with and without aircraft emissions. The tool that we use is the GEM-AC (Global Environmental Multiscale with Atmospheric Chemistry) chemical weather model where air quality, free tropospheric and stratospheric chemistry processes are on-line and interactive in an operational weather forecast model of Environment Canada. In vertical, the model domain is defined on 70 hybrid levels with model top at 0.1 mb. The gas-phase chemistry includes detailed reactions of Ox, NOx, HOx, CO, CH4, ClOx and BrO. Also, the model can address aerosol microphysics and gas-aerosol partitioning. Aircraft emissions are from the AEDT 2006 database developed by the Federal Aviation Administration (USA) and the future climate simulations are based on RCP8.5 projection presented by the IPCC in the fifth Assessment Report AR5. Results from model simulations on a global variable grid with 0.5o x 0.5o uniform resolution over the Arctic will be presented.

NASA's Upper Atmosphere Research Program (UARP) and Atmospheric Chemistry Modeling and Analysis Program (ACMAP): Research Summaries 1997-1999

NASA Technical Reports Server (NTRS)

Kurylo, M. J.; DeCola, P. L.; Kaye, J. A.

2000-01-01

Under the mandate contained in the FY 1976 NASA Authorization Act, the National Aeronautics and Space Administration (NASA) has developed and is implementing a comprehensive program of research, technology development, and monitoring of the Earth's upper atmosphere, with emphasis on the upper troposphere and stratosphere. This program aims at expanding our chemical and physical understanding to permit both the quantitative analysis of current perturbations as well as the assessment of possible future changes in this important region of our environment. It is carried out jointly by the Upper Atmosphere Research Program (UARP) and the Atmospheric Chemistry Modeling and Analysis Program (ACMAP), both managed within the Research Division in the Office of Earth Science at NASA. Significant contributions to this effort have also been provided by the Atmospheric Effects of Aviation Project (AEAP) of NASA's Office of Aero-Space Technology. The long-term objectives of the present program are to perform research to: understand the physics, chemistry, and transport processes of the upper troposphere and the stratosphere and their control on the distribution of atmospheric chemical species such as ozone; assess possible perturbations to the composition of the atmosphere caused by human activities and natural phenomena (with a specific emphasis on trace gas geographical distributions, sources, and sinks and the role of trace gases in defining the chemical composition of the upper atmosphere); understand the processes affecting the distributions of radiatively active species in the atmosphere, and the importance of chemical-radiative-dynamical feedbacks on the meteorology and climatology of the stratosphere and troposphere; and understand ozone production, loss, and recovery in an atmosphere with increasing abundances of greenhouse gases. The current report is composed of two parts. Part 1 summarizes the objectives, status, and accomplishments of the research tasks supported under NASA UARP and ACMAP in a document entitled, Research Summaries 1997- 1999. Part 2 is entitled Present State of Knowledge of the Upper Atmosphere 1999 An Assessment Report.

Wave Activity and Its Changes in the Troposphere and Stratosphere of the Northern Hemisphere in Winters of 1979-2016

NASA Astrophysics Data System (ADS)

Guryanov, V. V.; Eliseev, A. V.; Mokhov, I. I.; Perevedentsev, Yu. P.

2018-03-01

An analysis of spectra of wave disturbances with zonal wave numbers 1 ≤ k ≤ 10 is carried out using winter (November to March) ERA-Interim reanalysis geopotential data in the troposphere and stratosphere for 1979-2016. Contributions of eastward-traveling ( E), westward-traveling ( W), and stationary ( S) waves are estimated. The intensification of wave activity is observed in the tropical troposphere and stratosphere and in the upper stratosphere of the entire Northern Hemisphere. The intensification of wave activity in the tropics and subtropics is noted for waves of all types ( E, W, and S), while in the middle and higher latitudes it is related mainly to stationary and eastward waves. Near the subtropical tropopause, the energy of stationary waves has increased in recent decades. In addition, in the tropical and subtropical troposphere and in the subtropical lower stratosphere, the energy of the eastward-traveling waves in El Niño years may be one and a half times or twice the energy in La Niña years. The spectrally weighted zonal wave numbers for waves of all types ( E, W, and S) are the largest in the upper subtropical troposphere. The spectrally weighted zonal wave number for W and S waves is correlated with the Atlantic Multidecadal Oscillation index and varies by 15% in 1979-2016 (on an interdecadal time scale). The spectrally weighted wave period is larger in the stratosphere than in the troposphere. It is maximal in the middle extratropical stratosphere. The spectrally weighted wave periods correlate with the activity of sudden stratospheric warmings. The sign of this correlation depends on the latitude, atmospheric layer, and zonal wave number.

The environmental influence on tropical cyclone precipitation

NASA Technical Reports Server (NTRS)

Rodgers, Edward B.; Baik, Jong-Jin; Pierce, Harold F.

1994-01-01

The intensity, spatial, and temporal changes in precipitation were examined in three North Atlantic hurricanes during 1989 (Dean, Gabrielle, and Hugo) using precipitation estimates made from Special Sensor Microwave/Imager (SSM/I) measurements. In addition, analyses from a barotropic hurricane forecast model and the European Centre for Medium-Range Weather Forecast model were used to examine the relationship between the evolution of the precipitation in these tropical cyclones and external forcing. The external forcing parameters examined were (1) mean climatological sea surface temperatures, (2) vertical wind shear, (3) environmental tropospheric water vapor flux, and (4) upper-tropospheric eddy relative angular momentum flux convergence. The analyses revealed that (1) the SSM/I precipitation estimates were able to delineate and monitor convective ring cycles similar to those observed with land-based and aircraft radar and in situ measurements; (2) tropical cyclone intensification was observed to occur when these convective rings propagated into the inner core of these systems (within 111 km of the center) and when the precipitation rates increased; (3) tropical cyclone weakening was observed to occur when these inner-core convective rings dissipated; (4) the inward propagation of the outer convective rings coincided with the dissipation of the inner convective rings when they came within 55 km of each other; (5) in regions with the combined warm sea surface temperatures (above 26 C) and low vertical wind shear (less than 5 m/s), convective rings outside the region of strong lower-tropospheric inertial stability could be initiated by strong surges of tropospheric moisture, while convective rings inside the region of strong lower-tropospheric inertial stability could be enhanced by upper-tropospheric eddy relative angular momentum flux convergence.

The Environmental Influence on Tropical Cyclone Precipitation.

NASA Astrophysics Data System (ADS)

Rodgers, Edward B.; Baik, Jong-Jin; Pierce, Harold F.

1994-05-01

The intensity, spatial, and temporal changes in precipitation were examined in three North Atlantic hurricanes during 1989 (Dean, Gabrielle, and Hugo) using precipitation estimates made from Special Sensor Microwave/Imager (SSM/I) measurements. In addition, analyses from a barotropic hurricane forecast model and the European Centre for Medium-Range Weather Forecast model were used to examine the relationship between the evolution of the precipitation in these tropical cyclones and external forcing. The external forcing parameters examined were 1) mean climatological sea surface temperatures, 2) vertical wind shear, 3) environmental tropospheric water vapor flux, and 4) upper-tropospheric eddy relative angular momentum flux convergence.The analyses revealed that 1) the SSM/I precipitation estimates were able to delineate and monitor convective ring cycles similar to those observed with land-based and aircraft radar and in situ measurements; 2) tropical cyclone intensification was observed to occur when these convective rings propagated into the inner core of these systems (within 111 km of the center) and when the precipitation rates increased; 3) tropical cyclone weakening was observed to occur when these inner-core convective rings dissipated; 4) the inward propagation of the outer convective rings coincided with the dissipation of the inner convective rings when they came within 55 km of each other; 5) in regions with the combined warm sea surface temperatures (above 26°C) and low vertical wind shear (less than 5 m s1), convective rings outside the region of strong lower-tropospheric inertial stability could be initiated by strong surges of tropospheric moisture, while convective rings inside the region of strong lower-tropospheric inertial stability could be enhanced by upper-tropospheric eddy relative angular momentum flux convergence.

Climatology 2011: An MLS and Sonde Derived Ozone Climatology for Satellite Retrieval Algorithms

NASA Technical Reports Server (NTRS)

McPeters, Richard D.; Labow, Gordon J.

2012-01-01

The ozone climatology used as the a priori for the version 8 Solar Backscatter Ultraviolet (SBUV) retrieval algorithms has been updated. The Microwave Limb Sounder (MLS) instrument on Aura has excellent latitude coverage and measures ozone daily from the upper troposphere to the lower mesosphere. The new climatology consists of monthly average ozone profiles for ten degree latitude zones covering pressure altitudes from 0 to 65 km. The climatology was formed by combining data from Aura MLS (2004-2010) with data from balloon sondes (1988-2010). Ozone below 8 km (below 12 km at high latitudes) is based on balloons sondes, while ozone above 16 km (21 km at high latitudes) is based on MLS measurements. Sonde and MLS data are blended in the transition region. Ozone accuracy in the upper troposphere is greatly improved because of the near uniform coverage by Aura MLS, while the addition of a large number of balloon sonde measurements improves the accuracy in the lower troposphere, in the tropics and southern hemisphere in particular. The addition of MLS data also improves the accuracy of climatology in the upper stratosphere and lower mesosphere. The revised climatology has been used for the latest reprocessing of SBUV and TOMS satellite ozone data.

Improved simulation of aerosol, cloud, and density measurements by shuttle lidar

NASA Technical Reports Server (NTRS)

Russell, P. B.; Morley, B. M.; Livingston, J. M.; Grams, G. W.; Patterson, E. W.

1981-01-01

Data retrievals are simulated for a Nd:YAG lidar suitable for early flight on the space shuttle. Maximum assumed vertical and horizontal resolutions are 0.1 and 100 km, respectively, in the boundary layer, increasing to 2 and 2000 km in the mesosphere. Aerosol and cloud retrievals are simulated using 1.06 and 0.53 microns wavelengths independently. Error sources include signal measurement, conventional density information, atmospheric transmission, and lidar calibration. By day, tenuous clouds and Saharan and boundary layer aerosols are retrieved at both wavelengths. By night, these constituents are retrieved, plus upper tropospheric, stratospheric, and mesospheric aerosols and noctilucent clouds. Density, temperature, and improved aerosol and cloud retrievals are simulated by combining signals at 0.35, 1.06, and 0.53 microns. Particlate contamination limits the technique to the cloud free upper troposphere and above. Error bars automatically show effect of this contamination, as well as errors in absolute density nonmalization, reference temperature or pressure, and the sources listed above. For nonvolcanic conditions, relative density profiles have rms errors of 0.54 to 2% in the upper troposphere and stratosphere. Temperature profiles have rms errors of 1.2 to 2.5 K and can define the tropopause to 0.5 km and higher wave structures to 1 or 2 km.

Sources and distribution of NO(x) in the upper troposphere at northern midlatitudes

NASA Technical Reports Server (NTRS)

Rohrer, Franz; Ehhalt, Dieter H.; Wahner, Andreas

1994-01-01

A simple quasi 2-D model is used to study the zonal distribution of NO(x). The model includes vertical transport in form of eddy diffusion and deep convection, zonal transport by a vertically uniform wind, and a simplified chemistry of NO, NO2 and HNO3. The NO(x) sources considered are surface emissions (mostly from the combustion of fossil fuel), lightning, aircraft emissions, and downward transport from the stratosphere. The model is applied to the latitude band of 40 deg N to 50 deg N during the month of June; the contributions to the zonal NO(x) distribution from the individual sources and transport processes are investigated. The model predicted NO(x) concentration in the upper troposphere is dominated by air lofted from the polluted planetary boundary layer over the large industrial areas of Eastern North America and Europe. Aircraft emissions are also important and contribute on average 30 percent. Stratospheric input is minor about 10 percent, less even than that by lightning. The model provides a clear indication of intercontinental transport of NO(x) and HNO3 in the upper troposphere. Comparison of the modelled NO profiles over the Western Atlantic with those measured during STRATOZ 3 in 1984 shows good agreement at all altitudes.

Vertical and meridional distributions of the atmospheric CO2 mixing ratio between northern midlatitudes and southern subtropics

NASA Astrophysics Data System (ADS)

Machida, T.; Kita, K.; Kondo, Y.; Blake, D.; Kawakami, S.; Inoue, G.; Ogawa, T.

2003-02-01

The atmospheric CO2 mixing ratio was measured using a continuous measurement system onboard a Gulfstream-II aircraft between the northern midlatitudes and the southern subtropics during the Biomass Burning and Lightning Experiment Phase A (BIBLE A) campaign in September-October 1998. The vertical distribution of CO2 over tropical regions was almost constant from the surface to an altitude of 13 km. CO2 enhancements from biomass burning and oceanic release were observed in the tropical boundary layer. Measurements in the upper troposphere indicate interhemispheric exchange was effectively suppressed between 2°N-7°N. Interhemispheric transport of air in the upper troposphere was suppressed effectively in this region. The CO2 mixing ratios in the Northern and Southern Hemispheres were almost constant, with an average value of about 365 parts per million (ppm) and 366 ppm, respectively. The correlation between the CO2 and NOy mixing ratios observed north of 7°N was apparently different from that obtained south of 2°N. This fact strongly supports the result that the north-south boundary in the upper troposphere during BIBLE A was located around 2°N-7°N as the boundary is not necessary a permanent feature.

Vertical and meridional distributions of the atmospheric CO2 mixing ratio between northern midlatitudes and southern subtropics

NASA Astrophysics Data System (ADS)

Machida, T.; Kita, K.; Kondo, Y.; Blake, D.; Kawakami, S.; Inoue, G.; Ogawa, T.

2002-02-01

The atmospheric CO2 mixing ratio was measured using a continuous measurement system onboard a Gulfstream-II aircraft between the northern midlatitudes and the southern subtropics during the Biomass Burning and Lightning Experiment Phase A (BIBLE A) campaign in September-October 1998. The vertical distribution of CO2 over tropical regions was almost constant from the surface to an altitude of 13 km. CO2 enhancements from biomass burning and oceanic release were observed in the tropical boundary layer. Measurements in the upper troposphere indicate interhemispheric exchange was effectively suppressed between 2°N-7°N. Interhemispheric transport of air in the upper troposphere was suppressed effectively in this region. The CO2 mixing ratios in the Northern and Southern Hemispheres were almost constant, with an average value of about 365 parts per million (ppm) and 366 ppm, respectively. The correlation between the CO2 and NOy mixing ratios observed north of 7°N was apparently different from that obtained south of 2°N. This fact strongly supports the result that the north-south boundary in the upper troposphere during BIBLE A was located around 2°N-7°N as the boundary is not necessary a permanent feature.

Influence of sudden stratospheric warming and quasi biennial oscillation on western disturbance over north India

NASA Astrophysics Data System (ADS)

Remya, R.; Kottayil, Ajil; Mohanakumar, K.

2017-07-01

This study demonstrates the variability in Western Disturbance during the sudden stratospheric warming (SSW) period and its eventual influence on the north Indian weather pattern. The modulations in the north Indian winter under the two phases of the Quasi-biennial oscillation (QBO) during SSW periods are also examined. The analysis has been carried out by using the ERA interim reanalysis dataset for different pressure levels in the stratosphere and upper troposphere during the time period of 1980-2010. The daily minimum surface temperature data published by India Meteorological Department from 1969 to 2013 has been used for the analysis of temperature anomaly over north India during SSW. The period of intense stratospheric warming witnesses a downward propagation and intensification of kinetic energy from stratosphere to upper troposphere over the Mediterranean and Caspian Sea. When QBO is in easterly phase, the cooling over north India is much larger when compared to the westerly phase during instances of SSW. SSW coincident with the easterly phase of QBO causes an intensified subtropical jet over the mid-latitude regions. The modulation in circulation pattern in stratosphere and upper troposphere when ENSO occurs during SSW period is also analysed separately. This study provides the link among SSW, Western Disturbances and the north Indian cooling during winter season.

Investigating the differences of cirrus cloud properties in nucleation, growth and sublimation regions based on airborne water vapor lidar measurements

NASA Astrophysics Data System (ADS)

Urbanek, Benedikt; Groß, Silke; Wirth, Martin

2017-04-01

Cirrus clouds impose high uncertainties on weather and climate prediction, as knowledge on important processes is still incomplete. For instance it remains unclear how cloud optical, microphysical, and radiative properties change as the cirrus evolves. To gain better understanding of cirrus clouds, their optical and microphysical properties and their changes with cirrus cloud evolution the ML-CIRRUS campaign was conducted in March and April 2014. Measurements with a combined in-situ and remote sensing payload were performed with the German research aircraft HALO based in Oberpfaffenhofen. 16 research flights with altogether 88 flight hours were performed over the North-Atlantic, western and central Europe to probe different cirrus cloud regimes and cirrus clouds at different stages of evolution. One of the key remotes sensing instruments during ML-CIRRUS was the airborne differential absorption and high spectral lidar system WALES. It measures the 2-dimensional distribution of water vapor inside and outside of cirrus clouds as well as the optical properties of the clouds. Bases on these airborne lidar measurements a novel classification scheme to derive the stage of cirrus cloud evolution was developed. It identifies regions of ice nucleation, particle growth by deposition of water vapor, and ice sublimation. This method is used to investigate differences in the distribution and value of optical properties as well as in the distribution of water vapor and relative humidity depending on the stage of evolution of the cloud. We will present the lidar based classification scheme and its application on a wave driven cirrus cloud case, and we will show first results of the dependence of optical cloud properties and relative humidity distributions on the determined stage of evolution.

Gravity Wave Variances and Propagation Derived from AIRS Radiances

DTIC Science & Technology

2011-04-15

synoptically warm condition and susequently affect ozone depletion (Hamill and Toon, 1991). The importance of gravity waves on climate and weather... troposphere to upper stratosphere can those GWs grow into significant strengths. Locations of high occurrence of convectively generated GWs are also...maximum comes in one month later. A close look at the vertical config- uration of the zonal wind reveals that tropospheric westerlies in the SH high

Inhomogeneities in frontal cirrus clouds

NASA Astrophysics Data System (ADS)

Neis, Patrick; Krämer, Martina; Hoor, Peter; Reutter, Philipp; Spichtinger, Peter

2013-04-01

Frontal cirrus clouds have a scientifically proven effect on the Earth's radiation budget and thereby an influence on the weather and climate change in regional scale. The formation processes and structures of frontal cirrus clouds are still not fully understood. For a close investigation of typical frontal cirrus clouds, we use in situ measurements from the CIRRUS-III campaign over Germany and Northern Europe in November 2006. Besides water vapour, cloud ice water content, ice particle size distributions, condensation nuclei, and reactive nitrogen were measured during 6 flights. In this work the data of the 24th November flight is used to detect and to analyze warm frontal cirrus clouds in the mid latitudes on small temporal and spatial scale. Further, these results are compared with large-scale meteorological analyses from ECMWF and satellite data. Combining these data, the formation and evolution of inhomogeneities in the cirrus cloud structure are investigated. One important result is a qualitative agreement between the occurrence of cirrus clouds and the 'sharpness' of the Tropopause Inversion Layer (TIL).

The Vertical Structure of Relative Humidity and Ozone in the Tropical Upper Troposphere: Intercomparisons Among In Situ Observations, A-Train Measurements and Large-Scale Models

NASA Technical Reports Server (NTRS)

Selkirk, Henry B.; Manyin, Michael; Douglass, Anne R.; Oman, Luke; Pawson, Steven; Ott, Lesley; Benson, Craig; Stolarski, Richard

2010-01-01

In situ measurements in the tropics have shown that in regions of active convection, relative humidity with respect to ice in the upper troposphere is typically close to saturation on average, and supersaturations greater than 20% are not uncommon. Balloon soundings with the cryogenic frost point hygrometer (CFH) at Costa Rica during northern summer, for example, show this tendency to be strongest between 11 and 15.5 km (345-360 K potential temperature, or approximately 250-120 hPa). this is the altitude range of deep convective detrainment. Additionally, simultaneous ozonesonde measurements show that stratospheric air (O3 greater than 150 ppbv) can be found as low as approximately 14 km (350 K/150 hPa). In contrast, results from northern winter show a much drier upper troposphere and little penetration of stratospheric air below the tropopause at 17.5 km (approximately 383 K). We show that these results are consistent with in situ measurements from the Measurement of Ozone and water vapor by Airbus In-service airCraft (MOZAIC) program which samples a wider, though still limited, range of tropical locations. To generalize to the tropics as a whole, we compare our insitu results to data from two A-Train satellite instruments, the Atmospheric Infrared Sounder (AIRS) and the Microwave Limb Sounder (MLS) on the Aqua and Aura satellites respectively. Finally, we examine the vertical structure of water vapor, relative humidity and ozone in the NASA Goddard MERRA analysis, an assimilation dataset, and a new version of the GEOS CCM, a free-running chemistry-climate model. We demonstrate that conditional probability distributions of relative humidity and ozone are a sensitive diagnostic for assessing the representation of deep convection and upper troposphere/lower stratosphere mixing processes in large-scale analyses and climate models.

A three-dimensional total odd nitrogen (NO y ) simulation during SONEX using a stretched-grid chemical transport model

NASA Astrophysics Data System (ADS)

Allen, Dale; Pickering, Kenneth; Stenchikov, Georgiy; Thompson, Anne; Kondo, Yutaka

2000-02-01

The relative importance of various odd nitrogen (NOy) sources including lightning, aircraft, and surface emissions on upper tropospheric total odd nitrogen is illustrated as a first application of the three-dimensional Stretched-Grid University of Maryland/Goddard Chemical-Transport Model (SG-GCTM). The SG-GCTM has been developed to look at the effect of localized sources and/or small-scale mixing processes on the large-scale or global chemical balance. For this simulation the stretched grid was chosen so that its maximum resolution is located over eastern North America and the North Atlantic; a region that includes most of the Subsonic Assessment (SASS) Ozone and Nitrogen Oxide Experiment (SONEX) flight paths. The SONEX period (October-November 1997) is simulated by driving the SG-GCTM with assimilated data from the Goddard Earth Observing System-Stratospheric Tracers of Atmospheric Transport Data Assimilation System (GEOS-STRAT DAS). A new algorithm is used to estimate the lightning flash rates needed to calculate NOy emission by lightning. This algorithm parameterizes the flash rate in terms of upper tropospheric convective mass flux. Model-calculated upper tropospheric NOy and NOy measurements from the NASA DC-8 aircraft are compared. Spatial variations in NOy were well captured especially with the stretched-grid run; however, model-calculated peaks due to "stratospheric" NOy are occasionally too large. The lightning algorithm reproduces the temporally and spatially averaged total flash rate accurately; however, the use of emissions from observed lightning flashes significantly improves the simulation on a few days, especially November 3, 1997, showing that significant uncertainty remains in parameterizing lightning in chemistry and transport models. Aircraft emissions contributed ˜15% of the upper tropospheric NOy averaged along SONEX flight paths within the North Atlantic Flight Corridor with the contribution exceeding 40% during portions of some flights.

Aerosol indirect effect on tropospheric ozone via lightning

NASA Astrophysics Data System (ADS)

Yuan, Tianle; Remer, Lorraine A.; Bian, Huisheng; Ziemke, Jerald R.; Albrecht, Rachel; Pickering, Kenneth E.; Oreopoulos, Lazaros; Goodman, Steven J.; Yu, Hongbin; Allen, Dale J.

2012-09-01

Tropospheric ozone (O3) is a pollutant and major greenhouse gas and its radiative forcing is still uncertain. Inadequate understanding of processes related to O3 production, in particular those natural ones such as lightning, contributes to this uncertainty. Here we demonstrate a new effect of aerosol particles on O3production by affecting lightning activity and lightning-generated NOx (LNOx). We find that lightning flash rate increases at a remarkable rate of 30 times or more per unit of aerosol optical depth. We provide observational evidence that indicates the observed increase in lightning activity is caused by the influx of aerosols from a volcano. Satellite data analyses show O3is increased as a result of aerosol-induced increase in lightning and LNOx, which is supported by modle simulations with prescribed lightning change. O3production increase from this aerosol-lightning-ozone link is concentrated in the upper troposphere, where O3 is most efficient as a greenhouse gas. In the face of anthropogenic aerosol increase our findings suggest that lightning activity, LNOx and O3, especially in the upper troposphere, have all increased substantially since preindustrial time due to the proposed aerosol-lightning-ozone link, which implies a stronger O3 historical radiative forcing. Aerosol forcing therefore has a warming component via its effect on O3 production and this component has mostly been ignored in previous studies of climate forcing related to O3and aerosols. Sensitivity simulations suggest that 4-8% increase of column tropospheric ozone, mainly in the tropics, is expected if aerosol-lighting-ozone link is parameterized, depending on the background emission scenario. We note, however, substantial uncertainties remain on the exact magnitude of aerosol effect on tropospheric O3 via lightning. The challenges for obtaining a quantitative global estimate of this effect are also discussed. Our results have significant implications for understanding past and projecting future tropospheric O3forcing as well as wildfire changes and call for integrated investigations of the coupled aerosol-cloud-chemistry system.

Searching for possible effects on midlatitude sporadic E layer, caused by tropospheric lightning.

NASA Astrophysics Data System (ADS)

Barta, Veronika; Haldoupis, Christos; Sátori, Gabriella; Buresova, Dalia

2016-07-01

Thunderstorms in the troposphere may affect the overlying ionosphere through electrodynamic and/or neutral atmosphere wave coupling processes. For example, it is well known that lightning discharges may impact upper atmosphere through quasi-electrostatic fields and strong electromagnetic pulses, leading to transient luminous phenomena, such as sprites and elves, along with electron heating and ionization changes in the upper D and lower E-region ionosphere that have been detected in VLF transmissions propagating in the earth-ionosphere waveguide. On the other hand, mechanical coupling between the troposphere and the ionosphere may be caused by neutral atmosphere gravity waves which are known to have their origin in massive thunderstorms. The effects of troposphere-ionosphere coupling during thunderstorms, are not yet fully established and understood, therefore there is need for more correlative studies, for example by using concurrent ionospheric and lightning observations. In the present work an effort is made to investigate a possible relationship between tropospheric lighting and sporadic E layer, which are known to dominate at bottomside ionosphere and at middle latitudes during summer. For this, a correlative analysis was undertaken using lightning data obtained with the LINET lightning detection network in Central Europe, and E region ionospheric parameters (fmin, foE, foEs, fbEs) measured with the Pruhonice (50° N, 14.5° E) DPS-4D digisonde in the summer of 2009. For direct correlation with the digisonde data, the lightning activity was quantified every 15 minutes in coincidence with the measured ionogram parameters. In the search for relation between lightning and sporadic E, the digisonde observations during lightning were also compared with those taken during a number of tropospheric storm-free days in Pruhonice. The results of this correlative study did not provide evidence of significance that favors a relationship between tropospheric lightning and midlatitude sporadic E layer.

Tropospheric Ozone Over the North Pacific from Ozonesdonde Observations

NASA Technical Reports Server (NTRS)

Oltmans, S. J.; Johnson, B. J.; Harris, J. M.; Thompson, A. M.; Liu, H. Y.; Voemel, H.; Chan, C. Y.; Fujimoto, T.; Brackett, V. G.; Chang, W. L.

2003-01-01

As part of the TRACE-P mission, ozone vertical profile measurements were made at a number of locations in the North Pacific. At most of the sites there is also a multi-year record of ozonesonde observations. From seven locations in the western Pacific (Hong Kong; Taipei; Jeju Island, Korea; and Naha, Kagoshima, Tsukuba, and Sapporo, Japan), a site in the central Pacific (Hilo, HI), and a site on the west coast of the U.S. (Trinidad Head, CA) both a seasonal and event specific picture of tropospheric ozone over the North Pacific emerges. At all of the sites there is a pronounced spring maximum through the troposphere. There are, however, differences in the timing and strength of this feature. Over Japan the northward movement of the jet during the spring and summer influences the timing of the seasonal maximum. The ozone profiles suggest that transport of ozone rich air from the stratosphere plays a strong role in the development of this maximum. During March and April at Hong Kong ozone is enhanced in a layer that extends from the lower free troposphere into the upper troposphere that likely has its origin in biomass burning in northern Southeast Asia and equatorial Africa. During the winter the Pacific subtropical sites (latitude -25N) are dominated by air with a low-latitude, marine source that gives low ozone amounts particularly in the upper troposphere. In the summer in the boundary layer at all of the sites marine air dominates and ozone amounts are generally quite low (less than 25 ppb). The exception is near large population centers (Tokyo and Taipei but not Hong Kong) where pollution events can give amounts in excess of 80 ppb. During the TRACE-P intensive campaign period (February-April 2001) tropospheric ozone amounts were rather typical of those seen in the long-term records of the stations with multi-year soundings.

Cirrus cloud retrieval with MSG/SEVIRI using artificial neural networks

NASA Astrophysics Data System (ADS)

Strandgren, Johan; Bugliaro, Luca; Sehnke, Frank; Schröder, Leon

2017-09-01

Cirrus clouds play an important role in climate as they tend to warm the Earth-atmosphere system. Nevertheless their physical properties remain one of the largest sources of uncertainty in atmospheric research. To better understand the physical processes of cirrus clouds and their climate impact, enhanced satellite observations are necessary. In this paper we present a new algorithm, CiPS (Cirrus Properties from SEVIRI), that detects cirrus clouds and retrieves the corresponding cloud top height, ice optical thickness and ice water path using the SEVIRI imager aboard the geostationary Meteosat Second Generation satellites. CiPS utilises a set of artificial neural networks trained with SEVIRI thermal observations, CALIOP backscatter products, the ECMWF surface temperature and auxiliary data. CiPS detects 71 and 95 % of all cirrus clouds with an optical thickness of 0.1 and 1.0, respectively, that are retrieved by CALIOP. Among the cirrus-free pixels, CiPS classifies 96 % correctly. With respect to CALIOP, the cloud top height retrieved by CiPS has a mean absolute percentage error of 10 % or less for cirrus clouds with a top height greater than 8 km. For the ice optical thickness, CiPS has a mean absolute percentage error of 50 % or less for cirrus clouds with an optical thickness between 0.35 and 1.8 and of 100 % or less for cirrus clouds with an optical thickness down to 0.07 with respect to the optical thickness retrieved by CALIOP. The ice water path retrieved by CiPS shows a similar performance, with mean absolute percentage errors of 100 % or less for cirrus clouds with an ice water path down to 1.7 g m-2. Since the training reference data from CALIOP only include ice water path and optical thickness for comparably thin clouds, CiPS also retrieves an opacity flag, which tells us whether a retrieved cirrus is likely to be too thick for CiPS to accurately derive the ice water path and optical thickness. By retrieving CALIOP-like cirrus properties with the large spatial coverage and high temporal resolution of SEVIRI during both day and night, CiPS is a powerful tool for analysing the temporal evolution of cirrus clouds including their optical and physical properties. To demonstrate this, the life cycle of a thin cirrus cloud is analysed.

A one year Landsat 8 conterminous United States study of spatial and temporal patterns of cirrus and non-cirrus clouds and implications for the long term Landsat archive.

NASA Astrophysics Data System (ADS)

Kovalskyy, V.; Roy, D. P.

2014-12-01

The successful February 2013 launch of the Landsat 8 satellite is continuing the 40+ year legacy of the Landsat mission. The payload includes the Operational Land Imager (OLI) that has a new 1370 mm band designed to monitor cirrus clouds and the Thermal Infrared Sensor (TIRS) that together provide 30m low, medium and high confidence cloud detections and 30m low and high confidence cirrus cloud detections. A year of Landsat 8 data over the Conterminous United States (CONUS), composed of 11,296 acquisitions, was analyzed comparing the spatial and temporal incidence of these cloud and cirrus states. This revealed (i) 36.5% of observations were detected with high confidence cloud with spatio-temporal patterns similar to those observed by previous Landsat 7 cloud analyses, (ii) 29.2% were high confidence cirrus, (iii) 20.9% were both high confidence cloud and high confidence cirrus, (iv) 8.3% were detected as high confidence cirrus but not as high confidence cloud. The results illustrate the value of the cirrus band for improved Landsat 8 terrestrial monitoring but imply that the historical CONUS Landsat archive has a similar 8% of undetected cirrus contaminated pixels. The implications for long term Landsat time series records, including the global Web Enabled Landsat Data (WELD) product record, are discussed.

Correction of thin cirrus effects in AVIRIS images using the sensitive 1.375-micron cirrus detecting channel

NASA Technical Reports Server (NTRS)

Gao, Bo-Cai; Kaufman, Yorman J.

1995-01-01

Using spectral imaging data acquired with the Airborne Visible Infrared Imaging Spectrometer (AVIRIS) from an ER-2 aircraft at 20 km altitude during various field programs, it was found that narrow channels near the center of the strong 1.38-micrometer water vapor band are very effective in detecting think cirrus clouds. Based on this observation from AVIRIS data, Gao and Kaufman proposed to put a channel centered at 1.375 micrometers with a width of 30 nm on the Moderate Resolution Imaging Spectrometer (MODIS) for remote sensing of cirrus clouds from space. The sensitivity of the 1.375-micrometer MODIS channel to detect thin cirrus clouds during the day time is expected to be one to two orders of magnitude better than the current infrared emission techniques. As a result, much larger fraction of the satellite data is expected to be identified as being covered by cirrus clouds, some of them so thin that their obscuration of the surface is very small. In order to make better studies of surface reflectance properties, thin cirrus effects must be removed from satellite images. Therefore, there is a need to study radiative properties of thin cirrus clouds, so that a strategy for correction or removal of the thin cirrus effects, similar to the correction of atmospheric aerosol effect, can be formed. In this extended abstract, we describe an empirical approach for removing/correcting thin cirrus effects in AVIRIS images using channels near 1.375 microns - one step beyond the detection of cirrus clouds using these channels.

Gravity Waves and Mesospheric Clouds in the Summer Middle Atmosphere: A Comparison of Lidar Measurements and Ray Modeling of Gravity Waves Over Sondrestrom, Greenland

NASA Technical Reports Server (NTRS)

Gerrard, Andrew J.; Kane, Timothy J.; Eckermann, Stephen D.; Thayer, Jeffrey P.

2004-01-01

We conducted gravity wave ray-tracing experiments within an atmospheric region centered near the ARCLITE lidar system at Sondrestrom, Greenland (67N, 310 deg E), in efforts to understand lidar observations of both upper stratospheric gravity wave activity and mesospheric clouds during August 1996 and the summer of 2001. The ray model was used to trace gravity waves through realistic three-dimensional daily-varying background atmospheres in the region, based on forecasts and analyses in the troposphere and stratosphere and climatologies higher up. Reverse ray tracing based on upper stratospheric lidar observations at Sondrestrom was also used to try to objectively identify wave source regions in the troposphere. A source spectrum specified by reverse ray tracing experiments in early August 1996 (when atmospheric flow patterns produced enhanced transmission of waves into the upper stratosphere) yielded model results throughout the remainder of August 1996 that agreed best with the lidar observations. The model also simulated increased vertical group propagation of waves between 40 km and 80 km due to intensifying mean easterlies, which allowed many of the gravity waves observed at 40 km over Sondrestrom to propagate quasi-vertically from 40-80 km and then interact with any mesospheric clouds at 80 km near Sondrestrom, supporting earlier experimentally-inferred correlations between upper stratospheric gravity wave activity and mesospheric cloud backscatter from Sondrestrom lidar observations. A pilot experiment of real-time runs with the model in 2001 using weather forecast data as a low-level background produced less agreement with lidar observations. We believe this is due to limitations in our specified tropospheric source spectrum, the use of climatological winds and temperatures in the upper stratosphere and mesosphere, and missing lidar data from important time periods.

Tropospheric ozone over Siberia in spring 2010: long-range transport of biomass burning and anthropogenic emissions, stratospheric intrusion and remote boundary layer influence

NASA Astrophysics Data System (ADS)

Berchet, A.; Paris, J.-D.; Ancellet, G.; Law, K.; Stohl, A.; Nédélec, P.; Arshinov, M. Yu; Belan, B. D.; Ciais, P.

2012-04-01

Atmospheric pollution, including tropospheric ozone, has an adverse effect on humans and their environment. The Siberian air shed covers about 10% of Earth's land surface. Therefore, it can contribute significantly to the global tropospheric ozone budget due, in the region, to vast deposition losses on the boreal forest vegetation in the atmospheric surface layer on the one hand, and in-situ photochemical production from ozone precursors emitted by Siberian terrestrial ecosystems, and the influx of stratospheric ozone to the troposphere on the other hand. We have identified and characterized factors that influenced the tropospheric ozone budget over Siberia during spring 2010 by analyzing in-situ measurements of ozone, carbon dioxide, carbon monoxide, and methane mixing ratios collected by continuous analyzers during an intensive airborne measurement campaign of the YAK-AEROSIB Project, carried out between 15 and 18 April 2010. The observations, spanning over 3000 km and stretching from 800 to 6700 m above ground level, were analyzed using the Lagrangian model FLEXPART to simulate backward air mass transport. The analysis of trace gas variability and simulated origin of air masses origins showed that biomass burning and anthropogenic activity expectedly increased carbon monoxide and dioxide concentrations. Also, such plumes coming from east and west of West Siberian plain and from North-Eastern China were shown to increase ozone mixing ratio owing to photochemical processes taking place along the transport route. In the case of low ozone mixing ratios observed over a large area (800x200km) in the upper troposphere above 5500 m the air masses transported to the region under study were likely influenced by an Arctic ozone depletion event transported to lower latitudes and advected to the upper troposphere. The stratospheric source of ozone to the troposphere was observed directly in a well-defined stratospheric intrusion. Numerical simulations of this event suggest an input of 2.56 x 107 kg of ozone associated to a regional downward flux of 9.75 x 1010 molecules·cm-2·s-1.

Tropospheric Ozone from Assimilation of Aura Data using Different Definitions of the Tropopause

NASA Technical Reports Server (NTRS)

Stajner, Ivanka; Wargan, K.; Chang, L.-P.; Hayashi, H.; Pawson, S.; Pawson, Steven; Livesey, N.; Bhartia, P. K.

2006-01-01

Ozone data from Aura OMI and MLS instruments were assimilated into the general circulation model (GCM) constrained by assimilated meteorological fields from the Global Modeling and Assimilation Office at NASA Goddard. Properties of tropospheric ozone and their sensitivity to the definition of the tropopause are investigated. Three definitions of the tropopause are considered: (1) dynamical (using potential vorticity and potential temperature), (2) using temperature lapse rate, and (3) using a fixed ozone value. Comparisons of the tropospheric ozone columns using these tropopause definitions will be presented and evaluated against coincident profiles from ozone sondes. Assimilated ozone profiles are used to identify possible tropopause folding events, which are important for stratosphere-troposphere exchange. Each profile is searched for multiple levels at which ozone attains the value typical of the troposphere-stratosphere transition in order to identify possible tropopause folds. Constrained by the dynamics from a global model and by assimilation of Aura ozone data every 3-hours, this data set provides an opportunity to study ozone evolution in the upper troposphere and lower stratosphere with high temporal resolution.

The FIRE Cirrus Science Results 1993

NASA Technical Reports Server (NTRS)

Mcdougal, David S. (Editor)

1993-01-01

FIRE (First ISCCP (International Satellite Cloud Climatology Project) Regional Experiment) is a U.S. cloud-radiation research program that seeks to improve our basic understanding and parameterizations of cirrus and marine stratocumulus cloud systems and ISCCP data products. The FIRE Cirrus Science Conference was held in Breckenridge, CO, 14-17 Jun. 1993, to present results of cirrus research for the second phase of FIRE (1989-present) and to refine cirrus research goals and priorities for the next phase of FIRE (1994-future). This Conference Publication contains the text of short papers presented at the conference. The papers describe research analyses of data collected at the Cirrus Intensive Field Observations-2 field experiment conducted in Kansas, 13 Nov. - 7 Dec. 1991.

Impact of geostationary satellite water vapor channel data on weather analysis and forecasting

NASA Technical Reports Server (NTRS)

Velden, Christopher S.

1995-01-01

Preliminary results from NWP impact studies are indicating that upper-tropospheric wind information provided by tracking motions in sequences of geostationary satellite water vapor imagery can positively influence forecasts on regional scales, and possibly on global scales as well. The data are complimentary to cloud-tracked winds by providing data in cloud-free regions, as well as comparable in quality. First results from GOES-8 winds are encouraging, and further efforts and model impacts will be directed towards optimizing these data in numerical weather prediction (NWP). Assuming successful launches of GOES-J and GMS-5 satellites in 1995, high quality and resolution water vapor imagers will be available to provide nearly complete global upper-tropospheric wind coverage.

Heterogeneous Interactions of Acetaldehyde and Sulfuric Acid

NASA Technical Reports Server (NTRS)

Michelsen, R. R.; Ashbourn, S. F. M.; Iraci, L. T.

2004-01-01

The uptake of acetaldehyde [CH3CHO] by aqueous sulfuric acid has been studied via Knudsen cell experiments over ranges of temperature (210-250 K) and acid concentration (40-80 wt. %) representative of the upper troposphere. The Henry's law constants for acetaldehyde calculated from these data range from 6 x 10(exp 2) M/atm for 40 wt. % H2SO4 at 228 K to 2 x 10(exp 5) M/atm for 80 wt. % H2SO4 at 212 K. In some instances, acetaldehyde uptake exhibits apparent steady-state loss. The possible sources of this behavior, including polymerization, will be explored. Furthermore, the implications for heterogeneous reactions of aldehydes in sulfate aerosols in the upper troposphere will be discussed.

CSU FIRE 2 cirrus field experiment: Description of field deployment phase

NASA Technical Reports Server (NTRS)

Cox, S.; Beck, G.; Cornwall, C.; Davis, J.; Hein, P.; Lappen, C.; Song, R.; Withrow, J.; Wood, D.; Alvarez, J.

1992-01-01

The Colorado State University (CSU) surface observing systems are described. These systems were deployed at the Parsons, Kansas site during the FIRE 2 Cirrus Special Observing Period (SOP) from 13 Nov. - 7 Dec. 1991. The geographical coordinates of the site containing most of the CSU instrumentation are 37 deg. 18 min N. latitude and 96 deg. 30 min. W. longitude; site elevation was 269 meters. In addition, one surface meteorological and broadband flux observing site was maintained at the Tri City Airport which is approximately 18 miles due west of Parsons (37 deg. 20 min. N. latitude, 95 deg. 30 min. 30 sec. W. longitude). A map of the locations of the CSU deployment sites is presented. At the main Parsons site, the instrumentation was located directly adjacent to and north of a lake. Under most cirrus observing conditions, when the wing had a significant southernly component, the lake was upwind of the observing site. The measurements and observations collected during the experiment are listed. These measurements may be grouped into five categories: surface meteorology; infrared spectral and broadband measurements; solar spectral and broadband measurements; upper air measurements; and cloud measurements. A summary of observations collected at the Parsons site during the SOP are presented. The wind profiler, laser ceilometer, surface meteorology and surface broadband radiation instrumentation were operated on a continuous basis. All other systems were operated on an 'on demand' basis when cloud conditions merited the collection of data.

Does shortwave absorption by methane influence its effectiveness?

NASA Astrophysics Data System (ADS)

Modak, Angshuman; Bala, Govindasamy; Caldeira, Ken; Cao, Long

2018-01-01

In this study, using idealized step-forcing simulations, we examine the effective radiative forcing of CH4 relative to that of CO2 and compare the effects of CH4 and CO2 forcing on the climate system. A tenfold increase in CH4 concentration in the NCAR CAM5 climate model produces similar long term global mean surface warming ( 1.7 K) as a one-third increase in CO2 concentration. However, the radiative forcing estimated for CO2 using the prescribed-SST method is 81% that of CH4, indicating that the efficacy of CH4 forcing is 0.81. This estimate is nearly unchanged when the CO2 physiological effect is included in our simulations. Further, for the same long-term global mean surface warming, we simulate a smaller precipitation increase in the CH4 case compared to the CO2 case. This is because of the fast adjustment processes—precipitation reduction in the CH4 case is larger than that of the CO2 case. This is associated with a relatively more stable atmosphere and larger atmospheric radiative forcing in the CH4 case which occurs because of near-infrared absorption by CH4 in the upper troposphere and lower stratosphere. Within a month after an increase in CH4, this shortwave heating results in a temperature increase of 0.8 K in the lower stratosphere and upper troposphere. In contrast, within a month after a CO2 increase, longwave cooling results in a temperature decrease of 3 K in the stratosphere and a small change in the upper troposphere. These fast adjustments in the lower stratospheric and upper tropospheric temperature, along with the adjustments in clouds in the troposphere, influence the effective radiative forcing and the fast precipitation response. These differences in fast climate adjustments also produce differences in the climate states from which the slow response begins to evolve and hence they are likely associated with differing feedbacks. We also find that the tropics and subtropics are relatively warmer in the CH4 case for the same global mean surface warming because of a larger longwave clear-sky and shortwave cloud forcing over these regions in the CH4 case. Further investigation using a multi-model intercomparison framework would permit an assessment of the robustness of our results.

78 FR 55629 - Special Conditions: Cirrus Design Corporation, Model SF50; Inflatable Three-Point Restraint...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-09-11

...-0781; Special Conditions No. 23-261-SC] Special Conditions: Cirrus Design Corporation, Model SF50... conditions are issued for the Cirrus Design Corporation (Cirrus), model SF50. This airplane will have novel and unusual design features associated with installation of an inflatable three-point restraint safety...

A New Way to Measure Cirrus Ice Water Content by Using Ice Raman Scatter with Raman Lidar

NASA Technical Reports Server (NTRS)

Wang, Zhien; Whiteman, David N.; Demoz, Belay; Veselovskii, Igor

2004-01-01

High and cold cirrus clouds mainly contain irregular ice crystals, such as, columns, hexagonal plates, bullet rosettes, and dendrites, and have different impacts on the climate system than low-level clouds, such as stratus, stratocumulus, and cumulus. The radiative effects of cirrus clouds on the current and future climate depend strongly on cirrus cloud microphysical properties including ice water content (IWC) and ice crystal sizes, which are mostly an unknown aspect of cinus clouds. Because of the natural complexity of cirrus clouds and their high locations, it is a challenging task to get them accurately by both remote sensing and in situ sampling. This study presents a new method to remotely sense cirrus microphysical properties by using ice Raman scatter with a Raman lidar. The intensity of Raman scattering is fundamentally proportional to the number of molecules involved. Therefore, ice Raman scattering signal provides a more direct way to measure IWC than other remote sensing methods. Case studies show that this method has the potential to provide essential information of cirrus microphysical properties to study cloud physical processes in cirrus clouds.

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

NASA Astrophysics Data System (ADS)

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

2008-12-01

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

Tropical Cyclone Reconnaissance Over the Western North Pacific with the Global Hawk: Operational Requirements, Benefits, and Feasibility

DTIC Science & Technology

2012-09-01

Science mission conducted using the Global Hawk. Ten specialized instruments were installed on the aircraft to explore the upper troposphere and...shorelines and evaluate the potential for marine enforcement surveillance. The HALE UAV used in situ measurements of gases such as ozone , halocarbons...at altitudes of 65000 ft measurements may be obtained through the entire depth of the troposphere . Like many UAVs mentioned previously, the Global

Lidar cloud studies for FIRE and ECLIPS

NASA Technical Reports Server (NTRS)

Sassen, Kenneth; Grund, Christian J.; Spinhirne, James D.; Hardesty, Michael; Alvarez, James

1990-01-01

Optical remote sensing measurements of cirrus cloud properties were collected by one airborne and four ground-based lidar systems over a 32 h period during this case study from the First ISCCP (International Satellite Cloud Climatology Program) Regional Experiment (FIRE) Intensive Field Observation (IFO) program. The lidar systems were variously equipped to collect linear depolarization, intrinsically calibrated backscatter, and Doppler velocity information. Data presented describe the temporal evolution and spatial distribution of cirrus clouds over an area encompassing southern and central Wisconsin. The cirrus cloud types include: dissipating subvisual and thin fibrous cirrus cloud bands, an isolated mesoscale uncinus complex (MUC), a large-scale deep cloud that developed into an organized cirrus structure within the lidar array, and a series of intensifying mesoscale cirrus cloud masses. Although the cirrus frequently developed in the vertical from particle fall-streaks emanating from generating regions at or near cloud tops, glaciating supercooled (-30 to -35 C) altocumulus clouds contributed to the production of ice mass at the base of the deep cirrus cloud, apparently even through riming, and other mechanisms involving evaporation, wave motions, and radiative effects are indicated. The generating regions ranged in scale from approximately 1.0 km cirrus uncinus cells, to organized MUC structures up to approximately 120 km across.

Comparison of upper tropospheric carbon monoxide from MOPITT, ACE-FTS, and HIPPO-QCLS

NASA Astrophysics Data System (ADS)

Martínez-Alonso, Sara; Deeter, Merritt N.; Worden, Helen M.; Gille, John C.; Emmons, Louisa K.; Pan, Laura L.; Park, Mijeong; Manney, Gloria L.; Bernath, Peter F.; Boone, Chris D.; Walker, Kaley A.; Kolonjari, Felicia; Wofsy, Steven C.; Pittman, Jasna; Daube, Bruce C.

2014-12-01

Products from the Measurements Of Pollution In The Troposphere (MOPITT) instrument are regularly validated using in situ airborne measurements. However, few of these measurements reach into the upper troposphere, thus hindering MOPITT validation in that region. Here we evaluate upper tropospheric (~500 hPa to the tropopause) MOPITT CO profiles by comparing them to satellite Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) retrievals and to measurements from the High-performance Instrumented Airborne Platform for Environmental Research Pole to Pole Observations (HIPPO) Quantum Cascade Laser Spectrometer (QCLS). Direct comparison of colocated v5 MOPITT thermal infrared-only retrievals, v3.0 ACE-FTS retrievals, and HIPPO-QCLS measurements shows a slight positive MOPITT CO bias within its 10% accuracy requirement with respect to the other two data sets. Direct comparison of colocated ACE-FTS and HIPPO-QCLS measurements results in a small number of samples due to the large disparity in sampling pattern and density of these data sets. Thus, two additional indirect techniques for comparison of noncoincident data sets have been applied: tracer-tracer (CO-O3) correlation analysis and analysis of profiles in tropopause coordinates. These techniques suggest a negative bias of ACE-FTS with respect to HIPPO-QCLS; this could be caused by differences in resolution (horizontal, vertical) or by deficiencies in the ACE-FTS CO retrievals below ~20 km of altitude, among others. We also investigate the temporal stability of MOPITT and ACE-FTS data, which provide unique global CO records and are thus important in climate analysis. Our results indicate that the relative bias between the two data sets has remained generally stable during the 2004-2010 period.

CMAQ predictions of tropospheric ozone in the U.S. southwest: influence of lateral boundary and synoptic conditions.

PubMed

Shi, Chune; Fernando, H J S; Hyde, Peter

2012-02-01

Phoenix, Arizona, has been an ozone nonattainment area for the past several years and it remains so. Mitigation strategies call for improved modeling methodologies as well as understanding of ozone formation and destruction mechanisms during seasons of high ozone events. To this end, the efficacy of lateral boundary conditions (LBCs) based on satellite measurements (adjusted-LBCs) was investigated, vis-à-vis the default-LBCs, for improving the predictions of Models-3/CMAQ photochemical air quality modeling system. The model evaluations were conducted using hourly ground-level ozone and NO(2) concentrations as well as tropospheric NO(2) columns and ozone concentrations in the middle to upper troposphere, with the 'design' periods being June and July of 2006. Both included high ozone episodes, but the June (pre-monsoon) period was characterized by local thermal circulation whereas the July (monsoon) period by synoptic influence. Overall, improved simulations were noted for adjusted-LBC runs for ozone concentrations both at the ground-level and in the middle to upper troposphere, based on EPA-recommended model performance metrics. The probability of detection (POD) of ozone exceedances (>75ppb, 8-h averages) for the entire domain increased from 20.8% for the default-LBC run to 33.7% for the adjusted-LBC run. A process analysis of modeling results revealed that ozone within PBL during bulk of the pre-monsoon season is contributed by local photochemistry and vertical advection, while the contributions of horizontal and vertical advections are comparable in the monsoon season. The process analysis with adjusted-LBC runs confirms the contributions of vertical advection to episodic high ozone days, and hence elucidates the importance of improving predictability of upper levels with improved LBCs. Copyright © 2011 Elsevier B.V. All rights reserved.

AO/NAO Response to Climate Change. 2; Relative Importance of Low- and High-Latitude Temperature Changes

NASA Technical Reports Server (NTRS)

Rind, D.; Perlwitz, J.; Lonergan, P.; Lerner, J.

2005-01-01

Using a variety of GCM experiments with various versions of the GISS model, we investigate how different aspects of tropospheric climate changes affect the extratropical Arctic Oscillation (AO)/North Atlantic Oscillation (NAO) circulation indices. The results show that low altitude changes in the extratropical latitudinal temperature gradient can have a strong impact on eddy forcing of the extratropical zonal wind, in the sense that when this latitudinal temperature gradient increases, it helps force a more negative AO/NAO phase. In addition, local conditions at high latitudes can stabilize/destabilize the atmosphere, inducing negative/positive phase changes. To the extent that there is not a large temperature change in the tropical upper troposphere (either through reduced tropical sensitivity at the surface, or limited transport of this change to high levels), the changes in the low level temperature gradient can provide the dominate influence on the extratropical circulation, so that planetary wave meridional refraction and eddy angular momentum transport changes become uncorrelated with potential vorticity transports. In particular, the climate change that produces the most positive NAO phase change would have substantial warming in the tropical upper troposphere over the Pacific Ocean, with high latitude warming in the North Atlantic. An increase in positive phase of these circulation indices is still more likely than not, but it will depend on the degree of tropical and high latitude temperature response and the transport of low level warming into the upper troposphere. These are aspects that currently differ among the models used for predicting the effects of global warning, contributing to the lack of consensus of future changes in the AO/NAO.

Microbiome of the upper troposphere: Species composition and prevalence, effects of tropical storms, and atmospheric implications

PubMed Central

DeLeon-Rodriguez, Natasha; Lathem, Terry L.; Rodriguez-R, Luis M.; Barazesh, James M.; Anderson, Bruce E.; Beyersdorf, Andreas J.; Ziemba, Luke D.; Bergin, Michael; Nenes, Athanasios; Konstantinidis, Konstantinos T.

2013-01-01

The composition and prevalence of microorganisms in the middle-to-upper troposphere (8–15 km altitude) and their role in aerosol-cloud-precipitation interactions represent important, unresolved questions for biological and atmospheric science. In particular, airborne microorganisms above the oceans remain essentially uncharacterized, as most work to date is restricted to samples taken near the Earth’s surface. Here we report on the microbiome of low- and high-altitude air masses sampled onboard the National Aeronautics and Space Administration DC-8 platform during the 2010 Genesis and Rapid Intensification Processes campaign in the Caribbean Sea. The samples were collected in cloudy and cloud-free air masses before, during, and after two major tropical hurricanes, Earl and Karl. Quantitative PCR and microscopy revealed that viable bacterial cells represented on average around 20% of the total particles in the 0.25- to 1-μm diameter range and were at least an order of magnitude more abundant than fungal cells, suggesting that bacteria represent an important and underestimated fraction of micrometer-sized atmospheric aerosols. The samples from the two hurricanes were characterized by significantly different bacterial communities, revealing that hurricanes aerosolize a large amount of new cells. Nonetheless, 17 bacterial taxa, including taxa that are known to use C1–C4 carbon compounds present in the atmosphere, were found in all samples, indicating that these organisms possess traits that allow survival in the troposphere. The findings presented here suggest that the microbiome is a dynamic and underappreciated aspect of the upper troposphere with potentially important impacts on the hydrological cycle, clouds, and climate. PMID:23359712

[Retrieval of the Optical Thickness and Cloud Top Height of Cirrus Clouds Based on AIRS IR High Spectral Resolution Data].

PubMed

Cao, Ya-nan; Wei, He-li; Dai, Cong-ming; Zhang, Xue-hai

2015-05-01

A study was carried out to retrieve optical thickness and cloud top height of cirrus clouds from the Atmospheric Infrared Sounder (AIRS) high spectral resolution data in 1070~1135 cm-1 IR band using a Combined Atmospheric Radiative Transfer model (CART) by brightness temperature difference between model simulation and AIRS observation. The research is based on AIRS LIB high spectral infrared observation data combined with Moderate Resolution Imaging Spectroradiometer (MODIS) cloud product data. Brightness temperature spectra based, on the retrieved cirrus optical thickness and cloud top height were simulated and compared with brightness temperature spectra of AIRS observation in the 650~1150 cm-1 band. The cirrus optical thickness and cloud top height retrieved were compared with brightness temperature of AIRS for channel 760 (900.56 cm-1, 11. 1 µm) and cirrus reflectance of MODIS cloud product. And cloud top height retrieved was compared with cloud top height from MODIS. Results show that the brightness temperature spectra simulated were basically consistent with AIRS observation under the condition of retrieval in the 650~1150 cm-1 band. It means that CART can be used to simulate AIRS brightness temperature spectra. The retrieved cirrus parameters are consistent with brightness temperature of AIRS for channel 11. 1 µm with low brightness temperature corresponding to large cirrus optical thickness and high cloud top height. And the retrieved cirrus parameters are consistent with cirrus reflectance of MODIS cloud product with high cirrus reflectance corresponding to large cirrus optical thickness and high cloud top height. Correlation coefficient of brightness temperature between retrieved cloud top height and MODIS cloud top height was relatively high. They are mostly located in the range of 8. 5~11.5 km, and their probability distribution trend is approximately identical. CART model is feasible to retrieve cirrus properties, and the retrieval is reliable.

Development of ground-based lidars for measuring H2O and O3 profiles in the troposphere

NASA Astrophysics Data System (ADS)

Sakai, T.; Abo, M.; Pham, L. H. P.; Uchino, O.; Nagai, T.; Izumi, T.; Morino, I.; Ohyama, H.; Nagasawa, C.

2015-12-01

Water vapor is the strongest natural greenhouse gas and a highly variable atmospheric constituent. It plays an important role of the energy transfer and the meteorological phenomena such as evaporation, vapor transport, cloud formation, and rainfall in the troposphere. Ozone is an important air pollutant that at high concentrations impacts on human health and ecosystem including crops and also a greenhouse gas that plays an important role in climate change. Aerosol is an important climate parameter and also one of the largest error sources (causes) in retrieval from solar reflected short wavelength infrared radiances observed with greenhouse gases observing satellites such as the GOSAT and OCO-2. Therefore, we have been developing ground-based differential absorption lidars (DIALs) for measuring the tropospheric water vapor, ozone and aerosols.The water vapor DIAL employs two distributed Bragg reflector (DBR) lasers operating at 829.054 nm for the online wavelength and 829.124 nm for the offline wavelength with tapered semiconductor optical amplifier (TSOA) in a master oscillator power amplifier (MOPA) configuration, and utilizes pseudorandom coded pulse modulation technique.It has started to measure the vertical distribution of lower tropospheric water vapor in order to improve accuracy and lead time of numerical weather prediction of local heavy rainfalls. Well-organized and regularly spaced convective cells of which vertical thickness were 200 m and the periods were 10 minutes were observed in the top of planetary boundary layer at 2.5 km altitude over Tokyo (35.66°N, 139.37°E) on 22 June 2015.The ozone DIAL employs a Nd:YAG laser and a 2 m long Raman cell filled with CO2 gas which generates four Stokes lines (276.2, 287.2, 299.1, and 312.0 nm) of stimulated Raman scattering, and two receiving telescopes with diameters of 49 and 10 cm.It has started to measure the vertical distributions of the tropospheric ozone as well as aerosols and thin cirrus cloud in order to validate GOSAT product. High concentrations of ozone and aerosols were observed below 2 km altitude on 22 March 2015 over Saga (33.24°N, 130.29°E), which could be transported with spherical aerosols and dust particles from Northeast Asia. The observational result of ozone will be compared with a chemistry-climate model.

The effect of clouds on photolysis rates and ozone formation in the unpolluted troposphere

NASA Technical Reports Server (NTRS)

Thompson, A. M.

1984-01-01

The photochemistry of the lower atmosphere is sensitive to short- and long-term meteorological effects; accurate modeling therefore requires photolysis rates for trace gases which reflect this variability. As an example, the influence of clouds on the production of tropospheric ozone has been investigated, using a modification of Luther's two-stream radiation scheme to calculate cloud-perturbed photolysis rates in a one-dimensional photochemical transport model. In the unpolluted troposphere, where stratospheric inputs of odd nitrogen appear to represent the photochemical source of O3, strong cloud reflectance increases the concentration of NO in the upper troposphere, leading to greatly enhanced rates of ozone formation. Although the rate of these processes is too slow to verify by observation, the calculation is useful in distinguishing some features of the chemistry of regions of differing mean cloudiness.

Improvement of the basic knowledge of the climatology of the vertical ozone layer by enhanced balloon sounding

NASA Technical Reports Server (NTRS)

Attmannspacher, W.; Hartmannsgrubber, R.; Lang, P.

1984-01-01

Balloon sounding of the ozone in the Earth atmosphere was performed in order to determine the natural behavior of ozone and its recognizable deviations. The importance of ozone in the Earth atmosphere and the orographic situation of observatories and ozone sounding statistics since 1966 are explained. The physical processes governing the total amount of ozone, and the behavior of stratospheric ozone are described. Measurements in the upper stratosphere show a decrease of the ozone partial pressure above 26 km altitude since 1977. The behavior of tropospheric ozone is discussed. Data since 1977 show increasing ozone values in the troposphere, up to 50% to 70%. This increase is independent of the solar radiation intensity and the reinforced transport of stratospheric ozone into the troposphere. The increase in the troposphere cannot compensate the stratospheric decrease.

Troposphere-to-Stratosphere Transport in the Lowermost Stratosphere from Measurements of H2O, CO2, N2O and O3

NASA Technical Reports Server (NTRS)

Hintsa, E. J.; Boering, K. A.; Weinstock, E. M.; Anderson, J. G.; Gary, B. L.; Pfister, L.; Daube, B. C.; Wofsy, S. C.; Loewenstein, M.; Podolske, J.R.;

Troposphere-to-Stratosphere Transport in the Lowermost Stratosphere from Measurements of H2O, CO2, N2O and O3

NASA Technical Reports Server (NTRS)

Hintsa, E. J.; Boering, K. A.; Weinstock, E. M.; Anderson, J. G.; Gary, B. L.; Pfister, L.; Daube, B. C.; Wofsy, S. C.; Loewenstein, M.; Podolske, J. R.

1998-01-01

The origin of air in the lowermost stratosphere is investigated with measurements from the NASA ER-2 aircraft. Air with high water vapor mixing ratios was observed in the stratosphere at theta = 330-380 K near 40 N in May 1995, indicating the influence of intrusions of tropospheric air. Assuming that observed tracer-tracer relationships reflect mixing lines between tropospheric and stratospheric air masses, we calculate mixing ratios of H2O (12-24 ppmv) and CO2 for the admixed tropospheric air at theta = 352-364 K. Temperatures on the 355 K surface at 20-40 N were low enough to dehydrate air to these values. While most ER-2 CO2 data in both hemispheres are consistent with tropical or subtropical air entering the lowermost stratosphere, measurements from May 1995 for theta < 362 K suggest that entry of air from the midlatitude upper troposphere can occur in conjunction with mixing processes near the tropopause.

Troposphere-to-Stratosphere Transport in the Lowermost Stratosphere from Measurements of H2O, CO2, N2O, and O3

NASA Technical Reports Server (NTRS)

Hintsa, E. J.; Boering, K. A.; Weinstock, E. M.; Anderson, J. G.; Gary, B. L.; Pfister, L.; Daube, B. C.; Wofsy, S. C.; Loewenstein, M.; Podolske, J. R.;

Troposphere-to-Stratosphere Transport in the Lowermost Stratosphere from Measurements of H2O, CO2, N2O and O3

NASA Technical Reports Server (NTRS)

Hintsa, E. J.; Boering, K. A.; Weinstock, E. M.; Anderson, J. G.; Gary, B. L.; Pfister, L.; Daube, B. C.; Wofsy, S. C.; Loewenstein, M.; Podolske, J. R.;

Characterization of the Marine Boundary Layer and the Trade-Wind Inversion over the Sub-tropical North Atlantic

NASA Astrophysics Data System (ADS)

Carrillo, J.; Guerra, J. C.; Cuevas, E.; Barrancos, J.

2016-02-01

The stability of the lower troposphere along the east side of the sub-tropical North Atlantic is analyzed and characterized using upper air meteorological long-term records at the Canary Islands (Tenerife), Madeira (Madeira) and Azores (Terceira) archipelagos. The most remarkable characteristic is the strong stratification observed in the lower troposphere, with a strengthening of stability centred at levels near 900 and 800 hPa in a significant percentage of soundings (ranging from 17 % in Azores to 33 % in Güimar, Canary Islands). We show that this double structure is associated with the top of the marine boundary layer (MBL) and the trade-wind inversion (TWI) respectively. The top of the MBL coincides with the base of the first temperature inversion (≈ 900 hPa) where a sharp change in water vapour mixing ratio is observed. A second temperature inversion is found near 800 hPa, which is characterized by a large directional wind shear just above the inversion layer, tied to the TWI. We find that seasonal and latitudinal variations of the height and strength of both temperature inversions are driven by large-scale subsiding air from the upper troposphere associated with the descent branch of the Hadley cell. Increased general subsidence in summertime enhances stability in the lower troposphere, more markedly in the southern stations, where the inversion-layer heights are found at lower levels enhancing the main features of these two temperature inversions. A simple conceptual model that explains the lower tropospheric inversion enhancement by subsidence is proposed.

Observations and Modeling of Composition of Upper Troposphere/Lower Stratosphere (UTILS): Isentropic Mixing Events and Morphology of HNO3 as Observed by HIRDLS and Comparison with Results from Global Modeling Initiative

NASA Technical Reports Server (NTRS)

Rodriquez, J. M.; Douglass, A.R.; Yoshida, Y.; Strahan, S.; Duncan, B.; Olsen, M.; Gille, J.; Yudin, V.; Nardi, B.

2008-01-01

isentropic exchange of air masses between the tropical upper troposphere and mid-latitude lowermost stratosphere (the so-called "middle world") is an important pathway for stratospheric-tropospheric exchange. A seasonal, global view of this process has been difficult to obtain, in part due to the lack of the vertical resolution in satellite observations needed to capture the laminar character of these events. Ozone observations at a resolution of about 1 km from the High Resolution Dynamic Limb Sounder (HIRDLS) on NASA's Aura satellite show instances of these intrusions. Such intrusions should also be observable in HN03 observations; however, the abundances of nitric acid could be additionally controlled by chemical processes or incorporation and removal into ice clouds. We present a systematic examination of the HIRDLS data on O3 and HNO3 to determine the seasonal and spatial characteristics of the distribution of isentropic intrusions. At the same time, we compare the observed distributions with those calculated by the Global Modeling Initiative combined tropospheric-stratospheric model, which has a vertical resolution of about I km. This Chemical Transport Model (CTM) is driven by meteorological fields obtained from the GEOS-4 system of NASA/Goddard Global Modeling and Assimilation Office (GMAO), for the Aura time period, at a vertical resolution of about 1 km. Such comparison brings out the successes and limitations of the model in representing isentropic stratospheric-tropospheric exchange, and the different processes controlling HNO3 in the UTAS.

NMHC emissions from Asia: sources and transport

NASA Astrophysics Data System (ADS)

Shirai, T.; Blake, D. R.; Barletta, B.; Meinardi, S.; Rowland, F. S.; Chan, J. C.; Takegawa, N.; Kondo, Y.; Koike, M.; Kita, K.; Takigawa, M.; Kawakami, S.; Ogawa, T.

2002-12-01

Recent rapid industrialization and economic growth in Asia changed the industrial structure, land use, and people's lifestyle resulting in a dramatic change in the amount and composition of the gas emissions from Asia. Because emissions can be transported very rapidly once convected to the free troposphere, Asian emissions can affect both local and regional air quality and climate. To access the impact of changing emission from Asia, an airborne observation campaign PEACE (the Pacific Exploration of Asian Continental Emission) phase-A and B were conducted in January and April - May 2002, respectively, sponsored by NASDA (National Space Development Agency of Japan). The concentrations of NMHCs (nonmethanehydrocarbons) and halocarbons were obtained by whole air sampling and subsequent gas chromatography analyses in the laboratory. Quantified onboard the aircraft were CO, CO2, O3, NO, NO2, NOy, H2O, SO2, aerosols, and condensation nuclei. The experiment was conducted in the vicinity of Japan and PEACE-A and B represent the local winter and spring weather conditions. The trace gas distributions in the lower troposphere were often influenced by local pollution (i.e. from Japan, Korea) while those of the long-range transport (i.e. from Europe) were occasionally seen in the upper troposphere. This is confirmed by the airmass age estimation using the ratios of short-lived gases (i.e. C2H4) vs. more stable compounds (i.e. CO). Emissions from China were distinguished using data obtained from ground-based sampling and measurements. Transport from China was seen both in the lower troposphere and upper troposphere. Some case studies on source identification will be discussed.

Transport of sulfur dioxide from the Asian Pacific Rim to the North Pacific troposphere

NASA Astrophysics Data System (ADS)

Thornton, Donald C.; Bandy, Alan R.; Blomquist, Byron W.; Talbot, Robert W.; Dibb, Jack E.

1997-12-01

The NASA Pacific Exploratory Mission over the Western Pacific Ocean (PEM-West B) field experiment provided an opportunity to study sulfur dioxide (SO2) in the troposphere over the western Pacific Ocean from the tropics to 60°N during February-March 1993. The large suite of chemical and physical measurements yielded a complex matrix in which to understand the distribution of sulfur dioxide over the western Pacific region. In contrast to the late summer period of Pacific Exploratory Mission-West A (PEM-West A) (1991) over this same area, SO2 showed little increase with altitude, and concentrations were much lower in the free troposphere than during the PEM-West B period. Volcanic impacts on the upper troposphere were again found as a result of deep convection in the tropics. Extensive emission of SO2 from the Pacific Rim land masses were primarily observed in the lower well-mixed part of the boundary layer but also in the upper part of the boundary layer. Analyses of the SO2 data with aerosol sulfate, beryllium-7, and lead-210 indicated that SO2 contributed to half or more of the observed total oxidized sulfur (SO2 plus aerosol sulfate) in free tropospheric air. The combined data set suggests that SO2 above 8.5 km is transported from the surface but with aerosol sulfate being removed more effectively than SO2. Cloud processing and rain appeared to be responsible for lower SO2 levels between 3 and 8.5 km than above or below this region.

Tropical High Cloud Fraction Controlled by Cloud Lifetime Rather Than Clear-sky Convergence

NASA Astrophysics Data System (ADS)

Seeley, J.; Jeevanjee, N.; Romps, D. M.

2016-12-01

Observations and simulations show a peak in cloud fraction below the tropopause. This peak is usually attributed to a roughly co-located peak in radiatively-driven clear-sky convergence, which is presumed to force convective detrainment and thus promote large cloud fraction. Using simulations of radiative-convective equilibrium forced by various radiative cooling profiles, we refute this mechanism by showing that an upper-tropospheric peak in cloud fraction persists even in simulations with no peak in clear-sky convergence. Instead, cloud fraction profiles seem to be controlled by cloud lifetimes — i.e., how long it takes for clouds to dissipate after they have detrained. A simple model of cloud evaporation shows that the small saturation deficit in the upper troposphere greatly extends cloud lifetimes there, while the large saturation deficit in the lower troposphere causes condensate to evaporate quickly. Since cloud mass flux must go to zero at the tropopause, a peak in cloud fraction emerges at a "sweet spot" below the tropopause where cloud lifetimes are long and there is still sufficient mass flux to be detrained.

Investigation of the Physical Processes Governing Large-Scale Tracer Transport in the Stratosphere and Troposphere

NASA Technical Reports Server (NTRS)

Selkirk, Henry B.

2001-01-01

This report summarizes work conducted from January 1996 through April 1999 on a program of research to investigate the physical mechanisms that underlie the transport of trace constituents in the stratosphere-troposphere system. The primary scientific goal of the research has been to identify the processes which transport air masses within the lower stratosphere, particularly between the tropics and middle latitudes. This research was conducted in collaboration with the Subsonic Assessment (SASS) of the NASA Atmospheric Effects of Radiation Program (AEAP) and the Upper Atmospheric Research Program (UARP). The SASS program sought to understand the impact of the present and future fleets of conventional jet traffic on the upper troposphere and lower stratosphere, while complementary airborne observations under UARP seek to understand the complex interactions of dynamical and chemical processes that affect the ozone layer. The present investigation contributed to the goals of each of these by diagnosing the history of air parcels intercepted by NASA research aircraft in UARP and AEAP campaigns. This was done by means of a blend of trajectory analyses and tracer correlation techniques.

GCM simulations of intraseasonal variability in the Pacific/North American region

NASA Technical Reports Server (NTRS)

Schubert, Siegfried; Suarez, Max; Park, Chung-Kyu; Moorthi, Shrinivas

1993-01-01

General circulation model (GCM) simulations of low-frequency variability with time scales of 20 to 70 days are analyzed for the Pacific sector during boreal winter. The GCM's leading mode in the upper-tropospheric zonal wind is associated with fluctuations of the East Asian jet; this mode resembles, in both structure and amplitude, the Pacific/North American (PNA) pattern found in the observations on these time scales. In both the model and observations, the PNA anomaly is characterized by: (1) a linear balance in the upper-tropospheric vorticity budget with no significant Rossby wave source in the tropics, (2) a barotropic conversion of kinetic energy from the time mean Pacific jet, and (3) a north/south displacement of the Pacific storm track. In the GCM, the latter is associated with synoptic eddy heat flux and latent heat anomalies that appear to contribute to a strong lower-tropospheric source of wave activity over the North Pacific. This is in contrast to the observations, which show only a weak source of wave activity in this region.

Driving Roles of Tropospheric and Stratospheric Thermal Anomalies in Intensification and Persistence of the Arctic Superstorm in 2012

NASA Astrophysics Data System (ADS)

Tao, Wei; Zhang, Jing; Fu, Yunfei; Zhang, Xiangdong

2017-10-01

Intense synoptic-scale storms have been more frequently observed over the Arctic during recent years. Specifically, a superstorm hit the Arctic Ocean in August 2012 and preceded a new record low Arctic sea ice extent. In this study, the major physical processes responsible for the storm's intensification and persistence are explored through a series of numerical modeling experiments with the Weather Research and Forecasting model. It is found that thermal anomalies in troposphere as well as lower stratosphere jointly lead to the development of this superstorm. Thermal contrast between the unusually warm Siberia and the relatively cold Arctic Ocean results in strong troposphere baroclinicity and upper level jet, which contribute to the storm intensification initially. On the other hand, Tropopause Polar Vortex (TPV) associated with the thermal anomaly in lower stratosphere further intensifies the upper level jet and accordingly contributes to a drastic intensification of the storm. Stacking with the enhanced surface low, TPV intensifies further, which sustains the storm to linger over the Arctic Ocean for an extended period.

78 FR 36084 - Special Conditions: Cirrus Design Corporation Model SF50 Airplane; Function and Reliability...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-06-17

...; Special Conditions No. 23-248-SC] Special Conditions: Cirrus Design Corporation Model SF50 Airplane... granting special conditions for the Cirrus Design Corporation model SF50 airplane. We are withdrawing... Special Condition No. 23-248- SC for the Cirrus Design Corporation new model SF50 ``Vision'' Jet. The SF50...

FIRE Cirrus on October 28, 1986: LANDSAT; ER-2; King Air; theory

NASA Technical Reports Server (NTRS)

Wielicki, Bruce A.; Suttles, John T.; Heymsfield, Andrew J.; Welch, Ronald M.; Spinhirne, James D.; Parker, Lindsay; Arduini, Robert F.

1990-01-01

A simultaneous examination was conducted of cirrus clouds in the FIRE Cirrus IFO-I on 10/28/86 using a multitude of remote sensing and in-situ measurements. The focus is cirrus cloud radiative properties and their relationship to cloud microphysics. A key element is the comparison of radiative transfer model calculations and varying measured cirrus radiative properties (emissivity, reflectance vs. wavelength, reflectance vs. viewing angle). As the number of simultaneously measured cloud radiative properties and physical properties increases, more sharply focused tests of theoretical models are possible.

GEWEX Cloud System Study (GCSS) Working Group on Cirrus Cloud Systems (WG2)

NASA Technical Reports Server (NTRS)

Starr, David

2002-01-01

Status, progress and plans will be given for current GCSS (GEWEX Cloud System Study) WG2 (Working Group on Cirrus Cloud Systems) projects, including: (a) the Idealized Cirrus Model Comparison Project, (b) the Cirrus Parcel Model Comparison Project (Phase 2), and (c) the developing Hurricane Nora extended outflow model case study project. Past results will be summarized and plans for the upcoming year described. Issues and strategies will be discussed. Prospects for developing improved cloud parameterizations derived from results of GCSS WG2 projects will be assessed. Plans for NASA's CRYSTAL-FACE (Cirrus Regional Study of Tropical Anvils and Layers - Florida Area Cirrus Experiment) potential opportunities for use of those data for WG2 model simulations (future projects) will be briefly described.

Structural Variability of Tropospheric Growth Factors Transforming Mid-latitude Cyclones to Severe Storms over the North Atlantic

NASA Astrophysics Data System (ADS)

Wild, Simon; Befort, Daniel J.; Leckebusch, Gregor C.

2015-04-01

The development of European surface wind storms out of normal mid-latitude cyclones is substantially influenced by upstream tropospheric growth factors over the Northern Atlantic. The main factors include divergence and vorticity advection in the upper troposphere, latent heat release and the presence of instabilities of short baroclinic waves of suitable wave lengths. In this study we examine a subset of these potential growth factors and their related influences on the transformation of extra-tropical cyclones into severe damage prone surface storm systems. Previous studies have shown links between specific growth factors and surface wind storms related to extreme cyclones. In our study we investigate in further detail spatial and temporal variability patterns of these upstream processes at different vertical levels of the troposphere. The analyses will comprise of the three growth factors baroclinicity, latent heat release and upper tropospheric divergence. Our definition of surface wind storms is based on the Storm Severity Index (SSI) alongside a wind tracking algorithm identifying areas of exceedances of the local 98th percentile of the 10m wind speed. We also make use of a well-established extra-tropical cyclone identification and tracking algorithm. These cyclone tracks form the base for a composite analysis of the aforementioned growth factors using ERA-Interim Reanalysis from 1979 - 2014 for the extended winter season (ONDJFM). Our composite analysis corroborates previous similar studies but extends them by using an impact based algorithm for the identification of strong wind systems. Based on this composite analysis we further identify variability patterns for each growth factor most important for the transformation of a cyclone into a surface wind storm. We thus also address the question whether the link between storm intensity and related growth factor anomaly taking into account its spatial variability is stable and can be quantified. While the robustness of our preliminary results is generally dependent on the growth factor investigated, some examples include i) the overall availability of latent heat seems to be less important than its spatial structure around the cyclone core and ii) the variability of upper-tropospheric baroclinicity appears to be highest north of the surface position of the cyclone, especially for those that transform into a surface storm.

The analysis of in situ and retrieved aerosol properties measured during three airborne field campaigns

NASA Astrophysics Data System (ADS)

Corr, Chelsea A.

Aerosols can directly influence climate, visibility, and photochemistry by scattering and absorbing solar radiation. Aerosol chemical and physical properties determine how efficiently a particle scatters and/or absorbs incoming short-wave solar radiation. Because many types of aerosol can act as nuclei for cloud droplets (CCN) and a smaller population of airborne particles facilitate ice crystal formation (IN), aerosols can also alter cloud-radiation interactions which have subsequent impacts on climate. Thus aerosol properties determine the magnitude and sign of both the direct and indirect impacts of aerosols on radiation-dependent Earth System processes. This dissertation will fill some gaps in our understanding of the role of aerosol properties on aerosol absorption and cloud formation. Specifically, the impact of aerosol oxidation on aerosol spectral (350nm < lambda< 500nm) absorption was examined for two biomass burning plumes intercepted by the NASA DC-S aircraft during the Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) mission in Spring and Summer 2008. Spectral aerosol single scattering albedo (SSA) retrieved using actinic flux measured aboard the NASA DC-8 was used to calculate the aerosol absorption Angstrom exponents (AAE) for a 6-day-old plume on April 17 th and a 3-hour old plume on June 29th. Higher AAE values for the April 17th plume (6.78+/-0.38) indicate absorption by aerosol was enhanced in the ultraviolet relative to the visible portion of the short-wave spectrum in the older plume compared to the fresher plume (AAE= 3.34 0.11). These differences were largely attributed to the greater oxidation of the organic aerosol in the April 17th plume which can arise either from the aging of primary organic aerosol or the formation of spectrally-absorbing secondary organic aerosol. The validity of the actinic flux retrievals used above were also evaluated in this work by the comparison of SSA retrieved using actinic flux (AF SSA) to those retrieved using ratios of direct and diffuse irradiance (DDR SSA) at four wavelengths: 332, 368, 415, and 500 mn. Both actinic flux and irradiance were measured atop the University of Houston's Moody Tower in Houston, TX as part of the Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Relevant to Air Quality (DISCOVER-AQ) mission in September 2013. AF SSA values were consistently lower than DDR SSAs with largest offsets observed when aerosol optical depths was < ~0.2. AF SSA were also lower than those reported by the AErosol RObotic NETwork (AERONET) and column-averaged values calculated from aerosol scattering and absorption coefficients measured aboard the NASA P3-B aircraft at 450 and 550 nm. However, AAE values calculated from AF SSAs compared well to AERONET and column-averaged AAEs suggesting actinic flux retrievals can correctly resolve the spectral dependence of aerosol absorption. Recent work has suggested that mineral dust is the most important IN found in both anvil and synoptically formed cirrus clouds over North America. The vertical transport processes sustaining significant mineral dust in the upper troposphere (> 9 km) where these clouds form are not well understood, but deep convective systems (thunder storms) likely play a role. Bulk aerosol Ca2+ concentrations and volume size distributions were measured aboard the NASA DC-8 during the NCAR Deep Convective Clouds and Chemistry Experiment (DC-3) conducted in May/June 2012 in both the inflow and outflow regions of twelve isolated, high cloud base storms over CO and OK. Outflow/inflow ratios of both Ca2+ and total coarse (limn < diameter < 5 microm) aerosol volume (Vc)were high (> ~0.9) suggesting a significant fraction of ingested coarse mode dust was transported through these systems. Elevated Ca2+ and Vc in the outflow were most likely not artifacts of ice shattering given the general absence of a relationship between these parameters and two ice concentration measurements (e.g., ice water content, 2D-S particle concentrations). Because mineral dust is an efficient IN, unactivated mineral dust particles are not expected in cold clouds. However, for these storms, inflow total coarse (0.5 microm < diameter < 5 microm) aerosol number (Nc)generally exceeded anvil cirrus ice particle concentrations, supporting the presence of interstitial dust in storm outflow. Thus efficient IN were likely made available in the upper troposphere by these twelve convective systems.