A Coupled Cloud Physics–Radiation Parameterization of the Bulk Optical Properties of Cirrus and Its Impact on the Met Office Unified Model Global Atmosphere 5.0 Configuration

Abstract A new coupled cloud physics–radiation parameterization of the bulk optical properties of ice clouds is presented. The parameterization is consistent with assumptions in the cloud physics scheme regarding particle size distributions (PSDs) and mass–dimensional relationships. The parameterization is based on a weighted ice crystal habit mixture model, and its bulk optical properties are parameterized as simple functions of wavelength and ice water content (IWC). This approach directly couples IWC to the bulk optical properties, negating the need for diagnosed variables, such as the ice crystal effective dimension. The parameterization is implemented into the Met Office Unified Model Global Atmosphere 5.0 (GA5) configuration. The GA5 configuration is used to simulate the annual 20-yr shortwave (SW) and longwave (LW) fluxes at the top of the atmosphere (TOA), as well as the temperature structure of the atmosphere, under various microphysical assumptions. The coupled parameterization is directly compared against the current operational radiation parameterization, while maintaining the same cloud physics assumptions. In this experiment, the impacts of the two parameterizations on the SW and LW radiative effects at TOA are also investigated and compared against observations. The 20-yr simulations are compared against the latest observations of the atmospheric temperature and radiative fluxes at TOA. The comparisons demonstrate that the choice of PSD and the assumed ice crystal shape distribution are as important as each other. Moreover, the consistent radiation parameterization removes a long-standing tropical troposphere cold temperature bias but slightly warms the southern midlatitudes by about 0.5 K.

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A Classification of Ice Crystal Habits Using Combined Lidar and Scanning Polarimeter Observations during the SEAC4RS Campaign

Journal of Atmospheric and Oceanic Technology ◽

10.1175/jtech-d-20-0037.1 ◽

2020 ◽

Vol 37 (12) ◽

pp. 2185-2196

Author(s):

Natalie Midzak ◽

John E. Yorks ◽

Jianglong Zhang ◽

Bastiaan van Diedenhoven ◽

Sarah Woods ◽

...

Keyword(s):

Atmospheric Composition ◽

Crystal Habit ◽

Ice Crystal ◽

Cloud Physics ◽

Cloud Particle ◽

Clustering Technique ◽

Ice Crystal Habits

AbstractUsing collocated NASA Cloud Physics Lidar (CPL) and Research Scanning Polarimeter (RSP) data from the Studies of Emissions and Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys (SEAC4RS) campaign, a new observational-based method was developed which uses a K-means clustering technique to classify ice crystal habit types into seven categories: column, plates, rosettes, spheroids, and three different type of irregulars. Intercompared with the collocated SPEC, Inc., Cloud Particle Imager (CPI) data, the frequency of the detected ice crystal habits from the proposed method presented in the study agrees within 5% with the CPI-reported values for columns, irregulars, rosettes, and spheroids, with more disagreement for plates. This study suggests that a detailed ice crystal habit retrieval could be applied to combined space-based lidar and polarimeter observations such as CALIPSO and POLDER in addition to future missions such as the Aerosols, Clouds, Convection, and Precipitation (A-CCP).

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Bulk microphysical properties of semi-transparent cirrus from AIRS: a six year global climatology and statistical analysis in synergy with geometrical profiling data from CloudSat-CALIPSO

Atmospheric Chemistry and Physics ◽

10.5194/acp-12-503-2012 ◽

2012 ◽

Vol 12 (1) ◽

pp. 503-525 ◽

Cited By ~ 29

Author(s):

A. Guignard ◽

C. J. Stubenrauch ◽

A. J. Baran ◽

R. Armante

Keyword(s):

Statistical Analysis ◽

Single Scattering ◽

Ice Crystals ◽

Crystal Habit ◽

Ice Crystal ◽

Ice Clouds ◽

Mean Values ◽

Temperature Range ◽

Microphysical Properties ◽

Ice Water

Abstract. This article presents a retrieval method and a statistical analysis of the bulk microphysical properties of semi-transparent ice clouds using the Atmospheric Infrared Sounder (AIRS). The method relies on spectral differences of cirrus emissivities in the 8–12 μm range and is sensitive to the effective ice crystal diameter (De) and ice water path (IWP) of up to 85 μm and 120 g m−2, respectively. An indication of the most frequent ice crystal habit in the cirrus has been obtained by using separately single scattering properties of column-like and aggregate-like ice crystals in the simulations. Uncertainties due to hypotheses on atmospheric parameters and ice crystal single scattering properties are discussed and the cirrus emissivity and temperature range for the applicability of the method are determined. To be sure that the cirrus only includes ice crystals, one has to restrict the cloud temperature range to Tcld<230 K. On a global scale, these semi-transparent ice clouds (cirrus) represent about 25% of all high clouds and are mainly encountered in the midlatitudes during winter and in the tropics, with an average De and IWP of 52 μm and 27 g m−2, respectively. A comparison with bulk microphysical properties from the TIROS-N Operational Vertical Sounder (TOVS) shows an agreement on global mean values. The addition of spectral information revealed improvements at the limits of the cirrus emissivity range. Collocated Radar-Lidar Geometrical Profiling (GEOPROF) data have been used to study the vertical structure of these clouds and to infer average ice water content (IWC) for cirrus with a small vertical extent. This allowed us to compare and contrast parameterizations of De as functions of IWC and IWP, respectively.

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Observations and modelling of microphysical variability, aggregation and sedimentation in tropical anvil cirrus outflow regions

Atmospheric Chemistry and Physics ◽

10.5194/acp-12-6609-2012 ◽

2012 ◽

Vol 12 (14) ◽

pp. 6609-6628 ◽

Cited By ~ 21

Author(s):

M. W. Gallagher ◽

P. J. Connolly ◽

I. Crawford ◽

A. Heymsfield ◽

K. N. Bower ◽

...

Keyword(s):

Electric Fields ◽

Numerical Models ◽

Average Particle Size ◽

Average Particle ◽

Ice Crystal ◽

Crystal Aggregation ◽

Ice Water Content ◽

Differential Sedimentation ◽

High Electric Fields ◽

Ice Water

Abstract. Aircraft measurements of the microphysics of a tropical convective anvil (at temperatures ~−60 °C) forming above the Hector storm, over the Tiwi Islands, Northern Australia, have been conducted with a view to determining ice crystal aggregation efficiencies from in situ measurements. The observed microphysics have been compared to an explicit bin-microphysical model of the anvil region, which includes crystal growth by vapour diffusion and aggregation and the process of differential sedimentation. It has been found in flights made using straight and level runs perpendicular to the storm that the number of ice crystals initially decreased with distance from the storm as aggregation took place resulting in larger crystals, followed by their loss from the cloud layer due to sedimentation. The net result was that the mass (i.e. Ice Water Content) in the anvil Ci cloud decreased, but also that the average particle size (weighted by number) remained relatively constant along the length of the anvil outflow. Comparisons with the explicit microphysics model showed that the changes in the shapes of the ice crystal spectra as a function of distance from the storm could be explained by the model if the aggregation efficiency was set to values of Eagg~0.5 and higher. This result is supported by recent literature on aggregation efficiencies for complex ice particles and suggests that either the mechanism of particle interlocking is important to the aggregation process, or that other effects are occuring, such as enhancement of ice-aggregation by high electric fields that arise as a consequence of charge separation within the storm. It is noteworthy that this value of the ice crystal aggregation efficiency is much larger than values used in cloud resolving models at these temperatures, which typically use E~0.0016. These results are important to understanding how cold clouds evolve in time and for the treatment of the evolution of tropical Ci in numerical models.

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Ice water content (IWC) retrieval from cirrus clouds using millimeter-wave radar and in-situ ice crystal airborne data

Proceedings. 2005 IEEE International Geoscience and Remote Sensing Symposium, 2005. IGARSS '05. ◽

10.1109/igarss.2005.1526819 ◽

2005 ◽

Author(s):

J. Moralesa ◽

J. Trabal ◽

S.L. Cruz-Pol ◽

S.M. Sekelsky

Keyword(s):

Water Content ◽

Millimeter Wave ◽

Cirrus Clouds ◽

Ice Crystal ◽

Millimeter Wave Radar ◽

Wave Radar ◽

Ice Water Content ◽

Ice Water

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Observing the climate impact of large wildfires on stratospheric temperature

Scientific Reports ◽

10.1038/s41598-021-02335-7 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Matthias Stocker ◽

Florian Ladstädter ◽

Andrea K. Steiner

Keyword(s):

Lower Stratosphere ◽

Volcanic Eruptions ◽

Satellite Observation ◽

Atmospheric Temperature ◽

Climate Impact ◽

Atmospheric Composition ◽

Temperature Structure ◽

Climate Trends ◽

Short Term ◽

Climate Signal

AbstractWildfires are expected to become more frequent and intense in the future. They not only pose a serious threat to humans and ecosystems, but also affect Earth’s atmosphere. Wildfire plumes can reach into the stratosphere, but little is known about their climate impact. Here, we reveal observational evidence that major wildfires can have a severe impact on the atmospheric temperature structure and short-term climate in the stratosphere. Using advanced satellite observation, we find substantial warming of up to 10 K of the lower stratosphere within the wildfire plumes during their early development. The short-term climate signal in the lower stratosphere lasts several months and amounts to 1 K for the Northern American wildfires in 2017, and up to striking 3.5 K for the Australian wildfires in 2020. This is stronger than any signal from recent volcanic eruptions. Such extreme events affect atmospheric composition and climate trends, underpinning their importance for future climate.

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Saturn's Atmospheric Temperature Structure and Heat Budget

1980, Pioneer Saturn - Collected Reprint Series ◽

10.1002/9781118782101.ch21 ◽

2014 ◽

pp. 5871-5881

Author(s):

Glenn S. Orton ◽

Andrew P. Ingersoll

Keyword(s):

Heat Budget ◽

Atmospheric Temperature ◽

Temperature Structure

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Dust aerosol impact on North Africa climate: a GCM investigation of aerosol-cloud-radiation interactions using A-Train satellite data

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-11-31401-2011 ◽

2011 ◽

Vol 11 (11) ◽

pp. 31401-31432

Author(s):

Y. Gu ◽

K. N. Liou ◽

J. H. Jiang ◽

H. Su ◽

X. Liu

Keyword(s):

Direct Effect ◽

North Africa ◽

Indirect Effect ◽

Ice Crystal ◽

Ir Radiation ◽

Ice Clouds ◽

Cloud Forcing ◽

Dust Aerosols ◽

Ice Water Content ◽

Ice Water

Abstract. The climatic effects of dust aerosols in North Africa have been investigated using the atmospheric general circulation model (AGCM) developed at the University of California, Los Angeles (UCLA). The model includes an efficient and physically based radiation parameterization scheme developed specifically for application to clouds and aerosols. Parameterization of the effective ice particle size in association with the aerosol first indirect effect based on ice cloud and aerosol data retrieved from A-Train satellite observations have been employed in climate model simulations. Offline simulations reveal that the direct solar, IR, and net forcings by dust aerosols at the top of the atmosphere (TOA) generally increase with increasing aerosol optical depth (AOD). When the dust semi-direct effect is included with the presence of ice clouds, positive IR radiative forcing is enhanced since ice clouds trap substantial IR radiation, while the positive solar forcing with dust aerosols alone has been changed to negative values due to the strong reflection of solar radiation by clouds, indicating that cloud forcing associated with aerosol semi-direct effect could exceed direct aerosol forcing. With the aerosol first indirect effect, the net cloud forcing is generally reduced for an ice water path (IWP) larger than 20 g m−2. The magnitude of the reduction increases with IWP. AGCM simulations show that the reduced ice crystal mean effective size due to the aerosol first indirect effect results in less OLR and net solar flux at the top of the atmosphere over the cloudy area of the North Africa region because ice clouds with smaller size trap more IR radiation and reflect more solar radiation. The precipitation in the same area, however, increases due to the aerosol indirect effect on ice clouds, corresponding to the enhanced convection as indicated by reduced OLR. The increased precipitation appears to be associated with enhanced ice water content in this region. The 200 mb radiative heating rate shows more cooling with the aerosol first indirect effect since greater cooling is produced at the cloud top with smaller ice crystal size. The 500 mb omega indicates stronger upward motion, which, together with the increased cooling effect, results in the increased ice water content. Adding the aerosol direct effect into the model simulation reduces the precipitation in the normal rainfall band over North Africa, where precipitation is shifted to the south and the northeast produced by the absorption of sunlight and the subsequent heating of the air column by dust particles. As a result, rainfall is drawn further inland to the northeast. This study represents the first attempt to quantify the climate impact of the aerosol indirect effect using a GCM in connection with A-train satellite data. The parameterization for the aerosol first indirect effect developed in this study can be readily employed for application to other GCMs.

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Evolution of tracer and ice crystal distribution in the young plumes of overshooting turrets from the StratoClim golden flight

10.5194/egusphere-egu21-9756 ◽

2021 ◽

Author(s):

Sergey Khaykin ◽

Martina Krämer ◽

Elizabeth Moyer ◽

Silvia Bucci ◽

Armin Afchine ◽

...

Keyword(s):

Chemical Composition ◽

Asian Monsoon ◽

Convective Transport ◽

Ice Crystals ◽

Ice Crystal ◽

Satellite Measurements ◽

Cold Point ◽

Ice Water ◽

The Impact ◽

Stratospheric Water Vapour

<p>Deployment of the high-altitude M55-Geophysica aircraft in Kathmandu during Summer 2017 within StratoClim campaign has yielded a wealth of unique high-resolution measurements in the Asian Monsoon Anticyclone (AMA). In a particular flight (F8, 10 August 2017) the aircraft flew at the cold-point tropopause level through active overshoots and their outflows minutes to hours old. The measurements reveal up to 2500 ppmv of ice water above 17 km in large aggregated ice crystals up to 700 &#181;m in diameter. Smaller crystals were observed as high as 18.8 km (410 K). Tracer and thermodynamical measurements show manifestations of vigorous vertical motions and provide evidence for ongoing mixing of tropospheric and stratospheric air around the tropopause. We use an ensemble of airborne and satellite measurements inside and downwind of convective overshoots together with trajectory modeling to characterize the impact of overshooting convection on the thermodynamical structure and chemical composition of the Asian tropopause layer. The effect of cross-tropopause convective transport on the Asian lower stratospheric water vapour is discussed.</p>

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An Alternative Bias Correction Scheme for CrIS Data Assimilation in a Regional Model

Monthly Weather Review ◽

10.1175/mwr-d-18-0044.1 ◽

2019 ◽

Vol 147 (3) ◽

pp. 809-839 ◽

Cited By ~ 8

Author(s):

Xin Li ◽

Xiaolei Zou ◽

Mingjian Zeng

Keyword(s):

Data Assimilation ◽

Bias Correction ◽

Moving Average ◽

Atmospheric Temperature ◽

Lapse Rate ◽

Specific Humidity ◽

Convective Precipitation ◽

Temperature Structure ◽

The Impact ◽

Mean Square Errors

Bias correction (BC) is a crucial step for satellite radiance data assimilation (DA). In this study, the traditional airmass BC scheme in the National Centers for Environmental Prediction (NCEP) Gridpoint Statistical Interpolation (GSI) is investigated for Cross-track Infrared Sounder (CrIS) DA. The ability of the airmass predictors to model CrIS biases is diagnosed. Correlations between CrIS observation-minus-background ( O − B) samples and the two lapse rate–related airmass predictors employed by GSI are found to be very weak, indicating that the bias correction contributed by the airmass BC scheme is small. A modified BC scheme, which directly calculates the moving average of O − B departures from data of the previous 2 weeks with respect to scan position and latitudinal band, is proposed and tested. The impact of the modified BC scheme on CrIS radiance DA is compared with the variational airmass BC scheme. Results from 1-month analysis/forecast experiments show that the modified BC scheme removes nearly all scan-dependent and latitude-dependent biases, while residual biases are still found in some channels when the airmass BC scheme is applied. Smaller predicted root-mean-square errors of temperature and specific humidity and higher equivalent threat scores are obtained by the DA experiment using the modified BC scheme. If O − B samples are replaced by observation-minus-analysis ( O − A) samples for bias estimates in the modified BC scheme, the forecast impacts are reduced but remain positive. A convective precipitation case that occurred on 21 August 2016 is investigated. Using the modified BC scheme, the atmospheric temperature structure and the geopotential height structures near trough/ridge areas are better resolved, resulting in better precipitation forecasts.

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