scholarly journals Assessing the Radiative Effects of Global Ice Clouds Based on CloudSat and CALIPSO Measurements

2016 ◽  
Vol 29 (21) ◽  
pp. 7651-7674 ◽  
Author(s):  
Yulan Hong ◽  
Guosheng Liu ◽  
J.-L. F. Li
Keyword(s):  
Longwave Radiation ◽  
Cooling Effect ◽  
Radiation Budget ◽  
Radiative Effect ◽  
Radiative Effects ◽  
Ice Clouds ◽  
Cloud Optical Depth ◽  
Ice Cloud ◽  
Heating And Cooling ◽  
The Tropics

Abstract Although it is well established that cirrus warms Earth, the radiative effect of the entire spectrum of ice clouds is not well understood. In this study, the role of all ice clouds in Earth’s radiation budget is investigated by performing radiative transfer modeling using ice cloud properties retrieved from CloudSat and CALIPSO measurements as inputs. Results show that, for the 2008 period, the warming effect (~21.8 ± 5.4 W m−2) induced by ice clouds trapping longwave radiation exceeds their cooling effect (~−16.7 ± 1.7 W m−2) caused by shortwave reflection, resulting in a net warming effect (~5.1 ± 3.8 W m−2) globally on the earth–atmosphere system. The net warming is over 15 W m−2 in the tropical deep convective regions, whereas cooling occurs in the midlatitudes, which is less than 10 W m−2 in magnitude. Seasonal variations of ice cloud radiative effects are evident in the midlatitudes where the net effect changes from warming during winter to cooling during summer, whereas warming occurs all year-round in the tropics. Ice cloud optical depth τ is shown to be an important factor in determining the sign and magnitude of the net radiative effect. Ice clouds with τ < 4.6 display a warming effect with the largest contributions from those with τ ≈ 1.0. In addition, ice clouds cause vertically differential heating and cooling of the atmosphere, particularly with strong heating in the upper troposphere over the tropics. At Earth’s surface, ice clouds produce a cooling effect no matter how small the τ value is.

Influence of Ice Particle Surface Roughening on the Global Cloud Radiative Effect

2013 ◽  
Vol 70 (9) ◽  
pp. 2794-2807 ◽  
Author(s):  
Bingqi Yi ◽  
Ping Yang ◽  
Bryan A. Baum ◽  
Tristan L'Ecuyer ◽  
Lazaros Oreopoulos ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Particle Surface ◽  
Radiation Budget ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Radiative Effect ◽  
Ice Clouds ◽  
Ice Cloud ◽  
Ice Particles ◽  
Cloud Radiative Effect

Abstract Ice clouds influence the climate system by changing the radiation budget and large-scale circulation. Therefore, climate models need to have an accurate representation of ice clouds and their radiative effects. In this paper, new broadband parameterizations for ice cloud bulk scattering properties are developed for severely roughened ice particles. The parameterizations are based on a general habit mixture that includes nine habits (droxtals, hollow/solid columns, plates, solid/hollow bullet rosettes, aggregate of solid columns, and small/large aggregates of plates). The scattering properties for these individual habits incorporate recent advances in light-scattering computations. The influence of ice particle surface roughness on the ice cloud radiative effect is determined through simulations with the Fu–Liou and the GCM version of the Rapid Radiative Transfer Model (RRTMG) codes and the National Center for Atmospheric Research Community Atmosphere Model (CAM, version 5.1). The differences in shortwave (SW) and longwave (LW) radiative effect at both the top of the atmosphere and the surface are determined for smooth and severely roughened ice particles. While the influence of particle roughening on the single-scattering properties is negligible in the LW, the results indicate that ice crystal roughness can change the SW forcing locally by more than 10 W m−2 over a range of effective diameters. The global-averaged SW cloud radiative effect due to ice particle surface roughness is estimated to be roughly 1–2 W m−2. The CAM results indicate that ice particle roughening can result in a large regional SW radiative effect and a small but nonnegligible increase in the global LW cloud radiative effect.

scholarly journals Use of a Lidar Forward Model for Global Comparisons of Cloud Fraction between the ICESat Lidar and the ECMWF Model

2008 ◽  
Vol 136 (10) ◽  
pp. 3742-3759 ◽  
Author(s):  
Jonathan M. Wilkinson ◽  
Robin J. Hogan ◽  
Anthony J. Illingworth ◽  
Angela Benedetti
Keyword(s):  
Cloud Fraction ◽  
Forward Model ◽  
Laser Altimeter ◽  
Ice Clouds ◽  
Weather Forecasts ◽  
Ice Cloud ◽  
Skill Scores ◽  
Boundary Layer Cloud ◽  
The Tropics ◽  
Ecmwf Model

The performance of the European Centre for Medium-Range Weather Forecasts (ECMWF) model in simulating clouds is evaluated using observations by the Geoscience Laser Altimeter System lidar on the Ice, Cloud, and Land Elevation Satellite (ICESat). To account for lidar attenuation in the comparison, model variables are used to simulate the attenuated backscatter using a lidar forward model. This generates a new model cloud fraction that can then be fairly compared with the ICESat lidar. The lidar forward model and ICESat comparison is performed over 15 days (equivalent to 226 orbits of Earth, or roughly 9 million km) of data. The model is assessed by cloud fraction statistics, skill scores, and its ability to simulate lidar backscatter. The results show that the model generally simulates the occurrence and location of clouds well but overestimates the mean amount when present of the ice cloud by around 10%, particularly in the tropics. The skill of the model is slightly better over the land than over the sea. The model also has some problems representing the amount when present in tropical boundary layer cloud, particularly over land, where there is an underestimate by as much as 15%. Calculations of backscatter reveal that the ECMWF model predicts the lidar backscatter to within 5% on average, for a lidar ratio of 20 sr, apart from in thick ice clouds. Sensitivity tests show that realistic variations in extinction-to-backscatter ratio and effective radius affect the forward modeled mean cloud fraction by no more than 10%.

scholarly journals Use of spectral cloud emissivities and their related uncertainties to infer ice cloud boundaries: methodology and assessment using CALIPSO cloud products

2019 ◽  
Vol 12 (9) ◽  
pp. 5039-5054
Author(s):  
Hye-Sil Kim ◽  
Bryan A. Baum ◽  
Yong-Sang Choi
Keyword(s):  
North Pacific Ocean ◽  
Weather Prediction ◽  
Radiation Budget ◽  
Cloud Base ◽  
Ice Clouds ◽  
Ice Cloud ◽  
New Information ◽  
Infrared Imager ◽  
Cloud Temperature ◽  
Cloud Regimes

Abstract. Satellite-imager-based operational cloud property retrievals generally assume that a cloudy pixel can be treated as being plane-parallel with horizontally homogeneous properties. This assumption can lead to high uncertainties in cloud heights, particularly for the case of optically thin, but geometrically thick, clouds composed of ice particles. This study demonstrates that ice cloud emissivity uncertainties can be used to provide a reasonable range of ice cloud layer boundaries, i.e., the minimum to maximum heights. Here ice cloud emissivity uncertainties are obtained for three IR channels centered at 11, 12, and 13.3 µm. The range of cloud emissivities is used to infer a range of ice cloud temperature and heights, rather than a single value per pixel as provided by operational cloud retrievals. Our methodology is tested using MODIS observations over the western North Pacific Ocean during August 2015. We estimate minimum–maximum heights for three cloud regimes, i.e., single-layered optically thin ice clouds, single-layered optically thick ice clouds, and multilayered clouds. Our results are assessed through comparison with CALIOP version 4 cloud products for a total of 11873 pixels. The cloud boundary heights for single-layered optically thin clouds show good agreement with those from CALIOP; biases for maximum (minimum) heights versus the cloud-top (base) heights of CALIOP are 0.13 km (−1.01 km). For optically thick and multilayered clouds, the biases of the estimated cloud heights from the cloud top or cloud base become larger (0.30/−1.71 km, 1.41/−4.64 km). The vertically resolved boundaries for ice clouds can contribute new information for data assimilation efforts for weather prediction and radiation budget studies. Our method is applicable to measurements provided by most geostationary weather satellites including the GK-2A advanced multichannel infrared imager.

scholarly journals Using A-Train Observations to Evaluate Cloud Occurrence and Radiative Effects in the Community Atmosphere Model during the Southeast Asia Summer Monsoon

2019 ◽  
Vol 32 (14) ◽  
pp. 4145-4165 ◽  
Author(s):  
Elizabeth Berry ◽  
Gerald G. Mace ◽  
Andrew Gettelman
Keyword(s):  
Southeast Asia ◽  
Summer Monsoon ◽  
Cloud Fraction ◽  
Radiative Heating ◽  
Radiative Effects ◽  
Ice Clouds ◽  
Heating And Cooling ◽  
Community Atmosphere Model ◽  
Atmosphere Model ◽  
Good Agreement

Abstract The distribution of clouds and their radiative effects in the Community Atmosphere Model, version 5 (CAM5), are compared to A-Train satellite data in Southeast Asia during the summer monsoon. Cloud radiative kernels are created based on populations of observed and modeled clouds separately in order to compare the sensitivity of the TOA radiation to changes in cloud fraction. There is generally good agreement between the observation- and model-derived cloud radiative kernels for most cloud types, meaning that the clouds in the model are heating and cooling like clouds in nature. Cloud radiative effects are assessed by multiplying the cloud radiative kernel by the cloud fraction histogram. For ice clouds in particular, there is good agreement between the model and observations, with optically thin cirrus producing a moderate warming effect and cirrostratus producing a slight cooling effect, on average. Consistent with observations, the model also shows that the median value of the ice water path (IWP) distribution, rather than the mean, is a more representative measure of the ice clouds that are responsible for heating. In addition, in both observations and the model, it is cirrus clouds with an IWP of 20 g m−2 that have the largest warming effect in this region, given their radiative heating and frequency of occurrence.

scholarly journals Why we need radar, lidar, and solar radiance observations to constrain ice cloud microphysics

2021 ◽  
Author(s):  
Florian Ewald ◽  
Silke Groß ◽  
Martin Wirth ◽  
Julien Delanoë ◽  
Stuart Fox ◽  
...  
Keyword(s):  
Water Content ◽  
Cloud Microphysics ◽  
Accurate Estimation ◽  
Crystal Shape ◽  
Radiative Effect ◽  
Ice Crystal ◽  
Ice Clouds ◽  
Ice Cloud ◽  
Ice Water Content ◽  
Ice Water

Abstract. Ice clouds and their effect on Earth's radiation budget are one of the largest sources of uncertainty in climate change predictions. The uncertainty in predicting ice cloud feedbacks in a warming climate arises due to uncertainties in measuring and explaining their current optical and microphysical properties as well as from insufficient knowledge about their spatial and temporal distribution. This knowledge can be significantly improved by active remote sensing, which can help to explore the vertical profile of ice cloud microphysics, such as ice particle size and ice water content. This study focuses on the well-established variational approach VarCloud to retrieve ice cloud microphysics from radar-lidar measurements. While active backscatter retrieval techniques surpass the information content of most passive, vertically integrated retrieval techniques, their accuracy is limited by essential assumptions about the ice crystal shape. Since most radar-lidar retrieval algorithms rely heavily on universal mass-size relationships to parameterize the prevalent ice particle shape, biases in ice water content and ice water path can be expected in individual cloud regimes. In turn, these biases can lead to an erroneous estimation of the radiative effect of ice clouds. In many cases, these biases could be spotted and corrected by the simultaneous exploitation of measured solar radiances. The agreement with measured solar radiances is a logical prerequisite for an accurate estimation of the radiative effect of ice clouds. To this end, this study exploits simultaneous radar, lidar, and passive measurements made on board the German High Altitude and Long Range Research Aircraft. By using the ice clouds derived with VarCloud as an input to radiative transfer calculations, simulated solar radiances are compared to measured solar radiances made above the actual clouds. This radiative closure study is done using different ice crystal models to improve the knowledge of the prevalent ice crystal shape. While in one case aggregates were capable of reconciling radar, lidar, and solar radiance measurements, this study also analyses a more problematic case for which no radiative closure could be achieved. In this case, simultaneously acquired in-situ measurements could narrow this inability to an unexpected high ice crystal number concentration.

scholarly journals Evaluating the Diurnal Cycle of Upper-Tropospheric Ice Clouds in Climate Models Using SMILES Observations

2015 ◽  
Vol 72 (3) ◽  
pp. 1022-1044 ◽  
Author(s):  
Jonathan H. Jiang ◽  
Hui Su ◽  
Chengxing Zhai ◽  
T. Janice Shen ◽  
Tongwen Wu ◽  
...  
Keyword(s):  
Diurnal Cycle ◽  
Climate Models ◽  
Space Station ◽  
Temporal Patterns ◽  
Spatial And Temporal Patterns ◽  
Ice Clouds ◽  
Diurnal Variability ◽  
Diurnal Cycles ◽  
Ice Cloud ◽  
The Tropics

Abstract Upper-tropospheric ice cloud measurements from the Superconducting Submillimeter Limb Emission Sounder (SMILES) on the International Space Station (ISS) are used to study the diurnal cycle of upper-tropospheric ice cloud in the tropics and midlatitudes (40°S–40°N) and to quantitatively evaluate ice cloud diurnal variability simulated by 10 climate models. Over land, the SMILES-observed diurnal cycle has a maximum around 1800 local solar time (LST), while the model-simulated diurnal cycles have phases differing from the observed cycle by −4 to 12 h. Over ocean, the observations show much smaller diurnal cycle amplitudes than over land with a peak at 1200 LST, while the modeled diurnal cycle phases are widely distributed throughout the 24-h period. Most models show smaller diurnal cycle amplitudes over ocean than over land, which is in agreement with the observations. However, there is a large spread of modeled diurnal cycle amplitudes ranging from 20% to more than 300% of the observed over both land and ocean. Empirical orthogonal function (EOF) analysis on the observed and model-simulated variations of ice clouds finds that the first EOF modes over land from both observation and model simulations explain more than 70% of the ice cloud diurnal variations and they have similar spatial and temporal patterns. Over ocean, the first EOF from observation explains 26.4% of the variance, while the first EOF from most models explains more than 70%. The modeled spatial and temporal patterns of the leading EOFs over ocean show large differences from observations, indicating that the physical mechanisms governing the diurnal cycle of oceanic ice clouds are more complicated and not well simulated by the current climate models.

scholarly journals Degree of ice particle surface roughness inferred from polarimetric observations

2015 ◽  
Vol 15 (23) ◽  
pp. 34283-34323
Author(s):  
S. Hioki ◽  
P. Yang ◽  
B. A. Baum ◽  
S. Platnick ◽  
K. G. Meyer ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Function Analysis ◽  
Particle Surface ◽  
Roughness Parameter ◽  
Single Scattering ◽  
Global Scale ◽  
Ice Clouds ◽  
Atmospheric Scattering ◽  
Ice Cloud ◽  
The Tropics

Abstract. The degree of surface roughness of ice particles within thick, cold ice clouds is inferred from multi-directional, multi-spectral satellite polarimetric observations over oceans, assuming a column-aggregate particle habit. An improved roughness inference scheme is employed in the analysis that provides a more noise-resilient roughness estimate than the conventional best-fit approach. The improvements include the introduction of a quantitative roughness parameter based on empirical orthogonal function analysis and proper treatment of polarization due to atmospheric scattering above clouds. A global one-month data sample supports the use of a severely roughened ice habit to simulate the polarized reflectivity associated with ice clouds over ocean. The density distribution of the roughness parameter inferred from the global one-month data sample and further analyses of a few case studies demonstrate the significant variability of ice cloud single-scattering properties. The present theoretical results are in close agreement with observations in the extratropics but not in the tropics. Potential improvements are discussed to enhance the depiction of the natural variability on a global scale.

scholarly journals Global radiative effects of solid fuel cookstove aerosol emissions

2018 ◽  
Vol 18 (8) ◽  
pp. 5219-5233 ◽  
Author(s):  
Yaoxian Huang ◽  
Nadine Unger ◽  
Trude Storelvmo ◽  
Kandice Harper ◽  
Yiqi Zheng ◽  
...  
Keyword(s):  
Black Carbon ◽  
Solid Fuel ◽  
Surface Albedo ◽  
Mixed Phase ◽  
Radiative Effects ◽  
Ice Clouds ◽  
Ice Cloud ◽  
Radiative Impacts ◽  
Standard Deviations ◽  
Aerosol Emissions

Abstract. We apply the NCAR CAM5-Chem global aerosol-climate model to quantify the net global radiative effects of black and organic carbon aerosols from global and Indian solid fuel cookstove emissions for the year 2010. Our assessment accounts for the direct radiative effects, changes to cloud albedo and lifetime (aerosol indirect effect, AIE), impacts on clouds via the vertical temperature profile (semi-direct effect, SDE) and changes in the surface albedo of snow and ice (surface albedo effect). In addition, we provide the first estimate of household solid fuel black carbon emission effects on ice clouds. Anthropogenic emissions are from the IIASA GAINS ECLIPSE V5a inventory. A global dataset of black carbon (BC) and organic aerosol (OA) measurements from surface sites and aerosol optical depth (AOD) from AERONET is used to evaluate the model skill. Compared with observations, the model successfully reproduces the spatial patterns of atmospheric BC and OA concentrations, and agrees with measurements to within a factor of 2. Globally, the simulated AOD agrees well with observations, with a normalized mean bias close to zero. However, the model tends to underestimate AOD over India and China by  ∼  19 ± 4 % but overestimate it over Africa by  ∼  25 ± 11 % (± represents modeled temporal standard deviations for n = 5 run years). Without BC serving as ice nuclei (IN), global and Indian solid fuel cookstove aerosol emissions have net global cooling radiative effects of −141 ± 4 mW m−2 and −12 ± 4 mW m−2, respectively (± represents modeled temporal standard deviations for n = 5 run years). The net radiative impacts are dominated by the AIE and SDE mechanisms, which originate from enhanced cloud condensation nuclei concentrations for the formation of liquid and mixed-phase clouds, and a suppression of convective transport of water vapor from the lower troposphere to the upper troposphere/lower stratosphere that in turn leads to reduced ice cloud formation. When BC is allowed to behave as a source of IN, the net global radiative impacts of the global and Indian solid fuel cookstove emissions range from −275 to +154 mW m−2 and −33 to +24 mW m−2, with globally averaged values of −59 ± 215 and 0.3 ± 29 mW m−2, respectively. Here, the uncertainty range is based on sensitivity simulations that alter the maximum freezing efficiency of BC across a plausible range: 0.01, 0.05 and 0.1. BC–ice cloud interactions lead to substantial increases in high cloud (<  500 hPa) fractions. Thus, the net sign of the impacts of carbonaceous aerosols from solid fuel cookstoves on global climate (warming or cooling) remains ambiguous until improved constraints on BC interactions with mixed-phase and ice clouds are available.

scholarly journals Effect of Aerosols, Tropospheric NO2 and Clouds on Surface Solar Radiation over the Eastern Mediterranean (Greece)

2021 ◽  
Vol 13 (13) ◽  
pp. 2587
Author(s):  
Georgia Alexandri ◽  
Aristeidis K. Georgoulias ◽  
Dimitris Balis
Keyword(s):  
Solar Radiation ◽  
Radiative Transfer ◽  
Eastern Mediterranean ◽  
Radiative Effect ◽  
Santa Barbara ◽  
Surface Solar Radiation ◽  
Ice Clouds ◽  
Climatological Data ◽  
Ice Cloud ◽  
Tropospheric No2

In this work, the effect that two basic air quality indexes, aerosols and tropospheric NO2, exert on surface solar radiation (SSR) is studied, along with the effect of liquid and ice clouds over 16 locations in Greece, in the heart of the Eastern Mediterranean. State-of-the-art satellite-based observations and climatological data for the 15-year period 2005–2019, and a radiative transfer system based on a modified version of the Santa Barbara DISORT Atmospheric Radiative Transfer (SBDART) model are used. Our SSR simulations are in good agreement with ground observations and two satellite products. It is shown that liquid clouds dominate, with an annual radiative effect (RE) of −36 W/m2, with ice clouds (−19 W/m2) and aerosols (−13 W/m2) following. The radiative effect of tropospheric NO2 is smaller by two orders of magnitude (−0.074 W/m2). Under clear skies, REaer is about 3–4 times larger than for liquid and ice cloud-covered skies, while RENO2 doubles. The radiative effect of all the parameters exhibits a distinct seasonal cycle. An increase in SSR is observed for the period 2005–2019 (positive trends ranging from 0.01 to 0.52 W/m2/year), which is mostly related to a decrease in the aerosol optical depth and the liquid cloud fraction.

scholarly journals Why we need radar, lidar, and solar radiance observations to constrain ice cloud microphysics

2021 ◽  
Vol 14 (7) ◽  
pp. 5029-5047
Author(s):  
Florian Ewald ◽  
Silke Groß ◽  
Martin Wirth ◽  
Julien Delanoë ◽  
Stuart Fox ◽  
...  
Keyword(s):  
Water Content ◽  
Cloud Microphysics ◽  
Accurate Estimation ◽  
Crystal Shape ◽  
Radiative Effect ◽  
Ice Crystal ◽  
Ice Clouds ◽  
Ice Cloud ◽  
Ice Water Content ◽  
Ice Water

Abstract. Ice clouds and their effect on earth's radiation budget are one of the largest sources of uncertainty in climate change predictions. The uncertainty in predicting ice cloud feedbacks in a warming climate arises due to uncertainties in measuring and explaining their current optical and microphysical properties as well as from insufficient knowledge about their spatial and temporal distribution. This knowledge can be significantly improved by active remote sensing, which can help to explore the vertical profile of ice cloud microphysics, such as ice particle size and ice water content. This study focuses on the well-established variational approach VarCloud to retrieve ice cloud microphysics from radar–lidar measurements. While active backscatter retrieval techniques surpass the information content of most passive, vertically integrated retrieval techniques, their accuracy is limited by essential assumptions about the ice crystal shape. Since most radar–lidar retrieval algorithms rely heavily on universal mass–size relationships to parameterize the prevalent ice particle shape, biases in ice water content and ice water path can be expected in individual cloud regimes. In turn, these biases can lead to an erroneous estimation of the radiative effect of ice clouds. In many cases, these biases could be spotted and corrected by the simultaneous exploitation of measured solar radiances. The agreement with measured solar radiances is a logical prerequisite for an accurate estimation of the radiative effect of ice clouds. To this end, this study exploits simultaneous radar, lidar, and passive measurements made on board the German High Altitude and Long Range Research Aircraft. By using the ice clouds derived with VarCloud as an input to radiative transfer calculations, simulated solar radiances are compared to measured solar radiances made above the actual clouds. This radiative closure study is done using different ice crystal models to improve the knowledge of the prevalent ice crystal shape. While in one case aggregates were capable of reconciling radar, lidar, and solar radiance measurements, this study also analyses a more problematic case for which no radiative closure could be achieved. In this case, collocated in situ measurements indicate that the lack of closure may be linked to unexpectedly high values of the ice crystal number density.

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