Cloud effective radius(CER)is a fundamental microphysical property of clouds,critical for understanding cloud formation and radiative effects.Satellite spectral imagers,widely utilized in passive remote sensing,facili...Cloud effective radius(CER)is a fundamental microphysical property of clouds,critical for understanding cloud formation and radiative effects.Satellite spectral imagers,widely utilized in passive remote sensing,facilitate the monitoring of cloud characteristics,including CER,over extended time periods and spatial scales.Various observational methods have been employed to evaluate satellite cloud property products;however,in situ measurement evaluations of CER remain limited,particularly for products over China.This study utilized aircraft observations provided by the China Meteorological Administration Weather Modification Centre to evaluate the CER retrieved by Fengyun-4A Advanced Geosynchronous Radiation Imager(AGRI)and Himawari-8 Advanced Himawari Imager(AHI).Three flights were selected from the aircraft dataset for evaluation,involving flights through non-precipitating stratiform clouds with stable,high-quality measurements.Rigorous data selection and collocation procedures were employed to ensure a comprehensive comparison.Satellite retrievals from heterogeneous cloud fields were excluded,and representative in-cloud aircraft measurements were identified through multi-parameter filtering.The flight trajectory was adjusted to account for horizontal cloud movement corresponding to time differences between observations from different platforms.Additionally,in situ measurements from different vertical layers were adjusted to a comparable position near the cloud top.Results indicate that CER retrieved from satellites is generally overestimated compared to in situ measurements.For AGRI,the average difference(AD)is 2.90μm,with a root mean square difference(RMSD)of 3.53μm.For AHI,the AD is 2.92μm,and the RMSD is 3.59μm.To enhance future validation and evaluation of remote sensing results,factors such as instrument calibration,flight patterns,and cloud conditions will be carefully considered.Increasing the number of cases should further reduce errors associated with individual instances,enabling more precise assessments.展开更多
The impact of aerosols on clouds,which remains one of the largest aspects of uncertainty in current weather forecasting and climate change research,can be influenced by various factors,such as the underlying surface t...The impact of aerosols on clouds,which remains one of the largest aspects of uncertainty in current weather forecasting and climate change research,can be influenced by various factors,such as the underlying surface type,cloud type,cloud phase,and aerosol type.To explore the impact of different underlying surfaces on the effect of aerosols on cloud development,this study focused on the Yangtze River Delta(YRD)and its offshore regions(YRD sea)for a comparative analysis based on multi-source satellite data,while also considering the variations in cloud type and cloud phase.The results show lower cloud-top height and depth of single-layer clouds over the ocean than land,and higher liquid cloud in spring over the ocean.Aerosols are found to enhance the cumulus cloud depth through microphysical effects,which is particularly evident over the ocean.Aerosols are also found to decrease the cloud droplet effective radius in the ocean region and during the mature stage of cloud development in the land region,while opposite results are found during the early stage of cloud development in the land region.The quantitative results indicate that the indirect effect is positive(0.05)in the land region at relatively high cloud water path,which is smaller than that in the ocean region(0.11).The findings deepen our understanding of the influence aerosols on cloud development and the mechanisms involved,which could then be applied to improve the ability to simulate cloud-associated weather processes.展开更多
This paper documents a study to examine the sensitivity to cloud droplet effective radius and liquid water path and the alleviation the energy imbalance at the top of the atmosphere and at the surface in the latest ve...This paper documents a study to examine the sensitivity to cloud droplet effective radius and liquid water path and the alleviation the energy imbalance at the top of the atmosphere and at the surface in the latest version of the Grid-point Atmospheric Model of the State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics （LASG）, Institute of Atmospheric Physics （IAP） （GAMIL1.1.0）. Considerable negative biases in all flux components, and thus an energy imbalance, are found in GAMIL1.1.0. In order to alleviate the energy imbalance, two modifications, namely an increase in cloud droplet effective radius and a decrease in cloud liquid water path, have been made to the cloud properties used in GAMIL. With the increased cloud droplet effective radius, the single scattering albedo of clouds is reduced, and thus the reflection of solar radiation into space by clouds is reduced and the net solar radiation flux at the top of the atmosphere is increased. With the reduced cloud optical depth, the net surface shortwave radiation flux is increased, causing a net warming over the land surface. This results in an increase in both sensible and latent heat fluxes over the land regions, which is largely balanced by the increased terrestrial radiation fluxes. Consequently, the energy balance at the top of atmosphere and at the surface is achieved with energy flux components consistent with available satellite observations.展开更多
The characteristics of microphysical profiles of liquid clouds(i.e.,the cloud effective radius(ER)and liquid water content(LWC))are important factors in understanding the aerosol-cloud-precipitation process and improv...The characteristics of microphysical profiles of liquid clouds(i.e.,the cloud effective radius(ER)and liquid water content(LWC))are important factors in understanding the aerosol-cloud-precipitation process and improving the evaluation of cloud radiative effects on a global scale.However,the profiling of clouds is limited to measurements such as radars or lidars,and retrievals from active sensors are influenced by the attenuation of signals and surface clutter.Even when vast amounts of cloud property retrievals that express column or cloud-top/base characteristics from passive sensors are generated,these two-dimensional cloud products are scarcely ever used to further produce three-dimensional cloud profiles because of the lack of a reasonable analytical model to bridge the gap.Thus,this study developed a cloud profile reconstruction model(CPRM)based on our previous analytical cloud profile model and evaluated the sensitivities of visible-to-infrared bands of passive cloud observation sensors to each parameter of the model.The results indicated that the optical thickness,cloud-top ER,and geometrical thickness can be derived from multiwavelength measurements,whereas the slope of the cloud droplet number concentration(CDNC)and the cloud-base ER could hardly be directly estimated.Meanwhile,the analytical model was utilized to rebuild cloud profiles seen by CloudSat and Aircrafts.The analytical model could capture the shape and the vertical variations of the cloud ER and LWC.展开更多
基金Supported by the National Natural Science Foundation of China(42122038 and 42230604)。
文摘Cloud effective radius(CER)is a fundamental microphysical property of clouds,critical for understanding cloud formation and radiative effects.Satellite spectral imagers,widely utilized in passive remote sensing,facilitate the monitoring of cloud characteristics,including CER,over extended time periods and spatial scales.Various observational methods have been employed to evaluate satellite cloud property products;however,in situ measurement evaluations of CER remain limited,particularly for products over China.This study utilized aircraft observations provided by the China Meteorological Administration Weather Modification Centre to evaluate the CER retrieved by Fengyun-4A Advanced Geosynchronous Radiation Imager(AGRI)and Himawari-8 Advanced Himawari Imager(AHI).Three flights were selected from the aircraft dataset for evaluation,involving flights through non-precipitating stratiform clouds with stable,high-quality measurements.Rigorous data selection and collocation procedures were employed to ensure a comprehensive comparison.Satellite retrievals from heterogeneous cloud fields were excluded,and representative in-cloud aircraft measurements were identified through multi-parameter filtering.The flight trajectory was adjusted to account for horizontal cloud movement corresponding to time differences between observations from different platforms.Additionally,in situ measurements from different vertical layers were adjusted to a comparable position near the cloud top.Results indicate that CER retrieved from satellites is generally overestimated compared to in situ measurements.For AGRI,the average difference(AD)is 2.90μm,with a root mean square difference(RMSD)of 3.53μm.For AHI,the AD is 2.92μm,and the RMSD is 3.59μm.To enhance future validation and evaluation of remote sensing results,factors such as instrument calibration,flight patterns,and cloud conditions will be carefully considered.Increasing the number of cases should further reduce errors associated with individual instances,enabling more precise assessments.
基金supported by the National Natural Science Foundation of China(Grant No.42230601).
文摘The impact of aerosols on clouds,which remains one of the largest aspects of uncertainty in current weather forecasting and climate change research,can be influenced by various factors,such as the underlying surface type,cloud type,cloud phase,and aerosol type.To explore the impact of different underlying surfaces on the effect of aerosols on cloud development,this study focused on the Yangtze River Delta(YRD)and its offshore regions(YRD sea)for a comparative analysis based on multi-source satellite data,while also considering the variations in cloud type and cloud phase.The results show lower cloud-top height and depth of single-layer clouds over the ocean than land,and higher liquid cloud in spring over the ocean.Aerosols are found to enhance the cumulus cloud depth through microphysical effects,which is particularly evident over the ocean.Aerosols are also found to decrease the cloud droplet effective radius in the ocean region and during the mature stage of cloud development in the land region,while opposite results are found during the early stage of cloud development in the land region.The quantitative results indicate that the indirect effect is positive(0.05)in the land region at relatively high cloud water path,which is smaller than that in the ocean region(0.11).The findings deepen our understanding of the influence aerosols on cloud development and the mechanisms involved,which could then be applied to improve the ability to simulate cloud-associated weather processes.
基金This work was jointly supported by the 973 Project(Grant No.2005CB321703)the National Natural Science Foundation of China(Grant No.40221503)the Chinese Academy of Sciences International Partnership Creative Group entitled"The Climate System Model Development and Application Studies".
文摘This paper documents a study to examine the sensitivity to cloud droplet effective radius and liquid water path and the alleviation the energy imbalance at the top of the atmosphere and at the surface in the latest version of the Grid-point Atmospheric Model of the State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics （LASG）, Institute of Atmospheric Physics （IAP） （GAMIL1.1.0）. Considerable negative biases in all flux components, and thus an energy imbalance, are found in GAMIL1.1.0. In order to alleviate the energy imbalance, two modifications, namely an increase in cloud droplet effective radius and a decrease in cloud liquid water path, have been made to the cloud properties used in GAMIL. With the increased cloud droplet effective radius, the single scattering albedo of clouds is reduced, and thus the reflection of solar radiation into space by clouds is reduced and the net solar radiation flux at the top of the atmosphere is increased. With the reduced cloud optical depth, the net surface shortwave radiation flux is increased, causing a net warming over the land surface. This results in an increase in both sensible and latent heat fluxes over the land regions, which is largely balanced by the increased terrestrial radiation fluxes. Consequently, the energy balance at the top of atmosphere and at the surface is achieved with energy flux components consistent with available satellite observations.
基金supported by the National Natural Science Foundation of China(Grant Nos.42025504,42175152&42405145)the National Key Research and Development Program of China(Grant No.2023YFB3905900)+2 种基金the Youth Innovation Promotion Association of Chinese Academy of Sciences(Grant No.2021122)the Science and Disruptive Technology Program,AIRCAS(Grant No.E2Z202020F)the Natural Science Foundation of Sichuan Province(Grant No.2024NSFSC0770)。
文摘The characteristics of microphysical profiles of liquid clouds(i.e.,the cloud effective radius(ER)and liquid water content(LWC))are important factors in understanding the aerosol-cloud-precipitation process and improving the evaluation of cloud radiative effects on a global scale.However,the profiling of clouds is limited to measurements such as radars or lidars,and retrievals from active sensors are influenced by the attenuation of signals and surface clutter.Even when vast amounts of cloud property retrievals that express column or cloud-top/base characteristics from passive sensors are generated,these two-dimensional cloud products are scarcely ever used to further produce three-dimensional cloud profiles because of the lack of a reasonable analytical model to bridge the gap.Thus,this study developed a cloud profile reconstruction model(CPRM)based on our previous analytical cloud profile model and evaluated the sensitivities of visible-to-infrared bands of passive cloud observation sensors to each parameter of the model.The results indicated that the optical thickness,cloud-top ER,and geometrical thickness can be derived from multiwavelength measurements,whereas the slope of the cloud droplet number concentration(CDNC)and the cloud-base ER could hardly be directly estimated.Meanwhile,the analytical model was utilized to rebuild cloud profiles seen by CloudSat and Aircrafts.The analytical model could capture the shape and the vertical variations of the cloud ER and LWC.
