Aerosol particles can serve as cloud condensation nuclei(CCN)to influence orographic clouds.Autoconversion,which describes the initial formation of raindrops from the collision of cloud droplets,is an important proces...Aerosol particles can serve as cloud condensation nuclei(CCN)to influence orographic clouds.Autoconversion,which describes the initial formation of raindrops from the collision of cloud droplets,is an important process for aerosol-cloud-precipitation systems.In this study,seven autoconversion schemes are used to investigate the impact of CCN on orographic warm-phase clouds.As the initial cloud droplet concentration is increased from 100 cm^(-3)to 1000 cm^(-3)(to represent an increase in CCN),the cloud water increases and then the rainwater is suppressed due to a decrease in the autoconversion rate,leading to a spatial shift in surface precipitation.Intercomparison of the results from the autoconversion schemes show that the sensitivity of cloud water,rainwater,and surface precipitation to a change in the concentration of CCN is different from scheme to scheme.In particular,the decrease in orographic precipitation due to increasing CCN is found to range from-87%to-10%depending on the autoconversion scheme.Moreover,the surface precipitation distribution also changes significantly by scheme or CCN concentration,and the increase in the spillover(ratio of precipitation on the leeward side to total precipitation)induced by increased CCN ranges from 10%to 55%under different autoconversion schemes.The simulations suggest that autoconversion parameterization schemes should not be ignored in the interaction of aerosol and orographic cloud.展开更多
Based on the stochastic collision-coalescence equation for cloud droplets and the definition of the autoconversion rate from cloud droplets to raindrops(ARCR),this study analyzes and derives an ARCR equation from the ...Based on the stochastic collision-coalescence equation for cloud droplets and the definition of the autoconversion rate from cloud droplets to raindrops(ARCR),this study analyzes and derives an ARCR equation from the collision-coalescence process.This equation narrows the integration range of the stochastic collision-coalescence equation,providing a theoretical basis for accurately and efficiently calculating the ARCR.Utilizing the results of the turbulent collision kernel and turbulent collision efficiency,as well as the ARCR equation,an accurate and efficient model for the ARCR was established.Modeling results indicate the following:(1)The ARCR increases with the enhancement of turbulence.The rate of increase was fastest when the turbulent dissipation rate was between 0 and 20 cm^(2)s^(-3),slower when it was between 20 and 50 cm^(2)s^(-3),and intermediate when it was between 50 and 500 cm^(2)s^(-3).(2)Compared to the case without turbulence,the ARCR increased by approximately 20% when the turbulent dissipation rate was 100 cm^(2)s^(-3),and by over 100% when it was 500 cm^(2)s^(-3).Therefore,turbulence has a significant impact on the ARCR only when the turbulent dissipation rate exceeds 100 cm^(2)s^(-3).(3)The influence of turbulence on ARCR results increases with an increase in cloud water content.When there was no turbulence and the cloud water content exceeded 0.68 g m^(-3),a strong linear relationship existed between cloud water content and the ARCR.(4)The effect of turbulence on the ARCR results decreases rapidly with an increase in the cloud droplet number concentration.(5)The impact of turbulence on the ARCR becomes stronger with a decrease in the shape parameter,which corresponds to the increase in the relative dispersion of the cloud droplet spectrum(i.e.,as the cloud droplet spectrum broadens).展开更多
A double-moment cloud microphysics scheme requires an assumption for cloud droplet size distributions(DSDs).However,since observations of cloud DSDs are limited,default values for shape parameters and cloud condensati...A double-moment cloud microphysics scheme requires an assumption for cloud droplet size distributions(DSDs).However,since observations of cloud DSDs are limited,default values for shape parameters and cloud condensation nuclei activation parameters are often used in numerical simulations.In this study,the effects of cloud DSDs on numerical simulations of warm stratiform precipitation around Tokyo are investigated using the Japan Meteorological Agency's non-hydrostatic model,which incorporates a double-moment cloud microphysics scheme.Simulations using the default cloud DSD showed higher cloud droplet number concentrations and lower radar reflectivity than observed data,suggesting that the default cloud DSD is too narrow.Simulations with a cloud DSD based on in situ cloud observations corrected these errors.In addition,observation-based cloud DSDs affected rainfall amounts through the autoconversion rate of cloud water and improved the threat scores.These results suggest that realistic cloud DSDs should be provided for double-moment cloud microphysics schemes in scientific studies.展开更多
Cloud-to-rain autoconversion process is an important player in aerosol loading, cloud morphology, and precipitation variations because it can modulate cloud microphysical characteristics depending on the participation...Cloud-to-rain autoconversion process is an important player in aerosol loading, cloud morphology, and precipitation variations because it can modulate cloud microphysical characteristics depending on the participation of aerosols, and affects the spatio-temporal distribution and total amount of precipitation. By applying the Kessler, the Khairoutdinov-Kogan（KK）, and the Dispersion autoconversion parameterization schemes in a set of sensitivity experiments, the indirect effects of aerosols on clouds and precipitation are investigated for a deep convective cloud system in Beijing under various aerosol concentration backgrounds from 50 to 10000 cm^-3. Numerical experiments show that aerosol-induced precipitation change is strongly dependent on autoconversion parameterization schemes. For the Kessler scheme, the average cumulative precipitation is enhanced slightly with increasing aerosols, whereas surface precipitation is reduced significantly with increasing aerosols for the KK scheme. Moreover, precipitation varies non-monotonically for the Dispersion scheme, increasing with aerosols at lower concentrations and decreasing at higher concentrations.These different trends of aerosol-induced precipitation change are mainly ascribed to differences in rain water content under these three autoconversion parameterization schemes. Therefore, this study suggests that accurate parameterization of cloud microphysical processes, particularly the cloud-to-rain autoconversion process, is needed for improving the scientific understanding of aerosol-cloud-precipitation interactions.展开更多
Previous studies have shown that accurate descriptions of the cloud droplet effective radius （Re） and the autoconversion process of cloud droplets to raindrops （At） can effectively improve simulated clouds and sur...Previous studies have shown that accurate descriptions of the cloud droplet effective radius （Re） and the autoconversion process of cloud droplets to raindrops （At） can effectively improve simulated clouds and surface precipitation, and reduce the uncertainty of aerosol indirect effects in GCMs. In this paper, we implement cloud microphysical schemes including two-moment Ar and Re considering relative dispersion of the cloud droplet size distribution into version 4.1 of the Institute of Atmospheric Physics＇s atmospheric GCM （IAP AGCM 4.1）, which is the atmospheric component of the Chinese Academy of Sciences＇ Earth System Model. Analysis of the effects of different schemes shows that the newly implemented schemes can improve both the simulated shortwave and longwave cloud radiative forcings, as compared to the standard scheme, in lAP AGCM 4.1. The new schemes also effectively enhance the large-scale precipitation, especially over low latitudes, although the influences of total precipitation are insignificant for different schemes. Further studies show that similar results can be found with the Community Atmosphere Model, version 5.1.展开更多
This study investigated the second indirect climatic effect of anthropogenic aerosols,including sulfate,organic carbon(OC) ,and black carbon(BC) ,over East Asia.The seasonal variation of the climatic response to the s...This study investigated the second indirect climatic effect of anthropogenic aerosols,including sulfate,organic carbon(OC) ,and black carbon(BC) ,over East Asia.The seasonal variation of the climatic response to the second indirect effect was also characterized.The simulation period for this study was 2006.Due to a decrease in autoconversion rate from cloud water to rain as a result of aerosols,the cloud liquid water path(LWP) ,and radiative flux(RF) at the top of the atmosphere(TOA) changed dramatically,increasing by 14.3 g m-2 and decreasing by-4.1 W m-2 in terms of domain and annual average.Both LWP and RF changed most in autumn. There were strong decreases in ground temperature in Southwest China,the middle reaches of the Yangtze River in spring and autumn,while maximum cooling of up to-1.5 K occurred in the Chongqing district.The regional and annual mean change in ground temperature reached-0.2 K over eastern China.In all seasons except summer,precipitation generally decreased in most areas north of the Yangtze River,whereas precipitation changed little in South China.Precipitation changed most in summer,with alternating bands of increasing(～40 mm) and decreasing(～40 mm) precipitation appearing in eastern China.Precipitation decreased by 1.5-40 mm over large areas of Northeast China and the Huabei Plain.The domain and annual mean change in precipitation was approximately-0.3 mm over eastern China.The maximum reduction in precipitation occurred in summer,with mean absolute and relative changes of-1.2 mm and-3.8%over eastern China.This study revealed considerable climate responses to the second indirect effect of aerosols over specific regions of China.展开更多
Improvements to the Kessler-type parameterization of warm cloud microphysical conversion processes（also called autoconversion） are proposed based on a large number of Cloud Sat observations between June2006 and Apri...Improvements to the Kessler-type parameterization of warm cloud microphysical conversion processes（also called autoconversion） are proposed based on a large number of Cloud Sat observations between June2006 and April 2011 over Asian land areas. The emphasis is given to the vertical distribution of liquid water content（LWC）, particularly, the threshold values of LWC for autoconversion. The results warrant a new approach to the numerical parameterization of autoconversion in warm clouds. One feature of this new approach is that the autoconversion threshold, which has been treated as a constant in previous parameterization schemes, is diagnosed as a function of altitude by using a relationship between LWC and height（H）derived from Cloud Sat observations： LWCdig =-500.0 ln（ H/9492.2）. Under this framework, the threshold LWC decreases with increasing H, allowing autoconversion to occur in clouds with low LWC（approximately0.3 g m^-3） at levels above 5.5 km. Autoconversion rates calculated based on the new parameterization are compared to those calculated based on several commonly used parameterization schemes over a range of LWCs from 0.01 to 1.0 g m^-3. The new scheme provides reasonable simulations of autoconversion at various vertical levels.展开更多
基金sponsored by the National Key Basic Research and Development Program of China (Grant No. 2018YFC1505702)the National Natural Science Foundation of China (Grant No. 41705120, 41590873, 41975138)+1 种基金Weather Modification Ability Construction Project of Northwest China (Grant No. ZQC-R18211)a Guangdong Province Science and Technology Project (Grant No. 2017B020244002)
文摘Aerosol particles can serve as cloud condensation nuclei(CCN)to influence orographic clouds.Autoconversion,which describes the initial formation of raindrops from the collision of cloud droplets,is an important process for aerosol-cloud-precipitation systems.In this study,seven autoconversion schemes are used to investigate the impact of CCN on orographic warm-phase clouds.As the initial cloud droplet concentration is increased from 100 cm^(-3)to 1000 cm^(-3)(to represent an increase in CCN),the cloud water increases and then the rainwater is suppressed due to a decrease in the autoconversion rate,leading to a spatial shift in surface precipitation.Intercomparison of the results from the autoconversion schemes show that the sensitivity of cloud water,rainwater,and surface precipitation to a change in the concentration of CCN is different from scheme to scheme.In particular,the decrease in orographic precipitation due to increasing CCN is found to range from-87%to-10%depending on the autoconversion scheme.Moreover,the surface precipitation distribution also changes significantly by scheme or CCN concentration,and the increase in the spillover(ratio of precipitation on the leeward side to total precipitation)induced by increased CCN ranges from 10%to 55%under different autoconversion schemes.The simulations suggest that autoconversion parameterization schemes should not be ignored in the interaction of aerosol and orographic cloud.
基金supported by the Science and Technology Development Fund of Chinese Academy of Meteorological Sciences(CAMS)(Grant No.2024KJ001)。
文摘Based on the stochastic collision-coalescence equation for cloud droplets and the definition of the autoconversion rate from cloud droplets to raindrops(ARCR),this study analyzes and derives an ARCR equation from the collision-coalescence process.This equation narrows the integration range of the stochastic collision-coalescence equation,providing a theoretical basis for accurately and efficiently calculating the ARCR.Utilizing the results of the turbulent collision kernel and turbulent collision efficiency,as well as the ARCR equation,an accurate and efficient model for the ARCR was established.Modeling results indicate the following:(1)The ARCR increases with the enhancement of turbulence.The rate of increase was fastest when the turbulent dissipation rate was between 0 and 20 cm^(2)s^(-3),slower when it was between 20 and 50 cm^(2)s^(-3),and intermediate when it was between 50 and 500 cm^(2)s^(-3).(2)Compared to the case without turbulence,the ARCR increased by approximately 20% when the turbulent dissipation rate was 100 cm^(2)s^(-3),and by over 100% when it was 500 cm^(2)s^(-3).Therefore,turbulence has a significant impact on the ARCR only when the turbulent dissipation rate exceeds 100 cm^(2)s^(-3).(3)The influence of turbulence on ARCR results increases with an increase in cloud water content.When there was no turbulence and the cloud water content exceeded 0.68 g m^(-3),a strong linear relationship existed between cloud water content and the ARCR.(4)The effect of turbulence on the ARCR results decreases rapidly with an increase in the cloud droplet number concentration.(5)The impact of turbulence on the ARCR becomes stronger with a decrease in the shape parameter,which corresponds to the increase in the relative dispersion of the cloud droplet spectrum(i.e.,as the cloud droplet spectrum broadens).
基金supported by Grants in Aid from the Japan Society for the Promotion of Science(JSPS)KAKENHI[grant numbers JP21H01163 and JP23H00149].
文摘A double-moment cloud microphysics scheme requires an assumption for cloud droplet size distributions(DSDs).However,since observations of cloud DSDs are limited,default values for shape parameters and cloud condensation nuclei activation parameters are often used in numerical simulations.In this study,the effects of cloud DSDs on numerical simulations of warm stratiform precipitation around Tokyo are investigated using the Japan Meteorological Agency's non-hydrostatic model,which incorporates a double-moment cloud microphysics scheme.Simulations using the default cloud DSD showed higher cloud droplet number concentrations and lower radar reflectivity than observed data,suggesting that the default cloud DSD is too narrow.Simulations with a cloud DSD based on in situ cloud observations corrected these errors.In addition,observation-based cloud DSDs affected rainfall amounts through the autoconversion rate of cloud water and improved the threat scores.These results suggest that realistic cloud DSDs should be provided for double-moment cloud microphysics schemes in scientific studies.
基金Supported by the National Basic Research and Development(973)Program of China(2011CB403406)Strategic Priority Research Program of the Chinese Academy of Sciences(XDA05110101)National Natural Science Foundation of China(41105071and 41290255)
文摘Cloud-to-rain autoconversion process is an important player in aerosol loading, cloud morphology, and precipitation variations because it can modulate cloud microphysical characteristics depending on the participation of aerosols, and affects the spatio-temporal distribution and total amount of precipitation. By applying the Kessler, the Khairoutdinov-Kogan（KK）, and the Dispersion autoconversion parameterization schemes in a set of sensitivity experiments, the indirect effects of aerosols on clouds and precipitation are investigated for a deep convective cloud system in Beijing under various aerosol concentration backgrounds from 50 to 10000 cm^-3. Numerical experiments show that aerosol-induced precipitation change is strongly dependent on autoconversion parameterization schemes. For the Kessler scheme, the average cumulative precipitation is enhanced slightly with increasing aerosols, whereas surface precipitation is reduced significantly with increasing aerosols for the KK scheme. Moreover, precipitation varies non-monotonically for the Dispersion scheme, increasing with aerosols at lower concentrations and decreasing at higher concentrations.These different trends of aerosol-induced precipitation change are mainly ascribed to differences in rain water content under these three autoconversion parameterization schemes. Therefore, this study suggests that accurate parameterization of cloud microphysical processes, particularly the cloud-to-rain autoconversion process, is needed for improving the scientific understanding of aerosol-cloud-precipitation interactions.
基金partially supported by the National Key Research and Development Program of China (Grant No. 2016YFA0601904)the National Natural Science Foundation of China (Grant Nos. 41690115 and 41572150)+3 种基金the National Natural Science Foundation of China (Grant No. 61432018)supported by the National Major Research High Performance Computing Program of China (Grant No. 2016YFB0200800)supported by a “973” project (Grant No. 2014CB441302)supported by the US Department of Energy’s Atmospheric System Research program
文摘Previous studies have shown that accurate descriptions of the cloud droplet effective radius （Re） and the autoconversion process of cloud droplets to raindrops （At） can effectively improve simulated clouds and surface precipitation, and reduce the uncertainty of aerosol indirect effects in GCMs. In this paper, we implement cloud microphysical schemes including two-moment Ar and Re considering relative dispersion of the cloud droplet size distribution into version 4.1 of the Institute of Atmospheric Physics＇s atmospheric GCM （IAP AGCM 4.1）, which is the atmospheric component of the Chinese Academy of Sciences＇ Earth System Model. Analysis of the effects of different schemes shows that the newly implemented schemes can improve both the simulated shortwave and longwave cloud radiative forcings, as compared to the standard scheme, in lAP AGCM 4.1. The new schemes also effectively enhance the large-scale precipitation, especially over low latitudes, although the influences of total precipitation are insignificant for different schemes. Further studies show that similar results can be found with the Community Atmosphere Model, version 5.1.
基金supported by the Knowledge Innovation Program of the Chinese Academy of Sciences(Grant No. KZCX2-YW-Q11-03)the"Strategic Priority Research Program"of the Chinese Academy of Sciences(Grant No.XDA05100502)+1 种基金the R&D Special Fund for Public Welfare Industry(Meteorology) (Grant No.GYHY200906020)100 Talents Program of the Chinese Academy of Sciences
文摘This study investigated the second indirect climatic effect of anthropogenic aerosols,including sulfate,organic carbon(OC) ,and black carbon(BC) ,over East Asia.The seasonal variation of the climatic response to the second indirect effect was also characterized.The simulation period for this study was 2006.Due to a decrease in autoconversion rate from cloud water to rain as a result of aerosols,the cloud liquid water path(LWP) ,and radiative flux(RF) at the top of the atmosphere(TOA) changed dramatically,increasing by 14.3 g m-2 and decreasing by-4.1 W m-2 in terms of domain and annual average.Both LWP and RF changed most in autumn. There were strong decreases in ground temperature in Southwest China,the middle reaches of the Yangtze River in spring and autumn,while maximum cooling of up to-1.5 K occurred in the Chongqing district.The regional and annual mean change in ground temperature reached-0.2 K over eastern China.In all seasons except summer,precipitation generally decreased in most areas north of the Yangtze River,whereas precipitation changed little in South China.Precipitation changed most in summer,with alternating bands of increasing(～40 mm) and decreasing(～40 mm) precipitation appearing in eastern China.Precipitation decreased by 1.5-40 mm over large areas of Northeast China and the Huabei Plain.The domain and annual mean change in precipitation was approximately-0.3 mm over eastern China.The maximum reduction in precipitation occurred in summer,with mean absolute and relative changes of-1.2 mm and-3.8%over eastern China.This study revealed considerable climate responses to the second indirect effect of aerosols over specific regions of China.
基金Supported by the National Natural Science Foundation of China(41405006)China Meteorological Administration Special Public Welfare Research Fund(GYHY201006014 and GYHY201306005)+1 种基金National(Key)Basic Research and Development(973)Program of China(2012CB417204)Basic Research Fund of the Chinese Academy of Meteorological Sciences(2014R016 and2014Z001)
文摘Improvements to the Kessler-type parameterization of warm cloud microphysical conversion processes（also called autoconversion） are proposed based on a large number of Cloud Sat observations between June2006 and April 2011 over Asian land areas. The emphasis is given to the vertical distribution of liquid water content（LWC）, particularly, the threshold values of LWC for autoconversion. The results warrant a new approach to the numerical parameterization of autoconversion in warm clouds. One feature of this new approach is that the autoconversion threshold, which has been treated as a constant in previous parameterization schemes, is diagnosed as a function of altitude by using a relationship between LWC and height（H）derived from Cloud Sat observations： LWCdig =-500.0 ln（ H/9492.2）. Under this framework, the threshold LWC decreases with increasing H, allowing autoconversion to occur in clouds with low LWC（approximately0.3 g m^-3） at levels above 5.5 km. Autoconversion rates calculated based on the new parameterization are compared to those calculated based on several commonly used parameterization schemes over a range of LWCs from 0.01 to 1.0 g m^-3. The new scheme provides reasonable simulations of autoconversion at various vertical levels.
