Clouds are a dominant modulator of the energy budget.The cloud shortwave radiative effect at the surface(CRE)is closely related to the cloud macro-and micro-physical properties.Systematic observation of surface irradi...Clouds are a dominant modulator of the energy budget.The cloud shortwave radiative effect at the surface(CRE)is closely related to the cloud macro-and micro-physical properties.Systematic observation of surface irradiance and cloud properties are needed to narrow uncertainties in CRE.In this study,1-min irradiance and Total Sky Imager measurements from 2005 to 2009 at Xianghe in North China Plain are used to estimate cloud types,evaluate cloud fraction(CF),and quantify the sensitivities of surface irradiance with respect to changes in CF whether clouds obscure the sun or not.The annual mean CF is 0.50,further noting that CF exhibits a distinct seasonal variation,with a minimum in winter(0.37)and maximum in summer(0.68).Cumulus occurs more frequently in summer(32%),which is close to the sum of the occurrence of stratus and cirrus.The annual CRE is–54.4 W m^(–2),with seasonal values ranging from^(–2)9.5 W m^(–2)in winter and–78.2 W m^(–2)in summer.When clouds do not obscure the sun,CF is a dominant factor affecting diffuse irradiance,which in turn affects global irradiance.There is a positive linear relationship between CF and CRE under sun-unobscured conditions,the mean sensitivity of CRE for each CF 0.1 increase is about 1.2 W m^(–2)[79.5°<SZA(Solar Zenith Angle)<80.5°]to 7.0 W m^(–2)(29.5°<SZA<30.5°).When clouds obscure the sun,CF affects both direct and diffuse irradiance,resulting in a non-linear relationship between CF and CRE,and the slope decreases with increasing CF.It should be noted that,although only data at Xianghe is used in this study,our results are representative of neighboring areas,including most parts of the North China Plain.展开更多
Cloud-radiative forcing(CRF)at the top of the atmosphere(TOA)over the western Pacific warm pool(WP)shows unique characteristics in response to El Nino events.In this region,the responses of CRF to El Nino events have ...Cloud-radiative forcing(CRF)at the top of the atmosphere(TOA)over the western Pacific warm pool(WP)shows unique characteristics in response to El Nino events.In this region,the responses of CRF to El Nino events have been a useful metric for evaluating climate models.Satellite data are used to analyze the CRF anomalies to El Nino events simulated by the new and old versions of the Climate System Model of the Chinese Academy of Meteorological Sciences(CAMS-CSM),which has participated in the Atmospheric Model Intercomparison Project(AMIP).Here,simulations for super El Nino years,El Nino years,and normal years are compared with observations.The results show that the mean values of both longwave CRF(LWCRF)and shortwave CRF(SWCRF)in CAMS-CSM are weaker than the observations for each category of El Nino events.Compared with the old version of CAMS-CSM,the decrease in LWCRF during El Nino events is well simulated by the new version of CAMS-CSM.However,both new and old models cannot reproduce the anomalous SWCRF in El Nino events.The biases in the CRF response to El Nino events are attributed to the biases in the cloud vertical structure because of a weaker crash of the Walker circulation in CAMS-CSM.Due to the modification of the conversion rate from cloud droplets to raindrops in the cumulus convection scheme,the new version of CAMS-CSM has better CRF skills in normal years,but biases in El Nino events still exist in the new version.Improving the response of the Walker circulation to El Nino events is key to higher skills in simulating the cloud radiative responses.展开更多
Effects of vertical wind shear, radiation, and ice clouds on cloud microphysical budget associated with torrential rainfall during landfall of severe tropical storm Bilis （2006） are investigated by using a series of...Effects of vertical wind shear, radiation, and ice clouds on cloud microphysical budget associated with torrential rainfall during landfall of severe tropical storm Bilis （2006） are investigated by using a series of analysis of two-day grid-scale sensitivity experiment data. When upper-tropospheric upward motions and lower-tropospheric downward motions occur on 15 July 2006, the removal of vertical wind shear and ice clouds increases rainfall contributions from the rainfall type （CM） associated with positive net condensation and hydrometeor loss/convergence, whereas the exclusion of cloud radiative effects and cloud-radiation in- teraction reduces rainfall contribution from CM. The elimination of vertical wind shear and cloud-radiation interaction increases rainfall contribution from the rainfall type （Cm） associated with positive net conden- sation and hydrometeor gain/divergence, but the removal of cloud radiative effects and ice clouds decreases rainfall contribution from Cm. The enhancements in rainfall contribution from the rainfall type （cM） as- sociated with negative net condensation and hydrometeor loss/convergence are caused by the exclusion of cloud radiative effects, cloud-radiation interaction and ice clouds, whereas the reduction in rainfall contri- bution from cM results from the removal of vertical wind shear. When upward motions appear throughout the troposphere on 16 July, the exclusion of all these effects increases rainfall contribution from CM, but generally decreases rainfall contributions from Cm and cM.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.41875183,41805021)the National Key R&D Program of China(Grant No.2017YFA0603504).
文摘Clouds are a dominant modulator of the energy budget.The cloud shortwave radiative effect at the surface(CRE)is closely related to the cloud macro-and micro-physical properties.Systematic observation of surface irradiance and cloud properties are needed to narrow uncertainties in CRE.In this study,1-min irradiance and Total Sky Imager measurements from 2005 to 2009 at Xianghe in North China Plain are used to estimate cloud types,evaluate cloud fraction(CF),and quantify the sensitivities of surface irradiance with respect to changes in CF whether clouds obscure the sun or not.The annual mean CF is 0.50,further noting that CF exhibits a distinct seasonal variation,with a minimum in winter(0.37)and maximum in summer(0.68).Cumulus occurs more frequently in summer(32%),which is close to the sum of the occurrence of stratus and cirrus.The annual CRE is–54.4 W m^(–2),with seasonal values ranging from^(–2)9.5 W m^(–2)in winter and–78.2 W m^(–2)in summer.When clouds do not obscure the sun,CF is a dominant factor affecting diffuse irradiance,which in turn affects global irradiance.There is a positive linear relationship between CF and CRE under sun-unobscured conditions,the mean sensitivity of CRE for each CF 0.1 increase is about 1.2 W m^(–2)[79.5°<SZA(Solar Zenith Angle)<80.5°]to 7.0 W m^(–2)(29.5°<SZA<30.5°).When clouds obscure the sun,CF affects both direct and diffuse irradiance,resulting in a non-linear relationship between CF and CRE,and the slope decreases with increasing CF.It should be noted that,although only data at Xianghe is used in this study,our results are representative of neighboring areas,including most parts of the North China Plain.
基金Supported by the Ministry of Science and Technology of China(2017YFA0604004)National Natural Science Foundation of China(41775102,41420104006,and 41661144009).
文摘Cloud-radiative forcing(CRF)at the top of the atmosphere(TOA)over the western Pacific warm pool(WP)shows unique characteristics in response to El Nino events.In this region,the responses of CRF to El Nino events have been a useful metric for evaluating climate models.Satellite data are used to analyze the CRF anomalies to El Nino events simulated by the new and old versions of the Climate System Model of the Chinese Academy of Meteorological Sciences(CAMS-CSM),which has participated in the Atmospheric Model Intercomparison Project(AMIP).Here,simulations for super El Nino years,El Nino years,and normal years are compared with observations.The results show that the mean values of both longwave CRF(LWCRF)and shortwave CRF(SWCRF)in CAMS-CSM are weaker than the observations for each category of El Nino events.Compared with the old version of CAMS-CSM,the decrease in LWCRF during El Nino events is well simulated by the new version of CAMS-CSM.However,both new and old models cannot reproduce the anomalous SWCRF in El Nino events.The biases in the CRF response to El Nino events are attributed to the biases in the cloud vertical structure because of a weaker crash of the Walker circulation in CAMS-CSM.Due to the modification of the conversion rate from cloud droplets to raindrops in the cumulus convection scheme,the new version of CAMS-CSM has better CRF skills in normal years,but biases in El Nino events still exist in the new version.Improving the response of the Walker circulation to El Nino events is key to higher skills in simulating the cloud radiative responses.
基金Supported by the National (Key) Basic Research and Development (973) Program of China (2012CB417204)China Meteorological Administration Special Public Welfare Research Fund (GYHY200806007, GYHY201006014, and GYHY201206039)+1 种基金National Natural Science Foundation of China (40875022, 40633016, and 41175064)Basic Research Project of the State Key Laboratory of Severe Weather, Chinese Academy of Meteorological Sciences
文摘Effects of vertical wind shear, radiation, and ice clouds on cloud microphysical budget associated with torrential rainfall during landfall of severe tropical storm Bilis （2006） are investigated by using a series of analysis of two-day grid-scale sensitivity experiment data. When upper-tropospheric upward motions and lower-tropospheric downward motions occur on 15 July 2006, the removal of vertical wind shear and ice clouds increases rainfall contributions from the rainfall type （CM） associated with positive net condensation and hydrometeor loss/convergence, whereas the exclusion of cloud radiative effects and cloud-radiation in- teraction reduces rainfall contribution from CM. The elimination of vertical wind shear and cloud-radiation interaction increases rainfall contribution from the rainfall type （Cm） associated with positive net conden- sation and hydrometeor gain/divergence, but the removal of cloud radiative effects and ice clouds decreases rainfall contribution from Cm. The enhancements in rainfall contribution from the rainfall type （cM） as- sociated with negative net condensation and hydrometeor loss/convergence are caused by the exclusion of cloud radiative effects, cloud-radiation interaction and ice clouds, whereas the reduction in rainfall contri- bution from cM results from the removal of vertical wind shear. When upward motions appear throughout the troposphere on 16 July, the exclusion of all these effects increases rainfall contribution from CM, but generally decreases rainfall contributions from Cm and cM.
