Cloud radiative kernels were built by BCC_RAD(Beijing Climate Center radiative transfer model)radiative transfer code.Then,short-term cloud feedback and its mechanisms in East Asia(0.5°S−60.5°N,69.5°−15...Cloud radiative kernels were built by BCC_RAD(Beijing Climate Center radiative transfer model)radiative transfer code.Then,short-term cloud feedback and its mechanisms in East Asia(0.5°S−60.5°N,69.5°−150.5°E)were analyzed quantitatively using the kernels combined with MODIS satellite data from July 2002 to June 2018.According to the surface and monsoon types,four subregions in East Asia-the Tibetan Plateau,northwest,temperate monsoon(TM),and subtropical monsoon(SM)—were selected.The average longwave,shortwave,and net cloud feedbacks in East Asia are−0.68±1.20,1.34±1.08,and 0.66±0.40 W m^−2 K^−1(±2σ),respectively,among which the net feedback is dominated by the positive shortwave feedback.Positive feedback in SM is the strongest of all subregions,mainly due to the contributions of nimbostratus and stratus.In East Asia,short-term feedback in spring is primarily caused by marine stratus in SM,in summer is primarily driven by deep convective cloud in TM,in autumn is mainly caused by land nimbostratus in SM,and in winter is mainly driven by land stratus in SM.Cloud feedback in East Asia is chiefly driven by decreases in mid-level and low cloud fraction owing to the changes in relative humidity,and a decrease in low cloud optical thickness due to the changes in cloud water content.展开更多
Cloud radiative kernels(CRK)built with radiative transfer models have been widely used to analyze the cloud radiative effect on top of atmosphere(TOA)fluxes,and it is expected that the CRKs would also be useful in the...Cloud radiative kernels(CRK)built with radiative transfer models have been widely used to analyze the cloud radiative effect on top of atmosphere(TOA)fluxes,and it is expected that the CRKs would also be useful in the analyses of surface radiative fluxes,which determines the regional surface temperature change and variability.In this study,CRKs at the surface and TOA were built using the Rapid Radiative Transfer Model(RRTM).Longwave cloud radiative effect(CRE)at the surface is primarily driven by cloud base properties,while TOA CRE is primarily decided by cloud top properties.For this reason,the standard version of surface CRK is a function of latitude,longitude,month,cloud optical thickness(τ)and cloud base pressure(CBP),and the TOA CRK is a function of latitude,longitude,month,τand cloud top pressure(CTP).Considering that the cloud property histograms provided by climate models are functions of CTP instead of CBP at present,the surface CRKs on CBP-τhistograms were converted to CTP-τfields using the statistical relationship between CTP,CBP andτobtained from collocated CloudSat and MODIS observations.For both climate model outputs and satellites observations,the climatology of surface CRE and cloud-induced surface radiative anomalies calculated with the surface CRKs and cloud property histograms are well correlated with those calculated from surface radiative fluxes.The cloud-induced surface radiative anomalies reproduced by surface CRKs and MODIS cloud property histograms are not affected by spurious trends that appear in Clouds and the Earth's Radiant Energy System(CERES)surface irradiances products.展开更多
The climate in polar regions has experienced an obvious warming amplification due to global warming.In this study,the changes in polar amplification are analyzed in response to feedback mechanisms(including Planck,lap...The climate in polar regions has experienced an obvious warming amplification due to global warming.In this study,the changes in polar amplification are analyzed in response to feedback mechanisms(including Planck,lapse rate,cloud,water vapor,albedo feedback,CO_(2) radiative forcing,ocean heat uptake,and atmospheric heat transport)under three warming scenarios in CMIP6—namely,SSP1-2.6,SSP2-4.5,and SSP5-8.5.The results show that,by quantifying the warming contribution of different feedback mechanisms to surface air temperature with the“radiative kernel”method,Arctic amplification(AA)is stronger than Antarctic amplification(ANA),mostly resulting from the lapse rate feedback,followed by the albedo and Planck feedbacks.Furthermore,ocean heat uptake causes stronger polar warming in winter than in summer.During winter,the lapse rate feedback causes a larger AA than ANA.The intermodel spread for both AA and ANA decrease with increasing strength of global warming from SSP1-2.6 to SSP5-8.5,and the dominant mechanisms are the Planck,lapse rate,albedo,and ocean heat uptake feedbacks.These findings help to enhance our understanding of polar regions’responses to different strengths of global warming.展开更多
The response of the warming magnitude over the Tibetan Plateau(TP;elevation≥3000 m)to global climate change is not spatially uniform.Rather,it enhances with elevation,referred to as elevation-dependent warming(EDW).T...The response of the warming magnitude over the Tibetan Plateau(TP;elevation≥3000 m)to global climate change is not spatially uniform.Rather,it enhances with elevation,referred to as elevation-dependent warming(EDW).The degree of EDW over the TP is season-dependent,with the largest amplitude of 0.21℃km^(−1)observed during boreal winter.Several factors have been proposed in previous studies as possible drivers of TP EDW,but the relative importance of these factors has been less studied.To quantitatively identify the major drivers of TP EDW in winter over recent decades(1979-2018),the authors applied the radiative kernels diagnostic method with several datasets.The results robustly suggest that,the surface albedo feedback associated with changes in snow cover plays the leading role in TP EDW.Observations show that the snow cover has reduced significantly over regions with high elevation during the winters of the past four decades,leading to reductions in outgoing shortwave radiation and thus EDW.展开更多
基金supported by the National Key R&D Program of China(Grant No.2017YFA0603502)the National Natural Science Foundation of China(Grant Nos.91644211 and 41575002).
文摘Cloud radiative kernels were built by BCC_RAD(Beijing Climate Center radiative transfer model)radiative transfer code.Then,short-term cloud feedback and its mechanisms in East Asia(0.5°S−60.5°N,69.5°−150.5°E)were analyzed quantitatively using the kernels combined with MODIS satellite data from July 2002 to June 2018.According to the surface and monsoon types,four subregions in East Asia-the Tibetan Plateau,northwest,temperate monsoon(TM),and subtropical monsoon(SM)—were selected.The average longwave,shortwave,and net cloud feedbacks in East Asia are−0.68±1.20,1.34±1.08,and 0.66±0.40 W m^−2 K^−1(±2σ),respectively,among which the net feedback is dominated by the positive shortwave feedback.Positive feedback in SM is the strongest of all subregions,mainly due to the contributions of nimbostratus and stratus.In East Asia,short-term feedback in spring is primarily caused by marine stratus in SM,in summer is primarily driven by deep convective cloud in TM,in autumn is mainly caused by land nimbostratus in SM,and in winter is mainly driven by land stratus in SM.Cloud feedback in East Asia is chiefly driven by decreases in mid-level and low cloud fraction owing to the changes in relative humidity,and a decrease in low cloud optical thickness due to the changes in cloud water content.
基金supported by the National Natural Science Foundation of China(Grant No.NSFC 41875095,42075127).
文摘Cloud radiative kernels(CRK)built with radiative transfer models have been widely used to analyze the cloud radiative effect on top of atmosphere(TOA)fluxes,and it is expected that the CRKs would also be useful in the analyses of surface radiative fluxes,which determines the regional surface temperature change and variability.In this study,CRKs at the surface and TOA were built using the Rapid Radiative Transfer Model(RRTM).Longwave cloud radiative effect(CRE)at the surface is primarily driven by cloud base properties,while TOA CRE is primarily decided by cloud top properties.For this reason,the standard version of surface CRK is a function of latitude,longitude,month,cloud optical thickness(τ)and cloud base pressure(CBP),and the TOA CRK is a function of latitude,longitude,month,τand cloud top pressure(CTP).Considering that the cloud property histograms provided by climate models are functions of CTP instead of CBP at present,the surface CRKs on CBP-τhistograms were converted to CTP-τfields using the statistical relationship between CTP,CBP andτobtained from collocated CloudSat and MODIS observations.For both climate model outputs and satellites observations,the climatology of surface CRE and cloud-induced surface radiative anomalies calculated with the surface CRKs and cloud property histograms are well correlated with those calculated from surface radiative fluxes.The cloud-induced surface radiative anomalies reproduced by surface CRKs and MODIS cloud property histograms are not affected by spurious trends that appear in Clouds and the Earth's Radiant Energy System(CERES)surface irradiances products.
基金This work was supported by the National Natural Science Foundation of China[grant number 41420104002]the Natural Science Foundation of Jiangsu Province[grant numbers BK20150907 and 14KJA170002].
文摘The climate in polar regions has experienced an obvious warming amplification due to global warming.In this study,the changes in polar amplification are analyzed in response to feedback mechanisms(including Planck,lapse rate,cloud,water vapor,albedo feedback,CO_(2) radiative forcing,ocean heat uptake,and atmospheric heat transport)under three warming scenarios in CMIP6—namely,SSP1-2.6,SSP2-4.5,and SSP5-8.5.The results show that,by quantifying the warming contribution of different feedback mechanisms to surface air temperature with the“radiative kernel”method,Arctic amplification(AA)is stronger than Antarctic amplification(ANA),mostly resulting from the lapse rate feedback,followed by the albedo and Planck feedbacks.Furthermore,ocean heat uptake causes stronger polar warming in winter than in summer.During winter,the lapse rate feedback causes a larger AA than ANA.The intermodel spread for both AA and ANA decrease with increasing strength of global warming from SSP1-2.6 to SSP5-8.5,and the dominant mechanisms are the Planck,lapse rate,albedo,and ocean heat uptake feedbacks.These findings help to enhance our understanding of polar regions’responses to different strengths of global warming.
基金supported by the National Natural Science Foundation of China[grant number 4225502].
文摘The response of the warming magnitude over the Tibetan Plateau(TP;elevation≥3000 m)to global climate change is not spatially uniform.Rather,it enhances with elevation,referred to as elevation-dependent warming(EDW).The degree of EDW over the TP is season-dependent,with the largest amplitude of 0.21℃km^(−1)observed during boreal winter.Several factors have been proposed in previous studies as possible drivers of TP EDW,but the relative importance of these factors has been less studied.To quantitatively identify the major drivers of TP EDW in winter over recent decades(1979-2018),the authors applied the radiative kernels diagnostic method with several datasets.The results robustly suggest that,the surface albedo feedback associated with changes in snow cover plays the leading role in TP EDW.Observations show that the snow cover has reduced significantly over regions with high elevation during the winters of the past four decades,leading to reductions in outgoing shortwave radiation and thus EDW.
