Current global climate models cannot resolve the complex topography over the Tibetan Plateau(TP)due to their coarse resolution.This study investigates the impacts of horizontal resolution on simulating aerosol and its...Current global climate models cannot resolve the complex topography over the Tibetan Plateau(TP)due to their coarse resolution.This study investigates the impacts of horizontal resolution on simulating aerosol and its direct radiative effect(DRE)over the TP by applying two horizontal resolutions of about 100 km and 25 km to the Chinese Academy of Sciences Flexible Global Ocean-Atmosphere Land System(CAS FGOALS-f3)over a 10-year period.Compared to the AErosol RObotic NETwork observations,a high-resolution model(HRM)can better reproduce the spatial distribution and seasonal cycles of aerosol optical depth(AOD)compared to a low-resolution model(LRM).The HRM bias and RMSE of AOD decreased by 0.08 and 0.12,and the correlation coefficient increased by 0.22 compared to the LRM.An LRM is not sufficient to reproduce the aerosol variations associated with fine-scale topographic forcing,such as in the eastern marginal region of the TP.The difference between hydrophilic aerosols in an HRM and LRM is caused by the divergence of the simulated relative humidity(RH).More reasonable distributions and variations of RH are conducive to simulating hydrophilic aerosols.An increase of the 10-m wind speed in winter by an HRM leads to increased dust emissions.The simulated aerosol DREs at the top of the atmosphere(TOA)and at the surface by the HRM are–0.76 W m^(–2)and–8.72 W m^(–2)over the TP,respectively.Both resolution models can capture the key feature that dust TOA DRE transitions from positive in spring to negative in the other seasons.展开更多
Northwest China is recognized as a main source and a major transport channel of dust aerosols in East Asia.With a fragile ecological environment,this region is quite sensitive to global climate change.Based on the sat...Northwest China is recognized as a main source and a major transport channel of dust aerosols in East Asia.With a fragile ecological environment,this region is quite sensitive to global climate change.Based on the satellite-derived aerosol three-dimensional distribution,the direct radiative effects of dust aerosols over Northwest China are evaluated.Aerosols over Northwest China are mainly distributed in the Tarim Basin,Junggar Basin,Gobi Desert,and Loess Plateau.The aerosol extinction coefficients are greater than 0.36 km-1 over the Tarim Basin and 0.16 km^(-1) over the Gobi Desert and Loess Plateau,decreasing with height.Aerosols over Northwest China are mainly composed of pure dust and polluted dust.These dust aerosols can modify the horizontal temperature gradient,vertical thermodynamic structure,and diurnal temperature range by absorbing and scattering shortwave radiation and emitting longwave radiation.For the column atmosphere,the radiative effect of dust aerosols shows heating effect of approximately 0.3 K day^(-1) during the daytime and cooling effect of approximately-0.4 K day^(-1) at night.In the vertical direction,dust aerosols can heat up the lower atmosphere(0.5–1.5 K day^(-1))and cool down the upper atmosphere(about-1.0 K day^(-1))during the daytime,while they cool down the lower atmosphere(-3 to-1.5 K day^(-1))and heat up the upper atmosphere(1–1.5 K day^(-1))at night.There are also significant lateral and vertical variations in the dust radiative effects corresponding to their spatial distributions.This study provides some scientific basis for reducing uncertainty in the investigation of aerosol radiative effects and provides observation evidence for simulation studies.展开更多
Direct climate responses to dust shortwave and longwave radiative forcing (RF) are studied using the NCAR Community Atmosphere Model Version 3 (CAM3). The simulated RF at the top of the atmosphere (TOA) is-0.45 ...Direct climate responses to dust shortwave and longwave radiative forcing (RF) are studied using the NCAR Community Atmosphere Model Version 3 (CAM3). The simulated RF at the top of the atmosphere (TOA) is-0.45 W m-2 in the solar spectrum and +0.09 W m-2 in the thermal spectrum on a global average. The magnitude of surface RF is larger than the TOA forcing, with global mean shortwave forcing of-1.76 W m-2 and longwave forcing of +0.31 W m-2 . As a result, dust aerosol causes the absorption of 1.1 W m-2 in the atmosphere. The RF of dust aerosol is predicted to lead to a surface cooling of 0.5 K over the Sahara Desert and Arabian Peninsula. In the meantime, the upper troposphere is predicted to become warmer because of the absorption by dust. These changes in temperature lead to a more stable atmosphere, which results in increases in surface humidity. The upward sensible and latent heat fluxes at the surface are reduced, largely balancing the surface energy loss caused by the backscattering and absorption of dust aerosol. Precipitation is predicted to decrease moderately on a global scale.展开更多
基金supported by the National Natural Science Funds of China(Grant Nos.41875133,91937302)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA2006010302)+2 种基金the Second Tibetan Plateau Scientific Expedition and Research Program(STEP,Grant No.2019QZKK0206)the Youth Innovation Promotion Association CAS(2020078)the International Partnership Program of Chinese Academy of Sciences(Grant No.134111KYSB20200006).
文摘Current global climate models cannot resolve the complex topography over the Tibetan Plateau(TP)due to their coarse resolution.This study investigates the impacts of horizontal resolution on simulating aerosol and its direct radiative effect(DRE)over the TP by applying two horizontal resolutions of about 100 km and 25 km to the Chinese Academy of Sciences Flexible Global Ocean-Atmosphere Land System(CAS FGOALS-f3)over a 10-year period.Compared to the AErosol RObotic NETwork observations,a high-resolution model(HRM)can better reproduce the spatial distribution and seasonal cycles of aerosol optical depth(AOD)compared to a low-resolution model(LRM).The HRM bias and RMSE of AOD decreased by 0.08 and 0.12,and the correlation coefficient increased by 0.22 compared to the LRM.An LRM is not sufficient to reproduce the aerosol variations associated with fine-scale topographic forcing,such as in the eastern marginal region of the TP.The difference between hydrophilic aerosols in an HRM and LRM is caused by the divergence of the simulated relative humidity(RH).More reasonable distributions and variations of RH are conducive to simulating hydrophilic aerosols.An increase of the 10-m wind speed in winter by an HRM leads to increased dust emissions.The simulated aerosol DREs at the top of the atmosphere(TOA)and at the surface by the HRM are–0.76 W m^(–2)and–8.72 W m^(–2)over the TP,respectively.Both resolution models can capture the key feature that dust TOA DRE transitions from positive in spring to negative in the other seasons.
基金Supported by the Gansu Provincial Special Fund for Scientific and Technological Innovation and Development(2019ZX-06)Fundamental Research Funds for the Central Universities(lzujbky-2020-kb31)Meteorological Science and Technology Research Project of Shandong Meteorological Bureau(2019sdqxm14)。
文摘Northwest China is recognized as a main source and a major transport channel of dust aerosols in East Asia.With a fragile ecological environment,this region is quite sensitive to global climate change.Based on the satellite-derived aerosol three-dimensional distribution,the direct radiative effects of dust aerosols over Northwest China are evaluated.Aerosols over Northwest China are mainly distributed in the Tarim Basin,Junggar Basin,Gobi Desert,and Loess Plateau.The aerosol extinction coefficients are greater than 0.36 km-1 over the Tarim Basin and 0.16 km^(-1) over the Gobi Desert and Loess Plateau,decreasing with height.Aerosols over Northwest China are mainly composed of pure dust and polluted dust.These dust aerosols can modify the horizontal temperature gradient,vertical thermodynamic structure,and diurnal temperature range by absorbing and scattering shortwave radiation and emitting longwave radiation.For the column atmosphere,the radiative effect of dust aerosols shows heating effect of approximately 0.3 K day^(-1) during the daytime and cooling effect of approximately-0.4 K day^(-1) at night.In the vertical direction,dust aerosols can heat up the lower atmosphere(0.5–1.5 K day^(-1))and cool down the upper atmosphere(about-1.0 K day^(-1))during the daytime,while they cool down the lower atmosphere(-3 to-1.5 K day^(-1))and heat up the upper atmosphere(1–1.5 K day^(-1))at night.There are also significant lateral and vertical variations in the dust radiative effects corresponding to their spatial distributions.This study provides some scientific basis for reducing uncertainty in the investigation of aerosol radiative effects and provides observation evidence for simulation studies.
基金supported by the Key Project of Chinese Academy of Sciences under Grant KZCX2-YW-Q11-03supported by the National Basic Research Program of China ("973" program) under Grant2006CB403705+1 种基金the Key Project of Chinese Academy of Sciences under Grants KZCX2-YW-Q1-02, KZCX2-YW-205, and KZCX2-YW-219the National Natural Science Foundation of China under Grant No. 40631005
文摘Direct climate responses to dust shortwave and longwave radiative forcing (RF) are studied using the NCAR Community Atmosphere Model Version 3 (CAM3). The simulated RF at the top of the atmosphere (TOA) is-0.45 W m-2 in the solar spectrum and +0.09 W m-2 in the thermal spectrum on a global average. The magnitude of surface RF is larger than the TOA forcing, with global mean shortwave forcing of-1.76 W m-2 and longwave forcing of +0.31 W m-2 . As a result, dust aerosol causes the absorption of 1.1 W m-2 in the atmosphere. The RF of dust aerosol is predicted to lead to a surface cooling of 0.5 K over the Sahara Desert and Arabian Peninsula. In the meantime, the upper troposphere is predicted to become warmer because of the absorption by dust. These changes in temperature lead to a more stable atmosphere, which results in increases in surface humidity. The upward sensible and latent heat fluxes at the surface are reduced, largely balancing the surface energy loss caused by the backscattering and absorption of dust aerosol. Precipitation is predicted to decrease moderately on a global scale.