As part of the development work of the Chinese new regional climate model (RIEMS), the radiative process of black carbon (BC) aerosols has been introduced into the original radiative procedures of RIEMS, and the trans...As part of the development work of the Chinese new regional climate model (RIEMS), the radiative process of black carbon (BC) aerosols has been introduced into the original radiative procedures of RIEMS, and the transport model of BC aerosols has also been established and combined with the RIEMS model. Using the new model system, the distribution of black carbon aerosols and their radiative effect over the China region are investigated. The influences of BC aerosole on the atmospheric radiative transfer and on the air temperature, land surface temperature, and total rainfall are analyzed. It is found that BC aerosols induce a positive radiative forcing at the top of the atmosphere (TOA), which is dominated by shortwave radiative forcing. The maximum radiative forcing occurs in North China in July and in South China in April. At the same time, negative radiative forcing is observed on the surface. Based on the radiative forcing comparison between clear sky and cloudy sky, it is found that cloud can enforce the TOA positive radiative forcing and decrease the negative surface radiative forcing. The responses of the climate system in July to the radiative forcing due to BC aerosols are the decrease in the air temperature in the middle and lower reaches of the Changjiang River and Huaihe area and most areas of South China, and the weak increase or decrease in air temperature over North China. The total rainfall in the middle and lower reaches of the Changjiang River area is increased, but it decreased in North China in July.展开更多
The radiative forcing and climate response due to black carbon（BC） in snow and/or ice were investigated by integrating observed effects of BC on snow/ice albedo into an atmospheric general circulation model（BCC AGC...The radiative forcing and climate response due to black carbon（BC） in snow and/or ice were investigated by integrating observed effects of BC on snow/ice albedo into an atmospheric general circulation model（BCC AGCM2.0.1） developed by the National Climate Center（NCC） of the China Meteorological Administration（CMA）.The results show that the global annual mean surface radiative forcing due to BC in snow/ice is ＋0.042 W m 2,with maximum forcing found over the Tibetan Plateau and regional mean forcing exceeding ＋2.8 W m 2.The global annual mean surface temperature increased 0.071 C due to BC in snow/ice.Positive surface radiative forcing was clearly shown in winter and spring and increased the surface temperature of snow/ice in the Northern Hemisphere.The surface temperatures of snow-covered areas of Eurasia and North America in winter（spring） increased by 0.83 C（0.6 C） and 0.83 C（0.46 C）,respectively.Snowmelt rates also increased greatly,leading to earlier snowmelt and peak runoff times.With the rise of surface temperatures in the Arctic,more water vapor could be released into the atmosphere,allowing easier cloud formation,which could lead to higher thermal emittance in the Arctic.However,the total cloud forcing could decrease due to increasing cloud cover,which will offset some of the positive feedback mechanism of the clouds.展开更多
Black carbon （BC） aerosols can strongly absorb solar radiation in very broad spectral wavebands, from the visible to the infrared. As a potential factor contributing to global warming, BC aerosols not only directly ...Black carbon （BC） aerosols can strongly absorb solar radiation in very broad spectral wavebands, from the visible to the infrared. As a potential factor contributing to global warming, BC aerosols not only directly change the radiation balance of the earth-atmosphere system, but also indirectly affect global or regional climate by acting as cloud conden- sation nuclei or ice nuclei to alter cloud mierophysical properties. Here, recent progresses in the studies of radiative forcing due to BC and its climate effects are reviewed. The uncertainties in current researches are discussed and some suggestions are provided for future investigations.展开更多
Atmospheric aerosols have contributed to radiative forcing through direct and indirect mechanisms. Aerosol effects are important in computing radiative forcing estimates for the past, current and future climate. In th...Atmospheric aerosols have contributed to radiative forcing through direct and indirect mechanisms. Aerosol effects are important in computing radiative forcing estimates for the past, current and future climate. In this study, a comprehensive assessment of regional aerosol radiative forcing, Optical Properties of Aerosol and Clouds (OPAC) model (wavelength range of 0.25 - 4.0 μm) over selected sites in East Africa was done. Aerosol optical properties constituted the inputs of a Radiative Transfer Model (RTM). Op-tical properties investigated included Aerosol Optical Depth (AOD), Single Scattering Albedo (SSA) and Asymmetry Parameter (AP). Aerosol Radiative Forcing (ARF) during the study period at the surface (SFC), top of the atmosphere (TOA) and the atmosphere (ATM) was estimated to be -18.4 ± 1.4 W·m-2, +1.1 ± 0.3 W·m-2 and +19.5 ± 2.5 W·m-2, respectively. This corresponds to an increment in net atmospheric forcing at a heating rate of about 0.55 ± 0.05 K/day (0.41 ± 0.03 to 0.78 ± 0.03 K/day) in the lower troposphere. The study points out the significant role played by atmospheric aerosols in climate modification over the area of study. It is recommended that a further assessment be done in view of uncertainties that may impact on the findings and which were not within the scope of this research.展开更多
The first ever land campaign to study the spatial variability of the aerosol characteristics along the Brahmaputra river valley (BRV) in Assam, North-Eastern India, was conducted during 2011. Measurements were made ov...The first ever land campaign to study the spatial variability of the aerosol characteristics along the Brahmaputra river valley (BRV) in Assam, North-Eastern India, was conducted during 2011. Measurements were made over 13 locations for Aerosol Optical Depth (AOD), scattering coefficient, particulate matter, black carbon (BC) concentration and meteorological parameters. The BRV is divided into three sectors longitudinally viz western sector (WS), central sector (CS), and eastern sector (ES). Significant Spatial heterogeneity in AOD and BC concentration was observed (p < 0.05) with the highest values over WS and a continual decrease from WS to ES with aerosol dominance in PM2.5 category along the entire valley. The Angstrom coefficient measured using different wavelength pairs showed spatial variability indicating dominance of fine particles over WS and coarse particles in ES with a probable bimodal distribution. The scattering and absorption coefficient shows dominance of both types of aerosol over WS than other areas. The shortwave radiative forcing was higher over the WS than CS and ES of the valley. The campaign revealed that under favorable wind conditions, the BRV is loaded with significant amount of natural and anthropogenic aerosol during local winter and is influenced by the long-range transport of aerosols from the Indo-Gangetic plain.展开更多
In this paper,the RIEMS 2.0 model,source emission in 2006 and 2010 are used to simulate the distributions and radiative effects of different anthropogenic aerosols over China.The comparison between the results forced ...In this paper,the RIEMS 2.0 model,source emission in 2006 and 2010 are used to simulate the distributions and radiative effects of different anthropogenic aerosols over China.The comparison between the results forced by source emissions in 2006 and 2010 also reveals the sensitivity of the radiative effects to source emission.The results are shown as follows:(1) Compared with those in 2006,the annual average surface concentration of sulfate in 2010 decreased over central and eastern China with a range of-5 to 0 μg/m^3;the decrease of annual average aerosol optical depth of sulfate over East China varied from 0.04 to 0.08;the annual average surface concentrations of BC,OC and nitrate increased over central and eastern China with maximums of 10.90,11.52 and 12.50μg/m^3,respectively;the annual aerosol optical depths of BC,OC and nitrate increased over some areas of East China with extremes of 0.006,0.007 and 0.008,respectively.(2)For the regional average results in 2010,the radiative forcings of sulfate,BC,OC,nitrate and their total net radiative forcing at the top of the atmosphere over central and eastern China were-0.64,0.29,-0.41,-0.33 and-1.1 W/m^2,respectively.Compared with those in 2006,the radiative forcings of BC and OC in 2010 were both enhanced,while that of sulfate and the net radiative forcing were both weakened over East China mostly.(3)The reduction of the cooling effect of sulfate in 2010 produced a warmer surface air temperature over central and eastern China;the maximum value was 0.25 K.The cooling effect of nitrate was also slightly weakened.The warming effect of BC was enhanced over most of the areas in China,while the cooling effect of OC was enhanced over the similar area,particularly the area between Yangtze and Huanghe Rivers.The net radiative effect of the four anthropogenic aerosols generated the annual average reduction and the maximum reduction were-0.096 and-0.285 K,respectively,for the surface temperature in 2006,while in 2010 they were-0.063 and-0.256 K,respectively.In summary,the change in source emission lowered the cooling effect of anthropogenic aerosols,mainly because of the enhanced warming effect of BC and weakened cooling effect of scattering aerosols.展开更多
基金This research was sponsored by the National Key Program for Developing Basic Sciences of China(No.G1999043400)the National Natural Science Foundation of China(Grant Nos.40205016 and 40165001).
文摘As part of the development work of the Chinese new regional climate model (RIEMS), the radiative process of black carbon (BC) aerosols has been introduced into the original radiative procedures of RIEMS, and the transport model of BC aerosols has also been established and combined with the RIEMS model. Using the new model system, the distribution of black carbon aerosols and their radiative effect over the China region are investigated. The influences of BC aerosole on the atmospheric radiative transfer and on the air temperature, land surface temperature, and total rainfall are analyzed. It is found that BC aerosols induce a positive radiative forcing at the top of the atmosphere (TOA), which is dominated by shortwave radiative forcing. The maximum radiative forcing occurs in North China in July and in South China in April. At the same time, negative radiative forcing is observed on the surface. Based on the radiative forcing comparison between clear sky and cloudy sky, it is found that cloud can enforce the TOA positive radiative forcing and decrease the negative surface radiative forcing. The responses of the climate system in July to the radiative forcing due to BC aerosols are the decrease in the air temperature in the middle and lower reaches of the Changjiang River and Huaihe area and most areas of South China, and the weak increase or decrease in air temperature over North China. The total rainfall in the middle and lower reaches of the Changjiang River area is increased, but it decreased in North China in July.
基金supported by the National Basic Research Program of China (Grant Nos. 2010CB955608 and 2011CB403405)the Public Meteorology Special Foundation of MOST (Grant No.GYHY200906020)
文摘The radiative forcing and climate response due to black carbon（BC） in snow and/or ice were investigated by integrating observed effects of BC on snow/ice albedo into an atmospheric general circulation model（BCC AGCM2.0.1） developed by the National Climate Center（NCC） of the China Meteorological Administration（CMA）.The results show that the global annual mean surface radiative forcing due to BC in snow/ice is ＋0.042 W m 2,with maximum forcing found over the Tibetan Plateau and regional mean forcing exceeding ＋2.8 W m 2.The global annual mean surface temperature increased 0.071 C due to BC in snow/ice.Positive surface radiative forcing was clearly shown in winter and spring and increased the surface temperature of snow/ice in the Northern Hemisphere.The surface temperatures of snow-covered areas of Eurasia and North America in winter（spring） increased by 0.83 C（0.6 C） and 0.83 C（0.46 C）,respectively.Snowmelt rates also increased greatly,leading to earlier snowmelt and peak runoff times.With the rise of surface temperatures in the Arctic,more water vapor could be released into the atmosphere,allowing easier cloud formation,which could lead to higher thermal emittance in the Arctic.However,the total cloud forcing could decrease due to increasing cloud cover,which will offset some of the positive feedback mechanism of the clouds.
基金financially supported by the National Basic Research Program of China(2011CB403405 and 2010CB955608)the Public Meteorology Special Foundation of MOST(GYHY200906020)
文摘Black carbon （BC） aerosols can strongly absorb solar radiation in very broad spectral wavebands, from the visible to the infrared. As a potential factor contributing to global warming, BC aerosols not only directly change the radiation balance of the earth-atmosphere system, but also indirectly affect global or regional climate by acting as cloud conden- sation nuclei or ice nuclei to alter cloud mierophysical properties. Here, recent progresses in the studies of radiative forcing due to BC and its climate effects are reviewed. The uncertainties in current researches are discussed and some suggestions are provided for future investigations.
文摘Atmospheric aerosols have contributed to radiative forcing through direct and indirect mechanisms. Aerosol effects are important in computing radiative forcing estimates for the past, current and future climate. In this study, a comprehensive assessment of regional aerosol radiative forcing, Optical Properties of Aerosol and Clouds (OPAC) model (wavelength range of 0.25 - 4.0 μm) over selected sites in East Africa was done. Aerosol optical properties constituted the inputs of a Radiative Transfer Model (RTM). Op-tical properties investigated included Aerosol Optical Depth (AOD), Single Scattering Albedo (SSA) and Asymmetry Parameter (AP). Aerosol Radiative Forcing (ARF) during the study period at the surface (SFC), top of the atmosphere (TOA) and the atmosphere (ATM) was estimated to be -18.4 ± 1.4 W·m-2, +1.1 ± 0.3 W·m-2 and +19.5 ± 2.5 W·m-2, respectively. This corresponds to an increment in net atmospheric forcing at a heating rate of about 0.55 ± 0.05 K/day (0.41 ± 0.03 to 0.78 ± 0.03 K/day) in the lower troposphere. The study points out the significant role played by atmospheric aerosols in climate modification over the area of study. It is recommended that a further assessment be done in view of uncertainties that may impact on the findings and which were not within the scope of this research.
文摘The first ever land campaign to study the spatial variability of the aerosol characteristics along the Brahmaputra river valley (BRV) in Assam, North-Eastern India, was conducted during 2011. Measurements were made over 13 locations for Aerosol Optical Depth (AOD), scattering coefficient, particulate matter, black carbon (BC) concentration and meteorological parameters. The BRV is divided into three sectors longitudinally viz western sector (WS), central sector (CS), and eastern sector (ES). Significant Spatial heterogeneity in AOD and BC concentration was observed (p < 0.05) with the highest values over WS and a continual decrease from WS to ES with aerosol dominance in PM2.5 category along the entire valley. The Angstrom coefficient measured using different wavelength pairs showed spatial variability indicating dominance of fine particles over WS and coarse particles in ES with a probable bimodal distribution. The scattering and absorption coefficient shows dominance of both types of aerosol over WS than other areas. The shortwave radiative forcing was higher over the WS than CS and ES of the valley. The campaign revealed that under favorable wind conditions, the BRV is loaded with significant amount of natural and anthropogenic aerosol during local winter and is influenced by the long-range transport of aerosols from the Indo-Gangetic plain.
基金National Key Basic Research and Development Planning Program of China(Program 973)(2014CB441203)Special Research Program for Public Welfare Industries(GYHY201206011)
文摘In this paper,the RIEMS 2.0 model,source emission in 2006 and 2010 are used to simulate the distributions and radiative effects of different anthropogenic aerosols over China.The comparison between the results forced by source emissions in 2006 and 2010 also reveals the sensitivity of the radiative effects to source emission.The results are shown as follows:(1) Compared with those in 2006,the annual average surface concentration of sulfate in 2010 decreased over central and eastern China with a range of-5 to 0 μg/m^3;the decrease of annual average aerosol optical depth of sulfate over East China varied from 0.04 to 0.08;the annual average surface concentrations of BC,OC and nitrate increased over central and eastern China with maximums of 10.90,11.52 and 12.50μg/m^3,respectively;the annual aerosol optical depths of BC,OC and nitrate increased over some areas of East China with extremes of 0.006,0.007 and 0.008,respectively.(2)For the regional average results in 2010,the radiative forcings of sulfate,BC,OC,nitrate and their total net radiative forcing at the top of the atmosphere over central and eastern China were-0.64,0.29,-0.41,-0.33 and-1.1 W/m^2,respectively.Compared with those in 2006,the radiative forcings of BC and OC in 2010 were both enhanced,while that of sulfate and the net radiative forcing were both weakened over East China mostly.(3)The reduction of the cooling effect of sulfate in 2010 produced a warmer surface air temperature over central and eastern China;the maximum value was 0.25 K.The cooling effect of nitrate was also slightly weakened.The warming effect of BC was enhanced over most of the areas in China,while the cooling effect of OC was enhanced over the similar area,particularly the area between Yangtze and Huanghe Rivers.The net radiative effect of the four anthropogenic aerosols generated the annual average reduction and the maximum reduction were-0.096 and-0.285 K,respectively,for the surface temperature in 2006,while in 2010 they were-0.063 and-0.256 K,respectively.In summary,the change in source emission lowered the cooling effect of anthropogenic aerosols,mainly because of the enhanced warming effect of BC and weakened cooling effect of scattering aerosols.
