As the strongest subseasonal atmospheric variability during boreal winter, three remarkable sudden stratospheric major warming(SSW) events in the 2000 s are investigated in terms of the Brewer–Dobson circulation(BDC)...As the strongest subseasonal atmospheric variability during boreal winter, three remarkable sudden stratospheric major warming(SSW) events in the 2000 s are investigated in terms of the Brewer–Dobson circulation(BDC) response. Our study shows that the changes of cross-isentropic velocity during the SSWs are not only confined to the polar region, but also extend to the whole Northern Hemisphere: enhanced descent in the polar region, as well as enhanced ascent in the tropics. When the acceleration of the deep branch of the BDC descends to the middle stratosphere, its strength rapidly decreases over a period of one to two weeks. The acceleration of the deep branch of the BDC is driven by the enhanced planetary wave activity in the mid-to-high-latitude stratosphere. Different from the rapid response of the deep branch of the BDC, tropical upwelling in the lower stratosphere accelerates up to 20%–40% compared with the climatology, 20–30 days after the onset of the SSWs,and the acceleration lasts for one to three months. The enhancement of tropical upwelling is associated with the large-scale wave-breaking in the subtropics interacting with the midlatitude and tropical Quasi-Biennial Oscillation–related mean flow.展开更多
This paper uses Dobson spectrometer total ozone data,Total Ozone Mapping Spectrometer(TOMS) data and radiosonde reports from Kunming,which is located in southwest China,from 1980 to 2008 to analyze the total ozone-cli...This paper uses Dobson spectrometer total ozone data,Total Ozone Mapping Spectrometer(TOMS) data and radiosonde reports from Kunming,which is located in southwest China,from 1980 to 2008 to analyze the total ozone-climate relationship.The total ozone decadal long-term trend and abrupt change were studied using enhanced Dobson data whose missing data were amended by the TOMS data.Stepwise linear regression was used for the selection of the key factors that influence total ozone,including temperatures,geopotential heights,depressions of the dew point,wind velocities,and total solar radiation.The relationship between the selected factors and total ozone was analyzed using the methods of stepwise regression and partial least squares regression(PLSR).Results showed that although the PLSR method was slightly better and more reasonable to study the relationship than stepwise regression,while the two regression results were only slightly different.It was also suggested that local climate,especially local circulation and temperature,were important for the variations in total ozone,and the local climate could almost linearly explain 80% of the variance of total ozone.The relationship also indicated that the abrupt change of total ozone in the year 1994 may be related to abrupt local climate change.展开更多
The objective of this study is to evaluate the accuracy of the daily nadir total column ozone products derived from the nadir mapper instrument on the Ozone Mapping and Profiler Suite （OMPS） flying onboard the Suomi...The objective of this study is to evaluate the accuracy of the daily nadir total column ozone products derived from the nadir mapper instrument on the Ozone Mapping and Profiler Suite （OMPS） flying onboard the Suomi National Polar-orbiting Partnership satellite （S- NPP） launched as a part of the Joint Polar Satellite System （JPSS） program between NOAA and NASA. Since NOAA is already operationally processing OMPS nadir total ozone products, evaluations were made in this study on the total column ozone research products generated by NASA＇s science team, utilizing the latest version of their Backscatter Ultraviolet （BUV） retrieval algorithms, to provide insight into the performance of the operation system. Comparisons were made with globally distributed ground-based Brewer and Dobson spectrophotometer total column ozone measurements. Linear regressions show fair agreement between OMPS and ground-based total column ozone measurements with a root-mean-square error （RMSE） of approximately 3% （10 DU）. The comparison results indicate that the OMPS total column ozone data are 0.59% higher than the Brewer measurements with a standard deviation of 2.82% while 1.09% higher than the Dobson measurements with a standard deviation of 3.27%. Additionally, the variability of relative differences between OMPS and ground total column ozone were analyzed as a function of latitude, time, viewing geometry, and total column ozone value. Results show a 2% bias over most latitudes and viewing conditions when total column ozone value varies between 220 DU and 450 DU.展开更多
土壤水分是气象预报、农情监测以及水文模型的重要参数之一,利用被动微波遥感技术可以有效获取土壤水分。欧空局(ESA)计划于2009年发射卫星SMOS(Soil Moisture and Ocean Salinity),其主要目的是监测全球范围内的土壤水分和海洋盐度变...土壤水分是气象预报、农情监测以及水文模型的重要参数之一,利用被动微波遥感技术可以有效获取土壤水分。欧空局(ESA)计划于2009年发射卫星SMOS(Soil Moisture and Ocean Salinity),其主要目的是监测全球范围内的土壤水分和海洋盐度变化。根据SMOS的设置情况,寻找精度较高的半经验模型以便为进一步的土壤水分反演提供简化模型。对于裸露地表,地表粗糙度、土壤介电常数等因素影响最终的微波发射率。运用Dobson半经验介电常数模型计算土壤的介电常数,将计算结果输入高级积分方程模型(AIEM)。通过AIEM模拟的数据库,利用回归关系建立了一个精度相对较高的L波段多角度半经验模型。展开更多
Using a state-of-the-art chemistry-climate model,we analyzed the atmospheric responses to increases in sea surface temperature （SST）.The results showed that increases in SST and the SST meridional gradient could int...Using a state-of-the-art chemistry-climate model,we analyzed the atmospheric responses to increases in sea surface temperature （SST）.The results showed that increases in SST and the SST meridional gradient could intensify the subtropical westerly jets and significantly weaken the northern polar vortex.In the model runs,global uniform SST increases produced a more significant impact on the southern stratosphere than the northern stratosphere,while SST gradient increases produced a more significant impact on the northern stratosphere.The asymmetric responses of the northern and southern polar stratosphere to SST meridional gradient changes were found to be mainly due to different wave properties and transmissions in the northern and southern atmosphere.Although SST increases may give rise to stronger waves,the results showed that the effect of SST increases on the vertical propagation of tropospheric waves into the stratosphere will vary with height and latitude and be sensitive to SST meridional gradient changes.Both uniform and non-uniform SST increases accelerated the large-scale Brewer-Dobson circulation （BDC）,but the gradient increases of SST between 60°S and 60°N resulted in younger mean age-of-air in the stratosphere and a larger increase in tropical upwelling,with a much higher tropopause than from a global uniform 1.0 K SST increase.展开更多
Interest in the Moon started to increase at the beginning of the 21st century, and henceforth, more and more attention has been paid to the content and distribution of water ice in the lunar polar regions. The existen...Interest in the Moon started to increase at the beginning of the 21st century, and henceforth, more and more attention has been paid to the content and distribution of water ice in the lunar polar regions. The existence of water or ice in the regolith can apparently change its dielectric features. Therefore, in this article, the Dobson model is adopted and improved according to the Moon＇s environmental features, to construct the relationship between the volumetric water ice content and the di- electric constant. Thereafter, a lunar regolith dielectric distribution map is generated based on the improved Dobson model and the Clementine UVVIS data. The map indicates that the imaginary part of the dielectric constants in the lunar mare is much higher than that in the highlands. However, the maximum dielectric constants occur at the north- and south-pole regions, whose values are apparently bigger than those in the middle and low latitudes. Then, an abnormal map of the dielectric constant is gained if the threshold is put as 0.053 7, which is the highest value in the middle and low latitudes. The statistical results indicate that the number of abnormal pixels is 110 596, and the average is about 0.057 9. Assuming that the mean dielectric constant in the lunar mare is the normal dielectric constant at the south and north poles and ε1=11.58＋i0.057 9 is the abnormal one, the volumetric water ice content can be evaluated using the advanced Dobson model. The results show that the average volumetric water ice content is about 1.64%, and the total area is about 25 294 km^2, where 10 956 km2 belongs to the north pole and the rest is in the south pole.展开更多
文摘As the strongest subseasonal atmospheric variability during boreal winter, three remarkable sudden stratospheric major warming(SSW) events in the 2000 s are investigated in terms of the Brewer–Dobson circulation(BDC) response. Our study shows that the changes of cross-isentropic velocity during the SSWs are not only confined to the polar region, but also extend to the whole Northern Hemisphere: enhanced descent in the polar region, as well as enhanced ascent in the tropics. When the acceleration of the deep branch of the BDC descends to the middle stratosphere, its strength rapidly decreases over a period of one to two weeks. The acceleration of the deep branch of the BDC is driven by the enhanced planetary wave activity in the mid-to-high-latitude stratosphere. Different from the rapid response of the deep branch of the BDC, tropical upwelling in the lower stratosphere accelerates up to 20%–40% compared with the climatology, 20–30 days after the onset of the SSWs,and the acceleration lasts for one to three months. The enhancement of tropical upwelling is associated with the large-scale wave-breaking in the subtropics interacting with the midlatitude and tropical Quasi-Biennial Oscillation–related mean flow.
基金supported by the National Basic Research Program of China (973 Program) under Grant 2009CB421406 the Chinese Academy of Sciences under Grant KZCX-YW-Q1-02
文摘This paper uses Dobson spectrometer total ozone data,Total Ozone Mapping Spectrometer(TOMS) data and radiosonde reports from Kunming,which is located in southwest China,from 1980 to 2008 to analyze the total ozone-climate relationship.The total ozone decadal long-term trend and abrupt change were studied using enhanced Dobson data whose missing data were amended by the TOMS data.Stepwise linear regression was used for the selection of the key factors that influence total ozone,including temperatures,geopotential heights,depressions of the dew point,wind velocities,and total solar radiation.The relationship between the selected factors and total ozone was analyzed using the methods of stepwise regression and partial least squares regression(PLSR).Results showed that although the PLSR method was slightly better and more reasonable to study the relationship than stepwise regression,while the two regression results were only slightly different.It was also suggested that local climate,especially local circulation and temperature,were important for the variations in total ozone,and the local climate could almost linearly explain 80% of the variance of total ozone.The relationship also indicated that the abrupt change of total ozone in the year 1994 may be related to abrupt local climate change.
文摘The objective of this study is to evaluate the accuracy of the daily nadir total column ozone products derived from the nadir mapper instrument on the Ozone Mapping and Profiler Suite （OMPS） flying onboard the Suomi National Polar-orbiting Partnership satellite （S- NPP） launched as a part of the Joint Polar Satellite System （JPSS） program between NOAA and NASA. Since NOAA is already operationally processing OMPS nadir total ozone products, evaluations were made in this study on the total column ozone research products generated by NASA＇s science team, utilizing the latest version of their Backscatter Ultraviolet （BUV） retrieval algorithms, to provide insight into the performance of the operation system. Comparisons were made with globally distributed ground-based Brewer and Dobson spectrophotometer total column ozone measurements. Linear regressions show fair agreement between OMPS and ground-based total column ozone measurements with a root-mean-square error （RMSE） of approximately 3% （10 DU）. The comparison results indicate that the OMPS total column ozone data are 0.59% higher than the Brewer measurements with a standard deviation of 2.82% while 1.09% higher than the Dobson measurements with a standard deviation of 3.27%. Additionally, the variability of relative differences between OMPS and ground total column ozone were analyzed as a function of latitude, time, viewing geometry, and total column ozone value. Results show a 2% bias over most latitudes and viewing conditions when total column ozone value varies between 220 DU and 450 DU.
文摘土壤水分是气象预报、农情监测以及水文模型的重要参数之一,利用被动微波遥感技术可以有效获取土壤水分。欧空局(ESA)计划于2009年发射卫星SMOS(Soil Moisture and Ocean Salinity),其主要目的是监测全球范围内的土壤水分和海洋盐度变化。根据SMOS的设置情况,寻找精度较高的半经验模型以便为进一步的土壤水分反演提供简化模型。对于裸露地表,地表粗糙度、土壤介电常数等因素影响最终的微波发射率。运用Dobson半经验介电常数模型计算土壤的介电常数,将计算结果输入高级积分方程模型(AIEM)。通过AIEM模拟的数据库,利用回归关系建立了一个精度相对较高的L波段多角度半经验模型。
基金supported by the National Basic Research Program of China (Grant No. 2010CB428604)the National Natural Science Foundation of China (Grant Nos. 41175042 and 41225018)the Fundamental Research Funds for the Central Universities of China (Grant No. lzujbky2012-k04)
文摘Using a state-of-the-art chemistry-climate model,we analyzed the atmospheric responses to increases in sea surface temperature （SST）.The results showed that increases in SST and the SST meridional gradient could intensify the subtropical westerly jets and significantly weaken the northern polar vortex.In the model runs,global uniform SST increases produced a more significant impact on the southern stratosphere than the northern stratosphere,while SST gradient increases produced a more significant impact on the northern stratosphere.The asymmetric responses of the northern and southern polar stratosphere to SST meridional gradient changes were found to be mainly due to different wave properties and transmissions in the northern and southern atmosphere.Although SST increases may give rise to stronger waves,the results showed that the effect of SST increases on the vertical propagation of tropospheric waves into the stratosphere will vary with height and latitude and be sensitive to SST meridional gradient changes.Both uniform and non-uniform SST increases accelerated the large-scale Brewer-Dobson circulation （BDC）,but the gradient increases of SST between 60°S and 60°N resulted in younger mean age-of-air in the stratosphere and a larger increase in tropical upwelling,with a much higher tropopause than from a global uniform 1.0 K SST increase.
基金supported by the National Natural Science Foundation of China (Nos. 40901159, 40901187)the Doctoral Fund of Ministry of Education of China (No. 20090061120055)+1 种基金the Fundamental Research Funds for the Central Universities (No. 200903047)the National High Technology Research and Development Program of China (No. 2010AA122203)
文摘Interest in the Moon started to increase at the beginning of the 21st century, and henceforth, more and more attention has been paid to the content and distribution of water ice in the lunar polar regions. The existence of water or ice in the regolith can apparently change its dielectric features. Therefore, in this article, the Dobson model is adopted and improved according to the Moon＇s environmental features, to construct the relationship between the volumetric water ice content and the di- electric constant. Thereafter, a lunar regolith dielectric distribution map is generated based on the improved Dobson model and the Clementine UVVIS data. The map indicates that the imaginary part of the dielectric constants in the lunar mare is much higher than that in the highlands. However, the maximum dielectric constants occur at the north- and south-pole regions, whose values are apparently bigger than those in the middle and low latitudes. Then, an abnormal map of the dielectric constant is gained if the threshold is put as 0.053 7, which is the highest value in the middle and low latitudes. The statistical results indicate that the number of abnormal pixels is 110 596, and the average is about 0.057 9. Assuming that the mean dielectric constant in the lunar mare is the normal dielectric constant at the south and north poles and ε1=11.58＋i0.057 9 is the abnormal one, the volumetric water ice content can be evaluated using the advanced Dobson model. The results show that the average volumetric water ice content is about 1.64%, and the total area is about 25 294 km^2, where 10 956 km2 belongs to the north pole and the rest is in the south pole.
