Hyperspectral data are an important source for monitoring soil salt content on a large scale. However, in previous studies, barriers such as interference due to the presence of vegetation restricted the precision of m...Hyperspectral data are an important source for monitoring soil salt content on a large scale. However, in previous studies, barriers such as interference due to the presence of vegetation restricted the precision of mapping soil salt content. This study tested a new method for predicting soil salt content with improved precision by using Chinese hyperspectral data, Huan Jing-Hyper Spectral Imager(HJ-HSI), in the coastal area of Rudong County, Eastern China. The vegetation-covered area and coastal bare flat area were distinguished by using the normalized differential vegetation index at the band length of 705 nm(NDVI705). The soil salt content of each area was predicted by various algorithms. A Normal Soil Salt Content Response Index(NSSRI) was constructed from continuum-removed reflectance(CR-reflectance) at wavelengths of 908.95 nm and 687.41 nm to predict the soil salt content in the coastal bare flat area(NDVI705 < 0.2). The soil adjusted salinity index(SAVI) was applied to predict the soil salt content in the vegetation-covered area(NDVI705 ≥ 0.2). The results demonstrate that 1) the new method significantly improves the accuracy of soil salt content mapping(R2 = 0.6396, RMSE = 0.3591), and 2) HJ-HSI data can be used to map soil salt content precisely and are suitable for monitoring soil salt content on a large scale.展开更多
Some recent studies presented two existing types of ENSO events, one is the Eastern-Pacific(EP) type and the other the Central-Pacific(CP) type. This study examined the monitoring ability of several current operationa...Some recent studies presented two existing types of ENSO events, one is the Eastern-Pacific(EP) type and the other the Central-Pacific(CP) type. This study examined the monitoring ability of several current operational ENSO indices. The results indicated that a single index could not distinguish the EP and CP in the historical ENSO events during 1950-2009. The Nio 3 index may only be suitable for monitoring the EP-type ENSO, while the Nio 4 index works only for the CP-type ENSO. In order to capture the occurrence of ENSO events and distinguish the type, we considered a new monitoring index group using Nio 3 and Nio 4 indices. Further analysis confirmed that this index group can monitor different types of historical ENSO events with different spatial distribution of sea surface temperature. It has a good performance in determining the characteristics of the ENSO events, including peak intensity, onset,decay, and mature phase.展开更多
The fine-mode aerosol absorption optical depth（AAOD）retrieved from the Aerosol Robotic Network（AERONET）has been used in previous studies to calculate the radiative forcing of black carbon（BC）aerosol,assuming tha...The fine-mode aerosol absorption optical depth（AAOD）retrieved from the Aerosol Robotic Network（AERONET）has been used in previous studies to calculate the radiative forcing of black carbon（BC）aerosol,assuming that the absorption by fine-mode aerosols（diameter ≤ 1 μm）is primarily from BC while the absorption by larger particles（diameter 1 μm）is principally from dust.In the present study,the Community Earth System Model was used to simulate and quantify the contribution of fine-mode dust to fine-mode AAOD in eastern China（29–41°N,104–122°E）—an area where concentrations of BC are high.The simulated fine-mode dust concentrations were constrained by observations from nine sites belonging to the Chinese Meteorological Administration Atmosphere Watch Network.Averaged over eastern China,the simulated annual mean fine-mode dust AAOD was 3.6 × 10-3,with the maximum AAOD in spring and the minimum value in winter.The contribution of fine-mode dust to the total fine-mode AAOD（sum of fine-mode dust,BC,and organic carbon）in winter,spring,summer,and autumn was 3.4%,25.2%,12.5%,and 14.9%,respectively,with an annual mean value of 15.1%.The results indicate the importance of removing fine dust AAOD when the AERONET fine-mode AAOD is used for calculating the radiative forcing of BC in eastern China.展开更多
Averaged fractional composition of aerosol in Vietnam and Belarus was obtained and the maps of the column on near-ground aerosol content were built on the basics of model calculations. The results show the complexity ...Averaged fractional composition of aerosol in Vietnam and Belarus was obtained and the maps of the column on near-ground aerosol content were built on the basics of model calculations. The results show the complexity of the geographic ASEAN areas. It may cause variable of climate in local.展开更多
基金Under the auspices of National Natural Science Foundation of China(No.41230751,41101547)Scientific Research Foundation of Graduate School of Nanjing University(No.2012CL14)
文摘Hyperspectral data are an important source for monitoring soil salt content on a large scale. However, in previous studies, barriers such as interference due to the presence of vegetation restricted the precision of mapping soil salt content. This study tested a new method for predicting soil salt content with improved precision by using Chinese hyperspectral data, Huan Jing-Hyper Spectral Imager(HJ-HSI), in the coastal area of Rudong County, Eastern China. The vegetation-covered area and coastal bare flat area were distinguished by using the normalized differential vegetation index at the band length of 705 nm(NDVI705). The soil salt content of each area was predicted by various algorithms. A Normal Soil Salt Content Response Index(NSSRI) was constructed from continuum-removed reflectance(CR-reflectance) at wavelengths of 908.95 nm and 687.41 nm to predict the soil salt content in the coastal bare flat area(NDVI705 < 0.2). The soil adjusted salinity index(SAVI) was applied to predict the soil salt content in the vegetation-covered area(NDVI705 ≥ 0.2). The results demonstrate that 1) the new method significantly improves the accuracy of soil salt content mapping(R2 = 0.6396, RMSE = 0.3591), and 2) HJ-HSI data can be used to map soil salt content precisely and are suitable for monitoring soil salt content on a large scale.
基金The Definition of El Nio/La Nia Episodes,a National Standard ProjectSpecialized Project for Public Welfare Industries(GYHY201406018,GYHY200806009)+2 种基金Program 973(2012CB955901)National Science and Technology Support Program(2009BAC51B05)National Youth Foundation for Natural Science(41005038)
文摘Some recent studies presented two existing types of ENSO events, one is the Eastern-Pacific(EP) type and the other the Central-Pacific(CP) type. This study examined the monitoring ability of several current operational ENSO indices. The results indicated that a single index could not distinguish the EP and CP in the historical ENSO events during 1950-2009. The Nio 3 index may only be suitable for monitoring the EP-type ENSO, while the Nio 4 index works only for the CP-type ENSO. In order to capture the occurrence of ENSO events and distinguish the type, we considered a new monitoring index group using Nio 3 and Nio 4 indices. Further analysis confirmed that this index group can monitor different types of historical ENSO events with different spatial distribution of sea surface temperature. It has a good performance in determining the characteristics of the ENSO events, including peak intensity, onset,decay, and mature phase.
基金supported by the National Basic Research Program of China(973 Program,[grant number 2014CB441202])the Strategic Priority Research Program of the Chinese Academy of Sciences[grant number XDA05100503]
文摘The fine-mode aerosol absorption optical depth（AAOD）retrieved from the Aerosol Robotic Network（AERONET）has been used in previous studies to calculate the radiative forcing of black carbon（BC）aerosol,assuming that the absorption by fine-mode aerosols（diameter ≤ 1 μm）is primarily from BC while the absorption by larger particles（diameter 1 μm）is principally from dust.In the present study,the Community Earth System Model was used to simulate and quantify the contribution of fine-mode dust to fine-mode AAOD in eastern China（29–41°N,104–122°E）—an area where concentrations of BC are high.The simulated fine-mode dust concentrations were constrained by observations from nine sites belonging to the Chinese Meteorological Administration Atmosphere Watch Network.Averaged over eastern China,the simulated annual mean fine-mode dust AAOD was 3.6 × 10-3,with the maximum AAOD in spring and the minimum value in winter.The contribution of fine-mode dust to the total fine-mode AAOD（sum of fine-mode dust,BC,and organic carbon）in winter,spring,summer,and autumn was 3.4%,25.2%,12.5%,and 14.9%,respectively,with an annual mean value of 15.1%.The results indicate the importance of removing fine dust AAOD when the AERONET fine-mode AAOD is used for calculating the radiative forcing of BC in eastern China.
文摘Averaged fractional composition of aerosol in Vietnam and Belarus was obtained and the maps of the column on near-ground aerosol content were built on the basics of model calculations. The results show the complexity of the geographic ASEAN areas. It may cause variable of climate in local.
