Climate research relies heavily on good quality instrumental data; for modeling efforts gridded data are needed. So far, relatively little effort has been made to create gridded climate data for China. This is especia...Climate research relies heavily on good quality instrumental data; for modeling efforts gridded data are needed. So far, relatively little effort has been made to create gridded climate data for China. This is especially true for high-resolution daily data. This work, focuses on identifying an accurate method to produce gridded daily precipitation in China based on the observed data at 753 stations for the period 1951-2005. Five interpolation methods, including ordinary nearest neighbor, local polynomial, radial basis function, inverse distance weighting, and ordinary kriging, have been used and compared. Cross-validation shows that the ordinary kriging based on seasonal semi-variograms gives the best performance, closely followed by the inverse distance weighting with a power of 2. Finally the ordinary kriging is chosen to interpolate the station data to a 18 km× 18 km grid system covering the whole country. Precipitation for each 0.5°×0.5° latitude-longitude block is then obtained by averaging the values at the grid nodes within the block. Owing to the higher station density in the eastern part of the country, the interpolation errors are much smaller than those in the west （west of 100°E）. Excluding 145 stations in the western region, the daily, monthly, and annual relative mean absolute errors of the interpolation for the remaining 608 stations are 74%, 29%, and 16%, respectively. The interpolated daily precipitation has been made available on the internet for the scientific community.展开更多
The China Meteorological Administration(CMA)recently produced a CMA Global Atmospheric Interim Reanalysis(CRAI)dataset for the years 2007–2016.A comprehensive evaluation of the ability of CRAI to capture the spatiote...The China Meteorological Administration(CMA)recently produced a CMA Global Atmospheric Interim Reanalysis(CRAI)dataset for the years 2007–2016.A comprehensive evaluation of the ability of CRAI to capture the spatiotemporal variability of observed precipitation,in terms of both mean states and extreme indicators over China,is performed.Comparisons are made with other current reanalysis datasets,namely,the ECMWF interim reanalysis(ERAI),Japanese 55-yr reanalysis(JRA55),NCEP Climate Forecast System Reanalysis(CFSR),and NASA Modern-Era Retrospective analysis for Research and Applications version 2(MERRA2),as well as NCEP Climate Prediction Center(CPC)observations.The results show that,for daily variations of rainfall during warm seasons in eastern China,CRAI and CFSR overestimate the precipitation of the main rain belt,while the overestimation is confined to the area south of 25°N in JRA55 but north of 24°N in MERRA2;whereas ERAI tends to underestimate the precipitation in most regions of eastern China.Two extreme metrics,the total amount of precipitation on days where daily precipitation exceeds the 95 th percentile(R95 pTOT)and the number of consecutive dry days(CDDs)in one month,are examined to assess the performance of reanalysis datasets.In terms of extreme events,CRAI,ERAI,and JRA55 tend to underestimate the R95 pTOT in most of eastern China,whereas more frequent extreme rainfall can be found in most regions of China in both CFSR and MERRA2;and all of the reanalyses underestimate the CDDs.Among the reanalysis products,CRAI and JRA55 show better agreement with the observed R95 pTOT than the other datasets,with fewer biases,higher correlation coefficients,and much more similar linear trend patterns,while ERAI stands out in better capturing the amount and temporal variations of the observed CDDs.展开更多
It has been theoretically proven that at a high threshold an approximate expression for a quantile of GEV （Generalized Extreme Values） distribution can be derived from GPD （Generalized Pareto Distribution）. Afterw...It has been theoretically proven that at a high threshold an approximate expression for a quantile of GEV （Generalized Extreme Values） distribution can be derived from GPD （Generalized Pareto Distribution）. Afterwards, a quantile of extreme rainfall events in a certain return period is found using L-moment estimation and extreme rainfall events simulated by GPD and GEV, with all aspects of their results compared. Numerical simulations show that POT （Peaks Over Threshold）-based GPD is advantageous in its simple operation and subjected to practically no effect of the sample size of the primitive series, producing steady high-precision fittings in the whole field of values （including the high-end heavy tailed）. In comparison, BM （Block Maximum）-based GEV is limited, to some extent, to the probability and quantile simulation, thereby showing that GPD is an extension of GEV, the former being of greater utility and higher significance to climate research compared to the latter.展开更多
根据中国国家级地面气象站均一化降水数据集,使用1956~2015年512个台站的日降水量资料,通过旋转经验正交函数(REOF)得到七个分区。比较了各分区平均日降水量的年内变化和多年倾向率差异:我国偏南分区的小雨日数减少,大雨、暴雨日数、日...根据中国国家级地面气象站均一化降水数据集,使用1956~2015年512个台站的日降水量资料,通过旋转经验正交函数(REOF)得到七个分区。比较了各分区平均日降水量的年内变化和多年倾向率差异:我国偏南分区的小雨日数减少,大雨、暴雨日数、日降水量的区域年均值增加;偏北分区的小雨、大雨、暴雨日数、降水量年均值为递减;长江中下游区(东北区)日降水量、小雨日数、暴雨日数的年均值的近60年倾向率分别是0.0071 mm a^(-1)(-0.0010 mm a^(-1))、-0.0729 d a^(-1)(-0.0615 d a^(-1))、0.0132 d a^(-1)(-0.0007 d a^(-1))。100°E以西地区:小雨、中雨日数在增加,无雨日数显著减少,日降水量的年均值呈递增特点。通过自相关函数和小波功率谱估计,揭示了七个分区的日降水量年均值普遍存在2~4 a周期震荡。使用NCEP/NCAR月均再分析资料,以区域日降水量年均值为指数得到500 h Pa、700 h Pa、850 h Pa回归风系数场、旱涝年整场水汽通量和水汽通量散度差异场相结合分析,结果表明:"东高西低,南高北低"环流型和区域降水有密切关系,水汽差异场是上述环流特点的反映。展开更多
Daily precipitation amounts and frequencies from the CMORPH （Climate Prediction Center Morphing Technique） and TRMM （Tropical Rainfall Measuring Mission） 3B42 precipitation products are validated against warm seas...Daily precipitation amounts and frequencies from the CMORPH （Climate Prediction Center Morphing Technique） and TRMM （Tropical Rainfall Measuring Mission） 3B42 precipitation products are validated against warm season in-situ precipitation observations from 2003 to 2008 over the Tibetan Plateau and the regions to its east. The results indicate that these two satellite datasets can better detect daily precipitation frequency than daily precipitation amount. The ability of CMORPH and TRMM 3B42 to accurately detect daily precipitation amount is dependent on the underlying terrain. Both datasets are more reliable over the relatively flat terrain of the northeastern Tibetan Plateau, the Sichuan basin, and the mid-lower reaches of the Yangtze River than over the complex terrain of the Tibetan Plateau. Both satellite products are able to detect the occurrence of daily rainfall events; however, their performance is worse in regions of complex topography, such as the Tibetan Plateau. Regional distributions of precipitation amount by precipitation intensity based on TRMM 3B42 are close to those based on rain gauge data. By contrast, similar distributions based on CMORPH differ substantially. CMORPH overestimates the amount of rain associated with the most intense precipitation events over the mid-lower reaches of the Yangtze River while underestimating the amount of rain associated with lighter precipitation events. CMORPH underestimates the amount of intense precipitation and overestimates the amount of lighter precipitation over the other analyzed regions. TRMM 3B42 underestimates the frequency of light precipitation over the Sichuan basin and the mid-lower reaches of the Yangtze River. CMORPH overestimates the frequencies of weak and intense precipitation over the mid-lower reaches of the Yangtze River, and underestimates the frequencies of moderate and heavy precipitation. CMORPH also overestimates the frequency of light precipitation and underestimates the frequency of intense precipitation over the other three 展开更多
The precipitation regime of the low latitude highlands of Yunnan in Southwest China is subject to the interactions between the East Asian Summer Monsoon and the Indian Summer Monsoon, and the influence of surface orog...The precipitation regime of the low latitude highlands of Yunnan in Southwest China is subject to the interactions between the East Asian Summer Monsoon and the Indian Summer Monsoon, and the influence of surface orography. An understanding of changes in its spatial and temporal patterns is urgently needed for climate change projection, hydrologi- cal impact modelling, and regional and downstream water resources management. Using daily precipitation records of the low latitude highlands over the last several decades （1950s-2007）, a time series of precipitation indices, including annual precipitation, number of rainy days, mean annual precipitation intensity, the dates of the onset of the rainy season, degree and period of precipitation seasonal concentration, the highest 1-day, 3-day and 7-day precipitation, and precipitation amount and number of rainy days for precipitation above dif- ferent intensities （such as 〉~10 mm, 〉~25 mm and 〉~50 mm of daily precipitation）, was con- structed. The Trend-Free Pre-Whitening Mann-Kendall trend test was then used to detect trends of the time series data. The results show that there is no significant trend in annual precipitation and strong seasonal differentiation of precipitation trends across the low latitude highlands. Springs and winters are getting wetter and summers are getting drier. Autumns are getting drier in the east and wetter in the west. As a consequence, the seasonality of pre- cipitation is weakening slightly. The beginning of the rainy season and the period of the highest precipitation tend to be earlier. In the meantime, the low latitude highlands has also witnessed less rainy days, more intense precipitation, slightly longer moderate and heavy precipitation events, and more frequent extreme precipitation events. Additionally, regional differentiation of precipitation trends is remarkable. These variations may be associated with weakening of the East Asian summer monsoon and strengthening of the South Asian summer monsoon, as well as the ＂cor展开更多
利用探空资料、地基GPS/MET水汽监测资料,对恩施、宜昌、武汉三站地基GPS反演大气可降水量(GPS Precipitable Water Vapor,GPS/PWV)与探空进行了对比,表明GPS/PWV与探空RS/PWV具有良好的一致性。湖北省17站3 a GPS/PWV资料分析表明,GPS/...利用探空资料、地基GPS/MET水汽监测资料,对恩施、宜昌、武汉三站地基GPS反演大气可降水量(GPS Precipitable Water Vapor,GPS/PWV)与探空进行了对比,表明GPS/PWV与探空RS/PWV具有良好的一致性。湖北省17站3 a GPS/PWV资料分析表明,GPS/PWV具有明显的月变化及日变化特征,分布具有从南往北逐渐递减,从西至东逐渐增加的特点。强降水个例分析表明GPS/PWV峰值略早于降水以及雷达回波峰值出现时间,高时空分辨率的GPS/PWV配合雷达对天气形势的分析以及降水的判断有一定的指导作用。展开更多
基金supported by the Swedish Foundation for International Cooperation in Research and High Education through a grant to D.L.Chen.C.-H.Ho is supported by CATER 2006-4204
文摘Climate research relies heavily on good quality instrumental data; for modeling efforts gridded data are needed. So far, relatively little effort has been made to create gridded climate data for China. This is especially true for high-resolution daily data. This work, focuses on identifying an accurate method to produce gridded daily precipitation in China based on the observed data at 753 stations for the period 1951-2005. Five interpolation methods, including ordinary nearest neighbor, local polynomial, radial basis function, inverse distance weighting, and ordinary kriging, have been used and compared. Cross-validation shows that the ordinary kriging based on seasonal semi-variograms gives the best performance, closely followed by the inverse distance weighting with a power of 2. Finally the ordinary kriging is chosen to interpolate the station data to a 18 km× 18 km grid system covering the whole country. Precipitation for each 0.5°×0.5° latitude-longitude block is then obtained by averaging the values at the grid nodes within the block. Owing to the higher station density in the eastern part of the country, the interpolation errors are much smaller than those in the west （west of 100°E）. Excluding 145 stations in the western region, the daily, monthly, and annual relative mean absolute errors of the interpolation for the remaining 608 stations are 74%, 29%, and 16%, respectively. The interpolated daily precipitation has been made available on the internet for the scientific community.
基金Supported by the China Meteorological Administration Special Public Welfare Research Fund(GYHY201506002)National Natural Science Foundation of China(41790475,41675094,and 41605066).
文摘The China Meteorological Administration(CMA)recently produced a CMA Global Atmospheric Interim Reanalysis(CRAI)dataset for the years 2007–2016.A comprehensive evaluation of the ability of CRAI to capture the spatiotemporal variability of observed precipitation,in terms of both mean states and extreme indicators over China,is performed.Comparisons are made with other current reanalysis datasets,namely,the ECMWF interim reanalysis(ERAI),Japanese 55-yr reanalysis(JRA55),NCEP Climate Forecast System Reanalysis(CFSR),and NASA Modern-Era Retrospective analysis for Research and Applications version 2(MERRA2),as well as NCEP Climate Prediction Center(CPC)observations.The results show that,for daily variations of rainfall during warm seasons in eastern China,CRAI and CFSR overestimate the precipitation of the main rain belt,while the overestimation is confined to the area south of 25°N in JRA55 but north of 24°N in MERRA2;whereas ERAI tends to underestimate the precipitation in most regions of eastern China.Two extreme metrics,the total amount of precipitation on days where daily precipitation exceeds the 95 th percentile(R95 pTOT)and the number of consecutive dry days(CDDs)in one month,are examined to assess the performance of reanalysis datasets.In terms of extreme events,CRAI,ERAI,and JRA55 tend to underestimate the R95 pTOT in most of eastern China,whereas more frequent extreme rainfall can be found in most regions of China in both CFSR and MERRA2;and all of the reanalyses underestimate the CDDs.Among the reanalysis products,CRAI and JRA55 show better agreement with the observed R95 pTOT than the other datasets,with fewer biases,higher correlation coefficients,and much more similar linear trend patterns,while ERAI stands out in better capturing the amount and temporal variations of the observed CDDs.
基金supported jointly Science Foundation of China （Grant No. 40675043） Program of the Jiangsu Key Laboratory of Meteorological Disaster （Grant No. KLME050209）.
文摘It has been theoretically proven that at a high threshold an approximate expression for a quantile of GEV （Generalized Extreme Values） distribution can be derived from GPD （Generalized Pareto Distribution）. Afterwards, a quantile of extreme rainfall events in a certain return period is found using L-moment estimation and extreme rainfall events simulated by GPD and GEV, with all aspects of their results compared. Numerical simulations show that POT （Peaks Over Threshold）-based GPD is advantageous in its simple operation and subjected to practically no effect of the sample size of the primitive series, producing steady high-precision fittings in the whole field of values （including the high-end heavy tailed）. In comparison, BM （Block Maximum）-based GEV is limited, to some extent, to the probability and quantile simulation, thereby showing that GPD is an extension of GEV, the former being of greater utility and higher significance to climate research compared to the latter.
文摘根据中国国家级地面气象站均一化降水数据集,使用1956~2015年512个台站的日降水量资料,通过旋转经验正交函数(REOF)得到七个分区。比较了各分区平均日降水量的年内变化和多年倾向率差异:我国偏南分区的小雨日数减少,大雨、暴雨日数、日降水量的区域年均值增加;偏北分区的小雨、大雨、暴雨日数、降水量年均值为递减;长江中下游区(东北区)日降水量、小雨日数、暴雨日数的年均值的近60年倾向率分别是0.0071 mm a^(-1)(-0.0010 mm a^(-1))、-0.0729 d a^(-1)(-0.0615 d a^(-1))、0.0132 d a^(-1)(-0.0007 d a^(-1))。100°E以西地区:小雨、中雨日数在增加,无雨日数显著减少,日降水量的年均值呈递增特点。通过自相关函数和小波功率谱估计,揭示了七个分区的日降水量年均值普遍存在2~4 a周期震荡。使用NCEP/NCAR月均再分析资料,以区域日降水量年均值为指数得到500 h Pa、700 h Pa、850 h Pa回归风系数场、旱涝年整场水汽通量和水汽通量散度差异场相结合分析,结果表明:"东高西低,南高北低"环流型和区域降水有密切关系,水汽差异场是上述环流特点的反映。
基金Supported by the National Natural Science Foundation of China (41175080)National Basic Research and Development (973) Program of China (2012CB417205)Meteorological Key Technology Integration and Application Program (CMAGJ2011Z08)
文摘Daily precipitation amounts and frequencies from the CMORPH （Climate Prediction Center Morphing Technique） and TRMM （Tropical Rainfall Measuring Mission） 3B42 precipitation products are validated against warm season in-situ precipitation observations from 2003 to 2008 over the Tibetan Plateau and the regions to its east. The results indicate that these two satellite datasets can better detect daily precipitation frequency than daily precipitation amount. The ability of CMORPH and TRMM 3B42 to accurately detect daily precipitation amount is dependent on the underlying terrain. Both datasets are more reliable over the relatively flat terrain of the northeastern Tibetan Plateau, the Sichuan basin, and the mid-lower reaches of the Yangtze River than over the complex terrain of the Tibetan Plateau. Both satellite products are able to detect the occurrence of daily rainfall events; however, their performance is worse in regions of complex topography, such as the Tibetan Plateau. Regional distributions of precipitation amount by precipitation intensity based on TRMM 3B42 are close to those based on rain gauge data. By contrast, similar distributions based on CMORPH differ substantially. CMORPH overestimates the amount of rain associated with the most intense precipitation events over the mid-lower reaches of the Yangtze River while underestimating the amount of rain associated with lighter precipitation events. CMORPH underestimates the amount of intense precipitation and overestimates the amount of lighter precipitation over the other analyzed regions. TRMM 3B42 underestimates the frequency of light precipitation over the Sichuan basin and the mid-lower reaches of the Yangtze River. CMORPH overestimates the frequencies of weak and intense precipitation over the mid-lower reaches of the Yangtze River, and underestimates the frequencies of moderate and heavy precipitation. CMORPH also overestimates the frequency of light precipitation and underestimates the frequency of intense precipitation over the other three
基金National Natural Science Foundation of China, No.41061010 National Science and Technology Support Program, No.2013BAB06B03 No.2011BAC09B07
文摘The precipitation regime of the low latitude highlands of Yunnan in Southwest China is subject to the interactions between the East Asian Summer Monsoon and the Indian Summer Monsoon, and the influence of surface orography. An understanding of changes in its spatial and temporal patterns is urgently needed for climate change projection, hydrologi- cal impact modelling, and regional and downstream water resources management. Using daily precipitation records of the low latitude highlands over the last several decades （1950s-2007）, a time series of precipitation indices, including annual precipitation, number of rainy days, mean annual precipitation intensity, the dates of the onset of the rainy season, degree and period of precipitation seasonal concentration, the highest 1-day, 3-day and 7-day precipitation, and precipitation amount and number of rainy days for precipitation above dif- ferent intensities （such as 〉~10 mm, 〉~25 mm and 〉~50 mm of daily precipitation）, was con- structed. The Trend-Free Pre-Whitening Mann-Kendall trend test was then used to detect trends of the time series data. The results show that there is no significant trend in annual precipitation and strong seasonal differentiation of precipitation trends across the low latitude highlands. Springs and winters are getting wetter and summers are getting drier. Autumns are getting drier in the east and wetter in the west. As a consequence, the seasonality of pre- cipitation is weakening slightly. The beginning of the rainy season and the period of the highest precipitation tend to be earlier. In the meantime, the low latitude highlands has also witnessed less rainy days, more intense precipitation, slightly longer moderate and heavy precipitation events, and more frequent extreme precipitation events. Additionally, regional differentiation of precipitation trends is remarkable. These variations may be associated with weakening of the East Asian summer monsoon and strengthening of the South Asian summer monsoon, as well as the ＂cor
文摘利用探空资料、地基GPS/MET水汽监测资料,对恩施、宜昌、武汉三站地基GPS反演大气可降水量(GPS Precipitable Water Vapor,GPS/PWV)与探空进行了对比,表明GPS/PWV与探空RS/PWV具有良好的一致性。湖北省17站3 a GPS/PWV资料分析表明,GPS/PWV具有明显的月变化及日变化特征,分布具有从南往北逐渐递减,从西至东逐渐增加的特点。强降水个例分析表明GPS/PWV峰值略早于降水以及雷达回波峰值出现时间,高时空分辨率的GPS/PWV配合雷达对天气形势的分析以及降水的判断有一定的指导作用。
