新一代全球集合预报(global ensemble forecast system version 12,GEFSv12)是美国国家环境预报中心(National Centers for Environmental Prediction,NCEP)发布的最新的再预报数据集,对该数据集中的降水数据在淮河流域的适用性进行评...新一代全球集合预报(global ensemble forecast system version 12,GEFSv12)是美国国家环境预报中心(National Centers for Environmental Prediction,NCEP)发布的最新的再预报数据集,对该数据集中的降水数据在淮河流域的适用性进行评估。由于原始预报存在系统偏差,所以应用贝叶斯联合概率模型(Bayesian joint probability,BJP),对原始GEFSv12再预报数据进行统计后处理。预报验证的评价指标包括均方根误差(E)、Brier技巧评分(E)、连续等级概率技巧评分(E)、α指数及可靠性框图,注重从预报偏差、精度以及可靠性3方面评价原始预报及经过后处理的预报。结果表明:GEFSv12降水再预报数据对淮河流域具有较好的适用性,在预见期1~7 d具有预报技能;BJP统计后处理方法能有效降低预报系统性偏差,增加预报精度以及预报可靠性,经过后处理的降水集合预报将有利于进一步的水文集合预报应用。展开更多
基于山东省2021年3月—2022年2月1519个气象观测站2 m气温观测数据,对中国气象局高分辨率陆面数据同化系统(High Resolution China Meteorological Administration Land Data Assimilation System,HRCLDAS)和欧洲中期天气预报中心第五...基于山东省2021年3月—2022年2月1519个气象观测站2 m气温观测数据,对中国气象局高分辨率陆面数据同化系统(High Resolution China Meteorological Administration Land Data Assimilation System,HRCLDAS)和欧洲中期天气预报中心第五代陆面再分析数据集(ERA5-Land)逐小时2 m气温分析的日统计数据(平均气温、最高气温、最低气温)进行对比评估。结果显示:(1)HRCLDAS/ERA5-Land日统计平均气温、最高气温、最低气温的均方根误差分别为0.1/1.2℃、0.6/1.9℃、0.4/1.7℃,表明HRCLDAS具有更高的精度,且在不同地理区域、不同海拔高度的表现均优于ERA5-Land,大部地区的偏差(-0.5~0.5℃)远低于ERA5-Land(-2.0~2.0℃)。(2)两套数据对高温及寒潮过程的监测能力对比评估表明,HRCLDAS能够捕捉到大部分的高温以及寒潮过程,其与观测的高温日数及寒潮日数空间分布较为相似,但对影响范围存在一定的低估;ERA5-Land则只能监测到部分高温及寒潮过程,并对高温日数与寒潮日数存在严重的低估。展开更多
The characteristics of spring precipitation and water vapor transport in South China were analyzed by using observational data and the National Centers for Environmental Prediction (NCEP) reanalysis data. The results ...The characteristics of spring precipitation and water vapor transport in South China were analyzed by using observational data and the National Centers for Environmental Prediction (NCEP) reanalysis data. The results show that, during the spring, each component of the water cycle (precipitation, wind field, specific humidity, water vapor transport, etc.) in South China exhibits a notable interdecadal variability. An abrupt increase in spring precipitation occurred in the early 1970s. During the dry period from 1958 to 1971, a water vapor flux divergence (positive divQ) existed in South China, which may have led to the deficiency in rainfall. However, during the wet period from 1973 to 1989, there was a remarkable water vapor flux convergence (negative divQ) in South China, which may have resulted in the higher rainfall. The interdecadal variability of water vapor transport is closely related to the interdecadal variability of wind fields, although the interdecadal variability of specific humidity also plays a role to some extent, and the interdecadal variability of the zonal water vapor transport contributes much more to the interdecadal variability of spring precipitation than the meridional water vapor transport.展开更多
The global high-resolution marine reanalysis products that were independently developed by the National Marine Environmental Forecasting Center based on the Chinese Global Oceanography Forecasting System(CGOFS),are ev...The global high-resolution marine reanalysis products that were independently developed by the National Marine Environmental Forecasting Center based on the Chinese Global Oceanography Forecasting System(CGOFS),are evaluated by comparing their climatologies with internationally recognized data from WOA(Word Ocean Atlas),SODA(Simple Ocean Data Assimilation),AVISO(Archiving,Validation,and Interpretation of Satellite Oceanographic Data),and C-GLORS(Global Ocean Reanalysis System).The results show that the SST RMSEs of CGOFS and SODA against WOA are 0.51℃ and 0.43℃ respectively;and in the North Pacific,the SST of CGOGS is closer to that of WOA than SODA.The SSS RMSEs of CGOFS and SODA compared with WOA are 0.48 PSU and 0.40 PSU,respectively.CGOFS can reproduce the main large-scale ocean circulation globally,and obtain a similar vertical structure of the Equatorial Undercurrent as SODA.The RMSE of the CGOFS global sea-level anomaly against AVISO is 0.018 m.The monthly averaged sea-ice extents are between those of SODA and C-GLORS in each month;the growth and ablation characteristics of the ice volume are consistent with SODA and C-GLORS;but the ice volume of CGOFS is greater than that of SODA and C-GLORS.In general,the climatology of the CGOFS global high-resolution reanalysis products are basically consistent with similar international products,and can thus provide reliable data for the improvement of marine science and technology in China.展开更多
The wave Coriolis-Stokes-Force-modified ocean momentum equations are reviewed in this paper and the wave Stokes transport is pointed out to be part of the ocean circulations. Using the European Centre for Medium-Range...The wave Coriolis-Stokes-Force-modified ocean momentum equations are reviewed in this paper and the wave Stokes transport is pointed out to be part of the ocean circulations. Using the European Centre for Medium-Range Weather Forecasts 40-year reanalysis data(ERA-40 data) and the Simple Ocean Data Assimilation(SODA) version 2.2.4 data, the magnitude of this transport is compared with that of wind-driven Sverdrup transport and a 5-to-10-precent contribution by the wave Stokes transport is found. Both transports are stronger in boreal winter than in summers. The wave effect can be either contribution or cancellation in different seasons. Examination with Kuroshio transport verifies similar seasonal variations. The clarification of the efficient wave boundary condition helps to understand the role of waves in mass transport. It acts as surface wind stress and can be functional down to the bottom of the ageostrophic layer. The pumping velocities resulting from wave-induced stress are zonally distributed and are significant in relatively high latitudes. Further work will focus on the model performance of the wave-stress-changed-boundary and the role of swells in the eastern part of the oceans.展开更多
Previous studies show that temporal irreversibility(TI),as an important indicator of the nonlinearity of time series,is almost uniformly overestimated in the daily air temperature anomaly series over China in NCEP rea...Previous studies show that temporal irreversibility(TI),as an important indicator of the nonlinearity of time series,is almost uniformly overestimated in the daily air temperature anomaly series over China in NCEP reanalysis data,as compared with station observations.Apart from this highly overestimated TI in the NCEP reanalysis,some other important atmospheric metrics,such as predictability and extreme events,might also be overestimated since there are close relations between nonlinearity and predictability/extreme events.In this study,these issues are fully addressed,i.e.,intrinsic predictability,prediction skill,and the number of extreme events.The results show that intrinsic predictability,prediction skill,and the occurrence number of extreme events are also almost uniformly overestimated in the NCEP reanalysis daily minimum and maximum air temperature anomaly series over China.Furthermore,these overestimations of intrinsic predictability,prediction skill,and the number of extreme events are only weakly correlated with the overestimated TI,which indicates that the quality of the NCEP reanalysis should be carefully considered when conclusions on both predictability and extreme events are derived.展开更多
文摘新一代全球集合预报(global ensemble forecast system version 12,GEFSv12)是美国国家环境预报中心(National Centers for Environmental Prediction,NCEP)发布的最新的再预报数据集,对该数据集中的降水数据在淮河流域的适用性进行评估。由于原始预报存在系统偏差,所以应用贝叶斯联合概率模型(Bayesian joint probability,BJP),对原始GEFSv12再预报数据进行统计后处理。预报验证的评价指标包括均方根误差(E)、Brier技巧评分(E)、连续等级概率技巧评分(E)、α指数及可靠性框图,注重从预报偏差、精度以及可靠性3方面评价原始预报及经过后处理的预报。结果表明:GEFSv12降水再预报数据对淮河流域具有较好的适用性,在预见期1~7 d具有预报技能;BJP统计后处理方法能有效降低预报系统性偏差,增加预报精度以及预报可靠性,经过后处理的降水集合预报将有利于进一步的水文集合预报应用。
文摘基于山东省2021年3月—2022年2月1519个气象观测站2 m气温观测数据,对中国气象局高分辨率陆面数据同化系统(High Resolution China Meteorological Administration Land Data Assimilation System,HRCLDAS)和欧洲中期天气预报中心第五代陆面再分析数据集(ERA5-Land)逐小时2 m气温分析的日统计数据(平均气温、最高气温、最低气温)进行对比评估。结果显示:(1)HRCLDAS/ERA5-Land日统计平均气温、最高气温、最低气温的均方根误差分别为0.1/1.2℃、0.6/1.9℃、0.4/1.7℃,表明HRCLDAS具有更高的精度,且在不同地理区域、不同海拔高度的表现均优于ERA5-Land,大部地区的偏差(-0.5~0.5℃)远低于ERA5-Land(-2.0~2.0℃)。(2)两套数据对高温及寒潮过程的监测能力对比评估表明,HRCLDAS能够捕捉到大部分的高温以及寒潮过程,其与观测的高温日数及寒潮日数空间分布较为相似,但对影响范围存在一定的低估;ERA5-Land则只能监测到部分高温及寒潮过程,并对高温日数与寒潮日数存在严重的低估。
基金supported by the National Basic Research Program of China (Grant No. 2009CB421406)the National Key Technologies R&D Program of China (Grant No. 2007BAC03A00)
文摘The characteristics of spring precipitation and water vapor transport in South China were analyzed by using observational data and the National Centers for Environmental Prediction (NCEP) reanalysis data. The results show that, during the spring, each component of the water cycle (precipitation, wind field, specific humidity, water vapor transport, etc.) in South China exhibits a notable interdecadal variability. An abrupt increase in spring precipitation occurred in the early 1970s. During the dry period from 1958 to 1971, a water vapor flux divergence (positive divQ) existed in South China, which may have led to the deficiency in rainfall. However, during the wet period from 1973 to 1989, there was a remarkable water vapor flux convergence (negative divQ) in South China, which may have resulted in the higher rainfall. The interdecadal variability of water vapor transport is closely related to the interdecadal variability of wind fields, although the interdecadal variability of specific humidity also plays a role to some extent, and the interdecadal variability of the zonal water vapor transport contributes much more to the interdecadal variability of spring precipitation than the meridional water vapor transport.
基金supported by the National Key R&D Program of China[grant number 2016YFC1401802 and 2016YFB0201105]。
文摘The global high-resolution marine reanalysis products that were independently developed by the National Marine Environmental Forecasting Center based on the Chinese Global Oceanography Forecasting System(CGOFS),are evaluated by comparing their climatologies with internationally recognized data from WOA(Word Ocean Atlas),SODA(Simple Ocean Data Assimilation),AVISO(Archiving,Validation,and Interpretation of Satellite Oceanographic Data),and C-GLORS(Global Ocean Reanalysis System).The results show that the SST RMSEs of CGOFS and SODA against WOA are 0.51℃ and 0.43℃ respectively;and in the North Pacific,the SST of CGOGS is closer to that of WOA than SODA.The SSS RMSEs of CGOFS and SODA compared with WOA are 0.48 PSU and 0.40 PSU,respectively.CGOFS can reproduce the main large-scale ocean circulation globally,and obtain a similar vertical structure of the Equatorial Undercurrent as SODA.The RMSE of the CGOFS global sea-level anomaly against AVISO is 0.018 m.The monthly averaged sea-ice extents are between those of SODA and C-GLORS in each month;the growth and ablation characteristics of the ice volume are consistent with SODA and C-GLORS;but the ice volume of CGOFS is greater than that of SODA and C-GLORS.In general,the climatology of the CGOFS global high-resolution reanalysis products are basically consistent with similar international products,and can thus provide reliable data for the improvement of marine science and technology in China.
基金funded by the National Science Foundation of China (40976005 and 40930844)
文摘The wave Coriolis-Stokes-Force-modified ocean momentum equations are reviewed in this paper and the wave Stokes transport is pointed out to be part of the ocean circulations. Using the European Centre for Medium-Range Weather Forecasts 40-year reanalysis data(ERA-40 data) and the Simple Ocean Data Assimilation(SODA) version 2.2.4 data, the magnitude of this transport is compared with that of wind-driven Sverdrup transport and a 5-to-10-precent contribution by the wave Stokes transport is found. Both transports are stronger in boreal winter than in summers. The wave effect can be either contribution or cancellation in different seasons. Examination with Kuroshio transport verifies similar seasonal variations. The clarification of the efficient wave boundary condition helps to understand the role of waves in mass transport. It acts as surface wind stress and can be functional down to the bottom of the ageostrophic layer. The pumping velocities resulting from wave-induced stress are zonally distributed and are significant in relatively high latitudes. Further work will focus on the model performance of the wave-stress-changed-boundary and the role of swells in the eastern part of the oceans.
基金funded by the National Natural Science Foundation of China[grant numbers 41475048,41675049,41705041]。
文摘Previous studies show that temporal irreversibility(TI),as an important indicator of the nonlinearity of time series,is almost uniformly overestimated in the daily air temperature anomaly series over China in NCEP reanalysis data,as compared with station observations.Apart from this highly overestimated TI in the NCEP reanalysis,some other important atmospheric metrics,such as predictability and extreme events,might also be overestimated since there are close relations between nonlinearity and predictability/extreme events.In this study,these issues are fully addressed,i.e.,intrinsic predictability,prediction skill,and the number of extreme events.The results show that intrinsic predictability,prediction skill,and the occurrence number of extreme events are also almost uniformly overestimated in the NCEP reanalysis daily minimum and maximum air temperature anomaly series over China.Furthermore,these overestimations of intrinsic predictability,prediction skill,and the number of extreme events are only weakly correlated with the overestimated TI,which indicates that the quality of the NCEP reanalysis should be carefully considered when conclusions on both predictability and extreme events are derived.
