Based on site-observation data,NCEP–NCAR reanalysis data,and Climatic Research Unit gridded data,the rainfall variability over Tanzania during late austral summer(January–March,JFM)was analyzed for the period 1961–...Based on site-observation data,NCEP–NCAR reanalysis data,and Climatic Research Unit gridded data,the rainfall variability over Tanzania during late austral summer(January–March,JFM)was analyzed for the period 1961–2011.Further,the associated atmospheric circulation and SST anomalies(SSTAs)were explored to understand the mechanisms of dry-and wet-year cases based on an interannual time scale.The correlation,Morlet wavelet power spectrum,and composite analysis methods were employed.The results showed that the JFM standardized rainfall anomaly time series exhibited significant time scales of variability at interannual(2–8 years)and quasidecadal(8–12 years).During dry years,anomalous anticyclonic northeasterly flow originating from western tropical Indian and southeast trades from the Indian Ocean to the southeast were associated with subsiding dry air,which resulted in suppression of rainfall as observed.In the typical wet-year cases,meanwhile,anomalous westerlies from the tropical and southeast Atlantic were strengthened over the Congo basin,delivering more precipitation to the region.Significant correlation was exhibited over the western tropical and southeast Indian Ocean,as well as the southeast and tropical Atlantic Ocean.These SSTA patterns favored atmospheric general circulation anomalies that were closely related to JFM rainfall over Tanzania.展开更多
Based on the 1961-1990 observed daily precipitation in the Changjiang-Huaihe River Basin, the NCEP/NCAR reanalysis data, and the HadCM3 model data for IPCC SRES A1B climate projections, the simulation capabilities of ...Based on the 1961-1990 observed daily precipitation in the Changjiang-Huaihe River Basin, the NCEP/NCAR reanalysis data, and the HadCM3 model data for IPCC SRES A1B climate projections, the simulation capabilities of the BP-CCA downscaling approach for extreme precipitation indices of the current climate are assessed by applying canonical correlation analysis (CCA). In addition, future extreme precipitation indices in the middle and late 21st century are projected. The results show that simulation capability of the HadCM3 for regional climate characteristics can be effectively improved by the downscaling approach, with 30%-100% reduction of the relative errors of the climatological mean state of extreme precipitation indices. However, the downscaling results still show wetter winter and dryer summer than the observation. Under the SRES A1B emission scenario, frequency and intensity of extreme precipitation events are projected to increase, and the estimated increasing rate is higher for extreme precipitation indices than for mean precipitation index; and in summer than in winter. Extreme precipitations in the middle and late 21st century are expected to increase by 14% and 25% respectively in winter, and by 24% and 32% respectively in summer.展开更多
基金This study was supported by the Strategic Priority Research Program of the Chinese Academy of Sciences[XDA20060501]the National Natural Science Foundatin of China[91637208].
文摘Based on site-observation data,NCEP–NCAR reanalysis data,and Climatic Research Unit gridded data,the rainfall variability over Tanzania during late austral summer(January–March,JFM)was analyzed for the period 1961–2011.Further,the associated atmospheric circulation and SST anomalies(SSTAs)were explored to understand the mechanisms of dry-and wet-year cases based on an interannual time scale.The correlation,Morlet wavelet power spectrum,and composite analysis methods were employed.The results showed that the JFM standardized rainfall anomaly time series exhibited significant time scales of variability at interannual(2–8 years)and quasidecadal(8–12 years).During dry years,anomalous anticyclonic northeasterly flow originating from western tropical Indian and southeast trades from the Indian Ocean to the southeast were associated with subsiding dry air,which resulted in suppression of rainfall as observed.In the typical wet-year cases,meanwhile,anomalous westerlies from the tropical and southeast Atlantic were strengthened over the Congo basin,delivering more precipitation to the region.Significant correlation was exhibited over the western tropical and southeast Indian Ocean,as well as the southeast and tropical Atlantic Ocean.These SSTA patterns favored atmospheric general circulation anomalies that were closely related to JFM rainfall over Tanzania.
基金supported by the National Natural Science Foundation (No. 40875058)the National Key Basic Research Program (No. 2012CB955200) of Chinafunded by the Priority Academic Program Development (PAPD) of Jiangsu Higher Edusation Institutions
文摘Based on the 1961-1990 observed daily precipitation in the Changjiang-Huaihe River Basin, the NCEP/NCAR reanalysis data, and the HadCM3 model data for IPCC SRES A1B climate projections, the simulation capabilities of the BP-CCA downscaling approach for extreme precipitation indices of the current climate are assessed by applying canonical correlation analysis (CCA). In addition, future extreme precipitation indices in the middle and late 21st century are projected. The results show that simulation capability of the HadCM3 for regional climate characteristics can be effectively improved by the downscaling approach, with 30%-100% reduction of the relative errors of the climatological mean state of extreme precipitation indices. However, the downscaling results still show wetter winter and dryer summer than the observation. Under the SRES A1B emission scenario, frequency and intensity of extreme precipitation events are projected to increase, and the estimated increasing rate is higher for extreme precipitation indices than for mean precipitation index; and in summer than in winter. Extreme precipitations in the middle and late 21st century are expected to increase by 14% and 25% respectively in winter, and by 24% and 32% respectively in summer.
