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
The fate of urea-and ammonium bicarbonate (ABC)-nitrogen (N) applied by prevailing traditional techniques to winter wheat (Triticum aestivum L.) or maize (Zea mays L.) grown in the fields of Fluvo-aquic soil was inves...The fate of urea-and ammonium bicarbonate (ABC)-nitrogen (N) applied by prevailing traditional techniques to winter wheat (Triticum aestivum L.) or maize (Zea mays L.) grown in the fields of Fluvo-aquic soil was investigated using 15N tracer-micro-plot technique. Results show that:(1) at maturity of wheat, N recovery in plants and N losses of urea and ABC applied at seeding in autumn were 31-39%, and 34-46%, respectively, while the corresponding figures for side-banding at 10 cm depth in early spring were 51-57%, and 5-12%; surface-broadcast of urea followed by irrigation at early spring was as efficient as the side-banding in improving N recovery in plants and reducing N loss, however, such technique was found less satisfactory with ABC. (2) At the maturity of maize, N recovery in the plants and N loss of urea and ABC sidebanded at seedling stage or prior to tasseling ranged from 23% to 57%, and 9% to 26%, respectively. (3) Either in Wheat or in maize experiment, the majority of residual fertilizer N in soil profile (0-60 cm) was in the form of biologically immobilized organic N, however, the contribution of ammonium fixation by clay minerals increased markedly with depth in soil profile. (4) Though the proportion of residual fertilizer N was generally highest in the top 20 cm soil layer, considerable reaidual N (mostly 6-11 % of the N applied) was found in 60-100 cm soil layers.展开更多
Here we present the results from the composite analyses of the atmospheric circulations and physical quantity fields associated with rainy-season for the selected floods cases over the Yangtze and Huaihe River basins ...Here we present the results from the composite analyses of the atmospheric circulations and physical quantity fields associated with rainy-season for the selected floods cases over the Yangtze and Huaihe River basins for the 21 years(1990–2010),using the daily rain gauge measurements taken in the 756 stations throughout China and the NCEP/reanalysis data for the rainyseasons(June–July)from 1990 to 2010.The major differences in the atmospheric circulations and physical quantity fields between the Yangtze and Huaihe River basins are as follows:for flooding years of the Yangtze River Basin,the South Asia high center is located further east than normal,the blocking high over the Urals and the Sea of Okhotsk maintains,and the Meiyu front is situated near 30°N whereas for flooding years of the Huaihe River Basin,the South Asia high center is further west than normal,the atmospheric circulations over the mid and high latitudes in the Northern Hemisphere are of meridional distribution,and the Meiyu front is situated near 33°N.In addition,there are distinct differences in water vapor sources and associated transports between the Yangtze and Huaihe River basins.The water vapor is transported by southwesterly flows from the Bay of Bengal and monsoon flows over the South China Sea for flooding years of the Yangtze River Basin whereas by southeast monsoons from the eastern and southern seas off China and monsoon flows over the South China Sea for flooding years of the Huaihe River Basin.展开更多
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.
文摘The fate of urea-and ammonium bicarbonate (ABC)-nitrogen (N) applied by prevailing traditional techniques to winter wheat (Triticum aestivum L.) or maize (Zea mays L.) grown in the fields of Fluvo-aquic soil was investigated using 15N tracer-micro-plot technique. Results show that:(1) at maturity of wheat, N recovery in plants and N losses of urea and ABC applied at seeding in autumn were 31-39%, and 34-46%, respectively, while the corresponding figures for side-banding at 10 cm depth in early spring were 51-57%, and 5-12%; surface-broadcast of urea followed by irrigation at early spring was as efficient as the side-banding in improving N recovery in plants and reducing N loss, however, such technique was found less satisfactory with ABC. (2) At the maturity of maize, N recovery in the plants and N loss of urea and ABC sidebanded at seedling stage or prior to tasseling ranged from 23% to 57%, and 9% to 26%, respectively. (3) Either in Wheat or in maize experiment, the majority of residual fertilizer N in soil profile (0-60 cm) was in the form of biologically immobilized organic N, however, the contribution of ammonium fixation by clay minerals increased markedly with depth in soil profile. (4) Though the proportion of residual fertilizer N was generally highest in the top 20 cm soil layer, considerable reaidual N (mostly 6-11 % of the N applied) was found in 60-100 cm soil layers.
基金supported by the National Basic Research Program of China (Grant No. 2013CB430105)the National Natural Science Foundation of China (Grant Nos. 40775038, 40875031 & 40975036)the Foreign Professors Projects of Chinese Academy of Sciences (Grant No. 2010-c-6)
文摘Here we present the results from the composite analyses of the atmospheric circulations and physical quantity fields associated with rainy-season for the selected floods cases over the Yangtze and Huaihe River basins for the 21 years(1990–2010),using the daily rain gauge measurements taken in the 756 stations throughout China and the NCEP/reanalysis data for the rainyseasons(June–July)from 1990 to 2010.The major differences in the atmospheric circulations and physical quantity fields between the Yangtze and Huaihe River basins are as follows:for flooding years of the Yangtze River Basin,the South Asia high center is located further east than normal,the blocking high over the Urals and the Sea of Okhotsk maintains,and the Meiyu front is situated near 30°N whereas for flooding years of the Huaihe River Basin,the South Asia high center is further west than normal,the atmospheric circulations over the mid and high latitudes in the Northern Hemisphere are of meridional distribution,and the Meiyu front is situated near 33°N.In addition,there are distinct differences in water vapor sources and associated transports between the Yangtze and Huaihe River basins.The water vapor is transported by southwesterly flows from the Bay of Bengal and monsoon flows over the South China Sea for flooding years of the Yangtze River Basin whereas by southeast monsoons from the eastern and southern seas off China and monsoon flows over the South China Sea for flooding years of the Huaihe River Basin.
