The distribution of winter-spring snow cover over the Tibetan Plateau （TP） and its relationship with summer precipitation in the middle and lower reaches of Yangtze River Valley （MLYRV） during 2003-2013 have been ...The distribution of winter-spring snow cover over the Tibetan Plateau （TP） and its relationship with summer precipitation in the middle and lower reaches of Yangtze River Valley （MLYRV） during 2003-2013 have been investigated with the moderate-resolution imaging spectrometer （MODIS） Terra data （MOD10A2） and precipitation observations. Results show that snow cover percentage （SCP） remains approximately 20% in winter and spring then tails off to below 5% with warmer temperature and snow melt in summer. The lower and highest percentages present a declining tendency while the middle SCP exhibits an opposite variation. The maximum value appears from the middle of October to March and the minimum emerges from July to August. The annual and winter-spring SCPs present a decreasing tendency. Snow cover is mainly situated in the periphery of the plateau and mountainous regions, and less snow in the interior of the plateau, basin and valley areas in view of snow cover frequency （SCF） over the TP. Whatever annual or winter-spring snow cover, they all have remarkable declining tendency during 2003-2013, and annual snow cover presents a decreasing trend in the interior of the TP and increasing trend in the periphery of the TP. Hie multi-year averaged eight-day SCP is negatively related to mean precipitation in the MLYRV. Spring SCP is negatively related to summer precipitation while winter SCP is positively related to summer precipitation in most parts of the MLYRV. Hence, the influence of winter snow cover on precipitation is much more significant than that in spring on the basis of correlation analysis. The oscillation of SCF from southeast to northwest over the TP corresponds well to the beginning,development and cessation of the rain belt in eastern China.展开更多
This study investigates the spatial-temporal variability of winter-spring (February-March-April) precipitation (WSP) in Pakistan over the period of 1961-2006 by making use of Empirical Orthogonal Function (EOF). The E...This study investigates the spatial-temporal variability of winter-spring (February-March-April) precipitation (WSP) in Pakistan over the period of 1961-2006 by making use of Empirical Orthogonal Function (EOF). The EOF analysis is based on ground observed data, reanalysis NCEP/NCAR of various geopotential heights and NOAA extended reconstructed sea surface temperatures (ERSST.v3). The significant modes are obviously variable at interannual time scale. The leading mode shows the node of maximum spatial variability anchored over the Peshawar Valley and Azad Kashmir (PVAK) axis. The pattern is associated with strong (weak) westerly jet over the Middle East. The pattern is also found closely associated with post monsoon and early winter El Nino. The Nino4 index can be an appropriate predictor for the first consistent single node pattern. The second significant mode represents a tripole pattern with areas of prominent variability over northwestern Pakistan, Quetta-Kalat region and northeastern Punjab. The pattern is found to be pro-NAO and in relation to this pattern, warm and stable SST anomalies appearing in the southern mid-latitudes of Indian and Atlantic basins.展开更多
The nature and dynamics of climate change in central Asia since the late Pleistocene are controversial. Moreover,most of the published studies focus mainly on the evolution of moisture conditions, and there have been ...The nature and dynamics of climate change in central Asia since the late Pleistocene are controversial. Moreover,most of the published studies focus mainly on the evolution of moisture conditions, and there have been few attempts to address changes in seasonality. In this study, records of δ^(13)C_(org), TOC, TN, C/N and grain size were obtained from lacustrine sediments at Yili Basin, Xinjiang, NW China. Our aim was to reconstruct the trend in seasonality of precipitation from the last glaciation to the Holocene. The organic matter content of the sediments is derived predominantly from terrestrial plants. The δ^(13)C_(org)values vary from-19.4‰ to-24.8‰, indicating that the vegetation was dominated by C_3 plants. Winter-spring precipitation is identified as the factor determining the relative proportions of C_3 and C_4 plants in the region. A negative trend in δ^(13)C_(org)corresponding to an increase in the relative abundance of C_3 plants indicate a trend of increasing winter-spring precipitation from the last glaciation to the Holocene. The increased incidence of wintertime storms in the interior of Asia is suggested to result in the increase of winterspring precipitation in the Holocene.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.41130960)the Project of the China Meteorological Administration(Grant Nos.CCSF201515 and CMAGJ2013M51)
文摘The distribution of winter-spring snow cover over the Tibetan Plateau （TP） and its relationship with summer precipitation in the middle and lower reaches of Yangtze River Valley （MLYRV） during 2003-2013 have been investigated with the moderate-resolution imaging spectrometer （MODIS） Terra data （MOD10A2） and precipitation observations. Results show that snow cover percentage （SCP） remains approximately 20% in winter and spring then tails off to below 5% with warmer temperature and snow melt in summer. The lower and highest percentages present a declining tendency while the middle SCP exhibits an opposite variation. The maximum value appears from the middle of October to March and the minimum emerges from July to August. The annual and winter-spring SCPs present a decreasing tendency. Snow cover is mainly situated in the periphery of the plateau and mountainous regions, and less snow in the interior of the plateau, basin and valley areas in view of snow cover frequency （SCF） over the TP. Whatever annual or winter-spring snow cover, they all have remarkable declining tendency during 2003-2013, and annual snow cover presents a decreasing trend in the interior of the TP and increasing trend in the periphery of the TP. Hie multi-year averaged eight-day SCP is negatively related to mean precipitation in the MLYRV. Spring SCP is negatively related to summer precipitation while winter SCP is positively related to summer precipitation in most parts of the MLYRV. Hence, the influence of winter snow cover on precipitation is much more significant than that in spring on the basis of correlation analysis. The oscillation of SCF from southeast to northwest over the TP corresponds well to the beginning,development and cessation of the rain belt in eastern China.
文摘This study investigates the spatial-temporal variability of winter-spring (February-March-April) precipitation (WSP) in Pakistan over the period of 1961-2006 by making use of Empirical Orthogonal Function (EOF). The EOF analysis is based on ground observed data, reanalysis NCEP/NCAR of various geopotential heights and NOAA extended reconstructed sea surface temperatures (ERSST.v3). The significant modes are obviously variable at interannual time scale. The leading mode shows the node of maximum spatial variability anchored over the Peshawar Valley and Azad Kashmir (PVAK) axis. The pattern is associated with strong (weak) westerly jet over the Middle East. The pattern is also found closely associated with post monsoon and early winter El Nino. The Nino4 index can be an appropriate predictor for the first consistent single node pattern. The second significant mode represents a tripole pattern with areas of prominent variability over northwestern Pakistan, Quetta-Kalat region and northeastern Punjab. The pattern is found to be pro-NAO and in relation to this pattern, warm and stable SST anomalies appearing in the southern mid-latitudes of Indian and Atlantic basins.
基金supported by the Strategic Priority Research Program of Chinese Academy of Sciences (Grant No. XDB26000000)the National Natural Science Foundation of China (Grant Nos. 41772371, 41572161 & 41730319)+2 种基金the National Basic Research Program of China (Grant No. 2015CB953803)the Youth Innovation Promotion Association CASthe Australian Nuclear Science and Technology Organization
文摘The nature and dynamics of climate change in central Asia since the late Pleistocene are controversial. Moreover,most of the published studies focus mainly on the evolution of moisture conditions, and there have been few attempts to address changes in seasonality. In this study, records of δ^(13)C_(org), TOC, TN, C/N and grain size were obtained from lacustrine sediments at Yili Basin, Xinjiang, NW China. Our aim was to reconstruct the trend in seasonality of precipitation from the last glaciation to the Holocene. The organic matter content of the sediments is derived predominantly from terrestrial plants. The δ^(13)C_(org)values vary from-19.4‰ to-24.8‰, indicating that the vegetation was dominated by C_3 plants. Winter-spring precipitation is identified as the factor determining the relative proportions of C_3 and C_4 plants in the region. A negative trend in δ^(13)C_(org)corresponding to an increase in the relative abundance of C_3 plants indicate a trend of increasing winter-spring precipitation from the last glaciation to the Holocene. The increased incidence of wintertime storms in the interior of Asia is suggested to result in the increase of winterspring precipitation in the Holocene.
