Distribution of winter-spring snow over the Tibetan Plateau and its relationship with summer precipitation in Yangtze River

摘要

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.The 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.