Study Of Drought Monitoring And Evaluating Technique For Qinghai-Tibet Plateau Grassland

The drought is main meteorological disaster affecting on grassland ecology and animal husbandryproduction. The grassland drought and its influence are expected to understand by goverment to makepolicy for preventing and lightening disaster and protecting ecology. However, technique aboutgrassland drought monitoring and evaluating is shortage in meteorological service for agriculture,especially for Qinghai-Tibet Plateau and nationwide grassland.Mean temperatures, precipitation,sunlight hours, evapotranspiration, water income and output per year,season and in the grass-growingseason from April to September were systemically calculated using daily meteorological data for theperiod from1961to2007for Qinghai-Tibet Plateau.Their changes about temperature, precipitation,sunlight hours,evapotranspiration,water income and output, NPP were analyzed.The method andindicators of monitoring and evaluating grassland drought were studied and decided for Qinghai-TibetPlateau grassland. Results as follows:(1) Mean temperatures of a year and four seasons are distributed differently in space. The meantemperature in a year,Spring,Summer and Autumn are above0℃in peripheral region, below0℃incenter for Qinghai-Tibet Plateau. Mean temperatures are below-6℃in most of Qinghai-Tibet Plateauin Winter, are colder in north and warmer in south.The yearly, four seasons precipitation are reducedfrom southeast to northwest.The annual precipitation is between500to840mm in southeast, between300to500mm in center, below300mm in northwest, below50mm in parts of northwest. The sunlighthours of a year or four seasons are distributed consistently, higher in west and highest in northwest,lower in southeast.(2) The precipitation of Spring,Summer,grass-growing season from April to September arerespectively16.5%,60.9%,89.4%of a year in Qinghai-Tibet Plateau grassland. They are higher insoutheast, lower in west and lowest in northwest.The evapotranspiration in May,June,July,August arehigher, highest in June,lowest in December.The evapotranspiration of grass-growing season from Aprilto September was68.1%of a year. The evapotranspirations of Spring, Summer, grass-growing seasonfrom April to September are lower in southeast, higher in west and highest in northwest.（3）Month precipitations from January to December are below evapotranspirations, water is inshort supply all years for all of Qinghai-Tibet Plateau grassland. The water deficit in month is higher inMarch, April, May, June, and highest in May. The water deficit in seasons is the highest in Spring,higher in Summer, lowest in Winter. The accumulative water deficit from January to June is64.6%of ayear,51.4%of a year from March to June. The water is deficit for Spring, Summer, grass-growingseason from April to September in most of Qinghai-Tibet Plateau grassland, precipitations are higherthan evapotranspirations and water is surplus in some parts of southeast grassland.（4）According to climate suitability of grassland vegetation, water surplus and deficit,NPP ofQinghai-Tibet Plateau, grassland drought index was designed and had a very significant correlation withgrassland NPP. The indicaters of monitoring and evaluating drought could reflect the water surplus anddeficit, drought conditions and its influence on grassland productivity.The grassland drought index was checked up in2006and2007, applied in2012for Qinghai-Tibet Plateau grassland. The distribution ofgrassland drought and proportions in drought grades were accordant to actual conditions. The accuracyof grassland drought monitoring and evaluating was above90%, can be applied in meteorology serviceevery year. Now, the method and indicaters were built in agricultural meteorological operation system,are very important techniques for nationwide grassland and main grassland drought monitoring andevaluating.