Research Of Characteristics Of Rainfall In Abnormal Years Of Heat Flux In Northwest China

The exchange of energy and substance between earth-atmosphere system play an important role in weather and climate change.Sensible heat flux and latent heat flux are the main paths to transfer heat,reflecting the interchange between atmosphere and water of the surface making atmospheric circulation and region climate important.Based on the data of NCEP and PREC/L from 1971 to 2010 the spatial-temporal characteristics of sensitive heat and latent heat flux near surface atmosphere and the relationship with precipitation are analyzed,The main conclusions are as follows:(1)The highest multi-year average values of sensible heat flux and latent heat flux are in summer,which spring,autumn and winter are lower in northwest China.The area of higher value of sensible heat flux is in the middle and east part of Taklimakan Desert in Xinjiang,the middle and west part of Inner Mongolia and the north part of Gansu.The area of higher value of latent heat flux is in Kanas in Xinjiang,Mt.Tianshan and Mt.Kunlun.(2)First mode of sensible heat flux shows consistent changes,whose explained variance is 85.83%.First mode of latent heat flux shows that the value of most area in northwest China is negative,whose mode is 67.94%.First mode of rainfall shows consistent changes,whose mode is 62.02%.(3)During abnormal sensible heat flux and latent heat flux years,heat flux in spring and summer account for the most in a year.Compared with normal years,sensible heat flux in February and November changed the most,latent heat flux in November changed the most.During abnormal years of sensible heat flux,heat flux in autumn and winter changed the most.Heat flux in autumn changed the most during abnormal years of latent heat flux.(4)During strong sensible heat years,compared with normal years,the percentages of rainfall in February,April and September decreased the most,are-26.9%,-22.0% and-21.6%.During weak sensible heat years,compared with normal years,the percentages of rainfall in February,September and November decreased the most,are 18.8%,20.2% and 15.0%.During strong latent heat years,compared with normal years,the percentages of rainfall in February,April,September and November decreased the most,are 23.8%,24.9%,31.0% and 29.8%.During weak latent heat years,compared with normal years,the percentages of rainfall in January and October decreased the most,are-25.6% and-24.2%.(5)During years of strong sensible heat flux,geopotential height was enhanced to the north of 35°N,subtropical high and summer monsoon got weak,with abnormal cyclonic water vapor causing less water vapor transfer from the South China Sea and northwest pacific to northwest China,making northwest China dryer than the normal years.During years of weak sensible heat flux,subtropical high moved toward the west and the north,making water vapor transfer to the north.With the abnormal cyclonic water vapor of the yellow sea,making more water vapor transfer to the north,causing frontier lifting with long wave routers in Siberia which the east area of northwest China were wetter than the normal years.During years of strong sensible heat flux,the reason of strong sensible heat flux in spring was higher Siberian,enhancing the north wind of east side of Siberian High,beneficial to accumulate the sensible heat flux.The reason of less rainfall in summer was higher sensible heat flux of spring and summer,with the location of Subtropical High moving east and weak,making summer monsoon weaker,making the water vapor transfer to the west area of northwest China toward south,making less rainfall in summer in northwest China.Years of weak sensible heat flux were the opposite.(6)During years of strong latent heat flux,the South China Sea,northwest pacific and the Indian Ocean transferred more water vapor to the north,making northwest China more water vapor.Subtropical high was strong toward the west,with water vapor transferred from the South China Sea and northwest pacific through the edge of subtropical high to northwest China.Influenced with updraft in front of the long wave routers above Xinjiang,northwest China was wetter compared with normal years.During years of weak latent heat flux,Siberian high was high and subtropical high was weak,making summer monsoon weak and winter monsoon strong.Northwest china couldn't receive enough water vapor from the sea without enough water transfer to the north and changes of high attitude,making northwest china dryer to the normal years.During years of strong latent heat flux,the reason of latent heat flux in spring was zonal distribution in East Asia,changing from east to west.Because of weaker Siberia High and strong westerlies,making Indian sea transferred more water vapor to northwest China,with strong south wind from the coast,beneficial to transfer morewater vapor to northwest China.In summer,circulation in china distributed warp direction,which was positive negative positive position(+-+).The location of Subtropical high was west,beneficial to transfer more water vapor to northwest China,making more rainfall.Years of weak latent heat flux were the opposite.(7)From the point of forecast,if sensible heat flux in one year is stronger than that of the normal years,or latent heat flux is abnormal in northwest China,rainfall of next year will increase,consulting the mode that predicts more rainfall during forecast.