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Monitoring and Cause Analysis of Drought on Urat Grassland

in the First Half of 2018

LIANG Fengjuan，ZHANG Baolong
（Bayan Nur Meteorological Bureau，Linhe 015000，Inner Mongolia，China）

Abstract：Drought is a complex abnormal phenomena in nature，which is of great significance to drought analy‐
sis and research based on meteorological factors. Based on the precipitation and temperature data selected from
1971 to 2018 and the climate survey from March to June in 2018，the effect of meteorological factors on drought
was analysed combined with the evolution of atmospheric circulation in Eurasia. By methods of soil moisture
measurement and UAV aerial photography，22 typical regions were selected in Urat grassland，where the soil rel‐
ative humidity were measured at the depth of 10，20，30 and 40 cm. In order to study the spatial distribution of
drought grade and the occurrence degree of drought，the vegetation growth of Urat grassland in mid June was
monitored by remote sensing with high resolution satellite，and compared with that of the corresponding period
of last year and of the recent three year. The results show that：（1）In the spring of 2018，the East Asian Trough
was weak and the Asian zonal circulation was abnormally strong. From March to May，Urat grassland，at the
northern foot of Yinshan Mountain，whose 500 hPa was under the control of high pressure ridge，has abnormally
less precipitation，abnormally high temperature，long sunshine time，windy sand weather，large surface water
evaporation，and severe surface soil moisture loss，leading to the delay of grass returning to green.（2）At the
turn of spring and summer in 2018，the subtropical high was still southward and distributed in a latitudinal pat‐
tern，which hindered the water vapor of South，Southeast and Southwest to transport to the North. As a result，
there was no soaking rain in Urat grassland until the mid June. Soil moisture was not effectively replenished and
maintained；soil moisture conservation ability was poor，and dry soil layer was thick，which led to the occur‐
rence and development of drought in Urat grassland，resulting in severe drought.
Key words：Grassland drought；climatic characteristics；soil moisture；satellite remote sensing；causes of
drought