Analysis On The Temporal And Spatial Distribution Of Precipitation And Drought In Different Landforms Of The Loess Plateau

Drought is a restrictive factor affecting agricultural development in the Loess Plateau.In order to clarify the characteristics of precipitation and drought in different geomorphic units of the Loess Plateau,this paper selects basic meteorological data from 69meteorological stations in the Loess Plateau from 1961 to 2017,and uses Kriging interpolation,Origin mapping,wavelet analysis,and cross-wavelet transform methods were processed and analyzed,and the temporal and spatial distribution maps and trend maps of precipitation and rainfall erosivity in the Loess Plateau were obtained;the inter-annual variation map of different drought indicators and the distribution map of drought frequency in different topographic areas;The tele-correlation diagram of different circulation factors and precipitation,rainfall erosivity,and different drought indicators.The following conclusions can be drawn:(1)From the time point of view,the annual average precipitation on the Loess Plateau has shown a slight downward trend in the past 57 years;from the spatial point of view,it generally shows a downward trend from the south to the north;and the precipitation has a30-year period cycle.In terms of topographical area,there is more precipitation in the southern part of the hilly area and less precipitation in the northern part of the hilly area.The Taihang Mountains,Luliang Mountains and the northern Qinling Mountains in the mountainous areas have more precipitation,while the Wushaoling and Helan Mountains in the western mountain areas have less precipitation.The rainfall erosivity is generally at a relatively stable stage,with an average annual rainfall erosivity of 1475.24MJ·mm·hm^-2·h^-1·a^-1.From a spatial point of view,the rainfall erosivity presents a decreasing trend from southeast to northwest.The spatial distribution of rainfall erosivity in different topographical areas and the spatial distribution of precipitation show similar trends.The Mall-Kendall Z value of rainfall erosivity in the study area shows a trend of high in the northwest and low in the southeast;the coefficient of variation of the Loess Plateau generally shows a trend of decreasing from north to south.(2)On the whole,the different drought indicators in the study area showed a downward trend from 1961 to 2017,and the station ratio and drought intensity in the Loess Plateau both showed an upward trend.(3)In mountainous areas,the drought frequency is relatively high in the western part of the Loess Plateau,northern Taihang Mountain,and northern Luliang Mountain;drought frequency is high in the northern hilly area;drought occurs frequently in the Yinchuan Plain,Hetao Plain,and Fenhe Plain in the plain area.(4)Large-scale circulation factors such as PNA,ENSO,and AO have obvious responses to precipitation and rainfall erosivity in the study area.PNA,ENSO,AO and WPI all have a strong teleconnection relationship to different drought indicators.