Spatial and Temporal Characteristics of Precipitation in Yungui Plateau during 1961-2015

In this paper, the daily precipitation data of 19 meteorological stations in Guizhou Province from 1961 to 2015 are used. Using GIS spatial analysis method and linear trend analysis method, the distribution characteristics of annual and seasonal precipitation in Guizhou province were analyzed from space and time. The results show that: (1) From the perspective of spatial distribution, annual precipitation is generally less in the south and north and less in the east and west. The precipitation in winter and spring is east-west distribution and decreases from east to west in the four seasons. The precipitation in summer is roughly north-south and south-north less. The precipitation in autumn is mainly concentrated in southwest Guizhou and Chishui valley. (2) From the time distribution point of view, the precipitation in Guizhou Province showed a general downward trend, of which the precipitation in spring, autumn and winter showed a decreasing trend, the downward trend in autumn was more obvious, and the precipitation in summer increased but not obviously.


Introduction
Precipitation is an important element that reflects the climatic characteristics of a region and is an important climatic factor affecting or reflecting the ecological environment [1] .With the development of science and technology, people's requirements for meteorological services are increasing year by year.Research on the spatial distribution of precipitation must be intensive and meticulous in order to meet the needs of modern society [2] .Therefore, it is more and more urgent to evaluate and predict long-term precipitation characteristics [3] .
Most foreign experts and scholars believe that the average precipitation in the world and the northern hemisphere is a periodical change, but the trend of change in each stage is different.Hulme study shows that between 1950 and 1980, there was no significant decrease in the global average precipitation and a significant decrease in precipitation after the 1990s [4] .Vinnikov's study of precipitation in different regions of the Northern Hemisphere shows that precipitation increased by nearly 6% in the mid-latitudes of the Northern Hemisphere from the early 19th century to the 1990s [5] .Kattsov proposed that the precipitation in the northern hemisphere mid-latitudes has been increasing strongly since the 1920s [6] .Diaz et al.Obtained the study on the precipitation in the southern hemisphere, and the trend of precipitation in the mid-high latitudes and low latitudes showed consistent [7] .Zuo Hongchao et al.Conducted a study on the precipitation in our country, showing that the regional average precipitation characteristics are obvious and the trend of change is not obvious [8] ; Wang Yanjiao et al.The regional precipitation and decadal variation characteristics of precipitation in China during 1960-2010 show the precipitation There are obvious stages of change [9] ; Li Yonghua et al.Analyzed the spatio-temporal features of the summer precipitation in the eastern part of Southwest China.The summer precipitation in the eastern part of Southwest China is mainly consistent with the whole region, and the frequency of occurrence is above 60% [10] .
In recent years, although some scholars have done some research on precipitation in Guizhou Province, the characteristics analysis of precipitation in Guizhou Province in time and space is still relatively weak.Therefore, by applying the daily precipitation data of Guizhou Province in recent 55 years, the paper analyzes the precipitation characteristics of Guizhou Province in recent years by using ArcGIS technology and linear trend analysis method from different time scales and spatial analysis.
Guizhou Province is located in the southwestern part of China and is located in the southeast of the Qinghai-Tibet Plateau.It is a part of the Yunnan-Guizhou Plateau with an average elevation of about 1,100 m.It belongs to a subtropical monsoon climate and is humid and humid throughout the year with an average annual temperature of about 15-18°C [11] .The terrain is high in the west and low in the east, with complex and diverse topography.90% of the area is mountainous and hilly, with 73% of the area being karst.

Data and Processing
In this paper, the daily precipitation data of 19 meteorological stations in Guizhou province for 1962-2015 years are selected as the research data, and the data are derived from the China Meteorological Data Network (http://data.cma.cn).The quarterly and annual precipitation data used in this study are calculated by accumulating daily precipitation.

Linear trend method
The linear trend analysis refers to the use of n to express the sample size, the time is expressed in i t , the precipitation variable is expressed by i x , and the linear regression equation between i x and i t is established.
In the upper form, the precipitation factor is expressed by x , the a is the regression constant, the b indicates the regression coefficient and the t represents the time [10].

Kriging
Kriging is one of the most commonly used spatial interpolation methods, the general formula is as follows: the observations, they are located in the region i x position; 0 x is the observed point to be estimated; i  is the weighted coefficient; n is the total number of known observation points [12] .Precipitation performance of more than North South, East and West less.Among them, the precipitation in the eastern part of Tongren region, the southwestern part of Southeast Guizhou, the eastern part of Qiannan, most of Anshun and most of southwestern Guizhou are more than those of the other regions, and the average annual precipitation is basically above 1200mm; In Bijie region, southern Zunyi, the average annual rainfall is not higher than 1000mm (Figure 1).

Seasonal precipitation distribution
On the whole, the precipitation in spring decreased gradually from east to west, and the precipitation was more in the eastern part of Tongren, the eastern part of Guizhou Province and the southern part of Guizhou Province, with the precipitation reaching 390mm.The second part was the west of Tongren, the eastern part of Zunyi, Anshun And western Qiannan, the average precipitation is 360.3mm; the average precipitation in western Zunyi, Guiyang and western Guizhou is 311.0mm; in Bijie area, the average precipitation is only

Figure 1
Figure 1 1961-2015 year average annual precipitation distribution map of Guizhou