Interannual variation and correlation analysis of farmland NDVI, soil moisture and atmospheric relative humidity in Xinjiang during 2009-2020

Moisture is an important factor affecting crop growth in the field. It is of great practical significance to study the response of field crops to soil moisture and atmospheric relative humidity for preventing agricultural drought disaster in arid area of Northwest China. In this paper, use of farmland in Xinjiang from 2009 to 2020 the normalized difference vegetation index (NDVI) data set, the atmospheric relative humidity data set from May to October 2009-2020 of 61 meteorological stations in Xinjiang and the surface soil moisture content data set from May to October 2017 released by NASA were used to study interannual variability and correlation between NDVI, soil moisture, atmospheric mean relative humidity through correlation analysis, also the variation of NDVI, soil moisture and atmospheric relative humidity from May to October every year. The results showed that from 2009 to 2020, the interannual variation of NDVI and atmospheric relative humidity was large and both showed an upward trend, while the interannual variation of soil moisture was small and showed a slight upward trend, but it gradually decreased after 2016. NDVI was positively correlated with soil moisture and air relative humidity, but NDVI had a stronger correlation with soil moisture and was more affected by soil moisture. From May to August, the dependence of NDVI on soil water increased continuously, and began to decrease in September, and the correlation between NDVI and soil water was the least in October. The relationship between monthly NDVI and atmospheric relative humidity was consistent with soil moisture on the whole, but lower than that of soil moisture.