Abstract:

Based on the meteorological data of 224 stations in the Yellow River Basin from 1961 to 2020 and the MODIS NDVI vegetation data from 2000 to 2020, the spatiotemporal distribution patterns of aridity were analyzed, as well as its impacts on the vegetation NDVI. Results show that the tendency rate of annual averaged aridity in the Yellow River Basin is -0.03 per decade from 1961 to 2020, with a multi-year average value of 2.56. In terms of the regional variability, the northern stations are mainly characterized by a decreasing trend (52.2%), while the central and southern stations primarily exhibit an increasing trend (41.5%). As for the aridity spatial distributions, it generally decreases from northwest to southeast, with the highest values in the upper reaches (3.74), followed by the middle reaches (1.99) and lower reaches (1.74). The upper reaches include arid, semi-arid, and semi-humid subregions, while the middle and lower reaches are mostly semi-humid subregions. Stepwise regression analysis indicates that aridity is primarily impacted by the local precipitation. The reduction in annual average aridity in most areas could be attributed to decreased total solar radiation, increased precipitation, and lower temperatures. The averaged NDVI is 0.30 in the Yellow River Basin from 2000 to 2020, with a distribution of higher values in the southeast (lower reaches) and lower values in the northwest (upper reaches). The NDVI is a significantly negative correlation with the aridity (r=-0.52, P < 0.01, n=224), especially in upper and middle reaches of the Yellow River Basin.

Key words: Yellow River Basin, Aridity, Normalized Difference Vegetation Index (NDVI)