Abstract
Precipitation is a key climatic variable that connects the processes of atmosphere and land surface, and it plays a leading role in the water cycle. However, the vast area of Northwest China, its complex geographical environment, and its scarce observation data make it difficult to deeply understand the temporal and spatial variation of precipitation. This paper establishes a statistical downscaling model to downscale the monthly precipitation in the inland river basin of Northwest China with the Tarim River Basin (TRB) as a typical representation. This method combines polynomial regression and machine learning, and it uses the batch gradient descent (BGD) algorithm to train the regression model. We downscale the monthly precipitation and obtain a dataset from January 2001 to December 2017 with a spatial resolution of 1 km × 1 km. The results show that the downscaling model presents a good performance in precipitation simulation with a high resolution, and it is more effective than ordinary polynomial regression. We also investigate the temporal and spatial variations of precipitation in the TRB based on the downscaling dataset. Analyses illustrate that the annual precipitation in the southern foothills of the Tianshan Mountains and the North Kunlun Mountains showed a significant upward trend during the study periods, while the annual precipitation in the central plains presented a significant downward trend.
Highlights
Precipitation is a crucial part of the water and energy cycle [1,2]
The ecosystems based on the supply of precipitation and meltwater in the arid regions of Northwest China are more vulnerable under global warming [6,7,8]
The results showed that the annual precipitation around the southern foothills of the Tianshan Mountains and the North Kunlun Mountains presented a significant upward trend, while the annual precipitation in the Lop Nor and the North Altun Mountains exhibited a significant downward trend (Figure 10)
Summary
Precipitation is a crucial part of the water and energy cycle [1,2]. As an important indicator of climate change and hydrological processes, changes in precipitation will inevitably affect the distribution of water resources in the river basins [3,4]. The variations of precipitation and its impacts on ecosystems have gradually become crucial issues in hydrology and ecology, especially in Northwest. The ecosystems based on the supply of precipitation and meltwater in the arid regions of Northwest China are more vulnerable under global warming [6,7,8]. Northwest China is rich in natural resources with an extremely vulnerable ecological environment due to its limited water resources [6,7].
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