Abstract: With four precipitation data products (CHIRPS, GPM, ERA5, and PERSIANN-CDR) and three evapo-transpiration data products (GLEAM, FLDAS, and GLDAS), we addressed the insufficient validation of the applicability and accuracy of remote sensing-based precipitation and evapotranspiration data products in the Three-North Shelterbelt Project Region (hereafter referred to as the Three-North Region), as well as the lack of quantitative analysis of their variation characteristics, using high-resolution spatial datasets generated from ground-based observations as validation benchmarks. We used statistical metrics including the correlation coefficient, relative bias, root mean square error, and Nash-Sutcliffe efficiency to systematically evaluated the applicability of these data products across different climatic zones. Furthermore, we employed Mann-Kendall trend analysis, change-point analysis, and Morlet wavelet analysis to examine the spatiotemporal variations of precipitation and evapotranspiration in the Three-North Region from 2000 to 2020. The results showed that the applicability of the four precipitation products varied significantly across climatic zones. CHIRPS had higher accuracy in the middle temperate arid region, middle temperate semi-arid region, and middle temperate semi-humid region, while GPM performed better in the plateau temperate semi-arid region and middle temperate arid region. Among the three evapotranspiration products, FLDAS showed the highest applicability in the plateau temperate semi-arid region and warm temperate semi-humid region, whereas GLDAS performed better in the middle temperate semi-humid region, middle temperate semi-arid region, and middle temperate arid region. From 2000 to 2020, both precipitation and evapotranspiration in the Three-North Region showed an overall increasing trend, with rates of 2.69 and 1.56 mm·a^-1, respectively. There was a significant positive correlation between the two variables at the regional scale. However, the correlation between the two variables showed differences in different climatic zones. In the middle temperate semi-humid region, middle temperate semi-arid region, and warm temperate semi-humid region, the correlation between the two variables was strong, and an increase in precipitation drove an increase in evapotranspiration. In the middle tempe-rate arid region and plateau temperate semi-arid region, the correlation between the two variables was weaker, and evapotranspiration showed limited sensitivity to change in precipitation.

Key words: Three-North Shelterbelt Project Region, precipitation, evapotranspiration, applicability evaluation