Abstract:

The Meili Snow Mountains (MLSM) is characterized as high topographic relief and diversified climate patterns in Southwest China. Characterizing spatial-temporal changes of temperature and precipitation is helpful in the quantification of glacier changes and hydrological process in the region. The lack of observations and low spatial resolution in reanalysis data are the main constraints to comprehensively characterize the meteorological conditions in this area. In this study, the bias corrected and downscaled ERA5-Land product with 1 km resolution was applied to explore the heterogeneity and altitudinal effect in precipitation and temperature changes during 1990-2020. Results are as follows. There is a significant upward trend at a rate of 0.15℃ / (10 a) in air temperature with spatial and seasonal differences. Precipitation shows a significant downward trend at a rate of -41.19 mm/(10 a). The whole area has a tendency becoming “warming and drying”. The warming is not obvious in areas when the altitude is below 4000 m or above 5000 m, in-between, the warming is elevation dependent. Precipitation also has a significant altitudinal gradient. When the altitude is lower than 5000 m, the precipitation on the west slope decreases with the increase of altitude, but increases with the increase of altitude when the altitude is above 5000 m. Precipitation on the eastern slope increases with elevation from 2000 m to 6000 m. The atmospheric circulation background and complex geographical environment together determine the spatio-temporal differentiation of climate change in MLSM. Continued warming and reduction of precipitation may further aggravate the loss of water resources and accelerate glacial retreat in this area.

Key words: Meili Snow Mountains (MLSM), Temperature, Precipitation, Statistical downscaling, Spatio-temporal characteristic, Elevation gradient