Dynamic Drivers of Precipitation Variability in the Tarim River Basin

The Tarim River Basin has experienced a wetting trend since the 1960s, but its mechanisms remain unclear. Using CN05.1 observations and ERA5 reanalysis for 1961–2022, this paper attempts to explain the long-term trends of seasonal precipitation by: (i) decomposing variability into frequency (number of rainy days) changes and intensity changes, (ii) clarifying atmospheric stratification (relative humidity, static stability, and vertical motion), (iii) diagnosing vertically integrated moisture transport from convergent and advective terms, and (iv) quantifying boundary moisture budget. Precipitation increases in all seasons, but largest growth is in summer dominated by amplified rainfall intensity. Heavier summer rainfall is accompanied by increased low-level humidity, reduced static stability below 400 hPa, and persistent upward motion. These changes are driven by a strengthened easterly jet in the lower troposphere along the eastern Tarim River Basin and southerly moist inflow from the northern Tibetan Plateau that converges towards cross‑mountain westerlies. Changes in other seasons are relatively small. From a moisture budget perspective, the background westerly flow plays a notable, but not dominant, role in the moisture contribution to the basin. Effective moisture transports mainly come from the southern boundary and the summer easterly corridor. Future changes of precipitation in the region will, therefore, crucially depend on variability and change of large-scale atmospheric circulation.