Enhanced atmospheric water cycle processes induced by climate warming over the three rivers source region

Abstract

The relationship between the ocean, land, and atmosphere is greatly impacted by climate change, and the atmospheric water cycle constitutes the most active and crucial hub in this interaction. Two crucial components of the atmospheric water cycle are the precipitation recycle ratio (PRR) and the water vapor source. Accurate quantification of these components can greatly assist in a better understanding of the atmospheric water cycle processes and variations. In this study, measured data from radiosondes and meteorological stations are used to assess the accuracy of the ERA5 reanalysis dataset. The Mann-Kendall (M-K), empirical orthogonal function (EOF), and probability density function (PDF) are utilized to analyze the spatiotemporal variations in the components of the atmospheric water cycle and to trace the sources of water vapor. Based on the Brubaker model, the PRR is estimated, and the atmospheric water cycle process over the three rivers source region (TRSR) is quantified. The findings reveal that (1) there is a significant increase in temperature, precipitation, evaporation, and water vapor content over the TRSR from 1979 to 2020, and the distribution of precipitation and water vapor content decreases from southeast to northwest. (2) The South Asian monsoon and westerly winds are the predominant atmospheric cycle systems for water vapor transport over the TRSR. The water vapor input at the western, southern, and northern borders all exhibit an increasing trend (0.16 × 105 kg s−1 a−1, 0.18 × 105 kg s−1 a−1, 0.09 × 105 kg s−1 a−1, respectively, p > 0.05), while the water vapor output at the eastern border exhibits a decreasing trend (−0.009 × 105 kg s−1 a−1, p > 0.05), resulting in a significant increase in net water vapor influxes (0.43 × 105 kg s−1 a−1, p < 0.05). Water vapor convergence occurs in the southeast while water vapor dispersion occurs in the northwest regions of the TRSR. (3) The multi-year average PRR is 20.85%, with a slightly declining trend, and the contribution of external moisture transport to regional precipitation is dominant over the TRSR. Climate change has sped up the atmospheric water cycle over the TRSR between 1979 and 2020: for every 1 °C rise in temperature, water vapor content increased by 6.83%, precipitation increased by 4.71%, and evaporation increased by 3.62%.