Under global warming, the climate in semi-arid inland Eurasia (SAIE) has changed in an opposite manner, thereby seriously impacting the local ecological environment. However, the key influencing factors and physical mechanism remain inconclusive. In this paper, we remodel the precipitation recycling ratio (PRR) model to assess the contributions of moisture from different water vapor sources to local precipitation, analyze the characteristics of the PRR and precipitation in SAIE, and provide possible physical reasons based on the Clausius–Clapeyron equation. It is found that the PRR increased from 1970 to 2017 as the result of linear trend analysis, with obvious seasonality. Moreover, the component of precipitation contributed by locally evaporated moisture (Pl), and that contributed by advected moisture (Pa) as well as the total precipitation (P), increased during the past 48 years. In particular, the Pa, Pl, and P in autumn and winter all increased obviously during the past 20 years from the interdecadal change trend, as well as the PRR (Pl/P), which was opposite to the decrease in the total water vapor input I(Ω) in the horizontal direction. According to the Clausius–Clapeyron equation, one of the causes might be that global warming has accelerated the local water cycle and driven the increase in Pa, and the increase in atmospheric water holding capacity caused by global warming provides the power source. We suggest that the climate’s transformation from dry to wet in SAIE can only be temporary since SAIE is an inland area and the adjustment of atmospheric circulation did not lead to the increase in external water vapor.

Regular pattern is a typical feature of vegetation distribution and thus it is important to study the law of vegetation evolution in the fields of desertification and environment conservation. The saturated water absorption effect between the soil water and vegetation plays an crucial role in the vegetation patterns in semi-arid regions, yet its influence on vegetation dynamics is largely ignored. In this paper, we pose a vegetation-water model with saturated water absorption effect of vegetation. Our results show that the parameter 1/P, which is conversion coefficient of water absorption, has a great impact on pattern formation of vegetation: with the increase of P, the density of vegetation decrease, and meanwhile it can induce the transition of different patterns structures. In addition, we find that the increase of appropriate precipitation can postpone the time on the phase transition of the vegetation pattern. The obtained results systematically reveal the effect of saturated water absorption on vegetation systems which well enrich the findings in vegetation dynamics and thus may provide some new insights for vegetation protection.

The precipitation recycling rate (PRR) is an important index when trying to understand the physical mechanisms behind the effects of different sources of water vapor on regional precipitation. We studied the change in the PRR in the mid- and lower reaches of the Yangtze River (MLRYR), the correlation between the PRR and the external source of water vapor and local evaporation, and the possible reasons for the interannual variation of the PRR. Our study was based on an evaluation model of the PRR and used precipitation data from meteorological stations in China and NCEP/NCAR reanalysis datasets. Our results show that the mean PRR in the MLRYR for the time period 1961–2017 was largest in autumn (about 0.3) and smallest in summer (about 0.23), with a clear upward trend (passed the 95% significance F-test), except in summer. The highest trend coefficient of the PRR was in autumn (0.38), indicating that the contribution of an external source of water vapor to local precipitation was reduced. The PRR of the MLRYR was strongly correlated with the input of water vapor through the western and southern boundaries. Water vapor was mainly sourced from the Northwest Pacific Ocean, the South China Sea and the Bay of Bengal. The anomalous Northwest Pacific cyclone induced by the Pacific sea surface temperature restrained the input of water vapor into the MLRYR from the Western Pacific, the South China Sea and the Bay of Bengal, contributing to the upward trend in the PRR. We suggest that increases in the sea surface temperature in the Pacific Ocean, South China Sea and especially the Indian Ocean will have an important impact on precipitation in East Asia.

No abstract