The characteristics of moisture recycling and its impact on regional precipitation against the background of climate warming over Northwest China

Abstract

From 1961 to 2015, annual and seasonal precipitation have shown a significant increase over Northwest China (NW). The change of precipitation is a combination result of the changing recycling precipitation (Pw) contributed by local evapotranspiration (ET) and changing precipitation contributed by advection moisture (Po). In this paper, we calculated the ET based on the observation data of meteorological stations and the complementary relationship model. Then used an improved precipitation recycling model to analyse influential factors on the variation of precipitation over the NW from aspects of ET and advection moisture. The annual precipitation recycling ratio (ρ) fluctuates between 4% and 10% and shows an increasing trend at a rate of 0.3% /10a with a significance level of 0.01. ET, which is the internal supplier of the precipitable water, and advection moisture, which is the outside supplier of the precipitable water, both have displayed significantly increasing trends over the NW. The advection moisture contributes precipitation much more than ET, no matter in the annual scale or seasonal scales. In view of the spatial distribution, Pw shows an increasing trend over the whole NW, but distinctly opposite spatial patterns of Po are found between the western area of NW (WNW) and the eastern area of NW (ENW). Such differences caused the precipitation is characterized by a wetting trend in WNW but a drying trend in ENW.

The Mechanism of Increasing Summer Water Vapor Over the Tibetan Plateau

“…The PRE recycling ratio indicates the ratio of the PRE evaporated from local (internal cycle), with the remaining portion coming from remote moisture sources (external cycle). In summer time, solar radiation can efficiently heat the air column over the TP that is of smaller total mass than neighboring regions due to its high altitude, and it can induce large‐scale near‐surface cyclonic circulation (Wu et al., 2019). As a result, the TP becomes an immensely sensible‐heat‐driven air pump with large amounts of moisture converging from the surrounding region toward the TP.…”

Response of altitudinal vegetation belts of the Tianshan Mountains in northwestern China to climate change during 1989–2015

“…The reason why the eastern mountain steppe belt shifts to low elevation is that less precipitation (104 mm/a) and rising temperatures promote more soil moisture to enter the atmosphere through evapotranspiration, which aggravates drought in low elevation regions. In the central region, the rate of temperature increase is the fastest (0.6 °C/10a), which enhances the instability of air convection, and results in a significant increase in local evapotranspiration 32 . These factors will lead to more severe droughts in low-elevation areas and exceed the tolerance of desert vegetation.…”

Local Meteoric Water Lines in a Semi-Arid Setting of Northwest China Using Multiple Methods

“…This reflects that other mechanisms make a positive contribution to the variability of LMWLs, including sub-cloud evaporation and recycled moisture attributed to the increasing urban green coverage in the past decades, especially in summer. It's worth noting that the secondary evaporation is apparent in the summer monsoon period in Lanzhou, and that the potential contribution of recycled moisture has fluctuated during past decades [29,30]. able 3.…”