Dominant factor of dry‐wet change in China since 1960s

Abstract

The dry‐wet climate conditions of an area are mainly determined by the water input (e.g., precipitation, P) and output (e.g., potential evapotranspiration, PET). Based on three dry‐wet indices and the differential equation, this study designed a new attribution method to quantify the contributions of P and PET to the dry‐wet change, so as to determine the dominant factors of the dry‐wet change over whole China (CHINA) and various hydroclimate regions (i.e., arid region, AR; semi‐arid region, SAR; semi‐humid region, SHR; and humid region, HR) during 1960–2018 and six interdecadal periods. Results showed that the overall weak drying in CHINA was dominated by an increase in PET, while climate humidification in AR and HR was dominated by an increase in P, climate drying in SHR was dominated by the reduced P, and the weak drying in SAR was co‐dominated by P and PET during 1960–2018. The dominant factors of dry‐wet change over CHINA and each hydroclimate region varied in different decades. Briefly, climate humidification in CHINA and various hydroclimate regions was basically dominated by P in different decades, and the drying was mainly dominated by P in the 1960s–1980s, but the contribution of PET to climate drying began to become prominent after the 1980s. Besides, we found that P contributed more to dry‐wet change than PET on the station and regional scales, but the contribution of P to climate drying on a national scale was underestimated to some extent due to the regional offset effect of the increase/decrease in P during 1960–2018, as well as in the 1990s. These findings implied that the importance of research on the regional or local scale, and equal attention should be paid to the effects of P and PET changes in the future drought or dry‐wet change research.

Projected Changes in Abrupt Shifts Between Dry and Wet Extremes Over China Through an Ensemble of Regional Climate Model Simulations

“…In order to identify the onset and terminate of dry and wet spells for 10 climate divisions of China, the SPEI was calculated based on the difference between precipitation and PET to quantify water surplus and deficit (Vicente‐Serrano et al, 2010). Although the SPEI was originally proposed for drought monitoring, it can also be used as a tool to detect flood risk (Xu et al, 2020). The SPEI is typically calculated by summing up the difference between precipitation and PET for 1 month and then by fitting the difference to a parametric probability distribution from which probability distributions are converted to the standard normal distribution (Beguería et al, 2014; McKee et al, 1993; Vicente‐Serrano et al, 2010).…”

Evidence for Intensification in Meteorological Drought since the 1950s and Recent Dryness–Wetness Forecasting in China

“…However, a recent study found that there are still uncertainties about the dry gets drier, wet gets wetter pattern; the drought/wetness trends have been overestimated [60]. These contradicting studies indicate that there are obvious regional differences in dry-wet change [61]. Aimed at this issue, negative precipitation anomalies based on atmospheric dynamics provided helpful information to recognize the drying conditions and the intensifying droughts [48].…”

“…The spatial and temporal distribution of drought in China has changed under global climate change [4]. Owing to the vast territory and complex climate [15,61], the spatial-temporal pattern of droughts in China in the last few decades is far from fully understood [23]. Preceding studies focused on variations at the basin and local scales after the 1950s [18,59,60,[84][85][86], which poses a challenge to understanding the drywet variation in each region of China over long time periods [87].…”

“…China has many different types of topography, with terrain that is higher in the west and lower in the east, featuring a three ladder-like distribution [92]. The climate varies significantly from region to region due to its vast territory and complicated terrain [15,61]. China has a wide range of climatic regimes distributed from south to north, including tropical monsoon, subtropical monsoon, temperate monsoon, temperate continental, and alpine plateau climate [30,92].…”

“…Due to the complex topographic features in China [15,61], the main climate factors, precipitation and temperature, have an inherent spatial variability, which may result in different reactions of wet and dry events [31]. Taking one of the most drought-prone sub-regions, NWC [13], as an example, Figure 7b,c,e,f highlight the shift from warm-dry to warm-wet climate in the area.…”