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• Hot-dry wind denotes a significant (p < 0.01) weakening trend from 1960 to 2019 in Northern China. • Hot dry wind has become the primary driver of warm-season dryness in recent decades. • Hot dry wind is more influential than precipitation on variations of surface dryness/wetness in Northwest China. The concurrent occurrence of high temperature, low humidity, and specific wind speed, known as hot-dry wind (HDW), is a widespread agro-meteorological hazard in Northern China. HDW can significantly impact surface dryness/wetness by influencing atmospheric water demand. To understand the divergent effect of HDW and precipitation on the spatiotemporal variations of surface dryness/wetness, we collected meteorological data from 673 meteorological stations across Northern China for the warm season (May to September) during 1960–2019. Results reveal a significant (p < 0.05) wetting trend from 1983 to 2019 and a significant (p < 0.01) weakening of HDW across Northern China from 1960 to 2019. Notably, the primary driver of warm-season dryness has transitioned from precipitation before 1982 to HDW in recent decades. Regionally, the wetting trends observed in Northwest (NW) and North China (NC) are primarily attributed to the weakening HDW. Conversely, in Inner Mongolia (IM), a drying trend is noted due to a decline in precipitation that outweighs the reduction in water consumption caused by weakened HDW. During 1960–2019, our analysis affirms that the relative contribution of HDW to variations in warm-season dryness/wetness surpasses that of precipitation in Northern China, particularly in the hyper-arid NW. The persistent HDW is anticipated to exacerbate warm-season dryness and increase water demand for crop growth and animal husbandry in Northern China. [ABSTRACT FROM AUTHOR]

Ecosystem water use efficiency (WUE describes carbon-water flux coupling in terrestrial ecosystems. Understanding response and resilience of WUE to drought are essential for sustainable water resource and ecosystem management under increasing drought risks over China due to climate warming. Here we analyzed the response of ecosystem WUE to drought (spatiotemporal variability and resilience) over China during 1982–2015 based on an evapotranspiration (ET) dataset based on the model tree ensemble (MTE) algorithm using flux-tower ET measurements and satellite-retrieved GPP data. The results showed that the multiyear average WUE was 1.55 g C kg−1 H2O over China. WUE increased in 77.1% of Chinese territory during the past 34 years. During drought periods, the ecosystem WUE increased mainly in the northeast of Inner Mongolia, Northeast China and some regions in southern China with abundant forests but decreased in northwestern and central China. An apparent lagging effect of drought on ecosystem WUE was observed in the east of Inner Mongolia and Northeast China, the west and east regions of North China and the central part of Tibetan Plateau. Some ecosystems (e.g., deciduous needle-leaf forests, deciduous broadleaf forests, evergreen broadleaf forests and evergreen needle-leaf forests) in Central China, Northeast and Southwest China exhibited relatively greater resilience to drought than others by improving their WUE. Our findings would provide useful information for Chinese government to adopt a reasonable approach for maintaining the structure and functions of ecosystems under drought disturbance in future. [ABSTRACT FROM AUTHOR]

Compound hot and dry extremes have drawn extensive attention given the devastating impacts on natural ecosystem and social economy. However, the substantial dependence of compound hot and dry extremes upon individual ones is barely discussed at the daily level. In this study, we present the dependence of compound hot and dry days (CHDDs) and events (CHDEs) upon individual ones using summer (June–July–August) daily temperature and precipitation across China during 1961–2014. Results show more CHDDs and CHDEs over regions from northeast to southwest China, with stronger intensity over the transitional area between Northwest China (NW) and the Tibetan Plateau. Simultaneously, the period with the occurrence of compound extremes generally extends since compound extremes start earlier and end later. On average over China, hot extremes are significantly (p < 0.01) influential on the frequency (r = 0.42–0.83) of compound extremes, which contribute 55–78% to changes in the frequency. Dry extremes are significantly (p < 0.01) influential on the intensity (r = 0.60–0.79) and contribute 63–70% to changes in the intensity. Both hot and dry extremes are influential on the start and end of compound extremes. More importantly, largely influenced by the high probability of dry extremes in North China, the joint probability of compound extremes is higher in NW followed by Inner Mongolia. These findings highlight the new insights into compound extremes defined by relative thresholds at the daily level. • More compound extremes occur from NE to SW, with stronger intensity over the transitional area between NW and TP. • Hot (dry) extremes are more influential on the frequency (intensity) of compound extremes. • Influenced by dry extremes, the joint probability of compound extremes is higher in NW followed by IM. [ABSTRACT FROM AUTHOR]