Causes of the Extreme Drought in Late Summer–Autumn 2019 in Eastern China and Its Future Risk

Abstract

Eastern China (EC) suffered an extreme drought with long-lasting duration and record breaking intensity in late summer-autumn 2019. Our diagnosed results show that the central Pacific (CP) El Niño, in tandem with warm sea surface temperature anomalies (SSTAs) over the Kuroshio extension (KE) region, induces the meridionally elongated cyclonic circulation anomalies stretching from the western North Pacific (WNP) to the Yellow Sea. Its western flank corresponds to overwhelming low-level northerly wind anomalies over EC, which result in deficient moisture and anomalous descent over EC and hence cause the extreme drought in 2019. To investigate the relative contributions of SSTAs over different regions, we performed sensitivity experiments, and analyzed the relationship between the extreme drought like 2019 (2019Drought-like event) and the SSTAs in CMIP6 historical simulations. Modelling evidences reveal that both warm SSTAs over the central-equatorial Pacific and the KE region are indispensable for shaping the meridionally elongated cyclone anomaly. Specifically, the cyclone anomaly over the WNP induced by CP El Niño aligns with the cyclone anomaly over the Yellow Sea induced by the warm SSTAs over the KE region, merging into a meridionally stretched cyclone anomaly to the east of EC. Consequently, the northerly anomalies stretch across EC, leading to unfavorable atmospheric conditions and the rainfall deficit there. Projection results show the occurrence probability of 2019Drought-like event will increase by 20% (decrease by 40∼50%) under high (medium-low) emission scenario compared to present day climate, indicating the nonlinear response of extreme drought to different emission scenarios and the urgency of carbon emission reduction.

Persistent Meteorological Drought in the Yangtze River Basin during Summer–Autumn 2022: Relay Effects of Different Atmospheric Internal Variabilities

“…It is also worth noting that in summer-autumn 2022, the precipitation deficit co-occurred with a positive temperature anomaly, which would strengthen the severity of drought through increasing evaporation [33]. This implies a crucial role of the long-term warming trend in modulating the strength of YRB drought [34][35][36]. In future studies, through using large ensemble model simulations with anthropogenic forcing, the question of whether the concurrently dry and hot events analogous to the event in 2022 are likely to increase under global warming will be investigated.…”

Diverse impacts of strong and moderate intense El Niño–Southern Oscillation events on spring precipitation over Asia

“…To further diagnose the contribution of horizontal and vertical thermal and dynamic processes to precipitation anomalies, the moisture equation is analysed in this study. The specific formula in pressure coordinate with reference to Peng and Zhou (2017), Ai et al (2023) and Chen et al (2023) is expressed as follows: where P and E are precipitation and evaporation, = ( u , v ) and are the horizontal wind velocity and vertical velocity, q and p are specific humidity and pressure. The prime denotes the perturbation anomaly, and indicates vertical integral from the surface to 100 hPa.…”

“…To further diagnose the contribution of horizontal and vertical thermal and dynamic processes to precipitation anomalies, the moisture equation is analysed in this study. The specific formula in pressure coordinate with reference to Peng and Zhou (2017), Ai et al (2023) and Chen et al (2023) is expressed as follows:…”

ENSO and IOD contributions to seasonal meteorological droughts over the Yangtze River basin

“…For example, the winter–spring drought of 2010–2011 (Lu et al, 2014) affected 6.75 million hectares of crops and left 2.81 million people and 2.57 million livestock short of drinking water (Xinhua, 2011). The summer–autumn drought of 2019 (Chen et al, 2023) affected over 1 million residents and inflicted a direct economic loss of 227 million US dollars (Xinhua, 2019). At the peak of the 2022 megadrought, the affected cropland area in the YRB reached around 4 million hectares; 4.99 million people and 0.9 million livestock experienced difficulties accessing drinking water (Ma et al, 2022).…”