Impacts of record-breaking compound heatwave and drought events in 2022 China on vegetation growth

In the summer of 2022, China experienced a series of record-breaking heatwaves and unprecedented low rainfallinduced droughts across much of China's regions. Using a reanalysis of the meteorological dataset, we confirmed that the 2022 concurrent heatwaves in China were more frequent and widespread than in the past (1979-2021). The heatwaves presented the greatest record for heatwave count, heatwave days, and cumulative intensity, especially in the Yangtze River basin, Tibetan Plateau, and Northern China. Moreover, heatwaves often occur with concurrent droughts. We found heatwaves and droughts reduced vegetation growth over half of the vegetated areas in China, represented by the negative detrended anomalies of the Normalized Difference Vegetation Index (NDVI; 66.89 %), Enhanced Vegetation Index (EVI; 58.68 %), and contiguous solar-induced chlorophyll fluorescence (CSIF; 56.47 %). More importantly, nearly half of the land surface of China (48.28 %) in 2022 summer experienced warmer and drier climate conditions than in the historical period (1979-2021). As a result, 72.9 % of vegetation stress anomalies (i.e., negative detrended anomalies of vegetation indices) in those areas can be attributed to warmer and drier climate (20.3 %), individual extreme dry climate (2.0 %), individual extreme warm climate (43.1 %), and compound extreme events combining the driest and warmest conditions (7.5 %), respectively. These findings implied that heatwaves were more critical in limiting vegetation growth than drought this summer. Using a large ensemble model (i.e., CanESM5), we estimated the probability of exceeding the 2022 summer extreme daily maximum temperature (Tmax) in China and its subregions in the future climate. Generally, heat extremes greater than the observed record (i.e., 2022) are found in China every decade, with models indicating a likelihood of 0.42 % to 85.69 % from 2023-2032 to 2083-2092 in the SSP585 future scenario. Our study provides a timely and essential evaluation of the impacts of compound heatwaves and droughts on plant growth.

Automated summary

In the summer of 2022, China experienced record-breaking heatwaves and droughts, which had a significant impact on plant growth. The study also found that heatwaves were more critical than droughts in limiting vegetation growth.