Abstract: Based on daily meteorological data of 2000-2022 as well as vegetation and soil properties, we quantified the features of typical heat and drought events across southern China in 2022 with heat index, drought index, and net primary productivity (NPP) estimation model, and examined their impacts on vegetation NPP. The results showed that heat and drought events across in 2022 were characterized by long duration and high intensity, which was rare in history. The average number of heat days across Yangtze River Basin during 21th June and 25th August was 42.4 d. The average precipitation across Yangtze River Basin during 21th June and 20th November was 38.9% less than the mean value in 2000-2021. The average vegetation water deficit anomaly percentage were -163.1%, -176.7%, and -192.6% in the period from 21th June to 31th August, from 21th June to 30th September, and from 21th June to 20th November, respectively. In the same periods, vegetation water deficit was severe in Zhejiang, Jiangxi, Hunan, Chongqing, Fujian, and Guizhou, being 62.2-216.5, 86.6-307.3, and 149.3-400.2 mm in the three periods, respectively. The corresponding average vegetation water deficit anomaly percentage was -306.3%--134.3%, -525.4%--140.6%, and -447.8%--158.4% in the three periods, respectively. There was substantial reduction in NPP at the heat and drought events. Relative to the mean value of the corresponding period across 2000 to 2021, the average vegetation NPP across Yangtze River Basin decreased by 3.3%, 11.1%, and 10.2% in 31th August, 30th September, and 20th November, respectively. All the values were the lowest since 2000. NPP in 20th November in Zhejiang, Jiangxi, Hunan, Chongqing, and Fujian that suffered from serious heat and drought was 14.1%, 16.8%, 14.9%, 11.5%, and 18.9% lower than that in corresponding period in 2000-2021, respectively.

Key words: heat, drought, vegetation water surplus or deficit, vegetation net primary productivity