[A-AS04] Extreme Events and Mesoscale Weather: Observations and Modeling

[AAS04-03] Bivariate attribution of the compound hot and dry 2022 summer over the Tibetan Plateau

*Baiquan Zhou¹, Panmao Zhai¹ (1.Chinese Academy of Meteorological Sciences)

Keywords:event attribution, compound hot and dry event, Tibetan Plateau, anthropogenic influence

The extraordinarily high temperatures experienced during the summer of 2022 on the Tibetan Plateau (TP) demand attention when compared to its typical climatic conditions. The absence of precipitation alongside these elevated temperatures resulted in 2022 being the hottest and driest summer on record over the TP since at least 1961. Recognizing the TP's susceptibility to climate change, this study employed large-ensemble simulations from the HadGEM3-A-N216 attribution system and copula-based joint probability distribution to investigate the influence of anthropogenic forcing, particularly global greenhouse gas emissions, on this unprecedented compound hot and dry event (CHDE) over the TP. The findings reveal that the return period for the 2022 CHDE over the TP exceeds 4000 years, as determined by fitted joint distributions derived from observational data spanning 1961-2022. This CHDE is directly linked to large-scale circulation anomalies, including the control of equivalent-barotropic high-pressure anomalies and the northward displacement of the subtropical westerly jet stream. Moreover, anthropogenic forcing significantly contributed to surface warming and heightened precipitation variability on the plateau, establishing conducive conditions for the 2022 CHDE from a long-term climate change perspective. The return period for a 2022-like CHDE over the TP is estimated to be approximately 283 years (142-613 years) in the large ensemble forced by both human activities and natural factors. Conversely, in the ensemble simulations driven solely by natural forcing, the likelihood of a 2022-like CHDE occurring is almost negligible. These outcomes underscore that the contribution of anthropogenic forcing to the probability of a 2022-like CHDE is 100%, implying that without human-induced global warming, a comparable unprecedented CHDE akin to that observed in 2022 would not have been possible over the TP.