Preprints
https://doi.org/10.5194/egusphere-2022-1499
https://doi.org/10.5194/egusphere-2022-1499
 
20 Jan 2023
20 Jan 2023
Status: this preprint is open for discussion and under review for Weather and Climate Dynamics (WCD).

Atmospheric response to wintertime Tibetan Plateau cold bias in climate models

Alice Portal1,2, Fabio D'Andrea2, Paolo Davini3, Mostafa E. Hamouda4,5, and Claudia Pasquero1,3 Alice Portal et al.
  • 1Department of Earth and Environmental Sciences, Università di Milano - Bicocca, Milan, Italy
  • 2Laboratoire de Météorologie Dynamique/IPSL, École Normale Supérieure, PSL Research University, Sorbonne Université, École Polytechnique, IP Paris, CNRS, Paris, France
  • 3Consiglio Nazionale delle Ricerche, Istituto di Scienze dell’Atmosfera e del Clima (CNR-ISAC), Torino, Italy
  • 4Astronomy and Meteorology Department, Faculty of Science, Cairo University, Cairo, Egypt
  • 5Institute for Atmospheric and Environmental Sciences, Goethe University Frankfurt, Frankfurt am Main, Germany

Abstract. Central Asia orography sets important features of the winter climate over East Asia and the Pacific. By deflecting the mid-latitude jet polewards it contributes to the formation of the Siberian High and, on the lee side, to the advection of dry cold continental air over the East Asian coast and the Pacific Ocean, where atmospheric instability and cyclogenesis thrive. While the mechanical forcing by the orography is assessed by a number of modelling studies, it is still not clear how near-surface temperature over the two most prominent orographic barriers of the Central Asian continent, namely the Tibetan and Mongolian plateaux, influences the winter climate downstream. Moreover, a well known issue of state-of-the art climate models is a cold land temperature bias over the Tibetan Plateau related with the difficulty in modelling land processes and land–atmosphere interaction over complex orography. Here we take advantage of the large spread in representing near surface temperature over the Central Asia plateaux among climate models taking part in the Coupled Model Inter-comparison Project, Phase 6 (CMIP6) to study how temperatures over these regions impact the atmospheric circulation. Based on composites of the CMIP6 models' climatologies showing a cold bias over the Tibetan Plateau, we find that negative temperature anomalies over Asian orography intensify the East Asia winter monsoon and, by enhancing the low-level baroclinicity in the region of the East China Sea, reinforce the southern flank of the Pacific jet. The results of the CMIP6 composite analysis are supported by the response of an intermediate-complexity atmospheric model to a similar pattern of cold surface temperatures over the Central Asia plateaux; we also distinguish the relative influence of the Tibetan and the Mongolian Plateau surface conditions. Thereby, based on the intensification of the East Asia winter monsoon in models characterised by a cold land temperature (bias) over Central Asia plateaux, we prospect that advances in the modelling of the land energy budget over this region may improve the simulation of the mean climate over the Asia/Pacific sector, together with the reliability of climate projections and the performance of shorter term forecasts.

Alice Portal et al.

Status: open (until 03 Mar 2023)

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Alice Portal et al.

Alice Portal et al.

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Short summary
The differences between climate models can be exploited to infer how specific aspects of the climate influence the whole Earth system. This work analyses the effects of a negative temperature anomaly over the Tibetan Plateau on the winter atmospheric circulation. We show that models with a colder-than-average Tibetan Plateau present a reinforced East Asia winter monsoon and we discuss the atmospheric response to the enhanced transport of cold air from the continent toward the Pacific Ocean.