A climatology of surface–air temperature difference over the Tibetan Plateau: Results from multi‐source reanalyses. (13th April 2020)

• Record Type: Journal Article
• Authors: Wang, Xuejia; Chen, Deliang; Pang, Guojin; Ou, Tinghai; Yang, Meixue; Wang, Meng
• Is Part Of: International journal of climatology. Volume 40:Number 14(2020)
• Page Start: 6080
• Page End: 6094
• Publication Date: 2020-04-13
• Subjects: air temperature -- reanalysis dataset -- surface temperature -- surface–air temperature difference -- Tibetan Plateau; Climatology -- Periodicals; Climat -- Périodiques; Climatologie -- Périodiques; 551.605
• DOI: 10.1002/joc.6568
• Languages: English
• ISSNs: 0899-8418

Abstract

Abstract: The Tibetan Plateau (TP), known as earth's "Third Pole, " influences regional and even global weather and climate systems through its mechanical and thermal‐dynamical forcing. Near‐surface (2 m) air temperature ( T a ) and surface (skin) temperature ( T s ) are two crucial parameters of land–atmosphere interactions and climate change. Their difference (Δ T = T s − T a ) determines the heating source over the TP that drives the Asian summer monsoon. This study focuses on climatology, inter‐annual variability, and long‐term trend of Δ T over the TP in the last four decades (1979–2018), based on four latest reanalysis datasets including ERA‐Interim, ERA5, MERRA2, and JRA55, along with observational data. We show that Δ T ‐based different datasets display fairly different climatology in terms of seasonality, spatial distribution, and long‐term trend. Δ T exhibits a clear seasonality with negative value in winter and positive ones in summer despite different strengths and timings presented by the reanalyses. Along with global warming, all reanalyses except JRA55 exhibit obvious downwards trends of Δ T in a spatially non‐uniform way. The median Δ T among the four reanalyses features uniform decreases in all seasons, with the most distinct area on the northern TP, as well as the largest and least decreases in autumn and spring, respectively. Further analysis shows that the differences in Δ T are most likely associated with discrepancies in radiation forcing, snow cover, wind speed, and boundary layer height within the reanalyses. The present findings highlight the difficulty for the state‐of‐the‐art reanalyses to represent the climate change over the TP and point to possible factors behind the deficiencies identified. Abstract : Surface–air temperature difference (Δ T ) is a crucial contributor of sensible heat flux and heating source over the TP that drives the onset and maintenance of Asian summer monsoon. The TP sensible heating has decreased in recent years; however, the contributor Δ T is not well understood. We systematically investigated the TP Δ T in last decades, including the seasonality, inter‐annual variability, and long‐term trends together with the heat source evolutions. Moreover, several possible causes for the discrepancies of Δ T are discussed.