Trend in the atmospheric heat source over the central and eastern Tibetan Plateau during recent decades: Comparison of observations and reanalysis data

Abstract

The trend in the atmospheric heat source over the central and eastern Tibetan Plateau (CE-TP) is quantitatively estimated using historical observations at 71 meteorological stations, three reanalysis datasets from 1980-2008, and two satellite radiation datasets from . Results show that a weakening of sensible heat (SH) flux over the CE-TP continues. The most significant trend occurs in spring, induced mainly by decelerated surface wind speeds. The ground-air temperature difference shows a notable increasing trend over the last 5 years. Trends in net radiation flux of the atmospheric column over the CE-TP, evaluated by two satellite radiation datasets, are clearly different. Trends in the atmospheric heat source calculated by the three reanalysis datasets are not completely consistent, and even show opposite signals. Results from the two datasets both show a weakening of the heat source but the magnitude of one is significantly stronger, whereas an increase is indicated by the other data. Therefore, it is challenging to accurately calculate the trend in the atmospheric heat source over the CE-TP, particularly from the estimates of the reanalysis datasets. The Tibetan Plateau (TP) is situated on the subtropical eastcentral Eurasian continent. It is the highest (average elevation > 4000 m) plateau in the world, with complex topography and surface conditions. As a strong heat source, the plateau directly heats the middle troposphere [1][2][3]. In spring, sensible heat (SH) dominates the atmospheric heat source over the TP and works efficiently as a huge air pump [4], for not only the onset and maintenance of the Asian summer monsoon [5], but also for the development of weather systems over east China [6] and even the boreal summer climate pattern [6,7]. Changes in the thermal condition of the TP and the atmospheric circulation in East Asia are closely related [8]. Zhao and Chen [9] investigated the atmospheric heat source over the TP and its relationship with rainfall in China, and concluded that this heat source in spring may be regarded as a good indicator of a summer precipitation anomaly in east China. They also showed that it had a clear positive correlation with summer precipitation in the middle and lower reaches of the Yangtze River. Bai et al.[10] confirmed these results. Duan and Wu [11] pointed out that it is not adequate to study the influence of TP thermal forcing on the climate with an area-averaged heating index, because of the large area and various climate types of the TP. Under a global warming scenario, TP warming is powerful, and the warming trend is much greater than surrounding regions at the same latitudes [12][13][14][15]. The thermal condition of the TP is an important influence on atmospheric circulation, climate change and long-term weather processes. The relationship between TP heating and variability

Characterizing the surface radiation budget over the Tibetan Plateau with ground‐measured, reanalysis, and remote sensing data sets: 2. Spatiotemporal analysis

“…Such changes have invited crucial questions, such as how atmospheric variations and surface changes impact the SRB over the TP, how the decadal dimming and brightening affect the environment and climate [ Wild , ], how the SRB over the TP responds to rapid warming [ Qin et al ., ], and how the SRB and latent and sensible heat fluxes over the TP are related to the East Asian monsoon climate [ Duan et al ., ; Wu et al ., ]. However, few studies have attempted spatiotemporal characterization of the SRB components over the entire TP in recent decades, for several reasons: limited sites for ground measurement [ Stone , ; Bookhagen , ], poor accuracy of remote sensing products [ Pinker et al ., ], and inconsistent trends derived from multiple reanalysis products [ Tang et al ., ; Wang et al ., ]. Part 1 of this two‐paper series described an effective data fusion method that synthesized ground observations, reanalysis products, and remote sensing data sets at 0.5° spatial resolution from July 1983 to December 2007 with RMSEs <20 Wm −2 for radiation fluxes and 0.05 for albedo.…”

Modulation of surface sensible heating over the Tibetan Plateau on the interannual variability of East Asian dust cycle

“…Increasing greenhouse gas can significantly influence the global and regional dust cycle through affecting the climate, veg- 25 etation and dust-climate feedbacks although there exists large uncertainty in the response of the global dust loading to future climate change (Harrison et al, 2001;Tegen et al, 2004;Mahowald et al, 2006;Kok et al, 2018). Additionally, the surface sensible flux over TP exhibits a remarkable weakening trend under global warming, induced primarily by weakened surface wind speeds (Duan et al, 2011;Wang et al, 2012;Yang et al, 2014). Our study shows the importance of the TPSH on the change in East Asian dust cycle through affecting the westerly winds.…”

Recent recovery of the boreal spring sensible heating over the Tibetan Plateau will continue in CMIP6 future projections

“…According to previous studies (Monin and Obukhov 1954, Duan and Wu 2008, Wang et al 2012, Duan et al 2018b, SH can be calculated by the following equation:…”

“…In recent years, the SH over the TP has been proved to be undergoing a decreasing trend, especially in spring season (Duan and Wu 2008, Wang et al 2012, Wang and Ma 2018. Duan and Wu (2008) suggested that this weakening trend in SH was induced mainly by the steadily decreased surface wind speed, which was linked to climate warming (Duan and Wu 2009).…”