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

Abstract

Abstract. Previous observational evidence and numerical simulations have revealed that the surface sensible heating in spring (March–April–May, MAM) over the Tibetan Plateau (TPSH) can affect the Asian regional hydrological cycle, surface energy balance, and climate through altering atmospheric heat source of the Tibetan Plateau (TP). This study aims to investigate the impacts of MAM TPSH on the interannual variability of East Asian dust cycle by using CAM4-BAM (version 4 of the Community Atmosphere Model coupled to a bulk aerosol model), MERRA-2 (version 2 of the Modern-Era Retrospective analysis for Research and Applications) surface dust concentration, and TPSH measurements. Our simulations show that the surface dust concentrations over the East Asian (EA) dust source region and over the northwestern Pacific (NP) in MAM are significantly positively correlated with TPSH, with regionally averaged correlation coefficients of 0.49 for EA and 0.44 for NP. Similar positive correlations are also shown between the MAM TPSH measurements averaged over the 73 observation sites and the surface dust concentration from MERRA-2. Simulation-based comparisons between strongest and weakest TPSH years reveal that, the MAM surface dust concentration in the strongest TPSH years increases with relative differences of 13.1 % over EA and 36.9 % over NP. These corresponding differences are found in MERRA-2 with 22.9 % and 13.3 % over EA and NP, respectively. Further simulated results show that the processes of whole dust cycles (e.g., dust loading, emission, and transport, as well as dust deposition) are also significantly enhanced during the strongest TPSH years over EA and NP. Through enhancing the TP heat source, stronger TPSH in MAM generates an anticyclonic anomaly in middle and upper troposphere over the TP and over the downstream Pacific region, respectively. These atmospheric circulation anomalies induced by the increased TPSH result in increasing the westerly winds over both EA and NP, which in turn increases dust emissions over the dust source, and dust transport over these two regions, as well as the regional dust cycles. These results suggest that addressing the East Asian dust changes in the future climates requires considering not only increasing greenhouse gas emissions but also the variations of the TP's heat source under global warming.

Detecting upland glaciation in Earth’s pre-Pleistocene record

“…In the winter, the Tibetan Plateau's strength as a heat sink is proportional to snow cover, resulting in lower geopotential height and a stronger jet stream (e.g., Li et al, 2018). However, spring dust storm activity is dependent on positive spring sensible Frontiers in Earth Science frontiersin.org heat flux, so lower snow cover should lead to increased west Chinese dust storms (Xie et al, 2020). Therefore, we would hypothesize that lowered ELA and more widespread Tibetan Plateau glaciation would tend to transform the Tibetan Plateau into a year-round heat sink, suppressing the monsoonal circulations around it and favoring year-round cyclonic circulation aloft.…”

Dominant Modes of Tibetan Plateau Summer Surface Sensible Heating and Associated Atmospheric Circulation Anomalies

“…In the preceding spring, the variability of SH over the TP is well connected to the onset of the East Asian summer monsoon, as well as the precipitation anomalies of East China [14,15]. In addition, the interannual variation of SH can regulate surface dust concentrations over the East Asian dust source region and the northwestern Pacific through increasing the westerly winds [16].…”

Spatiotemporal trends and impact factors of PM<sub>2.5</sub> and O<sub>3</sub> pollution in major cities in China during 2015–2020

“…这与人为排放强度的时 空分布也体现出一致性 [36,37] , 为此进一步指出了区域人为减排对降低城市大气 PM 2.5 浓 度有直接的关联, 也进一步证明了我国近年严格的人为减排措施的实施对持续改善空气 质量有重要的作用. 然而, 对于我国西部极少数城市和地区(例如在新疆等地区)大气 中 PM 2.5 质量浓度并未呈现非常显著的下降趋势, 造成这一结果可能是在这些城市中大 气 PM 2.5 同时也受到非人为排放源(例如沙尘)的影响 [38] . 污染的重要原因之一 [17,21] .…”

“…在我国北部城市, 例如北京, 很多研究已发现液相化学过程是贡献冬 季 PM 2.5 的重要途径 [7, 39~42] , 即可导致 PM 2.5 与 MDA8-O 3 呈负相关或削弱的相关性. 此 外, 华北地区人为源(如燃煤) [43,44] 和自然源(如沙尘) [45] 的一次排放和对 PM 厚度水平 [46] 和沙尘排放 [38,45] 的地理分布高度一致. 由此可推断, 造成这一现象的原因可 能是在这些地区受沙尘的重要影响, 如沙尘天气中 PM 2.5 一次组分(即沙尘气溶胶)贡 献较高 [5,45] .…”