Role of Atlantic air–sea interaction in modulating the effect of Tibetan Plateau heating on the upstream climate over Afro-Eurasia–Atlantic regions

Abstract

Previous studies have demonstrated that atmospheric diabatic heating over the Tibetan Plateau (TP) exerts significant influences on the "upstream" climate of the Atlantic-African-European sector in boreal summer. Using the NCAR Community Earth System Model, this study demonstrates that the TP-induced change in North Atlantic sea surface temperature (SST) including evident warming over the mid-latitude North Atlantic and cooling over the south can in turn modulate the above TP impact. Compared with the TP heating experiment without Atlantic SST variation, anomalous wave train pattern appears with north-northeastward downstream influences when the change in Atlantic SST is considered. The wave train pattern is characterized by three positive centers over the North Atlantic, the Arctic Ocean, and east of Japan, and four negative centers over northeastern North America, North Europe, the mid-Atlantic, and the northwestern Pacific. It intensifies the northern portions of the TP-induced tropospheric anticyclones over the extratropical North Atlantic and the cyclones over northeastern North America and North Europe. Correspondingly, precipitation decreases over the northwestern Atlantic but increases over northeastern North America and North Europe. Due to the easterly anomalies on the southern side of the weakened thermal low over subtropical Africa, precipitation over the Sahel decreases, indicating a weakening of TP-induced precipitation dipole over the tropical eastern Atlantic and West Africa when the Atlantic SST influence is considered. Overall, the modulation of Atlantic SST variation accounts for above 20 percent of the upstream climate signals induced by the TP thermal effect.

Land–atmosphere–ocean coupling associated with the Tibetan Plateau and its climate impacts

“…Given the interactive nature between SST and its overlying atmosphere, the North Atlantic SST signals caused by the thermal impact of the TP in turn influence the variations of upstream climate. The feedback of these SST signals accounts for above 20% of the total upstream signals caused by TP heating, as assessed by numerical model experiments with and without Atlantic SST variations [ 17 ]. Compared with experiments in which TP heating is included but Atlantic SST variation is excluded, an anomalous wave pattern characterized by three positive centers (over the extratropical North Atlantic, Arctic Ocean and to the east of Japan) and four negative centers (over the central North Atlantic, North Europe, northeastern North America and northwestern Pacific) appears when Atlantic SST variation is involved.…”

Interannual Impact of the North Atlantic Tripole SST Mode on the Surface Potential Vorticity Over the Tibetan Plateau During Boreal Summer

“…Summer sensible heating and condensational heating over the TP could trigger a prominent potential vorticity (PV) forcing in the westerlies and therefore impact the downstream circulation via Rossby wave dispersion (Wu et al., 2016). In addition to the downstream climate, TP heating would exert a great impact on the upstream climate over West Asia, the Middle East, North Africa, and South Europe via zonal‐vertical overturning circulation and wave train patterns (Lu et al., 2018, 2019; Nan et al., 2019). Besides the thermal forcing, the mechanical effect is also recognized as an important forcing in regulating the climate and weather (e.g., Bolin, 1950; Boos & Kuang, 2013; Charney & Eliassen, 1949; Chiang et al., 2020; Son et al., 2021).…”

“…Some studies suggested that the spring NAT could influence the spring rainfall over southern China (Li et al., 2018) and subsequent summer rainfall over East Asia (e.g., Wu et al., 2009). The climate effect of NAT in winter and spring is the primary interest in the literature (e.g., Cui et al., 2015; Li et al., 2018; Li et al., 2019; Yu et al., 2021). However, research on the climate effects of NAT in summer when the thermal forcing of the TP peaks (Zhao et al., 2018) is still insufficient.…”

A zonally-oriented teleconnection pattern induced by heating of the western Tibetan Plateau in boreal summer

“…The SSHF and LH feature an out-of-phase variation over northern Europe, with a correlation coefficient of − 0.92 between the two heating components over northern Europe, which accounts for the out-of-phase association. Figure 10 shows a broader association between radiative heating and the CGT pattern over North Africa, the Mediterranean Sea, and southern Europe, which can be explained by the westward propagation of the Rossby wave from the TP and ISM region (Yang et al 1992;Rodwell and Hoskins 1996;He et al 2017;Lu et al 2018Lu et al , 2019. This suggests the critical upstream influence of the TP and ISM diabatic heating on North Africa via the propagation of the Gill-type Rossby wave.…”