Response of the Asian summer Monsoons to a high-latitude thermal forcing: mechanisms and nonlinearities

Abstract

This study investigates mechanisms and nonlinearities in the response of the Asian Summer Monsoons (ASM) to high-latitude thermal forcings of different amplitudes. Using a suite of runs carried out with an intermediate-complexity atmospheric general circulation model, we find that the imposed forcings produce a strong precipitation response over the eastern ASM but a rather weak response over the southern ASM. The forcing also causes a precipitation dipole with wet conditions over the eastern Tibetan Plateau (TP) and dry conditions over the Bay of Bengal (BoB) and southeast Asia. A moderate increase of precipitation along the southern margin of the TP is also produced. Simulations designed to isolate the causal mechanisms show that thermodynamic interactions involving the tropical surface oceans are far less important than the water-vapour feedback for the transmission of information from the high-latitudes to the ASM. Additionally, we assess the nonlinearity of the ASM precipitation response to the forcing amplitude using a novel application of the empirical orthogonal function method. The response can be decomposed in two overlapping patterns. The first pattern represents a precipitation dipole with wet conditions over the eastern TP and dry conditions over BoB, which linearly increases with forcing amplitude becoming quasi-stationary for large forcing amplitudes (i.e. amplitudes leading to Arctic temperature anomalies larger than 10 °C). The second pattern is associated with increased precipitation over the southeastern TP and is nonlinearly dependent on forcing, being most important for intermediate forcing amplitudes (i.e. amplitudes leading to Arctic temperature anomalies between 5 and 10 °C).

The monsoon hydroclimates in HadGEM3 model configurations GA3.0 and GA4.0: Impact of remote versus local circulations errors and horizontal resolution

“…We argue that this is crucial to improve the credibility of climate predictions and projections of future GM changes, and to increase the confidence that model development chains seen to improve performance in individual monsoon region are doing so by modelling accurately climate processes underpinning the GM variability. Thus, refining the understanding of climate model's uncertainty is an important step to mitigate the impact of monsoon-dominated climate extremes on human and natural systems, for a large population, mostly in developing countries (Cerezo-Mota et al, 2016;Novello et al, 2017;Chang et al, 2018;Huang et al, 2018;Mishra et al, 2018;Talento et al, 2020).…”