Current AMO mitigating extreme high temperatures in Central Asia under global warming

Abstract

AbstractUnder global warming, extreme high temperatures (EHTs) have become frequent and enhanced around the world. However, we found that the frequency and intensity of EHTs in Central Asia (CA) are decreasing over the last four decades when the effects of climate warming are removed. From 1979 to 2020, an interdecadal shift in CA's EHTs occurred around the mid‐1990s, preceded by high values (1983–1997) and followed by low values (1998–2016). The observational analysis and numerical simulations using National Center for Atmospheric Research Community Atmosphere Model version 5.3 both demonstrate that the phase transition of Atlantic multidecadal oscillation (AMO) has an important influence on this interdecadal shift. During 1998–2016, the AMO was in a positive phase (+AMO), meaning warmer sea surface temperature anomalies (SSTA) in the North Atlantic, which could lift the geopotential height and cause anticyclonic circulations over the basin. Through the cyclonic–anticyclonic circulation alternating teleconnection wave train over Eurasia, the atmospheric system over the North Atlantic could induce cyclonic circulations and reduce the geopotential heights over CA, that is, weaken the high pressure at the upper level, which is not conducive to warming and EHTs in CA. For the −AMO period (1983–1997), due to the similar atmospheric response mechanism, the negative SSTA in the North Atlantic and the wave train with reversed anomaly centres can be found, causing anticyclonic circulations and rising geopotential heights over CA. The high pressure at the upper level in CA would be strengthened, leading to favourable EHT conditions. Overall, we conclude that the current AMO (+AMO) has a mitigating role on the EHTs of CA, and the findings also emphasize that if the future AMO shifts to a negative phase, the EHTs of CA may worsen than at present.