Extreme heat event over Northwest China driven by Silk Road Pattern and its possible mechanism

Under the backdrop of global warming, heat events have become increasingly frequent and have garnered significant attention.  Northwest China, situated in the drylands of central Eurasia, exhibits a climate and ecological environment that is particularly vulnerable to global warming compared to other regions.  Over the past few decades, the frequency of heat waves in Northwest China has markedly increased, yet their underlying causes remain unclear.  Our research indicates that heat events in Northwest China are closely associated with the Silk Road teleconnection Pattern (SRP), where the occurrence of heat waves frequently corresponds to the strongly positive phase of SRP.  Furthermore, using the Linear baroclinic model, we determined that the wave source of SRP originates from the North Atlantic Ocean.  To explore the possible mechanism, we selected an extreme heat event in Northwest China in 2021 as a typical case study.  The regressed circulation fields to daily SRP were highly consistent with the anomalies observed during July 9–22, 2021, suggesting that the diurnal propagation of SRP modulates the circulation anomaly associated with the heat wave event.  Diabatic heating influenced by SRP was identified as the primary factor contributing to the thermal low over Northwest China.  Specifically, diabatic heating in the lower troposphere was intensified due to enhanced downward shortwave radiation and surface sensible heat flux, accompanied by strong descending motions and reduced cloud cover induced by an anticyclone guided by SRP over Northwest China.  This study enhances our understanding and confidence regarding the effects of large-scale circulation on local temperature anomalies in mid-latitudes.