资源环境科技发展态势分析平台

No tropical cyclone (TC) formed over the western North Pacific (WNP) in July 2020, which is record-breaking. Some recent studies suggested that this extreme event was mainly caused by the strong WNP subtropical high (WNPSH) in July 2020, which might not be the only reason. In this study, results from statistical and composite analyses indicate that the strong WNPSH, the strong South Asian high, the westward extended tropical upper-tropospheric trough, and the weak South Asian summer monsoon are all detrimental to TC genesis over the WNP and might contribute to the absence of TCs in July 2020. Results from sensitivity experiments using a regional atmospheric model that can resolve TCs further demonstrate that it was the collective effect, not any of the individual large-scale circulation anomalies, that induced the extremely unfavorable conditions for TC genesis and thus led to the record-breaking inactive TC month.