Gaoyuan qixiang (Feb 2024)
Progress of the Evolutionary Characteristics of Autumn Rain in Western China and Its Anomalous Mechanism for the Past 20 Years
Abstract
Autumn rain in western China is a unique and complex precipitation phenomenon that takes place during the autumn season in the western region of China， which is closely related to various aspects of economy， society and human life.This natural phenomenon has a profound impact on agriculture， transportation and other aspects of social production and life， sometimes even causes the phenomenon of autumn flood， which deserves full attention.Based on the basic understanding of the phenomenon in the 20th century， this paper compares and reviews the main research achievements of autumn rain in western China over the past 20 years from multiple perspectives.First of all， the spatial distribution range and temporal extent and precipitation intensity of autumn rain in West China are thoroughly explored， quantitative criteria and indexes such as ARI （Autumn Rain Index）， DARI （Daily Autumn Rain Index） and MARI （Modified Autumn Rain Index）are also proposed.In addition to this， the significant interannual differences， the "positive - negative - positive" interdecadal variations and the 4~8 years cycle of autumn rain in western China fully demonstrate its complexity and inhomogeneity.Secondly， the different but important influences of atmospheric circulation systems at low， middle， and high latitudes， tropical sea temperature forcing including Pacific Ocean， Indian Ocean， and Atlantic Ocean as well as the Qinghai-Xizang （Tibet） Plateau effect and other aspects on the autumn rain in western China are pointed out.These different factors all play significant roles in the evolution of the phenomenon， but the mechanisms are different.This leads to the recognition of the significance of the multi-system and multi-factor synergistic effect on the anomalous evolution of autumn rain in western China， which enriches the understanding of the autumn rain and its impact.Finally， according to the current cognition of autumn rain in western China， the main problems that exist in the combination of different monsoon systems like Indian monsoon， East Asian monsoon and Plateau monsoon， cold and warm air currents， evolution causes， weather processes， night rain characteristics， regional responses to the global warming and other aspects are pointed out.These problems highlight the challenges that researchers face in studying this complex phenomenon.However， despite the challenges， there are several promising areas for future research.The main development trend in the future about the research of autumn rain in western China is the comprehensive and elaborate analysis of the multi-scale synergy of autumn rain in western China and its physical mechanism under the complex and important topography of Qinghai-Xizang （Tibet） Plateau.
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