| Precipitation is the main influencing factor for the regional change of drought and flood,whereas water vapor transport is the key to restricting precipitation.The analysis of water vapor sources and transportation conditions that affect China's“dry and wet”climate conditions are essential for further understanding the temporal and spatial characteristics of regional precipitation.Yunnan Province and Guangxi Zhuang Autonomous Region,which are located in the typical subtropical monsoon zone of China,are used as the study areas.Isotope tracing,Hybrid Single-Particle LagrangianIntegrated Trajectory?HYSPLIT?,and construction of Self-Organizing Feature Map?SOFM?nonlinear classifierare adopted in this study,whichexplore the temporal and spatial variation characteristics of the rainy season precipitation andwater vapor transport processes under different monsoon circulations and the definition of the interactive influence area between them.Furthermore,innovative construction of SOFM nonlinear classifier based on multivariate data,the location of the intersection area of water vapor passage in southwest China and the South China Sea was further clarified and recognized.The differentiation boundary was concluded to be on the east side of Ailao Mountain.Theoretically,this study is helpful for further understanding the formation of drought and waterlogging in China's subtropical monsoon area,and practically,it promotes the strategy formulation of national disaster prevention and reduction.This research was conducted along the general idea of“Precipitation differentiation-Water vapor source-Transportation path-Boundary division of interaction effects of different water vapor.”The main conclusions of this study are as follows:?1?This work identified the characteristics of the beginning of the rainy season and clarified the temporal and spatial pattern of rainy season precipitation.On the basis of ArcGIS,daily precipitation data from 16 meteorological stations from 1971 to 2016were used to differentiate the rainy season time phase pattern of space and time,discuss the interannual and monthly variation trends of the composition characteristics?precipitation,number of days,and intensity?of rainy season precipitation and the differentiation characteristics of the contribution of different levels of precipitation intensity to precipitation,and clarify the contribution of precipitation in the rainy season precipitation spatial correlation characteristics and evolution.From 1971 to 2016,the rainy season precipitation in the study area showed significantly regional differences and was generally bounded by Ailao Mountain.The eastern region enters the rainy season earlier than the western region.The overall trend of precipitation is gradually decreasing from the east and west to the central region.The precipitation intensity fluctuates with time,decreasing from east to west.The precipitation fluctuates with year,and the stability of the eastern region is higher than that of the western region and gradually decreases from east to west.?2?This study revealed the differentiation characteristics of rainfall sources in the rainy season and discussed their interactive influence areas.On the basis of the stable isotope,measured data of hydrogen and oxygen stable isotopes of precipitation in 2014wereused to study the attenuation process of?2H?the thousandth deviation of the deuterium isotope ratio from the standard sample?and?18O?the thousandth deviation of the oxygen 18 isotope ratio from the standard sample?in the entire rainy season and precipitation process and the space pattern of water vapor transport.This study also investigated the rainfall effect and continental effect of hydrogen–oxygen stable isotope spatial mutation in atmospheric precipitation.The spatial distribution pattern of hydrogen and oxygen stable isotopes between the entire rainy season and a typical rainstorm is consistent.The same isotopes of meteoric water vapor from the Bay of Bengal in the southwest and from the South China Sea in the southeast are decreasing from west to east and from east to west,respectively.During the westward migration of the powerful South China Sea monsoon,at the Yunnan Plateau,it encountered the west-bound water vapor of the Bay of Bengal in the vicinity of Honghe and Gejiu after the Bay of Bengal water vapor across Ailao Mountain,which resulted in a rapid reduction of stable isotope values,namely,the spatial boundary features are relatively clear.?3?This research clarified the route and source of moisture transport in the rainy season and revealed the temporal and spatial evolution of moisture transport.On the basis of HYSPLIT,wind direction data from 2013 to 2016 in the GDAS format are used to track the route of moisture transport in each station during the rainy season and the temporal and spatial evolution of moisture contribution to precipitation in all directions on a monthly basis.Combined with cluster analysis,the interaction between southwest water vapor and southeast water vapor is discussed from the rainy season scale.The east and west parts of the study area are affected by the South China Sea water vapor and Bay of Bengal water vapor,respectively.Water vapor from the southwestern direction of the Bay of Bengal had the greatest influence on the rainy season in the western region of the study area.For the rainy season in the eastern region of the study area,water vapor from the southeast of the South China Sea and water vapor from the southwest of the Bay of Bengal are the main influences,namely,the rainy season east of Ailao Mountain is controlled not only by the South China Sea but also by the Bay of Bengal.?4?Constructing an SOFM nonlinear classifier quantitatively described the characteristics of moisture source differentiation in rainy season.Building the quantitative characterization system of water vapor source differentiation for developing a nonlinear classifier?SOFM?based on neural network technology quantitatively described the water vapor source differentiation rule and identified the dividing line in typical subtropical monsoon region of China.The boundary is Ailao Mountain.In the west part of thestudy area,the rainy season is controlled by the Bay of Bengalwater vapor,whereas the rainy season of Red River,Gejiu,and Mengzi in the east of Ailao Mountain are not only affected by the South China Sea water vapor but also significantly affected by the Bay of Bengalwater vapor.However,the east part of Yanshan Mountain was controlled by the South China Sea water vapor.Hence,Gejiu and Mengzi on the east side of Ailao Mountain are the interaction areas between the South China Sea water vapor and Bay of Bengal water vapor in the study area and the boundary between the southwest and southeast summer monsoons.Ailao Mountain plays a controlling role in the division between these monsoons. |
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