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The Role of Free‐Tropospheric Moisture Convergence for Summertime Heavy Rainfall in Western Japan
Author(s) -
Tsuji Hiroki,
Takayabu Yukari N.,
Shibuya Ryosuke,
Kamahori Hirotaka,
Yokoyama Chie
Publication year - 2021
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2021gl095030
Subject(s) - mesoscale meteorology , troposphere , precipitation , climatology , environmental science , atmosphere (unit) , atmospheric sciences , water vapor , boundary layer , convection , planetary boundary layer , meteorology , geology , geography , physics , thermodynamics
The role of vertically integrated water vapor flux convergence (IVFC) in heavy rainfall events in western Japan is investigated by dividing the atmosphere into a boundary layer and free troposphere using the Japan Meteorological Agency's mesoscale gridded analysis product and reanalysis product. Rainfall events are defined by peaks of area‐averaged precipitation. The results show an increase in the free‐tropospheric IVFC more than 15 h before rainfall events, contributing to atmosphere moistening. This preceding moistening is favorable for mesoscale convective systems (MCSs) with slantwise ascending deep inflow layers (layer lifting) that produce large precipitation amounts. Appearance frequency of the moist absolutely unstable layer (MAUL) increases around the precipitation peak times, which is especially notable for larger peaks. These results indicate that the free‐tropospheric IVFC contributes to heavy rainfall in western Japan by providing environments favorable for producing and maintaining MAUL, enhancing the organization of MCSs.