Effects of convection over the Tibetan Plateau on rainstorms downstream of the Yangtze River Basin

Abstract

This study investigated the effect of convection over the Naqu region of the central Tibetan Plateau (TP) on rainstorms in the downstream areas of the Yangtze River Basin (YRB) accompanied by water vapor transport during August 15–19, 2014. The hourly maximum C-band frequency-modulated continuous-wave (C-FMCW) radar echo intensity at Naqu obtained from the Third Tibetan Plateau Atmospheric Scientific Experiment (TIPEX-III) was applied to represent local convective motion during this rainstorm process. Results based on hourly rain-gauge station data, National Centers for Environmental Prediction (NCEP) Final (FNL) Operational Global Analysis data, and Weather Research and Forecasting (WRF) simulations revealed that convection at Naqu was a strong signal over the TP. Convection over the Naqu region could impact rainstorms in the middle and lower reaches of the YRB via a three-dimensional water vapor flux vortex (WVFV) structure with high-level divergence and low-level convergence. The eastward propagation of the WVFV structure would enhance convection and thereby develop rainstorms downstream of the YRB. A FLEXible PARTicle (FLEXPART) dispersion model tracked the trajectory of air masses originating from the TP toward the middle–lower reaches of the YRB, which supported the robustness of the diagnostic results.