Possible Influences of Mineral Dust Aerosols on Summertime Heavy Precipitation in the Taiwan Region

Taiwan is known to be highly influenced by heavy precipitations in summer. Located in the East Asia, Taiwan region is influenced by the long-range transported mineral dust from Mongolia, Northwestern China and the Middle East. Previous studies suggest that mineral dust can affect cloud and precipitation by serving as ice nuclei. The effects of dust on cloud properties and precipitation in July are analyzed over Taiwan region from 1989 to 2015, using precipitation observations, ERA‐Interim reanalysis and dust number concentration simulation by a global chemical transport model with size-resolved particle microphysics (GEOS-Chem/APM). The results show that, in the middle (C1) and southern (C2) parts of Taiwan, the orographic precipitations have high correlations (R_d-p >0.6) with dust number concentration (N_d,D>500nm) at 4 km level, and R_d-p is highly influenced by the wind direction. The long‐term statistical result show that, under the similar meteorological conditions (wind direction, wind speed and total column water vapor), precipitations in C1 and C2 increase with N_d,D>500nm, and the enhancement mainly happens in day-time (from 04:00 to 16:00). Compared to the average values during all July days, the mean liquid water path (LWP) and ice water path (IWP) on the top 10% dust event days increased by 43% and 42% (C1), 37% and 31% (C2), respectively. At the same time, the mean total column water vapor (TCWV) does not show obvious differences, which suggests that the enhanced precipitation and cloud water path is not caused by meteorological conditions (wind or water vapor). TCWV gradient along the wind direction (TCWV_upwind - TCWV_downwind) in different dust event days indicate that more atmospheric water vapor turns into cloud water with higher N_d,D>500nm, leading to the increasing precipitation.