The Remote Effect of Binary Typhoon Infa and Cempaka on the “21.7” Heavy Rainfall in Henan Province, China

Abstract

AbstractIn this study, the effect of binary Typhoons Infa and Cempaka on the “21.7” heavy rainfall event over Henan Province in China is investigated based on numerical simulations. According to the rain gauge data, the temporal‐spatial distribution of precipitation in the targeted area and the large‐scale circulation in the control run show reasonable agreement with the observations. By separately excluding the relative circulation of Typhoon Infa (N_Infa) and Cempaka (N_Cempaka) at initialization, less convergence of water vapor flux within the targeted area is obtained, leading to a reduction in accumulated precipitation and rainfall intensity, especially for the mid‐to‐late raining period. Plenty of moisture mainly comes from the south and east of the rainfall region. In terms of the 60‐hr back trajectories, an overwhelming proportion of moist air parcels entering the targeted area at 850 hPa is transported along the easterly flow, which prevails between Typhoon Infa and the subtropical high. A growing proportion of air parcels advected from the south band highlights the nonnegligible effect of Typhoon Cempaka and the southwesterly flow to water vapor supply at relatively higher levels. Additional test by excluding both typhoons at initialization (N_Infa&Cempaka) suggests the complicated interaction between binary typhoons and the surrounding large‐scale circulation (such as subtropical high) may influence the initiation and development of mesoscale convection in the targeted area. With the enhancement of convergence by southwesterly and easterly flow at the lower layer from N_Infa&Cempaka, larger accumulated precipitation is obtained with the shifted location of extreme rainfall compared to that from N_Infa.