Unveiling the differential effects of typhoon Doksuri and Khanun on the 2023 Beijing–Tianjin–Hebei extreme rainfall

A substantial number of severe convective storms caused flash flooding across Beijing–Tianjin–Hebei area(BTHA) from July 29th to August 1st, 2023. The prevailing view concerning the roles of the two typhoon, Doksuri and Khanun, posits that either both typhoons are of significant importance or the remnant of Doksuri play a predominant role. However, there is a lack of definitive analysis and evidence to substantiate the specific differential impacts of these two typhoons on this particular event. This article reveals that both Typhoon Doksuri and Khanun play crucial roles in the transportation of water vapor. Typhoon Doksuri primarily exerts its influence on the southern region of BTHA, whereas Typhoon Khanun predominantly affects the northern region. Water vapor below 925 hpa plays a dominant role in the southern region. Further analysis indicates that the impact of Typhoon Doksuri on the southern region stems from the fact that the typhoon nearly dissipated on the 31st, with less water vapor reaching the northern region. Meanwhile, Typhoon Khanun intensified on the 30th and 31st, primarily influencing the northern region through the key water vapor channel(120–125°E;5–30°N). Consequently, the distinct water vapor sources influenced by the typhoons in these two regions determine their varied responses to global warming.