Climatological Characteristics and Observed Trends of Tropical Cyclone–Induced Rainfall and Their Influences on Long-Term Rainfall Variations in Hong Kong

Abstract

his study examines the climatological features of tropical cyclone (TC) rainfall in Hong Kong in association with different TC-related parameters, and investigates the changes in TC rainfall, non-TC rainfall, and total rainfall during the past few decades in Hong Kong. On average, rainfall induced by TCs can account for about 25% of the total precipitation during summer and fall, and the contribution can be even greater in extreme cases. Composite analysis suggests that extreme TC rainfall is often related to TCs in closer proximity to Hong Kong, with higher intensity, and is associated with stronger convection and moisture convergence in the vicinity of Hong Kong.Evaluations of the observed trends of different rainfall indices suggest that the rainfall variability in Hong Kong is considerably affected by the TC rainfall, which has a decreasing trend in frequency and intensity in recent decades. Taking out the TC rainfall from the total rainfall reveals that there is an increasing trend in daily rainfall frequency and intensity for non-TC rainfall in Hong Kong. Moreover, time-dependent generalized extreme value analysis of non-TC rainfall also reveals an increase in the return values of the maximum daily rainfall in Hong Kong. Results of this study suggest that, in order to obtain a more comprehensive picture of the long-term rainfall variations in Hong Kong, the contributions of TC rainfall should definitely be taken into account in the analysis.