Rainfall processes can be classified by the relative timing of their intensity peak into Early-peaking and Late-peaking patterns, yet their contrasting diurnal behaviors and controlling environments remain insufficiently understood. Using hourly rainfall gauge observations and reanalysis data for June–September 2018–2022, this study investigates the diurnal differences between Early- and Late-peaking summer localized rainfall over the Yangtze–Huai River Basin (YHRB) and links them to large-scale atmospheric circulation. Early-peaking rainfall processes reach their maxima primarily in the afternoon and are characterized by shorter duration and higher intensity, whereas Late-peaking rainfall processes peak mainly in the early morning and feature longer duration with comparatively weaker intensity. Early-peaking rainfall is driven mainly by local thermodynamic instability. Prior to onset, the lower troposphere is warm and moist, accompanied by a pronounced dry layer in the mid-level. In contrast, Late-peaking rainfall is dominated by dynamic forcing, with near-surface vertical wind shear about twice that of Early-peaking rainfall, accompanied by a deep moist layer. Convective development height is also greater in Late-peaking rainfall than that in Early-peaking rainfall. This study provides an observational perspective for understanding localized summer rainfall over the YHRB. 根据降水强度峰值在降水生命史中的出现时间可将降水过程划分为前峰型和后峰型降水, 但目前对这两种降水类型的日变化特征及其环境条件的认识较为有限.本研究基于2018-2022年6-9月逐小时降水观测和再分析资料, 探讨江淮地区夏季局地降水中前峰型和后峰型两类降水的日变化特征及其环境条件差异.前峰型降水峰值主要出现在午后, 呈现出持续时间短,降水强度大的特征, 而后峰型降水峰值则主要出现在清晨, 呈现出持续时间长,降水强度相对较小的特点.前峰型降水主要由局地热力不稳定驱动, 发生前大气低层具备高温高湿特征, 且中层存在明显的干层.后峰型降水则主要受大气动力强迫, 近地面垂直风切变约为前峰型的2倍, 并伴有深厚湿层以及更高的对流发展高度.结论为理解江淮地区夏季局地降水提供了新的观测依据
Zhang et al. (Wed,) studied this question.