Spatiotemporal changes in heavy precipitation events in the Beijing-Tianjin-Hebei region revealed by hourly meteorological station observations

Abstract

Changes in heavy precipitation events (HPEs) are closely related to hydrological disasters, such as floods and urban water logging. This study investigated the spatiotemporal changes in HPEs by using hourly precipitation data from the warm season (from May to September) from 1980 to 2016 in the Beijing-Tianjin-Hebei (BTH) region. Sen’s slope estimator and the modified Mann-Kendall test were used to detect the temporal trend. A circular statistical approach was used to analyze the diurnal distribution of HPEs. The study found that the temporal changes in the HPEs in the BTH region could be divided into three stages: 1980–1994, 1994–2002, and 2002–2016. The first period and the last period witnessed an increase in the frequency and maximum intensity of HPEs, while the second period experienced a decreasing trend in the frequency and maximum intensity of HPEs. By comparing the HPEs in the first and last periods, the study revealed that the short-duration HPEs (HPEs of 1–6 h in duration) became more frequent and more extreme, while the long-duration HPEs (HPEs lasting longer than 6 h) became less frequent and less extreme. In addition, the study found that the peak time of the short-duration HPEs occurred from 19:00 local standard time (LST) to 24:00 LST; however, the peak time of the long-duration HPEs occurred from 01:00 LST to 06:00 LST. Moreover, the peak time of short-duration HPEs tended to be more concentrated than that of long-duration HPEs. Because an increasing number of short-duration HPEs occurred in the period of 2002–2016, the peak time of the HPEs in the BTH region was delayed and more concentrated. Local temperature showed an obvious correlation with the changes in HPEs at the decadal timescale. Our study provided useful information about spatiotemporal changes in precipitation events at the sub-daily scale in the BTH region.