Abstract
The Haihe River basin of North China is characterized by extremely low per capita water resources and a consistently long-term decreasing trend of precipitation and runoff over the last few decades. This study analyzes the climatological features of rainy season (May–September) precipitation in the Haihe River basin and its branch systems based on a high-density hourly observational dataset during 2007–2017. We show that there are two high-rainfall zones in the basin, with one along the south of the Yanshan Mountains to Taihang Mountains and another along the Tuma River in the south. Rainstorm centers exist amidst the two zones. July generally sees the highest precipitation, followed by August, and May has the lowest precipitation. The major flood season is reached between the third pentad of July and the fourth pentad of August. The precipitation is high at night but low in the daytime. In the pre-flood season before early July, rainfalls mostly arrive at 16:00–21:00 h. After entering the major flood season, the diurnal precipitation has two peaks, one at 17:00–22:00 h and the other at 0:00–7:00 h. In the post-flood season after mid-August, the most rain occurs at night, with the peak appearing at 0:00–8:00 h. The short-duration precipitation is mainly distributed in the mountainous areas, and the long-duration precipitation that contributes most to seasonal rainfalls appears in the plain areas, and the continuous precipitation mostly occurs in the windward slopes of the Taihang Mountains and the Yanshan Mountains. In addition, urbanization process around large city stations may have affected the rainy season precipitation to a certain extent in the Haihe River basin, with large and medium city stations experiencing around 10% higher precipitation than small city stations. However, this issue needs to be investigated exclusively.
Highlights
The Haihe River is the largest river in North China
The long-duration and continuous precipitation amounts contribute more to rainy season rainfalls than the short-duration precipitation, indicating that the continuous precipitation caused by the large-scale circulation of the East Asian summer monsoon has a greater impact on the precipitation in the Haihe River basin
The highest-rainfall zone in the basin is found on the windward slope of the Yanshan Mountains, with the rainy season precipitation exceeding 520 mm on average
Summary
The Haihe River is the largest river in North China. Beijing, the capital of China, and Tianjin, a municipality directly under the central government, are both located in the river basin. The basin is located in the northern rim of summer monsoon activities, which enables the monsoon weather systems to influence the precipitation in the flood season [6,7]; On the other hand, it is affected by the westerly circulation system at mid-high latitudes [2,8,9] These factors lead to uneven spatial and temporal precipitation in the basin, aggravating the difficulty and uncertainty of water resources exploitation. The high-density hourly precipitation observation data, which have been developed recently by the China Meteorological Administration, are used for the first time to analyze the refined spatial-temporal structure of precipitation with different durations in the Haihe River basin. The analysis reveals several novel features of precipitation in the basin, which is expected to lend support to a scientific understanding of the dynamic variations of atmospheric precipitation, surface and underground water resources in the region severely short of water
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