Abstract
The statistical characteristics of precipitation play important roles not only in flood and drought risk assessments but also in water resource management. This paper implements a statistical analysis to study the spatial and temporal variability in precipitation in the upper reaches of the Hongshui River basin (UHRB), southwestern China, by analysing time series of daily precipitation from 18 weather stations during the period of 1959 to 2015. To detect precipitation concentrations and the associated patterns, three indices, the precipitation concentration index (PCI), precipitation concentration degree (PCD), and precipitation concentration period (PCP), were used. The relationships between the precipitation concentration indices (PCI, PCD, and PCP) and geographic variables (latitude, longitude, and elevation), large-scale atmospheric circulation indices, and summer monsoon indices were investigated to identify specific dependencies and spatial patterns in the precipitation distribution and concentration. The results show that high PCI values were mainly observed in the northeastern portion of the basin, whereas low PCI values were mainly detected in the southwest. The Mann-Kendall test results demonstrate that the majority of the UHRB is characterized by nonsignificant trends in the PCI, PCD, and PCP from 1959 to 2015. The PCP results reveal that rainfall in the UHRB mainly occurs in summer months, and the rainy season arrives earlier in the eastern UHRB than in the western UHRB. Additionally, the PCD results indicate that the rainfall in the western UHRB is more dispersed throughout the year than that in the eastern UHRB. Compared with other geographical factors, longitude is the most important variable that governs the spatial distribution and variations in annual precipitation and the precipitation concentration indices. Due to a combination of topography, the Indian subtropical high, and monsoon weakening, precipitation may be more concentrated in one period, especially in the eastern part of the basin, which increases the risk of drought.
Highlights
As temperatures increase, the amount of water vapour in the atmosphere increases and the temporal and spatial distributions of precipitation change, resulting in large precipitation differences in different regions of the world [1,2,3]
This study investigates the spatial distribution of the precipitation concentration index (PCI), precipitation concentration degree (PCD), and precipitation concentration period (PCP) based on daily precipitation data and identifies and quantifies PCI, PCD, and PCP trends and the associated spatial and temporal patterns across the upper reaches of the Hongshui River basin (UHRB) from 1959 to 2015
PCI values were estimated for all stations throughout the Hongshui River basin from 1959 to 2015
Summary
The amount of water vapour in the atmosphere increases and the temporal and spatial distributions of precipitation change, resulting in large precipitation differences in different regions of the world [1,2,3]. Precipitation patterns are expected to spatially and temporally change around the world due to an increase in the water-holding capacity of the air, which in turn results in the acceleration of the hydrological cycle and affects the spatiotemporal characteristics of precipitation [4,5,6]. Both global [7] and regional [8, 9] precipitation characteristics have changed due to the influence of climate change and intensified human activities. Information regarding the changing patterns of precipitation is important for the accurate assessment of water resources, drought and flood control, efficient water management, and the understanding of climate change [24]
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