Spatial and temporal precipitation patterns using the CMOPRH CRT product over the Taihang Mountains

In order to effectively use precipitation over the Taihang Mountains, and to perform water resource management and ecological construction scientifically, we used satellite precipitation data to explore the spatio-temporal precipitation pattern and precipitation trend over the Taihang Mountains from 1998 to 2017. In general, the complex terrain and sparse meteorological stations lead to limited precipitation measurement in mountainous areas especially in high-altitude regions. Satellite-based precipitation measurement is an effective supplement for measuring precipitation information in such regions. The CMOPRH CRT product is recognized worldwide. A previous study had proved the applicability of CMORPH CRT over the Taihang Mountains owing to the lower root mean square error and relative bias in this region, which indicated that this product had applicability over the Taihang Mountains. Therefore, in this study, we adopted the method of time series analysis and trend analysis to explore the spatial and temporal patterns of precipitation and precipitation trend over the Taihang Mountains based on the data obtained using the CMORPH CRT product from 1998 to 2017. Meanwhile, the ground observations of 18 rain gauges were used to validate the precipitation trend measured using the CMOPRH CRT product over the Taihang Mountains with "Pixel to Point" extraction method via ArcGIS. The results showed that there was no significant variation trend in the annual and seasonal precipitation from 1998 to 2017 over the Taihang Mountains. Higher precipitation occurred in the southern and eastern regions of the Taihang Mountains than in the northern and western regions. On a monthly scale, the precipitation in July accounted for the highest rate of annual precipitation, 7.2%-32.4% of the total annual precipitation, followed by August and June. There was a decrease trend in the south and northwest regions of the Taihang Mountains, and decreased by 2-6 mm·a^-1 on an average. The increasing precipitation trend appeared in the western and northern regions of the Taihang Mountains, and the annual precipitation increased by more than 8 mm. The greatest difference in precipitation trend was found in July on a spatial scale with a variation range of -8.6 to 8 mm·a^-1. We used actual data obtained using rain gauges to validate the precipitation trend measured using CMORPH CRT. Two sets of data showed a strong significant correlation at the annual scale. On the seasonal scale, the precipitation trend in winter (dry season) and summer (wet season) had a strong significant correlation with the precipitation trend measured using rain gauges, but the precipitation trend in spring and autumn did not show a significant correlation with the precipitation measured using rain gauges. We extracted the pixel values according to the spatial pattern of precipitation trend from 1998 to 2017 over the Taihang Mountains, and further divided them into six different precipitation trend (PT) ranges (PT ≤ -5 mm·a^-1, -5 mm·a^-1 < PT ≤ 0 mm·a^-1, 0 mm·a^-1 < PT ≤ 5 mm·a^-1, 5 mm·a^-1 < PT ≤ 10 mm·a^-1, 10 mm·a^-1 < PT ≤ 15 mm·a^-1, and PT ≥ 15 mm·a^-1) depending on the actual precipitation trend over study areas. There was a significant increase in precipitation from 1998 to 2017 in the PT > 5 mm·a^-1 area.