Analysis of the relationship between precipitation and altitude over central and eastern China based on the Geographically Weighted Regression Model

The relationship between warm season precipitation and altitude over central and eastern China was studied using hourly rain-gauge data from national surface stations of China based on the Geographically Weighted Regression Model. Using the relationship between the two as an objective criterion, the ECMWF-IFS model's performance in predicting precipitation during the warm season in 2017 was also investigated. The main conclusions are as follows. (1) On the whole, the precipitation frequency (intensity) increases (decreases) with altitude over central and eastern China. The significant regional differences in the relationship between precipitation amount and altitude result from the distinct contribution of frequency and intensity in different regions. (2) By comparing the differences in the relationships between different kinds of precipitation events and altitude, it was found that the precipitation amount of short-afternoon precipitation events mainly increases with altitude, which comes from the contribution of the relationship between precipitation frequency and altitude. Meanwhile, the regional consistency of the relationship between precipitation amount of long-nighttime precipitation events and altitude is poor. Compared to short-afternoon precipitation events, there are more stations where precipitation amount decreases significantly with altitude in long-night-time precipitation events. This kind of difference is more pronounced in the stations at the steep terrain around large-scale topography than the stations at the eastern isolated topography. (3) According to the evaluation of the ECMWF-IFS model, it can be seen that the model can well forecast the spatial distribution of the precipitation climate state characteristics during warm season in 2017 over central and eastern China, with high spatial correlation coefficient with observation. But in terms of the prediction of the relationship between precipitation and altitude, the spatial correlation between observation and model forecast is weakened. Furthermore, the model can show the characteristic that precipitation intensity (frequency) mainly decreases (increases) with the increasing altitude. However, the negative (positive) regression relationship between precipitation intensity (frequency) and altitude is weaker (stronger) in model than that in observation.