Spatial interpolation of monthly average air temperature during winter-spring season using sparse samples: A case study in Manas River Basin in Xinjiang
For preparation of air temperature spatial data used in the simulation of snow cover to snow melting process in the Manas River Basin with sparse meteorological stations in the middle part of Tianshan Mountains, Xinjiang, this paper carried out the analysis of environmental variables influencing air temperature in winter and spring (2015-11-2016-04) using least square correlation method so as to determine the optimal set of environmental variables through collinearity detection. Here the optimal factor set is composed of five environmental variables: latitude, elevation, NDVI, terrain slope and aspect. Then the Generalized Regression Neural Network (GRNN) model was constructed for spatial interpolation of monthly mean air temperature. Finally, the proposed GRNN model was trained with observation data of 119 stations among the total 139 in the region, and the spatial interpolation model of monthly air temperature for the six months in winter and spring were determined. Also the regression error of the proposed model was analyzed with Root Mean Square Error (RMSE) and the Mean Relative Error (MRE) as measures using the rest observation data of 20 stations as test samples. Results show that the averagely RMSE value of this model is 1.46 in six months, which is superior to the traditional GWRK method with an average RMSE value of 2.22. In addition, from the spatial interpolation maps of air temperature of 6 months, the varying trend of the interpolated air temperature using our model is consistent with that of actual circumstances. The temperature of each spatial site is positively correlated with its elevation, and varies with the type of surface coverage. In summary, the proposed GRNN model with combination of interpolation strategy has shown an improved interpolation accuracy and better spatial consistency for spatial interpolation of air temperature even if few meteorological observation stations were provided.