Homogenization of Surface Pressure Data in Tianjin, China

Abstract

Based on a hydrostatic check, a preliminary quality control procedure was applied to the hourly surface air pressure (SAP) and sea level pressure (SLP) data from 13 surface observation stations in Tianjin, China. The daily and monthly series of the two pressures were tested for homogeneity with the RHtestsV5 software package and corrected by using the surface air temperature data as a reference. The results showed that 5 and 3 of the 13 stations had significant breakpoints in their SAP and SLP data, respectively, mainly caused by station relocation. Quantile matching adjustments showed that both pressures were dominated by positive deviation corrections and adjustments, with probability densities > 0.2 concentrated in the ranges 0.02 to 1.80 and −0.02 to 1.64 hPa. Comparison of the variances and trends of the two pressures before and after adjustment showed that homogeneity correction can greatly reduce the influence of abnormal discrete pressure data and make the long-term trends of the series more reasonable. Taking Baodi station (54525), which has the most significant correction results, as an example, the trend amplitude of the adjusted SAP and SLP was increased by 0.316 and 0.294 hPa (10 yr)−1 (95% confidence level), respectively, clearly weakening the sudden reduction induced in the two pressure series by the relocation of this station. Comparison with similar products showed that the adjusted data were better than those from the China Meteorological Administration. Therefore, the reliability of the surface pressure data and the processing techniques have been improved.