Interpretation of Monthly Dynamical Extended Range Forecast Products in Northwest China

Using monthly precipitation data of 163 observatory stations in Northwest China, reanalysis data of 500 hPa monthly average geopotential height from NCEP/NCAR, and monthly 500 hPa geopotential height of monthly dynamical extended range forecast, comparisons among the climatic forecast, persistence forecast, explanation test of reanalysis data, forecast experiment with the interpretation method of monthly dynamical extended range forecast products are made. The results show that the skill of the reanalysis data explanation test has the highest score, while the climatic forecast score is the lowest. The score of the interpretation method of monthly dynamical extended range forecast is a little lower than that of the interpretation test of reanalysis data, but higher than that of climatic forecast and persistence forecast. It indicates that by the spatial distribution of the PS score over Northwest China, the distribution of monthly dynamical extended range forecast is very similar with that of the analysis data of interpretation test. The regions with the highest PS score located in the south of Qinghai Province, south of Gansu Province and south of Shaanxi Province where the monthly precipitation climate value is relatively high. The regions with the lowest PS score locate in part of Xinjiang, west of Hexi of Gansu Province where the monthly precipitation climate value is relatively lower. And the downscaling tests show high skill when more data of observation stations are used.