Abstract:

Base on daily precipitation observational data at 62 meteorological stations in Heilongjiang province during 1961-2016 and the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis data, the characteristics of precipitation climate and atmospheric circulation from late July to early August in main flood seasons were analyzed. Precipitation and circulation in Heilongjiang province during main flood seasons were evaluated using the simulated results with different starting time from the Dynamic Extended Range Forecast Operational System 2.0 (DERF2.0) model. The results showed that the precipitation during the main flood season accounts for 25%-35% of the cumulative precipitation in summer, which is the major period of summer precipitation in Heilongjiang province. In the years with large precipitation, a wave train with the “+ - +” pattern in the east-west direction exists at 500 hPa and its center is located at the western region of the Northeast China. Meanwhile, cyclones are observed in the wind field at 850 hPa. The annual mean Ps score for the precipitation in the main flood season is about 60 when the starting time of the DERF2.0 simulation is 10 d and 5 d ahead, and the score reaches 70 for 1 d ahead. When the starting time of the DERF2.0 simulation is 1 d ahead, the annual mean anomaly correlation coefficient (ACC) for circulation salient region at 500 hPa is 0.58, and that for zonal wind at 850 hPa in the southern region and in the northern region of Heilongjiang province are 0.48 and 0.52, respectively. The DERF2.0 model can predict precipitation and circulation during the main flood season in Heilongjiang province to some extent, and the prediction skills improves  significantly as approaching the starting time.

Key words: Main flood season, Dynamic Extended Range Forecast Operational System 2.0 model, Evaluation