Evaluation of Prediction Effect of NCEP CFSv2 on Situation Field of Two Intense Freezing Processes
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Abstract:
The historical hindcast data of different starting dates provided by the second-generation climate forecasting system (NCEP CFSv2) of the United States Environmental Forecasting Centre are used to predict the wind, temperature, and height during the two strong freezing processes in 2008 and 2011. Through comparative analysis with the actual field, the predictive ability of the CFSv2 model for severe freezing processes is evaluated. The results show that at the different starting dates within one week in advance, the NCEP CFSv2 model has a certain ability to predict the wind field characteristics of the two processes (at 850 hPa: northeasterly return flow in the northeastern part of Guizhou, southerly wind in south Guizhou, southwest wind in west Guizhou; 700 hPa southwest jet stream), temperature field characteristics (the 0 ℃ line position of 850 hPa,700 hPa and whole layer temperature field; temperature gradient of middle and low layers; temperature inversion zone of 850 hPa and 700 hPa), and height field characteristics (the variation of the 500 hPa 564 dagpm characteristic line, the subtropical westerly jet stream). However, there are deviations in the forecast of wind speed at 850 hPa, the position of the South China quasi-stationary front, the north-south position of the 0 ℃ line on the entire layer temperature field, the north-south position of the 564 dagpm characteristic line, and the intensity of the subtropical westerly jet stream. At the same time, there are situations such as the wind speed of the 700 hPa southwest jet stream being relatively small, the temperature gradient of the 850 hPa temperature field being relatively small, the 0 ℃ line position of the 700 hPa temperature field being relatively south, the intensity of the inversion zone being relatively weak and the area being relatively small, and the temperature intensity of the middle and upper layers being relatively strong. Moreover, there is basically no predictive ability for the warm-core structure of the entire floor temperature field. From the prediction effect of different starting dates, the prediction effect of 1 d in advance is obviously better than that of 4 d and 7 d in advance.