| Summary: | As an important weather system, domestic and international scholars have studied the front for a long time. The Dian-Qian quasi-stationary front is also called the Yun-Gui quasi-stationary front, and many scholars call it the Southwest quasi-stationary front. It refers to the phenomenon that in East Asia, cold air outbreaks that spread southward cannot cross the plateau because they are obstructed by the topography of the plateau. The frontal system is formed when the cold air and the warm, wet air from the southwest of the Bay of Bengal meet. Every year, weak quasi-stationary fronts frequently affect Guizhou Province in late autumn and early winter. The appearance of such a stationary front is less obvious than that of winter, and is generally difficult to predict or forecast. However, when it appears, it is not only difficult to grasp the weather phenomenon, but also to forecast the temperature due to its influence. Moreover, the relative error of some observation sites can even reach 10.0℃ or higher. It has greatly affected forecasting services, production, and people's activities. Therefore, this study used the ECMWF fine-grid 2 m temperature forecast and ground comprehensive observation data from November to December 2010 to 2021, and the daily maximum and minimum temperature forecasts within 72 hours from 84 national observation stations in Guizhou were examined and evaluated. The results showed that the prediction accuracy was significantly reduced, whereas the mean root square error was significantly increased during the quasi-stationary front activity relative to the mean state. Furthermore, the forecast accuracy was less than 20% in 2014, nearly erasing the forecasting ability. Therefore, 19 cases of stationary front weakening and moving northward in 2014 were synthesized and their circulation characteristics were compared with the mean state. The results were as follows: at 200 hPa, compared with the mean state, the inlet of the jet stream moved eastward during the activity of the quasi-stationary front, the northern and southern boundary became narrower, and the average intensity of the jet stream center decreased from 65.0 m/s to 60.0 m/s; at 500 hPa, the characteristic of trough and ridge in the middle and high latitudes became less obvious, the cold air force weakened, and the latitude direction of circulation increased. In terms of factor characteristics, the temperature in the middle and lower layers showed a significant warming state relative to the average state, the inversion state of 700-850 hPa weakened or even dissipated, and the lower southerly wind strengthened and the vorticity increased. In conclusion, through the abnormal analysis of the circulation situation and the element field, when the Dian-Qian quasi-stationary front weakened and moved northward, the intensity and location characteristics of the circulation and the element field changed relative to the average state. Therefore, in our forecast, we can assess whether the Dian-Qian quasi-stationary front weakens the northward movement based on various characteristics of intensity and position. It can provide insights into the forecast and service work of temperature, as well as weather phenomena and other factors in our daily lives.
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