| Dalian is located in the Liaodong Peninsula. surrounded by the sea. it has ample moisture, so fog happened frequently, resulting disasters have also occurred, foggy weather is one of the major natural disasters in Dalian. Dalian traffic and people’s lives are have a great impact, and therefore accurate forecasting not only to avoid the occurrence of disasters, but also social activities and people travel weather guide. Dalian’s terrain is special.spring and summer ocean climate characteristics significantly, much fog occurs mainly in the stratospheric cooling fog. Changes in Dalian fog distinctive characteristics. With the increasingly serious pollution, and increasing year by year the number of days of fog. People on the fog forecast accuracy and demands are constantly increasing.In recent years, with the development of technology and meteorological career advancement, fog detection equipments in Dalian has in continuous improvemen. and therefore improving monitoring capacity in the fog on the basis of this article focuses on2001to2012data of fog on the basis of previous studies, focusing on strengthening the climate characteristics of fog in Dalian in recent years and the formation mechanism of the analysis, and the establishment of fog model to improve forecasting methods of fog. and thus help to improve the fog forecasting capabilities and the ability to prevent disasters of Dalian. From this study we concluded that:1)Due to the difference of sea land distribution in Dalian, number of fog days are diffrent. it appears most in Changhai. least in Jinzhou. the fog appears most in summer around the of the four seasons except Jinzhou. the second in spring, and lowest in the winter. But foggy seasons are spring and autumn in Jinzhou. the number of fog days in North Citys are more than Changhai in autumn. The fog days variation on Dalian area also has certain rules:most area of Dalian spring fog generated mostly at02～08(Beijing time, the same below) and at20～23. while in the14～17at least, and fog mostly produced in20～23and02～05in Changhai.11～14at least. The summer fog mostly occurs from night to next morning, with genetating mostly from20-08. more than80%.14-17at least.2) Fog weather situation mainly happened included of high pressure into the rear in Dalian (prevailing southerly or easterly winds. Chengshan cold water turned on in spring and summer, when the northern part of the Bohai Sea and the Yellow Sea over the Strait of warm advection. cold land surface because of its role easy cooled into mist in winter. warm air warming of the cold high pressure weakened in favor radiative cooling condenses into fog.cyclone(lower troposphere and warm air connected with the Dalian. Cooling condenses into fog invades from the northwest or northeast Dalian small stocks over the cold air flowing through the cold waters warm advection forcing its southern).cold front(Eastern offshore high voltage rear.Warm.moist air in front of the cold front, increasing the Dalian area of air humidity. Weak cold air sinks and warm air climbing uplift, lower atmosphere conducive to the establishment of stable stratification.Winter is conducive to the generation and maintenance of radiation fog. spring and summer are conducive to the development and maintenance of advection fog cooling). Equalizing field type(Pressure field is relatively weak. At this point the southerly winds bring plenty of water vapor in Dalian, when the radiative cooling at night, as the temperature decreases, the water vapor condenses to form fog. such as radiation fog. in the beginning of fogs the vapor are relatively abundant in the first. third, and fourth class, this type prevails south to southeast wind. and end with the north wind while the second type is not particularly abundant moisture. and prevails north wind from beginning to the end..It has a maintenance phase in the process of has a vapor gathering process near the ground. water vapor gathered stratification are about900hPa. when the fog dissipated high altitude are affected by cold advection.3) When the fogs happened in summer.the middle and horse latitude high of the500hPs was zonal circulation.and the most place kept the western airflow and controlled by low through.850hPa was in the front of the low through and at the back of horse latitude high and in the vapor transport field; the ground was in the bottom or in the front of low systerm.and surstained weak south or east wend;near the ground(between1000hPa and900hPa) had temperature inversion layer;at the level of800hPa to900hPa the number of divergency, vorticity and vertical velocity was0. weak convergency and divergency had existed near the ground, correspond with ascending and sinking motions.this condition helped the water vapor transported and^converged, it also helped with the formation and the surstaintion of the fog.4) The evolutionary process of this fog event is described based on the GOES (Geostationary Operational Environmental Satellite)-9visible satellite imagery. Also the synoptic situation prior to the sea fog formation and the temperature difference between the2m air and sea surface during the sea fog formation are analyzed. The stability of the lower atmosphere when the sea fog occurred are also examined by using sounding data at Cheju stations. Finally, this sea fog event is simulated with the RAMS model. The area of lower horizontal visibility calculated based upon the model outputs agrees surprisingly well with the sea fog region identified from the visible satellite imagery. |
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