무안국제공항의 안개특성 및 예측연구

Abstract

RKJB(Muan International Airport) is located in Piseo-ri, Mangun-meon, Muan-gun, Jeolanamdo, Korea. Among RKJB flight cancellations and delays, cancels which were caused by weather accounted for 20 percent, primarily which caused by fogs did 33 percent. We analyzed types of fog from 2008 to 2012 by using observation data from RKJB and buoy in Chilbaldo. In this research, we focused on days of fog occurrence and non-occurrence in connection with direction and velocity of wind, temperature, dew point, declination of dew point, clouds, atmospheric pressure, difference of sea air. Fogs were sorted into radiation fog, advection fog, steam fog, frontal fog according to cause of the fog. The weather chart used KMA(Korea Meteorological Administration) numerical model. Possibility of fog occurrence at RKJB used observation data from Mokpo weather station, Heuksando weather station, and upper-layer data from Gwangju weather station and Heuksando. Also sea-surface temperature for analyzing difference of sea air is from Chilbaldo buoy data.

(1) Radiation fog appears when air makes stability layer in col of migratory anticyclone. Mainly, it appears in spring and fall. Mostly it appears at 0300KST to 0600KST and disperses 0600KST to 1000KST. When fog occurred, the direction of the wind blows the kind of the east wind and the velocity of the wind is mainly below 5kts. Also low-level clouds account for 75%. By temperature rising, almost fogs are dispersed. Difference of sea air is 2~8 degree. 850hPa moisture flux(10⁻²g⁻¹m⁻²s⁻¹) is 7~15, 925hPa mixing ratio(g/kg) is 5~10 , T-Td is 1~4.

(2) Advection fog appears when cold air advect to warm sea surface in west high east low type pressure pattern. Mainly it is created in 2100 KST to 0400KSTand dispersed in 0600KST to 1000KST. The direction of wind is southwesterly in summer, northwesterly in winter, and the average of wind velocity degrees 4~8kts. Stream line converges near the RKJB. Humidity distribution is above 90%. And 850hPa moisture flux is 4~11, 925hPa mixing ratio is 6~14 .

(3) Steam fog occurs when the cold air flows into the high temperature sea surface at the back of migratory anticyclone. The higher temperature gradient the more it lasts. The time of appearance is 1800KST to 0200KST and the time of dissipation is 0700KST to 1300KST. The direction of wind is northwesterly or northerly wind in winter. While, but by the land and sea breeze, it changes Westerly wind in day and easterly wind in night in fall. When the velocity of wind is not strong, fog lasts for a long time. But when the velocity of wind is over 7kts, fog dissipate by mixing low and high level atmospheric layers. The kind of lower clouds distributed above 60% and middle level clouds did above 40%. So dissipation of fog lasts long time by thick clouds. Difference of sea air is 2~7 degrees in spring and 2~10 degrees in winter. And 850hPa moisture flux is 5~12, 925hPa mixing ratio is 8~15.

(4) Frontal fog occurs by a warm or cold front in spring, fall, winter. And it occurs by a stationary front in summer. Average duration time is almost 3hours. After occurrence of the fog, if wind is weakening or warm current flows in, fogs tend to last for a long time. The direction of wind is westerly wind in spring, northwesterly wind in winter, and southwesterly in summer. The velocity of wind is 8kts or so. It is somewhat stronger than that of radiation fog. 925hPa mixing ratio is 11~18 in summer and 5~10 in winter. So, mixing ratio of summer is higher than that of winter.

RKJB opened only 6 years ago. So it doesn't have sufficient data. As a result, it’s difficult to verify outcome. However, if we use research result by objective data to predict fog, it is contributed to improve accuracy rate of forecast.