~ a 3 h NCEP ~ 24 3 ~ ~ 8 9 ~ km m ~ 500 m 500 ~ 800 m 800 ~ m a 200

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1 Journal of Arid Meteorology Vol. 31 No. 1 March J doi /j. issn ~ h NCEP 2 5 ~ ~ 08 2 ~ 8 m /s T - T d > 0. 6 > 300 m T - T d > 1. 1 > 500 m T - T d > 2. 1 > 800 m hpa < 995 hpa > hpa doi /j. issn P A a ~ hpa ~ ~ E - mail lookforhim@ 126. com

2 ~ a 3 h NCEP ~ 24 3 ~ ~ 8 9 ~ km m ~ 500 m 500 ~ 800 m 800 ~ m a d RAMS SST Sea Surface Temperature a 20 d 6 30 d d 500 ~ 800 m 17 50% < 300 m ~ a ~ 7 80% 5 ~ ~ ~ 08

3 ~ ~ 800 m 300 m 02 ~ ~ ~ ~ m ~ 300 ~ 500 m Tab. 1 d Interannual variability of Bohai sea foggy days /m < ~ ~ ~ < Tab. 2 d Monthly variability of Bohai sea foggy days 12 /m < ~ ~ ~ < Tab. 3 d Daily variability of Bohai sea foggy days /m < ~ ~ ~ < m ~ 500 m 14 ~ ~ 800 m ~ m m

4 m /s 2 < 300 m 2 m /s 5 m /s 7 m /s m /s 300 ~ 500 m 2 m /s 5 m /s 7 m /s m /s 500 ~ 800 m 3 m /s 7 m /s 8 m /s m /s 800 ~ 1000 m 2 m /s 8 m /s 11 m /s m / s m 2 ~ 8 m /s m 2 ~ 8 m /s 2 ~ 3

5 66 31 T - T d > 0. 6 > 300 m T - T d > 1. 1 > 500 m T - T d > 2. 1 > 800 m 2 Fig. 2 The relationship between sea fog numbers with different visibility levels and wind speed T - T d hpa < 995 hpa > hpa T - T d < 1. 1 > 995 ~ hpa 75% m T - T d 0. 0 ~ ~ 500 m T - T d ~ ~ 800 m T - T d ~ ~ m T - T d ~ ~ hpa hpa ~ m ~ hpa < 800 m hpa hpa < 997 hpa > Fig. 4 The relationship between sea fog numbers with different visibility levels and the atmospheric pressure N 11 a hpa Fig. 3 The relationship between sea fog 5 40 N number with different visibility levels and the difference between temperature and dewpoint 20 N 125 E 588

1 67 30 N 6a 2005 16 95 E d 2000 1 d 6 588 35 N 5 2000 ~ 2010 6 500 hpa gpm Fig.

6 6 2005 a 2000 b 500 hpa gpm The 500 hpa geopotential height in more foggy days year 2005 a and less foggy days

6 N 6a E d d N ~ hpa gpm Fig. 5 The 500 hpa average geopotential height in June from 2000 to hpa 6b 150 E 160 E a > 90% Fig a 2000 b 500 hpa gpm The 500 hpa geopotential height in more foggy days year 2005 a and less foggy days year 2000 b Fig a 2000 b hpa % The hpa relative humidity in more foggy days year 2005 a and less foggy days year 2000 b

68 31 35 N 7b 35 N > 90% 32 N 25 N 8 8 2005 1 000 hpa a 850 hpa b 2000 1 000 hpa c 850 hpa d g cm - 1 hpa - 1 s - 1 Fig.

7 N 7b 35 N > 90% 32 N 25 N hpa a 850 hpa b hpa c 850 hpa d g cm - 1 hpa - 1 s - 1 Fig. 8 The hpa a and 850 hpa b water vapor flux in hpa c and 850 hpa d water vapor flux in the year of 2000 Unit g cm - 1 hpa - 1 s a

8 J J supplement J M J D J. J J J J.. J J J... J.. J.. J. 16. J J Characteristics and Generating Mechanism of Sea Fog in Dalian of Liaoning Province TANG Pengyu HE Hongrang YANG Xiangrong Meteorology College PLA University of Science and Technology Nanjing China Abstract Based on the conventional meteorological data of every three hours from 2000 to 2010 and the monthly average field reanalysis data of NCEP the various characteristics of atmospheric environmental elements during sea fog generation in Dalian was analyzed and infuluences of the environmental elements on the generating and dissipating of sea fog were studied then the environmental conditions which was beneficial to the sea fog s generation were obtained. At the same time the interannual variability and seasonal characteristics of Dalian sea fog were analyzed and the circulation situation and moisture conditions which causing the abnormal more and less sea fog were compared to study the circulation situations of Dalian sea fog generation and dissipation as well as the moisture sources. The results show that Dalian sea fog mainly occurred in spring and summer especially in May to July in a day sea fog mainly occurred from to and usually dissipated after sunrise in the morning. East or south winds with 2-8 m /s were most conducive to the occurrence of Dalian sea fog. When sea fog occurred and T - T d was more than 0. 6 the visibility would be forecasted more than 300 m and T - T d was more than 1. 1 the visibility would be forecasted more than 500 m and when T - T d was more than 2. 1 the visibility would be forecasted more than 800 m. Sea fog frequency reached a peak at hpa when air pressure was less than 995 hpa and more than hpa no sea fog generated basically. The sea fog in Dalian were mostly advection fog. The sea fog frequency was related to the south monsoon airflow at the west side of the western Pacific subtropical high when the subtropical high enhanced the moisture over the tropical ocean surface could be directly transported to the Dalian area by the southwest monsoon airflow and when the advection moisture encountered cold underlying surface the sea fog occurred in the coast of Dalian. Key words Dalian sea fog statistical characteristics generation mechanism

km <.5 km.5 < 1. km 4 1 km ~ % 23.3 % 23.3 % 36.5 %.5 km 64.5 % 7 % /%

km <.5 km.5 < 1. km 4 1 km ~ % 23.3 % 23.3 % 36.5 %.5 km 64.5 % 7 % /% 17 2 218 6 JOURAL OF ATOG VOCATIOAL & TCHICAL HIPPIG COLLG Vol.17 o.2 Jun. 218 218 doi: 1.3969/j.issn.1671-9891.218.2.7 (, 2261) :, 1981 21, :, 16 17, (.5 km) 6 % ;, ;, : 9 %, ---, 4 m/s, 1 1.5~1 3. kpa,