CHANGES IN SOME METEOROLOGICAL AND OCEANNOGRAPHIC FACTORS OF THE GULF TOKIN IN PERIOD 1/2019 - 6/2021

Abstract

The Gulf of Tonkin is located in the tropical monsoon region, which is governed by atmospheric circulation, so the meteorological and oceanic conditions have a distinct seasonal character in the northeast moonsoon season and southwest monsoon season. The article used statistical methods, spatial interpolation to clearly show the characteristics of the Gulf of Tonkin sea area. The northeast monsoon from November to March next year, the main wind direction is Northeast, North and East. The average wind speed is 5,4 m/s, the main wind level is wind level 2 and 3. The southwest monsoon season from May to September, the prevailing wind direction is South, Southeast and the main wind supply level 2 and level 3, 4. During the study period, there were 3 super typhoons appeared with wind speed up to 60 m/s. The air temperature fluctuates around 18,2°C - 30,9°C, the average was 25,1°C. The average air humidity reaches 81,6%. The pressure ranged from 1003.2 to 1018.8 Hpa, with an average. The pressure reached a high value in the northeast monsoon season (January, February) which was low in the southwest monsoon (June, July, August). In the northeast season, the surface sea water temperature ranged from 11,0°C to 34,0°C, the average temperature was 23,5°C, the common temperature threshold was 24,0°C - 26,0°C. In the southwest season, the temperature was about 20,7°C - 35,0°C and mostly in the range of 30,0°C - 31,0°C, distributed in increasing direction from North to South, from West to East. The average concentrations of Chlorophyll-a in the two wind seasons were 1,63 mg/m3 and 0,89 mg/m3 respectively and accounted for the highest percentage in the range of values 0 - 1 mg/m3 . The distribution trend was high in the coastal areas of Nam Dinh, Thanh Hoa, the lowest in the area between the bay and the mouth of the bay, about 0,2 - 0,6 mg/m3 .