The Impact Of The Typhoon On Sea Surface Temperature

The study of the impact of the typhoon on sea surface temperature(SST) has both scientific and economic significance to fisheries, transportation, maritime engineering and so on. In this thesis, the sea surface cooling caused by typhoon is analyzed with the newest daily mean SST data, and further discussion about the response of the sea surface cooling to the typhoon is made based on the numerical simulation of a three-dimensional ocean model POM.The response of the sea surface temperature to typhoon in the Western North Pacific Ocean is examined with the data from typhoon database, NCEP and Remote Sensing Systems (RSS). Six typhoon factors and four SST factors are chosen to study the response and the statistically maximal sea surface cooling on the first day and the next several days during the whole typhoon process are given. The results suggest that the response depends upon the intensity of the typhoon. Among all the correlation coefficients between SST cooling and typhoon factors, the largest ones are found with typhoon pressure gradient and the difference of pressure, while the smallest is found with the typhoon translation speed. Since the sea surface cooling is highly related to the upper ocean's condition, the relationship between the structure of the upper ocean and the sea surface cooling is discussed. It indicates that the impact of typhoon on SST decreases with the deepening of the water depth as water depth in the area deeper than 100m; with the deepening of the mixed layer depth, the SST cooling decreases, but not monotonously. If the thickness of the mixed layer is less than 10m, a weak typhoon can cause an intense surface cooling but when the typhoon is adequately strong, the cooling becomes not so obvious Most obvious sea surface cooling occurs in the area with mixed layer depth ranging from 20m to 25m.The Typhoon Sinlaku and Meral are simulated with the POM model, and the comparisons of the model result with the TMI data suggest that this model can well reproduce the process of the sea surface cooling related to typhoon. The impact of the typhoon on sea surface temperature is not instantaneous. The maximal sea surface cooling caused by the typhoon in the two cases lags two days and one day respectively, with the maximum decreasing of 5.0℃and 4.7℃. And the impact still exists on the 8th day. The position of the sea surface cooling relative to the typhoon track (left or right), is determined by the typhoon wind-stress dissymmetry, horizontal flow, distribution of the mixed layer depth, temperature of the sea water and vertical gradient of the temperature nearby the typhoon track. In the Northern Hemisphere, the sea surface cooling will occur in the area right to the typhoon track result of wind-stress dissymmetry and the horizontal flow. Shallow mixed layer, cold water and large vertical gradient of temperature on the right side of the typhoon track will cause a right-hand-side surface cooling and vice versa. When the surface cooling is caused by this effect occurring on the left hand side and it is more obvious than the right-hand-side cooling caused by the former effect, a surface cooling on the left side of the typhoon track will be found, otherwise, a surface cooling on the right side of the typhoon track will be found.