83rd Annual

Sunday, 9 February 2003
On the change of sea water characteristics caused by a typhoon
Eun-Soon Im Jr., Korea Meteorological Research Institute, Seoul, Korea; and H. M. Lee Jr., H. J. Oh Jr., T. H. Kim Jr., and Y. H. Youn Sr.
1. Introduction

Typhoons are supplied with energy to be required of that's growth from ocean, which has the change of characteristics from mixed layer to thermocline by vertical energy transmit such as strong wind stress and inverted barometric effect. This change is represented sea water temperature and salinity mainly. According to Ulrich and Price(1981), the sea surface temperature(SST) was decreased by the negative feedback mechanism between the SST response and typhoon intensity. Krauss(1981) observed increasing of mixed layer depth and decreasing of thermocline depth due to the high frequency internal wave generated between mixed layer and thermocline during a period of very stormy weather in a nearly enclosed basin, the Baltic sea. The change of upper ocean characteristics by a typhoon may show the bigger vertical change than research of Krauss(1981) that observed in shallow sea about 100m depth. According to Steve Riser, the sea temperature observed from float was reduced about 3.5degree in mixed layer and the salinity was increased about 0.5PSU(Practical Salinity Unit) in upper ocean. The aspect of these change was observed to 200m as the sea temperature and salinity gradient was decreased(JCOMM, 2001). Here we examined the response within upper ocean to a moving typhoon using Argo floats data. We considered the characteristics change not only mixed layer but also thermocline in this study

2. Data

Argo floats have measured temperature and salinity with cycling to 2000 m depth every 7-10 days. 17 typhoons occurred from January to September, 2002 in northwest Pacific Ocean. After sorting Argo float data that were observed in latitude and longitude within 1 range from the typhoon trajectory, we examined hydrographic conditions the before(7day or 10day) and after(7day or 10day) of the typhoon. The vertical profiles of the sea temperature and salinity observed from Argo float(ID:Q5900126) are available in the cases of the typhoon Chataan(No. 6).

3. The meteorological conditions

Typhoon Chatann passed over the point of 15.3 N, 141.9 E at 18UTC 5 July 2002. Fig. 1 shows the weather conditions in developing the typhoon Chatann at the mooring point of Argo float. Fig. 2 shows the trajectory, centeral pressure of typhoon Chatann and the location of Argo floats. Maximum wind speed was 110kt and central pressure was 965pha in the near the Argo float(ID:Q5900126).

4. Result

The vertical profiles of the hydrographic conditions before and after the typhoon were displayed in Fig.3. With comparing the characteristics between before and after the typhoon, the sea temperature was decreased about -1degree within the upper 80m while the salinity was increased about 0.24PSU and the sea temperature and salinity was decreased about -1.7degree and about -2.8PSU respectively in the layer between 80 and 200m depth. The temperature distribution measured vertically between 0 and 500m depth by means of Argo float is shown in Fig. 4. On 5 July the typhoon Chatann passed over while the Argo float was mooring. The change of hydrographic conditions means decreasing of sea temperature within the upper 80m and increasing of that within the upper 200m as we mentioned earlier. We briefly reviewed the ocean heat flux as typhoon Chatann passed over. According to the calculation, ocean heat flux is -6.10X104J per 1cm2 within the upper 200m. The negative means heat emittion from ocean to atmosphere

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