Saturday, Nov. 11, 2006

R/V MIRAI

"vortex on the equator ?"

Fine, later cloudy, sometimes shower.
Southerly 5m/sec, wave height 1.6m.

Observations:

We've shifted to the second stage since this morning. Namely, we conduct CTD observation 5 times/day, while CO2 measurement near the sea surface is done at 0730 and 1930 LST (photos-1, 2). Snow White sonde was launched at 1100 LST, while Videosonde was launched at 1441 LST.
When we conducted CO2 measurement, a large voretex was found just south-east from the MIRAI at (0.0015N, 80.4762E) (photo-3). After that, we continued to follow this cloud as much as possible. At first, we noticed this cloud at 0800 LST, and then it developed. It had clockwise flow in the southern hemisphere. Although it became difficult to see the center of the vortex by eye after 0900 LST, Doppler radar detected related cloud echo (Fig. 1, at 0.3S, 80.5-80.8E), and they moved southward with developing. We confirmed the wind shear in the lower troposphere using radiosonde data. But, at the present, any relationship to this phenomenon is not clear.

Remarks:

As noted above, we were lucky because we could see an equatorial vortex. We will surely analyze it in detail soon. In addition, we could see the rainbow just near the sea surface in front of the ship (photo-4).
Since today is Saturday, we had routine tasks of maintenance for both ship and scientific instruments (please see the past reports on Saturday). Furthermore, today we had a seminar (photo-5). His talk was on the variation of SST in the western Pacific Ocean and some results obtained from Argo floats.