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  • An Extraordinary Voyage - Exploratory Upper-air Sounding over the South China Sea (Part I)

  • Friday, 7th August 2015

The Observatory carries out upper-air sounding at 8 a.m. and 8 p.m. (i.e. 00 UTC and 12 UTC) every day by launching balloons carrying radiosonde from the automatic upper-air sounding system at King's Park Meteorological Station. In late 2014, the Observatory acquired a portable sounding system to explore the feasibility of conducting upper-air sounding operation elsewhere from King's Park to support operational and research needs. One of the ideas is to make sounding operation over the South China Sea. Back in the 1970's, the Observatory participated in a global weather experiment and had launched sounding balloons on board of ships. Sounding balloons were launched on a British warship and a merchant ship to collect meteorological data over the South China Sea (Figure 1)

Figure 1

Figure 1      The Observatory launched upper-air sounding balloons over the South China Sea in the 1970s.


After some 30 years, KC (Fung Kwok-chu, Senior Scientific Assistant) and I were excited to start our week-long historical mission on board of M.V. OOCL Busan [1] on the night of 12 June 2015. The destination was Singapore (Figure 2). Below is the excerpt from the journey diary:


Figure 2

Figure 2      The voyage from Hong Kong to Singapore and the 7 sounding balloon launching locations.



2015.6.12    Fine
In the afternoon, I felt a bit excited after knowing the ship had already arrived in Hong Kong. After dinner, I said goodnight and goodbye to the kids. KC and I then went to Kwai Chung Container Terminal and boarded M.V. OOCL Busan (Figure 3) after going through some immigration formalities. Ah Chow (Chow Chi-hung, Senior Scientific Assistant) also went on board to help checking the gears. In case something were found missing, he could rush back to King's Park and fetch them. After boarding, we asked the crew right away if the instruments and tools had been delivered on board and we then checked if they were functioning normally. The radio was quite noisy in the Terminal and the reception was barely acceptable. We believed that the condition should improve in the open seas. On the deck, we said goodbye to Ah Chow who went down the ship ladder and left the Terminal near midnight.

Figure 3

Figure 3      Picture of M.V. OOCL Busan.



2015.6.13    Fine
We were briefed about the escape and safety measures on board before leaving Hong Kong waters. Following a crew member, we got the chance to take a look at the engine room to feel the heat stress there. The ship stopped by Shekou Port first (Figure 4). The marine pilots from both the Hong Kong and the mainland sides took turns to lead us to the Port. During the few hours in Shekou, KC took the time to do some final checks of the portable system (Figure 5), getting ready for the first balloon of M.V. OOCL Busan on next morning. The ship left Shekou at around 10 p.m. It passed through the busy Urmston Road, Kap Shui Mun, East Lamma Channel, and left Hong Kong waters near Po Toi.

Figure 4

Figure 4      Container ship on route to Shekou Port on calm seas.



Figure 5

Figure 5       Adjusting the antennas of the portable sounding system.



2015.6.14    Fine
It was already 6 a.m. when I got up. The ship was about 200 km southwest of Hong Kong. Mobile phone signal had been lost for long. It was time to test out how we could survive without mobile phone and the Internet! KC seemed to be very keen expecting for the first launch. He was ready and had connected all the instruments at the bridge before 6:30 a.m. Though we were far away from landmass, there were still plenty of radio noises. It took us some time before we finally located a useable frequency and locked the radiosonde signal. Then KC proceeded to inflate the balloon at the bridge wing (Figure 6)

Figure 6

Figure 6      Inflating the balloon with helium gas.


The ship headed to the southwest with a cruising speed of about 16 knots. The winds near sea surface were over 10 knots, also from the southwest. The resultant winds were reaching gale force! Though KC is an expert for launching balloons, he still found it difficult to inflate and tie the balloon under near Signal No.8 wind conditions. The balloon turned into crescent shape under strong winds (Figure 7). Having seen that, the crew came over and helped out, not only to feel the fun of launching a balloon, but also to learn about the difficulties of our work.

Figure 7

Figure 7      Balloon in crescent shape under strong winds.


Without further ado, the balloon was released and the radiosonde flew quickly away. I then rushed back to the bridge to check if the data were sent back to the receiver. The hard work paid off and the data were successfully received. The whole process took about three and a half hours to complete. The 1st balloon of M.V. OOCL Busan was considered a success. Captain Duan Shaoda came over and congratulated us. However, the work was not completed yet. We still had to send the data back to the forecasters in the Observatory for their reference. Without optic fibers on the ship, the only way is to use Captain's exclusive email to send the data files as attachments via satellite transmission back to Hong Kong. Though it was Sunday, the Observatory operates 7/24 and colleagues in the forecasting office were waiting for this "1st balloon". Forecasters compared the data from the 1st balloon with that collected from King's Park regular launch (Figure 8). The relative humidity profile aloft was quite different although M.V. OOCL Busan and King's Park were only 200 km apart.

Figure 8

Figure 8      Upper-air meteorological data from the first sounding balloon of M.V. OOCL Busan (left) and King's Park
Meteorological Station (right) (8 a.m. HKT on 14 June 2015).


It was almost 6:30 p.m. after the siesta. The dinner was a BBQ party on the deck. I must say it was equivalent to the Captain's Dinner of luxury cruises, only without formal attires. It was our honour to dine with the Captain at the same table. Too bad KC and I needed to leave early, as we had to launch balloon at 8 p.m. (i.e. 12 UTC).

With some experience gained from the morning launch, we thought it would be easier this time. It was already dark and we had to pay extra caution. The radiosonde preparation work was smooth. Inflating and tying the balloon were easy jobs for KC. However, it was only 'the lull before the storm'. The winds tonight were not weaker than those in the morning. Given that we have so little experience in launching balloon on a ship, we were simply too confident about the launch. When we released the balloon, it crashed to the crane on board and burst in a split second. The radiosonde plummeted into the sea. The crew came over and checked us out. We were lucky that no instruments on board were damaged. While reflecting on what had happened and learning from the experience, we decided to take time and launch another balloon. This time Captain Duan suggested steering the ship a bit so that the sailing direction (the ship was heading southwest) would deviate from the wind direction (also from the southwest) by a small angle such that the balloon would not crash to the instruments on board (Figure 9). This method really worked and the balloon flew out smoothly (Figure 10). Captain Duan had made such a wise move and we used this method for every launch thereafter and the balloon releases were all very smooth!

Figure 9

Figure 9      Cruising route (white dotted line) as shown on the navigation radar of M.V. OOCL Busan.
Captain Duan steered the ship a little leading to a smooth balloon launch.



Figure 10

Figure 10      Capturing the moment when the balloon flied out smoothly as the sailing direction
of the ship changed a little.


The sky was not pith dark on that night. It was full of brilliant stars. I had never seen so many stars in my life, even more than those observed in Sai Kung, Southern District, Lantau South, or anywhere in foreign countries without much light pollution. Tens of thousands of stars and the visible Milky Way made me feel small. Too bad I do not know much about photography and I only had my mobile phone and a handycam with me. I was not able to record the spectacular scene, but that certainly left a remarkable impression in my memory.


To be continued ...



David Lam


Note:

[1] "M.V. OOCL Busan" is one of the members of the Hong Kong Volunteer Observing Ships Scheme.



Last revision date: <25 Sep 2015>