The intensive observation period of YMC-CSO2021 completed successfully

The last radiosonde was released on 3/8 18Z last night, and the whole schedule of YMC-CSO2021 was over.

Even in Indonesia, there were various obstacles due to Covid-19, which had a considerable impact on the implementation of observations.

Even in such a difficult situation, the BMKG operation staff continued to do a wonderful job until the end.

This was the first remote observation, and no one had the correct answer and/or experience for the trouble.
We are really grateful that everyone worked hard at each place.

Although we had a lot of trouble, the main target of the cold surge occurred more than usual, and we were able to obtain good data.

From now on, we will analyze the data obtained and investigate the air-sea interactions between cold surges and cold tongue, and the relationship between cold surge and extreme severe weather.

The sea surface temperature (SST) in the South China Sea was 1-2 °C lower than usual, so called “cold tongue” in the SST distribution, and it is suggested that this affected the process of strengthening the cold surge that occurred seven times in two months.

On the contrary, a strong cold surge may have an effect on the development of cold tongue, and it is speculated that positive feedback was working between the two.

In addition, heavy rainfall events accompanied by floods occurred on 1/9 and 2/19 due to cold surges, and elucidation of their formation process is strongly required in Indonesia.

A third of IOP has been done smoothly

A third of IOP that is started from 8 January 2021 has been done smoothly.

Today, the photos & movies that are sent from BMKG staff are shown here.

The northerly winds in Indonesia were intensified after the beginning of IOP and rainy/cloudy days were continued everyday.

The movie tells us the wind speed.

We confirmed that 66 mm of large precipitable water vapor was observed with the GNSS station installed at Soekarno Hatta International Airport in the early morning on 9 January.

MOTEKI Qoosaku

Let’s get started!

YMC-CSO2021 has finally started today.

BMKG staff sent us photos and videos of the radiosonde work for 00Z launching this morning.

In Japan, the bomb cyclone passed yesterday, and the cold air outbreak is intensifying.

Cold surge are expected to strengthen in Indonesia in the next few days.

This campaign is exciting from the beginning!

MOTEKI Qoosaku

YMC-CSO2021 will be started!

Cold air outbreaks from the Eurasian continent reach the tropics and affect the climate of the Maritime continent during the Boreal winter.

The variation of the cold air outbreaks which becomes strong or weak are called a “cold surge”.

JAMSTEC/DCOP will conduct a cold surge observation campaign as part of the YMC (Years of the Maritime Continent) in cooperation with Indonesian Agency for MeteorologicalClimatological and Geophysics (Badan Meteorologi, Klimatologi, dan Geofisika or simply BMKG). 

The intensive observation period (IOP) is from January 8 to March 8, 2021.

During this IOP, we will increase the number of upper air sounding in Jakarta and Pangkal Pinang from two to four times a day.

In addition, at Jakarta station, we use the balloons larger than usual to get data up to higher altitudes for 06Z launch.

The cold surge is a phenomenon in the lower layer near the sea/land surface. On the other hand, when convection develops associated with the cold surge, various atmospheric waves in upper layers are excited.

By obtaining observation data at the altitudes higher than 25 km, it is possible to investigate the structure of the waves that are difficult to be detected by usual operational observation.

In addition, a new GNSS sensor has been installed in Jakarta to acquire precipitable water data every 10 minutes.

The pictures show the BMKG staff installing the sensors.

In addition, we can use BMKG’s operational radar network and surface meteorological observations.

It was a lot of work to prepare, but the wonderful staff at BMKG did a great job.

We are looking forward to what kind of data we can get.

MOTEKI Qoosaku

YMC-BSM 2020 has been completed.

The R/V Mirai has returned to Shimizu port from her 45-days cruise in the tropical western Pacific. In addition, enhanced radiosonde soundings at Legaspi/Philippines, Yap/FSM, and Palau have been ended on September 14, 2020.

So, now we have completed our field campaign successfully against the threat of covid-19 pandemic. We really appreciate great support from the local agencies in those islands (PAGASA, Yap Weather Service, Palau Weather Service, and NOAA) and great effort done by all participants.

Hereafter, we will analyze data to see what really happened during the past 1.5 months. Numerical model will also help us to understand those phenomena.

We will also intend to release quality-controlled datasets in timely manner from this YMC data site.

You will see our progress through our websites as well as papers. Bye for now!




When I launched a radiosonde at 0830 UTC (1730 SMT), August 20, I could confirm a balloon was traveling in the rainbow sky.

We have spent here on-station over two weeks and could obtain various observation data. The sky was decorated with this beautiful rainbow, as if they had celebrated us. I had better say rain-ball rather than rainbow to indicate this nice combination.

by BG (edited at J-Office for English ver.)


Ocean surface drifter

Now the time for telling surface drifter after two talks on TRITON buoy and wave-gliders, which all form a special observation array around the MIRAI.

Yesterday, I wrote wave glider can measure ocean surface condition without disturbances around wave glider owing to its slim and thin body. The surface drifter, I introduce today, is much easier to obtain data without such noises than wave glider. This is because simply we use a small (O(10cm)) float equipped with temperature/salinity sensors. Since it drifts, it does not create any disturbances around the instrument. After we deploy it, we recover the next day or so. Indeed, we deployed its first trial yesterday, and could recover it today.

Having said that, it is not an easy task than you expect. You may recall that currently we are conducting on-station observation. Namely, while we need to keep the position, we also have to recover the drifter, which moves several 10 km away. Thus, we need to arrange observation as well as personnel schedule.

In addition, although GNSS-receiver is equipped on the float, it is very tough to find such 10-cm diameter ball in the ocean using only GNSS information. Of course, we need to avoid hitting it by the ship. Thus, after we reach the expected area, while we look for the drifter using telescope and binoculars, we also use a small boat. As usual, ship crew can find it earlier than researchers. As shown in photo-2, finally we caught it by hand from the small boat.

I have to talk about science derived from this trial. As noted, this drifter can measure temperature and salinity in a couple of centimeters of the ocean surface, which is greatly influenced by atmospheric condition, and vice versa. Through this knowledge, we’d like to know a life cycle of cloud and associated large-scale features.

Today we recovered the drifter under the heavy clouds (but no rain). According to the satellite cloud images, it was part of cloud cluster of O(1,000 km). In addition, weather forecast says low pressure area was formed around here and then it is expected to move northward. Thus, while I will watch its first data obtained by the drifter, I may also be aware of cloud ensemble movement to see any relation to weather condition over Japan…

by M. K. (edited at J-Office for English ver.)



The drifter we use is called Surpact, which was developed by our French collaborators of LOCEAN. This observation is conducted under the framework of French-Japan Science and Technology Cooperation.  Its details will be noted in the Cruise report.


Wave glider

During on-station period, we are deploying various observation systems around the Mirai. Yesterday, I introduced TRITON buoy, today I’d like to mention about wave-glider, autonomous surface vehicle.

A wave glider consists of float (yellow part in the photo-1) and glider (identified with many fins in the same photo). This photo does not show its exact configuration during its operation, because both are connected by 8-m long umbilical cable. As you can easily guess from its name, this ASV obtains propulsion power from waves. When the float moves up and down due to waves, its motion changes glider’s fin, so that it accelerates forward motion. The operator on land can control its direction via satellite. Various atmospheric and oceanic instruments are equipped, and solar energy is used for their operation. Namely, it is a nature-friendly new generation observation tool.

Photo-2 was taken when we launched. Owing to its slim configuration, it can measure ocean surface condition without significant turbulence around the vehicle.

This time in addition to standard surface meteorological sensors we have equipped GNSS-receiver, which can measure precipitable water vapor. Since water vapor plays an essential role in regulating convective activity and cloud development, this ASV equipped with various instruments can be used to monitor cloud formation from the viewpoint of air-sea interaction.

During this on-station period, we are deploying three wave gliders, which occupy west, north, and east 50 km away from the Mirai. As you may recall, we’ve already deployed one TRITON buoy at south of 50 km away from the Mirai. Namely, this time our observational configuration consists of six platforms within 50 km radius (five are fixed locations, and one is drifting, which will be mentioned later). This is irregular comparing to previous field campaigns, where we usually form an observation network over 100 km in space. I know, we should keep away from 3Cs on land to avoid any possible risk of COVID-19. However, we are challenging to conduct dense observation here. I believe this configuration will bring a new insight.

Note that after our one-month intensive observation here, we will recover all wave gliders as well as TRITON buoy. I do hope they work well and we can recover them. So do you.

by M. K. (edited at J-Office for English ver.)



One-third of the the R/V Mirai MR20-E01 cruise period has already passed. Today I would like to write about a TRITON bouy which we deployed almost a week ago.

This time we focus on air-sea interaction on the order of 100 km in space to study a relationship between cumulus convective development and ocean surface condition such as sea surface temperatures. For this purpose, while the Mirai keeps her position around 12N, 135E, we are also deploying several observation platforms and instruments around the Mirai. They include TRITON buoy, three wave-gliders (autonomous surface vehicle), and ocean surface drifters. TRITON buoy is originally developed to contribute to the global tropical moored buoy array, known as TAO/TRITON and RAMA array. This time, we use it (strictly speaking, we use its mini-version called m-TRITON) for the one-month measurement.

You can see the top of TRITON buoy or float in the first photo, that was taken when we deployed. Various surface meteorological sensors are mounted on this float to measure heat flux and momentum transfer through the ocean surface. This float is connected with long ropes, where many instruments which measure oceanic temperature, salinity, and depth are equipped from the surface to 500 m depth. This time, we have attached many instruments (5 m interval from the surface to 70 m depth), which is much denser than that by standard TRITON configuration. This TRITION buoy is anchored at the 5000 m depth.

You can see (I know it is difficult to see due to small size) those float, ropes, instruments, and anchor in the second photo, which was taken just prior to the start of deployment.

As you can see in this photo, many people are engaged in deploying of the TRITON buoy. It usually takes more than a half day for the deployment operation. I believe we can surely obtain high-quality data with this TRITON buoy. We are proud of our over 20-year experience of mooring observations done by skillful marine technicians as well as ship crew. Although at first I thought it was tough to keep good condition to measure atmospheric and oceanic condition for one month, now I realize that it must be easy for him (or her?), because it is originally designed to measure over one year against rough sea condition.

I am excited to see what data he will collect during the coming one month.

by M. K. (edited at J-Office for English ver.)


Start of on-station observations

The R/V Mirai is now on station at north of the Palau Islands in the tropical western Pacific. In addition to continuous atmospheric and oceanic measurements such as surface meteorology, weather radars, ADCP, and so on, that those have been carried out since the beginning of the cruise, we’ve started to launch radiosonde and cast CTD every three hours.

Scientists, technical staff, and crew members on board are making a concerted effort for smooth operation. This photo shows CTD observation conducted at night. It started raining in the middle of the operation. I cannot help appreciating the observation data even more after watching closely people working so hard to obtain them!

by SS (edited at J-Office for English ver.)