Drones are an up-and-coming data acquisition system, and the MISO-BOB expedition is an exciting opportunity to test the limits of what our existing platforms can achieve. We are using an infra-red camera to detect patterns of temperature in the sea surface, investigating the effects of flight altitude and sunlight reflections on these images. The goal is to make drones a valuable tool for physical oceanography, giving us novel insights into the workings of 7/10ths of our planet’s surface.
Stay tuned for some images from above!
The pilot is starting up the systems, as the drone fans watch in anticipation
>20kn winds make takeoffs and landings interesting. Especially under the watchful eye of the ship’s bridge, and in proximity to the many antennas and masts and instruments…
The IR-camera brings vision to nighttime operations, uncannily detecting warm shapes on the ship from far above.
Final landing for the night, impressive flying by S.K.
We typically take our measurements from the back of the ship. This keeps long lines away from the engine screws while moving (very good!!!), the downside is that the ship’s wake contaminates the upper 10 meters of the measurement, as it mixes up the surface waters. For this project, we really want to get undisturbed observations near the surface of the ocean… enter the bow chain!
This is a steel wire hanging over the side of the ship, pulled straight down by a 150 lb weight attached to its end. Along its length, we attach instruments, these then get dragged horizontally through the water as the ship moves. The bow chain measures temperature and salinity over the upper 10 meters of the ocean out in front of the ship’s wake.
In addition, to record water temperature right at the sea surface, we also have a “sea-snake” on the other side of the bow. This is basically a sensor in a garden hose that floats at about 5 cm below the sea surface, dragged along a few meters next to the ship.
We only have the bow chain in the water when the ship is moving slowly, so it has been recovered and deployed a few times now. Everyone enjoys the break from their typical jobs, so we often have a lot of hands out for this type of activity. The forward davit holds the line with the instruments. We use the aft davit to raise and lower a 150 lb. weight that keeps the instrument line vertical. E.S.
The top few thermistors (in yellow) are lifted out of the water as the boat heaves up. (GJ)
Two arms hold out a line of instruments with a weight hanging 10 m below the surface. (GJ)
Spray flies over the bow as the ship plunges into a wave. (AT)
A team pulls the line of instruments aboard while the weight is being lifted by crank. (AT)
A boathook steadies the bottom weight, about 150 lb. (AT)
A week ago, during a dark night, a rainstorm didn’t just rain, but swept sheets of water across the deck. Recording a peak rain rate of 140 mm/hour, or almost half a foot of water, we think the ship was thoroughly washed.
Yesterday we had a rare half-day of clear skies, instead of the usual hazy cover of humidity. Clouds quickly grew in the morning, sheared and swept away by the surface southwesterly monsoon winds. The wind and waves have been weakening over the past couple days, though it is still not calm.
Do you picture the tropical seas as placid glassy surfaces? Not quite what we are seeing!
The current conditions in the Bay of Bengal are on the rougher side, for the tropics. (Although certainly not close to conditions during a cyclone or Southern Ocean storm or wintertime North Seas… and it’s still muggy hot!)
The Monsoon “waves” or oscillations appear in 10-14 day active periods where rain can be heavy, sky very cloudy, and winds intense. In between are somewhat longer periods called “break” periods where rain is much less, its sunny and hot, and winds can often be low.
Well, we certainly have been in an active period for last 3-4 days, and will remain active till about June 13-14th here in the Central Bay of Bengal! We are near 14°N, 88°E .
The winds have been consistently hovering around 30 knots (30 nautical miles per hour is about 54 km/h) with occasional wind gusts of 50 knots (90 km/h). The wave heights have been above 6 m almost all day today, touching 7 m. Those are some significant numbers – a 7m wave height is about a 21feet high wall of water.
The ship rides very well, and the scientists and the crew are in good spirits. Two days ago we saw a rain squall which lasted for maybe 20-30 minutes with a rain rate exceeding 140 mm/hour at the peak heavy rain! In other units = drenched in 5 seconds. This is all good news in terms of the scientific data we are collecting.