Very clean clouds

After the dust of the last few days we had some very clean clouds today. PICT measured mean droplet diameters of up to 40 μm (see exapmle on the right) and there were only few CCNs. First we started flying a profile in our measurement area, which was soon cancelled to catch the few clouds above the sea (north of Ragged Point) before they move over land. The cloud base was about 1600 ft high. Afterwards we went back to the measurement area and finished the profile from 8000 ft down to 1000 ft. Meanwhile a lot of nice cumuli were carried with the southeastern wind towards us, which we started chasing then. Moving towards Barbados they grew quite fast. During chasing we got too far north, so we went back to the measurement area, where we catched tinier cumuli. Unfortunately, there was cirrus above us almost all the time. Then cloud chasing was finished and we stayed at about 1600 ft below the clouds so the Mini-CCNC could perform the scan mode. Heading back to the airport we finished with a low level leg.

Growing and towering cumulus

During the weather briefing, we recognized cumulus clouds above the sea. So we decided to catch clouds over the ocean in contrast to the flights of yesterday. After the profile from 180 ft (ACTOS height) to 8000 ft (helicopter height) in our measurement area, only very thin cumulus clouds were below us (see upper picture). Additionally, a slightly increased concentration of aerosols and CCNs was detected in 8000 ft. Thus, we decided to stay there for a 5 minutes long leg. Afterwards, we tried to catch the thin cumulus clouds and recognized growing ones over the island. In the middle of the island, the cumulus clouds towered and their tops were partly separated and drifted eastwards resulting in a compact altostratus layer. That is shown in the lower picture, which also shows a cumulus congestus at the west coast of Barbados including some showers. We catched the thicker cumulus clouds at the east coast of Barbados, while the developed altostratus covered the sky above us. Thus, the radiation measurements were handicapped. On our way back to the airport we found some cumulus clouds, which were not influenced by this layer - but there was cirrus above.

To show you all what Birgit meant with "a full round-trip around the island" here is a screenshot of our GPS tracking of flight 10.

Biomass burning on Barbados

After our contact to probably polluted clouds in the morning we had the chance to sample clouds at the same place in the afternoon.
Again we started with a vertical profile from 200 ft (ACTOS) to about 8000 ft (helicopter) in our measurement area. Since there were no clouds off the east coast we decided to fly to the west coast where a couple of mature cumuli stayed almost the complete day - the ones Birgit already observed in the morning.
On our way there we performed a horizontal leg at 6000 ft and recognized increased aerosol number concentration and CCN concentration probably due to biomass burning (see upper picture with one bigger fire in the north of the island).
Finally, we were able to catch the clouds near the west cost (but over land) and performed several cloud passages at different altitudes with ACTOS inside the cloud and at the very top. It was really amazing to watch these big cumuli growing and disappearing right next to each other. It is a pity that my camera ran out of power just as we reached the first clouds... The lower pictures shows one of my last pictures for today.

Clouds over Bridgetown

Today, we started earlier than usual: take off was already at 9:00 local time. We had almost blue sky above the ocean and only a few scattered clouds above the island. As on the days before, we flew at first a profile from approximately 60 m above sea surface to a height of 8000 ft helicopter height above the ocean. However there were still no clouds around us. We recognized a few small clouds above the northern part of Barbados and started flying there. It took some time to reach this region and the clouds were almost gone when we reached them. But PICT got a few droplets to measure to check if the new setup works better. From the north of the island we recognized that the area around Bridgetown was nearly covered with clouds and asked for permission to fly there.That was approved, thus we followed the west coast down to the area of Bridgetown. Finally we got some more cloud contacts above the city area and at least a chance to check the new settings of PICT. After spending a couple of minutes there the flight time was over and we flew back to the Concorde helipad. From the first quicklook it looks like the cloud was more polluted than those above the sea the last days and was probably influenced by the island (PICT was doing well!). During this flight we made a full round-trip around the island to catch our clouds in the end.

Flight #9

Today we started our measurement flight at 9:45 local. Directly after departure we performed a horizontal leg with ACTOS at 200 ft above sea level heading to our measurement area near Ragged Point. After reaching this area we began to ascent for a vertical profile up to 8000 ft heading north. During the ascent we recognized a field of small cumuli slightly north of our measurement area and we decided to hunt for them.All systems seemed to work well and we were lucky to catch more cumuli on our way back into the intended measurement area. Arriving there, unfortunately, nearly all clouds disappeared so we stopped cloud hunting to focus on aerosols. Therefore, we performed horizontal legs at 3000 ft and 1600 ft (helicopter) and in between a couple of vertical profiles (like porpoise dives) to characterize conditions near cloud base. First quicklooks from the aerosol data point to weaker dust concentrations which can also be verified by the MPI lidar quicklook.

It never rains in April