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

Again Dust and Clouds

Today the dust layer was still obvious from the lidar plot, but the concentration decreased and it seems to be mixed also into the marine boundary layer. We choose a similar flight pattern as the last days: first a vertical profile up to 8000 ft (helicopter height) followed by a horizontal leg for approximately 20 min within the dust layer. Both were done over the sea without any cloud contact. In general, there were no low clouds above the ocean today, but there were nice cumuli over the island (see the picture below).

Thus we went there and dipped ACTOS into them. Some were really thick up to more than 8000 ft and contained a lot of liquid water. We continued cloud chasing for approximately 40 min in height between 5000 and 6000 ft. Before going back to Concorde helipad we went below cloud level for another short horizontal leg. This layer was obviously influenced by biomass burning, the particle concentrations were relatively high and we could also smell it.

After all, another interesting flight giving probably interesting results about the influence of transported dust on trade wind cumulus clouds.

Evidence of Saharan dust in the marine boundary layer

A typical size distribution of marine aerosol was measured on April the 9^th at the ground-based measurement station at Ragged Point (red). The Aitken and accumulation mode, seperated by the so called Hoppel-minimum can be seen in the Figure. On April the 15^th a Saharan dust layer with a maximum total number concentration at 2-4 km height was situated above the measurement region. Through synoptic scale advection of these Saharan dust to the measurement region since 14/04/2011 and following downmixing of those particles into the boundary layer, the shape of the number size distribution has changed. Compared to the typical measured number concentration in this marine region (red), the entrainment of the Saharan dust causes an increased number concentration (black) and the typical shape of the Hoppel-minimum gets almost lost.

Flight #07 with a lot of cirrus

Today we performed our 7th flight with all systems running well. A Saharian dust layer between 2 and 4 km was indicated by the MPI lidar, therefore we startet our flight pattern ( 13:42 - 15:25 UTC) with a profile and a subsequent level flight in 2.5 km off the East coast to get a scan with the CCNC.

An Aster satellite overpass was scheduled for 10:37 local - unfortunately there were only very tiny cumulus clouds over the water and we decided to chase a few clouds over land. We sampled a lot of droplets but for the whole day the sky was covered with cirrus clouds so a direct comparison of our measurements with the satellite data will be difficult.

Finally, we got a few clouds over the ocean before we came back to Concorde helipad. An example of our quicklook monitor inside the helicopter is shown in the picture. The lower time series shows the liquid water content of a shallow cumulus clouds, the upper one is the uncalibrated temperature value.

From (Saharan) dust till droplet

Today we performed two quite successful measurement flights including a fully functioning PICT! Both flight pattern included a vertical profile up to 8000 ft off the coast near Ragged Point where the dust layer was located. Afterwards a horizontal flight leg was performed to get full aerosol number size distributions and CCN spectra.
Observed CCN concentration lay in the order of 700 per cubic centimeter and the dust was even visible to the naked eye (see picture).
After the leg in 8000 ft we descended and went for cloud chasing. Fortunately, PICT worked very well and recorded lots of drops - even some lucky ones around 55 microns. Thus, last night's work was definitely worth it.

Thanks to Tina - we both edited this post.