Today we conducted two flights on HALO, the last test flights before the aircraft is scheduled to leave for the Amazon, and my first experience as flight scientist on HALO. The weather in the morning was similar to what we had yesterday, a mostly cloudy sky, with all sorts of low and high clouds and the occasional glimpse of the sun, as well as the occasional rain shower.
We took off at 0828Z (or 1028 local time) and encountered some scattered small cumulus with bases below 1000'. On our way north we climbed though a variety of cloud types, with some fairly tall cu's reaching to about 18,000'.
We passed over a broad band of altostratus that was moving south from the German coast and reached its northern edge just east of Schwerin. The blue line in the track plot below shows the approximate location of this band. From our flight altitude of 41,000' we could nicely see the northern edge of the cloud band, and to the north of it a field of developing small cumulus. Note also the lack of cu's in the region shielded by the stratus cloud.
We took off at 0828Z (or 1028 local time) and encountered some scattered small cumulus with bases below 1000'. On our way north we climbed though a variety of cloud types, with some fairly tall cu's reaching to about 18,000'.
We passed over a broad band of altostratus that was moving south from the German coast and reached its northern edge just east of Schwerin. The blue line in the track plot below shows the approximate location of this band. From our flight altitude of 41,000' we could nicely see the northern edge of the cloud band, and to the north of it a field of developing small cumulus. Note also the lack of cu's in the region shielded by the stratus cloud.
At our altitude, we were clearly in the stratosphere. It was impressive to see how dark blue the sky was above us. At this level, only about 18% of the atmospheric mass is still above us!
To investigate the stratus cloud, we successively descended to 21,000' and headed south to enter the cloud (below).
To investigate the stratus cloud, we successively descended to 21,000' and headed south to enter the cloud (below).
The temperature in the cloud was about -40 C, and it consisted only of ice particles. The air in the cloud was almost smooth, only a slight bumpiness indicated the slow vertical motion of the air. Once our measurement objectives in the ice cloud were accomplished, we went on to investigate the cumulus clouds, that by now were growing quite impressively.
First, we aimed for the prominent cloud top that shows in the middle of the picture on the right, but when we reached it, the cloud had run out of steam, and the top was already decaying. We then looked for more promising targets and found some excellent candidates of growing cu's. We went through these clouds at 12,000' and at temperatures around -4 C. At these temperatures, the clouds consisted still of supercooled water, but a look at some of our PMS measurement probes on the wings showed a small amount of icing. The turbulence in these clouds was quite noticeable, but not enough to upset anyone's stomach. The cloud penetrations were conducted in the region outlined in red on the flight track below. |
Once we had enough data from the cumulus clouds, we climbed up again to 27,000 feet, and turned towards home. On the way back, we conducted some tests on the behavior of the PMS probes at different speeds and on the effect of a slight side-skid of the aircraft behavior. At 1140Z we landed back at Oberpfaffenhofen in very light rain.
(Thanks to Pilot Steffen Gemsa for some of the pictures above!)
Below, I include the flight track and the temperature soundings from Lindenberg.
(Thanks to Pilot Steffen Gemsa for some of the pictures above!)
Below, I include the flight track and the temperature soundings from Lindenberg.