AC15 was a HALO flight for early risers, the take-off was planned for 06:30 LT! To meet this schedule, the preparation of HALO and its scientific instrumentation had to start four hours before takeoff. Therefore, HALO was moved from the hangar to the apron at 03:30 am already. The scientists met at 04:00 LT at Terminal 2 to enter the airport.
The picture on the left shows the probes on the wings and the rainforest below during the albedo measurements
The picture on the left shows the probes on the wings and the rainforest below during the albedo measurements
Why so early? Well, this special mission required cloudless conditions; clouds would actually hurt the measurements. That sounds strange for a convective cloud campaign. However, the main objective of this flight was to measure the surface albedo of the rain forest (a measure of how much of the incoming solar radiation is reflected by the ground) and compare it with the albedo of deforested areas. This type of data is needed as a crucial input for radiative transfer simulations which are needed to analyze, for example, the satellite intercomparisons performed during AC10 and AC14. In general, albedo data are required to evaluate all the radiation measurements carried out during ACRIDICON. These albedo measurements have to be performed under cloudless conditions and, therefore, we had to schedule such an early flight, well before convective clouds would evolve.
It was not quite clear whether the 06:30 take-off would actually work. Too many ifs and buts could cause unexpected delays. The fueling turned out to be a potential problem so early in the morning. However, our colleagues from DLR-FX successfully managed to maintain the schedule. The flight preparation went very smoothly, and actually we took off two minutes ahead of the planned 06:30L.
The albedo measurements were performed at low level (3,000 feet). They worked very well; the timing was perfect and we were lucky because no clouds perturbed our measurements. We collected about two hours of albedo data before the regular, daily convective cloud evolution started. After the albedo measurements, we climbed to an altitude of 43,000 feet and sampled a huge outflow, which looked almost frightening from a distance. We probed the outflow at different altitudes and subsequently descended to measure above, within, and below convective clouds at lower levels.
Altogether we had a very successful flight. As usual, the collaboration with the pilots (Stefan & Steffen) was simply great; the team of instrument operators (Chrischi, Fabian, Adrian, Florian) and the mission PI had a lot of fun. Thanks to all of you!
(Guest blogger: Manfred Wendisch. Picture credits: Manfred Wendisch, Florian Ewald, Steffen Gemsa)
(Guest blogger: Manfred Wendisch. Picture credits: Manfred Wendisch, Florian Ewald, Steffen Gemsa)