Since ACRIDICON-CHUVA is a joint experiment with the IARA flight campaign using the US-DOE G1 aircraft, it is essential to compare the measurements taken on the two aircraft. And what better way to do this comparison than to have the two aircraft actually flying formation side-by-side in the air! So the flightplan for today had both aircraft taking off more or less at the same time, fly in formation over the ground sampling site near Manacapuru, study clouds over the same area, and then have them go their separate ways doing additional tasks.
Takeoff was just after 1100L, followed by formation flight at 1500’ below a cloud base of about 2500’. Rachel Albrecht was the flight scientist on HALO, and Luiz Augusto Machado was with Jason Tomlinson of the G1. Cloud sampling on HALO began at 1220L at about 4000’ and continued up to 14,000’, where the convection topped out at the time (1416L). The aircraft then went to 43,000’ for some radiation measurements, and descended again to lower levels to sample some more clouds and cloud outflow. Landing was at 1619L.
(Thanks to Stephan Mertes, Luiz Machado, and Rachel Albrecht for the pictures!)
If you enter Brazil on a researcher visa, you must register with the Federal Police within 30 days. That sounds easier than it is – but since we have to do this quite a lot in conjunction with our permanent station near Manaus, one of our colleagues has written a 5-page manual to explain the procedure. Well, over the previous days we had acquired the necessary bank receipts, notarized passport copies, appointment receipts, and so on, and so at 0700 we headed in two carloads to the Policia Federal. We got there at 0730, waited for them to open, signed in, and – waited. My turn came about 1100. I was looked over, photographed, and fingerprinted. That also sounds easier than it is. Fingerprinting was with some electronic scanner, which obviously didn’t like my fingers. For each finger, it took about 10 to 50 attempts, with the friendly young lady grabbing my finger and rolling it around on the glass plate, with varying amounts of pressure. Alternatingly, I was asked to rub my finger across my forehead to provide more grease, and then had my finger wiped with a Kleenex to remove excess grease and sweat. Well, after some 20 minutes the procedure was over, leaving both parties somewhat exhausted. At 1130, after only four hours, I was able to leave with a new piece of stamped and signed paper that made me a legal scientific visitor to Manus!
Since this amount of waiting really didn’t impress anyone all that much, we were looking for more pain and ventured to get our airport badges from Infraero (I was told some call it Infernaero). We left the hotel again at 1320, drove to the airport, got the badge that allowed us into the office where we were supposed to get the badge, and – waited. After about half an hour, an employee came out and declared that the airport computer network was down, and they weren’t sure if and when it was going to come up again. After debating at length whether it was better to wait and take a chance or to come back tomorrow - and take a chance – we decided to stick it out for a while. Well, at about 1530 the network came alive again, and at 1550 at least those of us had a badge, who were expected at the 1600 planning meeting. We spent the rest of the day planning for an intercomparison flight tomorrow and listening to presentations.
Today, finally, came the day we all had been waiting for! At 0915L I drove to the airport with the flight crew and met the other scientists who had been at work since 0700 to get the instruments prepared. The science team consisted of myself, our Brazilian scientist Rachel Albrecht, Florian Ewald, Daniel Fütterer, and Emma Järvinen.
The aircraft was already parked on the apron, since in spite of the fact that we had contracted (and paid) for a hangar, that hangar was still filled with an old ATR52 that was being repaired and painted. But actually, it was quite comfortably cool inside HALO, thanks to an efficient air conditioner. In the hectic hours before takeoff, the cabin is so crowded with all the scientists getting their instruments ready that it is almost impossible to move around, and I sat down in the hangar instead.
I was a bit anxious at this time: Was the aircraft really going to work? Would the instruments perform? Would we be able to convince ATC to let us do the “crazy” flight patterns that our work required? Would I be able to navigate the aircraft through the complex manoeuvers that cloud profiling required? Would the pilots consider the cloud passages safe enough to make these runs time after time? Would too much ice accumulate on the aircraft to keep working?
Looking at the sky I could see that the cirrus in Manaus region was quite dense, which might be a problem for some of our radiation measurements and might suppress cumulus convection. But, to my relief, cumulus had been building since about 1030L (1430Z) and the sky beckoned us to start cloud sampling.
Takeoff was at 1606Z and we climbed out into a quite hazy sky. The haze topped out at about FL130 and we saw abundant cu’s all around us. After climbing to FL300 through some cumulus outflows we held this altitude for about 5 min, and then descended again into the boundary layer (BL). We reentered the haze at 11,000’, passed cloud base at 4000’, and at 1652Z crossed the Rio Tapajos, a major tributary of the Amazon, at about 2000’ above ground. The hazy air contained about 2000 particles per cc. There was a small fire with a smoke plume along the river and the vegetation alternated between forest and regions of savanna vegetation, which is called cerrado in Brazil.
At 1703Z we began our climb again, passed cloud base at 4100’, and did another up and down profile to FL300. At 1704Z we turned west in the BL at Alta Floresta (ATF) and flew over large deforested areas to our cloud profiling region about 30 nm west of ATF. Cloud bases here were at 5800’ indicating that we were in a slightly different airmass from before. We began cloud profiling at 1750Z with a 5000’ run below cloud base at SAT 19°C and CN ~2000/cc. For the actual profiling, we made 23 passages through clouds at 16 different levels. Some of these passages were only slightly bumpy, but other shook us around quite a bit. At the lowest levels we encountered only water cloud drops, then a zone with water and ice between FL220 and FL300, and only ice particles above this level. In the higher ice clouds, we had some encounter with static electricity, which made us a little nervous, and we made sure to stay away from the bigger cumulonimbus clouds to avoid any chance of lightning. Then, according to our plan, we had wanted to sample the ice cloud region at the temperature around -40°C, but we did not see any young cloud elements at this level, which seemed safe to enter, and so we decided to head north towards Manaus. Massive cloud anvils to the west above us looked threatening enough to hasten our departure.
On the way west and north, we passed through large areas of cloud outflow at FL330 to FL430, which contained lots of ice particles, but also very high concentrations (~5000/cc) of small aerosol particles that we think are produced in these cumulus towers. They appear to consist mostly of organic matter. As we went further north, the bigger ice particles from the clouds appeared to mix with particles from the cirrus clouds that had been prevailing in the region.
The long transect through outflow – in the cockpit we called it “grey soup” – ended when we entered a large clear area about halfway to Manaus, where we observed a beautiful sunset. Another large outflow just south of Manaus, then a turn over MNS, and north towards Boa Vista. We descended to reach ARVUM, our northernmost point, at 8000’ where particle concentrations were only ~500/cc. Since it was quite dark at this time, we felt that it was not safe to descend any further and headed back to SBEG, where we landed at 2329Z.
We were greeted by the rest of the science team and excitedly told our stories from the flight. All in all, we had an extremely successful flight that put to rest all of the worries that I had before we took off. The instruments worked (well, most of them) and the flight management between science and flight crews functioned very smoothly. ATC turned out to be very cooperative and the only hiccups were due to the occasional loss of communication because of the limited range of radio contact. Our Brazilian scientist, Rachel Albrecht, and Tenente Fialho managed to iron out some linguistic communication problems and succeeded in obtaining the magic word “Autorizado!” We wrapped up the day talking over well-deserved beers in the meeting room. “Thank you” to the team that had made it all possible, especially to our Brazilian partners!
(Photo credits to Meinrat Andreae, Steffen Gemsa, Florian Ewald, Emma Järvinen, and Daniel Fütterer)
All expeditions seem to begin with a period of seemingly endless waiting for supplies, permits, and the like. ACRIDICON, of course, is no different. We are still waiting for our container with scientific and aircraft equipment to be released from customs, and we have spent many “fun-filled” hours waiting to get badges to enter the airport. Getting your passport stamped by the Federal Police to validate your visa requires lengthy online filling of forms, visits to banks and notaries, and finally a visit to the offices of the Police, all in all a day of your life.
Most of the rest of the time is filled with meetings to discuss logistical issues, flight planning, coordination with Air Traffic Control, and so on. The good side of all this is that it gives the instrument scientists a chance to fix the many small and large problems that come up when one takes an aircraft full of high-tech equipment through lots of atmospheric turbulence, shaking and bouncing into the hot and steamy atmosphere of the Amazon.
Wednesday, 3 September, the day after arrival, the aircraft was promptly released from customs and the scientists could begin to download their data from the transit flights and work on their instruments. A nice benefit from all this hanging around was that I got to try out the pilots seat of HALO on the ground :-))! We also found out that Friday and Sunday would be national holidays, and airport access would be limited. Nevertheless, we made plans for a research flight on Friday, always the optimists. A very interesting part of the day was a series of short presentations by the scientist to introduce their instruments and objectives to the entire team.
On Thursday we first met with the representatives of the Brazilian Air Traffic Control, two Air Force lieutenants and a Sergeant. We were also introduced to the two young Air Force lieutenants, who were going to be the observers on our research flights. We then made the detailed plans for Friday’s flight, which was going to be a 700 mile transect from the smoke-polluted area around Alta Floresta to the clean atmosphere around Boa Vista in the north.
In the afternoon, we were to go to the airport to work on our instruments. I was supposed to get trained to operate a couple of instruments in flight, in addition to my job of flight scientist. This consists of coordinating the science and flight crews in flight and making decisions about what maneuvers to execute to get the aircraft to the right place and altitude for our measurements. For the training, we obviously needed aircraft access, which required badges. To get these, we first had to wait for the handling agent at Terminal 2, where we were told to go to Terminal 1, where we would be issued temporary badges. We all packed into our cars and drove over to the other terminal, waited again for our handling agent, and then were led to the airport offices for processing. There, we got badges that allowed us to get to another waiting room, where lots of people were already waiting. After only three hours and filing out more forms, we had our temporary badges, which allowed us to work on the aircraft for another two hours or so, while we had power at the aircraft. After all this, the day took a frustrating end, when the handling agent announced that tomorrow, Friday, there could be definitely NO flight because of the national holiday.
Instead, Friday (5 Sep) was spent doing more instrument maintenance and refining our plans for a flight on Saturday. I also discussed with Danny Rosenfeld the details of the procedure for “cloud profiling”, which consists of making many passes through growing cumulus clouds from cloud base up to the ice plume that leaves the top of the clouds.
Two itineraries today - one that of HALO, which flew from the Cape Verde Islands to Manaus, the other my own on a commercial flight from Rio de Janeiro to Manaus.
HALO left Sal Airport in the cape Verde Islands at about 1500Z and first did two short sampling legs in the Sahara dust layer at 6000 and 11000 feet. Climbing up to flight altitude after these legs showed that the highest dust concentrations today were at levels above 11000', a bit higher than the day before. Then came the long crossing over the tropical Atlantic, which took HALO through the inter-tropical convergence zone (ITCZ) with some big convective systems, which show up as white blobs over the Atlantic on the satellite image below. Elevated aerosol concentrations were observed above some of these large convective clouds and cirrus outflow anvils. An example is on the picture to the right.
HALO reached the Brazilian coast at Fortaleza and then turned west to head for Manaus. Unfortunately, for legal reasons, we had to turn off our instruments an hour before reaching the continent, and could not get data during this part of the flight. Nevertheless, there are some beautiful pictures from this part of the flight. The images below show convective clouds growing out of a sometimes quite clean (first picture), sometimes smoke-polluted boundary layer over equatorial Brazil. Above Brazil HALO climbed up to test its ceiling altitude with its heave load of instruments, and reached an impressive 47,000 feet.
The picture below wins today's "Blogger's Choice Award"! It shows an long outflow from a cumulonimbus cloud, seen from an altitude of about 20,000' when approaching Manaus. Picture credits go to Steffen Gemsa for this one and to Johannes Schneider for the pictures above. At 2200Z (1800 local) HALO landed at the Manaus International Airport.
As promised, there is a second itinerary for this day! Since I was not on HALO, I took the commercial flight on Lufthansa to Rio de Janeiro (11:40 hours long), and then got to spend almost eight hours in beautiful Rio airport waiting for my connection for the 4:15 hour flight to Manaus. I was lucky enough to get a window seat on this flight, and could get a first survey of aerosol and cloud conditions along a stretch from about 23 S to 3 S. I'll show some pictures from this flight below, but keep in mind that pictures of aerosol hazes are, well, a bit hazy!
Starting from Rio, the aerosol burden increased going north, and my first image shows a typical sky at about 19 S. What it also shows is one of the big problems Brazil is facing at this time: the huge reservoir at Tres Marias in Minas Gerais State, like many other reservoirs in Brazil, is almost empty because of a severe drought that has been going on for a long time now. That makes our ACRIDICON-CHUVA research, which addresses the connections between aerosols, clouds, and rain, particularly relevant to this region.
From about 12°S on the air go so hazy that it became difficult to see the ground, and the densest haze was reached at around 10°S.
The cumulus convection was more active here as well than in the south, and many clouds were rising to our flight altitude of 36,000’ and even well above us.
On some of them, I could observe the typical wispy plumes of ice particles detraining from the cloud.
At about 6°S, the air became noticeably cleaner, and one could see small muddy rivers flowing through the rain forest.
Near Manaus, I had the first view of the Amazon River, which was below quite dense haze, apparently produced by some burning along the shores of the river further downstream to the east. North of the river was a line of cumulus convection.
Then came one of the main touristic features of Manaus, the Meeting of the Waters, where the muddy Solimões River to the South and the coffee-brown Rio Negro flow for a while side by side in the same channel, before they merge to form the actual Amazon River. This being the dry season, the view was a lot less clear than what one can see in the rainy season.
Finally, after a sweep by the city of Manaus, our home away from home for the next month or so, the Hotel Tropical and the Park Suites Hotel tower, located along the Rio Negro came into view just before landing at Manaus airport.
Today, the "real" ACRIDICON campaign began, as HALO left its home base in Bavaria and flew to the Cape Verde Islands, a stepping stone on the jump across the Atlantic to Brazil. I was not on this flight, but I could participate virtually through the satellite link with the plane. HALO took off punctually at 1200 local time (1000Z) and climbed to 39,000'. If flew across Bavaria, Lake Constance, Switzerland, and France, and crossed the Pyrenees to enter Spain. For a while HALO chased the contrail of another plane.
After leaving Spain, HALO went out over the Atlantic and flew along the coast of North Africa, across the Canary Islands, heading for Sal Island in the Cape Verde Islands. The meteorological models had forecast a big layer of Sahara dust, centered at an altitude of about 2 km, that was spreading out from Africa across the Atlantic. To test the models, and to learn more about the properties of the dust aerosols, we took HALO down to 11000' and then 6000' as we were approaching the islands, and indeed there was a dense layer of dust that we were able to take measurements in.
(Thanks to Steffen Gemsa, Johannes Schneider, and Andreas Minikin for the pictures in this blog entry!)
The goal of the second flight today was mostly to test the instrument operations in clouds, including the sampling of cloud drops and ice particles with an instrument called Counterflow Virtual Impactor, or CVI. The CVI inlet is one of the many probes and intakes that are mounted on top of the aircraft. You can see the probes on the picture to the left, which was taken during fueling of HALO. The CVI and some other inlets can be seen in more detail on the pictures below. For more information on these inlets see http://www.enviscope.de/engineering/inlet-systems/
The flight took off 1240Z (1440 local time) and followed the tracks shown at right. Unfortunately, by now all the high ice clouds had vanished, and only cumulus clouds could be sampled at 8000' over southern Germany. Nevertheless, the science team was able to successfully test the operation of the instruments, including switching back and forth between the different inlets.
HALO landed again at 1450Z in Oberpfaffen-hofen. This was the last of the test flights, and the next flight will be the transfer flight to Manaus in the Brazilian Amazon!
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.
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).
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.
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.
0800 LT: Morning briefing. The decision to hold two test flights on Wednesday, 26 August, was confirmed. The scientific instruments and aircraft systems are generally operational, with the exception of the Satcom system, which had failed on the Sunday test flight and was n/op Monday. A telecom with the Satcom group is scheduled for 1000LT. The mission sequence and characteristics for tomorrow are to be decided at the 1400LT briefing.
1000 LT: Satcom telecon discussion. There is no clear idea about the source of the problem. Ingrid will come at 1300LT to test the system. HALO will be rolled out of the hangar for this purpose.
Weather conditions: Mostly overcast, with few sunny spells. Strong westerly winds.
1330 LT: Satcom is working. Problem may have been with initialization of system. Chat and file transfer were successful, live tracking works partially.
1400 LT: Science team meeting. Weather forecast tomorrow is for mostly cloudy conditions tomorrow, with some clearing during the day. Light rain expected, decreasing in the afternoon/evening.
We are planning for two flights tomorrow. The first will emphasize aerosol and cloud microphysics measurements around and in the tops of growing clouds. The flight track will go to northern Germany and the cloud studies will take place in a specially designated area (TRA). The second flight will focus only on measurements in clouds and will follow a similar flight track.
I'm staying at a the Hotel Seehof, a nice small hotel in Wessling, a little village just a few km from the DLR and the airport that HALO flies from. The hotel is on a very small lake surrounded by reeds and a few small boathouses. The hotel's beer garden is right on the lake - all very idyllic, but unfortunately the weather is too cool to enjoy sitting outside, and that in August, in the middle of summer.