NAWDEX - North Atlantic Waveguide and Downstream Impact Experiment

*Living in the Alex Guesthouse huts*

After one week in Keflavík, the FX and Falcon teams have well settled in their huts belonging to the Alex Guesthouse which offers rustic, yet cozy, accommodation. Being located close to Keflavík airport, it is just a five-minute drive away from the Ops Center and the Silver Gate. Nevertheless, the location offers a fair amount of seclusion and tranquility. Each hut comes with a comfortable bed, a couch, a cooking area with refrigerator and a two-burner stove as well as a bathroom with shower. A special feature is the personal rainbow (see picture) which guides every resident to his private pot of gold (well… wood), provided suitable weather conditions.

Although the huts (or should they better be called chalets?) all look almost the same, there’s room for individuality. For instance, embellishing of the interior by hanging up a flag of your favorite football club or your mother's home country is highly recommended – and also helps to distinguish your own hut from the others. The degree of coziness has even doubled since the last campaign in May 2015 after a second heater was installed in each hut, boosting the temperature to a comfortable level regardless of the weather outside. The five-minute waiting time for warming up the water in the shower is still unchanged, though…

One of the amenities of the Alex Guesthouse is its close proximity to downtown Keflavík where we can choose from a variety of restaurants and shopping opportunities. Maybe more importantly, the local swimming pool, Vatnaveröld, is within walking distance of our temporary homes. The Vatnaveröld features multiple indoor and outdoor pools including hot-tubs and a sauna – the perfect place to unwind and wash away the cares of a day full of forecasting, planning, flying, data processing, etc. For the tough ones, there is also an ice water pool. Try it and you will get a taste of what it would feel like if you went for a swim in the Northern Atlantic. The sea survival course was a cakewalk compared to that!

Even though everyone has his own hut, people often gather for an evening beer or two. Our favorite: Hardcore IPA (no kidding!). The only question that needs to be answered every day is: “What hut are we meeting in tonight?”. No matter when the next flight is scheduled, there’s always time to get together for a chat, a good laugh or even a jam session. Yesterday, a classy (if not necessarily classical) quartet was formed by Philipp and Martina playing two ukuleles, Christian on the guitar and Axel who came all the way from the IGS Apartments with his drums. The band made quite a show and we are sure this wasn’t their last performance during our stay at the Alex Guesthouse. In the unlikely case that people can no longer stand each other’s idiosyncrasies, everybody simply retreats to his or her own private hut. So, in general, we are more than satisfied with our cute little houses just at the entry to Keflavík.

_(Oliver Lux)_

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*Living in the IGS Apartments*

_Showing where HALO and Falcon spend their days when not flying - we will have a closer look on the IGS apartments where some of the scientist are sleeping while they are not in the Operations Center or at the airport.

The first days were really basic. Frank promised us that there will be a fully equipped kitchen including everything we need to get something to eat. Unfortunately it was not. No(t) (enough) chairs, no kettle, no glasses, no cups,... Not even dishes or knifes. Therefore, the first day was a little bit like camping and the good old Swiss army knife served us well. At the second day we made a point and wrote a whish-list to the manager of the IGS apartments including all the mentioned basic stuff above. As it arrives we were very happy, the cupboard started to fill up and we were able to cook some easy meals. As more and more persons arrived the capacity of the pots and pans was not enough. So there was a second whish-list with more pots and pans on it and also some luxury stuff like a toaster, a coffee-machine and a kettle was added. When this whole load of things arrived it was like Christmas and you can see the joy in Mario’s eyes. With these utilities the expectations rise and wonderful variations of dishes were created. Looking back at the first evening (noodles with tomato-sauce) the menu was extended by cooked fish with rice, self-made pizza, fried fish with potatoes, goulash or pancakes. Between the meals the kitchen serves as a second Operations Center also where the flights of the aircrafts are followed, problems are solved and plans are made (for the day off).

The kitchen - which is obviously the central room of our living - is not the only part of the apartments. The private rooms also offered some surprises. Not all of them were available at the first day and are still under renovation. Some windows have to be fixed but no one has to sleep outside. All in all the rooms are nice and well equipped for the basic needs of a field scientist. Beautiful mattress ensure a good night sleep. For some roommates the functionality of the shower was not clear at the first glance because the button who activates the shower head was kind of hidden in the fitting. This provided some fun at the following morning.

In summary one can say that we arrange us well and like it to live together in such a nice community._

_(Kevin Wolf)_

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*Working at the hangar*

_After successfully arriving in Keflavik and spending our first day off discovering Iceland the real work started. This means: let’s got to the hangar. HALO and Falcon are already waiting for us.

Before starting the work at the aircraft the first hurdle has to be overcome, the security check. There, the airport visitor badges have to be distributed and everyone has to be checked for illegal things and weapons of all kind. Passing the inspection and being airside the friendly drivers of SouthAir guides us the hangar. There, the DLR FX stuff sorted all the shipped boxes and containers with the equipment. Luckily the second container arrived on Tuesday evening. Now all necessary tools are available at the hangar.

Already on Monday the WALES crew set-up their cooler to run WALES on the ground and keeping the lasers at the right operation temperature. During flight a cooling device at the top of the aircraft is used for this purpose. Shortly before flight they cleaned the window which covers the inlet of telescope.

For SMART the usual calibration has to be performed. For this, small Ulbricht spheres are used - which produce homogeneous distributed (the technical term is: lambertian) radiation. This ensures constant data quality between every flight and during the whole campaign. Taking them as a reference the calibration of the laboratory is transferred into the hangar. All this effort is needed because even small disturbances in along the optical path can influence the proper measurement of the instrument.

Not only are the instruments important but also the persons who are dealing with them. To ensure proper training of the instrument PI's they were teaching each other how to operate the instruments and how to launch the important dropsondes.   

On Wednesday shortly before flight specMACS flushed their spectrometer-system with gaseous nitrogen to reduce the humidity inside the instrument chamber. This lowers the propability of condensation at the outer window where the cameras look through HALO fuselage. Water and ice on the window reduces the transmissivity in the visible wavelength range and falsifies the infrared measurements. Therefore, decreasing the humidity is crucial to allow measurements in cold regions.

Further on the radiometers need a calibration. This is a 2-point-calibration using targets with an ambient temperature and a very low temperature - achieved with liquid nitrogen reaching a temperature of -196°C (77K). Using these two temperatures the calibration function is determined and used for data processing. The white devices on the photo show these targets which are made of special foam - opaque in the wavelength range of the human eye but transparent in the microwave range. Therefore the radiometers are looking directly on the liquid nitrogen measuring the low temperature.   

At the same time the Falcon aircraft is maintained which carries two lidar systems for measureing the wind speed and direction. They tried to optimize the system performance and adjusted the lasers for proper wavelength-stability.

With all this work done, clean windows and fueled-up completely HALO and Falcon are well prepared for their first flight starting from Iceland. As everyone is curios for the results - let's see what this flight will bring..._

_(Kevin Wolf)_

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*IOP-1: Go with the flow*

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_The planning of the transfer flights for HALO and FALCON from Munich to Keflavik –scheduled for Thursday and Saturday- started beginning of the week. On Tuesday it already became apparent that there might be a NAWDEX ‘Golden Case’ showing up on Saturday: An upper-level trough was located South of Greenland with a ridge (with warm conveyor belt [WCB] outflow) building up to Iceland and a second trough was over Western Europe - perfect conditions for our airplanes travelling from Southern Germany to Iceland to catch the diabatic butterflies that travel up the WCB and disturb the downstream flow. During the course of the week this synoptic situation became more and more certain and the flight planning team saw the opportunity of turning the transfer flight into the first intensive observation period (IOP). This gave a lucky subset of the 85(!) NAWDEX participants the early opportunity to practice their flexibility (that meant some crew members and onboard scientists spontaneously trying to find accommodation in Munich on the first day of Oktoberfest) and they already got a glimpse of how quickly things can change during the planning-process (and later how rewarding it can be to go with the flow!). 

On Saturday the Operation Center was turned fully operative and the first planning meeting took place – which, after the surprising encounter of a Golden Case right at the beginning of the campaign, revealed a very promising and exciting flow development for the coming days. In the early afternoon everyone on site rushed to the airport and bravely resisted the freezing Icelandic winds to welcome the airplanes – which arrived on schedule in the afternoon with satisfied mission scientists that reported on a successful zeroth campaign day._

_(Lotte Bierdel)_