Weather conditions during the HALO-(AC)³ campaign

Posted on 19. April 2023 by andreasw

As we reported earlier in this blog, we participated in the airborne field campaign HALO-(AC)³ In March and April 2022. The goal of the campaign was to improve the understanding of the airmasses transformation when transported into or out of the Arctic. Two types of airmass transports were of particular interest: First, moist and warm air intrusions that transport high amounts of heat and moisture from the mid-latitudes into the Arctic. Second, marine cold air outbreaks that lead to the formation of cloud streets and convective cells when cold and dry air from the central Arctic is transported southwards over the relatively warm North Atlantic. In our study, we analyse the weather (and sea ice) conditions during the HALO-(AC)³ campaign.

Map of the study area of the HALO-(AC)³ campaign including the flight tracks of the research aircraft HALO, Polar 5 (P5) and Polar 6 (P6). The study area has been separated into three subregions.

We separated the campaign into a warm and a cold period with the help of northwards humidity transport (IVT) and the so-called cold air outbreak index (MCAO index). The cold air outbreak indicates the strength of the temperature difference between the surface and the lower atmosphere. High differences suggest cold air outbreak conditions with strong interactions between the cold ocean and the atmosphere. The warm period was dominated by northward winds and warm air intrusions while the cold period featured several cold air outbreaks.

(a) Northward water vapour transport (IVTnorth) and (b) marine cold air outbreak (MCAO) index for the campaign duration in 2022 (black line). Grey shading indicates the climatology over the years 1979-2022. The red box shows the warm period, while the blue box illustrates the cold period.

During an extremely strong warm air intrusion, record breaking near-surface temperatures occurred in the central Arctic compared to the March 1979-2022 climatology. Also at Ny-Ålesund, the weather station recorded the highest near-surface temperatures for March since the beginning of the measurements in 1975. This warm air intrusion was detected as so-called Atmospheric River, a thin but long band of extremely strong moisture transport. Over the sea ice northwest of Svalbard, record breaking rainfall rates occurred.

Average 2 m temperature in March 2022 north of 80°N (red line). Thin black lines show the temperature for each year between 1979 and 2022 and the thick black line illustrates the average over those years.

At the beginning of the cold period, a strong cold air outbreak led to an extremely dry atmosphere over Ny-Ålesund with integrated water vapour content of just 1.1 kg m-2 (24 March 2022). Less than 3 % of all radiosondes launched since 1993 recorded drier conditions.

Humidity measurements from radiosondes (weather balloons) launched at Ny-Ålesund (Svalbard) during HALO-(AC)³. The colours indicate the specific humidity (fraction of water vapour mass to total air mass) while the black line shows the total humidity content of the troposphere (lowest layer of the atmosphere).

During the cold period, we also observed the Arctic version of a hurricane, a Polar Low. Polar Lows are characterised by convective (cumulus) clouds, relatively strong winds (at least gale force) and precipitation, while extending only over a few 100 kilometers. They also have a relatively cloud free centre like the eye of a hurricane. We analysed the environmental conditions for the formation of the Polar Low.

Photo taken from the research aircraft HALO during the flight to observe the Polar Low.

Luckily, the weather conditions were quite favourable to achieve the goals of the campaign because we could capture both types of airmass exchange between mid-latitudes and the Arctic. The publication has been submitted to the European Geosciences Union journal Atmospheric Chemistry and Physics.

Long-awaited first research flight: Joint adventure with three aircraft!

Posted on 22. March 2022 by Imke

What a successful day! P5, P6 and HALO had their first joint research flight on Sunday!

If you ask yourself “What is HALO? And what is special about a joint flight?” then read on…

First, let’s start with something you already know from the previous posts: P5 and P6 are polar aircraft, which participate in the HALO-(AC)³ campaign and which are stationed in Longyearbyen, Spitsbergen. The instruments belonging to the University of Cologne, namely the radar MiRAC and the microwave radiometer HATPRO, are installed on P5, which is a remote sensing aircraft. Contrary, P6 is equipped with in-situ instruments recording atmospheric parameters and cloud particles near the aircraft. Thus, P5 is mainly flying above the clouds at an altitude of around 3 km, whereas P6 is flying at lower altitudes directly through the clouds. Joint flight activities of the two polar aircraft provide in-situ and remote sensing observations of a lot of different parameters from the same cloud at the same time!

HALO at the airport in Kiruna, Sweden. (Photo: Henning Dorff)

Next, HALO comes into play. HALO stands for “High Altitude and Long Range Research Aircraft” and is operated by the German Aerospace Center (DLR). HALO carries remote sensing instruments similar to P5, but is able to fly at higher altitudes of about 10 km and travel much longer distances. During HALO-(AC)³ it is stationed in Kiruna, the northernmost city of Sweden, together with other scientists from our group. The aim is to observe how air masses change in the Arctic by measuring the temperature, humidity, cloudiness or aerosol concentration along the wind direction.

As often as possible, joint flights with all three aircraft will be realized, which is really difficult to coordinate! Another difficulty are the bad weather conditions in Longyearbyen making flights with the polar aircraft impossible. And sometimes the different platforms are interested in different clouds or air masses.

During the first joint flight, the flight conditions were very calm! Our instruments worked well and observed precipitating cloud structures over sea ice and open water. In one of the following posts we will have a first look at the observations!

If you are interested in a video diary with short daily updates on the work routine in Longyearbyen, just follow AWIexpedition on Instagram!

The race is on: Polar 5 and 6 arrived in Longyearbyen!

Posted on 19. March 2022 by Imke

Now the time has come: both aircraft, Polar 5 and 6, have arrived in Longyearbyen, Spitsbergen, yesterday afternoon!

Arrival of Polar 5 in Longyearbyen.

The aircraft belatedly started their ferry in Bremen on Thursday morning and had a stop for refueling in Tromsø over night. After the arrival in Longyearbyen, all hands were needed to unload the aircraft and prepare them for the first scientific flight.

Polar 5 after the landing at the airport Longyearbyen.

For Sunday, the first research flight is planned – provided that the weather condition is good enough for takeoff and landing! That means, that the cloud base has to be high enough to not directly fly into a low level cloud. This would bear the risk of a bad view and freezing of the propellers. And we do not want to risk a crash!

Hopefully, the plans can be realized. An update on the first flights will follow soon!

To stay up to date, check Twitter for the latest information! #HALOAC3 #AC3TR #MiRACradar #polar5 #Svalbard

Installation of the radar and radiometer on P5

Posted on 18. March 2022 by Imke

Last week we installed the radar MiRAC and radiometer HATPRO on the Polar 5. The whole installation took us three days, but the following time lapse video gives you an overall impression in only two minutes!

The video first shows the installation of the radar MiRAC which is covered by a belly pod below the aircraft. Then the screwing together of the HATPRO is shown.

MiRAC is a frequency-modulated continuous wave (FMCW) radar, an active remote sensing instrument, operating at 94 GHz with an additional microwave radiometer, which is a passive remote sensing instrument, recording at 89 GHz. The radar is hanging below the aircraft and is protected by a belly bod. The bottom of the pod has a hole so that the antennas of the instrument are able to transmit and receive microwave radiation. The transmitted signal is reflected by cloud droplets or the surface and received by the antennas again. These signals help us to detect clouds and to interpret their microphysical properties.

The radiometer HATPRO is installed inside the aircraft and is looking through a hole in the ground of the aircraft. HATPRO measures microwave radiation emitted by the surface and atmosphere below Polar 5. These observations contain information on the atmospheric humidity, precipitation, liquid water in clouds, as well as on the surface.

After the installation, it was time for a ground test, during which all instruments inside the P5 were connected to the aircraft electricity one after the other. Unfortunately, this did not work out as planned and after some minutes no electricity was available in the aircraft anymore. Nevertheless, the engineers repaired everything and the ground test could be completed successfully the very next day!

Before taking off to the Arctic, the instruments had to be tested during the flight as well. Thus, the first short flight took place over the North Sea and Helgoland. Luckily, all instruments on board worked properly!

Communication during the flight is only possible with a head set.

After the success in Bremen, we had to quickly pack our luggages. At the beginning of the week the great journey to the Arctic started. After a stop in Oslo and Tromsø, we arrived in Longyearbyen on Tuesday! Since then we are waiting for the Polar 5 and 6 and use the time to explore the area and plan the first research flights. We expect the aircraft to land in a few hours and will give an update on the arrival soon!

To stay up to date, check Twitter for the latest information! #HALOAC3 #AC3TR #MiRACradar #polar5 #Svalbard

How to prepare for an Arctic campaign (part 2)

Posted on 8. March 2022 by claudia

Part of preparing for a climate study in the Arctic involves preparing for polar bear emergencies. Blog followers will ask themselves: wait, but aren‘t we flying? Yes! But…safety training includes polar bear protection, as emergency landing on the ice is (an unlikely) possibility.

An image from the Arctic landscape… and a typical road sign in that region (photo credits: Pavel Krobot)

The ice is the home of the polar bears. Bears are very curious, and extraordinarily well adjusted to the Arctic environment. For a polar bear, a group of scientists means a great opportunity for some extra dinner. So even though many of us are faced by comments around „You‘re going to the Arctic: I hope you will see a polar bear“ we actually really want to avoid seeing one (other than from the plane).

But you never know, so better to prepare for the emergency case. This is why 6 of us spent a day at AWI Bremerhaven to learn about polar bears and their behaviors. We learned how to avoid meeting a bear, how to scare bears (hint: they don‘t like loud noises, including banging on cooking pots), and what to do when you see one from far away. For the troubling worst-case scenario of a bear attack, we were also trained on how to handle a rifle.

Insights from the group include: rifles are surprisingly heavy; we were lucky to have Arctic-like wind conditions as storm „Ylenia“ was passing the Bremerhaven area during our training; and fingers crossed for spotting a bear from the air!

From: Sabrina Schnitt

How to prepare for a campaign in the Arctic?

Posted on 1. March 2022 by Imke

During the past decades the Arctic climate is undergoing warming which impacts the local ecosystem and human infrastructure. To better understand the Arctic climate system and improve projections for the future, three aircraft will jointly observe various atmospheric processes over the North Atlantic near Spitsbergen during the HALO-(AC)³ campaign in March and April 2022.

Group picture after the final rescue challenge with survival suits and life vests.

Researchers from our group visited Bremerhaven for an exciting two-day safety training in preparation for this campaign. We learned, how to avoid dangerous encounters with polar bears which actually spend most of their lifetime on the sea ice beneath the aircraft. Additionally, an exhausting sea survival training demonstrated the use of life rafts and other equipment in case of an emergency landing. During the training huge waves and a thunderstorm were imitated, including flashes, rain and thunder in a complete dark surrounding.

Impressions from the sea survival training at RelyOn Nutec in Bremerhaven, Germany.

The cloud radar MiRAC-A is mounted below the Polar 5 aircraft.

Moreover, the first instrument belonging to our institute is already mounted below the aircraft Polar 5! It is a radar called MiRAC-A which will detect clouds below the aircraft. The Polar 5 will be equipped with several remote sensing instruments from different institutions. Our working group will additionally install the microwave radiometer HATPRO. Updates on this installation, the calibration of the instruments and the test flights will follow!

Do you want to follow the upcoming activities in the Arctic and learn more about the HALO-(AC)³ campaign? Then follow our AWARES blog and the HALO-(AC)³ website, where updates and interesting background information on the project are provided.

To stay up to date, check Twitter for the latest information! #HALOAC3 #AC3TR #MiRACradar #polar5 #Svalbard

Scientific News from AWARES

The Atmospheric Water Cycle and Remote Sensing group from the University of Cologne

Tag Archives: HALO-(AC)³

Weather conditions during the HALO-(AC)³ campaign

Long-awaited first research flight: Joint adventure with three aircraft!

The race is on: Polar 5 and 6 arrived in Longyearbyen!

Installation of the radar and radiometer on P5

How to prepare for an Arctic campaign (part 2)

How to prepare for a campaign in the Arctic?