Arctic Winter Special Observing Period (1 February to 31 March 2018)

Below we provide insights to additional observational efforts which has been done during the Arctic Winter Special Observing Period (1 February to 31 March 2018). A huge "thank you" goes out to all the colleagues out there who sent these great pictures to us.

Extra Radiosonde Launches from Arctic Meteorological Stations

At the AWIPEV research base in Ny-Alesund, Svalbard, radiosonde activities were increased to 4 launches per day. Vaisala RS41 sondes were flying at launch times 5, 11, 17, and 23 UTC. The AWIPEV station is registered as WMO radiosonde station 01004, and data transmission to GTS occurs via MET Norway.

The Bear Island meteorological station is maintained by MET Norway. Radiosonde activities were increased to 6 launches per day (2 daily extra launches) during the first Arctic Winter Special Observing Period. Weather balloons were launched at 0, 6, 9, 12, 15 and 18 UTC. Bear Island is registered as WMO radiosonde station 01028. 

The meteorological station in Danmarkshavn, Greenland is maintained by Danish Meteorological Institute (DMI). Radiosonde activities were increased to 3 launches per day with one extra weather balloon ascent daily at 18 UTC from 1 to 28 February and at 6 UTC from 1 to 31 March. Danmarkshavn is registered as WMO radiosonde station 04320. 

Eureka station is maintained by Environment and Climate Change Canada. Two additional radiosondes daily were deployed from here during the Arctic Winter Special Observing Period at 6 and 18 UTC, in addition to the routine weather balloon launches at 0 and 12 UTC. Eureka is registered as WMO radiosonde station 71917.

Jan Mayen Meteorological station (WMO radiosonde station 01001) is Norway’s most remote meteorological station. In the Arctic Winter Special Observing Period in February and March 2018, six (two extra) radiosondes were launched every day. All photos are kindly provided by Vera Lund.

With two extra launches, the Swedish autosonde station at the airport in Luleå (WMO station 02185) provided four ascents in total per day during the Arctic Winter Special Observing Period from 1 February to 31 March 2018. Observation times at this station which is maintained by the Swedish Meteorological and Hydrological Institute (SMHI) were 00, 06, 12 and 18 UTC.

At the Finnish Sodankylä observatory (WMO radiosonde station 02836) at 67°22'N, 26°38'E, the station staff of the Finnish Meteeorological Institute (FMI) launched radiosondes four times per day, at 00, 06, 12, and 18 UTC, the soundings at 06 and 18 UTC were the extra ones.

YOPP-Endorsed Field Campaigns during the Arctic Winter Special Observing Period

Although an unexpected shortage of Helium occurred, the project PIs of the YOPP-endorsed OASIS-YOPP Thule were still able to launch three radiosondes during their campaign from 23-27 February at Thule Air Base (76.5°N, 68.8°W). A team of two people  travelled to Thule at the end of February to launch the few available radiosondes and perform maintenance and calibrations of the ground-based microwave radiometers.

In 2016 the OASIS-YOPP team installed a RPG HATPRO microwave radiometer capable of measuring vertical profiles of tropospheric temperature with a time resolution of 30 minutes and water vapor column contents with a time resolution of 10 seconds. This instrument was operated and well calibrated throughout 2017 and has been running during the Arctic Special Observing Period from 1 February to 31 March. Additionally, starting in late February, the team has carried out measurements of stratospheric water vapor from 25 to 70 km altitude by means of a ground-based microwave spectrometer.

The YOPP-endorsed Iceland-Greenland Seas Project (IGP) is an atmosphere-ocean project encompassing
coupled wintertime observations and numerical modelling. The motivation and overall programme hypothesis is that wintertime convection in the northwest Iceland Sea and southeast Greenland Sea, forced by intermittent cold-air outbreaks, forms the densest component of the Atlantic Meridional Overturning Circulation (AMOC). In order to obtain in-situ observations of cold-air outbreaks, orographic flows and their associated air-sea fluxes over the Iceland Sea and the marginal-ice-zone, during an aircraft-based field campaign scheduled for the YOPP Arctic Winter Special Observing Period cold-air outbreaks, orographic jets and wakes were observed from an instrumented Twin Otter, operated by the British Antarctic Survey.

In addition to the aircraft campaign, an atmospheric observation programme from the wintertime research cruise aboard the research vessel Alliance included 100 radiosonde launches, radiometer measurements of the atmospheric boundary layer and a doppler wind lidar. 

Atmospheric sampling was thus closely coordinated with the shipboard measurements during cold-air outbreaks, and focused on the NW Iceland Sea where the deepest and densest mixed layers appear to be.

You can retrospectively follow the campaign by checking their twitter account @IGPresearch and their blog.

The full suite of ICECAPS observations has been continuous through the YOPP Arctic Winter SOP, except for a couple instruments that are currently being repaired (one microwave radiometer and a couple of precipitation instruments). The current suite includes a cloud radar, two depolarization lidars, ceilometer, infrared spectrometer, high-frequency microwave radiometer, precipitation sensor system, sodar, and twice-daily radiosoundings. Additionally, at Summit there are ongoing surface meteorology and radiation measurements provided by collaborators (NOAA, and ETH). Two radiosoundings per day at 00 and 12 UTC were launched, and these went out to the GTS. The ICECAPS suite of measurements has been in operation at Summit Station since 2010 and will remain until at least summer 2018 (and hopefully summer 2020 if the renewal funding comes through). The observations are supported year-round by a team of site science technicians from Polar Field Services, while the ICECAPS investigator team will visit the site every summer to fix and maintain equipment. All data is freely available for public access and has contributed to a great deal of important research into physical processes over the ice sheet, new measurements and observational techniques, model assessment and development, comparisons with satellites and aircraft, and many others.

The data is also yearly uploaded to the US Department of Energy Atmospheric Radiation Measurement Program's archive ( and to the NSF Arctic Data Center ( The most updated data is available on the ICECAPS FTP site (i.e., data up through yesterday) at:
Radiosonde data, for example, is at: