SUMO (Small Unmanned Meteorological Observer) has been used to monitor Arctic Atmospheric Boundary Layer (AABL) in Svalbard. SUMO can perform both vertical and horizontal surveys of the mean meteorological parameters: temperature, relative humidity, pressure and wind.

The structure of the Arctic atmospheric boundary layer (AABL), the heat and the moisture fluxes between relatively warm water and cold air are of great importance for the sensitive Arctic climate system. However, these processes are not sufficiently represented in numerical weather predictions and climate models. Especially for regions with complex topography (e.g. Svalbard mountains and fjords) the state and diurnalevolution of AABL is not well known yet.

More infromation can be gained using novel and flexible measurement techniques such as an unmanned aerial vehicle (UAV). An UAV can perform vertical profiles as well as horizontal surveys of the mean meteorological parameters: temperature, relative humidity, pressure and wind. A suitable UAV called Small Unmanned Meteorological Observer (SUMO) has been developed at the Geophysical Institute at the University of Bergen in cooperation with Müller Engineering (www.pfump.org) and the Paparazzi Project (http://paparazzi.enac.fr). From 21.03.-04.04.2009 SUMO performed 85 flights in Svalbard including 63 temperature, humidity and wind profiles up to 1400-1500 m above the ground which was the maximum altitude approved by the Norwegian Civil Aviation Authority (Luftfartstilsynet). For the first time simultaneous profiles could be performed.

The field campaign was conducted in the period 21.03.2009 until 04.04.2009 at two locations. One location was the old Auroral station in Adventdalen and the second location was the apron of Longyear airport. During the field campaign, a 10 m mast was installed at the old Auroral station in Adventdalen. The mast was equipped with 3 temperature and humidity sensors, anemometers and wind vanes to measure temperature, relative humidity, wind speed and wind direction in 1.8 m, 6.4 m and 9.9 m above the surface. Most of the experimental period was dominated by easterly wind conditions (which is typical for the area).

With SUMO, 85 flights including 63 temperature, humidity and wind profiles up to 1500 m agl could be measured. The maximum altitude of 1500 m agl was preset by limitations of the Norwegian Civil Aviation Authority. For the first time simultaneous profiles could be performed, i.e two SUMO aircrafts controlled by one ground control station (GCS) ascended at the same time in a horizontal distance of 1 km to get synchronized profiles over different surfaces. Totally, 9 simultaneous profiles were made during the campaign.

Two simultaneous profiles have been measured in Adventdalen. Both profiles were taken at the same time within a horizontal distance of 1 km above snow surface. As expected, both profiles showed almost identical behavior, i.e. horizontal homogeneity. There was extremely strong surface inversion with a temperature gradient of 10 K in a layer of 60 m thickness. There was a well mixed layer above the surface layer, up to 250 m agl topped by an inversion. Higher, up to 800-900 m agl the ABL shows weak stratification changing to clear stratification at higher altitudes. Taking the humidity profiles into account, the ABL height can be identified at approximately 800 m agl where the humidity decreases significantly.

SUMO has proved its reliable functionality at temperatures down to -30 deg.C and wind speeds up to 15 m/s. It might be possible for SUMO to reach max height of approximately 4000 m in the future campaigns in the Arctic. Structure of the AABL was investigated over homogeneous land surface (snow) and over heterogeneous surfaces (snow covered land and open water). The AABL over the open water is approx 2K warmer than the AABL over land. In contrast to the profiles over land, an inversion in 600 m agl could be observed over open water which is in agreement with an observed thin stratocumulus cloud at this height. This cloud is a clear sign for enhanced moisture and flux from the relatively warm water evaporating into the cold AABL.

Source & contact: Stephanie Mayer UiB (Stephanie.Mayer@gfi.uib.no)

This is Stephanie Mayer's report to SSF, Arctic Field Grant 2009 (AFG2009 ID466; RiS ID 3346)

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SUMO (Small Unmanned Meteorological Observer)

Screen of the ground control station showing the profiles made by SUMO.

Google Earth application with SUMO trajectories: blue line - over the sea and the red line - over the land (all illustrations: Stephanie Mayer, UiB)