For more information about PEARL Drone and data, please, contact Dr. Alexey Tikhomirov.
Air temperature at 1.25 to 2 m above the land surface (surface air temperature, SAT), is one of the key parameters used to study climate (World Meteorological Organization). SAT measurements are conducted using different types of in-situ and remote sensing instruments installed at meteorological observing stations on the ground as well as on marine, airborne and satellite platforms.
Normally the air temperature decreases with height above the ground in the troposphere. This is because solar radiation is absorbed by the Earth’s surface which warms the air above it promoting vertical mixing associated with turbulence and convection. Convection and turbulence play a vital role in transferring energy from the surface to the atmosphere.
The absence of sunlight during the winter in the High Arctic results in a strong surface-based atmospheric temperature inversion (SBI), especially during clear skies and light surface wind conditions (Bradley et al., 1992, Lesins et al., 2010). The inversion is defined as “a layer of the atmosphere in which air temperature increases with height”. The inversion suppresses the convective heat transfer. As a result, the difference between the SAT and the skin temperature of the ground can exceed several degrees Celsius. Such inversions occur very frequently in polar regions. They are of interest to understand the mechanisms responsible for surface–atmosphere heat, mass, and momentum exchanges and are critical for satellite validation studies.
Instrument Description
Since 2017, two commercially available Remotely Piloted Aircraft Systems (RPASs) or drones have been tested and flown at PEARL in February and March to study the SBI in Eureka (Tikhomirov et al., 2021). The RPASs are Matrice 100 and M210-RTK made by DJI (see Fig. 1 and 2). They have been equipped with a temperature measurement system built on a Raspberry Pi single-board computer, platinum wire temperature sensors, a Global Navigation Satellite System receiver, and a barometric altimeter.
The drones have been used in the extremely challenging High Arctic conditions to measure vertical temperature profiles up to 100 m above the ground and sea ice surface at ambient temperatures down to −46 °C. The results show that the inversion lapse rates within the 0–10 m layer can reach values of 10–30 C (100m)–1 (see Figs. 3–5). In the 10–100 m layer above the ground the SBI is characterized by smaller inversion lapse rates, which are in the range of ~2–4C (100m)–1 or less (see Figs. 3 and 5). Above the sea ice, the temperature profiles are found to be isothermal above a shallow unstable surface layer, revealing the impact of the heat flux through the ice (see Fig. 6). The results of the drone SBI measurements have been validated against the data from the NOAA Flux Tower (FT, Grachev et al., 2018), ECCC radiosondes (RS) and weather stations in Eureka (Eureka A and C).
Drone field studies of SBIs have the advantage of providing a rapid three-dimensional picture of the air temperature distribution, which allows researchers to identify spatial and temporal changes in the inversion lapse rates. The ability of the drones to perform flights and measure temperatures in the near-surface layer provides high potential for micro-meteorological observations. Drones are useful to study the influence of topography on the SBI structure and to measure extremely cold temperatures of the air that can pool in topographic depressions. All these unique capabilities by a drone can provide boundary layer meteorologists with a more realistic assessment of the processes that shape the temperature distribution in winter Arctic environments with important implications in the interpretation of regional variations in the skin–surface air temperature difference and the surface heat flux.
C (100m)–1 inversion lapse rate.
