In situ observed relationships between snow and ice surface skin temperatures and 2 m air temperatures in the Arctic

• Published in: The Cryosphere
• Main Authors: Nielsen-Englyst, Pia, Høyer, Jacob L., Madsen, Kristine S., Tonboe, Rasmus, Dybkjær, Gorm, Alerskans, Emy
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2019
• Subjects: Arctic; Arctic Ocean; Greenland; Ice Sheet; Sea ice; Alaska
• Online Access: https://orbit.dtu.dk/en/publications/fa3c1133-7ae9-45b3-b217-098dc4e947ae; https://doi.org/10.5194/tc-13-1005-2019; https://backend.orbit.dtu.dk/ws/files/173182041/marac_tc_13_1005_2019.pdf

To facilitate the construction of a satellite-derived 2 m air temperature( T 2 m ) product for the snow- and ice-covered regions in theArctic, observations from weather stations are used to quantify therelationship between the T 2 m and skin temperature( T skin ). Multiyear data records of simultaneous T skin and T 2 m from 29 different in situ sites have been analysed forfive regions, covering the lower and upper ablation zone and the accumulationzone of the Greenland Ice Sheet (GrIS), sea ice in the Arctic Ocean, andseasonal snow-covered land in northern Alaska. The diurnal and seasonaltemperature variabilities and the impacts from clouds and wind on the T 2 m – T skin differences are quantified. T skin is often (85 % of the time, all sites weighted equally)lower than T 2 m , with the largest differences occurring when thetemperatures are well below 0 ∘ C or when the surface is melting.Considering all regions, T 2 m is on average0.65–2.65 ∘ C higher than T skin , with the largestdifferences for the lower ablation area and smallest differences forthe seasonal snow-covered sites. A negative net surface radiation balance generally coolsthe surface with respect to the atmosphere, resulting in a surface-drivensurface air temperature inversion. However, T skin and T 2 m are often highly correlated, and the two temperatures canbe almost identical (<0.5 ∘ C difference), with the smallest T 2 – T skin differences around noon and early afternoon duringspring, autumn and summer during non-melting conditions. In general, theinversion strength increases with decreasing wind speeds, but for the siteson the GrIS the maximum inversion occurs at wind speeds of about5 m s −1 due to the katabatic winds. Clouds tend to reduce the verticaltemperature gradient, by warming the surface, resulting in a mean overcast T 2 m – T skin difference ranging from −0.08 to1.63 ∘ C, with the largest differences for the sites in thelow-ablation zone and the smallest differences for the seasonal snow-coveredsites. To assess the effect of using ...