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Discussion papers | Copyright
https://doi.org/10.5194/tc-2018-150
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 09 Aug 2018

Research article | 09 Aug 2018

Review status
This discussion paper is a preprint. It is a manuscript under review for the journal The Cryosphere (TC).

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

Pia Nielsen-Englyst, Jacob L. Høyer, Kristine S. Madsen, Gorm Dybkjær, Rasmus Tonboe, and Emy Alerskans Pia Nielsen-Englyst et al.
  • Danish Meteorological Institute, DK-2100 Copenhagen Ø, Denmark

Abstract. To facilitate the combined use of traditional 2m air temperature (T2m) observations from weather stations in the Arctic and skin temperature (Tskin) observations from satellites the relationship between high latitude snow and ice Tskin and T2m is quantified. Multiyear data records of simultaneous Tskin and T2m from 20 different in situ sites have been analysed, covering the Greenland Ice Sheet (GrIS), sea ice in the Arctic Ocean, and coastal snow covered land in North Alaska. The diurnal and seasonal temperature variabilities and the impacts from clouds and wind on the T2m-Tskin differences are quantified. Considering all stations, T2m is on average 1.37°C warmer than Tskin, with the largest differences at the GrIS stations (mean of diff. of 1.64°C). Tskin and T2m are often highly correlated, and the two temperatures are almost identical (<0.5°C) at particularly times of the day and year, and during certain conditions. The data analysed here indicate the best agreement between Tskin and T2m around noon and early afternoon during spring and fall. However, Tskin is often colder than T2m by 2°C or more, with the largest differences occurring during winter, when it is dark and during night. This is seen for all observation sites, where a negative surface radiation balance makes the surface colder than the atmosphere, resulting in a surface-driven surface air temperature inversion. The observation sites on sea ice and in Alaska show that the surface-based inversion decreases as a function of wind speed, because of turbulent mixing. The sites on the GrIS show an interesting feature, with the maximum inversion occurring not at calm winds, but at wind speeds of about 5ms−1, likely due to the katabatic winds, which are most prominent at this wind speed. Clouds tend to reduce the vertical temperature gradient, by warming the surface, resulting in a mean T2m-Tskin difference of 0.53°C considering all stations. Following that the influence of clouds on Tskin has been assessed by comparing clear-sky Tskin observations with all-sky observations averaged for the time windows of: 24h, 72h and 1 month. The largest clear-sky biases are generally found when 1 month averages are used and smallest for 24h. The mean clear-sky bias for the 24h average is −0.28°C, ranging from −0.10°C in summer to −0.95°C in winter. The expected clear-sky biases and the difference between Tskin and T2m are of practical value for researchers and operational users that aim at integrating satellite observations with ocean, sea-ice or atmospheric models.

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Short summary
To facilitate the combined use of T2m and Tskin from in situ observations, satellites and models, there is a need for a better understanding the relationship between the surface skin (Tskin) and 2 m air temperature (T2m). Using data from 20 ice covered sites in the Arctic we find that on average T2m is 1.37°C warmer than Tskin, with the smallest difference around noon and early afternoon during spring and fall. Clouds and strong winds are also found to decrease the temperature difference.
To facilitate the combined use of T2m and Tskin from in situ observations, satellites and...
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