Atmospheric Temperature Measurement Biases on the Antarctic Plateau

Abstract

Observations of atmospheric temperature made on the Antarctic Plateau with thermistors housed in naturally (wind) ventilated radiation shields are shown to be significantly warm biased by solar radiation. High incoming solar flux and high surface albedo result in radiation biases in Gill (multiplate)-styled shields that can occasionally exceed 108C in summer in cases with low wind speed. Although stronger and more frequent when incoming solar radiation is high, biases exceeding 88C are found even when solar radiation is less than 200 W m 22 . Compared with sonic thermometers, which are not affected by radiation but are too complex to be routinely used for mean temperature monitoring, commercially available aspirated shields are shown to efficiently protect thermistor measurements from solar radiation biases. Most of the available in situ reports of atmospheric temperature on the Antarctic Plateau are from automatic weather stations that use passive shields and are thus likely warm biased in the summer. In spite of low power consumption, deploying aspirated shields at remote locations in such a difficult environment may be a challenge. Bias correction formulas are not easily derived and are obviously shield dependent. On the other hand, because of a strong dependence of bias to wind speed, filtering out temperature reports for wind speed less than a given threshold (about 4-6 m s 21 for the shields tested here) may be an efficient way to quality control the data, albeit at the cost of significant data loss and records that are biased toward high wind speed cases.

Atmospheric moisture supersaturation in the near-surface atmosphere at Dome C, Antarctic Plateau

“…Temperature, wind, and moisture are measured, the latter again using solid-state film capacitive sensors. This profiling system is fully described in Genthon et al (2010Genthon et al ( , 2011Genthon et al ( , 2013. From the tower measurements, Genthon et al (2013) evaluate and compare 2 contrasting years, 2009 and 2010, respectively the warmest and coldest in a 10-year period.…”

“…At the same level, hosted in an aspirated but unheated radiation shield (see Fig. 1 of Genthon et al, 2011), an unmodified HMP155 allows for comparison with a traditional designand to exhibit biases of the latter. From now on, the original and modified HMP155 will be referred to as "HMP" and "HMPmod", respectively.…”

Archival processes of the water stable isotope signal in East Antarctic ice cores

“…and are therefore free of radiation biases (Genthon et al, 2011 In the field, snow metamorphism is difficult to quantify due to the large noise created by the spatial variability, requiring a 20 large number of samples every day. Therefore, we include grain index observations (Picard et al, 2012) obtained by satellite measurements using passive microwave satellite data.…”

Challenges associated with the climatic interpretation of water stable isotope records from a highly resolved firn core from Adélie Land, coastal Antarctica

“…The FELICS (Fast Electrochemical lightweight Ice Coring System) drill system was used (Ginot et al, 2002;Verfaillie et al, 2012). Firn core pieces were then sealed in polyethylene bags, stapled and stored in clean isothermal boxes.…”

“…The potential relationships between large-scale climate variability and regional precipitation isotopic composition was investigated through outputs of a nudged simulation performed with the atmospheric general circulation model ECHAM5-wiso (Roeckner et al, 2003), equipped with stable-water isotopes 20 (Werner et al, 2011). We chose this model due to demonstrated skills to reproduce spatial and temporal patterns of water stable isotopes in Antarctica Werner et al, 2011;Steen-Larsen et al, 2017), and in Greenland (Steen-Larsen et al, 2017).…”