Regime Transitions in the Wintertime Near-Surface Temperature Inversion at Dome C, Antarctica

Using 6 years of observations from the French-Italian Antarctic station Concordia at Dome C (75.06S, 123.2E, 3233 m above sea level), we investigate regime transitions in the wintertime near-surface temperature inversion over the Antarctic Plateau. Here we define 'near-surface' as within the domain of the 45-m measurement tower. The dynamics between the near-surface wind and the inversion strength has our particular attention.

The present work builds on the study of Vignon et al. (2017), who investigated the relation between the T_10m - T_s inversion strength and the 10-m wind speed. They demonstrated that two basic states can be distinguished. First, in conditions with strong winds the inversion strength is small and in the order of 5 K. Second, in case of weak winds the temperature difference in the lowest 10 m amounts to 20 – 25 K. The transition between the two states is abrupt and occurs at wind speeds of 5 – 7 m/s. These findings corroborate with the conceptual model that was published by Van de Wiel et al. (2017).

Here, we extend the work of Vignon et al. (2017) by studying all individual events for which the 10-m inversion strength (T_10m - T_s) increases or decreases continuously in time by more than 15 K. In this way the temporal relation between the considered variables is preserved. Composite time-series and vertical profiles of wind and temperature reveal specific characteristics of the transition from weak to very strong inversions and vice versa.

Results from a numerical atmospheric model are used to disentangle the underlying mechanisms of transitions in the inversion strength. Analysis of the temperature and momentum budgets provides a detailed picture of the processes that govern the erosion and build-up of the near-surface temperature inversion at the Antarctic Plateau.

References

Vignon E, van de Wiel BJH, van Hooijdonk IGS, Genthon C, van der Linden SJA, van Hooft JA, Baas P, Maurel W, Traullé O, Casasanta G. 2017. Stable boundary-layer regimes at Dome C, Antarctica: observation and analysis. Q. J. R. Meteorol. Soc., 143: 1241–1253.

Van de Wiel BJH, Vignon E, Baas P, van Hooijdonk IGS, van der Linden SJA, van Hooft JA, Bosveld FC, de Roode SR, Moene AF, Genthon C. 2017. Regime transitions in near-surface temperature inversions: a conceptual model. J. Atmos. Sci. 74 : 1057-1073.