Properties and temporal variability of summertime temperature inversions over Dronning Maud Land, Antarctica

Abstract

The occurrence, properties and temporal variations of temperature inversions over Dronning Maud Land, Antarctica, were examined on the basis of tethersonde and 10 m tower measurements during the austral summer 2010-2011. Temperature inversions occurred in 96% of the observed tethersonde profiles, and a surface-based inversion in 58% of the profiles. Although the sun did not set during the study period, the amplitude of solar radiation was large enough to generate a diurnal cycle in near-surface temperatures, temperature gradients and inversion properties. However, daytime heating was not strong enough to destroy the entire inversion layer and therefore a long-living inversion layer often persisted, the lowest part of which strengthened during the nights. The surfacebased inversions were strongly curved, with large negative values of the scaled curvature parameter. The majority of temperature change with height took place within the lowest ≈5-25 m (so-called strong inversion layer), and in the thicker part of the inversion above the temperature gradient was close to zero. The temporal evolution of near-surface temperature at fixed levels was notably affected by temporal changes of the depth of the strong inversion layer. A case-study, focusing on a typical nocturnal evolution of a surface-based inversion, demonstrated a deepening of the inversion layer during the night, presumably caused by radiative cooling at the top of the layer. Closer to the surface, where the temperature inversion was strongest, the warmer overlying layers caused a long-wave warming that probably compensated the large near-surface cooling due to sensible heat divergence. The factors most strongly favouring strong inversions with low base temperatures were the time of the day (early morning), a small cloud fraction, weak winds, and an air-mass of continental origin.

Interannual variability of air temperature inversions in ice-free area of northern James Ross Island, Antarctica

“…Another important factor influencing the relative frequency was the use of radio sounding in other studies, which enables better vertical resolution. Nygård et al (2017) used tethersondes over Aboa (Queen Maud Land) to study summertime TI and mostly detected several thin inversion layers with a vertical extension of less than 100 m. Consequently, it is likely that in our observations from 8 to 375 m a.s.l., we actually detected the base of one inversion layer and the top of another one above the surface-based TI. However, as the primary aim of this study was to reveal interannual variability, the length of the study period had a priority.…”

“…Stable boundary layer can be formed over larger areas or can further intensify in anticyclonic conditions due to subsidence (Schwerdtfeger 1970;Baas et al 2019). Nygård et al (2017) showed that both cold-air advection and long-wave radiative cooling can contribute to development and strengthening of surface-based inversion layer in Dronning Maud Land (Antarctica).…”

Measurement report: Properties of aerosol and gases in the vertical profile during the LAPSE-RATE campaign

“…The mixing height of the atmospheric boundary layer and wind speed and direction are influenced by a number of factors, including the amount of solar and surface stored energy and terrain inhomogeneity (Carbone et al, 2010). The atmospheric boundary layer can be investigated through various means, including balloon-borne soundings, tethersondes, dropsondes and hot-air balloons (e.g., Laakso et al, 2007;Greenberg et al, 2009;Nygård et al, 2017); towers (e.g., Heintzenberg et al, 2011;Andreae et al, 2015); remote sensors, including ceilometers, sodars, Doppler lidars and radar techniques (e.g., O'Connor et al, 2010;Schween et al, 2014;Vakkari et al, 2015); and conventional research aircrafts (Hermann et al, 2003;Twohy et al, 2002;Benson et al, 2008). Unmanned aerial systems (UASs) have recently gained popularity as measurement platforms in atmospheric research.…”

Atmospheric aerosol, gases, and meteorological parameters measured during the LAPSE-RATE campaign by the Finnish Meteorological Institute and Kansas State University

“…In situ observation of PBL Published by Copernicus Publications. D. Brus et al: Aerosol, gases, and meteorological parameters measured during LAPSE-RATE properties are obtained through various techniques, including balloon soundings, tethersondes, dropsondes and hot-air balloons (e.g., Laakso et al, 2007;Greenberg et al, 2009;Nygård et al, 2017), towers (e.g., Heintzenberg et al, 2011;Andreae et al, 2015), and recently by unmanned aerial systems (UASs) (e.g., Ramanathan et al, 2007;Jonassen et al, 2015;Kral et al, 2018;Nolan et al, 2018;Barbieri et al, 2019;Girdwood et al, 2020;Harrison et al, 2021;Jensen et al, 2021;Pinto et al, 2021;Wenta et al, 2021).…”