Abstract
A 25-year set of daily radiosonde data was used to investigate temperature and humidity inversions at Neumayer Station, coastal Dronning Maud Land, Antarctica. For the first time, inversions were studied differentiating between different synoptic conditions and different height levels. It was shown that, generally, inversions occurred on the majority (78 %) of the days, with simultaneous occurrence of humidity and temperature inversions being observed on approximately two thirds of all days. Multiple inversions are common in all seasons for both weather conditions, however, typically occur more frequently under cyclonic conditions. The seasonality of inversion occurrence and features, i.e. inversions strength, depth and vertical gradients, was analysed statistically. Different formation mechanisms depending on inversion levels and prevailing weather situations are related to typical annual courses of certain inversion features. Winter maxima were found for the features that are mostly connected to the temperature close to the surface, which is mainly a result of the negative energy balance, thus influencing surface-based inversions. At the second level, both temperature and humidity inversions are often caused by advection of comparably warm and moist air masses related to the passage of cyclones and their frontal systems. Thus maxima in several inversion features are found in spring and fall, when cyclonic activity is strongest. Monthly mean profiles of humidity and temperature inversions reveal that elevated inversions are often obscured in average profiles due to large variations in inversion height and depth.
Highlights
Temperature and humidity inversions are a common feature of the stable boundary layer (SBL) in polar regions (e.g. King and Turner 2007; Nygård et al 2013; Phillpot and Zillman 1970; Vignon et al 2019, Zhang et al 2011)
A 25-yr inversion climatology for Neumayer Station, Antarctica, was presented that takes into account different levels of occurrence and different weather situations
In spite of a relatively simple, dual weather classification clear differences were found for inversion features depending on inversion level and synoptic conditions
Summary
Temperature and humidity inversions are a common feature of the stable boundary layer (SBL) in polar regions (e.g. King and Turner 2007; Nygård et al 2013; Phillpot and Zillman 1970; Vignon et al 2019, Zhang et al 2011). Nygård et al (2013) used data from 11 coastal Antarctic stations, including Neumayer, to create a 10-year climatology of humidity inversions. They state that generally humidity inversions occur most 55 frequently in winter and spring and roughly half of the inversions occur simultaneously with temperature inversions. Vignon et al (2019) combined an 8-year data set from nine Antarctic coastal stations including Neumayer to analyse the vertical structure of the lowest 3 km of the tropophere. They found fundamentally different conditions at the various stations. The relationship between inversion features 80 as well as between temperature and humidity inversions and between inversions at different levels was investigated
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