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Air temperature inversions, a situation in which atmospheric temperature increases with height, are key components of the Arctic planetary boundary layer. The present study investigates the spatial and temporal variations of temperature inversions over different surface types (rock, gravel, snow, ice) along the Mittivakkat valley (southeast Greenland). For this purpose, 113 vertical profiles with high spatio-temporal resolution of air temperature and relative humidity were collected with unoccupied aerial vehicles (UAVs) during a 13-day field campaign in summer 2019. Air temperature inversions were present in 83% of the profiles, of which 24% were surface-based inversions and 76% were elevated inversions. The proglacial area covered with bare rock and gravel induces surface heating and convection during the day and, through interaction with local circulation patterns, leads to the frequent formation of elevated inversions. In contrast, the glacier surface itself acts as a persistent cooling surface and leads to the formation of surface-based inversions. A low-level fog layer that forms under the inversion layer may be causing non-linear vertical ablation gradients on Mittivakkat Gletsjer. Furthermore, we demonstrate that atmospheric measurements using UAVs can better capture small-scale processes than other products like radiosonde or modeled reanalysis data. [ABSTRACT FROM AUTHOR]

The climate in Northeast Greenland is shaped by complex topography and interaction with the cryosphere. To capture this complexity, we use an observational dataset from the Zackenberg region (ZR), (Northeast Greenland) to investigate the local and large-scale factors that determine the slope temperature gradients (STGs) i.e., the temperature gradient along the mountain slope. A synthesis of automated weather stations, reanalysis, and regional climate model were used. Our results show that the surface type and near fjord-ice condition are the dominating factors governing the temporal evolution of the STGs in the ZR. Considering large-scale drivers of STG, we find that shallow, i.e., more positive (inversions) or less negative than the mean condition, STGs are associated with a positive anomaly in geopotential height at 500 hPa and surface pressure over East Greenland. A strong connection between fractional sea-ice cover (SIF) in the Greenland Sea and the terrestrial climate of the ZR is found. Evidently, a positive SIF anomaly coincides with shallow STG since the temperature at the bottom of the valley decreases more than at the top. For example, the mean STG varies by ~4 ºC km−1 for a corresponding ~27 % change in SIF. Changing temperatures and precipitation patterns related to SIF variability also affect the surface mass balance (SMB) of the nearby A. P. Olsen Ice Cap. During summer, days with high SIF are associated with a positive SMB anomaly in the ablation area (~16 mm w.e. day−1; indicating less melt) and a negative anomaly in the accumulation area (~−0.3 mm w.e. day−1; indicating less accumulation). The decrease in temperature and snowfall related to the days with high SIF explain this opposite pattern in the ablation and accumulation area. [ABSTRACT FROM AUTHOR]

The arctic planetary boundary layer provides a favorable condition for the formation oftropospheric temperature inversions, a situation in which temperature increaseswith elevation forming inherently stable atmospheric configuration restricting theboundary layer mixing. This study focuses on both surface-base (SBI) and elevatedinversions (EI). At the surface level, the presence of SBI is relevant to radiativeimbalance between emitted longwave from the snow and ice surfaces and incomingsolar and longwave radiation, particularly in the (polar) night; EI are a result of twomechanisms: subsidence of the air in anticyclones and warm air advection overunderlying cold air masses. The intensity and thickness of EI are considerably less thanSBI. Strong and thick temperature inversions are predominantly persistent in largeparts of Greenland, because 80% of it is ice covered and hence cooling radiatively,manifested as quasi-permanent anticyclone in its central and northern parts; while thesouthern part of Greenland is mainly influenced by the Icelandic low and showscomparatively weak and thin inversions. This heterogeneity of inversion parameters isobservable in macroclimatic scales and thus, highlights the necessity for climaticregionalization for studying inversions, e.g. as precondition for ice melt models or ecologicalstudies. In this respect, we analyze the spatial and temporal variations of temperature inversionparameters in different climatic regions of Greenland based on the ERA-Interimdataset over the past four decades (1979 - 2017). Additionally, we quantify theeffect of changing temperature inversion strength on longwave cooling efficiencyat the top of atmosphere over Greenland including the role of clouds at differentheights. Preliminary results show that SBI occurred more frequently and intensively than EI in allclimatic regions for all seasons. SBI are more frequent during winter than summer whereasEI show an opposite pattern. Furthermore, we found statistically different magnitude ofinversion parameters in different regions of Greenland for different seasons. During winterSBI are stronger and thicker in northern region with the median SBI strength and thicknessoscillating between 10-15 ˚ C and 252-307 m respectively, whereas, the western part exhibitthree times weaker and eight times thinner SBI (5-5.6 ˚ C and 32-55 m). However, insummer, SBI show highest intensity in southeastern part compared to other regions.Moreover, EI parameters depict similar regional difference as SBI. Additionally, timeevolution of efficiency of atmospheric cooling to space shows decreasing trend in all theregions. [ABSTRACT FROM AUTHOR]