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Measurements of atmospheric variables (e.g. wind, temperature) are scarce in the Antarctic region. The default data are from automatic weather stations (AWS), manned station (MS) and radio soundings (RS). We investigate the benefits of wind lidar measurements for the verification of regional models. While the RS, MS and AWS data feature all a point or 1D perspective, the lidar data feature a 2D perspective with many vertical measurements in a short period of time. Thus atmospheric changes on a vertical scale of 1 km and a temporal scale of hours (e.g. low level jets) can be further investigated as well as the ability of regional models to simulate these. We use the model COSMO CLM (CCLM) with 5 and 15 km resolution and force it with ERA-Interim data for the years 2002 to 2016. The model domain covers the Weddell Sea. A long-term verification using standard data and an intercomparison with lidar data for a Polarstern cruise in 2015/16 is presented. The RMSE using radio sounding data for winter (April - September) is around 4 m/s for wind speed and 2°C for temperature. [ABSTRACT FROM AUTHOR]

Leads are elongated cracks within the pack ice more than 50 m in width and up to several hundreds of kilometers in length. Mechanical forces such as ocean currents or wind stress mainly drive the development of leads. Within these cracks open water and thin ice occurs. Subsequently, the lower atmosphere is influenced by increased fluxes of moisture and sensible heat from the ocean to the atmosphere. Sea-ice leads are also important for the production of sea ice and contribute to the formation of saline Antarctic shelf water. Since sea-ice leads are short-living objects an accurate monitoring of their temporal and spatial characteristics is required. We use satellite thermal imagery from the MODIS sensor to produce daily potential lead maps for the entire Southern ocean at a spatial resolution of 1.5 km. Data are analyzed for the winter periods from 2002 to 2017. By means of digital image processing and advanced filtering techniques leads are automatically identified in satellite thermal imagery due to their positive temperature anomaly in comparison to the surrounding sea-ice. Based on this information fuzzy logic is applied to minimize errors induced by a misclassification of leads caused by clouds. A variety of lead characteristics retrieved by digital image processing e.g. the object eccentricity is taken into account to distinguish between leads and artifacts. Here we present improvements of the filtering algorithms as well as adjusted concepts for the lead identification in the Southern Ocean. [ABSTRACT FROM AUTHOR]

A profound knowledge of the thin-ice thickness distribution and associated wintertime sea-ice production in polynyas is not only important to increase the understanding of atmosphere - seaice - ocean interactions, but also to evaluate frequently used climate and ocean models. In this study, we present a high-resolution (~2 km) MODIS thermal infrared satellite data set featuring spatial and temporal characteristics of 17 coastal polynya regions over the entire Arctic basin is presented for winter seasons 2002/2003 to 2016/2017. Besides the extended data record of 15 winter seasons, the data set features the most recent updates of the employed MOD/MYD29 sea ice product (Col. 6) which include improvements to the cloud masking and land/ocean separation. Thin-ice thickness distributions (≤ 20 cm) are calculated from MODIS ice-surface temperatures, combined with ECMWF ERA-Interim atmospheric reanalysis data in an energy balance model. Daily thin-ice thickness composites are subsequently computed. A gap-filling approach is applied to account for clouds and missing data in the thermal infrared imagery. The most recent winter season in the data set (2016/2017) features the so far highest annual ice production with a volume of 2,258 km³, presumably originating from highly active polynyas throughout the eastern Arctic (Laptev Sea, Kara Sea) and/or a particularly thin and less extensive wintertime sea-ice coverage that season. We additionally use thin-ice thicknesses from AMSR-E passive microwave data for the period 2002/2003 to 2010/2011 to evaluate and quantify sensor-specific differences. AMSR-E ice thickness data are based on an empirical approach that utilizes a distinct polarization ratio (PR) - ice thickness relationship for thin seaice. This direct comparison enables further insights into sensor-specific capabilities and error sources for a large-scale pan-Arctic polynya monitoring. Despite obvious differences, such as the acquired signal at the sensor, varying spatial resolutions or the individual sensitivity for cloud cover, both data sets are coherent in terms of capturing the general spatial and temporal characteristics of Arctic polynyas for the overlapping 9-yr period. [ABSTRACT FROM AUTHOR]

The high-resolution atmospheric model COSMO-CLM (CCLM, German Meteorological Service) is used to simulate the 2m-temperature and the boundary layer structures in the Arctic for the winter periods (Nov-Apr) from 1987/88 to 2016/17. The CCLM simulations have a horizontal resolution of 15 km and are nested in ERA-Interim data. CCLM simulations are compared with Arctic System Reanalysis data (ASR, Byrd Polar and Climate Research Center), which are available with a horizontal resolution of 30 km for the period 2000-2012. The analysis shows a high spatial and temporal variability of the recent 2-m air temperature increase. The warming in the 2-m air temperatures for the years before 2000 compared to the years after are extreme and are up to eight times higher since the beginning of the 21st century. The maximum warming is found for March in the Kara Sea and Barents Sea and amounts up to 20°C between 2003 and 2012. Land-based observations agree with the findings in this region, but do not cover the maximum increase that is located over the ocean and sea ice areas. The comparable ASR data also confirm the increase. The differences between CCLM and ASR are within a 1°C range. The sea ice decrease is identified as the likely reason for the warming. Vertical temperature profiles show that the warming reaches a height of up to 2 km but the maximum is located near the surface. Averaged over all sea ice and ocean area north of 70°N the increase amounts to 5°C for 2002/2003 to 2011/2012. Additionally to the mean temperature changes, first results of the changes in temperature extreme events will be shown. [ABSTRACT FROM AUTHOR]

The Weddell Sea in the Atlantic sector of the Southern Ocean is one of the most dynamic air/ ice/ocean interaction areas. Coastal polynyas occur frequently during winter, which leads to strong sea ice production, brine release and the formation of High-Salinity Shelf Water (HSSW). This dense water mass contributes to the formation of Weddell Sea Deep and Bottom Water, but also is considered to be one of the main drivers of the circulation in the large sub-ice shelf cavities beneath the Filchner-Ronne Ice Shelf (FRIS). Thus the quantification of quantification of sea ice production in Weddell Sea polynyas is of vital interest for the understanding the ocean circulation in this region. A multi-method approach is used to quantify sea ice production polynyas in the southern Weddell Sea for the period 2002-2016. We use 1) a regional climate model (CCLM) with 5 km and 15 km resolution (C05/15), 2) retrievals from MODIS data at a high resolution of 1-2 km and 3) simulations of a sea ice-ocean Model (FESOM) with a resolution down to 3 km. Methods 2) and 3) need atmospheric forcing, which is taken from different reanalyses (ERA-I, CSFR, JRA55, NCEP2) as well as from CCLM data. Estimates of sea ice production and comparisons of the different methods are presented for different polynya areas of the Weddell Sea. In all methods, the largest ice production is found for Ronne Ice Shelf and for Brunt Ice Shelf. Polynyas associated with iceberg A23a have the third largest ice production. However, significant differences between different methods and forcing data sets are found for polynya area and ice production. In conclusion, an overall sea ice production of 110±30 km³ per year from polynyas is found, which corresponds to about 15 % of the total ice production in the southern Weddell Sea. [ABSTRACT FROM AUTHOR]

The article discusses a study by Svenja Kohnemann and Günther Heinemann which used a Doppler wind LIDAR to measure the atmospheric boundary layer (ABL) in the Fram Strait area. Topics include the Doppler effect and its operational principle, the function of the Attitude Heading Reference System (AHRS), and how the measurement system is programmed. Also discussed are the expected results which include wind, turbulence and aerosols profiles and transition of boundary layer structure.

An abstract of the article "Ground-Based Remote Sensing of the Atmospheric Boundary Layer in the Laptev Sea Area and Comparisons With Regional Climate Simulations," by Pascal Schwarz et al is presented.

An abstract of the article "Pan-Arctic Polynya Dynamics and Thermodynamic Ice Production Estimates for 2002/2003-2014/2015 Based on MODIS Thermal Infrared Imagery and Era-Interim Reanalysis," by Sascha Willmes et al is presented.

An abstract of the article "Sea Ice Mass Balance Influenced by Ice Shelves (SIMBIS): Final Report," by Stephan Paul is presented.

An abstract of the article "Satellite-Derived Fast-Ice Climatology and Fast-Ice Growth Rates of Atka Bay, Antarctica," by Stephan Paul is presented.

An abstract of the article "Aircraft Measurements of Sea Ice/Ocean/Atmosphere Interactions During the Experiment Least Near Svalbard," by Günther Heinemann et al is presented.

An abstract of the article "Sensitivity of Sea-Ice Production of Laptev Sea Polynyas to the Representation of Subgrid-Scale Energy Fluxes in a Regional Climate Model," by Oliver Gutjahr et al is presented.