Wind and backscatter profiles measured by a wind lidar during POLARSTERN cruise PS96 (ANT-XXXI/2 FROSN)

This data set includes vertical profiles of wind speed (FF), wind direction (DD), fit deviation (FD) and the backscatter confident (BB) measured by a ship born wind lidar. The definition of the fit deviation, the main processing of the lidar data and an evaluation of the measurements is described in Zentek et al. (2018; doi:10.5194/amt-11-5781-2018 ). For this data set winds were computed every 50 m up to 1000 m and the data is averaged over time. The averaging time is one hour (+-30min around each full hour) and missing values are removed. A weighted arithmetic mean was used for the u- and v-component as well as for the fit deviation with the weights "1/fit deviation". The backscatter coefficient was averaged without weights. As backscatter was always measured, hours were included even if no wind could be computed due to atmospheric conditions but hours with no reliable data were excluded (e.g. the lidar was turned off; the ship was rocking to hard; etc.). Further detailed information for this measurement campaign: number of rays per VAD [8], averaging time [10-15 sec], chosen SNR threshold [-20 dB]

Low-Level-Jet and Inversion statistics for Weddell Sea region of Antarctica

This data set is a climatology (2002–2016) of low level jet (LLJ) and inversion parameters for the Weddell Sea region of Antarctica. Mean (Summer=April-Sept., Winter=Dez.-Jan., Annual) values were computed from hourly COSMO-CLM model output. To detect a LLJ the lowest 1 km of the atmosphere was searched for a wind maximum (>2m/s than above and below) and the following parameters were taken: height (m) and wind speed (m/s) of the wind maximum, relative wind speed increase (compared to above and below), and the difference (LLJ-height minus near-surface-height) of potential temperature (K) and wind direction (°). To detect an inversion the lowest 1 km of the atmosphere was searched for the point where the potential temperature gradient dropped below 2 K/100 m and the following parameters were taken: height (m) of the inversion and strengh (K) defined as difference of potential temperature (inversion-height minus near-surface-height). The frequency (%) gives fraction of time a LLJ / inversion was detected. Furthermore the dataset of the mean wind field at 10 m above ground was added. For more detail and the exact description on the search algorithm see doi:10.3390/atmos12121635. For more details on the simulation see doi:10.5194/gmd-13-1809-2020

A Model-Based Climatology of Low-Level Jets in the Weddell Sea Region of the Antarctic

Low-level jets (LLJs) are climatological features in polar regions. It is well known that katabatic winds over the slopes of the Antarctic ice sheet are associated with strong LLJs. Barrier winds occurring, e.g., along the Antarctic Peninsula may also show LLJ structures. A few observational studies show that LLJs occur over sea ice regions. We present a model-based climatology of the wind field, of low-level inversions and of LLJs in the Weddell Sea region of the Antarctic for the period 2002–2016. The sensitivity of the LLJ detection on the selection of the wind speed maximum is investigated. The common criterion of an anomaly of at least 2 m/s is extended to a relative criterion of wind speed decrease above and below the LLJ. The frequencies of LLJs are sensitive to the choice of the relative criterion, i.e., if the value for the relative decrease exceeds 15%. The LLJs are evaluated with respect to the frequency distributions of height, speed, directional shear and stability for different regions. LLJs are most frequent in the katabatic wind regime over the ice sheet and in barrier wind regions. During winter, katabatic LLJs occur with frequencies of more than 70% in many areas. Katabatic LLJs show a narrow range of heights (mostly below 200 m) and speeds (typically 10–20 m/s), while LLJs over the sea ice cover a broad range of speeds and heights. LLJs are associated with surface inversions or low-level lifted inversions. LLJs in the katabatic wind and barrier wind regions can last several days during winter. The duration of LLJs is sensitive to the LLJ definition criteria. We propose to use only the absolute criterion for model studies

Wind and backscatter profiles measured by a wind lidar during POLARSTERN cruise PS109 (ARK-XXXI/4)

This data set includes vertical profiles of wind speed (FF), wind direction (DD), fit deviation (FD) and the backscatter confident (BB) measured by a ship born wind lidar. The definition of the fit deviation, the main processing of the lidar data and an evaluation of the measurements is described in Zentek et al. (2018; doi:10.5194/amt-11-5781-2018 ). For this data set winds were computed every 50 m up to 1000 m and the data is averaged over time. The averaging time is one hour (+-30min around each full hour) and missing values are removed. A weighted arithmetic mean was used for the u- and v-component as well as for the fit deviation with the weights "1/fit deviation". The backscatter coefficient was averaged without weights. As backscatter was always measured, hours were included even if no wind could be computed due to atmospheric conditions but hours with no reliable data were excluded (e.g. the lidar was turned off; the ship was rocking to hard; etc.). Further detailed information for this measurement campaign: number of rays per VAD [6-8], averaging time [3-8 sec], chosen SNR threshold [-19 dB]

Wind and backscatter profiles measured by a wind lidar during POLARSTERN cruise PS106/1 (ARK-XXXI/1.1)

This data set includes vertical profiles of wind speed (FF), wind direction (DD), fit deviation (FD) and the backscatter confident (BB) measured by a ship born wind lidar. The definition of the fit deviation, the main processing of the lidar data and an evaluation of the measurements is described in Zentek et al. (2018; doi:10.5194/amt-11-5781-2018 ). For this data set winds were computed every 50 m up to 1000 m and the data is averaged over time. The averaging time is one hour (+-30min around each full hour) and missing values are removed. A weighted arithmetic mean was used for the u- and v-component as well as for the fit deviation with the weights "1/fit deviation". The backscatter coefficient was averaged without weights. As backscatter was always measured, hours were included even if no wind could be computed due to atmospheric conditions but hours with no reliable data were excluded (e.g. the lidar was turned off; the ship was rocking to hard; etc.). Further detailed information for this measurement campaign: number of rays per VAD [6], averaging time [8 sec], chosen SNR threshold [-20 dB]

Wind and backscatter profiles from the HALO wind lidar of the University of Trier for MOSAiC

Wind lidar measurements of the atmospheric boundary layer (ABL) were performed during the Multidisciplinary drifting Observatory for Study of Arctic Climate (MOSAiC) from September 2019 to October 2020. A "Halo-Photonics Streamline" (HPS) scanning wind lidar was used, which operates at a wavelength of 1.5 μm. The lidar can operate with a maximum range of 10km and is a programmable scanner, which enables vertical scans in all hemispheric directions. Vertical azimuth display (VAD) scan patterns were used for the determination of wind profiles above the lidar. The Doppler velocities were corrected for lidar orientation (pitch/roll/heading) and the ship speed, and different quality checks were performed (see Zentek et al. 2018). VAD scans were performed for the months of September and October 2019 and for March to September 2020 with major data gaps for 14 Feb. 2020 - 17 March 2020 and for 25 March 2020 - 28 March 2020. Wind profiles were measured also during the transfer periods of Polarstern between different drift phases. The profiles have a temporal resolution of about 10 min and a spatial resolution of 30m in the vertical. Heights are above sea level

Analysis of the performance of a ship-borne scanning wind lidar in the Arctic and Antarctic

In the present study a non-motion-stabilized scanning Doppler lidar was operated on board of RV Polarstern in the Arctic (June 2014) and Antarctic (December 2015–January 2016). This is the first time that such a system measured on an icebreaker in the Antarctic. A method for a motion correction of the data in the post-processing is presented. The wind calculation is based on vertical azimuth display (VAD) scans with eight directions that pass a quality control. Additionally a method for an empirical signal-to-noise ratio (SNR) threshold is presented, which can be calculated for individual measurement set-ups. Lidar wind profiles are compared to total of about 120 radiosonde profiles and also to wind measurements of the ship. The performance of the lidar measurements in comparison with radio soundings generally shows small root mean square deviation (bias) for wind speed of around 1 m s−1 (0.1 m s−1) and for wind direction of around 10∘ (1∘). The post-processing of the non-motion-stabilized data shows a comparably high quality to studies with motion-stabilized systems. Two case studies show that a flexible change in SNR threshold can be beneficial for special situations. Further the studies reveal that short-lived low-level jets in the atmospheric boundary layer can be captured by lidar measurements with a high temporal resolution in contrast to routine radio soundings. The present study shows that a non-motion-stabilized Doppler lidar can be operated successfully on an icebreaker. It presents a processing chain including quality control tests and error quantification, which is useful for further measurement campaigns

Wind and backscatter profiles measured by a wind lidar during POLARSTERN cruise PS111 (ANT-XXXIII/2, FROST)

This data set includes vertical profiles of wind speed (FF), wind direction (DD), fit deviation (FD) and the backscatter confident (BB) measured by a ship born wind lidar. The definition of the fit deviation, the main processing of the lidar data and an evaluation of the measurements is described in Zentek et al. (2018; https://doi.org/10.5194/amt-11-5781-2018 ). For this data set winds were computed every 50 m up to 1000 m and the data is averaged over time. The averaging time is one hour (+-30min around each full hour) and missing values are removed. A weighted arithmetic mean was used for the u- and v-component as well as for the fit deviation with the weights "1/fit deviation". The backscatter coefficient was averaged without weights. As backscatter was always measured, hours were included even if no wind could be computed due to atmospheric conditions but hours with no reliable data were excluded (e.g. the lidar was turned off; the ship was rocking to hard; etc.). Further detailed information for this measurement campaign: number of rays per VAD [8], averaging time [4 sec], chosen SNR threshold [-19 dB]

Wind and backscatter profiles measured by a wind lidar during POLARSTERN cruise PS85 (ARK-XXVIII/2)

This data set includes vertical profiles of wind speed (FF), wind direction (DD), fit deviation (FD) and the backscatter confident (BB) measured by a ship born wind lidar. The definition of the fit deviation, the main processing of the lidar data and an evaluation of the measurements is described in Zentek et al. (2018; doi:10.5194/amt-11-5781-2018 ). For this data set winds were computed every 50 m up to 1000 m and the data is averaged over time. The averaging time is one hour (+-30min around each full hour) and missing values are removed. A weighted arithmetic mean was used for the u- and v-component as well as for the fit deviation with the weights "1/fit deviation". The backscatter coefficient was averaged without weights. As backscatter was always measured, hours were included even if no wind could be computed due to atmospheric conditions but hours with no reliable data were excluded (e.g. the lidar was turned off; the ship was rocking to hard; etc.). Further detailed information for this measurement campaign: number of rays per VAD [8], averaging time [1.5 sec], chosen SNR threshold [-17 dB]

Wind and backscatter profiles measured by a wind lidar during POLARSTERN cruise PS106/2 (ARK-XXXI/1.2)

This data set includes vertical profiles of wind speed (FF), wind direction (DD), fit deviation (FD) and the backscatter confident (BB) measured by a ship born wind lidar. The definition of the fit deviation, the main processing of the lidar data and an evaluation of the measurements is described in Zentek et al. (2018; doi:10.5194/amt-11-5781-2018 ). For this data set winds were computed every 50 m up to 1000 m and the data is averaged over time. The averaging time is one hour (+-30min around each full hour) and missing values are removed. A weighted arithmetic mean was used for the u- and v-component as well as for the fit deviation with the weights "1/fit deviation". The backscatter coefficient was averaged without weights. As backscatter was always measured, hours were included even if no wind could be computed due to atmospheric conditions but hours with no reliable data were excluded (e.g. the lidar was turned off; the ship was rocking to hard; etc.). Further detailed information for this measurement campaign: number of rays per VAD [6], averaging time [8 sec], chosen SNR threshold [-20 dB]