Abstract:

dlidcsm_level1: This data set contains the level-1 data of the Doppler LIDAR measurements at the three supersites (Falkenberg, Lindenberg, Birkholz) operated during the Field Experiment on Sub-mesoscale Spatio-Temporal Variability in Lindenberg (FESSTVaL) during the period May 17 to August 31, 2021 (please also see the "Additional Notes" further down on this web page).
dlidcsm_level2: This data set contains two wind products: (i) vertical profiles of the mean wind vector and (ii) vertical profiles of wind gusts derived with two different kinds of processing (Level2dwd and Level2uzk, see "Methods") from the Doppler LIDAR level 1 data dlidcsm_level1.
sonic: This data set contains level 2 data of the mean wind vector and of the maximum gust wind speed derived from ultrasonic anemometer measurements at heights of 2.4 m, 50.3 m and 90.3 m at the Grenzschichtmessfeld (GM) Falkenberg during the Field Experiment on Sub-mesoscale Spatio-Temporal Variability in Lindenberg (FESSTVaL) over the period May 17 to August 31, 2021. The GM Falkenberg as part of the Lindenberg Meteorological Observatory – Richard-Aßmann-Observatory supersite is operated by the German national meteorological service (Deutscher Wetterdienst, DWD).

TableOfContents:

dlidcsm_level1: sensor azimuth angle; attenuated backscatter coefficient; radial velocity of scatterers away from instrument (doppler velocity); error of doppler velocity; backscatter intensity; range bands; zenith angle
dlidcsm_level2:

    Level2dwd: wind speed; wind direction; eastward wind component u; northward wind component v; upward air velocity w; wind speed of gust; wind direction of gust; eastward wind component of gust u_max; northward wind component of gust v_max; upward air velocity of gust w_max; condition number of gust; coefficient of determination of gust; number of radial velocities of gust; index of gust; autocorrelation function; condition number; coefficient of determination; number of radial velocities; wind quality flag; relative number of good circulations; relative number of good radial velocities
    Level2uzk: eastward wind component u; northward wind component v; upward air velocity w; eastward wind gust u_max; eastward weakest wind u_min; northward wind gust v_max; northward weakest wind v_min; upward air velocity of weakest wind w_min; wind speed; wind speed of gust; wind speed of weakest wind; wind direction; wind direction of gust; wind direction of weakest wind; covariance of wind; covariance of wind gust; covariance of weakest wind; standard deviation of wind speed; standard deviation of gust wind speed; standard deviation of weakest wind speed


sonic: eastward wind component u;  northward wind component v; upward air velocity w; quality flag for eastward wind component qc_u; quality flag for northward wind component qc_v; quality flag for upward air velocity qc_w; quality flag for wind speed and direction qc_wind; wind speed; wind direction; wind speed of gust; wind speed of weakest wind; gust factor 

Technical Info: (see also "Additional Notes" further down)

dlidcsm_level1: dimension01: 259200 (nominal maximum number of timesteps per day)  x 63 (Stream Line XR); dimension02: 259200 (nominal maximum number of timesteps per day)  x 100 (Stream Line); temporalExtent_startDate: 2021-05-18 00:00:00; temporalExtent_endDate: 2021-09-01 00:00:00; temporalResolution: 1/3; temporalResolutionUnit: seconds; spatialResolution: none; spatialResolutionUnit: none; horizontalResolutionXdirection: none; horizontalResolutionXdirectionUnit: none; horizontalResolutionYdirection: none; horizontalResolutionYdirectionUnit: none; rangeResolution01: 48 (Stream Line XR); rangeResolutionUnit01: meters; rangeResolution02: 30 (Stream Line); rangeResolutionUnit02: meters; verticalResolution01: 26.5; verticalResolutionUnit01: meters; verticalResolution02: 42.4; verticalResolutionUnit02: meters; verticalStart: 90; verticalStartUnit: meters; verticalEnd01: 2600; verticalEndUnit01: meters; verticalEnd02: 4200; verticalEndUnit02: meters; instrumentNames: Stream Line S/N 78, Stream Line S/N 172, Stream Line S/N 178; Stream Line XR S/N 44, Stream Line XR S/N 161; instrumentType: Doppler LIDAR; instrumentLocation: Birkholz, Grenzschichtmessfeld Falkenberg, Lindenberg; instrumentProvider: Halo Photonics Ltd.
dlidcsm_level2:

    Level2dwd: dimension01: 144 timesteps x 100 (Stream Line); dimension02: 144 timesteps x 63 (Stream Line XR); temporalExtent_startDate: 2021-05-18 00:10:00; temporalExtent_endDate: 2021-09-01 00:00:00; temporalResolution: 10; temporalResolutionUnit: minutes; spatialResolution: none; spatialResolutionUnit: none; horizontalResolutionXdirection: none; horizontalResolutionXdirectionUnit: none; horizontalResolutionYdirection: none; horizontalResolutionYdirectionUnit: none; verticalResolution: 42.4.; verticalResolutionUnit: meters; verticalStart: 90; verticalStartUnit: meters; verticalEnd: 4250; verticalEndUnit: meters; instrumentNames: Stream Line S/N 78, Stream Line S/N 172, Stream Line S/N 178; Stream Line XR S/N 44, Stream Line XR S/N 161; instrumentType: Doppler LIDAR; instrumentLocation: Birkholz, Grenzschichtmessfeld Falkenberg, Lindenberg; instrumentProvider: Halo Photonics Ltd..
    Level2uzk: dimension01: 144 timesteps x 101 (Stream Line); dimension02: 144 timesteps x 64 (Stream Line XR); temporalExtent_startDate: 2021-05-18 00:10:00; temporalExtent_endDate: 2021-09-01 00:00:00; temporalResolution: 10; temporalResolutionUnit: minutes; spatialResolution: none; spatialResolutionUnit: none; horizontalResolutionXdirection: none; horizontalResolutionXdirectionUnit: none; horizontalResolutionYdirection: none; horizontalResolutionYdirectionUnit: none; verticalResolution: 42.4.; verticalResolutionUnit: meters; verticalStart: 90; verticalStartUnit: meters; verticalEnd: 4250; verticalEndUnit: meters; instrumentNames: Stream Line S/N 78, Stream Line S/N 172, Stream Line S/N 178; Stream Line XR S/N 44, Stream Line XR S/N 161; instrumentType: Doppler LIDAR; instrumentLocation: Birkholz, Grenzschichtmessfeld Falkenberg, Lindenberg; instrumentProvider: Halo Photonics Ltd..


sonic: dimension: 144 timesteps per day x 3 heights; temporalExtent_startDate: 2021-05-17 00:10:00; temporalExtent_endDate: 2021-09-01 00:00:00; temporalResolution: 10; temporalResolutionUnit: minutes; spatialResolution: none; spatialResolutionUnit: none; horizontalResolutionXdirection: none; horizontalResolutionXdirectionUnit: none; horizontalResolutionYdirection: none; horizontalResolutionYdirectionUnit: none; verticalResolution: none; verticalResolutionUnit: none; verticalStart: 2.4; verticalStartUnit: meters; verticalEnd: 90.3; verticalEndUnit: meters; instrumentName: usa1_standard_1; instrumentType: Ultrasonic anemometer; instrumentLocation: Grenzschichtmessfeld Falkenberg at 2.4, 50.3 and 90.3 meters above ground; instrumentProvider: Metek GmbH.

Methods:

dlidcsm_level1: Doppler LIDAR profiles extend throughout the lower atmospheric boundary layer from 90 m up to a maximum height typically above 1500 m (for level2dwd V01 processing: 1000 m) dependent on the atmospheric backscatter conditions. The Doppler LIDAR measurements were based on a conically Doppler lidar scanning geometry with high temporal resolution (~3.4s for one full scan, azimuth resolution of approx. ~33 deg) and a constant zenith angle of 28 deg. The realization of such a scanning strategy was possible via the continuous scan mode option of the Doppler LIDAR system with a number of accumulated pulses per beam Npa = 3000. Two different types of Halo Photonics DL systems were used at the three sites during the campaign: (i) a Halo Photonics Streamline XR with a range gate length of 48 m and Halo Photonics Streamline with a range gate length of 30 m. For the non-XR systems the focus was set to 500 m, for XR systems it is set to infinity per default.  For more details concerning the scan configuration see also Steinheuer et al. (2022). These level 1 data are provided by DWD using the dl_toolbox (https://github.com/mkay-atm/dl_toolbox) and include both the instantaneous Doppler LIDAR measurements and related values (e.g. radial velocity and signal-to-noise ratio as function of range gate, time, and azimuth direction) and relevant information concerning the system’s specific parameters which are either fixed by the manufacturer (e.g. wavelength, pulse repetition frequency, pulse length) or can be configured by the user (e.g. range gate length, number of pulse accumulation, focus). Due to the short sampling time per ray, regular time synchronization vs. a reference at prescribed intervals occasionally resulted in a jump back of the time stamp assigned to each vector of radial velocity data. We did not correct that since we wanted to keep the original level-1 data as they were provided from the instrument. Note that the physical range resolution depends on the pulse length (see, e.g., Frehlich, R., 1997, https://doi.org/10.1175/1520-0426(1997)014<0054:EOWTOC>2.0.CO;2) which is set at a fixed value by the manufacturer, this value is different for each system. To harmonize the output, we configured the Streamline and Streamline XR systems each in the same way. This may imply that the range and height bounds given in the level 1 and level 2 data, respectively, may show a positive or negative overlap between neighbouring range / height gates.
dlidcsm_level2: Level-2 data represent 10-min averages of the derived mean wind vector and of wind gust speeds. Usually, gusts are defined as a 3s moving average (WMO). We try to match this by calculating first for each scan (sampling time 3.4 s) a wind estimate and then we search for the maximum value (= gust) within a pre-defined 10min interval. Reliability of both the derived mean wind and the gust wind speeds has been assessed for both methods (see below) by comparison with the sonic wind and gust product data at a reference level of 90 m for a several-months data set. RMSD values are in the order of 0.3 m/s for the mean wind speed, and 0.7 m/s for the maximum gust speed, respectively.

    The Level2dwd product of this release (Version 2024_v01) contains results based on the DWD processing V01. This processing is based on the data processing described in Päschke and Detring (2024, https://doi.org/10.5194/amt-17-3187-2024). Their publication deals with the analysis of Doppler Lidar TKE measurements. As the data processing has similar challenges (due to the small number of pulses per ray), the data handling for the DL gust mode was adapted to this. The new data set (version v01) is generated with this updated processing. A separate publication is in preparation and will be added to this description, for first information see Detring, C. et al., 2022). The quality control procedures implemented for the level2dwd product include an assessment of the signal-to-noise ratio of the backscattered lidar signal (snr), various statistical tests to remove outliers (acf, r2), and completeness tests concerning the availability of both single beam data per scan and single-scan wind values per 10-minute interval (n_good_data, n_good_circulation). Each lidar-based value is accompanied by a quality flag (qwind) where 0 = bad, and 1 = good.
    The Level2uzk product contains results based on the Uni Cologne processing (see Steinheuer et al., 2022) and https://github.com/JSteinheuer/DWL_retrieval). Here, the gust is provided if at least 50% of the individual scans within the 10 minutes have been processed. The quality control procedures implemented for the level2uzk product omits an assessment of the signal-to-noise ratio of the backscattered lidar signal (snr), but are instead based on statistical coherence. This involves fitting a wind vector to the radial observations and iteratively eliminating outliers that are inconsistent with the fit. The iteration stops when the fit has small uncertainties (wind is returned) or too many rejected observations (no wind is returned). The amount of included observations and the quality of the fit is combined to a covariance matrix for the wind vector describing the uncertainty of each estimate. Please check Steinheuer et al. (2022) for more details.


sonic: The sonic measurements are recorded at 20Hz and are quality checked. After quality control, both the 10min mean wind and the maximum gust speed for each interval are calculated. Here, the maximum of the 3s moving average is chosen as the maximum gust speed. This goes with the definition of wind gusts according to the WMO standard. Quality control of the sonic raw data follows Vickers and Mahrt (1997). It includes tests for non-physical values, constant values, and spikes. Constant values are eliminated, and spikes are detected and replaced by linearly interpolated values. Note that this spike-detection does not affect the identification of wind gusts, since it only removes significant outliers of at maximum three consecutive data values (corresponding to a duration of less than 0.2 s which is more than one magnitude shorter than the duration of a gust). Each sonic value is accompanied by a quality flag (qc_wind) where 0 = bad, and 1 = good.

Units: Units for all variables (see TableOfContents):

dlidcsm_level1: degrees; 1/ (m sr), m/s; m/s; 1; m; degrees
dlidcsm_level2:

    Level2dwd: m/s; degrees; m/s; m/s; m/s; m/s; degrees; m/s; m/s; m/s; 1; 1; 1; 1; 1; 1; 1; 1; 1; percent; percent
    Level2uzk: m/s; m/s; m/s; m/s; m/s; m/s; m/s; m/s; m/s; m/s; m/s; degrees; degrees; degrees; m²/s²; m²/s²; m²/s²; m/s; m/s; m/s


sonic: m/s; m/s; m/s; 1; 1; 1; 1; m/s; degrees; m/s; m/s; 1

geoLocations:

BoundingBox: westBoundLongitude: 14.122 degrees East; eastBoundLongitude: 14.192 degrees East; southBoundLatidude: 52.167 degrees North; northBoundLatitude: 52.209 degrees North; geoLocationPlace: Germany, UTM zone 33U
Locations:

    Birkholz: 52.200 degrees North, 14.192 degrees East, 70 meters above mean sea level
    Falkenberg: 52.167 degrees North, 14.123 degrees East, 73 meters above mean sea level
    Lindenberg: 52.209 degrees North, 14.122 degrees East, 115 meters above mean sea level

Size: All data are organized in daily files. For the ease of downloading all sonic, all Doppler LIDAR level-2, and Doppler LIDAR level-1 data of the three supersites are packed into one tar archive each; the total number of tar archives is hence 1 + 1 + 3. Files sizes of these archives are: sonic: ~3.6 MByte, Doppler LIDAR level-2: ~0.5 GByte, Doppler LIDAR level-1 Birkholz: ~26.1 GByte, Doppler LIDAR level-1 Falkenberg: ~34.4 GByte, Doppler LIDAR level-1 Lindenberg: ~13.1 GByte; the total amount is about 74 GByte.

Format: netCDF

DataSources:

dlidcsm: Single site ground-based remote sensing, see "Technical Info" for instruments
sonic: Single site tower-based in situ observations, see "Technical Info" for instruments

Contact:

general: carola.detring (at) dwd.de
sonic: carola.detring (at) dwd.de
Doppler LIDAR DWD processing: frank.beyrich (at) dwd.de
Doppler LIDAR UzK processing: julian.steinheuer (at) uni-koeln.de

Web page: LIDAR: https://www.cen.uni-hamburg.de/en/icdc/data/atmosphere/samd-st-datasets/samd-st-fesstval/fval-dlidcsm-wind-and-gust.html

and SONIC:  https://www.cen.uni-hamburg.de/en/icdc/data/atmosphere/samd-st-datasets/samd-st-fesstval/sups-rao-turb-l2-wind-and-gust.html

see also: https://www.cen.uni-hamburg.de/en/icdc/research/samd/observational-data/short-term-observations/fesstval.html

Data availability: For quality assurance purposes, an intercomparison experiment of the eight Doppler LIDAR systems participating in FESSTVaL was organized in Falkenberg between July 16 and August 09, 2021. This implies that no Doppler LIDAR wind_and_gust products are available for the Lindenberg and Birkholz sites during this period. The comparison experiment in Falkenberg included operation of Doppler LIDARs in the system configuration applied to determine gusts (see above "Methods") – thus for this site the wind_and_gust product is available also for the period July 29 to August 09, 2021. So, in summary, dlidcsm wind_and_gust data products are available for the following dates at the respective sites: Birkholz: 2021-05-18 to 2021-07-15 and 2021-08-10 to 2021-08-31 Falkenberg: 2021-05-18 to 2021-07-15 and 2021-07-29 to 2021-08-31 Lindenberg: 2021-06-11 to 2021-07-15 and 2021-08-10 to 2021-08-31

Due to configuration changes, system updates or location changes, there are single days for which the data are either missing or not complete. Operational decisions on the measurement strategy during FESSTVaL and the availability of the instruments led to different measurement tasks of the Doppler LIDAR systems during the experiment which implies that the data products at each site originate from different systems during sub-periods of the experiment.

Funding: FESSTVaL is funded by the Deutscher Wetterdienst within the Hans-Ertel Centre for Weather Research.