PIANO (Penetration and Interruption of Alpine Foehn) - Doppler wind lidar data set (Q13067)

ABSTRACT This is the data set of four scanning Doppler wind lidars (SL74, SL75, SL88 and SLXR142) operated during the field campaign of the research project PIANO (Penetration and Interruption of Alpine Foehn) in the Inn Valley at Innsbruck, Austria, during fall and early winter 2017. The goal of the campaign was to study the erosion of cold air pools during south foehn and the associated foehn breakthrough at the valley floor in the vicinity of Innsbruck as well as the subsequent foehn breakdown. The campaign comprises seven Intensive Observation Periods (IOPs), more specifically six south foehn events (IOP 2 to IOP 7) and one west foehn (IOP 1). DATA SET DESCRIPTION 1. Spatial coverage and locations Measurements with four scanning Doppler wind lidars (SL74, SL75, SL88 and SLXR142) were collected during the PIANO field campaign in the Inn Valley at Innsbruck, Austria. Three of the lidars (SL74, SL75 and SLXR142) were installed on tall buildings and arranged on a triangle to perform coplanar scans for dual- and triple-Doppler lidar analysis. The fourth lidar (SL88) was installed along the northern side of this triangle on a lower building to measure vertical wind profiles. The exact locations are given in the list below. A map showing the lidar locations can be found in Haid et al. (2020). SL74: PEMA Holding, Brunecker Strae 1, 6020 Innsbruck, 47.2660760 deg N, 11.4011756 deg E, 629.13 m MSL SL75: Lagerhaus, Duilenstrae 20, 6020 Innsbruck, 47.2533684 deg N, 11.3928383 deg E, 623.79 m MSL SL88: HTL Anichstrae, Anichstrae 26-28, 6020 Innsbruck, 47.2649805 deg N, 11.3893394 deg E, 584.88 m MSL SLXR142: University of Innsbruck, Innrain 52d, 6020 Innbruck, 47.2639112 deg N, 11.3846693 deg E, 619.64 m MSL 2. Temporal coverage The PIANO field campaign took place during fall and early winter 2017. The operation period is different for each of the four lidars (see list below). The SL88 lidar was in operation the longest, whereas SL74 and SL75 only operated during the main PIANO campaign from September to December 2017. The SL88 lidar performed conical scans throughout the campaign (6beam, see next section). The other three lidars (SL74, SL75 and SLXR142) were used to realize various different scan scenarios based on different scan patterns (see overview in list below and details in the next section). Between mid September and the beginning of October these three lidars were tested and the scan patterns were optimized. We do not provide data for this test period. After testing, scenario 1a started. During the operation period of this first scenario, several shorter tests were performed and smaller changes were applied to the lidar configuration. On 13/14 Oct 2017, scenario 2 was tested, but did not became operational. On 16 Oct, scenario 1b started, an optimized version of scenario 1a and the main scenario of the PIANO campaign. Scenario 1b was interrupted for about one day (2-3 Nov 2017) by scenario 2. After dismantling SL74 and SL75 on 18 December, SLXR142 continued to operate until February but performed scenario 3. Operation period: SL74, SL75: 12 Sep 2017 - 18 Dec 2017 SL88: 19 Jul 2017 - 8 Mar 2018 SLXR142: 18 Sep 2017 - 11 Feb 2018 Tests: SL74, SL75, SLXR142: 12 Sep - 6 Oct 2017, 16 Oct 2017, 5-6 Dec 2017 Scenario 1a: SL74, SL75, SLXR142: 7 Oct - 13 Oct 2017, 15 Oct 2017 Scenario 1b: SL74, SL75: 16 Oct - 18 Dec 2017 SLXR142: 16 Oct - 20 Dec 2017 Scenario 2: SL74, SL75, SLXR142: 13/14 Oct 2017, 2/3 Nov 2017 Scenario 3: SLXR142: 21 Dec 2017 - 10 Feb 2018 3. Instrument details General Measurements were taken with four scanning Doppler wind lidars, model Stream Line (SL74, SL75, SL88) and Stream Line XR (SLXR142), manufactured by HALO Photonics. Available are profiles of radial velocity and backscatter data collected in continuous scanner motion (CSM) mode, step-stare (SS) mode and constant staring mode as well as derived products. For CSM scans, the scanner moves continuously as data are acquired. In SS mode the scanner stops momentarily at each waypoint and acquires data for a predefined pulse integration time before moving to the next waypoint. In constant staring mode the scanner does not move at all and collects a series of profiles at a constant azimuth and elevation angle. For all lidars the integration time is 0.5 second in CSM mode and 1 second in SS and constant staring mode. The pulse repetition frequency is 15 kHz for SL74, SL75 and SL88 and 10 kHz for SLXR142. Therefore, each single profile (also called ray or beam) represents either a 0.5-s average over 7500 pulses or a 1-s average over 15000 pulses for the SL74, SL75 and SL88 lidars. For the SLXR142 lidar it is either an average over 5000 pulses (0.5 s) or 10000 pulses (1 s). The range gate length is 18 m for all lidars. Coplanar range height indicator (RHI) scans and plan position indicator (PPI) scans were performed in CSM mode with the lidars SL74, SL75 and SLXR142 to compute the two-dimensional wind field based on the dual- or triple-Doppler lidar analysis technique. Six-beam scans were conducted in SS mode with the SL88 lidar (five beams at 70 deg elevation uniformly distributed on a cone and a sixth pointing vertically; henceforth called 6beam scan). Moreover, 24-beam scans were performed in SS mode with the SL74 and SL75 lidars (24 beams at 70 deg elevation uniformly distributed on a cone; henceforth called VAD24). 6beam and VAD24 data are used to derive vertical profiles of the three-dimensional wind vector based on the velocity-azimuth display (VAD) analysis technique. Constant vertical stares (henceforth called stare) were conducted with the SL74 and SL75 lidar to measure vertical profiles of the vertical wind component at 1 Hz from which profiles of vertical velocity variance can be derived. More details can be found in Haid et al. (2020). Scan scenarios and scan patterns Terminology We distinguish between scan scenario and scan pattern. A scan pattern refers to one of the following scan types: RHI, PPI, step-and-stare (SS) or vertical stare (see further below for details). A scenario is based on a sequence of different scan patterns that are repeated after a certain time. For example, in scenario 1b, SLXR142 starts with a conical step-and-stare scan (vad24) at the full hour, proceeds with a sequence of RHI scans in easterly direction (rhiew), repeats again a vad24, continues with a series of RHI scans in southerly direction (rhisn), does another vad24 before finally ending the hour with a series of PPI scans (ppi3). In the next hour the same sequence of scan patterns is repeated. For the same scenario, the other lidars perform a slightly different sequence of scan patterns (see also Fig. 2 in Haid et al. 2020). Scan patterns stare: vertical stares performed by all lidars, however, most systematically and continuously by the SL74 and SL75 lidar. 6beam: step-and-stare scan performed only by the SL88 lidar based on 6 beams, i.e., five beams at 70 deg elevation uniformly distributed on a cone and a sixth pointing vertically. ppi3: synchronized coplanar PPI scans performed by three lidars (SL74, SL75 and SLXR142) in CSM mode on a nearly horizontal plane. The constant elevation angle of the PPI depends on the lidar site (0.5 deg for SL74, 1.0 deg for SL75, and 1.6 deg for SLXR142) and has been chosen to provide the best overlap with the smallest vertical distance between the three conical surfaces. rhiew: synchronized coplanar RHI scans performed by the SL74 and SLXR142 lidar in CSM mode on a vertical plane in east-west direction. At the same time SL75 performs vertical stares. rhisn: synchronized coplanar RHI scans performed by the SL75 and SLXR142 lidar in CSM mode on a vertical plane in south-north direction. At the same time SL74 performs vertical stares. vad24: step-and-stare scan performed by the SL74, SL75 and SLXR142 lidar based on 24 beams at 70 deg elevation uniformly distributed on a cone. rhiew3: synchronized coplanar RHI scans performed by the SL74 and SLXR142 lidar in CSM mode on a vertical plane in east-west direction. At the same time SL75 performs RHI scans orthogonally to this scan plane. rhisn3: synchronized coplanar RHI scans performed by the SL75 and SLXR142 lidar in CSM mode on a vertical plane in south-north direction. At the same time SL74 performs RHI scans orthogonally to this scan plane. rhi: RHI scans performed by the SLXR142 lidar in CSM mode in three different azimuth directions. This scan pattern was only conducted after the main campaign (scenario 3). Scan scenarios Scenario 1a Scan patterns: vad24, ppi3, rhiew, rhisn, stare, 6beam. For ppi3, rhiew, and rhisn, the corresponding PPI or RHI scan is repeated 32 times before moving on to the next scan pattern. The entire sequence of scan patterns takes one hour and is repeated each hour. Note that some of the scan patterns are repeated more than once an hour. Disadvantage: After a while, coplanar scans are no longer synchronized. Scenario 1b Improved version of scenario 1a and main scenario of the PIANO campaign (see Fig. 2 in Haid et al. 2020). Scan patterns: vad24, ppi3, rhiew, rhisn, stare, 6beam. For ppi3, rhiew, and rhisn, the corresponding PPI or RHI scan is repeated 16 times. Then the same scan pattern is repeated once with synchronized starting time (all lidars start at the same time) before moving on to the next scan pattern. The entire sequence of scan patterns takes one hour and is repeated each hour. Note that some of the scan patterns are repeated more than once an hour. Data products derived from coplanar scans (level 2 data; see below) are only available for this scenario. Note that the azimuth angles of the rhiew and rhisn scans performed by SL74 and SL75 were changed on 20 Oct to ensure a better overlap of the coplanar scans. Scenario 2 Scan patterns: vad24, ppi3, rhiew3, rhisn3, stare, 6beam Performed only on one day (from 2 to 3 November), no PIANO IOP Since the scan patterns performed by the SLXR142 lidar are the same as in scenario 1a, the files are named rhiew and rhisn instead of rhiew3 and rhisn3. Scenario 3 Scan patterns: rhi, vad24, 6beam SLXR142 performs RHI scans in three different directions. Data correction and data products Provided are level 1 and level 2 data. The level is indicated in the file name by the shortcut l1 and l2, respectively. The level 1 data set is a corrected version of the original data set produced in real time by the lidar system during its operation. Data correction includes an adjustment of the azimuth angle due to instrument misalignment (a corrected azimuth angle of 0 corresponds to true north) and a correction of the range gate distance (only necessary for SLXR142). Furthermore, data files are converted from the original vendor format (so-called HPL files in ASCII format) to netCDF. File names of level 1 data slightly differ from the original HPL files as they also include the name of the scan pattern. Software used to produce this data set is mentioned in section 5. The level 2 data set comprises products derived from level 1 data. These products are vertical wind profiles derived from conical scans based on the VAD analysis technique (shortcut vad in file names) and two-dimensional wind fields on two different vertical planes derived from coplanar RHI scans (shortcut rhisn and rhiew in file names) and on a nearly horizontal plane close to the surface derived from coplanar PPI scans (shortcut ppi3 in file names). Software used to derive this products is mentioned in section 5. CSM scan mode and effect on azimuth and elevation angle All PPI and RHI scans were performed as continuous motion scans (CSM mode). For a continuous motion scan, the scanner moves continuously as data are acquired. Therefore, the azimuth (elevation) angle continuously changes for PPI (RHI) scans over the pulse averaging interval of 0.5 second to create one profile at a 2 Hz frequency. It is important to notice, that *the azimuth and elevation angles in the 2-Hz data files of RHI and PPI scans provided here represent the starting point of the pulse averaging interval*. The same applies to the time stamp. Depending on the application, these angles may have to be corrected by the data user by shifting the azimuth and elevation angle by half an increment (i.e., \(\alpha_\mathrm{corr} = \alpha_\mathrm{orig} + \Delta \alpha/2\)). For deriving coplanar data retrievals (level 2 data), this correction has been applied. 4. Data file structure File format Provided are data in netCDF format. NetCDF data files are zipped together into zip files. Zip files level1_SL74.zip contains netCDF files of level 1 data of the SL74 lidar level1_SL75.zip contains netCDF files of level 1 data of the SL75 lidar level1_SL88.zip contains netCDF files of level 1 data of the SL88 lidar level1_SLXR142.zip contains netCDF files of level 1 data of the SLXR142 lidar level2.zip contains netCDF files of level 2 data stored in various subfolders: vertical wind profiles derived with the VAD analysis technique for all four lidars (subfolders SL74_vad_l2, SL75_vad_l2, SL88_vad_l2, SLXR142_vad_l2) two-dimensional wind fields derived on a horizontal plane (subfolder ppi3_l2) and on two vertical planes (subfolders rhiew_l2 and rhisn_l2). NetCDF files File names contain the lidar ID, the scan pattern, date and time information in UTC as well as the data level. The following wildcard characters are used in the file examples below: lidarID - SL74, SL75, SL88, or SLXR142; yyyy - year; mm - month; dd - day; HH - hour; MM - minute; SS - second. All date and time variables in the netCDF files are in UTC. Level 1 data (l1) lidarID_stare_yyyymmdd_l1.nc contains measurements conducted in constant staring mode (mostly vertical stares) aggregated in one file for each day. lidarID_6beam_l1_yyyymmdd.nc contains data of 6beam scans aggregated in one file for each day. Only available for the SL88 lidar. lidarID_vad24_l1_yyyymmdd_HHMMSS.nc contains data of a vad24 scan of the SL74, SL75 and SLXR142 lidar. This scan was performed every 20 minute and, hence, three times per hour. lidarID_ppi3_l1_yyyymmdd_HHMMSS.nc contains multiple PPI scans performed as part of the coordinated ppi3 scan pattern of the SL74, SL75 and SLXR142 lidar. The scan was performed on a nearly horizontal plane (the elevation angle depends on the lidar site and is 0.5 deg for SL74, 1.0 deg for SL75, and 1.6 deg for SLXR142) in an azimuth sector of 90 deg. The PPIs were repeated 33 times for scan scenario 1a and scenario 2 and 16 times for scenario 1b (the latter carried out twice in a row). lidarID_rhiew_l1_yyyymmdd_HHMMSS.nc contains multiple RHI scans performed as part of the coordinated rhiew scan pattern of the SL74 and SLXR142 lidar. The scan was performed in east-west direction in an elevation sector of 90 deg with SL74 and 45 deg with SLXR142. The RHIs were repeated 33 times for scan scenario 1a and 16 times for scenario 1b (the latter carried out twice in a row). lidarID_rhisn_l1_yyyymmdd_HHMMSS.nc contains multiple RHI scans performed as part of the coordinated rhisn scan pattern of the SL75 and SLXR142 lidar. The scan was performed in south-north direction in an elevation sector of 90 deg with SL75 and 45 deg with SLXR142. The RHIs were repeated 33 times for scan scenario 1a and scenario 2 and 16 times for scenario 1b (the latter carried out twice in a row). lidarID_rhiew3_l1_yyyymmdd_HHMMSS.nc contains multiple RHI scans performed as part of the coordinated rhiew3 scan pattern. The SL74 and SLXR142 lidar performed coplanar RHIs in east-west direction. The SL75 lidar performed RHIs orthogonal to this plane in south-north direction. This scan pattern was only part of scenario 2. lidarID_rhisn3_l1_yyyymmdd_HHMMSS.nc contains multiple RHI scans performed as part of the coordinated rhisn3 scan pattern. The SL75 and SLXR142 lidar performed coplanar RHIs in south-north direction. The SL74 lidar performed RHIs orthogonal to this plane in east-west direction. This scan pattern was only part of scenario 2. Level 2 data (l2) Level 2 data are only available for scan scenario 1b. lidarID_vad_l2_yyyymmdd.nc contains vertical profiles of the three-dimensional wind vector derived with the VAD analysis technique from 6beam scans for SL88 and from vad24 scans for SL74, SL75 and SLXR142. ppi3_l2_yyyymmdd_HH.nc contains two-dimensional wind fields derived from coplanar PPI scans of pattern ppi3 performed with the SL74, SL75 and SLXR142 lidar. All fields of one hour (between HH-1 and HH) are aggregated in one file. rhiew_l2_yyyymmdd_HH.nc contains two-dimensional wind fields derived from coplanar RHI scans of pattern rhiew performed with the SL74 and SLXR142 lidar. All fields of one hour (between HH-1 and HH) are aggregated in one file. rhisn_l2_yyyymmdd_HH.nc contains two-dimensional wind fields derived from coplanar RHI scans of pattern rhisn performed with the SL75 and SLXR142 lidar. All fields of one hour (between HH-1 and HH) are aggregated in one file. 5. Software, publications and related data sets Software used to create level 1 and level 2 data have been published by Haid (2021a,b). A description of the instruments and the scan patterns as well as a detailed analysis of IOP 2 can be found in Haid et al. (2020). PIANO Doppler wind lidar data was also used in Umek et al. (2021), Muschinski (2019) and Muschinski et al. (2020). 6. Contact Contact alexander.gohm (at) uibk.ac.at for any questions regarding the data set. 7. Acknowledgements The PIANO field campaign was supported by the Austrian Science Fund (FWF) and the Weiss Science Foundation under Grant P29746-N32, by KIT IMK-IFU, Austro Control GmbH, Zentralanstalt fr Meteorologie und Geodynamik (ZAMG), the Hydrographic Service of Tyrol, Innsbrucker Kommunalbetriebe AG (IKB), Bergisel Betriebsgesellschaft m.b.H., Innsbrucker Nordkettenbahnen Betriebs GmbH, T-Mobile Austria GmbH, Unser Lagerhaus Warenhandelsgesellschaft, PEMA Immobilien GmbH, HTL Anichstrae, Hilton Innsbruck, TINETZ-Tiroler Netze GmbH, Land Tirol, and the communities Patsch and Vls. 8. References Haid, M., 2021a: marenha/doppler_wind_lidar_toolbox: PIANO release (Version v1.1.2). Zenodo. http://doi.org/10.5281/zenodo.4719222 Haid, M., 2021b: marenha/PIANO: Second release (Version v1.0.1). Zenodo. http://doi.org/10.5281/zenodo.4719224 Haid, M., A. Gohm, L. Umek, H. C. Ward, T. Muschinski, L. Lehner, and M. W. Rotach, 2020: Foehn-cold pool interactions in the Inn Valley during PIANO IOP2. Quarterly Journal of the Royal Meteorological Society, 146, 12321263, https://doi.org/10.1002/qj.3735 Muschinski, T., 2019: Spatial heterogeneity of the pre-foehnic Inn Valley cold air pool and a relationship to Froude number: Observations from an array of temperature loggers during PIANO. Masters Thesis. Department of Atmospheric and Cryospheric Sciences, Unversity of Innsbruck, 101 pp., https://resolver.obvsg.at/urn:nbn:at:at-ubi:1-43559 Muschinsik, T., A. Gohm, M. Haid, L. Umek, and H. C. Ward, 2020: Spatial heterogeneity of the Inn Valley cold air pool during south foehn: Observations from an array of temperature loggers during PIANO. Meteorologische Zeitschrift, https://doi.org/10.1127/metz/2020/1043 Umek, L., A. Gohm, M. Haid, H. C. Ward, and M. W. Rotach, 2021: Large‐eddy simulation of foehncold pool interactions in the Inn Valley during PIANO IOP 2. Quarterly Journal of the Royal Meteorological Society, 147, 944982, https://doi.org/10.1002/qj.3954