PIANO (Penetration and Interruption of Alpine Foehn) - MOMAA weather station data set (Q13068)

ABSTRACT This is the data set of nine MOMAA weather stations operated during the field campaign of the research project PIANO (Penetration and Interruption of Alpine Foehn) in the Inn Valley and Wipp Valley near 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 Nine portable automatic weather stations (AWS), so-called MOMAA weather stations, were operated during the PIANO field campaign in the greater Innsbruck area, Austria. MOMAA stands for mobile measurement network for Alpine atmospheric research, which is an infrastructure that belongs to the Innsbruck Atmospheric Observatory (IAO). Most of the weather stations were operated at the floor of the Inn Valley between the villages Inzing (west of Innsbruck) and Volders (east of Innsbruck). One station was installed in Innsbruck on the rooftop of the former Hotel Hilton about 50 m above street level. Two stations were deployed at the slope of the Inn Valley at Ölberg in the north and Bergisel in the south of Innsbruck. One station was operated in the Wipp Valley at the village of Patsch close to the radiosonde site and not far from an eddy covariance station. The station coordinates and heights are listed in the data file and a description of the locations is given here (see also momaa_locations.png): M02: Vls M03: Innsbruck/Bergisel M04: Patsch/Pfaffenbichl M05: Innsbruck/Ölberg M06: Innsbruck/Hotel Hilton M07: Innsbruck/Saggen/Kettenbrcke M08: Volders M09: Unterperfuss M10: Inzing/Zirl/Modellflugplatz The MOMAA stations were installed to complement the operational AWS networks of the national weather service ZAMG and other institutions. 2. Temporal coverage The PIANO field campaign took place during fall and early winter 2017. However, the MOMAA data set is available for the period from about mid August 2017 to mid December 2017. Two stations (M04 and M06) remained in operation until the beginning of February 2018. Due to malfunctions, short data gaps occurred in early September 2017. Moreover, precipitation data is missing for M07 on 27 and 28 October due to a blocked rain gauge and soil temperature data for the same station is missing in mid September due to a damaged sensor. The exact operating times are: M02: 1300 UTC 15 Aug 2017 to 1359 UTC 11 Dec 2017 M03: 1230 UTC 12 Aug 2017 to 1059 UTC 11 Dec 2017 M04: 1200 UTC 15 Aug 2017 to 1459 UTC 08 Feb 2018 M05: 0630 UTC 13 Aug 2017 to 1359 UTC 11 Dec 2017 M06: 1100 UTC 13 Aug 2017 to 1459 UTC 08 Deb 2018 M07: 1730 UTC 29 Aug 2017 to 1429 UTC 11 Dec 2017 M08: 0830 UTC 18 Aug 2017 to 1429 UTC 11 Dec 2017 M09: 0800 UTC 28 Aug 2017 to 1329 UTC 11 Dec 2017 M10: 1330 UTC 29 Aug 2017 to 1329 UTC 11 Dec 2017 3. Instrument details Sensor type Measurements were taken with nine automatic weather stations manufactured by the Swiss company SensAlpin. Each station consists of the following sensors and hardware: Data logger (Campbell CR1000) Air temperature and humidity sensor (Rotronic HC2A-S3) mounted in an actively ventilated radiation shield (Rotronic RS12T) 2D ultra sonic anemometer (Gill WindSonic) Net radiometer (KippZonen NR Lite) Barometer (Campbell CS100, Sera model 278) Tipping bucket rain gauge (RM Young model 520202 or 52203) Two soil temperature sensors (Campbell thermistor 107) GSM modem Battery and solar panel Aluminum telescopic mast, side boom and tripod (Letrona) Two stations (M05 at Ölberg and M06 at Hotel Hilton) had no rain gauge, no net radiometer and no soil temperature sensors. MOMAA ID number and location The MOMAA ID numbers mentioned in the data file (02 to 10) correspond to the ID numbers (M02 to M10) used internally at ACINN (they are indicated on each logger box). Station M01 was not used during PIANO. GPS coordinates and heights of all MOMAA stations are provided in the data file. Time and measurement interval Time in the data file is in UTC. The measurement interval is 1 minute. A measurement value represents either a 1-minute average (arithmetic average for scalar quantities and vector average for wind quantities), a maximum within 1 minute or a sum over 1 minute. Installation height The wind sensor was mounted 3.5 m above ground (AGL). The air temperature and humidity sensor was installed at 2 m (AGL). The rain gauge and the net radiometer were mounted on a side boom at 1.8 m AGL. The height of the barometer is different for each station (between 0.5 and 1 m AGL) and is listed in the data file. Where possible, the two soil temperature sensors were placed at 2 and 6 cm below the surface, respectively. Note that station M06 was deployed at the rooftop of the former Hotel Hilton (now AC Hotel Innsbruck). Hence, the sensor heights for M06 are relative to the height of the rooftop, which is at about 50 m above street level. Data correction Here we provide so-called level 1 data that includes a bias correction for air temperature and relative humidity. Based on a preliminary data analysis after the PIANO campaign, a warm bias was detected in the time series of air temperature that was caused by high-frequency noise induced by the ventilation of the Rotronic radiation shield due to electromagnetic induction. This warm bias is proportional to the battery voltage as long as the ventilation is active. The higher the battery voltage, the higher the rotation speed of the fan and, hence, the larger the error due to induction. The status of the ventilation is indicated by the parameter vent_flag in the data file (off=0, on=1). The ventilation is automatically switched off if the battery voltage drops below a certain threshold. This only occurred a few times during the field campaign (see overview figure momaa_overview_ventilation_flag.png). In order to correct this bias, we performed a sensor intercomparison study in December 2018 with all MOMAA stations and an independent reference sensor (the same type of sensor but with a separate wiring for the temperature sensor and the ventilation). Based on these measurements, the air temperature bias was quantified for each station with the linear function \(\Delta T_\mathrm{bias} = k V_\mathrm{bat} + d\). Here, \(k\) and \(d\) are slope and intercept of the linear regression. The values of these coefficients are different for each station. \(V_\mathrm{bat}\) is the battery voltage. The bias is about 1 to 2 K. In the data file we provide values for \(k\) and \(d\) as well as corrected temperature ta and uncorrected (raw) temperature ta_raw. We strongly recommend to use corrected temperature. Based on the same intercomparison measurements, a notable bias in relative humidity of about 4 to 8 % was found for station M04. This bias is proportional to the measured humidity. The bias is much smaller for the other stations (about 0 to 2 %). Nevertheless, we applied a bias correction for all stations based on \(\Delta \mathrm{RH}_\mathrm{bias} = k \mathrm{RH}_\mathrm{raw} + d\). In the data file we provide values for \(k\) and \(d\) as well as corrected relative humidity rh and uncorrected (raw) temperature rh_raw. We did not calibrate the pressure sensors. Hence, values for air pressure may exhibit a station-dependent offset from the truth. In order to correct these potential offsets, the user may want to follow the approach of Muschinski et al. (2020; section 4.5). 4. Data file structure File format Provided are data in netCDF format as well as overview figures in PNG format. Data MOMAA_lev1_FINAL.nc is a netCDF file that contains the whole MOMAA data set. Time in the data file is given in UTC as a UNIX timestamp (seconds since 00:00 UTC 01 January 1970) and the measurement interval is 1 minute. The following parameters can be found in the data file: corrected and uncorrected air temperature (ta and ta_raw), corrected and uncorrected relative humidity (rh and rh_raw), mean and maximum horizontal wind speed (wspeed and wspeed_max; the latter is the maximum 3-second gust wind speed measured in 1 minute), mean wind direction and its standard deviation (wdir and wdir_stddev), net radiation (nr), air pressure (pa), precipitation accumulated over 1 minute and maximum precipitation intensity (prec and rrmax), soil temperature at two different depths (ts1 and ts2), ventilation flag (vent_flag), and battery voltage (batt_volt). The data file also contains information on the location and the absolute height of each station as well as the sensor heights above ground level. Overview figures momaa_locations.png illustrates the locations of the MOMAA stations on a terrain map. momaa_overview_[parameter].png illustrates the whole data set of a certain parameter. It is useful for assessing data availability. Overview figures for several different parameters are provided. 5. Publications MOMAA data of the PIANO field campaign have been analyzed in following publications: Muschinski (2019), Muschinski et al. (2020), Haid et al. (2020), Umek et al. (2021). 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., 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