The Rofental: a high Alpine research basin (1890–3770 m a.s.l.) in the Ötztal Alps (Austria) with over 150 years of hydrometeorological and glaciological observations

A comprehensive hydrometeorological and glaciological data set is presented, originating from a multitude of glaciological, meteorological, hydrological and laser scanning recordings at research sites in the Rofental (1891–3772 m a.s.l., Ötztal Alps, Austria). The data sets span a period of 150 years and hence represent a unique time series of rich high-altitude mountain observations. Their collection was originally initiated to support scientific investigation of the glaciers Hintereisferner, Kesselwandferner and Vernagtferner. Annual mass balance, glacier front variation, flow velocities and photographic records of the status of these glaciers were recorded. Later, additional measurements of meteorological and hydrological variables were undertaken, and over time a number of autonomous weather stations and runoff gauges were brought into operation; the available data now comprise records of temperature, relative humidity, shortand longwave radiation, wind speed and direction, air pressure, precipitation, and river water levels. Since 2001, a series of distributed (airborne and terrestrial) laser scans is available, along with associated digital surface models. In 2016 a permanent terrestrial laser scanner was installed on “Im hintern Eis” (3244 m a.s.l.) to continuously observe almost the entire area of Hintereisferner. The data and research undertaken at the sites of investigation in the Rofental area enable combined research of cryospheric, atmospheric and hydrological processes in complex terrain, and support the development of several state-of-the-art glacier mass balance and hydroclimatological models. The institutions taking part in the Rofental research framework promote their site in several international research initiatives. In INARCH (International Network for Alpine Research Catchment Hydrology, http://words.usask.ca/inarch), all original research data sets are now provided to the scientific community according to the Creative Commons Attribution License by means of the PANGAEA repository (https://doi.org/10.1594/PANGAEA.876120). Published by Copernicus Publications. 152 U. Strasser et al.: The Rofental


Introduction
Glaciers in the Rofental, Ötztal Alps, have been under observation since the early 17th century; in particular the Vernagtferner (VF) was known for its dangerous surge-type advances (Richter, 1892) with flow velocities up to 11.5 m day −1 (Nicolussi, 2013).In 1599, the tongue of VF reached the valley floor of the Rofental, blocking the valley and forming an ice-dammed lake which burst, causing a catastrophic lake outburst flood (GLOF) on 20 July in 1600.The painting of VF with its lake that was formed again in summer 1601 is the oldest known image of a glacier worldwide (Fig. 1).The lake was ∼ 1700 m in length, and the lake level was at ∼ 2260 m a.s.l.(Nicolussi, 1990).Further advances of VF are documented for the periods around 1680, 1770 (the maximum extent of VF in the little ice age, LIA), 1820 and 1848.Prior to the 19th century, each advance of VF formed the ice dam and lake in the Rofental, and the outflow of this lake was observed due to its dangerous nature (Nicolussi, 2013).The glacier changes were monitored with irregular glacier-front variation recordings.
The comprehensive pool of long-term observations available for the Rofental provides the basis for (i) manifold process studies on energy balance, ice dynamics, glacier hydrology and hydraulics (e.g., Kuhn et al., 1985a, b;Kuhn, 1987), (ii) new ground-based and remote sensing monitoring methods (Escher-Vetter and Siebers, 2013;Juen et al., 2013;Helfricht et al., 2014a), (iii) model development and application in glaciological and regional hydrological research (Kaser et al., 2010;Escher-Vetter and Oerter, 2013;Schöber et al., 2014Schöber et al., , 2016;;Hanzer et al., 2016;Schmieder et al., 2016Schmieder et al., , 2018)), (iv) the evaluation of potential future glacier evolution and changes of the hydrological regime in a changing climate (Weber et al., 2009;Marke et al., 2013;Marzeion and Kaser, 2014;Weber and Prasch, 2015a, b;Hanzer et al., 2017), (v) attributing observed glacier changes to different drivers (Painter et al., 2013;Marzeion et al., 2014a, b) and, finally, (vi) as calibration and validation site for estimating the contribution of glaciers to global sea level rise (Marzeion et al., 2012a, b;Marzeion and Levermann, 2014).For VF, a comprehensive collection of 50 years of significant scientific work of the Commission of Glaciology of the Bavarian Academy of Sciences and Humanities has been edited by Braun and Escher-Vetter (2013).Historical elevation and area changes of HEF, KWF and VF are documented in the Austrian glacier inventories, available for 1969, 1997and 2006(Abermann et al., 2009)): Between 1969 and 1997, the glacier area in the Rofental decreased from 42.9 to 37.7 km 2 , corresponding to 12 % (Kuhn et al., 2006); recently, the retreat of the glaciers has accelerated.The key glaciological results for HEF, KWF and VF are reported annually to the World Glacier Monitoring Service (WGMS, http://wgms.ch).The state of HEF and KWF in 2014 is shown in Fig. 3.
In addition to monitoring glacier mass balance with glaciological, geodetical and hydrological methods as well as the long-term recordings of respective variables, the Rofental has been an open laboratory for the development of new method-  ologies.For example, a series of airborne lidar-derived highresolution digital terrain models (DTMs) of HEF and its surroundings has been processed spanning 2001-2011 (Geist and Stötter, 2002;Helfricht et al., 2014b;Klug et al., 2017).They are subject to ongoing evaluations and method comparison studies as well as the monitoring and study of periglacial morphodynamics (Sailer et al., 2012(Sailer et al., , 2014)).Since 2016, a permanent terrestrial laser scanning station is operating at Im hintern Eis (3244 m a.s.l.), allowing for high-resolution, ondemand monitoring of almost the entire surface area of HEF.
Recordings of devices which still (as of fall 2017) undergo a test and development phase will be continuously made available in PANGAEA.These data will also be documented as continuation of this publication by means of the ESSD "living data process".The data collection that is already accessible comprises (i) image files, e.g., glacier topography maps, photographs or animations, and diagrams; (ii) raster grids, e.g., spatial data derived from laser scanning, as tabdelimited text files; (iii) time series of point observations, e.g., meteorological and hydrological recordings, as well as calculated results for points or areas such as mass balances, as tab-delimited text files; and (iv) the glacier inventories in ArcGIS shape file format.All data are comprised with the period of coverage, and the exact coordinates of the locations (in latitudes and longitudes).Areas are defined by In this paper, we document the available data from the Rofental area.It is structured in (i) glaciological data, i.e., recordings of glacier volume and geometry changes for HEF, KWF, VF and HJF; (ii) meteorological data as recorded by temporally installed or permanent AWSs; (iii) hydrological data characterizing the water balance of the respective glaciated (sub) catchment; and (iv) airborne and terrestrial laser scanning data.The link to the respective PANGAEA repository parent is https://doi.org/10.1594/PANGAEA.876120.This parent comprises all DOI links to download the data described.Nevertheless, the respective direct DOI links are explicitly referred to here as well.
The selection of data, documented here and available for download from PANGAEA, is only a portion of all the observations that have been collected.Countless documents, photographs, tables and analogue measuring tapes await digitization, and many older digital data still have to be processed and correctly documented.According to the purpose of the INARCH special issue to which this paper belongs we have concentrated our efforts on providing (i) a mostly complete picture of the water balance components of the Rofentalthe mass balances of the observed glaciers being an important highlight of these -and (ii) the meteorological data to force a typical hydrological catchment model.Particular attention is paid to the glaciological, meteorological and hydrological processes in the complex Alpine topography and their spatiotemporal variations in the valley.

The Rofental -site description
The Rofental (98.1 km 2 , Fig. 4) is a glaciated headwater catchment in the central eastern Alps, namely in the upper Ötztal Alps (Tyrol, Austria): as of 2008 approximately onethird of its area is ice-covered (Müller et al., 2009).The valley floor is a narrow discontinuous riparian zone typically less than 100 m in width.The Rofental stretches from 1891 m a.s.l. at the gauge at Vent, the lowest point of the catchment, to 3772 m a.s.l. at the summit of Wildspitze, the highest summit of Tyrol.The average slope is 25 • and the average elevation is 2930 m a.s.l..The Rofenache is a tributary to the Venter Ache, Ötztaler Ache and the Inn and as such contributes to the Danube system (i.e., the Black Sea).The river gauge at Vent (1891 m a.s.l., 46.85694 • N, 10.82361 • E) has been operated continuously from the Hydrographic Service of Tyrol since 1967.The characteristic water discharges (m 3 s −1 , 1971-2013) are NQ = 0.09 (lowest discharge), MQ = 4.6 (mean discharge) and HQ = 109 (highest discharge); further characteristic data are published as annual review in the "Hydrographisches Jahrbuch von Österreich" (e.g., BMLFUW, 2011; available at: http://bmlfuw.gv.at,data-downloadatehyd.gv.at).The runoff regime of the Rofenache has not been modified by any measures of hydropower generation and is dominated by the melt of snow and ice during spring and summer, respectively.The early melt-season onset is typically in April.The gauge at Vernagtbach (2635 m a.s.l.) has been operationally maintained by the Bavarian Academy of Sciences and Humanities since 1973 and is the highest streamflow recording site in Austria with measurements also documented at http://ehyd.gv.at (see above) since 2003.The Vernagtbach catchment stretches from 2635 m a.s.l. at the gauge to 3635 m a.s.l. at the summit of Hinterer Brochkogel.According to the glacier inventory of 2006 (https://doi.org/10.1594/PANGAEA.844985), the ice coverage of the Vernagtbach at that time was 71 %.The current rapid decrease of the glaciated area in the Rofental is documented in the WGMS database (http://wgms.ch).
The climate of the Rofental is characterized as an inner Alpine dry type (Fig. 5).The mean annual temperature at the station in Vent (1900 m a.s.l., 46.85833 • N, 10.91250 • E) is 2.5 • C, and total annual precipitation varies between 797 mm in Vent (1982( -2003( , Kuhn et al., 2006) ) and > 1500 mm in the higher altitudes around 3000 m a.s.l., confirmed by the recordings at the various totalisators (see Sect. 3.2.3,Table 4).In these higher regions, seasonal snow cover lasts from October until the end of June. Figure 5 shows temper-atures and precipitation of the station at Vent at 1900 m a.s.l. for the period 1969-2006.
The geological bedrock in the Rofental area mainly consists of biotite-plagioclase, biotite and muscovite gneisses, variable mica schists, and gneissic schists of the Austroalpine Ötztal nappe (Kreuss, 2012;Moser, 2012).Subordinate lithologies are quartzites and graphite schists.Granitic gneisses, amphibolites and diabase occur as layers ranging from a few meters to a few hundred meters thick within the metasedimentary sequence.Land cover in the Rofental is dominated by mountain pastures and coniferous forests in the lower areas, but these only cover little of the area (source: "Land Tirol", http://data.tirol.gv.at).Permafrost is likely to occur at north-facing slopes at higher altitudes (Klug et al., 2016).
Infrastructure in the valley is very good for monitoring instrumentation and fieldwork.A research station at HEF (built in 1966 in 3026 m a.s.l.) and one at Vernagtbach (built in 1973 in 2637 m a.s.l.) serve as logistic bases for fieldwork on the two glaciers.Several mountain huts are located in the Rofental, namely the "Vernagthütte/Würzburger Haus" (2755 m a.s.l.), the "Hochjoch-Hospiz" (2413 m a.s.l.), the "Brandenburger Haus" (3277 m a.s.l.) and close by the  Austrian-Italian borderline at the Hochjoch the "Schöne Aussicht" (also known as "Bella Vista", 2845 m a.s.l.), within the Schnalstal glacier ski resort (http://schnalstal.com/en/glacier).The "Rofenhöfe" (2014 m a.s.l.), the highest permanently settled mountain farm in Austria, is well situated as base camp in the lower valley floor.

The data
In the following chapter the Rofental data are presented in the chronological order in which it has been recorded (Fig. 6).First, we describe the long time series of glaciological data (Sect.3.1).HEF and KWF are monitored by the University of Innsbruck (Austria), whereas VF is monitored by the Bavarian Academy of Sciences and Humanities (Munich, Germany).Next, we describe the meteorological data, again structured by location, i.e., in the order HEF and KWF, VF, and then the valley area (Sect.3.2).Following that, we describe the hydrological data, firstly in the HEF and KWF catchments, then the VF catchment, and finally, the Rofental as a whole (Sect.3.3).In the last section (Sect.3.4), the airborne and terrestrial laser scanning data, which serves glaciological, geomorphological and wider modeling purposes, is described.

Hintereisferner and Kesselwandferner
Changes in the areas of HEF and KWF have been documented on the basis of maps, aerial photos, and more recently satellite and airborne derived digital elevation models (DEMs) since the early 19th century (Lambrecht and Kuhn, 2007; see also the introduction).The traditional glaciological method of determining glacier-wide mass balance involves spatial extrapolation of local measurements of ablation and accumulation to provide values of the climatic mass balance, encompassing changes at the glacier surface and in the near subsurface (Cogley et al., 2011).Uncertainties in the methods are discussed in Zemp et al. (2013).Since 1952, a network of measurement stakes and pits was continuously maintained at HEF to directly measure the mass balance of the glacier (Hoinkes, 1970).Summer and winter mass balances have been measured separately.Interpretation of the surface mass changes of HEF is supported by the availability of daily images from an automatic camera which views the upper part of the glacier to below the ELA, providing useful information on the distribution of snow cover and the pattern of snow melt over the glacier surface.From 1952-2013 the mass balance of KWF has also been recorded, but with a much smaller number of observations and the assumption that the spatial distribution of the mass balance is analogous to the one of the adjacent HEF.Since summer 2013 a full network of observations is also undertaken and maintained at KWF.The mass balance values of HEF and KWF are available at WGMS (ID 491 and507, since 1952 and1966; see Fig. 7) and are also archived in the PANGAEA database (https://doi.org/10.1594/PANGAEA.803830,https://doi.org/10.1594/PANGAEA.803829,https://doi.org/10.1594/PANGAEA.818898 and https://doi.org/0.1594/PANGAEA.818757).
Geodetic determinations of glacier mass balance involve determining the volume change of the whole glacier body, encompassing englacial and basal volume changes.The volume change must then be converted into a mass change which is complicated in the case of a rapidly changing glacier whose surface type can change significantly over the monitoring interval.Apart from the geodetic mass balances on the basis of the glacier inventories, airborne laser scanning images are available for HEF since 2001 (see Sect. 3.4).From these, a time series of geodetic mass balances was derived for 2001-2002to 2010-2011 (Fig. 8 (Fig. 8).This method allows for pixel-by-pixel correction of method-inherent discrepancies in the classical glaciological method (Klug et al., 2017).

Vernagtferner
Glaciological mass balance measurements for VF have been available since 1965 (Mayer et al., 2013a).Since the beginning, annual and winter balance was measured separately in order to discriminate ice melt and snow accumulation.The In 1976, an automatic analogue camera has been installed on "Schwarzkögele" (3075 m a.s.l., 46.86575 • N, 10.83245 • E), capturing one picture of VF and its surrounding per day during the ablation period.Since 2010, three digital pictures per day are produced throughout the year (Weber, 2013).A time series of maps is available for VF since 1889, derived from terrestrial and aerial photogrammetry, aerial laser scanning and optical line scanner images; these maps are used to determine area and volume changes of the glacier for longer periods (Table 1 and Mayer et al., 2013b).

Meteorological data
Due to its complex topography, the Rofental is characterized by steep environmental gradients and large spatiotemporal variations of meteorological conditions.An ongoing effort has been undertaken to supplement data available from the lower regions with additional AWS installations in the higher elevations.As of 2017, the Rofental offers a comprehensive pool of valuable observations and model forcing data for mountain catchment hydrology research (Fig. 4; see also the introduction in Sect.1).
Earth Syst.Sci.Data, 10, 151-171, 2018 www.earth-syst-sci-data.net/10/151/2018/  For all stations, the height of the sensors above ground is at least 1.5 m; in winter, the distance between the snow surface and the sensors can become much smaller, and in extreme snow-rich periods the instruments even can become completely snow-covered.Such periods can be recognized in the data by typical recordings of zero wind speed and increasing dampening of the other meteorological variables.

Hintereisferner and Kesselwandferner
The first meteorological observations at HEF and its surrounding began in 1968 and are documented in Kuhn et al. (1979).Short term projects, dedicated to measuring the surface mass balance of snow and ice on the glacier involved temporary installations of AWSs on the glacier (e.g., Siogas, 1977a;Harding et al., 1989;Obleitner, 1994).Since 2010, automatic meteorological measurements have been carried out at station "Hintereisferner" (3026 m a.s.l., 46.79867 • N, 10.76042 • E) (Fig. 10).The installation as of 2017 is detailed in Table 2.
Since 2014 an AWS has been seasonally operated on the glacier terminus, providing the meteorological data for surface energy balance assessments of the ice surface, complemented by surface height change observations with a sonic ranger.
From summer 2017, the permanent meteorological measurements at Hintereisferner will be complemented by recordings of the sensors on a 6 m high tower that has been equipped for detailed turbulent flux measurements (see Sect. 3.2.3).This new station is situated close to the permanent terrestrial laser scanner on Im hintern Eis (3244 m a.s.l., 46.79586 • N, 10.78277 • E; see Sect.3.4.2).For KWF, only the meteorological observations on the glacier from 1958 by Ambach and Hoinkes (1963) are documented.

Vernagtferner
After the start of the glacier monitoring program by the Bavarian Academy of Sciences and Humanities, meteorological observations were initiated at the glacier forefield with the installation of a precipitation gauge in 1970.With the completion of the gauging station "Vernagtbach" (2635 m a.s.l., 46.85675In 1975 hourly measurements of air temperature, relative humidity, air pressure, wind speed and direction were started.The same instruments were installed at the station "Gletschermitte" (3078 m a.s.l.), situated on a rock outcrop in the western part of the glacier at 46.86894 • N, 10.80299 • E, where hourly meteorological observations were collected during the summer months from 1968 until 1987 (with a varying beginning and end from year to year).The observed parameters were air temperature, relative humidity, wind speed and direction, and precipitation (https://doi.org/10.1594/PANGAEA.832562).
Radiation sensors were installed at Vernagtbach in 1976.However, especially during winter, data gaps frequently occurred.The situation was considerably improved by installation of a first digital data logger in 1984.Since then, all-year data records are available from the Vernagtbach station (Escher-Vetter and Siebers, 2013).The meteorological observations were revised in 2002 with the installation of a modern AWS (Fig. 11), and since then all data are automatically transferred to the Bavarian Academy of Sciences and Humanities via GSM and a satellite network.In August 2010, the  3.
On "Schwarzkögele" (3075 m a.s.l., 46.86575 • N, 10.83245 • E), a summit in the vicinity of VF, an autonomous climate station has been in operation since 1976 (Braun et al., 2013).Data recorded there comprise air temperature, relative humidity, global radiation, wind speed and direction as well as precipitation.After digitization these measurements will be made available in PANGAEA.Experiments and special investigations in the catchment of VF are listed in Escher-Vetter and Siebers (2013); since 2003, the meteorological observations have been extended to the ice surface of the glacier itself.Whereas in the first years these data have gaps (mainly in winter), they are mostly continuous since 2011.

Rofental apart from the glaciers
In the Rofental several totalizing rain gauges have are used to collect precipitation data, the first of which was installed in 1905 (see Fig. 6).The totalizing rain gauges are operated by the Department of Atmospheric and Cryospheric Sciences of the University of Innsbruck with financial support by the Hydrographic Service of Tyrol.These totalizing rain gauges provide a valuable picture of the historical evolution and temporal variability of precipitation, and they support the development of precipitation fields derived from interpolation of the recordings (Hoinkes and Steinacker, 1975), which is particularly important for distributed modeling exercises.Evaporation and freezing of the devices is inhibited by annual additions of oil and salt to the gauge reservoir.Readings of totals are undertaken every 2 months in summer with a 4-month break in winter.These totals are then redistributed to monthly values using the recordings of the weighing rain gauge in Vent.Altitude, geographical location and the period Earth Syst.Sci.Data, 10, 151-171, 2018 www.earth-syst-sci-data.net/10/151/2018/  of operation of these totalizing rain gauges are given in Table 4.
Meteorological observations have been made in close proximity to the village of Vent since 1934 (Lauffer, 1966;Siogas, 1977b).This long-term station provides a valuable reference for shorter series of meteorological observations and also the lower boundary conditions on the likely variation of meteorological variables with elevation across the catchment.Data are available for 1935-2011 at https://doi.org/10.1594/PANGAEA.806582, and for 2012-2016 at https://doi.org/10.1594/PANGAEA.876595.In September 2015 the weather station installation was updated and the position changed by a horizontal displacement of 102 m (new position: 1907 m a.s.l., 46.85745 • N, 10.91288 • E).The recordings of this station comprise the meteorological variables air temperature, relative humidity, wind speed and direction (since February 2016), and atmospheric pressure (since September 2016; same instruments and specifications as for station Hintereisferner, Table 2).Precipitation is recorded with a heated Ott Pluvio 2 in millimeters per hour with an accuracy of 0.1 mm h −1 .
In the uppermost parts of the Hochjoch valley, two AWSs have been more recently brought into operation: "Latschbloder" (2919 m a.s.l., 46.80106 • N, 10.80659 • E), installed in September 2013, and Bella Vista (2805 m a.s.l., 46.78284 • N, 10.79138 • E), installed in June 2015.The data of these two fully automatic stations complement the spatial picture of the meteorological variables in the upper zones of the Rofental.Both stations collect 10 min values of temperature, precipitation (unheated, but also recording by the type of precipitation), wind (mean and maximum speed and direction), relative humidity, radiative fluxes (incoming and outgoing short-and longwave) and air pressure (Table 5).The Latschbloder station is about 25 m from the totalizing rain gauge at the same site (see Table 4).Three continuous years of consistent records are available for 2014, 2015 and 2016 (mean annual temperature −1.3, −1.5 and −2.2 • C (WXT520), and annual precipitation: 1590, 1311 and 1118 mm (Pluvio 2 unheated)).
The weather station at Bella Vista includes a heated Ott Pluvio 2, supplied with main power from the "Schöne Aussicht-Hütte" approximately 90 m away.This site also includes fuller snow instrumentation (Table 6) to measure: snow water equivalent (by means of a snow pillow), snow depth (by means of an ultrasonic ranger) and snow temperature profile (by means of a series of temperature sensors at different height levels).These snow sensors are still undergoing technical examination and development, and as yet no check for consistency has been undertaken (e.g., by using the data as input in a snow model as in Morin et al., 2012).In 2016, mean annual temperature at the station was −0.4 • C, and annual precipitation was 1605 mm.The Bella Vista weather and snow monitoring station is one of the highest of its kind in the Alps.During summer 2017 an automatic camera that has the station in its field of view has been installed (Fig. 12).
In summer 2017, a 6 m high tower close to the permanent terrestrial laser scanner on Im hintern Eis (3244 m a.s.l., 46.79586 • N, 10.78277 • E; see Sect.3.4.2) was equipped for detailed turbulent flux measurements with the following sensors: three Lufft Ventus 2-D Sonic wind sensors at 1.5, 3 and 6 m altitude; two ventilated Rotronic HC2-S3 temperaturehumidity sensors at 3 and 6 m altitude; a Campbell SR50 AH heated ultrasonic snow depth sensor in 1.5 m altitude; a Campbell Krypton hygrometer at 3 m altitude (only for specific campaigns); a Kipp & Zonen CNR4 net radiometer at 1.5 m altitude; a Metek USA-1 3-D sonic turbulence sensor at 3 m altitude; and a Setra 278 barometric pressure sensor in the logger box.The data of these sensors will be made available in PANGAEA as soon as first tests have proven the installation to be reliable, and a time series of at least a year of data is available.Three additional AWSs are located south of the Rofental, in the Italian Schnalstal: "Teufelsegg" (3035 m a.s.l., 46.7847 • N, 10.7647 • E) close to the accumulation area of HEF, "Grawand" (3220 m a.s.l., 46.7703 • N, 10.7966 • E) in the Schnalstal glacier ski resort and "Vernagt" (1950 m a.s.l., 46.7357 • N, 10.8493 • E) close to the village and the lake with the same name.These stations are maintained by the Hydrographic Office of the Civil Protection Agency of the Autonomous Province of Bolzano -South Tyrol.Their data are available at http://daten.buergernetz.bz.it/de/dataset/ misure-meteo-e-idrografiche.

Hintereisferner and Kesselwandferner catchment
During the International Geophysical years 1957 to 1959 a gauging station was in operation at "Steg Hospiz" (2287 m a.s.l.), registering the combined streamflow from HEF and KWF (Lang, 1966).The measurements of this campaign are described here as an example for the many short-and longer-term monitoring activities carried out in the Rofental.The Steg Hospiz catchment is 26.6 km 2 in size, with a fraction of 58 % being covered by the glaciers at that time.Mean annual recorded streamflow for the catchment area amounted to 1848 mm (1957-1958) and 1770 mm (1958-1959), respectively (millimeters are equivalent to liters per square meter per year).Winter runoff (October through March) only was 5 and 10 % of the annual amount, whereas the three summer months (July through September) provided 76 and 72 %.Highest mean monthly streamflow amounts were registered in August 1958 (575 mm) and July 1959 (559 mm).The frequency distribution of daily streamflow for 1957-1958 shows a period of daily low flows of less than 0.5 m 3 s −1 (18.8 L s −1 km −2 ) for 217 days (October through May).Higher daily streamflow > 6.0 m 3 s −1 (225 L s −1 km −2 ) only occurred during July and August.The observed maximum daily streamflow was 16.9 m 3 s −1 .The glacier contribution, determined as the fraction of (observed) negative mass balance to recorded streamflow, was relatively high in this period: 24 and 20 % of annual streamflow, respectively.The exponential decrease of the hydrograph in fall to the minimum in spring suggests that the winter streamflow mainly originates as delayed meltwater of the previous season from the glaciers.The increase in the water flows after the beginning of the snow melt period occurs with a certain time delay -due to the refreezing of meltwater, and its retention in the snow cover (Lang, 1966).As of 2017, neither HEF nor KWF are equipped with a permanently registering discharge gauge; this is projected for future initiatives.

Vernagtferner catchment
The VF catchment is one of the very few glacierized catchments where simultaneous measurements of glacier mass balance and discharge exist for several decades since 1974 (Escher-Vetter and Reinwarth, 2013).Discharge is measured at the gauge Vernagtbach (46.85675 • N, 10.82886 • E), which at 2635 m a.s.l. is the highest streamflow gauge in Austria (Fig. 13).The water level is continuously monitored in the gauge since 1974, and water-level-to-discharge calibrations are regularly conducted by the salt injection method.The water level is simultaneously determined by three sonic rangers distributed across the runoff channel in order to detect the 2-D surface geometry of the water flow, and surface velocity is monitored by a Doppler system.The total catchment area covers 11.44 km 2 , 7.3 km 2 of

Rofental catchment
Streamflow in the Rofental catchment is recorded at the gauge "Vent-Rofenache" (1891 m a.s.l., 46.85722 • N, 10.91083 • E, 98.1 km 2 ) at the outlet of the catchment (https://doi.org/10.1594/PANGAEA.876119).Vent-Rofenache is one of the highest operational observation sites of the Hydrographic Service of Tyrol, providing a continuous time series of streamflow and sediment transport recordings since 1967 and 1999, respectively.The regime is dominated by snow melt and ice melt with a significant maximum in July and August (Fig. 14); the glaciated area has decreased from 44 % (in 1969) to 38 % (in 2009;Müller et al., 2009) and is expected to drop to almost zero during the course of the 21st century, due to the rapidly changing climatic conditions (Hanzer et al., 2017).The coexistence of the Vernagtbach gauge in the VF head watershed allows for combined hydrological investigations.Episodical recordings at smaller tributaries of the Rofenache were obtained during the spring snow melt season in 2014 (Schmieder et al., 2016), and during the glacier melt season in 2016 (Schmieder et al., 2018).

Laser scanning data
Laser scanning is an active remote sensing technique which uses a laser beam to acquire 3-D point data, representing the surface and objects on that surface in high spatial resolution.
In addition to high accuracy and resolution, additional information on the spectral properties intensity and reflectance of the scanned surface in the wavelength of the specific scanner is recorded.The DTMs derived from laser scanning measurements are becoming increasingly important for glaciological and geomorphological studies.DTM differencing is an important method for detection and quantification of surface changes and mass budget calculations (Sailer et al., 2014;Klug et al., 2017).Airborne laser scanning (ALS) and terrestrial laser scanning (TLS) are the most common methods for lidar data collection (Telling et al., 2017).The Rofental has been an intensive experimental site for both types of laser scanning data processing and analysis.

Airborne laser scans
ALS is well-suited for remote mountain areas, because no external light source is required and, due to overlapping flight strips, the entire surface is captured, even in very steep terrain (Höfle and Rutzinger, 2011).The vertical accuracy is in the order of 0.05 to 0.20 m, mainly dependent on the slope angle (Beraldin et al., 2010;Bollmann et al., 2011).Low vertical errors of 0.05 m were observed in the HEF catchment for areas with slope angle < 40 • by comparison of an ALS-derived DTM with dGNSS (differential global navigation satellite system) measurements.For the areas with slope angle > 40 • , an exponential increase of the vertical error was observed (1.0 m for 80 • , Bollmann et al., 2011; Geist et al.,  2005; Sailer et al., 2012).
DEMs of 1 × 1 m were generated by calculating the z value (altitude) from the mean z value inside the respective grid cell by excluding 5 % of the smallest and largest observations of the ALS points.For the provision of the GeoTIFF (UTM32N) raster files the high-resolution DEMs were resampled to DEMs with a cell size of 10 × 10 m, applying bilinear interpolation.The resulting DEMs are available at https://doi.org/10.1594/PANGAEA.875889.
The available ALS measurements for HEF were used to study the volume changes of the glacier complementary to direct glaciological surface mass balance measurements.At least one scan was performed at the end of every glacier mass balance year (end of September).From these, a time series of geodetic mass balances was derived for 2001-2002 to 2010-2011 (see Fig. 8).In 2001In -2002In , 2002In -2003In , 2007In -2008In , 2008In -2009In and 2010In -2011 additional project-based intermediate campaigns were carried out.An overview of the data (UTM32N, WGS84) including the technical details is given in Table 7. Klug et al. (2017) corrected the surface models as well as glacier mass balance data by considering method-inherent uncertainties originating from snow cover, survey dates and density assumptions to calculate corrected annual geodetic mass balances.The most negative balance year is 2002-2003, with a mean specific mass balance of −2.713 ± 0.20 m water equivalent (w.e.).In the subsequent mass balance year 2003-2004, the smallest mass loss is observed (mean specific mass balance −0.654 ± 0.09 m w.e.).For the entire observation period (2001 to 2011) a mean mass balance of −1.3 m w.e. was calculated with the HEF ALS data set (Klug et al., 2017).
With the same ALS data sets as described in Table 7, Helfricht et al. (2014b) investigated the spatial snow distribution and its interannual persistence for a partly glacierized mountain area including HEF and KWF (∼ 36 km 2 ).The utility of TLS in performing high-resolution glacier observations was tested for HJF from 2013-2015 when both glaciological and geodetic mass balances were measured.Likewise, a Riegl VZ-6000 TLS was used to produce surface models within 0.1 m of coincident high-accuracy ALS data for approx.80 % of the surface of HJF.The TLS surface models are of higher spatial resolution and surface details than the ALS.The TLS data were used -along with coincident optical imagery from the onboard camera -to produce high-resolution surface classifications to map snow-cover extent, and to explore the spatial patterns of the surface mass balance of HJF (Prantl et al., 2017).
In 2016, a permanent TLS was installed in a climate controlled container at 3244 m a.s.l.close to the summit Im hintern Eis (46.79586 • N, 10.78277 • E).The 3-D laser scanner VZ-6000 (manufactured by RIEGL Laser Measurement Systems GmbH) offers a long measurement range of more than 6000 m and operates with beam divergence of 0.12 mrad at a wavelength of 1050 nm, particularly suited for snow-and ice-related applications.The device operates with an angular step width of 0.01 • for a field of view of 60 • vertically and 120 • horizontally and a laser pulse repetition rate of 30 kHz, equivalent to an effective measurement rate of 23 000 measurements s −1 , leading to a point density of approx.10 pts m −2 for a distance of 1000 m, and to approx. 1 to 2 pts m −2 for the remote areas at a distance of > 3500 m.Hence, the instrument is ideal for static topographic applications such as monitoring of glaciological and geomorphological processes in high mountain terrain.Due to the large field of view, nearly the entire HEF catchment area can be covered by the instrument (Fig. 15); only a very small part of the terminus and small flat areas in the upper glacier zones cannot be sampled.The TLS surface point cloud is accompanied by high-quality optical imagery (5 megapixel).This installation not only allows high temporal and spatial resolution glacier volume changes for HEF to be determined; in addition, the high spatial resolution supports the monitoring of surface features such as crevasses, evolving surface roughness, the supraglacial drainage network and geomorphodynamically induced surface changes (e.g., debris flows) or snow avalanches.Seven scans have been carried out during the test phase (September 2016 to April 2017).

Data availability
The data sets presented here are available freely from PAN-GAEA (https://doi.org/10.1594/PANGAEA.876120).The data from the Rofental have been widely used for process studies and all kinds of method and model development ac- tivities.These data sets, however, represent only a small fraction of what has been observed and collected during the past few decades.Many measurements have been conducted during special field campaigns and are not yet documented for online data publication.For example, hydrological investigations have been conducted in the valley of the Hochjochbach, including streamflow observations with pressure sensors and tracer experiments since 2014 (Schmieder et al., 2016(Schmieder et al., , 2018)).Other data await digitization and processing.Originally published in analogue printwork, these data include 3 years of hourly ice temperatures from HEF (Markl and Wagner, 1978), observations of sublimation of ice and snow at HEF (Kaser, 1982(Kaser, , 1983)), firn investigations at KWF (Ambach et al., 1978), remote sensing experiments and many energy balance investigations at HEF (Jaffé, 1958(Jaffé, , 1960;;Hoinkes and Untersteiner, 1952;Hoinkes, 1953a, b;Ambach and Hoinkes, 1963;Wendler, 1967;Kuhn et al., 1979, Wagner, 1979, 1980), and many others.For VF, the situation is similar; a comprehensive overview of the research work has been published by Braun and Escher-Vetter (2013), including various descriptions and documentations of the used data, methods and models.Older longterm field experiments at VF are described in Moser et al. (1986).Runoff data of the gauge "Vent" have been widely used in hydrological studies, the most recent ones including Schmieder et al. (2016) and Hanzer et al. (2016Hanzer et al. ( , 2017)).On a regional scale, the Rofental data contributed to modeling exercises for future scenario climatic conditions and their effect on simulated streamflow discharge (Marke et al., 2011(Marke et al., , 2013)).The Hydrographic Service of Tyrol visualizes its data online at apps.tirol.gv.at/hydro, and provides their download at http://ehyd.gv.at.As of 2017, data of the sites Latschbloder and Schöne Aussicht are used in several ongoing research projects (listed at http://alpinehydroclimatology.net), and also provide valuable experimental material for application in various student courses.
Several initiatives are also ongoing at the international research network level.Apart from its long history within UNESCO IHP (http://en.unesco.org/themes/water-security/hydrology), the Rofental recently became a research basin in the framework of the GEWEX INARCH project (http:// words.usask.ca/inarch).It is a research catchment of the ERB Euro-Mediterranean Network of Experimental and Representative Basins (http://erb-network.simdif.com),and a regular complex site in the LTSER platform Tyrolean Alps (http://lter-austria.at/ta-tyrolean-alps), which belongs to the national and international long term ecological research network (LTER Austria, LTER Europe and ILTER).Hintereisferner station is part of the EU Horizon 2020 INTERACT framework of Arctic (and a few Alpine) research stations (https://eu-interact.org/field-sites/station-hintereis/).
The efforts to provide the Rofental data to the scientific community will continue in all of the currently involved institutions.

Conclusions and outlook
The Rofental in the Ötztal Alps (Austria) is a unique, high Alpine research basin (98.1 km 2 , 1890-3770 m a.s.l.) with available time series of 150 years of glaciological and hydrometeorological observations.The glaciers in the Rofental attracted early attention and were -for centuries -observed due to the dangerous nature of frequently occurring glacier lake outburst floods.Over the last 100 years, the glacier monitoring has been accompanied by systematic recordings of meteorological and hydrological variables.Today, a glaciological and hydrometeorological data set is available for the Rofental that is without comparison worldwide, with regard to both its amount and temporal coverage.The Rofental data sets support manifold investigations in the context of coupled climate and glacier evolution, snow and glacier hydrology, water resources availability in mountainous regions, or method development like laser scanning or modeling.The scales of such research range from local, like particular micrometeorological assessments at a single observation site, to global, e.g., the estimation of the glacier contribution to sea level rise.This paper gives an overview of what has been measured and what is available already.All the data described are comprehensively documented and made freely available according to the Creative Commons Attribution License by means of the PANGAEA repository (https://doi.org/10.1594/PANGAEA.876120).
This paper covers availability of data as of fall 2017.There are still many manual and analogue historical recordings which are being digitized, processed and documented.After completion they will be made available via PANGAEA and

Figure 1 .
Figure 1.The "Rofentaler Eissee" in 1601, the first known image of a glacier worldwide.Painted in water colors by Abraham Jäger.The original is in the Tiroler Landesmuseum Ferdinandeum in Innsbruck.FromNicolussi (1990).

Figure 6 .
Figure 6.Available data time series for the Rofental in PANGAEA, structured in glaciological data, meteorological data, hydrological data and laser scanning data.LIA = little ice age.

Figure 9 .
Figure 9. Graphical summary of the seasonal and annual mass balances of Vernagtferner from 1965 until 2014.The vertical bars represent seasonal values and the black line annual values.

Figure 10 .
Figure 10.The Hintereisferner AWS and research station in June 2013 (3026 m a.s.l., 46.79867 • N, 10.76042 • E), view to the northeast.Photo by Christian Wild.

Figure 12 .
Figure 12.Webcam picture of the Bella Vista weather station (2805 m a.s.l., 46.78284 • N, 10.79138 • E), view to the East.Left: Ott Pluvio 2 with wind shelter.Center: temperature profiler.Right: snow pillow (foreground) and mast with sensors (background) for wind speed and direction, snow height, temperature/humidity and radiative fluxes.The most recent picture is available at http://alpinehydroclimatology.net.

Figure 15 .
Figure 15.The terrestrial laser scanner in its container housing at Im hintern Eis (3244 m a.s.l., 46.79586 • N, 10.78277 • E).View to the west over the upper areas of Hintereisferner to the summit of Weisskugel (3739 m a.s.l.) and Langtauferer Spitze (3529 m a.s.l.).Photo by Rudolf Sailer.

Table 2 .
Weather and snow variables recorded by the sensors installed at the station Hintereisferner (3026 m a.s.l., 46.79867 • N, 10.76042 • E) in 2010, 2011 and 2012.Accuracy according to technical data sheets of the manufacturers.Original temporal resolution of the data records is 10 min.
*Further technical details can be found in Escher-Vetter and Siebers (2012).

Table 4 .
Totalizing rain gauges in the Rofental.

Table 5 .
Climate and snow variables recorded by the sensors installed at the station Latschbloder (2919 m a.s.l., 46.80106 • N, 10.80659 • E).Accuracy according to technical data sheets of the manufacturers.Original temporal resolution of the data records is 10 min.

Table 6 .
Weather and snow variables recorded by the sensors installed at the station Bella Vista (2805 m a.s.l., 46.78284 • N, 10.79138 • E).Accuracy according to technical data sheets of the manufacturers.Original temporal resolution of the data records is 10 min.