Spatial and temporal variability of meteorological variables at Haut Glacier d'Arolla (Switzerland) during the ablation season 2001: Measurements and simulations

Abstract

[1] During the ablation period 2001 a glaciometeorological experiment was carried out on Haut Glacier d'Arolla, Switzerland. Five meteorological stations were installed on the glacier, and one permanent automatic weather station in the glacier foreland. The altitudes of the stations ranged between 2500 and 3000 m a.s.l., and they were in operation from end of May to beginning of September 2001. The spatial arrangement of the stations and temporal duration of the measurements generated a unique data set enabling the analysis of the spatial and temporal variability of the meteorological variables across an alpine glacier. All measurements were taken at a nominal height of 2 m, and hourly averages were derived for the analysis. The wind regime was dominated by the glacier wind (mean value 2.8 m s À1 ) but due to erosion by the synoptic gradient wind, occasionally the wind would blow up the valley. A slight decrease in mean 2 m air temperatures with altitude was found, however the 2 m air temperature gradient varied greatly and frequently changed its sign. Mean relative humidity was 71% and exhibited limited spatial variation. Mean incoming shortwave radiation and albedo both generally increased with elevation. The different components of shortwave radiation are quantified with a parameterization scheme. Resulting spatial variations are mainly due to horizon obstruction and reflections from surrounding slopes, i.e., topography. The effect of clouds accounts for a loss of 30% of the extraterrestrial flux. Albedos derived from a Landsat TM image of 30 July show remarkably constant values, in the range 0.49 to 0.50, across snow covered parts of the glacier, while albedo is highly spatially variable below the zone of continuous snow cover. These results are verified with ground measurements and compared with parameterized albedo. Mean longwave radiative fluxes decreased with elevation due to lower air temperatures and the effect of upper hemisphere slopes. It is shown through parameterization that this effect would even be more pronounced without the effect of clouds. Results are discussed with respect to a similar study which has been carried out on Pasterze Glacier (Austria). The presented algorithms for interpolating, parameterizing and simulating variables and parameters in alpine regions are integrated in the software package AMUNDSEN which is freely available to be adapted and further developed by the community.

Air temperature variability over three glaciers in the Ortles–Cevedale (Italian Alps): effects of glacier fragmentation, comparison of calculation methods, and impacts on mass balance modeling

“…Lapse rates were also lower on the glaciers (−7.2 • C km −1 in 2010 and −6.7 • C km −1 in 2011), compared to high-altitude off-glacier weather stations, and close to the standard ambient lapse rate (−6.5 • C km −1 ). Much shallower on-glacier lapse rates and fewer dependency of air temperature on elevation were found by earlier works (e.g., Greuell and Böhm, 1998;Strasser et al, 2004;Petersen et al, 2013). As reported in Table 2, the average daily temperature range and the average standard deviation are largest at the valley floor and both decrease with altitude, reaching their minima over the glaciers as previously reported, for example, by Oerlemans (2001 …”

“…A peculiar behavior was found at the terminus of La Mare Glacier (Mar-gl_2709), where downglacier winds dominated at night, without a cooling effect, and were replaced by up-glacier winds from mid-morning to late afternoon, when the cooling effect increased sharply. Wind data were not available at Mar-gl_3438 due to instrumentation failure, but we can argue that katabatic winds were not prevalent at this site, which is close to the crest, based on results published for similar locations in previous works (e.g., Greuell et al, 1997;Strasser et al, 2004). Different weather conditions led to a considerable temporal variability of the glacier cooling effect during the two summer seasons of 2010 and 2011 (Fig.…”

“…Several experiments with automatic weather stations (AWSs) deployed over glaciers demonstrated that general assumptions in extrapolating air temperature, based on the application of fixed lapse rates which account for the linear dependency of ambient (i.e., off-glacier) temperature on altitude, have serious limitations (e.g., Greuell et al, 1997;Strasser et al, 2004;Petersen and Pellicciotti, 2011).…”

Projected cryospheric and hydrological impacts of 21st century climate change in the Ötztal Alps (Austria) simulated using a physically based approach

“…AMUNDSEN has specifically been designed as a scenario-capable model for the application in high-mountain regions, and has been set up and extensively validated for historical conditions in the study site in a recent study (Hanzer et al,5 2016). In the following, the most important model components are briefly discussed -for a more detailed model description, we refer to, e. g., Hanzer et al (2014Hanzer et al ( , 2016, Marke et al (2015), Pellicciotti et al (2005), Strasser (2004Strasser ( , 2008, .…”

The influence of resolution and topographic uncertainty on melt modelling using hypsometric sub‐grid parameterization

“…Essery and Marks, 2007) The cost of these simplifications inevitably is that any comparison with 'real' melt scenarios or observational data is not possible. However, in order to derive potential melt rates that lie within a realistic range, both melt models are tuned to approximately fit melt rates at selected locations reported by Strasser et al (2004), by slightly adjusting the values for DDF and F r used by Pellicciotti et al (2005) for our case study. All adjusted parameters used in both models are given in Table 1.…”