[1] We present a European land-only daily high-resolution gridded data set for precipitation and minimum, maximum, and mean surface temperature for the period . This data set improves on previous products in its spatial resolution and extent, time period, number of contributing stations, and attention to finding the most appropriate method for spatial interpolation of daily climate observations. The gridded data are delivered on four spatial resolutions to match the grids used in previous products as well as many of the rotated pole Regional Climate Models (RCMs) currently in use. Each data set has been designed to provide the best estimate of grid box averages rather than point values to enable direct comparison with RCMs. We employ a three-step process of interpolation, by first interpolating the monthly precipitation totals and monthly mean temperature using three-dimensional thin-plate splines, then interpolating the daily anomalies using indicator and universal kriging for precipitation and kriging with an external drift for temperature, then combining the monthly and daily estimates. Interpolation uncertainty is quantified by the provision of daily standard errors for every grid square. The daily uncertainty averaged across the entire region is shown to be largely dependent on the season and number of contributing observations. We examine the effect that interpolation has on the magnitude of the extremes in the observations by calculating areal reduction factors for daily maximum temperature and precipitation events with return periods up to 10 years.

ABSTRACT:The European Climate Assessment (ECA) dataset of daily observations, which has been widely used for studies on climate extremes, has been updated and extended. It now contains observational series of 2191 stations located in Europe and the Mediterranean (average inter-station distance: ∼75 km). About 1200 precipitation series and 750 temperature series cover the period 1960-2000. For a small number of stations (<15%) air pressure, cloud cover, sunshine duration, snow depth and relative humidity series have been collected. All series are quality controlled and the homogeneity of the precipitation and temperature series is assessed. About 50% of the daily series are publicly available for climate studies through the website http://eca.knmi.nl. The main potential of the ECA dataset follows from its daily resolution, enabling studies of impact relevant climate extremes and variability. To guide these studies, climate indices calculated from the ECA series are presented on the website too. Besides, gridded versions of the daily ECA data are available for easy comparison with climate model simulations. A trend analysis for the diurnal temperature range (DTR) demonstrates the utility of the dataset. Seasonal and annual DTR trends were calculated for 333 homogeneous temperature series in ECA and a Europe average trend was estimated. In spring and summer, the DTR increased from 1979 to 2005, whereas in autumn and winter the DTR generally decreased. The European average trend in annual DTR was 0.09°C decade −1 .

This paper presents a study of the climate sensitivity of the mass balance of Morteratschgletscher in Switzerland, estimated from a two-dimensional mass balance model. Since the albedo scheme chosen is often the largest error source in mass balance models, we investigated the impact of using different albedo parameterizations on the climate sensitivity of the mass balance. We first ran the mass balance model for the period 1980 to 2002 and calculated the mass balance sensitivity by perturbing the air temperature by values ranging from −2 to +2 K and precipsitation by values ranging from −20 to +20%. The albedo parameterization that we used for these simulations relates the snow albedo to snow age and snow depth, whereas it considers the ice albedo constant in time and space. The mass balance sensitivity to temperature and precipitation was estimated at −59 cmWE year −1 K −1 and at 17 cmWE year −1 per 10% respectively (cmWE: centimetres water equivalent). Then, we used three other albedo parameterizations. One parameterization uses ice albedo values that vary in space and were acquired from a Landsat image. Another parameterization calculates the snow albedo from accumulated daily maximum temperatures since snowfall. The third parameterization is the simplest and uses two constant albedo values, one for snow and one for ice. The differences between sensitivities calculated from the different albedo parameterizations were generally small. However, when the simplest parameterization was used, the mass balance sensitivity to temperature decreased to −52 cmWE year −1 K −1 . This is mainly due to the constant snow albedo, which implies that the albedo feedback is not fully considered. For an accurate estimate of the mass balance sensitivity, the albedo parameterization should capture the process of a decreasing snow albedo when a snow pack gets older or thinner.

A glacier submodel was successfully integrated into the distributed hydrological model WaSiM-ETH to simulate the discharge of a heavily glaciated drainage basin. The glacier submodel comprises a distributed temperature index model including solar radiation to simulate the melt rate of glaciated areas. Meltwater and rainfall are transformed into glacier discharge by using a linear reservoir approach. The model was tested on a high-alpine sub-basin of the Rhone basin (central Switzerland) of which 48% is glaciated. Continuous discharge simulations were performed for the period 1990-1996 and compared with hourly discharge observations. The pronounced daily and annual fluctuations in discharge were simulated well. The obtained efficiency criterion, R 2 , exceeds 0.89 for all years. The good performance of the glacier submodel is also demonstrated by integrating it into the hydrological model PREVAH. Modélisation hydrologique distribuée d'un bassin alpin caractérisé par une importante couverture glaciaireRésumé Un module de simulation glaciaire a été intégré avec succès dans le modèle hydrologique distribué WaSiM-ETH pour le calcul du débit d'un bassin versant recouvert en grande partie par les glaces. Le module comprend un modèle de température degrés-jour tenant compte du rayonnement solaire pour la simulation de la vitesse de fonte de la couverture glaciaire. L'eau de fonte et l'eau de pluie sont transformées en débit glaciaire par le moyen d'une approche de type réservoir linéaire. Le modèle a été testé sur une partie alpine du bassin versant du Rhône (Suisse centrale) qui présente une couverture glaciaire de 48%. Des simulations continues de débit ont été effectuées pour la période 1990-1996 et ont été comparées à des observations de débits horaires. Les fluctuations journalières et annuelles prononcées des débits sont bien simulées. Le critère d'évaluation R 2 dépasse 0.89 pour toutes les années. La bonne performance du module glaciaire a également été démontrée lors de son intégration dans le modèle hydrologique PREVAH.Mots clefs hydrologie de montagne; modélisation hydrologique distribuée; débit glaciaire; fonte glaciaire; méthode degrés-jour température/rayonnement; glacier du Rhône

We report on analysis of meteorological data for the period 27 May-20 August 2004, from two automatic weather stations on McCall Glacier, Alaska, USA, aimed at studying the relationship between climate and ablation. One station is located on a mountain ridge and the other in the ablation area where we also analyzed the energy balance. The weather station on the glacier measured an average temperature of 5.38C (at 2 m height above surface) and wind speed of 3.1 m s -1 (at 3 m height). A sonic height ranger and ablation stakes indicate a specific mass balance of À1.94 AE 0.09 m w.e between 15 June and 20 August. The specific mass balance calculated from the surface energy balance, À2.06 AE 0.18 m w.e., is in close correspondence to this. The latter is the sum of 0.12 m w.e. of snowfall, 0.003 m w.e. of deposition and À2.18 m w.e. of melt. Net radiation contributes 74% of the melt energy. Compared to ablation measurements in the early 1970s, summer ablation was large. This increase is explained by a combination of a relatively higher net radiation, a lower albedo and larger turbulent heat fluxes that led to more energy being available for melting. No single meteorological variable can be isolated as being the principal reason for the high ablation, however. The lower ice albedo (0.19) is possibly due to ash deposits from forest fires.