Abstract. During the summer of 1994 a glaciometeorological experiment was carried out on the Pasterze (a glacier in Austria). This paper reports on the data from six energybalance stations ranging in altitude from 2075 to 3225 m above sea level (asl). The wind regime was dominated by the glacier wind. On the tongue, directional constancies ranged between 0.94 and 0.97. Mean 2 m wind speed and specific humidity were almost constant along the glacier. The variation in the 2 m temperature along the glacier cannot be described by the usually assumed constant decrease with elevation. On the tongue the 2 m temperature even increased with elevation. A much better description of the temperature distribution is given by a linear relation between the potential temperature and the distance along the flow line. This can be understood from a simple thermodynamic analysis of the glacier-wind layer. It is further shown that changes in clear-sky global radiation with elevation are due mainly to changes in local albedo and relief and hardly at all to changes in absolute optical path length and atmospheric water vapor and aerosol content. On the tongue the laterally averaged ice albedo is almost constant with elevation. The flux of incoming long-wave radiation during clear-sky conditions at U2 (2310 m asl) was 48 W/m 2 higher than the flux at U5 (3225 m asl), on average. More than half of the difference was due to systematic differences in the shape of the temperature profile (probably the inversion depth is larger at U2). The rest can be ascribed to higher 2 m temperatures and larger amounts of upper hemisphere slopes at U2. The distributions of the meteorological variables and the parameterizations described in this paper might be incorporated in surface energy-balance models designed to simulate the surface mass balance.
International audienceWe present an assessment of the impacts of a +2°C global warming on extreme floods and hydrological droughts (1 in 10 and 1 in 100 year events) in Europe using eleven bias-corrected climate model simulations from CORDEX Europe and three hydrological models. The results show quite contrasted results between northern and southern Europe. Flood magnitudes are expected to increase significantly south of 60oN, except for some regions (Bulgaria, Poland, south of Spain) where the results are not significant. The sign of these changes are particularly robust in large parts of Romania, Ukraine, Germany, France and North of Spain. North of this line, floods are projected to decrease in most of Finland, NW Russia and North of Sweden, with the exception of southern Sweden and some coastal areas in Norway where floods may increase. The results concerning extreme droughts are less robust, especially for drought duration where the spread of the results among the members is quite high in some areas. Anyway, drought magnitude and duration may increase in Spain, France, Italy, Greece, the Balkans, south of the UK and Ireland. Despite some remarkable differences among the hydrological models’ structure and calibration, the results are quite similar from one hydrological model to another. Finally, an analysis of floods and droughts together shows that the impact of a +2°C global warming will be most extreme for France, Spain, Portugal, Ireland, Greece and Albania. These results are particularly robust in southern France and northern Spain
In calcul ations of the va ri ation in the 2 m temp er a ture along glaciers, the lapse rate is generall y ass umed to be consta nt. This implies th a t the ratio of cha nges in the 2 m temperature abo\·e a g lacier to changes in the tempera ture o utside the th ermal r egime of th a t g lac ier ("clim ate sensitivity" ) is equ a l to I. Howeve r, d a ta coll ected during th e ablation season on seve ra l mid-l atitude glac ie rs show that thi s se nsiti\·ity is sm a ll er th a n I. The lowes t measured \·alu e (0.3) was obta i ned on the to ng ue of th e Pas te r ze, a g lacier in Austri a . Th e measured temperat ure di stribution along the Pas terze ca nno t be d escribed by a consta nt lapse ra te either. However, there is alm os t a lin ear relati o nship b etween potenti a l temperature a nd the dista nce a long the glacier. This paper introduces a simple, a na ly tical, th erm od yna mi c glacier-wind m odel which can b e appli ed to melting g laciers and which expl ains the observed "c lim ate se nsiti viti es" a nd temperature di tributions much better th a n ca lcul a tions based on a co nsta nt lapse rate.This way of m odelling the 2 m temperatures h as implications for th e sensitivity o f th e surface mass ba la nce to atm os pheric warming outside the th erm a l regime of the g lacier. Th e mag nitud e of thi s se nsiti v ity is computed with a surface e ne rgy-ba lance m o del appli ed to the Pas terze. Wh e n a consta nt la pse r a te is used in stead of th e prop osed g lac ier-wind m o d el to compute cha nges in th e 2 m temperature a lo ng th e glac ie r, th e negative cha nge in mass bala nce due to I cC wa rming is o\·erestim a ted by 22% .
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