Global Change Abstracts The Swiss Contribution - SCNAT

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148 Global Change Abstracts – The Swiss Contribution | Oceans and Fresh Water Systems ing abstraction from the aquifer during the last few decades. All sources of contamination were investigated using hydrochemical data available from the 1980s. Water samples were taken from drains and observation wells tapping both the CT and the phreatic aquifers and analyzed with regard to chemistry, temperature, isotopes and other environmental tracers. Local salinization mechanisms are suggested, i.e. the upwelling of saline water from the underlying, confined Continental Intercalaire (CI) aquifer, as well as backflow of agricultural drainage water. At this stage, the main salt pan, the Chott el Djerid, is not a contamination source. A finite difference model was also developed to simulate groundwater flow and contaminant transport in the oases. Calibration for the period 1950-2000 was carried out in order to adjust geological and chemical system parameters. The simulation of planned extraction projects predicts a worsening of the present situation. Maintenance of the present abstraction regime will not reduce or stop the salinity increase. Hydrogeology Journal, 2007, V15, N7, NOV, pp 1357-1375. 08.1-290 Extreme heat and runoff extremes in the Swiss Alps Zappa M, Kan C Switzerland Meteorology & Atmospheric Sciences , Modelling , Cryology / Glaciology , Hydrology The hydrological response of Swiss river basins to the 2003 European summer heatwave was evaluated by a combined analysis of historical discharge records and specific applications of distributed hydrological modeling. In the summer of 2003, the discharge from headwater streams of the Swiss Central Plateau was only 40%-60% of the long-term average. For alpine basins runoff was about 60%-80% of the average. Glacierized basins showed the opposite behavior. According to the degree of glacierization, the average summer runoff was close or even above average. The hydrological model PREVAH was applied for the period 1982-2005. Even if the model was not calibrated for such extreme meteorological conditions, it was well able to simulate the hydrological responses of three basins. The aridity index phi describes feedbacks between hydrological and meteorological anomalies, and was adopted as an indicator of hydrological drought. The anomalies of phi and temperature in the summer of 2003 exceeded the 1982-2005 mean by more than 2 standard deviations. Catchments without glaciers showed negative correlations between phi and discharge R. In basins with about 15% glacierization, phi and R were not correlated. River basins with higher glacier percentages showed a positive correlation between phi and R. Icemelt was positively correlated with phi and reduced the variability of discharge with larger amounts of meltwater. Runoff generation from the non-glaciated sub-areas was limited by high evapotranspiration and reduced precipitation. The 2003 summer heatwave could be a precursor to similar events in the near future. Hydrological models and further data analysis will allow the identification of the most sensitive regions where heatwaves may become a recurrent natural hazard with large environmental, social and economical impacts. Natural Hazards and Earth System Sciences, 2007, V7, N3, pp 375-389. 08.1-291 Insights into the management of sea turtle internesting area through satellite telemetry Zbinden J A, Aebischer A, Margaritoulis D, Arlettaz R Switzerland, Greece Zoology , Marine & Freshwater Biology , Ecology , Biodiversity Female sea turtles typically lay several clutches during each nesting season and rest in the time between laying clutches (the internesting period) in the waters off the nesting beach. Adequate protection of turtles in the internesting area requires knowledge on their spatial behaviour and was so far hampered by methodological limitations. Satellite telemetry data of exceptionally high quality allowed us to scrutinize internesting area use of four logger-head sea turtles nesting in the Bay of Laganas (Zakynthos, Greece). We assessed the efficacy of two zones of a marine reserve with distinct levels of protection (boats are excluded from one zone). Most of the obtained locations of three of the four turtles were within the bay, a result consistent with a strategy to minimize energy expenditure. T Turtles showed no obvious preference for the highly protected area of the bay. The availability of warmer water in the less protected area may be more crucial than avoidance of boat disturbance. Biological Conservation, 2007, V137, N1, JUN, pp 157-162.
Global Change Abstracts – The Swiss Contribution | Energy Balance 1.6 Energy Balance 08.1-292 Impact of ice supersaturated regions and thin cirrus on radiation in the midlatitudes Fusina F, Spichtinger P, Lohmann U Switzerland Modelling , Meteorology & Atmospheric Sciences , Cryology / Glaciology (1) In this study we investigate the radiative impact of ice supersaturated regions (ISSRs, i.e., cloud free air masses in the upper troposphere that are supersaturated with respect to ice) and thin cirrus. For this purpose we use corrected radiosonde data obtained from routine measurements over the meteorological observatory in Lindenberg, Germany. The radiative effect of the measured ice supersaturation is determined. By constructing an idealized profile from the measurement data the radiative properties of ISSRs and thin cirrus containing ice supersaturation were studied. The impact of ISSRs on the surface forcing is negligible but locally, within the vertical profile, changes in the heating rates up to 1 K d (-1) for typical values of 130% relative humidity with respect to ice compared to the saturated profiles are found. This is also important for the local dynamics within the supersaturated layers. The outgoing longwave radiation due to the enhanced water vapor content inside ISSRs decreases up to 0.8 W m(-2). The radiative impact of thin cirrus is much stronger. Thin cirrus influence the surface budget, the top of the atmosphere radiation and the vertical profile of the heating rates. Changes in the outgoing longwave radiation and in the reflected shortwave flux at top of the atmosphere up to 64 W m(-2) and 79 W m(-2), respectively, are possible. Changes in the surface flux (downward) up to 89 W m(-2) are found. The maximal heating rate differences between thin cirrus and ISSR amount to 15 K d(-1). The radiative impact of thin cirrus clouds depends strongly on cloud ice content and the size of the ice crystals. Additionally, the radiative impact of cirrus formed by parameterizations not allowing ice supersaturations in large-scale models is estimated. The errors due to artificially formed cirrus are quite large; differences up to 3 K d(-1) in the vertical heating profiles and up to 38 and 40 W m(-2) in the outgoing longwave radiation and the surface flux, respectively, are found. Thus we recommend using physically based parameterizations in GCMs which allow ice supersaturation. Journal of Geophysical Research Atmospheres, 2007, V112, ND24, DEC 15 ARTN: D24514. 149 08.1-293 Year-round observation of longwave radiative flux divergence in Greenland Hoch S W, Calanca P, Philipona R, Ohmura A Switzerland Modelling , Meteorology & Atmospheric Sciences Longwave radiative flux divergence within the lowest 50 m of the atmospheric boundary layer was observed during the Eidgenossische Technische Hochschule (ETH) Greenland Summit experiment. The dataset collected at 72 degrees 35’N, 38 degrees 30’W, 3203 m MSL is based on longwave radiation measurements at 2 and 48 m that are corrected for the influence of the supporting tower structure. The observations cover all seasons and reveal the magnitude of longwave radiative flux divergence and its incoming and outgoing component under stable and unstable conditions. Longwave radiative flux divergence during winter corresponds to a radiative cooling of -10 K day(-1), but values of -30 K day(-1) can persist for several days. During summer, the mean cooling effect of longwave radiative flux divergence is small (-2 K day(-1)) but exhibits a strong diurnal cycle. With values ranging from -35 K day(-1) around midnight to 15 K day(-1) at noon, the heating rate due to longwave radiative flux divergence is of the same order of magnitude as the observed temperature tendency. However, temperature tendency and longwave radiative flux divergence are out of phase, with temperature tendency leading the longwave radiative flux divergence by 3 h. The vertical variation of the outgoing longwave flux usually dominates the net longwave flux divergence, showing a strong divergence at nighttime and a strong convergence during the day. The divergence of the incoming longwave flux plays a secondary role, showing a slight counteracting effect. Fog is frequently observed during summer nights. Under such conditions, a divergence of both incoming and outgoing fluxes leads to the strongest radiative cooling rates that are observed. Considering all data, a correlation between longwave radiative flux divergence and the temperature difference across the 2-48-m layer is found. Journal of Applied Meteorology and Climatology, 2007, V46, N9, SEP, pp 1469-1479. 08.1-294 Long-term changes in the cosmic ray intensity at Earth, 1428-2005 Mccracken K G, Beer J USA, Switzerland Meteorology & Atmospheric Sciences (1) The instrumental cosmic ray data recorded in the interval 1933-1965 by S. E. Forbush and H. V. Neher and cosmogenic 10 Be data are merged with
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