HIGH-LATITUDE SURFACE/ATMOSPHERE INTERACTION
(IAMAS, IAPSO, IAHS)
Location: Mechanical Engineering G33 LT
Tuesday 20 July AM
Presiding Chairs: A. Ohmura (Swiss Fed. Inst. of Tech., Zurich, Switzerland),
M.Kuhn (University of Innsbruk, Austria)
Exchange between stable boundary layer and snow
and ice surfaces
JSM04/W/02-A2 0930
SURFACE-LAYER FLUX PROFILE RELATIONSHIPS IN THE ARCTIC FROM THE
SEBA EXPERIMENT
C. W. FAIRALL (Environmental Technology Laboratory, NOAA, Boulder, CO 80304, USA,
email: cfairall@etl.noaa.gov) P. O. G. Persson (Cooperative Institute for Research in Environmental Sciences, NOAA/ETL, Boulder, CO 80303, USA, email: opersson@etl.noaa.gov) E. L. Andreas (US Army Cold Regions Engineering and Research Laboratory, Hanover, NH, 03755-1290, USA,
email: eandreas@crrel.usace.army.mil) P. S. Guest (US Naval Postgraduate School, Monterey, CA, 93950, email: guestps@ibis.met.nps.navy.mil)
From November 1997 to October 1998 the Surface Heat Budget of the Arctic (SHEBA) surface flux group made a variety of micrometeorological measurements on the Arctic icecap as part of ice station SHEBA. The ice station was launched at 143 W and 75 N and ended at 166 W and 80 N. The measurements included 5 levels of sonic anemometers and mean T/RH sensors, one fast hygrometer, upward and downward solar and IR fluxes, and snow/ice temperatures. We believe this is the first multi-level set of eddy-correlation flux data obtained over an entire annual cycle on the ice cap. In this paper we will describe an analysis of the turbulence statistics and mean profiles in the context of Monin-Obukhov similarity theory. The emphasis will be on evaluation of various dimensionless stability functions. We will also discuss deficiencies of MO scaling and examine other types of scaling (e.g., the local similarity scaling of Nieuwstadt).
JSM04/W/08-A2 0950
AN EXTENDED SIMILARITY-THEORY FORMULATION FOR THE STABLY STRATIFIED ATMOSPHERIC SURFACE LAYER
Sergej Zilitinkevich (Department of Earth Sciences - Meteorology, Uppsala University, Villavaegen 16, S-752 36 Uppsala, Sweden, email: sergej@big.met.uu.se) Pierluigi CALANCA (Department of Geography, Swiss Federal Institute of Technology, Winterthurerstr. 190, CH-8057 Zurich, Switzerland, email: calanca@geo.umnw.ethz.ch)
A similarity theory formulation for the wind and temperature profiles in the stably stratified atmospheric surface layer (ASL) is developed with due regard to the effect of the free-flow stability on the ASL. For the sake of simplicity the dry ASL is considered, although the treatment is immediately extended to cover the et ASLs. In the revised log-linear flux-profile relationships, empirical coefficients traditionally considered as universal constants, such as the slope factors in the $z$-less stratification layer (beyond the logarithmic layer), become functions of the dimensionless number S = N L/u*, where N is the Brunt-Vaisala frequency in the free flow, L is the Monin-Obukhov length, and u* is the friction velocity. This new formulation leaves room for occurrence of well-developed turbulence at much higher Richardson numbers, Ri, than has been suspected. Moreover, it results in a pronounced dependence of the turbulent Prandtl number, Pr, on Ri in a wide range of Ri, including the z-less stratification layer in correspondence with long-standing mpirical evidence. The traditional Monin-Obukhov similarity theory disregards the above essential features of the stably stratified ASL. New data from measurements over a slightly inclined plateau in West Greenland provide experimental support for the proposed theory.
JSM04/E/01-A2 1010
AN INTERCOMPARISON BETWEEN THREE MODELS OF BLOWING SNOW IN THE ATMOSPHERIC BOUNDARY LAYER
Jingbing XIAO (Dept. of Earth and Atmospheric Sciences, York University, 4700 Keele Street, Toronto, Canada, M3J 1P3, Email: jingbing@yorku.ca). Richard Bintanja (Institute for Marine and Atmospheric Research Utrecht, Email: r.bintanja@phys.uu.nl). Stephen Dery (Dept. of Atmospheric and Oceanic Sciences, McGill University, Quebec, Email: steph@zephyr.meteo.McGill.CA). Graham Mann (Environment Centre, University of Leeds, Email: gmann@lec.leeds.ac.uk). Peter A. Taylor (Dept. of Earth and Atmospheric Sciences, York University,Toronto, Email: pat@yorku.ca)
Blowing snow is a common phenomenon in many high latitude regions. Over parts of the Arctic and Antarctica, climatology suggests that blowing snow can occur on one out of three days. During blowing snow events, the sublimation of blowing snow particles can be a significant source of water vapor and sink of sensible heat. Near the windy and relative warm coast of Antarctica, sublimation of suspended snow can reach 17 cm/year Snow Water Equivalent (SWE). Model simulations indicate that the vertically integrated sublimation rate can reach 2-4 mm/day SWE under strong wind conditons, corresponding to a heat flux of 72-128 W/m2.
The physics of blowing snow is complex, and accurate blowing snow observations are hard to make. Several numerical models have been developed and their applications include helping to evaluate and design field experiments and to evaluate the sensitivity of the sublimation rate to various parameters. However, different models may give different results under given conditions. For example, the sublimation rate in a column of blowing snow calculated by the PBSM (Prairie Blowing Snow Model) is much higher that estimated by a fetch dependent blowing snow model PIEKTUK-F when the wind speed is at 20 m/s under certain conditions (Dery et al., 1998). Hence, the model intercomparisons and verification become especially necessary.
In idealised circumstances, blowing snow can be considered as a one-dimensional, time-dependent process. In this work,three one-dimensional time-dependent models have been intercompared. They are PIEKTUK-T developed by the group at York University in Canada (Dery et al., 1998), WINDBLAST developed by the group at Leeds University in United Kingdom (Mann, 1998) and SNOWSTORM developed by the group at Utrecht University in The Netherlands (Bintanja). These three models all show that the sublimation is a self-limiting process. As time increases after snow has become mobile, the sublimation rate first increases, reaches a maximum value and then decreases due to the increase of relative humidity and decreases of temperature. However, the value of the sublimation rate is not the same. Similarities and differences in model predictions will be reported and explanations considered.
JSM04/W/09-A2 1030
MESOSCALE MODELING OF GREENLAND'S KATABATIC WINDS AND THEIR INFLUENCE
Keith M. Hines, Lin Li and David H. BROMWICH (all at Byrd Polar Research Center, The Ohio State University, Columbus, OH 43210, USA, e-mail: bromwich@polarmet1.mps.ohio-state.edu)
Simulations performed at 40 km resolution with the Penn State/NCAR MM5 modified for ice sheet meteorology detail the influence of Greenland's topography and katabatic winds on synoptic and mesoscale atmospheric phenomena in the North Atlantic sector. Months simulated include January 1990 during a winter with a large positive phase of the North Atlantic Oscillation and April and May 1997 at the time of the Katabatic Wind and Boundary Layer Front Experiment around Greenland (KABEG) study. The simulations are compared to standard meteorological analyses by ECMWF and to 1997 observations at automatic weather stations in Greenland . Additionally, the University of Bonn compares katabatic wind simulations with MM5 to similar simulations with the NORLAM model. The simulations detail the frequent track of cyclones to the east of Greenland and have demonstrated the need for very high vertical resolution to adequately capture the katabatic boundary layer.
JSM04/E/06-A2 1120
measurements and numerical simulations of the katabatic wind over greenland
GUENTHER HEINEMANN and Thomas Klein, Universitaet Bonn, Auf dem Huegel 20, D-53121, Bonn, Germany
The katabatic wind system over Greenland is studied by means of surface and aircraft measurements, and by numerical simulations using the mesoscale model NORLAM. Measurements were carried out during the aircraft-based experiment KABEG'97 in the area of southern Greenland. The aircraft data allow the investigation of 3D structures of the katabatic wind, and can also be used for the validation of the boundary layer structures simulated by the numerical model. Comparisons of the numerical model results with AWS show good agreement in general. The validation of the simulations using aircraft profiles yields the result, that the correct simulation of the observed low-level jet in the stable boundary layer is highly sensitive to the correct simulation of the synoptic forcing above the boundary layer. The katabatic wind dynamics are also investigated using measurements and model results, showing that the classical katabatic force is the main driving mechanism for the flow regime.
JSM04/E/09-A2 1140
LONG-TERM MEASUREMENTS OF THE SURFACE ENERGY BALANCE AT HALLEY, ANTARCTICA
J.C. KING and P.S. Anderson (both at British Antarctic Survey, Cambridge CB3 0ET, UK,
email: j.c.king@bas.ac.uk)
Halley Research Station (75oS, 26oW) is situated on an expansive and uniform ice shelf and is thus an ideal location for making measurements of surface fluxes that are representative of a wide area. Continuous measurements of surface fluxes have been made at this site since 1995, using both eddy-correlation and profile techniques. Radiation measurements were added in 1996. We describe the instrumentation used and the problems encountered with making long-term flux measurements in a harsh polar environment. Data from the first three years of measurements will be presented. During winter, the mean net radiative cooling of the snow surface exceeds the measured net turbulent heat flux plus snowpack heat flux by about 10 W/m^2. Reasons for this apparent lack of closure of the surface energy budget are investigated.
JSM04/W/07-A2 1200
IMPLEMENTING AND TESTING OF A NEW SNOW SCHEME SAST IN SIMPLIFIED SIMPLE BIOSPHERE MODEL (SSIB)
Shufen Sun and YONGKANG XUE(both at Department of Geography, University of Maryland, College Park, MD 20742,USA Tel: 301-405-5880; fax: 301-314-9299,email: yxue@geog.umd.edu)
Based on up to date comprehensive and complex snow cover schemes, a Simple Snow-Atmosphere-Soil Transfer Model (SAST) has been developed. This model includes most important physical processes for simulation of seasonal snow cover change. The model also makes substantial simplification and improvement. For example, based on the analysis of the effect of vapor phase change and vapor movement on mass and energy balances, a formulation of effective heat conductivity has been derived which simplifies the description of complex processes without loss of accuracy. Base on analyses of diurnal and seasonal variations of snow temperature, an efficient snow cover layering system has been developed for better prediction. The volumetric specific enthalpy instead of temperature is used as the prognostic variable. It simplifies the formulations in phase change processes and reduces the computational procedures with an efficient implicit one step test numerical scheme. The SAST is coupled with SSIB to improve the SSIB prediction potential in snow cover regime. The coupled model includes the vegetation regime, snow cover regime and ground surface regime. Their physical properties are described by the mass and energy balance equations, respectively. Snow cover interacts with both vegetation cover above and ground surface below. In the coupled model, the snow surface temperature and canopy temperature are solved simultaneously to ensure the energy and water conservation in the vegetation-snow interface, which is crucial in the study of snow effects in global as well as regional climate models. The SAST model has been tested in off line model by using long term Russian and France field data. The results show its potential in predicting seasonal snow cover change. These two data sets along with the German snow data will be tested further to validate and evaluate the coupled SSiB/SAST model.
JSM04/W/06-A2 1220
AIR-SNOWPACK CHEMICAL INTERACTIONS AT LOW ACCUMULATION RATE SITES IN ANTARCTICA
Eric W. WOLFF, Anna E. Jones and Andrew M. Rankin (all at British Antarctic Survey, High Cross, Madingley Road, Cambridge CB3 0ET, UK, email: e.wolff@bas.ac.uk)
Understanding the processes that govern uptake of chemicals onto snow is fundamental to interpreting deep ice core records in terms of atmospheric chemical changes. For aerosol species, dry deposition processes dominate below a threshold snow accumulation rate. Ventilation by wind-pumping through topographic features is one dry deposition mechanism that could be important, but we show that it is unlikely to be at a site such as Dome C, Antarctica, which has a very low snow accumulation rate (about 30 kg m-3). We discuss the conditions (changed meteorology and surface roughness) that could make the wind-pumping mechanism dominate. For some gaseous species, post-depositional changes determine the ice core concentration. We investigate the case of nitrate, which shows large losses at a site such as Dome C, and discuss the possible controls on the nitrate concentration.
JSM04/E/04-A2 1240
AIR-SNOW EXCHANGE STUDIES OF NITROGEN SPECIES AT NEUMAYER, ANTARCTICA.
A.E. JONES, P.S. Anderson, H.K. Roscoe (British Antarctic Survey, NERC, Madingley Road, Cambridge, UK); R. Weller, H-W. Jacobi, G. Koenig-Langlo (Alfred-Wegener Institute, Am Handelshafen 12, Bremerhaven, Germany)
Processes of chemical exchange between air and snow surfaces at high latitudes will affect both ambient concentrations of trace gases and the incorporation of the chemical signature into ice cores. In order to understand both polar tropospheric chemistry and the ice core record it is
therefore necessary to understand the complex exchange mechanisms involved at the snow/air interface.
We report here on measurements made during Austral summer 1999, at the German Antarctic research base, Neumayer. An earlier campaign, designed to study the speciation within the NOy family, detected a diurnal variation in NOy with apparent links to processes at the snow surface. As part of a follow up campaign, we made measurements at Neumayer specifically to look for fluxes of nitrogen species into and out of the snow pack, with high time resolution gradient measurements of NO and NOx combined with meteorological data to derive fluxes. We present our results, and discuss possible influences on local photochemistry and the ice core nitrate record.
Tuesday 20 July PM
Presiding Chairs: P. Wadhams (Cambridge University, UK),
K. Steffen (University of Colorado, USA)
polar ocean – atmosphere interactions
JSM04/E/05-A2 1420
REDISTRIBUTION OF SOLAR RADIATION IN THE BARENTS SEA MARGINAL ICE ZONE DURING MELTING SEASON.
Reinert KORSNES (Norwegian Polar Institute, Polar Environmental Centre, N 9005 Tromso, Norway, Email: Reinert.Korsnes@npolar.no) Alexander P. Makshtas ( Arctic and Antarctic Research Institute, 38 Bering str., St. Petersburg, 199397, Russia, Email: maksh@aari.nw.ru)
Peculiarities of directional and spectral distributions of solar radiation under Arctic sea ice conditions are described based on field measurements during the Russian-Norwegian expedition"Barex-95" in the sea ice marginal zone of the Barents sea in the melting season. The results point out the importance of complex experimental investigations of radiation in the polar atmosphere under cloud and fog conditions. Cloud/fog conditions and the state of the sea ice surface control angular distribution of incoming solar radiation and its absorption by different types of sea ice covers (leads, melt ponds, wet snow and hummocks). A stochastic model of cloudy atmosphere is used to reproduce experimental data and to estimate sensitivity to angular and spectral distributions of solar radiation on the heat budget of the sea ice cover. An algorithm developed by Podgorny and Grenfell is modified to calculate melt pond bottom albedo and cardioidal radiance distribution parameters from hemispherical-directional reflectance distribution measurements.
JSM04/W/05-A2 1445
A GCM STUDY OF THE SENSITIVITY OF THE ANTARCTIC SEA ICE DISTRIBUTION TO SNOW COVER
Xingren WU (Antarctic CRC and Australian Antarctic Division, Hobart, Tasmania, Australia,
email: x.wu@utas.edu.au) William F. Budd (Antarctic CRC, Hobart, Tasmania, Australia,
email: w.f.budd@utas.edu.au) Victoria I. Lytle (Antarctic CRC and Australian Antarctic Division, Hobart, Tasmania, Australia, email: v.lytle@utas.edu.au) Robert A. Massom (Antarctic CRC, Hobart, Tasmania, Australia, email: r.massom@utas.edu.au)
This work estimates the effect of a snow layer and its depth on sea ice thickness accretion and ablation, using both a simple thermodynamic model and a coupled atmosphere-sea ice model including feedback and ice dynamics effects. The thermodynamic sea ice model is a 2-layer version model which treats snow, sea ice and snow-ice explicitly. The coupled model allows snow-ice to form when the snow cover is flooded. When snow is disregarded in the coupled model the averaged Antarctic sea ice becomes thicker. When only half of the snowfall predicted by the atmospheric model is allowed to accumulate on the ice surface, The sea ice gets thicker in most of the Weddell and Ross Seas but thinner in East Antarctic in winter, with the average slightly thicker. When twice as much snowfall as predicted by the atmospheric model is assumed to accumulate on the ice surface sea ice also gets much thicker due to the large increase of snow-ice formation. In this study we have also tested the use of a lower mean value of thermal conductivity of snow in the coupled model, namely 0.16 W/(mK) instead of the standard value 0.31. This value is based on the most recent observations in the eastern Antarctic and Bellingshausen and Amundsen Seas. We have found that the sea ice thickness distribution changes greatly, with the ice becoming thinner by about 0.2 m in the Antarctic and about 0.4 m in the Arctic on average.
JSM04/E/03-A2 1510
ROUGHNESS-DEPENDENT AIR - SEA ICE MOMENTUM FLUXES IN LARGE-SCALE MODELS
Nadja Steiner, Markus HARDER, Peter Lemke, Sandra Schuster (Institute of Marine Research at
the University of Kiel, Germany, Duesternbrooker Weg20, D-24105 Kiel, Germany,
email: nsteiner@ifm.uni-kiel.de,mharder@ifm.uni-kiel.de)
A quantitative relationship between observed sea-ice roughness and simulated large-scale deformation work is established in order to provide new means for model validation and a better representation of the sea ice component in coupled climate models. Sea ice roughness is introduced as an additional prognostic variable in the dynamic-thermodynamic Kiel Sea-Ice Simulation (KISS) with a viscous-plastic rheology. Ice roughness is defined as the accumulated work of internal forces acting upon an ice volume, given in energy per area. A fraction of this total deformation work is transformed into potential energy stored in pressure ridges. Observable quantities, such as mean pressure ridge height, ridge frequency as well as volumetric and areal fractions of deformed ice are derived from the simulated sea ice roughness by using observed ridge geometries and distribution functions. Roughness-dependent drag coefficients are introduced to account for the effect on the momentum exchange between ocean and atmosphere due to the form drag of roughness elements. Drag coefficients are parameterized as functions of deformation energy and ice concentration representing contributions of form drag due to pressure ridges and floe edges. This results in spatially and temporally varying drag coefficients, and yields significant differences in the magnitude and direction of ice drift velocities. A comparison with observed buoy drift velocities leads to an optimized parameterisation. The simulations indicate that the inclusion of sea-ice roughness provides for a more realistic representation of the boundary layer processes in climate models.
JSM04/W/12-A2 1535
EVALUATION OF HEAT FLUXES IN THE WEDDELL SEA USING BUOY DATA
O. EISEN (1) and C. Kottmeier (1,2) (1) Institute for Meteorology and Climate Research, Universit‰t Karlsruhe, Kaiserstr. 12, D-76133 Karlsruhe, Germany, (2) Institute for Meteorology and Climate Research, Forschungszentrum Karlsruhe, Hermann-von-HelmholtzPlatz 1, D-72344 Eggenstein-Leopoldshafen, Germany.
The surface energy balance of open and refrozen leads in sea ice is evaluated for a good areal coverage in the Weddell Sea for the winter period using a kinematic-thermodynamic sea ice model forced by data from drifting buoys. Additionally, two case studies reveal the influences of oceanic heat flux and tidal motion in specific regions. The relative contribution of open and refrozen leads to the total net heat flux increases from 30 % (10 - 15 W m~2) in the eastern Weddell Sea to 70 % (30 W m~2) in the western Weddell Sea and is on average about twice the areal lead percentage. Both, atmospheric forcing and the lead percentage cause this pattern. The monthly winter ice production in leads increases from 10 cm in the eastern part to 30 cm over the western shelf. The oceanic heat flux reduces the ice production under thick ice significantly and thus emphasizes the importance of leads for the total ice production. In the western Weddell Sea leads induced by motion in the diurnal and semi-dinrnal band contribute 7 % to net heat flux, 12 % to ice production and 37 % to the salt mass released during ice growth. The results emphasize the importance of leads for the interaction of ocean, sea ice and atmosphere.
JSM04/W/01-A2 1620
INVESTIGATIONS OF ATMOSPHERE/ICE/OCEAN INTERACTIONS USING SATELLITE SOUNDER DATA IN POLAR REGIONS
FRANCIS, Jennifer ( Institute of Marine and Coastal Sciences, Rutgers University, 71 Dudley Road, New Brunswick NJ 08901-8521 USA. E-mail:francis@imcs.rutgers.edu Telephone No: 732-708-1217 Fax No: 732-872-3088)
A wealth of new information is available from a recently completed 18-year data set of Arctic atmospheric and surface products derived from the TIROS Operational Vertical Sounder (TOVS). The TOVS Pathfinder data set comprises temperature and moisture profiles, cloud parameters, and surface characterists at a 100-km spatial and daily temporal resolution, north of 60 degrees northlatitude. We combine these fundamental variables with surface pressures and upper-level winds fromthe NCEP Reanalysis project to derive 10-meter wind fields, advected heat and moisture, and P-E. From the cloud information and atmospheric profiles we compute surface radiation fluxes. In this presentation we will describe the TOVS Pathfinder data set and present examples of air/ice/ocean exchange studies using these data.
JSM04/W/04-A2 1645
AIR-SEA-ICE INTERACTIONS OVER THE RONNE POLYNYA, ANTARCTICA
I. A. Renfrew and J. C. King, British Antarctic Survey, High Cross, Madingley Rd, Cambridge CB3 0ET, UK, email: i.renfrew@bas.ac.uk
Surface fluxes of heat and moisture are estimated for the coastal polynya that skirts the Ronne Ice Shelf, in the Weddell Sea, Antarctica. The air-sea-ice interactions of this region are responsible for changes in the surface waters that lead to the formation of Antarctic Bottom Water, an important water mass in the global thermohaline circulation. Automatic weather station (AWS) data have been used to generate a year long climatology of surface fluxes over the polynya. A simple one-dimensional convective boundary layer model has been developed. The model uses surface meteorological observations to grow a mixed layer over the polynya, and hence allow estimates of the surface sensible heat flux with fetch. The model has been tested with in situ data obtained from the Ronne Polynya Experiment (ROPEX) cruise of February 1998. The AWS data have been compared to ECMWF analysis products, with the aim of extending the flux climatology. Unfortunately the comparison illustrated a serious problem in the ECMWF model which was, until April 1998, treating the permanent ice shelves as sea-ice. This allowed an erroneous upward heat transfer through the sea-ice into the boundary layer, and meant that the model atmosphere was up to tens of degrees too warm.
JSM04/W/10-A2 1710
Air-sea-ice interaction processes in the Southern Ocean
XIAOJUN, Yuan, Lamont-Doherty Earth Observation, email: xyuan@ldeo.colombia.edu
Air-sea-ice interaction processes in the Southern Ocean are investigated utilizing space-observed surface winds, sea ice concentration, and sea surface temperature (SST) from September through December, 1996. The sea ice edge (SIE) shows three ice-extent maxima around the Antarctic during September and October when sea ice coverage is maximum. They are located in the central Indian Ocean, east of the Ross Sea, and in the eastern Weddell Gyre. During September and October, most of the strong and long lasting storms initiate northeast of the three sea ice maxima. Such spatial distributions of storms and sea ice reflect coupling processes of the air-sea-ice interaction. A relatively stable, wave number 3 atmospheric circulation pattern that is believed to be fixed by the land-ocean distribution prevails during the ice maximum season. The ice-extent maxima coincide with strong southerlies and divergent wind fields associated with this pattern, which suggests that the mean atmospheric circulation determines the ice distribution. The ice-extent maxima can enhance the regional meridional surface pressure gradient and therefore strengthen the westerly winds north of the ice edge. The decreasing ice extent east of the ice maxima creates a local zonal thermal gradient which enhances local southerlies. This positive feedback between the wave pattern in the mean atmospheric circulation and ice distribution partially causes the eastward propagation of the ice maxima and also provides a favorable condition for cyclogenesis northeast of the ice-extent maxima. The mechanism of the cyclogenesis is the baroclinic instability caused by the cold air blown from the ice pack to the warm open-ocean waters. Where the SST is warmest off the SIE and the southerlies are the strongest, the potential for cyclogenesis is most likely. This is consistent with the observations.
JSM04/W/11-A2 1735
AIR-SEA ICE INTERACTIONS SIMULATED WITH A REGIONAL CLIMATE MODEL FOR THE NORTH ATLANTIC AND THE ARCTIC
Hauke BERNDT, Markus Harder, Michael Hilmer, Rolf Jürrens, and Peter Lemke (all at Institut für Meereskunde, Universit‰t Kiel, Germany, email: hberndt@ifm.uni-kiel.de)
The atmospheric conditions in the Arctic and the Atlantic north of 35˚ N are investigated with the regional climate model REMO. REMO is based on the limited area numerical weather predictions system EM/DM of the Deutscher Wetterdienst (DWD). For the model the same physical parameterizations as implemented in the MPI global climate-model ECHAM4 are used.
The modeled domain is resolved with a mesh of 145x121 grid points and a mesh-size of 0.5˚ on a rotated spherical grid. The model is forced with boundary conditions from the NCEP/NCAR-reanalyses project. Different validations of REMO have been performed by comparing the model results with meteorological observations from the cruise of RV/KNORR during February/March 1997 in the Labrador Sea, accumulation measurements of snow over the glacial areas of Greenland and observed and modeled precipitation over Greenland. Comparing our results with the forcing global dataset we see horizontal patterns with higher detailed structures e.g. of precipitation in the coastal regions of Greenland which lead to major improvements of the simulated hydrological cycle. Driving REMO with ice-thickness distributions from a viscous-plastic sea-ice model leads to more realistically results. With the implementation of partial ice cover for a better representation of the heat fluxes in mixed grid boxes of sea ice and open water we expect further improvements e.g. in the marginal ice-zone. This work is a first step towards a fully coupled regional atmosphere-ice-ocean climate model for the North Atlantic and Arctic which is going to be set up at the Institut für Meereskunde.