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PARAMETRIZATION OF LAND SURFACE FLUXES FOR CLIMATE MODELLING

Objective

TO UNDERSTAND THE PHYSICAL PROCESSES YIELDING TO HEAT FLUXES OBSERVED OVER HETEROGENEOUS MEDIA AND THEREFORE TO A BETTER PARAMETRIZATION OF THESE FLUXES AT MESO-SCALE, INCLUDING PARAMETERS MEASURABLE FROM SATELLITES.

THE FIELD EXPERIMENT WILL BE CONDUCTED DURING THE MONTHS OF MAY AND JUNE 1988.THE LOCATION OF THE FIELD EXPERIMENT IN GREENLAND IS CLOSE TO A WEST-EAST CROSSING LINE AT A NORTHERN LATITUDE OF 67 DEG.10, STARTING AT THE COAST AT APPR.54 DEG W AND ENDING AT THE ICE-CAP AT APPR.50 DEG.W.THE EXPERIMENT WILL CONSIST OF A COMBINATION OF RECORDING FROM FIXED STATIONS, FIELD SURVEYS AND AIRBORN MEASUREMENTS.ALL MAJOR TOPOGRAPHICAL ELEMENTS WILL BE COVERED BY THE EXPERIMENT STARTING FROM WEST TO EAST WITH 1) THE COASTAL FJORD REGION 2) PLATEAU IN THE WESTERN REGION OF ALPINE RELIEF 3) THE EXTENSIVE CENTRAL PLATEAUS 4) THE BORDER ZONE AND 5) THE ICE-CAP.THE JOINT FIELD EXPERIMENT, 1988, WILL CONCENTRATE ESPECIALLY ON ADVECTIVE EFFECTS FROM THE ICE AS WELL AS FROM THE SEA.THE SPECIFIC LOCATION OF THE RECORDING MASTS WILL FURTHER BE DETERMINED BY THE FACT THAT ALL STATIONS ARE PLACED WITHIN WELL-DEFINED DRAINAGE BASINS ALLOWING ESTABLISHMENT OF A WATER BALANCE APPROACH FOR A DETERMINATION OF THE MAJOR COMPONENTS.THE FOLLOWING INSTRUMENTS WILL BE USED AT EACH SITE : 1) A 10M MAST WITH SENSORS FOR AIR TEMPERATURE, HUMIDITY AND WIND SPEED AT MINIMUM 3 LEVELS 2) A RADIATION MAST WITH UP- AND DOWNWARD LOOKING SOLARIMETERS, NET RADIOMETER, IR-RADIOMETER AND A SHADED SOLARIMETER FOR MEASURING THE DIFFUSE RADIATION COMPONENT 3) SNOW AND SOIL THERMOMETERS, ALLOWINGS A DETERMINATION OF THE FLUXES IN WATER VAPOR AND HEAT BY A BOWEN RATIO APPROACH. IN ORDER TO STUDY THE INFLUENCE OF THE SMALL-SCALE SURFACE IRREGULARITIES AND CORRESPONDING LOCAL BOUNDARY LAYERS, THE INTRUMENTATION IS DESIGNED FOR MEASUREMENT OF AT LEAST TWO SEPARATE ALTITUDE INTERVALS.DATA FROM THE FIELD OBSERVATIONS WILL ALL BE TRANSLATED TO AND ANALYZED USING ON-SITE COMPUTERS, PERMITTING DIRECT READOUT OF ALL BASIC PARAMETERS.THE MEASUREMENTS FROM THE FOUR MASTS WILL BE SUPPLEMENTED BY FIELD SURVEYS TO ESTABLISHED THE SPATIAL VARIATION IN SNOW-PACK AND LAND-SURFACE PROPERTIES.HERE SPECIAL ATTENTION WILL BE PAID TO DERIVE SIMULTANEOUS MEASUREMENTS OF THE PHYSICAL PROPERTIES OF THE SNOW-PACK WITH RESPECT TO SNOW STRUCTURE, COLD- AND WATER CONTENT AND SPECTRAL SIGNATURE RECORDINGS.THE BRITISH TEAM WILL ESPECIALLY CONDUCTS MEASUREMENTS OF SNOW WATER EQUIVALENT AND SOIL MOISTURE USING NEUTRON PROBES AND OF THE FREE WATER CONTENT USING A CAPACITANCE PROBE.THE DANISH TEAM WILL RECORD THE RUNOFF FROM THE RESEARCH BASIN, CARRY OUT MANUAL SNOW SURVEYS AND MEASURE THE SPECTRAL SIGNATURE OF THE SURFACE.THE REGIONAL VARIATION IN SURFACE WATER BALANCE, PARTLY DUE TO FOEH-WINDS FROM THE ICE-CAP, WILL BE STUDIED BY TAKING DAILY VALUES OF SOIL WATER TENSION IN ORDER TO ESTIMATE THE ACTUAL EVAPOTRANSPIRATION.THE INFLUENCE OF THE DEPLETION OF THE SNOW COVER ON THE INTEGRAD SPECTRAL SIGNATURES AND THE VEGETATION INDEX WILL BE ANALYZED DURING THE MELTING SEASON.IN ORDER TO DETERMINE THE SPATIAL REPRESENTATION OF THE POINT MEASUREMENTS, AIRBORNE MEASUREMENTS WILL BE CONDUCTED BY INSTALLATION OF A SPECTROMETER IN

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

KOEBENHAVNS UNIVERSITET
Address
Universitetsparken 5
2100 Koebenhavn
Denmark

Participants (4)

ARISTOTELIAN UNIV DEPT OF BIOLOGY
GROUPEMENT SCIENTIFIQUE DE TELEDETECTION
INST F METEOROLOGIE
LANDBOUWUNIVERSITEIT WAGENINGEN