Griddedtemperatureandaccumulationdistributionsfor Greenlandforuseincryosphericmodels Pierluigi Calanca, 1 Hans Gilgen, 1 Simon Ekholm, 2 Atsumu Ohmura 1 1 SwissFederalInstituteofTechnology,Winterthurerstrasse190,CH-8057ZÏrich,Switzerland 2 Kort-ogMatrikelstyrelsenKMS),Rentemestervej8,DK-2400Copenhagen,Denmark ABSTRACT . Gridded distributions of the annual meantemperature and annualtotal accumulation for Greenland are presented.They are objectively derivedby deterministic and statistical interpolation from measurements atcoastal stationsandat locations onthe ice sheet.They canbe used not only for driving cryospheric models, but also for verifying atmosphericsimulations. 1.INTRODUCTION The distributions of the annual mean surface temperature andof the annualtotalaccumulation are essential quantities for cryospheric modeling.They not only represent necessary boundaryconditionsbut also provide reference states for the modelvalidation. Moreover, these distributions are vital for the verification of climate simulations Ohmura and others, 1996). For the Greenland ice sheet, hand-drawn maps of these fields havebeenprepared in recent years at the SwissFeder- al Institute of Technology ETH) Ohmura,1987; Ohmura and Reeh,1991; Ohmura and others,1999), but these have not been available in digital form. The production of gridded distributionsby objective methods is tackled in the presentpaper. Objectiveproceduresaresuperiortothesimpletranslation of printed maps into digital form. They allow more flexible handling of the basic data inclusion of new data, removal of erroneous entries), as well as straightforward recalculation of the final fields if more refined interpolation algorithms are implemented. 2.CLIMATICDATA,TOPOGRAPHICMODELAND GRIDDEFINITION The basic data used in the present work are identical to those described in Ohmura 1987), Ohmura and Reeh 1991) and Ohmura and others 1999). Data of the monthly mean temperature at 27 regular meteorological stations along the coast and 22 short-term stations onthe ice sheet were extracted fromvarious sources. The length of the records varies significantly from location tolocation foradetailedaccount, see appendix in Ohmura, 1987), with data collectedby scientific expeditions often not extending beyond a few months. A reduction of all data to a standard period is therefore appropriate. For simplicity, the referencedecadeof 1951^60proposedbyOhmura1987)was maintained. The annual total accumulation was inferred using data frompitandcorestudiescarriedoutintheinterioroftheice sheet. In addition, the monthly amount of solid precipita- tion was considered for the analysis. It was inferred for meteorological stations of the operational network from the measured precipitation, using an empirical relation between the percentage of solid precipitation and the monthly meanair temperature Fig.1).The amountof solid precipitation was subsequently corrected for the error induced by the deformation of the wind-field around the precipitation gauge Sevruk,1986). The correction can be quantified inthe order of +20%. No attempt was made to reduce the data of the total accu- mulation and of the solid precipitation to the same standard periodas the temperature data or tha data altogether toan- other reference decade).The task is not trivial, because the decadal variations caused by the North Atlantic Oscillation Ohmura and others,1999) shouldbe considered. Concerning the topography, the model of the National Survey and Cadastre of Denmark KMS) Ekholm and others,1995; Ekholm,1996) was chosen, as it is probably the best product available to date. Its accuracy ranges from Annalsof Glaciology 31 2000 # International Glaciological Society Fig. 1. Percentage of solid precipitation in the monthly total precipitation asafunction ofthe monthly mean temperature. 118