THE SPATIAL AND TEMPORAL EFFECT OF CLOUD COVER ON THE ACQUISITION OF HIGH-QUALITY LANDSAT IMAGERY IN THE EUROPEAN ARCTIC SECTOR

Cloud cover is one of several constraints on the ability of VIS/NIR se nsors, such as those on board Landsat, to provide a continuing time se ries of data for glaciological studies in polar regions; for example, the long term observation of annual mass balance fluctuations or the s hortterm monitoring of surging glaciers. In order to ascertain the ext ent to which cloudiness prevents Landsat imagery from providing such d atasets in the European Arctic, cloud cover data for all imagery acqui red during April-September, 1983-92, for 15 glaciologically significan t areas (each represented by a Landsat path/row) were examined. Cloudi ness values were derived from the Eurimage LEDA (onLine Earthnet Data Availability) catalogue. The results indicate that regions of the Euro pean Arctic may be classified into three groups on the basis of the fr equency of availability of high quality imagery (<35% cloud cover). Ma rked seasonal differences are also evident between the groups. Compara ble findings from previous cloud cover studies using ground station da ta illustrate that the scenes used in this study are representative of the regions in which they lie. The relative abilities of Landsat MSS/ TM and ERS-1 SAR data to provide multitemporal datasets are compared; although SAR is unaffected by cloud, ERS-1 has a longer revisit interv al (multidisciplinary phase) than Landsat. Only in East Greenland has Landsat generated a sufficient number of high quality scenes to provid e a useful multitemporal dataset. Elsewhere in the European Arctic the prevalence of the cloud cover is such that it may prevent the effecti ve use of VIS/NIR data for certain glaciological studies. If the requi red information can be derived from radar data, the utilization of SAR should prove advantageous for obtaining future multitemporal datasets in these regions of the European Arctic sector.