Basic studies on the estimation of normals for decade air temperature at unit cell were performed using daily mean air temperature derived from satellite IR data. Analyses were taken with the assumption that “the difference between a daily mean air temperature and normals for decade air temperature is approximate among areas sharing similar climates”. Items and procedures for analyses are as follows.(1)Characteristic for mean decade air temperature and frequency for decade air temperature. (2)Classification for AMeDAS observation sites in Hokkaido to make some groups of areas sharing similar climates. (3) Characteristic of difference between a daily mean air temperature and normals for decade air temperature, and proof of the assumption. (4) Estimation of daily mean air temperature derived from satellite IR data. (5) Estimation of quasi-normals for decade air temperature using satellite IR data. The results for analyses are as follows. (1) The assumption that the difference between a daily mean air temperature and normals for decade air temperature is approximate among areas sharing similar climates was proved. Therefore, it is possible to estimate quasi-normals for decade air temperature using daily mean air temperature derived from satellite IR data. (2) There was a significance level of 1% between daily mean air temperature of AMeDAS data and surface temperature for 960m cell derived from Landsat TM data on July 8, 1993 in Ishikari Plain. And quasi-normals for decade air temperature in early July could be estimated to 0.1°C accuracy, except for data from Eniwa-Shimamatsu AMeDAS observation site.
