SOME CONSIDERATIONS FOR USING AVHRR DATA IN CLIMATOLOGICAL STUDIES .1. ORBITAL CHARACTERISTICS OF NOAA SATELLITES

Seven years of data are used to examine the orbital characteristics of five NOAA satellites and the implication for using AVHRR data in clim atological studies is investigated. Generally a steady drift from a no minally Sunsynchronous orbit results in the earlier arrival of even-nu mbered satellites and the later arrival of odd-numbered satellites. Th e most extreme example of drift, for the case of NOAA-6 resulted in a difference of average arrival time of 90 minutes over the operational lifetime of the satellite. Phasing results in a +/- 51 minute variatio n in arrival time. The combination of drift and phasing can have a sig nificant effect on the use of AVHRR and other NOAA satellite data in c limatological studies, particularly for the mid- and high-latitudes du ring the winter and summer solstices.