Land surface air temperature mapping using TOVS and AVHRR

Surface air temperature is an important variable in land surface hydrologic al studies. This paper evaluates the ability of satellites to map air tempe rature across large land surface areas. Algorithms recently have been devel oped that derive surface air temperature using observations from the TOVS ( TIROS Operational Vertical Sounder) suite of instruments and also from the AVHRR (Advanced Very High Resolution Radiometer), which have flown on the N OAA operational sun synchronous satellites TIROS-N NOAA-14 In this study we evaluate TOVS soundings from NOAA-10 (nominal local time of overpass 7:30 a.m./p.m.) and data from AVHRR aboard NOAA-9 (nominal local time 2:30 a.m./ p.m.). Instantaneous estimates from the AVHRR and TOVS were compared with t he hourly ground observations collected from 26 meteorological stations in the Red River-Arkansas River basin for a 3-month period from Map to July 19 87. Detailed comparisons between the satellite and ground estimates of surf ace air temperatures are reported and the feasibility of estimating the diu rnal variation is explored. The comparisons are interpreted in the geograph ical context, i.e. land cover and topography, and in the seasonal context, i.e. early and midsummer. The results show that the average bias over the 3 -month period compared with ground-based observations is approximately 2 de greesC or less for the three times of day with TOVS having lower biases tha n AVHRR. Knowledge of these error estimates will greatly benefit use of sat ellite data in hydrological modelling.