Inference of surface and air temperature, atmospheric precipitable water and vapor pressure deficit using Advanced Very High-Resolution Radiometer satellite observations: comparison with field observations

surface temperature (T-s), air temperature (T-a), atmospheric precipitable water (U), and vapor pressure deficit (D) have been derived from algorithms that use satellite observations of visible, near infrared and thermal infrared radiation in order to obtain higher spatial resolution data than is possible from meteorological station observations. The inferences of these four variables are compared with field instrument observations for sites with contrasted climates and vegetation including boreal forest (BOREAS), tropical bush savanna (HAPEX-Sahel), tall-grass prairie (FIFE) and a region with mountain, prairie and intensive agriculture (Red- and Arkansas-river catchments). The results showed that T-s could be retrieved with RMS errors of 3.5 degrees C for a range of 48 degrees C; T-a with 3.9 degrees C over a range of 36 degrees C; U with 0.6 cm over a range of 3.6 cm; and D with 10.9 mb over a range of 58 mb. Although the results had low absolute accuracies, the field data themselves are not without error-not least because, although the inferences were for a >1 km(2) area made instantaneously, they were compared with point field values generally not measured at exactly the same times in the day. Maps of retrieved variables had good relative accuracy and possibly better absolute accuracy than the comparisons with point measurements suggest. (C) 1998 Elsevier Science B.V. All rights reserved.