Time Files Distributed with Pathfinder EASE-Grid SSM/I Brightness Temperature Data

Figure 1 is an example of the EASE-Grid SSM/I 19 GHz, horizontal polarization brightness temperatures time file on 31 December 1989. Data in both images represent ascending passes only. The data in the upper image represent the GMT time of the sample from which the corresponding interpolated brightness temperature data (lower image) were derived.

At latitudes of approximately 55 degrees and poleward, there are multiple orbital passes over the same geographic area during a single day. Where these multiple passes occur, the pass whose local time is closest to the equator crossing time (ascending or descending) is selected. This is done in order to provide a consistent set of sample times for each daily image file. Within a given daily image (ascending or descending), the local times would not be expected to differ by more than about 100 minutes (the orbital period). This method results in a systematic spatial progression through GMT as seen in the "spiral" pattern of the upper figure.

Please refer to EASE-Grid, A Versatile Set of Equal-Area Projections and Grids for more information on the complete data set.

ease-grid time file
Figure 1. EASE-Grid SSM/I Brightness Temperatures Time File