Spatial and Temporal Resolution

GOES-R IFR Probabilities computed from MODIS data (upper left) and from GOES-East data (lower left);  Ceiling and visibility observations (upper right) and 10.7-micrometer brightness temperatures from GOES-East (lower right)

GOES-R IFR Probabilities can be computed using GOES-East Imager data (the Imager has 5 radiometric channels), with a nominal resolution of 4 kilometers at the sub-satellite point (The Equator, at 75 degrees W for GOES-East;  Actual resolution in the upper midwest is closer to 5 or 6 kilometers).  IFR Probabilities can also be computed using MODIS data from Terra or Aqua;  the MODIS instrument yields information at 36 different radiometric channels, with a nadir resolution of 1 km.  Thus, small-scale features, such as river valleys, or ridge-tops, are far more likely to be visible in the data.  However, MODIS data are available infrequently because Terra and Aqua are polar orbiters, and each satellite passes over a location in the upper Midwest only 2 times daily.

The strength of GOES-R IFR imagery is its temporal resolution.  Routine imaging every 15 minutes is typical, and that allows observations of fog development, as shown in the loop below.  The increase in GOES-R IFR probabilities alerts the forecaster to a region of interest, where more vigilant monitoring of sky conditions may be warranted.  The surface observations do show decreasing visibilities and ceilings where the IFR probabilities are increasing;  that is, the IFR probabilities and actual observations are consistent.

GOES-R IFR Probabilities computed using GOES-East imager data and surface observations of visibility and ceiling from 0400 UTC to 1400 UTC on 26 July 2012.

The ABI (Advanced Baseline Imager) on GOES-R will have twice the resolution of the current GOES Imager (that is, 2 kilometer for infrared channels at the subsatellite point) and higher temporal resolution as well.

Leave a Reply