Forecasts of Ducting Parameters

Description

COAMPS produces forecasts of EM trapping layers that are calculated from the modified refractivity profile at each numerical grid point.  The EM ducting parameters show where radar signal ranges may be extended over the horizon or where radar holes may hinder detection.  As described in the schematic refractivity profile, these parameters include duct strength, duct base height (DBH), duct thickness, and the evaporation duct height.  Additionally a 0/1 value is given at each grid point to indicate the existence of a duct.  From the grid point values, spatial distributions are color shaded to forecast locations of no ducting, strong elevated ducting, and surface-based ducting.    

Results

Figures 1 and 2 show examples of two forecast products of EM trapping produced operationally over the Arabian Sea, Red Sea, Arabian Gulf, and Bay of Bengal.  In Fig. 1, surface-based ducting (grey shading) is evident in the Arabian Gulf and Red Sea where trapping layers tend to be quite common.  The distribution of duct strength (M-units) is shown in Fig. 2.  Combined the graphics indicate that strong, surface-based ducting in the Arabian Gulf likely produced extended over-the-horizon signal ranges for ship-board radars in the region.