Weighting Function and Transmittance Plots

Below are links to loops of weighting function and transmittance plots for the 1.38um and 0.86um ABI bands.  The 50% power points with equal weights (of 1) were used as endpoints for the ABI 1.38um plots, while the 1% power points and their corresponding SRF values were used for the MODIS Band 26 plots.  The weighting function was computed using transmittance squared to reflect the incoming and outgoing paths that radiation at 1.38um and 0.86um, respectively, must take to be detected by satellite sensors.  The formula used for the weighting function is d (tau)^2 / d log(p).  The transmittance plots are also transmittance squared for the same reason as the weighting function.  The process of computing weighting function involved reading in raw MODTRAN data, using IDL to create ASCII files with the desired information, and finally using IDL to compute the weighting function and create the plots.  The weighting function and trasmittance plots below are for a tropical temperature profile, and encompass a wide range of total precipitable water values.  Notice how the 1.38um band (which is located in an atmospheric water vapor absorption feature) transmittance and weighting function plots change significantly with changes in TPW, while the 0.86 band (which is not in an atmospheric water vapor absorption feature) changes very little with changes in TPW.

ABI 1.38um Weighting Function Loop

ABI 1.38um Transmittance-Squared Loop

ABI 1.38um Transmittance Loop with X-Log Scale

MODIS Band 26 (1.375um) Transmittance-Squared Loop

ABI 0.86um Weighting Function Loop

ABI 0.86um Transmittance-Squared Loop

Miscellaneous Transmittance Plots