Cloud Clearing

Given the clear radiance, Rclr and the fraction of clouds, alphai in scene i.

Ri = (1-alphai) · Rclr + alphai · Rcld
Rclr = R1 + eta · ( R1 - R2 )
eta ident alpha1/(alpha2 - alpha1)

Chahine, M.T. 1974, J. Atmos. Sci. 31 p.233

Susskind, J., J. Joiner and C.D. Barnet 1995. Determination of atmospheric and surface parameters from simulated AIRS/AMSU sounding data. I. Retrieval methodology. submitted to J. Atmos. Oceanic Tech. (JAOT) Sep. 1995.

N* method

N* ident alpha1/alpha2 = (R1 - Rclr)/(R2 - Rclr)
Rclr = (R1 - N* R2)/(1 - N*)
eta = N* / (1 - N*)

McMillin, L.M. and C. Dean 1982. Evaluation of a new operational technique for producing clear radiances. J. Appl. Meteor. 21 p.1005-1014.

Smith, W.L. 1968. An improved method for calculating tropospheric temperature and moisture from satellite radiometer measurements. Monthly Weather Review 96 p.387-396.