ftam.m

function [Tatm,wlayers]=ftam(T,tau,tau_a,masterindex)

% function ftam
%
%
%            Calculate the brightness temperature, and weighting function for a given ray.
%            
%            VARIABLE DEFINITIONS:
%                        
%                         ->INPUT:
%                              ->  T: physical temperature of the layer
%                              ->tau: total optical depth from bottom to current layer
%                           -> tau_a: optical depth of each layer across ds
%                     ->  masterindex: layer index
%
%                        <-OUTPUT:
%                          <-Tatm: Brightiness temperature for each ray
%                          <-wlayers: weighting function for each ray    

%JPH function Tatm=ftam(T,tau,tau_a)
%JPH T is the vector from ?top to bottom of thermal temperatures
%JPH tau is the vector of integrated absorptions from top to bottom ?
%JPH tau_a is the vector of absorptions for each layer top to bottom
%JPH Units are kelvin and opdepths
%JPH The first layer is the ray from the craft to the surface
%JPH its tau, tau_a, T, are zero
%JPH So T(1) should always be zero

loss=exp(-tau);
emit=T(masterindex).*(1-exp(-tau_a));
wlayers=loss.*(1-exp(-tau_a));
layers=loss.*emit;

Tatm=sum(layers);