To compute Barrier Layer Thickness

This function compute BLT from gridded data sets as well as profile data

% It is defined as the positive discrepancy between temperature based MLD (or ILD) and
% density based MLD. i.e. when difference between ILD and MLD is positive, it
% regarded as Barrier Layer Thickness (BLT) otherwise Compensated Layer Thickness.
% USAGE: BLT=ra_blt(salt,temp,Z,dT)
%
% PREREQUISITE:
% In addition to SW Package, you must have following functions: ra_ild.m and ra_mld.m
%
% DESCRIPTION: This function determines Barrier Layer Thickness (BLT) from profile data
% sets based on subjective method. If you have 3D data sets i.e. level, lat and lon and want
% to compute the BLT, then this function will be very handy. Because this function is
% specifically designed for those cases. However, it can evaluate BLT from profile data too.
%
% INPUTS:
% salt = Salinity profiles over the study region [psu], either 3D or vector
% temp = Temperature profiles over the study region [deg. C], either 3D or vector
% Z = Levels [m], Must be vector
% dT = temperature difference criterion [deg. C], Must be scalar
%
% OUTPUT:
% blt = Barrier Layer Thickness, spatial output [m]