PDAF_correlation_function

This page documents the routine PDAF_correlation_function of PDAF. It was introduced with PDAF V2.3.

The routine provides the value of a chosen correlation function. It can be used, e.g. to generate non-diagonal observation error covariance matrices.

The interface is the following:

  SUBROUTINE PDAF_correlation_function(ctype, length, distance, value)

with the following arguments:

• ctype : integer, intent(in)
  Type of weight function:
  (1) Gaussian function scaled to f(0)=1
  (2) 5th order polynomial with support radius sradius (Gaspari&Cohn 1999; 0 for distance>sradius)
• length : real, intent(in)
  length scale:
  for (1) standard deviation
  for (2) cut-off length (f=0 for distance>=length)
• distance : real, intent(in)
  Distance at which the function is evaluated
• weight : real, intent(out)
  Function value