Correction of Negative Mixing Ratios in Spectral Models by Global Horizontal Borrowing

Abstract

A method based on global horizontal borrowing would seem more appropriate than the current method of local vertical borrowing for the correction of negative values of mixing ratios arising in spectral models as a consequence of finite truncation. Two practical algorithms are proposed for the implementation of this new method in spectral models. A numerical experiment shows that this global horizontal scheme has a tendency to produce more horizontal smoothing on the humidity field than the local vertical scheme.