There is no course textbook but some useful and relevant texts are listed below.

Amazon logo Durran, Dale R. Numerical Methods for Wave Equations in Geophysical Fluid Dynamics (Texts in Applied Mathematics Series, Vol. 32). New York, NY: Springer, 1998. ISBN: 9780387983769.

Amazon logo Haidvogel, Dale B. and Aike Beckmann. Numerical Ocean Circulation Modeling. River Edge, NJ: World Scientific Publishing Co., 1999. ISBN: 9781860941146.

Amazon logo Haltiner, George J., and Roger T. Williams. Numerical Prediction and Dynamic Meteorology, 2nd Ed. Hoboken, NJ: John Wiley & Sons, 1980. ISBN: 9780471059714.

Amazon logo Jacobson, Mark Z. Fundamentals of Atmospheric Modeling. Cambridge, MA: Cambridge University Press, 1998. ISBN: 9780521637176.

Amazon logo Kantha, Lakshmi H. Numerical Models of Oceans and Oceanic Processes. Academic Press; 1 edition, 2000. ISBN: 9780124340688.

Amazon logo Pedlosky, Joseph. Ocean Circulation Theory. New York, NY: Springer; 1st ed. Corr. 2nd printing edition, 2004. ISBN: 9783540604891.

A handy quick-reference for some methods is Numerical Recipes on-line.