1. Department of Applied Mathematics, University of Colorado Boulder, Boulder, CO 80303-0429 USA ().
2. Ann and H. J. Smead Department of Aerospace Engineering Sciences, University of Colorado Boulder, Boulder, CO, Department of Applied Mathematics, University of Colorado Boulder, Boulder, CO 80303-0429 USA ().
3. Global Modeling and Assimilation Office, NASA Goddard Space Flight Center, Greenbelt, MD 20771 USA ().