1 Department of Geosciences, and Earth and Environmental Systems Institute, The Pennsylvania State University, University Park, PA 16802, USA. rba6@psu.edu.
2 Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
3 Department of Meteorology and Atmospheric Science, and Center on Advanced Data Assimilation and Predictability Techniques, The Pennsylvania State University, University Park, PA 16802, USA.