EAGER: Adjustment to Balance in the Shallow Water Adjoint System

University Of Wisconsin-Madison, Madison WI

Investigators

Abstract

This one year EAGER project seeks to do the following: (i) conduct a set of numerical experiments to verify the investigator's previous analytic work demonstrating the adjustment process during weather model initialization using what are called "adjoint methods"; (ii) determine whether evidence for an adjoint adjustment holds in a time-dependent basic state and how adjustment is manifest in sensitivities to direct and diagnosed model variables; and (iii) describe how ensemble-derived sensitivities from the Weather Research and Forecasting (WRF) model compare with adjoint derived sensitivities and determine whether there is evidence that an adjustment process can be seen in these sensitivities as well. The key features of this EAGER project are: (i) it provides a robust, previously tested foundation for understanding the adjustment process seen in the adjoints of operational and research NWP models, (ii) a pathway to develop and interpret sensitivities to potential vorticity (PV) and the unbalanced components of the flow in diagnostic case studies of weather systems using adjoint models, and (iii) the work will provide insight into whether the balanced or unbalanced components of data innovations are preserved in 4DVAR data assimilation.