A Question of Adequacy of Observations in Variational Data Assimilation - Data Assimilation for Atmospheric, Oceanic and Hydrologic Applications - page 108

Chapter 5
A Question of Adequacy of Observations in
Variational Data Assimilation

John M. Lewis and S. Lakshmivarahan

Abstract The adequacy of observations to locate the minimum of the standard
cost function for variational data assimilation under strong constraint has been
investigated. A simplified yet meaningful Lagrangian air/sea interaction model
that captures key aspects of air mass modification over the Gulf of Mexico in
wintertime is the dynamical tool used to examine this question of adequacy. Two
mathematically different yet equivalent variational schemes are used in numerical
experiments with a fixed number of observations along a prior known trajectory over
the Gulf. Research clearly indicates that sensitivity of model output to elements of
control (initial condition, boundary condition, and physical parameter) is key to
placement of observations in order to minimize the cost function and determine
optimal corrections to control.

5.1 Introduction

From the early days of numerical weather map analysis as an aid to numerical
weather prediction (NWP) ( Wiin-Nielsen 1991 ), the adequacy of observations to
produce an analysis faithful to the weather and consistent with the dynamical
model has been an ever-present concern. In the earliest numerical map analysis
by Bergth orsson and Do os ( 1955 ) that spanned the North Pacific Ocean and the
bounding continental areas (northern Europe and eastern Canada), a climatological