A simple column model to explore anticipated problems in variational assimilation of satellite observations
Rudd, A.C., Roulstone, I. and Eyre, J. R. (2012) A simple column model to explore anticipated problems in variational assimilation of satellite observations. Environmental Modelling & Software, 27-28. pp. 23-39. ISSN 1364-8152
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To link to this item DOI: 10.1016/j.envsoft.2011.10.001
We investigate a simpliﬁed form of variational data assimilation in a fully nonlinear framework with the aim of extracting dynamical development information from a sequence of observations over time. Information on the vertical wind proﬁle, w(z ), and proﬁles of temperature, T (z , t), and total water content, qt (z , t), as functions of height, z , and time, t, are converted to brightness temperatures at a single horizontal location by deﬁning a two-dimensional (vertical and time) variational assimilation testbed. The proﬁles of T and qt are updated using a vertical advection scheme. A basic cloud scheme is used to obtain the fractional cloud amount and, when combined with the temperature ﬁeld, this information is converted into a brightness temperature, using a simple radiative transfer scheme. It is shown that our model exhibits realistic behaviour with regard to the prediction of cloud, but the effects of nonlinearity become non-negligible in the variational data assimilation algorithm. A careful analysis of the application of the data assimilation scheme to this nonlinear problem is presented, the salient difficulties are highlighted, and suggestions for further developments are discussed.