On Geopotential Data and Ellipticity of the Balance Equation: A Data Study

Abstract

One year of geopotential data obtained from the National Meteorological Center and the National Center for Atmospheric Research are diagnosed for the occurrence of non-elliptic regions with respect to the balance equation. The highest frequencies of such occurrences appear at 200 mb over the subtropical oceans where there are few radiosonde observations. Substantial 200 mb frequencies are also found over the United States in the summer season above a reliable data net. A diagnosis of flow divergence implied for the non-elliptic data by a theoretical analysis of Paegle and Paegle (1974) produces values greatly in excess of. typical observations. This suggests that the gridding of the data by objective analysis may not have been adequate and/or that the aforementioned theory overestimates flow divergence in these regions. It is likely that non-elliptic data are important for initialization of primitive equation forecast models. It may be inferred that greater data accuracy, as well as better initialization techniques within non-elliptic regions, are required.