资源环境科技发展态势分析平台

The problem of transforming geospatial data into polar coordinates, a common task in the analysis of data centered on geophysical phenomena, is examined. The azimuthal equidistant projection is shown to be the optimal transform for this purpose. A mathematical and observational analysis of the errors incurred by using a common alternative transform is conducted and reveals that such errors can be significant at radii as small as a few hundred kilometers. When evaluating observed 200-hPa wind fields near Atlantic tropical cyclones (TCs), median azimuthal maximum errors in total and radial wind range up to 10% within 700 km of the TC and up to 50% within 1,600 km of the TC. Errors are shown to depend strongly on the statistical characteristics of the data set and increase nonlinearly with latitude and radius.

Plain Language Summary Many analyses of Earth-relative data benefit from transforming the data into different coordinate systems. For vortices, such as hurricanes, a polar coordinate system is often desirable or necessary. While converting data to polar coordinates is common, the process by which this is done can contain errors that are detrimental to any analysis performed with the data. In order to provide a reference for the magnitude of this problem, we evaluate how large these errors can be for theoretical and real-world cases when using an approach commonly employed in contemporary studies. Results indicate that these errors can be substantial at radii as small as a few hundred kilometers, regardless of location on Earth. We show that utilizing a transform called the azimuthal equidistant projection will minimize these errors, so we recommend its use in vortex-relative analyses.