A New Climatology for Investigating Storm Influences in and on the Extratropics

Abstract

he NASA Modeling, Analysis, and Prediction (MAP) Climatology of Mid-Latitude Storm Area (MCMS) project is a set of tools for examining midlatitude cyclones in model-generated data. The MCMS software has two primary tasks. The first task identifies and tracks likely cyclones in sea level pressure fields. Special care is taken to minimize the known problems of this approach near steep or high topography. The second task finds the outermost closed pressure contour that uniquely surrounds each cyclone center, or collection of centers in the case of multicenter cyclones. This enclosed area is then used as a rough proxy for the domain over which a cyclone influences its immediate environment. Here the MCMS software is applied to several decades of reanalysis data. These results are shown to be consistent with the findings of a recent intercomparison of cyclone-finding methods. Besides providing details concerning cyclone storm area, the MCMS software departs from other cyclone-finding methods by providing a comprehensive record concerning every cyclone it processes. The MCMS software also provides extensive diagnostics about the actions of specific operations (filters) and adjustable parameters. The benefits of this accounting are demonstrated and discussed, as are those related to the use of cyclone storm area as a tool for climate research. MCMS datasets are available for several reanalysis products, as is the MCMS software itself, including the source code needed to generate new MCMS datasets and utilities for working with existing ones.