An Interactive Barnes Objective Map Analysis Scheme for Use with Satellite and Conventional Data

Abstract

An objective analysis scheme based on the Barnes technique and designed for use on an interactive computer is described. In order to meet the specific needs of the research meteorologist, the interactive Barnes scheme allows real-time assessments both of the quality of the resulting analyses and of the impact of satellite-derived data upon various meteorological data sets. Display of a number of statistical and mapped analysis quality control indicators aid the impact assessments. Simple means for taking account of the spatially clustered nature typical of satellite data are included in the internal computations of the relative weights of data at grid point locations. An analyst is allowed the capability of modifying values of certain input parameters to the interactive Barnes scheme within internally set limits. These constraints were objectively determined and tested in a number of different situations prior to implementation. The following constraints are employed: 1) calculation of the weights as a function of a data spacing representative of the data distribution; 2) automatic elimination of detail at wavelengths smaller than twice the representative data spacing; 3) placement of bounds upon the grid spacing by the data spacing; and 4) setting of a fixed limit on the number of passes through the data to achieve rapid and sufficient convergence of the analyzed values to the observed ones. A mathematical analysis of the convergence properties of the Barnes technique is presented to support the validity of the latter constraint. Despite these constraints, the interactive Barnes scheme remains versatile because it accepts limited inputs to the data and grid display areas, to the data and grid spacings, and to the rate of convergence of the analysis to the observations. Input parameter values are entered through a series of questions displayed on a computer video terminal and by manipulation of display function devices. The analyst immediately sees a plot of the data, the contoured grid values, superimposed in various colors if desired, and the effects of choice of analysis options. Examples of both meteorological and satellite data analyses are presented to demonstrate the objectivity, versatility and practicality of the interactive Barnes scheme.