OBJECTIVE WEATHER-MAP ANALYSIS

R. A. Panofsky New York University

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Abstract

Wind and pressure fields are fitted by third-degree polynomials in areas of the order of 106 square miles. Expressions involving derivatives of wind and pressure are computed and the question of computation of geostrophic deviations is re-examined. A method of connecting polynomials in separate areas is investigated.

The following conclusions are drawn:

  1. Isopleths and streamlines drawn from the polynomials greatly resemble subjective isopleths and streamlines. In all cases studied, the smoothing seems to be adequate.

  2. Horizontal divergence and vertical velocities can be determined as well from the polynomials objectively as by other subjective methods. The errors of observation influence the magnitude of these quantities considerably, but usually do not affect the sign.

  3. On the scale of these measurements, reliable pressure gradients can be obtained objectively; however, the Laplacian of pressure is very much affected by the technique of analysis and by observational errors.

  4. Reliable values of the geostrophic deviations can be obtained only under favorable conditions. Hence any method of integration of the fundamental equations which requires knowledge of the geostrophic deviations is to be avoided.

Abstract

Wind and pressure fields are fitted by third-degree polynomials in areas of the order of 106 square miles. Expressions involving derivatives of wind and pressure are computed and the question of computation of geostrophic deviations is re-examined. A method of connecting polynomials in separate areas is investigated.

The following conclusions are drawn:

  1. Isopleths and streamlines drawn from the polynomials greatly resemble subjective isopleths and streamlines. In all cases studied, the smoothing seems to be adequate.

  2. Horizontal divergence and vertical velocities can be determined as well from the polynomials objectively as by other subjective methods. The errors of observation influence the magnitude of these quantities considerably, but usually do not affect the sign.

  3. On the scale of these measurements, reliable pressure gradients can be obtained objectively; however, the Laplacian of pressure is very much affected by the technique of analysis and by observational errors.

  4. Reliable values of the geostrophic deviations can be obtained only under favorable conditions. Hence any method of integration of the fundamental equations which requires knowledge of the geostrophic deviations is to be avoided.

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