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Harold J. Brodrick

Abstract

The direct synoptic application of radiances measured in the 695 cm−1 channel of the 15 μm carbon dioxide band by the vertical sounding instruments aboard the NOAA operational satellites is described. The radiation measured in this channel is emitted from a layer centered around 150–100 mb, or above the level of the polar jet stream and tropopause. In this region above the baroclinic zone of the polar front, the horizontal temperature gradient is the reverse of that found in the troposphere. It is demonstrated that mapped radiance patterns are quite useful for describing the upper tropospheric circulation features at 300 mb, and that the gradients are well related to 300 mb wind speeds in and near the polar jet stream.

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Harold J. Brodrick

Abstract

Case studies are used to examine the horizontal and vertical temperature structure in baroclinic zones for three synoptic situations. The studies compare analyses of 1000–500 mb and 700–300 mb thicknesses made from satellite data only with National Meteorological Center (NMC) analyses made from conventional data. In addition, isentropic cross sections across baroclinic zones are shown using data from each of three sources; radiosondes, satellite soundings, and NMC global analyses. These cross sections demonstrate that the satellite soundings generally represent the baroclinic zones at least as well as the NMC analyses, with thermal wind speed maxima that are comparable with those obtained from either the radiosonde or NMC analysis cross sections. However, the computed speed maxima from the satellite data were achieved because the soundings depicted the frontal zones as being steeper than in the radiosonde versions. That condition, in which the principal horizontal temperature gradients were aligned in a nearly vertical fashion in the satellite data cross sections, thus contributed to the vertical summation of the gradients, even though temperature gradients at individual levels were usually weaker than the corresponding radiosonde gradients.

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E. PAUL McCLAIN
,
MARY ANN RUZECKI
, and
HAROLD J. BRODRICK

Abstract

Errors in operational forecasts produced by high-speed electronic computers can be classed broadly into two categories: (1) those resulting from inadequacies of the dynamic model, and (2) those resulting from poor specification of the initial fields. Many regions of the Northern Hemisphere, particularly oceanic areas, are poorly observed in terms of conventional meteorological data, especially upper-air data. The SINAP (Satellite Input to Numerical Analysis and Prediction) Project at the Weather Bureau's Meteorological Satellite Laboratory has been working to develop techniques for incorporating information derived from satellite cloud pictures into the operational numerical analysis in data-sparse areas.

Trial reanalyses of the National Meteorological Center (NMC) 500-mb. stream function analysis, or its Laplacian, were performed for data-sparse areas of the central and eastern Pacific Ocean using an analysis modification technique consisting of two steps: (1) inferring features of the flow pattern or of the field of large-scale vertical motion from an interpretation of the TIROS-viewed cloud patterns, and (2) modifying the 500-mb. analyses to produce an appropriate vorticity advection field. Underlying this method are certain simplifying assumptions about the relation of the cloud field to the vertical motion field on the one hand, and of the vertical motion to the vorticity advection on the other.

Application of the method and the results obtained are illustrated for one case. Thirty-six-hr. barotropic forecasts were run from both the original NMC analysis and the SINAP modified analysis and then compared with the verifying chart. Verification statistics, such as the root mean square (RMS) error of the stream values and of the vector geostrophic wind, are presented for the case illustrated and for five additional cases. Significant reductions in forecast error were achieved in most cases, the overall average reduction in the RMS error of the wind being 5.4 percent.

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