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Synoptic Climatology of Monthly Mean Surface Temperature in the Unit States during Summer in Relation to the Surrounding 700-mb Height Field

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  • 1 Department of Meteorology, University of Maryland College Park, MD 20742
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Abstract

The synoptic climatology of monthly mean temperature at 109 surface stations in the contiguous United States relative to 700-mb heights at 133 grid points is assessed. Two methods are used based on data for 102 summer months from June 1948 to August 1981. The first method involves analysis of fields of simple linear correlation coefficients between the monthly mean surface temperature anomaly at the reference station and the concurrent anomaly of 700-mb height at each grid point; the second involves analysis of a special type of anomaly composite map, constructed by multiplying the correlation coefficient at each grid point by the standard deviation of 700-mb height at the same point. The synoptic climatologies derived from each method are discussed, and inferences drawn about the relations between surface temperature and the surrounding 700-mb circulation, with geographical differences emphasized.

Previous results for winter showed two major centers of correlation: a primary positive near the station and a secondary negative about one-half wavelength upstream. During summer the local positive correlation is almost as 1arge as it is in winter, but the remote negative correlation is much smaller and closer to the reference station. The negative exceeds the positive in magnitude at 25% of the stations in winter, but at less than 3% in summer. Consequently, local heights have much greater influence than remote heights on surface temperature in summer, but remote heights are almost as important as local heights in winter. The almost universal positive correlation between local values of surface temperature and 700-mb height seems to be reduced by boundary layer and mesoscale phenomena, especially at low latitudes and coastlines during summer.

Abstract

The synoptic climatology of monthly mean temperature at 109 surface stations in the contiguous United States relative to 700-mb heights at 133 grid points is assessed. Two methods are used based on data for 102 summer months from June 1948 to August 1981. The first method involves analysis of fields of simple linear correlation coefficients between the monthly mean surface temperature anomaly at the reference station and the concurrent anomaly of 700-mb height at each grid point; the second involves analysis of a special type of anomaly composite map, constructed by multiplying the correlation coefficient at each grid point by the standard deviation of 700-mb height at the same point. The synoptic climatologies derived from each method are discussed, and inferences drawn about the relations between surface temperature and the surrounding 700-mb circulation, with geographical differences emphasized.

Previous results for winter showed two major centers of correlation: a primary positive near the station and a secondary negative about one-half wavelength upstream. During summer the local positive correlation is almost as 1arge as it is in winter, but the remote negative correlation is much smaller and closer to the reference station. The negative exceeds the positive in magnitude at 25% of the stations in winter, but at less than 3% in summer. Consequently, local heights have much greater influence than remote heights on surface temperature in summer, but remote heights are almost as important as local heights in winter. The almost universal positive correlation between local values of surface temperature and 700-mb height seems to be reduced by boundary layer and mesoscale phenomena, especially at low latitudes and coastlines during summer.

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