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Behind the curve: a comparison of historical sources for the Carnegie curve of the global atmospheric electric circuit

Harrison, R. G. ORCID: (2020) Behind the curve: a comparison of historical sources for the Carnegie curve of the global atmospheric electric circuit. History of Geo- and Space Sciences, 11 (2). pp. 207-213. ISSN 2190-5029

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To link to this item DOI: 10.5194/hgss-11-207-2020


The “Carnegie curve” describes the diurnal variation of the global atmospheric electric circuit. It was originally found from atmospheric electric Potential Gradient (PG) measurements, made on the Carnegie, effectively a floating atmospheric electrical observatory, which undertook global cruises between 1915 and 1929. These measurements confirmed that the single diurnal cycle PG variation, previously obtained in both polar regions, was global in extent. The averaged diurnal PG variation, represented by derived harmonic fits, provides a characteristic variation known as the “Carnegie curve”, against which modern measurements are still compared. The ocean air PG measurements were extensively described in reports of the Carnegie Institution of Washington (CIW) but widely used secondary sources of the Carnegie curve contain small differences, arising through approximations and transcription errors. Investigations using the historical CIW data show that the original harmonic fit coefficients are reproducible. Despite the inconsistencies, the secondary sources nevertheless mostly yield diurnal variations which fall within the variability of the original historical data.

Item Type:Article
Divisions:Science > School of Mathematical, Physical and Computational Sciences > Department of Meteorology
ID Code:92786
Publisher:Copernicus Publications


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