Reconstruction of cold front frequency over Cape Town, South Africa, using daily mean sea level pressure values: 1834–1899

Abstract

AbstractSurface pressure observations are invaluable for meteorological investigations as they enable reconstructions of and insights to historical large‐scale tropospheric circulation. This article endeavours to use a daily reduced mean sea level pressure (MSLP) series to reconstruct the monthly frequency of cold fronts, associated with mid‐latitude cyclones, overpassing Cape Town (southwestern Cape region of South Africa) during the 19th century. Using modern (2011–2017) daily MSLP data and synoptic charts, the relationship between MSLP values and the probability of a cold front overpassing, is established and applied to historical (1834–1899) MSLP data. Although no significant trend in cold front frequency is measured, greater interannual variability is noted during the first half of the study period (1837–1867). Results indicate a link between lower (higher) cold front frequencies and El Niño (La Niña) events, although not statistically significant. Additionally, correlations between cold front frequency and the Southern Annular Mode (SAM) appear to be weak. Although not statistically robust, we also note an apparent 1–2 year lagged association between years with above (below) average numbers of sunspots and above (below) average numbers of cold fronts.