Winter anticyclone changes on the central Gulf Coast of the USA

✍ Scribed by Rohli, Robert V.; Henderson, Keith G.

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 164 KB
• Volume: 17
• Category: Article
• ISSN: 0899-8418
• DOI: 10.1002/(sici)1097-0088(199709)17:11<1183::aid-joc184>3.0.co;2-q

✦ Synopsis

A modi®ed cyclone-model-based weather classi®cation system is used to identify long-term trends in anticyclonic weather type frequencies over the central Gulf Coast of the USA. Results suggest that days dominated by mid-latitude cold-season anticyclones of continental origin (CH days) have decreased in frequency from 1961 to 1989. At the same time, anticyclones of Paci®c origin (PH days) have become more common over the same region. In both cases, most of the trends are characterized by abrupt `step changes' rather than gradual changes. Principal components analysis in combination with a clustering procedure is used to analyse long-term trends in the surface air mass properties at New Orleans during times of in¯uence of these weather types. The intensities of these weather types as a whole do not display any signi®cant trends. However, several individual weather variables do show signi®cant change, especially on CH days. Although some trends may represent changes in trajectory and intensity of the air masses, many may be indicative of more general atmospheric tendencies not limited to CH and PH days, such as the urban heat island and reduced visibility associated with anthropogenic activity. Future research should be conducted to improve our understanding of how changes in the presence and properties of these anticyclones relate to changes in the larger scale steering ¯ow patterns governing their trajectories and intensities.