2002 Annual

Tuesday, 15 January 2002: 11:00 AM
Fog in the Los Angeles Basin: Influence of the El Nino Southern Oscillation and the Pacific Decadal Oscillation
Michael R. Witiw, Terabeam, Redmond, WA; and J. A. Baars and J. Ramaprasad
Over the past few decades, many studies have been completed to assess the impact of the El Niņo Southern Oscillation (ENSO) on various meteorological variables and phenomena, including temperature, rainfall, snowfall, and tropical cyclones. More recently, the effects of changes in the Pacific Decadal Oscillation (PDO) cycle have also been studied. Although both of theses cycles are thought to have worldwide teleconnections, the PDO is of a smaller amplitude and longer period than the ENSO. One weather element that has been given little attention in the study of these cycles is fog. However, fog can affect highway safety and specific industries, including aviation and free-space optics (FSO). This study relates the occurrence of fog in the Los Angeles Basin with ENSO and PDO cycles. Thirty years of surface data from two airports, Los Angeles International Airport and Long Beach International Airport, were analyzed for visibility occurrences below 400 meters (1/4 mile) and again for visibility occurrences below 100 meters (1/16 mile). Only the months of October through February were considered because very low surface visibilities are rare during the remaining months of the year. Regressions were run, and for both locations, a strong relationship with the PDO was observed for visibilities less than 400 meters (p<.01). At Long Beach International airport, an even stronger relation was observed for visibility occurrences less than 100 meters (p<.001), although this relationship was weaker at Los Angeles International Airport. In general, the relationship with ENSO cycles was much weaker but was significant at Los Angeles International Airport for visibilities less than 400 meters (p<.01).

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