Climatology and changes of north-east trade winds over the islands of Hawaii

M.S. University of Hawaii at Manoa 2011.Includes bibliographical references.Prevailing trade winds are a major component of the atmospheric circulation over the tropical Pacific and have significant influence on the climate in Hawaii. In order to determine if the frequency and intensity of the northeast trades have changed from 1984-2009, wind observation data from land and buoy stations around the Hawaiian Islands are analyzed. Using a nonparametric trend analysis, all stations are consistent in displaying a downward trend in northeast trade wind frequency, although the slope of the trend is variable for each station. On the contrary, the frequency of the east trade winds is shown to have increased over the past 26 years. After extending the period of study from 1973-2009, it was found that the northeast (east) trade frequency show decreasing (increasing) trends, similar to previous results found from the post 1984-2009 data set. When examining the trends for trade intensity, there is a discrepancy between the land and buoy stations. In order to relate station observation results to synoptic scale changes, Reanalysis II data are used to analyze surface winds and sea level pressure (SLP) over the central and eastern north Pacific. An east-northeast shifting of winds and an increase in SLP is found to occur from the 1980s epoch to the 2000s epoch. The analysis of land station surface pressure confirms the increase in SLP in the reanalysis data set