Detection of the inversion layer over the central north pacific ocean using gps radio occultation

Abstract

Sparse observations over the central North Pacific have inhibited our understanding of the spatial variations of the trade wind inversion. Since the launch of the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) in 2006, Global Positioning System radio occultation (GPS RO) observations allow for high-resolution atmospheric profiling with a vertical resolution on the order of 100 m to be extended over the open ocean where conventional data are sparse. In this study, the GPS RO data during the years 2006-2012 will be used to study the spatial variations of the inversion throughout the annual cycle over the region 5°N-45°N and 120°W-180°W. In addition, the impacts of El Niño and the diurnal heating cycle on the spatial and temporal variations of the inversion base height were also examined. Identification of the horizontal distribution of the inversion was achieved by combining seasonal data for the years 2007-2012 over the entire domain into 5° x 5° grids. The resulting horizontal distribution showed an annual difference in inversion height of approximately 200 m in the wake of the islands. When low level flow was restricted to northeasterly trade wind flow, the inversion base heights increased for each season, however the annual difference remained 200 m. Comparisons between El Niño and La Niña events as well as the diurnal variation during the summer season show a difference in the height of the inversion base of approximately 100 m, however, a larger data sample would be desirable for a more robust analysis. A two-tailed t test was performed for three 2.5° x 2.5° grid boxes in the wake of the islands to compare the annual variation of the inversion base height. The annual change within each of the two western most grid boxes is statistically significant at a 95% confidence interval. The third point, immediately downwind of the Big Island only showed a significant difference when low level flow was restricted to trade wind flow. The goal of this thesis is to determine if the effect the Hawaiian Islands have on the otherwise uniform flow within the marine boundary layer (BL) is detectable by the GPS RO observations method.