Oscillation modes of humidity over the Amazon basin derived from GPS RO profiles

Abstract

The Global Positioning System radio occultation (GPS RO) technique provides vertical profiles of refractivity from which water vapor can be derived. It is possible to reproduce global, synoptic, and regional climatological patterns. From Formosa Satellite 3/Constellation Observing System for Meteorology Ionosphere and Climate mission data (2006-2013), the variability of the moistest region of Southern Hemisphere as the Amazon basin is analyzed. Applying different spatial and temporal filters, oscillation modes of the integrated specific humidity (Q) are found. A slight decreasing trend in Q is found during the studied period. Zonal variability of this variable averaged in time between Amazon basin latitudes presents a main mode of oscillation of a wavelength of one quarter of the Earth (T4). A secondary mode of wavelength at around T6 wavelength is also found after high-pass filtering the original signal. In turn, temporal variability averaged over Amazon basin latitudes shows a wavelength at around 12 months, while secondary modes of 6 months are found. Key Points Humidity oscillation modes over Amazon basin is verified GPS-RO allows to determine the variability of water vapor over South America A decreasing trend of humidity is found over Amazon basin ©2013. American Geophysical Union. All Rights Reserved.