CHAMP observations of global gravity wave fields in the troposphere and stratosphere

Abstract

This paper presents the analysis of 56 months of CHAMP (Challenging Minisatellite Payload) RO (radio occultation) temperature profiles to study the global gravity wave fields in the troposphere and lower stratosphere. The relatively new GPS (Global Positioning System) RO technique is suitable for global monitoring and provides high vertical resolution, long-term stability, and opportunity of all-weather viewing. The CHAMP data set analyzed in this paper is the largest RO data set used for the investigation of global structure of gravity waves. The analysis also makes use of the global radiosonde data provided by the British Atmospheric Data Centre (BADC). First, the global winter temperature pattern and temperature fluctuations in the troposphere and lower stratosphere are discussed. The global structure of gravity wave variances in the upper troposphere and lower stratosphere for the summer and winter seasons indicate the dominance in the tropical region. The analysis reveals that the maximum potential energy (E p) is observed around the equator with considerable longitudinal variation. Comparison of the wave energy derived from the CHAMP and radiosonde data sets for the low-latitude region (20°S-20°N) shows good similarity. The observed vertical wave number power spectra were compared with a model spectrum. The low-latitude power spectra show considerable similarities with the model spectrum. However, the disparity increases in the midlatitude or high-latitude sectors; particularly, in the high latitudes the observed spectral power is much underestimated for longer wavelengths. The results demonstrate the usefulness of GPS RO data in determining the global gravity wave fields. Copyright 2008 by the American Geophysical Union.