Analysis of Gravity Waves from Radio Occultation Measurements

In the height range 10-30 km atmospheric gravity waves lead to periodic perturbations of the background temperature field in the order of 2-3 K, which can be resolved in temperature profiles derived from radio occultation measurements. Due to the spherical symmetry assumption in the retrieval algorithm and the low horizontal resolution of the measurement weakening in the amplitude and phase shift of the waves occurs. The influence of the geometric wave parameters and the measurement geometry on a homogeneous spectrum of plane gravity waves in the range 100-1000 km horizontal and 1-10 km vertical wavelength is investigated with a 2D-model ranging ±1000 km around the tangent point and 10-50 km in height. The investigation shows that with radio occultation measurements more than 90% of the simulated wave spectrum can be resolved with relative amplitudes above the 1/e level. Considering the total variance, about 80% is retrieved in the worst case when the GPS receiver scans perpendicular to the wave crests and about 88% as mean value when the view angle of the receiver through the gravity waves is arbitrarily oriented. More realistic wave spectra lead to slightly smaller values.