Earth Observation with CHAMP pp 549-554
Gravity Wave "Portrait" Reconstructed by Radio Holographic Analysis of the Amplitude of GPS Radio Occultation Signals
The analysis of the amplitude of the GPS/MET and CHAMP radio occultation (RO) events revealed clusters (quasi-regular structures) with a vertical size of about 10 km and an interior vertical period of ∼0.8 to 2 km in the tropopause and lower stratosphere. The height interval of the clusters changes from 10 to 40 km. Restored from the RO amplitude data, variations of the vertical temperature gradient in clusters dT/dh are from −8 to −9 K/km up to 6 to 8 K/km. These variations can be associated with the influence of internal waves (gravity waves; GWs) propagating through the atmosphere and mesosphere. We found a height dependence of the GW phase and amplitude (the GW “portrait”), using for example the amplitude data corresponding to the GPS/MET and CHAMP RO events. For a GPS/MET event we estimated the horizontal wind speed perturbations which are in fairly good agreement with radiosonde data. Between 10 and 40 km, the horizontal wind speed perturbations v(h) are changing in the range v from ∼±1 to ±9 m/s with vertical gradients dv/dh ∼±0.5 to ±15 m/(s km). The height dependence of the GW vertical wavelength was derived by differentiation of the GW phase. The analysis of this dependence led to the estimation of the GW intrinsic phase speed which changed for the considered events in the interval from 1.5 to 5 m/s. The analysis of RO data shows that the RO signal amplitude contains valuable information for studying the GW activity in the atmosphere.
Key wordsgravity waves radio occultation amplitude vertical gradient of temperature
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