Observation of the gravity waves from GPS/MET radio occultation data

Abstract We show that the amplitude of the Global Positioning System (GPS) signals in the radio occultation (RO) experiments is sensitive to the atmospheric wave structures. Earlier the phase of the GPS occultation signals have been used for statistical investigation of the gravity waves (GW) activity in the height interval 10–40 km on a global scale. Analysis of the RO amplitude data revealed wave clusters (quasi-regular structures) with the vertical size of about 10 km and interior vertical period ∼0.8–2 km in the tropopause and lower stratosphere. The amplitude RO data may be utilized to determine the temperature vertical profiles and its vertical gradient in the upper troposphere and stratosphere. In the considered RO events variations of the vertical temperature gradient dT(h)/dh corresponding to the amplitude clusters are in the range from −9 K/km to 6 K/km with vertical scales ∼1–3 km. We show that these variations can be linked to the GW propagation in the atmosphere. We use the polarization and dispersion relationships and Hilbert transform to find the 1-D GW image in the atmosphere by analyzing the vertical temperature gradient dT(h)/dh. The GW image consists of the phase and amplitude of the GW as functions of height. The GW amplitude is non-uniformly distributed with main contribution associated with the tropopause and the secondary maximums in height interval 18–35 km. Using our method we find vertical profiles of the horizontal wind perturbations and their vertical gradient associated with the GW influence. The horizontal wind perturbations are changing in the interval v∼2–12 m/s with vertical gradients dv/dh∼4–25 m s−1 km−1) in the tropopause area and v∼ 3–9 m/s, dv/dh ∼ 2–15 m/(s km) in the stratosphere for the considered events. For one RO event we compared the estimated values of the horizontal wind perturbations with aero-logical data and found fairly good agreement. The height dependence of the GW vertical wavelength was inferred through the differentiation of the GW phase. Analysis of this dependence using the dispersion relationship for the GW gives estimation of the GW intrinsic phase speed. For the considered events the magnitude of the intrinsic phase speed changes between 1.5–15 m/s at heights 10–40 km. We conclude that the amplitude of the GPS occultation signals contain important information about the GW propagation in the atmosphere on a global scale.

[1]  G. D. Nastrom,et al.  A comparison of gravity wave energy observed by VHF radar and GPS/MET over central North America , 2000 .

[2]  M. Alexander,et al.  Gravity wave dynamics and effects in the middle atmosphere , 2003 .

[3]  R. Garcia,et al.  Propagation and Breaking at High Altitudes of Gravity Waves Excited by Tropospheric Forcing , 1996 .

[4]  C. Reigber,et al.  CHAMP mission status , 2002 .

[5]  Benjamin M. Herman,et al.  Remotely Sensing the Earth’s Atmosphere Using the Global Positioning System (GPS)—The GPS/MET Data Analysis , 1999 .

[6]  S. W. Bowen,et al.  Gravity waves generated by a tropical cyclone during the STEP tropical field program: A case study , 1993 .

[7]  Kiyoshi Igarashi,et al.  Analytic method for observation of the gravity waves using radio occultation data , 2003 .

[8]  Rolf König,et al.  Atmosphere sounding by GPS radio occultation: First results from CHAMP , 2001 .

[9]  A. Zakharov,et al.  Radio holographic principle for observing natural processes in the atmosphere and retrieving meteorological parameters from radio occultation data , 2000 .

[10]  R. Sica,et al.  Measurements of the Effects of Gravity Waves in the Middle Atmosphere Using Parametric Models of Density Fluctuations. Part I: Vertical Wavenumber and Temporal Spectra , 1999 .

[11]  Jens Wickert,et al.  Observation of wave structures in the upper atmosphere by means of radio holographic analysis of the radio occultation data , 2001 .

[12]  Yuei-An Liou,et al.  Simultaneous observation of the vertical gradients of refractivity in the atmosphere and electron density in the lower ionosphere by radio occultation amplitude method , 2002 .

[13]  W. Bertiger,et al.  A technical description of atmospheric sounding by GPS occultation , 2002 .

[14]  T. Tsuda,et al.  Vertical Wave Number Spectrum of Temperature Fluctuations in the Stratosphere using GPS Occultation Data , 2002 .

[15]  Sergey Sokolovskiy,et al.  Inversions of radio occultation amplitude data , 2000 .

[16]  Christian Rocken,et al.  A Global Morphology of Gravity Wave Activity in the Stratosphere Revealed by the GPS Occultation Data (GPS/MET) , 2000 .

[17]  J. Wickert,et al.  First application of the radioholographic method to wave observations in the upper atmosphere , 2002 .

[18]  A. Semenov,et al.  Electromagnetic waves in the atmosphere and space , 1986 .

[19]  Steven Businger,et al.  GPS Sounding of the Atmosphere from Low Earth Orbit: Preliminary Results , 1996 .

[20]  R. Lindzen.  Turbulence and stress owing to gravity wave and tidal breakdown , 1981 .

[21]  G. Kirchengast,et al.  Gravity Wave Spectra from GPS/MET Occultation Observations , 2000 .

[22]  P. Preusse,et al.  Global Measurements of Stratospheric Mountain Waves from Space. , 1999, Science.

[23]  C. K. Yuen,et al.  Theory and Application of Digital Signal Processing , 1978, IEEE Transactions on Systems, Man, and Cybernetics.

[24]  G. D. Nastrom,et al.  Vertical wavenumber spectra of wind and temperature from high-resolution balloon soundings over Illinois , 1997 .

[25]  W. Hocking,et al.  Gravity wave and equatorial wave morphology of the stratosphere derived from long‐term rocket soundings , 1995 .

[26]  O. P. Nagpal.  The sources of atmospheric gravity waves. , 1979 .

[27]  Christian Rocken,et al.  Applications of COSMIC to Meteorology and Climate , 2000 .