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The potential utility of Mesosphere-Stratosphere-Troposphere (MST) radarmeasurements of zonal, meridional and vertical winds for divulging thegravity wave vertical wave number spectra is discussed. The data collectedduring the years 1995–2004 are used to obtain the mean vertical wave numberspectra of gravity wave kinetic energy in the tropical troposphere overGadanki (13.5° N, 79.2° E). First, the climatology of 3-dimensionalwind components is developed using ten years of radar observations, for thefirst time, over this latitude. This climatology brought out the salientfeatures of background tropospheric winds over Gadanki. Further, using thesecond order polynomial fit as background, the day-to-day wind anomalies areestimated. These wind anomalies in the 4–14 km height regions are used toestimate the profiles of zonal, meridional and vertical kinetic energy perunit mass, which are then used to estimate the height profile of totalkinetic energy. Finally, the height profiles of total kinetic energy aresubjected to Fourier analysis to obtain the monthly mean vertical wave numberspectra of gravity wave kinetic energy. The monthly mean vertical wave numberspectra are then compared with a saturation spectrum predicted by gravitywave saturation theory. A slope of 5/3 is used for the model gravity wavespectrum estimation. In general, the agreement is good during all themonths. However, it is noticed that the model spectrum overestimates thePSD at lower vertical wave numbers and underestimates it at higher vertical wavenumbers, which is consistently observed during all the months. The observeddiscrepancies are attributed to the differences in the slopes of theoreticaland observed gravity wave spectra. The slopes of the observed verticalwave number spectra are estimated and compared with the model spectrum slope,which are in good agreement. The estimated slopes of the observed monthlyvertical wave number spectra are in the range of −2 to −2.8. The significanceof the present study lies in using the ten years of data to estimate themonthly mean vertical wave number spectra of gravity waves, which will findtheir application in representing the realistic gravity wave characteristicsin atmospheric models

annales geophysicae

Long-term MST radar observations of vertical wave number spectra of gravity waves in the tropical troposphere over Gadanki (13.5° N, 79.2° E): comparison with model spectra