EQUATORIAL WAVE ACTIVITY DERIVED FROM FLUCTUATIONS IN OBSERVED CONVECTION

The spectrum of equatorial wave activity propagating vertically into t he stratosphere is calculated from high-resolution imagery of the glob al convective pattern. Synoptic Global Cloud Imagery (GCI), constructe d from six satellites simultaneously observing the earth, is used to d iabatically force the linearized primitive equations. Having resolutio n of 0.5 deg and 3 h, that imagery captures the dominant scales of org anized convection, including several harmonics of the diurnal cycle. I ts global coverage with high space-time resolution allows the GCI to r epresent heating variability and dynamical behavior excited by it over a wide range of scales. The dynamical response above the heating is e valuated globally in terms of a space-time spectrum of Hough modes, on e which includes planetary-scale Kelvin waves, Rossby waves, and gravi ty waves down to the resolution of the GCI. The geopotential response, which is indicative of temperature fluctuations observed by satellite , is very red in frequency. Therefore, planetary-scale waves with peri ods longer than two days dominate the spectrum of geopotential, while high-frequency gravity waves make a comparatively small contribution. Some 80% of the geopotential variance is accounted for by the Kelvin a nd gravest-symmetric Rossby modes, while the Rossby-gravity mode is co mparatively weak. In horizontal eddy motion, the excited wave spectrum is still dominated by planetary-scale components. However, meridional wind fluctuations associated with the Rossby-gravity mode have varian ce comparable to that of zonal wind fluctuations associated with the K elvin mode, even though the Rossby-gravity mode is nearly invisible in the geopotential response. Estimates of tropospheric heating lead to amplitudes and propagation characteristics that are broadly consistent with satellite and radiosonde observations of wave activity in the lo wer stratosphere. The space-time spectrum of EP flux is significantly whiter than the response in either geopotential or motion. Gravity wav es of small scale and high frequency carry a large fraction of the upw ard flux. Although it dominates eastward variance of geopotential and motion, the Kelvin mode carries only about 50% of the eastward EP flux at phase speeds of 20-40 m s(-1) and only 35% of the total eastward B ur transmitted to the stratosphere. The remainder is carried by the gr avity wave spectrum, which carries nearly all of the westward flux at phase speeds greater than 20 m s(-1). The gravity wave spectrum also c ontributes significantly at phase speeds of 10-20 m s(-1) where only 2 5% of the flux is accounted for by zonal wavenumbers less than 20. The broad nature of the gravity wave spectrum suggests its absorption at critical levels will be distributed over a deep layer of the middle at mosphere.