Global Ray Tracing Simulations of the SABER Gravity Wave Climatology

摘要

Since February 2002, the SABER (sounding of the atmosphere using broadband emission radiometry) satellite instrument has measured temperatures throughout the entire middle atmosphere. Employing the same techniques as previously used for CRISTA (cryogenic infrared spectrometers and telescopes for the atmosphere), we deduce from SABER V1.06 data 5 years of gravity wave (GW) temperature variances from altitudes of 20 to 100 km. A typical annual cycle is presented by calculating averages for the individual calendar months. Findings are consistent with previous results from various satellite missions. Based on zonal mean, SABER data for July and zonal mean GW momentum flux from CRISTA, a homogeneous and isotropic launch distribution for the GROGRAT (gravity wave regional or global ray tracer) is tuned. The launch distribution contains different phase speed mesoscale waves, some of very high-phase speed and extremely low amplitudes, as well as waves with horizontal wavelengths of several thousand kilometers. Global maps for different seasons and altitudes, as well as time series of zonal mean GW squared amplitudes based on this launch distribution, match the observations well. Based on this realistic observation- tuned model run, we calculate quantities that cannot be measured directly and are speculated to be major sources of uncertainty in current GW parameterization schemes. Two examples presented in this paper are the average cross-latitude propagation of GWs and the relative acceleration contributions provided by saturation and dissipation, on the one hand, and the horizontal refraction of GWs by horizontal gradients of the mean flow, on the other hand.