Seasonal Variability of Mesospheric Winds and Turbulence Layers over Jicamarca, Peru

The Jicamarca 50-MHz radar is capable of observing mesospheric layers in the daytime mesosphere all year around, typically between 60 and 85 km. From the Doppler spectra, using several narrow, off-zenith beams, we derive the full wind vector and turbulent velocities. Since 1987, winds and momentum fluxes were obtained occasionally on campaign basis revealing strong wind shears, tidal activity and mean zonal winds consistent with the semiannual oscillation. Long-term vertical wind and momentum flux estimates, however, exhibited biases, that remained largely unresolved, possibly due to low range resolution. Later, the range resolution had been improved to the current technical limit of ~200 m at a time resolution of one minute.

In 2004, digital receivers and faster data acquisition have been employed for a two-year study of equatorial mesospheric dynamics. The new data collected from 30 days distributed over a 24-month period show fascinating details of the instability processes responsible for the small-scale turbulence observed at 3-meter scales. In addition, horizontal and vertical wind estimates have been improved. We will focus on the seasonal variation in the wind field including SAO and tidal patterns, wind shears and turbulent energy dissipation rates estimated from the Doppler spectral width.