Comparisons between Satellite-derived Gradient Winds and Radar-derived Winds from the CIRA-86

Abstract

Satellite-radiance data (Nimbus 5, 6; ≤80 km) and the MSIS-83 model have been used to prepare global zonal-mean gradient winds (30?120 km) for the new CIRA-1986. Here these are supplemented by planetary-wave morphology from the same Nimbus data to provide local gradient winds?the zonal wind and the eddy portion of the meridional wind are calculated by this method. These data are then compared with radar-derived wind contours (?60?110 km), extending the comparisons done earlier (Manson et al.) for heights below 80 km. Overall the agreement for the zonal winds is good, especially below 80 km; differences are shown so the user can evaluate each product. The comparison of meridional winds is particularly valuable and unique as it reveals considerable ageostrophy, particularly in summer months near the height of the zonal wind's reversal from west- to eastward flow. Coriolis torques due to this meridional flow are available from Saskatoon (52°), Poker Flat (65°), and Tromsö (70°) in the Northern Hemisphere, and Adelaide (35°), Christchurch (44°), and Mawson (68°) in the Southern Hemisphere. Values of 60?100 m s?1 day?1 are generally consistent with estimates of the balancing gravity wave momentum deposition made by direct methods at the same locations.