INTERCOMPARISON OF DENSITY AND TEMPERATURE PROFILES OBTAINED BY LIDAR, IONIZATION GAUGES, FALLING SPHERES, DATASONDES AND RADIOSONDES DURING THE DYANA CAMPAIGN

During the course of the DYANA campaign in early 1990, various techniq ues to measure densities and temperatures from the ground up to the lo wer thermosphere were employed. Some of these measurements were perfor med near simultaneously (maximum allowed time difference: 1 h) and at the same location, and therefore offered the unique chance of intercom parison of different techniques. In this study, we will report on inte rcomparisons of data from ground-based instruments (Rayleigh- and sodi um-lidar), balloon-borne methods (datasondes and radiosondes) and rock et-borne techniques (falling spheres and ionization gauges). The main result is that there is good agreement between the various measurement s when considering the error bars. Only occasionally did we notice sma ll but systematic differences (e.g. for the datasondes above 65 km). T he most extensive intercomparison was possible between the Rayleigh li dar and the falling sphere technique, both employed in Biscarrosse (44 -degrees-N,1-degree-W). Concerning densities, excellent agreement was found below 63 km: the mean of the deviations is less than 1% and the root mean square (RMS) is approximately 3%. Systematic differences of the order of 5% were noticed around 67 km and above 80 km. The former can be accounted for by an instrumental effect of the falling sphere ( Ma = 1 transition; Ma = Mach number), whereas the latter is tentativel y explained by the presence of Mie scatters in the upper mesosphere. C oncerning temperatures, the agreement is excellent between 35 and 65 k m: the mean of the deviations is less than +/- 3 K and the variability is +/- 5 K. The two systematic density differences mentioned above al so affect the temperatures: between 65 and 80 km, the Rayleigh lidar t emperatures are systematically lower than the falling sphere values by approximately 5 K.