Temperatures, densities, and winds in the high latitude (78°N) mesosphere

Abstract

A field campaign called ROMA (“Rocket borne Observations in the Middle Atmosphere”) was conducted in 2001 close to Longyearbyen (Spitsbergen, 78°N) with temperature, density, and wind measurements by meteorological rockets and ground-based detection of noctilucent clouds (NLC) by lidar and polar mesosphere summer echoes (PMSE) by radar. A summary of the temperature data has been published recently [ Lübken and Müllemann, 2003 ]. Here we present a detailed comparison of temperatures and densities with empirical models (LIRA, MSIS) and with measurements at other latitudes. We also present falling sphere winds. It is very cold in the upper mesosphere during the summer season, cold enough for water ice particles to exist, i. e., the degree of saturation is larger than unity assuming reasonable [H 2O] values. Generally, PMSE and NLC are found at altitudes with super-saturation. There are striking differences and similarities between temperatures and densities at Longyearbyen, empirical reference models, and measurements at other latitudes, respectively. For example, around the mesopause in summer, temperatures are smaller by 6–9 K in Longyearbyen compared to Andøya (69°N). Much larger differences are observed relative to CIRA: temperatures are smaller by up to 20 K and mass densities in the upper mesosphere are almost 50% smaller compared to CIRA-1986. In the lower and middle atmosphere, temperatures and densities are very similar to values at Andøya and to empirical models. Zonal winds are westward in the mesosphere and generally agree with CIRA-1986, both in direction and magnitude. Meridional winds are smaller than zonal winds.