As part of the second SPARC (Stratosphere–troposphere Processes And their Role in Climate) water vapor assessment (WAVAS-II), we present measurements taken from or coincident with seven sites from which ground-based microwave instruments measure water vapor in the middle atmosphere. In the lower mesosphere, we quantify instrumental differences in the observed trends and annual variations at six sites. We then present a range of observed trends in water vapor over the past 20 years.

By computer simulations, we explore and quantify how to use radiation emitted by molecular oxygen in the Martian atmosphere to measure the magnetic field from the crust of the planet. This crustal magnetic field is important to understand the past evolution of Mars. Our method can measure the magnetic field at lower altitudes than has so far been done, which could give important information on the characteristics of the crustal sources if a mission with the required instrument is launched.

For the first time the shape of noctilucent cloud particles is analyzed with a 3-D Lagrangian model. Three-color lidar measurements are compared directly to optical modeling of NLC simulations with non-spherical shapes: a mix of elongated and flattened cylindrical ice particles consistent with measurements. Comparison is best if flattened particles form a majority, with mean axis ratio around 2.8. NLCs from cylindrical particles are slightly brighter and consist of fewer but larger ice particle.