I. Highlights, including authors and their institutions
The following highlights summarize research papers in Geophysical Research Letters (GL). The papers related to these Highlights are printed in the next paper issue of the journal following their electronic publication.
1. Evidence for unique particle distribution in noctilucent clouds
The first observations of the ultraviolet spectrum within polar mesospheric clouds may provide a clue to explain a mysterious "hump" previously seen within the cloud's spectrum. (The mesosphere ranges from 30 to 80 kilometers [20 to 50 miles] in altitude.) Carbary et al. analyzed satellite spectrographic images and were able to separate the particle scattering and distribution within the high-latitude clouds. The authors identified an unexpected hump in the clouds' middle spectrum that suggests that particles are separated into two distinct groups within the clouds. They report that the separation corresponds with previous observations indicating that smaller particles within the clouds fall in a sedimentation-like process to the lower portions of the cloud while larger particles remain at its top. They also propose that atmospheric gravity and tidal waves likely contribute to the two distinct sides of the noctilucent clouds [i.e., clouds that glow at night]. The new observations lend credence to the unique bi-modal distribution of particles within the clouds.
Title: Evidence for bimodal particle distribution from the spectra of polar mesospheric clouds
James Carbary, D. Morrison, G. J. Romick, Applied Physics Laboratory, Johns Hopkins University, Laurel, Maryland, USA.
Source: Geophysical Research Letters (GL) paper 10.1029/2004GL020101, 2004