SA14A-01 INVITED
PMC Measurements from the Solar Occultation For Ice Experiment (SOFIE)
The Solar Occultation For Ice Experiment (SOFIE) was launched onboard the Aeronomy of Ice in the Mesosphere (AIM) satellite to measure polar mesospheric clouds (PMCs) and the environment in which they form. SOFIE measurements are used to retrieve vertical profiles of temperature, O3, H2O, CO2, CH4, NO, and PMC extinction at 11 wavelengths from 0.33 to 5 microns. SOFIE offers unprecedented sensitivity to PMCs, and is able to detect clouds that are from 30 to 100 times dimmer than could be observed by previous satellite and ground based instruments. SOFIE PMC measurements are used to characterize the altitude dependence of particle shape, ice mass density, and particle size. This work describes results using PMC measurements from the 2007 northern polar summer. http://sofie.gats-inc.com
SA14A-02
The properties of noctilucent clouds particles above ALOMAR
The ALOMAR RMR-lidar located in Northern Norway at 69N is capable to observe noctilucent clouds (NLC) with three widely separated wavelengths (355nm, 532nm, 1064nm) since 1998. From the three color backscatter coefficients we can deduce the number density, size, and the width of the size distribution of the particles in the volume observed. The analysis procedure includes spherical and non spherical particles and is not affected by the unknown particle shape. The lidar sounds the clouds with a vertical resolution of about 150 m and allows to study the vertical variation of the particle properties. The vertical structure of NLC gives a unique chance to investigate the particle evaluation and test the micro physical parameterization in cloud models and our understanding of the particle growth process. For a statistical treatment the clouds are separated vertically into the peak layer and an upper and lower layer. We will present results on the mean vertical structure of particle properties, investigating the astonishing fact that the largest mean particle sizes are found below the peak of the layer, where one would expect the particles to melt. We compare the observations to the 3-d LIMA-ICE cloud model including the variability of the ambient atmosphere. Additionally we will investigate year to year variations of particle properties at the peak of the layer and cloud properties like the volume density and estimated ice mass.
SA14A-03
The Solar Occultation for Ice Experiment (SOFIE): In-Orbit Performance and Initial Results
The SOFIE instrument was launched on-board the AIM (Aeronomy of Ice in the Mesosphere) satellite on April 25, 2007. SOFIE provides measurements for the study of Polar Mesospheric Clouds (PMCs) that appear near 83km, just below the high latitude summer mesopause. The instrument has now operated nominally through the first northern hemisphere PMC season. SOFIE is designed to measure broadband transmission to extremely high precision (<10e-5), to obtain relative tangent altitude knowledge to high precision (sample spacing error ~ 1 meter), and to measure refraction bending angles to unprecedented accuracy (~ 0.1 arc second). Initial success in achieving these measurements and converting them to profiles of temperature, pressure, water vapor, ozone, methane, nitric oxide, carbon dioxide and ice extinction will be presented.
SA14A-04
Measurements of the Atmospheric Temperature Within a PMC
The OSIRIS instrument on the Odin satellite provides observations of both the airglow and the scattered sunlight limb spectra, over the wavelength range 280 – 810 nm. While the recorded spectra only have a 1 nm resolution it is possible to identify many highly structured emissions in the measured spectra. These spectra also contain the unambiguous signature of the PMCs. The spectrograph observations within these clouds also provide clear measurements of the oxygen atmospheric A-, B- and g-bands that can be used to provide common volume information of temperature and cloud brightness. In this paper we present some of the initial estimates of the atmospheric temperature within PMCs derived from the OSIRIS PMC observations.
SA14A-05 INVITED
Initial results of global imaging of PMCs from the CIPS experiment on the AIM satellite
The Aeronomy of Ice in the Mesosphere (AIM) spacecraft was launched into sun-synchronous orbit April 25, 2007. The objectives of AIM are to study why polar mesospheric clouds (PMCs) form and why they vary. One of the three instruments on AIM is the Cloud Imaging and Particle Size (CIPS) experiment. We will describe the CIPS instrument; a 4 camera wide-field UV imager designed to measure PMC morphology and particle properties. We will present the first science results from CIPS including new PMC features, particle size, and ice content. The CIPS images show oval cloud features with thin bright walls with dimmer clouds inside with sizes that vary from a few 10's of km to hundreds of km; very bright, spatially small (~10 km radius) clouds; and large (~10,000 sq. km) regions with no clouds present in the heart of the cloud season.
SA14A-06
Retrieval of PMC Scattering Phase Functions from Observations by the Cloud Imaging and Particle Size Experiment on the Aeronomy of Ice in the Mesosphere Explorer
The Cloud Imaging and Particle Size (CIPS) instrument on the AIM spacecraft is a 4-camera nadir pointed imager with a bandpass centered at 265 nm and a field of view of 120 by 80 degrees. CIPS observes Polar Mesospheric Clouds (PMCs) against the sunlit Rayleigh-scattered background. At individual polar locations approximately 5km by 5km in area, CIPS observes the same volume of air seven times over a range of scattering angles from about 35 to 150 degrees. These multi-angle observations allow the identification and extraction of the PMC scattered radiance from the Rayleigh-scattered background. The former has a highly asymmetric phase function about 90 degrees scattering angle, while the latter has a phase function that is symmetric about 90 degrees scattering angle. The retrieved PMC phase function can then be interpreted to obtain PMC particle size distributions as well as the PMC absolute albedo. We describe the technique for identification of PMC in the CIPS observations, the separation of the Rayleigh and PMC radiances, and the PMC phase function results from the first season of CIPS observations.
SA14A-07
Mesospheric Ice Mass determined from the AIM CIPS imaging experiment
The NASA Aeronomy of Ice in the Mesosphere satellite (AIM) was launched into a sun-synchronous orbit on April 25, 2007. The primary mission of AIM is to determine how Polar Mesospheric Clouds (PMC) are formed and how they evolve. One of the three instruments on board is a panoramic UV camera (the Cloud Imaging and Particle Size or CIPS experiment) designed to measure PMC structures at high (5 km) spatial resolution. The CIPS observing strategy provides images of the same cloud at up to 7 scattering angles. A major objective of AIM is to derive particle sizes and ice content of PMC. Given the PMC brightness at various scattering angles, we employ a method first used by Englert and Stephens to derive the column ice mass. The method uses the approximation of a power-law dependence of the scattering cross-section versus particle size r. The dependence varies from r6 at small scattering angles to r3 at large scattering angles. We call this a "moment method" since the scattered radiance is proportional (with an error up to 25 percent) to a moment of the size distribution. In particular, a measurement at a scattering angle of 115o is approximately a measurement of the third moment of the size distribution, in other words, is directly proportional to the total (columnar) ice particle volume. The method makes no assumptions about the particle radius (except that it is in the range of 30-100 nm), distribution width, or even to particle non-sphericity, as long as the crystals are not too elongated or flattened. We will derive maps of PMC ice mass for selected days, and compare with previous estimates of this important quantity for understanding PMC microphysics.
SA14A-08
Mesospheric planetary wave activity inferred from AIM-CIPS and TIMED-SABER for the northern summer 2007 PMC season
The Cloud Imaging and Particle Size (CIPS) instrument on the Aeronomy of Ice in the Mesosphere (AIM) satellite observed Polar Mesospheric Clouds (PMC) during the 2007 Northern hemisphere (NH) summer. The CIPS instrument provides detailed images of PMC occurrence and brightness. Daily global composites of the cloud images show an apparent clockwise zonal motion of the clouds indicating forcing from planetary waves. Planetary wave activity has been detected in previous coincident PMC/temperature observations including a 5-day and 2-day planetary wave in SNOE PMC data that strongly correlates with the same wave features in SABER temperature data. This indicates temperature as an important forcing mechanism in global variability of PMCs. Observations of the seasonal morphology of CIPS PMC occurrence and brightness correlate well with the day-to- day zonal mean changes in SABER temperature. We will present a first look at the observed planetary wave variance in CIPS observations of PMCs with a comparison to the planetary wave activity in the SABER 2007 temperature data.