The Mesospheric Metal Layers

Resonance lidar studies of the mesospheric sodium and iron layers have been on an ongoing basis at Poker Flat Research Range (PFRR), Chatanika, Alaska (65N, 147W) since 1995. The observations have supported studies of the seasonal cycle of the mesospheric metal layers, sporadic metal layers, and waves and tidal activity in the mesopause region (~75-115 km). The figure shows a false color image of the sodium concentration as a function of time and altitude. The color runs from black (minimum 0 atoms/cm3) to yellow (several thousand atom/cm3). Downward phase progressions associated with upwardly propagating waves are clearly visible. The overturning structures are associated with nonlinear wave activity.

The Auroral Thermosphere

Resonance lidar systems have the potential to probe the molecular spectroscopy of aurorally excited species in the thermosphere. These lidar systems would extend the scope off lidar measurements into the E- and F-regions and provide measurements of the N2+ profile from ~100-250 km. The lidar measurements could be combined with common volume incoherent scatter radar measurements of the total ion density to yield estimates of other auroral ionic and neutral species (e.g. O2+, NO+, NO). The figure shows the expected lidar signals from a design study based on photometric observations of the aurora plotted as function of altitude. A prototype system is currently under development at Poker Flat Research Range (PFRR), Chatanika, Alaska (65N, 147W).

The Advanced Modular Incoherent Scatter Radar

The Advanced Modular Incoherent Scatter Radar (AMISR) is a new ISR that employs modular solid-state and phased-array technologies and will yield measurements of the upper atmosphere and ionosphere with unprecedented versatility and power. This radar represents a new generation of ISRs for thermospheric research. The figure shows an artists representation of the AMISR facility. The first AMISR, the Poker Flat ISR (PFISR) is deployed at Poker Flat Research Range (PFRR), Chatanika, Alaska (65N, 147W) to investigate auroral processes. The AMISR facility establishes a new state-of-the-art for IS radar design by implementing fully electronic beam steering with a phased array of 4096 UHF transceivers. This beam pointing capability is available on a pulse-by-pulse basis.

Thermal Structure of the Stratosphere and Mesosphere

Rayleigh lidar studies have been ongoing at Poker Flat Research Range (PFRR), Chatanika, Alaska (65N, 147W) since 1997. These studies have been carried out collaboratively between the Geophysical Institute of the University of Alaska Fairbanks and the National Institute of Information and Communications Technology. The figure shows temperature profiles measured by the lidar (red solid), SABER instrument on the TIMED satellite (black dash), SPARC Climatology (green dash) and the MSIS model (blue dash). A mesospheric inversion layer (MIL) (~ 60 km) is seen above the stratopause (~50 km). The difference between the lidar and SABER measurements and the SPARC and MSIS profiles reflects strong planetary wave activity in the Arctic stratosphere. Ongoing studies aare being conducted in collaboration with reseachers at North West Reseach associates and the University of Colorado.

The Arctic Mesospause Region in Summer

Noctilucent clouds have been measured with lidar at Poker Flat Research Range (PFRR), Chatanika, Alaska (65N, 147W) since 1998. These studies have been carried out collaboratively between the Geophysical Institute of the University of Alaska Fairbanks and the National Institute of Information and Communications Technology. These clouds have been detected from early August through mid-August. The observations at PFRR confirm the view that the summer Arctic mesosphere is colder and wetter than represented in standard models. The figure shows a false-color image of a noctilucent cloud echo as a function of time and altitude. The evolution of the cloud shows wave perturbations. Wave activity is important in determining the structure of these clouds.

The Fourth International Polar Year

Pan-Arctic Study of the Stratospheric and Mesospheric Circulation (PASSMec) is a comprehensive observational and modeling study of the Arctic stratosphere and mesosphere during the International Polar Year. The observational study will include radiosonde, lidar and satellite measurements of the troposphere, stratosphere and mesosphere. The figure shows the location of a network of Arctic Rayleigh lidars in the PASSMeC study. The four lidar sites are; Poker Flat Research Range (PFRR), Eureka Stratospheric Observatory (ESO), Sondrestrom Upper Atmospheric Research Facility (SUARF), and Arctic Lidar Observatory for Middle Atmosphere Research (ALOMAR). Yellow boundary shows the Arctic Monitoring and Assessment Boundary

Tropospheric Aerosols

Lidars have been employed at Poker Flat Research Range (PFRR), Chatanika, Alaska (65N, 147W) to study wildfire smoke. In 1999 during the FROSTFIRE experiment, lidars provided measurements of the vertical distribution of nighttime smoke. The variation of the smoke aloft (measured by the lidar) relative to that near the surface (measured by tethersonde) revealed the influence of the nighttime inversion on the smoldering biomass smoke. The figure shows the integrated lidar signal plotted as a function of altitude during the FROSTFIRE experiment (red solid). The estimated clear sky profile (green dashed) is also plotted and shows the presence of clouds and smoke. Based on these earlier experiments, eyesafe lidar systems are under development to support more advanced studies of aerosols.


Richard Collins rlc@gi.alaska.edu