Laser Radar (LIDAR) Measurements of Ozone, Water Vapour, Temperature and Clouds
Dr. Robert Sica and his merry band *
*
Department of Physics and Astronomy, University of Western Ontario
Merry band, Jan ‘08:
About the Purple Crow LIDAR
Clouds and Pyro-Convective Layers
The Purple Crow LIDAR (PCL) is a laser radar which has been in operation since
1992 from the Delaware Observatory, a University of Western Ontario research
facility near London, Canada (42.87° N, 81.38° W, 225 m elevation). It consists of a
vertically-pointing laser, a co-axial mirror-telescope and a multi-wavelength detector
system. The PCL operates at night and is able to measure the vertical structure of
density, pressure, temperature and water vapour throughout the atmosphere. These
measurements help us to better understand the complex processes occurring in the
atmosphere – improving our ability to predict the weather and chart global warming.
While the PCL is primarily designed for use in the
middle-upper atmosphere, recent work has been
able to calibrate low-level returns to measure clouds
and lofted smoke layers in the lower stratosphere.
These layers are injected into high altitudes from
intense rising heat cells similar to thunderclouds
(“PyroCB” events) that are produced by hot-burning
forest fires.
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Paul Doucet
Blessing Iserhienhien
Andy Moss
Thamer Alrefay
Emily McCullough
June ‘02
By contributing to the detection and measurement of
these layers, the PCL is helping to understand the
impact of aerosol loading in global climate modeling
– currently one of the biggest uncertainties.
ACE Satellite Comparison - Temperatures
The Atmospheric Chemistry Experiment (ACE) is
a Canadian satellite mission for the remote sensing
of the Earth's atmosphere with a Fourier Transform
Spectrometer and a Spectrophotometer using solar
occultation techniques.
The powerful laser emits pulses of light as bright
as simultaneously turning on 1 million 75 W light
bulbs!
The PCL
is well-suited for comparison and
validation of ACE temperature measurements
particularly at high altitudes due to its high poweraperture product.
Coincidental ACE satellite and PCL measurements
are shown on this plot with good agreement
between 10-75 km.
Black line - ACE-FTS
Red line - Purple Crow LIDAR
Cloud…
Gravity Waves
Water Vapour - Eureka
The University of Western Ontario is involved with
the Canadian Network for the Detection of
Atmospheric Change (CANDAC), a network of
university and government scientists who
specialize in various areas of atmospheric
research and make measurements at the Polar
Environment Atmospheric Research Laboratory
(PEARL), Zero Altitude PEARL Auxiliary
Laboratory (0PAL), and the Surface and
Atmospheric Flux, Irradiance and Radiation
Extension (SAFIRE) facilities at Eureka, Nunavut.
As part of this project, a UWO graduate student
will be traveling to Eureka this year to use a
stratospheric LIDAR to take water vapour
measurements of the dry arctic atmosphere.
…Layer!
A gravity wave (or buoyancy wave) is an oscillation
caused by the displacement of an air parcel which
is restored to its initial position by gravity. Clouds
sometimes form in regular bands across the sky as
a result of gravity waves. Gravity waves carry
momentum and energy from the troposphere to the
middle and upper atmosphere and are responsible
for the large departure of the former from radiative
equilibrium.
Research with the PCL has found that the bulk of
the energy is carried by a small, discreet set of
waves.
Student Opportunities
The laser light reflects off air molecules and
small particles, such as water droplets in clouds.
The reflected light is collected by a large
telescope formed by rotating liquid mercury at
10 rpm in a 2.65 m diameter container.
•
Study opportunities at Delaware Observatory: Operate the Purple
Crow LIDAR during evenings throughout the year.
•
Graduate Studies: Masters and Ph.D. programs studying
atmospheric physics at Delaware Observatory just outside
London, Ontario or in Eureka, Nunavut.
http://pcl.physics.uwo.ca