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Hong Guan
,
André Tremblay
,
George A. Isaac
,
Kevin B. Strawbridge
, and
Catharine M. Banic

Abstract

The three-dimensional Canadian Mesoscale Compressible Community model has been run at high resolution (Δx = 2 km, Δz = 50 m) to simulate stratus clouds observed on 1 September 1995 during the Radiation, Aerosol and Cloud Experiment (RACE) conducted near the Bay of Fundy, Canada. A new explicit cloud scheme and the Canadian operational radiation scheme were validated at this resolution for the first time. The simulations show a reasonable agreement between the observed and modeled stratus cloud system. The cloud structure, position, cloud water content, temperature, and the qualitative properties of longwave and shortwave radiative fluxes were verified against the satellite imagery, lidar, and aircraft measurements taken during RACE. The simulated cloud thickness (∼150 m) was thinner than the observed one (200–250 m). The differences in the simulated and observed radiative fluxes were mainly due to errors in the simulation of cloud thickness. Sensitivity experiments demonstrate that the simulated cloud is extremely sensitive to longwave and shortwave radiation. Longwave (shortwave) radiation substantially increased (decreased) the total water path.

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John P. Gallagher
,
Ian G. McKendry
,
Paul W. Cottle
,
Anne Marie Macdonald
,
W. Richard Leaitch
, and
Kevin Strawbridge

Abstract

A ground-based lidar system that has been deployed in Whistler, British Columbia, Canada, since the spring of 2010 provides a means of evaluating vertical aerosol structure in a mountainous environment. This information is used to help to determine when an air chemistry observatory atop Whistler Mountain (2182 m MSL) is within the free troposphere or is influenced by the valley-based planetary boundary layer (PBL). Three case studies are presented in which 1-day time series images of backscatter data from the lidar are analyzed along with concurrent meteorological and air-chemistry datasets from the mountaintop site. The cases were selected to illustrate different scenarios of diurnal PBL evolution that are expected to be common during their respective seasons. The lidar images corroborate assumptions about PBL influence as derived from analysis of diurnal trends in water vapor, condensation nuclei, and ozone. Use of all of these datasets together bolsters efforts to determine which atmospheric layer the site best represents, which is important when evaluating the provenance of air samples.

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John P. Gallagher
,
Ian G. McKendry
,
Kevin Strawbridge
,
Anne Marie Macdonald
,
W. Richard Leaitch
, and
Paul W. Cottle
Full access
Paul Joe
,
Stella Melo
,
William R. Burrows
,
Barbara Casati
,
Robert W. Crawford
,
Armin Deghan
,
Gabrielle Gascon
,
Zen Mariani
,
Jason Milbrandt
, and
Kevin Strawbridge
Full access
Paul Joe
,
Stella Melo
,
William R. Burrows
,
Barbara Casati
,
Robert W. Crawford
,
Armin Deghan
,
Gabrielle Gascon
,
Zen Mariani
,
Jason Milbrandt
, and
Kevin Strawbridge

Abstract

The goal of the Canadian Arctic Weather Science (CAWS) project is to conduct research into the future operational monitoring and forecasting programs of Environment and Climate Change Canada in the Arctic where increased economic and recreational activities are expected with enhanced transportation and search and rescue requirements. Due to cost, remoteness and vast geographical coverage, the future monitoring concept includes a combination of space-based observations, sparse in situ surface measurements, and advanced reference sites. A prototype reference site has been established at Iqaluit, Nunavut (63°45'N, 68°33'W), that includes a Ka-band radar, water vapor lidars (both in-house and commercial versions), multiple Doppler lidars, ceilometers, radiation flux, and precipitation sensors. The scope of the project includes understanding of the polar processes, evaluating new technologies, validation of satellite products, validation of numerical weather prediction systems, development of warning products, and communication of their risk to a variety of users. This contribution will provide an overview of the CAWS project to show some preliminary results and to encourage collaborations.

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