Precipitation types and atmospheric conditions in complex terrain

Precipitation types and atmospheric conditions in complex terrain

Precipitation types and atmospheric
conditions in complex terrain
Julie M. Thériault
Université du Québec à Montréal
and
CCRN Third Annual General Meeting
Tuesday 3 November 2015
[email protected]
CCRN Third Annual General Meeting
UQAM
1
Summary of my activities in CCRN
1
Finished on going projects :
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2
Co-organized and conducted a mountain precipitation field experiment
in the Kananaskis area [Ronald Stewart and John Pomeroy]
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3
On the impact of snowflake types on the precipitation reaching the
surface
→ Housseyni Sankare, MSc Thesis, July 2015
On the precipitation occurrences during the Alberta flooding event
→ Submission of 3 journal articles : Liu et al (2015), Kochtubajda et al
(2015) and Li et al (2015)
Characterized precipitation types, rain-snow transitions and
atmospheric conditions
Investigated the microphysical processes associated with the rain-snow
transition during the Alberta flooding event
[email protected]
CCRN Third Annual General Meeting
UQAM
2
Overview of the field project
Objectives
To better document and understand precipitation and associated
atmospheric conditions in the Kananaskis area during the spring season
(March-April 2015).
• What are the types of precipitation observed ?
• What are the associated weather conditions aloft and at the surface ?
Approach
• To deploy instruments and collect detailed observations of
precipitation types and weather conditions in the Kananaskis Valley
• To analyze data collected in the field and to conduct numerical
simulations of selected case studies.
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Field project in the Kananaskis Valley
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Data collected at Fortress Mountain
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Temporal evolution of weather conditions at the surface
Type of events [# events] : Rain [4] Mixed precipitation [4] Snow [10]
• Temperature varied around 0◦ C
• Relative humidity varied from 20% to 95% during precipitation events
• Temporal evolution of precipitation type varied during the project
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Link among precipitation types, temperature and relative
humidity
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• Precipitation associated with dry
conditions
• Most of the solid particles were
rimed particles
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[Poster from Ida Hung]
• Mixed precipitation often reported
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Questions
• What is the relationship among the precipitation characteristics, atmospheric
conditions at KES and the large-scale flow field ?
[See poster from Paul Vaquer]
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Mixed phase precipitation event - 31 March 2015
• Combinations of rain and wet snow have been recorded at the surface (KES)
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• The
0◦ C-isotherm
is approximately 700 m higher than Zbright−band
• The radar bright-band is slightly below the height of Tw = 0◦ C
Questions
• What are the impacts of sublimation/accretion on the types of precipitation
reaching the surface and on rain-snow transitions ?
[See poster from Émilie Poirier]
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CCRN Third Annual General Meeting
UQAM
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Precipitation types at the surface
• Particle characteristics from 2200 to 2220 UTC
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• Particle types changed and mean diameter decreased
• Estimated fraction of liquid drops → 55% to 95%
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CCRN Third Annual General Meeting
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Summary
• 18 weather events were documented during March-April 2015 in the
Kananaskis area
• Temperatures were mainly near 0◦ C and dry conditions occurred during the
events documented
• Combinations of precipitation types were often observed and varied during a
single weather event
• Solid precipitation reached the surface at T>8◦ C
• The role of accretion is often critical and acts to increase amount of
precipitation reaching the surface in dry near-surface conditions
Overall, the preliminary analysis highlighted the importance to improve our
understanding of the precipitation processes and associated atmospheric
conditions in the Kananaskis area.
[email protected]
CCRN Third Annual General Meeting
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Thank you to all the participants !
Ron Stewart, John Pomeroy, Ida Hung, Juris Almonte,
Émilie Poirier, Paul Vaquer, Stephen Berg, Émilie Bresson,
Mélissa Cholette, Dominic Matte, Housseyni Sankare, Lucia
Scaff, May Guan, Angus Duncan, Craig Smith, Bruce Cole,
Scott Landolt, Al Jachick, the Biogeoscience Institute, the
firefighters at KES, Nakiska ski area, Fortress Mountain
people.
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CCRN Third Annual General Meeting
UQAM
11