Evaluation of Cloud-Radiation

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3 Νοε 2013 (πριν από 3 χρόνια και 11 μήνες)

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Evaluation of Cloud
-
Radiation
Interaction in the Canadian
GEM Model Using ARM
Observations

Danahé Paquin
-
Ricard
1

Colin Jones
1
, Paul Vaillancourt
2

1. CRCMD, UQAM

2. Environment Canada

Source:http://www.cs.pitt.edu/

Why the cloud
-
radiation interaction ?

Cloud
-
Radiation Interaction



Microphysics Macrophysics Environment



Precipitation


Surface Radiation Budget


Diurnal cycle of SWD & LWD, for summer & winter (SGP)


LWP, winter (SGP)


LWP at SGP vs. NSA

Model & Observations


GEM:


Prognostic total cloud water


Lateral boundary conditions: ERA40


Prescribed SSTs and ice fraction


Horizontal resolution ≈ 42km


time step 30 min



Observations:


ARM
-
SGP site: 37
°
N, 97
°
W, 318 m


ARM
-
NSA site: 71
°
N, 157
°
W


Microwave radiometer, tipping bucket,
radiometers …



Average over 3h period for all variables
(except precipitation: 3h accumulation) over 7
years (1998
-
2004)


LWP & IWV: removed when precipitation ≥
0,25mm/3h



SGP

NSA

Shortwave Down, Summer (SGP)

SZA≤30
°

30
°
<SZA≤60
°

Longwave Down, Summer (SGP)

Source: Bernard Dugas

Shortwave Down, Winter (SGP)

Longwave Down, Winter (SGP)


Overestimate of clear
-
sky occurrences


Precipitation too frequently triggered at too low LWP


Incorrect separation of cloud water between liquid & ice

*10

LWP (without precip.), Winter (SGP)

*10

*10

*10

*10

LWP (without precip.), SGP

LWP (without precip.),
NSA

Underestimate of LWP


LWD & SWD

SGP


NSA

JJA SON DJF MAM

SGP


NSA

Summary for SGP

Overestimate of light precipitation


Underestimate of

LWP, IWV & cloud fraction


Underestimate of


Overestimate of

LWD




SWD




Warm & dry bias



Overestimate of


Underestimate of

LWD for JJA


convection

Possible corrections to the microphysics scheme (autocon
-
version) to reduce light precipitation…

Thank you!

Source:http://www.cs.pitt.edu/

More SGP LWD

More SGP SWD

More NSA LWD

More NSA SWD

Cloud Fraction & Integrated Water Vapor