Ground-Based Observations of Clouds in the Arctic --
Implications for CloudSAT-related studies
Gijs de Boer (1)Edwin W. Eloranta (1), Gregory J. Tripoli (1), Jennifer Kay (2),
Matthew D. Shupe (3)
(1)(2)(3)
CloudSAT Science Team Meeting, Seattle, WA 19-21 August, 2008
CloudSAT Science Team Meeting, Seattle, WA 19-21 August, 2008
Introduction
Barrow9/04-11/04
Eureka8/05-present
70 N 80 N
CloudSAT Science Team Meeting, Seattle, WA 19-21 August, 2008
Introduction
Barrow9/04-11/04
Eureka8/05-present
1) Observation of Mixed-Phase Stratus clouds
70 N 80 N
CloudSAT Science Team Meeting, Seattle, WA 19-21 August, 2008
Introduction
Barrow9/04-11/04
Eureka8/05-present
1) Observation of Mixed-Phase Stratus clouds2) Representativeness of “point” comparisons
70 N 80 N
CloudSAT Science Team Meeting, Seattle, WA 19-21 August, 2008
Introduction: Mixed-Phase Stratus
Time (UT)
Alti
tude
(km
)
dar backscatter cross section (Masked values shown in black and white)
12:35 12:40 12:45 12:50 12:55
0.20.40.60.81.01.21.41.61.82.02.22.42.62.8
1D(m str)1e!8
1e!E
1e!6
1e!5
1e!4
1e!3
Li
CloudSAT Science Team Meeting, Seattle, WA 19-21 August, 2008
Introduction: Mixed-Phase Stratus
Time (UT)
Alti
tude
(km
)
Radar Reflectivity (Masked values shown in black and white)
12:35 12:40 12:45 12:50 12:55
0.20.40.60.81.01.21.41.61.82.02.22.42.62.8
dBZ
!40
!30
!20
!10
0
10
20
CloudSAT Science Team Meeting, Seattle, WA 19-21 August, 2008
Introduction: Mixed-Phase Stratus
• Low altitude stratus frequency of up to 70% during transition seasons (Herman and Goody, 1976; Curry et al., 1996)• Reduces wintertime net surface cooling by 40-50 W/m2 (Curry et al., 1996)• Commonly observed during several recent Arctic experiments (SHEBA, MPACE, SEARCH, ISDAC)• Often long-lived, surviving up to several days at a time (de Boer et al., 2008)• Difficult to simulate because of unstable state (Klein et al., 2008)
CloudSAT Science Team Meeting, Seattle, WA 19-21 August, 2008
Property Statistics
Time (UT)
)m
k( e
dutitl
A
13 14 15 16 17 18 19 20 21 22 23
1.0
2.0
3.0
4.0
Time (UT)
)m
k( e
dutitl
A
13 14 15 16 17 18 19 20 21 22 23
1.0
2.0
3.0
4.0
Single-layer mixed phase
stratus observations
- 216 hours from Barrow
- 1143 hours from Eureka
Cloud Height
Lon$itude (de$)
Altit
ude
(km
)
!88 !87.5 !87 !86.5 !86 !85.5 !85 !84.5 !84 !83.5
0.5
1
1.5
2
2.5
3
1e!5 1e!4 1e!3 1e!2 1e!1 1
!88 !87.5 !87 !86.5 !86 !85.5 !85 !84.5 !84 !83.50
500
1000
1500
2000
2500
3000
!3000 !2500 !2000 !1500 !1000 !500 0
CloudSAT Science Team Meeting, Seattle, WA 19-21 August, 2008
Cloud Height
0 1000 2000 3000 4000 50000
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Altitude (m)
Norm
aliz
ed #
Cloud Base Altitude (DJF)
200620072008
0 1000 2000 3000 4000 50000
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Altitude (m)
Norm
aliz
ed #
Cloud Base Altitude (JJA)
20052007
0 1000 2000 3000 4000 50000
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Altitude (m)
Norm
aliz
ed #
Cloud Base Altitude (MAM)
20062007
0 1000 2000 3000 4000 50000
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Altitude (m)
Norm
aliz
ed #
Cloud Base Altitude (SON)
2004200520062007
CloudSAT Science Team Meeting, Seattle, WA 19-21 August, 2008
CloudSAT Science Team Meeting, Seattle, WA 19-21 August, 2008
Cloud Thickness
CloudSAT Vertical Resolution: ~500 m
CloudSAT Science Team Meeting, Seattle, WA 19-21 August, 2008
Cloud Thickness
0 500 1000 1500 20000
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Thickness (m)
Norm
aliz
ed #
Cloud Thickness (DJF)
200620072008
0 500 1000 1500 20000
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Thickness (m)
Norm
aliz
ed #
Cloud Thickness (JJA)
20052007
0 500 1000 1500 20000
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Thickness (m)
Norm
aliz
ed #
Cloud Thickness (MAM)
20062007
0 500 1000 1500 20000
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Thickness (m)
Norm
aliz
ed #
Cloud Thickness (SON)
2004200520062007
CloudSAT Science Team Meeting, Seattle, WA 19-21 August, 2008
Cloud Mean Reflectivity
CloudSAT sensitivity: ~-29 dBZ
CloudSAT Science Team Meeting, Seattle, WA 19-21 August, 2008
Cloud Mean Reflectivity
!50 !40 !30 !20 !10 0 10 20 300
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Reflectivity (dBZ)
Nor
mal
ized
#Cloud Mean Reflectivity (DJF)
200620072008
!50 !40 !30 !20 !10 0 10 20 300
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Reflectivity (dBZ)
Nor
mal
ized
#
Cloud Mean Reflectivity (JJA)
20052007
!50 !40 !30 !20 !10 0 10 20 300
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Reflectivity (dBZ)
Nor
mal
ized
#
Cloud Mean Reflectivity (MAM)
20062007
!50 !40 !30 !20 !10 0 10 20 300
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Reflectivity (dBZ)
Norm
aliz
ed #
Cloud Mean Reflectivity (SON)
2004200520062007
CloudSAT Science Team Meeting, Seattle, WA 19-21 August, 2008
Precipitation Mean Reflectivity
!50 !40 !30 !20 !10 0 10 20 300
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Reflectivity (dBZ)
Nor
mal
ized
#Precipitation Mean Reflectivity (FGH)
200620072008
!50 !40 !30 !20 !10 0 10 20 300
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Reflectivity (dBZ)
Nor
mal
ized
#
Precipitation Mean Reflectivity (JJA)
20052007
!50 !40 !30 !20 !10 0 10 20 300
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Reflectivity (dBZ)
Nor
mal
ized
#
Precipitation Mean Reflectivity (MAM)
20062007
!!0 !40 !30 !20 !10 0 10 20 300
0.1
0.2
0.3
0.4
0.!
0.6
0.7
0.8
0.9
1
,e.lecti3it4 (789)
Norm
ali@
e7 #
PreciCitation Eean ,e.lecti3it4 (FGN)
2004200!20062007
CloudSAT Science Team Meeting, Seattle, WA 19-21 August, 2008
Cloud Temperature
Temperature range for mixed-phase clouds used in CloudSAT Radar-Only Microphysical Retrievals: -20-0 C
CloudSAT Science Team Meeting, Seattle, WA 19-21 August, 2008
Cloud Temperature
230 240 250 260 270 2800
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Temperature (K)
Norm
aliz
ed #
Cloud Minimum Temperature (DJF)
200620072008
230 240 250 260 270 2800
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Temperature (K)
Norm
aliz
ed #
Cloud Minimum Temperature (JJA)
20052007
230 240 250 260 270 2800
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Temperature (K)
Norm
aliz
ed #
Cloud Minimum Temperature (MAM)
20062007
230 240 250 260 270 2800
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Temperature (K)
Norm
aliz
ed #
Cloud Minimum Temperature (SON)
2004200520062007
CloudSAT Science Team Meeting, Seattle, WA 19-21 August, 2008
Summary #1
Single Layer Mixed-Phase Stratus
•Significant amounts have cloud bases <1000 m, particularly during transition seasons (MAM, SON)
• Low Reflectivities (<-30 dBZ) can often be found in the cloud layer, particularly during summer (JJA), when less ice is present
• Precipitation typically has reflectivities higher than -30 dBZ, but often falls within 1km of the surface
• Mixed-phase layer is often <500 m thick• Cloud minimum temperatures range from 0 to -40 C, with a maximum of occurrence at around -20 C.
CloudSAT Science Team Meeting, Seattle, WA 19-21 August, 2008
Introduction: Representativeness
CloudSAT Science Team Meeting, Seattle, WA 19-21 August, 2008
- Distance of overpass from ground site
Introduction: Representativeness
CloudSAT Science Team Meeting, Seattle, WA 19-21 August, 2008
}}}
- Distance of overpass from ground site
- Along-track averaging window
Introduction: Representativeness
Alt
itu
de
(k
m)
5:10 5:20 5:3 0 5:40 5:50
0.2
0.4
0.6
0.8
1.0
CloudSAT Science Team Meeting, Seattle, WA 19-21 August, 2008
- Distance of overpass from ground site
- Along-track averaging window
- Ground-based averaging window
Introduction: Representativeness
Alt
itu
de
(k
m)
5:10 5:20 5:3 0 5:40 5:50
0.2
0.4
0.6
0.8
1.0
CloudSAT Science Team Meeting, Seattle, WA 19-21 August, 2008
- Distance of overpass from ground site
- Along-track averaging window
- Ground-based averaging window
Introduction: Representativeness
- Wind Direction, etc.
Alt
itu
de
(k
m)
5:10 5:20 5:3 0 5:40 5:50
0.2
0.4
0.6
0.8
1.0
CloudSAT Science Team Meeting, Seattle, WA 19-21 August, 2008
- Distance of overpass from ground site
- Along-track averaging window
- Ground-based averaging window
Introduction: Representativeness
- 437 cases @ <50km- 181 cases @ <20km
- Wind Direction, etc.
CloudSAT Science Team Meeting, Seattle, WA 19-21 August, 2008(CloudSAT data from Jennifer Kay)
0 5 10 15 20 25 30 350
5000
10000
15000
Cloud Fraction (%)
Altit
ude
(m)
CloudSAT 10kmCloudSAT 5kmMMCR 5min
Overpasses<50 km
Ground Track Averaging Interval
CloudSAT Science Team Meeting, Seattle, WA 19-21 August, 2008(CloudSAT data from Jennifer Kay)
0 5 10 15 20 25 30 350
5000
10000
15000
Cloud Fraction (%)
Altit
ude
(m)
CloudSAT 10kmCloudSAT 5kmMMCR 5min
Overpasses<50 km
Ground Track Averaging Interval
CloudSAT Science Team Meeting, Seattle, WA 19-21 August, 2008
Ground-Based Averaging Interval
!0.6 !0.4 !0.2 0 0.2 0.40
5000
10000
15000
() +i--e/en1e (3)
Alti
tude
(m)
5 minute4 miniute3 minute2minute
0 5 10 15 20 25 30 350
5000
10000
15000
Cloud Fraction (%)
Altit
ude
(m)
CloudSAT 10kmCloudSAT 5kmMMCR 5min
CloudSAT Science Team Meeting, Seattle, WA 19-21 August, 2008
Overpass Distance
Overpasses<20 km(CloudSAT data from Jennifer Kay)
CloudSAT Science Team Meeting, Seattle, WA 19-21 August, 2008
Summary #2
Single Location Comparison
• Some significant differences (up to ~5%) exist between original CloudSAT and ground-based estimates. • Ground-based and along track averaging intervals seem to have little effect on cloud-fraction calculation (within reason)• Overpass distance considered has significant effect• Future work will broaden this topic to come up with statistical analysis on how representative “point” comparisons are for different distances, averaging intervals, etc.
CloudSAT Science Team Meeting, Seattle, WA 19-21 August, 2008
ReferencesCurry, J.A., W.B. Rossow, D. Randall and J.L. Schramm (1996), Overview of Arctic Cloud and
Radiation Characteristics. J. Climate, 9, 1731-1764.de Boer, G., E.W. Eloranta and M.D. Shupe (2008), Arctic Mixed-Phase Stratus Properties from
Multiple Years of Surface-Based Measurements at Two High-Latitude Locations. In Preparation.Herman, G., and R. Goody (1976), Formation and Persistence of Summertime Arctic Clouds. J.
Atmos. Sci., 33, 1537-1553.Klein, S.A., R. McCoy, H. Morrison, A. Ackerman, A. Avramov, G. de Boer, M. Chen, J. Cole, A.D.
DelGenio, M. Falk, M. Foster, A. Fridlind, J.-C. Golaz, T. Hashino, J. Harrington, C. Hoose, M. Khairoutdinov, V. Larson, X. Liu, Y. Luo, G. McFarquhar, S. Menon, R. Neggers, S. Park, K. von Salzen, J.M. Schmidt, I. Sednev, B. Shipway, M. Shupe, D. Spangenberg, Y. Sud, D. Turner, D. Veron, G. Walker, Z. Wang, A. Wolf, S. Xie, K.-M. Xu, F. Yang, and G. Zhang (2008), Intercomparison of model simulations of mixed-phase clouds observed during the ARM Mixed-Phase Arctic Cloud Experiment. Part I: Single layer cloud. Submitted to the Quarterly Journal of the Royal Meteorological Society.
EXTRA SLIDES
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WMO Cloud Modeling Workshop, Cozumel, Mexico--14-17 July 2008
CloudSAT Science Team Meeting, Seattle, WA 19-21 August, 2008
2B-RO Microphysical Retrievals
1.0
3.0
2.0
4.0
1.0
3.0
2.0
4.0
1.0
3.0
2.0
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2.0
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Radar Reflectivity (Liquid Cloud Shown by Gray Shading)
Alt
itu
de
(k
m)
dBZ
!35
!30
!25
!20
!15
!10
!5
0
5
10
10 Minutes
30 October 2006
17 December 2006
16 August 2007
23 August 2007
2 November 2007
10!1
100
101
102
103
104
105
106
10!1
100
101
102
103
104
105
106
N (CloudSAT Liquid Composite)
100
101
102
103
100
101
102
103
Reff (CloudSAT Liquid Composite)
10!1
100
101
102
103
10!1
100
101
102
103
Water Content (CloudSAT Liquid Composite)
10!1
100
101
102
103
10!1
100
101
102
103
Water Content (CloudSAT Ice Composite)
100
101
102
103
100
101
102
103
Reff (CloudSAT Ice Composite)
10!1
100
101
102
103
104
105
106
10!1
100
101
102
103
104
105
106
N (CloudSAT Ice Composite)
10 10 10 10 1010
100
101
102
103
10 10 10 10 1010
100
101
102
103
10
10
10
10
10 100
101
102
103
104
105
106
10
100
101
102
103
104
105
106
CloudSAT Science Team Meeting, Seattle, WA 19-21 August, 2008
Cloud Maximum Reflectivity
!50 !40 !30 !20 !10 0 10 20 300
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Reflectivity (dBZ)
Nor
mal
ized
#Cloud MaE Reflectivity (FJH)
200620072008
!50 !40 !30 !20 !10 0 10 20 300
0.1
0.2
0.3
0.4
0.5
0.6
0.)
0.8
0.9
1
,e.lecti3it4 (dB9)
;or
mal
i@ed
A
Bloud DaE ,e.lecti3it4 (FFA)
2005200)
!50 !40 !30 !20 !10 0 10 20 300
0.1
0.2
0.3
0.4
0.5
0.6
0.)
0.8
0.9
1
,eflecti3ity 6d89:
;or
mal
i@ed
A
Cloud MaE ,eflecti3ity 6MFM:
2006200)
!!0 !40 !$0 !20 !10 0 10 20 $00
0.1
0.2
0.$
0.4
0.!
0.(
0.)
0.*
0.+
1
,eflectivity 6d89:
Norm
ali@
ed A
Cloud Dax ,eflectivity 6FGN:
2004200!200(200)
CloudSAT Science Team Meeting, Seattle, WA 19-21 August, 2008
Precipitation Maximum Reflectivity
!50 !40 !30 !20 !10 0 10 20 300
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Reflectivity (dBZ)
Nor
mal
ized
#Precipitation MaF Reflectivity (GHI)
200620072008
!50 !40 !30 !20 !10 0 10 20 300
0.1
0.2
0.3
0.4
0.5
0.6
0.)
0.8
0.+
1
,e.lectivity (d89)
Nor
mal
i@ed
A
BreciCitation MaF ,e.lectivity (GGA)
2005200)
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P=eciCi1a1i<n Max ,e.lec1i3i1y 6MAM:
%""(%"")
!50 !40 !30 !20 !10 0 10 20 300
0.1
0.2
0.3
0.4
0.5
0.6
0.)
0.8
0.9
1
Re.lectivit4 (dB9)
;orm
ali@
ed A
BreciCitation MaF Re.lectivit4 (SH;)
200420052006200)
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