university of wisconsin lidar group - ground-based...

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


Introduction

Barrow9/04-11/04

Eureka8/05-present

70 N 80 N


Introduction

Barrow9/04-11/04

Eureka8/05-present

1) Observation of Mixed-Phase Stratus clouds

70 N 80 N


Introduction

Barrow9/04-11/04

Eureka8/05-present

1) Observation of Mixed-Phase Stratus clouds2) Representativeness of “point” comparisons

70 N 80 N


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



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



• 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)


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


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



Cloud Thickness

CloudSAT Vertical Resolution: ~500 m


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


Cloud Mean Reflectivity

CloudSAT sensitivity: ~-29 dBZ


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


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


Cloud Temperature

Temperature range for mixed-phase clouds used in CloudSAT Radar-Only Microphysical Retrievals: -20-0 C


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


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.


Introduction: Representativeness


- Distance of overpass from ground site



}}}


- Along-track averaging window


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




- Ground-based averaging window


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






- 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






- 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


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


Overpass Distance

Overpasses<20 km(CloudSAT data from Jennifer Kay)


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.


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


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

1.0

3.0

2.0

1.0

3.0

2.0

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


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)


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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,e.lec1i3i1y 6789:

;<=

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ize7

A

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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