Comparison of RUC Cloud Analyses and Forecasts with Satellite-derived Cloud Properties

NASA Langley Research Center / Atmospheric Sciences

Comparison of RUC Cloud Analyses and Forecasts with

Satellite-derived Cloud Properties

Bill Smith, Patrick MinnisNASA LaRC

Stan Benjamin, Steve WeygandtNOAA/ESRL/GSD/AMD


Outline

• Recent satellite validation (GOES Cloud height, water path)

• Statistical Comparisons (several months)– Cloud Amount– Cloud Height– Cloud Thickness– Cloud Water Path

• Summary

Goal: Perform statistical comparison between RUC and LaRC satellite-derived cloud properties to help guide the assimilation of satellite cloud parameters and provide baseline for future model evaluations.


Satellite Data• NASA LaRC Real-Time 8-km CONUS cloud products

derived from GOES-E and GOES-W (Cloud top phase, height, water path)

• CLOUDSAT cloud water path

• NOAA NESDIS Operational Cloud top Height Product (CO2-slicing)


RUC Data

Dataset 1 (4 months):• Feb 12 - Apr 27, 2007; May 10 - July 4, 2007• Analyses, 1-hr, 3-hr and 6-hr forecasts valid at 18 UTC• Obtained to test Model analyses and forecasts with GOES

Note: Jan 8, 2008 RUC crisis change implemented for improved cloud/vis assimilation.

Dataset 2 (55 days):• March 17 - May 28, 2008 (18, 19, 20, 21, 22 UTC Analyses)• No Forecasts• Obtained for GOES and Cloudsat Comparisons over CONUS


RUC Cloud AssimilationUse multiple data types to modify cloud,hydrometeor, and moisture fields:

-- NESDIS GOES cloud-top pressure/temp(implemented in 2002 w/ RUC20)

-- Surface METAR (clouds, weather, visibility)(2005 w/ RUC13)

• Construct 3-d logical arrays (YES/NO/UNKNOWN)for clouds and precipitation from all info

• Clear/build moisture, cloud, precipitation fields• Safeguards for known problems (marine stratus,

convective clouds, snow, nocturnal inversion)


Satellite Validation


LaRC and NESDIS Cloud Top Height Comparisons with ARM ARSCL data

Smith et al. 2008 (GRL)

5-yr datasetSingle-layer clouds

X - CO2 slicingLaRC

Satellite-derived Cloud Top HeightBias Errors (km)


Satellite Liquid Water Path Validation

LWP

(MO

DIS

)

Dong et al., JGR, 2007

• Unbiased over wide range of LWP (up to 500 g/m2)• Excellent correlation • Instantaneous Uncertainty ~30%• Note mean value ~150 g/m2


Cloud Ice Water Path (From Waliser et al. 2008)Cloud Ice Water Path (From Waliser et al. 2008)

LaRC CERES (analogous to LaRC GOES) compares well with CloudSat IWP


Instantaneous matched GOES-CloudSat Water Path1930 UTC, 1 March 2007

010002000300040005000

19.4919.519.5119.5219.5319.5419.55UTC

Wat

er P

ath

(g/m

2)CloudSat TWPGOES IWP

CloudSat Reflectivity


GOES Cloud Water Path Comparisons with Cloudsat

Dec 2006 – May 2007

• Excellent agreement between GOES and Cloudsat monthly mean total water path for high thick clouds.

• Thin ice cloud IWP also in good agreement

• LWP from Cloudsat is unreliable

Low Cloud LWP Hi Thin Cloud TWP Hi Thick Cloud TWP

Ocean Land Ocean Land Ocean Land Mean (CloudSat) 252 117 61 64 617 573

Mean (GOES) 167 200 56 65 637 731 Bias 85 -83 5 -1 -20 -157 rms 199 200 68 120 586 751

StdErr of Fit 125 165 31 35 581 661 R2 0.10 0.02 0.3 0.2 0.5 0.3

Npts 594 848 1086 1018 2843 4225

Statistical Summary for All Months


GOES/RUC Cloud Parameter Comparisons


Matching ProceduresSpatial Matching: GOES 8-km pixel products averaged to RUC 20 km

grid.

Temporal Matching: 1745 UTC GOES within 15 minutes of RUC analyses and forecasts with valid times at 18 UTC.

RUC grid box either OVC or CLR. GOES is OVC, CLR or PC

RUC Total Water Path: Computed from 5 species level mixing ratios (cloud water, cloud ice, rain water, snow, graupel).

RUC Cloud Phase: Only analyzed in the top layer.

Comparisons shown here are stratified by cloud phase (I.e. clouds with either liquid or ice water tops


GOES INFRARED GOES VISIBLE

GOES CLOUD TOP PHASE RUC CLOUD TOP PHASE (0-hr fcst)

Example Cloud Top Phase Comparison - May 8, 2008 (1800 UTC)

Ice

Liquid

Mixed

SLW

Clear


2007 Cloud/Clear Frequency Comparison (%)

GOES RUC 0-hr RUC 1-hr RUC 3-hr RUC 6-hr

CLEAR 33 43 45 47 47

PC 19 NA NA NA NA

OVC 48 57 56 53 53

ICE 18 40 43 37 25

LIQUID 21 12 12 14 16


2007 Cloud/Clear Frequency Comparison (%)

GOES RUC 0-hr RUC 1-hr RUC 3-hr RUC 6-hr

CLEAR 33 43 45 47 47

PC 19 NA NA NA NA

OVC 48 57 56 53 53

ICE 18 40 43 37 25

LIQUID 21 12 12 14 16


RUC/GOES CLOUD FREQUENCY DIFFERENCES (%)

FOR LAND and OCEAN

RUC ANALYSIS minus GOES RUC ANALYSIS minus GOES

Land Ocean

All cloudsIce

Liquid

322

-10

1019-4

Land Ocean

All cloudsIce

Liquid

323

-10

1015

0

2007 dataset 2008 dataset

RUC has too much high-level ice cloud (land & ocean) and too little low-level liquid cloud (over land) relative to GOES.


RUC Cloud Frequencies with and without NESDIS Satellite Data

Compared to LaRC GOES

RUC GOES

All cloudsIce

Liquid

7968

5

773329

RUC GOES

All cloudsIce

Liquid

543810

441617

(Lat > 50˚ N) (Lat ≤ 50˚ N)

Low-level liquid cloud frequency difference largest over Canada where no satellite data are used. Large ice cloud frequency differences in both regions.

No NESDIS Data With NESDIS Data


Distribution of Ice Cloud Frequency for GOES and RUC (2008)

Relative Frequency (%) ofTotal Water Path for

Clouds with Ice Phase Tops

2008 Test Dataset

0

2

4

6

8

10

0

2

4

6

8

10

0 3000+25 50 100 300 500200 750 1000 20001500

TWP (gm-2)

Rel

ativ

e Fr

eque

ncy

(%)

All

GOES

RUC Analysis

35% of the ice cloud difference is found in the lowest bin

Other possible reasons for discrepancy:

• Cloud phase differences (mixed phase regime)• Poor GOES phase ID (multilayer systems)


RUC CLEAR/CLOUD FREQUENCIES FOR GOES 100% OVERCAST REGIONS

RUC CLOUD %

RUC CLEAR %

ANAL 1-hr 3-hr 6-hr0

20

40

60

80

100

Freq

uenc

y

Forecast Period

13

87

19

81

22

78

23

77

ANAL0

20

40

60

80

100

Freq

uenc

y

Forecast Period

10

90

20082007


RUC CLEAR/CLOUD FREQUENCIES FOR GOES 100% CLEAR REGIONS

20082007

RUC CLOUD %

RUC CLEAR %

RUC LIQUID %

RUC ICE %


20

40

60

80

100

Freq

uenc

y

Forecast Period

83

1812 5

78

2216 6

80

2013

7

79

21

11 9

ANAL0

20

40

60

80

100

Freq

uenc

y

Forecast Period

83

1711 5


RUC CLOUD FREQUENCIES FOR GOES OVERCAST ICE CLOUD REGIONS

20082007


20

40

60

80

100

Freq

uenc

y

Forecast Period

89

2 3 6

88

2 1 9

82

4 1

13

78

51

16

ANAL0

20

40

60

80

100

Freq

uenc

y

Forecast Period

88

2 6 4

RUC CLOUD FREQUENCY

CLEARLIQUID CLOUDS

ICE CLOUDS

MIXED PHASE


RUC CLOUD FREQUENCIES FOR GOES OVERCAST LIQUID CLOUD REGIONS

20082007

RUC CLOUD FREQUENCY

CLEARLIQUID CLOUDS

ICE CLOUDS

MIXED PHASE


20

40

60

80

100

Freq

uenc

y

Forecast Period

3339

1117

3535

2

28 29

40

3

28 26

43

4

27

ANAL0

20

40

60

80

100

Freq

uenc

y

Forecast Period

31

47

102


Water Path Comparison Nov 8, 2008 (1800 UTC)

GOES WP

GOES minus RUC WP

RUC WP

GOES Cloud Phase


Liquid Water Cloud Parameter Comparison

Ocean

Land

WP (gm-2) Zt (km) Z (km) Dataset

GOES RUC %diff GOES RUC BIAS GOES RUC BIAS 2008 Analysis 193 133 -31 2.9 2.6 -0.3 1.0 1.2 0.2 2007 Analysis 174 65 -63 3.0 2.1 -0.9 1.0 0.7 -0.3 2007 1-hr fcst 183 65 -64 3.0 1.9 -1.1 1.0 0.7 -0.3 2007 3-hr fcst 189 90 -52 3.0 2.0 -1.0 1.0 0.8 -0.2 2007 6-hr fcst 192 93 -52 3.0 1.9 -1.1 1.0 0.8 -0.2


GOES RUC %diff GOES RUC BIAS GOES RUC BIAS 2008 Analysis 109 79 -28 1.8 1.2 -0.6 0.8 0.6 -0.2 2007 Analysis 105 57 -46 1.6 0.8 -0.8 0.8 0.4 -0.4 2007 1-hr fcst 107 59 -45 1.6 0.7 -0.9 0.8 0.4 -0.4 2007 3-hr fcst 108 67 -38 1.6 0.8 -0.8 0.8 0.5 -0.3 2007 6-hr fcst 107 70 -35 1.6 0.8 -0.8 0.8 0.5 -0.3

• GOES LWP >> RUC LWP, 2008 RUC compares better• LaRC GOES cloud top heights and thicknesses exceed RUC values• Accounting for cloud thickness differences would yield better LWP agreement over Ocean but not Land.


Ice Cloud Parameter Comparison

Ocean

Land

• GOES IWP >> RUC IWP• LaRC GOES and RUC cloud top heights agree for Analyses• RUC forecasted cloud top height exceeds GOES by over 0.5 km• GOES cloud thickness likely underestimated (poor Deep Convective estimates)• Land/Ocean differences generally consistent


GOES RUC %diff GOES RUC BIAS GOES RUC BIAS 2008 Analysis 473 328 -31 8.5 8.3 -0.2 4.2 5.3 1.1 2007 Analysis 416 254 -39 7.9 7.9 0.0 3.4 4.5 1.1 2007 1-hr fcst 418 260 -38 7.9 8.5 0.6 3.4 5.0 1.6 2007 3-hr fcst 428 275 -36 7.8 8.6 0.8 3.5 5.0 1.5 2007 6-hr fcst 430 251 -42 7.8 8.4 0.6 3.5 4.7 1.2


GOES RUC %diff GOES RUC BIAS GOES RUC BIAS 2008 Analysis 350 214 -39 9.3 9.3 0.0 3.7 4.8 1.1 2007 Analysis 355 184 -48 8.9 8.9 0.0 3.0 4.3 1.2 2007 1-hr fcst 361 191 -47 8.8 9.4 0.6 3.0 4.6 1.6 2007 3-hr fcst 377 204 -46 8.8 9.4 0.6 3.1 4.6 1.5 2007 6-hr fcst 376 190 -49 8.8 9.2 0.4 3.1 4.3 1.2


Summary• The RUC is one of the more advanced NWP models

worldwide that assimilates cloud observations.

• Comparison of RUC cloud parameters with similar parameters derived from GOES indicate the RUC assimilation works reasonably well.

• However, significant differences have been identified that exceed the satellite-derived uncertainties which implies that assimilation of LaRC GOES-derived cloud products could lead to improved cloud analyses and forecasts in the model.

• Results from this study are being used to guide the assimilation of satellite-derived cloud parameters and also provide a baseline for future model evaluations.


Extra slides


Regional Liquid Water Path Comparison (g/m2)

Atlantic Pacific Gulf of Mex0

20

40

60

80

100

120

140

160

180

LWP

(g/m

**2)

GOES

RUC-Analysis

2008

Poor agreement over the Atlantic but good

over Pacific and Gulf of Mexico


Regional Ice Water Path Comparison (g/m2)

2008

RUC does track GOES regional differences.

Atlantic Pacific Gulf of Mex0

50100150200250300350400450500

IWP

(g/m

**2)

GOES

RUC-Analysis


Cloud Ice Water Path (From Waliser et al. 2008)Cloud Ice Water Path (From Waliser et al. 2008)

CERES-MODIS most similar to CloudSat values

CloudSat

CERES-MODIS ISCCP

MODIS MYD06

Documents

Comparison of RUC Cloud Analyses and Forecasts with Satellite-derived Cloud Properties