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

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Comparison of RUC Cloud Analyses and Forecasts with Satellite-derived Cloud Properties Bill Smith, Patrick Minnis NASA LaRC Stan Benjamin, Steve Weygandt – PowerPoint PPT presentation

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


1
Comparison of RUC Cloud Analyses and Forecasts
with Satellite-derived Cloud Properties
  • Bill Smith, Patrick Minnis
  • NASA LaRC
  • Stan Benjamin, Steve Weygandt
  • NOAA/ESRL/GSD/AMD

2
Outline
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.
  • Recent satellite validation (GOES Cloud height,
    water path)
  • Statistical Comparisons (several months)
  • Cloud Amount
  • Cloud Height
  • Cloud Thickness
  • Cloud Water Path
  • Summary

3
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)

4
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

5
RUC Cloud Assimilation
  • Use 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)

6
Satellite Validation
7
LaRC and NESDIS Cloud Top Height Comparisons
with ARM ARSCL data
Smith et al. 2008 (GRL)
5-yr dataset Single-layer clouds
Satellite-derived Cloud Top Height Bias Errors
(km)
8
Satellite Liquid Water Path Validation
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

9
Cloud Ice Water Path (From Waliser et al. 2008)
LaRC CERES (analogous to LaRC GOES) compares well
with CloudSat IWP
10
Instantaneous matched GOES-CloudSat Water
Path 1930 UTC, 1 March 2007
CloudSat Reflectivity
11
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
Statistical Summary for All Months
12
GOES/RUC Cloud Parameter Comparisons
13
Matching Procedures
  • Spatial 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

14
Example Cloud Top Phase Comparison - May 8, 2008
(1800 UTC)
GOES INFRARED
GOES VISIBLE
GOES CLOUD TOP PHASE
RUC CLOUD TOP PHASE (0-hr fcst)
Ice Liquid Mixed SLW Clear
15
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
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
17
RUC/GOES CLOUD FREQUENCY DIFFERENCES () FOR
LAND and OCEAN
RUC ANALYSIS minus GOES
RUC ANALYSIS minus GOES
2008 dataset
2007 dataset
Ocean
Ocean
Land
Land
All clouds Ice Liquid
3 22 -10
10 19 -4
All clouds Ice Liquid
3 23 -10
10 15 0
RUC has too much high-level ice cloud (land
ocean) and too little low-level liquid cloud
(over land) relative to GOES.
18
RUC Cloud Frequencies with and without NESDIS
Satellite Data Compared to LaRC GOES
No NESDIS Data
With NESDIS Data
(Lat gt 50 N)
(Lat 50 N)
GOES
GOES
RUC
RUC
All clouds Ice Liquid
79 68 5
77 33 29
All clouds Ice Liquid
54 38 10
44 16 17
Low-level liquid cloud frequency difference
largest over Canada where no satellite data are
used. Large ice cloud frequency differences in
both regions.
19
Distribution of Ice Cloud Frequency for GOES and
RUC (2008)
Relative Frequency () of Total Water Path
for Clouds with Ice Phase Tops
  • Other possible reasons for discrepancy
  • Cloud phase differences (mixed phase regime)
  • Poor GOES phase ID (multilayer systems)

35 of the ice cloud difference is found in the
lowest bin
2008 Test Dataset
20
RUC CLEAR/CLOUD FREQUENCIES FOR GOES 100
OVERCAST REGIONS
2008
2007
21
RUC CLEAR/CLOUD FREQUENCIES FOR GOES 100 CLEAR
REGIONS
2008
2007
22
RUC CLOUD FREQUENCIES FOR GOES OVERCAST ICE
CLOUD REGIONS
2008
2007
23
RUC CLOUD FREQUENCIES FOR GOES OVERCAST LIQUID
CLOUD REGIONS
2008
2007
24
Water Path Comparison Nov 8, 2008 (1800 UTC)
GOES WP
RUC WP
GOES minus RUC WP
GOES Cloud Phase
25
Liquid Water Cloud Parameter Comparison
Land
Ocean
  • GOES LWP gtgt 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.

26
Ice Cloud Parameter Comparison
Land
Ocean
  • GOES IWP gtgt 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

27
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.

28
Extra slides
29
Regional Liquid Water Path Comparison (g/m2)
2008
Poor agreement over the Atlantic but good over
Pacific and Gulf of Mexico
30
Regional Ice Water Path Comparison (g/m2)
2008
RUC does track GOES regional differences.
31
Cloud Ice Water Path (From Waliser et al. 2008)
CloudSat
MODIS MYD06
CERES-MODIS
ISCCP
CERES-MODIS most similar to CloudSat values
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