Current System Applications: Cloud Analysis and Forecasting

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Current System ApplicationsCloud Analysis and
Forecasting

• PolarMax
• 25 October 2005

Dr. Thomas Kopp The Aerospace Corporation Meteoro
logical Satellite Systems
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Overview

• A Brief History of Operational Satellite-Based
  Cloud Analysis
• The Two-channel Approach (RTNEPH)
• Adding the Mid-wave (CDFS II CLAVR)
• Throwing In the Kitchen Sink (MODIS)
• Operational Cloud Forecasting
• Trajectory Based Approaches (ADVCLD)
• The Problems With NWP
• Putting It All Together, Where We Stand Today
  (Stochastic)

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The Two Channel Approach

• The Real-Time NEPHanalysis (RTNEPH)
• Produced Global, Three-Dimensional Cloud Analyses
  For AFWA From 1973-2002 (30 years!)
• Produced Cloud Cover Over An 8th Mesh Grid (25
  NM) Along With Cloud Top Temperature/Height
  Cloud Base Height
• Used the Two Visual/IR Channels On the DMSP
• If the Reflectance/Brightness Temperature Was
  Brighter/Colder Than the Surface, It Was A Cloud
• Three-Dimensional Characteristics Were Based On
  the IR Temperature and Associated Ancillary Data
  (NWP)

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DMSP Visual Over S. America

• Scene is Over Chile and the Eastern Pacific
• Can You Find the Clouds?

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DMSP IR Over S. America

• How About This One?

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And Heres The Result

• Everything Appears Correct
• But Snow Over Andes Was Identified As Cloud

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DMSP 3D Cloud Analysis

• Example Cloud Products
• Source CMNS
• Algorithm SERCAA
• F15 07Oct04 16Z
• Total Cloud Amount ()
• Visual Imagery (2.8km)

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The Next Source - AVHRR

• Included Three Additional Channels
• Broke the Visual Channel Into Two Components
• Added Additional Channels In the IR, One Mid-wave
  and the Other Long-wave
• These Channels Led To Improved Cloud Detection
  Techniques
• Two Visual Channels Allow For Ratio Calculations
  Between the Two Reflectances
• Significant Improvement In Nighttime Cloud
  Detection Possible From the Addition Of the
  MWIR/LWIR
• Besides Further Detection Algorithms, Cloud
  Detection Became Less Dependent On Ancillary Data

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Different Approaches

• AFWA Brought In These Newer Methods Via SERCAA
• Science Basis For CDFS II Replaced the RTNEPH
  In 2002
• Techniques Applied To Both Geostationary and
  Polar-Orbiting Satellite Data
• Three-dimensional Aspects Unchanged
• NOAA/NESDIS Scientists Developed CLAVR
• Also Based Their Product On Applying All Five
  Channels In An Optimum Manner
• But, Unlike CDFS II, Focus Included A Cloud
  Clearing Mode
• Spatial Uniformity Test Designed For Partly
  Cloudy Conditions and Subpixel Scale Clouds

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A CLAVR Example

• N-18, Visual
• Southeast Asia
• Wheres the Cloud?

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A CLAVR Example

• N-18, IR

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A CLAVR Example

• The Result
• Clouds Are White
• Probably Cloudy Condition Indicated By Shades of
  Gray

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The Latest Wrinkle - MODIS

• Virtual Explosion Of Visual/IR Channels Available
• MODIS Contains 32 Channels In the Visual/IR Range
• Not All Employed For Clouds, Though Some Are Used
  To Find Non-Cloud Features That Could Appear As
  Clouds
• Approximately 10 Cloud Detection Tests Have Been
  Developed, Each Designed For Specific Situations
• Main Users However Desire Clear Conditions, Not
  Cloudy Ones
• Has Led To Multiple Cloud Masks Depending On Need
• Main Algorithm the Basis For VIIRS (NPOESS)
• Significant Increase in Number of Tuning
  Thresholds Complicates Development and Evaluation

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MODIS Example
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MODIS Example
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Cloud Forecasting

• Forecasting Cloud Cover And 3D Cloud
  Characteristics Has Proven Difficult With Only
  Limited Advances In the Last 30 Years
• AFWA Has Based Short-Term Cloud Forecasts On
  Trajectory Based Methods, And Still Does Today
• ADVect CLouD (ADVCLD) Combines 3D Wind Flow From
  NWP With Cloud Characteristics From CDFS II
• Method Rapidly Deteriorates After 9 Hours
• NWP Approaches Do Not Use or Produce Cloud Cover
• No Direct Cloud Inputs Are Used In NWP
• Output Is Cloud Liquid/Ice Content, No Clear
  Correlation Between These And Cloud Cover

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The Newest Addition To theForecasting Arsenal

• Stochastic Cloud Forecast Model
• Combines CDFS II Cloud Parameters And the NCEP
  Global Forecast System (GFS)
• Uses 9 Pressure Levels and the Output of CDFS II
  (WWMCA)
• Products Include Total Cloud Cover and Cloud
  Freeness Across Various Atmospheric Layers
• Now in routine operations at AFWA, Including
  JAAWIN
• Diagnostic Cloud Forecast Model
• Combines CDFS II and Regional MM5 Model Output
• Statistically Correlates WWMCA to MM5 Model
  Predictors

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Stochastic Forecast Example
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Summary

• Operational Cloud Analysis Has Taken Advantage of
  the Increased Number of Channels On Various
  Polar-Orbiting Satellites
• Trend Is For More Tests Identifying Specific
  Types of Clouds
• Recently Developed Cloud Masks Account For
  Subpixel Clouds
• Cloud Forecasting Remains A Challenge, Especially
  For Cloud Amounts and Layers
• Trajectory Based Models Still Best in the Short
  Term
• NWP Advances Have Not Crossed the Bridge Between
  Cloud Amount and Cloud Liquid Water/Ice
• Newest Operational Methods Combine Cloud Analyses
  and NWP Without An Explicit Forecast From the NWP
  Models
• NPOESS is the Next Step In Operational Cloud
  Analysis