GEWEX INTERESTS IN THE MEASUREMENT OF SNOW

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GEWEX INTERESTS IN THE MEASUREMENT OF SNOW

• Rick Lawford
• UCAR/ NOAA Office of Global Programs

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What Feedbacks Will These Changes Cause?
The unknowns and uncertainties are many, and
the hydrological cycle figures prominently in
each. A knowledge of snowfall and snow on the
ground is important for reducing this uncertainty.
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SOURCES OF UNCERTAINTY IN SOLID PRECIPITATION
MEASUREMENTS

• DIFFERENCES IN SNOW MEASUREMENTS IN TERMS OF THE
  INSTRUMENTS, CORRECTION PROCEDURES, QUALITY
  CONTROL PROCEDURES AND ARCHIVING PRACTICES OF
  INDIVIDUAL COUNTRIES
• THE PROBLEM OF WIND EFFECTS ON THE CATCH OF SOLID
  PRECIPITATION BY DIFFERENT GAGES.
• THE DIFFICULTY OF MEASURING SNOW REMOTELY DUE TO
  THE DIVSERSITY OF CRYSTAL STRUCTURES, DENSITY,
  PRESENCE OF LIQUID WATER ON THE CRYSTAL, ETC.

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ONE PERSPECTIVE ON TIMELINESS
THERE ARE EMERGING OPPORTUNITIES FOR ADDRESSING
SNOW MEASUREMENT PROBLEMS AT BOTH THE
INTERNATIONAL AND NATIONAL LEVELS. THESE
INCLUDE - CLIMATE CHANGE RESEARCH (WCRP)
- CEOP - IGOS-P WATER CYCLE THEME,
GCOS AND GTN-H - US GLOBAL WATER CYCLE
INITIATIVE. TO TAKE ADVANTAGE OF THESE
OPPORTUNITIES THE SNOW COMMUNITY NEEDS - A
SCIENTIFIC FRAMEWORK FOR ITS AGENDA - A
PROCESS TO DEVELOP COMMITMENT TO THE
ISSUE BY FUNDERS - STRONG PROPOSALS TO
NATIONAL (AND INTERNATIONAL) FUNDING
AGENCIES.
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SOLID PRECIPITATION MEASUREMENTS

• SOURCES OF ERRORS IN SOLID PRECIPITATION
  ESTIMATES INCLUDE
• WIND EFFECTS ON GAGE CATCH
• SITING OF GAGES
• VERY SPARSE DATA NETWORKS
• SNOW MEASUREMENTS AND REPORTING BY AUTOMATIC
  STATIONS
• TREATMENT OF TRACE AMOUNTS
• INADEQUATE METADATA FOR MAKING CORRECTIONS AND
• FAILURE TO PERIODICALLY CALIBRATE INSTRUMENTS.
• ADDITIONAL APPROACHES TO MEASURING SNOWFALL
  INCLUDE
• USE OF NEXRAD REFLECTIVITIES WITH APPROPRIATE
  ALGORITHMS
• USE OF HOT PLATES TO WEIGH SNOW ON THE GROUND
• INCORPORATING SATELLITE DATA WITH DATA
  ASSIMILATION SYSTEMS TO GIVE BETTER ESTIMATES
  AND
• INCORPORATION OF NON-STANDARD DATA SUCH AS ICE
  CORES AND SNOW PITS.

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GEWEX Americas Prediction Project (GAPP)

• Develop a capability to predict water cycle
  variables on monthly/
• seasonal time scales based on improved
  understanding and
• representation of land-atmosphere
  interactions.
• Interpret climate predictions for water
  management.

(short) objectives
GAPP Components
Predictability in Land Surface Processes
Hydrometeorology of Orographic Systems
Predictability in Monsoonal Systems
Integration of Predictability into Prediction
Systems
CEOP Data and Studies for Model Development
Testing of Models in Special Climate Regimes
a community based effort bringing hydrologists,
land surface specialists and atmospheric
scientists together to address climate issues.
Use of Predictions for Water Resource Management
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REPRESENTATIONS OF SNOW COVER AND SNOW WATER
EQUIVALENT ARE NEEDED FOR MODEL INITIALIZATION
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ACCURATE SNOW MEASUREMENTS ARE NEEDED TO CLOSE
WATER BUDGETS IN NORTHERN ENVIRONMENTS
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GCIP USED TECHNIQUES DEVELOPED BY PECK AND
GROISMANN TO CORRECT WINTER SNOW MEASUREMENTS FOR
A NUMBER OF NORTHERN STATES
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ACHIEVEMENT JULY 2001 NOAH LSM IMPROVEMENTS IN
NCEPS COUPLED ETA MODEL
July 2001 NOAH LSM improvements in coupled Eta
model Successfully Targeted Impacts 1 - Cold
season processes (snow melt, frozen soil)
reduce near-surface cool bias over snow cover
2 -
Early spring wet soils (soil heat flux, bare soil
evaporation) reduce near-surface moist
bias 3 - Summer over non-sparse green
vegetation reduce near-surface warm bias
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Coordinated Enhanced Observing Period (CEOP)
CEOP is the first step toward meeting the
challenge to provide coordinated observations of
the global water cycle.
CEOP will offer the first globally integrated
data sets
CEOP will strongly promote study of the water
cycle adding to improved accuracy of weather
predictions in the near future.
Long-term Guiding Goal and Overall Objectives
Schedule
Organization
CEOP HP http//www.ceop.net
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The First Global Integrated Data Sets of Water
Cycle
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SUMMARY
THERE ARE EMERGING OPPORTUNITIES FOR ADDRESSING
SNOW MEASUREMENT PROBLEMS AT BOTH THE
INTERNATIONAL AND NATIONAL LEVELS. THESE
INCLUDE - CLIMATE CHANGE RESEARCH (WCRP/
CCRI) - CEOP - IGOS-P WATER CYCLE
THEME - US GLOBAL WATER CYCLE
INITIATIVE. TO TAKE ADVANTAGE OF THESE
OPPORTUNITIES THE SNOW COMMUNITY NEEDS - A
SCIENTIFIC FRAMEWORK FOR ITS AGENDA - A
PROCESS TO DEVELOP COMMITMENT TO THE
ISSUE BY FUNDERS - STRONG PROPOSALS TO
NATIONAL (AND INTERNATIONAL) FUNDING
AGENCIES.
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SUGGESTIONS FOR RECOMMENDATIONS

• GUIDELINES SHOULD BE DEVELOPED ON FACTORS
  AFFECTING CLIMATE ANALYSES SUCH AS MINIMUM
  STATION DENSITY, GAGE TYPE, APPLICATION OF MODELS
  (E.G. PRISM), ETC.
• NATIONAL AGENCIES SHOULD SUPPORT THE DEVELOPMENT
  AND TESTING OF NEW INSTRUMENTS FOR SNOW
  MEASUREMENT
• ESTABLISH INTERCOMPARISONS SITES FOR UNIFORM
  TESTING OF SNOW SITES.
• CARRY OUT INVESTIGATIONS AND IMPLEMENT PROCEDURES
  TO ACQUIRE QUALITY DATA FROM AUTOMATED STATIONS.
• DEVELOP EXTENSIVE METADATA FOR EXISTING
  MEASUREMENT STATIONS.
• ASSESS THE IMPLICATIONS OF MAKING CORRECTIONS TO
  SNOW RECORDS FOR CLIMATE AND HYDROLOGIC MODELS
  AND FOR DESIGN CRITERIA SHOULD BE ASSESSED.
• CLiC WILL ADDRESS THE ISSUE OF SNOW MEASUREMENT
  TECHNIQUES.