EGPM Algorithms: fundamentals for extratropical precipitation retrievals

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EGPM Algorithmsfundamentals for extra-tropical
precipitation retrievals

• Chris Kidd
• The University of Birmingham
• EGPM-MAG

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The ideal world (where we would like to be)
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Into the unknown?

• TRMM
• Relatively safe environment steep rainfall
  gradients, with medium-heavy rainfall.

Convergence of results BUT are these politically
or scientifically correct? (EZ)
What lies outside the Tropics?
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What can we expect?
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Precipitation regimes
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ECMWF model rainfall estimates
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Seasonality

• Mid- and high-latitudes experience greater
  seasonality than the Tropics
• day-to-day variations can also be large
• Implications for
• Freezing levels (liquidfrozen ratio)
• Surface variability (retrieval ability)
• Snow/rain boundaries (user applications)

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Freezing levels
Only one thing we do know is that the freezing
level is relatively stable Tom Wilheit
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Current activities

• Quantifying light precipitation events
  implications for retrieval accuracy
• Analysing high-quality mid-latitude radar data
  European and Baltic radar networks (what are
  realistic mid- and high-latitude profiles?)
• Modelling mid-latitude precipitation events
  (precipitation characteristics)
• Identification and quantification of the
  variability of background surfaces

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Light precipitation
Light precipitation regimes must be properly
addressed despite the contributions to the
amount being generally small
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ECMWF (e40) vs GPI
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ECMWF (e40) vs 3B40RT
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Surface Variability

• Effects and contribution of surface variability
  to precipitation retrievals.

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Radar profile studies

• Characteristics of mid- and high-latitude
  precipitation profiles.
• Surface radar data from UK Chilbolton radar
  (3GHz)
• Scheme shown here is an unsupervised
  classification scheme based upon 350,000 profiles
  during 2003
• (TRMM produces 7 million per day!)

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Example 1 3km maximum
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Example 2 lt1km maximum
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Example 3 1km maximum (light precipitation)
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Conclusions

• EGPM will concentrate upon
• Light/medium precipitation retrievals
• Heavy precipitation events for flood forecasting
  applications (esp. Mediterranean region) 15
  minute data requirement
• Snow retrievals including precipitation over
  cold surfaces
• through the combination of imaging and sounding
  channels, and the radar.

Ultimately, algorithms/techniques must not only
be physically correct, but also intelligently
sophisticated
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ECMWF (e40) vs 3B41RT
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ECMWF (e40) vs 3B42RT
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Freezing level variation