RADAR-OBSERVED CHARACTERISTICS OF PRECIPITATING SYSTEMS Tim Lang, Dave Ahijevych, Steve Nesbitt, Rit Carbone Steve Rutledge, Rob Cifelli

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RADAR-OBSERVED CHARACTERISTICS OF PRECIPITATING
SYSTEMS Tim Lang, Dave Ahijevych, Steve
Nesbitt, Rit Carbone Steve Rutledge, Rob
Cifelli
CSU NCAR
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GUASAVE
S-Pol
CABO SAN LUCAS
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(No Transcript)
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The Rainfall Timeseries
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31 Jul
1 Aug
2 Aug
3 Aug
4 Aug
5 Aug
6 Aug
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Composite Reflectivity from 00 Z 5 Aug - 00 Z 7
Aug
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Diurnal Cycle 43 day period of
record
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Diurnal Cycle Regime A (14) vs Other Days (29)
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Diurnal CycleRegime B (14) vs Other Days (29)
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Period of Record StatisticsIt rains more on
regime days and the rain is mainly from organized
convection.
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Diurnal StatisticsIt rains more on regime days,
most of the rain is from organized convection.
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Diurnal StatisticsStratified by
locationOpposing phases of organized convection
over land and sea
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More Shear, Stronger SE Wind
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Easterly Waves and Humidity
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Preliminary Conclusions

• Most rainfall is triggered by the SMO heat
  source and sea breeze.
• Intraseasonal variability appears to be
  systematic.
• Surges were associated with a small fraction
  of this variability and may not be as important
  to the big picture as originally hypothesized.
• The A, B, and AB Regimes are associated with
  the capacity for convection to organize, scale
  upwards and propagate.
• Regime days have enhanced shear, enhanced CIN,
  and ordinary CAPE.
• The organized convection produces more
  rainfall, and propagates with respect to the
  local forcings and the steering winds (6m/s).
• Propagation, combined with triggering by the
  elevated heat source, leads to a well defined
  pattern of the diurnal cycle (globally phase
  locked).
• Rainfall patterns are also consistent with the
  GoC acting as a nocturnal heat source and the
  land breeze front as triggering topography.

New convective parameterizations are needed to
get this stuff right.
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These findings are part of a larger picture
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RESULTS published, emerging, analysis in
progress, new study
Continental Warm Season Rainfall Studies

Background after Laing and Fritsch 1997
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EPISODESSequences of convective systems
often result from a coherent regeneration of
organized convection. Episodes span
substantial distances over North America on a
daily basis in summer.(1000 km, 20 h)
Original US Findings, JAS 2002
Radar ltRainrategt

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Diurnal Cycle July 1997
Original US Findings, JAS 2002
Time Radar Precipitation Echo
We refer to this pattern as
globally phase-locked
Essentially all forcing is diurnal. Effects are
both local and remote. Remote effects result
from coherent regeneration of convection and
propagation
Longitude
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AFRICA NH Summer (5S 20N)
Arlene Laing
Diurnal Cycle July 1999
1 7 July 1999
UTC
UTC
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RADAR-OBSERVED CHARACTERISTICS OF PRECIPITATING
SYSTEMS Tim Lang, Dave Ahijevych, Steve
Nesbitt, Rit Carbone Steve Rutledge, Rob
Cifelli
THANKS!
CSU NCAR