LWC in CUMULUS

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LWC in CUMULUS
Hermann Gerber
GSI, Reston, VA
dedicated to Joanne Simpson
Simpson
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Cloud Particle Imager (SPEC INC.)
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WHY LWC?
1. Thermodynamics - Heat of Condensation
2. Microphysics Adiabatic LWC
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Pruppacher and Klett, 1978 Reidel ( Pub.)
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CORE
(Hess, 1959 Holt, Rinehart, and Winston, NY)
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small Cu, non-precipitating
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ADIABATIC CORE IN CUMULUS CONGESTUS
(2. Heymsfield, et al., 1978 J.A.S. 1689-1703)
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UNDILUTED CORES IN CCOPE CUMULI
PLATFORM Canadian Twin Otter J-W LWC (1hz
10-15) 10 clouds

• CRITERIA
• LWC max., LWC and T constant over several hundred
  m
• Constant droplet concentration

• DATA
• Height above cloud base, 750m 1390m mean
  1016m
• LWC/LWCa, 0.86 1.07 g/m3 mean LWC 0.95 g/m3

(3. Jensen, 1985 Ph.D Thesis J.A.S., 173-192.)
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SMALL CUMULUS MICROPHYSICS STUDY
(SCMS, 1995)
C-130 LWC PROBES
King Hot Wire CDS 4. FSSP (Blyth et al., 2003
J.A.S.) 5. PVM (Gerber, 2000 13th ICCP)
(PLWCC)
(PLWCF_LPC)
(XGLWC)
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?
(4. Blyth et al., 2003 J.A.S., 2557-2572)
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FSSP-100 Coincidence and Dead-Time Corrections
x 1.20
530
(Baumgardner et al., 1985 J.A.S., 626-632)
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(PLWCF_LPC)
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1hz (100m) vs 1000hz (10 cm) LWC
SCMS 28 July 1434
PVM
(XGLWC)
(5. Gerber, 2000 13th ICCP)
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605 SCMS Cloud Passes
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CORE CRITERION
Adiabatic Core for 1000-hz LWC data Measured
LWC is within /-10 of Predicted Adiabatic LWC
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ADIABATIC CLOUD PARCEL
PVM
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ADIABATIC CLOUD PARCEL
PVM
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ADIABATIC CLOUD PARCEL
SCMS July 24, 1527
PVM
ADIABATIC
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Adiabatic Parcel Width vs Height
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Pdf of Adiabatic Parcel Width
SCMS
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Linear-Eddy Model Predictions vs Measurements
SCMS
(6. Krueger et al., 1997 J.A.S., 2697-2712)
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DATA RATE MEASUREMENT ERROR MEASUREMENT
UNCERTAINTY
RECONCILIATION
SCMS
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LWC and Droplet Concentration, N
SCMS
(as in Paluch, I.R., 1986 J.A.S., 1984-1993)
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Reff vs LWC in a Horizontal Cloud Pass
(as in Blyth, A.M., and J. Latham, 1991 J.A.S.,
2367-2371)
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FSSP Cumulative Mass Distribution
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Large Droplet Response of PVM (XGLWC)
(Gerber et al., 1994 Atmos. Res., 235-252)
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CONCLUSIONS

1. Indentification of LWCa requires a fast and
   accurate LWC sensor
2. LWCa exists in SCMS Cu
3. Classical Adiabatic Cores in SCMS Cu none
4. Entrainment/mixing already starts near cloudbase
   (one turn-over distance)
5. Large LWCa parcels found only near cloud base
6. Above cloud base mean LWC approaches 20 of LWCa

QUESTIONS

1. How does entrainment/mixing affect the evolution
   of LWC in Cu?
2. What is the proper description of adiabatic
   cores?
3. What size of LWCa parcel must be considered for
   modeling drop spectra evolution?
4. Does the size and vigor of Cu affect the presence
   of LWCa?
5. Does LWCa in RICO Cu differ from other small Cu,
   e.g., CCOPE or SCMS?

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REFERENCES
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RICO WORKING GROUP1 (see twiki
Web site linked to RICO field catalogue)
http//gerberscience.com