moisture variability and nocturnal convection
DESCRIPTION
Moisture Variability and Nocturnal Convection. David B. Parsons, Crystal Pettet, and Tammy Weckwerth NCAR/ATD. Acknowledgements to Ed Browell et al., Cyrille Flamant et al., and Steve Koch and the bore folks. Sounding-based Schematic of Nocturnal Convection Initiation. - PowerPoint PPT PresentationTRANSCRIPT
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Moisture Variability and Nocturnal Convection
David B. Parsons, Crystal Pettet, and Tammy Weckwerth
NCAR/ATD
Acknowledgements to Ed Browell et al., Cyrille Flamant et al., and Steve Koch andthe bore folks
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Sounding-based Schematic of Nocturnal Convection Initiation
From Trier and Parsons 1993
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Moisture Upstream of MCS Inflow
LLJ
2nd LLJDeeper Mixed Layer from near the dryline
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Nocturnal MCS June 6th
~Frontal Position
~DC-8 Flight track1
2
3
4
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MCS Inflow
Conv
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Water Vapor: 20 June
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Sounding Susceptible to Elevated ConvectionSounding Susceptible to PBL-Based Convection
DVN (0000 UTC 9/12/2000) GRB (0000 UTC 9/12/2000)
From Trier et al. 2002, abstract 130, Reading QPF meeting
A key factor in nocturnal convection is the depth of the moist inflow, which can be aloft
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Research Goals
• How common are bores and wave train events?
• What are the characteristics of these events?
• How are they generated and in what environments?
• How strong is the lifting and does it modify the inflow thermodynamics?
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Research Technique
• Identify events in S-Pol and NEXRAD composites
• Independently identify events in MAPR and ISS surface data
• Identify event characteristics
• Link to environmental characteristics
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Time of Occurrence
Bore/Wave Passage at MAPR
0
1
2
3
CST (h)
# of
Eve
nts
End Time of Bore/waves Event
0
1
2
3
4
5
6
CST (h)
# of
Eve
nts
Time of Generation (S-Pol)
0
1
2
3
4
5
Local Time (h)
# of
Wav
e/B
ore
Even
ts
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1 3 5 7 9
11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43
S1
0
2
4
6
8
10
12
14
16
IHOP Date
Max Nocturnal Wind Speed (m/s)
Max Surface Wind vs. Bore/Wave Events
S-Pol and MAPRbore/wave events
~18 bore and 8 S-Pol and MAPR wave events were observed. Bore events are observed in the later stages of LLJ periods when precipitation occurs.
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BOREExample From MAPR4 June
Pre-bore height Post height
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Bore Height Displacements
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
0 5 10 15 20 25 30 35 40 45 50 60 65 75
Time (mins)
LayerHeight(km)
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Approximate Spatial Dimension of S-Pol Bore/Wave Events
0123456789
10
50 150 250 350 450 550Along line length (km)
# of
Eve
nts
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Implications and Speculations•Undular bore-like disturbances are ubiquitous over
this region when convection and low-level jets are present. Bore lifting varies.
•These disturbances can promote intense lifting with displacements of up to ~2 km. Theyinitiate convection and help maintain existing systems by lifting their inflow (removing CIN) and by creating a deeper moist inflow.
•These disturbances surely contribute to the nocturnalprecipitation maximum over this region allowingsystems to cross over this unfavorable environment into more moist air.