1. 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

2. Sounding-based Schematic of Nocturnal Convection Initiation
From Trier and Parsons 1993

3. Moisture Upstream of MCS Inflow
2nd LLJ
Deeper Mixed Layer from near the dryline
LLJ

4. Nocturnal MCS June 6th 2
~Frontal Position 3 1
~DC-8
Flight track 4

5. MCS Inflow
Conv

6. Water Vapor: 20 June

7. A key factor in nocturnal convection is the depth
of the moist inflow, which can be aloft
Sounding Susceptible to PBL-Based Convection
Sounding Susceptible to Elevated Convection
DVN (0000 UTC 9/12/2000)
GRB (0000 UTC 9/12/2000)
From Trier et al. 2002, abstract 130, Reading QPF meeting

8. 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?

9. 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

10. Time of Occurrence

11. ~18 bore and 8 S-Pol and MAPR wave events were
S-Pol and MAPR bore/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.

12. BORE
Example
From
MAPR
4 June
Pre-bore height
Post height

13. Bore Height Displacements
Layer
Height
(km)
Time (mins)

20. 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. They
initiate 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 nocturnal
precipitation maximum over this region allowing
systems to cross over this unfavorable
environment into more moist air.