Ziegler1
Hypothesis (Ziegler1) concerning convective initiation along mesoscale
boundaries


Conrad Ziegler
on August 27, 1997 at 22:17:36:
Environments supporting deep convective initiation are characterized
by the joint occurrence of locally strong convergence and high relative
humidities extending through the depth of the Convective Boundary
Layer (CBL). Specifically, convective initiation requires two factors,
namely; (i) mesoscale (Lx = 110 km across boundary, Ly = 10100
km along boundary) lift providing sufficient kinetic energy to overcome
local CIN; (ii) minimized loss of CAPE (with attendant increase
of LCL, LFC, and CIN) due to mixing of the parcel with warm, dry
ambient air. The latter implies the existence of moisture plumes
and/or layers prior to and in the region of the first deep convection.


Estimate the horizontal distribution of nearsurface
parcel CAPE, LCL, LFC, and CIN using MCLASS soundings, low level
aircraft traverses, and fixed mesonet and NWS surface observations.
Use MCLASS soundings and aircraft traverses to estimate profiles
of stability parameters. Use aircraft stepped traverses and Doppler
radar clear air measurements to estimate airflow, air parcel trajectories,
and especially vertical circulations in the CBL. Use GOES8, WSR88D
network, and P3 surveillance radar data and videorecorded cloud
observations to identify significant deep convection. Stratify cases
with or without deep convection according to: (i) ratio of mesoscale
updraft kinetic energy to CIN; (ii) lapse rates of stability parameters
and length and extent of mixing along parcel trajectories. 

Based on a sufficient sample of cases (both with without
convection), the hypothesis is refuted if deep convection: (i) occurs
with weak convergence and/or strong stability parameters lapse rates;
(ii) does not occur despite strong convergence and negligable stability
parameters lapse rates. 

The following appear in order; discussion points may directly
refer to one or more comments preceeding it.
Steve Koch on October
22, 1997 at 16:49:39:
How will trajectories be determined in the presence of mixing?
Will you have to assume some property conservation, or will some
Newtonian method by used? If property conservation (e.g, equivalent
potential temperature) conservation is not to be assume, then
what data will be of high enough quality to derive the needed
trajectories? I really don't see where any of the measurement
systems that have been suggested in your list will be adequate.
Click here to comment on this hypothesis.
Please reference: ZIEGLER1.

