Decoding the nomenclature for COMPASS experiments:
Each COMPASS simulation experiment occupies
a unique spot in an eightdimensional parameter space. Thus, eight numeric descriptors
are needed in identifying each simulation. For mnemonic purposes, we also
include an alphabetic identifier for each parameter. Thus each experiment
name consists of a series of eight pairs of characters, with the
first member of each pair being the alphabetic character suggesting the
name of the parameter, and the second being the representation of the numerical
value assumed by that parameter in that particular experiment. While
this nomenclature design may at first seem cumbersome, we have concluded
that it is the simplest way to assign unique names to each experiment.
With just a little experience, we have found it quite easy to describe
the various subregions of the large parameter space using our nomenclature.
For example, discussion of "p3 versus p6" is our
shorthand way of saying we are discussing how the simulations behave as the "p" parameter
(which is the designation for environmental precipitable water, a
good proxy for the temperature at cloud base) varies, all other parameters
being held constant.
In most cases, we have opted to do experiments having only two values
of each parameter, one large, the other small. The values are chosen to
be realistic, but different enough so that any real convective sensitivity
to the changes in the parameter will be evident in the simulations. In a
few cases (such as "e" and "c") we have decided to add a third, "medium"
value of the parameter, so that commonly encountered values of those
parameters will be given proper consideration. In the case of the "m"
and "n" parameters (which regulate the shapes of the buoyancy and vertical
shear profiles, respectively), we have opted to use different paired values
in the different parts of the "e" (CAPE, see below) space. This is because
of some fundamental relationships between the way the "m" parameter can
vary as "e" varies. To be more precise, when "e" is small, there exists
a greater range of possible physically realizable values of "m" than at
large "e"; one could use the same values of "m" for all values of "e",
but they would have to be restricted to only those values that are
physically realizable at large "e." It turns out that interesting
sensitivities are evident for large values of "m" when "e" is small,
and we have chosen to let our pairs of values of "m" increase at small
"e" to allow for proper exploration of these important sensitivities.
In physical terms, this means that when CAPE is small, it is possible to
generate soundings with lower altitudes of maximum buoyancy, as compared
to what happens when CAPE becomes very large, where flexibility in shaping
the buoyancy profile starts to get lost. Note that although it is the
relationship between the largest value feasible for "m" as "e" decreases
that dictates our choices of "m" as a function of "e," we also have
decided to let the shear shape parameter "n" assume the same values as
"m" for each value of "e" studied. This is done partly for convenience,
and partly because observational data suggest that larger values of "n"
do indeed tend to be correlated with lower values of "e."
What follows is an example experiment name, and instructions on how
to decode it. With the information below, it is possible to decode the
structure of each experiment's design. In the graphical results section, we
always add each experiment's full name to each image, so that the results are
unambiguously attached to the proper experiment.
In the legend information below, the following abbreviations are used:

CAPE = convective available potential energy, a quantitative measure of
the maximum bulk amount of vertical kinetic energy updraft parcels can
acquire from their environment; updrafts seldom manage to convert all
the CAPE into vertical kinetic energy, because of adverse effects of
certain combinations of the other seven environmental parameters;
one of COMPASS's main interests is in seeing which combinations
of parameters lead to the most efficient convective overturning;

LCL = lifted condensation level, or the level of cloud base,
dictated by surface temperature and moisture and boundary layer lapse rate;
LFC = level of free convection, or the level above which ascending parcels
begin to experience positive buoyancy relative to the environment;
this level can never be below the LCL due to physical realizability
constraints.
Note that although the table below gives three possible values of LCL and
LFC height, we are currently using only the smallest and largest values.
Note also that although the experiment framework readily allows for either
curved (semicircular) or straight hodographs, curved hodographs are used
exclusively in the first phase of this work.
Sample experiment name = e2c2m2n4k2f6p6h9
CAPE parameter e:
1 = 800 J/kg
2 = 2000 J/kg
3 = 3200 J/kg
Hodograph radius parameter c (or s):
c = curved
s = straight
1 = 8 m/s
2 = 12 m/s
3 = 16 m/s
Buoyancy shape parameter m:
1 = 1.56 > Zb' = 9.30 km
2 = 1.88 > Zb' = 7.71 km
3 = 2.38 > Zb' = 6.09 km
4 = 3.22 > Zb' = 4.50 km
5 = 5.00 > Zb' = 2.90 km
where Zb' is the altitude of maximum buoyancy, relative to the
LFC
Wind profile shape parameter n:
1 = 1.56 > Zv' = 9.30 km
2 = 1.88 > Zv' = 7.71 km
3 = 2.38 > Zv' = 6.09 km
4 = 3.22 > Zv' = 4.50 km
5 = 5.00 > Zv' = 2.90 km
where Zv' is the altitude of maximum vwind, relative to the
LFC, in an assumed curved hodograph situation; for straight
hodographs, a curved hodograph is first constructed, then unfolded
into a straight line, ensuring that the shear profiles are identical
for both curved and straight hodographs with similar specifications.
LCL height (actually mixed layer depth) index k:
2 = 0.5 km
4 = 1.0 km
6 = 1.6 km
LFC height (actually moist layer depth) index f:
2 = 0.5 km
4 = 1.0 km
6 = 1.6 km
Precipitable water (PW; implemented as LCL Temperature) parameter
p:
3 = 30 mm ( > T_LCL = 15.5 C for k = 2)
6 = 60 mm ( > T_LCL = 23.5 C for k = 2)
Midtropospheric relative humidity parameter h:
5 = 50% everywhere in the troposphere above the LFC
6 = 60% everywhere in the troposphere above the LFC
7 = 70% everywhere in the troposphere above the LFC
8 = 80% everywhere in the troposphere above the LFC
9 = 90% everywhere in the troposphere above the LFC
Using the above legend, the sample experiment name "e2c2m2n4k2f6p6h9"
means that CAPE = 2000 J/kg, the radius of the curved hodograph
= 12 m/s, the buoyancy shape parameter = 1.88, the shear shape
parameter = 3.82, the LCL level = 2 (0.5 km), the LFC level
= 6 (1.6 km), the precipitable water = 60 mm, and the relative
humidity = 90%.