Abstract:
The First ISCCP Regional Experiments have been designed to improve
data products and cloud/radiation parameterizations used in general
circulation models (GCMS). Specifically, the goals of FIRE are (1) to
improve basic understanding of the interaction of physical processes
in determining life cycles of cirrus and marine stratocumulus systems
and the radiative
... properties of these clouds during their life cycles
and (2) to investigate the interrelationships between the ISCCP data,
GCM parameterizations, and higher space and time resolution cloud
data.
To-date, four intensive field-observation periods were planned and
executed: a cirrus IFO (October 13-November 2, 1986); a marine
stratocumulus IFO off the southwestern coast of California (June
29-July 20, 1987) a second cirrus IFO in southeastern Kansas (November
13-December 7, 1991); and a second marine stratocumulus IFO in the
eastern North Atlantic Ocean (June 1-June 28, 1992). Each mission
combined coordinated satellite, airborne, and surface observations
with modeling studies to investigate the cloud properties and physical
processes of the cloud system.
The microphysical parameters in the data set were derived from 2D
probe data collected by the NCAR aircraft during FIRE II. The 2D-C
data are converted to size spectra according to the guidelines given
in Heymsfield and Baumgardner (1985, Bull. Amer. Meteoro. Soc.), where
one element is added to the size of a particle along the the flight
direction to account for the probe's intrinsic start-up time. Size is
determined as the maximum dimension ($D_{max}$) along the flight
direction or optical array axis. The nominal size resolution for the
Sabreliner 2D probe is 50 microns/per shadowed optical array element,
for the King Air is 25 microns/bin. Sample area (SA) is derived using
the depth of field estimates reported by Knollenberg (1970).
Particles are binned into 32 size categories, nonuniformly spaced with
higher resolution in the smaller classes. Particles within each size
bin are subdivided into 10 ``area ratio (AR)'' bins, where AR
represents the ratio of particle area to the area of discs of diameter
$D_{max}$.
The microphysical parameters in the data set were derived from 2D
probe data collected by the NCAR Sabreliner during FIRE II. The
derivation of the microphysical parameters is outlined in the later
reference to Heymsfield (1977). The vertical velocity is the
"steady-state" velocity in cm s-1 to keep the relative humidity at
it's currently measured value. Differential growth rate represents
the growth rate of the particle population of different sizes at the
current relative humidity. The Total differential growth rate is the
sum of the growth rate in all channels. The assumptions used for the
IWC calculations are reported in Heymsfield; also, generic size to
mass equations are used. Precipitation rate is calculated from
particle size and terminal velocity data, integrated over the size
spectrum. Concentration data are as derived above. Number of
crystal-crystal collisions are derived from the data reported by
Hindman and the crystal terminal velocities. Water vapor density and
supersaturation information in this data set should not be used--it is
unreliable. Curve fits to the data using least squares methods are
provided.
VARIABLE DESCRIPTION UNITS
-------------------------------------------------------------------------------
IT1, ITMEASUREMENT TIME INTERVAL HH/MM/SS
PS STATIC PRESSURE mb
TEMP AMBIENT TEMPERATURE degreesC
ALT PRESSURE ALTITUDE m
USTAR VERTICAL VELOCITY NEEDED TO KEEP THE cm/s
RELATIVE HUMIDITY CONSTANT
DBARM MEDIAN PARTICLE MASS WEIGHTED DIAMETER cm
DMAX MAXIMUM PARTICLE DIAMETER cm
W1 DIFFUSIONAL GROWTH RATE IN CHANNEL 1 g/sec
W2 DIFFUSIONAL GROWTH RATE IN CHANNEL 2 g/sec
W3 DIFFUSIONAL GROWTH RATE IN CHANNEL 3 g/sec
W4 DIFFUSIONAL GROWTH RATE IN CHANNEL 4 g/sec
WTOT TOTAL DIFFUSTIONAL GROWTH RATE g/sec
DT8 DEPLETION TIME (8 micron droplets) sec
DT12 DEPLETION TIME (12 micron droplets) sec
TMASS1 IWC IN CHANNEL 1 g/m^3
TMASS2 IWC IN CHANNEL 2 g/m^3
DPTC DEW POINT TEMPERATURE (EG&G) degrees C
RH RELATIVE HUMIDITY (EG&G) %
RIWC ICE WATER CONTENT g/m^3
XM1 ICE WATER CONTENT BASED ON SNOW HABIT g/m^3
XM2 ICE WATER CONTENT BASED ON SMALL g/m^3
SNOW HABIT
XM3 ICE WATER CONTENT BASED ON LARGE g/m^3
SNOW HABIT
R PRECIPITATION RATE mm/hr
DBZ RADAR REFLECTIVITY FACTOR decibels
VBAR MEAN REFLECTIVITY WEIGHTED WITH THE cm/s
TERMINAL VELOCITY
TTCONC TOTAL PARTICLE CONCENTRATION #/L
CBIN1 PARTICLE CONCENTRATION WITHIN THE #/L
RANGE LE 200
CBIN2 PARTICLE CONCENTRATION WITHIN THE 200-500 #/L
RANGE
CBIN3 PARTICLE CONCENTRATION WITHIN THE 500-800 #/L
RANGE
CBIN4 PARTICLE CONCENTRATION WITHIN THE #/L
RANGE GT 800
CE8 COLLECTION EFFICIENCY (8 micron none
droplets)
CE12 COLLECTION EFFICIENCY (12 micron none
droplets)
TMASS3 IWC IN CHANNEL 3 g/m^3
TMASS4 IWC IN CHANNEL 4 g/m^3
TIMP # OF CRYSTAL-CRYSTAL COLUMNS sec^(1-)
RHORH WATER VAPOR DENSITY g/cm^3
SI SUPERSATURATION WITH RESPECT TO ICE %
SW SUPERSATURATION WITH RESPECT TO WATER %
LAMBDA COEFFICIENTS USED TO FIT THE EQUATION #/cm^3
NZERO N=N0*EXP(-LAMBDA*D) #/L/mm
RSQ COEFFICIENT OF THE FIT
ICP PROBE TYPE (C OR P) none