First ISCCP Regional Experiment (FIRE) Cirrus Phase II NCAR Kingair Aircraft Microphysical Data

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 seek the 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 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 systems. 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 andsupersaturation 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 TM