A HIGH-VOLUME PARTICLE SPECTROMETER FOR ATMOSPHERIC RESEARCH

RECENT IN SITU OBSERVATIONS OF LIGHT TO MODERATE PRECIPITATION DURING THE 1985 HAWAIIAN WARM RAIN PROJECT REVEALED DROPS WITH DIAMETERS >2MM IN MUCH HIGHER CONCENTRATIONS THAN PREVIOUSLY REPORTED. IT NOW APPEARS THAT THESE LARGER DROPS HAVE OFTEN BEEN MISSED DUE TO THE LIMITED SAMPLE VOLUME OF THE IN SITU DISTROMETERS. ACCURATE MEASUREMENTS OF PRECIPITATION SPECTRA ARE CRITICAL TO UNDERSTANDING AND MODELING PRECIPITATION EVOLUTION, AND ARE A PREREQUISITE FOR QUALITY ESTIMATION OF RAINFALL INTENSITY USING RADAR. INCREASING THE SAMPLE VOLUME OF THE PRESENT GENERATION OF AIRBORNE DISTROMETER (I.E., THE PMS PRECIPITATION SPECTROMETER) IS NOT STRAIGHT-FORWARD. EXTRAPOLATING THE PMS DISTROMETER TO THE REQUIRED SAMPLE VOLUME VIOLATES PHYSICAL CONSTRAINTS ANDINTRODUCES VERY HIGH DATA RATES (>100 MBYTES S(-1). THE DESIGN OF A NEW PRECIPITATION SPECTROMETER INCORPORATING COMPONENTS ON THE CUTTING EDGE OF ELECTRO-OPTICAL AND DATA PROCESSING TECHNOLOGIES IS DESCRIBED. MODERATE POWER (20-50 MW) LASER DIODES AND VERY HIGH-SPEED CCD ARRAYS ARE USED IN CONJUNCTION WITH ON-THE-FLY DATA COMPRESSION TECHNIQUES RESULTING IN THE DESIGN OF AN IMAGING SPECTROMETER WITH A VERY HIGH SAMPLE VOLUME (5M(-3)S(-1) AT 100MS(-1)).