Conduct of Cloud Spectra Measurements.
Abstract
The reasons for instrumental errors in cloud particle spectra and liquid water measurements were investigated. Calibrations and tests were performed on four probes and on a hot-wire liquid water device. The 1D and 2D cloud probes (1D-C & 2D-C) were found to undercount particles in the smaller size channels due to reduced depths of field for these sizes (approx. 100 m). The problem is both one of undercounting and missing. An iterative correction scheme is necessary to truly account for both but would be too cumbersome, for real time use. A channel-by-channel correction scheme was found the the 1D-C probe (which is similar to that provided by PMS) and gives satisfactory corrections for many spectral shapes. Use of a constant depth of field was found to be best for the 2D-C probe. An artifact-rejection scheme for the 2D-C probe is discussed. The phase discrimination option for the 2D-C probe was found to be approx 25% effect in detecting the ice phase in mixed cloud. The PMS Axially Scattering Spectrometer Probe (ASSP) and Forward Scattering Spectrometer Probe (FSSP) artificially broaden droplet spectra, up to twice the standard deviation around the mean size measured by the cloud gun (CG), due to nonuniformities in beam itensities. Uncertainties in sample volume and losses during instrument dead times incur errors in droplet concentrations. Comparisons were made between the ASSP, FSSP, CG and CSIRO liquid water device.
Document Details
- Document Type
- Technical Report
- Publication Date
- Feb 06, 1981
- Accession Number
- ADA102944
Entities
People
- Darrel G. Baumgardner
- Gabor Vali
- Marcia K. Politovich
Organizations
- University of Wyoming