The purpose of this work is to compare visibility (Vis) measurements obtained from five sensors to human-based observations of Vis values and to a numerical model forecast runs to better understand issues related to low visibility conditions. These ground-based observations were made during the Fog Remote Sensing and Modeling Project in St. John’s (FRAM-S), which took place in March-April 2009. The instruments used to measure Vis were 1) the Biral HSS VPF- 730 Combined Visibility & Present Weather Sensor, 2) Sentry VIS sensor, 3) Vaisala FD12P present weather sensor, 4) Vaisala PWD12 sensor (two of them), and 5) Belfort Vis sensor. Human-based Vis observations were also available during the project and used for validations. Validations were also performed by estimating Vis from the particle measurements of a) CAP (Climatronic Aerosol Profiler) sensor (for aerosols and droplets; 0.3-10 micron), b) DMT Fog Measuring Device (FMD; 2-50 micron), and c) DMT Ground Cloud Imaging Probe (GCIP; 7.5- 900 micron). Results representing various low Vis conditions because of freezing fog and warm fog are presented and probability curves developed earlier based on only FD12P measurements are discussed. Possible applications of the results are offered for nowcasting issues.
展开▼
