Forward Scatter Sensor FD70 Features • Precipitation type identification, intensity, and accumulation • Droplet size distribution and reflectivity • Exceptional precipitation detection sensitivity • Superior liquid/frozen differentiation • Look-down geometry to minimize measurement disturbances • Enhanced visibility measurement in sand dust conditions Novel use of a single thin light sheet instead of the conventional light cone results in high detection sensitivity, enabling scatter-property analysis of each single particle and allowing detection of even the smallest drizzle droplets. Particle size and fall speed distributions provide additional information, enhancing precipitation type identification. The receiver measures forward scattered light at an angle of 42° with a very high sampling rate and powerful signal processing. Measurement arrangement and method is patented. FD70 forward scatter technology provides the most representative extinction coefficient (EXCO) determination possible. Scatter-property analysis reliably calculates the visibility-reducing effect of precipitation, allowing meteorological optical range (MOR) reporting in the most challenging conditions. FD70 covers all application needs, including measurement performance and capability requirements for runway visual range (RVR). Due to its innovative technology, FD70 reliably detects and identifies precipitation types that have been challenging for conventional technologies. Present weather identification 15 2) • Snow grains • Freezing drizzle • Freezing rain • Snow pellets 2) In addition to listed types, reports a variety of mixed precipitation types FD70 has multiple features to ensure reliable operation even in extreme weather conditions. Effective hood heating and proven look-down geometry protect the sensor windows against external disturbances. These are complemented with independent optical path monitoring and window contamination compensation. Self-diagnostics and modular design enable short service times. Redundancy of data communication is available for critical cases such as airport use. FD70 complies with ICAO, FAA, and WMO requirements and uses WMO and NWS weather codes in reporting. To ensure specific visibility and rain performance, Vaisala continuously compares calibrated FD70 units against reference sensors in the Vaisala outdoor test field. Every delivered unit can be traced back to this set of calibrated

Reporting uncertainty in operational ±10 % or ±1 m at 1 m-10 km conditions (±3 ft at 3 ft-6.2 mi) ]) Operating principle Look-down forward scatter Scattering angle (main receiver) 42° ±0.25° Scattering angle (side receiver) 90° ±0.25° Light source Near-infrared 1) Fulfills ICAO Annex 3: ±50 m (164 ft) up to 600 m (1968 ft). Present weather identification Drizzle, rain, snow, snow grains, ice crystals, ice pellets, freezing rain / drizzle, snow pellets, hail, fog / freezing fog, mist, haze Weather codes SYNOP: WMO table 4680 METAR: WMO table 4678 NWS codes Light, moderate, and heavy intensities...