Snow Water Equivalent Sensors

A snow water equivalent product refers to a sensor or system that measures and reports the liquid water content of snowfall. OSI's APG-815-DS and APG All Precipitation Gauges are purpose-built SWE products using optical scintillation technology to measure snow rate from 0.03 to 500 mm/hr, discriminating snow from other precipitation types automatically.

On average, approximately 10 inches of snow equals 1 inch of water, though this ratio varies significantly based on snow density, temperature, and crystal structure — ranging from 3:1 for wet, heavy snow to 20:1 or more for dry, powdery snow. OSI's optical sensors directly measure actual water equivalent rather than relying on this approximation, delivering more accurate results.

Snow is detected by optical precipitation sensors using technologies such as optical scintillation and forward scattering. OSI's DSP-WIVIS and APG-series sensors use in-beam optical scintillation combined with forward scatter and acoustic detection to identify snow, distinguish it from rain, drizzle, freezing rain, and mixed precipitation, and report precise snow water equivalent accumulation.

OSI's snow water equivalent sensors achieve 5% accumulation accuracy across their full measurement dynamic range of 0.03 to 500 mm/hr for snow. With a resolution of 0.001 mm and data updates every minute, they provide highly precise and reliable measurements suitable for NWS, WMO, and FAA-compliant weather observation systems.

Yes. OSI sensors are rated for operating temperatures from -50°C to 60°C (-58°F to 140°F) and are deployed globally from Antarctica to tropical rainforests. Adaptive Heater Technology (AHT) prevents lens frost and snow buildup, enabling unattended 24/7 operation in the harshest environments without maintenance intervention.

No. OSI's all-digital DSP-based sensors require no field calibration thanks to patented environmentally adaptive algorithms. There are no moving parts, no antifreeze chemicals, and no scheduled optic cleaning required. The APG-815-DS includes a comprehensive self-test updating every minute, with field calibration recommended only every two years as standard practice.