Why is Raindrop spectrometer called a precipitation weather phenomenon meter?

Raindrop spectrometer, also known as a precipitation weather phenomenon meter, is a sensor based on optical principles that automatically and continuously monitors the spectral distribution of precipitation particles and identifies and outputs the type of precipitation weather phenomenon in real time.

As a modern automatic meteorological observation device, Raindrop spectrometer is gradually replacing traditional manual observation methods, providing accurate precipitation data support for meteorology, transportation, agriculture, and other fields. This device typically uses laser or video technology to perform non-contact measurement of high-speed precipitation particles.

In terms of technical principles, taking the laser-type Raindrop spectrometer as an example, it actively emits an infrared light band. When precipitation particles pass through the sampling area, the receiver detects the change in light energy attenuation. Based on this, the device calculates the particle's falling velocity and size, and automatically identifies the precipitation phenomenon, such as drizzle, rain, snow, or hail, according to a built-in particle spectrum empirical model. Video-type devices use a high-speed scanning camera to capture particle cross-sections, thereby reconstructing their three-dimensional shape and velocity.

The Raindrop spectrometer measurement capabilities cover a wide range of precipitation conditions. Its particle size measurement range is 0.2 to 5 mm for liquids and 0.2 to 25 mm for solids, while its velocity measurement range is 0.2 to 20 m/s. The equipment typically divides particle size and velocity into 32 levels for precise spectral analysis. In precipitation type identification, modern Raindrop spectrometer instruments can distinguish between various types, including freezing rain, rain, hail, and snow, with an automatic identification accuracy exceeding 97% for specific types, superior to manual observation. Furthermore, the instrument can output key data such as precipitation intensity (up to 1200 mm/h), radar reflectivity, and meteorological codes (e.g., SYNOP, METAR).

The Raindrop spectrometer has a wide range of applications. In meteorological operations, it provides real-time data support for weather forecasting, severe weather warnings, and weather modification operations. In hydrological research, high-precision precipitation particle spectral data helps in establishing and validating hydrological models and assessing rainfall runoff and soil erosion. In the transportation sector, particularly in aviation and highway management, instruments can detect hazardous weather such as freezing rain or hail in advance, providing a basis for operational decisions. For example, the two-dimensional video surveillance system Raindrop spectrometer installed by the Hong Kong Observatory at Chek Lap Kok Airport once measured over 140,000 raindrops in six minutes during a heavy rain. This data is not only used to calculate rainfall rates but also to infer radar reflectivity for comparison and correction of radar data, serving precipitation physics research.

In conclusion, with its high precision, automation, and multi-dimensional measurement capabilities, Raindrop spectrometer has become an indispensable component of modern meteorological observation networks. Its data products are of great significance for improving the accuracy of precipitation forecasts and understanding cloud physics mechanisms.