Automated Meteorological Data Acquisition System

Automated Meteorological Data Acquisition System (AMeDAS), commonly known in Japanese as "アメダス" (amedasu), is a high-resolution surface observation network developed by the Japan Meteorological Agency (JMA) used for gathering regional weather data and verifying forecast performance.

The system began operating on 1 November 1974, and currently comprises 1,300 stations throughout Japan (of which over 1,100 are unstaffed), with an average separation of 17 km (11 mi).

Observations at staffed stations cover weather, wind direction and speed, types and amounts of precipitation, types and base heights of clouds, visibility, air temperature, humidity, sunshine duration, and atmospheric pressure.

For about 280 stations (staffed or unstaffed) located in areas of heavy snowfall, snow depth is also observed.

All the observational data is transmitted to the AMeDAS Center at JMA Headquarters in Tokyo on a real time basis via dedicated telephone lines.