Automated Meteorological Data Acquisition System

Lore & Background

AMeDAS comprises 1,300 stations throughout Japan, of which over 1,100 are unstaffed. 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. All of these except weather, visibility, and cloud-related elements are observed automatically. At unstaffed stations, observations are performed every 10 minutes. About 700 of the unstaffed stations observe precipitation, air temperature, wind direction and speed, and sunshine duration, while the other stations observe only precipitation.

Reader's Guide

AMeDAS is significant as a foundational tool for regional weather data collection and forecast verification in Japan. Its dense network of 1,300 stations, with an average separation of 17 km, provides high-resolution surface observations that are transmitted in real time to the AMeDAS Center at JMA Headquarters in Tokyo via dedicated telephone lines. After a quality check, the data is delivered nationwide. The system also supports natural disaster observation, with temporary observation points set up in areas showing signs of volcanic eruptions or earthquakes. For about 280 stations in heavy snowfall areas, snow depth is also observed. AMeDAS's legacy lies in its continuous, automated monitoring of weather conditions across Japan, enabling improved forecasting and disaster preparedness.

Did You Know?

• AMeDAS began operating on 1 November 1974.
• Over 1,100 of its 1,300 stations are unstaffed.
• About 700 unstaffed stations observe precipitation, air temperature, wind direction and speed, and sunshine duration.
• Temporary observation points are set up in areas with signs of volcanic eruptions or earthquakes.