The Automated Meteorological Data Acquisition System (AMeDAS) is a collection of Automatic Weather Stations (AWSs) run by JMA for automatic observation of precipitation, wind direction/speed, temperature and humidity to support real-time monitoring of weather conditions with high temporal and spatial resolution. AMeDAS data play an important role in mitigating the risk of weather-related disasters.
An AMeDAS observing station measuring precipitation, wind direction/speed,
temperature and humidity (with snow cover meter)
JMA began operating the AMeDAS system, which currently includes as many as 1,300 rain gauges at average intervals of 17 km nationwide, on 1st November 1974. Around 840 stations also observe wind direction/speed, temperature and humidity in addition to precipitation, and snow depth is observed at about 330 manned and unmanned stations in snowy districts.
List of Observation Sites
Display of AMeDAS data on the JMA website
|Precipitation amount||Amount of rainfall or snowfall||Expressed in units of 0.5 mm. Snow, hailstone and graupel amounts are given as melted-water equivalents.|
|Wind direction||Direction of wind origin||Expressed using 16 compass points (north (N), north-northeast (NNE), northeast (NE), east-northeast (ENE), east (E), east-southeast (ESE), southeast (SE), south-southeast (SSE), south (S), south-southwest (SSW), southwest (SW), west-southwest (WSW), west (W), west-northwest (WNW), northwest (NW) and north-northwest (NNW)) based on the average for the 10-minute period before the observation time. By way of example, “northeast” represents wind blowing from the northeast.|
|Wind speed||Velocity of wind||Expressed in units of 0.1 m/s (1 m/s on maps) based on the average for the 10-minute period before the observation time.|
|Temperature||Air temperature||Expressed in units of 0.1 degrees Celsius.|
|Sunshine duration*||Number of hours of sunshine||Expressed in units of 0.1 hours (6 minutes). By way of example, an hour of sunshine (e.g., from 11:00 to 12:00) is expressed as 1 hour.|
|Snow depth||Height of snow surface from the ground||Expressed in units of 1 cm.|
|Humidity||Air relative humidity||Expressed as a percentage|
Examples of AMeDAS Data on the JMA Website
|Name||Time||Temperature||Precipitation amount||Wind direction and speed||Sunshine duration*||Snow depth||Humidity|
*Sunshine durations are estimated from meteorological satellite observation on unmanned stations (other than Special Automated Weather Stations). The element is displayed as “Sunshine duration (estimate)”.
AMeDAS Observation Network
AMeDAS observation network (as of 1 January 2023)