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Surface Observation

Overview

  A total of approximately 60 manned weather stations are run by the Japan Meteorological Agency (JMA), including Local Meteorological Offices. Located nationwide, these stations routinely observe various meteorological elements such as surface pressure, temperature, humidity, wind direction/speed, precipitation, snow depth, snowfall, sunshine duration, solar radiation, cloud and weather phenomena. Cloud conditions, visibility and weather phenomena are observed with the human eye, while other variables are automatically observed by surface weather observing system equipment.

  In addition to observation at manned stations, automatic observation is conducted at around 90 unmanned Special Automated Weather Stations equipped with surface weather observing systems.

  The observation data recorded are used for the issuance of weather forecasts, weather warnings/advisories and related information, and are also utilized in a range of operational and research fields including those related to climate change and socio-economic activities.


Surface Observation Sites

Surface observation network (As of 1 April 2016)

Surface observation network (As of 1 April 2016)


Surface Weather Observing System

  Surface weather observing system equipment at Local Meteorological Offices and Special Automated Weather Stations is used to observe weather-related elements such as surface pressure, temperature, humidity, wind direction/speed, precipitation, snow depth and sunshine duration. The system's elements are mostly installed in observation fields (Note 1) or on observatory rooftops, while their barometers and signal converters are located in indoor observation spaces.

  Surface weather observing system equipment includes electrical thermometers, electrical hygrometers, tipping bucket rain gauges, electronic barometers, propeller anemometers, electrical global pyranometers, rotating mirror sunshine recorders (measuring how long the ground surface is subjected to direct solar radiation), laser-based snow depth gauges and visibility meters.


Note 1) Observation fields: Spaces where observing instruments are placed to secure a stable environment free from the effects of surrounding artificial objects. Observation fields are usually covered with grass to mitigate heat influence from the ground.


Surface weather observing system

Surface weather observing system


Note 2) Double circular cylinders: Equipment in which thermometers and hygrometers are embedded. Insulating material is installed between cylinders, and artificial ventilation is provided to eliminate the influence of solar radiation. An extra shield plate is also attached to the bottom of the cylinders to prevent any effect from solar radiation absorbed by the ground.


Observation equipment

Observation equipment


Surface Weather Observation Elements
Observation element Observation equipment Number of stations** Observation spot Observation site
Temperature
  • Temperature
  • Daily maximum/minimum temperature*
  • Electrical thermometer
931 Observation
field
Manned
stations
and all
automated weather stations
Rain
  • Precipitation amount
  • Daily maximum 1-hour and 10-min precipitation amounts*
  • Tipping bucket rain gauge
1304
Snow
  • Snow depth
  • Snow cover meter
323
Wind
  • Wind direction/speed
  • Daily maximum gust speed and direction*
  • Daily maximum wind speed and direction*
  • Combined wind vane and propeller anemometer
931 Wind tower or rooftop
Sunshine
  • Sunshine duration (length of time in direct solar radiation)
  • Rotating mirror sunshine recorder
  • Solar-powered sunshine recorder
843
Pressure and
moisture
  • Surface pressure
  • Type and amount of pressure change
  • Daily minimum sea level pressure*
  • Electronic barometer
156 Observation
room
Manned
stations
and special automated weather stations
(unmanned)
only
  • Water vapor pressure
  • Dew point
  • Relative humidity
  • Daily minimum relative humidity*
  • Electrical hygrometer
  • Electrical thermometer
  • Portable aspiration psychrometer
Observation
Field
Presence and intensity of precipitation
  • Precipitation intensity
  • Weather phenomenon (presence/absence of precipitation event)
  • Rain sensor
  • Tipping bucket rain gauge
Solar radiation
  • Global solar radiation amount
  • Electrical pyranometer
Visibility, weather and atmospheric phenomena
  • Visibility
  • Present weather
  • Weather phenomenon
  • Cloud amount
  • Cloud type
  • Direction of cloud/cloud mass movement
  • Visual or auditory observation
61 Manned stations
only
Visibility and weather
  • Visibility
  • Present weather
  • Weather phenomenon
  • Visibility meter
  • Rain sensor
  • Electrical thermometer
  • Electrical hygrometer
95 Special
automated weather stations only

*Observation dates and times are recorded.
**As of 1 January 2016


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