Radiation Observation data - Columns in the RO table

Table Description - Columns in the RO table - Definition of Radiation terms - How to start filtering the rows of data out

The surface observation data are in a simple ASCII format.

Table Description:

This entity contains hourly and daily radiation amounts, including those no longer being reported. In all cases, ob_end_time and ob_hour_count define the observation period. Values are either for an hour or for 24 hours.

Columns in the RO table:

For the convenience of users, the RO file column headers are available for download in Excel or as a comma separated text file

PK Attribute Description / Units
* id  
* id_type Identifier type
* ob_end_time Date and time at end of observation
* ob_hour_count Observation hour count
* version_num Observation version number - Use the row with '1', as this has been quality checked by the Met Office
* met_domain_name Message type
  src_id Unique source identifier or station site number
  rec_st_ind State indicator for the record**
  glbl_irad_amt Global solar irradiation amount
Kjoules/ sq metre over the observation period
  difu_irad_amt Diffuse solar irradiation amount
Kjoules/ sq metre over the observation period
  glbl_irad_amt_q QC code - global irradiation amt
  difu_irad_amt_q QC code - diffuse irradiation amt
  meto_stmp_time Met Office receipt stamp time
  midas_stmp_etime Elapsed time to storage in MIDAS
  direct_irad Direct irradiation amount
Kjoules/ sq metre over the observation period
  irad_bal_amt Irradiation balance amount
Kjoules/ sq metre over the observation period
  glbl_s_lat_irad_amt Mean global S latitude radiation
Kjoules/ sq metre over the observation period
  glbl_horz_ilmn Global horizontal illumination
Kjoules/ sq metre over the observation period
  direct_irad_q QC code - direct irradiation
  irad_bal_amt_q QC code - irradiation balance amt
  glbl_s_lat_irad_amt_q QC code - global S lat irad amt
  glbl_horz_ilmn_q QC code - global horizontal illumination

** Details available to registered users only.

More information about the Met Office surface data is available in the documentation provided by the Met Office.

Definition of radiation terms:

The global irradiance is the total received on a horizontal surface direct from the whole sky including the sun. The diffuse irr adiance is the radiation on a horizontal surface from the sky other than that direct from the sun. The direct irradiance figure (to complicate things) is however the value coming directly from the sun itself but measured at normal incidence.
Direct and diffuse radiation are measured using a horizontally-mounted pyranometer, essentially thermopile with a black- coated upper surface. For diffuse radiation the sun needs to be obscured using a shading ring or a tracked (i.e. mechanically driven to follow the sun) shading ball or disc. The direct irradiance is measured using a pyrheliometer, in essence a pyranometer with a t ube on it blocking out the diffuse radiation. This does naturally require to be pointed at the sun and is normally mounted on a trac ker.
Specifically in MIDAS, the various radiation observation terms are defined as follows:

NOTE about Diffuse radiation:

Diffuse radiation measurements have largely been discontinued as a result of automation, which meant that staff were no longer available to adjust the diffuse radiation shading ring. However prior to around 2001/2002 a number of stations did record hourly diffuse radiation, nameley Aberport, Aviremore, Aldergrove, Beaufort Park, Camborne, Eskdalemuir, Hemsby, Hillsborough, Leeds Weather Centre, Lerwick and Stornoway. These data are available in MIDAS.

Diffuse radiation data only goes up to Jul 2006 in MIDAS.

It is possible to calculate diffuse radiation from a combination of direct and global measurements but this cannot be done accurately with hourly average figures as the sun changes position too much during this time period. It is recommended to use the diffuse data where these are available.

Note that the Met Office do still record diffuse radiation data at Camborne and Lerwick but these are not recorded in MIDAS; they do however get submitted to the World Radiation Data Centre in St Petersburg. Minute resolution values are also provided to the Baseline Surface Radiation Network.

How to start filtering the rows of data out:

  1. As the data arrive at the Met Office it undergoes quality control to check that the data are correct and consistent with the surrounding data points. Whether the process has occured or not is indicated by the version number (1 is the one to use as indicated in the table above).

  2. To show the progress of the data through the quality control the various variables will have an associated _q value (e.g. direct_irad_q). This _q value will have different values for each record (see details in table above).

  3. While the Met Office MIDAS system overwrites the existing entry in their database the BADC's MIDAS entries do not as the BADC takes snapshots of the the MIDAS database from time to time leading to duplicate entries occuring in our archive. If duplicate records are found, check the associated meto_stmp_time to determine which record is the most recent one - this is the one to use and the other(s) can be ignored.