Global Weather Observation data - Columns in the GL table


The surface observation data are in a simple ASCII format.

Description: This entity contains meteorological values observed at 3-hrly intervals by non-UK stations, as reported in SYNOP and METAR codes. The primary use of the entity requires the data in climatological sequence, i.e. all times for a station. New observations are added daily.

The attributes of this entity are similar to those of the UK Hourly Weather table, but with significant differences. Some of the attributes refer to 24hr values, but the primary user has requested that the data are not normalised. The period of maximum and minimum temperatures are defined by WMO Regional Reporting Practices. Where there is a 'WMO commitment', data will be retained permanently, but oldest data for other stations will be deleted annually. No QC is performed on the attribute values listed below, but QC flags may have been set. The flags themselves are held in attributes qc_flag_list_1 and qc_flag_list_2, each 1-bit flag in it corresponding to an attribute with a QC-flag. For software to interpret the flag lists please contact the MIDAS Team.

The table has two-dimensional partitioning, using wmo_region_code and ob_time.

For the convenience of users, the GL 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_time Date and time of observation
* met_domain_name Message type
  src_id Unique source identifier or station site number
  wmo_region_code '1' - '7'
'1' Africa; '2' Asia; '3' South America; '4' North and Central America; '5' South-west Pacific; '6' Europe; '7' Antarctic
  rec_st_ind State Indicator for the record**
  wind_direction Degs true
  wind_speed Knots
  prst_wx_id Present weather code
  past_wx_id_1 Past weather code #1
  past_wx_id_2 Past weather code #2
  cld_ttl_amt_id Total cloud amount code
oktas
  cld_base_amt_id Cloud base amount code
  cld_base_ht Cloud base height code
decametres
  low_cld_type_id Low cloud type code
  med_cld_type_id Medium cloud type code
  hi_cld_type_id High cloud type code
  wind_speed_unit_id Wind speed unit code describes how the wind reading was made and what units it was stored in (before converted to knots in MIDAS).
  visibility Decametres
  air_temperature Surface air temperature
0.1 deg C
  wetb_temp Wet bulb temperature
0.1 deg C
  dewpoint Dewpoint temperature
0.1 deg C
  stn_pres Station air pressure
0.1 hpa
  pres_sfc Pressure surface
  pres_sfc_ht Height of pressure surface
  msl_pressure Mean sea level air pressure
0.1 hpa
  pres_tdcy_amt Air pressure tendency
  prcp_ob_hr_cnt Precipitation hour count
  prcp_amt Precipitation amount
millimetres
  cld_amt_id_1 Layer cloud amount code #1
  cloud_type_id_1 Cloud type code #1
  cld_base_ht_id_1 Cloud base height code #1
decametres
  cld_amt_id_2 Layer cloud amount code #2
  cloud_type_id_2 Cloud type code #2
  cld_base_ht_it_2 Cloud base height code #2
decametres
  cld_amt_id_3 Layer cloud amount code #3
  cloud_type_id_3 Cloud type code #3
  cld_base_ht_id_3 Cloud base height code #3
decametres
  max_air_temp Maximum air temperature. The period of maximum and minimum temperatures are defined by WMO Regional Reporting Practices.
  min_air_temp Minimum air temperature. The period of maximum and minimum temperatures are defined by WMO Regional Reporting Practices.
  ground_state_id Ground state id
  min_grss_temp Grass temperature
  snow_depth Snow depth
  sun_ob_hr_cnt Sunshine observation hour count
  sun_dur Sunshine duration
  q24hr_prcp_amt 24hr precipitation amount
millimetres
  q24hr_pres_tdcy_amt 24hr air pressure tendency
  vert_vsby Vertical visibility
decametres
  src_opr_type Source operation type code - refers to whether the observation is manual or automatic
1 = Manned Observation, 7 group included in observation
2 = Manned Observation, 7 group omitted (no significant weather)
3 = Manned Observation, 7 group omitted (not observed, not available)
4 = Automatic Observation, 7 group included (code taken from WMO table 4677)
5 = Automatic Observation, 7 group omitted (no significant weather)
6 = Automatic Observation, 7 group omitted (not observed, not available)
7 = Automatic Observation, 7 group included (code taken from WMO table 4677)
Code 2 shoudl be used when present weather code is 00,01,02,03 AND past weather code is 00,11,22.
  gust_spd_type_code Gust speed type code
0 = 10 minute gust
1 = As past weather, etc.
See 910 - 914 of code 3778 in WMO documentation
  max_gust_speed Maximum gust speed
  runway_name Runway name
  rnwy_vis_rnge Runway visual range
  alt_pres Altimeter pressure
0.1 hpa
  qc_flag_list_1 QC bit flags for 9 specified items - please see note below for details.
  qc_flag_list_2 Please see note below for details.


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

NOTES:

The Met Office MIDAS Team is not responsible for the quality of the global weather data. This data is not flagged in the same way that data from the weather hrly and temp drnl tables etc would be flagged. In these tables the data is flagged by element but in the global weather table it is not as simple.

QC flag list 1 gives a bit flag for the following 15 values listed:

pres_tdcy, prcp_amt, cld_amt_id_1, cloud_type_id_1, cld_base_ht_id_1, cld_amt_id_2, cloud_type_id_2, cld_base_ht_id_2, cld_amt_id_3, cloud_type_id_3, cld_base_ht_id_3, max_air_temp, min_air_temp, q24hr_prcp_amt, q24hr_pres_tdcy_amt

QC flag list 2 gives a bit flag for the following 16 values listed:

wind_speed_unit_id, wind_speed, wind_direction, prst_wx_id, past_wx_id_1, past_wx_id_2, cld_ttl_amt_id, cld_base_amt_id, cld_base_ht, low_cld_type_id, med_cld_type_id, hi_cld_type_id, visibility, air_temperature, dewpoint, msl_pressure

The bit flag is based on a binary number generated from the 16 different bit sets shown below:

Bit set Description

0 (0) MetDB quality control performed
1 (1) Data correction performed 1 = performed
2 (2) MetDB suspect flag. MetDB flag=tendency flag)
3 (4) Spare
4 (8) MetDB hydrostatic check performed
5 (16) MetDB interpolation check performed
6 (32) MetDB substitution/correction applied
7 (64) spare
8 (128) rejected by forecasters (1=rejected)
9 (256) spare
10 (512) used in assimilation
11 (1024) checked by model quality control (at least background check)(1=not checked)
12 (2048) A priori rejection (rejected prior to knowledge of observed value; i.e. permanent rejection or deactivation)
13 (4096) model mode 1 quality control flag (background check)
14 (8192) model mode 2 quality control flag ('buddy' check)
15 (16384) model final quality control flag

*binary number in brackets

The QC flag number found in MIDAS could just correspond to one flag or multiple flags (ie bit set 5 (16) and bit set 6 (32)) which would equal 48. However this is just for the whole observation and does not specify which of the elements have caused these flags to be set. If any of bits 13 to 15 have flags set then this indicates that the observation has failed the quality control check.