STATION_NAMES is the station name (see station_list for full details).
YEAR is the year expressed in full, ie 1996. Details of the data coverage are also given in station_list.
The .syn extension shows that the file contains synoptic data as opposed to climate data which is denoted .cli.
The synoptic data in .syn files is in a simple ASCII format.
* indicates a missing value.
The fields in each file are as follows ...
| PARAMETER | FIELDS | COLUMNS | UNITS | COMMENTS |
|---|---|---|---|---|
| Year | 1 | 1-6 | - | - |
| Month | 2 | 7-9 | - | - |
| Day | 3 | 10-12 | - | - |
| Hour | 4 | 13-15 | - | Hour of observation UTC (GMT) 0000, 0300 ... 2100 |
| 10 minute wind direction | 5 | 16-19 | Deg.from true North | At stations with an anemograph, the mean direction is for a period of 10 minutes ending at the hour of observation. However, if there has been a significant change in direction (30 degrees or more) and the mean value has been maintained for at least 3 minutes then this value is used instead. Where there are indicating instruments only, the means of several 15 to 20 second readings taken over the period of observation are used, but again, if there has been a significant change, the means of several readings after the change are used instead. |
| 10 minute wind speed | 6 | 20-21 | knots | Speeds are adjusted to a standard height of 10 m. At stations with an anemograph, the mean speed is for a period of 10 minutes ending at the hour of observation. However, if there has been a significant change in speed (10 knots or more) and the mean value has been maintained for at least 3 minutes then this value is used instead. Where there are indicating instruments only, the means of several 15 to 20 second readings taken over the period of observation are used, but again, if there has been a significant change, the means of several readings after the change are used instead. |
| Present weather | 7 | 22-24 | WMO Code | Weather observation is made hourly at the observing station. |
| Past weather | 8 | 25-27 | WMO Code | Past weather is defined as weather occurring in the past 6 hours at 00, 06, 12, 18 UTC, and the past 3 hours at 03, 09, 15, 21 UTC. |
| Total cloud amount | 9 | 28-29 | oktas | The unit used to indicate the proportion of the sky covered by clouds is the 'okta' or eighth of the sky. The scale runs from 0, which indicates a cloudless sky, to 8, which is a completely overcast sky (see WMO code). |
| Low cloud amount | 10 | 30-31 | oktas | Cloud bases below 8000 ft.
If no low cloud, medium cloud amount. |
| Base of lowest cloud | 11 | 32-35 | kft | Height above ground of the base of the lowest cloud seen. |
| Low cloud type | 12 | 36-37 | WMO Code | Form of Low cloud |
| Medium cloud type | 13 | 38-39 | WMO Code | Form of Medium cloud |
| High cloud type | 14 | 40-41 | WMO Code | Form of High cloud |
| Horizontal visibility | 15 | 42-46 | km | The greatest distance an observer can see and identify prominent objects. Units for visibility are kilometers |
| Dry-bulb temperature | 16 | 47-52 | deg C | The measurements of air temperature are obtained from thermometers exposed in white-painted louvred screens supported over short grass in the open, the bulbs of the thermometers being 1.25m above ground. The nearest object should be at least twice its height away from the screen. The louvres are arranged such that there is a free, but reduced, flow of air past the thermometer, and that sunlight cannot penetrate directly into the screen. Commercial Automatic Weather Stations AWSs often use smaller circular 'Gill' screens which are mounted on metal poles. The Dry thermometer gives the current air temperature or dry-bulb temperature. |
| Wet-bulb temperature | 17 | 53-58 | deg C | The web-bulb temperature is the lowest temperature that can be obtained by evaporating water into the air. It measures the humidity of the air. |
| Dew-point temperature | 18 | 59-64 | deg C | The dew point temperature is the temperature to which the air must be cooled to produce saturation with respect to water at its existing atmospheric pressure and humidity. |
| Water vapour pressure | 19 | 65-69 | mb | The vapour pressure corresponds to the pressure exerted by the water vapor molecules in a given volume of air. |
| Relative humidity | 20 | 70-73 | % | The relative humidity is the ratio of the amount of water vapour in the air compared to the amount required for saturation (at a particular temperature and pressure). It is the ratio of the air's actual vapour pressure to its saturation vapour pressure. |
| Mean sea level pressure | 21 | 74-80 | mb | Atmospheric pressure is expressed in millibars (1 millibar = 100 pascals = 100 newtons per square metre). Precision aneroid barometers are now in general use for measuring pressure and a correction for altitude is applied to obtain the value at mean sea level (MSL). |
| Pressure change over last 3 hours | 22 | 81-85 | mb | Pressure change is reported in mb. |
| Pressure characteristic over last 3 hours | 23 | 86-87 | WMO Code | The pressure characteristic (e.g. lower, higher or the same at the time of observation than three hours ago) is recorded following the Met Office WMO code. |
| Cloud layer 1 - Amount | 24 | 88-90 | oktas | - |
| Cloud layer 1 - Type | 25 | 91-93 | Code | CI=Cirrus, CC=Cirricumulus,
CS=Cirrostratus, AC=Altocumulus, AS=Altostratus, NS=nimbostratus, SC=stratocumulus, ST=stratus, CU=Cumulus, CB=cumulonimbus |
| Cloud layer 1 - Base | 26 | 94-97 | kft | Tops are not reported |
| Cloud layer 2 - Amount | 27 | 98-99 | oktas | - |
| Cloud layer 2 - Type | 28 | 100-102 | Code | CI=Cirrus, CC=Cirricumulus,
CS=Cirrostratus, AC=Altocumulus, AS=Altostratus, NS=nimbostratus, SC=stratocumulus, ST=stratus, CU=Cumulus, CB=cumulonimbus |
| Cloud layer 2 - Base | 29 | 103-106 | kft | Tops are not reported |
| Cloud layer 3 - Amount | 30 | 107-108 | oktas | - |
| Cloud layer 3 - Type | 31 | 109-111 | Code | CI=Cirrus, CC=Cirricumulus,
CS=Cirrostratus, AC=Altocumulus, AS=Altostratus, NS=nimbostratus, SC=stratocumulus, ST=stratus, CU=Cumulus, CB=cumulonimbus |
| Cloud layer 3 - Base | 32 | 112-115 | kft | Tops are not reported |
| Gust speed | 33 | 116-118 | knots | - |
| Maximum temperature | 34 | 119-124 | deg C | 0600-2400 |
| Minimum temperature | 35 | 125-130 | deg C | 0600-2400 |
| 12-hour rainfall | 36 | 131-134 | 0.1 mm | Rainfall amount is measured for a period 0600-2400. |
| Station level pressure | 37 | 135-141 | mb | 0600-2400 For some european stations only. Atmospheric pressure as measured at the station level. Correction for altitude is not applied. |
| State of ground | 38 | 142-144 | WMO Code | Note that
the code range 10-19 corresponds to the WMO code range 0-9 (no
snow) and the code range 20-29 corresponds to the WMO code range 0-9 (with snow) |
| Snow depth | 39 | 145-148 | cm | Snow depth in cm. |
| Quality control flag | 40 | 149-153 | bits | - |
| Quality control flag | 41 | 154-158 | bits | - |