bms measurements

Since April 25th 2018, measured by an automatic EE181 E+E Relative Humidity and Temperature probe (E+E Elektronic Corporation, supplied by Campbell Scientific). Prior to this measured with an automatic HMP45C Relative Humidity and Temperature sensor. New temperature sensors were installed on 8th November 2012.

Before November 1996, manually recorded with a mecury-in-glass sheathed maximum thermometer, housed in a naturally aspirating temperature screen.

Data from August 2009-May 2012; 16-17/08/2016; 30/10/2016-3/11/2016 and 18/4/2018-25/4/2018 provided by the Met. Office. © Crown Copyright 2009-2012, 2016, 2018, published by the Met. Office.

Recorded over the 24 hour period up to 0900GMT, for the current day's minimum temperature.

Since April 25th 2018, measured by an automatic EE181 E+E Relative Humidity and Temperature probe (E+E Elektronic Corporation, supplied by Campbell Scientific). Prior to this measured with an automatic HMP45C Relative Humidity and Temperature sensor. New temperature sensors were installed on 8th November 2012.

Before November 1996, manually recorded with a spirit-in-glass with indicator bar minimum thermometer, housed in a naturally aspirating temperature screen.

Data from August 2009-May 2012, 16-17/08/2016; 30/10/2016-3/11/2016 and 18/4/2018-25/4/2018 provided by the Met. Office. © Crown Copyright 2009-2012, 2016, 2018, published by the Met. Office.

Recorded at 0900GMT. Until 2009 used with DRYB to calculate RELH, VAP and DEWP.

Since November 1996, calculated from an automatic Relative Humidity and Temperature sensor. Prior to this measured with a mercury-in-glass sheathed thermometer housed in a naturally aspirating temperature screen, the bulb covered by a cotton wick kept moist from a water reservoir. Discontinued September 2009 and replaced by a HMP45C Relative Humidity and Temperature sensor, to measure relative humidity (RELH), from which VAP and DEWP are now calculated after the method of Buck (1981).

Recorded at 0900GMT.

Since April 25th 2018, measured by an EE181 E+E Relative Humidity and Temperature probe (E+E Elektronic Corporation, supplied by Campbell Scientific). Prior to this it was measured with an automatic HMP45C Relative Humidity and Temperature sensor. New temperature sensors were installed November 2012.

Before November 1996, recorded with a mecury-in-glass sheathed thermometer housed in a naturally aspirating temperature screen.

Data from August 2009-May 2012; 16-17/08/2016; 30/10/2016-3/11/2016 and 18/4/2018-25/4/2018 provided by the Met. Office. © Crown Copyright 2009-2012, 2016, 2018, published by the Met. Office.

Recorded at 0900GMT.

Until August 2009, derived from DRYB and WETB, calculated by the datalogger (see derived variables). Before November 1996 calculated from hygrometric tables.

Since September 2009, available as a derived variable within e-RA, derived from DRYB and RELH calculated after the method of Buck (1981).

Recorded at 0900GMT, for the minimum temperature on grass over the previous 24 hours.

Recorded by a thermistor (electronic temperature probe, Campbell Scientific, type 107). Before Nov 1996, recorded manually with a spirit-in-glass with indicator bar minimum thermometer, with cotton sleeve and anti-condensation shield on upper part of the instrument.

Data from 16-17/08/2016 provided by the Met. Office. © Crown Copyright 2016, published by the Met. Office.

Recorded at 0900GMT.

Measured by thermistors (electronic temperature probes, Campbell Scientific, type 107), buried in the soil at the appropriate depth.

G30T data from 16-17/08/2016 and 18/4/2018-25/4/2018 provided by the Met. Office. © Crown Copyright 2016, 2018, published by the Met. Office.

Recorded at 0900GMT.

Measured by thermistors (electronic temperature probes, Campbell Scientific, type 107), buried in the soil at the appropriate depth.

S10T data from 16-17/08/2016 and 18/4/2018-25/4/2018 provided by the Met. Office. © Crown Copyright 2016, 2018, published by the Met. Office.

Recorded at 0900GMT for the total rainfall over the previous 24 hours.

Since Sept 8th 2020 recorded with an SBS500 tipping bucket rain gauge, funnel diameter 25.2cm and calibrated to tip at 0.2mm, manufactured by Environmental Measurements Ltd (EML), supplied and calibrated by Campbell Scientific. From 1996 until Sept 2020, recorded with electronic tipping bucket rain gauge of 25.4cm diameter, calibrated to tip at 0.2mm, ARG100 manufactured by EML, supplied and calibrated by Campbell Scientific. Before November 1996 recorded manually using a 5" (12.7cm) copper cylindrical rain gauge.

EML state that the "ARG100 rain gauge typically captures over 5% more rainfall than most traditionally-shaped cylindrical gauges due to its unique aerodynamic shape and reduced evaporation-loss properties". This has been found to be the case at Rothamsted, where rainfall in the 5" rain gauge continued to be measured on a twice weekly basis. The 5" gauge at Brooms Barn ceased to be used at the time of automation, so it is not possible to make a comparison.

Data from August 2009-May 2012; 01/10/2014-03/11/2014; 30/10/2016-3/11/2016; 9/11/2016; 18/4/2018-25/4/2018 provided by the Met. Office. © Crown Copyright 2009-2012, 2014, 2016, 2018 published by the Met. Office.

Hours of bright sunshine recorded over the previous 24 hours, 0000 to 2400GMT.

Since Jan 15 1998 recorded automatically, calculated using the Campbell-Stokes equation from total radiation measurements using a Kipp and Zonen CM3 thermopile pyranometer. From 2012 calculated using Campbell Scientific's algorithms (Tech Note 18).

Previously measured manually with a Campbell-Stokes sunshine recorder, at 2m above the ground. The sun's rays are focused onto a card (treated to prevent it from catching fire) and the brown scorch mark on the card is then measured. The cards are of varying lengths applicable to the time of year (winter, equinox, and summer).

Total radiation recorded in the previous 24 hours, 0000 to 2400GMT

Total (or global) radiation is total incoming radiation. Recorded automatically using a Kipp and Zonen CM3 thermopile pyranometer. Before November 1996, it was recorded manually.

Net radiation in previous 24 hours, 0000 to 2400GMT.

Net radiation is the balance between incoming and outgoing radiation under outdoor conditions. Since September 2002 it has been measured by a Kipp & Zonen NR-LITE net-radiometer. An automatic Q7 net radiometer was installed in January 1998.

Recorded at 0900GMT.

Wind direction is shown as an angle (0-360 degrees), going clockwise from North. 360 = North, 90 = East, 180 = South, 270 = West. The reading 0 indicates that there is no wind, ie the windspeed is 0 m/s. A WDIR reading of 0 with a windspeed greater than 0 implies that the WDIR is 360 degrees (North).

Measured by an electronic wind vane (Vector Instruments, W200P) at 2m height.

Recorded at 0900GMT.

Windspeed is measured by automatic cup anemometer Vector Insturment type A100R at 2m and adjusted to the standard height of 10m by multiplying by 1.28. Between 24th May 2012 and 11th December 2012, windspeed was a 10 minute average, recorded between 0850 and 0900GMT. Since 2013 it has been a point value recorded at 0900GMT.

Average daily (24 hour) windspeed can be calculated from total daily WINDRUN, correcting for height (see Conversion factors).

Recorded at 0900GMT, the run of wind in the previous 24 hours.

Windrun is currently measured by automatic cup anemometer Vector Insturment type A100R at standard height of 2m. Before November 1996 it was manually measured with a cup anemometer at 2m high, with a calibrated counter.

Recorded at 0900GMT.

Since April 25th 2018, measured by an EE181 E+E Relative Humidity and Temperature probe (E+E Elektronic Corporation, supplied by Campbell Scientific). Prior to this it was measured with a HMP45C Relative Humidity and Temperature sensor.

Data from September 2009-May 2012; 16-17/08/2016; 30/10/2016-3/11/2016 and 18/4/2018-25/4/2018 provided by the Met. Office. © Crown Copyright 2009-2012, 2016, 2018 published by the Met. Office.

Before September 2009 available as a derived variable within e-RA, derived from WETB and DRYB (see derived variables)

Recorded at 0900GMT.

Derived from DRYB and WETB until 2009 (see derived variables). From 2009 available as a dervied variable within e-RA, calculated from RELH and DRYB after the method of Buck (1981).