The following is a list of the instruments used at the COSMOS-UK monitoring sites. Instrumentation differs between sites and has changed through time. Use of any instrument should not be interpreted as an endorsement by CEH.

 

InstrumentPhoto

Cosmic-Ray Soil Moisture Sensor

The sensor counts fast neutrons which can be converted to soil moisture after field calibration. Data processing accounts for variations in atmospheric pressure, humidity, and the intensity of incoming cosmic rays.

The measurement volume of the sensor is many tens of meters horizontally (possibly up to 200m) although measurement is inversely related to distance from the sensor. The effective depth varies with soil moisture but is typically in the range 15-40cm.

Model: Hydroinnova CRS-1000/B and Hydroinnova CRS-2000

Rain gauge

Provides data on the amount and intensity of solid and liquid precipitation. Onboard processing algorithms account for spurious changes due to temperature or wind speed.

Model: The OTT Pluvio²

Point soil moisture sensor

Point soil moisture sensors at various depths use the TDT (time domain transmissometry) technique and provide absolute volumetric water content and soil temperature.

Note that the soil moisture data are not calibrated to the site specific soil type, but rely on generic calibration information.

The sampling volume is a region around the waveguide which has a total length of 30cm. Published evidence suggests that the sampling volume is no greater than 15 cm (half length of wave guide) x 6 cm(horizontal)x3 cm(vertical).

Model: Acclima Digital TDT® Soil Moisture Sensor

COSMOS-UK

Profile soil moisture sensor

A profile probe with three sensors provides soil moisture at depths of 0.15, 0.40 and 0.65 m. The probe sits within a specially-designed access tube and is sensitive over a radius of around 0.10 m, although the region of highest sensor sensitivity is closest to the access tube. Each sensor utilises the TDT (time domain transmissometry) technique.

Note that the soil moisture data are not calibrated to the site specific soil type, but rely on generic caliration information.

According to the manufacturer’s documentation Each of the sensors has a measurement field of 11cm vertically and the effective penetration depth of the probe is 10cm (note that this is not uniform around the sensor but elliptical. Air gaps around the installation tube can have a detrimental effect on instrument accuracy.

Model: IMKO Digital TDT® Soil Moisture Sensor

Soil heat flux plate

Two heat flux plates per site provide the soil heat flux at a depth of 0.03 m. These plates have a self-calibrating feature to maximise measurement accuracy.

Model: Hukseflux heat flux plate (HFP01SC).

COSMOS-UK

Soil temperature sensor

The near-surface soil temperature is measured at five depths (0.02, 0.05, 0.10, 0.20 and 0.50 m) using a profile of thermocouples, shown in the photo during installation. The soil temperature gradient is used to estimate the surface soil heat flux. 

Model: Hukseflux (STP01)

COSMOS-UK

Radiometer

A four-component radiometer measures the individual radiation components using upward and downward facing pyranometers (for the shortwave components) and pyrgeometers (for the longwave components). The net radiation is calculated as the sum of the incoming minus the outgoing components and is usually the dominant term in the surface energy balance. In the photo the radiometer at the right-hand end of the horizontal support. 

Model: Hukseflux four-component radiometer

Lullington Heath

Automatic weather station

Air temperature and relative humidity are measured by a probe situated within a naturally aspirated radiation shield; and barometric pressure is also measured.

Model: Gill Metpak Weather Station 

Lullington Heath

3D Sonic Anemometer

Monitors wind speeds of 0-45m/s (0-100mph), in three dimensions

Model: Gill WindMaster3D
Lullington Heath

Snow depth sensor

Sonic rangefinder designed specifically to measure snow depth.

Model: Campbell SR50A

Snow depth sensor

Snow water equivalent

The sensor records the intensity of downward-directed secondary cosmic-rays that penetrate the snow pack. This intensity is proportional to the mass of snow traversed by cosmic-rays, and is related to soil water content through a calibration function.

Model: Hydroinnova SnowFox

SnowFox

Phenocam

A pair of cameras each with almost 180° field of view provides visual information about the land cover (e.g. when crops are harvested, greenness of vegetation - hence the name which is a contraction of "phenology camera"). It can also provide information on cloud cover, snow cover, surface ponding and atmospheric visibility.

Model: Motobotix S14

Lullington Heath

Micrologger

Module to manage data and control communication.

Model: Campbell CR3000 Micrologger.