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 UKCEH.
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
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).
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.
For overall system operational reasons, it has been decided to withdraw the deployment of the IMKO soil moisture profile sensors during planned maintenance visits in the period to March 2020. Note that at sites installed since March 2016 there is a depth profile of TDT point soil moisture sensors, and consideration is being given to similar profile arrays at sites from which IMKO sensors have been withdrawn.
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).
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).
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.
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.
Barometric pressure sensor
A barometric pressure sensor which incorporates a Barocap® silicon capacitive pressure sensor encased in a plastic shell with an intake valve for pressure equalisation. Measures barometric pressure equivalent to an elevation range from below sea level to 4.5km.
Temperature and humidity sensor
Humidity and air temperature are measured by a capacitive thin film HUMICAP© polymer sensor and resistive platinum sensor (Pt100) respectively. Both the humidity and temperature sensors are located at the tip of the probe protected by a removable filter.
3D Sonic anemometer
Monitors wind speeds of 0-50m/s (0-100mph), and wind direction.Model: Gill WindMaster 3D Sonic Anemometer
Integrated 2D sonic anemometer
High accuracy wind speed and direction integrated with automatic weather station.
Model: Gill Integrated WindSonic
A pair of cameras with almost 360° 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.
Snow depth sensor
Sonic rangefinder designed specifically to measure snow depth.
Model: Campbell Scientific SR50A
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
Module to manage data and control communication.Model: Campbell CR3000 Micrologger.