COSMOS-UK: A New Observation Network for Near Real-time Soil Moisture and Land Surface Energy Fluxes

Soil moisture has an important role in controlling land-surface energy fluxes as well as hydrological processes required for water resource, flood and drought modelling. In meteorological models the soil water content is determined as part of the land surface scheme and the performance of this soil moisture component requires evaluation and may benefit from data assimilation; however, there are few in situ data representative of a suitable scale that is comparable to model data i.e. large area measurements at the field scale or greater (which integrate across local spatial heterogeneity).

Here we describe the new near real-time COsmic ray Soil Moisture Observation System in the UK (COSMOS-UK) to systematically measure soil moisture across the country. These new COSMOS-UK stations also record other key components of the land surface energy balance and driving meteorological variables. In particular, they have the capability to measure most of the land surface energy budget components: sensible heat fluxes (by the eddy covariance method), four-component radiation exchange, and soil heat fluxes. The strengths of this network are: a) its size – with 35 stations across the UK, representing a wide range of climates, land cover and soil types; b) the consistency of research grade observations and data streams which will make all sites directly comparable; c) public availability of near real-time data for model testing, development and data assimilation.

We describe in detail the long-term network capabilities and site locations. Early results show the soil moisture and energy fluxes, with their responses to meteorological and land surface forcing. A first analysis of results across a number of sites is presented. The wide scope for exploitation of the COSMOS-UK network is explored, demonstrating its value to the land surface and boundary layer modelling communities.