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Temperature and relative humidity measurements were made within and outside a lowland fen in eastern England during 2009 and 2010. Summer temperatures were found to be on average 0.24°C lower within the fen than outside, whilst summer vapour pressures were found to be on average 0.074 kPa higher within the fen. In contrast, winter temperatures were found to be higher within the fen by an average of 0.03°C. These differences may be expected to influence evapotranspiration estimates derived using data from each of the sites. The influence of the location of meteorological measurements on evapotranspiration estimates was therefore evaluated. The existence of a wetland microclimate results in up to a 7% reduction in annual reference evapotranspiration compared to a site surrounded by arable farmland only 5.5 km away.

This manuscript describes the energy and water components of a new community land surface model called the Joint UK Land Environment Simulator (JULES). This is developed from the Met Office Surface Exchange Scheme (MOSES). It can be used as a stand alone land surface model driven by observed forcing data, or coupled to an atmospheric global circulation model. The JULES model has been coupled to the Met Office Unified Model (UM) and as such provides a unique opportunity for the research community to contribute their research to improve both worldleading operational weather forecasting and climate change prediction systems. In addition JULES, and its forerunner MOSES, have been the basis for a number of very highprofile papers concerning the land-surface and climate over the last decade. JULES has a modular structure aligned to physical processes, providing the basis for a flexible modelling platform.

The Joint UK Land Environment Simulator (JULES) is a process-based model that simulates the fluxes of carbon, water, energy and momentum between the land surface and the atmosphere. Many studies have demonstrated the important role of the land surface in the functioning of the Earth System. Different versions of JULES have been employed to quantify the effects on the land carbon sink of climate change, increasing atmospheric carbon dioxide concentrations, changing atmospheric aerosols and tropospheric ozone, and the response of methane emissions from wetlands to climate change. This paper describes the consolidation of these advances in the modelling of carbon fluxes and stores, in both the vegetation and soil, in version 2.2 of JULES. Features include a multi-layer canopy scheme for light interception, including a sunfleck penetration scheme, a coupled scheme of leaf photosynthesis and stomatal conductance, representation of the effects of ozone on leaf physiology, and a description of methane emissions from wetlands. JULES represents the carbon allocation, growth and population dynamics of five plant functional types. The turnover of carbon from living plant tissues is fed into a 4-pool soil carbon model. The process-based descriptions of key ecological processes and trace gas fluxes in JULES mean that this community model is well-suited for use in carbon cycle, climate change and impacts studies, either in standalone mode or as the land component of a coupled Earth system model.

It is widely recognised that healthy ecosystems can provide considerable benefits to people, including food, timber, freshwater, protection from floods and much of what we call quality of life. A global review of these ecosystem services carried out as part of the Millennium Ecosystem Assessment (MA) provided a framework for national and local studies. Using the MA approach, this paper reviews the ecosystem services provided by the Somerset Levels and Moors wetland system in south-west England. This wetland provides a series of important services that are beneficial locally, regional and globally, including grazing for cattle, potential carbon sequestration, flood water storage, recreation and archaeology. Some services are synergistic and reinforcing; for example, maintaining wet conditions supports wetland bird life that maintains biological diversity, attracts tourists, protects archaeological artefacts and reduces CO2 emissions. Other services are potentially conflicting, for example raising water levels may reduce potential flood water storage and increase methane emissions. Comparison of the services of the wetland with those of drier habitats reveals for example that carbon sequestration, bird habitat provision and hay production is greater in wetlands, whilst grazing quality and plant diversity may be reduced and distributions of disease vectors may be altered by wetland restoration through raising water levels. Management decisions affecting wetlands may necessitate a trade-off of ecosystem services.

Reliable measurements of the land surface evaporation are required for hydrological modelling and water resource management, as well as for boundary layer modelling and numerical weather prediction. Catchment models and satellite estimates usually operate at large grid scales of at least 1 km2. To validate these models, and measure catchment water balances, requires up-scaled measurements that must average land surface variability, in particular, the wide range and mixture of vegetation types and soil moisture conditions that are often found at such scales. Traditional methods are difficult to apply at these scales, invoking many replications across the different land-surface types. Two-wavelength scintillometry allows the determination of evaporation over paths of many kilometres, without the disadvantages of in situ sensors. Low maintenance transceivers were installed at both ends of a 2.4 km path over mixed agriculture on chalk downland at Sheepdrove Organic Farm, West Berkshire, UK. Infra-red and millimetre-wave beams sensed the path-averaged turbulent changes of temperature and moisture (scintillations) and Monin-Obukhov Similarity Theory was applied to determine the evaporation. Results show that large scale evaporation can be reliably determined by scintillometry, under most conditions. Recommendations for deployment and the limitations of scintillometry to determine evaporation are discussed.

klima, økosystemer, Arktis, Global Change