From soils to clouds - An integrated atmospheric boundary layer observatory in a temperate forest of eastern Canada

Temperate forests have been shown to substantially impact near-surface climate and atmospheric boundary layer dynamics through a range of complex land-atmosphere feedback mechanisms. For example, forests can reduce water loss to the atmosphere during periods of high vapour pressure deficit, thereby preventing or delaying severe drought impacts. Reducing water loss during periods of high atmospheric water demand comes at the expense of reduced forest productivity and may contribute to additional warming of near-surface air temperatures through increased partitioning of energy to sensible heat. Understanding how land-atmosphere interactions in forested landscapes modify regional and local climate is thus crucial for the design of efficient national and international climate mitigation and adaptation strategies.

To better understand complex land-atmosphere interactions in a typical forested landscape of eastern Canada, we have established an integrated atmospheric boundary layer observatory in a temperate forest in New Brunswick, Canada. Observations will be used to quantify environmental, plant physiological, and atmospheric feedbacks and their impacts on near-surface climate. Here, we present the instrumental setup and preliminary results from the integrated observatory. Forest soils are monitored using soil temperature, volumetric soil moisture, soil water potential, and snow depth measurements and are complemented by soil CO₂ efflux measurements using forced diffusion chamber systems. Detailed vertical profiles of air temperature and humidity, wind speed and direction, and light are measured from the forest floor to a height of 28 m (i.e., 18 m above the forest canopy) using six weather stations. At the top of the flux tower at 28 m above ground, net ecosystem CO₂ exchange and evapotranspiration of the forested landscape is measured using the eddy covariance technique along with longwave and shortwave radiation fluxes. A ceilometer will be added to the observatory in spring 2023 to continuously observe cloud base height and atmospheric boundary layer height. The integrated measurements will produce datasets that can be used to diagnose complex land-atmosphere interactions, to characterise forest microclimate, and to validate coupled land-atmosphere models.