Land Surface Interactions with the Atmosphere over the Iberian Semi-Arid Environment (LIAISE): Land–Atmosphere Interaction Observations and Modeling Framework

Land surface-atmosphere interactions play a critical role in the development of the boundary layer and help to determine the near surface temperature and humidity throughout the diurnal cycle. Previous studies have shown that these interactions are strongest in semi-arid regions where there is both a sensitivity of the surface fluxes to the soil moisture profile, and a sensitivity in the atmosphere to these surface fluxes. However our knowledge of the dominant processes that control these interactions is still limited. The LIAISE (Land surface Interactions with the Atmosphere over the Iberian Semi-arid Environment) observational campaign has been designed to help develop our understanding of land/atmosphere interactions and surface heterogeneity within such a semi-arid environment. The observational campaign will bring together ground-based and atmospheric measurements, and will be complemented by real time regional modelling studies to help improve understanding of processes affecting soil moisture, evapotranspiration, precipitation coupling and the subsequent feedbacks to the Mediterranean boundary layer. A network of surface energy budget observing sites will be installed over the Lleida (Spain) region of the Ebro basin, details of which will be given in a second presentation.
In this presentation we will outline the plans for extensive measurements of the lowest few kilometres of the atmosphere at two sites (one irrigated, the other natural rain-fed) using UHF wind profilers, Dial Doppler Lidar, UAVs, tethered balloons and regular radio-sounding releases. A Special Observation Period (SOP) is planned for a two–three week period in mid-July 2020, when contrasts between irrigated and natural surfaces will have their maximum impact on boundary layer evolution. In addition, two–three day SOPs are planned for April and May in order to capture the influence of soil moisture dry down.
The observations from LIAISE will be utilised in an international modelling experiment, following a simulation protocol similar to that used by DICE (Diurnal land/atmosphere Coupling Experiment) where the sonde observations and Limited Area Model (LAM) simulations are used to diagnose large-scale atmospheric forcing that can then be applied in large-eddy and single-column model simulations. We will apply an idealised methodology for assessing the impact of land/atmosphere feedbacks by first assessing the individual components constrained by observational data and then identifying changes due to coupling. The LIAISE modelling will extend to irrigated and natural semi-arid surface processes in order to explore how the surface fluxes and their spatial heterogeneity impact on boundary layer development and evolution.
Current plans for the modelling experiments will be presented in order to obtain early engagement with the international land surface and boundary layer communities. This will provide an opportunity for feedback on modelling protocols and establish initial interest in participation.