Perdigão

Atmospheric flow in complex terrain has received increased attention in recent years because of its numerous applications, including air pollution, contaminant dispersion, aviation, Alpine warfare and wind energy harvesting. While past research has mainly focused on and improved upon weather prediction at the mesoscale (resolution on the order of km), wind energy and dispersion applications demand improved accuracy of predictions at the microscale (tens to hundreds of meters). To this end, ERANET+, a European Union (EU) funding instrument, has granted a consortium of EU scientists a megaproject to provide the wind energy sector with more detailed wind resource mapping capabilities. This is to be accomplished through the creation and publication of a New European Wind Atlas (NEWA) based on the development of improved models for wind energy physics and forecasting.

Embedded in the ERANET+ project is a comprehensive field campaign dubbed "Perdigão" in 2016-17, which will collect a reference data set at unprecedented spatial resolutions, characterizing both the mean and turbulent wind fields in a natural setting. Augmenting the basic measurement and modeling capabilities of EU scientists with those from the US investigators will add considerable value to the ERANET+ project while allowing US investigators to pursue scientific endeavors of their choosing.

The NEWA emphasis will be to measure wind velocity. Since airflow, especially close to the Earth’s surface, depends on the thermodynamic stability of the atmosphere, a major aspect of the US participation is to measure the mean and turbulent temperature and humidity fields as well. The US investigators will use these data to understand complex terrain physical and thermodynamic processes and create new models that better represent the physics of flow over complex terrain. The requested LAOF facilities are essential to meet these objectives:

• ISFS will acquire the data from all (including an extensive set of investigator-supplied) tower-based sensors, including those to measure turbulence and thermodynamic fluxes.
• ISS will measure the in-flow and out-flow velocity and temperature profiles during the entire observation period, which is essential for setting model initial conditions.
• Water-vapor DIAL will provide humidity profiles during conditions when humidity gradients may have a large effect on boundary-layer thermodynamics.
• Radiosondes will provide the primary in-situ validation for the vast array of remote sensor data in the boundary layer. 

Scientific Objectives

The long-term goal of the Perdigão project is to create numerical models that better represent flow over complex terrain than those currently in common practice. In the European context, the new models are expected to contribute to a new European Wind Atlas. In the US context, the objectives are to create new scientific knowledge and develop better parameterizations for complex terrain processes, with broad impacts of future microscale model developments for wind energy prospecting, flow and dispersion in heterogeneous complex terrain as well as human resources development. To improve microscale models, better physics is needed which, in turn, requires detailed observations and analysis. We propose to observe the flow and thermodynamic fields at unprecedented spatial and temporal resolutions, including direct turbulence measurements down to dissipation scales using hot-film anemometry. To validate key inputs to these models, we also will directly measure all components of the surface energy balance (incoming and outgoing visible and infrared radiation and surface/soil heat exchange, in addition to sensible and latent heat fluxes). An extensive suite of individual and coordinated lidar scans will allow mean flow, turbulence and Reynolds stress measurements up to hundreds of meters vertically and kilometers horizontally.

Observational Periods