MiRadOr - Microwave radiometer for the detection and assessment of offshore wind resources
In the light of intensifying climate change, European governments have in recent years increased their efforts to accelerate the decarbonisation of electricity generation. A key component to achieving these ambitious decarbonisation targets is the deployment of increasingly large wind turbines, particularly within offshore wind farms.
To maximise the effectiveness of these projects and accelerate the green energy transition, research is needed into cost-optimised wind farm layouts, improved forecasts of wind potential and wind power yield and optimised operational strategies.
What is MiRadOr?
The Microwave Radiometer for the Detection and Assessment of Offshore Wind Resources (MiRadOr) Project investigates how microwave radiometer (MWR) technologies can improve the assessment of offshore wind resources, and enhance models for wind energy applications.
The MiRadOr project combines the analysis of existing datasets with new data from a year-long measurement campaign in marine atmospheric conditions in Northern Germany, building on the successes of the Carbon Trust's Offshore Wind Accelerator Radiometry and Atmospheric Profiling Scoping Study (OWA RAP) project, that funded the foundational scientific work published by Cimini et al. (2025).
The project will evaluate atmospheric profiles obtained from microwave radiometers and compare them to traditional radiosonde measurements as well as data from numerical weather prediction (NWP) models and climate simulations. The goal is to assess the accuracy and applicability of each method in the context of wind energy site assessment and forecasting.
Understanding the Atmosphere: Stability and Winds in the Boundary Layer
The dynamics in the lowest 300 meters of the atmosphere are of particular interest for wind energy applications. Within this layer, meteorological conditions directly affect wind turbine performance and energy output.
Atmospheric Stability
Atmospheric stability significantly influences wind turbine performance, with key influencing factors including vertical profiles of air temperature and derived stability metrics.
Wind turbines generally perform better under unstable or neutral conditions. Stability is commonly assessed using buoyancy, which describes the vertical acceleration of an air parcel.
A common indicator is the gradient of potential temperature, which is defined as the temperature an air parcel would have if brought adiabatically to a reference pressure. A negative value of the gradient indicates unstable conditions, while a positive value gradient indicates stable conditions.
Temperature profiles can be measured using MWR or radiosondes. MiRadOr focuses on evaluating the quality and reliability of these measurements and their potential contribution to wind farm development and atmospheric modelling.
Wind Speed Profile
Due to surface friction, wind speeds are typically lower near to the ground and increase steadily with height. However, the actual wind profile can be complex, influenced by weather patterns, such as mid-latitude high- and low-pressure systems, and the near-surface stability that may lead to the formation of low-level jets (LLJs).
Even the presence of the wind turbines themselves can alter the wind profile by creating wakes and so-called blockage effects, both of which can affect wind energy yields. Therefore, accurately measuring wind speed profiles using techniques such as radiosondes and predicting them through modelling is highly relevant for wind energy applications.
LLJs are narrow, fast-moving streams of air occurring within the lowest few 100 meters of the troposphere and typically form at night under clear skies, when radiative cooling near the surface leads to a temperature inversion. Both LLJs (Weide Luiz and Fiedler, 2022) and weather patterns (Ho-Tran and Fiedler, 2023) influence wind power production.
During our MiRadOr campaign, we aim to measure and analyse LLJs and mid-latitude storms to deepen our understanding of their dynamics and implications for wind energy development.
Measurement Methods: Capturing the Vertical Profile
To better understand the atmospheric conditions that affect wind energy production and improve modelling data, the MiRadOr project makes use of a suite of complementary measurement techniques. Each provides a unique perspective on the vertical structure of the atmosphere—from near the surface up to several kilometres in altitude.
Microwave Radiometer (MWR)
Microwave radiometry is a passive remote sensing technique that measures naturally emitted thermal microwave radiation from atmospheric gases, primarily oxygen and water vapour. As the concentration of oxygen is nearly constant throughout the atmosphere, the emitted radiation primarily depends on the temperature. For frequencies with strong oxygen emissions (e.g. 50-70 GHz), the observed radiation is strongly correlated with atmospheric temperature. By observing multiple frequencies in that range which are more opaque (in the centre of the absorption band) or less opaque (away from the centre), the vertical temperature profile can be estimated. Additionally, resolving the dependency of observations at several varying elevation angles (from vertical down to the horizon) also increases the accuracy and resolution of the temperature profile. Similarly, observations at 22-32 GHz provide information about the humidity.
MWRs operate continuously in almost all weather conditions, making them particularly valuable in offshore and remote environments where frequent radiosonde launches are impractical. Despite their coarser vertical resolution, compared to other methods, MWRs provide near-real-time, continuous data that can be used to detect for instance changes in atmospheric stability.
Wind LiDAR (Light Detection and Ranging)
Wind lidars emit short pulses of laser light into the atmosphere and measure shift of the backscattered signal, according to the Doppler effect, coming from aerosol particles. From this, wind speed and direction can be retrieved at multiple heights up to a few hundred metres.
LiDAR systems can for instance characterise wind shear, turbulence intensity, and low-level jets—key drivers of turbine loading and wake behaviour. When combined with MWRs, they allow the characterization of both wind and stability in the lower atmosphere.
Radiosondes
Radiosondes are compact weather sensor packages launched on helium balloons through the atmosphere, typically reaching altitudes of 10–30 km. As they ascend, they transmit high-quality in-situ measurements of temperature, humidity, and pressure, along with wind speed and direction derived from GPS tracking. Although radiosondes provide high-quality in-situ data, each launch provides only a snapshot in time, rather than the temporally continuous coverage of instruments like MWRs.
MiRadOr will deploy radiosondes during an intensive observation period to validate remote sensing data from both MWR and LiDAR, serving as a benchmark “truth” for evaluating models.
Key Project dates
Project kick-off: April 2025
Intense Observing Period: September 2025
Project duration: 2 years
Consortium
University of Heidelberg (leading partner), Fraunhofer IWES, RPG Radiometer Physics, The Carbon Trust (set up under the Offshore Wind Accelerator)
This project receives public funding from the German Government via the “German Energy Research Programme” through Projektträger Jülich (PtJ).
Industry partners
EnBW, RWE, TotalEnergies, Vattenfall
Project Office
MiRadOr Project Office
Institut für Umweltphysik
Universität Heidelberg
Im Neuenheimer Feld 229
D-69120 Heidelberg
Contact
Dr. Justin Shenolikar
MiRadOr Project Coordinator
justin.shenolikar@iup.uni-heidelberg.de
+ 49 6221 54-6308
