Is global terrestrial stilling reversal really happening? Climate change-related wind resource assessment in Poland.

A global decrease in near surface wind speed at mid latitudes since the 1980ies has been formalised as "The Global Terrestrial Stilling" theory[1]. Such continuing trend would be problematic for the wind power community and requires careful investigation.

A recent study[2] claimed that the stilling reversed since year 2010, leading to a recovery of global wind circulation. However the climate projections of the IPCC do not clearly show this recovery and instead predicts a global wind speed decrease over most land areas in the Northern hemisphere at mid latitudes.

The case of Poland seems particular as it displays the most important decrease in wind speed in climate projections from the IPCC.

In this presentation, we investigate the past and future wind speed and power resource close to the city of Bydgoszcz, Poland. Our study includes a set a various steps to go from the very broad resolution of climate change models to site specific tens of meters resolution features.

We first use multi-model climate projections and advanced statistical techniques to build a very high quality wind speed time serie. Second, we merge our result with high quality reanalysis data to enhance the quality of our time series in absolute value. Third, we perform a final downscaling to tens of meter precision using our CFD approach. And additionally, we extract the power output of a hypothetical wind farm.

Using these many steps, we can provide an advanced view of the wind resource in the future including meso-scale effects and site effects thanks to a hybrid approach including meso-scale, statistical and CFD tools.

[1] McVicar et al. (2012), Jour. of Hydrology, V416–417, p182-205, https://doi.org/10.1016/j.jhydrol.2011.10.024.
[2] Zeng et al. (2019), Nature Climate Change, 9, p979-985, https://doi.org/10.1038/s41558-019-0622-6