DOI: 10.5281/zenodo.13154213
title: Mesoscale Low-Level Jet Climatology for the North and Baltic Seas

description: Mesoscale Low-Level Jet Climatology for the North and Baltic Seas

This dataset contains a mesoscale low-level jet (LLJ) climatology for the Baltic and North Seas.

The dataset consists of many individual raster layers of LLJ characteristics zipped in the "llj_climatology.zip" file. Each layer is a netCDF4 file, which can be read directly by QGIS, Python, and many other tools. In the "figures" folder, plots showing most of the layers can be found. A more comprehensive description of the layers is given below.

Some examples of layers contained:



LLJ rate-of-occurrence

LLJ height

LLJ duration

Wind speed and direction for at LLJ peak

Max shear above and below the LLJ peak

Wind speed and direction at 100, 150, 200 m

Rotor-equivalent wind speed (REWS) for IEA 15 MW reference turbine


Because of strong seasonality in offshore LLJ occurrences, most layers come as long-term means, including the full five years and seasonality-averaged layers. Several aggregate statistics are available for each layer, such as mean, median, and standard deviation. 

The data was created using the Weather Research and Forecasting model v4.2.1 running a five-year hindcast from 2019-06-26 to 2024-06-26. A two-domain setup was used to downscale ERA5 boundary data to 3 km horizontal grid spacing. See the associated paper for a full data generation process and validation description.

Based on user feedback, future versions could be expanded to hold additional layers/variables, such as sector-wise Weibull parameters or time-series samples for representative points.  Contact btol@dtu.dk for feedback and requests for future versions. 

Full list of variables



ws100, ws150, ws200: wind speed at 100, 150, and 200 meters

wd100, wd150, wd200: wind direction at 100, 150, 200 meters

rews_iea15mw: rotor-equivalent wind speed for the IEA 15 MW reference turbine

cf_iea15mw: capacity factor for the IEA 15 MW reference turbine

llj_rate: LLJ detection rate 

height_of_llj_max: height of LLJ peak in meters

llj_ws_max: wind speed of LLJ peak in meters per second

llj_wind_direction: wind direction of LLJ peak in degree

llj_duration: LLJ duration in hours

llj_most_prevalent_hour: most prevalent hour-of-day during LLJ events as hour integers (0-23)

llj_most_prevalent_hour_freq: relative frequency of most prevalent hour-of-day during LLJ events

llj_most_prevalent_season: most prevalent month-of-year during LLJ events as 0-based month integers (0-11 JAN-DEC)

llj_most_prevalent_season_freq: relative frequency of most prevalent month-of-year during LLJ events 

llj_max_shear_below: maximum shear between the LLJ peak and the minimum below

llj_min_shear_above: minimum (maximum negative) shear between the LLJ peak and the minimum above

height_of_max_shear_below_llj: height of maximum shear detected below the LLJ peak in meters

height_of_min_shear_above_llj: height of minimum shear detected above the LLJ peak in meters

llj_depth: the depth of the LLJ measured from "height_of_max_shear_below_llj" to "height_of_min_shear_above_llj" in meters

llj_rews_iea15mw: rotor-equivalent wind speed for the IEA 15 MW reference turbine during LLJ events

llj_cf_iea15mw: capacity factor for the IEA 15 MW reference turbine during LLJ events

llj_abs_falloff_above: absolute wind speed fall-off above the LLJ peak in meters per second

llj_rel_falloff_above: relative wind speed fall-off above the LLJ peak 

llj_abs_falloff_below: absolute wind speed fall-off below the LLJ peak in meters per second

llj_rel_falloff_below: relative wind speed fall-off below the LLJ peak 


Several layers exist for different aggregation and seasons for each variable. Suffixes describe the aggregation (_mean, _median, _std) and season (_DJF, _MAM, _JJA, _SON)

This work is part of the FLOW project and was supported by the European Union Horizon Europe Framework Programme (HORIZON-CL5-2021-D3-03-04) under grant agreement no. 101084205.