Purpose

The Wind Speed Histogram shows the annual frequency distribution of wind speed classes, independent of wind direction.

It provides a clear view of the intensity structure of the wind regime over the selected analysis year.

How It Is Computed

Wind speed is deterministically reconstructed from the ERA5 10u and 10v components.

Each hourly value is assigned to a wind speed class according to the classification scheme selected in the Analyze GRIBtab.

Available schemes include:

• Calm + 5 classes + open maximum

• Calm + 6 classes + open maximum

• Calm + 7 classes + open maximum

The histogram reflects the active configuration.

Representation

Each bar represents one wind speed class.

The bar height corresponds to:

• The percentage of valid hourly records in percentage mode.

The first class may represent calm conditions, depending on the selected scheme.

The last class is open-ended and includes all wind speeds above the highest defined threshold.

Interpretation

Unlike the Wind Rose, the histogram does not retain directional information.

It provides a marginal distribution of wind speed over the entire annual dataset.

This view is useful to assess:

• Dominant wind speed ranges

• Frequency of calm conditions

• Presence of high-speed events

Data Scope

The histogram:

• Uses only the validated main analysis year.

• Excludes extra records outside annual boundaries.

• Is computed dynamically based on the active class configuration.

• Applies no spatial or temporal interpolation.

Relation to Other Outputs

The histogram represents the overall wind speed distribution.

It corresponds to the column totals of the Frequency Table when expressed in percentage form.