Preparing and Importing Weather Data for Simulations
Weather data can be added to the platform from Input Library > Weather and used to model weather-dependent operations, vessel limitations, accessibility, and other operational restrictions.
This guide explains how to prepare the weather file, which data is required, which parameters are optional, and how to configure the dataset during import.
Overview
A valid weather dataset requires two mandatory weather parameters — wind speed and significant wave height — plus a small set of import settings such as start date, interval, and location. Optional parameters can be added to support additional operational restrictions in the model.
Where to Find It
- Open Input Library.
- Select Weather.
- Start the weather-file import.
How to Use It
File format
Weather data must be uploaded as a CSV (.csv) file. The file should contain:
- One header row
- One row for each weather time step
- Consistent column order throughout the file
- Numerical values for each mapped weather parameter
Example CSV:
Wind speed 100m;Significant wave height;Mean wave period;Visibility
9.8;1.4;6.5;12.0
10.2;1.5;6.7;11.5
9.5;1.3;6.2;10.8
8.9;1.2;6.0;12.5
In this example, ; is the column delimiter, . is the decimal delimiter, and each row represents one weather time step. The column names themselves do not determine how the data is interpreted. During import, each CSV column is mapped to the appropriate weather parameter.
Required weather parameters
A valid weather dataset must contain at least the following data.
| Parameter | Unit | Required | Description |
|---|---|---|---|
| Wind speed | m/s | Yes | Wind speed measured at a specified reference height |
| Significant wave height | m | Yes | Significant height of combined wind waves and swell |
Wind speed
At least one wind-speed column must be included. Each wind-speed column must have a corresponding reference height configured during import.
| CSV column | Parameter | Reference height |
|---|---|---|
| Wind speed 10m | Wind speed | 10 m |
| Wind speed 100m | Wind speed | 100 m |
If several wind-speed measurements are available, multiple wind-speed columns can be imported at different reference heights. Both columns should be mapped as Wind speed, with reference heights of 10 m and 100 m respectively.
Significant wave height
Map the required wave-height parameter as Significant height of combined wind waves and swell. The expected unit is metres (m). This parameter represents the significant wave height used by the simulation when evaluating wave-height restrictions.
Required dataset information
In addition to the values in the CSV, several properties are configured during import.
| Setting | Required | Example | Description |
|---|---|---|---|
| Title | Yes | North Sea Weather 2000-2025 | Name shown in the Input Library |
| Start date | Yes | 2000-01-01 | Date corresponding to the first weather record |
| Data interval | Yes | 1 hour | Time between consecutive rows |
| Latitude | Yes | 56.25 | Latitude associated with the dataset |
| Longitude | Yes | 3.15 | Longitude associated with the dataset |
| Column delimiter | Yes | ; |
Character separating CSV columns |
| Decimal delimiter | Yes | . |
Character used for decimal values |
| Wind reference height | Yes for wind columns | 100 m | Measurement height for each wind-speed column |
| End date | No | 2025-12-31 | Optional dataset end date |
Date and time handling
A timestamp column is not required for regularly spaced data. The platform constructs the weather timeline using the configured start date, the configured data interval, and the order of rows in the CSV.
For example, with a start date of 2020-01-01 and an interval of 1 hour:
| CSV row | Timestamp |
|---|---|
| First data row | 2020-01-01 00:00 |
| Second data row | 2020-01-01 01:00 |
| Third data row | 2020-01-01 02:00 |
| Fourth data row | 2020-01-01 03:00 |
The weather file must have a regular time interval with no missing rows. Hourly data is the most common format and is recommended where available.
Optional weather parameters
Additional parameters can be included when relevant to the operations, vessels, processes, or restrictions being modelled.
| Parameter | Unit | Typical use |
|---|---|---|
| Mean wave period | s | Wave-period operational restrictions |
| Swell wave height | m | Swell-specific operational restrictions |
| Wind direction | degrees | Directional weather analysis |
| Wave direction | degrees | Directional wave restrictions and matrices |
| Current speed | m/s | Current-related operational limits |
| Tide | m | Minimum tide or draft-related restrictions |
| Visibility | km | Visibility-dependent vessel or aviation operations |
| Zero-crossing wave period | s | Additional wave-period restrictions |
| Lightning | 0 / 1 | Lightning-related operational restrictions |
Include only parameters that are used by the operational restrictions in your model. If a parameter is not used anywhere in the model, adding it normally provides no additional benefit. For example:
- If a vessel has a maximum wave-height restriction, include significant wave height.
- If a process has a maximum wind-speed restriction, include wind speed at an appropriate reference height.
- If an operation requires a minimum visibility, include visibility.
- If vessel access depends on minimum tide, include tide.
- If a weather matrix uses wave period or wave direction, include the corresponding parameters.
A typical full mapping looks like this:
| CSV column | Import parameter | Unit / setting |
|---|---|---|
| Wind speed 10m | Wind speed | Reference height = 10 m |
| Wind speed 100m | Wind speed | Reference height = 100 m |
| Significant wave height | Significant height of combined wind waves and swell | m |
| Mean wave period | Mean wave period | s |
| Swell wave height | Significant height of total swell | m |
| Wind direction | Wind direction | degrees |
| Wave direction | Mean wave direction | degrees |
| Current speed | Current speed | m/s |
| Tide | Tide | m |
| Visibility | Visibility | km |
| Lightning | Lightning | 0 / 1 |
Recommended dataset for offshore wind simulations
For a general-purpose offshore wind weather file, include the following where data is available:
- Wind speed at one or more relevant reference heights
- Significant wave height
- Mean wave period
- Swell wave height
- Wind direction
- Wave direction
- Current speed
- Tide
- Visibility
Delimiters
Both the column delimiter and decimal delimiter must match the contents of the CSV.
For a semicolon-separated file with . as the decimal delimiter:
- Column delimiter:
; - Decimal delimiter:
.
For a semicolon-separated file with , as the decimal delimiter:
- Column delimiter:
; - Decimal delimiter:
,
Avoid using the same character for both purposes.
Import steps
- Open Input Library.
- Select Weather.
- Start the weather-file import.
- Select the CSV file.
- Specify the column and decimal delimiters.
- Review the file preview.
- Map the relevant CSV columns to weather parameters.
- Specify the reference height for every wind-speed column.
- Enter the dataset title.
- Enter the start date.
- Enter the data interval.
- Enter the latitude and longitude.
- Complete the import.
- Select the new weather dataset where required in the relevant asset, vessel, route, or experiment configuration.
Frequently Asked Questions
What is the minimum file I can import?
The minimum valid file requires only wind speed and significant wave height (CSV):
Wind speed;Significant wave height
9.8;1.4
10.2;1.5
9.5;1.3
8.9;1.2
| Setting | Value |
|---|---|
| Wind speed | Map as Wind speed |
| Wind reference height | For example, 100 m |
| Significant wave height | Map as Significant height of combined wind waves and swell |
| Start date | Date of the first row |
| Interval | For example, 1 hour |
| Latitude | Dataset location |
| Longitude | Dataset location |
| Column delimiter | ; |
| Decimal delimiter | . |
Why are my weather dates not aligning with the simulation period?
Check the start date, data interval, number of rows, and whether any time steps were removed from the source file. Timestamps are derived from row order, so any gaps will shift all subsequent rows.
Why are values being parsed incorrectly?
Check the configured decimal and column delimiters. If the data contains 9,8;1,4, the decimal delimiter must be set to ,, not ..
Why can't I upload the file?
Confirm the file extension is .csv. Other file formats are not supported.
Why is the import failing with "Required field(s) missing from file"?
Check that the file maps at least one Wind speed column and Significant height of combined wind waves and swell. Also confirm that every wind-speed column has a reference height assigned.
Data Quality Recommendations
Before importing, check the following.
- Consistent time interval. An hourly file should not contain a mix of 1-hour and 3-hour intervals.
- No missing rows. Removing individual time steps shifts all subsequent weather data relative to the intended dates.
- Consistent units. Use the same unit throughout each column — do not mix m/s and knots within a wind-speed column, for example.
- Correct wind reference height. A series measured at 100 m must be configured with a reference height of 100 m, not 10 m.
- Numerical values only. Avoid text labels, unit strings inside cells, empty values, or placeholders such as
-,N/A, ormissing. Use9.8, not9.8 m/s