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What is Resultant Wind Speed?

Published in Wind Measurement 3 mins read

Resultant wind speed is the magnitude of a single hourly vector derived by converting the 5-minute wind speeds and directions measured over an entire hour. This specific measurement is measured in miles per hour.

Understanding Resultant Wind Speed

While instantaneous wind speed tells you how fast the wind is blowing at a given moment, resultant wind speed provides a more comprehensive hourly summary. It accounts for not just the speed but also the direction of the wind throughout the hour, offering a single value that represents the net effect of all wind movements.

How is Resultant Wind Speed Calculated?

The process for determining resultant wind speed involves a precise vector analysis, as described in the provided reference. Resultant wind speed values are obtained by:

  • Collecting Data: Wind speed and direction are recorded at 5-minute intervals for the entire hour. This means there are 12 distinct data points (60 minutes / 5 minutes per point) contributing to the hourly calculation.
  • Vector Conversion: Each of these 5-minute wind observations (speed and direction) is transformed into a vector. A vector is a mathematical representation that possesses both magnitude (the speed) and direction.
  • Vector Summation: All the individual 5-minute wind vectors for that hour are then added together vectorially. This isn't a simple arithmetic sum; rather, it considers both the speed and the direction of each segment. The outcome of this addition is a single hourly vector.
  • Magnitude Extraction: The resultant wind speed is then defined as the magnitude (or length) of this single hourly vector. Essentially, it quantifies the total distance a hypothetical air parcel would have traveled in a straight line if it moved according to the net effect of all the winds during that hour.

Why is Resultant Wind Speed Important?

This metric offers a deeper insight into prevailing wind conditions compared to a simple average of wind speeds, which can be misleading. For instance:

  • If wind blows east at 15 mph for 30 minutes and then west at 15 mph for the next 30 minutes, the simple average speed would be 15 mph. However, the resultant wind speed would be close to zero, accurately indicating no net movement of air over the hour.
  • It is particularly valuable in various applications, including:
    • Meteorology: For analyzing true prevailing wind patterns and understanding air mass transport.
    • Environmental Sciences: Crucial for modeling the dispersion of pollutants or the movement of airborne particulates.
    • Renewable Energy: Assessing the consistent energy potential for wind turbine placement and optimizing wind farm operations.

Key Attributes of Resultant Wind Speed

To summarize the essential characteristics of resultant wind speed:

Attribute Description
Definition The magnitude of a single hourly vector, which is derived from combining 5-minute wind speed and direction measurements over the course of an hour.
Measurement It is explicitly measured in miles per hour (mph).
Data Basis Calculated from 5-minute interval data of both wind speed and direction, consolidated over a full hour.
Calculation Involves converting each 5-minute observation into a vector, performing a vector summation of all hourly vectors, and then extracting the magnitude (length) of the resulting single vector.
Utility Provides a robust, directionally-aware summary of hourly wind activity, revealing net air movement rather than just average speed, making it vital for precise environmental and meteorological analyses.

Understanding resultant wind speed is fundamental for applications that demand an accurate, directionally-sensitive representation of wind activity over a defined period.