Lab 12.2 – Understanding Wind Movement
Fundamental concept:
Estimated time to complete: 15 minutes
Data skills preparation:
Materials needed:
How Winds Are Named: Two Scientific Approaches
Different scientific disciplines use distinct conventions to describe wind and current movement, different scientific fields use different naming systems. Understanding both is essential for accurate interpretation of meteorological and oceanographic data.
Oceanographers: Direction of Motion (Destination)
Oceanographers describe winds and currents based on their direction of motion—in other words, the destination toward which the wind is moving.
- A westward wind flows toward the west.
- An eastward current moves toward the east.
Example: The Equatorial Countercurrent flows eastward, meaning it is moving in the direction of the eastern horizon.
Atmospheric Scientists: Direction of Origin (Source)
In contrast, atmospheric scientists describe winds based on their direction of origin—that is, the source from which the wind originates.
- A north wind originates in the north and flows toward the south.
- A south wind originates in the south and flows toward the north.
This approach emphasizes the origin point of the air mass.
12.2.1 Comparison of wind terms in both oceanography and atmospheric sciences.
To summarize:
- Oceanographers describe wind based on its destination direction.
- Atmospheric scientists describe wind based on its source direction.
Wind Direction and the 360° Compass
We use a 360° compass to describe the direction wind is coming from. This is a standard way that weather scientists (atmospheric scientists) report wind.
Here’s how it works:
- 0° or 360° = Wind is coming from the north
- 90° = Wind is coming from the east
- 180° = Wind is coming from the south
- 270° = Wind is coming from the west
Intermediate directions fall in between:
If the wind direction is 135°, that means it’s blowing from the southeast. A wind at 315° is coming from the northwest.
So when you see a wind direction in degrees, think:
What direction is the wind blowing from?
12.2.2 Comparison between compass degrees and wind direction.
Why Are 0° and 360° the Same?
The compass is a full circle: just like the hour hand on a clock, when you rotate all the way around, you end up pointing in the same direction where you started.
- 0° and 360° both point due north, so a wind from either degree is still a north wind.
12.2.3 Rose Compass showing wind degrees from 0 to 360.
Rose Compass showing degrees and directions of wind.Quick Check: Name Wind Direction:
Drag and drop the appropriate naming scheme in each of the empty cells.
Measuring Wind Speed
Common Units of Measurement
Wind speed is measured in several ways:
- Meters per second (m/s): This is the standard unit used in scientific research and atmospheric modeling. It tells us how many meters the wind moves in one second.
- Miles per hour (mph): This unit is familiar from weather forecasts in the U.S. It shows how many land miles the air travels in an hour.
- Knots (kt): Common in aviation and marine settings, knots measure nautical miles per hour. One knot equals approximately 1.15 mph.
You can convert between units using simple multipliers:
- To convert from m/s to mph, multiply by 2.24
- To convert from m/s to knots, multiply by 1.94
For example, if the wind speed is 7 m/s:
- 7 × 2.24 = 15.68 mph
- 7 × 1.94 = 13.58 knots
Conversion Calculator
Instruments Used to Measure Wind
Wind speed tells us how fast the air is moving and is key to studying storms, ocean conditions, and climate patterns.Wind speed is typically measured using specialized instruments that detect how fast air is moving past a fixed point:
- Anemometer – The most common tool. It usually has spinning cups or propeller blades that rotate faster as wind speed increases. The number of rotations per second is converted into wind speed.
- Ultrasonic Anemometer – Uses sound waves to measure wind speed and direction without moving parts. These are often used in research and high-precision applications.
- Wind Vanes – Often paired with anemometers, these indicate wind direction by pointing into the wind.
These instruments are mounted on weather stations, buoys, towers, and even satellites.
How the OOI Measures Wind
The Ocean Observatories Initiative (OOI) measures wind speed and direction using:
- Sonic anemometers mounted on surface buoys in places like the Pioneer and Endurance Arrays.
- Ship-based sensors used during research cruises to compare and validate buoy data.
- Direct flux packages that measure wind and heat exchange between the ocean and atmosphere.
These instruments are mounted 10 meters above the ocean surface, which is the standard height for wind measurements like U10.
U10 and Directional Wind Speed Values
In many data systems, wind speed values are shown as positive or negative numbers. These signs tell us which direction the wind is moving along a specific axis.
- A positive value means wind is blowing in the specified direction
- A negative value means wind is blowing in the opposite direction
What Is U10?
U10 stands for the wind’s east–west component, measured 10 meters above the surface.
- A positive U10 means the wind is blowing from west to east (eastward)
- A negative U10 means the wind is blowing from east to west (westward)
- The U component represents the east-west (zonal) direction.
