# Windy Weather II: The Correlation Between Barometric Pressure and Wind Velocity

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### Abstract

The purpose of this science project was to find the correlation between barometric pressure and wind velocity. I did this by recording the wind velocity in rotations per minute by using an anemometer. I used barometer readings, which I got off an Internet site. The readings measured air pressure in inches. I did this procedure daily starting on October 27, 2003 and ending December 1, 2003. I took the readings at 6:30 am, 11:30 am, 6:00 pm, and 9:30 pm. I converted the wind velocity from rotations per minute to miles per hour using an algebraic formula. I graphed my data on a scatter plot to find the correlation between barometric pressure and wind velocity. I used a scatter plot because it shows the correlation between two variables.

I found out that I had a negative correlation between barometric pressure and wind velocity. I knew this because the x-axis (barometric pressure) increased as the y-axis (wind velocity) decreased. I calculated the correlation and found that it was -0.45, not a perfect negative correlation of -1. This showed that there was a relationship between barometric pressure and wind velocity. The data proved that my hypothesis was correct. I hypothesized that as the barometric pressure increased the wind velocity would decrease which my plot showed.

My background information also stated that when air currents are rising in a low-pressure zone, the upper atmosphere rotates faster than the lower atmosphere’s high pressure sinking currents. This causes wind to move faster in low pressure than in high pressure because of the faster rotation of air in a low pressure system.

### Problem

What is the correlation between barometric pressure and wind velocity? I wanted to research this as a continuation of my last year’s science project. Last year I tested how much wind speeds varied from October to December. This year I hope to find out how barometric pressure affects wind velocity based on comparing the readings of each variable on a scatter plot.

Wind is the movement of air. It is caused when warm and cold air mix or upper and lower air mix causing the air to rotate.

Air moves in a horizontal fashion but also rotates due to pressure currents. In low pressure air rises and rotates fast in the high atmosphere forming fast winds. In high pressure the air sinks instead of rising forming slow moving air currents or slow wind. A low pressure system brings rain, snow, and high winds, while a high pressure system brings cold air. Warm highs bring warm maritime air. Winds travel in curved patterns because of the Coriolis affect or the Earth’s rotation. Wind is also controlled by pressure gradients or pressure differences developed between two air masses. Pressure gradients are caused by the varied heating of the Earth and the Coriolis Effect. This controls the wind speed of a wind that moves from a high to a low because of diffusion. Diffusion is the need to equalize the air pressure. For example, when you pour water in a cup there isn’t more water on one side of the cup than the other it levels out to fill the cup. This happens between high and low pressure systems, the result is wind. The air passes to the systems making an equal amount of air in each system. In a low the faster the air in the center rises the faster it rotates so the faster the wind speed is.

### Hypothesis

I hypothesize that as the barometric pressure increases the wind velocity will decrease. This is based on my background information, which states that in a low pressure zone air rise and rotates faster in the high atmosphere forming high winds. In high pressure zones the air sinks and doesn’t rotate as fast as the rising low pressure air in the higher atmosphere, forming low speed winds.

### Materials

1. Anemometer
2. Formula to convert rotations per minute into miles per hour
4. Data log
5. Stop watch/clock

### Procedure

Independent variable – barometric pressure Dependent variable - wind velocity

1. First, I recorded the date, time, and barometer readings that I got off the Internet web site, Weather.com in my data log.
2. Next, I took the wind velocity by timing myself for one minute, and then I counted on my anemometer the rotations per minute. I measured the wind speed from the same location everyday holding the anemometer above my head.
3. I performed this procedure from October 27, 2003 until December 1, 2003. I recorded my findings at the times of 6:30 am, 11:30 am, 6:00 pm, and 9:30 pm.
4. I converted the wind velocity from rotations per minute to miles per hour. (See instructions for 05-005 anemometer)

### Discussion

The data tells us that there is a negative correlation between barometric pressure and wind velocity. On my scatter plot the highest wind velocities show this by decreasing as the barometric pressure increases. I had a correlation of - .447172. This tells me that there is a relationship between barometric pressure and wind velocity but not a perfect negative correlation of -1.

### Conclusion

By conducting this science experiment I wanted to find the correlation between barometric pressure and wind velocity. I hypothesized that as the barometric pressure rose the wind velocity would fall. I chose this hypothesis because my background information stated in low pressure zones air rise and rotates faster than high pressure sinking air, forming fast wind currents. Each day I took the barometric pressure and wind velocity at 6:30 am, 11:30 am, 6:00 pm, and 9:30 pm and recorded them in my data log. I started collecting my data October 27, 2003 and ended December 1, 2003. When I completed my data collection I converted my wind velocity from measurements of rotations per minute to miles per hour and then compared the wind velocity and barometric pressure on a scatter-plot. I found that my hypothesis was correct that as barometric pressure increase wind velocity decreases. The correlation was -0. 447172.

The wind velocity decreased as the barometric pressure increased on my scatter-plot. This answered the problem because the relationship the correlation between barometric pressure and wind velocity is that as the pressure rises the wind velocity falls. This was the same as what my background information stated. My background information stated that wind velocity rises as barometric pressure falls. This is caused by rising air currents in the center of a low pressure system. Since the upper atmosphere currents move faster than the low atmosphere, the rising air currents in the low pressure system move faster than the sinking air currents in a high pressure system. This causes winds speeds in low pressure systems to be faster than in high pressure systems. I found this information on the web-page http://www.personal.psu.edu/faculty/j/e/jea4/earth/windsystem.html. The data supports that barometric pressure and wind velocities are related. On my graph the highest of the wind speeds showed a negative correlation between barometric pressure and wind velocity because as the wind velocities decreased the barometric pressure increased. The wind speeds varied from 0 to 45 miles per hour with many outliers and the barometric pressure varied from 29.4 to30.8 inches with many outliers. My highest wind velocities give support that as the barometric pressure increases the wind velocities fall in an almost straight diagonal line on my scatter plot. This shows a negative correlation.

My conclusion is very accurate because I have a great amount of data. I had much more than I needed to find the relationship between barometric pressure and wind velocity. I think I could have taken more data and still have had the same relationship between the two variables. Knowing that high winds come with lower pressure systems is important because you can predict if a storm is coming. For one more example, tornadoes occur in low pressure zones. It is important to know that high winds come with low pressures because you can prepare for the consequences, you can take down your umbrella, go sailing, or if you are in an area usually threatened by tornadoes you know to be extra cautious because of the low pressure. The correlation between barometric pressure and wind velocity is that as pressure increase wind velocity decreases.

### Applications

• Use pressure gradient differences to predict possible high winds
• Help us prepare for severe weather events