Meteorology p1 - humidity

Summary

This video lesson introduces key concepts in meteorology, following a review of energy-related topics. It highlights extreme weather statistics in the U.S., such as the hottest and coldest recorded temperatures and the driest and wettest locations. The video then explains the difference between weather (short-term atmospheric conditions) and climate (long-term trends), with a focus on understanding humidity. Key terms like absolute and relative humidity, dew point, and how to use a sling psychrometer to measure them are introduced. The lesson ends with a brief look at how to calculate dew point and relative humidity using reference charts.

Takeaways

• 🌡️ Meteorology continues from energy topics, with many energy concepts applicable to weather.
• 🔥 Hottest temperature recorded: 134°F in Death Valley, California.
• ❄️ Coldest temperature recorded: -80°F in Prospect Creek, Alaska.
• 🌧️ Wettest location: Hawaii with 460 inches of rain in one month.
• 💨 Windiest location: Mount Washington, New Hampshire, with winds up to 231 mph.
• ⛅ Weather refers to short-term atmospheric conditions, while climate covers long-term conditions over years.
• 💧 Humidity refers to the moisture content in the air, with relative humidity being the percentage of water vapor saturation.
• 📈 As relative humidity increases, the chance of rain also increases due to higher water vapor content.
• 🧊 Dew point is the temperature at which air becomes fully saturated and can no longer hold water vapor, leading to precipitation.
• 🧪 A sling psychrometer is used to measure dew point and relative humidity by comparing the wet and dry bulb temperatures.

Q & A

What is the difference between weather and climate?

Weather refers to the short-term conditions of the atmosphere, such as changes in temperature, moisture, air pressure, and wind, which can fluctuate from hour to hour or day to day. Climate, on the other hand, is the long-term pattern of weather conditions over several years or decades.

What are some extreme weather records in the United States?

The hottest recorded temperature is 134°F in Death Valley, California. The coldest is -80°F in Prospect Creek, Alaska. The wettest location is Hawaii, which once received 460 inches of rain in one month. The snowiest location is in California with 390 inches of snow in a month, while Baghdad, California holds the record for the longest dry spell at 767 days without rain. The windiest location is Mount Washington, New Hampshire, with winds reaching 231 mph.

What is absolute humidity?

Absolute humidity is the actual amount of water vapor in the air. For example, a parcel of air might have 10 grams of water vapor. However, this measurement is not commonly used because it doesn’t give a real sense of current weather conditions.

What is relative humidity, and why is it more useful than absolute humidity?

Relative humidity is the percentage of saturation of the air, indicating how much water vapor the air is holding compared to the maximum it can hold. For instance, 50% relative humidity means the air is holding half of its capacity. It is more useful because it correlates with how comfortable or humid the air feels.

How is relative humidity related to the chance of rain?

As relative humidity increases, the chance of precipitation also rises. For example, 90% relative humidity indicates a high chance of rain since the air is nearly saturated with moisture.

What is the dew point?

The dew point is the temperature at which the air becomes fully saturated with water vapor, meaning it cannot hold any more moisture. If the air temperature drops to this point, condensation occurs, often leading to rain or dew formation.

How can the dew point temperature be measured?

The dew point temperature can be measured using a sling psychrometer, which consists of a wet bulb and a dry bulb thermometer. By finding the difference in temperatures between the wet and dry bulbs, the dew point can be calculated using a reference chart.

How does a sling psychrometer work?

A sling psychrometer has two thermometers: one with a wet bulb and one with a dry bulb. The wet bulb is moistened and both are swung around. The difference in temperatures between the two bulbs helps calculate relative humidity and dew point using a reference chart.

How do you calculate the dew point using a sling psychrometer?

To calculate the dew point, subtract the wet bulb temperature from the dry bulb temperature. Find the dry bulb temperature on a reference chart, then find the temperature difference on the top of the chart. Where these values intersect gives the dew point.

How do you calculate relative humidity using a sling psychrometer?

To calculate relative humidity, subtract the wet bulb temperature from the dry bulb temperature. Using a reference chart, find the dry bulb temperature on the left and the temperature difference on the top. The intersection of these two values gives the relative humidity.