WEATHER Weather vs. Climate Weather – the atmospheric conditions over a relatively short period of time Weather – the atmospheric conditions over a relatively short period of time Climate – the weather in some location averaged over a long period of time Climate – the weather in some location averaged over a long period of time

Weather Measurements What weather phenomena do we need to measure? What instruments do we use to measure them?

Coe Lake Weather Measurements Tradition & Electronic Temperature Temperature Atmospheric Pressure Atmospheric Pressure Rainfall Rainfall Relative Humidity Relative Humidity Wind Direction Wind Direction Wind Speed Wind Speed

CLOUD TYPE REVIEW These cloud types should be familiar to you. Write down the website if you need to go back to revisit them. These cloud types should be familiar to you. Write down the website if you need to go back to revisit them. “Cirrus” or “Cirro” – high (base above 6000 m) “Cirrus” or “Cirro” – high (base above 6000 m) “Alto” – mid (base 2000 m-6000 m) “Alto” – mid (base 2000 m-6000 m) No prefix – low clouds No prefix – low clouds

Temperature Two scales – Celsius & Fahrenheit Two scales – Celsius & Fahrenheit –Boiling Point of Water212 °F100 °C –Average Body Temperature98.6 °F37 °C –Hot Summer Day85 °F29.4 °C –Average Room Temperature68 °F20 °C –Cool Fall Day55 °F12.8 °C –Warm Winter Day40 °F4.4 °C –Freezing point of Water32 °F0 °C You must know ABT & ART in °C You must know ABT & ART in °C You must know the BP & FP of Water in °C You must know the BP & FP of Water in °C

Thermometers We use a variety of thermometers at Coe Lake We use a variety of thermometers at Coe Lake –All measurements will be done in Metric! –Digital thermometers –Thermometers with various scale markings that make it challenging for students to read –“What’s Hot & What’s Not?” –“Weatherwise”

Thermometers

ATMOSPHERIC PRESSURE Atmospheric pressure (or air pressure) is the weight of Earth's atmosphere on the surface at a given location and is generated by the downward force of Earth's gravity. Atmospheric pressure (or air pressure) is the weight of Earth's atmosphere on the surface at a given location and is generated by the downward force of Earth's gravity. Atmospheric pressure depends on the amount of air above the location where the measurement is taken, consequently the pressure drops as you go higher. Atmospheric pressure depends on the amount of air above the location where the measurement is taken, consequently the pressure drops as you go higher. Also known as Barometric Pressure because it is measured with a barometer. Also known as Barometric Pressure because it is measured with a barometer.

Barometric Pressure Unit Craziness! National Weather Service: National Weather Service: –inches of Mercury (inHg) –mm of Mercury (mmHg) –hectoPascals (hPa) A Pascal is the metric unit for air pressure and 100,920 Pa is equal to hPa A Pascal is the metric unit for air pressure and 100,920 Pa is equal to hPa –millibars (mb) (same as hPa)

Average Atmospheric Pressure at Sea Level In Weatherspeak: In Weatherspeak: –29.9 inHg – hPa – mb In Chemspeak: In Chemspeak: – kPa –760 mmHg –1.00 atm –14.7 psi

Barometers

Rainfall (Snowfall) Rainfall impacts all of us, from the lack of rain during times of drought to the dangers of flash floods when we receive too much rain too fast. Rainfall impacts all of us, from the lack of rain during times of drought to the dangers of flash floods when we receive too much rain too fast. It is the depth of water reaching the ground, typically in inches or millimeters. It is the depth of water reaching the ground, typically in inches or millimeters. Rainfall rate Rainfall rate –Light = 0.10 inches of rain per hour –Moderate = 0.10 to 0.30 inches of rain per hour –Heavy = over 0.30 inches of rain per hour

Rainfall An inch of rain is exactly that, water that is one inch deep. An inch of rain is exactly that, water that is one inch deep. One inch of rainfall equals 4.7 gallons of water per square yard or 22,650 gallons of water per acre! Wow! One inch of rainfall equals 4.7 gallons of water per square yard or 22,650 gallons of water per acre! Wow! Measured with a Rain Gauge. Measured with a Rain Gauge.

Rain Gauges

Relative Humidity The amount of moisture in the air relative to how much moisture the air can hold. The amount of moisture in the air relative to how much moisture the air can hold. Temperature dependent. Temperature dependent. Higher temperatures – the air can hold more moisture. (Think about hot, humid summer days…) Higher temperatures – the air can hold more moisture. (Think about hot, humid summer days…) Lower temperatures – the air holds less moisture. (The relative humidity might be the same as a hot summer day, but less moisture will be in the air.) Lower temperatures – the air holds less moisture. (The relative humidity might be the same as a hot summer day, but less moisture will be in the air.)

Relative Humidity Humidity is measured with a hygrometer. Humidity is measured with a hygrometer. Relative humidity is measured with a Sling Psychrometer. Relative humidity is measured with a Sling Psychrometer. Humidity measurements can be used to calculate dew point and heat index. Humidity measurements can be used to calculate dew point and heat index.

Relative Humidity Chart

Heat Index

Measuring Humidity

Wind Measurement Wind is the natural motion of the air roughly parallel to the Earth's surface. Wind is the natural motion of the air roughly parallel to the Earth's surface. It is caused by the unequal heating and cooling of the Earth and atmosphere by the sun, which produces differences in air pressure. It is caused by the unequal heating and cooling of the Earth and atmosphere by the sun, which produces differences in air pressure. Air tends to flow from areas of higher pressure to lower pressure. Air tends to flow from areas of higher pressure to lower pressure.

Wind Measurement Wind occurs at all scales. Global winds (trade winds) Global winds (trade winds) Upper level winds (jet streams) Upper level winds (jet streams) Synoptic winds (resulting from the pressure differences of surface air masses) Synoptic winds (resulting from the pressure differences of surface air masses) Local (mesoscale) winds (such as gust fronts) Local (mesoscale) winds (such as gust fronts) Winds that develop because of geographical features (like sea breezes). Winds that develop because of geographical features (like sea breezes). Winds also occur on a much smaller scale, for example dust devils or tornadoes. Winds also occur on a much smaller scale, for example dust devils or tornadoes.

Wind Measurement Wind measurements are taken at a fixed location and measure two parameters: Wind Speed – mph, kph, knots Wind Speed – mph, kph, knots Wind Direction – cardinal directions; always naming the wind for the direction from which it comes Wind Direction – cardinal directions; always naming the wind for the direction from which it comes –EX: a SE wind comes from the southeast

Wind Speed – Anemometer

Wind Direction – Wind Vane

What do you need to know?  What are the various weather phenomena and –What are the definitions? –What tool is used to measure it? –What metric unit is used to measure it?  Match the name of the cloud to its altitude using the correct prefixes (alto & cirro)  What are the metric and English (F) temperatures for the bp & mp of water, body temperature & room temperature?  What is the difference between weather and climate?