Unit 6 Part 2 Notes - Humidity, Clouds, Air Masses, Fronts, Severe Weather PDF

Unit 6 - Weather Part 2 - Relative Humidity, Clouds, Air Masses, Fronts, Severe Weather Great Neck South Middle School Atmospheric Moisture Water vapor is gaseous water in the atmosphere _____________ Water enters the atmosphere by: Evaporation liquid to gas ______________: AND...

Unit 6 - Weather Part 2 - Relative Humidity, Clouds, Air Masses, Fronts, Severe Weather Great Neck South Middle School Atmospheric Moisture Water vapor is gaseous water in the atmosphere _____________ Water enters the atmosphere by: Evaporation liquid to gas ______________: AND Transpiration ________________: plants releasing water vapor Net evaporation rate is determined by : Insolation 1. ___________: more insolation, more energy for evaporation Surface area more 2. ____________: area exposed, the greater the evaporation rate Net evaporation rate is determined by : Humidity 3. _______________: the drier the air, the faster the rate of evaporation Wind speed 4. ______________: the greater the wind speed, the faster the evaporation rate. What is Humidity? Relative humidity tells us “how full” the air is ________________ with water. Expressed as a %  MORE water vapor than Hotter air can hold _________ colder air (more space available due to expansion). THEREFORE, if the temperature of the air changes, but the amount of water vapor stays the same, the relative humidity will change. ~50% _________ % full _________ ~30% % full _________ ~25% % full Temperature vs. Relative Humidity Let’s establish the relationships. 1. As the temperature of air increases, its capacity to hold water vapor ______________ increases 2. If the temperature of a parcel of air increases, and the amount of water vapor stays the same, the relative humidity decreases _____________  The dew point ____________________ is the air temperature when the air is full to capacity with water vapor (100% relative humidity) At 100% RH we say the saturated air is ________________ ○ When this happens, some of it starts to condense (gas to liquid). Dew Point increase as the air Relative humidity will _________ temperature gets closer to the dewpoint temperature. And chance of precipitation will also increase ________________. (Rel. humidity & chance of precip. will decrease when the 2 temperatures get further apart.) Air Temperature Dew point Relative Humidity Chance of Temperature Precipitation 70 60 51% Moderate 70 65 74% High 70 68 85% Highest  Now look at this relationship graphically: Relative humidity will increase as the air temperature gets closer to the dew point temperature. Which station model shows the greatest relative humidity? Why/how do you know?? Measuring Moisture Sling Psychrometer __________________ instruments used to measure relative humidity and dew point Both use wet-bulb and dry-bulb thermometer readings ○ **IMPORTANT** The wet bulb temperature is always less than or equal to the dry bulb temperature. ______________________ To determine Relative Humidity and Dew Point You must use these 2 charts on page 12 of ESRT  DRY BULB = 22 °C WET BULB = 16 °C 1. Locate dry bulb on left side 2. Find the difference (Subtract: dry bulb temp – wet bulb) 3. Locate answer to step 2 on top of chart 4. See where those two numbers meet **Make sure you are using the correct chart** Try a couple examples: 1. What is the relative humidity where the dry bulb temperature is equal to 18oC and a wet bulb temperature of 15oC? Step 1: Dry bulb temp = ________ Step 2: difference between wet & dry = _____ Step 3: Locate number from step 1 in left hand column, and number from step 2 across top of chart Step 4: Find where the two numbers meet Try a couple examples: 2. What is a possible dew point temperature when dry bulb temperature is equal to 3oC and a wet bulb temperature of 7oC? Try a couple examples: 2. What is the dew point temperature when dry bulb temperature is equal to 18oC and a wet bulb temperature of 10oC? Try a couple examples: 3. What is the relative humidity when the dry bulb temperature is equal to 26oC and a wet bulb temperature of 24oC? Try a couple examples: 4. What is the WET BULB temperature when the dry bulb temperature is 20oC and relative humidity is 66%? Cloud Formation - R.E.C.C 1. Rises and Expands Air heats at surface __________________ 2. Cools Air ____________ , contracts and reaches its dew point temp. 3. Water begins to ______________, Condense or change from a gas to liquid. – Water droplets form on __________________ condensation nuclei (dust particles / aerosols in the air) Cloud Formation - R.E.C.C Precipitation https://www.noaa.gov/jetstream/syn optic/types-of-weather-phenomena Precipitation - The falling of liquid or solid water from clouds towards Earth’s surface (after R.E.C.C.) – The solid/liquid particles collide until they are heavy enough to fall under the influence gravity of _________ Forms include: rain, drizzle, snow, sleet, freezing rain and hail Measuring Precipitation rain gauge is used to A ____________ measure liquid precipitation. It is measured in depth, usually inches or centimeters.  Air Masses ▪ __________ Air Mass – large body of air in the troposphere with similar characteristics throughout (pressure, moisture, temp.) ▪ Forms when air remains stationary over an area - which characteristics determines its _______________  Characteristics of an Air Mass ▪ An air mass takes its characteristics from the Earth surface source region over which it forms, called its _______________ – _________________ Moisture Level ▪ Land/Continental regions = dry ▪ Ocean/Maritime regions = humid/wet – _________________ Temperature ▪ Polar or arctic/high latitudes = cold ▪ Tropical/low latitudes = warm Air Mass symbols on reference table (PG 13) ▪ cA = continental arctic = very dry and very cold ▪ cP = continental polar = dry and cold ▪ cT = continental tropical = dry and warm ▪ mP = maritime polar = wet and cold ▪ mT = maritime tropical = wet and warm  4 Major Air Masses Affect the U.S./North America Air Mass Name Symbol Temperature Humidity Specific Source Region Continental Polar Maritime Polar Maritime Tropical Continental Tropical Jet Streams & Planetary Winds help move air masses around the globe. What patterns do you see in the path of storms over the US?  Weather Fronts ▪ Air masses do not mix (different densities, warm air rises, cold sinks), the boundary between two front different air masses is called a _______ ▪ There are four types of fronts – Cold – Warm – Occluded – Stationary  Cold Front The boundary where a cold air mass moves in on an existing warm air mass. Rapidly pushes up warm air → air cools, condenses Thunderstorms common right at the cold front** **_______________ Cold Front Side/Profile View 2D map view  Warm Front Boundary where a warm air mass moves in on an area of cool air Warm air rises over cool air → air cools, condenses well ahead **Rain common ______________ of a warm front** Warm Front Side/Profile View 2D map view  Precipitation and Fronts A view of typical precipitation patterns for a cold and warm front on a weather map. Cold front - precipitation at the frontal boundary Warm front - at the boundary and a little bit head  Occluded Front ▪ Warm air gets __________ trapped between two cold fronts (cold front takes over a warm front) warm air forced up → cools, condenses 2D map Side/Profile View view  Stationary Front ▪ No mixing (neither air mass is advancing) ▪ Air masses push against each other, but neither moves _______________ Side/Profile View 2D map view  Front Symbols ESRT PG 13 **The triangles and half circles point in the direction the fronts and associated air masses are moving.** Draw in the frontal boundary Draw in the frontal boundary Severe/Extreme Weather ▪ A storm is a ________________________ violent or severe disturbance of the atmosphere that usually creates dangerous, destructive, or unpleasant conditions on Earth’s surface. Ex. hurricanes, thunderstorms, tornadoes, hail and blizzards  Mid-Latitude Cyclone Storms ▪ Severe weather events with precipitation are low pressure _______________ storm systems – Remember: winds move counterclockwise and inward – Air rising from Earth’s surface to atmosphere, R.E.C.C.  What is a Hurricane? Definition: A strong storm of tropical origin, with sustained 74 mi/hr winds exceeding _________  What is needed for a hurricane to form? 1. _________ Humid air 2. _______________ Warm ocean water 3. Weak Jet Stream ______________ 4. Extremely low pressure _________________  How Does it Happen? warm tropical Low pressure centers are formed over ____________ Hurricanes ocean waters are that created when:to fuel the system provide energy late summer or early fall Hurricanes usually occur in _______________________ Temperature lag! WHY??? _______________  General Paths of Hurricanes off the coast of West Africa Hurricanes first form ______________________________ , are pushed W by the planetary winds, then NE by the southwesterlies!  lose their strength when they travel Hurricanes will _______________________ over land or cool water Saffir Simpson Scale - categories wind speed based on _____________  To prepare for a hurricane you should: 1. Prepare an escape route 2. Tape/Board up windows 3. Store up on food, water, candles 4. Go to higher ground  More Severe Weather: Thunderstorms Heavy rain storms accompanied by thunder and lightning ____________________________. Form from rising warm air associated with fronts, as well as part of hurricanes. ▪ Cumulonimbus clouds (anvil clouds) Hazards include: flooding, hail, high winds and lightning  More Severe Weather: Tornadoes low pressure funnel that hangs A tornado is a _____________________ down towards Earth’s surface ▪ Most tornadoes only last a few minutes ▪ The most violent of storms How Tornadoes Form: Video  Fujita Scale __________________ - Measuring Tornadoes Just like hurricanes, the rating scale is based on wind speed  Tornadoes To prepare for a tornado, you should to a basement or lowest go ___________________________ level of home/building _____________________ Tornado Alley the most _____________: prone area in the U.S. for tornadoes. Where mT air mass from the South meets cP air mass from the North  Blizzards Blizzards are intense storms composed of snow and ice. Dangerous conditions including: ▪ Heavy snowfall ▪ High wind speeds ▪ Low visibility ▪ Below-freezing temperatures How To Prepare: ▪ Stock up on supplies like food, bottled water, batteries, blankets ▪ Stay off roads, stay inside