Weather and Storms

Weather • Is a condition of the atmosphere in terms of

heat, wind, pressure and moisture in a particular place and a particular time.

• There is weather because there is no atmosphere.

• Atmosphere dense and heavy, which is why there are ever changing ,dramatic violent weather conditions.

Air Masses

• Air mass is a large body of air, usually 1600 km or more across and perhaps several km thick.

• It is characterized by a homogeinity of temperature and moisture at any given altitude.

Air mass weather-it is a situation wherein region under its influence experience fairly constant weather.

• Fronts-boundary between two adjoining air masses having contrasting characteristics.

-Marks change in weather.

• Source Region-area where air mass acquires its characteristics properties of temperature and moisture.

Air masses are classified according to their source region

• Polar (P) air masses -originate in high latitudes

• Tropical (T)-Those that form in low latitudes

Air masses are classified according to the nature of the surface in the

source region

• Continental -designates land

• Maritime-Indicates water

Four basic types of air masses according to this scheme of

classification:

• Continental polar (cP)

• Continental tropical (cT)

• Maritime polar ( mP)

• Maritime tropical (mT)

Fronts

• Boundaries that separate air masses of different densities, one warmer and often higher in moisture content than the other.

• Thin transition zone about 5 to km thick.

Cold front

• It is formed when a cold air mass moves into water, displacing it in the process.

• Generally steep , and when it runs into the warmer air it forces it to rise quickly.

STATIONARY FRONT

• The forces influencing the movement of a cold or warm air mass lessen or become balanced, and the front stops advancing. When this happens a stream of cold air moves along the north side of the front and a stream of warm air moves along the south side in an opposite direction.

• It is called a stationary front because the edge of the front is not advancing.

• It represents an unstable situation that can result in a major atmospheric storm.

Waves and Cyclones

• Occluded front –The boundary between cold front and warm air masses

• Two Types of Occluded Front

Cold Front Occlusion-When the advancing cold air is colder than the air ahead

Warm Front Occlusion-When the air ahead is colder than the advancing air

Wave cyclones are formed by air moving in opposite directions along a front

• Lows or cyclones-The low moves away carrying with it rising air

current,clouds,precipitation,generally a bad weather.

• Highs or anticyclones-Highs are relatively stable because of

descending air motion.

-as a result dry air and lack of precipitation characterize high

Rainstorms

• Storms are atmospheric disturbances associated with vertical air motion that may develop locally within a single air mass or may be due to frontal activity between two air masses.

• The rate of rainfall depends on the rate of condensation and coalescence process

• If the considerable amount of water vapor present,a heavy downpour of air called rainstorm,results

• If the water vapor is continuously fed into the precipitating cloud, a prolonged, heavy rainfall occurs. This condition is called cloudburst

• The water runoff may produced a flash flood

Thunderstorms

• Is a rainstorm distinguished by thunder and lightning and sometimes hail.

• Thunderstorms may result from frontal cyclonic disturbances or strong local heating.

• Strong updrafts of air that produces the rain cloud are essential for thunderstorm formation.

Stages in the development of a Thunderstorm

Cumulus Stage Mature Stage Dissipating Stage

UPDRAFTS

DOWNDRAFTS

During the cumulus stage, strong updrafts act to build the storm, the mature stage is marked by heavy precipitation and cool downdrafts in part of the storm. When the warm updrafts disappear completely, precipitation becomes light, and the cloud begins to evaporate.

• Lightning is a discharge of electrical energy.

• In the upper part of the thunderstorm develops an accumulation of positive charges as cloud droplets are uplifted and the middle position develops an accumulation of negative charges from lager drops that fall.

• Lightning discharges occur from the cloud to the ground, from the ground to a cloud, from one part of the cloud to another part or between two different clouds.

LIGHTNING AND THUNDER

• The air it travels through is heated quickly, expanding into a sudden pressure wave that one hears as thunder.

• A nearby lightning strike produces a single, loud crack.

• Farther away strikes sound more like a rumbling boom as the sound from the separate strokes become separated over distance.

Tornadoes

• are local storms of short duration.

• Are violent windstorms that take the form of a rotating column of air that extends downward from a cumulonimbus cloud.

• The pressure within some tornadoes has been estimated to be as much as 10% lower than immediately outside the storm.

• Tornadoes form in association with severe thunderstorms that produce high winds, heavy rainfall, and often damaging hail.

HURRICANES

HURRICANES

Whirling tropical cyclones that can have wind speeds up to 300 km per hour.

Greatest storms on earth that can generate 15 meter sea waves capable of inflicting destruction hundreds of kilometers from their source

They are known by different names:

Typhoons – western Pacific

Cyclones – Indian Ocean

The North Pacific – has greatest number of storms , averaging 20 per year.

EyeIt is the center

of the storm

Averages 20 km in diameter

This is a zone of calm and scattered cloud cover.

By international agreement

Lesser tropical cyclones are given different names based on the strength of their winds.

Tropical depression

When a cyclone’s winds do not exceed 61 km per hour

Tropical storm

When winds are between 61 and 119 km perhour.

Damage caused by hurricanes can be divided into three categories:

• Wind damage

The force of wind can cause great destruction and can also create a dangerous barrage of flying debris.

Storm Surge

It is the most devastating damage.

A dome of water 65 to 80 km long that sweeps across the coast near the point where the eye makes landfall.

Superimposed upon the surge is tremendous wave activity which can inflict damage on low-lying coastal areas.

Flooding

The torrential rains that accompany most hurricanes represent flooding.

Weather predictions

Based on information about the characteristics, location , and rate of air masses and associated fronts and pressure systems.

The information is summarized as average values , then fed into a computer model of the atmosphere

Model

It is a scaled down replica of the real atmosphere , and changes in one part of the model result in the changes in another part of the model just as they do in the atmosphere.

Basic scientific laws concerning

Solar radiation , heat, motion and the gas laws

All these laws are written as series of mathematical equations – which are applied to thousands of data points in three-dimensional grid that represents the atmosphere

Computer- given instructions about the starting conditions at each data point , that is the average values of temperature , atmospheric pressure humidity , wind speed , and so forth.

Climate

• General pattern of the weather that occurs for a region over a number of years.

• Determines the types of plants and animals that live in a location, the type of houses that people build, and the life styles of people.

• Influences the processes that shape the landscape, the types of soils that form, the suitability of the region for different types of agriculture, and how productive the agriculture will be in that region

Major Climate Groups

• Uneven distribution of the incoming solar radiation results in variations of temperature conditions, moisture patterns, and general circulation of the atmosphere at different latitudes of the earth.

• Three groups of latitude:– Low latitudes

– High latitudes

– Middle latitudes

Principal climate zones

• Defined in terms of yearly temperature averages, which occur in broad regions

1. Tropical climate zone- low latitudes (18°C)

2. Polar climate zone- high latitudes (below 10°C)

3. Temperate climate zone- middle latitudes (10°C to 18°C)

Major Climate Zones

• The principal polar, temperate, and tropical climate zones are subdivided into:

– Marine climate- an area near the ocean that is influenced by air masses from the ocean; has abundant precipitation with an average of 50 to 75 cm yearly.

– Continental climate- an area far from the ocean and influenced mostly by air masses from large land areas; does not have an even temperature

Climates can be further classified as:• Arid climate- dry and receives less than 25 cm

of precipitation per year

• Humid climate- moist and receives 50 cm or more precipitation per year

• Semiarid- receives between 25 and 50 cm precipitation per year

Atmospheric Ozone

Atmospheric Ozone

• Ozone Layer

refers to a region of Earth's stratosphere that absorbs most of the Sun's UV radiation.

Atmospheric Ozone

• CFCs(chlorofluorocarbons)

molecules that damage the ozone layer through depletion

Sources of CFCs

- aerosol spray cans

- Refrigerants

- Plastic foam containers

- Spray propellants

How CFCs affect the Ozone Layer

Effects of ozone depletion

• increase cases of skin cancer

• Increase cases of cataracts

• Crops and climate will be affected

• Sea levels will increase

Effects of Ozone Depletion

El Niño

El Niño

• It is a spectacular oceanographic-meteorological phenomenon that develops in the Pacific and associated with extreme climatic variability.

El Niño

Presented by Group 3

Group members: Garcia, Sharmaine M. Idanan , Dea Marielle Javier , Ria Latonio , Dannila Audrey B. Limbo, Colet Litang , Ella Magalona , Rheanne Deniese Manlapaz, Ryan Onguda, Kimberly