and Society Weather, Climate Change Science 1206 - Chapter 2 · 2018. 10. 27. · There are several different atmospheric conditions that are measured to forecast weather condiitons:

Science 1206 - Chapter 2: Weather, Climate Change and Society2.1 - Measuring Weather Data (pp. 44-51)

Weather Forecasting

weather forecasting : process of predicting future weather based on ongoing observations of

atmospheric conditions

Scientists use both qualitative and quantitative observations to make predictions about the weather

Qualitative - descriptions that do not involve numerical values (ex. How something looks, feels, etc)

Quantitative - descriptions that have a numerical value (ex. Temperature, wind speed, etc)

Weather Components (see table 2.1 p. 45)

There are several different atmospheric conditions that are measured to forecast weather condiitons:

1) Air temperature

2) Precipitation

3) Atmospheric pressure

4) Relative humidity

5) Wind speed and direction

Air temperature

Temperature: the average kinetic energy of particles of a substance

Air temperature is measured using a thermometer. Liquid thermometers

use alcohol sealed in a narrow glass tube (previously they used mercury)

Other types of thermometers work on differences in expansion

between metals or the flow of an electric current between metal wires.

Precipitation

Precipitation: water, in liquid or solid form, that falls from the

atmosphere; includes rain, snow, hail, sleet, and fog

Rainfall is measured using a rain gauge. A rain gauge has a funnel at the

top to catch rainfall across a large surface area. The simplest way to

measure snowfall is with a stick or pole that is marked vertically in

centimetres.

Atmospheric Pressure

Atmospheric Pressure : the force that a column of air applies on the

air or a surface below it

Atmospheric pressure is measured with a barometer. Like

temperature and precipitation, atmospheric pressure can also be

measured with electronic sensors. Atmospheric pressure is measured

in kilopascals (kPA). Some home barometers show changes in

atmospheric pressure in millibars or mmHg.

Relative Humidity

Relative Humidity: amount of water vapour in the

air compared to the maximum amount of water

vapour in the air at that temperature

Relative humidity is measured with a hygrometer.

A digital hygrometer gives electronic readings.

Another type is based on the effects of

evaporation. It uses two thermometers.

Wind speed and direction

Wind speed is the speed at which air is moving through the atmosphere parallel to Earth’s surface. Wind

direction is the direction from which wind originates.

Wind speed is measured with an anemometer, and wind direction is measured with a wind vane. An

anemometer is designed to “catch” the wind in its open cups. The wind rotates the cups and this rotation

is translated into a wind speed measurement. A wind vane is shaped like an arrow with a large, finned tail.

Wind turns the tail, pointing the arrow in the direction from which the wind originates.

Wind speed is generally measured in km/h. Wind direction measurements indicate the direction from

which the wind is blowing

Wind speed and direction

Weather Observation Systems and Remote sensing technology

remote sensing technology - technology that collects weather data from a distance without actually

being in physical contact with the object being observed

Examples of remote sensing technology include weather radar and weather satellites.

Weather balloons incorporate weather instruments into an observation system that is sent high into the

atmosphere. Therefore, they are not considered remote sensing.

Weather balloons

Meteorologists often send weather balloons into the atmosphere to take weather measurements. These

measurements are taken by a radiosonde. A radiosonde, is a device carried by the balloon that contains

various weather-measuring instruments. It also carries a radio transmitter. A radiosonde’s instruments

measure atmospheric conditions, such as temperature, pressure, and humidity. The radio transmitter

continuously sends these data back to radio receivers on the surface.

Additionally, by tracking the balloon itself, meteorologists gather data on wind speed and direction. As

the balloon rises in the atmosphere and air density decreases, the hydrogen gas that keeps it aloft

expands. The balloon eventually bursts and a small parachute carries the radiosonde back to Earth

Weather radar

weather radar - remote sensing technology that measures weather data by analyzing radio waves that

are reflected off objects in the atmosphere

Radio waves sent out by weather radar are reflected by rain, snow, hailstones, or other objects in the air.

The heavier the precipitation is, the greater the amount of reflection. The reflected signals are

interpreted and converted into images that show the location and intensity of precipitation.

A special radar technology called Doppler radar also determines whether the objects it detects are

moving away from or toward the radar antenna. It can also measure their speed. This enables

meteorologists to calculate the direction and speed of a weather system

Weather satellites

Weather satellites contain specialized remote sensing technology that has been launched into orbit

around Earth. The technology on these satellites monitors the atmosphere near Earth, and it helps

meteorologists understand the development and movement of weather systems.

Weather satellites rely on various sensors to detect weather systems. These include sensors that detect

infrared (heat) radiation. Sensors also detect visible light that has been reflected or scattered by

precipitation and other particles in the air. Visible light sensors detect different types of clouds.

Weather satellites

There are two types of orbiting weather satellites, Geostationary Operating Environmental Satellites

(GOES) and Polar Operating Environmental Satellites (POES).

GOES orbit Earth about 36 000 km above the equator. They travel at the same speed as Earth rotates.

These satellites are essentially hovering over a fixed location on Earth. Thus, they observe the same

location on a continuous basis

POES orbit Earth about 14 times per day. As Earth rotates beneath POES, they cover the entire globe

during the course of the day). This allows them to track various weather systems.

Science 1206 - Chapter 2: Weather, Climate Change and Society

2.2 - Forecasting the Weather (pp. 52-59)

Short-range and long-range forecasts

short-range forecast - a forecast that predicts how weather conditions will change over a period of up to

48 hours

long-range forecast - a forecast that predicts how weather conditions will change over a period of 3 to 7

days

Short-range forecasts

Meteorologists use a variety of techniques to make short-range forecasts.

The simplest, called persistence forecasting, assumes that current weather patterns will persist

(continue) into the future. Because atmospheric conditions are always changing, persistence forecasts

are most accurate for up to a few hours

Another technique, called nowcasting, forecasts weather up to about 6 hours. Nowcasting relies on

remote sensing technology and is especially helpful in predicting storm movement.

Weather symbols and maps (table 2.2, p. 53)

All the components that make up weather are recorded at regular intervals. These data are then analyzed

to identify trends that help predict weather in a certain area. To ensure that information is presented as

clearly and concisely as possible, meteorologists use a set of symbols for weather conditions.

Meteorologists combine data recorded hourly by many weather stations to create weather maps

The most detailed maps are used by meteorologists themselves. Such maps use a more extensive array of

symbols, because they communicate many more atmospheric conditions.

Analyzing Weather Maps for Short-range Forecasting

One important factor to consider when analyzing weather maps to create a short-range forecast is the

location of weather fronts, as well as the speed and direction of their motion

The locations of pressure systems and their boundaries can also help you predict how the weather will

change. Atmospheric conditions often become unsettled where two pressure systems meet.

If the maps include isotherms or isobars, observe how close or far apart the lines are and how this

distance is changing with time. This will give you an idea of how quickly the temperature or pressure is

changing. Often, quickly changing temperature or pressure indicates an approaching front

Long-range Weather Forecasts

Long-range forecasting relies on computer-based statistical analysis of past weather data and computer

models of atmospheric circulation and behaviour. The farther into the future a forecast is made, the less

reliable its accuracy becomes

Why are long-range forecasts less accurate? The main reason is that computer models have to make

certain assumptions about how the atmosphere will behave. Yet, these assumptions may be correct in

some situations and less so in others. To help alleviate this, meteorologists use several models to help

make long term forecasts

Long-range forecasts

Because computer models deal with global atmospheric conditions, long-range forecasts are much

better at predicting large-scale weather patterns than small-scale ones.

Example: long-range forecasting may well be correct when it predicts a colder than average winter for

the east coast of Canada. However, it is harder to predict what kind of winter any given location will

experience

Science 1206 - Chapter 2: Weather, Climate Change and Society2.3 - Importance and Limitations of Weather Forecasting (pp. 60-67)

Canada’s weather

Because of its location in the mid-latitudes, Canada experiences a wide variety of weather, much of which

can be extreme and hazardous. Such weather events include floods, hurricanes, ice storms, heat waves,

and so on. They result in loss of life and hundreds of millions of dollars in property damage in Canada

each year. As well, weather influences many of our day-to-day and long term decisions.

How Weather Influences Our Lives

Weather affects individuals on a daily basis, but also affects larger groups and entire industries such as

the following:

1) Effects on agriculture

2) Effects on marine industries

3) Effects on transportation

Effect of Weather on Agriculture

Our food supply depends to a large degree on favourable weather conditions. If amounts of rainfall and

sunshine are appropriate, crops will grow and harvests will be bountiful. Both animals and plants are

affected by extremes of weather.

Ex. - Late frosts in the spring will kill some crops and prevent flowering trees from forming fruit.

- Heavy rain or hail storms can spell disaster for many crops.

- Similarly, dry spells or droughts are often associated with extreme heat waves. Plants may wilt

because of the lack of water, and will die if the drought is prolonged. Crop yields and the farmers’

incomes are reduced.

- Animals, too, require more water for proper growth and reproduction, and, ultimately, survival.

Effect of Weather on Marine Industries

People who work in marine industries such as fishing and offshore oil development face high risks for

injury or fatality. The risks in these occupations are due in large part to bad weather.

Weather often determines when and if a person can engage in the fishing industry. Even equipped with

good information, the pressure to earn a living often forces individuals to assume risks that they would

not normally take. Meteorologists provide marine forecasts for inland and coastal waters

Effect of Weather on Transportation

The majority of the Canadian population lives in urban centres, but the population as a whole is spread

out over a huge land area. Transportation of people and goods around the country requires an elaborate

network of roads, ferries, railways, and air traffic.

Bad weather and poor road conditions are responsible for a great number of traffic accidents and

significant road damage each year

The cost of maintaining roads due to severe weather is also great, due to winter weather and other

events such as hurricanes, etc.

Air transportation is particularly sensitive to weather conditions and relies heavily on weather forecasts.

Limitations of Weather Forecasting

While short-range forecasts, those for the next 48 hours, are quite accurate, long-range forecasts are

much less reliable because the atmosphere, by its very nature, is unpredictable.

Yet, as technology improves, so will our ability to forecast the weather. Because of new technology,

today’s 5-day predictions are just as accurate as the 2-day predictions from 20 years ago.

Science 1206 - Chapter 2: Weather, Climate Change and Society2.4 - Climate Change (pp. 68-77)

Climate

Climate - the pattern of weather conditions in a region over a long period of time

A change in the weather conditions that a region experiences over a long time is called climate change.

Climate change refers not only to changes in temperature, but also to changes in other aspects of

weather, such as precipitation (rain and snow), wind, and storms. When scientists talk about climate

change, they mean changes in patterns that involve all parts of weather, not just temperature.

Climate Change—Past and Present

Earth’s climate has undergone changes throughout Earth’s past. Some of these changes have been

dramatic and have occurred over millions of years. Some of these changes have been less dramatic and

have occurred over hundreds and thousands of years. As well, there have been alternating periods of

warming and cooling of Earth’s climate throughout Earth’s history.

Although climate change can result from both natural causes and from human actions, scientists have

shown that there is a connection between the changes in the concentration of carbon dioxide in the

atmosphere and the changes in Earth’s surface temperature. Notice that as carbon dioxide levels have

increased, Earth’s surface temperature has increased. When carbon dioxide levels decreased, Earth’s

surface temperature decreased

Monitoring Climate Change

Scientists look at three main sources of information to learn about past climates: trees, fossils, and ice cores. By identifying how and when Earth’s climate changed in the past, they gain a better idea of how today’s climate responds to change

Tree Rings

As a tree grows, it adds two new layers of wood under its bark each year. These layers of wood are visible to us as tree rings. A light-coloured ring represents rapid spring growth, when growing conditions are more favourable. A dark-coloured ring represents slower summer growth, when conditions are drier and hotter. Since trees can be hundreds (and sometimes thousands) of years old, tree rings are valuable sources of information about climate in recent past.

Fossils

Fossil: the remains or traces of ancient organisms

Because all organisms are adapted to their environment, the type of fossil in a certain place tells scientists what the climate must have been like there during that period.

Ice Cores

Permanent ice fields in the Arctic and Antarctica have existed for hundreds of thousands of years. Each

year, a new thin layer of ice is deposited. Each ice layer holds a record of what the atmosphere was like

when the ice formed. This record of the past can be retrieved with special drills that take core samples

from the ice. Different materials found in the various layers give clues to what happened during that

period of time.

Ex. Dust and ash trapped in the ice indicate events such as volcanic eruptions and forest fires. Plant

pollen tells the species of plants alive at the time. Temperature and humidity can be inferred from the size

and shape of the ice crystals

Assessing Present Climate Change

Scientists use many tools to record the daily state of the hydrosphere, atmosphere, and other parts of Earth’s climate. Direct measurements of temperature, humidity, precipitation, and other data have been collected for about 200 years. These data are compared with present data that are collected from tools that include weather balloons, radar, and satellites.

Human Activities That Affect Climate Change

Most scientists agree that current climate changes are happening so quickly because human activities

are adding more greenhouse gases into the atmosphere. In other words, human activities are enhancing

the natural greenhouse effect.

The greenhouse effect is a process in which certain gases in the atmosphere absorb heat from the Sun

and heat that is radiated from Earth’s surface. This process results in warming of the atmosphere. The

greenhouse effect is a natural part of Earth’s climate system.

Greenhouse Effect (fig 2.23 p. 71)

anthropogenic greenhouse effect - a process in which human-produced greenhouse gases in

Earth’s atmosphere absorb heat energy from the Sun and Earth’s surface

The anthropogenic greenhouse effect is linked to the start of the Industrial Revolution about 300

years ago. At that time, people who lived in the countryside began moving to cities to work in

factories. Since the Industrial Revolution, people have been adding more and more greenhouse

gases into the atmosphere, whether they be gases that occur naturally or purely human-produced

ones.

Greenhouse gases (fig 2.24, p. 71)

There are a number of greenhouse gases that humans have cause the release of into the atmosphere,

including:

1) Carbon dioxide

2) Methane

3) Nitrous oxides

4) halocarbons

Carbon dioxide

Most anthropogenic carbon dioxide comes from burning fossil fuels (coal, oil, and natural gas). Fossil fuels are burned to carry out industrial processes, generate electricity, heat homes, and power vehicles.

Deforestation also has added carbon dioxide to the atmosphere. When large areas of forest are cleared of their trees, less carbon dioxide is removed from the atmosphere through photosynthesis. As well, the branches, leaves, and other debris that result from logging are often burned. This also adds carbon dioxide to the atmosphere

Methane

Methane is produced when bacteria break down vegetation in an oxygenfree environment.

Methane absorbs 25 times more heat than carbon dioxide does. So even though there is less

methane in the atmosphere than carbon dioxide, methane is a more potent greenhouse gas

Farming is the main human activity that produces methane

Ex. Cows, goats, and sheep have methane-releasing bacteria in their guts to help them

break down the food they eat.

Nitrous Oxides

Nitrous oxide is an even more potent greenhouse gas than methane. In fact, nitrous oxide absorbs 300 times more heat than carbon dioxide does. Human sources of nitrous oxide include farming of crops and livestock, use of fertilizers, and vehicle exhaust.

Halocarbons

Halocarbons are the only greenhouse gases produced solely by human beings. Halocarbons are industrial chemical compounds

The best known are the chlorofluorocarbons, or CFCs. In the past they were used as solvents and as coolants in refrigerators. CFCs were banned many years ago because of the damage they cause to the atmosphere’s ozone layer. However, the ones already released take thousands of years to break down and they are much more potent of a greenhouse gas than carbon dioxide.

Climate Change Affects Aquatic Ecosystems (table 2.3, p. 73)Climate change can affect aquatic ecosystems in a number of ways, such as:

- Melting sea ice

- New food chains

- Warmer oceans

- Rising sea levels

- More violent storms

Climate Change Affects Terrestrial Ecosystems (table 2.4, p. 74)

Climate change can affect terrestrial ecosystems in a number of ways, such as:

- Changing organisms

- Melting land ice

- New deserts

- More flooding

- Effects on human health