SEBA Class 9 Elective Geography Chapter 1 Weather and Climate

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SEBA Class 9 Elective Geography Chapter 1 Weather and Climate

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Weather and Climate

TEXTUAL QUESTIONS AND ANSWERS

1. What do you mean ‘weather’ and ‘climate”? Distinguish between weather and climate.

Ans. The term ‘climate’ refers to the sum total of weather conditions and variations over a large area for a long period of time, i.e., more than thirty years. The term weather refers to the atmospheric conditions over an area at any point of time.

The differences between weather and climate are:

Sl. NO.	Basis ofdifference	Weather	Climate
(i)	Period	Considered over a short period of time such as a day, a week, etc.	Considered over a long period of time (at least 30 years).
(ii)	Area	Indicates the atmospheric conditions over a small area.	Refers to the atmospheric conditions over a large area.

2. Mention the elements of weather and climate. 

Ans. The elements of weather and climate are those quantities or properties that are measured regularly. 

The six main elements are weather and climate are:

(i) Temperature.

(ii) Pressure of air. 

(iii) Humidity.

(iv) Wind.

(v) Precipitation.

3. State the elements of weather and climate.

Ans. The main elements of weather and climate are temperature pressure of air, humidity, wind and precipitation.

1. Temperature: is the most important determinant of weather and climate since it tends to affect other elements of the weather. Temperature is the degree of hotness or coldness of a place, measured in Degrees Celsius or Fahrenheit. When the Sun heats up the ground during the day, the air in contact with it gets warmed up. As you move further away from the ground, the temperature begins to drop, hence the reason why highland areas tend to be cooler than plains. Temperatures are also affected by proximity to large water bodies, mountains and most importantly, latitudinal positioning (Equator versus the Poles). Temperatures are measured using various types of thermometers and  usually given as a mean or average for the day, month or year.

2. Wind: is air in motion. Air molecules tend to move from areas of high pressure to low pressure. Theoretically, cold dense air from the Polar regions should blow towards the equator and fill the void where heat warms up the air and causes air molecules to rise and spread out . However, the spinning of the Earth exerts a force on these currents of air, making them deflect to the left in the Northern Hemisphere and to the right in the Southern Hemisphere.

3. Wind: The movement of air from high pressure area to low pressure area is called wind. Winds originate due to the variation in pressure and pressure is created by variation in temperature over place and time. Wind can reduce or increase temperature of a place and thereby influence its climatic conditions.

4. Humidity: is the level of moisture in the air. The more water vapour in the air, the higher the humidity. If the humidity level exceeds the amount that the air can hold, then condensation takes place, forming dew if it is warm and frost if it is cold. At higher altitudes, clouds begin to form. Humidity also varies with temperature. 

5.  Precipitation: can be rain, hail, drizzle, sleet snow, fog or mist. It is the collective term given to moisture that falls to the ground from the atmosphere. The water cycle moves water from the oceans to the air by heating, then to the land by precipitation, then back to the sea. Rainfall which is the most common form of precipitation is measured in units of millimeters or inches by an instrument called a rain gauge.

4. Explain the relationships among temperature, pressure and humidity.

Ans. There is a close relationship among temperature, pressure and humidity.

For example, a completely saturated parcel of air at constant pressure cannot hold any more water molecules, giving it a relative humidity of 100 percent. As air temperature increases, air can hold more water molecules, and its relative humidity decreases. When temperatures drop, relative humidity increases.

5. How are the variations in atmospheric pressure caused? 

Ans. Atmospheric pressure refers to the force created by air on per unit area. 

It varies on the basis of:

(i) Air temperature: Distribution of temperature is not uniform over the earth’s surface due to the difference in the inclination of sunrays. Due to temperature variations, some regions of the earth are cold, some regions are hot while some other regions have medium temperature. High temperature has low pressure while low temperature has high pressure. That is why, the equatorial region which has high temperature experiences low pressure and polar regions which have low temperature, experience high pressure.

(ii) Surface elevation or height: The atmospheric pressure decreases with increase in surface elevation or height. The atmospheric pressure decreases at the rate of 34mb (milibar) per 900 feet of height in the troposphere.

6. Why does wind blow?

Ans. The wind blows because of differences in air pressure between the two regions. The wind blows from the region of high pressure towards the region of low pressure. The speed of air depends on the difference in air pressure.  

7. What is precipitation? Name the different types of precipitation.

Ans. Precipitation is any liquid or frozen water that forms in the atmosphere and falls back to the earth. It comes in many forms, like rain, sleet, and snow. Along with evaporation and condensation, precipitation is one of the three major parts of the global water cycle.

The different types of precipitation are:

(i) Dew.

(ii) Fog.

(iii) Mist.

(iv) Sleet.

(v) Snowfall.

(vi) Rainfall.

(vii) Drizzle.

8. Mention the factors affecting weather and climate.

Ans. The main factors affecting weather and climate are:

(i) Latitude.

(ii) Elevation.

(iii) Nearness to sea.

(iv) Ocean currents.

(v) Location of hills and mountains.

(vi) Wind.

(vii) Characteristics of land.

(viii) Slope of the land.

(ix) Vegetation.

9. Explain with examples the factors of weather and climate. 

Ans. There are many factors that influence weather and climate. 

They are given below:

(a) Latitude or the Distance from the Equator:

1. The vertical rays heat up the earth more than the inclined rays.

2. Thus the place near the equator where the sun’s rays fall vertically are warmer than the places which are far away from the equator.

(b) Altitude:

1. Altitude refers to the height above sea level. Temperature decreases at the rate of 1 °C as we cross every 165 meters in height. This is called Normal Lapse Rate.

2. So places at a higher altitude have a lower temperature.

(c) Nearness to the sea:

1. The climate of a place varies according to its nearness to the sea.

2. Places near the coast experience equable climates due to the influence of the winds from the sea.

3. Places located in the land, far from the sea, do not experience the moderating influence of the sea, such places experience a continental type of climate.

(d) Nature of the prevailing winds:

1. The winds change the climate of a place based on, where they blow.

2. When the wind blows from a warm region, it makes the place warm and cold, when blows from a colder region.

3. The on-shore winds cause rainfall making the place and where as the off-shore winds bring dry weather.

(e) Mountain barriers:

1. The location of the mountains influences the climate of a place.

2. The mountain chains act as a natural barrier to the wind.

3. Sometimes they prevent the entry of cold winds into the country or the escape of monsoon winds.

(f) Cloud cover:

1. Clouds reflect a large amount of radiation from the sun.

2. This prevents the entry of heat to the earth’s surface.

3. In areas generally of cloudless sky like the deserts, the temperature is very high.

4. On the other hand under a cloudy sky, the temperature is low.

(g) Ocean Currents:

1. The warm ocean currents raise the temperature of the nearby coastal areas, while the cold current lowers the temperature of the place.

(h) Natural vegetation:

1. The trees release water vapor into the air and make it cool.

2. Thus forest areas have a lower range of temperature throughout the year in contrast to non-forested areas.

10. What are the types of climate? 

Ans. The various types of climates are:

(i) Equatorial climate.

(ii) Monsoon climate.

(iii) Savanna or sudan type climate.

(iv) Hot desert climate.

(v) Temperate desert climate.

(vi) Mediterranean climate.

(vii) Temperate humid or Chinese climate. 

(viii) Temperate grassland climate.

(ix) Temperate maritime climate.

(x) Humid east-coast climate.

(xi) Sub-polar (taiga) climate.

(xii) Tundra climate.

(xiii) Mountain climate.

11. State the various types of climate with suitable diagram. 

Ans. The various types of climate on the basis of latitudinal extension is shown below:

12. Write short notes on the following:

(a) Relative humidity.

Ans. Relative humidity: Relative humidity is normally expressed as a percentage; a higher percentage means that the air–water mixture is more humid. At 100% relative humidity, the air is saturated and is at its dew point. In the absence of a foreign body on which droplets or crystals can nucleate, the relative humidity can exceed 100%, in which case the air is said to be supersaturated. Introduction of some particles or a surface to a body of air above 100% relative humidity will allow condensation or ice to form on those nuclei, thereby removing some of the vapour and lowering the humidity.

(b) Atmospheric pressure.

Ans. Atmospheric pressure: Atmospheric pressure means the force exerted by air on per unit area. The average atmospheric pressure at sea level at 15°C is 1013.2 mb (milibar). It is measured with the help of an instrument named barometer. Pressure differences are caused by variations in temperature and elevation. High temperature brings about low pressure and vice versa. Pressure decreases at the rate of 34 mb per 900 feet of height of atmosphere.

(c) Pressure belts.

Ans. Pressure belts: Due to variation in temperature, different places have different atmospheric pressure. On the basis of pressure variations on the surface of the earth, the following permanent pressure belts have been identified in the northern and southern hemisphere:

(i) Equatorial low pressure belt.

(ii) Sub-tropical high pressure belt.

(iii) Sub-polar low pressure belt.

(iv) Polar high pressure belt.

(d) Types of rainfall.

Ans. Types of rainfall: Rainfall is one of the main forms of precipitation. It has a great influence on climate. 

Rainfall is of Three types:

(i) Convectional rainfall.

(ii) Orographic or relief rainfall.

(ii) Cyclonic or frontal rainfall.

(e) Effect of latitudes on climate.

Ans. Effect of latitudes on climate: At higher latitudes, the Sun’s rays are less direct. The farther an area is from the equator, the lower its temperature. At the poles, the Sun’s rays are least direct. Much of the area is covered with ice and snow, which reflect a lot of sunlight.

(f) Effect of vegetation on climate.

Ans. (f) Effect of vegetation on climate: Vegetation can affect climate and weather patterns due to the release of water vapor during photosynthesis. The release of vapor into the air alters the surface energy fluxes and leads to potential cloud formation.

(g) Monsoon climate.

Ans. Monsoon climate: A monsoon is a seasonal change in the direction of the prevailing, or strongest, winds of a region. Monsoons cause wet and dry seasons throughout much of the tropics. Monsoons are most often associated with the Indian Ocean. Monsoons always blow from cold to warm regions.

(h) Taiga type of climate.

Ans. Taiga type of climate: The sub-polar (Taiga) climate is experienced in the sub-polar region lying between 50° and 65° N and S lines of latitude. The average summer temperature ranges from 10°C to 30°C while average winter temperature goes down to 2.5°C. This climatic region experiences heavy snowfall and very little rainfall. The main vegetation found in this region is the coniferous forests. These coniferous forests are called Taiga in Siberia.

(i) Mediterranean climate.

Ans. Mediterranean climate: Mediterranean climate, major climate type of the Köppen classification characterized by hot, dry summers and cool, wet winters and located between about 30° and 45° latitude north and south of the Equator and on the western sides of the continents.

(j) Savanna climate.

Ans. Savanna climate: The savanna type of climate is also known as sudan type climate. This climate prevails in regions such as Sudan, Central India, North-central Africa, Southern Brazil, Argentina, Venezuela and Central parts of Central Australia. The average summer temperature is 27°C-28°C and average winter temperature varies from 10°C to 15°C. The rainfall varies from 25cm to 40cm which encourages the growth of extensive grasslands. Such grasslands of Africa are called ‘Savanna’ while those of Brazil are called ‘Campos’.

(k) Tundra climate.

Ans. Tundra climate: Tundra climate, major climate type of the Köppen classification characterized by sub-freezing mean annual temperatures, large annual temperature ranges (but not as large as in the adjacent continental subarctic climate), and moderately low precipitation.

(l) Mountain climate.

Ans. Mountain climate: Thus, there exists no single, clearly defined, mountain climate. The most common climatic results of high elevation are those of decreased pressure, reduced oxygen availability, decreased temperature, and increased insolation; the last two combine to produce a typical “hot sun and cold shade” condition.

13. Answer the following questions:

(a) How far does the atmosphere extend above from the earth’s surface?

Ans. The atmosphere extends up to a height of nearly 10,000 km from the earth’s surface.

(b) What is lapse rate?

Ans. Lapse rate is the rate of decrease of temperature in the Troposphere on the basis of increase in altitude. This lapse rate is 6.5°C per km with increase in elevation along the atmosphere from the earth’s surface.

(c) What is the average atmospheric pressure on the sea level?

Ans. The air pressure at the sea level is found to be 760 mm Hg. This is also equal to 101.325 kilopascals.

(d) What is humidity of air? 

Ans. Humidity is the amount of water vapor in the air. If there is a lot of water vapor in the air, the humidity will be high. The higher the humidity, the wetter it feels outside. On the weather reports, humidity is usually explained as relative humidity.

(e) What you mean by the term ‘saturated air’?

Ans. Saturated air is the air that contains or holds the maximum capacity of water vapour in it. If a particular volume of air with particular temperature has exactly that amount of water vapour which it can hold at a particular temperature condition, then such a parcel of air is known as saturated air.

(f) What is the latitudinal extension of the equatorial climate? 

Ans. The equatorial climate prevails in the region bounded between the equator and 10° N and S lines of latitudes.

(g) In which climate is the ‘campos’ grassland found? 

Ans. The grassland named ‘campos’ is found in the savanna climate that exists in the grasslands of Brazil. 

(h) Mention the latitudinal extension of the temperate desert climate region.

Ans. The temperate desert climate region lies between 30° and 40° N and S of the equator.

(i) What is the other name of the Chinese climate? 

Ans. The other name of the Chinese climate is temperate humid climate.

(j) Give an example of the irregular wind.

Ans. Cyclone is an example of the irregular wind.

(k) Why does the warm airmass have the capacity to hold more water vapour?

Ans. Temperature causes air to expand and thus density of air decreases. When air density decreases, air becomes light and light air is able to hold more water vapour. Such air goes up and is able to collect the moisture present in the atmosphere. In this way, the warm air mass have the capacity to hold more water vapour.

(l) Why there is more atmospheric pressure at the lower level of the atmosphere?

Ans. Air is compressible and hence the air at the lower layer of the atmosphere gets much compressed resulting in the increase in its density. When density of air increases, its pressure also increases. Therefore, there is more atmospheric pressure in the lower layer of the atmosphere.