Sir Basit Notes

Pakistan Studies Class 9 Unit 5: Climate of Pakistan and Environmental Hazards Notes

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Key notes

Short questions 5 marks, 5 points each

1. [Model] Describe the climatic zones of Pakistan by writing five points on temperature and different types of precipitation.

  1. Highland zone. Highland zone (north, north-west, west): long, cold, snowy winters and mild short summers. Heavy snow and rain from relief rainfall and western depressions. Gilgit and Chitral are in a rain shadow.
  2. Lowland zone. Lowland zone (Indus Plain): very hot summers, mild to cool winters. Rain mainly from the monsoon (June to September), with the north getting more than the south.
  3. Desert zone. Desert or arid zone (Kharan, Cholistan, Thal, Thar): hot dusty summers, cold nights, high diurnal range and scanty rain, with permanent dust storms.
  4. Coastal zone. Coastal zone (Makran coast, Karachi, Indus Delta): moderate temperature due to sea breezes, high humidity and very little rain, with some from western depressions and tropical cyclones.
  5. Types of rain. Types of precipitation: monsoon rain, western depressions (rain and snow in winter), convectional rain (early summer, north Punjab and KPK), relief rain and cyclonic rain on the coast.

2. [School] Explain orographic (relief) rainfall. (5 points)

  1. Definition. It occurs when moist air is forced to rise over a mountain range.
  2. Rising air. As the air rises it expands and cools.
  3. Condensation. Water vapour condenses into clouds.
  4. Windward and leeward. Heavy clouds give rain on the windward side, while the leeward side stays dry (a rain shadow).
  5. Where it occurs. It is common in the Himalayas and Karakoram (Murree, Abbottabad, Swat, Gilgit-Baltistan, Quetta) and gives water for agriculture and groundwater recharge.

3. [School] What are tropical cyclones? How do they form and what are two major ways they cause destruction? (5 points)

  1. Meaning. Tropical cyclones are large rotating storms with strong winds, heavy rain and storm surges.
  2. Formation. Formation: they form over warm ocean water, where warm moist air rises, creates a low pressure and winds spiral in.
  3. Affected areas. They affect the coastal areas of Sindh and Balochistan (Karachi, Thatta, Badin, Pasni, Jiwani and Gwadar).
  4. Wind damage. Destruction 1: strong winds and storm surges damage houses, roads, power lines and ports.
  5. Flood damage. Destruction 2: heavy rain causes floods and coastal erosion, and destroys crops and fishing boats.

4. [School] How do latitudinal effect and cloud cover contribute to temperature variation? (5 points)

  1. Latitude. At the equator the sun's rays hit vertically and give more heat. At higher latitudes the rays are oblique and give less heat.
  2. Northern and southern Pakistan. So southern Pakistan is hotter than the north.
  3. Cloud cover by day. Cloud cover blocks sunlight during the day, so days stay cooler.
  4. Cloud cover at night. At night clouds trap heat, so nights stay warmer.
  5. Other factors. Cloudy monsoon months are cooler than dry clear months such as May and June. Altitude, the angle of the sun and distance from the sea also matter.

5. [School] How do human activities contribute to flooding in Pakistan? (Any five points)

  1. Deforestation. Deforestation reduces infiltration and increases surface run-off.
  2. Flood plains. Building settlements on flood plains and riverbanks.
  3. Weak dams. Reduced capacity of dams to store flood water (siltation).
  4. Poor management. Poor flood management and an under-prepared Federal Flood Commission.
  5. Urbanization. Unplanned urbanization (cemented surfaces) and blocked drains, and weak river embankments.

6. [School] What is a drought? How can it be managed effectively in Pakistan? (5 points)

  1. Definition. A drought is a long spell of dry weather with low rainfall that causes water shortage and damages crops and livestock. Types: permanent, seasonal, invisible (agricultural) and unpredictable.
  2. Water saving. Water conservation: lining of canals, water tanks, small dams and reservoirs.
  3. Warning and help. Early warning systems and financial help for affected farmers.
  4. Crops and irrigation. Growing drought-resistant crops (sorghum, millet) and using drip irrigation.
  5. Harvesting. Rainwater harvesting, and a proposed canal from Sukkur Barrage to Thar.

7. [School] How does rainfall affect farming in Pakistan? (5 points)

  1. Balochistan. Rainfall in Balochistan (below 250 mm) is too low, so farming depends on irrigation and karez.
  2. Himalayan areas. Himalayan areas (over 2,000 mm) get too much rain, so drainage is needed to prevent waterlogging.
  3. Pothwar. Pothwar (500-1,000 mm) is rainfed, so farmers must manage water in dry years.
  4. Indus Plain. The Indus Plain (250-500 mm) needs canal irrigation to supplement rain.
  5. Seasonal effect. Monsoon rain fills rivers and reservoirs, and winter rain and snow recharge groundwater. Floods and droughts damage crops.

8. [School] Define doab, rain shadow area and diurnal range of temperature.

Doab

A doab is a piece of land lying between two rivers. The word comes from "do" (two) and "ab" (water). Examples are Bari Doab, Rachna Doab and Chaj Doab. A doab has flat land, and good soil deposited by the rivers, so it attracts people for settlements, farming, industry and business. Alluvial terraces such as Nili Bar, Sandal Bar and Kirana Bar are found in the doabs.

Rain Shadow Area

A rain shadow area is a place behind a mountain, on the side facing away from the prevailing winds (the leeward side), where the rainfall is much less. The moist winds give their rain on the windward side while rising over the mountains, so by the time they cross over, they are dry. Gilgit and Chitral are examples of rain shadow areas, and that is why they get less rain than other places in the same highland zone.

Diurnal Range of Temperature

The diurnal range of temperature is the difference between the highest and the lowest temperature in a period of 24 hours. It is high in desert areas such as Thar and Cholistan, where the days are very hot and the nights are cold, because the dry air and the clear sky let the heat escape quickly after sunset. It is low in coastal areas where sea breezes keep the temperature moderate.

9. Explain western depressions. (5 points)

  1. Meaning. They are low pressure systems formed over the Mediterranean Sea that move east.
  2. Effect. They bring rain and snow to the northern and western parts of Pakistan (Chitral, Dir, Peshawar, Quetta).
  3. Season. They are most common from November to April.
  4. Importance. They are important for winter crops and the snow melts in summer to give water.
  5. Hazards. They can cause floods and landslides.

10. Explain monsoon winds and how they form. (5 points)

  1. Meaning. Monsoon means seasonal winds that reverse direction twice a year.
  2. Summer pattern. In summer the land heats faster than the sea and a low pressure forms over land.
  3. Rainfall. Moist winds from the Bay of Bengal and the Arabian Sea rush in, giving rain from June to September.
  4. Winter pattern. In winter the pressure pattern reverses and dry winds blow from land to sea, so there is little rain.
  5. Effects. Monsoon gives water for agriculture but can cause floods and landslides.

Long questions 10 marks, 10 points each

1. [School] Describe the major climatic zones of Pakistan, including temperature, rainfall and seasonal variations.

Four Climatic Zones

Climate means the average weather of a place over a long time, usually thirty years or more. Pakistan's climate is mostly tropical or subtropical, and semi-arid or arid, but cooler and wetter in the north. Because of its different landforms it is divided into four zones: Highland, Lowland, Desert (arid) and Coastal. Even within one zone there can be great differences in rain, temperature and humidity.

Highland Climate

The highland zone includes the northern, north-western and western mountains. Winters are long, cold and snowy, with very low temperatures. The summers are mild and short, and wet in the north and north-west, but warm and dry in the western mountains. Temperature depends on height. The high northern mountains get a lot of rain, so places like Muzaffarabad, Skardu, Astor, Dir, Parachinar and Kakul get the most rain in Pakistan. The western mountains are lower and get less rain, for example Kohat and the Waziristan hills. Chitral and Gilgit get little rain because they are in a rain shadow area.

Lowland Climate

The lowland zone is the plain area of Punjab and Sindh except the coast. Summers are hot and sometimes extreme, and winters are mild to cool. The monsoon lasts from June to September, and most rain and thunderstorms come in July and August. The north and north-west of the plain receive the tail end of the monsoon, and the southern part gets much less rain. The Pothwar plateau is wetter than the Indus plain because it gets rain from both the monsoon and western depressions.

Desert Climate

The desert zone includes Kharan, Cholistan, Thal and Thar. Summers are hot and dry, and there is very little rain throughout the year. Hot and dusty winds blow across the plains from May to September. The diurnal range of temperature is high, which means the difference between the day and night temperature is large. Dust storms are a regular feature. Winters are cold, with a minimum temperature of about 4 degrees Celsius.

Coastal Climate

The coastal zone stretches from the Rann of Kutch to the Makran coast, and includes the Indus Delta, Thatta and Karachi. It has a maritime climate with sea breezes all through the year. Because the sea is near, humidity is high, especially from April to September. Very little rain falls in the monsoon season, and some rain comes from western depressions.

Seasons

There are four seasons. Spring is from March to May (15 to 25 degrees Celsius), summer from June to September (25 to 40 degrees, with monsoon rains), autumn from October to November, and winter from December to February (5 to 15 degrees, with snow in the north). The northernmost region is the coldest, central Pakistan has a moderate climate, and southern Pakistan is the hottest. May and June are the hottest months and December and January are the coldest.

2. Explain the sources of rainfall in Pakistan and how they vary seasonally. Give examples.

Monsoon Winds

The word monsoon comes from the Arabic word "mausim", which means season. Monsoon winds are seasonal winds that change their direction twice a year. In summer the land heats up faster than the sea, so a low pressure area forms over the land and warm, moist air from the sea rushes in to fill it, giving heavy rain. Pakistan gets monsoon rain from two sources, from June to September. The Bay of Bengal winds cross India and hit the Himalayas, giving rain to northern Punjab. For example, Lahore gets most of its rain in July. The Arabian Sea monsoon brings rain to the south-east and the coastal areas. It gives water for farming and fills the groundwater, but it can also cause floods and landslides.

Western Depressions

Western depressions are low pressure systems that form over the Mediterranean Sea and travel east. They bring rain and snow to the northern and western parts of Pakistan, such as Chitral, Dir, Peshawar, Loralai, Quetta, Kharan and the Makran coastal range. They are most common from November to April. Their winter rain and snow are important for farming, as the snow melts in summer and gives water for irrigation. They can also cause floods and landslides.

Convectional and Relief Rain

Convectional rain happens when the sun heats the land, which heats the air above it. The warm air rises, cools, and forms clouds. When the clouds become heavy the water falls as rain. This type of rain falls in early summer in northern Punjab and KPK, for example in Rawalpindi and Peshawar. It does not fall in the south in summer because of a temperature inversion layer, which stops clouds from forming, so Karachi stays dry even at 40 degrees Celsius.

Relief or orographic rain happens when moist air is forced to go up over a mountain range. As it rises it cools, and the water vapour turns into clouds and falls as rain. It is common in the Himalayas and Karakoram, and at places such as Murree, Abbottabad, Swat, Gilgit-Baltistan, Kohat, Bannu and Quetta.

Tropical Cyclones and Pattern

Tropical cyclones are large rotating storms that form over warm sea water. They bring strong winds, heavy rain and storm surges. The coast of Sindh and Balochistan is most at risk, such as Karachi, Thatta, Badin, Pasni, Jiwani and Gwadar. In general, rainfall in Pakistan decreases from the Himalayas in the north to the south. The Himalayas get over 2,000 mm a year, the Pothwar plateau 500 to 1,000 mm, the Indus Plain 250 to 500 mm and Balochistan less than 250 mm.

3. To what extent do storms, floods and droughts cause problems for the people of Pakistan? Suggest preventive measures and management strategies.

Storms

Thunderstorms are most common in the summer months of April to June and in September and October. They can happen anywhere, but are most common in the north and north-western areas and in the foothills of the Himalayas and Safed Koh. They cause strong winds, heavy rain, lightning and hail. These destroy crops and orchards, cause floods and landslides, and cut off electricity when power lines are damaged.

Floods

A river flood is a natural disaster which happens when a river overflows its banks and covers the land around. Floods bring fresh soil and refill the groundwater, but they also do a lot of damage to people and property. The 2010 flood, called the flood of the century, affected over 20 million people and made over 10 million people leave their homes. Natural causes are record rainfall (in 2010, 312 mm of rain fell in Peshawar alone in 24 hours), fast melting of snow due to climate change, natural embankments that are too low, and storm surges in the sea. Human causes are cutting down of forests, which means more run-off, building houses on flood plains, the reduced capacity of dams to store water, and poor flood control and preparation.

Droughts

Drought is a natural hazard in which there is a long dry period. The lack of rain causes severe water shortage and damages crops and animals. Pakistan has permanent drought in desert areas, seasonal drought in the barani areas of Pothwar and southern Punjab, invisible or agricultural drought caused by deforestation and soil erosion, and unpredictable drought caused by suddenly low rain. Drought causes crop failure, animal deaths, loss to farmers and migration of rural people.

Preventive Measures

To prevent floods we need to give early warnings so that farmers can move their animals and harvest early, plant more trees, reduce building on flood plains, build roads and bridges that can stand high water, improve drains, build flood walls and small dams, and teach people about flood safety. Rehabilitation centres should give medical and social support to those affected. To manage drought, the government and communities make water-saving plans such as lining canals, building water tanks, small dams and reservoirs. They set up early warning systems and help farmers with money. Farmers grow drought-resistant crops like sorghum and millet, use drip irrigation, and collect rain water from roofs and other surfaces.

4. Explain how temperature and climate affect the lifestyle and economy of people in different zones of Pakistan.

Highland Zone

The highland zone has cooler temperatures and more rain and snow than the lowlands. Winters are so hard that people move with their animals to lower areas, which is called transhumance. Many people practise subsistence farming and herding, and in the far north people also earn from tourism. In Balochistan it is hard to grow crops in most places because of the lack of water, which also keeps people from settling there. Climate change makes things worse. Farmers find it hard to grow crops because of less water, droughts, floods and landslides, and this leads to food shortage and poverty. It is also harder for herders to reach their old grazing lands.

Lowland Zone

The lowland zone is warmer and drier than the highlands, and covers the Indus plains of Punjab and Sindh. People depend on farming, manufacturing and services. But rising temperatures are bringing more extreme weather such as heat waves, droughts, floods and storms. Heat waves can destroy crops and kill animals. Droughts reduce the crop yield and make it hard to find water, and floods and storms damage buildings and roads and disturb transport and communication.

Arid Zone

The arid zone is mainly the desert areas, with a very dry climate. There is a shortage of water because of very low rain and a high rate of evaporation. People depend on mining, livestock herding and tourism. In spite of the dry conditions many people practise farming. In Balochistan they use karez, an underground irrigation system, to water farms, orchards and date palms. They keep sheep, goats and camels, which give them food, milk, wool and transport. Many people are skilled artisans who make carpets, ajrak, ralli quilts, embroidered shawls, leather goods and pottery. These are sold in local markets and exported to countries like the USA, UK, Canada, Germany and the UAE. Tourists also visit Cholistan and Thar for camel safaris and jeep tours.

Coastal Zone

The coastal zone has the delta coast of Sindh and the hilly Makran coast of Balochistan, with a maritime climate. Cool sea breezes make the summer heat easier to bear. The beaches, estuaries and wetlands attract tourists in winter. People depend on fishing, tourism and trade, and the Karachi and Qasim ports are very important for the economy. Karachi is the busiest port and handles containers, bulk cargo and liquid cargo. But climate change is bringing more frequent and severe storms, which damage buildings and cost the economy a lot.