Question 1

The energy received by the earth from the sun is known as:

Accepted Answer

Insolation

Question 2

Duration its revolution around the sun, the earth is farthest from the sun on 4 th July. What we call to this position of the earth?

Accepted Answer

Aphelion

Question 3

The transfer of heat through horizontal movement of air is called:

Accepted Answer

Advection

Question 4

Which of the following statement is incorrect?

Accepted Answer

The insolation received by the earth is in long waves forms and heats up its surface.

Question 5

In the normal lapse rate temperature ……………….

Accepted Answer

Decreases with increase in elevation.

Question 6

Which of the following is an ideal condition for the inversion of temperature?

Accepted Answer

Long winter night

Question 7

Multiple choice questions.

(i) If the surface air pressure is 1,000 mb, the air pressure at 1 km above the surface will be:

(a) 700 mb

(b) 1,100 mb

(c) 900 mb

(d) 1,300 mb

(ii) The Inter Tropical Convergence Zone normally occurs:

(a) near the Equator

(b) near the Tropic of Cancer

(c) near the Tropic of Capricorn

(d) near the Arctic Circle

(iii) The direction of wind around a low pressure in northern hemisphere is:

(a) clockwise

(b) perpendicular to isobars

(c) anti-clock wise

(d) parallel to isobars

(iv) Which one of the following is the source region for the formation of air masses?

(a) the Equatorial forest

(b) the Himalayas

(c) the Siberian Plain

(d) the Deccan Plateau

Accepted Answer

(i) The air pressure decreases with height. At 1 km above the surface, the pressure is approximately 900 mb.

Hence, correct answer: (c) 900 mb.

(ii) The Inter Tropical Convergence Zone (ITCZ) is a belt of low pressure near the Equator where trade winds converge.

Hence, correct answer: (a) near the Equator.

(iii) In the northern hemisphere, winds around a low pressure system blow anti-clockwise due to the Coriolis force.

Hence, correct answer: (c) anti-clock wise.

(iv) The source region for the formation of air masses is usually a large, uniform area such as the Siberian Plain.

Hence, correct answer: (c) the Siberian Plain. — Step-by-step explanation:

(i) Atmospheric pressure decreases with altitude because the weight of the air column above decreases. At 1 km, pressure is roughly 900 mb.

(ii) ITCZ forms near the Equator where trade winds from both hemispheres meet.

(iii) Coriolis force deflects winds to the right in the northern hemisphere, causing anti-clockwise circulation around lows.

(iv) Air masses form over large uniform surfaces; Siberian Plain is a classic source region for cold air masses.

Question 8

Answer the following questions in about 30 words.

(i) What is the unit used in measuring pressure? Why is the pressure measured at station level reduced to the sea level in preparation of weather maps?

(ii) While the pressure gradient force is from north to south, i.e. from the subtropical high pressure to the equator in the northern hemisphere, why are the winds north easterlies in the tropics.

(iii) What are the geotrophic winds?

(iv) Explain the land and sea breezes.

Accepted Answer

(i) Pressure is measured in millibars (mb). Pressure at station level is reduced to sea level to eliminate altitude effects and allow comparison of pressure readings from different locations.

(ii) Although the pressure gradient force is from north to south, the Coriolis force deflects the winds to the right in the northern hemisphere, making them north easterlies.

(iii) Geostrophic winds are winds that blow parallel to isobars due to the balance between pressure gradient force and Coriolis force.

(iv) Land breeze occurs at night when land cools faster than sea, causing air to flow from land to sea. Sea breeze occurs during day when sea is cooler than land, causing air to flow from sea to land. — Detailed explanation:

(i) Pressure unit is millibar (mb). Sea level reduction standardizes pressure readings for weather analysis.

(ii) Coriolis force deflects winds to the right in northern hemisphere, changing wind direction from pressure gradient force direction.

(iii) Geostrophic winds result from balance of pressure gradient and Coriolis forces, flowing parallel to isobars.

(iv) Differential heating causes pressure differences between land and sea, resulting in land and sea breezes.

Question 9

Answer the following questions in about 150 words.

(i) Discuss the factors affecting the speed and direction of wind.

(ii) Draw a simplified diagram to show the general circulation of the atmosphere over the globe. What are the possible reasons for the formation of subtropical high pressure over 30° N and S latitudes?

(iii) Why does tropical cyclone originate over the seas? In which part of the tropical cyclone do torrential rains and high velocity winds blow and why?

Accepted Answer

(i) Factors affecting speed and direction of wind include pressure gradient force, Coriolis force, friction, and topography. The pressure gradient force causes air to move from high to low pressure. Coriolis force deflects wind to the right in northern hemisphere and to the left in southern hemisphere. Friction with Earth's surface slows wind and changes direction near the surface. Topography can channel or block winds.

(ii) The general circulation of the atmosphere consists of three cells in each hemisphere: Hadley cell (0°-30°), Ferrel cell (30°-60°), and Polar cell (60°-90°). Subtropical high pressure forms near 30° N and S due to descending air from the Hadley cell, causing dry and stable conditions.

(iii) Tropical cyclones originate over warm seas where sea surface temperature is above 27°C, providing heat and moisture. Torrential rains and high velocity winds blow in the eye wall region due to intense convection and low pressure causing strong inflow and upward motion. — Stepwise explanation:

(i) Wind speed and direction depend on forces acting on air: pressure gradient initiates movement; Coriolis force alters direction; friction reduces speed and modifies direction near surface; terrain influences local wind patterns.

(ii) Atmospheric circulation cells redistribute heat. Subtropical highs form due to descending dry air at 30° latitudes, creating high pressure zones.

(iii) Warm ocean waters fuel cyclones. The eye wall has strongest winds and rains due to concentrated convection and pressure gradients.

Question 10

Project Work

(i) Collect weather information over media such as newspaper, TV and radio for understanding the weather systems.

(ii) Read the section on weather in any newspaper, preferably, one having a map showing a satellite picture. Mark the area of cloudiness. Attempt to infer the atmospheric circulation from the distribution of clouds. Compare the forecast given in the newspaper with the TV coverage, if you have access to TV. Estimate, how many days in a week was the forecast were accurate.

Accepted Answer

Project work involves practical engagement:

(i) Collect weather data from various media to understand weather systems.

(ii) Analyze weather maps and satellite images to identify cloud patterns and infer atmospheric circulation. Compare forecasts from different sources and evaluate their accuracy over a week. — This project encourages students to apply theoretical knowledge by observing real weather data and forecasts, enhancing understanding of atmospheric processes and forecasting accuracy.

Question 11

What is atmospheric pressure and how is it measured? Provide the average atmospheric pressure at sea level.

Accepted Answer

Atmospheric pressure is the force exerted by the weight of the air column above a unit area on the Earth's surface. It is measured using instruments like the mercury barometer and the aneroid barometer. The average atmospheric pressure at sea level is approximately 1,013.2 millibars. — Atmospheric pressure results from the weight of air molecules pulled by gravity on a unit area. It is measured by mercury barometers, which use mercury column height, or aneroid barometers, which use a sealed flexible metal chamber. The standard average pressure at sea level is 1,013.2 mb, which is a key reference for meteorological studies.

Question 12

The atmospheric pressure decreases with height. According to the standard atmosphere table, what is the approximate pressure at 5 km elevation?

Accepted Answer

540.48 mb — According to the standard pressure table, the pressure at 5 km elevation is about 540.48 mb. Pressure decreases with height due to thinning air, from 1,013.25 mb at sea level to 898.76 mb at 1 km, then to 540.48 mb at 5 km, and further to 265.00 mb at 10 km.

Question 13

Explain why we do not experience strong upward winds despite a large vertical pressure gradient force in the atmosphere.

Accepted Answer

Strong upward winds are not experienced because the vertical pressure gradient force is nearly balanced by the downward gravitational force. This balance, called hydrostatic equilibrium, prevents significant vertical air movement under normal conditions. — The vertical pressure gradient force pushes air upward due to decreasing pressure with height. However, gravity pulls air downward with almost equal strength. This balance keeps the atmosphere stable vertically, preventing strong upward winds except in special conditions like convection.

Question 14

Describe what isobars represent on a weather map and how they help in understanding wind patterns.

Accepted Answer

Isobars are lines on a weather map connecting points of equal atmospheric pressure at sea level. They help identify pressure systems and pressure gradients, which determine wind direction and velocity; closely spaced isobars indicate strong winds, while widely spaced isobars indicate weak winds. — Isobars eliminate altitude effects by reducing pressure to sea level, allowing comparison across regions. The spacing of isobars shows the pressure gradient force magnitude, crucial for predicting wind speed and direction, as wind moves from high to low pressure areas.

Question 15

Identify the pressure belts found near the equator and at approximately 30° latitudes in both hemispheres, and explain their characteristics.

Accepted Answer

Near the equator is the equatorial low-pressure belt characterized by low atmospheric pressure due to intense heating and rising air. Around 30°N and 30°S latitudes are the subtropical high-pressure belts characterized by high pressure caused by sinking cool air. — The equatorial low forms because strong solar heating causes air to rise, creating low pressure. The subtropical highs form where this air descends around 30° latitudes, causing high pressure and dry conditions. These belts shift seasonally with the sun's apparent movement.

Solar Radiation, Heat Balance and Temperature

Solar Radiation, Heat Balance and Temperature — Study Notes

Atmospheric Pressure

Vertical Variation of Pressure

Horizontal Distribution of Pressure

Practice Questions — Solar Radiation, Heat Balance and Temperature

All 14 Chapters in Fundamental of Physical Geography