Meteorological Hazards and Disasters – UGC NET Geography – Detailed Notes

Introduction

• Meteorological hazards occur as a result of processes in the atmosphere. Meteorological hazards include extreme temperatures, hurricanes, tornadoes, droughts, and severe storms.
• Meteorological disasters are caused by extreme weather such as rain, drought, snow, extreme heat or cold, ice, or wind. Violent, sudden and damaging alteration in the atmosphere associated with, created by, or touching the earth’s atmosphere, particularly the weather-forming processes.
• Examples of weather disasters embrace blizzard, cyclones, droughts, hailstorms, heat waves, hurricanes, floods (caused by rain) and tornadoes.
• Cyclone, tropical cyclone, hurricane, and storm are different names for a similar development of storm that forms over the oceans.
• Extra-tropical cyclones, typically known as mid-latitude cyclones, are a bunch of cyclones outlined as synoptic scale low weather systems that occur within the middle latitudes of the planet (outside the tropics) not having tropical characteristics, are connected with fronts and horizontal gradients in temperature and temperature otherwise called “baroclinic zones”.
• Drought is uncommon condition of soil, leading to failure and lack of water for alternative uses, caused by considerably lower rain than average over a chronic amount. Hot dry winds, high temperatures and ensuant evaporation of wetness from the bottom will contribute to conditions of drought.
• Hailstorms are rain drops that arrive as ice, instead of melting before they hit the bottom. a very damaging storm hit Muenchen, Germany, on July 12, 1984, inflicting two billion greenbacks in insurance claims.
• A wave is an atmospheric condition. The worst wave in recent history was the eu wave of 2003. A tornado could be a violent, dangerous, rotating column of air that’s up-to-date with each the surface of the planet and a thundercloud or, in rare cases, the bottom of a cumulus.
• It’s additionally named as a twister or a cyclone, though the word cyclone is employed in meteorology during a wider sense, to talk over with any closed low circulation. Tornadoes are available in several shapes and sizes; however they are usually within the style of a plain condensation funnel, whose slim finish touches the planet and is usually encircled by a cloud of trash and dirt.
• Most tornadoes have wind speeds but a hundred and ten miles per hour (177 km/h), are just about 250 feet (80 m) across, and travel a number of miles (several kilometers) before dissipating. The foremost extreme tornadoes will attain wind speeds of over three hundred mph (480 km/h), stretch over 2 miles (3 km) across, and remain the bottom for dozens of miles (perhaps over a hundred km).

Cyclone

Introduction

Cyclones are among the most powerful and destructive meteorological hazards on Earth. They are large-scale atmospheric systems characterized by low pressure at the center, inward-spiraling winds, and intense weather conditions including heavy rainfall, strong winds, and storm surges. When cyclones interact with human settlements, infrastructure, and vulnerable environments, they often escalate from natural hazards into large-scale disasters. Understanding cyclones as meteorological hazards and disasters requires a detailed examination of their physical processes, spatial distribution, impacts, and the factors that determine their severity.

Concept of Meteorological Hazards

Meteorological hazards are extreme weather events caused by atmospheric processes that pose risks to life, property, and the environment. These hazards include cyclones, droughts, floods, heatwaves, cold waves, and thunderstorms. Cyclones are particularly significant because they involve multiple hazardous elements occurring simultaneously, such as windstorms, flooding rains, coastal inundation, and landslides.

Cyclones differ from other meteorological hazards due to their spatial extent, duration, and cumulative impacts. A single cyclone can affect vast areas over several days and trigger secondary disasters, making them one of the most complex natural hazards to manage.

Definition and Terminology of Cyclones

A cyclone is a rotating atmospheric system with a low-pressure center, formed over warm ocean waters in tropical and subtropical regions. The term “cyclone” is a generic name used globally, while regional terminologies vary:

• In the Atlantic Ocean and northeastern Pacific Ocean, cyclones are called hurricanes.
• In the western Pacific Ocean, they are known as typhoons.
• In the Indian Ocean and South Pacific, they are commonly referred to as cyclones.

Despite differences in naming, the physical structure and dynamics of these systems remain fundamentally the same.

Global Distribution of Cyclones

Tropical cyclones occur primarily between latitudes 5° and 30° north and south of the equator. They do not form directly at the equator due to the absence of the Coriolis force, which is necessary to initiate rotational motion.

Major cyclone-prone regions include:

• The Bay of Bengal
• The Arabian Sea
• The western North Pacific Ocean
• The Atlantic Ocean
• The southwestern Indian Ocean
• The South Pacific Ocean

Among these regions, the Bay of Bengal is particularly notorious for producing cyclones with high storm surges that cause extensive loss of life along densely populated coastlines.

Conditions Necessary for Cyclone Formation

Cyclones develop only when specific atmospheric and oceanic conditions are present simultaneously.

• Warm Ocean Waters: Sea surface temperatures must generally exceed 26.5°C to a depth of at least 50–60 meters. Warm water provides the latent heat energy required to fuel cyclone intensification.
• Atmospheric Instability: A condition where warm, moist air near the surface rises rapidly into cooler upper layers of the atmosphere supports deep convection and cloud development.
• Coriolis Force: The Earth’s rotation causes moving air to deflect, enabling the development of cyclonic rotation. This force increases with distance from the equator.
• Low Vertical Wind Shear: Minimal variation in wind speed and direction with height allows the cyclone structure to remain vertically aligned, which is essential for strengthening.
• Pre-existing Disturbance: Cyclones often originate from tropical waves, low-pressure systems, or disturbances in the intertropical convergence zone.

Structure of a Cyclone

A mature cyclone exhibits a well-organized structure with distinct components.

• The Eye: The eye is the central region of the cyclone characterized by calm winds, clear or partly cloudy skies, and the lowest atmospheric pressure. Its diameter typically ranges from 20 to 60 kilometers.
• The Eyewall: Surrounding the eye is the eyewall, where the most intense winds, heaviest rainfall, and strongest thunderstorms occur. This region is responsible for the greatest destruction during landfall.
• Spiral Rainbands: These are curved bands of clouds and thunderstorms extending outward from the eyewall. Rainbands produce intermittent heavy rainfall, gusty winds, and sometimes tornadoes.

Classification of Cyclones

Cyclones are classified based on their maximum sustained wind speeds. Different meteorological agencies use slightly varying scales, but the general categories include:

• Tropical Depression
• Tropical Storm
• Severe Tropical Storm
• Cyclonic Storm
• Severe Cyclonic Storm
• Very Severe Cyclonic Storm
• Extremely Severe Cyclonic Storm
• Super Cyclonic Storm

Higher categories correspond to greater wind speeds, lower central pressure, and increased destructive potential.

Cyclones as Meteorological Hazards

As meteorological hazards, cyclones present multiple simultaneous threats.

• High-Velocity Winds: Cyclonic winds can exceed 250 km/h in intense systems. Such winds uproot trees, damage buildings, topple power lines, and disrupt communication networks.
• Heavy Rainfall: Cyclones often produce prolonged and intense rainfall, leading to river flooding, flash floods, and waterlogging. In mountainous regions, this rainfall can trigger landslides and mudflows.
• Storm Surge: Storm surge is the abnormal rise of sea level caused by strong onshore winds and low atmospheric pressure. It is the deadliest component of cyclones in coastal regions, especially in low-lying deltas.
• Coastal and Inland Flooding: Combined effects of storm surge, high tides, and heavy rainfall can inundate large coastal and inland areas, contaminating freshwater sources and destroying crops.