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Presented by: Beenish Zunnoon AGENDA Weather Pakistan's weather Measuring weather Global warming Climate Thunderstorm Factors affecting climate Tornadoes Worlds climate Tropical cyclone atmosphere WEATHER The state of the atmosphere at a given time and place, with respect to variables such as temperature, moisture, wind velocity, and barometric pressure. Can change rapidly. Small geographical area. WEATHER (cont) The study of weather is meteorology. Someone who studies weather is called a meteorologist. MEASURING WEATHER Measurement Temperature Air Pressure Wind (direction) Wind (speed) Relative Humidity Precipitation Instrument Thermometer Barometer Wind Vane Anemometer Hygrometer Rain Gauge CLIMATE Climate is commonly defined as the weather averaged over a long period of time. The standard average period is 30 years. Large geographical area. It is determined by two main factors: temperature and rainfall. FACTORS AFFECTING CLIMATE ( temperature & rainfall) Elevation (height) Topography (geography) latitude ocean currents prevailing wind direction Elevation Elevation is the distance above sea level. The air pressure decreases as the distance increases from the sea level. The farther above sea level you are, the lower the temperature will be. latitude Latitude measures how far you are north or south of the equator. Latitude determines the amount of solar energy received by that region. Regions close to the equator receive direct rays of the sun and therefore are warmer. At the areas closer to the poles, the suns rays are at an angle so these areas receive less radiant energy and are cooler. Ocean currents Water in the ocean travels in paths called currents. The temperature of the water affects the temperature of the air above it. Ocean currents traveling away from the equator are warm, warming the air above it. Currents flowing toward the equator are colder, so the air masses, moving over these currents, are cooled. topology The features of the land also influences the climate. The amount of rainfall in a region is affected by mountain ranges in that area. Mountains cause air to rise. Rising air becomes less dense allowing the condensation of water. rainfall occurs. Air moving down the other side of the mountain becomes more dense. Sinking air does not produce precipitation. The leeward side, or side facing away from the wind, receives less precipitation. Prevailing winds Prevailing winds are the winds which blow more often from one direction than another. Winds can greatly affect the amount of precipitation an area receives depending on the amount of moisture they are carrying. These prevailing winds can move air masses from the ocean onto a continent bringing moisture onto the continent. Or prevailing winds may move air masses from continent to the ocean, moving drier air from the continent. Prevailing winds affect the climate of an area. EARTH’S CLIMATE EARTH’S CLIMATE (cont) Rainforests receive a lot of rain. The temperature stays warm in the rainforest all year long. Grasslands are typically found on the dry interior of continents. Temperate forest contains moist climate which allows leafy deciduous trees to thrive. Deserts receive less rainfall than other tropical ecosystems but are just as warm. EARTH’S CLIMATE (cont) Chaparral has wet-winters and dry-summers. Tundra: Ocean winds in arctic coastal areas keep the temperatures from being as severe as interior regions. A long, chilly winter season is followed by a mild season. Taiga: The forests of the taiga ecosystem survive despite long and very cold winters. Summers are short and still quite cool. ATMOSPHERE The layer of air surrounding the Earth. The atmosphere is commonly divided into the troposphere, the stratosphere, and the ionosphere. Troposphere contains the majority of the atmospheric mass and all of the atmospheric water vapor, most weather events occur within it. The average composition of atmosphere is 79% nitrogen, 20% oxygen, 0.03% carbon dioxide, and traces of rare gases. Also present are atmospheric moisture, ammonia, ozone, and salts and solid particles. PAKISTAN’S WEATHER Depending on the topography there is an extreme variation in the temperature. The country is essentially arid except for the southern slopes of the Himalayas and the submountainous tract PAKISTAN’S WEATHER (cont) The controlling factors of the Pakistan's climate are Sub-Tropical location that tends to keep the temperature high, particularly in summer. The oceanic influence of the Arabian Sea that keeps down the temperature contrast between summer and winter at the coast. PAKISTAN’S WEATHER (cont) Higher altitudes in the west and north that keep the temperature down throughout the year. The Monsoon winds that bring rainfall in summer. The Western Depression originating from the Mediterranean region and entering Pakistan from the west that brings rainfall in winter. RAINFALL IN PAKISTAN The major part of Pakistan experiences dry climate. Humid conditions prevail but over a small area in the north. The whole of Sindh, most of Balochistan, the major part of the Punjab and central parts of Northern Areas receive less than 250 mm of rainfall in a year. Northern Sindh, southern Punjab, north-western Balochistan and the central parts of Northern Areas receive less than 125 mm of rainfall. RAINFALL IN PAKISTAN (cont) True humid conditions appear after the rainfall increases to 750 mm in plains and 625 mm in highlands. There are two sources of rainfall in Pakistan: the Monsoon and the Western Depression. The former takes place from July to September and the latter, December to March. GLOBAL WARMING What is Global Warming? Global warming is the increase in the average temperature of the Earth's near-surface air and oceans in recent decades and Is projected to continue. Causes of Global Warming Carbon Dioxide Methane Nitrous oxide Deforestation Effects Of Global Warming Melting Of Glaciers Sea level rise Rise in temperature Ocean Acidification FUTURE OF NEW YORK CITY FUTURE OF GLACIERS TYPES OF STORMS THUNDERSTORM A thunderstorm, also called an electrical storm or lightning storm Thunderstorms form when significant condensation— resulting in the production of a wide range of water droplets and ice crystals— occurs in an atmosphere that is unstable and supports deep, rapid upward motion. THUNDERSTORM (cont) It generates lightning, thunder and is normally accompanied by heavy rainfall. Thunderstorms occur throughout the world, with the highest frequency in tropical rainforest regions where there are conditions of high humidity and temperature. TYPES OF STORMS TORNADO A tornado is a storm with a twist It is a violently rotating column of air which is in contact with both a cumulonimbus cloud or a cumulus cloud base and the surface of the earth. Tornadoes come in many sizes but are typically in the form of a visible condensation funnel, whose narrow end touches the earth and is often encircled by a cloud of debris. TROPICAL CYCLONE Also known as hurricane A tropical cyclone is a meteorological term for a storm system characterized by a low pressure system center and thunderstorms that produces strong wind and flooding rain. A tropical cyclone feeds on the heat released when moist air rises and the water vapor it contains condenses They develop over large bodies of warm water, and lose their strength if they move over land THANK YOU!