Weather is described to be the state of the atmosphere at a certain place during a brief period of time. Weather is made up of numerous atmospheric phenomena such as air pressure, wind speed and direction, temperature, humidity, precipitation, and cloud cover. Weather pertains to atmospheric conditions over a shorter period of time as compared to climate. On the other hand, climate is the summation of all weather conditions during very long time periods.
Weather occurs in the lowest region of the Earth’s atmosphere. This region, called the troposphere, stretches from the surface of the Earth 6-8 kilometres from the poles, and around 17 kilometres at the Equator. The troposphere is the part of the atmosphere wherein the great majority of clouds are found and where almost all precipitation forms. Thus, weather usually happens within its range. Jet streams, upper-air waves, are phenomena that happen in the higher regions of the troposphere and beyond.
Weather data and collection explains these phenomena which have prominent effects on atmospheric pressure patterns at sea level, thus affecting weather conditions on land. Weather is also affected by geographic features such as mountains, lakes, oceans, and other large bodies of water. One prominent example of interactions between the atmosphere and ocean that affect weather is the El Nino/Southern Oscillation (ENSO).
In general, the variability of weather has much to do with where in the world weather occurs. Weather varies the most in the mid-latitude belts of the westerly winds. In these areas, constantly changing weather patterns are produced by travelling high and low-pressure centres. On the other hand, weather in tropical regions hardly changes at all from day to day or even from month to month.
Weather has significant implications on many human activities such as patterns of settlement, the production of food, and personal comfort. Weather events such as the extreme highs and lows of temperature and humidity can cause great discomfort to people, and may even lead to the spreading of sickness and disease. Large amounts of rainfall can cause flooding and displace people from their homes and disrupt economic activities. Other weather events such as tornadoes, thunderstorms, sleet storms, and hail can cause significant damage to crops, roads and routes, vehicles, and transportation.
Powerful storms can also lead to the injury or death of people and livestock. In areas situated near the coast, tropical cyclones, otherwise known as hurricanes or typhoons, have the potential to damage areas with torrential rainfall, flooding, strong winds, large waves, and storm surges. In colder climates, heavy snowfall, snowstorms, and blizzards can make transportation very difficult and also increase accident rates. Contrary to these, the absence of rainfall for long periods of time can result in severe droughts and dust storms
The variability of weather and its various phenomena have long inspired human interest towards the prediction of weather conditions in the future as well as weather forecasting. Historically, intense weather phenomena were once attributed to the ire of powerful gods and deities. Since the middle of the 1800s however, weather prediction has progressed towards the scientific methods of measuring temperature, humidity, air pressure, wind speed, and wind direction.
Since their development in the 1980s, weather satellites have allowed meteorologists to follow the movement of storms, cyclones, anticyclones and their fronts around the world. Meteorologists also use radar to monitor clouds, tropospheric winds, and precipitation. Computers combine weather models to predict weather a week or more in advance. These models are constructed based on physics principles along with measurements of weather variables like wind speed and current temperature. These scientific and technological advancements have brought significant improvements to the accuracy of local forecasts and have resulted in the development of extended and long-range forecasts.
Collecting Weather Data
Developments in science, meteorological methodology, technology, and data collection have allowed weather forecasts to be the most accurate today. The World Meteorological Organization (WMO) has even claimed that the present day’s 5-day weather forecast is as reliable as a 2-day forecast was 20 years ago.
At present, powerful computers are used to process and synthesize meteorological data collected by advanced instruments to create accurate and complex atmospheric models. These models can be then programmed to forecast how weather and atmospheric conditions would change. However, it is important to note that despite these advancements, weather forecasts are still not totally accurate. Weather is still very much a complex and chaotic natural system, and it still remains to be difficult to predict.
In order to create accurate weather forecasts, a given location and the surrounding area’s atmospheric conditions must be measured and taken into account. Data pertaining to variables such as temperature, air pressure, and other atmospheric conditions must be collected using various meteorological instruments.
Temperature is the physical property of matter that expresses the notions of hotness and coldness in quantitative measures. Temperature is an intensive property and is not dependent on the quantity of matter available.
Relative humidity is the amount of moisture or water vapour present in the atmosphere as compared to how much water vapour can be contained in the air at a certain temperature.
Precipitation is any water particle, whether in its solid or liquid state, that falls from clouds to the ground. Precipitation can come in the form of rain, snow, hail, drizzle, sleet, ice crystals, snow pellets, etc.
Cloud Type and Cloud Cover
Clouds are masses of condensing water vapour found in the atmosphere. Clouds are formed from the evaporation of water from seas, oceans, lakes, rivers, and other bodies of water. The water vapour from these water sources would then ascend to the colder parts of the atmosphere through convective or frontal lifting. The water vapour would then attach itself to condensation nuclei, which are potentially dust or other small particles such as salt and debris. When the water vapour is saturated, it cools and condenses into visible clouds.
Clouds are classified into three categories according to their formation process and physical characteristics. The cirrus cloud is formed at high altitudes and usually comes in the form of filaments. Stratus clouds are commonly observed as being sheet-like in shape. Cumulus clouds are often regarded to be the typical image associated with clouds. These types of clouds appear rolled, rippled, and heaped.
Instruments that collect weather data
Thermometers are instruments used to measure temperature. Older, analogue thermometers are long, narrow, graded tubes, with a bulb at the end. These thermometers were commonly filled with temperature-sensitive mercury that expands when temperatures are high and contracts when temperatures are low. The sides of the tube are marked with gradations that correspond to the degree of air temperature.
Modern temperatures mostly yield digital data that can easily be inputted into a computer. Some modern thermometers utilise a coiled strip made up of two kinds of metal that each conducts heat differently. When the temperature rises or falls, the coil either curls up or unfurls. Another type of modern thermometer measures infrared radiation or electrical resistance in order to measure temperature.
Barometers measure air pressure. These meteorological instruments typically have water, air, or mercury inside of them. However, much like thermometers, most modern barometers are digital. A change in the air pressure as indicated by a barometer can mean that a change in weather is incoming. A rise in air pressure signals an incoming high-pressure cell, which means that clear skies can be anticipated. A drop in air pressure tells of an incoming low-pressure cell which is almost guaranteed to bring storm clouds along with it. The barometric pressure data recorded over a vast area can be used to spot fronts, pressure systems, and other weather systems.
Weather stations are commonly equipped with a thermometer and a barometer. Weather stations also have a variety of instruments that measure other atmospheric conditions such as the amount of precipitation, humidity, wind speed, and wind direction. These instruments are situated in many different locations in order to measure the characteristics of the atmosphere in those locations. The World Meteorological Organization (WMO) states that weather data is collected from 15 satellites, 100 stationary buoys, 600 drifting buoys, 3,000 aircraft, 7,300 ships, and 10,000 land-based stations.
A Radiosonde is a weather balloon that moves through the air and measures many atmospheric conditions such as temperature, humidity and pressure as it floats by. Radiosondes in the air may be tracked to measure wind speed and wind direction. These weather data collecting instruments communicate the data they gather to computers through radio waves. From around 800 sites around the globe, radiosondes are launched into the atmosphere two times a day. Radiosondes may also be used to obtain measurements as they fall by releasing them from balloons or aeroplanes. This method is especially used for monitoring storms, as it is dangerous for aeroplanes to fly through storms.
Radar, short for radio detection and ranging, utilises radio waves to detect weather phenomena. Incorporated into this device is a transmitter that sends out radio waves in a certain direction. The radio waves would then return to the transmitter after bouncing back from the first object it collides with. Radar as used in weather data collection is effective in determining the aspects of precipitation. Characteristics of precipitation such as motion, location, intensity, and even the possibility of future precipitation can be detected and measured by radar. Meteorologists also use radar to determine the shape and structure of a storm and gauge its potential hazards and effects.
Since the launching of the first weather satellite in 1952, these meteorological instruments have increased in usefulness and importance over the decades. Weather satellites are by far the best way to observe and monitor storms and other large scale weather systems. Satellites are also able to record changes that happen in the long term.
Numerical Weather Prediction
Highly advanced computers, coupled with the analysis and interpretation of skilled meteorologists, make the most accurate weather predictions. These computers take large amounts of weather data and run them through up-to-date mathematical models, doing a lot more calculations and predictions than scientists working by hand. Meteorologists use the computers’ calculations to produce more accurate weather and climate predictions. Numerical Weather Processing, like all weather forecasts, does not yield perfectly accurate predictions. However, its high level of accuracy is invaluable for disaster risk management and reduction.
Numerical Weather Processing (NWP) involves the collection of atmospheric data from a variety of sources, and then later synthesizing them using the complex mathematical models of supercomputers. These computers would then effectively calculate what weather patterns will occur over time at different altitudes. They would then produce a grid composed of points spread out evenly, commonly 10 to 200 kilometres apart. The results of the model would then be used to predict weather that may happen as far into the future as meteorologists would like. A finished forecast would then be broadcast by satellites, reaching over 1000 sites all over the globe.
Weather maps, otherwise known as synoptic maps, are graphical illustrations of the meteorological conditions in the atmosphere from the perspective of space. The graphical representations depicted in a weather map is based on data gathered from computer models or human observations. Weather maps may either display a single atmospheric feature or many features at once.
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