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Jet Streams

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MEANING OF JET STREAMS The strong and rapidly moving circumpolar westerly air circulation in a narrow belt of a few hundred kilometres width in the upper limit of troposphere is called jet stream. The circulation of westerly jet stream is confined between poles and 20° latitudes in both the hemispheres at the height of 7.5-14 km. According to  WHO, ‘a strong narrow current concentrated along a quasi- horizontal axis in the upper troposphere or in the stratosphere characterized by strong vertical and lateral wind shear and featuring one or more velocity maxima is called jet stream’. Click here for 3D Visualization of Jet streams PROPERTIES OF JET STREAMS: (1) The circulation of jet streams is from west to east in a narrow belt of a few hundred kilometres width at the height of 7.5 -14 km in the upper troposphere. (2) On an average, jet steams measure thousands of kilometers in length, a few hundred kilometers in width and a few kilometers (2-4 km) depth. (3) Generally,...
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Numerical Weather Prediction

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 Numerical weather prediction (NWP) uses mathematical models of the atmosphere and oceans to predict the weather based on current weather conditions.  A more fundamental problem lies in the chaotic nature of the partial differential equations that govern the atmosphere. It is impossible to solve these equations exactly, and small errors grow with time (doubling about every five days). Present understanding is that this chaotic behavior limits accurate forecasts to about 14 days even with perfectly accurate input data and a flawless model. In addition, the partial differential equations used in the model need to be supplemented with parameterizations for solar radiation, moist processes (clouds and precipitation), heat exchange, soil, vegetation, surface water, and the effects of terrain. There is only one method that ‘comes to mind’. It is called the semi-implicit method in the meteorology community. It is ‘clear’ that this can only be achieved by an unconditionally s...
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Atmospheric Motion

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The horizontal movement of air is controlled by - Pressure Gradient force- This is the main driving force of global winds. This creates a wind from high-pressure, surplus areas to low-pressure, deficit areas. The closer isobars are together, the stronger the wind is. Coriolis force - This is the deflection of wind due to the Earth’s rotation. Deflecting right in the northern hemisphere and left in the southern, with an increasing effect towards the poles. It is not present in the equator. Geostropic wind - In mid-latitudes, the Pressure Gradient and Coriolis force are balanced. Therefore, air moves parallel to the isobars rather than from regions of high pressure to low pressure. Centripetal force- Air moving towards a low-pressure area in a defected path accelerates towards the centre of low pressure Frictional forces - Frictional drag from the Earth's surface decreases wind speed and modifies it's direction, crossing isobars as it moves from high-pressure regions ...
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