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PPT12 - Heat Distribution

PPT12 - Heat Distribution - What is climate Mean and...

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What is climate? Mean and variability of temperature , precipitation and wind at the surface of the Earth over a period of time ranging from months to millions of years Geographic & temporal variations of climate on Earth Wind & precipitation patterns So far, we have looked at what control the mean temperature of the Earth. This is not the whole story when it comes to climate. Climate is important because of its effect on living organisms Organisms do not care about the mean temp of the earth. They care about the temp at the location where they live. Besides climate is not just referring to temperature but also precipitation and wind intensity. We therefore need to have a closer look at the geographic and temporal distribution of climate on Earth as well as wind and precipitation patterns and what control them In particular, if we want to truly understand the Mesozoic climate, we need to consider the development of monsoons in relation to changes in continental configuration Here’s what you should already know: 1. The Earth is (almost) a sphere. 2. The Earth rotates from west to east (the Sun rises in the east, right?). 3. The tropics are warmer than the poles. 4. Hot air rises. The only part of the process that you are unlikely to develop from these things you know is that our planet, given our particular size and rate of rotation, ends up with three wind bands in each hemisphere. Jupiter, which is much larger and spins faster, has many more wind bands in each hemisphere. Venus, which is about our size but rotates much slower, has only one. The atmospheric circulation partially explains why the tropics do not get hotter and hotter and hotter, and the poles do not get infinitely colder. What processes help transfer that energy from one part of Earth to another? As you work with the material for this class, refer back to your previous class about Earth’s radiation balance. Incoming solar radiation is not received uniformly over Earth surface
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sun's angle decreases with latitude amount of solar energy received per unit area at the equator is greater than at the poles Climate is of course not uniform on Earth The main reason is because Earth is a sphere… The Sun’s angle above the horizon at noon decreases with latitude and therefore the amount of solar energy reaching the Earth per unit surface area is larger at the equator and decrease towards the pole, where the same amount of incoming solar energy is spread over a larger area Energy received by the AVERAGE square meter Ein = 1.75*10 17 W (this is the total intercepted) Spread this over the entire surface area of the Earth to get the AVERAGE W/m2 (Fin) Fin = 1.75*10 17 / 4π(6.37*10 6 m) 2 = 342 W/m2 We have calculated earlier the mean amount of energy reaching the top of the atmosphere: 342 W/m2 (i.e. the solar constant divided by 4) Incoming solar radiation decreases from equator to poles Mean = 342 W/m2 This value however, is just an average In fact, the amount of solar radiation reaching the top of the atmosphere near the equator
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