Our Atmosphere as seen from the bottom of it near Grand Pre, NS. Info modified from various sources by TWebb HHS

Transcription

1 Our Atmosphere as seen from the bottom of it near Grand Pre, NS Info modified from various sources by TWebb HHS

2 Properties of the Atmosphere A) Mobility B) Expansion (MOST important!) C) Compression These properties are the cause of all weather phenomena.

3 Our Atmosphere The earth's atmosphere is a very thin layer wrapped around a very large planet. Two gases make up the bulk of the earth's atmosphere: nitrogen, which comprises 78% of the atmosphere, and oxygen, which accounts for 21%. Various trace gases make up the remainder. Our atmosphere acts like a greenhouse, to a point keeping some heat energy from escaping

4 Primary Contributors to the Natural Greenhouse Effect Carbon Dioxide Other ~25% ~10% ~65% Water Vapour

5 Other planets also have Greenhouse Effects, but these are unsuitable for life Sun Venus Atmosphere: mass 90x earth s GH Gases: >90% CO 2 Sfc. Temp.: 477 C GH Effect: 523 C FAR TOO HOT! Earth GH Gases: ~0.04% CO 2 ~ 1% H2O Sfc. Temp.: 15 C GH Effect: 33 C NOT BAD! Mars Atmosphere: mass <1% earth s GH Gases: >80% CO 2 Sfc. Temp.: -47 C GH Effect: 10 C FAR TOO COLD!

6 The atmosphere s energy budget is determined by net heat flow Reflected Energy ~31% Outgoing Heat Energy Incoming Solar Energy Energy Trapped By Greenhouse Gases CO % CH % N2O %

7 and provides several important life supporting services Protection from solar uv-b (stratospheric ozone) Suitable, stable climate and weather stratosphere surface troposphere thunderstorm The air we breath (21% oxygen)

8 Latitudinal differences in net energy balance cause atmosphere and ocean circulation

9 However, the climate system is also influenced by many other complex interactions and feedbacks

10 The layers of our atmosphere - Based on temperature, the atmosphere is divided into four layers: the troposphere, stratosphere, mesosphere, and the thermosphere, which includes the ionosphere and exosphere.

11 The Atmosphere

12 Troposphere: (from tropein, meaning to turn or change.) All of the earth's weather occurs in the troposphere. It extends from the earth's surface to an average of 12 km. The temperature generally decreases with increasing height up to the tropopause (top of the troposphere); this is near 12,000 m. The temperature averages 15 C near the surface and drops to -57 C by the tropopause. The layer ends at the point where temperature no longer varies with height. This area, known as the tropopause, marks the transition to the stratosphere. The moisture concentration decreases with height up to the tropopause.

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14 The air is much drier above the tropopause, in the stratosphere. The sun's heat that warms the earth's surface is transported upwards largely by convection and is mixed by updrafts and downdrafts.

15 The Stratosphere (stratos=layer) In the stratosphere, the temperature increases with altitude. The naturally occurring ozone causes the increasing temperature in the stratosphere. Ozone is concentrated around an altitude of 25 kilometers. The ozone molecules absorb dangerous kinds of sunlight (UV), which heats the air around them, and is critical to life on earth as we know it. Water and air currents are almost nonexistent. The top layer of the stratosphere is called the stratopause.

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17 The Mesosphere (meso = middle) In the Earth's mesosphere, the air is relatively mixed together and the temperature decreases with altitude. The atmosphere reaches its coldest temperature of around -90 C in the mesosphere. This is also the layer in which a lot of meteors burn up while entering the Earth's atmosphere. The temperature drops rapidly to -100 C at the mesopause.

18 The Thermosphere (thermos = heat) The thermosphere is located above the mesosphere. The air is very thin in the thermosphere. A small change in energy can cause a large change in temperature. When the sun is active, the thermosphere can heat up to 1,500 C or higher!

19 Thermal structure of the Atmosphere

20 The Earth's thermosphere also includes the region called the ionosphere, filled with charged particles. For this reason, all low, medium and high frequency radiowaves cannot pass through this layer. As well, the outermost layer is called the Exosphere and is little more than a vacuum. And now we ex it (Exo = outside)