Презентация Water vapor. Nitrous oxide. Aerosols онлайн

Содержание слайда: Water vapor Nitrous oxide Aerosols

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Содержание слайда: Climate Change - Greenhouse Gases To be an effective greenhouse gas, a molecule must: - absorb light in the infrared region (must have dipole moment for vibration mode) - 3 modes of vibration for CO2 shown

Содержание слайда: Earth’s Atmospheric Gases

Содержание слайда: Greenhouse Gases

Содержание слайда: Greenhouse Gases Molecules must absorb light in the right regions - roughly 7 to 25 μm region - however, in some regions (5 to 7 and 13 to 17 μm), essential no light from surface makes it to space due to current gases present - for this reason, CO2 is less effective as a greenhouse gas (at least for additional CO2)

Содержание слайда: - Greenhouse Gases Molecules absorbing light in the “IR window” regions are more effective Additional CO2 is not as effective as additional N2O (absorbs at 7.5 to 9 μm) on a forcing per ppm basis

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Содержание слайда: The climate engine II Since earth does rotate, air packets do not follow longitude lines (Coriolis effect) Speed of rotation highest at equator Winds travelling polewards get a bigger and bigger westerly speed (jet streams) Air becomes unstable Waves develop in the westerly flow (low pressure systems over Northern Europe) Mixes warm tropical air with cold polar air Net transport of heat polewards

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Содержание слайда: Cloud effects Low clouds over ocean more clouds reflect heat (cooling) fewer clouds trap heat (warming) High clouds more clouds trap heat (warming) high: 5-14 km; low < 2km

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Содержание слайда: - Greenhouse Gases H2O as a greenhouse gas - the molecule responsible for the most greenhouse effect heating - the third most prevalent molecule in the atmosphere (on average, but composition is variable) - direct anthropogenic sources are insignificant (at least outside of deserts and the stratosphere) - also responsible for cooling through increasing albedo (in clouds) so normally kept separate from other greenhouse gases - water vapor is important indirectly as planet heating increases water vapor (this is covered under feedbacks)

Содержание слайда: The sun plays a key role in the earth’s temperature The sun plays a key role in the earth’s temperature Researchers think that atmospheric warming is not due to an increase in energy output from the sun Since 1975 Troposphere has warmed Stratosphere has cooled Warmer temperatures create more clouds Thick, low altitude cumulus clouds – decrease surface temperature Thin, cirrus clouds at high altitudes – increase surface temperature

Содержание слайда: Water vapor is one of the most important elements of the climate system. A greenhouse gas, like carbon dioxide, it represents around 80 percent of total greenhouse gas mass in the atmosphere and 90 percent of greenhouse gas volume. Water vapor is one of the most important elements of the climate system. A greenhouse gas, like carbon dioxide, it represents around 80 percent of total greenhouse gas mass in the atmosphere and 90 percent of greenhouse gas volume. Water vapor and clouds account for 66 to 85 percent of the greenhouse effect, compared to a range of 9 to 26 percent for CO2. So why all the attention on carbon dioxide and its ilk? Is water vapor the real culprit causing global warming? The answer is that water vapor is indeed responsible for a major portion of Earth’s warming over the past century and for projected future warming. However, water vapor is not the cause of this warming. This is a critical, if subtle, distinction between the role of greenhouse gases as either forcings or feedbacks. In this case, anthropogenic emissions of CO2, methane, and other gases are warming the Earth. This rising average temperature increases evaporation rates and atmospheric water vapor concentrations. Those, in turn, result in additional warming.

Содержание слайда: Nitrogen Nitrogen (N) is an essential component of DNA, RNA, and proteins, the building blocks of life. All organisms require nitrogen to live and grow. The majority (78%) of the Earth’s atmosphere is N2.

Содержание слайда: Nitrogen’s triple bond Although the majority of the air we breathe is N2, most of the nitrogen in the atmosphere is unavailable for use by organisms. This is because the strong triple bond between the N atoms in N2 molecules makes it relatively inert (like a noble gas).

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Содержание слайда: Forms of Nitrogen Urea  CO(NH2)2 Ammonia  NH3 (gaseous) Ammonium  NH4 Nitrate  NO3 Nitrite  NO2 Atmospheric Dinitrogen N2 Organic N

Содержание слайда: How can we use N2? In order for plants and animals to be able to use nitrogen, N2 gas must first be converted to more a chemically available form such as ammonium (NH4+) or nitrate (NO3-).

Содержание слайда: Nitrogen Fixation (N2 --> NH3 or NH4+) ENVIRONMENTAL High-energy natural events which break the bond N2 Examples: lightning forest fires hot lava flows

Содержание слайда: Nitrogen Fixation

Содержание слайда: Nitrogen Fixation N2 --> NH3 or NH4+ How? HUMAN IMPACT Burning fossil fuels, using synthetic nitrogen fertilizers, and cultivation of legumes all fix nitrogen.

Содержание слайда: Ammonification or Mineralization

Содержание слайда: Nitrogen Mineralization also called Ammonification Organic N --> NH4+ Decay of dead things, manure, etc. Done by decomposers (bacteria, fungi, etc.) During this process, a significant amount of the nitrogen contained within the dead organism is converted to ammonium (NH4+).

Содержание слайда: Nitrification

Содержание слайда: Nitrification NH3 or NH4+ --> NO2- --> NO3- (Nitrifying) Bacteria add oxygen to nitrogen in two steps:

Содержание слайда: Denitrification

Содержание слайда: Denitrification NO3- --> N2 (Denitrifying) Bacteria do it. Denitrification removes nitrogen from ecosystems, and converts it back to atmospheric N2.

Содержание слайда: Denitrification Removes a limiting nutrient from the environment 4NO3- + C6H12O6 2N2 + 6 H20 Inhibited by O2 Not inhibited by ammonia Microbial reaction Nitrate is the terminal electron acceptor

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Содержание слайда: Nitrous oxide N2O Nitrous oxide, commonly known as laughing gas, nitrous, nitro, or NOS is a chemical compound with the formula N2O. At room temperature, it is a colorless, odorless non-flammable gas, with a slightly sweet taste. It is used in surgeryand dentistry for its anaesthetic and analgesic effects. It is known as "laughing gas" due to the euphoric effects of inhaling it, a property that has led to its recreational use as a dissociative anaesthetic. It is also used as an oxidizer in rocket propellants, and in motor racing to increase the power output of engines. At elevated temperatures, nitrous oxide is a powerful oxidizer similar to molecular oxygen. Nitrous oxide gives rise to nitric oxide (NO) on reaction with oxygen atoms, and this NO in turn reacts with ozone. As a result, it is the main naturally occurring regulator of stratospheric ozone.

Содержание слайда: N2O/O2 sedation It is necessary to use oxygen with nitrous oxide so that the blood remains appropriately oxygenated. A mixture of 20% nitrous oxide and 80% oxygen has the same analgesic equipotence as 15 mg of morphine.

Содержание слайда: Nitrous oxide can be used as an oxidizer in a rocket motor In vehicle racing, nitrous oxide (often referred to as just "nitrous") allows the engine to burn more fuel by providing more oxygen than air alone, resulting in a more powerful combustion. The gas itself is not flammable at a low pressure/temperature, but it delivers more oxygen than atmospheric air by breaking down at elevated temperatures. Therefore, it is often mixed with another fuel that is easier to deflagrate. 

Содержание слайда: The gas is approved for use as a food additive (also known as E942), specifically as an aerosol spray propellant. Its most common uses in this context are in aerosol whipped cream canisters, cooking sprays, and as an inert gas used to displace oxygen, to inhibit bacterial growth, when filling packages of potato chips and other similar snack foods.

Содержание слайда: Of the entire anthropogenic N2O emission (5.7 teragrams N2O-N per year), agricultural soils provide 3.5 teragrams N2O–N per year.  Nitrous oxide is produced naturally in the soil during the microbial processes of nitrification, denitrification, nitrifier denitrification and others.

Содержание слайда: Cumulative effect Recent experiments show that interaction between water vapor, N2O and cosmic radiation increases cloud production.

Содержание слайда: - Other Effects on Climate Tropospheric Ozone Anthropogenic emissions have lead to increase Increases are heterogeneous, plus hard to determine pre-industrial concentrations Stratospheric Ozone Loss in Stratosphere leads to cooling (more loss of energy out to space) However, loss of stratospheric ozone also leads to greater UV absorption (and heating) in troposphere As ozone loss is reversed, some heating may occur

Содержание слайда: - Other Effects on Climate Aerosol Effects – Light Scattering Aerosol As was discussed previously in visibility, aerosol particles of diameter 0.2 to 1 mm is very efficient in scattering light A significant fraction is scattered in the backwards direction, so this effectively increases planetary albedo Increase in albedo leads to cooling

Содержание слайда: - Other Effects on Climate Aerosol Effects – Light Absorption Most aerosol constituents do not absorb significantly in the visible region (where light is most prevalent) A big exception is soot (elemental carbon emitted in inefficient combustion) Soot clouds lead to atmospheric warming (even if cooling the surface over short-term)

Содержание слайда: - Other Effects on Climate Indirect Effect of Aerosols One type is through modification of cloud reflectivity

Содержание слайда: Climate Change - Other Effects on Climate Indirect Effect of Aerosols Larger droplets reflect light more poorly per g of cloud water Polluted clouds look whiter from space

Содержание слайда: Outdoor Air Pollution Can Temporarily Slow Atmospheric Warming Aerosol and soot pollutants Can enhance or counteract projected global warming Sulfate particles reflect sunlight Soot particles absorb sunlight

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Содержание слайда: Feedback Effect The climate system is very complicated. A change in one component of the system may cause changes in other components. Sometimes the changes in other components enhance the initial change, then we say that these changes have positive feedback to the system. If the changes result in the reduction of the original change, then they have negative feedback. Both positive and negative feedback processes may exist in the climate system. In studying the global climatic change, we cannot make conclusions based on intuition, but have to take all such possible complicated effects into account. A good climate model would have treated all of them realistically.

Содержание слайда: An example of positive feedback When the climate becomes warmer (either due to the increase of CO2 in the atmosphere or other unknown mechanisms), the ocean may also become warmer. A warmer ocean has lower solubility of CO2 and hence will release more CO2 into the atmosphere. This may cause the climate to become even warmer than before. Thus the dependence of solubility of CO2 on temperature has a positive feedback on the climate system.

Содержание слайда: An example of negative feedback Consider a clear region over the ocean. Since there is no cloud, the sun shines on the ocean surface, causing it to warm up. This makes this part of the ocean warmer than other parts and the air over it tends to rise (causing convection). Rising air expands and cools, causing clouds to form. The formation of clouds will block out the sun and the solar heating of the ocean surface will cease. The surface will start to cool down. Thus the cloud formation due to surface heating and convection is a negative feedback to the climate system.