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Environmental Science
Walter Peace

1. Introduction to weather and climate: The Atmosphere is a mixture of gas molecules, microscopically small suspended particles of solid and liquid, and falling precipitation. The Meteorology is the study of atmosphere and the processes (such as cloud formation, lighting and wind movement) that cause what we refer to as the “weather”. Weather is distinct from climate in that the former deals with short-term phenomena and the latter with long-term patterns. Climate is what you expect but weather is what you get. Climatologist and meteorologist study the same thing but in different scale. Climatologist wants to know the variability of the weather elements: the average temperature of the month, the highest rainfall… frequencies of occurrence of weather events- such as hailing or lighting- are the aspect of climates. 2. The Atmosphere: a. Thickness of the atmosphere: Most of the atmosphere is contained within a relatively shallow envelope surrounding the oceans and continents. Because of the shallowness of the atmosphere, its motions over large areas are primary horizontally. However, the vertical motions also determine the atmospheric behavior. b. Composition of the atmosphere: Molecules in the atmosphere can be exchanged with the Earth’s surface through physical processes (volcanic eruptions) or biological processes (plant and animal respiration). Molecules can also be destroyed or produced by internal processes (chemical reactions between gases). The concentration of the gas exists in a steady rate: the gas concentration of the input rate (from the earth to the atmosphere)= the output rate. Residence time:--- the time that the gas molecules stay in the atmosphere before being removed. ---- = mass of the substance ( kg)/ the rate at which the substance enters and exits the atmosphere (kg/year) Atmospheric gases: ----- Permanent gases:  form a constant proportion of the atmospheric mass  account for 99.999% of the atmosphere  occur nearly constant proportion throughout the atmospheres lowest 80km, which is the homosphere.  The homosphere contains mostly nitrogen (in N form). and 2 oxygen, with small amount of the insert gases, such as neon, argon. The process of add and removing N is very slowly so 2 it has a very long residence time- 42 million years.2N has really little effect on most meteorological or climatological processes.  Second most dominant gas, oxygen (O ), in form of paired 2 atom, called diatomic oxygen. The residence time is extremely long as well. ------ Variable gases:  gases whose distribution in the atmosphere varies in both time and space.  Above the homosphere is the heterosphere, where lighter gases( hydrogen, helium) become increasingly dominant with increasing altitude.  Heterosphere contains no truly permanent gases.  Water vapor’s concentration decreases rapidly with altitude and most atmospheric water vapor is found in the lowest 5km of the atmosphere. Water is constantly being cycled between the planet and the atmosphere in what is called the hydrologic cycle. Water vapor has a short residence time- 10 days. Water vapor is not in form of liquid (rainfall) so it’s similar to 2 or O2but it is different in term of its easiness to change into liquid or solid forms both at Earth’s surface and in the atmosphere.  Carbon dioxide-CO , 2s supplied to the atmosphere through plant and animal respiration, the decay of organic material, volcanic eruption and natural anthropogenic (human- produced) combustion. CO is 2emoved from the atmosphere through photosynthesis, has residence time of about 150 years.  CO 2ike water vapor, effectively absorbs radiation emitted by Earth’s surface.  CO 2s greatest amount in the early spring and lowest in late summer.  Ozone :is the part of the upper atmosphere called the stratosphere is vital to life on Earth because it absorbs the UV rays from the Sun.  Methane: CH has4been increasing, due to rice cultivation, biomass burning and fossil fuel extraction; residence time of 10 years and is an extremely effective absorber of thermal radiation emitted by Earth’s surface( >> CH leads4to global warming)  Aerosols: small solid particles and liquid droplets( not cloud droplets and precipitation), life span of few days or several weeks; affects: urban smog( dust storm), cloud droplets. c. Vertical structure of the atmosphere:  Density: > Is the amount of mass of the substance(kg) contained in a unit of volume(m ) 3 > One characteristic of gas is that no limit to the amount of mass that can fill in a given volume. > Density decreases as altitude increases.-> the greatest density is at the lower level > Mean free path: one way to think about density is in term of the average distance a molecule travels before colliding with another.  Tempurature:  The Troposphere: - the lowest of the four temperature layers - temperature decreases with height - contains 80% of the atmosphere’s mass - The depth of the troposphere varies depend on the average
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