GRG 366C Lecture Notes
GRG 366C Lecture Notes GRG 366C
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This 13 page Bundle was uploaded by Cassidy Schap on Sunday September 27, 2015. The Bundle belongs to GRG 366C at University of Texas at Austin taught by Thoralf Meyer in Summer 2015. Since its upload, it has received 32 views. For similar materials see Comparative Ecosystems in Geography at University of Texas at Austin.
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Date Created: 09/27/15
Environmental Monitoring ScaHnglssues Monitoring environmental conditions is an essential part of society Scaling issues from in situ conditions such as the Oxygen concentration in Waller creek to global measures of NPP PET etc Methods highly depend on the underlying question It is often necessary to quotaveragequot parameters when dealing with larger global scales Small scale mainly in situ measurements Often not ef cient andor to expensive on a larger eg global scale Parameters need to be summed up in situ measurements We have learned That objects exposed to incoming solar radiation absorb transmit some parts and re ect outgoing radiation We know the incoming part Remote Sensing underlying principles Signals are traversing the atmosphere twice Passive remote sensing uses an existing source of energy satellite sensing Active remote sensing is where you send something out and its re ectance is measured radar lidar sonar Atmospheric Windows So in order for radiation to be sensed at a platform the radiation needs to pass the atmosphere TWICE Interference In real life this looks like a lot of noise on a grah Clear skies are important Images are made up of individual pixels that make up the image Each pixels has 1 assigned value Climate Absorption incoming radiation hits an atom or molecule producing an excited state reradiated at longer wavelength Re ection radiation bounces off a surface complex process The process has a direction Unlike Scattering differs from re ection since direction is unpredictable Rayleigh matter 01 lt incoming raditation 02 N Mie matter incoming radiation aerosols particles Unselective matter 10 times gt incoming radiation water vapor Atmosphere closes down in certain parts of the spectrum Short wave energy in long wave energy out Remember radiation from sun in converted into long wave radiation by earth and radiated back These molecules and atoms form a heating blanket Without it the earth would be 30 degrees cooler and uninhabitable Atmospheric layers Troposphere Stratosphere Mesosphere Thermosphere The areas between the Tropic of Cancer and the Tropic of Capricorn are called the Paleotropics and Neotropics biogeographical term Latent heat heat that evaporates water wet air parcels rise cool down condensateprecipitate water Sensible heat heat is conducted by the earth and moved upwards due to convchon PET potential evapotranspiration PET depends on the amount of incoming solar radiation It is a measure of how much water would be evapotranspirated if there would be an unlimited supply of water In a biome where water is not limited rainforest tropical swamp PET Actual ET In a biome where water is limited desertsavanna PET gt Actual ET Different kinds of precipitation are snow sleet fog rain Precipitation is measured in a distance unit mm Amount of precipitation received over an area depends on topography prevailing winds proximity to ocean general latitude Short term changes in observed weather patterns Difference between day and night today and yesterday Annual changes shift in the place where Sun39s radiation hits most seasonality in precipitation and temperature Midterm changes Normal situation La Nina Cool water ows west El Nino Warm water ows west wetter than average winter across North America For most research questions the consideration of daily seasonal and midterm changes is sufficient Long term changes Large changes in temperatures such as ice ages and heating Determined by observing air bubbles within ice cores Distribution of biomes is largely a function of precipitation and temperature Important climatic weather parameters General Barometric pressure precipitation temperature wind speed wind direction humidity Special Incoming solar radiation outgoing terrestrial radiation Tundra Treeless biome in the far north Consists of boggy plains covered by lichens Steep temperature curve large difference in range of temperatures Water only available between May and August 4 months of the year Soil is permafrost soil High organic content in a tundra because of slow decomposition process due to cold temperatures Lower latent heat loss lower evapotranspiration Higher sensible het loss high surface temperature High albedo Coniferous Forest Higher rainfall than tundra but still low Low albedo Highly acidic soils Deciduous Forest Very high rainfall Higher temperatures Low albedo Tropical Wet Forest VERY high rainfall except for one month of the year Mainly in Southern Hemisphere Tropical Rainforest VERY high rainfall year round Grasslands Medium rainfall throughout year except for winter time Relatively high temperatures in summer Savanna Low Rainfall most of the months in the summer but really high rainfall during winter Stable temperature throughout Desert Almost zero rainfall Very high temperature High albedo All of these factors in uence biodiversity and productivity Biodiversity is highest in the equatorial regions NPP Net Primary Productivity How much carbon is sequestered from the atmosphere carbon converted to organic matter stored in plants carbon transferred then on to consumers NPP has increased rather signi cantly due to decreased cloud cover More energy and more carbon means productivity goes up because water stays the same Productivity depends on the radiation budget and water budget of an ecosystem Radiation budget Radiation 1albedoshortwave radiation in stefan Boltzmann constantemissivity skytemperaturequot4sky same of surf ALBEDO EXAMPLES Ocean amp Lakes 031 Bare soi 054 Forests 1 Grasslandssavannas 2 Deserts 245 Seaice345 Snow 49 emissivity of sky temperaturequot4 of slq depends of weather condition different for clear and overcast skies can be calculated as a function of temperature and water vapor pressure humidity EFFECT clear nights are cold and temperature drops in deserts at night The radiation budget is highly connected to the water cycle in fact it drives it Rnet Sensible heat latent heat ground heat ux energy stored as chemical energy photosynthesis or heat ux biomass This forms the basis of productivity calculations Increasing photosynthesis drop the temperature or increase the net radiation Plants can decrease temperature through evapotranspiration This is what leaf adaptation strategies are based on Relatively high water potential in the roots lower in stem lower in atmosphere This pressure is responsible for the water being sucked up then released through the stomata if they are open Water is always lost no matter how ef cient the organism is Energy and water budgets are closely connected Evapotranspiration is one of the largest terms in the equation Factors effecting ET determine the linkage Physical properties of water High speci c heat Hence evapotranspiration takes up energy cooling effect it is driven by differences in pressure This process also moves water from SOILS D PLANTS D ATMOSPHERE Water has highest density at 4 degrees Celsius After that it goes down again Has a high heat capacity means heat is stored and slowly released Throughfall water that precipitates out moves through tree without being taken in hits the ground and may runoff smaller percentage makes it into the soil some of it evaporates from the soil as well Available Incoming Radiation Tundra 300 Available Incoming Radiation Rainforest 600 Latent Heat Tundra 150 Sensible Heat Tundra 150 Thus Tundra is cold Latent Heat Rainforest 400 Sensible Heat Rainforest 200 Rainforest is hot Carbon Budget and Photosynthesis Net Plant Photosynthesis Soil Respiration Carbon Storage Carbon Budget Most of Carbon is in marine sediments and sedimentary rocks because of CaCO3 NBP vs NPP vs NEP NPP is amount of plant respiration that occurs shortterm carbon uptake NEP is amount decomposition within ecosystem that occurs mediumterm carbon storage NBP is amount of longterm storage of carbon Depends on C02 concentrations sunlight etc for NPP As microbes breath during breakdown and decomposition release C02 affecting NEP Disturbance also leads to storage of carbon re in a forest leaves ash and coals both forms of carbon compounds Can get eaten as well stored for a mediumterm converted in to animal matter breathing it out 5 C02 releases it in to the atmosphere How much an ecosystem can sequester depends on the type and condition of the ecosystem Factors such as lts species composition Diversity Structure and in the case of forests age distribution Site conditions including climate and soils Natural disturbances and Management Gross Primary Productivity denotes the total amount of carbon xed in the process of photosynthesis by plants in an ecosystem such as a stand of trees GPP is measured on photosynthetic tissues Global total GPP is estimated to be about 120 Gt C yr391 Net Primary Productivity denotes the net production of organic matter by plants in an ecosystem that is GPP reduced by losses resulting from respiration of the plants autotrophic respiration NPP GPP Rh NEP is the difference between the rates of production of living organic matter NBP is the net production of organic matter a biome and includes other process leading to loss of living and dead organic matter and longer periods of time NBP is comparatively small globally when looking at atmosphere and oceans Forests are not in state of equilibrium they are a sink for carbon Grasslands store most of their carbon in soils rather than plants Wetlands are signi cant and important reservoirs of carbon They have low decomposition process that is then reduced by low temperatures They have a low form of carbon storage called peat that stores lots of carbon ln agricultural lands most carbon is stored below ground Responsible for most losses of carbon from terrestrial systems during the past 200 years through conversion of grassland and forests Plowing planting and harvesting leads to enhanced oxidization of carbon Photoautotrophs perform photosynthesis Limits of productivity in an ecosystem Water Energy Light Nutrients Nitrogen and Phosphorous Main source of phosphorous is the weathering of rocks The older the soil the less phosphorous is in there generally Phosphorous also released through decomposition Leaf Stuff I E 5 u l MIKEsin fr merit Environmental Monitoring Monitoring environmental conditions is an essential part of society Scaling issues from in situ conditions such as the Oxygen concentration in Waller creek to global measures on NPP PET etc Methods highly depend on the underlying question It is often necessary to average parameters when dealing with larger global scales Small scale mainly in situ measurements Often not ef cient andor to expensive on a larger global scale Parameters need to be summed up from in situ measurements or sensed remotely Each pixel in an image has 1 assigned value A normal photo has only one pixel at a certain location In the visible light section the pixel value represents its color Electronically this color 1 byte Let s take multiple photos of the same object and lets make each pixel sensible to a certain part of the spectrumAnd lets go beyond visible light and add near infrared Stack the photos and now we have A blue pixel A green pixel A red pixel A near infrared pixel Where each pixel has an assigned value Photo band Image pixels Each pixel has a value with four pixels the data is now 4 times higher The red line and the solid line are from the same object Loss of information limitation Endmember Spectra SMlAstandard 80 70 60 II D Reflectance in 1 D U D 20 10 469 555 645 8585 1240 1640 2130 MDDIS BAND reflectance nrn GVstanolarol NPVstandard SOILstandard Fix this by adding more bands and slicing the spectrum into shorter increments of the spectrum Higher spectral resolution This increases the le size The pixel size matters Smaller pixel size higher spatial resolution more information data This increases the le size again It matters how much area is covered in the ground what the satellite sees Swath width Ideally high spatial resolution high spectral resolution and a large swath width All that makes the system expensive and the amount of information goes beyond the computing capabilities of most conventional computers In reality its about the balance between spatial and spectral resolution and the swath width With regards to the extraction of environmental information it also matters how OFTEN the satellite looks at a certain object temporal resolution Can observe different species but hard to pick out the different species in a remote sensing image Note differences in red and NIR bands use difference to calculate the leaf s productivity Normalized Difference Vegetation Index NDVI NDVI NIRredNIRred this equals the sum of all ongoing photosynthesis in a given pixel and thus an image It is not quotthe bestquot index to use especially on a more localized smaller scale Images taken on different days of the same year Problems It does not tell you HOW MUCH is produced with regards to area unit Need additional factors to calculate leaf area index to calculate productivity Forest vs golf course vs forest But it gives you an indication of change
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