posted 02-01-2003 02:30 PM
'If aluminum particles were in jet fuel, then they would burn up in the combustion chambers.'Here we go, 'round and 'round.
How many times does it need to be pointed out that contrails are chemtrails. Hey don't take my word for it. Here's an excerpt from
'Aviation and the Global Atmosphere' - published by The Intergovernmental panel on Climate Change www.ipcc.ch
'Aerosol particles from aviation—comprising soot, metals, sulfuric acid, water vapor, and possibly nitric acid and unburned hydrocarbons—may influence the state of the atmosphere in many ways. ...'
3.2.3.2 Metal Particles
Aircraft jet engines also directly emit metal particles. Their sources include engine erosion and the combustion of fuel containing trace metal impurities or metal particles that enter the exhaust with the fuel (Chapter 7). Metal particles—comprising elements such as Al, Ti, Cr, Fe, Ni, and Ba—are estimated to be present at the parts per billion by volume (ppbv) level at nozzle exit planes (CIAP, 1975; Fordyce and Sheibley, 1975). The corresponding concentrations of 107 to 108 particles/kg fuel (assuming 1-mm radius; see below) are much smaller than for soot. Although metals have been found as residuals in cirrus and contrail ice particles (Chen et al., 1998; Petzold et al., 1998; Twohy and Gandrud, 1998), their number and associated mass are considered too small to affect the formation or properties of more abundant volatile and soot plume aerosol particles. '
Here is the on-line summary for policymakers. http://www.ipcc.ch/pub/av(E).pdf
The entire publication is no longer available on-line but here's the sections I copied a few months back
Aviation and the Global Atmosphere
3.1. Introduction
Recent advances in our understanding of heterogeneous chemistry in the lower stratosphere and the role of aerosols and clouds in climate forcing have increased the need to understand the influence of these aircraft emissions on atmospheric composition. Aerosol particles from aviation—comprising soot, metals, sulfuric acid, water vapor, and possibly nitric acid and unburned hydrocarbons—may influence the state of the atmosphere in many ways. These particles may provide surfaces for heterogeneous chemical reactions, both in the exhaust plume and on regional and global scales; represent a sink for condensable atmospheric gases; absorb or scatter radiation directly; and change cloud properties that may affect radiation indirectly. Persistent contrails can directly cause additional cirrus clouds to form. In addition, aerosol particles may enhance sedimentation and precipitation of atmospheric water vapor, hence affecting the hydrological cycle and the budget of other gases and particles. Changes in cloud formation properties and cloud cover may also affect actinic fluxes in the atmosphere and ultraviolet-B (UV-B) radiation at the surface.
3.2. Aerosol Emission and Formation in Aircraft Plumes
Aircraft jet engines directly emit aerosol particles and condensable gases such as water vapor (H2O), sulfuric acid (H2SO4), and organic compounds, which lead to the formation of new, liquid (volatile) particles in the early plume by gas-to-particle conversion (nucleation) processes. Other gas-phase species and charged molecular clusters (chemi-ions, or CIs) are also generated at emission, including nitric acid (HNO3) and nitrous acid (HNO2). Emission and formation of H2SO4 depend on fuel sulfur content, or sulfur emission index [EI(S)], and the conversion fraction of fuel sulfur to H2SO4. Formation of HNO3 and HNO2 depends on reactions of nitrogen oxides (NOx = NO + NO2) with hydroxyl radicals (OH). Particle formation depends on mixing of exhaust gases with ambient air, plume cooling rate, plume chemistry, and ambient aerosol properties. Soot particles formed during fuel combustion and emitted metallic particles constitute the solid (nonvolatile) particle fraction present in exhaust plumes. Under certain thermodynamic conditions, emitted water vapor condenses and freezes to form water-ice particles, thereby producing a condensation trail (contrail). These line clouds evaporate rapidly if the ambient humidity is low but may change the size and chemical composition of the remaining liquid aerosol particles. If the humidity is above ice saturation, contrails persist and grow through further deposition of ambient water.
An invisible aerosol trail is always left behind cruising aircraft. Aerosol and contrail formation processes in an aging plume determine the number, surface area, and mass of particles that are formed per mass of fuel consumed. Exhaust particle properties change in the presence of a contrail. Exhaust particle morphology and surface properties and aircraft-induced perturbations of background aerosol surface areas (Section 3.3) are of central importance for ozone changes caused by heterogeneous chemical reactions (Chapters 2 and 4). Particle number and freezing probability are key for the formation of ice (cirrus) clouds after passage of an aircraft in a region where otherwise no clouds would form (Section 3.4). Finally, aviation-produced aerosol can directly or indirectly influence the radiation budget of the atmosphere (Section 3.6 and Chapter 6). For recent reviews see Schumann (1996a), Fabian and Kärcher (1997), Friedl (1997), and Brasseur et al. (1998).
3.2.1.1. Water Vapor
Water vapor is present in aircraft exhaust in known amounts because the emission index is specified by the stoichiometry of near-complete fuel combustion (Chapter 7). Water vapor concentrations of a few percent at the engine exhaust nozzle far exceed the concentrations of other aerosol precursor gases. Ambient water vapor also participates in aerosol processes, with concentrations that vary widely depending on flight altitude and meteorological processes. Because of its abundance and thermodynamic properties, water vapor participates in nearly all aerosol formation and nucleation processes (e.g., Pruppacher and Klett, 1997).
3.2.1.2. Sulfur Species
Aviation fuels (kerosene) contain sulfur in trace amounts….
3.2.1.3. Chemi-ions
A large number of chemi-ions (CIs) are expected to be present in aircraft exhaust because ion production via high-temperature chemical reactions is known to occur in the combustion of carbon-containing (not necessarily sulfur-containing) fuels (e.g., Burtscher, 1992). In the jet regime, some recent models indicate that CIs effectively promote formation and growth of electrically charged droplets containing H2SO4 and H2O (Yu and Turco, 1997). In addition, CIs may contribute to the activation of exhaust soot. Positive ions include H3O+ and organic molecules like CHO+, C3H3+, and larger molecules (Calcote, 1983), whereas the free electrons rapidly attach to other molecules to form negative ions with sulfate and nitrate cores. Measurements of positive CIs in exhaust plumes are not available, and only very few in situ measurements of negative CIs are available to date. …
3.2.1.4 Nitrogen Species
The primary nitrogen emission from aircraft is in the form of NOx (Chapter 2).
…
3.2.1.5. Hydrocarbons
Aircraft engines emit non-methane hydrocarbons (NMHCs) as a result of incomplete fuel combustion. These species include alkenes (mostly ethene), aldehydes (mostly formaldehyde), alkines (mostly ethine), and a few aromates.
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Aircraft also occasionally introduce hydrocarbons by jettisoning fuel at low altitudes in the troposphere. Most of the fuel evaporates while it falls to the ground (Quackenbush et al., 1994), which leads to a small increase of hydrocarbons in this region. Because of the small amounts of fuel released in this way, no essential impacts on atmospheric aerosols are expected.
3.2.2. Volatile Particles
3.2.2.1. Basic Processes
Volatile particles form in the exhaust plume of an aircraft as a result of nucleation processes associated with the emission of aerosol precursors (Hofmann and Rosen, 1978). Typical aerosol parameters in a young plume are included in Table 3-1 for reference. The newly formed particles grow by condensation (uptake of gaseous species) and coagulation (particles collide and attach) in the expanding plume. Coagulation processes involving charged particles originating from CI emissions are more effective because charge forces enhance collision rates. These processes are schematically presented in Figure 3-1. Key processes at young plume ages are determined mainly from the results of simulation models because of the lack of suitable plume measurements.
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Once formed, the new volatile particles interact with nonvolatile and contrail ice particles through the processes of coagulation, freezing, condensation, and evaporation (Figure 3-1). Calculations show that the new liquid particles grow and shrink as a function of relative humidity, whereas H2SO4 molecules that enter the droplets stay in the liquid phase because of their very low saturation vapor pressure (Mirabel and Katz, 1974). They also suggest that volatile particles may take up HNO3 and H2O in the near field (Kärcher, 1996) to form particles with compositions similar to those found in cold regions of the stratosphere. These particles may persist in cold (< 200 K), HNO3-rich stratospheric air but will be short-lived (< 1 min) otherwise. As the plume continues to dilute with ambient air, abundant newly formed volatile particles remain at nanometer sizes and therefore add substantially to the overall aerosol surface area and abundance (Danilin et al., 1997). Their efficiency for heterogeneous chemistry and cloud formation, however, is size- and composition-dependent (Kärcher, 1997). They may be too small to act as efficient cloud- or ice-forming nuclei in the background atmosphere unless the air mass containing the aerosol is lifted or cooled or the relative humidity increases. Although studies exist on heterogeneous plume processing along selected trajectories (Danilin et al., 1994), systematic investigations of heterogeneous chemistry coupled to plume aerosol dynamics remain to be performed (Chapter 2).
Figure 3-2: Size distribution of various aerosol types present in young jet aircraft exhaust plumes (adapted from Kärcher, 1998a).
The evolution of volatile particles is significantly altered if a contrail forms. In contrails, volatile particles have to grow to sizes greater than about 100 nm via uptake of ambient H2O before most of them freeze (Section 3.2.4.2). As ice particles grow in size by deposition of H2O, they may also scavenge other volatile and soot particles (Anderson et al., 1998a,b; Schröder et al., 1998a). Thus, contrails are expected to contain fewer small particles than non-contrail plumes because of enhanced scavenging losses. After evaporation of contrail ice crystals, the residual volatile and soot cores remain as particles in the atmosphere (Figure 3-1). This contrail processing is expected to modify the particle size distribution and composition and may lead to efficient cloud condensation nuclei production (Yu and Turco, 1998b).
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In situ measurements detailing particle volatility and size distributions such as those included in Figure 3-3 have involved relatively young plumes. Further observations in aging plumes (> 1 h) as they dilute with the background atmosphere are currently lacking. Without detailed observations of the microphysical evolution and chemical composition of volatile exhaust particles from the engine exhaust plume to the global scale, important uncertainties remain in assessing the potential global impact of exhaust products on chemistry and cloudiness.
3.2.3. Soot and Metal Particles
3.2.3.1. Soot
Aircraft jet engines directly emit solid soot particles. Soot encompasses all primary, carbon-containing products from incomplete combustion processes in the engine. Besides the pure (optically black) carbon fraction, these products may also contain nonvolatile (gray) organic compounds (e.g., Burtscher, 1992; Bockhorn, 1994). Soot parameters of importance for understanding plume processes are concentration and size distribution at the engine exit, nucleating and chemical properties, and freezing ability.
3.2.3.2 Metal Particles
Aircraft jet engines also directly emit metal particles. Their sources include engine erosion and the combustion of fuel containing trace metal impurities or metal particles that enter the exhaust with the fuel (Chapter 7). Metal particles—comprising elements such as Al, Ti, Cr, Fe, Ni, and Ba—are estimated to be present at the parts per billion by volume (ppbv) level at nozzle exit planes (CIAP, 1975; Fordyce and Sheibley, 1975). The corresponding concentrations of 107 to 108 particles/kg fuel (assuming 1-mm radius; see below) are much smaller than for soot. Although metals have been found as residuals in cirrus and contrail ice particles (Chen et al., 1998; Petzold et al., 1998; Twohy and Gandrud, 1998), their number and associated mass are considered too small to affect the formation or properties of more abundant volatile and soot plume aerosol particles.
3.3.3. Observations of Aircraft-Produced Aerosol and Sulfate Aerosol Changes
Observations of aircraft-induced aerosols have increased substantially in recent years (see Section 3.2). Concentrations of aerosol particles and aerosol precursor gases well above background values have been observed in the exhaust plumes of aircraft operating in the upper troposphere and lower stratosphere. Although aircraft emissions are quickly diluted by mixing with ambient air to near background values, the accumulation of emissions in flight corridors used in the routing of commercial air traffic has the potential to cause notable atmospheric changes.
3.2.4. Contrail and Ice Particle Formation
3.2.4.1. Formation Conditions and Observations
Contrails consist of ice particles that mainly nucleate on exhaust soot and volatile plume aerosol particles. Contrail formation is caused by the increase in relative humidity (RH) that occurs in the engine plume as a result of mixing of warm and moist exhaust gases with colder and less humid ambient air (Schmidt, 1941; Appleman, 1953). The RH with respect to liquid water must reach 100% in the young plume behind the aircraft for contrail formation to occur (Höhndorf, 1941; Appleman, 1953; Busen and Schumann, 1995; Jensen et al., 1998a). The thermodynamic relation for formation depends on pressure, temperature, and RH at a given flight level; fuel combustion properties in terms of the emission index of H2O and combustion heat; and overall efficiency h (Cumpsty, 1997). h, defined as the fraction of fuel combustion heat that is used to propel the aircraft, can be computed from engine and aircraft properties (Schumann, 1996a; see also Section 3.7). Only the fraction (1-h) of the combustion heat leaves the engine with the exhaust gases. As the value of h increases, exhaust plume temperatures decrease for a given concentration of emitted water vapor, hence contrails form at higher ambient temperatures and over a larger range of altitudes in the atmosphere (Schmidt, 1941). Several recent studies reported formation and visibility of contrails at temperatures and humidities as predicted by thermodynamic theory for a variety of aircraft and ambient conditions (Busen and Schumann, 1995; Schumann, 1996b; Schumann et al., 1996; Jensen et al., 1998a; Petzold et al., 1998). These data are compiled in Figure 3-4. The mixing process in the expanding exhaust plume is close to isobaric, so the specific excess enthalpy and water content of the plume decrease with a fixed ratio as plume species dilute from engine exit to ambient values. Hence, plume conditions follow straight “mixing lines” in a plot of H2O partial pressures versus temperature (Schmidt, 1941) (Figure 3-4). The thermodynamic properties of H2O are such that the saturation pressures over liquid water and water-ice (solid and dashed lines) increase exponentially with temperature. Therefore, within the first second in the plume, the exhaust RH increases to a maximum, then decreases to ambient values. The ambient temperature reaches threshold values for contrail formation when the mixing lines touch the liquid saturation curve in Figure 3-4b. Contrails persist when mixing-line endpoints fall between the liquid and ice saturation pressures—that is, when the ambient atmosphere is ice-supersaturated. Without ambient ice supersaturation, contrail ice crystals evaporate on time scales of seconds to minutes. Short-lived contrails may also form without ambient water vapor if ambient temperatures are sufficiently low.
Contrails become visible within roughly a wingspan distance behind the aircraft, implying that the ice particles form and grow large enough to become visible within the first tenths of a second of plume age. Ice size distributions peak typically at 0.5 to 1 µm number mean radius (Figure 3-2). A lower limit concentration of about 104 cm-3 of ice-forming particles in the plume (at plume ages between 0.1 and 0.3 s) is necessary for a contrail to have an optical depth above the visibility threshold (Kärcher et al., 1996b). These values and the corresponding mean radii of 1 µm of contrail ice particles are in agreement with in situ measurements in young plumes (Petzold et al., 1997). Initial ice particle number densities increase from 104 to 105 cm-3 and mean radii decrease from 1 to 0.3 µm when the ambient temperature is lowered by 10 K from a typical threshold value of 222 K (Kärcher et al., 1998a). Although aerosol and ice particle formation in a contrail are influenced by the fuel sulfur content (Andronache and Chameides, 1997, 1998), it has only a small (< 0.4 K) impact on the threshold temperature for contrail formation (Busen and Schumann, 1995; Schumann et al., 1996).
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Contrail ice crystals evaporate quickly when the ambient air is subsaturated with respect to ice, unless the particles are coated with other species such as HNO3 (Diehl and Mitra, 1998). Simulations suggest that a few monolayers of HNO3 may condense onto ice particle surfaces and form NAT particles in stratospheric contrails (Kärcher, 1996). These particles would be thermodynamically stable and longer lived and would cause a different chemical perturbation than would short-lived stratospheric contrails composed of water ice. However, the relevance of this effect on larger scales has not yet been studied because no parameterization of NAT particle nucleation in aircraft plumes exists for use in atmospheric models (Chapter 4).
3.3.6. Polar Stratospheric Clouds and Aircraft Emissions
During winter in the polar regions, low temperatures lead to the formation of polar stratospheric cloud (PSC) particles, which contain H2SO4, HNO3, and H2O (e.g., WMO, 1995; Carslaw et al., 1997; Peter, 1997). PSCs activate chlorine, leading to significant seasonal ozone losses in the lower stratosphere, particularly in the Southern Hemisphere (WMO, 1995). PSC formation may be enhanced by the atmospheric accumulation of aircraft emissions of NOx, H2O, and sulfate, as well as through direct formation in aircraft plumes in polar regions (Section 3.2 and Chapter 4). If aircraft emissions change the frequency, abundance, or composition of PSCs, the associated ozone loss may also be modified (Peter et al., 1991; Arnold et al., 1992; Considine et al., 1994; Tie et al., 1996; Del Negro et al., 1997).
3.4. Contrail Occurrence and Persistence and Impact of Aircraft Exhaust on Cirrus
Aircraft cause visible changes in the atmosphere by forming contrails that represent artificially induced cirrus clouds.
3.4.1. Cirrus and Contrails
Ice crystal number densities are limited by competition between increasing saturation as a result of cooling in vertical updrafts and decreasing saturation as a result of growth of ice crystals. The depletion of vapor as a result of growth of the first few ice crystals nucleated prevents further ice nucleation on the remaining particles (Jensen and Toon, 1994). Once ice crystals form and take up available water vapor, supersaturation declines and further nucleation of ice ceases. This selectivity causes ice crystals in cirrus to be larger relative to droplets in liquid water-containing clouds—apart from differences in saturation vapor pressures over ice compared to water, which causes more water vapor to be available for deposition on ice particles than on water droplets. Large ice particles may precipitate rapidly. Many cirrus clouds have a “fuzzy” appearance because rapid precipitation causes optically thin edges of clouds to be diffuse, and precipitation allows particles to spread in the wind, forming long tails of cloud. Ice crystal nucleation also depends on available aerosol in the upper troposphere, the properties of which are only poorly known (Ström and Heintzenberg, 1994; Podzimek et al., 1995; Sassen et al., 1995; Schröder and Ström, 1997). In some locations, upper tropospheric particles are dominated by sulfates (Yamato and Ono, 1989; Sheridan et al., 1994). However, more recent data show that minerals, organic compounds, metals, and other substances may often be present in significant quantities (Chen et al., 1998; Talbot et al., 1998).
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Persistent contrail formation requires air that is ice-supersaturated (Brewer, 1946). Ice-supersaturated air is often free of visible clouds (Sassen, 1997) because the supersaturation is too small for ice particle nucleation to occur (Heymsfield et al., 1998b). Supersaturated regions are expected to be quite common in the upper troposphere (Ludlam, 1980). The presence of persistent contrails demonstrates that the upper troposphere contains air that is ice-supersaturated but will not form clouds unless initiated by aircraft exhaust (Jensen et al., 1998a). Aircraft initiate contrail formation by increasing the humidity within their exhaust trails, whereas local atmospheric conditions govern the subsequent evolution of contrail cirrus clouds. Indeed, the ice mass in long-lasting contrails originates almost completely from ambient water vapor (Knollenberg, 1972).
Ice-supersaturated air masses are often formed when ice-saturated air masses are lifted by ambient air motions. While the air lifted, it may remain cloud-free until it is cooled adiabatically to near-liquid saturation (Ludlam, 1980). Other evidence for large supersaturation occurring in the upper troposphere is provided by cirrus fallstreaks that grow while falling through supersaturated air layers (Ludlam, 1980) and by a few localized humidity measurements (Brewer, 1946; Murphy et al., 1990; Ovarlez et al., 1997; Heymsfield et al., 1998b). Recent humidity measurements by commercial aircraft show that—in flights between Europe, North and South America, Africa, and Asia—14% of flight time was in air masses that were ice-supersaturated with a mean value of 15% (Helten et al., 1998; Gierens et al., 1999).
3.4.3. Contrail Occurrence
Aged contrails often cannot be distinguished from cirrus, which poses an observational problem in determining the frequency and area of coverage by contrails. An important example of the persistence of contrails and their evolution into more extensive cirrus is shown in Figure 3-13. An initial oval contrail observed in GOES-8 satellite images diffused as it was advected over California until it no longer resembled its initial shape 3 h later (Minnis et al., 1998a). The exhaust from this single aircraft flying for less than 1 h in a moist atmosphere caused a cirrus cloud that eventually covered up to 4,000 km2 and lasted for more than 6 h. Other contrails and contrail clusters were observed to develop over periods of 7 to 17 h, spreading to cover areas of 12,000 to 35,000 km2. Such dispersed contrails are usually indistinguishable from natural cirrus; hence, satellite detection algorithms based on the linear structures of young contrails will not detect these dispersed contrails.
3.4.5. Impact of Aircraft Exhaust on Cirrus Clouds and Related Properties
Aircraft may perturb natural cirrus through the addition of water vapor, soot, and sulfate particles and by inducing vertical motions and turbulent mixing (Gierens and Ström, 1998). Observations of cirrus coverage in certain regions have found perturbations from anthropogenic aerosol (Ström et al., 1997). Persistent contrails are often associated with or embedded in natural cirrus (Minnis et al., 1997; Sassen, 1997). Such in-cloud contrails may be formed slightly above the Schmidt-Appleman temperature threshold because ambient ice particles that enter the engine inlet increase the humidity in the exhaust plume (Jensen et al., 1998a; Kärcher et al., 1998a). Some evidence associates in-cloud contrails with regions of enhanced absorbing material and enhanced ice crystal number densities (Ström and Ohlsson, 1998). The presence of HNO3 may increase the hygroscopic growth of supercooled cloud droplets (Laaksonen et al., 1997), and HNO3 dissolved in sulfate solution droplets may change their freezing behavior. The importance of such perturbations has not been quantified.
Soot particles originating from aircraft exhaust may act as freezing nuclei. In an atmosphere with few freezing nuclei, this perturbation could lead to an expansion of cirrus cover, a change in average particle size, and related changes in cloud surface area and optical depth (Jensen and Toon, 1997)—hence have consequences for radiative forcing (see Section 3.6.5).
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Aircraft measurements in and near clouds have indicated the presence of light-absorbing material contained inside ice crystals. The distribution pattern and the amount of measured absorbers suggest that the material is related to aircraft soot (Ström and Ohlsson, 1998) (Figure 3-17).
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Sedimentation of large particles in persistent contrails may remove water vapor from the upper troposphere, possibly reducing radiative heating by water vapor, and cause seeding of lower level clouds (Murcray, 1970; Knollenberg, 1972). Sedimentation of ice crystals, which has been observed occasionally (Konrad and Howard, 1974; Schumann, 1994; Heymsfield et al., 1998a), becomes important only in strongly supersaturated air (Hauf and Alheit, 1997) when large ice crystals form and have the potential to fall through lower-lying saturated air in which they will not evaporate readily. Because no attempts have been made to quantify the precipitation rate from contrails, the significance of this precipitation has not been assessed.
3.5. Long-Term Changes in Observed Cloudiness and Cloud-Related Parameters
Contrails have long been considered possible modifiers of regional climate (Murcray, 1970; Changnon, 1981). Contrails may increase total cloud and cirrus cloud amounts, and consequently change the Earth’s radiation balance. As a result, surface and upper tropospheric temperatures may change (Detwiler, 1983; Frankel et al., 1997). …
3.5.2. Changes in Other Climate Parameters
A substantial decrease in diurnal surface temperature range (DTR) has been observed on all continents (Karl et al., 1984; Rebetez and Beniston, 1998). The reasons for this decrease are not clear; it could be caused by a change in aerosol burden, cloud amount, cloud ceiling height (Hansen et al., 1995), soil moisture, or absorption of solar radiation by increased water vapor in the atmosphere (Roeckner et al., 1998).
3.6. Radiative Properties of Aerosols, Contrails, and Cirrus Clouds
Aircraft emissions have an impact on the Earth’s radiation budget and climate through direct and indirect changes in aerosols and cloudiness. Recent climate assessments have stressed the importance of natural and anthropogenic changes in aerosols on direct radiative forcing (Charlson et al., 1990; Schwartz, 1996). Aerosols and contrails have direct effects (scattering and absorbing solar and longwave radiation) and indirect effects (modifying the formation of cloud particles and radiative properties of clouds). Several studies have addressed the direct impact of contrails (e.g., Detwiler and Pratt, 1984; Grassl, 1990; Liou et al., 1990; Sassen, 1997). The indirect effect of contrails has not yet been investigated in detail. The direct radiative impacts of aircraft soot emissions (Pueschel et al., 1992, 1997) and sulfate aerosol have been evaluated as being small (Friedl, 1997; Brasseur et al., 1998). The indirect radiative effect of aircraft-induced aerosols on clouds is essentially unknown. In fact, the indirect radiative effect of non-aviation aerosol has been studied for liquid water clouds (IPCC, 1996), but the indirect effect of changing cirrus is not yet known either. Here, the discussion focuses on the impact of aircraft-generated aerosol and that of contrails and changed cirrus clouds.
3.6.5. Radiative Impact of Additional or Changed Cirrus and Other Indirect Effects
Aircraft emissions may also change the properties of natural cirrus clouds (see Section 3.4.5). In a high-traffic region, cirrus was found to be affected by soot emissions from aircraft, causing an approximate doubling of the ice particle concentration (Ström and Ohlsson, 1998). Smaller particles cause larger optical depth for constant ice water content. Radiative forcing is strongly sensitive to particle size (see Table 3-7). As Figure 3-20 indicates, an increase in optical depth causes additional heating if the cirrus cloud was optically thin but cooling if it was optically thick (Wyser and Ström, 1998). One recent study suggests that the indirect heating effect of aviation-induced changes in cirrus ice particle number density for fixed cloud cover may be positive and comparable to or even larger than that from increases in cloud cover (Meerkötter et al., 1999).
3.7. Parameters of Future Changes in Aircraft-Produced Aerosol and Cloudiness
The future effects of aircraft depend on trends in climate and air traffic amount and changes in the technical properties of aircraft. Our current understanding of the formation of aviation-induced aerosol and cloudiness can be used to estimate how future changes may affect the impacts of aviation and to identify mitigation options that would be effective in reducing these impacts.
3.7.1 Changes in Climate Parameters
If climate change occurs in the future, atmospheric parameters related to aerosols and contrails will also have changed. Of particular importance to aviation-induced aerosol and cloudiness are changes in temperature and humidity in the upper troposphere and lower stratosphere; changes in the height, temperature, and humidity of the tropopause region; changes in the abundance of particles; and changes in cloudiness. Table 3-10 summarizes how changes in these parameters may be reflected in aviation-related impacts. General circulation models of the atmosphere predict that the climate of 2050 will reflect global warming from the accumulation of greenhouse gases. In this new climate, models predict increases in the amounts of cirrus clouds, the height of the tropopause, and upper tropospheric temperature (IPCC, 1996; Timbal et al., 1997). A higher tropopause would cause more contrails, at least at high latitudes. Observed temperature changes (e.g., Parker et al., 1997) do not reveal the expected temperature increase in the upper troposphere. Some models predict a higher tropopause if the surface temperature increases (about 200-m altitude increase for 1 K surface temperature increase) (Thuburn and Craig, 1997). Increases on the order of 100 m were analyzed in polar regions and at mid-latitudes (Hoinka, 1998; Steinbrecht et al., 1998). Such changes may be forced by cooling of the lower stratosphere as a result of changes in ozone concentration (Hansen et al., 1997) and increases in moisture as a result of increasing methane concentrations. Stratospheric temperatures between 50 and 100 hPa have decreased by about 1 to 2 K since 1980 (Ramaswamy et al., 1996; Halpert and Bell, 1997). An increase in water vapor concentration has been observed in the lower stratosphere, with the largest trend (0.8%/yr) in the 18- to 20-km region (Oltmans and Hofmann, 1995). Because few contrails currently form in the lower stratosphere, small changes in stratospheric conditions will not create significant changes in contrail abundance. Aerosol loading in the troposphere and lower stratosphere may increase because of changed climate conditions and increased surface emissions. Surface emissions from fossil fuel burning were projected to grow by a factor of 1.5 to 2.1 from 1990 to 2040 (Wolf and Hidy, 1997).
6.1.2. Aircraft-Induced Climate Change
Aircraft emissions are expected to modify the Earth’s radiative budget and climate as a result of several processes (see also Figure 6-1): emission of radiatively active substances (e.g., CO2 or H2O); emission of chemical species that produce or destroy radiatively active substances (such as NOx, which modifies O3 concentration, or SO2, which oxidizes to sulfate aerosols); and emission of substances (e.g., H2O, soot) that trigger the generation of additional clouds (e.g., contrails).
rainheart- So now that we are all understanding that contrails ARE chemtrails and that they DO have a direct effect on climate and the Earth's ecology, here's a little reading providing the motive for intentional climate and environmental change.
A Research Paper
Presented To
Air Force 2025
by
Col Tamzy J. House
Lt Col James B. Near, Jr.
LTC William B. Shields (USA)
Maj Ronald J. Celentano
Maj David M. Husband
Maj Ann E. Mercer
Maj James E. Pugh
August 1996
Disclaimer
2025 is a study designed to comply with a directive from the chief of staff of the Air Force to examine the concepts, capabilities, and technologies the United States will require to remain the dominant air and space force in the future. Presented on 17 June 1996, this report was produced in the Department of Defense school environment of academic freedom and in the interest of advancing concepts related to national defense. The views expressed in this report are those of the authors and do not reflect the official policy or position of the United States Air Force, Department of Defense, or the United States government.
This report contains fictional representations of future situations/scenarios. Any similarities to real people or events, other than those specifically cited, are unintentional and are for purposes of illustration only.
This publication has been reviewed by security and policy review authorities, is unclassified, and is cleared for public release.
Contents
Chapter
Disclaimer
Illustrations
Tables
Acknowledgments
Executive Summary
1. Introduction
2. Required Capability
o Why Would We Want to Mess with the Weather?
o What Do We Mean by "Weather-modification"?
3. System Description
o The Global Weather Network
o Applying Weather-modification to Military Operations
4. Concept of Operations
o Precipitation
o Fog
o Storms
o Exploitation of "NearSpace" for Space Control
o Opportunities Afforded by Space Weather-modification
o Communications Dominance via Ionospheric Modification
o Artificial Weather
o Concept of Operations Summary
5. Investigation Recommendations
o How Do We Get There From Here?
o Conclusions
Appendix
A Why Is the Ionosphere Important?
B Research to Better Understand and Predict Ionospheric Effects
C Acronyms and Definitions
Bibliography
Notes
Illustrations
Figure
3-1. Global Weather Network
3-2. The Military System for Weather-Modification Operations
4-1. Crossed-Beam Approach for Generating an Artificial Ionospheric Mirror
4-2. Artificial Ionospheric Mirrors Point-to-Point Communications
4-3. Artificial Ionospheric Mirror Over-the-Horizon Surveillance Concept
4-4. Scenarios for Telecommunications Degradation
5-1. A Core Competency Road Map to Weather Modification in 2025
5-2. A Systems Development Road Map to Weather Modification in 2025
Tables
Table
1 - Operational Capabilities Matrix
Acknowledgments
We express our appreciation to Mr Mike McKim of Air War College who provided a wealth of technical expertise and innovative ideas that significantly contributed to our paper. We are also especially grateful for the devoted support of our families during this research project. Their understanding and patience during the demanding research period were crucial to the project's success.
Executive Summary
In 2025, US aerospace forces can "own the weather" by capitalizing on emerging technologies and focusing development of those technologies to war-fighting applications. Such a capability offers the war fighter tools to shape the battlespace in ways never before possible. It provides opportunities to impact operations across the full spectrum of conflict and is pertinent to all possible futures. The purpose of this paper is to outline a strategy for the use of a future weather-modification system to achieve military objectives rather than to provide a detailed technical road map.
A high-risk, high-reward endeavor, weather-modification offers a dilemma not unlike the splitting of the atom. While some segments of society will always be reluctant to examine controversial issues such as weather-modification, the tremendous military capabilities that could result from this field are ignored at our own peril. From enhancing friendly operations or disrupting those of the enemy via small-scale tailoring of natural weather patterns to complete dominance of global communications and counterspace control, weather-modification offers the war fighter a wide-range of possible options to defeat or coerce an adversary. Some of the potential capabilities a weather-modification system could provide to a war-fighting commander in chief (CINC) are listed in table 1.
Technology advancements in five major areas are necessary for an integrated weather-modification capability: (1) advanced nonlinear modeling techniques, (2) computational capability, (3) information gathering and transmission, (4) a global sensor array, and (5) weather intervention techniques. Some intervention tools exist today and others may be developed and refined in the future.
Table 1 - Operational Capabilities Matrix
DEGRADE ENEMY FORCES ENHANCE FRIENDLY FORCES
Precipitation Enhancement Precipitation Avoidance
- Flood Lines of Communication - Maintain/Improve LOC
- Reduce PGM/Recce Effectiveness - Maintain Visibility
- Decrease Comfort Level/Morale - Maintain Comfort Level/Morale
Storm Enhancement Storm Modification
- Deny Operations - Choose Battlespace Environment
Precipitation Denial Space Weather
- Deny Fresh Water - Improve Communication Reliability
-- Induce Drought - Intercept Enemy Transmissions
Space Weather - Revitalize Space Assets
- Disrupt Communications/Radar Fog and Cloud Generation
- Disable/Destroy Space Assets - Increase Concealment
Fog and Cloud Removal Fog and Cloud Removal
- Deny Concealment - Maintain Airfield Operations
- Increase Vulnerability to PGM/Recce - Enhance PGM Effectiveness
Detect Hostile Weather Activities Defend against Enemy Capabilities
Current technologies that will mature over the next 30 years will offer anyone who has the necessary resources the ability to modify weather patterns and their corresponding effects, at least on the local scale. Current demographic, economic, and environmental trends will create global stresses that provide the impetus necessary for many countries or groups to turn this weather-modification ability into a capability.
In the United States, weather-modification will likely become a part of national security policy with both domestic and international applications. Our government will pursue such a policy, depending on its interests, at various levels. These levels could include unilateral actions, participation in a security framework such as NATO, membership in an international organization such as the UN, or participation in a coalition. Assuming that in 2025 our national security strategy includes weather-modification, its use in our national military strategy will naturally follow. Besides the significant benefits an operational capability would provide, another motivation to pursue weather-modification is to deter and counter potential adversaries.
In this paper we show that appropriate application of weather-modification can provide battlespace dominance to a degree never before imagined. In the future, such operations will enhance air and space superiority and provide new options for battlespace shaping and battlespace awareness.1 "The technology is there, waiting for us to pull it all together;"2 in 2025 we can "Own the Weather."
Chapter 1
Introduction
Scenario: Imagine that in 2025 the US is fighting a rich, but now consolidated, politically powerful drug cartel in South America. The cartel has purchased hundreds of Russian-and Chinese-built fighters that have successfully thwarted our attempts to attack their production facilities. With their local numerical superiority and interior lines, the cartel is launching more than 10 aircraft for every one of ours. In addition, the cartel is using the French system probatoire d' observation de la terre (SPOT) positioning and tracking imagery systems, which in 2025 are capable of transmitting near-real-time, multispectral imagery with 1 meter resolution. The US wishes to engage the enemy on an uneven playing field in order to exploit the full potential of our aircraft and munitions.
Meteorological analysis reveals that equatorial South America typically has afternoon thunderstorms on a daily basis throughout the year. Our intelligence has confirmed that cartel pilots are reluctant to fly in or near thunderstorms. Therefore, our weather force support element (WFSE), which is a part of the commander in chief's (CINC) air operations center (AOC), is tasked to forecast storm paths and trigger or intensify thunderstorm cells over critical target areas that the enemy must defend with their aircraft. Since our aircraft in 2025 have all-weather capability, the thunderstorm threat is minimal to our forces, and we can effectively and decisively control the sky over the target.
The WFSE has the necessary sensor and communication capabilities to observe, detect, and act on weather-modification requirements to support US military objectives. These capabilities are part of an advanced battle area system that supports the war-fighting CINC. In our scenario, the CINC tasks the WFSE to conduct storm intensification and concealment operations. The WFSE models the atmospheric conditions to forecast, with 90 percent confidence, the likelihood of successful modification using airborne cloud generation and seeding.
In 2025, uninhabited aerospace vehicles (UAV) are routinely used for weather-modification operations. By cross-referencing desired attack times with wind and thunderstorm forecasts and the SPOT satellite's projected orbit, the WFSE generates mission profiles for each UAV. The WFSE guides each UAV using near-real-time information from a networked sensor array.
Prior to the attack, which is coordinated with forecasted weather conditions, the UAVs begin cloud generation and seeding operations. UAVs disperse a cirrus shield to deny enemy visual and infrared (IR) surveillance. Simultaneously, microwave heaters create localized scintillation to disrupt active sensing via synthetic aperture radar (SAR) systems such as the commercially available Canadian search and rescue satellite-aided tracking (SARSAT) that will be widely available in 2025. Other cloud seeding operations cause a developing thunderstorm to intensify over the target, severely limiting the enemy's capability to defend. The WFSE monitors the entire operation in real-time and notes the successful completion of another very important but routine weather-modification mission.
This scenario may seem far-fetched, but by 2025 it is within the realm of possibility. The next chapter explores the reasons for weather-modification, defines the scope, and examines trends that will make it possible in the next 30 years.
[Edited 1 times, lastly by rainheart on 02-01-2003]
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