Hydrology

Current Understanding Of Tropospheric Ozone Budget

Tropospheric And Stratospheric Ozone

The global distribution of tropospheric ozone presented earlier in this chapter illustrates its heterogeneity and underscores the difficulty of quantifying a global budget using the simplistic assumptions about its vertical distribution that had been employed when budgets neglecting photochemical processes were formulated. It is clear from the depiction in Figure 1 that local-scale photochemical generation of ozone has had a considerable impact on the global distribution as evidenced by the...

Examples Of Visibility Impairment

The camera ean be an effective tool in capturing the visual impact that pollutants have on a visual resource. Figures 12a to 12d show the effect that various levels of uniform haze have on a Glacier National Park vista. These photographs were taken of the Garden Wall from across Lake McDonald. Figures 13 and 14 show similar hazes of vistas at Mesa Verde and Bryce Canyon National Parks. The Chuska Mountains in Figure 13 are 95 km away, Navajo Mountain in Figure 14 is 130 km distant. This...

Modeling Cloud Scale

Transport Pathways Hydrology

The Goddard Cumulus Ensemble (GCE) model (Tao and Simpson, 1993) has been used by Pickering et al. (1991, 1992a,b, 1993, 1996), Scala et al. (1990), and Stenchikov et al. (1996) in the analysis of convective transport of trace gases. The cloud model is nonhydrostatic and contains detailed representation of cloud micro-physical processes. Two- and three-dimensional versions of the model have been applied in transport analyses. The initial conditions for the model are usually from a sounding of...

Chemical Forms Sources And Concentration Levels

Davis Reagent Mechanism

As shown in Figure 2, some I I different sulfur compounds define over 98 of the sulfur speciation in the atmosphere. Those in which sulfur is found bonded to either 2 CHEMICAL FORMS, SOURCES, AND CONCENTRATION LEVELS 129 TABLE 1 Global Sulfur Emission Inventory TABLE 1 Global Sulfur Emission Inventory For DMS, the data indicate that 97 of the global flux of 15 to 26 Tg S yr results from emissions from the ocean (Berresheim et al., 1995). Of this marine total, 61 is from the SH and 39 from the...

The Hydrologic Cycle

Lake Cycle Hydrologic

Figure represents a conceptual model of the hydro logic cycle and shows Earth's water movement between the ocean, land, and atmosphere. As with all cycles, it is ongoing and continuous, and there is no specific start or end point however, because the main focus of this handbook is meteorology, precipitation is an appropriate place to begin an evaluation. Precipitation is water released from the atmosphere in the form of rain, snow, sleet or hail. During precipitation, some of the moisture is...

Aerosol Processes In The Stratosphere

Vapor Pressures Aerosol Propellants

It is now well established that chemical reactions involving aerosol particles play a key role in stratospheric ozone depletion.1-3 Some of these reactions take place on the surface of solid particles, while others occur inside liquid particles both are commonly referred to as heterogeneous processes because they involve both the gas and the condensed phase. The aerosol layer is located in the lower stratosphere and consists predominantly of aqueous sulfuric acid droplets, commonly labeled SSAs...

Snow Hydrology And Water Resources Western United States

Seasonally snow-covered areas of Earth offer special challenges for water resources management, challenges that arise from both hydrologic and social factors. Seasonal snowpacks account for the major source of the runoff for streamflow and groundwater recharge over wide areas of the midlatitudes. For example, in the western United States over 85 of the annual runoff from the Colorado River basin originates as snowmelt. Most of this is from a few small source areas in four western states, mostly...

Harrison 1986 Simulating Drought In Sa Reference

Abrams, L., Drought policy water issues, The African Water Page, http www.african- water.org.drghtwater.htm 1997. Abrams, L., R. Short, and J. Evans, Root cause and relief restraint report, National Consultative Forum on Drought, Secretarial and Ops Room, Johannesburg, October 8, 1992. Adams, L., A rural voice, strategies for drought relief, Indicator S. Afr., 10(4), 41-46, 1993. Alexander, W. J. R, Floods, droughts and climate change, S. Afr. J. Sci., 91, 403 08. Allan, R. J, J. A. Lindesay,...

How Is Photogrametry Applied To Hydrology

E., Topographic partition of watersheds with digital elevation models, Water Resour. Res., 22(1), 15-24, 1986. Barrett, E. C., The estimation of monthly rainfall from satellite data, Monthly Weather Rev., 98, 322-327, 1970. Bondelid, T. R., T. J. Jackson, and R. H. McCuen, Estimating runoff curve numbers using remote sensing data, in Proceedings of the International Symposium on Rainfall-Runoff Modeling, Applied Modeling in Catchment Hydrology, Water Resources Publications, Littleton,...

[03 H0x0jAm

Phenol Henry Constant

Combining the kinetic and solubility data permits the rate of reaction to be evaluated for known or assumed conditions of cloud liquid water content and partial pressures of reagent gases (Fig. 3). Here the left-hand ordinate gives the rate of aqueous-phase reaction. The right-hand ordinate gives the effective first-order rate coefficient of aqueous-phase reaction, referred to the gas-phase mixing ratio for indicated conditions, expressed in units of percent per hour. Note the strong pH...

D D Davis G Chen And M Chin

Simplified Sulfur Cycle

The focus of this chapter is that of providing the reader with an overview of atmospheric sulfur. It will address the issues of where sulfur comes from, how it is processed, and how it gets returned to the planetary surface. It will also endeavor to show how sulfur, during its atmospheric cycle, plays a significant role in helping to maintain a stable global environment. Sulfur is an element that is essential to life on this planet. Living organisms at nearly all levels of sophistication ingest...

References

Bhowmik, N., Physical effects A changed landscape, in The Great Flood of 993, Westview, Boulder, CO, 1996, pp. 101-131. Changnon, S. A., W. C. Ackermann, G. F. White, and L. Ivens, A Plan for Research on Floods and Their Mitigation in the United States, Contract Report 302, Illinois State Water Survey, Champaign, IL, 1983. Changnon, S. A., Losers and winners A summary of the flood's impacts, in The Great Flood of 1993, Westview, Boulder, CO, 1996a, pp. 276-299. Changnon, S. A., The lessons from...

Impacts Of Stratospheric Ozone Depletion

In 1928, Charles Kettering and Thomas Midgley, Jr., scientists with General Motor's Research Corporation in Dayton, Ohio, invented chlorofluorocarbons (CFCs) as a safe alternative to toxic and flammable refrigerants. In 1974, Mario Molina and F. Sherwood Rowland published a paper in Nature that linked the use of CFCs to destruction of Earth's stratospheric ozone layer. Today, the international community has made substantial progress toward phasing out the production and consumption of CFCs and...

Stochastic Forecasting Of Precipitation And Streamflow Processes

VAL D S, PAOLO BURLANDO, AND JOS D. SALAS Over the past two decades, considerable research has been carried out in hydrology on developing mathematical tools and approaches for short- and long-term precipitation and streamflow forecasting. The forecasts may be concerned with flood warning, flood control, water quality control, navigation, energy production, and irrigation. Hydrologie forecasting signifies estimating the time of occurrence and the magnitude of a hydrological event before...

Stochastic Simulation Of Precipitation And Streamflow Processes

RAMIREZ, PAOLO BURLANDO, AND ROGER A. PIELKE, Sr. Stochastic simulations of hydroclimatic processes such as precipitation and stream-flow have become standard tools for analyzing many water-related problems. Simulation signifies mimicking the behavior of the underlying process so that realistic representations of it can be made. For this purpose a number of empirical, mathematically physically based, mathematically stochastically based, analog physically based, and...

Atmospheric Observations

Atmospheric concentrations of methane have been measured systematically for nearly 20 years (Rasmussen and Khalil, 1981 Khalil and Rasmussen, 1983, 1990a Blake and Rowland, 1988 Steele et al., 1992 Khalil et al., 1993 Dlugokencky et al, 1994). There is an additional record from many independent measurements spanning another 15 years or so back to the early 1960s (Khalil et al., 1989). For earlier times, the ice core record is the only source of information. It extends back over 150,000 years,...

Changing Vulnerability in Central and Eastern Kenya

The failure of the first rains in 1984, following poor second rains in 1983, triggered a serious food crisis in central and eastern Kenya. The drought illustrates diverse impacts and responses in different environments. The study area comprises six districts in central and eastern Kenya Kiambu, Murang'a, Embu, Machakos, and Kitui, spanning five agroecological zones (Table 1) see Downing (1988) and Downing et al. (1989ft), for details . The highland zones (I and II) are suitable for coffee and...

Impacts to Government

Government entities at all levels from local to federal levels experienced severe impacts due to the flooding. Many government activities fell within the broad definition of responses, but many others were more impacts. In 1993, 532 counties were identified as federal disaster areas 11 counties in 1996 and in 1997, 79 counties were similarly declared. The federal government ultimately paid 6.2 billion for flood aid, insurance, and loans in 1993, and the total for 1997 is estimated at over 0.4...

Acid Rain And Deposition

The first mention of acid rain in print was by Robert Boyle in which he referred to nitrous or salino-sulphureous spirits in air in his 1692 book A General History of the Air. The Scottish chemist Robert Angus Smith began to study acid rain in Manchester, England, in 1852 and extended the work in England, Scotland, and Germany for 20 years. His 1872 book, Air and Rain The Beginnings of a Chemical Climatology, pointed out the link between sulfur pollution and acid rain. He warned that acid rain...

Efforts To Control Flooding 1851 To Present Levees and Warnings

Flood Dirt

Extensive floods in 1849 and 1850 (followed by an all-time record flood in 1858) led to action in Washington. Congress established the Delta Survey in 1851 to address the design and construction of works to control floods and to aid navigation on the Lower Mississippi River. The river's massive 1858 flood gave the survey team of army engineers a benchmark to work from. The Delta Survey team recommended a levee-only policy in 1861, a policy followed well into the twentieth century. The...

Stratospheretroposphere Exchange

Tropospherer Stratosphere Exchange Ozone

The exchange of mass between the stratosphere and troposphere is important to the chemistry of both regions as it brings chemical species with sources in the troposphere (such as CFCs) into the stratosphere, while species with stratospheric origin (such as ozone) can be brought into the troposphere. Thus, the transport can be important for driving the chemistry in both regions. Analogous to the boundary layer being isolated from the free troposphere because of the presence of a substantial...

Approaches for Determining Available Energy

A number of approaches using remote sensing have been developed for estimating the available energy components in Eq. (10). Generally, Rn is evaluated in terms of its four radiation components (Sellers et al., 1990), namely, Rn (l -i)Rs + sRld- saT h (11) where Rs is the incoming shortwave solar radiation (W m2), is the incoming longwave radiation (W m2), a is the surface shortwave albedo, ss is the surface Reflective Thermal Microwave Satellite Advanced Very High-Resolution Radiometer...

Kenneth E Pickering

In the early 1980s it was recognized that observed free tropospheric mixing ratios of some trace gases could not be explained simply by large-scale transport and eddy diffusion. Crutzen and Gidel (1983), Gidel (1983), and Chatfield and Crutzen (1984) hypothesized that convective clouds played an important role in rapid atmospheric vertical transport of trace species and tested parameterizations of convective transport in atmospheric chemical models. At nearly the same time evidence was shown of...

Introduction

Some trace gases and pollutants are readily removed from the atmosphere by becoming incorporated into cloudwater and then falling to Earth's surface in precipitation. In cloud-free air, small amounts of condensable species such as sulfates, ammonia, and nitrates coagulate with water vapor to form or nucleate extremely small atmospheric aerosol particles. Through gaseous diffusion and aerosol coagulation, smaller aerosols generally grow in size with time, while continuously maintaining an...

Evaluating The Spatial Distribution Of Evaporation

SUSAN MORAN, AND JOHN M. NORMAN Evaporation of water from soil and plant surfaces forms the connecting link between the energy balance and the water balance at Earth's surface. This phenomenon influences the large-scale circulation of the planetary atmosphere, affects soil moisture content that in turn affects hydrologie response, and regulates the microscale carbon dioxide uptake of stomata in individual plant leaves. The vast range of scales encompassed by the process of...

Mass Movement Events

A variety of mass movement events, while strictly not fluvial events, behave in a similar way to floods (Carson, 1976). The gravitationally fueled downhill movement of poorly consolidated regolith results from the introduction of meteoric water that adds weight and decreases hillslope cohesion. These events can do significant damage. Several types of mass movement events are composed of a larger percentage of sediments than a typical stream. Events such as mudflows, or lahars, commonly may...

Basin Characteristics

Surface characteristics influence infiltration and runoff rates (Roberts, 1989 Kuhnle et al., 1996). Impervious surfaces such as exposed bedrock or a paved road accelerate surface runoff, thus decreasing lag time between the precipitation event and entrance of water into a nearby channel. Urbanized areas, therefore, with large percentages of impervious surface such as roofs, streets, and parking lots coupled with an engineered drainage system designed to move water quickly to stream channels...

Integrated Ozone in Dobson Units

Figure 1 (see color insert) Climntological distribution of tropospheric ozone derived from satellite measurements between 1979 and 2000 (from Fishman et al, 2002). Units of contours and Dobson Units (DU). Regions greater than 40 DU have been shaded. See ftp site for color image. 4 TROPOSPHERfC OZONE TRENDS IN NONURBAN TROPOSPHERE 4 TROPOSPHERfC OZONE TRENDS IN NONURBAN TROPOSPHERE Figure 2 (a) (Upper left) monthly mean surface ozone at Barrow and the linear trend tor the entire data record....

Biomass Burning

Biomass fires are both natural and anthropogenic in origin. The natural trigger is lightning, which leads to mid- and high-latitude fires and episodes of smoke and pollution associated with them. Lightning is also prominent in tropical regions when the dry season gives way to the wet season and lightning in convective systems ignites dry vegetation. Atmospheric consequences of biomass fires are complex. When considering the impacts of fires for a given ecosystem, inputs of fires must be...

Stratospheric Ozone Observations

The accurate knowledge of the distributions of ozone (03) in the global atmosphere is important for several reasons. First, the amount of ozone in the atmosphere plays a significant role in determining the amount of biologically damaging ultraviolet (UV) radiation that can reach Earth's surface. Second, ozone both absorbs and emits radiation in the atmosphere this must be accounted for in atmospheric circulation models if they are to correctly represent the temperature and wind distributions in...

Airborne Snow Surveys by State 198098

National Operational Hydrologie Remote Sensing Center Figure 4 Number of airborne snow survey flight lines by state (1980-1998). National Operational Hydrologie Remote Sensing Center (NOHRSC). Figure 4 Number of airborne snow survey flight lines by state (1980-1998). National Operational Hydrologie Remote Sensing Center (NOHRSC). pack, thereby providing an opportunity to collect volume integrated data (e.g., SWE). Because of the difficulty of making field measurements in snow-covered...

Precipitation

Precipitation is the process by which liquid and solid-phase aqueous particles, such as rain, snow, sleet, and hail, fall from the atmosphere to Earth's surface. The occurrence of precipitation over land is typically cited as the driving force of the hydrologie cycle, since it triggers the commencement of other fluxes ( vapotranspiration, runoff, infiltration) by providing a new source of moisture to the system. The intensity and frequency of precipitation vary considerably both spatially and...

Acid Deposition

Polar Hydrology

An acid is essentially any subslance that releases hydrogen ions (H+) when dissolved in water. Several atmospheric trace constituents dissociate into positive and negative ions when dissolved in water, and some are acidic to varying degrees. The strongest acids in atmospheric waters are dissolved sulfuric acid (H2S04) and nitric acid (HN03). Numerous other acidic substances have been identified in the atmosphere, such as sulfur dioxide (S02), organic acids, hydrochloric acid (HCl), carbon...

What Is Enso

The El Ni o-Southern Oscillation (ENSO) is a coupled atmospheric-oceanic phenomenon that has global manifestations and recurs approximately every 2 to 10 years. The atmospheric component of ENSO is the Southern Oscillation, an interannual seesawing of sea-level atmospheric pressure anomalies between northern Australia (Darwin) and the southeast Pacific (near Tahiti). There is both a warm phase (El Ni o) and a cold phase (La Ni a). The warm phase involves an extensive warming of the upper ocean...

Net and Longline Fishermen

Net fishermen also fish for a range of finfish close to shore in small vessels (5 to 7 m), using gill nets that sometimes stretch over a kilometer in length. Once they have set their nets and are waiting for a couple hours to retrieve them, they will often fish with hook and line for bottom dwelling fish such as flounder (Paralychthys adspersus). Longline fishermen tend to use larger vessels (10 to 15 m in length with inboard diesel motors), targeting shark, mahi-mahi (Coriphaena hippurus), and...

Tropical Deforestation And Climate

Tropical forests cover a large portion of the globe's land surface running along the equator, roughly between the Tropic of Cancer and the Tropic of Capricorn. The largest expanse of tropical forest is found in the South American equatorial region, predominantly in the Amazon Basin, but extending up into Central America and down into northern Argentina. Large tropical forests are also found in the equatorial regions of Africa and West Africa and in Southeast Asia, running from India to...

Changing Approaches for Handling the Flood Hazard

National recognition emerged in the 1950s that the structural approach to flood control was inadequate (White, 1958). This led to the development of a new thrust based on floodplain management through altering land use in floodplains and use of flood insurance, or working with the river. The National Flood Insurance Program was established by Congress in 1968. Emerging environmental concerns in the 1960s led to the National Environmental Protection Act (NEPA) in 1968, bringing environmental...

Overview of Floods

The 1993 flood rated physically as the worst on the Upper Mississippi and Missouri Rivers, and the losses and costs of responding to the flood made it the most expensive flood on the Mississippi River system. Major losses included 52 dead, the highest since the floods of 1951, 56,000 homes damaged, 8.5 million farm acres either unplanted or unharvested, crop losses equating to 1.4 billion in corn and soybeans, and more than 1.9 billion losses to transportation systems including 920 million to...

Summary

Have the lessons taught by recent floods on the Mississippi River system been learned The new (1994) law relating to flood insurance has not changed coverage purchased in areas flooded in 1996 and 1997. Obviously, floodplain residents continue to rely, as in the past, on relief as their insurance against floods and other hazards. Changes in the crop insurance laws in 1994 have led to increased purchases with less reliance on relief payments for flooding. Participation by at-risk populations...

Acquisition and Relocation

The most effective measure to reduce losses is to keep the floodplains free of development. However, in many river valleys in the world, it is too late for that option. One of the most promising strategies for reducing flood losses is the public acquisition of developed land susceptible to flooding (Conrad, 1998 www.fema. gov mit homsups.htm). The authorization for U.S. federal cost sharing for relocation is more than 30 years old. However, only recently have communities, tired by chronic...

Physical and Biological Transformations Storage Diversions and Landscape Changes

Human-built structures can either increase or decrease hydrologic connectivity of freshwater systems, rates of water movement, and transport and movement of organisms, materials, and heat. Construction of dams and diversions and modification of watersheds have greatly altered the natural flow regimes in streams and rivers (see, e.g., Fig. 3). Many existing flow regimes, particularly in large rivers, reflect human demands for water rather than natural cycles (Naiman et al., 1995). Two of the...

Evapotranspiration

In general, remote-sensing techniques cannot measure evaporation or vapotranspiration directly. However, remote sensing does have two potentially very important roles in estimating vapotranspiration. First, remotely sensed measurements offer methods for extending point measurements or empirical relationships, such as the Thornthwaite (1948), Penman (1948), and Jensen and Haise (1963) methods, to much larger areas, including those areas where measured meteorological data may be sparse. Secondly,...

Flow Equation For An Unconfined Aquifer

In contrast to confined aquifers, an unconfined aquifer has a free surface (water table) boundary, a boundary at atmospheric pressure. Water released from storage occurs due to gravity drainage as the water table in the aquifer responds to pumping, drainage, or natural or artificial recharge. The unconfined flow problem is commonly analyzed using the Dupuit assumptions (1) uniform and horizontal flow within any vertical cross section, and (2) the velocity at the free surface may be expressed as...

Hydroxyl Radical Oh Processes Controlling OH Concentrations

A detailed and still fairly current discussion of OH chemistry in the troposphere is given by Logan et al. (1981). The primary source of OH is the photolysis of 03 to produce an excited state of atomic oxygen, O('D), which then reacts with water vapor 03 + hv -> 02 + O('D) 0('Z)) + M-* 0(3P) + M Here M is an inert molecule (N2 or 02). Only 1 of the 0( D) atoms produced by (Rl) react with H20 most are deactivated to the ground-state 0(3P) and recombine with 02 to return 03. Photolysis of 03 to...

Space Based Remote Sensing

The ozone profiling technique with the greatest heritage uses the BUV technique. By using several wavelengths shorter than those used for total column measurements, information on the ozone distribution in the middle and upper stratosphere can be obtained. This technique makes use of the fact that with decreasing wavelengths light is absorbed at higher altitudes in the atmosphere because of the corresponding increased absorption cross section (see Fig. 1). The vertical resolution of this...

Peruvian Fisheries Sector

In 1996, Peru was second to China in terms of the volume of fish landings and accounted for more than 10 of the world's catch. In 1997, this sector generated more than 2 of Peru's gross domestic product and consistently accounts for approximately 16 of all export products (second only to mining products). Bordered to the north by Ecuador and the south by Chile, the Peruvian coastline stretches 3100km (01 0l'48 and 18 2103 south latitude), and has a continental shelf of 87,200km2. Its stark...

Recharge and Downslope Flow in a Saturated Zone

In fully saturated soil the propagation of the effects of changes in the boundary conditions, such as those due to recharge, is much more rapid than in the unsaturated zone. In shallow subsurface systems, such as where a shallow soil overlays an impermeable rock bed, most of the downslope flow toward stream channels will take place in the saturated zone. Because of the more rapid dissipation of local pressure differences in the saturated zone, a description of flow processes based on Darcy's...

Kinematic Wave Model

The most simple type of distributed hydraulic routing model is the kinematic wave model. It is based on the following simplified form of the momentum equation (2) in which S0 is the bottom slope of the channel (waterway) and a component of the term, dh dx dy dx S0, in which dy dx is assumed to be zero. This assumes that the momentum of the unsteady flow is the same as that of steady, uniform flow described by the Manning equation or a similar expression in which discharge is a single-valued...

Field Research To Assess Linkages Between Human Activities And Drought

To help assess the linkages between human activities and drought in northwest Africa as well as the region's increasing vulnerability to drought, the authors organized an extensive field research project in Morocco during the early 1990s. A project team led by one of the authors (Bencherifa) intensively interviewed farmers about farming practices and drought-coping strategies. These interviews were conducted in three different regions of Morocco the Chaouia (a subhumid region), the northeast,...

Desertification

Desertification is commonly understood to mean the spread of desertlike conditions. The term came to international attention with the environmental devastation and loss of human and animal life accompanying extensive droughts in West Africa's Sahel region over the period 1968 to 1973, which were captured on televised documentary programs and in the print media. This media coverage likely played an important part in the subsequent extensive United Nations-sponsored international and national aid...

Human Judgments of Visual Air Quality

The previous section discussed methodologies for establishing the change in atmospheric particulate loading required to be noticeable either as a layered haze or as a change in scenic quality. It should be emphasized that calculations of detection thresholds and JNCs are statements about changes in information content in an image. JNC changes in the appearance of an image are not necessarily good indicators of judged image quality. For instance, a change in 10 JNCs in a scene with low overall...

Global Distribution Of Tropospheric Ozone

The distribution of tropospheric ozone can be determined from the analyses of satellite data sets obtained independently from two different instruments The Total Ozone Mapping Spectrometer (TOMS) and the Stratospheric Aerosol and Gas Experiment (SAGE). Between October 1978 and May 1993, TOMS functioned on the Nimbus 7 satellite and provided daily maps of the distribution of total ozone. Additional TOMS were launched in 1991 (on the Russian Meteor satellite) and two in 1996 (see Chapter 21...

Biophysical Dimensions Of Drought In South Africa

Hydrology Africa

Several factors interact to produce the climate and weather of South Africa (for good overviews see Tyson, 1986 Mason and Jury, 1997 Lindesay, 1998 Tyson and Preston-Whyte, 2000). The physical location of the country in the subtropics shapes climate and weather (Fig. 1). The local orography and landscape features of the country (most of the country is situated on a plateau approximately 1500 m above mean sea level) and sea surface temperatures (SSTs) of the cooler Atlantic and warmer Indian...

Observational Techniques

Their rates of exchange with the overlying atmosphere. There are many ways to measure fluxes in the PBL. However, the two most widely used platforms are (l) tower measurements in the surface layer and (2) airplane measurements in the mixed layer. There are, of course, other platforms that are used. For example, in the marine surface layer, ship-mounted instruments are used and in the mixed layer tethered balloons and neutrally buoyant airships have been used. The most direct and fundamental...

Atmospheric Chemistry Within Global Carbon Cycle

Despite its dominance as a member of the global carbon cycle, carbon dioxide does not play any significant role in atmospheric chemistry. The most abundant carbon species that is an active player in atmospheric chemistry is methane (CH4), which reacts in the troposphere with the hydroxyl radical (OH) to initiate a series of reactions that were shown to play important roles in the global cycles of a number of atmospheric trace species. The seminal work in tropospheric chemistry was published by...

Global Mean OH Concentration

The short lifetime of OH implies that its concentration is highly variable. Deriving the atmospheric lifetimes of gases removed by oxidation by OH requires an estimate of OH concentrations averaged appropriately over time and space. Mass-balance arguments for proxy species with known sources can assist for this purpose. The most successful application, first proposed by Singh (1977) and Lovelock (1977), has been the use of the industrial solvent CH3CC13 to estimate the global mean OH...

Tropospheric Distribution Of Reactive Nitrogen

Knowledge concerning the tropospheric distribution of NO, is critical given its importance to ozone photochemistry. Over much of the remote atmosphere, NO concentrations hover near the critical level necessary for net photochemical produc tion of ozone. This critical NO level varies from as low as about 5 pptv to near 20 pptv depending on ambient conditions (Crawford et al, 1997). As a general rule, observations have shown NO to typically fall below critical levels over remote marine boundary...

Biogenic Nonmethane Hydrocarbons

Nonmethane volatile organic compounds (NMVOCs) are emitted from a wide variety of both anthropogenic and biogenic sources. Major anthropogenic sources of NMVOCs include combustion of fossil fuels, solvent evaporation and biomass burning, while direct emissions from plants are the largest biogenic source. Over 90 of the total NMVOCs entering the atmosphere are biogenic (Guenther et al., 1995 Miiller, 1992). Recent estimates of the upper limit of global NMVOC emissions from biogenic sources range...

General Features Of Photochemical Smog Diurnal and Seasonal Cycle

Diurnal Ozone Concentraties Cities

Ozone and other secondary reaction products show a pronounced diurnal cycle with peak concentrations typically occurring in late afternoon. The diurnal cycle of 03 shows a sharp contrast with the diurnal cycle of primary species, including NOx, HC, and CO (see Fig. 1). The primary species typically have peak concentrations in early morning and much lower concentrations during the daytime as concentrations are diluted through the process convection-driven vertical mixing. Because production of...

Keeping A Broad Basis Of Assessment And Action

To review, acid deposition is an end product of a complex series of interactions among atmospheric chemical species emitted by both natural and human sources. For policy assessment purposes, the most important groups of chemical species are compounds containing sulfur and nitrogen compounds that are emitted from factories, power plants, and automobiles based on fossil-fuel combustion. In addition, volatile organic carbon compounds and fine particles play a role in modulating chemical processes...

Tropospheric Chemistry A Complex Interaction Of Biogeochemical Cycles

Somewhat analogous to the chemical cycles just described for the stratosphere, atmospheric chemistry in the troposphere can also be viewed as a complex interaction of chemical cycles. These cycles, however, involve direct interaction with the biosphere and are also greatly complicated by the presence of the more complicated meteorology found only in the lower atmosphere. The biosphere serves as the exclusive source of carbon, and the carbon cycle, in turn, has important linkages that transcend...

Overview Atmospheric Chemistry

The study of atmospheric chemistry focuses on how chemical constituents cycle through the atmosphere. Excluding water vapor (which can account for as much as 2 to 3 of the volume of the atmosphere under extremely moist conditions), more than 99.9 of the remaining dry atmosphere is comprised of nitrogen (78.1 ), oxygen, (20.9 ), and argon (0.93 ). Unlike the study of conventional meteorology, where the atmosphere is generally treated as a bulk medium, atmospheric chemistry focuses on each...

Methodology For Impact Assessment Of Climate Change Scenarios

Unlike assessments of current and historical events, impact assessment of projected climate change is based on scenarios, or plausible pictures of the future. This kind of research can include analysis of past observed events (e.g., the Dust Bowl in the United States during the 1930s), which could serve as societal analogs of a future warm climate (Glantz, 1988), or as climate change analogs superimposed on twenty-first-century society (Rosenberg, 1993), but there are also many studies at...

Hurricanes In North American History

The word hurricane derives from the Spanish hurac n, itself derived from the dialects of indigenous peoples of the Caribbean and Latin America (Dunn and Miller, 1964). 'Hunraken' was the name of the Mayan storm god, and 'Huraken' was the god of thunder and lightning for the Quiche of southern Guatemala (Henry et al., 1994). The Tainos and Caribe tribes of the Caribbean called their God of Evil by the name Huracan. Other indigenous dialects included words such as aracan, urican, and hurivanvucan...

Nonurban Continental Aerosol

Nonurban continental aerosol is often acidic as a result of anthropogenic sulfate or nitrate. Typical aerosol number concentrations of nonurban continental aerosol are in the range of 103 cm3, with mass concentrations around 30 pg m3 (Anderson et al., 1993). The aerosol mass distribution usually exhibits a trimodal structure similar to that of urban aerosol. Figure 2 shows approximate atmospheric aerosol number concentration N and volume concentration V as a function of altitude z. Because of...

Particle Size Distribution

Size is the most important single characteristic of an aerosol particle. For a spherical particle, diameter (or radius) is the usual reported dimension. When a particle is not spherical, the size can be reported either in terms of a length scale characteristic of its silhouette or of a hypothetical sphere with equivalent dynamic properties, such as settling velocity in air. For example, the aerodynamic diameter of a particle represents the diameter of a unit density (pp 1 g cm3) sphere having...

Hydrologic Modeling For Runoff Forecasting

The problem of forecasting streamflow levels given precipitation data has received the time and attention of a great many hydrologists. Models developed for this purpose have ranged from simple to extremely complex. The simplest ones are based on input-output regression-type relationships, while the most complex ones attempt to represent the detailed water and energy balance physics occurring in the watershed. The complex models are motivated largely by experimental evidence that the...

Ck T7 Tytk yy y m i

Where N is the sample size and k is the time lag. The plot of rk versus k, i.e., the correlogram, may give an idea of the degree of persistence of the underlying time series, and it may be useful for choosing the type of stochastic model that may represent the series. When the correlogram decays rapidly to zero after a few lags, it may be an indication of small persistence or short memory in the series, while a slow decay of the correlogram is an indication of large persistence or long memory....

Carbon Monoxide In The Atmosphere

Carbon monoxide (CO) is present in trace quantities in the atmosphere. Although first detected in the late 1940s using solar spectroscopic methods,1'2 few measurements of CO were made during the period between the early 1950s and the mid-1960s. However, as chromatographic and related detection techniques were developed, discrete measurements of CO were made in many locations around the world. These provided considerable insight on global tropospheric distributions most notable among these was...

Old and New Water Contributions to Storm Runoff

There have been many studies in the last 30 years that have made use of the natural geochemical characteristics of runoff to give at least an approximate separation of the storm hydrograph into a contribution from the rainstorm itself (the new water) and water stored in the catchment prior to the event (old water) (see, e.g., Sklash, 1990). Most such studies have used a two-component separation (into old and new water), which requires the assumptions that the geochemical characteristics of the...

DAVldx dAldt

And the conservation of momentum equation dV dt + V dV dx + g(dh dx + Sf) 0 (2) in which t is time, x is distance along the longitudinal axis of the waterway, A is cross-sectional area, V is velocity, g is the gravity acceleration constant, and h is the water-surface elevation above a datum Sf is the friction slope, which may now be Handbook of Weather, Climate, and Water Atmospheric Chemistry, Hydrology, and Societal Impacts, Edited by Thomas D. Potter and Bradley R. Colman. ISBN 0-471-21489-2...

Levee Overtopping Floodplain Interactions

Flows that overtop levees located along either or both sides of a main-stem river and or its tributaries can be treated as lateral flow (q) in Eqs. (29) and (30) where the lateral flow diverted over the levee is computed as broad-crested weir flow. This overtopping flow is corrected for submergence effects if the floodplain water-surface elevation sufficiently exceeds the levee crest elevation. After the flood peak passes, the overtopping flow may reverse its direction when the floodplain...

Generation Of Surface Runoff Infiltration Excess Surface Runoff Generation

The classical model of surface runoff generation is by an infiltration excess mechanism in which rainfall intensity exceeds the local infiltration capacity of the soil for a sufficient period of time for any depression storage at the soil surface to be satisfied such that downslope flow is initiated. This will not occur where the permeability of the soil is high in comparison with expected rainfall intensities, and even when this is not the case there may be an initial period when all the...

Introduction Understanding Societal Responses To Extreme Weather Events

In the 1970s, many decision makers became increasingly interested in climate because of numerous weather-related impacts around the world. Events that helped to stimulate this interest included the failed Peruvian anchovy harvest in 1972 and 1973, the 1968 to 1973 drought in the African Sahel, a severe winter freeze in 1972 in the Soviet Union, and in 1974 floods, drought, and early frost in the U.S. Midwest. In 1977, winter in the eastern United States was the coldest ever recorded and summer...

Infiltration Measurement

Infiltration rates can be measured at a point using a variety of methods described here, each appropriate for certain conditions. However, because of the large temporal and spatial variability of infiltration processes, catchment average infiltration rates may be desired, which can be obtained through the water balance analysis of rainfall-runoff observations.31 Ring Infiltrometer. This simple method is most appropriate for flood irrigation or pond seepage infiltration. A cylindrical metal ring...

Global Tropospheric Ozone Budget

The components of the global tropospheric ozone budget can be broken into four general categories transport from the stratosphere, destruction at Earth's surface, photochemical destruction, and in situ photochemical production. The primary mechanism by which ozone is transported from the stratosphere into the troposphere is through meteorological events referred to as stratospheric intrusions. These events occur in conjunction with the movement of air associated with rapid changes in the...

Stratospheric Chemistry Understanding The Ozone Layer

Stratospheric Chemistry

Ozone was discovered in 1839 by the German scientist Christian Frederich Schonbein at the University of Basel in Switzerland. Because of its pungent odor, its name was taken from the Greek word ozein, meaning odor. Schonbein's research, subsequent to his discovery, focused on verifying his hypothesis that ozone was a natural trace constituent of the atmosphere. As a result of interest in the late nineteenth century, there are a surprisingly large number of ambient measurements during that time....

Stratospheretroposphere Chemical And Climate Interaction

Although it is convenient to describe the chemistry of the stratosphere and the chemistry of the troposphere separately, both chemical and meteorological processes in one domain play an important role on the chemistry in the other. As previously Figure 8 Contributions of various trace gases to global warming. Top graph shows the calculations using a model that does not include contributions from tropospheric ozone increases or from feedback relating to photochemical processes bottom chart shows...

Mechanically Generated Aerosols

Particles produced by mechanical processes tend to be larger than those resulting from gas-to-particle conversion. In general particles larger than a micrometer are mechanically formed by processes such as the wind erosion of soils, the bursting of bubbles in seawater, the shedding of plant fragments, etc. Although the relationship between the size of an aerosol particle and length of time it remains suspended in the atmosphere is complex, larger particles generally fall out of suspension more...

Sources Of Acidity

Atmospheric acids mainly are produced in the air as a result of complex chemical reactions of the acid precursor gases. Direct emissions of acids such as sulfuric acid, hydrogen chloride, and hydrogen fluoride have been estimated but are not thought to play a significant role in the acidic deposition processes (NAPAP, 1991). Sources of the harmful chemical precursors affecting the acidity of deposited materials can be natural or human caused. The three pollutants of most concern in the acidic...

Current Conditions

As of the completion of the first report to Congress, several observations have been made regarding the success of Title IV It appears that the market-based approach has lowered compliance costs. Costs are lower than expected, probably due to a number of factors such as railroad deregulation, technological innovation, and lower operating costs for scrubbers. In addition, all affected utilities have fulfilled the compliance requirements of Title IV In the first annual reconciliation of...

Global Carbon Cycle

Climat Change Antropogenic Input

Measurements of the concentration of air trapped in Antarctic ice cores indicate that over the last 200,000 years, atmospheric concentrations of C02 have fluctuated between 200 and 280ppmv, until the last century. Data for the period ad 1000 and 1800 indicate that the concentration was quite stable, averaging 280ppmv and varying over that period by only about 10 ppmv, indicating that the C02 cycle was in equilibrium in the centuries prior to the industrial revolution. Over the past 200 years,...

Atmospheric Chemistry And Global Warming

The links of trace gas chemistry to climate change extend beyond the observed increase in C02 concentrations. Increases in CH4, tropospheric 03, and anthropo-genically produced concentrations of the chlorofluorocarbons (CFCs) also contribute to global warming (see Fig. 8). If only the direct radiative effects of the trace gas increases are considered, 62 of the increase would be due to C02, 20 to CH4,4 to N20, and 14 to the CFCs. If chemical feedbacks are considered, the global warming due to...

Sources Of Reactive Nitrogen

Unlike most trace species that are emitted only at the surface, NO, sources exist both at the surface and in the free troposphere. Surface sources include both natural and anthropogenic sources e.g., soil microbial emission, fossil fuel combustion, and biomass burning. In the free troposphere, NO, sources include lightning, aircraft emissions, and stratosphere-troposphere exchange. Table 1 gives estimated source strengths and uncertainties for each of these sources. While there are still...

Satellite Measurements

Global distributions of CO in the middle troposphere have been determined by the Measurement of Air Pollution from Satellite (MAPS) instrument. MAPS uses a nadir viewing gas filter correlation radiometry with a maximum signal between 400 and 300mbar and has been flown aboard the U.S. space shuttle four times between 1981 and 1994. Results obtained in October 1984 and 1994 show very high levels of CO over the southern tropics,25'34 evidence of the strong effect the transport of emissions from...

Sources And Sinks

Usually the global emission rate from a source is estimated by using a measured emission factor (grams of CH4 emitted day unit source) and multiplying it by the number of such units in the world (units of source) and the time of year when emissions take place (days year), which results in the grams of CH4 year emitted by the source. The complexity of the estimate varies depending on the information available. Once the budget is assembled, it must comply with the constraints discussed earlier....

Aerosols from Biomass Burning

The burning of living and dead vegetation (biomass burning) is widespread over Earth, and this is a globally significant source for aerosols and for a variety of radiatively active and chemically reactive trace gases. Most of the biomass burned is caused by human activities as opposed to natural fires, and this mainly occurs in the tropics, involving savannas more than forests (Hao and Liu, 1994). Some burning sources are persistent, but emissions from savanna burning vary biennially because...

Other Pollution Derived Aerosols

Aerosols, both primary and secondary, are generated by a variety of pollution sources in addition to biomass burning these include industrial processes, electric utilities, transportation, construction, and other fuel combustion. While large-scale urban air pollution is a consequence of modern industrial and technological development, smoke produced by indoor fires was perhaps the earliest form of air pollution (Brimblecombe, 1995). It is remarkable that the emissions from many anthropogenic...

Cloud Physical Properties Pertinent To Cloud Chemistry

Clouds consist of a suspension of liquid or solid (ice) particles in air. Thus, formally, a cloud is an aerosol, a suspension of particles in air. However, it is useful to distinguish clouds from clear-air (noncloud) aerosols. The cloud environment is slightly supersaturated with respect to liquid water or ice, respectively. The typical amount of condensed-phase water is 0.1 to 1 g m3 (roughly equivalent to 0.1 to 1 kg This chapter has been co-authored under Contract No. DE-AC02-98CH10886 with...

Introduction Defining Runoff

Runoff Generation Process

There are a number of different definitions of runoff that have been used either explicitly or implicitly in hydrological analyses over the years. In what follows we will use a working definition that runoff is that part of the rainfall falling on a catchment area that eventually leaves the catchment as a surface streamflow, whatever the flow pathway that the water has followed on its way to the stream channel. Thus this definition includes both surface and subsurface runoff pathways. Dunne...

Global Co Distributions Surface CO

Background Atmosphere, CO varies both temporally and spatially. Figure I presents a smoothed representation of the surface distribution of CO in the background marine boundary layer (MBLI as a function of latitude and time. The surface illustrates that CO mixing ratios in both hemispheres exhibit seasonal variation, and Figure 1 Smooth surface representing she distribution of CO in the marine boundary layer. The surface was created from 38 time series determined from sampling locations in the...

Residence Times Of Particles In The Troposphere

Particles are eventually removed from the atmosphere by two mechanisms deposition at Earth's surface, so-called dry deposition, and scavenging by droplets, so-called wet deposition (Seinfeld and Pandis, 1998). Because wet and dry deposition lead to relatively short residence times in the troposphere and because the geographical distribution of particle sources is highly nonuniform, tropospheric aerosols vary widely in concentration and composition over Earth. Whereas atmospheric trace gases...

Parameter Estimation Parameter Identification

The accuracy of model prediction depends on the reliability of the estimated model parameters as well as on the accuracy of the prescribed initial and boundary conditions. In general, parameters used in deriving the governing equations are not directly measurable from the physical point of view. In practice, model parameters are required to be estimated from historical input-output observations using an inverse procedure of parameter estimation. The inverse problem of parameter estimation in...

Importance Of Runoff In Gridscale Land Surface Modeling For Gcms

In all past general circulation model (GCM) land surface model components, runoff has not been considered to be very important. It has generally been treated simply as an excess of water that magically disappears from the local water balance. In real catchments, of course, runoff does not disappear but may have an effect on the hydrology and energy balance of areas downslope or downstream. Far more effort, computer time, and parameters have been devoted to formulating the controls on the local...

Water And Energy Balance Models

In recent work, Dubayah and Lettenmaier (1997) have attempted to maximize the use of remote-sensing data as drivers for a large-scale coupled water and energy balance model. They used the V1C-3L model (Liang et al., 1994) applied to the Arkansas-Red River basins in the Southern Great Plains in the United States. There were two objectives to this research (1) to develop and test a land surface hydrologic model capable of using remote-sensing data and (2) to develop and test algorithms for...

Climate Change Hypothesis

Today, most Russian scientists believe that climatic factors are the real cause of the Caspian Sea level rise. Studies by Golitsyn (1989) and Golitsyn and McBean (1992) indicate that recent changes of the Caspian Sea level are 90 associated with corresponding changes in the water balance components of the sea, as opposed to possible tectonic activity. The volume of inflow from rivers to the sea increased sharply after 1978. During certain years (e.g., 1979, 1985, and 1990), more than 350 km3 of...

Definition Of Floods

Streams are linear water features that flow under the impetus of gravity. The amqunt of water contained in a stream is usually regulated by contributions of groundwater and surface runoff to the stream channel (Zaslavsky and Sinai, 1981 Knighton, 1998). Much of the time water in a stream flows within the confines of its channel. When inputs of water increase sufficiently, stream discharge leaves the stream channel and covers all or parts of the adjacent floodplain. Since the floodplain surface...

Parameter Adjustment Procedure

The parameter adjustment procedure is a directed trial-and-error process by which the parameters are iteratively adjusted to move the model behavior closer to the observed data. The choice of procedure is related to the measure of closeness selected (see above). If the calibration is performed by an expert hydrologist having a great deal of familiarity with the nuances of the model, the method of manual parameter adjustment guided by visual comparison can be extremely effective. However, manual...

Parameterization

The number of observations is finite and limited, whereas the spatial domain is continuous. For an inhomogeneous aquifer, the dimension of, for example, the transmissivity is theoretically infinite. In practice, the infinite parameter dimension must be reduced to a finite dimensional form. The reduction of the number of parameters from the infinite dimension to a finite dimensional form is called parameterization (Yeh and Yoon, 1976, 1981 Yeh, 1986 Sun, 1994a). Parameterization can be achieved...

Parameter Uncertainty Parameter Structure And Optimum Parameter Dimension

Parameter identification in a distributed-parameter system should, in principle, include the determination of both the parameter structure and its value. If zonation is used to parameterize the unknown parameters, the zonation pattern (parameter structure) is represented by the number and shape of zones. On the other hand, if the finite-element method is used for parameterization, parameter structure is represented by the number and location of nodal values of parameters. Identifying parameter...