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NASA NTRS1980

NASA Global Atmospheric Sampling Program (GASP) data report for tape VL0014

The data currently available from GASP, including flight routes and dates, instrumentation, data processing procedures, and data tape specifications are described. Measurements of atmospheric ozone, cabin ozine, carbon monoxide, water vapor, particles, clouds, condensation nuclei, filter samples and related meteorological and flight information obtained during 562 flights of aircraft N533PA, N4711U, N655PA, and VH-EBE from October 3, 1977 through January 5, 1978 are reported. Data representing tropopause pressures obtained from time and space interpolation of National Meteorological Center archived data for the dates of the flights are included.

Briehl, D.↗

NASA NTRS1981

NASA Global Atmospheric Sampling Program (GASP) data report for tape VL0015, VL0016, VL0017, VL0018, VL0019, and VL0020

This is the twelfth of a series of reports which describes the data currently available from GASP, including flight routes and dates, instrumentation, data processing procedures, and data tape specifications. In-situ measurements of atmospheric ozone, cabin ozone, carbon monoxide, water vapor, particles, clouds, condensation nuclei, filter samples and related meteorological and flight information obtained during 1732 flights of aircraft N533PA, N4711U, N655PA, and VH-EBE from January 5, 1978 through October 9, 1978 are reported. These data are now available from the National Climatic Center, Asheville, NC, 22801. In addition to the GASP data, tropopause pressures obtained from time ans space interpolation of National Meteorological Center archived data for the dates of the flights are included.

Papthakos, L. C.↗

NASA NTRS1981

Stratospheric CCN sampling program

When Mt. St. Helens produced several major eruptions in the late spring of 1980, there was a strong interest in the characterization of the cloud condensation nuclei (CCN) activity of the material that was injected into the troposphere and stratosphere. The scientific value of CCN measurements is two fold: CCN counts may be directly applied to calculations of the interaction of the aerosol (enlargement) at atmospherically-realistic relative humidities or supersaturations; and if the chemical constituency of the aerosol can be assumed, the number-versus-critical supersaturation spectrum may be converted into a dry aerosol size spectrum covering a size region not readily measured by other methods. The sampling method is described along with the instrumentation used in the experiments.

Rogers, C. F.↗

NASA NTRS1981

An airborne isothermal haze chamber

Thermal gradient diffusion cloud chambers (TGDCC) are used to determine the concentrations of cloud condensation nuclei (CCN) with critical supersaturations greater than or equal to about 0.2%. The CCN concentrations measured with the airborne IHC were lower than theoretically predicted by factors ranging between 7.9 and 9.0. The CCN concentrations measured with the airborne IHC were lower than the concentrations measured with the larger laboratory IHC's by factors ranging between 3.9 and 7.5. The bounds of the supersaturation ranges of the airborne IHC and the CSU-Mee TGDCC do not overlap. Nevertheless, the slopes of the interpolated data between the bounds agree favorably with the theoretical slopes.

Hindman, E. E.↗

NASA NTRS1981

Simultaneous operation of three CCN counters and an isothermal haze chamber at the 1980 International CCN Workshop

Four devices were operated for the detection and characterization of cloud condensation nuclei (CCN) and fog condensation nuclei (FCN). In chronological order of development, the CCN devices are the conventional continuous-flow diffusion chamber (CFD), the rapid-cycle CCN spectrometer, and the instantaneous CCN spectrometer. The FCN detection device is an isothermal haze chamber (IHC). These four instruments are discussed and general comments on their performance at the workshop are given.

Hudson, J. G.↗

NASA NTRS1981

Review of isothermal haze chamber performance

The theory of this method of characterizing cloud condensation nuclei (CCN) over the critical supersaturation range of about 0.01% to 0.2% was reviewed, and guidelines for the design and operation of IHC's are given. IHC data are presented and critically analyzed. Two of the four IHC's agree to about 40% over the entire range of critical. a third chamber shows similar agreement with the first two over the lower part of the critical supersaturation range but only a factor of two agreement at higher supersaturation. Some reasons for the discrepancies are given.

Fitzgerald, J. W.↗

NASA NTRS1982

Study to perform preliminary experiments to evaluate particle generation and characterization techniques for zero-gravity cloud physics experiments

Methods of particle generation and characterization with regard to their applicability for experiments requiring cloud condensation nuclei (CCN) of specified properties were investigated. Since aerosol characterization is a prerequisite to assessing performance of particle generation equipment, techniques for characterizing aerosol were evaluated. Aerosol generation is discussed, and atomizer and photolytic generators including preparation of hydrosols (used with atomizers) and the evaluation of a flight version of an atomizer are studied.

Katz, U.↗

NASA NTRS1982

Stratospheric CCN sampling program

Two one liter grab samples of stratospheric aerosol were returned from each of six U-2 sampling missions. Cloud condensation nuclei (CCN) spectra from each sample were obtained. Interest was centered on the effects of volcanic activity. Spurious particle generation was found to be a serious problem in container 9 LFT and a much smaller problem in container 9 RT. Initial studies of an option for improved sample containers and values were completed. A CCN spectrometer, able to operate at an internal pressure of 300 mb, was designed.

Rogers, C. F.↗

NASA NTRS1980

Ground cloud related weather modification effects

The principal concerns about inadvertent weather modification by the solar power satellite system rocket effluents are discussed, namely the possibility that the ground cloud might temporarily modify local weather and the cumulative effects of nearly 500 launches per year. These issues are discussed through the consideration of (1) the possible alteration of the microphysical processes of clouds in the general area due to rocket effluents and debris and cooling water entrained during the launch and (2) the direct dynamical and thermodynamical responses to the inputs of thermal energy and moisture from the rocket exhaust for given ambient meteorological conditions. The huge amount of thermal energy contained in the exhaust of the proposed launch vehicle would in some situations induce a saturated, wet convective cloud or enhance an existing convective activity. Nevertheless, the effects would be limited to the general area of the launch site. The observed long lasting high concentrations of cloud condensation nuclei produced during and after a rocket launch may appreciably affect the frequency of occurrence and persistence of fogs and haze. In view of the high mission frequency proposed for the vehicle launches, a potential exists for a cumulative effect.

Lee, J.↗

NASA NTRS1989

Cirrus crystal nucleation by homogeneous freezing of solution droplets

A numerical model consisting of a system of differential equations is used to study cirrus crystal nucleation in a rising parcel containing a distribution of cloud condensation nuclei. The evolution of the particle population and the thermodynamic variables in the parcel are examined. The results suggest that, if homogeneous freezing is not considered, liquid water should be detected below -40 C. If homogeneous freezing is considered, the rapid growth of ice crystals and vapor depletion prevent water saturation from being reached. It is shown that the likelihood of a droplet being frozen is increased by lower temperatures, larger droplet diameter, or lower solution density.

Heymsfield, Andrew J.↗

NASA NTRS1991

Plume and wake dynamics, mixing, and chemistry behind an HSCT aircraft

The chemical evolution and mixing and vortical motion of a High Speed Civil Transport's engine exhausts must be analyzed in order to track the gas and its speciation as emissions are mixed to atmospheric scales. Attention is presently given to an analytic model of the wake dynamical processes which accounts for the roll-up of the trailing vorticity, its breakup due to the Crow instability, and the subsequent evolution and motion of the reconnected vorticity. The concentrated vorticity is noted to wrap up the buoyant exhaust and suppress its continued mixing and dilution. The species tracked encompass those which could be heterogeneously reactive on the surfaces of the condensed ice particles, and those capable of reacting with exhaust soot particle surfaces to form active contrail and/or cloud condensation nuclei.

Miake-Lye, R. C.↗

NASA NTRS1991

Global biomass burning - Atmospheric, climatic, and biospheric implications

The present volume discusses the biomass burning (BMB) studies of the International Global Atmospheric Chemistry project, GEO satellite estimation of Amazonian BMB, remote sensing of BMB in West Africa with NOAA-AVHRR, an orbital view of the great Chinese fire of 1987, BMB's role in tropical rainforest reduction, CO and O3 measurements of BMB in the Amazon, effects of vegetation burning on the atmospheric chemistry of the Venezuelan savanna, an assessment of annually-burned biomass in Africa, and light hydrocarbon emissions from African savanna burnings. Also discussed are BMB in India, trace gas and particulate emissions from BMB in temperate ecosystems, ammonia and nitric acid emissions from wetlands and boreal forest fires, combustion emissions and satellite imagery of BMB, BMB in the perspective of the global carbon cycle, modeling trace-gas emissions from BMB, NO(x) emissions from BMB, and cloud-condensation nuclei from BMB.

Levine, Joel S.↗

NASA NTRS1993

Review of recent research on the climatic effect of aerosols

A review of recent research on the climatic effects of aerosols is presented. A representative aerosol and climate models were used to study the generation, growth transport, and removal of aerosols. The structure of the radiative-convective models and general circulation models used is described. Large-scale temperature effects, effects on clouds, and local urban effects of trophospheric aerosols are examined. The effects of volcanic eruptions and stratospheric aerosols are also considered. Results indicate that solar radiation backscatter by aerosols increases the planetary albedo. Solar radiation absorption may offset cooling caused by aerosol backscatter but the absorption and emission of terrestrial radiation by aerosols produces a warming effect. It appears that the role of aerosols as cloud condensation nuclei is probably the most significant cause of the radiative effects observed.

Charlock, Thomas P.↗

NASA NTRS1992

Gas exchange in wetlands: Controls and remote sensing

This project was directed toward the quantification of fluxes of gaseous biogenic sulfur compounds from freshwater wetlands. These compounds (primarily hydrogen sulfide (H2S), dimethyl sulfide (DMS), and carbonyl sulfide (OCS)) have been implicated in the regulation of planetary albedo by the formation of microscopic atmospheric aerosols when they oxidize, and the further role of these aerosols as cloud condensation nuclei (CCN). The role of continental sources and sinks for these compounds is poorly understood. The present study was undertaken to quantify the source and sink strength of high latitude wetlands, and to delineate factors that regulate this flux.

Hines, Mark E.↗

NASA NTRS1997

Anthropogenic Sulfate, Clouds, and Climate Forcing

This research work is a joint effort between research groups at the Battelle Pacific Northwest Laboratory, Virginia Tech University, Georgia Institute of Technology, Brookhaven National Laboratory, and Texas A&M University. It has been jointly sponsored by the National Aeronautics and Space Administration, the U.S. Department of Energy, and the U.S. Environmental Protection Agency. In this research, a detailed tropospheric aerosol-chemistry model that predicts oxidant concentrations as well as concentrations of sulfur dioxide and sulfate aerosols has been coupled to a general circulation model that distinguishes between cloud water mass and cloud droplet number. The coupled model system has been first validated and then used to estimate the radiative impact of anthropogenic sulfur emissions. Both the direct radiative impact of the aerosols and their indirect impact through their influence on cloud droplet number are represented by distinguishing between sulfuric acid vapor and fresh and aged sulfate aerosols, and by parameterizing cloud droplet nucleation in terms of vertical velocity and the number concentration of aged sulfur aerosols. Natural sulfate aerosols, dust, and carbonaceous and nitrate aerosols and their influence on the radiative impact of anthropogenic sulfate aerosols, through competition as cloud condensation nuclei, will also be simulated. Parallel simulations with and without anthropogenic sulfur emissions are performed for a global domain. The objectives of the research are: To couple a state-of-the-art tropospheric aerosol-chemistry model with a global climate model. To use field and satellite measurements to evaluate the treatment of tropospheric chemistry and aerosol physics in the coupled model. To use the coupled model to simulate the radiative (and ultimately climatic) impacts of anthropogenic sulfur emissions.

Ghan, Steven J.↗

NASA NTRS2003

The MODIS Aerosol Algorithm, Products and Validation

The MODerate resolution Imaging Spectroradiometer (MODIS) aboard both NASA's Terra and Aqua satellites is making near global daily observations of the earth in a wide spectral range. These measurements are used to derive spectral aerosol optical thickness and aerosol size parameters over both land and ocean. The aerosol products available over land include aerosol optical thickness at three visible wavelengths, a measure of the fraction of aerosol optical thickness attributed to the fine mode and several derived parameters including reflected spectral solar flux at top of atmosphere. Over ocean, the aerosol optical thickness is provided in seven wavelengths from 0.47 microns to 2.13 microns. In addition, quantitative aerosol size information includes effective radius of the aerosol and quantitative fraction of optical thickness attributed to the fine mode. Spectral aerosol flux, mass concentration and number of cloud condensation nuclei round out the list of available aerosol products over the ocean. The spectral optical thickness and effective radius of the aerosol over the ocean are validated by comparison with two years of AERONET data gleaned from 133 AERONET stations. 8000 MODIS aerosol retrievals colocated with AERONET measurements confirm that one-standard deviation of MODIS optical thickness retrievals fall within the predicted uncertainty of delta tauapproximately equal to plus or minus 0.03 plus or minus 0.05 tau over ocean and delta tay equal to plus or minus 0.05 plus or minus 0.15 tau over land. 271 MODIS aerosol retrievals co-located with AERONET inversions at island and coastal sites suggest that one-standard deviation of MODIS effective radius retrievals falls within delta r_eff approximately equal to 0.11 microns. The accuracy of the MODIS retrievals suggests that the product can be used to help narrow the uncertainties associated with aerosol radiative forcing of global climate.

Remer, L. A.↗

NASA NTRS2002

A Downscaling Analysis of the Urban Influence on Rainfall: TRMM Satellite Component AMS Conference on Satellite Meteorology and Oceanography

A recent publication by Shepherd et al. (2002) demonstrated the feasibility of using TRMM precipitation radar (PR) estimates to identify precipitation anomalies caused by urbanization. The approach is particularly useful for investigating this global process because TRMM data span large portions of the globe and comprise an extended temporal dataset. Recent literature suggests that urbanized regions of Houston, Texas may be influencing lightning and precipitation formation over and downwind of the city. Possible mechanisms include: (1) enhanced convergence through interactions between the sea breeze, Galveston bay breeze, and urban heat island circulations, (2) enhanced convergence due to increased surface roughness over the city and/or destabilization of the boundary layer by the UHI, or (3) enhanced cloud condensation nuclei due to urban and industrial aerosol sources. In this study, a downscaling analysis of spatial and temporal trends in rainfall around the Houston Area is being conducted. The downscaling analysis concept involves identifying and quantifying urban rainfall anomalies at progressively smaller spatial and temporal scales using the TRMM satellite, ground-based radar, and a dense network of rain gauges. The goal is to test the hypothesis that the Houston urban district and regions in the climatological downwind region of the city exhibit enhanced rainfall amounts relative to the climatological upwind regions. TRMM was launched in 1997 and currently operates in a low-inclination (35 deg), non-sun-synchronous orbit at an altitude of 402 km (350 km prior to August 2001). The satellite analysis follows the methodologies described in Shepherd et al. (2002). Nearly five years of TRMM PR-derived mean monthly rainfall estimates are utilized to produce annual and warm season isohyetal analyses around Houston. Early results indicate that rainfall rates (mm/h) for the entire period are largest within 100 km northeast and east of Houston (e.g. the "hypothesized downwind region"). The mean rainfall rate over the Houston urban center is 30.5% larger than the upwind control region. The mean rainfall rate in the downwind region is 34.4% larger than the upwind region. An analysis of a parameter called the urban rainfall ratio (URR) illustrates that 65% (88%) of the satellite-derived rainfall rates in the downwind (upwind control) region are greater (less) than the mean background rainfall rate of the entire study region. When the data is stratified by summer months from 1998 to 2001 (June-August), even greater influence over and downwind of the urban area is observed in the statistics. This result is consistent with published reports of urban-generated rainfall being more prevalent in the warm season. The research demonstrates that the evolving TRMM satellite climatology is a credible way to detect mesoscale precipitation signatures that may be linked to urbanization. Early results also corroborate recent findings on Houston-induced convection/drainfall anomalies. Burian and Shepherd will report on other aspects of the downscaling analysis in future forums, but early rain gauge results are consistent with the satellite-based observations.

Shepherd, J. Marshall↗

NASA NTRS2003

Emissions of Trace Gases and Particles from Two Ships in the Southern Atlantic Ocean

Measurements were made of the emissions of particles and gases from two diesel-powered ships in the southern Atlantic Ocean off the coast of Namibia. The measurements are used to derive emission factors from ships of three species not reported previously, namely, black carbon, accumulation-mode particles, and cloud condensation nuclei (CCN), as well as for carbon dioxide, carbon monoxide (CO), methane (CH4), non-methane hydrocarbons, sulfur dioxide (SO2), nitrogen oxides (NOx), and condensation nuclei. The effects of fuel grade and engine power on ship emissions are discussed. The emission factors are combined with fuel usage data to obtain estimates of global annual emissions of various particles and gases from ocean-going ships. Global emissions of black carbon, accumulation- mode particles, and CCN from ocean-going ships are estimated to be 19-26 Gg yr(sup -1), (4.4-6.1) x 10(exp 26) particles yr(sup -1), and (1.0-1.5) x l0(exp 26) particles yr(sup -1), respectively. Black carbon emissions from ocean-going ships are approximately 0.2% of total anthropogenic emissions. Emissions of NOx and SO2 from ocean-going ships are approximately 10-14% and approximately 3-4%, respectively, of the total emissions of these species from the burning of fossil fuels, and approximately 40% and approximately 70%, respectively, of the total emissions of these species from the burning of biomass. Global annual emissions of CO and CH4 from ocean-going ships are approximately 2% and approximately 2-5%, respectively, of natural oceanic emissions of these species.

Sinha, Parikhit↗