Engineering topics

Fishman, J.

Publications and source records attributed to Fishman, J..

At least 19 records

NASA NTRS2012

The United States' Next Generation of Atmospheric Composition and Coastal Ecosystem Measurements: NASA's Geostationary Coastal and Air Pollution Events (GEO-CAPE) Mission

The Geostationary Coastal and Air Pollution Events (GEO-CAPE) mission was recommended by the National Research Council's (NRC's) Earth Science Decadal Survey to measure tropospheric trace gases and aerosols and coastal ocean phytoplankton, water quality, and biogeochemistry from geostationary orbit, providing continuous observations within the field of view. To fulfill the mandate and address the challenge put forth by the NRC, two GEO-CAPE Science Working Groups (SWGs), representing the atmospheric composition and ocean color disciplines, have developed realistic science objectives using input drawn from several community workshops. The GEO-CAPE mission will take advantage of this revolutionary advance in temporal frequency for both of these disciplines. Multiple observations per day are required to explore the physical, chemical, and dynamical processes that determine tropospheric composition and air quality over spatial scales ranging from urban to continental, and over temporal scales ranging from diurnal to seasonal. Likewise, high-frequency satellite observations are critical to studying and quantifying biological, chemical, and physical processes within the coastal ocean. These observations are to be achieved from a vantage point near 95deg-100degW, providing a complete view of North America as well as the adjacent oceans. The SWGs have also endorsed the concept of phased implementation using commercial satellites to reduce mission risk and cost. GEO-CAPE will join the global constellation of geostationary atmospheric chemistry and coastal ocean color sensors planned to be in orbit in the 2020 time frame.

Atmospheric composition↗

NASA NTRS2009

Radiation from Relativistic Shocks with Turbulent Magnetic Fields

Recent PIC simulations of relativistic electron-positron (electron-ion) jets injected into a stationary medium show that particle acceleration occurs at shocked region. The simulation results show that the Weibel instability is responsible for generating and amplifying highly nonuniform, small-scale magnetic fields. These magnetic fields contribute to the electron's transverse deflection behind the shock. The "jitter" radiation from deflected electrons in turbulent magnetic fields has different properties than synchrotron radiation which is calculated in a uniform magnetic field. This jitter radiation may be important to understanding the complex time evolution and/or spectral structure in gamma-ray bursts, relativistic jets, and supernova remnants. New recent calculation of spectra with various different Lorentz factors of jets (two electrons) and initial magnetic fields. New spectra based on small simulations will be presented.

Nishkawa, K.↗

NASA NTRS1999

Infrared Solar Spectroscopic Measurements of Free Tropospheric CO, C2H6, and HCN above Mauna Loa, Hawaii: Seasonal Variations and Evidence for Enhanced Emissions from the Southeast Asian Tropical Fires of 1997-1998

High spectral resolution (0.003 per cm) infrared solar absorption measurements of CO, C2H6, and HCN have been recorded at the Network for the Detection of Stratospheric Change station on Mauna Loa, Hawaii, (19.5N, 155.6W, altitude 3.4 km). The observations were obtained on over 250 days between August 1995 and February 1998. Column measurements are reported for the 3.4-16 km altitude region, which corresponds approximately to the free troposphere above the station. Average CO mixing ratios computed for this layer have been compared with flask sampling CO measurements obtained in situ at the station during the same time period. Both show asymmetrical seasonal cycles superimposed on significant variability. The first 2 years of observations exhibit a broad January-April maximum and a sharper CO minimum during late summer. The C2H6 and CO 3.4-16 km columns were highly correlated throughout the observing period with the C2H6/CO slope intermediate between higher and lower values derived from similar infrared spectroscopic measurements at 32'N and 45'S latitude, respectively. Variable enhancements in CO, C2H6, and particularly HCN were observed beginning in about September 1997. The maximum HCN free tropospheric monthly mean column observed in November 1997 corresponds to an average 3.4-16 km mixing ratio of 0.7 ppbv (1 ppbv = 10(exp -9) per unit volume), more than a factor of 3 above the background level. The HCN enhancements continued through the end of the observational series. Back-trajectory calculations suggest that the emissions originated at low northern latitudes in southeast Asia. Surface CO mixing ratios and the C2H6 tropospheric columns measured during the same time also showed anomalous autumn 1997 maxima. The intense and widespread tropical wild fires that burned during the strong El Nino warm phase of 1997- 1998 are the likely source of the elevated emission products.

Rinsland, C. P.↗

NASA NTRS1999

Infrared Solar Spectroscopic Measurements of Free Tropospheric CO, C2H6, and HCN above Mauna Loa, Hawaii: Seasonal Variations and Evidence for Enhanced Emissions from the Southeast Asian Fires of 1997-1998

High spectral resolution (0.003/ cm) infrared solar absorption measurements of CO, C2H6, and HCN have been recorded at the Network for the Detection of Stratospheric Change station on Mauna Loa, Hawaii, (19.5 deg N, 155.6 deg W, altitude 3.4 km). The observations were obtained on over 250 days between August 1995 and February 1998. Column measurements are reported for the 3.4 - 16 km altitude region, which corresponds approximately to the free troposphere above the station. Average CO mixing ratios computed for this layer have been compared with flask sampling CO measurements obtained in situ at the station during the same time period. Both show asymmetrical seasonal cycles superimposed on significant variability. The first two years of observations exhibit a broad January-April maximum and a sharper CO minimum during late summer. The C2H6 and CO 3.4 - 16 km columns were highly correlated throughout the observing period with the C2H6/CO slope intermediate between higher and lower values derived from similar infrared spectroscopic measurements at 32 deg N and 45 deg S latitude, respectively. Variable enhancements in CO, C2H6, and particularly HCN were observed beginning in about September 1997. The maximum HCN free tropospheric monthly mean column observed in November 1997 corresponds to an average 3.4 - 16 km mixing ratio of 0.7 ppbv (1 ppbv = 10(exp -9) per unit volume), more than a factor of 3 above the background level. The HCN enhancements continued through the end of the observational series. Back-trajectory calculations suggest that the emissions originated at low northern latitudes in southeast Asia. Surface CO mixing ratios and the C2H6 tropospheric columns measured during the same time also showed anomalous autumn 1997 maxima. The intense and widespread tropical wild fires that burned during 3 the strong El Nino warm phase of 1997-1998 are the likely source of the elevated emission products.

Rinsland, C. P.↗

NASA NTRS1998

Development of a Compact, Ground-Based Ozone DIAL System

We are developing a portable, eye-safe, ground-based ozone lidar instrument specialized for ozone differential absorption lidar (DIAL) measurements in the troposphere. This prototype instrument is intended to operate at remote field sites and to serve as the basic unit for future monitoring projects requiring multi-instrument networks, such as that proposed for the Global Tropospheric Ozone Project (GTOP). GTOP is currently being formulated by a scientific panel of the International Global Atmospheric Chemistry Project to meet its goal to better understand the processes that control the global distribution of tropospheric ozone. In order for the lidar to be widely deployed in networks, it must be fairly easy to use and maintain as well as being cost-competitive with ground station launching ozone sondes which operate several times a day. To achieve these goals, emphasis is placed upon the incorporation of: (1) all-solid state transmitters which can reliably produce 20-40 mJ pulses; (2) a highly efficient, narrow-bandpass receiver; (3) dual analog and photon-counting detector channels; and (4) flexible, user-friendly control software.

Chyba, T. H.↗

NASA NTRS1996

Validation of UARS Microwave Limb Sounder Ozone Measurements

This paper describes the validation of ozone data from the Upper Atmosphere Research Satellite (UARS) Microwave Limb Sounder (MLS). The MLS ozone retrievals are obtained from the calibrated microwave radiances (emission spectra) in two separate bands, at frequencies near 205 and 183 GHz. Analyses described here focus on the MLS Version 3 data (the first set of files made publicly available). We describe results of simulations performed to assess the quality of the retrieval algorithms, in terms of both mixing ratio and radiance closure. From actual MLS observations, the 205-GHz ozone retrievals give better closure (smaller radiance residuals) than that from the 183-GHz measurements and should be considered more accurate from the calibration aspects. However, the 183-GHz data are less noise limited in the mesosphere and can provide the most useful scientific results in that region. We compare the retrieved 205-GHz ozone profiles in the middle-to lower stratosphere to ozonesonde measurements at a wide range of latitudes and seasons. Ground-based lidar data from Table Mountain, California, provide a good reference for comparisons at higher altitudes. Based on these analyses, comparisons with balloon-borne measurements and others, as well as a detailed budget of estimated uncertainties, MLS results appear to be generally of high quality, with some biases worth mentioning. Results for the lowermost stratosphere (approx. 50 to 100 bPa) are still in need of improvement. A set of estimated precision and accuracy values is derived for the MLS ozone data sets. We also comment on recent updates in the retrieval algorithms and their impact on ozone values.

Froidevaux, L.↗

NASA NTRS1995

The application of network synthesis to repeating classical gamma-ray bursts

It has been suggested that the Burst and Transient Source Experiment (BATSE) gamma-ray burst catalog contains several groups of bursts clustered in space or in space and time, which provide evidence that a substantial fraction of the classical gamma-ray burst sources repeat. Because many of the bursts in these groups are weak, they are not directly detected by the Ulysses GRB experiment. We apply the network synthesis method to these events to test the repeating burst hypothesis. Although we find no evidence for repeating sources, the method must be applied under more general conditions before reaching any definite conclusions about the existence of classical gamma-ray burst repeating sources.

Hurley, K.↗

NASA NTRS1994

Large-scale circulation patterns associated with high concentrations of tropospheric ozone in the tropical South Atlantic Ocean

Several years of satellite observations indicate the presence of enhanced amounts of tropospheric ozone over the tropical South Atlantic during the austral springs. Wide-spread biomass burning is prevalent over Africa and South America during the same time of the year. Another recent satellite technique has identified the locations of fires over the continents. In this study, we present an analysis of the prevailing meteorological conditions when the highest amounts of tropospheric ozone are present.

Fakhruzzaman, K. M.↗

NASA NTRS1994

Volcanic-aerosol-induced changes in stratospheric ozone following the eruption of Mount Pinatubo

Measurements of lower stratospheric ozone in the Tropics using electrochemical concentrations cell (ECC) sondes and the airborne UV Differential Absorption Lidar (DIAL) system after the eruption of Mt. Pinatubo are compared with the Stratospheric Aerosol and Gas Experiment 2 (SAGE 2) and ECC sonde measurements from below the eruption to determine what changes have occurred as a result. Aerosol data from the Advanced Very High Resolution Radiometer (AVHRR) and the visible and IR wavelengths of the lidar system are used to examine the relationship between aerosols and ozone changes. Ozone decreases of 30 percent at altitudes between 19 and 26 km, partial column (16-28 km) decreases of about 27 D.U., and slight increases (5.4 D.U.) between 28 and 31 km are found in comparison with SAGE 2 climatological values.

Grant, W. B.↗

NASA NTRS1994

Validation of UARS MLS Ozone Measurements

Microwave Limb Sounder (MLS)↗

NASA NTRS1992

Observations of reduced ozone concentrations in the tropical stratosphere after the eruption of Mt. Pinatubo

Two independent sets of data, one of aerosols from an airborne lidar system, and one of ozone from ozonesonde measurements indicate that significant ozone decreases may have happened as a result of the injection of debris by the Mt. Pinatubo volcano in June 1991. The amount of this reduction maximizes at 24-25 km, near the peak of the aerosol distribution, though a deficit is seen throughout the lower stratosphere between 19 and 28 km. The greatest differences observed prior and subsequent to the eruptions at these altitudes is 18-20 percent.

Grant, W. B.↗

NASA NTRS1992

Distribution of tropospheric ozone in the tropics from satellite and ozonesonde measurements

Measurements from two independent satellite data sets have been used to derive the climatology of the integrated amount of ozone in the troposphere. These data have led to the finding that large amounts of ozone pollution are generated by anthropogenic activity originating from both the industrialized regions of the Northern Hemisphere and from the southern tropical regions of Africa. To verify the existence of this ozone anomaly over this region of the world, an ozonesonde capability has been established at Ascension Island, located downwind of the primary source region of this ozone pollution, which likely results from the photochemical oxidation of emissions emanating from the widespread burning of savanna. These first ozonesonde profiles suggest that much of the ozone generated over Africa during the 'burning season' (primarily July-October) reaches Ascension Island. These high levels of ozone in the lower troposphere become much lower by December. Elevated ozone concentrations in the middle troposphere are once again evident in February, which may be the result of biomass burning emissions being transported from western and northern Africa.

Fishman, J.↗

NASA NTRS1991

Identification of widespread pollution in the Southern Hemisphere deduced from satellite analyses

Vertical profiles of ozone obtained from ozonesondes in Brazzaville (Congo) and Ascension Island show that large quantities of tropospheric ozone are present over southern Africa and the adjacent eastern tropical South Atlantic Ocean. The origin of this pollution is widespread biomass burning in Africa. These measurements support satellite-derived tropospheric ozone data that demonstrate that ozone originating from this region is transported throughout most of the Southern Hemisphere. Seasonally high levels of CO2 and methane observed at middle- and high-latitude stations in Africa, Australia, and Antarctica likely reflect the effects of this distant biomass burning. These data suggest that even the most remote regions on this planet may be significantly more polluted than previously believed.

Fishman, J.↗

NASA NTRS1988

Carbon monoxide over the Amazon Basin during the 1985 dry season

During the Amazon Boundary Layer Experiment, approximately 100 hours of in situ carbon monoxide measurements were obtained using a tunable diode laser sensor that provided continuous, fast-response (about 1 s) measurements. This data set, taken on board the NASA Electra between July 12 and August 12, 1985, characterizes the temporal and spatial changes in the CO distribution over the Amazon Basin as meteorological conditions progressed from the early to middle phases of the 1985 day season. Early dry-season CO values of 75-95 ppbv were generally observed in the PBL. As the dry season became well established, biomass burning and a persistent capping inversion at about 3 km profoundly altered the CO distribution, with PBL values typically reaching 150-275 ppbv. Concentrations as high as 800 ppbv were measured within identifiable haze layers. An analysis of satellite imagery shows that biomass burning was occurring along the Amazon River system and in savannah areas located more than 1000 km south of the region sampled.

Sachse, G. W.↗

NASA NTRS1985

The photochemistry of synoptic-scale ozone synthesis Implications for the global tropospheric ozone budget

The oxidation of nonmethane hydrocarbons represents a source of tropospheric ozone that is primarily confined to the boundary layers of several highly industrialized regions. (Each region has an area greater than one million km/sq cm). Using a photochemical model, the global tropospheric ozone budget is reexamined by including the in-situ production from these localized regimes. The results from these calculations suggest that the net source due to this photochemistry, which takes place on the synoptic scale, is approximately as large as the amount calculated for global scale photochemical processes which consider only the oxidation of methane and carbon monoxide. Such a finding may have a considerable impact on our understanding of the tropospheric ozone budget. The model results for ozone show reasonable agreement with the climatological summer distribution of ozone and the oxides of nitrogen at the surface and with the vertical distribution of ozone and nonmethane hydrocarbons obtained during a 1980 field program.

Fishman, J.↗

NASA NTRS1985

Evaluation of spacecraft technology programs (effects on communication satellite business ventures), volume 1

Commercial organizations as well as government agencies invest in spacecraft (S/C) technology programs that are aimed at increasing the performance of communications satellites. The value of these programs must be measured in terms of their impacts on the financial performane of the business ventures that may ultimately utilize the communications satellites. An economic evaluation and planning capability was developed and used to assess the impact of NASA on-orbit propulsion and space power programs on typical fixed satellite service (FSS) and direct broadcast service (DBS) communications satellite business ventures. Typical FSS and DBS spin and three-axis stabilized spacecraft were configured in the absence of NASA technology programs. These spacecraft were reconfigured taking into account the anticipated results of NASA specified on-orbit propulsion and space power programs. In general, the NASA technology programs resulted in spacecraft with increased capability. The developed methodology for assessing the value of spacecraft technology programs in terms of their impact on the financial performance of communication satellite business ventures is described. Results of the assessment of NASA specified on-orbit propulsion and space power technology programs are presented for typical FSS and DBS business ventures.

Greenburg, J. S.↗

NASA NTRS1985

The reservoir of ozone in the boundary layer of the eastern United States and its potential impact on the global tropospheric ozone budget

An analysis of available ozone data in the eastern two-thirds of the United States indicates that a substantial reservoir of ozone is present in the summertime. Five-year mean concentrations range from 40 to 65 ppbv. The reservoir covered an area of several million square kilometers and extends vertically from the surface to 1 to 2 km. The vertical distribution of ozone in the reservoir during midday supports a transport of additional ozone from the boundary layer to the free troposphere. Data are presented demonstrating the potential effect of transport by convective clouds and by the sea breeze circulation - mechanisms by which ozone may be transported out of the boundary layer into the free troposphere. The potential impact of this reservoir on the tropospheric ozone budget is discussed. It is shown that if less than half of the ozone mass in this reservoir is transported to the free troposphere, then the amount of ozone transported out of the boundary layer approximates the amount of ozone transported downward during a tropopause fold event.

Vukovich, F. M.↗

NASA NTRS1984

A one-dimensional photochemical model of the troposphere with planetary boundary-layer parameterization

A time-dependent, one-dimensional photochemical model of the troposphere is used to describe the vertical distribution of atmospheric trace constituents for summer-time conditions at midlatitudes in the Northern Hemisphere. The model incorporates a planetary boundary layer (PBL) parametrization and a detailed chemical mechanism that includes the photochemistry of important nonmethane hydrocarbon species formed during the oxidation process. One result of the parametrized PBL is that the concentrations of some trace species in the free troposphere are 20-30 percent higher than when mixing processes are described by a vertical eddy diffusion coefficient which is held constant with respect to height and time. The lifetime of the oxides of nitrogen against photochemical conversion to nitric acid during summertime conditions is on the order of six hours. This lifetime is short enough to deplete most of the NO(x) in the PBL so that other reactive nitrogen species are more abundant than NO(x) throughout the free troposphere.

Fishman, J.↗