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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 253 records · Page 14
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NASA NTRS1994

Solar Mesosphere Explorer satellite measurements of el Chichon stratospheric aerosols. 1: Cloud morphology

Data from the Solar Mesosphere Explorer (SME) is used to track the time, latitude, and altitude (above 18 km) development of the aerosol cloud injected into the stratosphere by the eruption of el Chichon. This unique data set, using scattering data from the near-infrared (1.27 and 1.87 microns) and visible (440 nm) spectrometers on SME, covers the period from the initial injection in April 1982 through the end of 1986. Although the bulk of the mass is contained in the latitude band from 10 deg S to 30 deg N for the entire duration of the measurements, transport of material to high latitudes is apparent in the data in the post eruption period. The times aerosol density maxima vary greatly as a function of altitude and latitude.

Rusch, D. W.↗
NASA NTRS1994

Solar Mesosphere Explorer satellite measurements of el Chichon stratospheric aerosols. 2: Aerosol mass and size parameters

Spatially and temporally extensive observations of the stratospheric aerosol cloud produced by the eruption of el Chichon in 1982 were made by the Solar Mesosphere Explorer satellite. Measurements of thermal emission at 6.8 microns are inverted to give aerosol extinction coefficients. At this wavelength the extinction coefficient is proportional to the cube of the particle radius, so the measured radiance is proportional to the slant column mass density of aerosols, independent of size distribution. Vertical column mass densities of aerosols and total aerosol mass are found from the 6.8-microns data. The evolution of the aerosol cloud in time and space is discussed. A peak column mass density above 22 km of 0.43 g/sq m occurred near 20 deg N latitude 8 weeks after the eruption. A maximum total global aerosol burden above 22 km of 1.3 x 10(exp 13) g occurred a week later. The aerosol mass determinations are used in conjunction with observations of scattered sunlight from the aerosols at 1.27 and 1.87 microns to derive single-mode log normal columnar size distributions for the aerosol cloud. The results are presented and the time evolution of the particle sizes is discussed.

Eparvier, F. G.↗
NASA NTRS1994

Angular momentum exchange among the solid Earth, atmosphere, and oceans: A case study of the 1982-1983 El Nino event

The 1982-1983 El Nino/Southern Oscillation (ENSO) event was accompanied by the largest interannual variation in the Earth's rotation rate on record. In this study we demonstrate that atmospheric forcing was the dominant cause for this rotational anomaly, with atmospheric angular momentum (AAM) integrated from 1000 to 1 mbar (troposphere plus stratosphere) accounting for up to 92% of the interannual variance in the length of day (LOD). Winds between 100 and 1 mbar contributed nearly 20% of the variance explained, indicating that the stratosphere can play a significant role in the Earth's angular momentum budget on interannual time scales. Examination of LOD, AAM, and Southern Oscillation Index (SOI) data for a 15-year span surrounding the 1982-1983 event suggests that the strong rotational response resulted from constructive interference between the low-frequency (approximately 4-6 year) and quasi-biennial (approximately 2-3 year) components of the ENSO phenomenon, as well as the stratospheric Quasi-Biennial Oscillation (QBO). Sources of the remaining LOD discrepancy (approximately 55 and 64 microseconds rms residual for the European Centre for Medium-Range Forecasting (EC) and U.S. National Meteorological Center (NMC) analyses) are explored; noise and systematic errors in the AAM data are estimated to contribute 18 and 33 microseconds, respectively, leaving a residual (rms) of 40 (52) microseconds unaccounted for by the EC (NMC) analysis. Oceanic angular momentum contributions (both moment of inertia changes associated with baroclinic waves and motion terms) are shown to be candidates in closing the interannual axial angular momentum budget.

Dickey, J. O.↗
NASA NTRS1994

Shortwave feedbacks and El Nino-Southern Oscillation: Forced ocean coupled ocean-atmosphere experiments

Changes in tropical sea surface temperature (SST) can produce changes in cloudiness that modify incoming solar shortwave (SW) radiation, which in turn affects SST. The effects of this negative feedback on Pacific interannual variability are examined in forced ocean model and hybrid coupled ocean-atmosphere model simulations. Two empirical schemes are used to model the large-scale, low-frequency response of surface SW to SST anomalies. The first scheme attempts to account for the nonlocal nature of the atmospheric response to SST based patterns of covariability analyzed through singular value decomposition. In the observations the primary coupled mode of variability is composed of a SW anomaly in the central Pacific that covaries with anomalous SST in the eastern Pacific. This is applied in the model as a nonlocal feedback. The second scheme examines the effects of a purely local feedback with a spatially varying coefficient of magnitude chosen similar to the first scheme. In almost all cases the second scheme behaved similarly to the first, presumably because the correlation scale of SST is large enough for El Nino-Southern Oscillation (ENSO) dynamics that there is little sensitivity to the local approximation in the SW feedback. In simulations forced by time series of observed wind stress the SW feedback induced very minor SST damping. Results for a simpified heat budget analysis showed that while the SW feedback increased the local heat flux damping on SST, it also induced a mean shallowing of the mixed layer. The resulting changes in both the local mean vertical temperature gradient and the zonal velocity response to the wind stress acted to oppose the local heat flux damping effects. When the observed SW anomalies were applied to forced simulations, the simulated SST anomalies were modified as expected, and agreement with observed SST improved. In coupled simulations the SW feedbacks had greater impact than in the case of specified stress. The main effects were to decrease the magnitude of the warm and cold SST anomalies in the central Pacific, while leaving the pattern and evolution of ENSO anomalies essentially unchanged elsewhere. The SW feedbacks thus produce a modest improvement of the model ENSO SST pattern compared with observations, although they tended to shorten the period of the model ENSO cycle. Overall the results suggest that large-scale SW feedbacks are of quantitative importance to simulating some aspects of the ENSO cycle but are not critical to the overall occurrence of the phenomenon.

Waliser, Duane E.↗
NASA NTRS1995

Application of Spaceborne Scatterometer to Study Typhoon, Tropical Hydrologic Balance and El Nino

The high spatial resolution and global coverage of a spaceborne microwave scatterometer make it a power instrument to study phenomena ranging from typhoon to El Nino Southern Oscillation which have regional and short term economic and ecological impacts as well as effects on long term and global climate changes. In this report, the application of scatterometer data, by itself, to study the intensity and the evolution of typhoon is demonstrated. The potential of combining wind vector and precipitable water derived from two spaceborne sensors to study the hydrologic balance in the tropics is discussed. The role of westerly wind bursts as a precursor of anomalous warming in the equatorial Pacific is investigated with coincident data from microwave scatterometer, altimeter and radiometer.

Liu, W. Timothy↗
NASA NTRS1999

Rocket/Radar Sporadic-E Experiment Conducted during the El Coqui 2 Campaign

In order to investigate the complex electrodynamics and neutral-plasma coupling inherent to sporadic-E layers in the earth's mid-latitude ionosphere, a series of rocket/radar experiments were planned as part of the NASA El Coqui H Campaign from Tortuguero Launch Range, Puerto Rico, in March-April, 1998. The rocket experiments consisted of two pairs of "mother-daughter" payloads with limited apogees so that the payloads "hovered" in the sporadic-E region (95-125 km). Each payload pair included vector DC and AC electric field detectors, a highly accurate flux-gate DC magnetometer, an ion mass spectrometer, an ionization gauge, and spaced-electric field receivers to measure the wavelength and phase velocity of the unstable plasma waves. Separate rockets were included to simultaneously carry aloft TMA trails to measure the neutral wind and its velocity shear, believed responsible for the sporadic-E layer formation. In addition to the rocket experiments, incoherent scatter radar measurements of plasma density and drift velocity were gathered almost every night during the 3 week campaign. Continuous VHF backscatter radar operations were carried out from a site near Salinas, Puerto Rico, where 3-m backscatter echoes were observed associated with sporadic-E and other types of low altitude ionospheric layers. Other radars that operated during the campaign included an HF backscatter system near Ponce, Puerto Rico, and a second VHF backscatter radar set up near Aguadila Puerto Rico. On 24 March 1998, one of the instrumented rockets was launched, attaining an apogee of 129 km. The payloads successfully pierced an intense sporadic-E layer observed by both the Arecibo radar and the in-situ density and ion mass spectrometer probes. In-situ DC electric fields revealed very low (about 1-2 mV/m) ambient fields with small amplitude structures of the same order. No high frequency (short scale) waves were observed, consistent with the VHF backscatter observations at the time of the launch. An overview of the observations will be presented.

Pfaff, R.F.↗
NASA NTRS1999

The 1997-98 El Nino Event and Related Wintertime Lightning Variations in the Southeastern United States

The El Nino Southern Oscillation (ENSO) is a climate anomaly responsible for world-wide weather impacts ranging from droughts to floods. In the United States, warm episode years are known to produce above normal rainfall along the Southeast US Gulf Coast and into the Gulf of Mexico, with the greatest response observed in the October-March period of the latest warm-episode year. The 1997-98 warm episode, notable for being the strongest event since 1982-83, presents our first opportunity to examine the response to a major ENSO event and determine the variation of wintertime thunderstorm activity in this part of the world. Due to the recent launch of a lightning sensor on NASA's Tropical Rainfall Measuring Mission (TRMM) in November 1997 and the expanded coverage of the National Lightning Detection Network (NLDN), we are able to examine such year-to-year changes in lightning activity with far greater detail than ever before.

Goodman, S. J.↗
NASA NTRS1999

Lightning Variations in the Southeastern United States Related to the Winter 1997-98 EL NINO Event

Significant enhancements of wintertime (December-February) lightning in the Southeastern US and northern Gulf Of Mexico have been observed in association with the 1997-98 El Nino event. Positive rainfall anomalies have often been observed during prior warm ENSO events along the Gulf coast of the US. Based on our analysis of 10 years of reprocessed National Lightning Detection Network (NLDN) data, a large area of the northern Gulf was found to have experienced its greatest number of cloud-to ground (surface) flashes during the period of record. In addition, a statistically significant increase in the number of hours with lightning was observed in contrast to the mean for the winter months. We attribute the enhancement of thunderstorm activity to the increased strength of the upper level Jet stream over the Gulf and the attendant increase in cyclogenesis within the region.

Buechler, Dennis↗
NASA NTRS1999

The 1997-98 El-Nino Event and Related Lightning Variations in the Southeastern United States

The El Nino Southern Oscillation (ENSO) is a climate anomaly responsible for world-wide weather impacts ranging from droughts to floods. In the United States, warm episode years are known to produce above normal rainfall along the Southeast US Gulf Coast and into the Gulf of Mexico, with the greatest response observed in the October-March period of the current warm-episode year. The 1997-98 warm episode, notable for being the strongest event since 1982-83, presents our first opportunity to examine the response to a major ENSO event and determine the variation of wintertime thunderstorm activity in this part of the world. Due to the recent launch of a lightning sensor on NASA's Tropical Rainfall Measuring Mission (TRMM) in November 1997 and the expanded coverage of the National Lightning Detection Network (NLDN), we are able to examine such year-to-year changes in lightning activity with far greater detail than ever before.

Buechler, D. E.↗
NASA NTRS1998

A TOMS-Based View of Tropical Tropospheric Ozone (OTTO) From Large Fires Associated with the 1997-1998 El Nino

Since the launch of Earth-Probe TOMS in July 1 996, we have been producing tropical tropospheric ozone (TTO) maps (10S - 10N), in gridded format, l x 2 degrees, in near-real time. These images, along with images from the full ADEOS-TOMS record of TTO (Sept. 1996 - May 1997) can be viewed on a homepage: http://metosrv2.umd,edu/-tropo). The TTO maps, based on the modified-residual method of Hudson and Thompson [1998], have been validated using ozonesondes from Ascension (8S, 15W), Nairobi (2S, 36E) and American Samoa (14S, 171W). The fires associated with El Nino-induced dryness are exhibited regionally as high tropospheric ozone column (> 60 Dobson Units) with high absorbing aerosol (smoke) signal in TOMS [J. R. Herman, personal communication, 1998]. Episodes of high TTO in 1997-98 will be shown. Regional TTO over Indonesia during the 1997-98 period will be highlighted and comparisons will be made with TTO in that region taken from the 1979-92 Nimbus/TOMS TTO record.

Thompson, Anne M.↗
NASA NTRS1998

Impact of the 1997-1998 El Nino on Atmospheric Circulation

The 1997-1998 E1 Nino created significant anomalies in global circulation patterns. We monitored the E1 Nino event, using TOVS (TIROS Operational Vertical Sounder) data, as part of the Laboratory for Atmospheres TOVS Pathfinder Data Set. TOVS has flown on the NOAA operational polar orbiting satellites from November 1978 to present. We have analyzed data from NOAA 9, 10, 11, 12, and 14, covering January 1985 to the present, using a consistent processing scheme. The data set contains 2-4 times daily global fields of land/ocean surface skin temperature, atmospheric temperature-moisture profiles, cloud top pressure and fractional cloud cover, OLR and clear sky Outgoing Longwave Radiation (OLR), and precipitation estimate. We have generated anomalies of all fields compared to a 12 year climatology of our data set, covering the period 1985-1996. Anomalies during the current E1 Nino were compared to those of other E1 Nino-La Nina episodes since 1985, with particular attention paid to tropical anomalies of surface skin and air temperature, precipitation, upper tropospheric water vapor, OLR, and clear sky OLR. All the El Nino-La Nina events produce similar patterns, but the magnitude of the current anomalies in all fields is considerably greater than those during the previous weaker surface skin temperature anomaly episodes. Significant extra-tropical anomalies were found during the current E1 Nino as well.

Susskind, Joel↗
NASA NTRS1999

The 1997-98 El Nino Event and Related Wintertime Lightning Variations in the Southeastern United States

The El Nino Southern Oscillation (ENSO) is a climate anomaly responsible for world-wide weather impacts ranging from droughts to floods. In the United States, warm episode years are known to produce above normal rainfall along the Southeast US Gulf Coast and into the Gulf of Mexico, with the greatest response observed in the October-March period of the latest warm-episode year. The 1997-98 warm episode is notable for being the strongest event since 1982-83. With the recent launch of a lightning sensor on NASA's Tropical Rainfall Measuring Mission (TRMM) in November 1997 and the expanded coverage of the National Lightning Detection Network (NLDN), such year-to-year changes in lightning activity can be examined with far greater detail than ever before. For the recent ENSO event the greatest year-to-year changes in lightning frequency occur within a broad swath across the northern Gulf of Mexico basin where there is nearly a 200% increase in lightning days year-to-year (35 days in 1997-98 vs. 13 days in 1996-97) and a 200% increase in lightning hours (150 hours vs. 50). These changes occur in association with a 100% increase in the number of synoptic scale cyclones and an anomalously strong jet stream encompassing much of the Gulf basin.

Goodman, S. J.↗
NASA NTRS1997

El Nino Southern Oscillation and Tuna in the Western Pacific

Nearly 70% of the world's annual tuna harvest, currently 3.2 million tonnes, comes from the Pacific Ocean. Skipjack tuna (Katsuwonus pelamis) dominate the catch. Although skipjack are distributed in the surface mixed layer throughout the equatorial and subtropical Pacific, catches are highest in the western equatorial Pacific warm pool, a region characterized by low primary productivity rates that has the warmest surface waters of the world's oceans. Assessments of tuna stocks indicate that recent western Pacific skipjack catches approaching one million tonnes annually are sustainable. The warm pool, which is fundamental to the El Nino Southern Oscillation (ENSO) and the Earth's climate in general, must therefore also provide a habitat capable of supporting this highly productive tuna population. Here we show that apparent spatial shifts in the skipjack population are linked to large zonal displacements of the warm pool that occur during ENSO events. This relationship can be used to predict (several months in advance) the region of highest skipjack abundance, within a fishing ground extending over 6,000 km along the Equator.

Lehodey, P.↗
NASA NTRS1997

Zonal and Meridional Mass Redistribution in the Tropical Pacific During El Nino Southern Oscillation Events

This note aims at documenting the ENSO-related sea level changes for the whole tropical Pacific, and for the 1979-1996 period which covers numerous El Nino and La Nina events. For this purpose, we rely on (a) 0/450 dbar surface dynamic height anomaly (an alias for sea level) derived from XBT and TOGA-TAO measurements during 1979-1996, (b) TOPEX/Poseidon derived sea level anomaly during 1993-1996, and (c) Murtugudde et al. [1996] model sea level output during 1979-1995.

Delcroix, Thierry↗
NASA NTRS2000

The 1997-98 El Nino Event and Related Wintertime Lightning Variations in the Southeastern United States

The El Nino Southern Oscillation (ENSO) is a climate anomaly responsible for worldwide weather impacts ranging from droughts to floods. In the United States, warm episode years are known to produce above normal rainfall along the Southeast U.S. Gulf Coast and into the Gulf of Mexico, with the greatest response observed in the October-March period of the warm episode year. The 1997-98 warm episode is notable for being the strongest event since 198283. With the recent launch of a lightning sensor on NASA's Tropical Rainfall Measuring Mission (TRMM) in November 1997 and the detailed coverage of the U.S. National Lightning Detection Network (NLDN), such interannual changes in lightning activity can be examined with far greater detail than ever before. For the 1997-98 ENSO event the most significant year-to-year changes in lightning frequency worldwide occurred along the Gulf Coast and within the Gulf of Mexico basin during the Northern Hemisphere winter. Within a broad swath across the northern Gulf of Mexico basin there is a 100-150% increase in lightning days year-to-year (a peak of 33 days in the winter of 1997-98 vs. only 15 days or fewer in both the 1996-97 and 1998-99 winter). In addition, there is a nearly 200% increase in lightning hours (a peak of 138 hours in 1996-97 vs. 50 hours in both 1996-97 and 1998-99). The increase in lightning activity during ENSO occurs in association with a 100% increase in the number of synoptic scale cyclones that developed within or moved through the Gulf basin. The primary variables controlling these enhancements in thunderstorm activity are the position and strength of the jet stream.

Goodman, S. J.↗
NASA NTRS1999

Use of Data to Improve El Nino Southern Oscillation Simulations and Forecasts

Various data over the period 1980-1998 have been used to improve El Nino Southern Oscillation (ENSO) simulations and forecasts performed by coupled ocean/atmosphere models. For such a study, oceanic and atmospheric satellite data are necessary. Models assume a baroclinic ocean with a mixed layer coupled to a baroclinic atmosphere to simulate the anomalous fields. The various data have been used to revisit the parameterizations of the subsurface temperature in the mixed layer, atmospheric convection, and friction in the baroclinic ocean. This new model, named Tsub.Conv, simulates 4-year oscillations like the model with the original parameterization, but with anomalous thermocline and wind anomalies that agree a lot better with reality. The atmospheric model still presents some deficiencies in the eastern Pacific and when it is replaced by a statistical atmosphere, the coupled model (Tsub.Astat) performs even better. It is found that the off-equatorial ocean and wind curl anomalies play a crucial role for all these models and that Tsub.Astat simulates an ocean heat content recharge coming from the north prior to a warm event like the ones observed during the 1985-1992 period. The ENSO forecasts over 1980-1998 are considerably improved with Tsub.Astat. One needs to add the simulation of westerly wind bursts to be able to forecast the 1997 event one year in advance. Additional information is contained in the original.

Perigaud, Claire↗
NASA NTRS1997

Minority Universities Systems Engineering (MUSE) Program at the University of Texas at El Paso

In 1995, The University of Texas at El Paso (UTEP) responded to the suggestion of NASA Jet Propulsion Laboratory (NASA JPL) to form a consortium comprised of California State University at Los Angeles (CSULA), North Carolina Agricultural and Technical University (NCAT), and UTEP from which developed the Minority Universities Systems Engineering (MUSE) Program. The mission of this consortium is to develop a unique position for minority universities in providing the nation's future system architects and engineers as well as enhance JPL's system design capability. The goals of this collaboration include the development of a system engineering curriculum which includes hands-on project engineering and design experiences. UTEP is in a unique position to take full advantage of this program since UTEP has been named a Model Institution for Excellence (MIE) by the National Science Foundation. The purpose of MIE is to produce leaders in Science, Math, and Engineering. Furthermore, UTEP has also been selected as the site for two new centers including the Pan American Center for Earth and Environmental Sciences (PACES) directed by Dr. Scott Starks and the FAST Center for Structural Integrity of Aerospace Systems directed by Dr. Roberto Osegueda. The UTEP MUSE Program operates under the auspices of the PACES Center.

Robbins, Mary Clare↗
NASA NTRS2001

Precipitation Anomalies in the Tropical Indian Ocean and Possible Links to the Initiation of El Nino

A pattern of variability in precipitation and 1000mb zonal winds for the tropical Indian Ocean during, 1979 to 1999 (AtmIO mode) is described using EOFs. The AtmIO mode consists of a cross-equatorial gradient of precipitation anomalies and equatorial wind anomalies of alternating signs on the Equator. The positive phase is defined as enhanced precipitation to the In "n south of the equator, suppressed precipitation to the north, and anomalous westerlies centered on the island of Sumatra. In September-October 1981, February-March 1990, and October-December 1996 the AtmIO mod-, was positive and there was a significant 30-60 day variability in the gradient of precipitation anomalies. These cases coincided with moderate to heavy ,activity in the Madden-Jullan Oscillation (MJO). Links between the AtmIO, MJO, and El Nino are discussed.

Curtis, Scott↗