Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “arctic”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 541 records · Page 30
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

Atmospheric chemistry in the Arctic and subarctic - Influence of natural fires, industrial emissions, and stratospheric inputs

Layers with enhanced concentrations of trace gases intercepted by the NASA Electra aircraft over Alaska during the Arctic Boundary Layer Expedition (ABLE 3A) in July-August 1988 are discussed. Haze layers apparently associated with boreal fires were enriched in hydrocarbons and NO(y), with emission factors corresponding closely to laboratory data for smoldering combustion. It is argued that atmospheric composition was strongly modified by wildfires during several periods of the ABLE 3A mission. The associated enhancement of NO(y) was smaller than observed for most other combustion processes but was nonetheless significant in the context of very low background concentrations. Ozone production in fire plumes was negligible. Ambient O3 was supplied by the stratosphere, with little direct input from midlatitude source during summer. It is argued that NO(y) was supplied about equally by the stratosphere and by wildfires. Hydrocarbons and CO appear to derive from biomass fires and from human activities.

Wofsy, S. C.↗
NASA NTRS1992

Modeling the seasonal variability of a coupled Arctic ice-ocean system

The seasonal variability of the ice-ocean system in the Arctic Basin and the Norwegian, Greenland, and Barents Seas was modeled using a three-dimensional coupled ice-ocean model developed at Princeton University. The snow-ice model uses a three-level thermodynamic scheme similar to Semtner's (1976), but is extended to include the effect of leads. It is shown that simulations using the climatological monthly forcing fields produce a realistic seasonal variability of the ice cover. The ice thickness had a considerable sensitivity to the choice of the long-wave back radiation scheme, but these effects can be reduced through dynamical factors.

Hakkinen, Sirpa↗
NASA NTRS1992

A one-dimensional modeling study of carbonaceous haze effects on the springtime Arctic environment

The effect of carbonaceous Arctic haze on the surface energy balance was investigated using a specially developed one-dimensional three-component numerical model which accounts for the transfer of IR and solar radiation through the atmosphere, turbulent mixing within the boundary layer, and heat conduction through snow-capped sea ice. The results of calculations indicate that, when haze is present, the surface temperature increases, provided the relative humidity through the column does not change. The increase is due to an increase in the absorbed radiation at the surface.

Emery, Christopher A.↗
NASA NTRS1991

Airborne lidar observations of ozone and aerosols in the wintertime Arctic stratosphere

The procedures used in making the lidar measurements of O3 and aerosols are discussed, and selected data samples of O3 and aerosol distributions observed during flights between Stavanger (59 deg N, 3 deg E) and the North Pole between about 40 deg W and 20 deg E meridians are presented. The 'on' and 'off'; laser wavelengths used for the DIAL measurements during the Airborne Arctic Stratospheric Expedition (AASE) were 301.5 and 311 nm, respectively. An intercomparison between airborne DIAL and ozonesonde measurements of O3 in the vicinity of Bear Island is shown. The DIAL profiles were obtained by averaging the lidar returns over a 5-min period and then calculating the DIAL O3 profile. Lidar measurements at 603 and 1064 nm are used to infer physical characteristics of the different types of aerosols observed during the AASE.

Browell, Edward V.↗
NASA NTRS1993

Arctic sea ice signatures for passive microwave algorithms

Two new sets of global pure type signatures are defined, and the precision of the concentration estimates made using the Team algorithm and the new signatures is estimated. One set varies temporally but not spatially and is defined by the modes of major peaks in histograms of brightness temperature. The other set is defined as the overall means of the temporally varying signatures; these are called 'new constant signatures'. Both sets of new signatures have essentially the same precision: 0.05 (fractional area) for winter ice concentration, 0.10 for summer ice concentration, and 0.15 to 0.3 for winter multilayer ice concentrations. Both sets result in about 0.6 to 0.7 winter multiyear ice for the Arctic Ocean, substantially more than the 0.3 to 0.4 computed using the original team algorithm signatures, and in the same range as several independent estimates of the multiyear ice, 0.54 to 0.75.

Thomas, D. R.↗
NASA NTRS1993

Intercomparison of haloe and ER-2 aircraft H2O and CH4 observations collected during the second Airborne Arctic Stratospheric Experiment (AASE-II)

HALOE observations of H2O and CH4 are compared with in situ techniques aboard the ER-2 aircraft during the northern winter of 1991/92, in particular for the dates 911208, 920108, 920217, 920222, and 920320 when the spatial coincidences are close, within +/- 1 deg latitude and +/- 12 deg longitude. The results reveal the limitations of comparing high resolution in situ aircraft data with a remote sounding limb scanner. Of the five comparison dates, three had HALOE/ER-2 coincidences which occurred near the edge of the Arctic vortex; the vertical variability in the HALOE results and the horizontal variability in the ER-2 observations on these days show that the vortex edge is not a region where exact agreement can be expected except by chance. On a 4th comparison date, there was substantial overlap away from the vortex edge, although for some species the aircraft data show considerable variability near the coincidence point. On the 5th comparison date, the ER-2 had no overlap in altitude with the lowest HALOE observations; however, a short linear interpolation over about 1 km altitude results in smooth composite profiles. Generally speaking the agreement between HALOE and the ER-2 at overlap altitudes is about 12 percent in the case of water vapor, which shows low horizontal and vertical variability. The agreement for methane, with limited data having altitude overlap, is better than 6 percent.

Tuck, A. F.↗
NASA NTRS1992

Comparison of radar backscatter from Antarctic and Arctic sea ice

Two ship-based step-frequency radars, one at C-band (5.3 GHz) and one at Ku-band (13.9 GHz), measured backscatter from ice in the Weddell Sea. Most of the backscatter data were from first-year (FY) and second-year (SY) ice at the ice stations where the ship was stationary and detailed snow and ice characterizations were performed. The presence of a slush layer at the snow-ice interface masks the distinction between FY and SY ice in the Weddell Sea, whereas in the Arctic the separation is quite distinct. The effect of snow-covered ice on backscattering coefficients (sigma0) from the Weddell Sea region indicates that surface scattering is the dominant factor. Measured sigma0 values were compared with Kirchhoff and regression-analysis models. The Weibull power-density function was used to fit the measured backscattering coefficients at 45 deg.

Hosseinmostafa, R.↗
NASA NTRS1993

The detectability of Arctic leads using thermal imagery under varying atmospheric conditions

The way in which thermal contrast between leads of varying widths and thickness can be distinguished from the background multiyear ice surface under varying atmospheric conditions is examined. The normalized brightness temperature difference between image pixels that include lead fractions and of the background ice is employed to determine thresholds of detection accounting for sensor FOV and various atmospheric phenomena that influence the Arctic radiation balance during winter. Surface temperatures are prescribed as a function of ice thickness, and the effects of the intervening atmosphere are simulated by varying the optical depths of hypothetic cloud or haze layers varying in microphysical characteristics. It is found that the limits of lead detection may be determined as a function of pixel lead fraction and atmospheric optical depth if suitable values of normalized contrast are used as detection criteria.

Stone, Robert S.↗
NASA NTRS1993

Airborne observations of the 1992 Arctic winter stratosphere by FTIR solar absorption spectroscopy

The JPL MkIV interferometer, a Fourier Transform Infra-Red (FTIR) spectrometer designed specifically for atmospheric remote sensing, made measurements of the composition of the Arctic stratosphere in January, February and March 1992. These measurements were made from the NASA DC-8 aircraft as part of the AASE2 campaign. The data reveal that despite 5 to 6 km of subsidence inside the vortex, which more than doubled the vertically integrated column amounts (burdens) of HF and HNO3 with respect to outside the vortex, considerable losses of NO2, HCl and ClNO3 were evident by mid-January. Temporary freeze-out of HNO3 was observed only on one occasion, Jan. 19, and was accompanied by substantial reductions in HCl and ClNO3. During February and March, ClNO3 and NO2 amounts increased dramatically. HCl also recovered but at a much slower rate, so that by March ClNO3 was the major reservoir of inorganic chlorine, at times exceeding HCl by a factor 2.

Toon, G. C.↗
NASA NTRS1993

Arctic coastal polynya observations with ERS-1 SAR and DMSP SSM/I

Work to improve the characterization of the distribution of new and young sea ice types and open water amount within Arctic coastal polynyas through the combined use of ERS-1 SAR (Synthetic Aperture Radar) and DMSP SSM/I (Defense Meteorological Satellite Program Special Sensor Microwave/Imager) data is described. Two St. Lawrence Island polynya events are studied using low resolution, geocoded SAR images and coincident SSM/I data. The SAR images are analyzed in terms of polarization and spectral gradient ratios. Results of the combined analysis show that the SAR ice type classification is consistent with that from SSM/I and that the combined use of SAR and SSM/I can improve the characterization of thin ice better than either data set can do alone.

Cavalieri, D. J.↗
NASA NTRS1989

Arctic Ozone Expedition

Recent research on ozone done in the Arctic region is detailed and an update on information is gained from the previous Antarctic research.

Source record↗
NASA NTRS1992

Arctic and Antarctic Sea Ice, 1978-1987: Satellite Passive-Microwave Observations and Analysis

This book contains a description and analysis of the spatial and temporal variations in the Arctic and Antarctic sea ice covers from October 26, 1978 through August 20, 1987. It is based on data collected by the Scanning Multichannel Microwave Radiometer (SMMR) onboard the NASA Nimbus 7 satellite. The 8.8-year period, together with the 4 years of the Nimbus 5 Electrically Scanning Microwave Radiometer (ESMR) observations presented in two earlier volumes, comprises a sea ice record spanning almost 15 years.

Gloersen, Per↗
NASA NTRS1993

Elemental depletions in Antarctic micrometeorites and Arctic cosmic spherules: Comparison and relationships

Antarctic micrometeorites (MM's) and Arctic cosmic spherules (CS's) have bulk compositions comparable to those of chondritic meteorites. However, abundance of Na, Ca, Mn, Ni, Co, and S are commonly lower in MM's and CS's as compared to chondrites. Our SEM, EMP, and INAA studies suggest that these elemental depletions in unmelted MM's are likely to be due to leaching of soluble components from the MM's in the upper atmosphere and the melt ice water. Depletions in CS's appear to be mainly due to volatilization during melting in the atmosphere or to sampling bias during aggregate formation or parent rock break-up.

Presper, T.↗
NASA NTRS1994

Remote sensing of global snowpack energy and mass balance: In-situ measurements on the snow of interior and Arctic Alaska

This project is continuing along the lines of the semiannual report dated January 1993. Four major tasks have been addressed: analysis of variability in the seasonal snow of interior and arctic Alaska, the interpretation of microwave brightness temperature across Alaska on transects from south to north, study of nonclimatic controls which affect glaciers, and the location of glacier facies boundaries.

Benson, Carl S.↗
NASA NTRS1989

Ozone Hole Airborne Arctic Stratospheric Expedition (Pre-Flight)

The first segment of this video gives an overview of the Ozone Hole Airborne Arctic Stratospheric Expedition, an international effort using balloon payloads, ground based instruments, and airborne instruments to study ozone depletion and the hole in the ozone over Antarctica which occurs every spring. False color imagery taken from NASA's Nimbus 7 satellite which documents daily changes in ozone is also shown. The second segment of this video shows actual take-off and flight footage of the two aircraft used in the experiment: the DC-8 Flying Laboratory and the high flying ER-2.

Source record↗
NASA NTRS1993

Chlorine chemistry on polar stratospheric cloud particles in the Arctic winter

Simultaneous in situ measurements of hydrochloric acid (HCl) and chlorine monoxide (ClO) in the Arctic winter vortex showed large HCl losses of up to 1 ppbv, which were correlated with high ClO levels of up to 1.4 ppbv. Air parcel trajectory analysis identified that this conversion of inorganic chlorine occurred at air temperatures of less than 196 -/+ 4 kelvin. High ClO was always accompanied by loss of HCl mixing ratios equal to 1/2(ClO+ 2Cl2O2). These data indicate that the heterogeneous reaction HCl + ClONO2 - Cl2 + HNO3 on particles of polar stratospheric clouds establishes the chlorine partitioning, which, contrary to earlier notions, begins with an excess of ClONO2, not HCl.

Webster, C. R.↗
NASA NTRS1993

Stratospheric meteorological conditions in the Arctic polar vortex, 1991 to 1992

Stratospheric meteorological conditions during the Airborne Arctic Stratospheric Expedition II (AASE II) presented excellent observational opportunities from Bangor, Maine, because the polar vortex was located over southeastern Canada for significant periods during the 1991-1992 winter. Temperature analyses showed that nitric acid trihydrates (NAT temperatures below 195 K) should have formed over small regions in early December. The temperatures in the polar vortex warmed beyond NAT temperatures by late January (earlier than normal). Perturbed chemistry was found to be associated with these cold temperatures.

Newman, P.↗
NASA NTRS1990

Comparison of active and passive microwave signatures of Arctic sea ice

In March 1988, overlapping active and passive microwave instrument data were acquired over Arctic sea ice using the NASA DC-8 aircraft equipped with multifrequency, variable polarization SAR and radiometer. Flights were conducted as a series of coordinated underflights of the DMSP SSM/I satellite radiometer in order to validate ice products derived from the SSM/I radiances. Subsequent flights by an NRL P-3 aircraft enabled overlapping high-resolution, single frequency image data to be acquired over the same regions using a Ka-band scanning microwave radiometer. In this paper, techniques are discussed for the accurate coregistration of the three aircraft datasets. Precise coregistration to an accuracy of 100 m plus or minus 25 m has, for the first time, enabled the detailed comparison of temporally and spatially coincident active and passive airborne microwave datasets. Preliminary results from the intercomparisons indicate that the SAR has highly frequency- and polarization-dependent signatures, which at 5.3 GHz (C-band) show an extremely high correlation with the 37 GHz radiometric temperatures.

Drinkwater, M. R.↗