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At least 595 records · Page 33
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

Interannual variability of Indian monsoon rainfall

The interannual variability of the Indian summer monsoon and its relationships with other atmospheric fluctuations were studied in hopes of gaining some insight into the predicability of the rainfall. Rainfall data for 31 meteorological subdivisions over India were provided by the India Meteorological Department (IMD). Fifty-three years of seasonal mean anomaly sea-level pressure (SLP) fields were used to determine if any relationships could be detected between fluctuations in Northern Hemisphere surface pressure and Indian monsoon rainfall. Three month running mean sea-level pressure anomalies at Darwin (close to one of the centers of the Southern Oscillation) were compiled for months preceding and following extreme years for rainfall averaged over all of India. Anomalies are small before the monsoon, but are quite large in months following the summer season. However, there is a large decrease in Darwin pressure for months preceding a heavy monsoon, while a deficient monsoon is preceded by a sharp increase in Darwin pressure. If a time series is constructed of the tendency of Darwin SLP between the Northern Hemisphere winter (DJF) and spring (MAM) and a correlation coefficient is computed between it and 81 years of rainfall average over all of India, one gets a C. C. of -.46, which is higher than any other previously computed predictor of the monsoon rainfall. This relationship can also be used to make a qualitative forecast for rainfall over the whole of India by considering the sign of the tendency in extreme monsoon years.

Paolino, D. A.↗
NASA NTRS1983

Dominant modes of relationship between U.S. temperature and geomagnetic activity

Eigen-analysis is applied to a matrix of cross-correlation coefficients between the geomagnetic aa-index for 0 to 23-yr lag and the monthly mean temperature at 32 United States stations. About 75 percent of the relationship between the two fields is contained in three dominant modes. A secular trend (about 90 yr) and two 11-yr cycles dominate the mode time series. The month-to-month changes in the temperature anomaly patterns indicate a slow eddy-like motion to the east of the Continental Divide for all three dominant modes.

Prohaska, J. T.↗
NASA NTRS1985

Comparison of wind velocity in thunderstorms determined from measurements by a ground-based Doppler radar and an F-106B airplane

As a part of the NASA Storm Hazards Program, the wind velocity in several thunderstorms was measured by an F-106B instrumented airplane and a ground-based Doppler radar. The results of five airplane penetrations of two storms in 1980 and six penetrations of one storm in 1981 are given. Comparisons were made between the radial wind velocity components measured by the radar and the airplane. The correlation coefficients for the 1980 data and part of the 1981 data were 0.88 and 0.78, respectively. It is suggested that larger values for these coefficients may be obtained by improving the experimental technique and in particular by slaving the radar to track the airplane during such tests.

Usry, J. W.↗
NASA NTRS1985

The corotating variation of the north-south anisotropy of cosmic rays

Correlation analysis on the relation of the north-south (N-S) anisotropy of cosmic rays, observed by the Nagoya multidirectional meson telescope, with the interplanetary magnetic field (IMP) as well the solar wind velocity within solar Carrington rotation for the period 1971 to 1976 is discussed. It is found that the N-S anisotropy of cosmic rays correlates quite well with the Bx component of the IMF. The correlation coefficient is nearly equal to 0.8.

Xue, S.↗
NASA NTRS1985

Cosmogenic Mn-53 in meteorites

The distributions of the Mn-53 contents in 106 nonantarctic and 112 antarctic chondrites were analyzed. A correlation analysis of these distributions showed that the correlation coefficient is a maximum r sub max = 0.75 plus or minus 0.03) when the histogram for antarctic chondrites is displaced by 40 plus or minus 8 dpm kg-1Fe towards lower Mn-53 contents. The distribution of Mn-53 saturated contents in nonantarctic ordinary chondrites was investigated as a function of their radiation age (T). It is found that the Mn-53 average content is higher by (21 plus or minus 9)% in H-chondrites with radiation age T approximately 12 Myr than in thse with T 12 Myr. This effect can be attributed to the fact that a considerable proportion of H-chondrites with T 12 Myr originates from a comet or from the objects of Chiron like, with the orbits more inclined to the ecliptic plane and/or more extended, which caused their irradiation by cosmic rays of higher intensity.

Alexeev, V. A.↗
NASA NTRS1985

The neutron moderated detector and groundbased cosmic ray modulation studies

Reports appear on modulation studies with the neutron monitor without lead. Some of these studies cast doubt on the reliability of this detector. The stability of the neutron moderated detector (NMD) at Sanae, Antarctic is discussed. The barometric coeficient of the 4NMD for epoch 1976 appears not to differ statistically from the 0.73%/mb of the 3NM64. The monthly averaged hourly counting rate of our 4NMD and 3NM64 correlates very well (correlation coefficient: 98%) over the years from 1974-1984, with the 4NMD showing a 8% larger long term modulation effect than the 3NM64, indicating a difference in sensitivities of the two detectors. From this difference in sensitivities spectra of ground level solar proton events and modulation functions of Forbush decreases are deduced.

Stoker, P. H.↗
NASA NTRS1985

Detection of the response of ozone in the middle atmosphere to short-term solar ultraviolet variations

The response of ozone to solar UV variation is determined in the middle atmosphere between the heights of 10 and 0.2 mb. The definitive isolation of the smaller variations associated with short-term solar variability is accomplished only after removal of the larger changes of ozone related to temperature variations. Using this approach the correlation coefficients between detrended ozone (Nimbus 7 LIMS) and short-term 205 nm solar variation (Nimbus 7 SBUV) are found to be much higher (0.9) than achieved in previous studies. The theoretical response time and amplitude of response of ozone in the middle atmosphere to observed short-term solar UV variations is found to be in good agreement with observations, except near 0.2 mb. The corresponding long-term response over the solar cycle is also estimated.

Keating, G. M.↗
NASA NTRS1985

Urban, Forest, and Agricultural AIS Data: Fine Spectral Structure

Spectra acquired by the Airborne Imaging Spectrometer (AIS) near Lafayette, IN, Ely, MN, and over the Stanford University campus, CA were analyzed for fine spectral structure using two techniques: the ratio of radiance of a ground target to the radiance of a standard and also the correlation coefficient of radiances at adjacent wavelengths. The results show ramp like features in the ratios. These features are due to the biochemical composition of the leaf and to the optical scattering properties of its cuticle. The size and shape of the ramps vary with ground cover.

Vanderbilt, V. C.↗
NASA NTRS1985

Analysis of Terrestrial Conditions and Dynamics

An ecological model is developed to estimate annual net primary productivity of vegetation in twelve major North American biomes. Three models are adapted and combined, each addressing a different factor known to govern primary productivity, i.e., photosynthesis, respiration, and moisture availability. Measures of intercepted photosynthetically active radiation (1PAR) for input to the photosynthesis model are derived from spectral vegetation index data. Normalized Difference Vegetation Index (NDVI) data are produced from NOAA-7 Advanced Very High Resolution Radiometer (AVHRR) observations for April 1982 through March 1983. NDVI values are sampled from within the biomes at locations for which climatological data are available. Monthly estimates of Net Primary Productivity (NPP) for each sample location are generated and summed over the twelve month period. These monthly estimates are averaged to produce a single annual estimated NPP value for each biomes. Comparison of estimated NPP values with figures reported in the literature produces a correlation coefficient of 85.

Goward, S. N.↗
NASA NTRS1985

Comparison of manually produced and automated cross country movement maps using digital image processing techniques

The Image-Based Information System (IBIS) was used to automate the cross country movement (CCM) mapping model developed by the Defense Mapping Agency (DMA). Existing terrain factor overlays and a CCM map, produced by DMA for the Fort Lewis, Washington area, were digitized and reformatted into geometrically registered images. Terrain factor data from Slope, Soils, and Vegetation overlays were entered into IBIS, and were then combined utilizing IBIS-programmed equations to implement the DMA CCM model. The resulting IBIS-generated CCM map was then compared with the digitized manually produced map to test similarity. The numbers of pixels comprising each CCM region were compared between the two map images, and percent agreement between each two regional counts was computed. The mean percent agreement equalled 86.21%, with an areally weighted standard deviation of 11.11%. Calculation of Pearson's correlation coefficient yielded +9.997. In some cases, the IBIS-calculated map code differed from the DMA codes: analysis revealed that IBIS had calculated the codes correctly. These highly positive results demonstrate the power and accuracy of IBIS in automating models which synthesize a variety of thematic geographic data.

Wynn, L. K.↗
NASA NTRS1984

Experimental and analytical investigation of a freezing point depressant fluid ice protection system

A glycol-exuding porous leading edge ice protection system was tested in the NASA Icing Research Tunnel. Stainless steel mesh, laser drilled titanium, and composite panels were tested on two general aviation wing sections. Two different glycol-water solutions were evaluated. Minimum glycol flow rates required for anti-icing were obtained as a function of angle of attack, liquid water content, volume median drop diameter, temperature, and velocity. Ice accretions formed after five minutes of icing were shed in three minutes or less using a glycol fluid flow equal to the anti-ice flow rate. Two methods of predicting anti-ice flow rates are presented and compared with a large experimental data base of anti-ice flow rates over a wide range of icing conditions. The first method presented in the ADS-4 document typically predicts flow rates lower than the experimental flow rates. The second method, originally published in 1983, typically predicts flow rates up to 25 percent higher than the experimental flow rates. This method proved to be more consistent between wing-panel configurations. Significant correlation coefficients between the predicted flow rates and the experimental flow rates ranged from .867 to .947.

Albright, A. E.↗
NASA NTRS1986

Immunological analyses of U.S. Space Shuttle crewmembers

Changes in the immunoresponsiveness of 'T' lymphocytes following space flight have been reported previously. Additional data collected before and after 11 Shuttle space flights show that absolute lymphocyte numbers, lymphocyte blastogenic capability, and eosinophil percent in the peripheral blood of crewmembers are generally depressed postflight. These responses resemble those associated with physical and emotional stress and may not be related to flight per se. Additional data from Space Shuttle flights 41B and 41D, involving 11 crewmembers, indicate a postflight decrease in cells reacting with 'B' lymphocyte and monocyte monoclonal antibody tags. Further, the loss of 'T' lymphocyte blast capability correlates with the decreased monocyte count (correlation coefficient = 0.697). This finding implies that the previously reported loss of blastogenic capability may be a function of decreased monocyte control, as noted in several nonspaceflight related studies.

Taylor, G. R.↗
NASA NTRS1986

Jupiter - New estimates of the mean zonal flow at the cloud level

In order to reexamine the magnitude differences of the Jovian atmosphere's jets, as determined by Voyager 1 and 2 images, a novel approach is used to ascertain the zonal mean east-west component of motion. This technique is based on digital pattern matching, and is applied on pairs of mapped images to yield a profile of the mean zonal component that reproduces the exact locations of the easterly and westerly jets between + and - 60 deg latitude. Results have been obtained for all of the Voyager 1 and 2 cylindrical mosaics; the correlation coefficient between Voyagers 1 and 2 in mean zonal flow between + and - 60 deg latitude, determined from violet filter mosaics, is 0.998.

Limaye, S. S.↗
NASA NTRS1986

Automated remote sensing of sea ice using synthetic aperture radar

Two techniques for automated sea ice tracking: image pyramids (hierarchical correlation) and feature tracking were applied to a pair of SEASAT SAR sea ice images. The results compare well with each other and manually tracked estimates of the ice velocity field. Refinement of the image pyramid technique should include removal of a small number of erroneous velocity vectors using constraints dependent on correlation coefficient, near neighbor velocities, and velocity gradients. Estimates of sea ice velocity are successfully obtained over limited areas using the boundary segment tracking technique. Refinement of the feature tracking technique should include use of pressure ridge features, constrained search, and relaxation techniques.

Vesecky, J. F.↗
NASA NTRS1984

A diagnostic approach to obtaining planetary boundary layer winds using satellite-derived thermal data

The feasibility of using satellite derived thermal data to generate realistic synoptic scale winds within the planetary boundary layer (PBL) is examined. Diagnostic modified Ekman wind equations from the Air Force Global Weather Central (AFGWC) Boundary Layer Model are used to compute winds at seven levels within the PBL transition layer (50 m to 1600 m AGL). Satellite derived winds based on 62 predawn TIROS-N soundings are compared to similarly derived wind fields based on 39 AVE-SESAME II rawinsonde (RAOB) soundings taken 2 h later. Actual wind fields are also used as a basis for comparison. Qualitative and statistical comparisons show that the Ekman winds from both sources are in very close agreement, with an average vector correlation coefficient of 0.815. Best results are obtained at 300 m AGL. Satellite winds tend to be slightly weaker than their RAOB counterparts and exhibit a greater degree of cross-isobaric flow. The modified Ekman winds show a significant improvement over geostrophic values at levels nearest the surface.

Belt, Carol L.↗
NASA NTRS1986

Jupiter: New estimates of mean zonal flow at the cloud level

In order to reexamine the magnitude differences of the Jovian atmosphere's jets, as determined by Voyager 1 and 2 images, a novel approach is used to ascertain the zonal mean east-west component of motion. This technique is based on digital pattern matching, and is applied on pairs of mapped images to yield a profile of the mean zonal component that reproduces the exact locations of the easterly and westerly jets between + and 60 deg latitude. Results were obtained for all of the Voyager 1 and 2 cylindrical mosaics; the correlation coefficient between Voyagers 1 and 2 in mean zonal flow between + and - 60 deg latitude, determined from violet filter mosaics, is 0.998.

Limaye, Sanjay S.↗
NASA NTRS1987

Calibration of the spin-scan ozone imager aboard the dynamics Explorer 1 satellite

The calibration technique, which contains the calibrated backscattered radiance values necessary for performing the calibrations, is presented. The calibration constants for September to October 1981 to determine total columnar ozone from the Spin-Scan Ozone Imager (SOI), which is a part of the auroral imaging instrumentation aboard the Dynamics Explorer 1 Satellite, are provided. The precision of the SOI-derived total columnar ozone is estimated to be better than 2.4 percent. Linear regression analysis was used to calculate correlation coefficients between total columnar ozone obtained from Dobson ground stations and SOI which indicate that the SOI total columnar ozone determination is equally accurate for clear or cloudy weather conditions.

Bressette, Walter E.↗
NASA NTRS1987

Transport of passive scalars in a turbulent channel flow

A direct numerical simulation of a turbulent channel flow with three passive scalars at different molecular Prandtl numbers is performed. Computed statistics including the turbulent Prandtl numbers are compared with existing experimental data. The computed fields are also examined to investigate the spatial structure of the scalar fields. The scalar fields are highly correlated with the streamwise velocity; the correlation coefficient between the temperature and the streamwise velocity is as high as 0.95 in the wall region. The joint probability distributions between the temperature and velocity fluctuations are also examined; they suggest that it might be possible to model the scalar fluxes in the wall region in a manner similar to the Reynolds stresses.

Kim, John↗