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At least 109 records · Page 6
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NASA NTRSDate not supplied

Climate change signal in global agriculture emerges earlier in new generation of climate and crop models

Potential climate-related impacts on future crop yield are a major societal concern first surveyed in a harmonized multi-model effort in 2014. We report here on new 21st-century projections using ensembles of latest-generation crop and climate models. Results suggest markedly more pessimistic yield responses for maize, soybean, and rice compared to the original ensemble. Mean end-of-century maize productivity is shifted from +5 to -6% (SSP126) and +1 to -24% (SSP585) — explained by warmer climate projections and improved crop model sensitivities. In contrast, wheat shows stronger gains (+9 shifted to +18%, SSP585), linked to higher CO2 concentrations and expanded high-latitude gains. The ‘emergence’ of climate impacts — when the change signal emerges from the noise — consistently occurs earlier in the new projections for several main producing regions before 2040. While future yield estimates remain uncertain, these results suggest that major breadbasket regions will face distinct anthropogenic climatic risks sooner than previously anticipated.

climate change↗
NASA NTRS2021

Climate Impacts on Global Agriculture Emerge Earlier in New Generation of Climate and Crop Models

Potential climate-related impacts on future crop yield are a major societal concern. Previous projections of the Agricultural Model Intercomparison and Improvement Project’s Global Gridded Crop Model Intercomparison based on the Coupled Model Intercomparison Project Phase 5 identified substantial climate impacts on all major crops, but associated uncertainties were substantial. Here we report new twenty-first-century projections using ensembles of latest-generation crop and climate models. Results suggest markedly more pessimistic yield responses for maize, soybean and rice compared to the original ensemble. Mean end-of-century maize productivity is shifted from +5% to −6% (SSP126) and from +1% to −24% (SSP585)—explained by warmer climate projections and improved crop model sensitivities. In contrast, wheat shows stronger gains (+9% shifted to +18%, SSP585), linked to higher CO 2 concentrations and expanded high-latitude gains. The ‘emergence’ of climate impacts consistently occurs earlier in the new projections—before 2040 for several main producing regions. While future yield estimates remain uncertain, these results suggest that major breadbasket regions will face distinct anthropogenic climatic risks sooner than previously anticipated.

crop model↗
NASA NTRS1974

Estimate of winter wheat yield from ERTS-1

A model for estimating wheat yield per acre has been applied to acreage estimates derived from ERTS-1 imagery to project the 1973 wheat yields for a ten county area in southwest Kansas. The results (41.04 million bushels) are within 3 per cent of the preharvest estimates for the same area prepared by the USDA Statistical Reporting Service (39.91 million bushels). The projection from ERTS data is based on a visual enumeration of all detectable wheat fields in the study area and was completed while the harvest was in progress. Visual identification of winter wheat is readily achieved by using a temporal sequence of images (band 5 for Sept.-Oct.; band 5 for Dec.-Jan.; and band 5 and 7 for March-April). Identification can be improved by stratifying the project area into subregions having more or less homogeneous agricultural practices and crop mixes. By doing this, small changes in the spectral appearance of wheat related to soil type, irrigation, etc. can be accounted for. The interpretation rules developed by visual analysis can be automated for rapid computer surveys.

Morain, S. A.↗
NASA NTRS1968

Buckling of thin-walled circular cylinders

This monograph indicates current practices for predicting buckling of uniform stiffened and unstiffened circular cylindrical shells under various types of static loading, and suggests the procedures that yield estimates of static buckling loads considered to be conservative. The buckling of truncated conical shells and shells of double curvature will be treated in separate monographs.

V. I. Weingarten↗
NASA NTRS1973

Thermal surveillance of volcanoes of the Cascade Range and Iceland utilizing ERTS DCP systems and imagery

The author has identified the following significant results. Significant results of the thermal surveillance of volcanoes experiment during 1972 included the design, construction, emplacement, and successful operation at volcanic sites in the Cascade Range, North America and on Surtsey, Iceland, of automated thermistor arrays which transmit ground and fumarole temperatures via the ERTS-1 data communication system to Goddard Space Flight Center. Temperature, radiance, and anomalous heat flow variations are being plotted by a U.S. Geological Survey IBM 360/65 computer program to show daily fluctuations at each of the sites. Results are being compiled in conjunction with NASA and USGS aircraft infrared survey data to provide thermal energy yield estimates during the current repose period of several Cascade Range volcanic systems. ERTS-1 MSS images have provided new information on the extent of structural elements controlling thermal emission at Lassen Volcanic National Park.

Friedman, J. D.↗
NASA NTRS1973

Automatic photointerpretation for plant species and stress identification (ERTS-A1)

The author has identified the following significant results. Automatic stratification of forested land from ERTS-1 data provides a valuable tool for resource management. The results are useful for wood product yield estimates, recreation and wildlife management, forest inventory, and forest condition monitoring. Automatic procedures based on both multispectral and spatial features are evaluated. With five classes, training and testing on the same samples, classification accuracy of 74 percent was achieved using the MSS multispectral features. When adding texture computed from 8 x 8 arrays, classification accuracy of 90 percent was obtained.

Swanlund, G. D.↗
NASA NTRS1973

Automatic interpretation of ERTS data for forest management

Automatic stratification of forested land from ERTS-1 data provides a valuable tool for resource management. The results are useful for wood product yield estimates, recreation and wild life management, forest inventory and forest condition monitoring. Automatic procedures based on both multi-spectral and spatial features are evaluated. With five classes, training and testing on the same samples, classification accuracy of 74% was achieved using the MSS multispectral features. When adding texture computed from 8 x 8 arrays, classification accuracy of 99% was obtained.

Kirvida, L.↗
NASA NTRS1972

Investigation of the Martian environment by infrared spectroscopy on Mariner 9.

Preliminary analysis of Mariner 9 IR spectroscopic data through May 1972 shows spectral features due to carbon dioxide, water vapor, and silicate dust suspended in the atmosphere. Measurements obtained during and after the planet-wide dust storm indicate that large diurnal variations in atmospheric temperature existed up to at least 30 km. Analysis of spectral features due to the atmospheric dust provides a SiO2 content of 60 (plus or minus 10)%, implying substantial geochemical differentiation. Water vapor estimates yield abundances of 10 to 20 precipitable microns, and no water vapor was detected over the north polar region.

Hanel, R.↗
NASA NTRS1973

Responses to rotating linear acceleration vectors considered in relation to a model of the otolith organs

Human subjects were exposed to a linear acceleration vector that rotated in the transverse plane of the skull without angular counterrotation. Lateral eye movements showed a sinusoidal change in slow phase velocity and an asymmetry or bias in the same direction as vector rotation. A model is developed that attributes the oculomotor response to otolithic mechanisms. It is suggested that the bias component is the manifestation of torsion of the statoconial plaque relative to the base of the utricular macula and that the sinusoidal component represents the translational oscillation of the statoconia. The model subsumes a hypothetical neural mechanism which allows x- and y-axis accelerations to be resolved. Derivation of equations of motion for the statoconial plaque in torsion and translation, which take into account forces acting in shear and normal to the macula, yield estimates of bias and sinusoidal components that are in qualitative agreement with the diverse experimental findings.

Benson, A. J.↗
NASA NTRS1974

The effect of microstructure and strength on the fracture toughness of an 18 ni, 300 grade maraging steel

Methods for increasing the strength of maraging steels are discussed. An investigation was conducted to systematically vary the strength of 18 weight percent nickel, 300 grade maraging steel, to isolate any attending microstructural changes, and to study the effects of these changes on the fracture toughness of the alloy. A study aimed at determining the aging behavior of the program alloy was carried out to provide data by which to estimate yield strength. The effects of various alloying materials on the strength of the maraging steel are examined. The mechanical properties of the 300 grade maraging steel were determined by tension tests, fatigue precracked Charpy impact tests, and plane strain fracture toughness tests.

Psioda, J. A.↗
NASA NTRS1976

EarthSat spring wheat yield system test 1975

The results of an operational test of the EarthSat System during the period 1 June - 30 August 1975 over the spring wheat regions of North Dakota, South Dakota, and Minnesota are presented. The errors associated with each sub-element of the system during the operational test and the sensitivity of the complete system and each major functional sub-element of the system to the observed errors were evaluated. Evaluations and recommendations for future operational users of the system include: (1) changes in various system sub-elements, (2) changes in the yield model to affect improved accuracy, (3) changes in the number of geobased cells needed to develop an accurate aggregated yield estimate, (4) changes associated with the implementation of future operational satellites and data processing systems, and (5) detailed system documentation.

Source record↗
NASA NTRS1976

Analysis of EUV limb brightening observations from ATM. II - Influence of spicules

A comparison of limb brightening measurements with theoretical limb brightening curves calculated for simple atmospheric models indicates that a significant fraction of the EUV emission from lines formed in the transition layer comes from spicules. We find that spicules contribute about 20% of the total quiet sun intensity for lines of the C II, C III, N III, and O VI ions. The uncertainty in the magnitude of the percentage is about a factor of 2. The EUV-emission scale heights above the limb are consistent with the assumption that the variation with height of the number of EUV-emitting spicules is the same as for H-alpha-emitting spicules. Optical depths derived for the C II 1335 A and C III 977 A lines yield estimates for the pressure in the transition layer that are in good agreement with pressures derived under the assumption that the transition layer is in pressure equilibrium with the chromosphere and corona.

Withbroe, G. L.↗
NASA NTRS1977

The Large Area Crop Inventory Experiment

Determination of wheat acreages in the central U.S., as well as the development and testing of yield models, is discussed in the framework of the Large Area Crop Inventory Experiment (LACIE). Particular attention is given to the goal of obtaining a 90% accuracy in yield forecasts in nine out of ten years. Current results of LACIE indicate that Landsat remote sensing data, in conjunction with information from agricultural meteorological surveys, can provide highly accurate early-season and at-harvest yield estimates in the principal wheat-growing regions of the world.

Macdonald, R. B.↗
NASA NTRS1977

On the transfer of remote sensing technology to an operational data system

Data processing techniques for the transfer of remote sensing technology to an operational data system are evaluated. The study is aimed at developing a scheme for the improvement of the quantifying cost/performance ratio, noting the timeliness of the results, the ease of system development, system operating costs, and accuracy. The method is applicable to the Production Area and Yield Estimation System (PAYES) and the Large Area Crop Inventory Experiment (LACIE).

Tarbet, J. D.↗
NASA NTRS1979

Recent results of radio interferometric determinations of a transcontinental baseline, polar motion, and earth rotation

Results are discussed for radio interferometric observations of extragalactic radio sources with antennas at Haystack Observatory in Massachusetts and the Owens Valley Radio Observatory in California (3900-km baseline) during 14 separate experiments distributed between September 1976 and May 1978. Simultaneous analysis of the data from several experiments yields estimates of changes in the x component of pole position and in earth's rotation (UT1). Comparison with the corresponding results obtained by the Bureau International de l'Heure (BIH) reveals systematic differences. In particular, the trends in the radio interferometric determinations of the changes in pole position are found to agree more closely with those from the International Polar Motion Service and from Doppler observations of satellites than with those from the BIH.

Robertson, D. S.↗
NASA NTRS1979

Accuracy assessment: The statistical approach to performance evaluation in LACIE

A statistical methodology was developed to check the accuracy of the products of the experimental operations throughout crop growth and to determine whether the procedures are adequate to accomplish the desired accuracy and reliability goals. It has allowed the identification and isolation of key problems in wheat area yield estimation, some of which have been corrected and some of which remain to be resolved. The major unresolved problem in accuracy assessment is that of precisely estimating the bias of the LACIE production estimator. Topics covered include: (1) evaluation techniques; (2) variance and bias estimation for the wheat production estimate; (3) the 90/90 evaluation; (4) comparison of the LACIE estimate with reference standards; and (5) first and second order error source investigations.

Houston, A. G.↗
NASA NTRS1981

Evaluation of multiband, multitemporal, and transformed LANDSAT MSS data for land cover area estimation

Sample segments of ground-verified land cover data collected in conjunction with the USDA/ESS June Enumerative Survey were merged with LANDSAT data and served as a focus for unsupervised spectral class development and accuracy assessment. Multitemporal data sets were created from single-date LANDSAT MSS acquisitions from a nominal scene covering an eleven-county area in north central Missouri. Classification accuracies for the four land cover types predominant in the test site showed significant improvement in going from unitemporal to multitemporal data sets. Transformed LANDSAT data sets did not significantly improve classification accuracies. Regression estimators yielded mixed results for different land covers. Misregistration of two LANDSAT data sets by as much and one half pixels did not significantly alter overall classification accuracies. Existing algorithms for scene-to scene overlay proved adequate for multitemporal data analysis as long as statistical class development and accuracy assessment were restricted to field interior pixels.

Stoner, E. R.↗
NASA NTRS1980

The magnetic field of Saturn - Further studies of the Pioneer 11 observations

Analysis of magnetic field observations by the Goddard Space Flight Center high-field flux gate magnetometer on the Pioneer 11 spacecraft during Saturn encounter yields estimates of the planetary field. The field is mainly dipolar but rather weaker than expected, with a moment equal to 0.20 G cubic Saturn radii or 4.3 x 10 to the 28th G cu cm, opposite in polarity to earth's. Surprisingly, the field appears to be axially symmetric but with a small (0.04 Saturn radii) offset to the north so that N (S) polar field intensities are 0.6 (0.4) G, respectively. The deduced polar offset appears not to be an artifact of the limited spatial extent of the observations or the presence of fields of external origin. The average stand-off distance of the magnetopause is expected to be 20 Saturn radii, i.e., at the orbit of Titan, so that this largest of solar system satellites is immersed not only in the Saturnian magnetosphere but also at times in its magnetosheath and sometimes even in the interplanetary medium.

Acuna, M. H.↗