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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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1976

Comparisons of cloud cover evaluated from LANDSAT imagery and meteorological stations across the British Isles

The author has identified the following significant results. This stage of the study has confirmed the initial supposition that LANDSAT data could be analyzed to provide useful data on cloud amount, and that useful light would be thrown thereby on the performance of the ground observer of this aspect of the state of the sky. This study, in comparison with previous studies of a similar nature using data from meteorological satellites, has benefited greatly from the much higher resolution data provided by LANDSAT. This has permitted consideration of not only the overall performance of the surface observer in estimating total cloud cover, but also his performance under different sky conditions.

Barrett, E. C.↗
NASA NTRS2019

A Relationship Between Blue and Near‐IR Global Spectral Reflectance and the Response of Global Average Reflectance to Change in Cloud Cover Observed From EPIC

We performed a detailed analysis of Earth Polychromatic Imaging Camera (EPIC) spectral data. We found that the vector composed of blue and near-infrared (NIR) reflectance follows a counterclockwise closed-loop trajectory from 0 to 24 UTC as Earth rotates. This non-linear relationship was not observed by any other satellites due to limited spatial or temporal coverage of either low earth orbit (LEO) or geostationary (GEO) satellites. We found that clouds play an important role in determining the non-linear relationship in addition to the well-known cloud free land-ocean reflectance contrast in the two bands. The non-linear relationship is the result of three factors: (1) a much larger cloud free land-ocean contrast in the NIR band compared to the blue band; (2) significantly larger difference between cloudy-land and cloudy-ocean reflectance in theNIR band compared to the blue band; (3) the periodic variation of fractions of clear land, clear ocean, cloudy land, and cloudy ocean in the sunlit hemisphere as Earth rotates. We found that the green vegetation contributes significantly to the NIR global average reflectance when the South and North Americas appear and disappear in the EPIC's field-of-view. The blue and NIR relationship can be useful for exoplanet research. Clouds impose a strong impact on global spectral reflectance and the reflectance response to a change in cloud cover depends on whether the change is over land or over the ocean. On average, an increase of 0.1 in cloud coverage will lead to a 7%increase in spectrally integrated global average reflectance.

EPIC↗
NASA NTRS1987

Cloud cover over the equatorial eastern Pacific derived from July 1983 International Satellite Cloud Climatology Project data using a hybrid bispectral threshold method

A set of visible and IR data obtained with GOES from July 17-31, 1983 is analyzed using a modified version of the hybrid bispectral threshold method developed by Minnis and Harrison (1984). This methodology can be divided into a set of procedures or optional techniques to determine the proper contaminate clear-sky temperature or IR threshold. The various optional techniques are described; the options are: standard, low-temperature limit, high-reflectance limit, low-reflectance limit, coldest pixel and thermal adjustment limit, IR-only low-cloud temperature limit, IR clear-sky limit, and IR overcast limit. Variations in the cloud parameters and the characteristics and diurnal cycles of trade cumulus and stratocumulus clouds over the eastern equatorial Pacific are examined. It is noted that the new method produces substantial changes in about one third of the cloud amount retrieval; and low cloud retrievals are affected most by the new constraints.

Minnis, Patrick↗
NASA NTRS1987

Time-cumulated visible and infrared histograms used as descriptor of cloud cover

To study the statistical behavior of clouds for different climate regimes, the spatial and temporal stability of VIS-IR bidimensional histograms is tested. Also, the effect of data sampling and averaging on the histogram shapes is considered; in particular the sampling strategy used by the International Satellite Cloud Climatology Project is tested.

Seze, G.↗
NASA NTRS1988

Observations of the 30-60 day oscillation in zonal mean atmospheric angular momentum and high cloud cover

Zonally averaged momentum and high-cloud data were analyzed for the periods of April-October 1979 and November 1982-October 1983 periods. The analysis yielded belt correlation fields implying a symmetry and propagation of momentum out of the tropics in the momentum data and an asymmetrical oscillation across the equatorial zone in the high-cloud data. The 30-60 day oscillation was found to be the dominant periodicity in tropical and subtropical belts in both the momentum and cloud fields, with variation of time spectra evident between 1979 and 1983. The lag correlations between high cloud belts and momentum belts showed strong correlations with the 30-60 day oscillation present. Anomalously high/low zonal mean high cloudiness in the tropics was accompanied by anomalously high/low zonal mean momentum in the tropics, with the latter anomalies subsequently propagating into midlatitudes.

Risbey, James S.↗
NASA NTRS2009

Spatial and Temporal Inter-Relationship between Anomalies and Trends of Temperature, Moisture, Cloud Cover and OLR as Observed by AIRS/AMSU on Aqua

AIRS/AMSU is the advanced IR/MW atmospheric sounding system launched on EOS Aqua in May 2002. Products derived from AIRS/AMSU by the AIRS Science Team include surface skin temperature and atmospheric temperature profiled; atmospheric humidity profiles, fractional cloud clover and cloud top pressure, and OLR. Products covering the period September 2002 through the present have been derived from AIRS/AMSU using the AIRS Science Team Version 5 retrieval algorithm. In this paper, we will show results covering the time period September 2006 - November 2008. This time period is marked by a substantial warming trend of Northern Hemisphere Extra-tropical land surface skin temperatures, as well as pronounced El Nino - La Nina episodes. These both influence the spatial and temporal anomaly patterns of atmospheric temperature and moisture profiles, as well as of cloud cover and Clear Sky and All Sky OLR. The relationships between temporal and spatial anomalies of these parameters over this time period, as determined from AIRS/AMSU observations, will be shown with particular emphasis on which contribute significantly to OLR anomalies in each of the tropics and extra-tropics. Results will also be shown to evaluate the anomalies and trends of temperature profiles and OLR as determined from analysis of AIRS/AMSU data. Global and regional trends during the 6 1/3 year time period are not necessarily indicative of what has happened in the past, or what may happen in the future. Nevertheless, the inter-relationships of spatial and temporal anomalies of atmospheric geophysical parameters with those of surface skin temperature are indicative of climate processes, and can be used to test the performance of climate models when driven by changes in surface temperatures.

Susskind, Joel↗
NASA NTRS1986

The effect of spatial resolution on satellite derived cloud cover

The effects of a varying sensor spatial resolution on the cloud fraction derived by reflectance threshold (RT), IR temperature threshold (IRT), hybrid bispectral threshold (HBT) and spatial coherence (SC) methods for cloud retrieval from remotely sensed data were examined experimentally. Eight subscenes from four scenes acquired with the Landsat Thematic Mapper (TM) in 1982, 1983 and 1985 were used in the trials. All cloud retrieval methods were applied to extract the cloud fraction in all the subscences for comparison with the total cloud amount determined from the TM band 4 data, which had 28.5 m resolution.

Wielicki, B. A.↗
NASA NTRS1989

Cloud cover determinations with multispectral VAS observations - A two year study

The daily cloud statistics over North America from October 1985 to February 1988 were calculated from multispectral GOES/VAS observations in the CO2 absorption band at 15 microns. The CO2 technique is outlined and the mean statistics for the period are presented. The seasonal and geographical distributions of the VAS observations and diurnal changes in the cloud observations are summarized. It is found that there is a high incidence of transmissive cirrus clouds over North America and that these clouds have smaller geographical and seasonal variances than opaque clouds over the continental U.S. The possible use of multispectral techniques in the International Satellite Cloud Climatology Project is noted.

Menzel, W. P.↗
NASA NTRS1986

Spatial and temporal characteristics of global cloud cover as observed from the Nimbus-7 satellite

The spatial and temporal characteristics of the total cloud amount (TCA) were determined on the bases of 2 yr of data collected by Nimbus-7. The instruments used were the 11.5 microns channel of the Temperature Humidity IR radiometer and the 0.38 micron channel of the Total Ozone Mapping Spectrometer. Comparisons were made between long-term averages and large variations during the El Nino/Southern Oscillation event of 1982/83. Separate attention was also given to the TCA for the Northern and Southern Hemispheres, and to TCA averages over specific large-scale global features such as deserts.

Stowe, L. L.↗
NASA NTRS1974

Geographical correlation of earth cloud cover pictures obtained from unoriented satellites

Mathematical models have been developed for the determination of the geographic coordinates of cloud photographs taken from earth satellites. The proposed methods were realized on a Minsk-22 computer, and were used to process the earth cloud pictures obtained from the communications satellite Molyniya 1 and the automatic stations Zond 5 and 7. Experience using these methods showed that the accuracy of orientation angular element determination is on the order of 1 deg.

Solovyev, V. I.↗
NASA NTRS1985

Utilization of satellite-derived cloud cover to improve the estimation of latent heat release in a winter extratropical cyclone

A simple scheme for utilizing satellite cloud pattern information to improve the estimation of parameterized stable and convective latent heat release is proposed and tested for an extratropical cyclone occurring over the United States during January 9-11, 1975. Calculations are done over the standard North American rawinsonde data region and over a sparse data region simulated by ignoring one-third of the original rawinsonde stations. Results indicate 15 percent and 30 percent improvements in latent heating estimates derived from the total and sparse data sets, respectively. A larger improvement was found using the sparse data set because the parameterized latent heat release estimates obtained using these data were poorer than those obtained using the total data set.

Lin, S.-J.↗
NASA NTRS1992

On the determination of cloud cover from satellite sensors - The effect of sensor spatial resolution

The effect of sensor spatial resolution on satellite-derived estimates of cloud fractional coverage is quantified on the basis of Landsat satellite radiance data. Cloud fraction is found to depend on cloud algorithm as much as it depends on sensor spatial resolution. Even for 28.5-m spatial resolution data, large cloud fraction differences exist between algorithms. Satellite cloud retrieval algorithms depend strongly on sensor spatial resolution and/or on the optical depth of the cloud field. When present, spatial resolution effects are small (less than 0.01) for pixel diameter less than 1/4 km and are large for pixel diameter larger than 1 km. The International Satellite Cloud Climatology Project bispectral threshold gives an increase in cloud fraction of 0.11 as spatial resolution degrades from 20 m to 8 km. The spatial coherence algorithm underestimates boundary layer cloud fraction by 0.18. The use of functional box counting and an assumption of fractal scale invariance overestimates the dependence of cloud fraction for spatial scales below 1 km.

Wielicki, Bruce A.↗
NASA NTRS1990

Cloud cover analysis with Arctic Advanced Very High Resolution Radiometer data. II - Classification with spectral and textural measures

The spectral and textural characteristics of polar clouds and surfaces for a 7-day summer series of AVHRR data in two Arctic locations are examined, and the results used in the development of a cloud classification procedure for polar satellite data. Since spatial coherence and texture sensitivity tests indicate that a joint spectral-textural analysis based on the same cell size is inappropriate, cloud detection with AVHRR data and surface identification with passive microwave data are first done on the pixel level as described by Key and Barry (1989). Next, cloud patterns within 250-sq-km regions are described, then the spectral and local textural characteristics of cloud patterns in the image are determined and each cloud pixel is classified by statistical methods. Results indicate that both spectral and textural features can be utilized in the classification of cloudy pixels, although spectral features are most useful for the discrimination between cloud classes.

Key, J.↗
NASA NTRS2006

Seasonal and Interannual Variations of Top-of-Atmosphere Irradiance and Cloud Cover over Polar Regions Derived from the CERES Data Set

The semi-direct effects of dust aerosols are analyzed over eastern Asia using 2 years (June 2002 to June 2004) of data from the Clouds and the Earth s Radiant Energy System (CERES) scanning radiometer and MODerate Resolution Imaging Spectroradiometer (MODIS) on the Aqua satellite, and 18 years (1984 to 2001) of International Satellite Cloud Climatology Project (ISCCP) data. The results show that the water path of dust-contaminated clouds is considerably smaller than that of dust-free clouds. The mean ice water path (IWP) and liquid water path (LWP) of dusty clouds are less than their dust-free counterparts by 23.7% and 49.8%, respectively. The long-term statistical relationship derived from ISCCP also confirms that there is significant negative correlation between dust storm index and ISCCP cloud water path. These results suggest that dust aerosols warm clouds, increase the evaporation of cloud droplets and further reduce cloud water path, the so-called semi-direct effect. The semi-direct effect may play a role in cloud development over arid and semi-arid areas of East Asia and contribute to the reduction of precipitation.

Kato, Seiji↗
NASA NTRS2010

A 10-Year Climatology of Cloud Cover and Vertical Distribution Derived from Both Surface and GOES Observations Over the DOE ARM SGP Site

Analysis of a decade of ARM radar-lidar and GOES observations at the SGP site reveal that 0.5 and 4-hr averages of the surface cloud fraction correspond closely to 0.5deg and 2.5deg averages of GOES cloudiness, respectively. The long-term averaged surface and GOES cloud fractions agree to within 0.5%. Cloud frequency increases and cloud amount decreases as the temporal and spatial averaging scales increase. Clouds occurred most often during winter and spring. Single-layered clouds account for 61.5% of the total cloud frequency. There are distinct bimodal vertical distributions of clouds with a lower peak around 1 km and an upper one that varies from 7.5 to 10.8 km between winter and summer, respectively. The frequency of occurrence for nighttime GOES high-cloud tops agree well with the surface observations, but are underestimated during the day.

Xi, Baike↗