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Kim, Hongsuk H.

Publications and source records attributed to Kim, Hongsuk H..

7 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

Newly found evidence of Sun-climate relationships

Solar radiation cycles drive climatic changes intercyclically. These interdecadal changes were detected as variations in solar total irradiances over the time period of recorded global surface-air-temperature (SAT) and have been restored utilizing Earth Radiation Budget Channel 10C measurements (1978-1990), Greenwich Observatory faculae data (1874-1975), and Taipei Observatory Active Region data (1964-1991). Analysis of the two separate events was carried out by treating each as a discrete time series determined by the length of each solar cycle. The results show that the global SAT responded closely to the input of solar cyclical activities, S, with a quantitative relation of T = 1.62 * S with a correlation coefficient of 0.61. This correlation peaks at 0.71 with a built-in time lag of 32 months in temperature response. Solar forcing in interannual time scale was also detected and the derived relationship of T = 0.17 * S with a correlation coefficient of 0.66 was observed. Our analysis shows derived climate sensitivities approximately fit the theoretical feedback slope, 4T(sup 3).

Kim, Hongsuk H.↗
NASA NTRS1991

Surface radiation budget imagery

Linear regressions which summarize the relationships between the turbulent fluxes of heat and latent heat of vaporization leaving the surface and surface albedos are given. This observation is based on a semi-empirical analysis of the data collected from sets of Landsat/TM (Thematic Mapper) imagery as the top of the atmosphere images have been converted into maps of surface radiation budget. A preliminary analysis shows that in spite of the land surface's temporal and spatial variability, the transfer of latent and sensible heat into the atmosphere would appear to be governed by the land surface albedo.

Kim, Hongsuk H.↗
NASA NTRS1990

Normalization of satellite imagery

Sets of Thematic Mapper (TM) imagery taken over the Washington, DC metropolitan area during the months of November, March and May were converted into a form of ground reflectance imagery. This conversion was accomplished by adjusting the incident sunlight and view angles and by applying a pixel-by-pixel correction for atmospheric effects. Seasonal color changes of the area can be better observed when such normalization is applied to space imagery taken in time series. In normalized imagery, the grey scale depicts variations in surface reflectance and tonal signature of multi-band color imagery can be directly interpreted for quantitative information of the target.

Kim, Hongsuk H.↗
NASA NTRS1989

Differential imaging system

In this study, a technique which enhances image contrast using differentials of radiances being measured from successively overlapping footprints is discussed. One of the immediate advantages of this approach is to improve spatial resolution when the practical size limitation of detectors is reached. When diffraction is considered, radiometric accuracy at the higher spatial frequencies is decreased even though edge response (boundary crossing sharpness) will improve. For instance, an imager system based on this principle could have a primary aperture no larger than 30 cm diameter yet be capable of resolving a ground footprint as small as 2 m from a 780 km altitude.

Kim, Hongsuk H.↗
NASA NTRS1988

Atmospheric effect removal from space imagery

A method to derive a ground reflectance scene from space imagery by removing the contribution of atmospheric radiance was developed. The method utilizes a multiple scattering radiative transfer code to model the Earth-atmosphere system and converts the output into a set of quadratic coefficients which best fit the relationships between the upwelling radiance reaching the sensor and the lower boundary conditions of the ground reflectance. Pixel by pixel correction of the atmospheric effects is done by invoking these coefficients. The algorithm was applied to a number of Thematic Mapper and CZCS data to generate interesting ground scenes and was used to simulate space imagery from ground reflectance scenes.

Kim, Hongsuk H.↗
NASA NTRS1986

Sunlight induced 685 nm fluorescence imagery

The capability of a new fluorescence method is evaluated using data from an aircraft fluorescence experiment conducted on the Elbe River on August 10-14, 1981. The technique measures chlorophyll concentrations by monitoring sunlight-induced fluorescence at 685 nm. Upwelling radiance spectra and vertical profiles of upwelling radiances are presented and analyzed. The image-processing algorithm used to retrieve fluorescence signals from raw data is described.

Kim, Hongsuk H.↗