Kiyoshi Tsuchiya

Classification of cloud types based on data of multiple satellite sensors

Abstract Taking advantage of multispectral radiometers of VTIR of MOS-1 consisting of water vapor absorption and split-window channels, an attempt is made to develop an algorithm to classify cloud types of synopic meteorological significance. Verification of the algorithm based on the data of 4 channels of VTIR ( 1 visible, 1 water vapor absorption, 2 split window channels) onboard MOS-1 indicate that the algorithm works well for identifying well developed cumulonimbus, multilayered thick clouds and stratus/dense deep fog.

Ground surface features of the Taklimakan Desert

Abstract In an attempt to utilize satellite data to obtain land surface features of Taklimakan Desert in China, in situ measurements of spectral reflectance of the land surface is made the portable spectro radiometer in the spectral range of 400 ∼ 2500 nm. The analyses of the data show following features. (1) The difference in spectral reflectance of different soils is comparatively small. (2) There is a tendency that spectral reflectance of soils increases with increases of wavelength, for example, the average reflectance of the sands in the periphery areas of Taklimakan Desert is 21 and 38% in visible and near infrared spectra respectively. (3) It is found that reflectance of the soils decreases with increase of moisture content. The large decrease is recognized in 1450 and 1950 nm spectra, water absorption bands. This fact suggests that the monitoring of soil moisture is possible by measuring the radiance at these spectra, thus Landsat TM Bands 5 and 7 will be effective for monitoring soil moisture content.

Calibration of VISSR on board GMS-5

Operational Calibration method of visible and IR channels of GMS-5 VISSR is as follows. In the visible channel, albedo is computed by the following equation. A={(C−b0)b1}2a−V0a, where C and V0 are digital counts from VISSR and V0 is bias voltage corresponding to 0 albedo respectively, other coefficients are determined from prelaunch test data. A principle of IR channel calibration depends upon a linear relation between incoming IR radiance and output voltage of IR channel. Taking the space as a cold source and a calibration shutter in VISSR as a high source, a calibration regression equation to convert output voltage of IR channel into temperature is determined. A little correction is necessary to compensate non-linear response characteristics of IR detector at low temperature. To cope with a malfunction of calibration shutter (not frequent occurrence) a method of calibration without a shutter information is developed. The monitoring of solar radiance for one year indicates a small degradation in visible channel detectors. The degradation among 4 detectors is not uniform.

Influence of look-angle on the water surface temperature observed with an IR radiometer

Abstract The analysis of the data of sea surface temperature observed with a portable infrared radiometer from the fixed point on the seashore indicates a significant effect of observation(look) angle when it becomes larger than 70 degrees. An attempt is made to explain the effect by applying Fresnels reflection law. A verification indicates a good agreement between the sea surface temperature observed with a portable thermal IR radiometer at large observation angles and that computed from Fresnels reflection equation.

Normalized back scattering radar cross section of tropical rain forest in Rondonia, northern Brazil

Abstract Taking an advantage of Synthetic Aperture Radar (SAR) on board Japanese Earth Resources Satellite-1 (JERS-1) in capability of observing land surfaces through clouds, an attempt is made to extract deforested areas of tropical rain forests in Rondonia, Brazil. During the study the features of the normalized back scattering radar cross section σ ° are clarified. It was found that dense forests are characterized with the high values while sparse forests, bushes, range lands are characterized with the low values of σ ° depending on the density and physical characteristics of scatterers. In average following values are found: primary forests −6 ∼ −7 dB, secondary forests −7.5 ∼ −8.5 dB, pastures −10 ∼ −13 dB, rivers −15 ∼ −17 dB. It was also found that there is a seasonal effect on the values of σ ° reflecting the variation of the surface condition during the rainy and dry seasons.

Calibration of GMS-VISSR, features of MOS-VTIR and Landsat MSS

Abstract The analyses of sensitivity of visible channel of Visible and Infrared Spin Scan Radiometer onboard Geostationary Meteorological Satellite(GMS)-3 and -4 indicate stable for low reflective targets while a significant decreasing tendency with time for high reflective targets. Equations to correct the effect of temporal degradation are derived. Verification of data acquired with Visible and Thermal Infrared Radiometer onboard Marine Observation Satellite indicates that the Calibration is reasonable. Comparison of Landsat MSS image data processed at NASDA and NASA indicates a slight difference. It is found that the gain of Landsat-2 and -3 MSS is influenced by brightness of targets.

Integration of multiple satellite data for estimating sea surface transport

Abstract A sea surface transport model integrating the non-divergent geostrophic surface transport model with an input of sea surface temperature and the wind impact model with an input of sea surface wind speeds has been developed to estimate the sea surface transport, south of Japan under the influence of winter monsoon. The estimated transport by the model is verified by the transport from the surface to the depth of 120 meters obtained from the data of a ship-board acoustic doppler current profiler(ADCP) and the geostrophic transport estimated from the dynamic calculation along the observation lines. Results indicate that the sum of the geostrophic transport obtained by the dynamic calculation and the wind-driven transport estimated by the model along the observation line accounts most of the observed transport from the ADCP data.

Features of ozone distribution obtained from NIMBUS-7 TOMS data around typhoons

Abstract The pattern of total ozone distribution around typoons is studied in reference with NIMBUS-7 TOMS data and typhoon trck charts made by Japan Meteorological Agency. Out of 174 samples of typhoons in the area bounded by 10N/45N and 105E/160E latitude and longitude lines during the period 1980 through 1989, characterisitic patterns are recognized in 62 samples. The pattern is roughly classified into two types, i. e. the one with higher concentration in a central part while the other with higher concentration in the shape of spiral bands converging into the center. It is found that the latter appears when a typhoon is coupled with a trough of a large scale pressure system in the westerly zone. It is also found that the duration of the specific pattern of ozone distribution is comparatively short.

Selection method of initial guess values for surface temperature estimation from the satellite data

Abstract For the estimation of sea surface temperature on the basis of linearized inversion of the radiative transfer equation (Rodgers method), the selection method of the initial guess values of sea surface temperature and atmospheric condition is proposed. The selection method uses the temporal statistics of air temperature profile and precipitable water profiles as an atmospheric models. The satellite observed brightness temperature is calculated from the atmospheric models and some surface models, and the atmospheric model and surface model which makes the difference between the calculated and the observed radiance minimize is selected as the initial guess values. The sea surface temperature estimation from MOS-1/VTIR data shows a good correspondence to the sea truth data.