Sulfur dioxide (SO2) absorbs ultraviolet (UV) radiation, and airborne spectrometers can measure its spatial distribution using backscattered solar light. A new algorithm was developed to estimate the SO2 vertical column amount. This algorithm is based on the Differential Optical Absorption Spectroscopy (DOAS) technique and the radiative transfer calculation. Aircraft-borne measurements using a ultraviolet spectrometer, the Airborne-OPUS, were performed above Miyake-jima (34°N, 139.5°E) in January 2002. The amount of SO2 estimated by the Airborne-OPUS was validated using SO2 mixing ratios measured simultaneously by an onboard air-sampling sensor during the spiral-down flight above and inside volcanic plumes. The results suggested that the above algorithm is capable of quantifying the column amount of volcanic SO2.
The effect of the dependence of the satellite data on sun/sensor geometry must be considered in the case of monitoring vegetation from satellites. Vegetation structure causes uneven scattering of sunlight, which is expressed by bi-directional reflectance distribution function (BRDF). The purpose of this study is to estimate the effect of BRDF on monitoring vegetation using the reflectance of visible and near-infrared bands. We investigated the vegetation in succession stages after forest fire (main species : spruce) in the northwestern Canada. BRF (Bidirectional Reflectance Factor) was measured in the seven sites of some succession stages, along with the measurements of leaf area index (LAI) and biomass. The main results obtained in this study are summarized as follows. (1) In each site, the difference of Normalized Difference Vegetation Index (NDVI) value around 0.1-0.2 was caused by BRDF when the sensor angle was changed from -15°to 15°, being equivalent to the standard image of IKONOS. Also, LAI estimated by NDVI varied from 22% to 65% of the average. (2) The robustness of other vegetation indices to BRDF was compared. The reflectance of the near-infrared band normalized by the sum of other bands (nNIR), and Global Environmental Monitoring Index (GEMI) were investigated along with NDVI. It is clarified that nNIR was most robust in the site where vegetation existed. GEMI was most robust in the sites of scarce vegetation, while NDVI was strongly affected by BRDF in such sites.
This research aims to develop a remote sensing method for monitoring rice production in Japan. A photosynthesis-based crop production index CPI for rice is proposed that takes into consideration the solar radiation, the effective air temperature, and normalized vegetation index NDVI as a factor representing vegetation biomass. The CPI index incorporates temperature influences such as the effect of temperature on photosynthesis by grain plant leaves, low-temperature effects of sterility, cool summer damage due to delayed growth, and high-temperature injury. These latter factors are significant at around the heading period of rice. The CPI index for rice was modeled at ten monitoring sites in the Kanto, Tohoku, and Hokkaido districts, which occasionally tend to suffer poor harvests as a result of low temperatures. The photosynthesis-based crop production index CPI proposed here can predict the crop situation index of rice by using NDVI, solar radiation at meteorological observatories and air temperature at AMeDAS sites. The method is based on routine observation data, allowing automated monitoring of rice situation index at arbitrary sites in Japan. However, it is possible to further refine the estimation formula for the rice situation index for early monitoring.
In this study, spatio-temporal patterns of continuous paddy fields were examined using the patterns observed in metrics calculated for 1-year of MODIS over China. Four analytical approaches were used ; calculation of temporal mean, maximum and minimum layers for selected metrics showing significant spatial variability of channel 1, 2 and NDVI ; linear discriminant for input into the un-mixing analysis was derived from the same multi-temporal metrics used for the classification product using National Land Cover Data (NLCD) set of China ; the continuous percentage of paddy field was generated based on un-mixing technique with the training data derived from the above mentioned NLCD data. The derived metrics were not sensitive to time of year or the seasonal cycle and can limit the inclusion of atmospheric contamination. The comparison of 250m MODIS product with the past efforts on lkm AVHRR, MODIS and SPOT-VEGETATION product, and statistics by IRRI showed that the finer resolution and its un-mixing played a crucial role in depicting the paddy field cover over China.
The warm ocean water filaments generated periodically from the meandering Kuroshio Current at the East China Sea influences to the south coast of Kyushu such as the intermittent warm ocean water intrusion into Kagoshima bay well known as Kyucho phenomenon. From the observation with satellite-derived sea surface temperature (SST), the warm water intrusion not only into Kagoshima Bay but also offshore of Fukiage seashore are found. The intrusions occur when the warm water comes into touch with the bay water at the mouth of the bay. In addition to the warm water intrusion, SST image shows the cold-water mass emanating at the coast of Osumi peninsula. While warm water passes through the Osumi strait, it is found that the region of the cold-water is formed along the coast of Osumi peninsula. Then the numerical analysis using a multi-leveled finite difference method (FDM) is performed for the purpose to investigate these phenomena. It is found from the numerical analysis : (1) The intrusions occur when the warm water comes into touch with the mouth of Kagoshima bay or the east edge of Noma cape. (2) Intruding speed and thickness of the warm water into Kagoshima bay show the same tendency as the existing report from buoy robot data and the simulation of a limited domain. (3) The cold-water mass emanated at the coast of Osumi peninsula forms vortex and stagnation region, and the calculated vertical velocity structure shows anticlockwise circulation at the mouth of Kagoshima Bay.