The GCOM-C (SHIKISAI) satellite was developed to understand the mechanisms of global climate change. The Second-generation Global Imager (SGLI) onboard GCOM-C is an optical sensor observing wavelengths from 380 nm to 12.0 μm in 19 bands. One of the notable features is that the resolution of the 1.63-, 10.8-, and 12.0-µm bands is 250 m, with an observation frequency of 2-3 days. To investigate the effective use and potential of the 250-m resolution of these SGLI bands in the study of eruptive activities, we analyzed four practical cases. As an example of large-scale effusive activity, we studied the 2018 Kilauea eruption. By analyzing the series of 10.8-μm band images using cumulative thermal anomaly maps, we could observe that the lava effused on the lower East Rift Zone, initially owed down the southern slope to the sea, and then moved eastward. As an example of lava dome growth and generation of associated pyroclastic ows, the activity at Sheveluch between December 2018 and December 2019 was analyzed. The 1.63-and 10.8-µm bands were shown to be suitable for observing growth of the lava dome and occurrence of pyroclastic ows, respectively. We found that the pyroclastic ows occurred during periods of rapid lava dome expansion. For the study of an active crater lake, the activity of Ijen during 2019 was analyzed. The lake temperature was found to rise rapidly in mid-May and reach 38 °C in mid-June. We also analyzed the intermittent activities of small-scale Vulcanian eruptions at Sakurajima in 2019. The 1.63-µm band was useful for detecting activities that are associated with Vulcanian eruptions. Analytical results for these case studies demonstrated that the GCOM-C SGLI images are bene cial for observing various aspects of volcanic activity, and their real-time use may contribute to reducing eruption-related disasters.
We propose a possible mechanism for the influence of the Northern Hemisphere annular mode/Arctic Oscillation (NAM/AO) on westerly wind bursts (WWB). Using 26‐year reanalysis data, we statistically demonstrate and evidentially confirm that the NAM intensifies WWB through Asian cold and dry surges. Twin cyclones with anomalous westerlies and updrafts were dominant in the western tropical Pacific in positive NAM years. This structure was caused by the inflow of cold and dry advections associated with cold and dry surges, which excited anomalous heat transport from the western tropical Pacific Ocean. This thermodynamic structure is similar to that of the Matsuno‐Gill pattern. Observational evidence indicates that the surge associated with the NAM is a probable cause of El Niño outbreaks through the intensification of WWB, stemming from the WWB association with the Matsuno‐Gill pattern.
The interferometric monitor for greenhouse gases (IMG) was the precursor of the high-resolution Fourier-transform infrared radiometer (FTIR) onboard a satellite for observation of the Earth. The IMG endured the stress of a rocket launch, demonstrating that the high-resolution, high-throughput spectrometer is indeed feasible for use onboard a satellite. The IMG adopted a newly developed lubricant-free magnetic suspension mechanism and a dynamic alignment system for the moving mirror with a maximum traveling distance of 10 cm. We present the instrumentation of the IMG, characteristics of the movable mirror drive system, and the evaluation results of sensor specifications during space operation.
A night-time OLS (Operational Linescan System) visible± near-infrared (VNIR) channel image of the DMSP (Defense Meteorological Satellite Program) was overlaid on the simultaneously corrected OLS thermal infrared (TIR) channel image for the area around Japan. The OLS composite image showed a clear relationship between the location of ® shing¯eet lights detected by the VNIR channel and the sea surface temperature (SST) distribution observed by the TIR channel. Many ® shing¯eets were located at the cold side of the boundary area between warm currents and cold currents. Since some types of ® sh are likely to gather in certain sea temperature zones, the OLS composite image may provide useful information for the monitoring of ® shing¯eets as well as for marine resources management.
We investigate the cloud detection efficiency of existing and future spaceborne visible-to-infrared imagers, focusing on several threshold tests for cloud detection over different types of ground surfaces, namely, the ocean, desert, vegetation, semibare land, and cryosphere. In this investigation, we used the CLoud and Aerosol Unbiased Decision Intellectual Algorithm (CLAUDIA), which was developed for unbiased cloud detection. It was revealed that imagers with fewer bands than the Moderate Resolution Imaging Spectroradiometer tend to have cloudy shifts. An imager without any infrared bands could yield cloudy shifts up to 17% over the ocean. To avoid false recognition of Sun glint as clouds, the 0.905 and 0.935 μm bands are needed in addition to the infrared bands. In reflectance ratio tests, the 0.87 and 1.6 μm bands can effectively distinguish clouds from desert. In the case of desert, thermal-infrared bands are ineffective when the desert surface temperature is low during winter. The 3.9 and 11 μm bands are critical for distinguishing between clear and cloudy pixels over snow-/ice-covered areas. The results and discussions of this research can guide CLAUDIA users in the optimization of thresholds. Here, we propose a virtual imager called the cloud detection imager, which has seven or eight bands for efficient cloud detection.
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