Kazuhiro Naoki

Estimating energy consumption from night-time DMPS/OLS imagery after correcting for saturation effects

A methodology is presented to accurately estimate electric power consumption from saturated night-time Defense Meteorological Satellite Program (DMSP) Operational Linescan System (OLS) imagery using a stable light correction. An area correction for the stable light image of DMSP/OLS for the year 1999 was performed and the build-up area rate data were used to clarify the intensity distribution characteristics of the stable light. Based on the spatial distribution characteristics of the stable light, the saturation light of the electric power supply area of Japan was corrected using a cubic regression equation. The regression between the correction calculations by the cubic regression equation and the statistical electric power consumption data was applied in Japan and also in China, India and 10 other Asian countries. The correction method was then evaluated. This study confirms that electric power consumption can be estimated with high precision from the stable light.

Observation of sea-ice thickness in the sea of Okhotsk by using dual-frequency and fully polarimetric airborne SAR (pi-SAR) data

To investigate the possibilities of using dual-frequency, multipolarization synthetic aperture radar (SAR) data to monitor sea ice, we derived the relationship between various polarization characteristics and the physical parameters of sea ice. We discuss the frequency and polarization characteristics of the backscattering coefficients of sea ice and then characterize its thickness by comparing the corresponding backscattering coefficient for each polarization with the physical parameters of the ice. We first propose a methodology for classifying sea-ice types by using a polarimetric decomposition technique, before comparing an estimation of the sea-ice thickness with the corresponding dual-frequency, multipolarization SAR data. We utilized the backscattering ratio to estimate the thickness of the sea ice. This ratio canceled the effect of roughness on the backscattering. The method was validated using Pi-SAR (polarimetric and interferometric airborne SAR) observation data obtained at ground-truth sites.

Thin sea ice thickness as inferred from passive microwave and in situ observations

[1] Microwave radiometric signals from sea ice strongly reflect physical conditions of a layer near the ice surface. This study examines the extent to which the relationships of thickness with brightness temperature and with emissivity hold for thin sea ice, approximately <0.2-0.3 m, and how those relationships may arise from changes in brine characteristics through modification of dielectric properties near the ice surface. In order to address these questions we made concurrent measurements of sea ice thickness in the Sea of Okhotsk from a ship and passive microwave radiometry from an over-flying aircraft. The results show that the brightness temperature and emissivity increase with thickness approximately within the thin ice for a frequency range of 10-37 GHz. The relationship is more pronounced at lower frequencies and at the horizontal polarization. We also established an empirical relationship between ice thickness and salinity in the layer near the ice surface from a field experiment, which qualitatively supports the idea that changes in the near-surface brine characteristics contribute to the observed thickness-brightness temperature/emissivity relationship. On the basis of our results, we conclude that for thin ice, passive microwave radiometric signals likely contain indirect information on ice thickness through the dependence of dielectric properties on brine, which provides a plausible and common explanation for previously proposed passive microwave thickness algorithms.

AMSR2 validation results

The Advanced Microwave Scanning Radiometer 2 (AMSR2) on board the Global Change Observation Mission - Water 1st (GCOM-W1 or “SHIZUKU”) was launched on May 18, 2012 (JST), and continuous its observation from the A-Train orbit more than one year successfully. Validation results of eight geophysical parameters of AMSR2 standard products show that all products satisfied required release accuracy, and JAXA has released AMSR2 geophysical parameters to public though the GCOM-W1 Data Providing Service System (https://gcom-w1.jaxa.jp) since May 17, 2013.

Annual-layer determinations and 167 year records of past climate of H72 ice core in east Dronning Maud Land, Antarctica

Abstract To determine annual layers for reconstructing the past environment at annual resolution from ice cores, we employed snow-stake data back to 1972, tritium content, solid electrical conductivity measurements (ECM) and stratigraphic properties for the 73m ice core at the H72 site, east Dronning Maud Land, Antarctica. the average annual surface mass balance at H72 is 307 mma–1w.e. during the last 27 years from continuous accumulation data, 317 mma–1 w.e. according to the densification model and 311 mma–1 w.e. according to the average surface mass balance for 167 years based on annual-layer counting. the ECM age is closely coincident with tritium age, and corresponds with the snow-stake record back to AD 1972 from the surface to 15 m depth. the H72 ice core is dated as AD 1831by ECMat 73.16 mdepth.The time series of yearly surface mass balance at H72 shows an almost constant 311 mm a–1 w.e. for the last 167 years. the oxygen-isotope records indicate a significant trend to lower values, with negative gradient of 1.7% (100 years)–1.

Sea-ice thickness retrieval in the Sea of Okhotsk using dual-polarization SAR data

Abstract We investigated the feasibility of using multi-polarization Synthetic aperture radar (SAR) data to estimate the thickness of undeformed first-year ice. Analysis of the radar Signatures for the C- and L-bands Showed that the correlation between the ice thickness and VV-to-HH backscattering ratio is larger than the correlation between the ice thicknesses and the backscattering coefficients. This is in part because the ice Surface Salinity and hence the Surface reflection coefficient decreases as the ice thickens. The backscattering ratio had low Sensitivity to the Small-scale ice Surface roughness for the C-band and is almost independent of roughness at L-band. Given that the ratio is most Sensitive to ice Surface dielectric constants, which depend on Salinity, we developed an algorithm for retrieving the ice thickness that is based on the backscattering ratio and on the integral-equation-method (IEM) Surface Scattering model. Comparison of the observed and estimated ice thicknesses Showed that the correlation was much better when the thicknesses were estimated using the backscattering ratio than when the backscattering coefficient was used directly. The algorithm also performed better than previous retrievals using an empirical technique.

Status of AMSR2 on GCOM-W1

The Global Change Observation Mission (GCOM) consists of two polar orbiting satellite observing systems, GCOM-W (Water) and GCOM-C (Climate), and three generations to achieve global and long-term monitoring of the Earth. GCOM-W1, which is the first satellite of the GCOM-W series, was launched from the Tanegashima Space Center on May 18, 2012 (Japan Standard Time), and moved to the regular observation operation on August 10, 2012 (JST) after the early orbit checkout had been completed. The early initiation of the Advanced Microwave Scanning Radiometer-2 (AMSR2) on GCOM-W1 observation was highly desired since the Advanced Microwave Scanning Radiometer for the Earth Observing System (AMSR-E) had halted its observation in October 2011 due to the increase of antenna rotation torque. The calibration activity of AMSR2 is going on toward the data release of Level-1 product scheduled in the beginning of 2013. The initial checkout of the ground segment, including systems for receiving, processing, archiving, and distributing the GCOM-W1 data, is also completed successfully. At-launch retrieval algorithms were used for the checkout. These algorithms will be validated and updated through calibration and validation activities. Public data release is scheduled one year after launch for geophysical parameters. Standard products will be available via online, free of charge, from the GCOM-W1 data providing service system. The AMSR-E products are already available from the same system.

Status of GCOM-W1/AMSR2 development, algorithms, and products

The Global Change Observation Mission (GCOM) consists of two polar orbiting satellite observing systems, GCOM-W (Water) and GCOM-C (Climate), and three generations to achieve global and long-term monitoring of the Earth. GCOM-W1 is the first satellite of the GCOM-W series and scheduled to be launched in Japanese fiscal year 2011. The Advanced Microwave Scanning Radiometer-2 (AMSR2) will be the mission instrument of GCOM-W1. AMSR2 will extend the observation of currently ongoing AMSR-E on EOS Aqua platform. Development of GCOM-W1 and AMSR2 is progressing on schedule. Proto-flight test (PFT) of AMSR2 was completed and delivered to the GCOM-W1 satellite system. Currently, the GCOM-W1 system is under PFT at Tsukuba Space Center until summer 2011 before shipment to launch site, Tanegashima Space Center. Development of retrieval algorithms has been also progressing with the collaboration of the principal investigators. Based on the algorithm comparison results, at-launch standard algorithms were selected and implemented into the processing system. These algorithms will be validated and updated during the initial calibration and validation phase. As an instrument calibration activity, a deep space calibration maneuver is planned during the initial checkout phase, to confirm the consistency of cold sky calibration and intra-scan biases. Maintaining and expanding the validation sites are also ongoing activities. A flux tower observing instruments will be introduced into the Murray-Darling basin in Australia, where the validation of other soil moisture instruments (e.g., SMOS and SMAP) is planned.

Sea ice thickness observation in the sea of okhotsk using ENVISAT/ASAR data

To investigate the possibilities of multi-polarization synthetic aperture radar (SAR) data to monitor sea-ice, we derived the relationship between polarization characteristics and the physical parameters of the sea-ice. We discuss the polarization characteristics of the backscattering coefficients of the sea-ice and then describe the sea-ice thickness by comparing the corresponding backscattering coefficient for each polarization with the physical parameters of the ice. We propose a retrieval algorithm for sea-ice thickness, which apply a backscattering ratio to estimate the thickness of the sea-ice. This ratio is calculated using a surface scattering model, which cancels the effect of roughness on backscattering. The method was validated using the Advanced SAR (ASAR) onboard ENVISAT satellite observation data obtained at ground-truth sites.

PiSAR-L2 observation of agricultural area damaged by seawaterduring the Great East Japan Earthquake in 2011

On March 11, 2011, a massive earthquake occurred on the eastern coast of Japan. The magnitude 9.0 quake was the most powerful ever recorded in Japan. The height of the tsunami that followed the earthquake was estimated to be more than 10 m. The water reached a few kilometers inland and resulted in thousands of casualties as well as serious damage to buildings and agricultural areas along the coastline. Several PiSAR-L2 observations were carried out in these tsunamiaffected areas from April to September in 2012, and field experiments were performed in agricultural areas that had been damaged by seawater. The complex dielectric constant and the electrical conductivity of the soil were measured to estimate the soil’s salinity. The imaginary part of the dielectric constant for a tsunami-damaged area 0.7 km from the coastline was shown to be 37.1 at 1 GHz, and the electric conductivity was shown to be 7.8 mS/cm. These values exceeded those from non-damaged inland areas. One of the full polarimetric parameters, co-polarization backscattering ratio (σ0HH/σ0VV) derived from PiSAR-L2 data, were examined and compared for damaged/non-damaged areas. The analysis indicates that the higher-salinity area was well detected by σ0HH/σ0VV. However, water areas and flat surfaces covered by gravel exhibit similar characteristics, and this may result in the false detection of salt-affected agricultural areas.