Hiroaki Kuze

An intercomparison of lidar-derived aerosol optical properties with airborne measurements near Tokyo during ACE-Asia

[1] During the ACE-Asia intensive observation period (IOP), an intercomparison experiment with ground-based lidars and aircraft observations was conducted near Tokyo. On 23 April 2001, four Mie backscatter lidars were simultaneously operated in the Tokyo region, while the National Center for Atmospheric Research C-130 aircraft flew a steppedascent profile between the surface and 6 km over Sagami Bay southwest of Tokyo. The C-130 observation package included a tracking Sun photometer and in situ packages measuring aerosol optical properties, aerosol size distribution, aerosol ionic composition, and SO2 concentration. The three polarization lidars suggested that the observed modest concentrations of Asian dust in the free troposphere extended up to an altitude of 8 km. We found a good agreement in the backscattering coefficient at 532 nm among lidars and in situ 180� backscatter nephelometer observations. The intercomparison indicated that the aerosol layer between 1.6 and 3.5 km was a remarkably stable and homogenous in mesoscale. We also found reasonable agreement between the aerosol extinction coefficients (sa � 0.03 km � 1 ) derived from the airborne tracking Sun photometer, in situ optical instruments, and those estimated from the lidars above the planetary boundary layer (PBL). We also found considerable vertical variation of the aerosol depolarization ratio (da) and a negative correlation between da and the backscattering coefficient (da) below 3.5 km. Airborne measurements of size-dependent optical parameters (e.g., the fine mode fraction of scattering) and of aerosol ionic compositions suggests that the mixing ratio of the accumulation-mode and coarse-mode (dust) aerosols was primarily responsible for the observed variation of da. Aerosol observations during the intercomparison period captured the following three types of layers in the atmosphere: a PBL (surface to 1.2–1.5 km) where fine (mainly sulfate) particles with a low da (<10%) dominated; an intermediate layer (between the top of the PBL and 3.5 km) where fine particles and dust particles were moderately externally mixed, giving moderate da; and an upper layer (above � 3.5 km) where dust dominated, giving a high da (30%). A substantial dust layer between 4.5 and 6.5 km was observed just west of Japan by the airborne instruments and found to have a lidar ratio of 50.4 ± 9.4 sr. This agrees well with nighttime Raman lidar measurements made later on this same dust layer as it passed over Tokyo, which found a lidar ratio of 46.5 ± 10.5 sr. INDEX TERMS: 0305 Atmospheric Composition and Structure: Aerosols and particles

Assessment of pan-sharpening methods applied to image fusion of remotely sensed multi-band data

Abstract Image fusion is a useful tool for integrating a high resolution panchromatic image (PI) with a low resolution multispectral image (MIs) to produce a high resolution multispectral image for better understanding of the observed earth surface. Various methods proposed for pan-sharpening satellite images are examined from the viewpoint of accuracies with which the color information and spatial context of the original image are reproduced in the fused product image. In this study, methods such as Gram-Schmidt (GS), Ehler, modified intensity-hue-saturation (M-IHS), high pass filter (HPF), and wavelet-principal component analysis (W-PCA) are compared. The quality assessment of the products using these different methods is implemented by means of noise-based metrics. In order to test the robustness of the image quality, Poisson noise, motion blur, or Gaussian blur is intentionally added to the fused image, and the signal-to-noise and related statistical parameters are evaluated and compared among the fusion methods. And to achieve the assessed accurate classification process, we proposed a support vector machine (SVM) based on radial basis function kernel. By testing five methods with WorldView2 data, it is found that the Ehler method shows a better result for spatial details and color reproduction than GS, M-IHS, HPF and W-PCA. For QuickBird data, it is found that all fusion methods reproduce both color and spatial information close to the original image. Concerning the robustness against the noise, the Ehler method shows a good performance, whereas the W-PCA approach occasionally leads to similar or slightly better results. Comparing the performance of various fusion methods, it is shown that the Ehler method yields the best accuracy, followed by the W-PCA. The producers and users accuracies of the Ehler method are 89.94% and 90.34%, respectively, followed by 88.14% and 88.26% of the W-PCA method.

One-year observation of urban mixed layer characteristics at Tsukuba, Japan using a micro pulse lidar

Abstract One-year characteristics of the urban mixed layer is observed by an eye-safe, compact micro pulse lidar (MPL). Retrieval method of the mixed layer height (MLH) and the encroachment model of the mixed layer growing are presented. Two case studies are carried out using summer and late winter data. Comparisons are made between the aerosol optical thickness, the rawinsonde data and the model calculation. The development of the mixed layer exhibits temporal behavior similar to that of the aerosol optical thickness, but with a time difference of about 1– 2 h . The growth rate of the MLH agrees well with the encroachment model only in the morning, with considerate deviation during the daytime because of the wind effect. One-year growth rate and the maximum MLH are estimated from the MPL measurement between May 1999 and May 2000. The results show that the properties of mixed layer are strongly correlated with the seasonal meteorological conditions. This work also demonstrates that an automated, compact lidar system such as a MPL is quite useful for long-term monitoring of the mixed layer.

Field-of-view dependence of lidar signals by use of Newtonian and Cassegrainian telescopes

The dependence of lidar return signals on the aperture size of the field stop is examined. Observational results are presented for both Newtonian and Cassegrainian telescopes. Analytic expressions are derived for the lidar geometric form factors, in satisfactory agreement with the experiments.

Development of Circularly Polarized Array Antenna for Synthetic Aperture Radar Sensor Installed on UAV

We have developed an array antenna consisting of 12 elements of simple square-shaped, corner-truncated patches for circularly polarized synthetic aperture radar (CP-SAR) operated in the L-band. The corporate feed design concept is implemented by combining a split-T and a 3-way circular-sector-shape power divider to excite circularly polarized radiation. The fabricated antenna based on the simulation using moment method gives a good circular polarization at the center frequency of 1.27GHz with an impedance bandwidth of 6.1% and 3-dB axial ratio bandwidth of 1.0%, satisfying the speciflcation for our circularly polarized synthetic aperture radar intended for use onboard an unmanned aerial vehicle and a small satellite.

ALOS PALSAR D-InSAR for land subsidence mapping in Jakarta, Indonesia.

Differential synthetic aperture radar interferometry (D-InSAR) is a technique capable of detecting land surface deformation. In this research, we use Advanced Land Observing Satellite (ALOS) Phased Array L-band SAR (PALSAR) data to investigate land subsidence in Jakarta during 2007 and 2008. It is found that four northern areas in the city exhibit clear indications of land subsidence. The location of the centre of subsidence is estimated, and the subsidence volume is evaluated for each area using the unwrapping method as a further process of using D-InSAR results. The subsidence depth and volume around the centre are estimated to be 10–22 cm and 0.2 × 105 – 4.2 × 105 m3, respectively, in the study time period. Comparison with ground survey data indicates that the D-InSAR analysis gives reliable estimates of the subsidence in an urban environment.

Comparison of Landsat image classification methods for detecting mangrove forests in Sundarbans

Remote-sensing images taken from the Landsat Enhanced Thematic Mapper Plus (ETM+) sensor with a spatial resolution of 30 m were applied for mapping and inventory of mangrove forest areas in Sundarbans, on both sides of the border between Bangladesh and India. Three different classification methods – unsupervised classification with k-means clustering, supervised classification using the maximum likelihood decision rule, and band-ratio supervised classification – were tested and compared in terms of the top of the atmosphere reflectance images. Spectral signature and principal component analyses were applied to select the appropriate band combinations prior to the band ratio–supervised classification. Our results show that the band ratio method is superior to the unsupervised or supervised classification methods considering the visual inspection, producers and users accuracy, as well as the overall accuracy of the all the classes in the image. The best discrimination of mangrove/nonmangrove boundary can be achieved when the combinations of B4/B2 (band 4/band 2), B5/B7, and B7/B4 are employed from the ETM+ bands.

Long-path measurement of atmospheric NO2 with an obstruction flashlight and a charge-coupled-device spectrometer

A novel method of differential optical absorption spectroscopy (DOAS) is proposed and demonstrated to monitor the concentration of atmospheric pollutant gas. In contrast to conventional DOAS measurements with continuous light sources, the present method relies on white flashlights such as aviation obstruction lights that are generally installed on tall constructions. A simple detection system is devised by means of a telescope and a compact CCD spectrometer. A path length of 5.5 km allows us to measure atmospheric NO2 concentration with a detection limit of approximately 1 part per billion. We also discuss the possibility of deriving the aerosol optical thickness through the horizontal atmosphere from this pulsed DOAS measurement.

Lidar network observation of Asian dust (Kosa) in Japan

We have organized a network campaign for the observation of Asian dust in the spring of 1997 and 1998 in Japan. Through the communication with electric mail, we have successfully observed Kosa events by lidar, sunphotometer, and particle counter, etc. These data must be useful to analyze the transport mechanism of Asian dust and validate the satellite observations.

Rotationally excited NO molecules incident on a graphite surface: molecular rotation and translation after scattering

Abstract The redistributions of rotational and kinetic energies of NO molecules scattered from an atomically flat graphite surface have been investigated. With the use of a heatable nozzle the rotational temperature of the incident molecules could be varied between 20 K and 650 K, the average incident kinetic energy remained constant at about 1000 cm −1 . Usually the in-plane angular distributions consist of a broad lobe of specularly scattered molecules together with a diffuse background. The diffuse component exhibits rotational accommodation to the surface temperature irrespective of the rotational energy of the incident molecules. The rotational temperature of the specular component is linearly proportional to the incident rotational temperature of NO. Saturation behavior is found when the surface temperature is increased up to 700 K. Additional molecular rotational energy in the incident channel is partially converted into kinetic energy of the scattered molecules. The relation between translational and rotational degrees of freedom is discussed on the basis of our observations.