Makoto Kuji

OPTIMIZATION OF THE ADVANCED EARTH OBSERVING SATELLITE II GLOBAL IMAGER CHANNELS BY USE OF RADIATIVE TRANSFER CALCULATIONS

The channel specifications of the Global Imager onboard the Advanced Earth Observing Satellite II have been determined by extensive numerical experiments. The results show that there is an optimum feasible position for each ocean color channel. The bandwidth of the 0.763-microm channel should be less than 10 nm for good sensitivity to the cloud top height and geometric thickness of the cloud layer; a 40-nm bandwidth is suitable for the 1.38-microm channel to have the strongest contrast between cloudy and clear radiance with a sufficient radiant energy; and a 3.7-microm channel is better than a 3.95-microm channel for estimation of the sea surface temperature (SST) and determination of the cloud particle size when the bandwidth of the channel is 0.33 microm. A three-wavelength combination of 6.7, 7.3, and 7.5 microm is an optimized choice for water vapor profiling. The combination of 8.6, 10.8, and 12.0 microm is suitable for cloud microphysics and SST retrievals with the split-window technique.

Air truth validation of cloud albedo estimated from NOAA advanced very high resolution radiometer data

A comparison was carried out between cloud albedos observed in situ by aircraft and cloud albedos calculated with visible optical thickness retrieved from the NOAA advanced very high resolution radiometer channel 1 radiance data. The results show that the observed and calculated cloud albedos in the visible region are coincident with each other in a few percent for both homogeneous stratus and rather inhomogeneous stratocumulus clouds as long as the cloud amount is large. In the near-infrared region, on the other hand, the observed albedo is lower than that evaluated from the satellite data for stratocumulus clouds, while the observed and calculated albedos are consistent for stratus clouds. From the aircraft observation of solar radiative flux this discrepancy is not ascribed to the uncertainty in the near-infrared absorption processes as discussed in previous studies.

Retrieval of cloud geometrical parameters using remote sensing data

It is of great interest to investigate the properties on the cloud optical, microphysical, and geometrical parameters, in particular, of low-level marine clouds which play crucial influence on the global climate system. Top height, base height, and geometrical thickness of cloud layer are considered here as cloud geometrical parameters. These parameters are very important to retrieve, because top and base heights are the factors which govern the strength of greenhouse effect through the thermal radiation from/to cloud layer, whereas the geometrical thickness is the key parameter for the estimation of gaseous absorption in cloud layer where multiple scattering process dominates. In this study, an algorithm was developed to retrieve simultaneously cloud optical thickness, effective particle radius, top height, and geometrical thickness of cloud layer from the spectral information of visible, near infrared, thermal infrared, and oxygen A band channels. This algorithm was applied to FIRE (First ISCCP Regional Experiment, 1987) airborne data which included the above four channels and targeted at the low-level marine clouds off the coast of California in summer. The retrieved results seems to be comparable to the in situ microphysical observation although further validation studies are required for the cloud geometrical parameters in particular.

Retrieval of Asian dust amount over land using ADEOS-II/GLI near UV data

We propose a retrieval method of Asian dust (Yellow sand or Kosa aerosol) columnar amount around source regions using a near ultraviolet radiometry observation from space. The method simultaneously retrieves an optical thickness and mode radius of Kosa aerosol, and then derives its columnar amount. The method was applied to ADEOS-II / GLI data in the spring of 2003 around Taklimakan desert source region, inland China. The retrieved optical thickness and mode radius were about 0.34 and 1.75 μm, respectively, at a validation site. They are comparable to the in situ observations conducted within the framework of ADEC project. The estimated columnar amount around a validation site is about 2.77 g m-2, which seems reasonable under a relatively calm situation. The method should be further validated with a regional model simulation study, and then it is useful to monitor Asian dust around source regions from space in the future.

Retrieval of cloud geometrical properties using ADEOS-II/GLI data for radiation budget studies

Clouds play a crucial role in the climate system. The investigation of their radiative properties on the cloud optical, microphysical, and geometrical characteristics is of great interest. Here, top height, base height, and geometrical thickness of cloud layer are considered as cloud geometrical properties. Several studies show that information of some spectral regions including oxygen A-band, enables us to retrieve the cloud geometrical properties as well as the optical thickness and the effective particle radius of cloud. In this study, an algorithm was developed to retrieve simultaneously the cloud optical thickness, effective particle radius, top height, and geometrical thickness of cloud layer with the spectral information of visible, near infrared, thermal infrared, and oxygen A-band channels. This algorithm was applied to ADEOS-II / GLI. For the preparation of global analysis, we look into the look up tables for the sensitivity of cloud optical thickness, particle size, top height, and geometrical thickness. This study will expand to the global analysis and is anticipated to contribute to the earth climate studies in terms of cloud optical, microphysical, and geometrical properties.

Retrieval of precipitable water using ADEOS-II/GLI near infrared data

Retrieval of vertically integrated water vapor amount (precipitable water) is proposed using near infrared channels of Global Imager onboard Advanced Earth Observing Satellite-II (GLI/ADEOS-II). The principle of retrieval algorithm is based upon that adopted with Moderate Resolution Imaging Spectroradiometer (MODIS) onboard Earth Observing System (EOS) satellite series. Simulations were carried out with GLI Signal Simulator (GSS) to calculate the radiance ratio between water vapor absorbing bands and non-absorbing bands. As a result, it is found that for the case of high spectral reflectance background (a bright target) such as the land surface, the calibration curves are sensitive to the precipitable water variation. It turns out that aerosol loading has little influence on the retrieval over a bright target for the aerosol optical thickness less than about 1.0 at 500 nm wavelength. A preliminary analysis of GLI data was also carried out and the retrieved result is discussed. It is also anticipated that simultaneous retrieval of the water vapor amount using GLI data along with other channels will lead to improved accuracy of the determination of surface geophysical properties, such as vegetation, ocean color, and snow and ice, through the better atmospheric correction.

Retrieval of cloud geometrical properties using optical remote sensing data

It is of great interest to investigate the properties on the cloud optical, microphysical, and geometrical parameters, in particular, of low-level marine clouds which play crucial influence on the global climate system. Top height, base height, and geometrical thickness of cloud layer are considered here as cloud geometrical parameters. These parameters are very important to retrieve, because top and base heights are the factors which govern the strength of greenhouse effect through the thermal radiation from/to cloud layer, whereas the geometrical thickness is the key parameter for the estimation of gaseous absorption in cloud layer where multiple scattering process dominates. In this study, an algorithm was developed to retrieve simultaneously cloud optical thickness, effective particle radius, top height, and geometrical thickness of cloud layer from the spectral information of visible, near infrared, thermal infrared, and oxygen A band channels. This algorithm was applied to FIRE (First ISCCP Regional Experiment, 1987) airborne data which included the above four channels and targeted at the low-level marine clouds off the coast of California in summer. The retrieved results seems to be comparable to the in situ microphysical observation although further validation studies are required for the cloud geometrical parameters in particular.

DRAGON-West Japan campaign in 2012: regional aerosol measurements over Osaka

It is known that the aerosol distribution in Asia is complicated due to the increasing emissions of anthropogenic aerosols in association with economic growth and natural dust significantly varied with the seasons. Therefore it is clear that local spatially and temporally resolved measurements of atmospheric aerosols in Asian urban city are necessary. Since Osaka, Kobe, Kyoto, and Nara are located in very close each others (all cities are included in around 70×70 km2 area). The population of the region is around 13 millions including neighbor prefectures, accordingly air quality in this region is slightly bad in comparison with the remote area. Furthermore, in recent years, Asian dusts and anthropogenic small particles some times transported from China and cover these cities throughout year. DRAGON (Distributed Regional Aerosol Gridded Observation Network) is a project of dense sun/sky radiometer network in the urban area. The DRAGON-West Japan field campaign was performed over Osaka and neighbor cities with 7 AERONET instruments from March to end of May in 2012. As results, DRAGON measurements indicate small differences among the values of AOT over Osaka region.

Retrieval of water cloud top and bottom heights and the validation with ground-based observations

It is of great interest to investigate the optical, microphysical, and geometrical properties of clouds that play crucial role in the earth climate system. Water clouds are generally optically thick and consequently have a great cooling effect on earth-atmosphere radiation budget. The water clouds usually exist in a lower troposphere where aerosol-cloud interaction occurs frequently, and then cloud droplet size variation in uences re ection of solar radiation as well. Further, a cloud layer height is one of the key properties that determine downward longwave radiation and then surface radiation budget. In this study, top height, geometrical thickness and bottom height of a water cloud layer are investigated as cloud geometrical properties in particular. Several studies show that observation data of some spectral regions including oxygen A-band, enables us to retrieve the cloud geometrical properties as well as the optical thickness and the effective particle radius. In this study, an algorithm was developed to retrieve simultaneously the cloud optical thickness, effective particle radius, top height, geometrical thickness and then bottom height of a cloud layer with the spectral observation of visible, near infrared, thermal infrared, and oxygen A-band channels. This algorithm was applied to Advanced Earth Observing Satellite － II / Global Imager (ADEOS-II / GLI) dataset so as to retrieve global distribution of cloud geometrical properties. The retrieved results around Japan were compared with other observation such as ground-based active sensors, which suggest this algorithm works for cloud system over ocean at least although the cloud bottom height was underestimated. The underestimation is attributed to cloud inhomogeneity at this stage and should be investigated in detail.

Retrieval of cloud top and bottom heights using advanced Earth observing satellite / global imager (ADEOS-II / GLI) data

An algorithm was developed to retrieve simultaneously the cloud optical thickness, effective particle radius, top height, geometrical thickness and then bottom height of a cloud layer with the spectral observation of visible, near infrared, thermal infrared, and oxygen A-band channels. The algorithm was applied to Advanced Earth Observing Satellite-II / Global Imager (ADEOS-II / GLI) dataset so as to retrieve global distribution of cloud geometrical properties. The retrieved results around Japan were compared with other observations such as ground-based active sensors and aircraft. It was found that the retrieved cloud base height was comparable, but underestimated by a few hundred meters from the ground-based active cloud radar observation even though there possibly existed a drizzling mode in the observed cloud system. The comparison suggests the algorithm works for water cloud system over ocean at least, while it is necessary to make further validation study with other studies such as ground-, space-ba...