Takashi Y. Nakajima

A Global determination of cloud microphysics with AVHRR remote sensing

An algorithm is developed for determining the cloud optical thickness and effective particle radius simultaneously on a global scale using Advanced Very High Resolution Radiometer (AVHRR) multispectral radiance data. In the algorithm, the treatment of thermal radiation in Nakajima and Nakajima is improved by reformulating the thermal emission in the atmospheric layers. At the same time, the lookup table for thermal emission is parameterized in terms of the equivalent water vapor path in order to include the effect of various vertical water vapor profiles. The algorithm is applied to AVHRR radiance data corresponding to reported aircraft and balloon measurements of cloud microphysical parameters. A comparison shows a good agreement between in situ and satellite-retrieved values thus obtained. The algorithm is further applied to 4-month Global Area Coverage data of 1987 to generate global distributions of the cloud optical thickness and effective particle radius for every 0.5 83 0.58 box in a 2608‐608 latitudinal region. Similarities and differences in the global features of the effective particle radius and the optical thickness are found as compared with the previous studies.

Significance of direct and indirect radiative forcings of aerosols in the East China Sea region

� 8W /m 2 at the top of atmosphere (TOA) and � 10 to � 23 W/m 2 at Earth’s surface of Gosan (33.28N, 127.17E) and Amami-Oshima (28.15N, 129.30E) sites, though there is a large regional difference caused by changes in the aerosol optical thickness and single scattering albedo. The cloud forcing is estimated as � 20 to � 40 W/m 2 , so that the aerosol direct forcing can be comparable to the cloud radiative forcing at surface. However, the estimate of the aerosol direct forcing thus obtained strongly depends on the estimation method of the aerosol properties, especially on the single scattering albedo, generating a method difference about 40%. The radiative forcing of the aerosol indirect effect is roughly estimated from satellite method and SPRINTARS model as � 1t o� 3W /m 2 at both TOA and surface. INDEX TERMS: 0305 Atmospheric Composition and Structure: Aerosols and particles (0345, 4801); 0345 Atmospheric Composition and Structure: Pollution—urban and regional (0305); 1610 Global Change: Atmosphere (0315, 0325); 9320 Information Related to Geographic Region: Asia;

The EarthCARE Satellite: The Next Step Forward in Global Measurements of Clouds, Aerosols, Precipitation, and Radiation

AbstractThe collective representation within global models of aerosol, cloud, precipitation, and their radiative properties remains unsatisfactory. They constitute the largest source of uncertainty in predictions of climatic change and hamper the ability of numerical weather prediction models to forecast high-impact weather events. The joint European Space Agency (ESA)–Japan Aerospace Exploration Agency (JAXA) Earth Clouds, Aerosol and Radiation Explorer (EarthCARE) satellite mission, scheduled for launch in 2018, will help to resolve these weaknesses by providing global profiles of cloud, aerosol, precipitation, and associated radiative properties inferred from a combination of measurements made by its collocated active and passive sensors. EarthCARE will improve our understanding of cloud and aerosol processes by extending the invaluable dataset acquired by the A-Train satellites CloudSat, Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO), and Aqua. Specifically, EarthCARE’s c...

Droplet Growth in Warm Water Clouds Observed by the A-Train. Part II: A Multisensor View

Abstract Hydrometeor droplet growth processes are inferred from a combination of Aqua/Moderate Resolution Imaging Spectroradiometer (MODIS) cloud particle size observations and CloudSat/Cloud Profiling Radar (CPR) observations of warm water clouds. This study supports the inferences of a related paper (Part I) (i) that MODIS-retrieved cloud droplet radii (CDR) from the 3.7-μm channel (R37) are influenced by the existence of small droplets at cloud top and (ii) that the CDR obtained from 1.6- (R16) and 2.1-μm (R21) channels contain information about drizzle droplets deeper into the cloud as well as cloud droplets. This interpretation is shown to be consistent with radar reflectivities when matched to CDR that were retrieved from MODIS data. This study demonstrates that the droplet growth process from cloud to rain via drizzle proceeds monotonically with the evolution of R16 or R21 from small cloud drops (on the order of 10–12 μm) to drizzle (CDR greater than 14 μm) to rain (CDR greater than 20 μm). Thus, R...

Droplet Growth in Warm Water Clouds Observed by the A-Train. Part I: Sensitivity Analysis of the MODIS-Derived Cloud Droplet Sizes

This study examines the sensitivity of the retrieved cloud droplet radii (CDR) to the vertical inhomogeneity of droplet radii, including the existence of a drizzle mode in clouds. The focus of this study is warm water-phase clouds. Radiative transfer simulations of three near-infrared Moderate Resolution Imaging Spectroradiometer (MODIS) channels centered on wavelengths of 1.6, 2.1, and 3.7 mm reveal that the retrieved CDR are strongly influenced by the vertical inhomogeneity of droplet size including (i) the existence of small cloud droplets at the cloud top and (ii) the existence of the drizzle mode. The influence of smaller droplets at cloud top affects the 3.7-mm channel most, whereas the presence of drizzle influences radiances of both the 2.1- and 1.6-mm channels more than the 3.7-mm channel. Differences in the CDR obtained from MODIS 1.6-, 2.1-, and 3.7-mm channels that appear in global analysis of MODIS retrievals and the CDR derived from data collected during the First International Satellite Cloud Climatology Project (ISCCP) Regional Experiment (FIRE) intensive observation period in 1987 can be explained by the results obtained from the sensitivity experiments of this study.

Particle Growth and Drop Collection Efficiency of Warm Clouds as Inferred from Joint CloudSat and MODIS Observations

This study describes an approach for combining CloudSat and Moderate Resolution Imaging Spectroradiometer (MODIS) satellite observations to investigate the microphysical processes of warm clouds on the global scale. MODIS column optical thickness is vertically distributed between the cloud top and cloud bottom according to adiabatic and condensational growth assumptions and used as a vertical coordinate system to analyze profiles of CloudSat-observed radar reflectivity. The reflectivityprofiles thus rescaled as a function of the in-cloud optical depth clearly depict how the cloud-to-rain particle growth processes take place within the cloud layer and how these processes vary systematically with variations in MODIS-derived effective particle radius. It is also found that the effective radii retrieved using two different wavelengths of MODIS tend totracethe microphysical change of reflectivity profiles in a different way because of the difference in the layer depth that characterizes these two effective radii. The reflectivity profiles as a function of optical depth are also interpreted in terms of drop collection processes based on the continuous collection model. The slope of the reflectivity change with optical depth provides a gross measure of the collection efficiency factor. The systematic changes of reflectivity profiles with MODIS-derived particlesizesaretheninterpretedasdemonstratingastrongdependencyofthecollectionefficiencyonparticlesize. Theseresultsprovideaquantitativeinsightintothedropcollectionprocessofwarmcloudsintherealatmosphere.

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.

Satellite Data Simulator Unit: A Multisensor, Multispectral Satellite Simulator Package

AmerIcAN meTeOrOLOGIcAL SOcIeTY | 1625 AffiliAtions: Masunaga—Hydrospheric Atmospheric Research Center, Nagoya University, Nagoya, Japan; Matsui, tao, Hou, and olson—NASA Goddard Space Flight Center, Greenbelt, Maryland; KuMMerow—Department of Atmospheric Science, Colorado State University, Fort Collins, Colorado; te. naKajiMa—Atmosphere and Ocean Research Institute, University of Tokyo, Chiba, Japan; Bauer—European Centre for Medium-Range Weather Forecasts, Reading, United Kingdom; seKigucHi—Faculty of Marine Technology, Tokyo University of Marine Science and Technology, Tokyo, Japan; ta. Y. naKajiMa— Research and Information Center, Tokai University, Tokyo, Japan Corresponding Author: Hirohiko Masunaga, Hydrospheric Atmospheric Research Center, Nagoya University, F3-1(200) Furocho Chikusa-ku, Nagoya 464-8601, Japan E-mail: masunaga@hyarc.nagoya-u.ac.jp

Diagnosis of the Warm Rain Process in Cloud-Resolving Models Using Joint CloudSat and MODIS Observations

AbstractThis study examines the warm rain formation process in global and regional cloud-resolving models. Methodologies developed to analyze CloudSat and Moderate Resolution Imaging Spectroradiometer (MODIS) satellite observations are employed to investigate the cloud-to-precipitation processes and are applied to model results for comparisons with corresponding statistics from the observations. Three precipitation categories of no precipitation, drizzle, and rain are defined according to nonattenuated near-surface radar reflectivity, and their fractional occurrences and the probability of precipitation are investigated as a function of cloud properties such as droplet size, optical thickness, droplet number concentration, and liquid water path. The comparisons reveal how the models are qualitatively similar to, but quantitatively different from, observations in terms of cloud-to-rainwater conversion processes. Statistics from one model reveal a much faster formation of rain than observed, with drizzle oc...

Comparison of Cloud-Screening Methods Applied to GOSAT Near-Infrared Spectra

Several existing and proposed satellite remote sensing instruments are designed to derive concentrations of trace gases, such as carbon dioxide (CO2) and methane (CH4), from measured spectra of reflected sunlight in absorption bands of the gases. Generally, these analyses require that the scenes be free of cloud and aerosol, necessitating robust screening algorithms. In this work, two cloud-screening algorithms are compared. One applies threshold tests, similar to those used by the MODerate resolution Imaging Spectrometer (MODIS), to visible and infrared reflectances measured by the Cloud and Aerosol Imager aboard the Greenhouse gases Observing SATellite (GOSAT). The second is a fast retrieval algorithm that operates on high-resolution spectra in the oxygen A-band measured by the Fourier Transform Spectrometer on GOSAT. Near-simultaneous cloud observations from the MODIS Aqua satellite are used for comparison. Results are expressed in terms of agreement and disagreement in the identification of clear and cloudy scenes for land and non-sun glint viewing over water. The accuracy, defined to be the fraction of scenes that are classified the same, is approximately 80% for both algorithms over land when comparing with MODIS. The accuracy rises to approximately 90% over ocean. Persistent difficulties with identifying cirrus clouds are shown to yield a large fraction of the disagreement with MODIS.