Takashi M. Nagao

Aerosol data assimilation using data from Himawari-8, a next-generation geostationary meteorological satellite

Himawari-8, a next-generation geostationary meteorological satellite, was launched on 7 October 2014 and became operational on 7 July 2015. The advanced imager on board Himawari-8 is equipped with 16 observational bands (including three visible and three near-infrared bands) that enable retrieval of full-disk aerosol optical properties at 10 min intervals from geostationary (GEO) orbit. Here we show the first application of aerosol optical properties (AOPs) derived from Himawari-8 data to aerosol data assimilation. Validation of the assimilation experiment by comparison with independent observations demonstrated successful modeling of continental pollution that was not predicted by simulation without assimilation and reduced overestimates of dust front concentrations. These promising results suggest that AOPs derived from Himawari-8/9 and other planned GEO satellites will considerably improve forecasts of air quality, inverse modeling of emissions, and aerosol reanalysis through assimilation techniques.

Interpretation of Multiwavelength-Retrieved Droplet Effective Radii for Warm Water Clouds in Terms of In-Cloud Vertical Inhomogeneity by Using a Spectral Bin Microphysics Cloud Model

AbstractThis study examines the impact of in-cloud vertical inhomogeneity on cloud droplet effective radii (CDERs) of water-phase cloud retrieved from 1.6-, 2.1-, and 3.7-μm-band measurements (denoted by r1.6, r2.1, and r3.7, respectively). Discrepancies between r1.6, r2.1, and r3.7 due to in-cloud vertical inhomogeneity are simulated by using a spectral bin microphysics cloud model and one-dimensional (1D) remote sensing simulator under assumptions that cloud properties at the subpixel scale have horizontal homogeneity and 3D radiative transfer effects can be ignored. Two-dimensional weighting functions for the retrieved CDERs with respect to cloud optical depth and droplet size are introduced and estimated by least squares fitting to the relation between the model-simulated droplet size distribution functions and the retrieved CDERs. The results show that the 2D weighting functions can explain CDER discrepancies due to in-cloud vertical inhomogeneity and size spectrum characteristics. The difference bet...

On the cloud observations in JAXA's next coming satellite missions

The use of JAXA’s next generation satellites, the EarthCARE and the GCOM-C, for observing overall cloud systems on the Earth is discussed. The satellites will be launched in the middle of 2010-era and contribute for observing aerosols and clouds in terms of climate change, environment, weather forecasting, and cloud revolution process study. This paper describes the role of such satellites and how to use the observing data showing concepts and some sample viewgraphs. Synergistic use of sensors is a key of the study. Visible to infrared bands are used for cloudy and clear discriminating from passively obtained satellite images. Cloud properties such as the cloud optical thickness, the effective particle radii, and the cloud top temperature will be retrieved from visible to infrared wavelengths of imagers. Additionally, we are going to combine cloud properties obtained from passive imagers and radar reflectivities obtained from an active radar in order to improve our understanding of cloud evolution process. This is one of the new techniques of satellite data analysis in terms of cloud sciences in the next decade. Since the climate change and cloud process study have mutual beneficial relationship, a multispectral wide-swath imagers like the GCOM-C SGLI and a comprehensive observation package of cloud and aerosol like the EarthCARE are both necessary.

Synergistic use of next-generation geostationary and polar orbit satellites for investigating aerosols, clouds, and radiation

In this paper, we propose the synergistic use of geostationary and polar orbital satellites, namely the thirdgeneration Himawari-8, GCOM-C and EarthCARE. These satellites have been or will be launched in the middle of the 2010s to the early of 2020s will contribute to observing aerosols, clouds, and radiation in the Earth system. Because aerosols and clouds exert great effects on the planet’s water, energy, and radiation balances and processes, it is important to gather more observations and improve our understanding of the lifecycle of these particles. Complementing existing passive sensors, CloudSat and CALIPSO have ushered in a new era in aerosol and cloud observations to reveal the particle transition, from cloud condensation nuclei to rain droplets via clouds and drizzle particles. Contoured Frequency by Optical Depth Diagrams (CFODDs), a method of visualizing the CloudSat radar reflectivities, clearly show the transition of cloud growth, from cloud droplet mode to rain mode via drizzle mode. Moreover, the thirdgeneration geostationary weather satellite, which began its operation in 2015, observes global-scale aerosols and cloud systems every 10 min (or 2.5min). Therefore, the combined use of polar orbital passive/active sensors and geostationary satellites will reveal details of the cloud evolution process by using the multi-spectral and vertical observations of the passive/active sensors.

Regional properties of aerosol-cloud interaction estimated from long-term satellite analysis

The present study investigated the correlations between aerosol and cloud parameters derived from satellite remote sensing to estimate properties of aerosol-cloud interactions. The global statistics showed that effective particle radius and optical thickness of low clouds correlate well with column number concentration of the aerosol particles in small – moderate amount of atmospheric aerosol loading (about Na < 109 [particles/cm2]), which are consistent with an aerosol indirect effect. In case of turbid atmosphere, inverse trends between aerosol and cloud microphysics parameters are appeared. These inverse tendencies can be founded in case of smaller LWP cases.