[A-CG33] 静止軌道衛星による陸面観測

[ACG33-01] Using the Diurnal Variability in GeoNEX TOA Reflectances for Earth Monitoring

★Invited Papers

*Weile Wang^1,2、Hirofumi Hashimoto^1,2、Andrew Michaelis¹、Taejin Park^1,5、Ramakrishna Nemani¹、Yujie Wang^3,4、Alexei Lyapustin³、Tsengdar Lee⁶、Satya Kalluri⁷ (1.NASA Ames Research Center、2.California State University Monterey Bay、3.NASA Goddard Space Flight Center、4.University of Maryland Baltimore、5.Bay Area Environment Research Institute、6.NASA Headerquarter、7.NOAA NESDIS Center for Satellite Applications and Research)

キーワード：GeoNEX, Remote Sensing, Geostationary Satellites, Diurnal Variabilty, Surface Reflectance, Aerosol Optical Depth

Observations from the third-generation geostationary satellite instruments (GOES 16/17 ABI, Himawari 8/9 AHI, and etc.) have spatial resolution and spectral band configurations comparable to flagship LEO sensors (e.g., MODIS/VIIRS). More importantly, these data are acquired at very high temporal resolution, faithfully recording the variations of the full disk of Earth at every 5-10 minutes. They thus provide unique information about Earth’s atmosphere and surface. In order to explore the unique information content of geostationary data, this study systematically analyzes the diurnal variability in the GeoNEX L1G TOA reflectance products and compares them to simulated results by state-of-the-art radiative transfer codes. Our results show that

The smoothness of the TOA reflectance diurnal cycle provides a convenient and reliable way to identify stable atmospheric conditions and filter out passing clouds/shadows.

The diurnal variability of the blue band (0.47µm) reflectance is regulated mainly by atmospheric optical conditions over a majority of land cover types. As such, the diurnal variability of the blue band data allows us to retrieve AOD without invoking the use of spectral band ratios (SRC) as in previous algorithms.

In comparison, the diurnal variability of the short-wave infrared band (2.2µm) BRFs is mainly regulated by surface reflectance and the sun-target-satellite geometry. This information allows us to test and, if suitable, retrieve surface BRDF parameters.

Spectral band ratios, especially those between the 2.2µm and 0.47µm bands, are not constant but vary by locations and sun-target-satellite geometries.

Our analysis clearly demonstrates that the information provided in high-frequent geostationary observations is unique and complementary to LEO sensors. Therefore, a synergy of GEO and LEO (and other) sensors has the great potential to improve existing remote sensing models and algorithms for better Earth monitoring.