Preprints
https://doi.org/10.5194/egusphere-2022-736
https://doi.org/10.5194/egusphere-2022-736
 
05 Aug 2022
05 Aug 2022
Status: this preprint is open for discussion and under review for Atmospheric Measurement Techniques (AMT).

Evaluation of the smile effect on the Earth Clouds, Aerosols and Radiation Explorer (EarthCARE)/Multi-Spectral Imager (MSI) cloud product

Minrui Wang1, Takashi Y. Nakajima1, Woosub Roh2,3, Masaki Satoh3, Kentaroh Suzuki3, Takuji Kubota4, and Mayumi Yoshida5 Minrui Wang et al.
  • 1Research & Information Center, Tokai University, Kanagawa, 2591292, Japan
  • 2Tokyo University of Marine Science and Technology, Tokyo, 1358533, Japan
  • 3Atmosphere and Ocean Research Institute, The University of Tokyo, Chiba, 2778564, Japan
  • 4Earth Observation Research Center, Japan Aerospace Exploration Agency, Ibaraki, 3058505, Japan
  • 5Remote Sensing Technology Center of Japan, Ibaraki, 3058505, Japan

Abstract. A cloud identification and profiling algorithm is being developed for the Multi-Spectral Imager (MSI), which is one of the four instruments that the Earth Clouds, Aerosols and Radiation Explorer (EarthCARE) spacecraft will feature. During recent work, we noticed that the MSI response function could shift substantially among some wavelengths (0.67 and 1.65 µm bands) owing to the smile effect, that is an effect in which a shift in the center wavelength appears as a distortion in the spectral image. We evaluated how the smile effect affects the cloud retrieval product qualitatively and quantitatively. We chose four detector pixels from bands 1 and 3 with the nadir pixel as the reference to elucidate how the smile effect error affects the cloud optical thickness (τ) and effective cloud droplet radius (re) by simulating the MSI forward radiation with Comprehensive Analysis Program for Cloud Optical Measurement (CAPCOM). We also evaluated the error in simulated scenes from a global cloud system resolving model and a satellite simulator to measure the effect on actual observation scenes. For typical shallow warm clouds (τ = 8, re = 8 μm), the smile effect on the cloud retrieval was not significant in most cases (up to 6 % error). For typical deep convective clouds (τ = 8, re = 40 μm), the smile effect on the cloud retrieval was even less significant in most cases (up to 4 % error). Moreover, our results from two oceanic scenes using the synthetic MSI data agreed well with the forward radiation simulation, indicating that the error from the smile effect was generally within 10 %.

Minrui Wang et al.

Status: open (until 10 Sep 2022)

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Minrui Wang et al.

Minrui Wang et al.

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Short summary
Smile effect (an effect in which a shift in the center wavelength appears as a distortion in the spectral image) was detected during our recent work. To evaluate how it affects the cloud retrieval product, we did a simulation of MSI forward radiation, then evaluated the error in simulated scenes from a global cloud system resolving model and a satellite simulator. Our results indicated that the error from the smile effect was generally small and could be seen as negligible for oceanic scenes.