RGB in Broadcast Meteorology

Transcription

1 RGB in Broadcast Meteorology AHI Imagery for Weather Commentary on Clouds Yuki Takano Atmosphere and Ocean Research Institute The University of Tokyo collaborated with Shotaro Watanabe (Weather Map Co. Ltd.) RGB Experts and Developers Workshop 2017 Tokyo, Japan 7-9 November 2017

2 Himawari-8 and Weather Commentary 2 Before Himawari-8 operation, monochromatic imagery (IR/VIS) overlaid on land/sea map is commonly used for weather commentary on TV show AHI/Himawari-8 increases available satellite imageries used for weather commentary including True Color RGB Since True Color RGB imagery explicitly represents color and shade of clouds, the imagery attracts the audience B03(VIS) over land/sea map True Color RGB

3 True Color Reproduction RGB 3 True Color Reproduction RGB (Miller et al. 2016) uses virtual green band (0.55μm) and processed with Rayleigh correction. B G R scattered light entering the sensor Human eye Himawari s eye (AHI) crisper/cleaner than the traditional True Color imagery of AHI good choice for explanation about aerosols or land surface as well as low clouds Kosa (Asian dust) Volcanic eruption decaying by scattering Autumn leaves Mt. Shinmoe-dake 12JST 7 May :30JST 11 Oct JST 3 Nov 2017

4 Weaknesses of for Weather Commentary 4 For non-professional TV audience, is sometimes troublesome to focus on clouds 1. The audience sometimes confuse aerosols with clouds or fogs 2. Non-uniform land color (e.g. autumn leaves) could unintentionally attract audience attention 3. Over-enhancement of RGB brightness makes it difficult to discern cloud thickness 15JST 19 Mar JST 8 Aug 2015

5 How to make Green Color RGB? 5 We propose Green Color RGB optimized for cloud commentary R,G,B = VIS0.64, NIR0.86, VIS0.51 band # NIR0.86 is sensitive to both soil and vegetation and not to ocean, land surface looks uniform green color on Since VIS0.47 is not used, is less affected by Mie scattering by aerosols wavelength (μm) resolution (km) T C G C RGB Brightness Use the special level curve Land surface (NIR0.86) Aerosol Cloud log linear Rayleigh-corrected Reflectance Aerosol Cloud

6 An example of Green Color RGB Land looks green because of NIR0.86 Green Color RGB Easily distinguish b/w clouds and others Land is almost uniform color regardless of vegetation True Color Reproduction RGB Green Color RGB 6

7 Clouds 7 Unlike traditional visible imagery, cloud looks solid on because shade of cloud is explicitly represented B03 cumulonimbus Hiroshima pref. Thin cloud such as cirrus looks less whitish because of wider brightness range for clouds we can easily distinguish cloud types cirrus over cumulus Kanto Region (13JST 8 Aug 2015)

8 Aerosols 8 Owing to the used bands and the special level curve of, the aerosols are more unremarkable on. A weather reporter can still easily explain about aerosols because the aerosols don t look white (look purple in this case) True Color Reproduction Green Color RGB Aerosol color calculated by RTM thick aerosol layer over Japan 15JST 19 Mar 2017

9 Summary 9 We propose a new AHI imagery called Green Color RGB suitable for cloud commentary especially on TV show using Rayleigh corrected reflectance of VIS0.64, NIR0.86 and VIS0.51 for RGB, and made with the special level curve that does not enhance low brightness region. The proposed imagery has good cloud representation, such as unremarkable aerosols land looked nearly uniform green, and discernable cloud thickness. Reference Takano, Y., Watanabe, S.: A proposed method of compositing Himawari RGB Imagery for Weather Commentary on Clouds, Tenki, in revision (in Japanese)