Satellite detection of volcanic aerosol at Miyakejima and Sakurajima

Transcription

1 Nagasaki Workshop on Aerosol-Cloud Radiation Interaction and Asian Lider Network, Nagasaki, Japan, Nov Satellite detection of volcanic aerosol at Miyakejima and Sakurajima M. Koyamada, K. Kinoshita, N. Iino and C. Kanagaki

2 1. Introduction Miyakejima volcano in Izu Islands, about 160 km south of Tokyo started eruptive activities at the summit Oyama (814 m) on 8 July High concentration of SO 2 in the Main Island of Japan amount of SO 2 about 10 times of Sakurajima

3 In this study analyze NOAA/AVHRR images to detect the volcanic clouds from Miyakejima, and compare them with Sakurajima plumes. discuss the SO 2 high concentration episodes recorded in the central part of Japan (satellite images, gas information and the upper wind data.)

4 2. Methods of analyses 2-1. Satellite data analysis of Sakurajima plumes The split-window method.taking the difference of AVHRR 4 and 5 Aerosol Vapor Index: AVI = n (5) - n (4) + c AVHRR-4 sensitive to aerosol...11 m AVHRR-5 sensitive to vapor...12 m very effective for the discrimination of the volcanic clouds from the meteorological ones. Also applied to GMS-5

5 2-2. Satellite data analysis of Miyakejima plumes Fig. 3. Miyakejima plume, 2001/7/12 13:27JST NOAA16 R:G:B=1:2:3 Fig. 4. The data values of the bands1 5(left scale) and the difference band1 - band2(right scale) along a section in the NOAA16/AVHRR image on 2001/7/12 13:27JST volcanic cloud of Miyakejima vapor ash

6 AVHRR-1 more sensitive to volcanic clouds m AVHRR-2 sensitive to volcanic clouds m AVHRR-3 sensitive to meteorological clouds m We were able to distinguish volcanic clouds and meteorological ones by making color images of R:G:B= bands1:2:3.

7 2-3. SO 2 concentration COSPEC. GSJ and Japan Meteorological Agency The Tokyo Metropolitan Government.. continuous measurement of SO 2 and H 2 S since November 2000 in Miyakejima (one-hour values ). Internet bulletin board in Internet Atmospheric Environmental Regional Observation System AEROS

8 2-4.Upper wind data The nearest station Hachijo-jima station to the south of Miyakejima. height of Miyakejima 814m, used the wind data at 925hPa about 830m above sea level The observation 4 times / day at 03, 09, 15, 21JST.

9 3. Results and discussions 3-1. Volcanic clouds at Sakurajima V-shaped long-range advection more than 300km AVHRR-4 at 07:26 on 20 October 1992

10 White parts of AVI images are volcanic clouds at Sakurajima NOAA14 AVI image at 07:16JST on 1996/12/14

11 NOAA AVI image at 06:17 on 10 December 1999 White parts of AVI images are volcanic clouds at Sakurajima, and Karman Vortex is formed with Cheju Island.

12 This demonstrates the dispersion of ash clouds from Sakurajima Volcano toward east over the Kuroshio Current in Pacific Ocean at 14:13JST on 28 January 1992.

13 3-2. Hotspots at Sakurajima, Aso and Swanose volcanoes NOAA/AVHRR band 3 temperature of the crater Hotspots of Sakurajima and Aso are shown as black points NOAA image at 02:35JST on 30 October 1989 NOAA image at 01:42JST on 4 November 1989

14 Hotspots of Sakurajima and Swanose-jima are seen as black point. they are not found at Aso and Unzen.

15 3-3. Volcanic clouds at Miyakejima NOAA-14/b1-b2 image at 15:12JST on 5 December 2000 wind velocity about 10m/s the SO 2 concentration at the foot of Miyakejima stayed low, since the gas and plume were not blown down with the wind velocity 3-6m/s.

16 NOAA image at 13:28 on 2 July 2001 SO 2 =158ppb at 14:00 at Toba in Mie information of AEROS

17 About 5 hours earlier than the time of This figure, SO 2 = 423ppb at Oyasu also in Mie (11:00, information in AEROS). This figure indicates the change of the wind direction after affecting westwards.

18 SO 2 =423ppb Sodegaura, Chiba Prefecture at 16:00.information in AEROS In the NOAA image received at 7:27, the plume had reached already Boso Peninsula.

19 4. Concluding remarks We were able to detect the volcanic ash clouds at Sakurajima by the difference images of AVHRR 4 and 5. The difference images of AVHRR 1 and 2 were found to be effective to discriminate Miyakejima plumes from meteorological clouds. The AVHRR images of them are consistent with the high concentration events of SO 2 at leeward directions. Many images that we analyzed here are shown in the following homepage. SiNG: ac.jp/sing/index-e.htm