Ash from Kilauea Eruption Viewed by NASA's MISR 基拉韋厄火山噴發灰燼

Editor: Tony Greicius

On May 3, 2018, a new eruption began at a fissure of the Kilauea volcano on the Island of Hawaii. Kilauea is the most active volcano in the world, having erupted almost continuously since 1983. Advancing lava and dangerous sulfur dioxide gas have forced thousands of residents in the neighborhood of Leilani Estates to evacuate. A number of homes have been destroyed, and no one can say how soon the eruption will abate and evacuees can return home.

On May 6, 2018, at approximately 11 a.m. local time, the Multi-angle Imaging SpectroRadiometer (MISR) instrument on NASA's Terra satellite captured this view of the island as it passed overhead. Much of the island was shrouded by clouds, including the fissure on its eastern point. However, an eruption plume is visible streaming southwest over the ocean. The MISR instrument is unique in that it has nine cameras that view Earth at different angles: one pointing downward, four at various angles in the forward direction, and four in the backward direction. This image shows the view from one of MISR's forward-pointing cameras (60 degrees), which shows the plume more distinctly than the near-vertical views.

The information from the images acquired at different view angles is used to calculate the height of the plume, results of which are superimposed on the right-hand image. The top of the plume near the fissure is at approximately 6,500 feet (2,000 meters) altitude, and the height of the plume decreases as it travels south and west. These relatively low altitudes mean that the ash and sulfur dioxide remained near the ground, which can cause health issues for people on the island downwind of the eruption. The "Ocean View" air quality monitor operated by the Clean Air Branch of the State of Hawaii Department of Health recorded a concentration of 18 μg/m3 of airborne particles less than 2.5 micrometers in diameter at 11 a.m. local time. This amount corresponds to an air quality rating of "moderate" and supports the MISR results indicating that ash was most likely present at ground level on this side of the island.

These data were acquired during Terra orbit 97780. The smoke plume height calculation was performed using the MISR INteractive eXplorer (MINX) software tool, which is publicly available at https://github.com/nasa/MINX. The MISR Plume Height Project maintains a database of global smoke plume heights, accessible at https://www-misr.jpl.nasa.gov/getData/accessData/MisrMinxPlumes2/.

MISR was built and is managed by NASA's Jet Propulsion Laboratory in Pasadena, California, for NASA's Science Mission Directorate in Washington. The Terra spacecraft is managed by NASA's Goddard Space Flight Center in Greenbelt, Maryland. The MISR data were obtained from the NASA Langley Research Center Atmospheric Science Data Center in Hampton, Virginia. JPL is a division of Caltech in Pasadena.

2018年5月3日，夏威夷大島基拉韋厄火山的裂縫開始了新的噴發。基拉韋厄火山是世界上最活躍的火山，自 1983 年以來幾乎連續噴發。前進的熔岩和危險的二氧化硫氣體迫使萊拉尼莊園附近的數千名居民撤離。許多房屋已被摧毀，沒有人能說噴發多久會減弱，撤離人員可以傳回家園。

2018年5月6日，當地時間上午 11 點左右，美國宇航局 Terra 衛星上的多角度成像光譜輻射計 (MISR) 儀器在島嶼經過頭頂時捕捉到了這張島嶼的景色。島上的大部分地區都被雲層籠罩，包括東端的裂縫。然而，可以看到一股噴發羽流在海洋的西南方向流動。 MISR儀器的獨特之處在于它有九個以不同角度觀察地球的相機：一個指向下方，四個向前方向的不同角度，四個向後方向。這張圖檔顯示了 MISR 的一個前向錄影機（60度）的視圖，它比近乎垂直的視圖更清楚地顯示了羽流。

從不同視角擷取的圖像資訊用于計算羽流的高度，其結果疊加在右側圖像上。靠近裂縫的羽流頂部大約在6,500英尺（2,000米）的高度，随着羽流向南和向西移動，其高度會降低。這些相對較低的海拔意味着火山灰和二氧化硫留在地面附近，這可能會給火山噴發順風島上的人們帶來健康問題。夏威夷州衛生部清潔空氣分部營運的“海洋景觀”空氣品質監測儀在當地時間上午 11 點記錄到空氣中直徑小于 2.5 微米的顆粒物濃度為 18 微克/立方米。這一數量對應于“中等”的空氣品質等級，并支援 MISR 結果表明灰燼最有可能出現在島嶼這一側的地面上。

這些資料是在 Terra 軌道 97780 期間獲得的。煙羽高度計算是使用 MISR INteractive eXplorer (MINX) 軟體工具進行的，該工具可在 https://github.com/nasa/MINX 上公開獲得。 MISR 羽流高度項目維護一個全球煙羽高度資料庫，可在 https://www-misr.jpl.nasa.gov/getData/accessData/MisrMinxPlumes2/ 通路。

MISR 由位于加利福尼亞州帕薩迪納的 NASA 噴氣推進實驗室為位于華盛頓的 NASA 科學任務理事會建造和管理。Terra宇宙飛船由位于馬裡蘭州格林貝爾特的美國宇航局戈達德太空飛行中心管理。MISR 資料來自位于弗吉尼亞州漢普頓的美國宇航局蘭利研究中心大氣科學資料中心。JPL 是加州理工學院在帕薩迪納的一個部門。