Satellite

https://blog-assets.ringsaturn.me/pic/2026/2026-10-12-arxan-fire/arxan-fire-spread-960.en.mp4 VIIRS 375 m active fire (NASA) detections accumulated hour by hour, 10-08 11:00 to 10-16 14:00 UTC+8, one frame per hour. Bright yellow: detected within 3 h; orange: 3–12 h; dark red: earlier. Lower right: total FRP per overpass. At the end the 10-16 NOAA-21 false colour (M11-I2-I1) fades in, where dark red is burn scar; yellow circles are MODIS fire detections (FIRMS) of the new fire south of the main fire on 10-15. Base map: Copernicus DEM hillshade; dashed line: border (OSM). Overpass times are L2 granule start times, a few minutes earlier than the FIRMS acquisition times used in the text and in the other fire-detection figures; the first detection, for example, is at 12:06 here and at 12:08 in FIRMS. Around noon on 2026-10-08, a fire started near Nömrög (Нөмрөг; also romanised Numrug or Nomrog) in Khalkhgol soum, Dornod Province, Mongolia, about 27 km from the China–Mongolia border. Two geostationary satellites put the ignition between 11:41 and 11:51, the first FY-4C detection published by the National Satellite Meteorological Centre (NSMC) was at 11:501, and Mongolia’s National Emergency Management Agency (NEMA) received the call at 11:552. The Mongolian telecom operator Mobicom is a subsidiary3 of Japan’s KDDI. Its statement of 10-124 says that a vehicle caught fire while a group was handing over telecommunications work at border outposts and the Sümber border crossing and surveying local conditions, and that this started the grassland fire. The statement5 of Mongolia’s General Authority for Border Protection says the vehicle caught fire “due to the carelessness of citizens who entered the border zone”. The Dornod Province police department began investigating6 the cause of the fire on 10-17; as of 10-25 no findings have been published. The fire peaked twice, on the evening of 10-10 and during the day on 10-11, and on 10-11 and 10-12 its front reached the border west of Arxan City, Hinggan League, Inner Mongolia. After a cold front passed early on 10-12 the fire weakened. Residual burning continued intermittently inside the Mongolian fire area until the afternoon of 10-15, after which the satellites detected no more fire pixels; NEMA declared the fire fully extinguished at 07:00 on 10-167. From the afternoon of 10-22 several new fires started in western Hulunbuir and eastern Mongolia, at least 172 km from this burn scar and unrelated to this fire; see New fires on 10-22. The burned area is about 4,900 km². Montsame, quoting the Mongolian emergency services, reports that about 80% of the Nömrög Strictly Protected Area burned8; the preliminary estimate of Mongolia’s Ministry of Environment and Climate Change on 10-20 is 528,765.5 hectares, of which 468,965.7 hectares, or 79.8% of the protected area, lie inside it9. On 10-28 the ministry set the official figure, from Sentinel-2 10 m imagery of 10-25, at 504,960.4 hectares in total (about 5,050 km²), of which 448,993.6 hectares, or 76.4% of the protected area, lie inside it10. China deployed first more than 2,00011 and then more than 3,40012 personnel along the border, and its reports say the fire did not cross the border line. The satellites show no contiguous burned area extending into China. On the Sentinel-2 scenes of 10-20, 54–62 km² burned on the Chinese side within 2 km of the border, of which 34–38 km² lies within 0.5 km of the line, consistent with the hundred-metre buffer that Hinggan League counter-burned (对冲点烧, backburning toward the oncoming fire) along the border from 10-11. The parts more than 1 km from the line are concentrated in three sections: about 21 km² in the south section on the East Ujimqin Banner side, up to 3.6 km from the line, whose main patch is consistent with the backburning operations that the East Ujimqin Banner authorities reported publicly; about 11.5 km² west of Arxan, up to 2.2 km, where VIIRS fire pixels crossed the border at midday on 10-12; and about 6 km² on the east front, up to 1.7 km. The imagery cannot distinguish fire that crossed from Mongolia from backburning on the Chinese side. Smoke reached Hailar on 10-11 and Baicheng on 10-12, and the PM2.5 peaks in the two cities on those days contain smoke from this fire. This post records the accounts from the parties involved, the ignition time and the spread, the weather at the fire area, the burned area, the assessment of burning near the border, and the smoke transport. The confidence in each conclusion is listed at the end. ...

ringsaturn/shachen The DEBRA algorithm (Miller et al. 2017, doi:10.1002/2017JD027365) is a method I have been following for a long time for identifying dust from satellite data. The unique aspect of this algorithm is its background estimation method, which avoids interference from special ground backgrounds such as deserts and lakebeds. Furthermore, the algorithm is designed for highly targeted engineering applications, aiming to be an all-weather recognition algorithm that provides users with fast, high-contrast output, bypassing the traditional need to introduce aerosol optical thickness.

Note The satellite data in this post (Sentinel-1, NISAR and the optical scenes) was retrieved, processed and composited by the author. Claude compiled the text from those processed results and from public news reporting. Processing parameters and acquisition times are taken from the data itself; the event description and casualty figures come from the public sources linked in the text. At 02:52:10 UTC on 2026-08-26 (08:37 Nepal time, 10:52 China time), an ice and rock cliff on the north side of Langtang Lirung collapsed inside Langtang National Park. USGS located the source from seismic waves, on the north face of a peak roughly 7,200 m high; the main event released energy equivalent to M5.2, followed about 3 hours later by a secondary collapse equivalent to M4.2. AntarcticGlaciers gives the detachment coordinates as 28.2853°N, 85.5252°E and states that the present evidence does not support a glacial lake outburst flood (GLOF); the proposed mechanism is a multi-hazard cascade of ice and bedrock failure, rock/ice avalanche and debris flow, temporary river blockage, then outburst flooding. The author describes all of these as preliminary. The debris flow travelled about 100 km down the Bhote Koshi and Trishuli rivers and destroyed the customs facilities at the Rasuwagadhi border crossing along with the China–Nepal highway. The Wikipedia article records, as of 28 August, 547 dead and 977 missing on the Nepali side and 5 dead and 558 missing on the Chinese side; the search is ongoing, sources differ in what they count and when they were updated, and the figures are still changing. The same area saw a large ice and rock avalanche during the 2015 Gorkha earthquake that buried villages in the Langtang valley and killed more than 350 people. This post records the data work done in the two weeks after the event: building the Sentinel-1 pre-event baseline, processing the first obtainable post-event SAR data (NISAR, L-band) and the first post-event Sentinel-1 scene, and then the four viewing geometries that followed. ...