Here in southwest France ski lovers did not really enjoy the beginning of the snow season... But how does it compare to the previous years? Using Sentinel-2 and Landsat-8 data, we computed the snow cover duration since September 01 until January 20 for the past three snow seasons in the Alps and Pyrenees.
Snow cover duration (in days) from 01 September of year N-1 to 20 January of year N
Si vous avez vu le JT du 26 mars dernier, vous savez que le lac de Serre-Ponçon est à un niveau exceptionnellement bas en ce moment .
Extrait du journal 12/13 de France 3 du 26/03/2018
Theia just published the first Venµs images today, including a beautiful view of the Pyrenees. Once you have dezipped/untared/unzipped the files you can make a true color composite using the command:
gdal_translate -b 7 -b 4 -b 3 -scale 0 300 0 255 -ot byte VE_VM01_VSC_PDTIMG_L1VALD_ES_LTERA_20180419.DBL.TIF myColorCompo.tif
I tend to focus on the snow so I stretched the colors between reflectances 0-1000 instead of 0-300:
gdal_translate -b 7 -b 4 -b 3 -scale 0 1000 0 255 -ot byte VE_VM01_VSC_PDTIMG_L1VALD_ES_LTERA_20180419.DBL.TIF mySnowColorCompo.tif
First, I was a bit puzzled by the orange shade in the northern part of the image. We inspected carefully the image with Olivier because at this stage radiometric calibration issues are still possible..
Connaissiez-vous ce dicton coréen "On n'est jamais trop prudent" ?
Voici une série d'images Sentinel-2 près du site olympique de Pyeongchang. On voit de la neige artificielle apparaître dès le mois de novembre !
Les images suivantes montrent qu'au cours du mois de janvier de la neige naturelle a finalement recouvert le site...
Great news, we can announce that the operational production of the Theia snow collection has started well. It means that maps of the snow cover area are now constantly added to the Theia portal. These maps are automatically generated from Sentinel-2 observations and have a spatial resolution of 20 m. The Snow collection will progressively cover most mountain regions in west Europe, but also the Atlas in Morocco, eastern Canada... The Snow collection can be freely downloaded from http://theia.cnes.fr by any registered user.
Today's front page of the Theia website featured this nice example in Sierra de Ancares (western end of the Cantabrian Mountains, Spain). In the southeast, snow was also detected on the Montes Aquilanos, including the small ski resort El Morredero. The image was captured yesterday! It illustrates well the value of multispectral imagery to discriminate the snow cover from the clouds. There is a cloud which looks alike snow but it is actually a valley fog confined by local topography.
Theia Sentinel-2 level 2A and snow product in the region de los Ancares, Spain. Image captured by Sentinel-2A on 30 Jan 2018.
Olivier pointed to me that ESA's ground segment, PEPS and MUSCATE were all in really good shape today... And the sky was clear yesterday at the time of the Sentinel-2A acquisition!
So I could download the Level-2A product from theia.cnes.fr, run our let-it-snow processor, start QGIS and here it is: the map of yesterday's snow cover area at 20 m resolution. If you know the region, you might notice that there is currently a big contrast in the snow cover extent between the French and the Spanish Pyrenees. This is due to the blocking of the moist air masses coming from the north.
Snow cover area on 22 Nov 2017. blue: snow, grey: no snow, white: cloud.
Stay tuned! Theia should start to distribute these Sentinel-2 snow products in near real time very soon.
TIROS-1 weather satellite was launched by NASA on 01 April 1960. It took the first weather satellite picture on 02 April 1960 , and also the real first weather satellite picture on 01 April 1960 .
On 02 April 1960, it also captured what I believe is the first publicly available satellite picture of the snow cover in the Alps (picture 1 below). A few weeks later, on 13 May 1960, it captured a stunning view of the snow cover over the High Mountain Asia, including the Himalayas, Hindu Kush, Pamir and Karakoram ranges. These pictures are shown in the TIROS-1 final report .
Villarrica volcano is one of the most active volcanoes in the Chilean Andes. A colleague of mine (Esteban Alonso) told me that last week he went ski touring up there and when he reached the summit he could see the bubbling lava in the bottom of the crater, and could even feel its heat...
Yesterday Theia shifted into high gear and released 1300 snow products!. These products correspond to 13 Sentinel-2 tiles covering the Western Alps (France/Italy/Switzerland), the Pyrenees (France/Spain) and the Hight Atlas (Morocco).
Hier Theia est passé à la vitesse supérieure et a mis à disposition 1300 produits neige ! Ces produits correpondent aux 13 tuiles Sentinel-2 qui couvrent les Alpes Occidentales (France/Italie/Suisse), les Pyrénées (France/Espagne) et le Haut-Atlas (Maroc).
This was made possible thanks to the great work of Dominique Clesse, Joëlle Donadieu, Céline L'Helguen, Arnaud Selle and Simon Baillarin at CNES. Merci à eux !