Evaluation of cloudiness over Monte San Valentín, Northern Patagonia Icefield, from 2000 to 2008 using MODIS satellite images: implications for paleoclimate investigations from ice cores

• Published in: Journal of Glaciology
• Main Authors: Vimeux, Françoise, Maignan, Fabienne, Reutenauer, Corentin, Pouyaud, Bernard
• Other Authors: Hydrosciences Montpellier (HSM), Institut de Recherche pour le Développement (IRD)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire des Sciences du Climat et de l'Environnement Gif-sur-Yvette (LSCE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Glaces et Continents, Climats et Isotopes Stables (GLACCIOS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Modélisation des Surfaces et Interfaces Continentales (MOSAIC)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2011
• Subjects: [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces; environment; Journal of Glaciology
• Online Access: https://hal.science/hal-03106355; https://hal.science/hal-03106355/document; https://hal.science/hal-03106355/file/fichier8.pdf; https://doi.org/10.3189/002214311796405915

International audience An unexpectedly low annual net accumulation (20 cm w.e. a-1) has been inferred from analyses of a firn core extracted from Glaciar Monte San Valentín, Northern Patagonia Icefield (46835' S, 73819' W; 3747 m a.s.l.). We test a hypothesis linking the low accumulation to a frequent lack of cloud cover over the mountain range at this altitude. The cloudiness over Monte San Valentín and surrounding regions is examined using $3000 daily MODIS satellite images from 2000 to 2008. The visual evaluation of the synoptic situation leads to the definition of a daily cloudiness index (EI) for the San Valentín summit and for the regions to the southwest (SW) and northeast (NE). We check its robustness by applying different tests and comparisons. Three levels are assigned for the EI: 'clear' (EI = 0), 'cloudy' (EI = 1) and 'mixed' (EI = 0.5). The results show that the SV cloud cover is similar to the regional cloudiness for more than half the year (54%) and that the case in which the San Valentín summit is clear while both SW and NE regions are cloudy is exceptional (2%). As clouds are necessary to provide precipitation, we show that the low annual net accumulation cannot be explained by an uncommon low cloudiness. This result implies that net accumulation inferred from ice cores in this Andean region must be cautiously interpreted. We also point out that the Andes at this latitude acts as an orographic barrier but without a total blocking of air masses.