Semi‐idealized simulations of wintertime flows and pollutant transport in an Alpine valley. Part II: Passive tracer tracking

• DOI: 10.1002/qj.3710
• Publication Date: 2019-11-23T16:34:27Z
• Authors: Tiphaine Sabatier; Yann Largeron; Alexandre Paci; Christine Lac; Quentin Rodier; Guylaine Canut; Valéry Masson
• Keywords: TRACER; Diurnal cycle; Stratification (seeds)

Abstract Under wintertime quiescent conditions, thermally driven circulations represent one of the only sources tracer dispersion over mountainous terrain. Those can be unequally developed at a valley scale since they strongly depend on local morphological arrangement. At same time, very heterogeneous pollutant distribution observed, as for instance in French Alpine basin located Arve River valley. This complex regularly shows large variations concentrations with certain sectors suffering from poor air quality. On other hand, surrounding tributary valleys appear to less affected, suggesting that dynamics may participate trapping. The present study intends classify transport mechanisms terms efficiency and identify most dynamically vulnerable atmospheric volumes regarding accumulation. is achieved through set semi‐idealized high‐resolution numerical simulations reproducing full diurnal cycle passive tracers released continuously constant rate. model used laboratory order quantify influence several processes mechanism efficiency. approach underlines high vertical by anabatic winds while horizontal up‐valley wind systems remains weak, leaving almost unaffected pollution during daytime. night, down‐valley depends source location within basin. In addition, emitted do not reach bottom because thermal stratification arrangement but rather degrade quality mid‐altitude villages lying along sidewalls.