Coupling embedded weather observations and high-resolution climate modeling to identify dynamical and thermal mechanisms of diurnal convection patterns in the Cordillera Blanca, Peru.

Authors: Robert Hellström*, Bridgewater State University, Alfonso Fernández, Concepción, Chile, Bryan Greenwood Mark, The Ohio State University
Topics: Mountain Environments, Climatology and Meteorology, Water Resources and Hydrology
Keywords: embedded sensor network, climate modeling, lapse rate, proglacial valley, freezing elevation, valley wind
Session Type: Paper
Day: 4/13/2018
Start / End Time: 3:20 PM / 5:00 PM
Room: Regent, Marriott, River Tower Elevators, 4th Floor
Presentation File: No File Uploaded

Much of current global and regional climate studies neglect the meteorological forcing of lapse rates (LRs) and valley and slope wind dynamics on critical components of the Peruvian Andes' water cycle that dominates precipitation during the wet season. In 2004 and 2005 we installed an embedded sensor network (ESN) within the glacierized Llanganuco Valley, Cordillera Blanca (9° S), consisting of discrete, cost-effective, automatic temperature loggers located along the pro-glacial valley axis and anchored by two automatic weather stations. A combination of hourly ESN and climate modeling by dynamical downscaling using the Weather Research and Forecasting model revealed distinct diurnal and seasonal characteristics of the mountain wind regime and LRs. Wind, temperature, humidity, and cloud simulations point to thermally driven up-valley and slope winds converging with easterly flow aloft that enhances late afternoon and evening cloud development and the early evening peak in rainfall. Our evidence suggests strong heating at the mouth of the valley during mid-day hours destabilizing the overlying air column in the later afternoon, persistent down-slope (katabatic) flow off the flanking glacierized peaks leading to convergent flow at about 50 m above ground level in the valley, some of which rises along the valley axis and diverges aloft while the remainder moves down-valley as an elevated valley-exit jet, and convergence between the valley wind and prevailing moist easterly free-air flow promotes convection.

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