EOL Seminar: Toward a Pan-Andean Hydrometeorological Observing System

Tuesday, November 3, 2015 - 15:30 to 16:30
FL2-1022 Main Auditorium
Contact Name: 
Steve Oncley
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Toward a Pan-Andean Hydrometeorological Observing System – Understanding the intertwined roles of topography and evapotranspiration on precipitation processes with implications for Water Resources and Bioconservation
Ana P. Barros
Duke University
Topography and landform complexity favors the establishment of low level moisture convergence zones, and ridge-valley circulations organize the uplift and condensation of moist air, and CN (Condensation Nuclei) distribution, which in turn strongly impact the vertical structure of clouds and precipitation. In the Andes, the spatial organization of first order streams along the headwaters of the Amazon follows closely the distribution of precipitation features from the TRMM satellite mission with elevation. Comprehensive observations of the spatial heterogeneity and diurnal and seasonal cycle of precipitation microphysics in the Southern Appalachian Mountains in the US suggest an active role for cove forests in regulating local hydrometeorology including fog immersion and light rainfall processes, and promoting seeder-feeder interactions (SFI) among propagating synoptic systems, low level clouds (LLC) and fog as an enhancement mechanism of orographic precipitation. Analysis of preliminary observations and high resolution modeling studies in the Central Andes suggests that the same processes are active on the hydrometeorology along the altitudinal envelope from the Amazon rainforest up to the cloud forest, though the massive orography and 3D complexity of the eastern slopes of the Andes play a key role on space-time organization of these processes.
Additional modeling studies were conducted using realistic and quasi-idealized ET (Evapotranspiration) withdrawal experiments with the WRF model at very high resolution (~1 km grid spacing) in the Central Andes and in the adjacent Amazon to elucidate the impact of land-atmosphere interactions on precipitation processes. The results show that evapotranspiration fluxes modulated by landform govern convective activity in the lower troposphere, including cloud formation and precipitation processes that account for daily precipitation amounts as high as 50-70% depending on synoptic conditions and season in the Andes. The impact of Amazonia evapotranspiration (ET) on moisture transport and convection along the eastern flanks of the Andes (EADS) was investigated using similar quasi-idealized simulations over the Amazon lowlands (AMZL). The results show that, without surface ET, daily precipitation within the AMZL drops by up to ~75%, but nearly doubles over the surrounded mountainous regions. This dramatic influence is attributed to changes in regional circulations, and further analysis of moist static energy indicates that although the related large-scale circulation change tends to compensate for convective available potential energy (CAPE), elimination of surface ET results in the spatial reorganization of convective activity resulting in dramatic shifts in the diurnal cycle of precipitation over the EADS from daytime to nighttime maxima. This day-to-night changes in the diurnal cycle of clouds and precipitation has important implications for the eco-hydrology of EADS forests and their long-term sustainability. These results support the notion of dynamic forest controls of climate over a wide range of scales from local/valley-scale to regional/continental-scale linking the AMZL to the EADS via atmospheric moist processes within the Amazon airshed. Ongoing efforts toward developing a pan-Andean observing system of transects to elucidate the spatial and temporal variability of clouds and orographic precipitation and implications at the water-energy-climate and bio-conservation nexus will be presented.
Seminar will be webcast at: http://www.fin.ucar.edu/it/mms/fl-live.htm
Tuesday November 3, 2015 3:30pm
Refreshments 3:15 PM
NCAR-Foothills Laboratory
3450 Mitchell Lane Bldg 2 Main Auditorium (Rm1022)
EOL SEMINAR COORDINATORS: Steve Oncley and Stuart Beaton oncley@ucar.edu, beaton@ucar.edu https://www.eol.ucar.edu/workshops-seminars