Local boundary-layer development over burnt and unburnt tropical savanna: an observational study

Local boundary-layer development over burnt and unburnt tropical savanna: an observational study

Title
Publication TypeJournal Article
Year of Publication2007
AuthorsWendt, CK, Beringer, J, Tapper, NJ, Assoc Prof Hutley, LB
JournalBoundary-Layer Meteorology: an international journal of physical and biological processes in the atmospheric boundary layer
Volume124
Issue2
Pagination291 - 304
Date Published01/01/07
ISSN0006-8314
Keywordsalbedo, boreal forest, climate, emissions, feedbacks, fire, fire scar, impacts, monsoon, northern australia, Northern Territory, surface energy budget, territory, tethered balloon, tropical savanna, vegetation
Abstract

Fire scars have the ability to radically alter the surface energy budget within a tropical savanna by reducing surface albedo, increasing available energy for partitioning into sensible and latent heat fluxes and increasing substrate heat flux. These changes have the potential to alter boundary-layer conditions and ultimately feedback to local and regional climate. We measured radiative and energy fluxes over burnt and unburnt tropical savanna near Howard Springs, Darwin, Australia. At the burnt site a low to moderate intensity fire, ranging between 1,000 and 3,500 kW m(-1), initially affected the land surface by removing all understorey vegetation, charring and blackening the ground surface, scorching the overstorey canopy and reducing the albedo. A reduction in latent heat fluxes to almost zero was seen immediately after the fire when the canopy was scorched. This was then followed by an increase in the sensible heat flux and a large increase in the ground heat flux over the burnt surface. Tethered balloon measurements showed that, despite the presence of pre-monsoonal rain events occurring during the measurement period, the lower boundary layer over the burnt site was up to 2 degrees C warmer than that over the unburnt site. This increase in boundary-layer heating when applied to fire scars at the landscape scale can have the ability to form or alter local mesoscale circulations and ultimately create a feedback to regional heating and precipitation patterns that may affect larger-scale processes such as the Australian monsoon.

URLhttp://espace.cdu.edu.au/view/cdu:5123

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Wendt, C. K., Beringer, J., Tapper, N. J. & Assoc Prof Hutley, L. B. Local boundary-layer development over burnt and unburnt tropical savanna: an observational study. Boundary-Layer Meteorology: an international journal of physical and biological processes in the atmospheric boundary layer 124, 291 - 304 (2007).

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