Presentation on theme: "Sandra Isay Saad Humberto da Rocha IAG / Department of Atmospheric Sciences International Scientific Conference Amazon in Perspective Integrated Science."— Presentation transcript:
Sandra Isay Saad Humberto da Rocha IAG / Department of Atmospheric Sciences International Scientific Conference Amazon in Perspective Integrated Science for a Sustainable Future Variation of size and alignment of deforestation patches in Amazonia: trying to understand secondary circulation and likely effects on rainfall
INTRODUCTION Large scale amazonian deforestation evapotranspiration decreases rainfall decreases patchy deforestation: deforestation breeze ?! (Avissar 2002) rainfall increases or decreases ?! currently: cloud increases over deforestation in dry season forests in wet season Simulations of deforestation in meso-scale Ramos da Silva 2007, 2008 Baidya Roy 2002 Gandu 2004
Objective Evaluate impacts of tropical patchy deforestation on local circulation and rainfall, using atmospheric modelling With dependence of size & alignment relative to large scale wind also: how large scale flow might combine deforestation breeze, and thus controls rainfall
Othe configuration Atmospheric nudging: NCEP reanalysis Number of grids: 3 Cumulus parameterization: Grel Simulations period: 2 months, starting on 1 October 2002 (dry season) 1 February 2002 (rainy season) BRAMS We used the atmospheric mesoscale model BRAMS (Brazilian Regional Atmospheric Modeling System). Land surface scheme: LEAF Material & methods Initial soil moisture profile: horizontally homogeneous (figure), varying with depth and season Based on field observations Bruno et al. (2006) & Rosolem (2005)
Grids Extension (km²) Grid spacing (km) Grid x Grid 2992 x Grid 3784 x 7208 Grid 1 Topography
deforestation patches: rectangles ~ 4,000 to 60,000 km² aligned N-S (AREA1 to 4), and aligned w/ prevailing wind (AREA1W... 4W) EXPERIMENTS Forest Vegetation: Control case = CTL Pasture (Deforestation) case = DFO
Diference (DFO–CTL) sensible heat flux (H) (Wm -2 ) Dry Season Rainy season Increasing of H specially during dry season.
Diference (DFO–CTL) latent heat flux (LE) (W m -2 ) Dry Season Rainy season Decreasing of LE only during dry season.
Dry Season Precipitation (DFO – CTL)
Rainy Season Precipitation (DFO – CTL)
Thermodynamics of circulation : Difference (DFO–CTL) q (g/kg) (colour filled); Θ (K) (contour) wind(V H ;w×10) (m s -1 ) (A) vortex counter-flow Upwd motion downwind the patch (C) ascending motion centered over patch (D) strongest upward motion
CTLDFO Horizontal slice 4392 m vertical profile in 7°S Impacts on clouds processed with grid spacing = 1 km hydrometeors: (cloud + pristine + snow + aggregates + graupel + hail), (g kg -1 ) 21:50 UTC deforestation Cloud strenghtening over deforestation CTLDFO
Aligned N-SAligned with prevailing wind CONCLUSION Simulated pattern of deforestation circulation inflow to deforestation accelerates (reduces drag) Temperature gradient & cell much stronger in dry season increases rainfall extensively along deforestation Reduces upwind abruptly Stronger upwd motion Tend to Increase net rainfall depend on the alignment with the prevailing wind Cross wind; increases rainfall downwind and reduces upwind the deforestation tend to decrease net rainfall