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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. Sandra Isay Saad Humberto da Rocha

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Sandra Isay Saad Humberto da Rocha IAG / Department of Atmospheric Sciences

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  1. International Scientific ConferenceAmazon 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 Sandra Isay Saad Humberto da Rocha IAG / Department of Atmospheric Sciences

  2. 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

  3. also: • how large scale flow might combine deforestation breeze, and thus controls rainfall 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

  4. Material & methods We used the atmospheric mesoscale model BRAMS (Brazilian Regional Atmospheric Modeling System). Land surface scheme: LEAF • 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) Initial soil moisture profile: horizontally homogeneous (figure), varying with depth and season Based on field observations Bruno et al. (2006) & Rosolem (2005)

  5. Grids Grid 1 Topography

  6. EXPERIMENTS Forest Vegetation: Control case = CTL Pasture (Deforestation) case = DFO • deforestation patches: rectangles ~ 4,000 to 60,000 km² • aligned N-S (AREA1 to 4), and aligned w/ prevailing wind (AREA1W ... 4W)

  7. Diference (DFO–CTL) sensible heat flux (H) (Wm-2) Dry Season Rainy season • Increasing of H specially during dry season.

  8. Diference (DFO–CTL) latent heat flux (LE) (W m-2) Dry Season Rainy season • Decreasing of LE only during dry season.

  9. Dry Season Precipitation (DFO – CTL)

  10. Rainy Season Precipitation (DFO – CTL)

  11. Thermodynamics of circulation : Difference (DFO–CTL) q (g/kg) (colour filled); Θ(K) (contour) wind(VH;w×10) (m s-1) • (A) vortex counter-flow • Upwd motion downwind the patch • (C) ascending motion centered over patch • (D) strongest upward motion

  12. Impacts on clouds CTL DFO • processed with grid spacing = 1 km • hydrometeors: • (cloud + pristine + snow + aggregates + graupel + hail), • (g kg-1) • 21:50 UTC Horizontal slice 4392 m CTL DFO vertical profile in 7°S deforestation • Cloud strenghtening over deforestation

  13. CONCLUSION • Simulated pattern of deforestation circulation Aligned with prevailing wind Aligned N-S • inflow to deforestation accelerates (reduces drag) • Temperature gradient & cell much stronger in dry season • depend on the alignment with the prevailing wind • Cross wind; • increases rainfall downwind and reduces upwind the deforestation • tend to decrease net rainfall • increases rainfall extensively along deforestation • Reduces upwind abruptly • Stronger upwd motion • Tend to Increase net rainfall

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