Amazonian deforestation: experiments with the RegCM GROUP 3: Rosmeri de Rocha (Brasil), Yamina Silva (Peru), Daniel Martinez (Cuba) ICTP Workshop on the Theory and Use of Regional Climate Models 26 May - 6 June

Objectives: Making a first test of the RegCM3 model’s capability to reproduce the main climatic features in South America. Preliminary assessment of the immediate climatic consequences of land use changes in the Amazon forest.

Experiments January 1998 (From 16 Dec.1997 to 01 Feb. 1998) Number of grid points: 81x69x18 Grid size: 80km (Mercator) Time step: 200s Convective scheme: Grell + FC (d  =60 min) Landuse 1) Amazon forest (landuse=6)  EXP1 2) Forest replaced by short grass (2)  EXP2

The Domain Forest was changed With Short grass

Total Precipitation: With Forest (EXP1) Underestimation of precipitation over the Amazon area Observed Simulated

Mean Temperature: With Forest (EXP1) Simulated temperatures are lower than observed Observed Simulated

Low level circulation (850 mb) low level jet Over Amazon area the simulated winds are weaker than reanalysis Observed Simulated

High Trough High Trough The model reproduces the more important features of the summer circulation over South America Observed Simulated Upper level circulation (200 mb)

Differences between simulated parameters: Short grass - Forest Decrease in precipitation Increase in precipitation Local temperature increase reaching until 5°C

Differences between simulated parameters: Short grass - Forest The increase in maximum temperature is greater than in the minimum temperature

Foliage Temperature Ground Temperature Ground and foliage temperature is higher in the short grass in the Amazon region, and is lower in other areas Differences between simulated parameters: Short grass-Forest

Differences between simulated parameters: Short grass-Forest Dryer Moister

Differences between simulated parameters: Short grass-Forest Over the Amazon the lower level winds ( σ=1) became more intense in the short grass

Diurnal cycle AM NE SE

AM NE SE Diurnal cycle of convective precipitation (Short grass v.s. forest) Short grass Forest More important impacts: -increase of the afternoon precip. in the SE -decrease of nocturnal precip. in the AM. Minimum impact in the NE

Diurnal cycle of sensible heat (Short grass and forest) AM NE SE Short grass Forest More important impacts: - increase of the afternoon sensible heat in the AM an SE. Minimum impact in the NE.

Diurnal cycle of evapotranspiration (Short grass and forest) AM NE SE Short grass Forest The more impact is: -Decrease in the AM -increase in the SE of the afternoon evapotranspiration Minimum impact in the NE.

Control run: the model adequately reproduces the main features of the regional circulation. Underestimates precipitation and temperature In the Amazonian region. In January 1998 simulation: Preliminary results

Deforestation impacts Local effects: Central Amazon: - lower precipitation and reduce the nocturnal precipitation - warmer air - dryer soil - lower evapotranspiration and higher sensible heat Peruvian Amazon: - increase of the total precipitation Remote effects: - increase of the precipitation and evapotranpiration in the SE - Minimal effects in the NE

Some problems The intense precipitation in the east boundary diminished the Northeast trade winds and so the convergence in the Amazon region. Is this responsible for lower precipitation in the Amazon? Possible solution: move away the east-west boundaries

Thanks !!!