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)

Landuse1) Amazon forest (landuse=6) EXP12) 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 TemperatureGround 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

SEShort 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

Preliminary results

Deforestation impactsLocal 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 !!!