Brazil: Forest land cover drives cloud cover which is being lost due to deforestation

Shallow clouds tend to form over deforested areas of the Amazon while
deep clouds are more prevalent above the remaining forest. Now
researchers from the US and Brazil have studied the mechanism behind
this phenomenon and found that the mix of forested and deforested
patches in damaged areas causes local atmospheric circulations that
affect cloud distribution.

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Together with colleagues at MIT, the University of Michigan, the
Instituto Nacional Presquisa Espaciais, Brazil, and the University of
California, Irvine, Jingfeng Wang studied an area of rainforest in the
Rondonia, Brazil using radiosonde data taken in 1994 as part of the
Rondonian Boundary Layer Experiment (RBLE-3) under the Anglo-Brazilian
Amazonian Climate Observation Study (ABRACOS).

Cloud information was provided by ivisible and infrared images from two NOAA satellites – GOES-7 and GOES-8. The area of deforestation studied contained a typical “fishbone” pattern of strips of tree removal. While partially deforested areas exhibited a less unstable atmosphere than the neighbouring dense forest, the team found that shallow clouds formed over them.

The researchers believe this was most likely due to mesoscale circulations developing from the contrast between forested and unforested strips and acting as a lifting mechanism. Boundary layer turbulence appeared to play a secondary role. Over the forest, a lack of lifting mechanism suppressed convective activity even though the atmosphere was more unstable. Those shallow clouds that did develop over forested areas eventually became deep clouds. “The Amazon rainforest has some resilience in response to human-related disturbances – deforestation, fire etc. – but only to a certain degree,” said Wang.

“The clouds-landcover interplay may provide a negative feedback mechanism to restore the lost forest as long as the forest over a large domain is not completely removed. Whether the Amazon ecosystem is able to recover from the deforestation, in my opinion, depends on the size and shape of the land-cover caused by the deforestation.”

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Comments (1)

MikeDecember 23rd, 2009 at 3:14 am

My Brazilian wife insists that the climate is changing. Last year was a very wet one in Brazil with higher temperatures. And there have also been a number of tornadoes, which she says never used to happen.

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