Scientists examining the Amazon River rain forest in Brazil during 2005 noted what appeared to be a significant die-off of trees, which they originally attributed to a severe drought in the region.
A study performed by researchers at Tulane University, in press for publication in Geophysical Research Letters, determined that the actual cause of the die-off was the passage of a brutal squall line of severe thunderstorms that crossed the Amazon basin from January 16-18, 2005. According to the Tulane group, analysis of Landsat images showed that this single storm system knocked down about half a billion trees (their estimate ranged from 441-663 million trees). This destruction amounted to about 23% of the estimated annual mean carbon accumulation in the Amazon rain forest.
The researchers note that climate change could lead to increased frequency and severity of storms, potentially causing even larger disruptions to the immense carbon uptake by the Amazon rain forest flora. Still, the destruction of trees by mankind is significantly greater than even this powerful storm event – the researchers estimated that between 300,000 and 500,000 trees were killed by the storm in the Manaus region of Brazil, which is about 30% of the annual toll of trees taken by human deforestation in that region.
This remarkable event illustrates the interplay of several different facets of the Earth's climate system, particularly the way that the energy and water cycle system can drive weather events which have a significant effect on the carbon cycle. Furthermore, this event illustrates the scale of natural events and human-caused alteration of large regional ecosystems.
Utilizing Tropical Rainfall Measuring Mission (TRMM) precipitation data and Merged Infrared (IR) data from geostationary satellites, the progression of the January 2005 from its inception in Peru and Bolivia to its final stages on the Atlantic coast of South America can be observed. Strong, fast-moving storms similar to these provide a significant amount of the rain that falls during the Amazonian rainy season, which occurs from roughly November to March. One of the main mechanisms of destruction by these storms was intense downbursts, with wind velocities of 26 to 41 meters per second (46-91 miles per hour), easily surpassing the hurricane wind speed threshold at their upper limit; the downbursts caused deaths and property damage in Brazilian cities. According to the researchers, a ten-year survey of TRMM data, utilizing TRMM 3-hourly rainfall data from the GES DISC, indicated that squall lines like the January 2005 event occur on average about twice a year.
Figure 1: Merged IR data from geostationary satellites, showing cloud movement associated with the passage of the squall line, January 17-18, 2005.
Figure 2: Tropical Rainfall Measuring Mission (TRMM) precipitation data, showing the position of the squall line on January 16, 2005, over Peru and Bolivia.
Figure 3: TRMM precipitation data, showing the position of the squall line on January 17, 2005, over the western region of the Amazon rain forest in Brazil.
Figure 4: TRMM precipitation data, showing the position of the squall line on January 18, 2005, extending from Guyana and Surimane to the north, extending south to just west of the mouth of the Amazon River.
Negron-Juarez, R. I., J. Q. Chambers, G. Guimaraes, H. Zeng, C. F. M. Raupp, D. M. Marra, G. H. P. M. Ribeiro, S. S. Saatchi, B. W. Nelson, and N. Higuchi (2010) Widespread Amazon forest tree mortality from a single cross-basin squall line event. Geophysical Research Letters, doi:10.1029/2010GL043733, in press.
Related GES DISC Data Resources: