1. Hydroclimatological Teleconnections from Tropical Forests
Roni Avissar and David Werth
Department of Civil & Environmental Engineering
Duke University
Presented by
Pedro L. Silva Dias
LBA 3rd Science Conference
Brazilia, Brazil
July 27-29, 2004

2. We use the data collected during the joint “Wet Atmospheric Mesoscale Campaign – TRMM validation (WetAMC – TRMM),” in January – February 1999. 8 9 10 11 12 13

3. Average Precipitation Rate (mm/hr)
RAMS (400m)
S-POL (2km)

4. 36% increase in the daily mean accumulation!
Current deforestation pattern
10.76 mm (daily mean accumulation)
No deforestation
7.94 mm (daily mean accumulation)
36% increase in the daily mean accumulation!

6. The Issue...

7. ?
The Issue...

11. Conclusions
The atmospheric boundary layer is significantly affected by landscape structure. Frequently, landscape heterogeneity created by land use generates horizontal pressure gradients strong enough to create and sustain organized mesoscale circulations, which can trigger thunderstorm activity. In tropical regions, this happens in all seasons;
Tropical deforestation significantly affects the regional hydroclimatology of these regions and, to a lesser but still quite significant degree, the mid-latitude hydroclimatology (e.g., the US Midwest and the Arabian Peninsula). Among tropical regions, the Amazon Basin seems to have the largest impact, probably due to the fact that water recycling in that region is more important than in Africa and South-East Asia;
Simultaneous deforestation of Amazonia, Central Africa and South-East Asia has a cumulative impact in a few regions (notably, in the Arabian Peninsula) and synergistic impact in others (including in the US by shifting the main impact to California);
Convective activity is one of the key factors that triggers teleconnections between tropical regions and higher latitudes but our GCMs do not account for (mesoscale) landscape-generated convection. Clearly, this limits our capability to estimate the real magnitude of teleconnections between Amazonia and the rest of the world.

12. Ocean-Land-Atmosphere Model (OLAM)
The Duke University
Ocean-Land-Atmosphere Model (OLAM)

13. Relevant Publications
Published:
Avissar, R., P. L. Silva Dias, M. A. F. Silva Dias, and C. A. Nobre, The Large-Scale Biosphere-Atmosphere Experiment in Amazonia (LBA): Insights and future research needs, J. Geophys. Res., 107, 8086, doi: /2002JD
Werth, D., and R. Avissar, The local and global effects of Amazon deforestation, J. Geophys. Res., 107, 8087, doi: /2001JD
Werth, D. and R. Avissar, The regional Evapotranspiration of the Amazon. J. Hydromet., 5,
To be published:
Avissar, R. and D. Werth. Global Hydroclimatological Teleconnections Resulting from Tropical Deforestation. J. Hydromet., in revision.
Werth, D., and R. Avissar. The local and global effects of Central African deforestation, Geophys. Res. Lett., submitted.
Werth, D., and R. Avissar. The local and global effects of South-East Asia deforestation, Geophys. Res. Lett., submitted.
Werth, D. and R. Avissar. The mechanism of land-cover teleconnections from tropical regions. J. Atm. Sci., in preparation.
Ramos da Silva, R. and R. Avissar. Does Amazonian deforestation enhances local rainfall? J. Hydromet., in preparation.