 |
| Titel |
The effect of atmospheric aerosol particles and clouds on net ecosystem exchange in the Amazon |
| VerfasserIn |
G. G. Cirino, R. A. F. Souza, D. K. Adams, P. Artaxo |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1680-7316
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 14, no. 13 ; Nr. 14, no. 13 (2014-07-01), S.6523-6543 |
| Datensatznummer |
250118848
|
| Publikation (Nr.) |
 copernicus.org/acp-14-6523-2014.pdf |
|
|
|
|
|
| Zusammenfassung |
| Carbon cycling in the Amazon is closely linked to atmospheric processes and
climate in the region as a consequence of the strong coupling between the
atmosphere and biosphere. This work examines the effects of changes in net
radiation due to atmospheric aerosol particles and clouds on the net
ecosystem exchange (NEE) of CO2 in the Amazon region. Some of the major
environmental factors affecting the photosynthetic activity of plants, such
as air temperature and relative humidity, were also examined. An algorithm
for clear-sky irradiance was developed and used to determine the relative
irradiance, f, which quantifies the percentage of solar radiation absorbed
and scattered due to atmospheric aerosol particles and clouds. Aerosol
optical depth (AOD) was calculated from irradiances measured with the MODIS
(Moderate Resolution Imaging Spectroradiometer) sensor, onboard the Terra and
Aqua satellites, and was validated with ground-based AOD measurements from
AERONET (Aerosol Robotic Network) sun photometers. Carbon fluxes were
measured using eddy covariance technique at the Large-Scale
Biosphere-Atmosphere Experiment in Amazonia (LBA) flux towers. Two sites were
studied: the Jaru Biological Reserve (RBJ), located in Rondonia, and the
Cuieiras Biological Reserve at the K34 LBA tower (located in a preserved
region in the central Amazon). Analysis was performed continuously from 1999
to 2009 at K34 and from 1999 to 2002 at RBJ, and includes wet, dry and
transition seasons. In the Jaru Biological Reserve, a 29% increase in
carbon uptake (NEE) was observed when the AOD ranged from 0.10 to 1.5 at
550 nm. In the Cuieiras Biological Reserve, the aerosol effect on NEE was
smaller, accounting for an approximate 20% increase in NEE. High aerosol
loading (AOD above 3 at 550 nm) or high cloud cover leads to reductions in
solar flux and strong decreases in photosynthesis up to the point where NEE
approaches zero. The observed increase in NEE is attributed to an enhancement
(~50%) in the diffuse fraction of photosynthetic active radiation
(PAR). The enhancement in diffuse PAR can be done through increases in
aerosols and/or clouds. In the present study, it was not possible to separate
these two components. Significant changes in air temperature and relative
humidity resulting from changes in solar radiation fluxes under high aerosol
loading were also observed at both sites. Considering the long-range
transport of aerosols in the Amazon, the observed changes in NEE for these
two sites may occur over large areas in the Amazon, significantly altering
the carbon balance in the largest rainforest in the world. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|