We propose to continue monitoring aerosol optical
properties, water vapor, and surface irradiance within our existing network.
Our highly successful network currently includes eight established sites,
with seven located in the Amazon basin, that have provided regular measurements
at some locations since the early phase of the LBA project dating back to
January 1999. Further observations
will enhance the multi-year dataset already acquired, and allow for a
comprehensive study of inter-annual variability of aerosol optical properties
(biomass-burning and background aerosols) both seasonally and spatially.
We plan to continue our studies of the attenuation of
broadband irradiance by biomass burning aerosols across the region. These studies have produced two LBA related journals papers to date.
At least two funded LBA investigators are producing surface irradiance
products from satellite data, and they will be relying on our flux measurements
for validation of their products and on our AOD data for smoke attenuation
Our previous studies have presented fractional reductions
in expected flux due to smoke, and we now plan to also assess the radiative
effects of clouds at all our network sites. MODIS cloud products (fractional coverage and optical thickness
parameters) will be used with the observed local irradiance reductions to
develop algorithms for estimating cloud attenuation of surface flux. The large spatial aspect of MODIS data will allow us to scale our point
source observations to a basin-wide quantification of cloud effect. The characterization of diurnal trends in cloud attenuation, which varies
greatly with month, will provide time-of-day corrections that can be applied to
MODIS observations. The accuracy of
MODIS measurements, necessarily limited to a short duration, can thus be
improved for application to non-overpass periods of the day.
Collection of additional aerosol properties data sets
from our LBA network will enable us to study the regional aerosol optical
properties in detail and to investigate seasonal trends. We plan to investigate
possible differences in aerosol single scattering albedo and size distribution
between sites in central Amazonia versus in the southern arc of deforestation,
that may result due to differences in the severity of the dry season and thus
differences in fuel moisture content. Additionally, seasonal trends in aerosol
absorption at each site will be studied, which may result from differences in
transport and aging of aerosols and in the fuel moisture as the dry season
transitions to the wet season.
In addition to our permanent installations, a number of
additional CIMEL sunphotometer and flux sensors will be deployed in support of
intensive field campaigns planned for the next two years (SMOCC, Dry-to-Wet
Season Field Campaign (August-November 2002)) with Brazilian and European
collaborators. A micro-pulse
lidar (providing details of vertical aerosol distribution), 4-5 additional CIMEL
sun-sky radiometers, and a temporary network of 20-30 hand-held sunphotometers
will be operated in Rondônia during select experiments.