TG-03 Abstract

Characterization of Aerosol Optical Properties and Solar Flux for LBA-ECO

Paulo Artaxo, USP (SA-PI)
Alejandro Fonseca Duarte, UFAC (SA-PI)
Brent Norman Holben, NASA/GSFC (US-PI)
Alberto Setzer, INPE (SA-PI)

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 analyses.

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 Rond˘nia during select experiments.