ALBERT

Description: Studies are performed on both the Stratospheric Aerosol and Gas Experiment (SAGE) II (1985-1989) and Solar Backscatter Ultraviolet Spectrometer (SBUV)-Version 6 (1979-1986) global ozone vertical structure satellite data sets to determine the long-term trends in ozone as a function of altitude (pressure) and latitude. SAGE II data are only available during the period of increasing solar activity and show increases in ozone with time in the upper stratosphere which are attributed largely to rising solar activity. Looking at this data set independently, the solar effects and trends are highly coupled and cannot be clearly separated. However, a study of combined SBUV and SAGE II data over the 11-year solar cycle shows a clear response of ozone to 11-year solar variations and allows a decoupling of solar effects, quasibiennial oscillations (QBO), and trends. The detailed pattern of long-term ozone trends become clear using this approach. In the upper stratosphere, ozone depletion increases sharply with latitude. Global trends are fairly symmetric about the equator but are somewhat stronger in the Southern Hemisphere. Near the equator, some layers of ozone are decreasing with time while others appear to be increasing. Near 30 mb, there is evidence of intrusion to mid latitudes of high latitude negative trends. Near 15 mb, trends appear to be very weak. Near the tropopause there appears to be strong ozone depletion on a global scale. Two regions of unexpectedly strong ozone response to 11-year solar variations were detected: the first near 2 mb and the second near 30 mb at low latitudes and near 15 mb at mid latitudes.

Description: Recent studies suggest that airborne Asian dust may not only play an important role in the regional radiation budget, but also influence the air quality over North America through long-range transport. In this paper, we use satellite data to investigate the long-term variability of airborne Asian dust as well as the daily variation of the dust aerosol distribution. By combining the Total Ozone Mapping Spectrometer (TOMS) aerosol index with National Centers for Environmental Prediction (NCEP) wind data, our analysis shows a strong correlation between the generation of dust storms in the region and the passage of springtime weather fronts. This is consistent with earlier studies performed by other researchers. According to both the Nimbus-7 and Earth-Probe TOMS data the Takla Makan desert, the Gobi desert, and the and region of Inner Mongolia are major sources of the eastward-flowing airborne Asian dust. Heavily populated areas in eastern China (e.g., Beijing) are often on the primary path of the dust storms originating in these desert regions. The increasing desertification north of the Beijing region has served to exacerbate problems stemming from these storms. The time series derived from 20 years of TOMS aerosol index data shows the first significant satellite evidence of the atmospheric effect of increasing desertification, indicating that the amount of dust blown eastward has increased strongly during the past few years including the year 2000.

Description: The total column ozone response to 11-year solar ultraviolet (UV) variations is estimated here from the observed response to 27-day solar variations adjusted for the theoretical difference between the 27-day response and 11-year response. The estimate is tested by comparing two data sets where long-term drifts have been removed, the Nimbus 7 TOMS Version 6 total column ozone and the 280 nm core-to-wing ratio (a proxy for solar UV variations). The 365-day running means of data area-weighted between 40 deg N to 40 deg S latitude give a 1.9% ozone variation related to the 11-year solar cycle compared with the estimate of 1.8%. Estimates of linear trends were reduced by a factor of 2 by including solar effects. The standard deviation from the empirical model was reduced from 1.0 to 0.6 Dobson Units, by including the quasi-biennial oscillation (QBO), but the QBO did not significantly alter trend estimates. Both the ozone responses to 27-day and 11-year solar variations were considerably stronger than predicted by a 2-D theoretical model.

Description: Calculations of the Northward eddy fluxes of stratospheric ozone in a three-dimensional chemical-dynamical model are discussed. It is shown that, although approximately 50 percent of the zonal mean flux is produced by stationary planetary wavenumbers 1 and 2, the wintertime flux due to the chemical eddies is substantially underestimated when a quasi-linear representation is used.

Description: Biomass burning has been a regular practice for land clearing and land conversion in many countries, especially those in Africa, South America, and Southeast Asia. However, the unique climatology of Southeast Asia is very different than that of Africa and South America, such that large-scale biomass burning causes smoke to interact extensively with clouds during the peak-burning season of March to April. Significant global sources of greenhouse gases (e.g., CO2, CH4), chemically active gases (e.g., NO, CO, HC, CH3Br), and atmospheric aerosols are produced by biomass burning processes. These gases influence the Earth- atmosphere system, impacting both global climate and tropospheric chemistry. Some aerosols can serve as cloud condensation nuclei, which play an important role in determining cloud lifetime and precipitation, hence, altering the earth s radiation and water budget. Analyses from satellite measurements reveal the reflected solar (emitted thermal) radiation from clouds due to smoke aerosols can be reduced (enhanced) by 100 (20) Watts per square meter over the month of March 2000. In addition, the reduction in cloud spectral reflectance is large enough to lead to significant errors in satellite retrievals of cloud properties (e.g., optical thickness and effective radius). The fresh water distribution in this region is highly dependent on monsoon rainfall; in fact, the predictability of the tropical climate system is much reduced during the boreal spring. Therefore, to accurately assess the impact of smoke aerosols in this region requires continuous observations from satellites, aircraft, ground-based networks and dedicated field experiments. BASE-ASIA initiative has been proposed and will be discussed.

Description: Satellite based estimates of aerosol single scattering albedo (ssa), over both land and water surfaces, have been obtained for the first time using measurements of backscattered radiation in the near ultraviolet by the Total Ozone Mapping Spectrometer (TOMS). The retrieval of ssa and aerosol optical depth is based on the strong spectral contrast in the near-UV resulting from the interaction between the particle absorption and scattering (both Rayleigh and Mie) processes. We use the multi-year data set on backscattered radiances by the TOMS family of instruments to analyze the time and space variability of biomass burning generated carbonaceous aerosols. Results of a comparative analysis of satellite derived optical depth and available sunphotometer measurements will also be presented.