Omar Torres

Tropical ozone loss following the eruption of Mt. Pinatubo

Total Ozone Mapping Spectrometer (TOMS) measurements of equatorial total ozone following the eruption of Mt. Pinatubo show a decrease of up to 6% over climatology. Ozone losses begin approximately a month following the eruption, consistent with the time required for the SO[sub 2] to convert to sulfuric acid aerosol. The thick aerosol layer interferes with the TOMS retrieval, but this interference is small and easily accounted for in the retrieval. Ozone values remain below climatology until December, 1991. Ozonesonde data from Natal, Brazil taken before and two months after the eruption support TOMS observations of ozone loss. These sondes show that the ozone loss region is confined to a 2-3 km thick layer between 24 and 28 km. 19 refs., 4 figs.

Effect of stratospheric aerosol on ozone profile from BUV measurements

Results of a simulation study on the effects of optically thick stratospheric sulfate aerosol layers on the backscattered ultraviolet radiation (buv) in the range 256-340 nm are presented. In general, the increased Mie scattering produced by the aerosols results in an enhancement of the buv radiation. The increase is approximately linear with optical depth and strongly depends on solar zenith angle and aerosol layer altitude in relation to the ozone maximum. The effect is greatest at those wavelenghts whose contribution functions peak in the vicinity of the densest part of the aerosol layer. The aerosol induced perturbation of the buv field affects the ozone profile retrieval from space measurements by the Solar Backscatter Ultraviolet Experiment (SBUV) experiment. In the tropical stratosphere, the retrieved ozone between 25 and 45 km is underestimated as a result of increased Mie scattering. On the other hand, an algorithm related effect causes the retrieved ozone below 25 km to be overestimated by an amount similar to the stratospheric deficit.

Retrieval of Reflected Direct Broadcast Satellite (DBS) Signals for Earth Science Applications

This paper presents the results of a pilot study that provides an initial assessment of the applicability of reflected DBS signals for Earth remote sensing. The study uses off-the-self hardware and signals from a Dish Network satellite at 12 GHz (Ku-band) reflected from soil and water to characterize the power reflected from these surfaces. Power levels directly from the satellite are compared to the power levels obtained from reflections from the soil and water. It is shown that the power reflected from water reaches 54 % of the direct power. Conversely, the power reflected from the soil is shown to be within the noise floor of the off-the-shelf hardware. The high DBS reflected power from water, much stronger than that found in the already successful use of reflected GPS, gives rise to high expectations for oceanographic remote sensing applications.

Utilizing Space-Based GPS Technology to Determine Hydrological Properties of Soils for Watershed Management

Water resources protection at the local level is becoming more complicated, largely due to non-point source (NPS) pollution. NPS pollution control requires identification of pollutant sources within a watershed and assessment of the hydrologic transport system (runoff) from the source to the water resource of concern. The amount of polluted runoff depends on many factors, including watershed land use, rainfall, and antecedent moisture conditions of the soil.

Airborne bistatic radar for external hazard detection and avoidance

The detection and avoidance of external hazards is an important aspect of overall efforts to improve the safety of future aircraft. Advanced sensor concepts may enhance the detection and quantification of risk due to external hazards. Such sensors, when integrated into cockpit operations, may substantially improve vehicle safety. This paper will describe research efforts to develop a simulation environment to evaluated advanced microwave sensor concepts such as airborne bistatic radars utilizing multiple non-cooperative illuminators or emitters-of-opportunity to detect weather hazards, area traffic, runway incursions, or other potential aircraft hazards. We will present initial efforts to develop a flexible microwave sensor simulation and assessment tool. This tool will be developed to assess the feasibility of various sensor concepts. Existing and potential future capability of the simulation environment will be described. In addition, the results of the application of the simulation tool to a bistatic sensor concept will be presented.