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- Front Matter: Volume 7462
- UV and VIS Ground and Space I
- UV and VIS Ground and Space II
- Poster Session
Front Matter: Volume 7462
Front Matter: Volume 7462
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This PDF file contains the front matter associated with SPIE
Proceedings Volume 7462, including the Title Page, Copyright
information, Table of Contents, Introduction (if any), and the
Conference Committee listing.
UV and VIS Ground and Space I
MAX-DOAS observations from ground, ship, and research aircraft: maximizing signal-to-noise to measure 'weak' absorbers
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Multi AXis Differential Optical Absorption Spectroscopy (MAX-DOAS) instruments, as solar straylight satellites,
require an accurate characterization and elimination of Fraunhofer lines from solar straylight spectra to measure the
atmospheric column abundance of reactive gases that destroy toxic and heat trapping ozone and form climate cooling
aerosols, like glyoxal (CHOCHO), iodine oxide (IO), or bromine oxide (BrO). The currently achievable noise levels
with state-of-the-art DOAS instruments are limited to δ'DL ≈ 10-4 (noise equivalent differential optical density, δ');
further noise reductions are typically not straightforward, and the reason for this barrier is not well understood. Here we
demonstrate that the nonlinearity of state-of-the-art CCD detectors poses a limitation to accurately characterize
Fraunhofer lines; the incomplete elimination of Fraunhofer lines is found to cause residual structures of δ' ≈ 10-4, and
only partially accounted by fitting of an "offset" spectrum. We have developed a novel software tool, the CU Data
Acquisition Code that overcomes this barrier by actively controlling the CCD saturation level, and demonstrates that
δ'DL on the order of 10-5 are possible without apparent limitations from the presence of Fraunhofer lines. The software
also implements active control of the elevation angle (angle with respect to the horizon) by means of a Motion
Compensation System for use with mobile MAX-DOAS deployments from ships and aircraft. Finally, a novel approach
to convert slant column densities into line-of-sight averaged concentrations is discussed.
Aerosol column absorption measurements using co-located UV-MFRSR and AERONET CIMEL instruments
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Column aerosol absorption properties in the visible wavelengths are measured routinely in worldwide
locations by NASA AERONET network (http://aeronet.gsfc.nasa.gov), while similar optical properties in UV
can be derived from diffuse and global irradiance measurements measured with Multifilter Rotating
Shadowband Radiometer (MFRSR) instruments of the USDA UV-MFRSR network
(http://uvb.nrel.colostate.edu). To enable direct comparisons between the two techniques, we have modified
our UV-MFRSR by replacing standard 300nm filter with 440nm filter used in AERONET network. The
modified UV/VIS-MFRSR has been mostly deployed at AERONET calibration site at NASA GSFC in
Greenbelt, MD, but also at number of field campaigns. While the UV-MSFRSR instrument is highly
susceptible to calibration drifts, these drifts can be accurately assessed using co-located AERONET direct-sun
AOT data. In 2006 quartz dome has been installed atop the MFRSR diffuser, which stabilized calibration
drifts in 2007-2009. After correcting for remaining calibration changes, the AOT and single scattering albedo
(SSA) at the UV wavelengths can be accurately inferred by fitting the measurements of global and diffuse
atmospheric transmittances with the forward RT model at each UV-MFRSR spectral channel. Derived AOT
and SSA at common wavelength 440nm by two different techniques are generally in good agreement. We
also found that SSA becomes smaller in the UV wavelengths and has strong wavelength dependence across
blue and near-UV spectral range. The measured enhanced UV absorption might suggest the presence of
selectively UV absorbing aerosols. High spectral resolution SSA measurements in UV-VIS wavelengths are
called for.
UV and VIS Ground and Space II
Global increases in UVB irradiance from changes in ozone and cloud-aerosol amounts 1979 to 2008
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Ultraviolet irradiance (UV from 290 nm to 325 nm) reaching the earth's surface has significantly increased at all latitudes
except the equatorial zone since 1979. The annual average increase was caused by a corresponding decrease in ozone
amount from1979 to 1998. After 1998, mid-latitude annual average ozone amounts and UV irradiance levels have been
approximately constant. Cloud plus aerosol changes over the period from 1979 to 2008 have caused significant
moderation of the clear-sky UVB trends based on a preliminary analysis of UV (340 nm) scene reflectivity data from
multiple satellites.
Nitrogen detection in the vegetation of prototype constructed wetlands using chlorophyll fluorescence
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Constructed wetlands are a very efficient, clean and economical way to remove organic contaminants from waste water.
In the whole water cleaning process, some other complex processes, such as physical sedimentation, filtration, chemical
precipitation, and material absorption by vegetation, are involved. The Nitrogen absorption efficiency by heliconnia
psitacorumm, was studied at laboratory scale in a small reactor simulating a subsurface flow constructed wetland.
Chlorophyll increasing was measured by fluorescence, using blue LED, 460 [nm] as excitation light source. Besides,
spectral differences were observed in the spectral signal and in its derivative, indicating changes in the plant
physiological response.
Poster Session
Aerosol single scattering albedo retrieval with various techniques in the UV and visible wavelength range
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The most important aerosol properties for determining aerosol effect in the solar radiation reaching the earth's surface
are the aerosol extinction optical depth and the single scattering albedo (SSA). Most of the latest studies, dealing with
aerosol direct or indirect effects, are based on the analysis of aerosol optical depth in a regional or global scale, while
SSA is typically assumed based on theoretical assumptions and not direct measurements. Especially for the retrieval of
SSA in the UV wavelengths only limited work has been available in the literature.
In the frame of SCOUT-O3 project, the variability of the aerosol SSA in the UV and visible range was investigated
during an experimental campaign. The campaign took place in July 2006 at Thessaloniki, Greece, an urban environment
with high temporal aerosol variability. SSA values were calculated using measured aerosol optical depth, direct and
diffuse irradiance as input to radiative transfer models. The measurements were performed by co-located UV-MFRSR
and AERONET CIMEL filter radiometers, as well as by two spectroradiometers. In addition, vertical aerosol profile
measurements with LIDAR and in-situ information about the aerosol optical properties at ground level with a
nephelometer and an aethalometer were available.
The ground-based measurements revealed a strong diurnal cycle in the SSA measured in-situ at ground level (from 0.75
to 0.87 at 450nm), which could be related to the variability of the wind speed, the boundary layer height and the local
aerosol emissions. The reasons for SSA differences obtained by different techniques are analyzed for the first time to
provide recommendations for more accurate column SSA measurements.
Ozone monitoring instrument satellite UV irradiance product correction using a global aerosol climatology
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Lately a number of studies related with UV irradiance estimates from satellite data based on the Ozone Monitoring
Instrument (OMI) have shown a high correlation with ground-based measurements but a positive bias in many locations,
the satellite derived UV being higher. One of the key factors that this bias has been attributed to is the boundary layer
aerosol absorption not taken into account in the current OMI UV algorithm. In this work we have used a correction
procedure based on climatological global aerosol absorption data taken from AeroComm aerosol initiative. This dataset
includes aerosol optical depth and aerosol single scattering albedo assembled by combining, ground-based aerosol
measurements from AERONET and information from several global aerosol models. The results of this correction were
compared with synchronous ground-based measurements from 9 UV monitoring stations. The results generally showed a
significantly reduced bias of 7-20%, a lower variability, and an unchanged, high correlation coefficient.
Dissemination of data from the National Science Foundation's UV monitoring network
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The U.S. National Science Foundation's (NSF's) Ultraviolet Spectral Irradiance Monitoring Network (UVSIMN) has
been measuring global UV irradiance at seven locations in Antarctica, South America, Southern California, and the Arctic,
starting in 1988. Data products include spectra of global (sun and sky) irradiance, sampled quarter-hourly between
280 and 600 nm; integrated irradiance (e.g., UV-B, UV-A); biologically effective dose-rates (e.g., the UV Index); total
ozone; effective albedo; cloud optical depth; actinic flux; photoloysis rates; and complementing spectra calculated with a
radiative transfer model. Data are disseminated via the project's website www.biospherical.com/NSF. During the last
year, data have also been submitted to international data repositories, including (1) the World Ozone and UV Data Center
(WOUDC), which is part of the World Meteorological Organization's Global Atmosphere Watch (GAW) program;
(2) the Cooperative Arctic Data and Information Service (CADIS), which supports the Arctic Observing Network
(AON), an NSF initiative for the International Polar Year (IPY); and (3) the SeaWiFS Bio-optical Archive and Storage
System (SeaBASS), which serves NASA's calibration and validation activities for ocean-viewing satellites. We also
plan to submit a subset of the dataset to (4) the Network for the Detection of Atmospheric Composition Change
(NDACC). The main objective of NDACC is to further understanding of stratospheric changes to the troposphere.
UVSIMN data have been adjusted to better serve the needs of these diverse research communities. This paper details the
background, format, and volume of these new datasets.
Effects of terrestrial UV radiation on selected outdoor materials: an interdisciplinary approach
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Modern polymeric materials possess an ever increasing potential in a large variety of outdoor objects and structures
offering an alternative for many traditional materials. In outdoor applications, however, polymers are subject to a
phenomenon called weathering. This is primarily observed as unwanted property changes: yellowing or fading, chalking,
blistering, and even severe erosion of the material surface. One of the major weathering factors is UV radiation.
In spring 2005, the Finnish Meteorological Institute with its research and industrial partners launched a five-year
material research project named UVEMA (UV radiation Effects on MAterials). Within the framework of the project, a
weathering network of seven European sites was established. The network extends from the Canary Islands of Spain
(latitude 28.5°N) to the Lapland of Finland (latitude 67.4°N), covering a wide range of UV radiation conditions. Since
autumn 2005, the sites of the network have been maintaining weathering platforms of specimens of different kinds of
polymeric materials. At the same time, the sites have been maintaining their long-term monitoring programmes for
spectrally resolved UV radiation. Within UVEMA, these data are used for explaining the differences between the
degradation rates of the materials at each site and for correlating the UV conditions in accelerated ageing tests to those
under the Sun.
We will present the objectives of the UVEMA project aiming at deeper understanding of the ageing of polymers and
more reliable assessments for their service life time. Methodologies adopted within the project and the first results of the
project will be summarized.
Light emitting diode cavity enhanced differential optical absorption spectroscopy (LED-CE-DOAS): a novel technique for monitoring atmospheric trace gases
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The combination of Cavity Enhanced Absorption Spectroscopy (CEAS) with broad-band light sources (e.g. Light-
Emitting Diodes, LEDs) lends itself to the application of cavity enhanced DOAS (CE-DOAS) to perform sensitive and
selective point measurements of multiple trace gases with a single instrument. In contrast to other broad-band CEAS
techniques, CE-DOAS relies only on the measurement of relative intensity changes, i.e., does not require knowledge of
the light intensity in the absence of trace gases and aerosols (I0). We have built a prototype LED-CE-DOAS instrument
in the blue spectral range (420-490nm) to measure nitrogen dioxide (NO2), glyoxal (CHOCHO), iodine monoxide (IO),
water (H2O) and oxygen dimers (O4). Aerosol extinction is retrieved at two wavelengths by means of observing water
and O4 and measuring pressure, temperature and relative humidity independently. The instrument components are
presented, and the approach to measure aerosol extinction is demonstrated by means of a set of experiments where
laboratory generated monodisperse aerosols are added to the cavity. The aerosol extinction cross section agrees well with
Mie calculations, demonstrating that our setup enables measurements of the above gases in open cavity mode.
The CLEO spectrometer system: first results
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We present first results from the newly developed remote sensing instrument CLEO (CLear Sky Observatory). CLEO
consists of a commercially available CCD miniature spectrometer (Hamamatsu C10082CAH) and foreoptics to measure
the global and diffuse solar irradiance. The irradiance is measured through a teflon diffuser. The diffuse irradiance is
obtained moving a 180° metal band in the optical path to block the solar direct beam. CLEO measures simultaneously
UV and Visible radiation from 163nm to 845nm, in steps of 0.3nm with a resolution of 1nm. The spectrometer is
temperature controlled to 10°C to stabilize its optical properties. The dark count is frequently measured using a
motorized four positions filterwheel with an opaque disc at one position that acts as a shutter used to block the light
input. The system automatically adjusts the integration time to optimize the signal-to-noise. Another difference to
previous shadowband instruments is that CLEO moves the shadowband over the whole hemisphere instead of just a few
positions in and around the sun's direction. This has the advantage of simplifying the installation procedure and solves
the problem with the shadow only partially covering the diffuser due to instrument misalignment.
A simulation of stratospheric ozone in response to the increased surface CFCs emissions
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To evaluate the stratospheric process in the response to the increased surface CFCs emissions, some simulations were
carried out by the NCAR interactive chemical, dynamical and radioactive two-dimensional (SOCRATES) model. The
investigation showed that when the surface CFCs emissions increased by 30%, these chemical components would be
transported into the stratosphere and would play an important roles in stratospheric chemistry and radiation. In the layers
from 40km to 48km, the relative variety of active component was ClOx by 20%, HOx by -2%, NOx by -2% and O3 by
-5%, respectively. At the same time, temperature reduced by 0.6K.
Losses in the fluorescent tracer used in hydrodynamic modeling of constructed wetlands studied by laser induced fluorescence
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Fluorescent tracer trials are performed to obtain useful information for hydrodynamic modeling. Particularly they have
been used in constructed wetlands, aimed for residual water treatment, in order to find residence time distribution for
particles entering the system and, in general, to know the flux pattern. Nevertheless, it has been reported that some
tracers, as Rhodamine WT, exhibit adsorption phenomena over the substrate. This situation has to be considered in the
analysis of residence time distribution curves, taking into account advection-dispersion processes which are given by the
diffusion modified equation. Laser Induced Fluorescence (LIF) with a Nd:YAG laser (532 nm; 35mW), was used to
determine Rhodamine WT accumulated concentration. Through adsorption coefficients obtained experimentally, an
advection - dispersion model for solute transport in a subsurface flow constructed wetland was evaluated. Including this
phenomenon allows to optimize the model, and another important condition is added in the behavior prediction of these
complex ecosystems.