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- Front Matter: Volume 7107
- Remote Sensing of Clouds
- Lidar, Radar, and Passive Atmospheric Measurement Techniques
- Radiative Transfer
- Ultraviolet Ground- and Space-Based Measurements, Retrievals, and Models
- Remote Sensing by FTIR, DOAS, and Other Spectometric Methods
- Atmospheric Profiling of Aerosols, Trace Gases, and Meteorological Parameters
- Poster Session
Front Matter: Volume 7107
Front Matter: Volume 7107
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This PDF file contains the front matter associated with SPIE Proceedings Volume 7107, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and the Conference Committee listing.
Remote Sensing of Clouds
Robust cloud estimation for GMS images considering the dynamic changes on VIS/IR data
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This paper proposes a method that estimates the position of clouds from VIS images (visible), and IR images (infrared)
of GMS (Geostationary Meteorological Satellite). In estimating the position of clouds, because the brightness value of
land and sea is lower than cloud, and the brightness value of land and sea is continually varied by altitude of sun, the
cloud area cannot be estimated by threshold processing. In this study, Variation character of brightness value is classified
in each area, and the processing method of each area is proposed based on this variation character. In land area, there is
correlation between brightness value of VIS and IR image if the area is not covered by cloud. Thus, the object domain is
estimated cloud area using the correlation between them. In sea area, due to temperature is stable, cloud area is estimated
by background subtraction method. This method was used to estimate and evaluated in the 202 GMS-5 images. The
evaluated results shown that the proposed method is more accurate than the previous method, which estimated by
threshold processing (Omi, 2003).
Near-real time cloud retrievals from operational and research meteorological satellites
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A set of cloud retrieval algorithms developed for CERES and applied to MODIS data have been adapted to analyze
other satellite imager data in near-real time. The cloud products, including single-layer cloud amount, top and base
height, optical depth, phase, effective particle size, and liquid and ice water paths, are being retrieved from GOES-
10/11/12, MTSAT-1R, FY-2C, and Meteosat imager data as well as from MODIS. A comprehensive system to
normalize the calibrations to MODIS has been implemented to maximize consistency in the products across platforms.
Estimates of surface and top-of-atmosphere broadband radiative fluxes are also provided. Multilayered cloud properties
are retrieved from GOES-12, Meteosat, and MODIS data. Native pixel resolution analyses are performed over selected
domains, while reduced sampling is used for full-disk retrievals. Tools have been developed for matching the pixel-level
results with instrumented surface sites and active sensor satellites. The calibrations, methods, examples of the
products, and comparisons with the ICESat GLAS lidar are discussed. These products are currently being used for
aircraft icing diagnoses, numerical weather modeling assimilation, and atmospheric radiation research and have
potential for use in many other applications.
Studying the potential of terahertz radiation for deriving ice cloud microphysical information
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With wavelengths in the order of the size of typical ice cloud particles and therefore being sensitive to ice clouds,
the Terahertz (THz) region is expected to bear a high potential concerning measuring ice cloud properties, in
particular microphysical parameters. In this paper we give an introduction to the characteristics of atmospheric
THz radiation between 0-5THz (wavelengths >60 μm and wavenumber<170 cm-1 respectively) as well as ice
cloud optical properties and cloud effects in the THz region. Using radiative transfer model simulations we
analyze the sensitivity of THz spectra to ice content and particle size. For tropical cases cloud effects in the
order of 0.1 K/(g/m2) are found. Assuming instrumental sensitivities of typically around 1K these effects allow
for detection of clouds with columnar ice content of 10 g/m2. It is demonstrated that submillimeter (SMM)
instruments are sensitive to particles with sizes larger than 100 μm, while THz observations potentially can
measure particles as small as 10 μm.
ASTER nighttime cloud mask database using MODIS cloud mask (MOD35) products
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Cloud assessment for ASTER nighttime scenes is not accurate because the ASTER Cloud Coverage Assessment
Algorithm (ACCAA) thresholds with only one thermal infrared (TIR) band for nighttime scenes. First in the present
paper, it is shown that the original ACCAA cloud masks differ considerably from the masks interpolated from MODIS
Cloud Mask Products (MOD35), and this discrepancy is caused from errors in the ACCAA masks by visual check for
543 scenes. In addition, uncertain pixels included in MOD35 masks, which are classified to neither cloud nor clear, are
visually checked for 76 scenes. Then, the ASTER nighttime cloud mask database using MOD35 products is introduced.
It provides the interpolated MOD35 cloud masks for almost all ASTER nighttime scenes (143,242 scenes as of July
2008) through Internet. The database also shows that clear scenes with cloud coverage of 20% or less are about 34% of
the total nighttime scenes. In the final part of the paper, an algorithm for reclassifying an interpolated MOD35 mask
using ASTER measurements is proposed and applied to 42 test scenes. The algorithm will work well for some scenes,
but less well for snow/ice surfaces, and thin, cirrus, and high clouds, due to the band limitation of ASTER/TIR. If a
spatial uniformity test is added, the algorithm performance may be improved.
In-scene-based atmospheric correction of uncalibrated VISible-SWIR (VIS-SWIR) hyper- and multi-spectral imagery
Show abstract
The QUAC (Quick Atmospheric Correction) algorithm for in-scene-based atmospheric correction of VIS-SWIR
(VISible-Short Wave InfraRed) Multi- and Hyperspectral Imagery (MSI and HSI) is reviewed and applied to
radiometrically uncalibrated data. Quite good agreement was previously demonstrated for the retrieved pixel spectral
reflectances between QUAC and the physics-based atmospheric correction code FLAASH (Fast Line-of-sight
Atmospheric Analysis of Spectral Hypercubes) for a variety of HSI and MSI data cubes. In these code-to-code
comparisons, all the data cubes were obtained with well-calibrated sensors. However, many sensors operate in an
uncalibrated manner, precluding the use of physics-based codes to retrieve surface reflectance. The ability to retrieve
absolute spectral reflectances from such sensors would significantly increase the utility of their data. We apply QUAC
to calibrated and uncalibrated versions of the same Landsat MSI data cube, and demonstrate nearly identical retrieved
spectral reflectances for the two data sets.
Lidar, Radar, and Passive Atmospheric Measurement Techniques
An overview of the EarthCARE mission and end-to-end simulator
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The Earth Clouds, Aerosols and Radiation Explorer (EarthCARE) mission aims at improving the representation and
understanding of the Earth's radiative balance in climate and numerical weather forecast models by acquiring
vertical profiles of clouds - including vertical motion within clouds - and aerosols, as well as measuring the broadband
radiances at the top of the atmosphere for flux estimates in relation of the observed clouds and aerosols fields.
The EarthCARE payload comprises an High Spectral Resolution (HSR) Lidar (ATLID) operating at 355 nm and
equipped with a high-spectral resolution (HSR) receiver and the Cloud Profiling Radar (CPR), a highly sensitive
94GHz cloud radar with Doppler capability. A Multi-Spectral Imager (MSI) supporting the active instruments
consists of a push-broom imager with 7 channels in the visible, near infrared, short-wave infrared and thermal
infrared. Finally, a Broad-Band Radiometer (BBR) measures the outgoing top-of-atmosphere radiances in a short
wave channel and a total wave channel, from which the long wave contribution can be deduced.
The EarthCARE end-to-end Simulator (ECSIM) encompasses the full EarthCARE observation chain from scene
definition to single-instrument and synergistically derived multi-instrument Level 2 products. Level 2 retrieval
algorithms can be tested in the full chain (provision of input data, algorithm performance tests by comparison of
outputs with known inputs) by using a single framework with well-defined interfaces helping to harmonise
algorithm developments.
The CPR is developed and procured by JAXA (Japanese Aerospace Exploration Agency) and NiCT (National
Institute of Information and Communications Technology) and will be embarked as an integral part of the
EarthCARE satellite in the context of the ESA/JAXA cooperation for EarthCARE.
Sub-visual cirrus LIDAR measurements for satellite masking improvement
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Understanding the impact of cirrus cloud on modifying both the solar reflected and terrestrial emitted radiations
is crucial for climate studies. Unlike most boundary layer stratus and stratocumulus clouds that have a net
cooling effect on the climate, high-level thin cirrus clouds have a warming effect on our climate. However,
the satellites as GOES from the NOAA series are limited to the cloud top and its reflectivity or brightness
temperature, without assessing accurately the optical depth or physical thickness. Other more recent sensors
as MODIS are able to determine optical depths for aerosols and clouds but when related to cirrus they are still
inaccurate. Research programs as First ISCCP, FIRE, HOIST, ECLIPS and ARM have concentrated efforts
in the research of cirrus, being based mainly on the observations of combined terrestrial remote sensing and
airplanes instruments. LIDARs are able to detect sub-visual cirrus cloud (SVCs) in altitudes above 15 km and
estimate exactly their height, thickness and optical depth, contributing with information for satellites sensors
and radiative transfer models. In order to research characteristics of SVCs, the LIDAR system at Instituto
de Pesquisas Energeticas e Nucleares has as objective to determine such parameters and implement a cirrus
cloud mask that could be used in the satellite images processing as well as in the qualitative improvement of
the radiative parameters for numerical models of climate changes. The first preliminary study shows where we
compare the data lidar with Brightness temperature differences between the split-window data from GOES-10
(DSA/INPE) and CALIPSO.
Evaluation of the atmospheric correction procedure for the APEX level 2/3 processor
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The Airborne Prism Experiment (APEX) is a hyperspectral instrument built in a Swiss - Belgian collaboration within the
ESA-PRODEX program. It aims at highest possible accuracy of its delivered surface reflectance image data products.
The atmospheric correction of hyperspectral imagery is a critical element of a complete processing chain towards
unbiased reflectance and for the creation of higher level products. As the first data of APEX is expected to become
available in 2009, an appropriate processing chain for higher level processing needs to be defined and evaluated.
Standard products have been identified in all application fields of hyperspectral imaging, i.e., geology, vegetation,
cryosphere, limnology and atmosphere. They are being implemented at the APEX science center. The according
processing procedures rely on data of well-defined processing states which range from calibrated at-sensor radiance to
(bihemispherical) spectral albedo.
In this paper, the atmospheric processing which is implemented as part of the automated data processing chain for level 2
in the APEX processing and archiving facility (PAF) at VITO (Mol, Belgium) is evaluated together with the
ATCOR-4 atmospheric correction program. The evaluation is done regarding flexibility, reflectance output
accuracy and processing efficiency. Two test data sets are taken for this purpose: a well-documented set of HYMAP data and a high resolution HYSPEX data set. Both data sets exhibit areas of overlap, which are taken for self-contained
analysis of the atmospheric correction procedure. The accuracy tests include plausibility checks on selected
regions of interest including a variety of known surfaces in the imagery. As some of the observed effects are related to
BRDF differences, the results also give an indication for the inaccuracy related to these reflectance anisotropies. Speed
measurements of the processing are then compared to the demand for operational processing of series of data acquisition.
Further comparison information is drawn from the by-products of atmospheric correction such as water vapor
distribution maps.
The study shows performance and limitations of atmospheric correction using the state-of-the-art technology, which are
mainly found in the field of BRDF effects. This points towards improvements to be implemented in course of the further
development of the higher level processing chain for the APEX sensor.
New results from continuous mixing layer height monitoring in urban atmosphere
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Mixing layer height was continuously monitored by uninterrupted remote sensing measurements with ceilometer, sodar
and RASS in Augsburg. The Vaisala ceilometers LD40 and CL31 were used which are eye-safe commercial lidar
systems. Special software for these ceilometers provides routine retrievals of lower atmosphere layering from vertical
profiles of laser backscatter data. These remote sensing instruments were operated at three different sites: at the northern
edge (CL31 or LD40, RASS), in the middle (CL31) and at the southern edge of the town (sodar). A comparison of the
different results during simultaneous measurements was performed. The information content of the different remote
sensing instruments for mixing layer height was analysed further. The ceilometer measurements add information about
the range-dependant aerosol concentration; gradient minima within this profile mark the borders of mixed layers. The
sodar measurements detect the height of a turbulent layer characterized by high acoustic backscatter intensities due to
thermal fluctuations and a high variance of the vertical velocity component. The RASS measurements provide the
vertical temperature profile from the detection of acoustic signal propagation. Different measurement examples will be
presented to demonstrate the information about the mixing layer height.
Superresolution multispectral imaging polarimetric space surveillance LADAR sensor design architectures
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This study consists of the exploitation of novel ladar design principles and architectures aimed at the increasing of the
superresolution, and imaging capabilities of the space surveillance ladars for efficient detection, discrimination, and
monitoring of space objects and man-made materials detection. Ladar interferometric techniques relying on Vertical-
Cavity Surface-Emitting Laser (VCSEL) coherent arrays would provide enhanced lightweight imaging solutions, with
unsurpassable dynamic range, at low power consumption, remarkable reliability, and reduced cost. The experimental
results of this study indicate that the signal-to-noise ratio of backscattered optical signals can be enhanced significantly,
by utilizing efficient single-pixel polarimetric techniques; as a result the ladar range accuracy would be improved
significantly. In addition, several space materials and man-made materials are shown to exhibit distinct depolarization
signatures which can be used to characterize, classify, and identify those materials.
Radiative Transfer
Improved full spectrum cloudy scene simulation
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This paper will discuss recent improvements made to the MCScene code, a high fidelity model for full optical spectrum
(UV through LWIR) hyperspectral image (HSI) simulation. MCScene provides an accurate, robust, and efficient means
to generate HSI scenes for algorithm validation. MCScene utilizes a Direct Simulation Monte Carlo approach for
modeling 3D atmospheric radiative transfer (RT) including full treatment of molecular absorption and Rayleigh
scattering, aerosol absorption and scattering, and multiple scattering and adjacency effects, as well as scattering from
spatially inhomogeneous surfaces, including surface BRDF effects. The model includes treatment of land and ocean
surfaces, 3D terrain, 3D surface objects, and effects of finite clouds with surface shadowing. This paper will provide an
overview of how RT elements are incorporated into the Monte Carlo engine. Several new examples of the capabilities
of MCScene to simulate 3-dimensional cloud fields will also be discussed, and sample calculations will be presented.
Atmospheric property retrievals from infrared atmospheric sounding interferometer (IASI)
Show abstract
Retrieving atmospheric and surface properties from hyperspectral sensors is a challenging task due to the requirement of
performing extensive radiative transfer calculations for thousands of channel radiances. We will present a retrieval
algorithm, which uses a Principal Component-based Radiative Transfer Model (PCRTM) to perform radiative transfer
calculation in Empirical Orthogonal Functions (EOF) domain. By compressing thousands of channel radiances into
one hundred EOFs, the dimensionality of the problem is greatly reduced while the information content is preserved.
The PCRTM provides the EOF coefficients and associated derivatives with respect to atmospheric and surface
parameters needed by the inversion algorithm. The inversion algorithm is based on a non-linear Levenberg-Marquardt
method with climatology covariance and a priori information as constraints. We will show results obtained from data
collected during the Joint Airborne IASI Validation Experiment (JAIVEx). The campaign took place in late April and
early May of 2007. Spectra observed by Infrared Atmospheric Sounder Interferometer (IASI) onboard of METOP-A
satellite will be used to retrieve atmospheric (temperature, moisture, and trace gas profiles, cloud top, cloud particle size
and cloud optical depth) and surface properties (surface skin temperature and surface emissivity). Collocated
radiosondes and dropsondes will be used in retrieval product inter-comparisons and validation.
TITAN: a new infrared radiative transfer model for the study of heterogeneous 3D surface
Show abstract
An innovative transfer radiative code, TITAN (Thermal Infrared radiance simulaTion with Aggregation modeliNg),
in the infrared domain (3-14μm) is presented. It takes into account the 3D structure of the landscape and, thus, is able
to model the different radiative terms existing in such medium at ground and at-sensor levels. These different terms
are solar radiance, atmospheric radiance, emitted radiance and radiance due to the environment. Thus, it allows an
accurate spectral analysis of radiative components and of their relative impact to the total signal. Phenomenological
analysis of a street is proposed by assessing each term on every points of the modelled surface. Illustrations of the
potential of TITAN are given over urban area. Moreover, the impact on the signal when the 3D structure is taken into
account by comparing with a "equivalent" flat ground is estimated by calculating the percentage of each terms
contribution to the total signal at ground level for different wavelengths. Also, directional effects for each component
of total signal are simulated over a 3D street by varying sensor positions. Thus, these simulations angular variations
allow us to quantify the radiative temperature anisotropy and to understand the contribution of each term to the
directional behaviour.
Comparison of atmospheric radiative transfer with statistical wave approach
Show abstract
The radiative transfer (RT) approach is widely used for studying scattering from layered random media with
rough interfaces. Although it has been successful in several applications it is well known that this approach
involves certain approximations. In this paper these assumptions and approximations are reexamined and explained.
To enable this a statistical approach is employed to this problem and the governing equations for the
first and second moments of the wave fields are derived. A transition is hence made to arrive at a system of
equations corresponding to that of the RT approach. It is thus found that more conditions are implicitly involved
in the RT approach than generally believed to be necessary.
The application of atmospheric correction algorithms for monitoring atmospheric pollution using Landsat TM images
Show abstract
This paper focused on the application of effective atmospheric correction algorithm for assessing the atmospheric
pollution based on the determined aerosol optical thickness. Field spectro-radiometers such as GER 1500 and HR-1024
have been used to retrieve the ground reflectance values of certain proposed calibration targets. Sun-photometers
(MICROTOPS II) have been used to measure the aerosol optical thickness. Retrieved aerosol optical thickness from
satellite images have been directly compared with the values found from the sun-photometer measurements as well those
found from the visibility data obtained during the satellite overpass. The determined aerosol optical thickness obtained
from the atmospheric path radiance component and those found from ground measurements (sun-photometer and
meteorological data) acquired during the satellite overpass show very high correlations after regression analysis
application.
The influence of sea fog inhomogeneity on its microphysical characteristics retrieval
Show abstract
A study on the effect of sea fog inhomogeneity on its microphysical parameters retrieval is presented. On the condition
that the average liquid water content is linear vertically and the power spectrum spectral index sets 2.0, we generate a 3D
sea fog fields by controlling the total liquid water contents greater than 0.04g/m3 based on the iterative method for
generating scaling log-normal random field with an energy spectrum and a fragmentized cloud algorithm. Based on the
fog field, the radiance at the wavelengths of 0.67 and 1.64 μm are simulated with 3D radiative transfer model SHDOM,
and then the fog optical thickness and effective particle radius are simultaneously retrieved using the generic look-up-table
AVHRR cloud algorithm. By comparing those fog optical thickness and effective particle radius, the influence of
sea fog inhomogeneity on its properties retrieval is discussed. It exhibits the system bias when inferring sea fog physical
properties from satellite measurements based on the assumption of plane parallel homogeneous atmosphere. And the bias
depends on the solar zenith angel. The optical thickness is overrated while the effective particle radius is under-estimated
at two solar zenith angle 30° and 60°. Those results show that it is necessary for sea fog true characteristics retrieval to
develop a new algorithm using the 3D radiative transfer.
Ultraviolet Ground- and Space-Based Measurements, Retrievals, and Models
3D OMI observations of aerosol plumes released from December 2006 Australian forest fires
Show abstract
In the December 2006 severe forest fires raged in south east Australia. We used the OMI instrument to study the
transport of the aerosols emitted by these fires. On 14 December a freshly released plume was lofted by a passing
weather system to high altitudes in the atmosphere and was transported around the planet in 10 days. We used the OMI
cloud product to retrieve the altitude of the aerosol plume, 8-10km. We compare our findings to CALIPSO observations
of the same plume, which yields 11-14km. We performed radiative transfer calculations to investigate the sensitivity of
the OMI cloud algorithm to the plume altitude.
Remote Sensing by FTIR, DOAS, and Other Spectometric Methods
Cloud and thermodynamic parameters retrieved from satellite ultraspectral infrared measurements
Show abstract
Atmospheric thermodynamic parameters and surface properties are basic meteorological variables for weather
forecasting. A physical geophysical parameter retrieval scheme dealing with cloudy and cloud-free radiances observed
with satellite ultraspectral infrared sounders has been developed and applied to data from the Infrared Atmospheric
Sounding Interferometer (IASI) and the Atmospheric InfraRed Sounder (AIRS). The retrieved parameters presented
herein are from radiance data gathered during the Joint Airborne IASI Validation Experiment (JAIVEx). JAIVEx
provided intensive aircraft observations obtained from airborne Fourier Transform Spectrometer (FTS) systems, in-situ
measurements, and dedicated dropsonde and radiosonde measurements for the validation of the IASI products. Here,
IASI atmospheric profile retrievals are compared with those obtained from dedicated dropsondes, radiosondes, and the
airborne FTS system. The IASI examples presented here demonstrate the ability to retrieve fine-scale horizontal features
with high vertical resolution from satellite ultraspectral sounder radiance spectra.
Aerosols in urban areas: optical properties and impact on the signal incident to an airborne high-spatial resolution camera
Show abstract
The study of urban areas by remote sensing is currently in significant development thanks to the availability of
new high spatial resolution cameras (metric and decimetric scale). However, at those resolutions, the measured signal is
complex to analyse, mainly because of the 3D structure of the scene (inducing sunny and shady areas) and of the spatial
variability of the urban materials. As in the shady areas the signal is predominantly due to aerosol scattering, a precise
characterisation of those particles is required.
Today, no efficient method has been implemented to characterise urban aerosols directly from remote sensing at
this scale. In order to develop such a method, based on the transitions between sunny and shady areas, we need to have a
clear idea of the properties of urban aerosols and to assess their impact on the relative contributions of the different
components of the signal.
To this end, a statistical study of urban aerosols optical properties is first conducted. Data obtained for several
years from 161 urban AERONET stations are processed and exhibit a huge variability of those properties. A
phenomenological study is carried out afterwards with a 3D direct radiative transfer code, AMARTIS. It allows to assess
the significant impact of those particles on the signal for an urban canyon, in the sun and especially in the shade where
up to 90% of the signal can be due to atmospheric scattering. It shows the necessity to model correctly all the
components of the signal to be able to retrieve efficiently the aerosols.
Comparative study of wintertime NO and NO2 measured by DOAS near a motorway in the Inn Valley
Show abstract
A comparative study of wintertime NO and NO2 concentrations and the investigation of the influences of meteorological
conditions upon air quality in a valley near a motorway was performed in the Inn valley near Innsbruck, Austria. A
DOAS with emitter/receiver unit and three retroreflectors was used for this study. One retroreflector was installed at a
mast on the other side of the motorway (120 m path length) so that the path was about 10 m above motorway level.
Another retroreflector was set up for a path parallel to the motorway and the third retroreflector was used to measure at a
path perpendicular and away from the motorway. The path across the motorway was directly above the air quality
monitoring station Vomp of Land Tyrol which is only three meters away from the motorway.
The first measurement campaign was performed during winter 2005 / 2006 and the second one during the winter 2007 /
2008. The concentrations above the motorway are clearly dominated by the traffic volume. Higher concentration values
are found during week days than during the weekend. The diurnal differences in air pollution e.g. due to temporal
variations of motorway emissions (10 times higher during peak hours in the morning and afternoon compared to night
hours) and meteorological conditions (stable from late afternoon until mid-morning) are investigated. The mean NO2 /
NOx ratio from these DOAS measurements is 0.3 which can be caused by the high amount of heavy duty vehicles at that
motorway.
During synoptically undisturbed winter periods persistent inversion conditions determined by a SODAR as mixing layer
heights lead to relatively high air pollutant concentrations from late afternoon until mid-morning. In this context the
influence of the quasi-regular mountain wind system (valley and slope winds) is studied. The colder winter 2005 / 2006
with a persistent snow cover is characterised by higher concentration of pollutants (e.g. NO2).
Athens airport air quality study by remote sensing with DOAS, FTIR, and ceilometer
Show abstract
The impact of air traffic on the atmosphere was subject to several works in the last years. But little scientific work has
been done concerning airport air quality. Airports themselves often measure concentrations of the main pollutants and
use dispersion models to asses the air quality situation. Emission inventories of airport are not well known generally
because a lot of different emission sources exist. A database is required to characterise real-world emission source
strengths as well as air quality and meteorological data at airports that will serve as an input and as validation data for
modelling work. Dedicated studies were performed to follow these objectives.
To develop a database of air quality and meteorological data a measurement campaign was carried out at the Athens
International Airport (AIA). The campaign from 13 until 25 September 2007 was realised with the application of in situ
(two mast equipped with fast (sonic anemometers) and slow sensors at various heights) and remote sensing techniques as
DOAS, FTIR, SODAR with RASS and ceilometer as well as the aid of existing equipment available by the participant
partners that was transferred to the AIA, allowing the sharing of knowledge and infrastructure. The concept of this
measurement campaign will be presented. Some results of interpretation of measured data will be discussed as aircraft
emission indices during take-off, influence of aircraft emissions upon airport air quality, estimation of the airport
emission source strengths and influence of airport emissions upon air quality in the surroundings.
Atmospheric Profiling of Aerosols, Trace Gases, and Meteorological Parameters
Data analysis and retrieval algorithms for the ozone mapping and profiler suite/limb profiler instrument
Show abstract
Three candidate algorithms for the retrieval of ozone profile for the NPP OMPS Limb Profiler are described. The first
one relies on the well established Doublet/Triplet method coupled with Optimal Estimation. The second one performs
spectral fitting and uses Multiple Linear Regression. The last one is a direct application of the Optimal Estimation
method on the actual CCD array measurements. The fundamentals of each technique are reviewed and their
advantages/disadvantages are discussed. Sample results are given to illustrate the performance of each method.
Correction of atmospheric scattering effects in space-based observations of methane and carbon dioxide: model study for synthesized GOSAT spectra
Show abstract
This paper concerns development of a new retrieval algorithm for the processing of the Greenhouse gases Observing
SATellite (GOSAT) data. GOSAT is scheduled to be launched in 2009 to monitor column amounts of CO2 and CH4. A
nadir-looking Fourier-Transform Spectrometer (FTS) of Short Wavelength Infrared (SWIR, 1.6 microns and 2 microns)
and 0.76 microns oxygen A-band regions are mounted on GOSAT.
We focus on the methane retrievals from 1.67 μm spectral band under conditions of strong optical path modification due
to atmospheric scattering. First, the algorithm of spectral channel selection is proposed to reduce the effects of
uncertainties in water vapor content and solar spectrum. Two techniques for the atmospheric scattering correction are
compared: one uses CO2 as a proxy gas; the second is based on the simple parameterization of photon path-length
probability density function (PPDF). The latter technique includes the following steps: estimation of PPDF parameters
from radiance spectra in the O2 A-band and 2.0 -μm CO2 band, the necessary correction to use these estimated
parameters in the 1.58-μm CO2 and 1.67-μm CH4 bands; and, finally, CO2 and methane retrievals. Both approaches were
verified by numerical simulations using an independent radiative transfer approach to produce radiance spectra expected
for the GOSAT sensor. The accuracy of the retrievals in the presence of aerosols and cirrus cloud is discussed.
Retrieval of aerosol optical depth in vicinity of broken clouds from reflectance ratios: a novel approach
Show abstract
A novel method for the retrieval of aerosol optical depth (AOD) under partly cloudy conditions has been suggested. The
method exploits reflectance ratios, which are not sensitive to the three-dimensional (3D) effects of clouds. As a result,
the new method provides an effective way to avoid the 3D cloud effects, which otherwise would have a large (up to
140%) contaminating impact on the aerosol retrievals. The 1D version of the radiative transfer model has been used to
develop look-up tables (LUTs) of reflectance ratios as functions of two parameters describing the spectral dependence of
AOD (a power law). The new method implements an innovative 2D inversion for simultaneous retrieval of these two
parameters and, thus, the spectral behavior of AOD. The performance of the new method has been illustrated with a
model-output inverse problem. We demonstrated that the new retrieval has the potential for (i) detection of clear pixels
outside of cloud shadows, (ii) increased "harvest" of such pixels, and (iii) accurate (~15%) estimation of AOD for the
majority of them.
Improved MODIS aerosol retrieval using modified VIS/MIR surface albedo ratio over urban scenes
Show abstract
In this paper, we focus on the use of simultaneous MODIS and AERONET sky radiometer data to refine
the surface albedo models regionally and improve on the current AOD operational retrieval. In particular,
over New York City, we show that the correlation coefficient assumption used in the MODIS Collection
(5) model between the VIS and MIR channels used for surface reflection parameterization are still severely
underestimated in comparison with high spatial imagery data from Hyperion thereby leading to an
underestimate in the VIS ground albedos and explaining the subsequent overestimate of the VIS optical
depth. Furthermore, we find that the VIS/MIR ratios depend only weakly on the scattering geometry
allowing us to generate a regional VIS/MIR surface reflectance correlation coefficient map at spatial
resolutions down to 1.5km. When applying the new VIS/MIR surface reflectance ratio model, we show the
MODIS and AERONET derived optical thickness agreement is significantly improved for the operational
10km resolution product. Moreover, we also show the high resolution surface model allows us to improve
the resolution of the retrieved AOD to 3km. Although direct comparisons for a given day can only be made
at the AERONET site, we find the AOD spatial variability from the improved MODIS retrievals is in far
better agreement with temporal statistics seen in the AERONET time series retrievals. In addition to that,
we also process and validate with another urban area, Mexico City, and the result is also significantly
improved by using refined regional VIS/MIR surface reflectance ratio model.
Geostationary imaging Fabry-Perot spectrometer (GIFS): measurement of clouds and trace gases
Show abstract
Long-term measurements of the global distributions of clouds, trace gases, and surface reflectance are needed for
the study and monitoring of global change and air quality. The Geostationary Imaging Fabry-Perot Spectrometer
(GIFS) instrument is an example of a next-generation satellite remote sensing concept. GIFS is designed
to be deployed on a geostationary satellite, where it can make continuous hemispheric imaging observations of
cloud properties (including cloud top pressure, optical depth, and fraction), trace gas concentrations, such as tropospheric
and boundary layer CO, and surface reflectance and pressure. These measurements can be made with
spatial resolution, accuracy, and revisit time suitable for monitoring applications. It uses an innovative tunable
imaging triple-etalon Fabry-Perot interferometer to obtain very high-resolution line-resolved spectral images of
backscattered solar radiation, which contains cloud and trace gas information. An airborne GIFS prototype and
the measurement technique have been successfully demonstrated in a recent field campaign onboard the NASA
P3B based at Wallops Island, Virginia. In this paper, we present the preliminary GIFS instrument design and
use GIFS prototype measurements to demonstrate the instrument functionality and measurement capabilities.
Aerosol characterization and transport pathway using ground-based measurement and space borne remote sensing
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Using two years measurements of aerosol extinction coefficient retrieval from CALIPSO as a joint NASA-CNES satellite mission along with ground-based measurements of particle
mass concentration (PM2.5), we assess particulate matter air quality over different urban and periurban areas in France.
In order to understanding the influence of the long range transport onto the local aerosol load we have focused on
analysing of pollution event in Lille - urban area and Dunkerque - industrial area. We compared ground- based
measurements with CALIPSO measurements. The CALIPSO level 2 aerosol records are more useful because the
extinction coefficient is available. We use the extinction coefficient profiles which are provided by CALIPSO to depict
the vertical structure of the aerosol properties. The combination of ground- based measurements of PM2.5, aerosol
optical thickness (AOT's) obtained by Aeronet network data and CALIOP data enhances
the possibilities of studying transport pathway of aerosol in the atmosphere and aerosol optical properties (aerosol
extinction coefficient, aerosol optical depth, atmosphere transparency). The linear relationship between AOT _CALIPSO
and AOT _ Aeronet network shows a slop of 0.4 in north of France. Moreover, we observed the good relationship
between PM2.5 and AOT by CALIPSO profiles with a slope of 57.59 and correlation coefficient of 0.75 over France.
Poster Session
Pursuing atmospheric water vapor retrieval through NDSA measurements between two LEO satellites: evaluation of estimation errors in spectral sensitivity measurements
Show abstract
NDSA (Normalized Differential Spectral Absorption) is a novel differential measurement method to estimate the total
content of water vapor (IWV, Integrated Water Vapor) along a tropospheric propagation path between two Low Earth
Orbit (LEO) satellites. A transmitter onboard the first LEO satellite and a receiver onboard the second one are required.
The NDSA approach is based on the simultaneous estimate of the total attenuations at two relatively close frequencies in
the Ku/K bands and of a "spectral sensitivity parameter" that can be directly converted into IWV. The spectral sensitivity
has the potential to emphasize the water vapor contribution, to cancel out all spectrally flat unwanted contributions and
to limit the impairments due to tropospheric scintillation. Based on a previous Monte Carlo simulation approach, through
which we analyzed the measurement accuracy of the spectral sensitivity parameter at three different and complementary
frequencies, in this work we examine such accuracy for a particularly critical atmospheric status as simulated through the
pressure, temperature and water vapor profiles measured by a high resolution radiosonde. We confirm the validity of an
approximate expression of the accuracy and discuss the problems that may arise when tropospheric water vapor
concentration is lower than expected.
Analysis of aerosol characteristics over the China Sea by MODIS data
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MODIS Collection005 aerosol product is validated by a new method over the China Sea. We use aerosol optical at
550nm(AOT550) and fine mode fraction(FMF) in its aerosol product to analyze the spatial distribution and season
variation of aerosol over the China Sea. Then meteorological data will be used to discuss the reason of aerosol
characteristics. The results show that firstly MODIS Collection005 aerosol product has a good quality over the China
Sea and it is better than MODIS Collection004 data over the China Sea. Secondly, AOT550 and FMF have a notable
season variation influenced by the meteorological condition and the transport from continental source. AOT550 reaches
the largest value in spring and winter, and it reaches the least value in summer and fall; oppositely, FMF reaches the
largest value in summer and fall, and it reaches the least value in spring and winter. In the third, AOT550 and FMF have
marked longitudinal variation. AOT550 appear the maximum value between 30°N-40°N and decrease towards to north
and south. Meanwhile, FMF increase from south to north and the tendency of the increase became slow at 30°N. And
they have an obvious meridional variation. AOT550 and FMF both decrease with the increase of longitude, which
suggest that anthropogenic aerosol have an important role over the China Sea. Finally, based on seven years
meteorological data, the reason of the aerosol characteristics over the China Sea are discussed. Wind and rainfall are the
two important factors.
Analyses of scattering characteristics of chosen anthropogenic aerosols
Show abstract
In the work, analyses of scattering profile of chosen anthropogenic aerosols for two wavelengths (λ1 = 1064 nm and
λ2 = 532 nm) were made. As an example of anthropogenic aerosol three different pyrotechnic mixtures (DM11, M2,
M16) were taken. Main parameters of smoke particles were firstly analyzed and well described, taking particle shape and
size into special consideration. Shape of particles was analyzed on the basis of SEM pictures, and particle size was
measured. Participation of particles in each fixed fraction characterized by range of sizes was analyzed and parameters of
smoke particles of characteristic sizes and function describing aerosol size distribution (ASD) were determinated.
Analyses of scattering profiles were carried out on the basis of both model of scattering on spherical and nonspherical
particles. In the case of spherical particles Rayleigh-Mie model was used and for nonspherical particles analyses firstly
model of spheroids was used, and then Rayleigh-Mie one. For each characteristic particle one calculated value of four
parameters (effective scattering cross section σSCA, effective backscattering cross section σBSCA, scattering efficiency
QSCA, backscattering efficiency QBSCA) and value of backscattering coefficient β for whole particles population. Obtained
results were compared with the same parameters calculated for natural aerosol (cirrus cloud).
A review of satellite remote sensing of aircraft-induced contrails and investigation of their potential role in regional climate change
Show abstract
Condensation-trails, or 'contrails', have a net warming effect on the climate system. They form in the wake of jet
aircraft, as exhaust-gases mix with cold and humid ambient air. The climate impact of contrails is largest at night and in
winter; even though air-traffic densities are lowest at these times. Depending on ambient atmospheric conditions,
contrails can; persist for several hours; grow to several kilometers in length, and trigger additional cirrus cloud formation
as they spread. Cirrus cloud cover is increasing in flight corridors as they become increasingly congested. A small, but
statistically significant, increase in cirrus coverage has been observed for the North Atlantic flight corridor; in contrast to
small negative trends in cirrus elsewhere. Presently, a complete set of validation data for model studies of contrail-cirrus
is missing. However, by building upon existing automated-contrail-detection techniques, a satellite-derived cloud and
contrail climatology for Ireland will be compiled based on two decades of archived high-resolution satellite imagery.
Combining meteorological measurements concurrent with satellite overpasses, the optimal meteorological conditions for
contrail formation and persistence will be investigated. The radiative effect of contrails on the atmospheric column
radiation budget, and their contribution to regional atmospheric warming, can then be assessed. This paper provides a
review of different methods by which contrails and cirrus clouds have been observed from satellite imagery and a
discussion of their potential role in climate change.
Cloud microphysical characterization in the presence of a desert dust event over Portugal: a study based on atmospheric modeling and satellite remote sensing
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The aim of this work is the study of the Saharan desert dust storms effects on clouds properties and respective radiative
forcing during a strong desert dust transport that occurred in 27, 28 and 29 May 2006. This is done by examining the
results obtained from a mesoscale atmospheric model (MesoNH), over Portugal area and nearby Atlantic Ocean.
The assessment of the aerosol properties provides information on the altitude of the aerosol layers and the determination
of the cloud properties, influenced by the presence of desert dust aerosol, gives the information about the possible
modifications that the cloud may suffer when they develop in an atmosphere where desert dust aerosols are present. The
cloud radiative forcing (CRF) at the top of the atmosphere (TOA) is also estimated. The CRF at the TOA, in a dust free
atmosphere, present lower values when compared with the TOA CRF over the regions where dust aerosols are present.
Comparative study on Doppler weather radar products from strong convective weather
Show abstract
Using Doppler radar products from three intense convective precipitation events occurring on
the night of June 12, early morning and night on July 12, 2006 over the Tianjin area, a comparative study
is made, showing that typically, the radial velocity field changes earlier than does the echo-intensity field
at the initial and mature stages of precipitation, such that much attention should be paid to the variation in
the velocity field in doing nowcasts of rainfall, and the Doppler velocity variation in conjunction with
Auto-Nowcaster predictions helps determine the change in radar echo intensity and its movement
direction, thereby improving the accuracy of nowcasts of strongly convective precipitation.
Improving ocean surface wind speed retrieval from SSM/I data by channel combinations
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After Analyzing correlations of ocean surface wind speeds and the channel combinations of brightness
temperature, it is found that the difference of brightness temperature between 22GHz vertical polarization and
19GHz horizontal polarization and the ratio of the difference between 19GHz vertical polarization and 19GHz
horizontal polarization to the difference between 37GHz vertical polarization and 37GHz horizontal polarization
should be used to retrieve ocean surface wind speed. So we add these two channel combinations to improve the
Goodberlet's algorithm and derive wind speeds from the brightness temperature of SSM/I five channels measured in
2005. Comparing the results of two algorithms against in-situ buoy wind speeds shows that the improved wind speed
retrieval algorithm is better than Goodberlet's algorithm, the wind speed estimation accuracy improves by 0.9m/s
and 0.5m/s under clear condition and cloudy condition respectively.