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).

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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 / NO_x 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).

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.

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.

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.

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.

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.

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.

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.

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 K_u/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.

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.

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 σ_SCA, effective backscattering cross section σ_BSCA, scattering efficiency Q_SCA, backscattering efficiency Q_BSCA) and value of backscattering coefficient β for whole particles population. Obtained results were compared with the same parameters calculated for natural aerosol (cirrus cloud).

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.

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.

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.

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.