This PDF file contains the front matter associated with SPIE Proceedings Volume 7475, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

The CLIM (Cloud Imager) infrared camera, currently being defined, has same channels as AVHRR and has been designed to assist sounders by spotting areas of clear sky from a satellite. The article outlines a simulation of CLIM, based on real data, and presents its estimated performances for different spectral band configurations associated with a cloud detection algorithm. The study shows that up to 40% more cloud-free zones can be explored by a sounder supported by such an imager, compared with the same sounder pointing fixedly at the nadir.

Shallow cumuli are ubiquitous over large areas of the globe, including both the interior of continents and the trade wind regions over the oceans. Measurements made at the Atmospheric Radiation Measurement (ARM) Climate Research Facility, located in central North America, provide a unique long-term data set that can be used to investigate the influence that these clouds have on the shortwave surface energy budget at a continental location. Using data collected for the summers of 2000 through 2007, inclusive, over 900 hours with fair-weather cumuli were identified using data from a Total Sky Imager, cloud-radar and lidar. Data from a suite of surface radiometers was used to determine the shortwave forcing. This analysis estimates the three-dimensional effects of shallow cumuli by examining the occurrences of both positive and negative shortwave forcing. We show that the average surface shortwave forcing is approximately -45.5 W m^-2. When the data are adjusted to account for periods without shallow clouds, the shortwave forcing over the entire summer (defined as May through August) are reduced in magnitude, with forcings of -2.1 W m^-2.

Cirrus clouds in the upper troposphere and the lower stratosphere have recently drawn much attention due to their important role and impact on the atmospheric radiative balance. To understand and quantify its impact on earth's atmosphere radiative transfer it is necessary to have information about its optical properties. Such a knowledge is necessary both for comparison with others datasets of cirrus measurements as well as for its influence on radiative transfer models. Cirrus clouds measurements have been performed since 2005 in the Metropolitan Sao Paulo, Brazil (23°33'S, 46o44'W). From MSP-lidar backscatter profiles at 532 nm, and eventually 355 nm, the cloud optical depth (COD) as well as the high of base and top of the clouds are retrieved. A preliminary climatology of cirrus clouds over Sao Paulo using this method has been set. The measurements from Aerosol Robotic Network (AERONET), the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) and GOES-10 observations are compared with a ground based lidar dataset for a wide range of cloud types.

Several techniques exist to correct the estimation of the cloud top pressure for semi-transparency effect, and the advent of Meteosat Second Generation (MSG) enables the simultaneous use of the IR/CO2 ratioing methodology in addition to the IR/WV intercept method. This paper presents the performances of these two methods using simulated data. The FASDOM radiative code has been used to simulate MSG radiances for various types of clouds at different levels in the troposphere, using different atmospheric profiles. Performances of the methods are presented as function of several atmospheric and cloud parameters.

Auroral infrared emission observed from the TIMED/SABER broadband 4.3 um channel is used to develop an empirical geomagnetic storm correction to the International Reference Ionosphere (IRI) E-region electron densities. The observation-based proxy used to develop the storm model is SABER-derived NO⁺(v) 4.3 um volume emission rates (VER). A correction factor is defined as the ratio of storm-time NO+(v) 4.3 um VER to a quiet-time climatological averaged NO⁺(v) 4.3 um VER, which is linearly fit to available geomagnetic activity indices. The initial version of the E-region storm model, called STORM-E, is most applicable within the auroral oval region. The STORM-E predictions of E-region electron densities are compared to incoherent scatter radar electron density measurements during the Halloween 2003 storm events. Future STORM-E updates will extend the model outside the auroral oval.

This paper presents results that demonstrate the auroral modeling capabilities of the Air Force Research Laboratory (AFRL) SAMM2 (SHARC And MODTRAN® Merged 2) radiance code. A scene generation capability is obtained by coupling SAMM2 with a recently developed Clutter Region Atmosphere and Scene Module (CRASMO), which provides an approach for rapid generation of time sequences and images of radiance clutter. Modeled results will be compared to data collected by the Midcourse Space Experiment (MSX)1 in the IR and UV-visible spectral regions during an auroral event on November 10, 1996. The paper is organized as follows. We first present a brief history of the AFRL SHARC/SAMM codes, leading up to the current version, SAMM2 v.2. The SAMM2 UV-visible auroral kinetic model will then be described, followed by a comparison of modeled results to the MSX data.

Lidars provide an important tool to measure temperature and minor constituents in the atmosphere up to ~110 km altitude with high accuracy and temporal resolution. The Leibniz-Institute of Atmospheric Physics operates various lidars for the whole range between troposphere and lower thermosphere. The lidars are installed at Kühlungsborn, Germany (54°N, 12°E), at the ALOMAR site, Norway (69°N, 16°E), or in a mobile 20-foot container. Summertime soundings in polar regions as well as coverage of tides and gravity waves require measurements during full daylight. With a standard lidar the daylight background is several magnitudes larger than the signal in the mesosphere. Narrowband spectral filtering by etalons as well as spatial filtering by small fields of view (~50 μrad) are realized instead. At this low FOV turbulence and jitter of the beam pointing affects the signal and have to be compensated. We describe the techniques applied at our lidars. Additionally we will discuss the influence of the etalon filter technique on calculated temperature profiles. The etalon transmission of the Doppler-broadened backscatter signal is temperature dependent and has to be taken into account to avoid systematic errors. Overall, narrow-band lidars provide temperature profiles in the whole range up to the lower thermosphere. We will present observations of temperatures profiles of the lower and middle atmosphere as well as noctilucent clouds (NLC). These quantities provide important insights into the dynamics of the middle atmosphere. Time-resolved and averaged profiles of observations at the different locations will be shown and the results from different latitudes compared.

The forthcoming ESA/JAXA EarthCARE (Earth Clouds Aerosols and Radiation Explorer)Mission addresses the need to improve the understanding of the interactions between cloud, aerosol and radiation processes. These play a critical role in the Earth's radiative balance in climate models. The broad-band radiometer (BBR) on-board the EarthCARE spacecraft provides measurements of broad-band reflected solar and emitted thermal radiances and fluxes at the top-of-atmosphere (TOA) over the along-track (AT) satellite path at three different viewing angles. This angular information together with the spectral information on the radiation from the EarthCARE's multi-spectral imager (MSI) is exploited to construct accurate radiance-to-flux conversion algorithms.

A Clouds and the Earth's Radiant Energy System instrument (FM2) on board the Terra satellite has been used in field campaigns to provide TOA radiance measurements. Using a special programmable azimuth plan scan (PAPS) mode, a scanner collects data over a specified Earth target or of a prescribed spatial orientation. This paper covers operational aspects of four field campaigns in which FM2 participated in 2008. These include the annual CERES/GERB comparison campaign carried out at the summer and winter solstices, an aerosol campaign over Beijing ran before, during and after Summer Olympics, calibration and validation of GERB radiances at the ground station in Alacar/Spain, and also a bi-weekly true long-track scan for comparison to true nadir instruments.

It is of vital interest to understand how cloud particles interact with ambient atmospheric radiation fields. We developed a comprehensive analytical radiative transfer model for passive infrared remote sensing applicable to ground-based and airborne sensors. We show the qualitative difference between simple non-scattering aerosols (pseudo vapor cloud) and an aerosol cloud where scattering, absorption and emission occur. Simulations revealed two interesting observations: aerosol cloud detection from an airborne platform may be more challenging than for a ground-based sensor, and the detection of an aerosol cloud in emission mode is different from the detection of an aerosol cloud in absorption mode.

This paper discusses the effects of broken cloud fields on solar illumination reaching the ground. Application of aerosol retrieval techniques in the vicinity of broken clouds leads to significant over prediction of aerosol optical depth because of the enhancement of visible illumination from the scattering of photons from clouds into clear patches. These illumination enhancement effects are simulated for a variety of broken cloud fields using the MCScene code, a high fidelity model for full optical spectrum (UV through LWIR) spectral image simulation. MCScene provides an accurate, robust, and efficient means to generate spectral 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. The model includes treatment of land and ocean surfaces, 3D terrain, 3D surface objects, and effects of finite clouds with surface shadowing. The paper includes an overview of the MCScene code and a series of calculations for broken 3D cloud fields demonstrating the effects of clouds on downwelling flux.

We outline a new method, called the ratio method, developed to retrieve aerosol optical depth (AOD) under broken cloud conditions and present validation results from sensitivity and case studies. Results of the sensitivity study demonstrate that the ratio method, which exploits ratios of reflectances in the visible spectral range, has the potential for accurate AOD retrievals under different observational conditions and random errors in input data. Also, we examine the performance of the ratio method using aircraft data collected during the Cloud and Land Surface Interaction Campaign (CLASIC) and the Cumulus Humilis Aerosol Processing Study (CHAPS). Results of the case study suggest that the ratio method has the ability to retrieve AOD from multi-spectral aircraft observations of the reflected solar radiation.

Most numerical methods used in radiation transfer problems decompose the radiation field in Fourier series and solve a reduced radiative transfer equation for each Fourier mode. Classically, Legendre polynomials expansions provide the kernels of these reduced transfer equations. For highly peaked phase functions, the Legendre series expansion converges very slowly. We show in this paper that this expansion can advantageously be replaced by a direct numerical evaluation using the trapezoidal rule. The improvement afforded by this direct evaluation yields highly accurate results with orders of magnitude fewer arithmetic operations than the Legendre series, avoids the very slow convergence of the Legendre series and exploits instead the rapid decay of the Fourier coefficients for exponential convergence, and finally bypasses the need for phase function truncations.

Meso-scale atmospheric models outputs are valuable data for cloud and aerosols retrievals. In view of the launch the Global Change Observation Mission-Climate/Second generation Global Imager (GCOM-C/SGLI) satellite, atmospheric models products are tested against satellite observations data in order to evaluate the degree of reliability and the sensitivity of these models outputs to variations of atmospheric conditions. The analyses presented in this study are based on two models outputs: the Nonhydrostatic Icosahedral Atmospheric Model (NICAM) and the National Center for Environmental Protection/Department Of Energy (NCEP/DOE) re-analysis-2 data. Terra/Moderate Resolution Imaging Spectrometer (Terra/MODIS) satellite sensor observations of water vapor radiances are used as the verification data set for the tests conducted. These tests are based on the comparison between upper tropospheric water vapor properties (clear sky and above-low clouds) observed by satellite and radiative transfer forward calculations (using models' predicted atmospheric profiles, the satellite sensor spectral response and geometrical characteristics) derived from NICAM and NCEP/DOE. The parameters measured are the upper tropospheric brightness temperature (UTBT) and relative humidity (UTRH). Discrepancies between simulated data and observations are analyzed in terms of atmospheric instability, cloud convection movements and, effective emissivity. The results obtained show that both NICAM and NCEP/DOE simulated UTBT and UTRH outputs have a relatively comparable distribution pattern. However, simulations performed with the NCEP/DOE outputs present generally fewer discrepancies with satellite observations. For the interpretation of these results, the stability index study shows that differences between models and observation data tend to be high in unstable atmospheres. This atmospheric instability can be attributed to cloud convection processes affecting areas adjacent to convective clouds. As the amount of convective clouds increases, the errors in the water vapour depiction by the models increase also. Analyses of heat movements studied through the variation of the cloud effective emissivity suggest that the discrepancies between the observations and the models increase with the decrease of the clouds' effective emissivity. Adjustments of some of the models parameters, notably the microphysical parameterization of the clouds resolving scheme, are suggested in order to improve the accuracy of the models' results.

A novel scanning water vapor differential absorption lidar (DIAL) system has been developed. This instrument is mobile and was applied successfully in two field campaigns: COPS 2007 (Convective and Orographically-induced Precipitation Study), a research and development project of the World Weather Research Programme, and FLUXPAT2009 within the German Research Foundation project Patterns in Soil-Vegetation-Atmosphere Systems: monitoring, modeling and data assimilation". In this paper, the instrument is described and its capabilities are illustrated with measurements examples. The DIAL provides remote sensing data of the atmospheric water-vapor field with previously unachieved resolution. The data products of the DIAL are profiles of absolute humidity with typical resolutions of 15 to 300 m with a temporal resolution of 1 to 10 s and a maximum range of several kilometers at both day and night. But spatial and temporal resolution can be traded off against each other. Intercomparisons with other instruments confirm high accuracy. Beside humidity, also the backscatter field and thus aerosols and clouds are observed simultaneously. The DIAL transmitter is based on an injection-seeded Titanium:Sapphire laser operated at 820 nm which is end-pumped with a diode-pumped Nd:YAG laser. By use of a scanning transmitter with an 80-cm receiving telescope, the measurements can be performed in any direction of interest and the 3-dimensional structure of the water vapor field can be observed.

Monitoring of mixing layer height (MLH) was performed during different measurement campaigns in urban and suburban area (Hannover, Munich, Budapest, Zürich, Augsburg) by the Vaisala ceilometer LD40. It is an eye-safe commercial lidar and designed originally to detect cloud base heights and vertical visibility for aviation safety purposes. Software for routine retrieval of mixing layer height from ceilometer data was developed and improved continuously. MLH was determined during a one-week-campaign at the airport Mexico City. Air pollutants like NO, NO_x, CO and O₃ as well as meteorological parameters like wind, temperature and irradiance are measured at the airport in addition to the air quality monitoring network RAMA in Mexico City. The influence of MLH together with wind, temperature and cloudiness upon air pollution is investigated. These continuous MLH and meteorological data are correlated with simultaneous measured air pollutants. The influence of mixing layer height upon air quality is shown.

Beijing air quality suffers from frequently occurring inversion layers. These inversion layers can last for several days and below these layers, pollution is accumulated. In the absence of inversions an urban boundary layer still exists delimiting the urban atmosphere from the free atmosphere. The height of this layer can potentially influence the urban atmospheric pollution. In both cases, particle concentration might change with height. A measurement campaign was performed to study those meteorological conditions, which are one of the causes for intensive air pollution in the region of Beijing during spring 2009. The mixing layer height (MLH) was studied by a ceilometer continuously. It was used to analyse the actual development of the height of inversion and boundary layers and the distribution of particles. Additionally, meteorological data from a radiosonde station are available. The measurements to study the vertical distribution of atmospheric layers in combination with particulate concentrations for specific times will be presented. The results of that campaign will be discussed.

The enhanced single lens optical concept and fast electronics improve the lidar ceilometer Vaisala CL31 for a reliable workhorse to profile the boundary layer and determine mixing layer height. Lately there have been several developments of the system regarding hardware, measurement routine, and evaluation software. Backscatter profiles collected during measuring campaigns in two German towns are presented to show the effect of these further developments on overall system performance. The main focus of this paper is the ability of the CL31 ceilometer to determine very low mixing layer heights, e.g. during winter temperature inversion periods. Temperature and wind profiles from a RASS co-located to a CL31 in Augsburg and from a weather mast in Hamburg are used for comparison.

The Roque de los Muchachos Observatory, located on the island of La Palma in the Canary Islands, is home of many astronomical facilities. In the context of the Extremely Large Telescope Design Study, an intensive lidar campaign was performed in the ORM near the Jacobus Kapteyn Telescope (17°52'41.2" W, 28°45'40.1" N, 2395 m asl) between 26th May and 14th June 2008. The goal of the campaign was to characterize the atmosphere in terms of planetary boundary layer height and aerosol stratification vs. synoptic conditions. As a by-product an estimate of the aerosol optical thickness was also obtained and compared to the total atmospheric extinction coefficient measured by the Carlsberg Meridian Telescope.

We present a new algorithm for the retrieval of the volume distribution - and thus, other relevant microphysical properties such as the effective radius - of stratospheric and tropospheric aerosols from multiwavelength lidar data. We consider the basic equation as a linear ill-posed problem and solve the linear system derived from spline collocation. Starting from here, algorithmical improvements for the inversion process are proposed. While a standard approach consisting of spline collocation and a regularization method such as truncated singular value decomposition or Tikhonov-Philips regularization proves sufficient in some cases, that kind of algorithm is not suitable for a more general case; the base points of the spline collocation take a key role here. Indeed, there is a direct connection between the number and position of the base points on the solution, as the problem of the correct regularization parameter - which is represented here by both location and number of base points - and its implications on over- or underregularization of the solution have to be investigated. Here, we present an algorithm that makes use of the fact that smoother areas of the solution require less base points in the vicinity for a proper reconstruction, combined with a Padé-type iterative regularization method. The algorithm starts with equidistant base points, then moves these base points during the calculation away from the smoother areas of the solution. This algorithm proved to work very well in many different simulation cases. Different weight functions for the base point shift are investigated, leading to slightly different results. Also, an improvement on this algoritm is proposed which, in addition to the position of the base points, also actively controls the actual number of base points, as solutions that more smooth in a global sense require less base points. Finally, we also take a look at how this new algorithm can also help us in simultaneously retrieving the particle distribution and the complex refractive index of the particles.

Measurements of the depolarization ratio of water droplets were performed to study the relationship between layer integrated depolarization and layer integrated backscattered light for linear and circular polarization illumination. Since those particles are spherical, the depolarization of the signal is attributed to multiple scattering effects. The experimental data reported in this article support Hu relationship between the single scattering fraction A_s and the linear accumulated depolarization ratio. For circular polarization, a modified Hu relationship is established and it is shown that the use of the accumulated depolarization parameter instead of the accumulated depolarization ratio allows harmonization of the linear and circular polarization measurements into a simple mathematical expression.

URMS was proposed within the framework of a German priority program (PP 1294, Atmosphären- und Erdsystemforschung mit dem Forschungsflugzeug HALO (High Altitude and Long Range Research Aircraft)). The project proposal resulted of the facts that experimental setups with state-of-the-art measurement principles and multidirectional geometries in the field of scientific aircraft radiation measurements are very difficult or not possible to achieve with the existing aircrafts and their openings and mounting points. Thus it is very difficult to develop and enhance remote sensing instruments and the corresponding new models and algorithms to analyze the resulting data. URMS will give the possibility to perform multi directional measurements with experimental instrument setups. An optical entrance head with a dual mirror system simular to a coleostat in front of a Wing-Pod will guide the light scattered from surfaces and/or the atmosphere into a Wing-Pod frame. A temperatur stabilized container will hold the optical instrument inside a stable environment. An Airborne Multispectral Sunphoto- and Polarimeter was proposed as a first state-of-the-art instrument setup.

This paper presents the results obtained by collecting systematically the following: - spectro-radiometric measurements of dark and white targets that can be served pseudo-invariant targets using the GER 1500 and SVC HR-1024 field spectroradiometers; sun-photometer measurements using MICROTOPS II sun-photometer for measuring the AOT and water vapour. These field data assists the assessment of the effectiveness of the existing atmospheric correction algorithms either simple or sophisticated such as atmospheric modeling. The in-situ measurements have been already collected on June-August 2008 and from March to July 2009. Six targets are selected to be served as calibration targets in order to assess the effectiveness of the existing atmospheric corrections. For this paper only the following atmospheric correction methods have been tested: darkest pixel atmospheric correction, covariance matrix method, multi-temporal normalization method, 6S model, 'new method using pseudo-invariant targets and empirical line empirical line regression method'. The accuracy assessment has been done based on the reflectance and aerosol optical thickness. Results of the accuracy assessment based on the reflectance retrieval values are presented. The duration of the project is three years started from 2008 up to 2011 and further measurements are still undertaken. The most effective atmospheric correction applied for the three ASTER bands was the 'New method using pseudo-invariant targets and empirical line' (Hadjimitsis et al., 2009) and then the Darkest Pixel correction method (which has been provided a reasonable correction only for bands 1, 2 bands). The future task consists of creating 'a complete database of the spectral signatures of several target's that can be served non-variant and calibration targets.

The atmospheric aerosol particles have variable optical properties, depending on their composition and their size distribution. The aim of this paper is to use six measured parameters with a Nephelometer, to derive optical properties of sub-micrometric and micrometric particles. The analysis of the backscatter to total scattering ratio and the wavelength dependence of particle scattering showed a daily and monthly variability, the ratio being bigger for the summer month than the autumn month. This result can affect seasonal variation of radiative forcing at surface. The results were compared with those obtained from sun - photometer data.

Sulfur dioxide, a short-lived atmospheric constituent, is oxidized to sulfate aerosols, a climate agent. Main sources are volcanoes, smelters, and fossil fuel combustion. Satellite monitoring of SO₂ began with TOMS data in 1978 that detected volcanic eruption clouds. Hyperspectral instruments, like OMI and GOME, have a twenty-fold improvement in sensitivity. Degassing volcanoes, smelters, and large power plants are now monitored for a database of SO₂ emission to the atmosphere. SO₂ is a distinctive marker for volcanic ash clouds, a hazard to aircraft.

Hazardous compounds may be released into the atmosphere in the case of fires, chemical accidents, terrorist acts, or war. In these cases, information about the released compounds is required immediately in order to take appropriate measures to protect workers, residents, emergency response personnel at the site of the release, and the environment. Remote sensing by infrared spectroscopy allows detection and identification of hazardous clouds in the atmosphere from long distances. In addition, imaging spectroscopy allows an assessment of the location, the dimensions and the dispersion of a potentially hazardous cloud. This additional information may contribute significantly to a correct assessment of a situation by emergency response forces. Therefore an imaging remote sensing system based on a Fourier-transform spectrometer with a focal plane array detector for automatic identification and imaging of gases has been developed. Imaging systems allow the use of spatial information in addition to spectral information. Thus, in order to achieve low limits of detection, algorithms that combine algorithms for spectral analysis and image analysis have been developed. In this work, the system and first results of measurements are presented.

It is widely known that methane, together with carbon dioxide, is one of the most effective greenhouse gases contributing to climate global change. According to EMEP/CORINAIR Emission Inventory Guidebook¹, around 25% of global CH4 emissions originate from animal husbandry, especially from enteric fermentation. However, uncertainties in the CH4 emission factors provided by EMEP/CORINAIR are around 30%. For this reason, works addressed to calculate emissions experimentally are so important to improve the estimations of emissions due to livestock and to calculate emission factors not included in this inventory. FTIR spectroscopy has been frequently used in different methodologies to measure emission rates in many environmental problems. Some of these methods are based on dispersion modelling techniques, wind data, micrometeorological measurements or the release of a tracer gas. In this work, a new method for calculating emission rates from livestock buildings applying Open-Path FTIR spectroscopy is proposed. This method is inspired by the accumulation chamber method used for CO2 flux measurements in volcanic areas or CH₄ flux in wetlands and aquatic ecosystems. The process is the following: livestock is outside the building, which is ventilated in order to reduce concentrations to ambient level. Once the livestock has been put inside, the building is completely closed and the concentrations of gases emitted by livestock begin to increase. The Open-Path system measures the concentration evolution of gases such as CO₂, CH₄, NH₃ and H₂O. The slope of the concentration evolution function, dC/dt, at initial time is directly proportional to the flux of the corresponding gas. This method has been applied in a cow shed in the surroundings of La Laguna, Tenerife Island (Spain). As expected, evolutions of gas concentrations reveal that the livestock building behaves like an accumulation chamber. Preliminary results show that the CH4 emission factor is lower than the proposed by the Emission Inventory.

The path-averaging, multi-component Fourier Transform Infrared (FTIR) absorption spectrometry at an open path of 100 m length is applied for the up-scaling of greenhouse gas (GHG) flux measurements from soil surfaces. For the detection of the emissions of N₂O and further GHG from arable field soils a measuring tunnel for controlled enrichment of released gases was installed at the soil surface covering an area of 495 or 306 m². The concentrations of GHG were measured by FTIR across the whole measuring tunnel. The precision of the FTIR system is discussed to detect the concentration increases during a time period of up to two hours. During a 2-years-time frame the N₂O fluxes between the soil and the atmosphere at the agricultural field varied between 1.0 and 21 μg N₂O-N m^-2 h^-1. A non-intrusive emission and flux measurement method at a scale from 100 m up to 27.000 m² on the basis of the fluxgradient method (0.50 and 2.70 m height above surface) was developed and tested by means of FTIR (N₂O and further GHG concentrations) and area averaging meteorological measurements (determination of horizontal winds and friction velocity using acoustic tomography). To detect the concentration gradient between the two heights the precision of the FTIR system is discussed. Two campaigns in October 2007 and June 2008 were performed with this new methodology when wind speeds were low. The measurement errors are discussed and the results compared with the measurement tunnel results that were higher by up to 25 %.

In the current study, the cloud base height obtained from the ceilometer measurements, in Evora (south of Portugal), are compared with the results obtained from atmospheric modelling. The atmospheric model adopted is the nonhydrostatic MesoNH model, initiated and forced by ECMWF (European Centre for Medium-Range weather Forecasts) analyses. Also the simulated cloud depth results are presented. The availability of mesoscale modelling for the region, as well as the cloud local vertical distributions obtained from the ceilometer, provide a good opportunity to compare cloud base height and estimate the errors associated. From the obtained results it is possible to observe that the simulated cloud base height values are in good agreement with the correspondent values obtained from the ceilometer measurements.

Separating and classifying clouds in remote sensing multispectral imagery is a complex task, especially when optically thin clouds and multilayer systems are present in the images. Many methods, based on both supervised and unsupervised techniques, have been developed previously, but most of them are based on independent pixel processing, using their spectral and textural features. In this work a procedure for segmentation of clouds from multispectral MSG-SEVIRI (Meteosat Second Generation - Spinning Enhanced Visible and Infrared Imager) images is developed. It is based on a nonparametric clustering method, mean shift, which is able to delineate arbitrarily shaped clusters in the feature space. This is an important property, because the clusters that correspond to different kinds of clouds follow complex shapes in the spectral feature space and they cannot be separated by parametric models, usually assuming spherical or elliptical clusters. Some variations of mean shift technique have been also analyzed, and the adaptive version of the algorithm, where the density estimator for every point takes into account the nearest neighbours in the feature space, provided the best performance. Segmentation results were evaluated using different ground true data: MSG SEVIRI cloud data provided by an operational EUMETSAT product and manual human expert segmentation based on the visual inspection and other related information.

Clouds are the major factor regulating the Earth radiation budget, therefore their detection and characterization is of major importance. Cloud detection and classification is a requirement in order to allow for accurate studies of cloud microphysical and optical properties, as well as subsequent assessment of their radiative effects. In the present work, a method for the detection and classification of clouds, over the Iberian Peninsula, is presented. The methodology developed relies on the use of Meteosat-8 satellite images in different spectral bands combined to form different color composites, which are then analyzed, in an unsupervised way. The results show that more features are distinguished in the cloud mask, with respect to the use of traditional methods.

To achieve sea fog detection in China Sea with EOS MODIS data, the reflectance between band 1-7 of sea fog and other cloud regions is the pre-work. Base on satellite observations sampling from known sea fog and cloud regions, the spectral characteristics of sea fog and other clouds are analyzed. It shows that the visible reflectance (band 1-4) is generally from 0.2 to 0.4 in sea fog, while the reflectance of cloud regions is higher than 0.4. The near-infrared reflectance over different fog/cloud regions expresses some especial characteristics. At band 7, the reflectance varies observably relative to band 1-4 over sea fog/cloud regions and it is smallest. And the reflectance of band 5 and 6 may be higher than other bands in sea fog regions. Those results deduced from some instances with statistical method maybe present individual property. Therefore, with the Streamer radiative transfer model, the reflectance at the satellite altitude of the sea fog, low-cloud, mid-cloud and high-cloud with different cloud microphysical and observational conditions is simulated and re-analyzed. The simulations also show those results in extent and are consistent with the satellite observations. It shows that the near-infrared wavelength band 6 is useful to detect sea fog by MODIS. The reflectance of sea fog satisfies band3>band6>band2 while the general cloud is band3>band2>band6. Those properties are also simply explained by Mie scattering theory. It is the different scattering efficiency of sea fog and clouds at different wavelength that make some results. Those properties at sea fog in seven bands that is different from other clouds is nice for fog autodetection from EOS MODIS.

A new algorithm is presented for land fog detection from daytime image of Earth Observation System Moderate Resolution Imaging Spectroradiometer (EOS/MODIS) data. Due to its outstanding spatial and spectral resolutions, this image is an ideal data source for fog detection. The algorithm utilizes an object-oriented technique to separate fog from other cloud types. In this paper, MOD35 product is first introduced to exclude cloud-free areas, and high clouds are removed with MODIS 26 band, and then a parameter named Normalized Difference Fog Index (NDFI) is proposed based on Streamer radiative model and MODIS data for fog detection. Through segmenting NDFI image into regions of pixels, and computing attributes (e.g. mean value of brightness temperature) for each region to create objects, each object could be identified based on the attributes selected to determine whether belongs to fog or cloud. Algorithm's performance is evaluated against ground-based measurements over China in winter. The algorithm is proved to be effective in detecting fog accurately based on two different test cases.

Radiance measurements within the O2A-absorption band contain information about height distribution of scattering particles. This is widely used for estimation of cloud-top height from satellite data. Within cloud free scenes over the ocean, there is still enough information contained for separation of aerosol loading within the maritime boundary layer and enhanced aerosol loading in the upper troposphere or stratosphere. If stratospheric aerosol content is low, then thin cirrus clouds can be observed. Alternatively, a volcanic ash cloud within the stratosphere or upper troposphere can be investigated after volcanic eruptions. This is demonstrated within this paper by one application example.

Spectral surface albedo is an important input for GOME-2 trace gas retrievals. An algorithm was developed for estimation of spectral surface albedo from top-of-atmosphere (TOA)-radiances measured by the Global Ozone Monitoring Experiment GOME-2 flying on-board MetOp-A. The climatologically version of this algorithm estimates Minimum Lambert-Equivalent Reflectivity (MLER) for a fixed time window and can use data of many years in contrast to the Near-real time version. Accuracy of surface albedo estimated by MLER-computation increases with the amount of available data. Unfortunately, most of the large GOME pixels are partly covered by clouds, which enhance the LER-data. A plot of LER-values over cloud fraction is used within this presentation to account for this influence of clouds. This "cloud fraction plot" can be applied over all surface types. Surface albedo obtained using the "cloud fraction plot" is compared with reference surface albedo spectra and with the FRESCO climatology. There is a general good agreement; however there are also large differences for some pixels.

The method to define the form of particles according to remote sensing is given in this work. The method consists in calculation of a phase matrix of environment, on the basis of the data of the solution of a direct scattering problem, by the formulation and the solution of a inverse problem of the transport theory by the least squares method. The form of particles is defined on the received scattering matrix. The solution of a direct scattering problem is spent on the basis of the representation of required spatial distribution of Stokes vector-parameter in the form of superposition of an anisotropic part and rather smooth not small-angular additive. The function of some expansion coefficients from harmonic number is represented by the slowly varying monotonous function owing to strongly marked anisotropy of scattering indicatrix that allows us to limit the number of members in expansion of coefficients at the generalised spherical functions. It greatly simplifies the expressions for the coefficients of the vector equation solution of radiative transfer in the form of matrix exponent - vector small-angular modification of spherical harmonics method (VMSH). In calculation of the smooth additive the anisotropic part received by means of VMSH represents itself as a function of sources.

In the frame of DOAS, a Monte Carlo code has been developed, to calculate, for a given detector with assigned diameter and field of view, the single and multiple scattering radiance. Very general 3-D geometry is foreseen. Spatial distribution along the detector axis for the single and total scattering radiance are computed. Ground reflected contributions to the solar radiance are estimated. Differential effects due to small perturbations in physical parameters, such as ozone density, can simultaneously be taken into account in the same calculation. The code has been applied to ToTaL-DOAS (Topographic Target Light scattering-Differential Optical Absorption Spectroscopy) measurements.

NDSA (Normalized Differential Spectral Absorption) was recently proposed as a differential attenuation 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 during a relative set/rise (occultation) event. The NDSA approach is based on the simultaneous estimate of the total attenuations at two relatively close frequencies and of a "spectral sensitivity parameter" that can be directly converted into IWV through empirical relationships that can be previously derived based on statistical regressions between spectral sensitivity and IWV simulated through real radiosonde data and a propagation model. In this paper we present the error performance in the IWV profile retrievals in the troposphere (up to 14 km) on the basis of an entire day of occultation events in a ECMWF-model simulated atmosphere. For the first time, we present results of simulations of NDSA measurements made in the millimeter band (in addition to the K_u/K bands analysed in previous works), specifically at 179 and 182 GHz.

Green house gases observational satellite (GOSAT) was successfully launched on 23 January in 2009 by JAXA. The satellite carries two sensors, Fourier Transform Spectrometer (FTS) and Cloud Aerosol Imager (CAI). The CAI has four observing wavelengths as 0.38, 0.67, 0.87 and 1.6 μm. It is shown here that this CAI/0.38μm is a unique observing band among usual sensors as MODIS and so on, and it is useful to distinguish the aerosol characteristics of absorbing (e.g., biomass burning) or non-absorbing (e.g., sulfate). In other word, this work proposed a space based retrieval algorithm for atmospheric aerosols including estimation of the optical constant for biomass burning particles. Our algorithm aims to apply the combination use of near UV data with GOAT/CAI, the violet data with Aqua/MODIS and near-IR polarization data with PARASOL/POLDER. In practice the algorithm has been partly examined by using ADEOS-2 / GLI data.

A wide variety of aerosols are suspended in the atmosphere. Especially in East Asia, a huge amount of fossil fuel burning aerosols are emitted throughout the year. Further it seems that the characteristics of aerosols change with the season, and hence the influence impact of aerosols over the climate also varies according to the season. Thus an accurate estimation of seasonal aerosol properties is an urgent subject on the global climate problem. This work is based on the Moderate-resolution Imaging Spectroradiometer (MODIS) data and the simulation results with a three-dimensional aerosol transport-radiation model. It is of interest to mention that aerosol distribution explicitly shows the seasonal change. For example, aerosol concentration in summer is larger than that in winter from eastern China to Japan. This result is drawn from both MODIS data and model simulations. The model simulations suggest that the seasonal change is due to the variations in the photochemical reaction process and transportation process. MODIS data shows that the sulfate aerosols are much more dominant in summer than those in winter at Beijing which is influenced strongly by fossil fuel burning aerosols. This fact is also supported by model simulations. From the present study I can draw such a result in respect of surface radiation budget as the aerosol impact on the reduction of solar radiation is more dominant in summer than that in winter in East Asia.

It is well known that the heavy soil dust has been transported from the China continent to Japan on westerly winds, especially in spring. It is also known that the increasing emissions of anthropogenic aerosols associated with continuing economic growth in Asia has caused serious air pollution over the wide range of East Asia. Accordingly the dust particles involve anthropogenic aerosols as well as soil dust. Thus aerosols in Asia are very complex due to mixing of small anthropogenic particles and large dust particles, which are called Asian dust. The satellite observation is an effective tool for global monitoring of the Asian dust. A new algorithm for detection of Asian dust from space is proposed based on the multispectral satellite (Terra/Aqua/MODIS) data. The derived space-based results are validated with the ground-based measurements and/or model simulations. The sun/sky photometry has been undertaken at NASA/AERONET stations at Higashi-Osaka in Japan, where the suspended particulate matter (SPM) sampling and NIES/LIDAR network equipment have been simultaneously working. In order to validate the satellite results with these surface-level data, an aerosol transportation model is available. In other word, the space-based and/or surface-based measurements are examined with the model simulations, and vice-versa.

The requirements for current large and future extremely large telescopes as well as the quick development of IR instrumentation demand a proper characterization of precipitable water vapour (PWV) above astronomical sites. A comparison of PWV estimations from a photometer and a GPS (Global Positioning System) above the Observatorio del Roque de los Muchachos (ORM, La Palma, Canary Islands, Spain) was carried out and it was found a linear relation between both measurements. Such relationship will allow the calibration of the GPS measurements recorded at ORM for the period June 2001- December 2008. These large time series of PWV estimations from GPS were used to perform a statistical analysis of water vapour content above this astronomical site. Average annual value of night-time PWV of 4.86 mm was found. It was also found a clear seasonal behavior of the PWV above ORM, with smaller water-vapour columns during winter nights (average 3.36 mm). The largest values of PWV are reached in the summer nights (average 6.75 mm). The data indicate that a significant percentage of nights (~38%) are well suited for thermal infrared observations (with PWV < 3 mm), and 71% of nights present a "fair" or better IR observation opportunity at ORM.

The GASCOD (Gas Analyzer Spectrometer Correlating Optical Differences) has been installed at the 'Mario Zucchelli' Antarctic station since 1996. It measures the zenith sky radiation in the 405-465 nm spectral range in unattended and automatic mode. The application to the spectral data of the DOAS (Differential Optical Absorption Spectroscopy) algorithms coupled with a Radiative Transfer Model (RTM) for the computation of the Air Mass Factor (AMF), allows for the retrieval of the total content of the main absorber in this spectral range, namely nitrogen dioxide (NO2). Moreover, the application of sophisticated inversion schemes to the output of the DOAS program, using the AMF matrix as the kernel of the inversion algorithm, permits the determination of the vertical distribution of the above mentioned compound. The full dataset of the spectral data obtained with GASCOD during the period 1996-2008, was re-analyzed with a modified version of the software tool previously utilized. Even if the spectral range examined with GASCOD is not the most favorable for the ozone total column and vertical profile retrieval, the re-processing of the spectral data allowed for the determination of the total ozone columns (TOC). The uncertainties range from 4% to 8% for ozone and 3% to 6% for NO2. The peculiar features of the seasonal variation of NO2 total columns (i.e. the normal decreasing during the austral fall and the irregular growing towards the summer month) are presented and discussed. The confirmations of the significant declining of the ozone total columns during the 'Ozone Hole' periods (mid-August to mid-October) are reported. The vertical distributions obtained for the preceding atmospheric compounds are shown and examined.

The multi purpose UV-Vis. Spectrometer for Atmospheric Tracers Measurement (SPATRAM) is installed at the Observatory of the Geophysics Centre of Evora (38.5º N, 7.9º W) - Portugal, since 2004, measuring the zenith scattered radiation in the 300-550 nm spectral range. The main products are the total column and the vertical profiles of NO₂ and O3 obtained with the application of the Differential Optical Absorption Spectroscopy (DOAS) algorithms and with inversion schemes based on the Optimal Estimation methods respectively. Recently (February 2009), the MIGE (Multiple Input Geometry Equipment) was coupled to the SPATRAM instrument allowing for the measurements of the diffused radiation in directions away from the zenith one (Off-Axis). MIGE is an alt-azimuth platform based on a very simple optical layout, using an optical fibre to transmit the radiation inside the monochromator of the SPATRAM equipment. Thanks to the solution adopted in the developing phase, MIGE is able to scan the whole hemisphere. In this work, after a brief description of the MIGE, the first and preliminary results for vertical profiles of NO₂ in the Planetary Boundary Layer (PBL), and the values of Slant Column Densities (SCD) of O₃ and SO₂ measured in Off-Axis configuration at Evora Station, are presented and discussed.

Since the recognition during the seventies of the importance played by the minor atmospheric compounds in the climate system (gases and aerosols), the studies regarding the chemistry and dynamical processes of Ozone (O₃) and of nitrogen dioxide (NO₂) at high and mid-latitudes, became a fruitful field of research. This work deals mainly with the retrieval and analysis of O₃ and NO₂ total columns and vertical profiles over the Evora Observatory (South of Portugal) for the period 2007-2008. The products presented in this paper are obtained from spectral measurements carried out with the UV-Vis. Spectrometer for Atmospheric Tracers Monitoring - SPATRAM, installed at the Observatory of the Geophysics Centre of Evora (CGE) since 2004. The application of the Differential Optical Absorption Spectroscopy (DOAS) algorithms to the spectral zenith-sky measurements is presented and discussed. The inversion technique applied to the output of the DOAS procedures (the trace gases content along the optical path of measurements: the slant column densities -SCD- of the analyzed absorber) are examined. The first observations obtained with the SPATRAM instrument regarding stratospheric bromine oxide (BrO) are shown. In addition, the comparison of the ground-based measurements with data derived from satellite equipments (OMI and SCIAMACHY), are discussed.

We present an approach to simulate cloud radar signals on the basis of cloud model output, the radar simulator. The simulator is being developed to aid validation of the cloud model. The cloud model applies double-moment bulk warm-rain and ice schemes developed by Morrison and Grabowski.^{1, 2} As an input, the simulator uses profiles of the mixing ratios and number concentrations of cloud droplets, rain/drizzle drops, and ice crystals, as well as the air temperature. For the ice crystals, the rimed mass fraction predicted by the ice scheme is also used. The simulator applies precomputed look-up tables containing scattering properties of cloud and precipitation particles, such as reflectivities, extinction and absorption coefficients. For each grid point, the coefficients are integrated over particle size distributions and summed over hydrometeor types. Consistent with assumptions in the cloud model microphysical scheme, modified gamma size distributions are assumed for cloud droplets and ice crystals, whereas the exponential Marshall-Palmer size distribution is assumed for the rain/drizzle drops. Application of the radar simulator to a simulation of clouds observed during the TWP-ICE campaign over northern Australia is presented.

Ground-based remote-sensing systems, designed for environmental meteorology, are increasingly forced to have their results certified according to the criteria of present-day quality assurance. To this aim, the need for dedicated guidelines is growing and the German Commission on Air Pollution Prevention has been active in this field for more than a decade now. The present paper gives a brief account of the intended purpose, and of the procedure followed to get the guidelines written, discussed, approved, and issued. As an example, parts of the ongoing work on the Raman lidar guideline are presented, including measuring examples provided by the German Meteorological Service in Lindenberg.