This paper deals with the retrieval of atomic oxygen concentration profiles in the Earth's upper mesosphere/lower thermosphere region from SCIAMACHY observations of oxygen green line airglow emissions. Atomic oxygen is one of the most important chemical constituents of this atmospheric region, and long-term satellite data sets are rare. The paper includes a detailed description of the retrieval algorithm, an error budget, validation results and some first scientific analyses. Hide

A water vapor lidar has been designed and tested which has the potential to enable a national-scale network. The system is low-maintenance, low-cost, eye-safe, and provides continuous profiles of water vapor with complete coverage, including periods of daytime bright clouds, from 300m above ground level to 4km with 150m nominal vertical resolution and 1 min temporal resolution. The sensor may be useful in improving our understanding of the distribution of atmospheric water vapor. Hide

The effect of contrails on global shortwave radiation (sum of direct and downward diffuse solar radiation) and on solar energy gain was investigated. The results show that contrails moving between sun and observer/sensor may reduce the global radiation by up to 72%. An analysis of contrail persistence and influence of contrails on global irradiance and solar energy gain is presented. The losses in solar energy gain that were recorded may be critical under specific circumstances. Hide

We demonstrate the feasibility of using FT-IR spectra of aerosols and a multivariate calibration to estimate organic carbon (OC) from thermal-optical reflectance analysis. Using 800 IMPROVE samples, we establish that prediction error can be explained by differences in distributions of OC and aerosol composition between calibration and test set. This work is an initial step in proposing a non-destructive analysis method that can reduce the operating costs of large air quality monitoring networks. Hide

The main goal of this article was to validate the total water vapour column (TWVC) measured by the Global Ozone Monitoring Experiment-2 (GOME-2) satellite sensor highly accurate sounding measurements. The smallest relative differences found in this satellite-sounding comparison (below 10%) were achieved for those cloud-free cases with satellite SZA below 50º which can be considered as a good result for satellite retrievals. Hide

Measurements of upper tropospheric-lower stratospheric water vapor amounts in the tropics were made using the 1400 and 1900nm water vapor bands present in airborne solar spectral irradiance data. These were validated with radiative transfer modeling using in situ profiles of water vapor, temperature, and pressure. An approach to extending these types of measurements from aircraft altitudes to the top of the atmosphere to infer stratospheric water vapor amount is outlined. Hide

We demonstrate a post-processing technique to improve MISR-retrieved aerosol optical properties when information content is low. By filtering the list of aerosol mixtures that pass the MISR retrieval acceptance criteria using pre-defined discrepancy thresholds between MISR and GOCART model simulations, the adjusted MISR Angstrom exponent (ANG) and absorbing AOD (AAOD) agree significantly better with sun-photometer validation data, especially when AOD<0.2 for ANG and AOD<0.5 for AAOD. Hide

This work performs cloud classification on all-sky images. To deal with mixed cloud types, we propose performing block-based classification. The proposed method combines local texture features with classical statistical texture features. The experimental results have shown that applying the combined feature results in higher classification accuracy. It is also validated that using block-based classification outperforms classification on the entire images. Hide

This paper describes a newly designed cold electrodynamic balance (EDB) which can be used to study the evaporation kinetics and freezing properties of aerosols at temperatures down to -40˚C. The abilities of the new EDB are exemplified through the study of the immersion freezing properties of water droplets containing extracts of water birch pollen (Betula fontinalis occidentalis). Protein-rich pollen extracts are found to be significantly more ice-active than non-proteinaceous extracts. Hide

The CCA algorithm is applicable to any modern passive microwave radiometer on board polar orbiting satellites; it has been developed using a data set of co-located SSMIS and TRMM-PR measurements and AMSU-MHS and TRMM-PR measurements. The algorithm shows a small rate of false alarms and superior detection capability and can efficiently detect (POD between 0.55 and 0.71) minimum rain rate varying from 0.14 mm/h (AMSU over ocean) to 0.41 (SSMIS over coast). Hide

KIAPS has been developing a next-generation numerical weather prediction model and an advanced data assimilation system. We recently implemented a GPS-RO data processing system and then tested the processed data within an ensemble-based data assimilation system. The systems for the data processing and the data assimilation are fully coupled and cycled with a numerical weather prediction model. As a result, data processing and assimilation work properly to give reasonable innovation. Hide

In preparation for the launch of the first six satellites of the COSMIC-2 mission in equatorial orbit, and the larger number of observations that such a mission will provide in the lower tropical troposphere, work is underway at NOAA to improve the assimilation of RO observations. This paper describes the limitations of the current standard quality controls for RO data and discusses the implementation of additional quality control procedures. Hide

We present the capability of an aerosol retrieval algorithm, intended for multi-angle, multi-wavelength photopolarimetric measurements, to intrinsically screen for sub-pixel liquid water cloud contamination. The screening is based on goodness-of-fit criteria. The algorithm has been applied to a synthetic data set of partially clouded scenes and (non-cloud-screened) POLDER3/PARASOL observations. Hide

Presented is a robust retrieval algorithm that demonstrates the capabilities of utilizing Cross-track Infrared Sounder (CrIS) satellite observations to globally retrieval ammonia (NH3) concentrations. Initial NH3 retrieval results show that CrIS is (i) sensitive to NH3 in the boundary layer, with peak vertical sensitivity typically around 850–750hPa (~2km), (ii) has a minimum detection limit of ~1ppbv (peak profile value typically at the surface), and (iii) typically has up to ~1 DOFS. Hide

This paper investigates the potential of the upcoming TROPOspheric Monitoring Instrument (TROPOMI) instrument for the retrieval of the chlorophyll fluorescence signal emitted in the 650–850nm spectral range by the photosynthetic machinery of green plants. We find that TROPOMI will allow substantial improvements in the space monitoring of fluorescence with respect to current spaceborne instruments such as GOME-2 and SCIAMACHY. Hide

Cloud properties are obtained via transmitted light that has interacted with cloud particles throughout its vertical extent. To achieve this, we introduce a new retrieval based on spectrally resolved measurements. We used 15 parameters to quantify spectral features in transmitted light modulated by cloud optical thickness, effective radius, and thermodynamic phase. When applied to ground-based measurements, this method results in a closer match to measured spectra than two other methods. Hide

Two-wavelength scintillometry, a ground-based remote sensing technique for deriving large-area heat fluxes, has been used over an urban area for the first time. The long data set enables investigation of the performance of the technique and characteristics of turbulent transport processes at sub-daily to inter-annual timescales. In this first paper, the structure parameters of temperature and humidity, and the correlation between temperature and humidity, are presented and analysed. Hide

Two-wavelength scintillometry, a ground-based remote sensing technique for deriving large-area heat fluxes, has been used over an urban area for the first time. The long data set enables investigation of the performance of the technique and characteristics of turbulent transport processes at sub-daily to inter-annual timescales. In this second paper, sensible and latent heat fluxes representative of an area of 5--10 km2 are presented and analysed. Hide

This paper describes a cross-validation study of tropospheric δD (HDO/H2O ratio) profiles retrieved from IASI spectra (retrieval performed at ULB). We document how these profiles compare to profiles derived from TES/AURA sounder and from three ground-based FTIRs of the NDACC network (produced within the MUSICA project). We show that empirical differences are in agreement with the theoretical expected differences which are dominated by IASI observational and the smoothing error components. Hide

A new offline technique for retrieving tropospheric NO2 slant columns from space over urban regions is proposed in this work. An Earth radiance reference measurement from a remote unpolluted region is used instead of the standard solar irradiance measurement used by operational retrieval algorithms. Testing with spectra measured by the Ozone Monitoring Instrument (OMI) shows that the technique largely removes the presence of stratospheric NO2 and also greatly suppresses instrumental biases. Hide

We test if ground-based sun photometers/radiometers like those in the Aerosol Robotic Network (AERONET) can use the polarization sensitivity of some instruments for improved cloud optical property retrieval. Our radiative transfer simulations show that the direction of linear polarization indicates cloud thermodynamic phase for optically thin clouds. In practice, data analysis shows a weak response with AERONET instruments, most likely due to noise and orientation/calibration ambiguity. Hide

In this study, comprehensive ground-based data sets (Europe, China, Africa and United States) are used to evaluate NH3 measurements from IASI. Global yearly and regional monthly comparisons show fair agreement, while hourly measurements are used to investigate the limitations of direct comparisons. In addition, dense airborne measurements are explored and show the highest correlation coefficients in this study. Finally, the urgent need for independent NH3 column measurements is discussed. Hide

Comparisons on the FAAM BAe 146-301 aircraft show good agreement between chilled mirror hygrometers and a WVSS-II fed from a modified Rosemount inlet (wvssR) in coud-free conditions, but a WVSS-II fed from the standard flush inlet (wvssF) over-reads, except at higher humidities. Case studies in cloudy conditions show that wvssF is immune to liquid water and ice, whilst wvssR is susceptible to both. Both WVSS-II inlets respond much more rapidly than the chilled mirror devices, especially wvssF. Hide