ALBERT

Description: The Geostationary Earth Radiation Budget Intercomparison of Longwave and Shortwave radiation (GERBILS) was an observational field experiment over North Africa during June 2007. The campaign involved 10 flights by the FAAM BAe-146 research aircraft over southwestern parts of the Sahara Desert and coastal stretches of the Atlantic Ocean. Objectives of the GERBILS campaign included characterisation of mineral dust geographic distribution and physical and optical properties, assessment of the impact upon radiation, validation of satellite remote sensing retrievals, and validation of numerical weather prediction model forecasts of aerosol optical depths (AODs) and size distributions. We provide the motivation behind GERBILS and the experimental design and report the progress made in each of the objectives. We show that mineral dust in the region is relatively non-absorbing (mean single scattering albedo at 550 nm of 0.97) owing to the relatively small fraction of iron oxides present (1–3%), and that detailed spectral radiances are most accurately modelled using irregularly shaped particles. Satellite retrievals over bright desert surfaces are challenging owing to the lack of spectral contrast between the dust and the underlying surface. However, new techniques have been developed which are shown to be in relatively good agreement with AERONET estimates of AOD and with each other. This encouraging result enables relatively robust validation of numerical models which treat the production, transport, and deposition of mineral dust. The dust models themselves are able to represent large-scale synoptically driven dust events to a reasonable degree, but some deficiencies remain both in the Sahara and over the Sahelian region, where cold pool outflow from convective cells associated with the intertropical convergence zone can lead to significant dust production. Copyright © 2011 Royal Meteorological Society and British Crown Copyright, the Met Office

Description: Predictions of the geometric optics approximation for scattering from two rough interfaces that separate three homogeneous media (the “GO-layer” model) are examined for their implications for radar remote sensing. A previous formulation of the rough layer normalized radar cross section (NRCS) is also extended to allow calculation of the polarimetric covariance of the scattered field. Example results are presented for both bistatic and monostatic configurations, and show the influence of subsurface interfaces on scattered field properties. In particular, complete hemispherical bistatic patterns of both NRCS and polarimetric correlations are illustrated to provide insight into the impact of subsurface layers on these quantities. It is shown that the observability of sub-surface contributions in general is larger for geometries where upper interface returns are smaller (i.e. angles outside the quasi-specular return of the upper interface), and it is also shown that significant decorrelations between polarizations can occur in the presence of sub-surface layers. Variations of field properties with medium physical parameters (inner layer thickness and relative permittivity, upper and lower surface RMS slopes, radar frequency) are also shown. A problem that has received extensive previous interest (subsurface sensing in arid regions having an upper sand layer over a granite bedrock) is re-examined for remote sensing at higher frequencies, and it is shown that subsurface contributions can impact backscattered NRCS returns even up to X-band frequencies. The examples presented can be utilized to assess the potential detectability of sub-surface layers for both monostatic radar observations and near specular observations (as in GNSS reflection observations of land surfaces).

Description: Crystal Growth & Design DOI: 10.1021/cg201170w

Description: The snowfall in the Baltimore/Washington metropolitan area during the winter of 2009/2010 was unprecedented and caused serious snow-related disruptions. In February 2010, snowfall totals approached 2 m, and because maximum temperatures were consistently below normal, snow remained on the ground the entire month. One of the biggest contributing factors to the unusually severe winter weather in 2009/10, throughout much of the mid latitudes, was the Arctic Oscillation. Unusually high pressure at high latitudes and low pressure at mid-latitudes, forced a persistent exchange of mass from north to south. In this investigation, a concerted effort was made to link remotely sensed falling snow observations to remotely sensed snow cover and snowpack observations in the Baltimore/Washington area. Specifically, the Advanced Microwave Scanning Radiometer (AMSR-E) onboard the Aqua satellite was used to assess snow water equivalent (SWE), and the Advanced Microwave Sounding Unit-B (AMSU-B) and Microwave Humidity Sounder (MHS) were employed to detect falling snow. AMSR-E passive microwave signatures in this study are both related to snow on the ground and to surface ice layers. In regards to falling snow, signatures indicative of snowfall can be observed in high frequency brightness temperatures of AMSU-B/MHS. Indeed, retrievals show an increase in SWE after the detection of falling snow. Yet this work also shows that falling snow intensity and or the presence of liquid water clouds impacts the ability to reliably detect SWE. Moreover, changes in the condition of the snowpack, especially in the surface features, negatively affect retrieval performance. Copyright © 2011 John Wiley & Sons, Ltd.

Description: Precise control of the innate immune response is essential to ensure host defense against infection while avoiding inflammatory disease. Systems-level analyses of Toll-like receptor (TLR)-stimulated macrophages suggested that SHANK-associated RH domain-interacting protein (SHARPIN) might play a role in the TLR pathway. This hypothesis was supported by the observation that macrophages derived from chronic proliferative dermatitis mutation (cpdm) mice, which harbor a spontaneous null mutation in the Sharpin gene, exhibited impaired IL-12 production in response to TLR activation. Systems biology approaches were used to define the SHARPIN-regulated networks. Promoter analysis identified NF-κB and AP-1 as candidate transcription factors downstream of SHARPIN, and network analysis suggested selective attenuation of these pathways. We found that the effects of SHARPIN deficiency on the TLR2-induced transcriptome were strikingly correlated with the effects of the recently described hypomorphic L153P/panr2 point mutation in Ikbkg [NF-κB Essential Modulator (NEMO)], suggesting that SHARPIN and NEMO interact. We confirmed this interaction by co-immunoprecipitation analysis and furthermore found it to be abrogated by panr2. NEMO-dependent signaling was affected by SHARPIN deficiency in a manner similar to the panr2 mutation, including impaired p105 and ERK phosphorylation and p65 nuclear localization. Interestingly, SHARPIN deficiency had no effect on IκBα degradation and on p38 and JNK phosphorylation. Taken together, these results demonstrate that SHARPIN is an essential adaptor downstream of the branch point defined by the panr2 mutation in NEMO.

Description: The radiative properties of mineral dust aerosol during the GERB Intercomparison of Long-wave and Short-wave (GERBILS) are presented. GERBILS consisted of aircraft flights over land areas between Mauritania and Niger during June 2007. During one case of large aerosol optical depth (AOD=1.0 at 0.55 μ m), a short-wave spectrometer measured sky radiances versus scattering angle that are compared to modelled data. The modelling used phase functions of spheres, spheroids and irregular-shaped particles using T-matrix and ray-tracing methods. Irregular particles provided the most satisfactory solution. In another case of full short-wave and long-wave radiative closure, measurements and modelled clear sky conditions allowed calculation of the direct radiative effect (DRE) at high and low level. The modelled AOD (0.92) required to simulate the measured spectral irradiances agrees with the aircraft AOD (0.79) within measurement uncertainty. The simulated irradiances are less sensitive to particle shape than radiances. However, it is shown through modelling of the surface and top-of-atmosphere (TOA) DRE over all daylight hours that significant differences exist at TOA due to variation in the asymmetry parameter. The TOA short-wave diurnally averaged DRE was modelled as between 0 and –20 W m −2 depending on particle shape. A long-wave interferometer measured downwelling and upwelling radiances to derive surface emissivity across the window region. Measured nadir brightness temperatures from high level show signature of dust. A drop in brightness temperature of 14K was determined using modelled pristine-sky spectra. The modelled outgoing long-wave DRE due to dust from this case was +14 W m −2 averaged over 24 h, or +17 W m −2 per unit AOD. Modelling studies illustrate the sensitivity to aerosol refractive index and size distribution for both short-wave and long-wave DREs. Considering the full spectrum, a refractive index dataset from the literature has been selected that best represents the Saharan dust encountered during GERBILS. Copyright © 2011 Royal Meteorological Society and British Crown Copyright, the Met Office

Description: This paper uses aircraft, ground-based and satellite observations to assess the performance of Met Office dust forecasts during the Geostationary Earth Radiation Budget Intercomparison of Long-wave and Short-wave radiation (GERBILS) campaign. The dust forecasts were produced from a 20 km resolution limited-area numerical weather prediction configuration of the Met Office Unified Model, based over North Africa. Dust uplift was modelled using two modified versions of the Woodward (2001) dust parametrization scheme. The model produced widespread dust over the Sahara desert in response to synoptically driven strong wind events. The modelled aerosol size distribution and short-wave optical properties compared well with aircraft in situ measurements and retrievals from the Aerosol Robotic Network (AERONET). Better size distributions and extinction coefficients were achieved by fixing the emitted dust size distribution rather than attempting to predict this dynamically. The two versions performed similarly compared to observations of other variables. The interaction of dust with short-wave and long-wave radiation compared well with aircraft observations when scaled to allow for local differences in Aerosol Optical Depth (AOD). AODs were on average 50–100% too high over south-western parts of the Sahara but 20–50% too low over the Sahel when compared to AERONET sites, aircraft profile estimates and satellite retrieval products. This implicated excessive dust emission over central parts of the Sahara and insufficient dust emissions from the Bodélé depression and semi-arid regions on the southern border of the Sahara. These biases were linked to potential errors in wind speed, soil texture, soil moisture and vegetation, and possible limitations in the dust parametrization, such as the lack of an observationally constrained or geomorphologically based preferential source term. Copyright © 2011 Royal Meteorological Society and Crown copyright, the Met Office

Description: Physically based passive microwave precipitation retrieval algorithms require a set of relationships between satellite-observed brightness temperatures (TBs) and the physical state of the underlying atmosphere and surface. These relationships are nonlinear, such that inversions are ill-posed especially over variable land surfaces. In order to elucidate these relationships, this work presents a theoretical analysis using TB weighting functions to quantify the percentage influence of the TB resulting from absorption, emission, and/or reflection from the surface, as well as from frozen hydrometeors in clouds, from atmospheric water vapor, and from other contributors. The percentage analysis was also compared to Jacobians. The results are presented for frequencies from 10 to 874 GHz, for individual snow profiles, and for averages over three cloud-resolving model simulations of falling snow. The bulk structure (e.g., ice water path and cloud depth) of the underlying cloud scene was found to affect the resultant TB and percentages, producing different values for blizzard, lake effect, and synoptic snow events. The slant path at a 53° viewing angle increases the hydrometeor contributions relative to nadir viewing channels. Jacobians provide the magnitude and direction of change in the TB values due to a change in the underlying scene; however, the percentage analysis provides detailed information on how that change affected contributions to the TB from the surface, hydrometeors, and water vapor. The TB percentage information presented in this paper provides information about the relative contributions to the TB and supplies key pieces of information required to develop and improve precipitation retrievals over land surfaces.

Description: This paper presents aircraft measurements of the physical and optical properties of mineral dust from the GERBILS campaign. The campaign involved ten flights of the UK Facility for Airborne Atmospheric Measurements (FAAM) BAe-146 aircraft over the western region of the Sahara desert. Vertical profiles showed dust layers at varying altitudes extending as high as 6.5 km. Dust layers were typically associated with a deep well-mixed boundary layer or a residual boundary layer above (the Saharan air layer). Aerosol optical depths (AODs), measured by integrating vertical profiles of extinction coefficient, ranged from 0.3 to 2.4 (at 0.55 μm). Aircraft AODs were generally within 20% of AERONET and Microtops sun-photometer measurements. Single-scattering albedos at 0.55 μm were measured in the range 0.92–0.99 with a campaign mean of 0.97. The in situ size distribution compared well with AERONET retrievals made at Banizoumbou (Niger) and Dakar (Senegal). The proportion of aerosol volume associated with particles of radii 〉1.5 μm was highly variable and also more difficult to measure. Models of dust as spheres, spheroids and more complex irregular-shaped particles were used to calculate single-scattering optical properties. The single-scattering albedo showed a low sensitivity to particle shape. The asymmetry parameter and specific extinction coefficient showed greater sensitivity to particle shape. Copyright © 2011 British Crown copyright, the Met Office. Published by John Wiley & Sons Ltd.

Description: Using Hidden Markov Models (HMMs) as a recognition framework for automatic classification of animal vocalizations has a number of benefits, including the ability to handle duration variability through nonlinear time alignment, the ability to incorporate complex language or recognition constraints, and easy extendibility to continuous recognition and detection domains. In this work, we apply HMMs to several different species and bioacoustic tasks using generalized spectral features that can be easily adjusted across species and HMM network topologies suited to each task. This experimental work includes a simple call type classification task using one HMM per vocalization for repertoire analysis of Asian elephants, a language-constrained song recognition task using syllable models as base units for ortolan bunting vocalizations, and a stress stimulus differentiation task in poultry vocalizations using a non-sequential model via a one-state HMM with Gaussian mixtures. Results show strong performance across all tasks and illustrate the flexibility of the HMM framework for a variety of species, vocalization types, and analysis tasks.