G band atmospheric radars: New frontiers in cloud physics

Clouds and associated precipitation are the largest source of uncertainty in current weather and future climate simulations. Observations of the microphysical, dynamical and radiative processes that act at cloud scales are needed to improve our understanding of clouds. The rapid expansion of ground-based super-sites and the availability of continuous profiling and scanning multi-frequency radar observations at 35 and 94 GHz have significantly improved our ability to probe the internal structure of clouds in high temporal-spatial resolution, and to retrieve quantitative cloud and precipitation properties. However, there are still gaps in our ability to probe clouds due to large uncertainties in the retrievals. The present work discusses the potential of G band (frequency between 110 and 300 GHz) Doppler radars in combination with lower frequencies to further improve the retrievals of microphysical properties. Our results show that, thanks to a larger dynamic range in dual-wavelength reflectivity, dual-wavelength attenuation and dual-wavelength Doppler velocity (with respect to a Rayleigh reference), the inclusion of frequencies in the G band can significantly improve current profiling capabilities in three key areas: boundary layer clouds, cirrus and mid-level ice clouds, and precipitating snow. © 2014 Author(s)

Neurodegeneration and Epilepsy in a Zebrafish Model of CLN3 Disease (Batten Disease)

The neuronal ceroid lipofuscinoses are a group of lysosomal storage disorders that comprise the most common, genetically heterogeneous, fatal neurodegenerative disorders of children. They are characterised by childhood onset, visual failure, epileptic seizures, psychomotor retardation and dementia. CLN3 disease, also known as Batten disease, is caused by autosomal recessive mutations in the CLN3 gene, 80–85% of which are a ~1 kb deletion. Currently no treatments exist, and after much suffering, the disease inevitably results in premature death. The aim of this study was to generate a zebrafish model of CLN3 disease using antisense morpholino injection, and characterise the pathological and functional consequences of Cln3 deficiency, thereby providing a tool for future drug discovery. The model was shown to faithfully recapitulate the pathological signs of CLN3 disease, including reduced survival, neuronal loss, retinopathy, axonopathy, loss of motor function, lysosomal storage of subunit c of mitochondrial ATP synthase, and epileptic seizures, albeit with an earlier onset and faster progression than the human disease. Our study provides proof of principle that the advantages of the zebrafish over other model systems can be utilised to further our understanding of the pathogenesis of CLN3 disease and accelerate drug discovery

Knock-Down of Cathepsin D Affects the Retinal Pigment Epithelium, Impairs Swim-Bladder Ontogenesis and Causes Premature Death in Zebrafish

The lysosomal aspartic protease Cathepsin D (CD) is ubiquitously expressed in eukaryotic organisms. CD activity is essential to accomplish the acid-dependent extensive or partial proteolysis of protein substrates within endosomal and lysosomal compartments therein delivered via endocytosis, phagocytosis or autophagocytosis. CD may also act at physiological pH on small-size substrates in the cytosol and in the extracellular milieu. Mouse and fruit fly CD knock-out models have highlighted the multi-pathophysiological roles of CD in tissue homeostasis and organ development. Here we report the first phenotypic description of the lack of CD expression during zebrafish (Danio rerio) development obtained by morpholino-mediated knock-down of CD mRNA. Since the un-fertilized eggs were shown to be supplied with maternal CD mRNA, only a morpholino targeting a sequence containing the starting ATG codon was effective. The main phenotypic alterations produced by CD knock-down in zebrafish were: 1. abnormal development of the eye and of retinal pigment epithelium; 2. absence of the swim-bladder; 3. skin hyper-pigmentation; 4. reduced growth and premature death. Rescue experiments confirmed the involvement of CD in the developmental processes leading to these phenotypic alterations. Our findings add to the list of CD functions in organ development and patho-physiology in vertebrates

Summer Snowfall Workshop : Scattering Properties of Realistic Frozen Hydrometeors from Simulations and Observations, as well as Defining a New Standard for Scattering Databases

Peer reviewe

Neuropathology in Mouse Models of Mucopolysaccharidosis Type I, IIIA and IIIB

Mucopolysaccharide diseases (MPS) are caused by deficiency of glycosaminoglycan (GAG) degrading enzymes, leading to GAG accumulation. Neurodegenerative MPS diseases exhibit cognitive decline, behavioural problems and shortened lifespan. We have characterised neuropathological changes in mouse models of MPSI, IIIA and IIIB to provide a better understanding of these events

Validation of Microphysical Snow Models Using In Situ, Multifrequency, and Dual-Polarization Radar Measurements in Finland

As complex forward models for snow have become common in radar-based retrievals, there is a demand to validate these models in different environments. In this study, we perform a qualitative, general validation for nine different snow models that have been published and are available to users. The chosen models span a variety of different snow types, such as aggregates, rimed aggregates, melted aggregates, graupel, and single crystals, mainly because these particles are commonly observed in the Finnish climate. Fitted power law formulas for mass, fall velocity, aspect ratio, and area ratio are compared between the models and 5-year winter measurements in the Hyytiala forestry field station in Finland. We also compare the backscattering properties of the models to triple-frequency dual-polarization radar measurements during the Biogenic Aerosols Effects on Clouds and Climate campaign in 2014. We find that the denser models, regardless of the exact shapes, fit the in situ measurements best due to the prevalence of rime in the falling snow. However, when comparing also to the triple-frequency radar measurements at X, Ka, and W bands, and the linear depolarization ratio at Ka band, the physical snow models fit overall better than the empirical ones

Scattering of Hydrometeors

A profound understanding of the scattering properties of hydrometeors is key to extract information from passive and active MW observations. The natural variety of hydrometeor properties also leads to the complexity of how they interact with electromagnetic radiation. The challenge of calculating hydrometeor scattering properties is not only the scattering method itself but starts with an accurate characterization of the hydrometeors themselves. The number and sophistication of those hydrometeor models has rapidly grown during recent years, as has the number of publicly available databases of their scattering properties. This development opens up new possibilities to improve the quality of retrievals but also raises new questions on how to best coordinate the scattering community efforts in the future. While sufficient confidence exists for liquid hydrometeor scattering properties, frozen hydrometeors remain challenging and the questions of how to best model their physical properties and how to derive average properties representative for global applications are still under discussion