Microphysical Effects of Cloud Seeding in Supercooled Stratiform Clouds Observed from NOAA Satellite

Based on the satellite retrieval methodology, the spectral characteristics and cloud microphysical properties were analyzed that included brightness temperatures of Channels 4 and 5, and their brightness temperature difference (BTD), the particle effective radius of seeded cloud track caused by an operational cloud seeding and the microphysical effects of cloud seeding were revealed by the comparisons of their differences inside and outside the seeded track. The cloud track was actually a cloud channel reaching 1.5-km deep and 14-km wide lasting for more than 80 min. The effective radius of ambient clouds was 10-15μm, while that within the cloud track ranged from 15 to 26μm. The ambient clouds were composed of supercooled droplets, and the composition of the cloud within the seeding track was ice. With respect to the rather stable reflectance of two ambient sides around the track, the visible spectral reflectance in the cloud track varied at least 10%, and reached a maximum of 35%, the reflectance of 3.7μm in the seeded track relatively decreased at least 10%. As cloud seeding advanced, the width and depth were gradually increased. Simultaneously the cloud top temperature within the track became progressively warmer with respect to the ambient clouds, and the maximum temperature differences reached 4.2 and 3.9℃at the first seeding position for Channels 4 and 5. In addition, the BTD in the track also increased steadily to a maximum of 1.4℃, compared with 0.2-0.4℃of the ambient clouds. The evidence that the seeded cloud became thinner comes from the visible image showing a channel, the warming of the cloud tops, and the increase of BTD in the seeded track. The seeded cloud became thinner mainly because the cloud top descended and it lost water to precipitation throughout its depth. For this cloud seeding case, the glaciation became apparent at cloud tops about 22 min after seeding. The formation of a cloud track in the supercooled stratiform clouds was mainly because that the seeded cloud volume glaciated into ice hydrometeors that precipitated and so lowered cloud top height. A thin line of new water clouds formed in the middle of the seeded track between 38 and 63 min after seeding, probably as a result of rising motion induced by the released latent heat of freezing. These clouds disappeared in the earlier segments of the seeded track, which suggested that the maturation of the seeding track was associated with its narrowing and eventual dissipation due to expansion of the tops of the ambient clouds from the sides inward.     

Resolution issues in numerical models of oceanic and coastal circulation

The baroclinic and barotropic properties of ocean processes vary on many scales. These scales are determined by various factors such as the variations in coastline and bottom topography, the forcing meteorology, the latitudinal dependence of the Coriolis force, and the Rossby radius of deformation among others. In this paper we attempt to qualify and quantify scales of these processes, with particular attention to the horizontal resolution necessary to accurately reproduce physical processes in numerical ocean models. We also discuss approaches taken in nesting or down-scaling from global/basin-scale models to regional-scale or shelf-scale models. Finally we offer comments on how vertical resolution affects the representation of stratification in these numerical models.     

Magnetic mapping for the detection and characterization of UXO: Use of multi-sensor fluxgate 3-axis magnetometers and methods of interpretation

Fluxgate vector magnetometers can be powerful instruments in magnetic mapping and in the detection of unexploded ordnance (UXO). Being lightweight and having low power requirements, they allow the development of multi-sensor use. The main problems in using fluxgate magnetometers arise from calibration errors and drift but these can be overcome using a quick and simple method of calibration in the field. This method also has the advantage of compensating permanent and induced magnetic fields generated by magnetized objects carried with the sensors. Measurement accuracy is similar to that obtained with scalar magnetometers. Multi-magnetometer profiling allows direct inversion of raw magnetic data along profiles in order to locate and characterize dipoles typically generated by UXO. The method used is a non-linear inverse procedure that estimates the three coordinates and magnetization vector of the dipole. Application of the technique to both a synthetic case and a field example illustrates the advantages of the method compared with the use of the analytic signal.     

Micro-spectroscopic investigation of selenium-bearing minerals from the Western US Phosphate Resource Area

Mining activities in the US Western Phosphate Resource Area (WPRA) have released Se into the environment. Selenium has several different oxidation states and species, each having varying degrees of solubility, reactivity, and bioavailability. In this study we are investigating the speciation of Se in mine-waste rocks. Selenium speciation was determined using bulk and micro-x-ray absorption spectroscopy (XAS), as well as micro-x-ray fluorescence mapping. Rocks used for bulk-XAS were ground into fine powders. Shale used for micro-XAS was broken along depositional planes to expose unweathered surfaces. The near edge region of the XAS spectra (XANES) for the bulk rock samples revealed multiple oxidation states, with peaks indicative of Se(-II), Se(IV), and Se(+VI) species. Micro-XANES analysis of the shale indicated that three unique Se-bearing species were present. Using the XANES data together with ab initio fitting of the extended x-ray absorption fine structure region of the micro-XAS data (micro-EXAFS) the three Se-bearing species were identified as dzharkenite, a di-selenide carbon compound, and Se-substituted pyrite. Results from this research will allow for a better understanding of the biogeochemical cycling of Se in the WPRA.     

Development of a coral cDNA array to examine gene expression profiles in Montastraea faveolata exposed to environmental stress

The development of a cDNA array of coral genes and its application to investigate changes in coral gene expression associated with stressful conditions is described. The array includes both well-characterized and previously unidentified coral genes from Acropora cervicornis and Montastraea faveolata. Corals were exposed to either natural or anthropogenic stressors to elicit the expression of stress genes for isolation and incorporation onto the array. A total of 32 genes involved in protein synthesis, apoptosis, cell signaling, metabolism, cellular defense and inflammation were included on the array. Labeled cDNA from coral (Montastraea faveolata) exposed to elevated seawater temperature, salinity and ultraviolet light was tested against the microarray to determine patterns of gene expression associated with each stressor. Carbonic anhydrase, thioredoxin, a urokinase plasminogen activator receptor (uPAR) and three ribosomal genes demonstrated differential expression across all replicates on the array and between replicate colonies. Specific gene expression patterns produced in response to different stressors demonstrate the potential for gene expression profiling in characterizing the coral stress response.     

The northwestern Argentina Tarija Basin: Stratigraphy, depositional systems, and controlling factors in a glaciated basin

The Tarija Basin, shared by Bolivia and Argentina, was subjected to glacial conditions during the Late Carboniferous and Early Permian. The Macharetí and Mandiyutí groups deposited during these times record in their facies advances and retreats of the Gondwanan ice cap. The lithostratigraphic subdivision of these groups presents stages with minor glacial influence in the basal formations of each group (Tupambi and Escarpment formations), whereas in the upper units, glacially related deposition prevails (Tarija and San Telmo formations). Typical facies deposited in relation to glacial settings are diamictites and mudstones mainly related to proglacial, lacustrine environments. During the stages of main ice retreat, deposition was dominated by fluvial and deltaic sandstones. Significant erosion and deep valley incision characterize the basal surfaces of both groups. Conversely, the stratigraphic surface that separates the sandy formations from the overlying diamictites tends to be rather flat. The dynamics of the glacial cap are not only reflected in the facies distribution but also were a key factor in creating accommodation space; the changes in the glacial-driven subsidence linked to the advance and retreat of the ice were its main control.