Quantifying and predicting the accuracy of radar-based quantitative precipitation forecasts

On the basis that hydrological users need to know the forecast uncertainty at the time that the forecast is issued, we computed distributions of radar rainfall forecast uncertainty as a function of forecast lead time, basin size, and forecasted rainfall intensity using data from the US 3-D National Mosaic of radar data. We document how exceptional forecasts such as those of heavy rainfall are generally biased. Since forecast uncertainty is also weather dependent, we tried to find good predictors to help either reduce the forecast uncertainty or better define it. These predictors were based either on characteristics of the current precipitation field or on the performance of the nowcast in the immediate past. The value of some predictors, especially those based on the properties of large-scale rainfall patterns, was significant though modest, the predictors being generally more skillful at characterizing forecast uncertainty than at improving forecast accuracy.     

Controlling mechanisms for the trace metals, (Cu,Zn, Cd,Fe, Co and Ni) in anoxic sea water in Saanich Inlet,British Columbia,Canada

A study was conducted on Cu, Zn, Cd, Fe, Co and Ni levels in Saanich Inlet anoxic seawater. Data on the concentration of these trace metals and H₂S, and other oceanographic parameters were obtained in four cruises. Equilibrium models are presented together with in situ data. The results strongly support the assumption that the solubilities of Cu, Zn, Cd, Fe, Co and Ni are controlled by bisulfide and/or polysulfide complexes. The species of Cu, Zn, Cd and Ni are shown to be Cu(S₄) ₂ ³⁻ and Cu(Sn₄S₅)³⁻, Zn(HS) ₂ ⁰ and ZnHS ₂ ⁻ , Cd(HS) ₂ ⁰ and Ni(HS) ₂ ⁰ , respectively. The solid species controlling Fe²⁺ and Co²⁺ are respectively the pyrohotites FeS and CoS. The data illustrates that thermodynamic equilibrium has been established in the H₂S-controlled seawater of Saanich Inlet, and that equilibrium has not been established in the H₂S−O₂-coexisted seawater of Saanich Inlet. The lack of equilibrium in the H₂S−O₂-coexisted seawater is a result of the flushing or mixing of oxygenated seawater with anoxic water. The new species of trace metals are still in the processes of reduction and precipitation. Contribution No. 1428 from Institute of Oceanology, Academia Sinica     

A study on the flux,speciation, and budget of mercury in controlled experimental ecosystems

The lowest addition of mercury (0.1 ug Hg 1⁻¹) was used in CEEs for research on mercury flux, speciation and budget. The removal behavior of mercury by phytoplankton in water columns of CEEs can be described by first order kinetic equations for total and particulate mercury in the CEE spiked by mercury. The removal rate of mercury in water columns depends on the size and productivity of phytoplanton in a water column to which mercuric ions were added. A 4.4 day half-life time and a 2.8 day half-life time for total and particulate mercury respectively was obtained in diatom bloom. During microflagellate bloom a 30 day total mercury half-life time was estimated with increase of particulate mercury in the water column. The 0.010 ug Hg cm⁻²y⁻¹ mercury flux rate that was attained in the control bag agreed with the values from field measurements in Saanich Inlet where the bags were launched. The proportion of total mercury to dissolved and particulate mercury depended also on the size, productivity, and concentration of mercury in a water column. A more or less constant distribution of mercury species in the control bag was observed as follows: dissolved Hg 0.73, particulate Hg 0.27, inorganic Hg 0.42, dissolved organic Hg 0.31. After spiking with mercury, the particulate mercury rose rapidly and reached to over 70% of the total mercury. The concentration factor of mercury by phytoplankton in the CEEs in the order of 10⁵ was consistent with the results from field measurements in Saanich Inlet. The mercury recovery from the water column, sediment, water with sediment, and the CEE bag walls was only 52.3% of total mercury spiked in the CEE. The losses of mercury by vaporization into the ambient air and diffusion through the wall of the enclosure should be considered. This paper was published in Chinese inOcean. Limn. Sinica,17(4):307–317, 1986.     

Problems with biogenic silica measurement in marginal seas

Surface sediment samples from the Bohai, Yellow Sea, and the Pacific were used to assess biogenic silica (BSi) content and to study uncertainties in BSi measurements. The contents of BSi in the Bohai and Yellow Sea are all less than 1%. The dissolution of BSi in sediments from the Bohai and Yellow Sea is very important to maintain high levels of silicate in the water column. The non-biogenic silica from clay minerals has an obvious effect on BSi of sediment samples in the Bohai and Yellow Sea with low BSi and high clay minerals. The solid to solution ratio was found to have a great influence on BSi measurement, which can induce uncertainties up to 75%. The effect of loss by sorption and centrifugation is negligible. Interlaboratory comparison of techniques for BSi measurement by the wet alkaline extraction technique of Mortlock and Froelich [Deep-Sea Res. 36 (1989) 1415-1426] with clay correction was suggested to give no significant differences. However, differences in sediment compositions and reagent to sample ratio may limit the application of the wet alkaline extraction method.     

A fluid inclusion study of the porphyry-greisen,tungsten-molybdenum deposit at Mount Pleasant,New Brunswick,Canada

Homogenization temperatures and salinity data are presented for fluid inclusions from hydrothermal gangue minerals (quartz and fluorite) associated with porphyry wolframite-molybdenite-arsenopyrite-sphaleritebismuth-chalcopyrite-cassiterite mineralization within the Fire Tower ore zone, Mt Pleasant, New Brunswick. The data indicate that ore mineral precipitation occurred within a temperature range of 260° to 490°C from moderate to high salinity (10–42 wt% NaCl equivalent) aqueous fluids. Two stages of hydrothermal activity characterized by high (>30 wt% NaCl equivalent) salinity fluids are recognized; one which occurred at relatively high temperature (350°–490°C); and one which took place at lower temperature (180°–250°C). The high salinity, high temperature stage is interpreted to be the result of resurgent boiling. Dilution of these early fluids by convecting meteoric water resulted in low to moderate salinity fluids, which dominate the inclusion population. The low temperature, high salinity fluid inclusions are interpreted to represent late residual fluids derived from boiling which occurred as a result of a change in the pressure regime from dominantly lithostatic to hydrostatic conditions.     

Crustal structure of the western Arafura Sea from ocean bottom seismograph data

Refraction data taken from ocean bottom seismograph recordings in the western Arafura Sea indicate a continental‐type structure for the region. This structure is characterised by a thin column (2 km) of sediments, with velocities ranging from about to 2 to 4 km s^‐1, overlying an essentially two layer crust. The compressional wave velocities in the upper and lower crust are 5.97 and 6.52 km s^‐1, respectively, with the boundary between the layers at a depth of 11 km. Very weak mantle‐refracted arrivals with a velocity of about 8.0 km s^‐1 were recorded. Large‐amplitude, later arrivals, beginning at distances near 100 and 150 km, have been interpreted to be part of the retrograde branches from the 8.0 and 7.33 km s^‐1 layers, respectively. Model studies indicate that a small positive velocity gradient is required between 17 and 30 km, and that the Moho is at a depth of 34 km. A third set of large amplitude, later arrivals starting at a distance near 250 km has been interpreted as most probably multiple refraction‐reflection arrivals from the 5.97 and 6.52 km s^‐1 layers. Correlation of this structure with the stratigraphic logs from exploratory oil wells in the Arafura Sea using layer velocities indicates that rocks younger than Jurassic appear to thin towards the east.     

Tectonometamorphic Evolution of the Eastern Tibet Plateau: Evidence from the Central Songpan-Garze Orogenic Belt, Western China

The Songpan–Garzê Orogenic Belt (northeastern TibetPlateau) experienced polyphase deformation and metamorphismthat is best developed in the Danba Domal Metamorphic Terrane(DDMT), in which three tectonometamorphic events can be identified.The first event (D₁–M₁) is characterized by prograde sericite-to kyanite-grade Barrovian metamorphism during late Indosinian(     

The transition from peraluminous to peralkaline granitic melts: Evidence from melt inclusions and accessory minerals

Fractional crystallization of peraluminous F- and H₂O-rich granite magmas progressively enriches the remaining melt with volatiles. We show that, at saturation, the melt may separate into two immiscible conjugate melt fractions, one of the fractions shows increasing peraluminosity and the other increasing peralkalinity. These melt fractions also fractionate the incompatible elements to significantly different degrees. Coexisting melt fractions have differing chemical and physical properties and, due to their high density and viscosity contrasts, they will tend to separate readily from each other. Once separated, each melt fraction evolves independently in response to changing T/P/X conditions and further immiscibility events may occur, each generating its own conjugate pair of melt fractions. The strongly peralkaline melt fractions in particular are very reactive and commonly react until equilibrium is attained. Consequently, the peralkaline melt fraction is commonly preserved only in the isolated melt and mineral inclusions.

We demonstrate that the differences between melt fractions that can be seen most clearly in differing melt inclusion compositions are also visible in the composition of the resulting ore-forming and accessory minerals, and are visible on scales from a few micrometers to hundreds of meters.