High-resolution precipitation and temperature downscaling for glacier models

The spatial resolution gap between global or regional climate models and the requirements for local impact studies motivates the need for climate downscaling. For impact studies that involve glacier modelling, the sparsity or complete absence of climate monitoring activities within the regions of interest presents a substantial additional challenge. Downscaling methods for this application must be independent of climate observations and cannot rely on tuning to station data. We present new, computationally-efficient methods for downscaling precipitation and temperature to the high spatial resolutions required to force mountain glacier models. Our precipitation downscaling is based on an existing linear theory for orographic precipitation, which we modify for large study regions by including moist air tracking. Temperature is downscaled using an interpolation scheme that reconstructs the vertical temperature structure to estimate surface temperatures from upper air data. Both methods are able to produce output on km to sub-km spatial resolution, yet do not require tuning to station measurements. By comparing our downscaled precipitation (1 km resolution) and temperature (200 m resolution) fields to station measurements in southern British Columbia, we evaluate their performance regionally and through the annual cycle. Precipitation is improved by as much as 30% (median relative error) over the input reanalysis data and temperature is reconstructed with a mean bias of 0.5°C at locations with high vertical relief. Both methods perform best in mountainous terrain, where glaciers tend to be concentrated.     

The Development of Camera Calibration Methods and Models

Correction for image distortion in cameras has been an important topic for as long as users have wanted to faithfully reproduce or use observed information. Initially the main application was mapping. While this task continues today, other applications also require precise calibration of cameras, such as close range three dimensional measurement and many two dimensional measurement tasks. In the past, the cameras used were few in number and highly expensive whereas today a typical large industrial company will have many inexpensive cameras being used for highly important measurement tasks. Cameras are used more today than they ever were but the golden age of camera calibration for aerial mapping is now well in the past. This paper considers some of the key developments and attempts to put them into perspective. In particular the driving forces behind each improvement have been highlighted.     

Characterisation of the carbonate content of atmospheric aerosols

A programme of aerosol sampling by dichotomous sampler has been undertaken with analysis of soluble ions plus carbonate. The technique for carbonate involved release of CO₂ by HCl vapour and quantitative measurement of the CO₂ by FTIR spectroscopy. The method is suitable for amounts down to below 10g CO₃ ^2- per filter. The prevailing atmospheric levels in an urban area were found to be below 1g m^-3. Information on the particle size from the dichotomous sampler was supplemented by use of a cascade impactor. Although CaCO₃ is clearly the dominant species initial analyses demonstrated higher carbonate levels than could be accounted for on the basis of the concentrations of calcium and magnesium ions which are the most likely cations in mineral carbonates. Analysis with and without heating to 100°C in a vacuum oven demonstrates the presence of carbonate in volatile form. This could be due to carbon dioxide adsorbed onto particulate matter such as soot.     

Trace element partitioning during high-P partial melting and melt-rock interaction; an example from northern Fiordland, New Zealand

Pods of granulite facies dioritic gneiss in the Pembroke Valley, Milford Sound, New Zealand, preserve peritectic garnet surrounded by trondhjemitic leucosome and vein networks, that are evidence of high‐P partial melting. Garnet‐bearing trondhjemitic veins extend into host gabbroic gneiss, where they are spatially linked with the recrystallization of comparatively low‐P two‐pyroxene‐hornblende granulite to fine‐grained high‐P garnet granulite assemblages in garnet reaction zones. New data acquired using a Laser Ablation Inductively Coupled Plasma Mass Spectrometer (LA‐ICPMS) for minerals in various textural settings indicate differences in the partitioning of trace elements in the transition of the two rock types to garnet granulite, mostly due to the presence or absence of clinozoisite. Garnet in the garnet reaction zone (gabbroic gneiss) has a distinct trace element pattern, inherited from reactant gabbroic gneiss hornblende. Peritectic garnet in the dioritic gneiss and garnet in trondhjemitic veins from the Pembroke Granulite have trace element patterns inherited from the melt‐producing reaction in the dioritic gneiss. The distinct trace element patterns of garnet link the trondhjemitic veins geochemically to sites of partial melting in the dioritic gneiss.     

Discriminating between background and mine-impacted groundwater at the Phoenix mine,Nevada USA

Differentiating between mineralized and non-mineralized background groundwater chemistry at a mine site can be challenging if there is an overprint of past and/or current mining on naturally mineralized conditions. At the Phoenix mine in the Copper Canyon mining district of Nevada, quantile–quantile H⁺/SO₄ plots were used to segregate four wells clearly impacted by historical mining activity. The mineralogy of rock at the elevation of the well screen interval was used to partition the 53 remaining wells into mineralized and non-mineralized populations. For each class, groundwater chemistry was examined to identify if SO₄ and H⁺ trends were stable (unimpacted) or increasing (impacted). Then each well was mapped as one of four resulting groundwater types across the mine site, defining the spatial extent of the different groups. Several groundwater regions were identified. A group of mineralized, mine-impacted wells (Type II) are located in Philadelphia Canyon adjacent to the Cu leach facility, with the anthropogenically impacted area bounded by several hydrologically downgradient, mineralized, unimpacted wells (Type I) to the south and east. There is a set of non-mineralized, impacted wells (Type III) downgradient from the tailings pond facility, where a historical release of SO₄ is apparent in the well record. However, in some downgradient wells the tailings pond pump-back mitigation system has resulted in recovery of the groundwater quality to a non-mineralized background condition. Finally, in the vicinity of the Reona heap leach pad, there is a group of non-mineralized, unimpacted wells (Type IV). Not surprisingly, most mineralized wells (Types I and II) are located in or near mined areas, while non-mineralized wells (Types III and IV) tend to be in the southern portion of the facility in the alluvia of Buffalo and Reese River valleys.     

The Salem,Oregon L6 Chondrite

Abstract— The Salem, Oregon meteorite fall of 1:05 a.m. (07:05 GMT) May 13, 1981 (lat. 44°58′45″N., long. 123°58′10″W) was heard by two observers. A 22.2 g fragment was recovered immediately from a total recovery of 61.4 g from a single individual. No other fall related phenomena were observed. It is a heavily fusion-crusted, shock-veined, L6 chondrite.     

A Frame Grabber Related Error In Subpixel Target Location

The accuracy of subpixel target image location is an important factor that contributes to the overall precision of three dimensional measurement when using CCD cameras. This shorter contribution reports the effect of an electrical adjustment of a frame grabber that results in a significant and systematic error in the accuracy of target image location using some target location methods.     

Determination of dead-time in photon counting photometers by a polarimetric method

Experiments are described which demonstrate that the dead-time constant associated with a photon counting stellar photometer/polarimeter is readily determinable by the application of the Malus law. It is also proposed that corrections for dead-time losses should be applied by an iteration technique to the exact equation rather than using the available approximation formulae.     

On the Regulation of Climate: A Sulfate Particle Feedback Loop Involving Deep Convection

We propose a climate stabilizing feedback loop involving biogenic sulfur. The mechanism is similar to the "CLAW" hypothesis (Charlson et al., 1987) but does not require the active participation of the ocean biota. The magnitude of the feedback response in this loop is derived by convective transport of biogenic sulfur over tropical oceans into the middle and high troposphere. Once aloft, the sulfur is oxidized into low-volatile species which nucleate new particles that later subside back into the subtropical marine boundary layer (MBL) and serve as cloud condensation nuclei (CCN). The MBL clouds are susceptible to albedo modification by changes in CCN concentrations (Platnick and Twomey, 1995). We envision that as global temperatures rise the sea surface warms, convective mass transport of sulfur will rise and the increased mass of sulfur in the upper troposphere will lead to higher numbers of particles or a shift in the particle size distribution to larger sizes. In either case, there is an increase in the number of particles large enough to act as CCN in the air subsiding backinto the MBL. The increase in CCN increases the cloud albedo, decreases the solar input to the surface and the temperature decreases. More measurements are needed to confirm whether the magnitude of increased sulfur carried through the loop as a function of increased sea surface temperature is sufficient to close the loop and regulate the climate.