Temporal sampling strategies and uncertainty in calibrating a conceptual hydrological model for a small boreal catchment

How much data is needed for calibration of a hydrological catchment model? In this paper we address this question by evaluating the information contained in different subsets of discharge and groundwater time series for multi‐objective calibration of a conceptual hydrological model within the framework of an uncertainty analysis. The study site was a 5·6‐km² catchment within the Forsmark research site in central Sweden along the Baltic coast. Daily time series data were available for discharge and several groundwater wells within the catchment for a continuous 1065‐day period. The hydrological model was a site‐specific modification of the conceptual HBV model. The uncertainty analyses were based on a selective Monte Carlo procedure. Thirteen subsets of the complete time series data were investigated with the idea that these represent realistic intermittent sampling strategies. Data subsets included split‐samples and various combinations of weekly, monthly, and quarterly fixed interval subsets, as well as a 53‐day ‘informed observer’ subset that utilized once per month samples except during March and April—the months containing large and often dominant snow melt events—when sampling was once per week. Several of these subsets, including that of the informed observer, provided very similar constraints on model calibration and parameter identification as the full data record, in terms of credibility bands on simulated time series, posterior parameter distributions, and performance indices calculated to the full dataset. This result suggests that hydrological sampling designs can, at least in some cases, be optimized. Copyright © 2009 John Wiley & Sons, Ltd.     

Two new species of the marine genus Limnodriloides and a record of Tubificoides fraseri Brinkhurst (Oligochaeta: Tubificidae) from New Zealand

We characterised seasonal and ontogenetic changes in diet and prey energy density of rainbow trout (Oncorhynchus mykiss) in Lake Rotoiti, New Zealand, to better understand the prey requirements of trout in central North Island lakes. Common smelt (Retropinna retropinna) was the dominant prey item of rainbow trout larger than 200 mm (77.8% of diet by weight), followed by kōura (freshwater crayfish Paranephrops planifrons; 6.3%), common bully (Gobiomorphus cotidianus; 5.5%), and kōaro (Galaxias brevipinnis; 3.4%). Juvenile rainbow trout (<200 mm) consumed amphipods, aquatic and terrestrial insects, oligochaetes, tanaid shrimps, and smelt. Trout consumed kōaro only in autumn and winter; consumption of other species did not vary seasonally. The maximum size of smelt consumed increased with increasing trout size, but trout continued to consume small smelt even as large adults. Consumption of larger prey items (kōaro and kōura) also increased with increasing trout size. This study indicates the importance of smelt for sustaining rainbow trout populations, as predation on other species was relatively low. These findings provide a basis for bioenergetic modelling of rainbow trout populations in lakes of the central North Island of New Zealand.     

Combining limnology and palaeolimnology to investigate recent regime shifts in a shallow,eutrophic lake

In this study, we demonstrate that an integrated approach, combining palaeolimnological records and limnological monitoring data, can increase our understanding of changing ecological patterns and processes in shallow lakes. We focused on recent regime shifts in shallow Lake Krankesjön, southern Sweden, including the collapse of the clear-water state in 1975 and its subsequent recovery in the late 1980s. We used diatom, hydrocarbon and biogenic silica sediment records, in concert with limnological data sets on nutrient concentrations, water clarity, chlorophyll-a and water depth, to investigate the shifts. The shift from clear to turbid conditions was abrupt and occurred over 1 to 2 years, whereas recovery of the clear-water state was more gradual, taking 4–5 years. In 1978, shortly after the first regime shift in water clarity, the diatom community underwent a significant shift. It became less diverse, with decreased abundance of epiphytic and planktonic taxa. Despite rising phosphorus concentrations and lower abundance of submerged macrophytes, Lake Krankesjön has remained in the clear-water state over the past 20 years, although this state seems to be increasingly unstable and susceptible to collapse. The complex reactions of the entire lake ecosystem to major changes in lake-water clarity, as shown by the palaeolimnological variables investigated in this study, emphasize the importance of careful lake and catchment management if a stable, clear-water state is desired.     

Anomalous Fe II spectral effects and high H I Lyα temperature in gas blobs near η Carinae

We consider the origin of the anomalously high intensity of the ultraviolet Fe II λλ2507/2509 Å lines observed with high spatial and spectral resolutions from gas blobs (GBs) near η Carinae. This rare effect in stellar spectra is attributable to a combination of several factors: (1) the high hydrogen density(>10⁸ cm^?3) that ensures the blockingof the Lyman continuum by GBs and, accordingly, the formation of a cold H I region with completely ionized Fe atoms; (2) the small distance between the GBs and the central star that ensures a high (>8000–10000 K) Lyα H spectral temperature, which photoexcites Fe II selectively; and (3) the population of Fe II levels and, accordingly, the opening of a stimulated emission channel, which together with spontaneous transitions creates a radiative cycle where a single Fe II ion can multiply absorb Lyα emission.     

Vertical crustal motion observed in the BIFROST project

This paper reports from investigations on the robustness of estimated rates of intraplate motion from the continuous GPS project BIFROST (Baseline Inferences from Fennoscandian Rebound Observations, Sealevel and Tectonics). We study loading effects due to ocean, atmosphere and hydrology and their impact on estimated rate parameters. We regularly find the admittance of a modelled perturbation at less than fifty percent of the full effect. We think that the finding relates to a difficult noise situation at all periods, and that a satisfying model for the dominating noise source has not been found yet. An additional reason for low admittance is found in the mapping process of the no-fiducial network solution into a conventional reference frame.     

Spectral scan of the star-forming region DR21(OH). Observations and LTE analysis

Seventy-eight molecules have been detected as a result of a spectral survey of the star-forming region DR21(OH) at 84–115 GHz. The abundances of most molecules are typical of those in the dense cores of molecular clouds. The rotational temperatures derived using the lines of most molecules fall in the range 9–56 K, which is also typical for dense cores. However, emission from high-lying levels of methanol and sulfur dioxide was detected; since the rotational temperatures for methanol and sulfur dioxide are 252 and 186 K, this indicates the presence of hot regions. Another fact indicating the existence of hot regions is the detection of CH₃OCHO, CH₃CH₂OH, and CH₃OCH₃, which have thus far been observed only in hot cores and shock-heated regions. An interesting result is the tentative detection of the J = 2 − 1, v = 1 SiO line, with the upper level energy of 1775 K. This is probably a maser line, similar to but weaker than the well-known SiO masers in the star-forming regions Orion-KL,W51(N), and Sgr B2(N).     

An Auxiliary Tool to Determine the Height of the Boundary Layer

Results from radiosoundings, performed both over land and over sea, show that the ascent rate of a radiosounding balloon, the vertical velocity of the balloon, can be used to determine the height of the boundary layer. In many cases the balloon has a higher ascent rate in the boundary layer and a lower, less variable, ascent rate above. The decrease in ascending velocity appears as a jump at the top of the boundary layer. Two examples of potential temperature profiles for unstable stratification and one profile for stable conditions are shown with the corresponding ascent rates. A comparison between the boundary-layer height determined from potential temperature profiles and from ascent rates is presented for a larger dataset. The different ascent rates of the balloon in the boundary layer and above can be explained by a decrease in drag on the balloon in combination with a lowering of the critical Reynolds number in the boundary layer caused by turbulence. Hence, by simply logging the time from release of a radiosonde, it is possible to obtain additional information that can be used to estimate the height of both the unstable and stable boundary layers.     

The Cost of Using Global Warming Potentials: Analysing the Trade off Between CO2, CH4 and N2O

The metric governing the trade-off between different greenhouse gases in the Kyoto Protocol, the Global Warming Potentials (GWPs), has received ample critique from both scientific and economic points of view. Here we use an integrated climate-economic optimization model to estimate the cost-effective trade-off between CO₂, CH₄ and N₂O when meeting a temperature stabilization target. We then estimate the increased cost from using GWPs when meeting the same temperature target. Although the efficient valuation of the gases differs significantly from their respective GWPs, the potential economic benefit of valuing them in a more correct way amounts to 3.8 percent of the overall costs of meeting the temperature stabilization target in the base case. In absolute value, this corresponds to an additional net present value cost of US$₂₀₀₀100 billion. To corroborate our findings we perform a Monte Carlo-analysis where several key parameters are randomly varied simultaneously. The result from this exercise shows that our main result is robust to a wide range of changes in the key parameter values, giving a median economic loss from using GWPs of 4.2 percent.     

Economics- and physical-based metrics for comparing greenhouse gases

A range of alternatives to the Global Warming Potential (GWP) have been suggested in the scientific literature. One of the alternative metrics that has received attention is the cost-effective relative valuation of greenhouse gases, recently denoted Global Cost Potential (GCP). However, this metric is based on complex optimising integrated assessment models that are far from transparent to the general scientist or policymaker. Here we present a new analytic metric, the Cost-Effective Temperature Potential (CETP) which is based on an approximation of the GCP. This new metric is constructed in order to enhance general understanding of the GCP and elucidate the links between physical metrics and metrics that take economics into account. We show that this metric has got similarities with the purely physical metric, Global Temperature change Potential (GTP). However, in contrast with the GTP, the CETP takes the long-term temperature response into account.