Does increasing the spatial resolution of a regional climate model improve the simulated daily precipitation?

Three different resolution (50, 12, and 1.5 km) regional climate model simulations are compared in terms of their ability to simulate moderate and high daily precipitation events over the southern United Kingdom. The convection-permitting 1.5-km simulation is carried out without convective parametrisation. As in previous studies, increasing resolution (especially from 50 to 12 km) is found to improve the representation of orographic precipitation. The 50-km simulation underestimates mean precipitation over the mountainous region of Wales, and event intensity tends to be too weak; this bias is reduced in both the 12- and 1.5-km simulations for both summer and winter. In south–east England lowlands where summer extremes are mostly convective, increasing resolution does not necessary lead to an improvement in the simulation. For the 12-km simulation, simulated daily extreme events are overly intense. Even though the average intensity of summer daily extremes is improved in the 1.5-km simulation, this simulation has a poorer mean bias with too many events exceeding high thresholds. Spatial density and clustering of summer extremes in south–east England are poorly simulated in both the 12- and 1.5-km simulations. In general, we have not found any clear evidence to show that the 1.5-km simulation is superior to the 12-km simulation, or vice versa at the daily level.     

Piecemeal or combined? Assessing greenhouse gas mitigation spillovers in US forest and agriculture policy portfolios

ABSTRACT

Forest and agricultural sector response to comprehensive climate policy is well represented in the literature. Less analysis has been devoted to piecemeal solutions. We use the Forest and Agriculture Sector Optimization Model with Greenhouse Gases (FASOMGHG) to project the individual and combined effect of three existing U.S. Department of Agriculture programmes with potential to increase greenhouse gas (GHG) mitigation. We find that a combined policy scenario may achieve greater mitigation than individual constituent programmes, suggesting the possibility of complementary spillover effects in some periods. Mitigation varies over time, however, and some periods experience net emissions as markets and management practices respond to initial policy shocks. The regional distribution of GHG mitigation also varies between policy scenario. Differences in the magnitude and imputed cost of mitigation under each scenario, generating negative values for some programmes and time periods, reinforces the need to evaluate portfolio design to cost-effectively achieve near-term GHG mitigation.

Key policy insights

• Increased near-term GHG mitigation in the forest and agriculture sectors in the US may be possible by expanding or refocusing the emphasis of existing programmes.

• Implementing several such forest and agricultural programmes simultaneously may lead to greater GHG mitigation than when implemented separately, indicating the possibility of positive spillover effects.

• Programmes targeted to agricultural management may hold outsized potential to achieve near-term GHG mitigation; Policies aimed at influencing land use conversion appear to be more vulnerable to reversion and subject to larger inter-annual swings.

• The staged implementation of programmes could also be useful, helping to encourage increased mitigation (or the retention of already achieved mitigation) over time as markets re-equilibrate to initial shocks.

• Though the particular scenarios assessed here are unique to the US, our findings may be applicable to other locations outside the US where land management is influenced by individual market actors and there is competition between forest and agricultural land uses.

     

1961-2012年6-8月内蒙古降水异常及环流特征分析

利用内蒙古自治区100个站1961-2012年6-8月各月降水量资料,以降水距平百分率划分了单站和全区各月的多、少雨年份,分析了6-8月全区多雨和少雨站点百分率变化特征。针对异常多雨和少雨年份,探讨了同期北半球欧亚地区大气环流的分布特征。结果表明：8月降水存在减少趋势,6月和7月则主要表现为阶段性多（少）雨,且少雨年多于多雨年。在多雨月份,100hPa高度场上,欧亚中高纬度呈径向环流分布,极涡较弱。其中,6月为两槽一脊型,内蒙古位于高压脊区前部,7、8月为两脊一槽型,内蒙古位于高压脊区后部;500 hPa高度场上,6月,亚洲区主要表现为变形场,内蒙古处于锋生区,或是亚洲中高纬度环流为两脊一槽型,内蒙古处于两高之间的宽广低槽中, 7月、8月欧亚中高纬度环流主要表现为东高西低,内蒙古自治区位于低压槽区中;850hPa流场图上内蒙古为气旋性切变区域或为风场辐合区域控制。在少雨月份,100hPa和500hPa高度场上,欧亚中高纬度呈纬向环流分布,极涡较强,内蒙古位于南亚高压北边的正距平区域;850hPa流场图上表现为弱的风场特征,无明显的水汽输送。     

Sonic Anemometer as a Small Acoustic Tomography Array

The spatial resolution of a sonic anemometer is limited by the distance between its transducers, and for studies of small-scale turbulence and theories of turbulence, it is desirable to increase this spatial resolution. We here consider resolution improvements obtainable by treating the sonic anemometer as a small tomography array, with application of appropriate inverse algorithms for the reconstruction of temperature and velocity. A particular modification of the sonic anemometer is considered when the number of its transducers is doubled and the time-dependent stochastic inversion algorithm is used for reconstruction. Numerical simulations of the sonic anemometer and its suggested modification are implemented with the temperature and velocity fields modelled as discrete eddies moving through the sonic’s volume. The tomographic approach is shown to provide better reconstructions of the temperature and velocity fields, with spatial resolution increased by as much as a factor of ten. The spatial resolution depends on the inverse algorithm and also improves by increasing the number of transducers.     

A statistical power analysis of woody carbon flux from forest inventory data

At a national scale, the carbon (C) balance of numerous forest ecosystem C pools can be monitored using a stock change approach based on national forest inventory data. Given the potential influence of disturbance events and/or climate change processes, the statistical detection of changes in forest C stocks is paramount to maintaining the net sequestration status of these stocks. To inform the monitoring of forest C balances across large areas, a power analysis of a forest inventory of live/dead standing trees and downed dead wood C stocks (and components thereof) was performed in states of the Great Lakes region, U.S. Using data from the Forest Inventory and Analysis (FIA) program of the U.S. Forest Service, it was found that a decrease in downed wood C stocks (?1.87 Mg/ha) was nearly offset by an increase in standing C stocks (1.77 Mg/ha) across the study region over a 5-year period. Carbon stock change estimates for downed dead wood and standing pools were statistically different from zero (α?=?0.10), while the net change in total woody C (?0.10 Mg/ha) was not statistically different from zero. To obtain a statistical power to detect change of 0.80 (α?=?0.10), standing live C stocks must change by at least 0.7 %. Similarly, standing dead C stocks would need to change by 3.8 %; while downed dead C stocks require a change of 6.9 %. While the U.S.’s current forest inventory design and sample intensity may not be able to statistically detect slight changes (<1 %) in forest woody C stocks at sub-national scales, large disturbance events (>3 % stock change) would almost surely be detected. Understanding these relationships among change detection thresholds, sampling effort, and Type I (α) error rates allows analysts to evaluate the efficacy of forest inventory data for C pool change detection at various spatial scales and levels of risk for drawing erroneous conclusions.     

The Meteoritical Bulletin,No. 102

Meteoritical Bulletin 102 contains 3141 meteorites including 12 falls (Boumdeid (2003), Boumdeid (2011), Braunschweig, Chelyabinsk, Dongyang, Draveil, Heyetang, Indian Butte, Katol, Ladkee, Ouadangou, Xining), with 2611 ordinary chondrites, 264 HED achondrites, 124 carbonaceous chondrites, 30 ureilites, 20 Martian meteorites, 16 primitive achondrites, 16 Rumuruti chondrites, 15 mesosiderites, 12 iron meteorites, 10 lunar meteorites, 9 enstatite chondrites, 4 enstatite achondrites, 4 Pallasites, 4 ungrouped achondrites, and 2 angrites, and with 1708 from Antarctica, 956 from Africa, 294 from South America, 126 from Asia, 47 from North America, 6 from Europe (including Russia), and 4 from Oceania. Information about approved meteorites can be obtained from the Meteoritical Bulletin Database (MBD) available on line at http://www.lpi.usra.edu/meteor/ .     

Mineralogy,petrology, and distribution of meteorites at the Whitecourt crater,Alberta, Canada

The Whitecourt meteorite impact crater, Alberta, Canada is a rare example of a well‐preserved small impact structure, with which thousands of meteorite fragments are associated. As such, this crater represents a unique opportunity to investigate the effect of a low‐energy impact event on an impacting iron bolide. Excellent documentation of meteorite fragment locations and characteristics has generated a detailed distribution map of both shrapnel and regmaglypted meteorite types. The meteorites' distribution, and internal and external characteristics support a low‐altitude breakup of the impactor which caused atmospherically ablated (regmaglypted) meteorites to fall close to the crater and avoid impact‐related deformation. In contrast, shrapnel fragments sustained deformation at macro‐ and microscales resulting from the catastrophic disruption of the impactor. The impactor was significantly fragmented along pre‐existing planes of weakness, including kamacite lamellae and inclusions, resulting in a bias toward low‐mass (<100 g) fragments. Meteorite mineralogy was investigated and the accessory minerals were found to be dominated by sulfides and phosphides with rare carlsbergite, consistent with other low‐Ni IIIAB iron meteorites. Considerations of the total mass of meteoritic material recovered at the site relative to the probable fraction of the impactor that was preserved based on modeling suggests that the crater was formed by a higher velocity, lower mass impactor than previously inferred.     

A reference typology of low alkalinity lakes in the UK based on pre-acidification diatom assemblages from lake sediment cores

This paper has two aims: (1) to show for the first time how a natural typology can be established using palaeoecological methods; and (2) to show how it can be used in lake restoration studies with respect to the definition of recovery targets for acidified lakes. By defining the characteristic reference assemblages for low alkalinity site types rather than for a specific site it allows success to be measured more broadly, unconstrained by the specific composition of the pre-acidification flora. We analyse statistically the pre-acidification diatom assemblages of sediment cores from 121 low alkalinity lakes in the UK in order to assess whether a reference typology for such lakes can be defined on the basis of their diatom floras. We use samples dating to ~1850 AD to represent pre-acidification conditions. The results show that three main clusters can be identified, two dominated by benthic taxa (Clusters 1 and 3) and one dominated by planktonic taxa (Cluster 2). Cluster 1 is characterised by taxa such as Brachysira vitrea, Cymbella microcephala and Fragilaria spp., Cluster 2 by Cyclotella comensis, C. radiosa, Asterionella formosa, Aulacoseira subarctica and Achnanthes minutissima and Cluster 3 by Eunotia incisa, Frustulia rhomboides var. saxonica, Fragilaria virescens var. exigua, and Cymbella perpusilla. Although environmental data for 1850 AD are not available it is apparent from the contemporary distribution of the taxa in the different clusters that Cluster 2 represents the most alkaline pre-acidification conditions. Some sites in this cluster have been acidified, but some, especially the larger, deeper lakes have been enriched. Cluster 1 includes sites that contain diatoms with relatively high pH optima (pH 6.4–7.4) whereas Cluster 3 sites contain diatoms with the lowest pre-acidification pH conditions in the data-set. Sites in this cluster also have the lowest base cation concentrations at the present day and include the sites in the UK that have been most affected by acid deposition.     

Callocystites fresti sp. nov., and the significance of ambulacral branching in the Callocystitidae (Echinodermata,Glyptocystitoida)

Callocystites fresti sp. nov. is characterized by an elongate theca, protuberant periproct and raised ambulacral facets. Ambulacral branching in Callocystites is isotomous, but left‐ and right‐handed branches occur because the ambulacral groove branches in the same direction twice, interrupting the regularly alternating branching to brachioles. Branching in Strobilocystites does not interrupt the alternation of brachioles and lateral food grooves always pass adoral to the first brachiole of each branch. Sphaerocystites branched as in Strobilocystites. Other morphological features suggest Callocystites, Sphaerocystites and Strobilocystites are not closely related. Callocystites has open infra‐lateral and lateral circlets and five ambulacra; Sphaerocystites and Strobilocystites have closed/modified circlets and four ambulacra. In Callocystites and Sphaerocystites the B and D ambulacra differ from the others and they have one hydropore; in Strobilocystites all four ambulacra are the same and the hydropore is double. All three genera have large, globular thecae. Ambulacral branching was a response to increased food‐gathering requirements. The following are phylogenetically informative callocystitid characters: truly open vs closed/modified plate circlets; number of pectinirhombs; number of ambulacra; presence vs absence of the ‘B D different’ pattern of primary brachioles; single vs double hydropore. In echinoderms with five ambulacra in a 2–1–2 pattern ambulacral homologies are unambiguous: the single amb is A (III). In echinoderms without this pattern or with less than five ambulacra the hydropore or a single gonopore is best for orientation. Both always occur in the CD (V‐I) interambulacrum. The position of the periproct is unreliable. Different patterns and numbers of ambulacra in Palaeozoic echinoderms render a single developmental sequence improbable. Cystoids (blastozoans) had radial water vessels in their ambulacra and added new ambulacral plates terminally. Functional morphological considerations suggest tube feet were essential for food gathering. Copyright © 2014 John Wiley & Sons, Ltd.     

A cystoid with two left facets: the significance of Tetracystis in the evolution and classification of the Callocystitidae (Echinodermata,Glyptocystitoida)

Revision of some North American Silurian callocystitid cystoids shows that Tetracystis Schuchert has the first two brachioles to the left in ambulacra B and D (B D different pattern), whereas Troosticystis Paul and Lovenicystis Regéll have only the first brachiole to the left in all four ambulacra (B–E the same pattern). ‘Apiocystites’ elegans Hall is transferred to Tetracystis because it has the B D different pattern. Lovenicystis kopfi sp. nov. is characterized by four short ambulacra. Salirocystis gen. nov. has the B D different pattern and two hydropores. All callocystitids that lack ambulacrum A are assigned to a new subfamily, the Tetracystinae; those with five ambulacra are referred to informally as ‘lepadocystines’. The previously recognized subfamily Callocystitinae is reduced in rank to a tribe within the ‘lepadocystines’. Preliminary character analysis suggests that the loss of ambulacrum A was the most significant evolutionary event within the family Callocystitidae, but has been overlooked in taxonomy. Character analysis also shows that all ‘lepadocystines’ had the B D different pattern of primary brachioles, which is retained in four tetracystine genera, Lepocrinites Conrad, Sphaerocystites Hall, Tetracystis and Salirocystis. Since Salirocystis has the plesiomorphic B D different pattern plus the apomorphic double hydropore, one cannot define a monophyletic taxon characterized by the B–E the same pattern plus one characterized by a double hydropore. Both alternatives are equally parsimonious. Here a new monophyletic tribe Lipsanocystini is defined characterized by a double hydropore. The B–E the same pattern evolved independently twice. Among current characters the loss of ambulacrum A, development of the B–E the same pattern and development of two hydropores are the most significant evolutionary events. Number of periproct border plates, length and structure of ambulacra are less significant. Copyright © 2014 John Wiley & Sons, Ltd.