Derivation of Structure Parameters of Temperature and Humidity in the Convective Boundary Layer from Large-Eddy Simulations and Implications for the Interpretation of Scintillometer Observations     

Björn Maronga  Arnold F. Moene  Daniëlle van Dinther  Siegfried Raasch  Fred C. Bosveld  Beniamino Gioli 《Boundary-Layer Meteorology》2013,148(1):1-30

We derive the turbulent structure parameters of temperature $C_{T}^2$ and humidity $C_q^2$ from high-resolution large-eddy simulations (LES) of a homogeneously-heated convective boundary layer. Boundary conditions and model forcing were derived from measurements at Cabauw in The Netherlands. Three different methods to obtain the structure-parameters from LES are investigated. The shape of the vertical structure-parameter profiles from all three methods compare well with former experimental and LES results. Depending on the method, deviations in the magnitude up to a factor of two are found and traced back to the effects of discretization and numerical dissipation of the advection scheme. Furthermore, we validate the LES data with airborne and large-aperture scintillometer (LAS) measurements at Cabauw. Virtual path measurements are used to study the variability of $C_{T}^2$ in the mixed layer and surface layer and its implications for airborne and LAS measurements. A high variability of $C_{T}^2$ along a given horizontal path in the LES data is associated with plumes (high values) and downdrafts (low values). The path average of $C_{T}^2$ varies rapidly in time due to the limited path length. The LES results suggest that measured path averages require sufficient temporal averaging and an adequate ratio of path length to height above the ground for the LAS in order to approach the domain average of $C_{T}^2$ .  相似文献   

Cross-national patterns of governance mechanisms in nationally determined contributions (NDCs) under the Paris Agreement     

Maria Jernnäs  Jens Nilsson  Björn-Ola Linnér  Andreas Duit 《Climate Policy》2013,13(10):1239-1249

ABSTRACT

The continuous submission and scaling-up of Nationally Determined Contributions (NDCs) constitutes a key feature of the Paris Agreement. In their NDCs, states propose governance mechanisms for implementation of climate action, in turn distinguishing appropriate roles for the state in climate governance. Clarity on Parties’ suggested roles for the state makes explicit assumptions on the premise of climate policy, in turn contributing to enhanced transparency in negotiations on the scaling-up of NDCs. This also speaks to ongoing debates on roles for the state in climate governance literature. This article identifies the governance mechanisms proposed by states in their NDCs and the roles for the state envisioned by those governance mechanisms, and also examines how cross-national patterns of roles for the state break or converge with conventional patterns of international politics. The analysis shows that states propose a plurality of roles, which to different extents may be complementary or conflictual. We conclude that income, region, and the Annexes under the United Nations Framework Convention on Climate Change (UNFCCC) are important for understanding suggested roles for the state, but that there are nuances to be further explored. We argue that this paper has three key findings: i) a majority of states rely on market mechanisms to implement their NDCs while rules on implementation and assessment of market mechanisms are still an outstanding issue in the negotiations, meaning that resolving this issue will be essential; ii) the process for evaluating and assessing qualitative governance mechanisms needs to be specified; and iii) increased awareness of differing views on the state’s roles makes explicit different perspectives on what constitutes an ambitious and legitimate contribution to combating climate change.

Key policy insights

• A majority of states (> 75%) envision the state as regulator (creating and strengthening legislation), market facilitator (creating and maintaining market structures), or facilitator (creating more favourable material conditions for climate-friendly behaviour).

• Greater awareness of differing views on roles for the state can increase understanding of different perspectives on ambition and legitimacy of contributions, in turn facilitating trust in negotiations.

• A distinction between substantive and procedural qualitative governance mechanisms and their function and interaction would facilitate the stocktaking dialogues.

  相似文献   

On the deep minimum state in the Seyfert galaxy MCG−6-30-15     

Christopher S. Reynolds  Jörn Wilms  Mitchell C. Begelman  Rüdiger Staubert  Eckhard Kendziorra 《Monthly notices of the Royal Astronomical Society》2004,349(4):1153-1166

  相似文献   

Filament activation and magnetic reconnection     

Deng  Yuanyong  Lin  Yong  Schmieder  Brigitte  Engvold  OddbjØrn 《Solar physics》2002,209(1):153-170

Solar Physics - A curved filament in a decaying active region (AR&;nbsp;8329) was observed on 9 September 1998 with a combination of several instruments. The main data base is a 4-hour long time...  相似文献   

Calibration of estuarine current crosses     

Björn Kjerfve 《Estuarine, Coastal and Shelf Science》1982,15(5):553-559

Tethered current crosses are simple, reliable tools in making measurements of estuarine currents in the absence of surface waves. The standard error of the estimate of current speed is less than 5 cm s^?1 for the particular crosses and weights used in a calibration experiment. The useful velocity range of these current crosses was 8–147 cm s^?1, corresponding to a measured angle, α, from 2° to 30°. Regression of the independently measured current speed on $\text{(tan α)}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ yielded coefficients of determination greater than 0·94, indicating that the drag coefficient is not a function of current speed. However, the calculated drag coefficients varied widely from 0·66 to 2·55, depending on the particular combination of cross and weight, varying drastically from the commonly assumed drag coefficient value of 1·12. Thus, in using current crosses, it is imperative to calibrate each cross against a current meter reading to determine an appropriate value for the drag coefficient for a particular current cross and weight.  相似文献   

X-ray,Hα, and radio observations of the two-ribbon flare of 16 May, 1981     

F. Fárník  J. Kaastra  B. Kálmán  M. Karlický  C. Slottje  B. Valniček 《Solar physics》1983,89(2):355-378

The paper is a contribution to the study of two-ribbon flares. A variety of observational material, i.e. Hα pictures, radio spectrum in the frequency band of 150–1000 MHz, radio map at 6 cm, fluxes at other frequencies, magnetograms and X-ray flux in a broad energy interval, enabled us to study the development of the 16 May, 1981 flare. The onset of the flare could be described by the model of Van Tend and Kuperus. A diminishing of the magnetic shear during the activation of the filament was observed. From radio and X-ray data it was found that pulsed acceleration took place in the region under the rising filament, the electrons propagating in a limited region both upwards to greater heights and downwards into the footpoints. Internal oscillations of the filament were observed. A manifestation of the primary process of interplanetary shock-wave generation was found. The 6 cm radio sources could be localized in the footpoints of magnetic loops.  相似文献   

Formation of De Geer moraines and implications for deglaciation dynamics     

Eiliv Larsen  Oddvar Longva  Bjrn A. Follestad 《第四纪科学杂志》1991,6(4):263-277

De Geer moraines are very common in the Møre area, western Norway. These moraines occur below the marine limit and outside the Younger Dryas ice limit and occupy tributaries that connect the main fjords through the mountain passes. During deglaciation, ice in these tributaries flowed to the major ice streams. Sections across three De Geer moraines show that the ridges are composed of diamictons and fine-grained sediment, partly in stacked sequences. The diamicton units are interpreted as being composed of water-lain tills, lodgements tills and subaqueous flow deposits. The fine-grained sediment is though to have formed in a proglacial marine environment. Clast fabric of diamictons and deformation structures in underlying sands show that depositional directions for diamicton units and the direction of deformation for the sands is perpendicular to the ridge crests. Mainly based on this evidence, the ridges are thought to have formed by push at the glacier grounding line. The formation of transverse ridges (relative to ice flow) do occur in basal crevasses on modern glaciers, as do swarms of ridges along the front of retreating glaciers. The first mechanism of deposition does not seem to explain the ridges studied in the present paper and hence the importance of this process in the formation of De Geer moraines is questioned. The De Geer moraines were deposited by ice lobes advancing from one main fjord into another; therefore by studying the drainage pattern of the tributary lobes and their sequence of deglaciation, many features of the style of deglaciation of the ice sheet across the area can be determined. The northwestern part of the area was deglaciated earliest. After that, deglaciation proceeded to the southwest parallel to the coast. Subsequently the outer and the central part of Romsdalsfjorden were deglaciated causing ice to drain towards this fjord from both the north and south. The last fjord to be deglaciated was Storfjorden in the south.  相似文献   

Are all maps mental maps?     

Axelsen Bjørn  Jones Michael Dr. 《GeoJournal》1987,14(4):447-464

The article focuses on the way in which map content reflects the cartographer's World view and system of values. Different World views are illustrated historically. Examples of topographical, land-use and vegetation maps from different parts of the World indicate the prevalence of Eurocentric perceptions in cartography. Different geological maps of Norden show how the visual image depends on the classification system adopted. All maps are mental maps in that their content is culturally determined and ethnocentric in origin.  相似文献   

The evershed flow in the transition region chromosphere-photosphere     

J. Bønes  P. Maltby 《Solar physics》1978,57(1):65-71

The Mgb₁ line profile is studied as a function of spatial position in the sunspot region. Comparing the wavelengths of the core and the wing, in and just outside the penumbra, a reversal in the shift is detected. The displacements of the core and the wing are interpreted as horizontal motions directed into the spot in the chromosphere and as a flow directed out of the spot in deeper layers.Systematic wavelength shifts are detected in the line core in some regions outside the penumbra. This is interpreted as a chromospheric velocity field usually directed horizontally away from the spot.  相似文献   

A magnetostratigraphic comparison between 14C years and varve years during the Late Weichselian,indicating significant differences between the time-scales     

Svante Bjrck  Per Sandgren  Bjrn Holmquist 《第四纪科学杂志》1987,2(2):133-140

A ¹⁴C-dated magnetostratigraphy of absolute declination and inclination between 12500 and 10000 ¹⁴C yr BP was recently developed for southern Sweden. Recently also the Swedish geochronological time-scale, based on c. 11 500 annually deposited clay-varves, was connected with the present. It should therefore be possible to compare the two chronologies with a reliable magnetostratigraphic record in an appropriate clay-varve section. We have found such a site within the Middle Swedish end-moraine zone. Statistical correlations between the two independently dated time-scales suggest that at 10500–10200 ¹⁴Cy r BP the varve chronology exceeds the ¹⁴C chronology by the order of 500-600 varve yr. Other correlations indicate that the difference between the two chronologies was less at 11000 ¹⁴C yr BP, and further correlations between the time-scales at 12000 ¹⁴C yr BP suggest that the difference between the chronologies increased steadily from 12000 to 10000 ¹⁴C yr BP. If these correlations are correct they imply that the ¹⁴C production rate increased steadily during the Late Weichselian.  相似文献