Top PDF An improved representation of physical permafrost dynamics in the JULES land surface model

An improved representation of physical permafrost dynamics in the JULES land surface model

An improved representation of physical permafrost dynamics in the JULES land surface model

Boike, J., Kattenstroth, B., Abramova, K., Bornemann, N., Chetverova, A., Fedorova, I., Fröb, K., Grigoriev, M., Grüber, M., Kutzbach, L., Langer, M., Minke, M., Muster, S., Piel, K., Pfeiffer, E.- M., Stoof, G., Westermann, S., Wischnewski, K., Wille, C., and Hubberten, H.-W.: Baseline characteristics of climate, permafrost and land cover from a new permafrost observatory in the Lena River Delta, Siberia (1998–2011), Biogeosciences, 10, 2105–2128, doi:10.5194/bg-

45 Ler mais

Present and LGM permafrost from climate simulations: contribution of statistical downscaling

Present and LGM permafrost from climate simulations: contribution of statistical downscaling

To complement this study, some points would deserve to be deepened to improve our results. Permafrost is an het- erogeneous variable with few observations. Climate mod- els temperature, used to derive permafrost distribution, is a global and continuous variable. Therefore, we need local- scale predictors that will add local variability to climate sig- nal. Our SDMs use local-scale topography but other vari- ables used in permafrost dynamic models, such as vegetation or soil properties (Marchenko et al., 2008), are required to have a representative physics of permafrost processes and a better distribution. The potential of the multinomial logis- tic models lies in the control of the physics included in the predictors. In this study we used the same predictors for both approaches. It is obvious that they can and should be changed in the ML-GAM methods to represent more accu- rately the permafrost distribution. Future research should include snow cover and thickness and soil temperature, es- pecially for mountain permafrost influenced by snow cover. We can also imagine building new “geographical” predic- tors such as exposure to the sun depending on the orientation of the topography slope (Brown, 1969). The balancing and choice of “geographical” and “physical” predictors is cru- cial to maintain good local representation and a consistent and robust physical model applicable to different climates. To reconcile models and data, it would also be interesting to downscale permafrost at colder periods simulated by climate models, such as Heinrich events (Kageyama et al., 2005). We would be able to determine the needed temperatures to obtain the best permafrost limits according to the data from Vanden- berghe et al. (2011). In this context, we also have to keep in mind our strong assumption of a near-surface permafrost in equilibrium with climate signal. Downscaling of transient climate simulations could help us to evaluate how large the difference is due to this disequilibrium.
Mostrar mais

22 Ler mais

JULES-crop: a parametrisation of crops in the Joint UK Land Environment Simulator

JULES-crop: a parametrisation of crops in the Joint UK Land Environment Simulator

Abstract. Studies of climate change impacts on the terres- trial biosphere have been completed without recognition of the integrated nature of the biosphere. Improved assessment of the impacts of climate change on food and water security requires the development and use of models not only repre- senting each component but also their interactions. To meet this requirement the Joint UK Land Environment Simulator (JULES) land surface model has been modified to include a generic parametrisation of annual crops. The new model, JULES-crop, is described and evaluation at global and site levels for the four globally important crops; wheat, soybean, maize and rice. JULES-crop demonstrates skill in simulat- ing the inter-annual variations of yield for maize and soy- bean at the global and country levels, and for wheat for ma- jor spring wheat producing countries. The impact of the new parametrisation, compared to the standard configuration, on the simulation of surface heat fluxes is largely an alteration of the partitioning between latent and sensible heat fluxes dur- ing the later part of the growing season. Further evaluation at the site level shows the model captures the seasonality of leaf area index, gross primary production and canopy height better than in the standard JULES. However, this does not lead to an improvement in the simulation of sensible and la- tent heat fluxes. The performance of JULES-crop from both an Earth system and crop yield model perspective is en- couraging. However, more effort is needed to develop the parametrisation of the model for specific applications. Key future model developments identified include the introduc- tion of processes such as irrigation and nitrogen limitation
Mostrar mais

17 Ler mais

Evaluating spatial-temporal dynamics of net primary productivity of different forest types in northeastern China based on improved FORCCHN.

Evaluating spatial-temporal dynamics of net primary productivity of different forest types in northeastern China based on improved FORCCHN.

Forest’s hydrological effect is an important function of forest ecosystem. With dense forest canopy foliage, there are twice distribution processes of the atmospheric precipitation mainly through the canopy interception. When the precipitation reaches the canopy of forest, the first precipitation redistribution occurs. Part of the precipitation is intercepted by the canopy, and part of the precipitation reaches the ground surface across the canopy gaps. The second redistribution of precipitation reached the woodland take places. Part is underground infiltration, and part is surface runoff. Through adding variables and modules of precipitation (rainfall and snowfall) interception by tree crown, understory plants and litter, Zhao et al. further improved FORCCHN and applied it to estimate net carbon budget of forest ecosystems and its response to climate change in northeast- ern China [12]. The detailed descriptions of the improved FORCCHN model9s features, mathematical representation, building strategy and validation were previously provided by Zhao et al. [12]. This current study presents our first attempt to apply the improved FORCCHN model for studying the spatial- temporal dynamics of NPP of different forest types (evergreen broadleaf forest?deciduous broadleaf forest?evergreen needleleaf forest?deciduous needleleaf forest) in northeastern China from 1981 to 2002.
Mostrar mais

14 Ler mais

Simulation of permafrost and seasonal thaw depth in the JULES land surface scheme

Simulation of permafrost and seasonal thaw depth in the JULES land surface scheme

is based on a smaller number of precipitation observations. Clearly, the latter of the two datasets considerably underes- timates the amount of cold season precipitation at this lo- cation. Over the 2000–2001 winter season, the total pre- cipitation between October and April in WATCH-CRU is only 16 mm or about 10 % of the amount in WATCH-GPCC. As a consequence, the model simulates only a very shallow snow pack that disappears too early in spring. The WATCH dataset using the GPCC precipitation, which is based on a larger number of stations than CRU, performs much better in this respect and the simulated amount of snow is much closer to the satellite-derived SWE, although the snow vol- ume is still lower and disappears about half a month ear- lier. The latter is at least partly due to the WATCH forc- ing being somewhat warmer than observed at Toolik in the weeks preceding snowmelt, with daytime temperature fre- quently climbing above zero degrees Celsius from early May onwards (Fig. 7b). Note that in general there are also un- certainties associated with satellite-based estimates of SWE, especially at high values. The observed snow depth at Toolik at 2 May 2001 (Oberbauer, 2003) amounted to 0.66 m with a standard deviation of 0.09 m. Assuming a snow density in the range of 260–310 kg m −3 (e.g. Sturm and Wagner, 2010) this translates into a SWE of 172–205 ± 28 mm. The SSM/I estimate on this day is 181 mm but day-to-day variability in these data is considerable with values as low as 125 mm in the 10 days around the measurement date. JULES, using a prognostic snow density, calculates a snow depth on this day of 0.30 m and an SWE of 115 mm when using the WATCH- GPCC forcing.
Mostrar mais

18 Ler mais

Impact of model developments on present and future simulations of permafrost in a global land-surface model

Impact of model developments on present and future simulations of permafrost in a global land-surface model

The active layer thickness is determined by both the annual cycle of soil temperatures and the thermal offset between the air and the soil. Table 3 compares these dynamics in JULES with observations from the IPY-TSP data set and cold sites from the Russian soil temperature data set (see Sects. 2.4.4 and 2.6). The root mean squared error (RMSE) is calculated using the mean value of the metric for each site, so it quan- tifies the extent to which the variability between the sites is correctly simulated. In this table the most relevant values are the offset and attenuation of the annual cycle between the air and 1 m depth in the soil, since the soil surface is not so well defined in the observations. In the standard JULES set-up (min4l) the total offset is approximately correct, suggesting that the mean soil temperatures are simulated well. However, the annual cycle is nearly 25 % too large at 1 m depth.
Mostrar mais

17 Ler mais

Criterion for selection the optimal physical and chemical properties of cobalt aluminate powder used in investment casting process

Criterion for selection the optimal physical and chemical properties of cobalt aluminate powder used in investment casting process

The first stage of the research work took over the investigations of physical and chemical properties of cobalt aluminate manufactured by three different companies: Remet, Mason Color and Permedia Lublin. There were determined the grain size distribution of cobalt aluminate powder, the average diameter and morphology of powder particles, phase composition, as well as sodium and cobalt content, pH value of water suspension and the bulk density. In the next step, the ceramic moulds were made with different kind of cobalt aluminate (Mason Color, Remet, Permedia Lublin) and its concentration (0, 5%) in the primary slurry. The samples of stepped shape were poured in the ceramic moulds prepared earlier. The average gr ain size of the γ phase was determined on the stepped samples.
Mostrar mais

6 Ler mais

Investigating The Use Of Mobile Computing In Zimbabwe Polytechnics Case Of A Polytechnic In Zimbabwe

Investigating The Use Of Mobile Computing In Zimbabwe Polytechnics Case Of A Polytechnic In Zimbabwe

1. INTRODUCTION In the period prior to 2003 Polytechnics in Zimbabwe had a mix of Information Communication Technologies (ICTs), varying from one institution to the other. There was no uniformity as to what ICTs individual institutions invested in, so while some institutions had several computer laboratories of clone desktops, some did not have even a single lab. While some had connected to the internet through the dialup system which came through telephone lines, some had no idea what internet was.A breakthrough came in 2003 when a non- governmental organization called VVOB, a Belgian abbreviation which translates in English to Flemish for Technical Assistance, came in with a project called the College Information Technology Enhancement Programme (CITEP), which helped to finance, train personnel and equip polytechnics with standard computer and network infrastructure (VVOB project document, 2003). They conducted training workshops for personnel, procured standard desktops, and installed fibre internet connectivity and setup Ethernet networks in these institutions. This project became the basis for mobile computing in Polytechnics. When the project ended in 2008, the institutions were now coordinated and some managed to go a step further by installing wireless access points within institutions using the fibre backbone. This allowed staff and students who had WIFI enabled devices to be able to access internet and research
Mostrar mais

5 Ler mais

Assessment Of Some Acceleration Schemes In The Solution Of Systems Of Linear Equations.

Assessment Of Some Acceleration Schemes In The Solution Of Systems Of Linear Equations.

Richardson with SOR, Chebyshev with Gauss-Seidel and Chebyshev with SOR. The iterative schemes were applied to Banded system, Tridiagonal systems and SPD system with varying dimensions. The Krylov subspace methods: GMRES, QMR, MINRES and BiCGSTAB converged to an approximate solutions less than or equal to the dimension of the coefficient matrix for each identified systems of linear equations. Again, Chebyshev and Richardson acceleration methods were the fastest convergence methods in terms of number of iterations. Again, Residual smoothing and the accelerated gradient schemes should be used for large and sparse systems of linear equations. The acceleration processes were very efficient when solving large and sparse systems of linear equation and therefore useful especially for systems resulting from the solution of partial differential equations.
Mostrar mais

8 Ler mais

CAM-chem: description and evaluation of interactive atmospheric chemistry in the Community Earth System Model

CAM-chem: description and evaluation of interactive atmospheric chemistry in the Community Earth System Model

Abstract. We discuss and evaluate the representation of at- mospheric chemistry in the global Community Atmosphere Model (CAM) version 4, the atmospheric component of the Community Earth System Model (CESM). We present a va- riety of configurations for the representation of tropospheric and stratospheric chemistry, wet removal, and online and of- fline meteorology. Results from simulations illustrating these configurations are compared with surface, aircraft and satel- lite observations. Major biases include a negative bias in the high-latitude CO distribution, a positive bias in upper- tropospheric/lower-stratospheric ozone, and a positive bias in summertime surface ozone (over the United States and Europe). The tropospheric net chemical ozone production varies significantly between configurations, partly related to variations in stratosphere-troposphere exchange. Aerosol op- tical depth tends to be underestimated over most regions, while comparison with aerosol surface measurements over the United States indicate reasonable results for sulfate , es- pecially in the online simulation. Other aerosol species ex- hibit significant biases. Overall, the model-data comparison indicates that the offline simulation driven by GEOS5 me- teorological analyses provides the best simulation, possibly due in part to the increased vertical resolution (52 levels in- stead of 26 for online dynamics). The CAM-chem code as described in this paper, along with all the necessary datasets needed to perform the simulations described here, are avail- able for download at www.cesm.ucar.edu.
Mostrar mais

43 Ler mais

SOCIAL ECONOMY – A FORM OF INCLUSION AND OF ''REACTIVATING'' OF LABOR IN THE CONTEXT OF THE CURRENT CRISIS

SOCIAL ECONOMY – A FORM OF INCLUSION AND OF ''REACTIVATING'' OF LABOR IN THE CONTEXT OF THE CURRENT CRISIS

than they produce, which means over the real incomes obtained through social work. Văduva, . We are talking about New Zeeland. Most countries present important sovereign debts , an increasing deficit between incomes and expenses, practical risks of making new loans that bring them close to the insolvency area or to bankruptcy The European Commission, . Such a process is explained by the confusion between the exigencies of social economy – based on work – and the passive social protection policies, which ignore or place labor between brackets . )nstead of the minimum guaranteed salary, some irrational social policies have promoted the minimum guaranteed income, independent from the work resources of the beneficiaries, poverty is perceived as a state characterizing the majority Vîrjan , p. . Successes, but also limits recorded in the labor market today are similar to those defining the reform of the Romanian economy as a whole Aceleanu and Cretu , p. , marked by a public‐private partnership are organizationally weak and frail, the tensions between labor market structures and mechanisms that interfere with legislative‐institutional tensions.
Mostrar mais

13 Ler mais

UV induced surface modification on improving the cytocompatibility of metallocene polyethylene

UV induced surface modification on improving the cytocompatibility of metallocene polyethylene

The surfaces with higher wettability allow the displacement of undesired plasma proteins (like fibrinogen) by cell adhesive serum proteins, such as fibronectin and vitronectin, due to protein- specific affinity (Balaji et al. 2015). This property of controlling and translating protein adsorption is greatly needed to avoid the complication of blood component activation. Moreover, the obtained contact angle falls in the optimum range of 70º-30º which has previously been reported to be suitable for regeneration of cells like fibroblasts, HUVECs, osteoblasts and cardiomyocytes (Anderson 2001). The above discussed effect of improved surface roughness and wettability was clearly observed in the cytocompatibility tests. The hemolysis assay of the surface treated samples are indicated in Fig. 3. The results of hemolysis assay showed that untreated sample exhibited 15.40% hemolysis,
Mostrar mais

10 Ler mais

Combining surface reanalysis and remote sensing data for monitoring evapotranspiration

Combining surface reanalysis and remote sensing data for monitoring evapotranspiration

Reichstein, M., Falge, E., Baldocchi, D., Papale, D., Aubinet, M., Berbigier, P., Bernhofer, C., Buchmann, N., Gilmanov, T., Granier, A., Grunwald, T., Havrankova, K., Ilvesniemi, H., Janous, D., Knohl, A., Laurila, T., Lohila, A., Loustau, D., Matteucci, G., Meyers, T., Migli- etta, F., Ourcival, J.-M., Pumpanen, J., Rambal, S., Rotenberg, E., Sanz, A., Tenhunen, J., Seufert, G., Vaccari, F., Vesala, T., Yakir, D., and Valentini, R.: On the separation of

41 Ler mais

Modeling of stability of gas hydrates under permafrost in an environment of surface climatic change – terrestrial case, Beaufort-Mackenzie basin, Canada

Modeling of stability of gas hydrates under permafrost in an environment of surface climatic change – terrestrial case, Beaufort-Mackenzie basin, Canada

Further surface cooling below −5 ◦ C caused the IBP base to descend into the layer already occupied by GH. For 30 % porosity and 60 % GH saturation, the remaining water available to freeze occupied not 30 %, but only 12 % of the whole volume and the latent heat released by its freezing was 2.5 times smaller than in the IBP interval above the GH. The question is, “what had happened with the methane in the uppermost

29 Ler mais

WP114 No Impact of Rural Development Policies? No Synergies with Conditional Cash Transfers? An Investigation of the IFAD-Supported Gavião Project in Brazil

WP114 No Impact of Rural Development Policies? No Synergies with Conditional Cash Transfers? An Investigation of the IFAD-Supported Gavião Project in Brazil

Despite having provided US$18.5 billion in grants and low-interest loans since 1977, there is little rigorous evidence on the impact of IFAD projects around the world. There is a similar lack of evidence on synergies between rural development projects and conditional cash transfer policies. In an effort to address this gap in the literature, we explored the impacts of an IFAD- supported rural development project —Pro-Gavião—in 13 municipalities of Brazil, and possible synergies with the Bolsa Família conditional cash transfer program. The paper used a matching technique to create a control group of untreated census tracts, and a difference-in-differences estimation to identify policy impacts. The findings were unexpected. When examining the main outcomes of land productivity, agricultural income, and child labor—all available in the Agricultural Censuses—we found no statistically significant evidence to support a positive impact of Pro-Gavião or of synergies between the two programs. The presence of Bolsa Família seems to have improved access to credit, and there was some evidence showing a likely association between the interaction of the policies and improved access to electricity. These results are robust to different matching techniques, ways of defining the treated locations, and heterogeneity by initial level of poverty.
Mostrar mais

36 Ler mais

Geodiversity : a theoretical and applied concept

Geodiversity : a theoretical and applied concept

describes habitats as «terrestrial or aquatic areas differ- entiated by their geographical, abiotic and biotic char- acteristics, whether they be wholly natural or semi-nat- ural» (Habitats Directive, 92/43/EEC). Thus, habitats include abiotic and spatial components. The variety of abiotic elements forming habitats can also be referred to as geodiversity. The framing of the coneept of geo¬ diversity in this context is of special interest because it refiects an understanding of natural diversity, and links

8 Ler mais

Impact of an improved radiation scheme in the MAECHAM5 General Circulation Model

Impact of an improved radiation scheme in the MAECHAM5 General Circulation Model

The enhanced easterlies and westerlies for the EXP simulation with respect to the CTRL simulation are a direct radiative response: They are due to the increased North Pole to South Pole temperature gradient (Fig. 3), resulting from the summer hemi- sphere and tropical radiative warming. Therefore, the direct impact of the change in the radiation parameterization is an enhancement of the climatological solsticial condition

26 Ler mais

Sub-grid scale representation of vegetation in global land surface schemes: implications for estimation of the terrestrial carbon sink

Sub-grid scale representation of vegetation in global land surface schemes: implications for estimation of the terrestrial carbon sink

McGuire, A. D., Sitch, S., Clein, J. S., Dargaville, R., Esser, G., Foley, J., Heimann, M., Joos, F., Kaplan, J., Kicklighter, D. W., Meier, R. A., Melillo, J. M., Moore, B., Prentice, I. C., Ra- mankutty, N., Reichenau, T., Schloss, A., Tian, H., Williams, L. J., and Wittenberg, U.: Car- bon balance of the terrestrial biosphere in the twentieth century: analyses of CO 2 , climate and land use effects with four process-based ecosystem models, Global Biogeochem. Cy.,

39 Ler mais

Sensitivity of the Amazon biome to high resolution climate change projections

Sensitivity of the Amazon biome to high resolution climate change projections

Figures 1 compare temperature, precipitation, cloud cover, and specific humidity output from Eta-HadGEM2- ES against CFSR reanalyses. These are the atmospheric variables used as input to the Inland model. This figure shows averages for January and June, and for the period 1981-2005. These variables are input to Inland model at daily frequency. The months are chosen as representative of opposite precipitation regimes in the Amazon region. The differences in temperature and precipitation mean fields between the two datasets are generally small in terms of the spatial pattern. In general, Eta-HadGEM2-ES simulation is colder than CFSR reanalyses in the central part of the continent and over tropical Atlantic Ocean (Figure 1A-D). In June in Central Brazil, the Eta-HadGEM2-ES mean precipitation shows higher values than CFSR (Figure 1G,H). In both months, the Intertropical Convergence Zone (ITCZ) over the Atlantic Ocean is better defined as a band in the reanalyses. In January, precipitation in the reanalysis data is excessive, showing values over 12 mm/day over the central southern Amazon (Figure 1F), while in the Eta-HadGEM2- ES precipitation does not exceed 9 mm/day (Figure 1E). Silva et al. (2011) have shown that CFSR overestimates precipitation in this region. Actually, the Eta simulated precipitation agrees closer to the CRU observations (Chou et al. 2014a). Similar to precipitation field, CFSR data presents greater values of cloud cover over central southern Amazon than the Eta-HadGEM2-ES simulation in January (Figure 1I,J). On the other hand, in June over the Amazon, these two data sets show close similarities with one another (Figure 1K,L). It should be remarked that CFSR cloud cover is a model 6-h mean product. The mean specific humidity shows more disagreement between Eta and CFSR. For this variable, the major differences is over the Andes Mountains in both months and over the Amazon in January. The CFSR data shows less humidity over the Andes and more humidity over the Amazon than the Eta-HadGEM2-ES simulations in both months (Figure 1M-P).
Mostrar mais

14 Ler mais

Stable water isotopes in the coupled atmosphere–land surface model ECHAM5-JSBACH

Stable water isotopes in the coupled atmosphere–land surface model ECHAM5-JSBACH

In ECHAM5-JSBACH the same land hydrology model is used as in ECHAM5. The model comprises three surface wa- ter reservoirs: a snow layer (sn), water at the skin layer of the canopy or bare soil (wl), and a soil water layer (ws). These three types are each represented by a single layer bucket model, and each of them has a prescribed maximum field ca- pacity. The snow reservoir is filled by snowfall and depleted by snowmelt or sublimation. The skin layer and the soil layer are filled by rainfall and snowmelt in the following order: first the skin layer is filled until its water holding capacity is ex- ceeded, and secondly the non-intercepted water fills the soil reservoir. The modeled depletion of the skin layer can only occur by evaporation; the depletion of the soil water reservoir occurs by evapotranspiration. There is no exchange between these two reservoirs. If the soil water reservoir is saturated, surface runoff occurs. Drainage occurs independent of the new precipitation, and it is calculated if the amount of soil water reaches 5 % or more of the maximal soil water capac- ity. The runoff and drainage scheme is based on examination of variations of the field capacity for soil water over the land surface (D¨umenil and Tondini, 1992). Furthermore, lakes are prescribed by a lake mask; to calculate the evaporation over larger lakes (i.e., grid cells with a lake fraction greater than 50 %) the same scheme as for the ocean is used. A more de- tailed description of the land hydrology model can be found in Roeckner et al. (2003).
Mostrar mais

18 Ler mais

Show all 10000 documents...

temas relacionados