Grid point surface air temperature calculations with a fast turnaround: Combining the results of IMAGE and a GCM     

Matthias Jonas  Katharina Fleischmann  Andrey V. Ganopolski  Jaroslav Krabec  Uta Sauer  Krzysztof Olendrzyński  Vladimir K. Petoukhov  Roderick W. Shaw 《Climatic change》1996,34(3-4):479-512

This paper describes a methodology that combines the outputs of (1) the Integrated Model to Assess the Greenhouse Effect (IMAGE Version 1.0) of the Netherlands National Institute of Public Health and Environmental Protection (RIVM) (given a greenhouse gas emission policy, this model can estimate the effects such as global mean surface air temperature change for a wide variety of policies) and (2) ECHAM-1/LSG, the Global Circulation Model (GCM) of the Max-Planck Institute for Meteorology in Hamburg, Germany. The combination enables one to calculate grid point surface air temperature changes for different scenarios with a turnaround time that is much quicker than that for a GCM. The methodology is based upon a geographical pattern of the ratio of grid point temperature change to global mean values during a certain period of the simulation, as calculated by ECHAM-1/LSG for the 1990 Scenarios A and D of the Intergovernmental Panel on Climate Change (IPCC). A procedure, based upon signal-to noise ratios in the outputs, enabled us to estimate where we have confidence in the methodology; this is at about 23% to 83% of the total of 2,048 grid points, depending upon the scenario and the decade in the simulation. It was found that the methodology enabled IMAGE to provide useful estimates of the GCM-predicted grid point temperature changes. These estimates were within 0.5K (0.25K) throughout the 100 years of a given simulation for at least 79% (74%) of the grid points where we are confident in applying the methodology. The temperature ratio pattern from Scenario A enabled IMAGE to provide useful estimates of temperature change within 0.5K (0.25K) in Scenario D for at least 88% (68%) of the grid points where we have confidence; indicating that the methodology is transferable to other scenarios. Tests with the Geophysical Fluid Dynamics Laboratory GCM indicated, however, that a temperature ratio pattern may have to be developed for each GCM. The methodology, using a temperature ratio pattern from the 1990 IPCC Scenario A and involving IMAGE, gave gridded surface air temperature patterns for the 1992 IPCC radiative-forcing Scenarios C and E and the RIVM emission Scenario B; none of these scenarios has been simulated by ECHAM-1/LSG. The simulations reflect the uncertainty range of a future warming.The work reported by the authors was carried out during their stay at the project Forestry and Climate Change of the International Institute for Applied Systems Analysis, Laxenburg, Austria.  相似文献   

CPR sampling: the technical background, materials and methods, consistency and comparability     

S. D. Batten  R. Clark  J. Flinkman  G. Hays  E. John  A. W. G. John  T. Jonas  J. A. Lindley  D. P. Stevens  A. Walne 《Progress in Oceanography》2003,58(2-4):193

The Continuous Plankton Recorder has been deployed for 70 years. Although modifications to the machine have been relatively minor, there has been a steady increase in the speed at which it is towed, creating a need to quantify what effects this may have had on its sampling characteristics. Additionally, because the CPR database is one of the longest and most geographically extensive biological time series in the world, and scientists are currently focusing on gaining understanding about climate-induced ecological changes, there is increasing pressure to quantify the sampling performance and relate the CPR data to data collected by other plankton samplers. Many of these issues of consistency and comparability have been investigated throughout the decades of the CPR survey. The primary aim of this study is to draw together the results of those investigations, updating or integrating them where applicable. A secondary aim is to use the CPR database to address other previously unexamined issues. We show that the increase in speed of tow has had no effect on the depth of sampling and the mechanical efficiency of the internal mechanism, but that at the highest tow speeds there is some evidence that flow may be reduced. Depth of tow may also be dependent on the ship operating a particular route. We describe the processing procedures used to ensure consistency of analysis and detail the changes in taxonomic resolution that have occurred through the course of the survey. Some consistency issues remain unresolved, such as the effects of adding heavy instrumentation to the attitude of the CPR in the water and possible effects on sampling performance. The reduction of flow caused by clogging of the filtering mesh has now been quantified through the addition of flowmeters and each CPR sample can now be calibrated for measured, or derived, filtered volume. Although estimates of abundances for large areas have been shown to be unaffected by recalibration, absolute quantification of plankton abundance is necessary to enable comparisons with other sampling devices. Several studies have now been undertaken that compare plankton abundances obtained with the CPR with those obtained using vertical nets at specific locations on the European continental shelf. Although catches by the CPR are almost always lower, seasonal cycles are replicated in each comparison, and interannual variability generally agrees between time series. The relative catch rates for an individual species by each device appear to be consistent, probably because of the organisms’ behaviour and attributes of the sampling device. We are now able to develop calibration factors to convert CPR catches to absolute abundances that can be integrated with other data sets where appropriate, which should increase the applicability and utility of CPR data.  相似文献   

Using continuous plankton recorder data     

A.J. Richardson  A.W. Walne  T.D. Jonas  D.W. Sims  M. Witt 《Progress in Oceanography》2006,68(1):27-74

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Climate simulations for 1880–2003 with GISS modelE     

J. Hansen  M. Sato  R. Ruedy  P. Kharecha  A. Lacis  R. Miller  L. Nazarenko  K. Lo  G. A. Schmidt  G. Russell  I. Aleinov  S. Bauer  E. Baum  B. Cairns  V. Canuto  M. Chandler  Y. Cheng  A. Cohen  A. Del Genio  G. Faluvegi  E. Fleming  A. Friend  T. Hall  C. Jackman  J. Jonas  M. Kelley  N. Y. Kiang  D. Koch  G. Labow  J. Lerner  S. Menon  T. Novakov  V. Oinas  Ja. Perlwitz  Ju. Perlwitz  D. Rind  A. Romanou  R. Schmunk  D. Shindell  P. Stone  S. Sun  D. Streets  N. Tausnev  D. Thresher  N. Unger  M. Yao  S. Zhang 《Climate Dynamics》2007,29(7-8):661-696

We carry out climate simulations for 1880–2003 with GISS modelE driven by ten measured or estimated climate forcings. An ensemble of climate model runs is carried out for each forcing acting individually and for all forcing mechanisms acting together. We compare side-by-side simulated climate change for each forcing, all forcings, observations, unforced variability among model ensemble members, and, if available, observed variability. Discrepancies between observations and simulations with all forcings are due to model deficiencies, inaccurate or incomplete forcings, and imperfect observations. Although there are notable discrepancies between model and observations, the fidelity is sufficient to encourage use of the model for simulations of future climate change. By using a fixed well-documented model and accurately defining the 1880–2003 forcings, we aim to provide a benchmark against which the effect of improvements in the model, climate forcings, and observations can be tested. Principal model deficiencies include unrealistically weak tropical El Nino-like variability and a poor distribution of sea ice, with too much sea ice in the Northern Hemisphere and too little in the Southern Hemisphere. Greatest uncertainties in the forcings are the temporal and spatial variations of anthropogenic aerosols and their indirect effects on clouds. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   

Identification of typical synoptic patterns causing heavy rainfall in the rainy season in Japan by a Self-Organizing Map     

Koji Nishiyama  Shinichi Endo  Kenji Jinno  Cintia Bertacchi Uvo  Jonas Olsson  Ronny Berndtsson   《Atmospheric Research》2007,83(2-4):185-200

In order to systematically and visually understand well-known but qualitative and complex relationships between synoptic fields and heavy rainfall events in Kyushu Islands, southwestern Japan, during the BAIU season, these synoptic fields were classified using the Self-Organizing Map (SOM), which can convert complex non-linear features into simple two-dimensional relationships. It was assumed that the synoptic field patterns could be simply expressed by the spatial distribution of (1) wind components at the 850 hPa level and (2) precipitable water (PW) defined by the water vapor amount contained in a vertical column of the atmosphere. By the SOM algorithm and the clustering techniques of the U-matrix and the K-means, the synoptic fields could be divided into eight kinds of patterns (clusters). One of the clusters has the notable spatial features represented by a large PW content accompanied by strong wind components known as low-level jet (LLJ). The features of this cluster indicate a typical synoptic field pattern that frequently causes heavy rainfall in Kyushu during the rainy season.In addition, an independent data set was used for validating the performance of the trained SOM. The results indicated that the SOM could successfully extract heavy rainfall events related to typical synoptic field patterns of the BAIU season. Interestingly, one specific SOM unit was closely related to the occurrence of disastrous heavy rainfall events observed during both training and validation periods. From these results, the trained SOM showed good performance for identifying synoptic fields causing heavy rainfall also in the validation period. We conclude that the SOM technique may be an effective tool for classifying complicated non-linear synoptic fields and identifying heavy rainfall events to some degree.  相似文献   

Quantitative evaluation of different hydrological modelling approaches in a partly glacierized Swiss watershed     

Jan Magnusson  Daniel Farinotti  Tobias Jonas  Mathias Bavay 《水文研究》2011,25(13):2071-2084

Mountain water resources management often requires hydrological models that need to handle both snow and ice melt. In this study, we compared two different model types for a partly glacierized watershed in central Switzerland: (1) an energy‐balance model primarily designed for snow simulations; and (2) a temperature‐index model developed for glacier simulations. The models were forced with data extrapolated from long‐term measurement records to mimic the typical input data situation for climate change assessments. By using different methods to distribute precipitation, we also assessed how various snow cover patterns influenced the modelled runoff. The energy‐balance model provided accurate discharge estimations during periods dominated by snow melt, but dropped in performance during the glacier ablation season. The glacier melt rates were sensitive to the modelled snow cover patterns and to the parameterization of turbulent heat fluxes. In contrast, the temperature‐index model poorly reproduced snow melt runoff, but provided accurate discharge estimations during the periods dominated by glacier ablation, almost independently of the method used to distribute precipitation. Apparently, the calibration of this model compensated for the inaccurate precipitation input with biased parameters. Our results show that accurate estimates of snow cover patterns are needed either to correctly constrain the melt parameters of the temperature‐index model or to ensure appropriate glacier surface albedos required by the energy‐balance model. Thus, particularly when only distant meteorological stations are available, carefully selected input data and efficient extrapolation methods of meteorological variables improve the reliability of runoff simulations in high alpine watersheds. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Estimating the snow water equivalent from snow depth measurements in the Swiss Alps   总被引：3，自引：0，他引：3  

T. Jonas  C. Marty  J. Magnusson   《Journal of Hydrology》2009,378(1-2):161-167

The snow water equivalent (SWE) characterizes the hydrological significance of snow cover. However, measuring SWE is time-consuming, thus alternative methods of determining SWE may be useful. SWE can be calculated from snow depth if the bulk snow density is known. Thus, a reliable estimation method of snow densities could (a) potentially save a lot of effort by, at least partly, sampling snow depth instead of SWE, and would (b) allow snow hydrological evaluations, when only snow depth data are available. To generate a useful parameterization of the bulk density a large dataset was analyzed covering snow densities and depths measured biweekly over five decades at 37 sites throughout the Swiss Alps. Four factors were identified to affect the bulk snow density: season, snow depth, site altitude, and site location. These factors constitute a convenient set of input variables for a snow density model developed in this study. The accuracy of estimating SWE using our model is shown to be equivalent to the variability of repeated SWE measurements at one site. The technique may therefore allow a more efficient but indirect sampling of the SWE without necessarily affecting the data quality.  相似文献   

An approximate nearest neighbors search algorithm for low-dimensional grid locations     

Adriano Petry  André Grahl Pereira  Jonas Rodrigues de Souza 《Earth Science Informatics》2017,10(2):183-196

We propose a new algorithm for the problem of approximate nearest neighbors (ANN) search in a regularly spaced low-dimensional grid for interpolation applications. It associates every sampled point to its nearest interpolation location, and then expands its influence to neighborhood locations in the grid, until the desired number of sampled points is achieved on every grid location. Our approach makes use of knowledge on the regular grid spacing to avoid measuring the distance between sampled points and grid locations. We compared our approach with four different state-of-the-art ANN algorithms in a large set of computational experiments. In general, our approach requires low computational effort, especially for cases with high density of sampled points, while the observed error is not significantly different. At the end, a case study is shown, where the ionosphere dynamics is predicted daily using samples from a mathematical model, which runs in parallel at 56 different longitude coordinates, providing sampled points not well distributed that follow Earth’s magnetic field-lines. Our approach overcomes the comparative algorithms when the ratio between the number of sampled points and grid locations is over 2849:1.  相似文献   

Holocene tephra horizons at Klocka Bog,west‐central Sweden: aspects of reproducibility in subarctic peat deposits     

Jonas Bergman  Stefan Wastegrd  Dan Hammarlund  Barbara Wohlfarth  Stephen J. Roberts 《第四纪科学杂志》2004,19(3):241-249

This paper presents one of the most extensive Holocene tephra records found to date in Scandinavia. Microtephra horizons originating from Icelandic eruptions were recorded in two ca. 2 m thick peat profiles at Klocka Bog in west‐central Sweden. Five of the microtephra horizons were geochemically correlated to the Askja‐1875, Hekla‐3, Kebister, Hekla‐4 and Lairg A tephras respectively. Radiocarbon‐based dating of these tephras broadly agree with previously published ages from Iceland, Sweden, Germany and the British Isles. The identification of the Lairg A tephra demonstrates a more widespread distribution than previously thought, extending the usefulness of Icelandic Holocene tephrochronology further north into west‐central Scandinavia. Long‐lasting snow cover and seasonal wind distribution in the lower stratosphere are suggested as factors that may be responsible for fragmentary tephra deposition patterns in peat deposits of subarctic Scandinavia. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

Nonlinear wave propagation along a magnetic flux tube     

Jonas Lundberg 《Solar physics》1994,154(2):215-230

The weakly nonlinear wave propagation of a slow sausage surface wave traveling along a magnetized slab with a thin nonuniform boundary layer is considered. The ideal incompressible MHD equations are used and the nonlinearities are assumed to be due to second harmonic generation. A nonlinear dispersion relation and the related nonlinear Schrödinger equation is derived. The existence of a continuous thin interface leads to sharply peaked field amplitudes due to resonant interaction with local Alfvén waves. It is shown that the nonlinear effects from processes within the thin layer are much more important than those from the main slab. Furthermore, the nonlinear interaction with local Alfvén waves yields a nonlinear damping rate of the wave that is much larger than the linear damping rate when the transition layer is sufficiently thin.  相似文献