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Forecasts
Kinds of Forecasts Terms modified by Forecasts Selected AbstractsIMPROVING FORECAST ACCURACY BY COMBINING RECURSIVE AND ROLLING FORECASTS,INTERNATIONAL ECONOMIC REVIEW, Issue 2 2009Todd E. Clark This article presents analytical, Monte Carlo, and empirical evidence on combining recursive and rolling forecasts when linear predictive models are subject to structural change. Using a characterization of the bias,variance trade-off faced when choosing between either the recursive and rolling schemes or a scalar convex combination of the two, we derive optimal observation windows and combining weights designed to minimize mean square forecast error. Monte Carlo experiments and several empirical examples indicate that combination can often provide improvements in forecast accuracy relative to forecasts made using the recursive scheme or the rolling scheme with a fixed window width. [source] SUB-SAHARAN AFRICA: ECONOMIC FORECASTS 2009-2010AFRICA RESEARCH BULLETIN: ECONOMIC, FINANCIAL AND TECHNICAL SERIES, Issue 4 2009Article first published online: 4 JUN 200 No abstract is available for this article. [source] CLIMATE FORECASTS IN FLOOD PLANNING: PROMISE AND AMBIGUITY,JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 6 2002Kris Wernstedt ABSTRACT: Recent technical and scientific advances have increased the potential use of long term, seasonal climate forecasts for improving water resource management. This paper examines the role that forecasts, in particular those based on the El Niño Southern Oscillation (ENSO) cycle, can play in flood planning in the Pacific Northwest. While strong evidence exists of an association between ENSO signals and flooding in the region, this association is open to more than one interpretation depending on: (a) the metric used to test the strength of the association; (b) the definition of critical flood events; (c) site specific features of watersheds; and (d) the decision environment of flood management institutions. A better understanding and appreciation of such ambiguities, both social and statistical, will help facilitate the use of climate forecast information for flood planning and response. [source] SYMMETRIC VERSUS ASYMMETRIC CONDITIONAL COVARIANCE FORECASTS: DOES IT PAY TO SWITCH?THE JOURNAL OF FINANCIAL RESEARCH, Issue 3 2007Susan Thorp Abstract Volatilities and correlations for equity markets rise more after negative returns shocks than after positive shocks. Allowing for these asymmetries in covariance forecasts decreases mean-variance portfolio risk and improves investor welfare. We compute optimal weights for international equity portfolios using predictions from asymmetric covariance forecasting models and a spectrum of expected returns. Investors who are moderately risk averse, have longer rebalancing horizons, and hold U.S. equities benefit most and may be willing to pay around 100 basis points annually to switch from symmetric to asymmetric forecasts. Accounting for asymmetry in both variances and correlations significantly lowers realized portfolio risk. [source] VOLATILITY FORECASTS, TRADING VOLUME, AND THE ARCH VERSUS OPTION-IMPLIED VOLATILITY TRADE-OFFTHE JOURNAL OF FINANCIAL RESEARCH, Issue 4 2005R. Glen Donaldson Abstract We investigate empirically the role of trading volume (1) in predicting the relative informativeness of volatility forecasts produced by autoregressive conditional heteroskedasticity (ARCH) models versus the volatility forecasts derived from option prices, and (2) in improving volatility forecasts produced by ARCH and option models and combinations of models. Daily and monthly data are explored. We find that if trading volume was low during period t,1 relative to the recent past, ARCH is at least as important as options for forecasting future stock market volatility. Conversely, if volume was high during period t,1 relative to the recent past, option-implied volatility is much more important than ARCH for forecasting future volatility. Considering relative trading volume as a proxy for changes in the set of information available to investors, our findings reveal an important switching role for trading volume between a volatility forecast that reflects relatively stale information (the historical ARCH estimate) and the option-implied forward-looking estimate. [source] A NEW MEASURE OF US POTENTIAL OUTPUT, INFLATION FORECASTS, AND MONETARY POLICY RULES,THE MANCHESTER SCHOOL, Issue 5 2009CHARLES HARVIE This paper proposes a new measure of potential output for the USA. The key idea is that potential output is constructed as the level of output which would correspond to a forecast of no inflation change over the policy horizon. The resultant output gap has a clear interpretation as a measure to gauge future inflationary pressures. It also exhibits better predictability for future inflation changes in comparison with previous output gap measures. Simulation results further demonstrate its usefulness as a feedback variable in the Taylor monetary policy rule for interest rates. [source] Forecast-Based Monetary Policy: The Case of SwedenINTERNATIONAL FINANCE, Issue 3 2003Per Jansson Central banks are dominant players in financial markets and economic policy. For both democratic and efficiency reasons, it is important that central banks' actions can be understood, predicted, and evaluated. Inflation-targeting central banks that publish their forecasts provide unique opportunities for detailed studies of monetary policy based on real-time data. This paper demonstrates how a central bank's forecasts can be used to identify two different forms of discretionary monetary policy: ,policy shocks' (deviations from systematic policy) and ,judgements' in forecasting. [source] Valuation Accuracy and Infinity Horizon Forecast: Empirical Evidence from EuropeJOURNAL OF INTERNATIONAL FINANCIAL MANAGEMENT & ACCOUNTING, Issue 2 2009Lucio Cassia This paper focuses on the assumptions of infinite-horizon forecasting in the field of firm valuation. The estimate of long-run continuing values is based on the hypothesis that companies should have reached the steady state at the end of the period of explicit forecasts. It is argued that the equivalence between cash accounting and accrual accounting is the way of verifying the steady-state assumption, defined as the state when a firm earns exactly its cost of capital, i.e., what we would expect in pure-competition settings. From this definition, we derive that the "ideal" growth rate to use in steady state is equal to the reinvestment rate times Weighted Average Cost of Capital. To validate our approach, we collect a sample of 784 analyst valuations and compare how the implied target prices deviate from what the target prices would have been using the "ideal" steady-state growth rates. Using Logit and Cox regression models, we find that this deviation has predictive value over the probability that actual market price reaches the target price over the following 12-month period,the smaller the deviation the greater is the likelihood that the market price reaches the target price. [source] Why Has U.S. Inflation Become Harder to Forecast?JOURNAL OF MONEY, CREDIT AND BANKING, Issue 2007JAMES H. STOCK Phillips curve; trend-cycle model; moving average; great moderation We examine whether the U.S. rate of price inflation has become harder to forecast and, to the extent that it has, what changes in the inflation process have made it so. The main finding is that the univariate inflation process is well described by an unobserved component trend-cycle model with stochastic volatility or, equivalently, an integrated moving average process with time-varying parameters. This model explains a variety of recent univariate inflation forecasting puzzles and begins to explain some multivariate inflation forecasting puzzles as well. [source] The Future of Purchasing and Supply: A Ten-Year Forecast,JOURNAL OF SUPPLY CHAIN MANAGEMENT, Issue 1 2000Phillip L Carter SUMMARY The purpose of this research was the development of the 10-year forecasts for purchasing and supply based upon a close examination of key change drivers. The authors aimed at highlighting the most important areas of concern for purchasing executives. The research included trends of importance for organizations of all sizes, in all major industries , profit and nonprofit, private and public. To this end, the research team: ,,Identified the major economic, demographic, societal, competitive, and technological trends most likely to have major implications for the purchasing and supply management profession, its professionals, and organizationalprocesses ,,Projected the identified trends for 10 years (2008) ,,Determined the impact of these trends on purchasing and supply executives ,,Forecasted the environment for purchasing and supply in 10 years (2008) ,,Projected the changes to the purchasing and supply profession, its professionals, and organizational processes implied as a result of the research [source] Storm prediction over Europe using the ECMWF Ensemble Prediction SystemMETEOROLOGICAL APPLICATIONS, Issue 3 2002Roberto Buizza Three severe storms caused great damage in Europe in December 1999. The first storm hit Denmark and Germany on 3 and 4 December, and the other two storms crossed France and Germany on 26 and 28 December. In this study, the performance of the Ensemble Prediction System (EPS) at the European Centre for Medium-Range Weather Forecast (ECMWF) in predicting these intense storms is investigated. Results indicate that the EPS gave early indications of possible severe storm occurrence, and was especially useful when the deterministic TL319L60 forecasts issued on successive days were highly inconsistent. These results indicate that the EPS is a valuable tool for assessing quantitatively the risk of severe weather and issuing early warnings of possible disruptions. The impact of an increase of the ensemble system horizontal resolution (TL255 integration from a TL511 analysis instead of the operational TL159 integration from a TL319 analysis) on the system performance is also investigated. Results show that the resolution increase enhances the ensemble performance in predicting the position and the intensity of intense storms. Copyright © 2002 Royal Meteorological Society. [source] Focusing high energy X-rays with stacked Fresnel zone platesPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 8 2007I. Snigireva Abstract Stacking technique was developed in order to increase focusing efficiency of Fresnel zone plates at high energies. Two identical Si chips each of which containing Fresnel zone plates were used for stacking. Alignment of the chips was achieved by on-line observation of the moiré pattern from the two zone plates. The formation of moiré patterns was studied theoretically and experimentally at different experimental conditions. To provide the desired stability Si-chips with zone plates were bonded together with slow solidification speed epoxy glue. Technique of angular alignment in order to compensate a linear displacement in the process of gluing was proposed. Two sets of stacked FZPs were produced and experimentally tested to focus 15 and 50 keV X-rays. Gain in the efficiency by factor 2.5 was demonstrated at 15 keV. Focal spot of 1.8 ,m vertically and 14 ,m horizontally with 35% efficiency was measured at 50 keV. Forecast for the stacking of nanofocusing Fresnel zone plates was discussed. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Long-term Forecast of the Demographic Transition in Japan and AsiaASIAN ECONOMIC POLICY REVIEW, Issue 1 2009Takao KOMINE J11 Abstract The demographic structure of Asia is expected to change rapidly from around 2020 up to around 2050. Following Japan, which is already at an advanced stage of aging and birthrate decline, China, South Korea, Thailand, and Singapore will also witness a further decline in their birthrates and an aging of their populations. Next in line will be the remaining countries of the Association of South-East Asian Nations as well as India. Such changes, accompanied by a decline in the labor force, will not only adversely affect economic growth, but also have a major impact on voting structures, savings rates, and social security systems. Moreover, the process of demographic aging in Asia will be faster than in Japan, and its extent will be substantial, both of which exacerbates the negative effects. On positive side, these trends will give rise to the emergence of new markets. [source] Impact of environmental flows on the daytime urban boundary layer structures over the Baltimore metropolitan regionATMOSPHERIC SCIENCE LETTERS, Issue 1 2010Yi-Xuan Shou Abstract The three-dimensional structures of the urban daytime boundary layer (UDBL) over Baltimore are examined using a coupled Weather Research and Forecast,Urban Canopy model. Results show the upward growth of the urban heat island (UHI) effects as the surface-based ,hot plumes' with pronounced rising motions and thermal gradients. The UDBL tends to exhibit different vertical structures and intensities, depending on the magnitude and direction of environmental flows with respect to urban morphometric distributions and its interaction with the circulations induced by differential land covers. They are determined by both the local UHI effects and the nonlocal advective processes. Copyright © 2010 Royal Meteorological Society [source] Verformungsvorhersage von vorgespannten und nicht vorgespannten BetonbauteilenBETON- UND STAHLBETONBAU, Issue 6 2009Wolfgang Krüger Prof. Dr.-Ing. habil. Baustoffe; Berechnungs- und Bemessungsverfahren; Spannbeton Abstract Wie vergleichende Untersuchungen zeigen, führt eine Begrenzung der Verformung auf der Grundlage des Schlankheitsnachweises, wie er nach DIN 1045-1 bei Stahlbetonbauteilen möglich ist, nicht immer zu dem gewünschten Erfolg. In diesen Fällen und bei Spannbetonkonstruktionen ist grundsätzlich ein Nachweis der Verformungen erforderlich. Ausgehend von allgemeinen Betrachtungen zum Nachweis der Bauteilverformungen, werden wesentliche materialseitige Einflüsse auf die Verformungsvorhersage diskutiert. Es wird deutlich, dass eine genaue Berechnung der Verformung nur bedingt möglich ist. Im Anschluss wird für die tägliche Berechnungspraxis ein Näherungsansatz zur Vorhersage der Verformung bewehrter Betonbauteile formuliert. Im Rahmen von vergleichenden Betrachtungen wird die Genauigkeit des entwickelten Näherungsansatzes abgeschätzt. Hierbei zeigt sich eine gute baupraktische Übereinstimmung zwischen komplexen Berechnungen und dem vereinfachten Berechnungsansatz. Deformation Forecast of Prestressed and Non-Prestressed Concrete Members Comparative investigations have shown that the limitation of deformation, based on a permitted slenderness ratio as possible according to DIN 1045-1 for reinforced concrete elements, do not always achieve the desired success. An exact calculation of the structure deformation is absolutely necessary for prestressed components and in the case of a non-accomplished slenderness proof for reinforced concrete members. In this paper significant material influences of the deformation forecast will be discussed, proceeding from universal views of the component deformation proof. It will be clear, that an exact deformation calculation is only restricted possible. An approximation procedure for practical use to the forecast of deformations of reinforced and prestressed concrete structures will be formulated, afterwards. The accuracy of this developed approximation procedure will be estimated with the aid of comparative studies. At this, the results of the simplified formulation correlate well with the values of complex, numeric investigations in a range of practical use. [source] From Model to Forecasting: A Multicenter Study in Emergency DepartmentsACADEMIC EMERGENCY MEDICINE, Issue 9 2010Mathias Wargon MD ACADEMIC EMERGENCY MEDICINE 2010; 17:970,978 © 2010 by the Society for Academic Emergency Medicine Abstract Objectives:, This study investigated whether mathematical models using calendar variables could identify the determinants of emergency department (ED) census over time in geographically close EDs and assessed the performance of long-term forecasts. Methods:, Daily visits in four EDs at academic hospitals in the Paris area were collected from 2004 to 2007. First, a general linear model (GLM) based on calendar variables was used to assess two consecutive periods of 2 years each to create and test the mathematical models. Second, 2007 ED attendance was forecasted, based on a training set of data from 2004 to 2006. These analyses were performed on data sets from each individual ED and in a virtual mega ED, grouping all of the visits. Models and forecast accuracy were evaluated by mean absolute percentage error (MAPE). Results:, The authors recorded 299,743 and 322,510 ED visits for the two periods, 2004,2005 and 2006,2007, respectively. The models accounted for up to 50% of the variations with a MAPE less than 10%. Visit patterns according to weekdays and holidays were different from one hospital to another, without seasonality. Influential factors changed over time within one ED, reducing the accuracy of forecasts. Forecasts led to a MAPE of 5.3% for the four EDs together and from 8.1% to 17.0% for each hospital. Conclusions:, Unexpectedly, in geographically close EDs over short periods of time, calendar determinants of attendance were different. In our setting, models and forecasts are more valuable to predict the combined ED attendance of several hospitals. In similar settings where resources are shared between facilities, these mathematical models could be a valuable tool to anticipate staff needs and site allocation. [source] Accounting Policy Disclosures and Analysts' ForecastsCONTEMPORARY ACCOUNTING RESEARCH, Issue 2 2003Ole-Kristian Hope Abstract Using an international sample, I investigate whether the extent of firms' disclosure of their accounting policies in the annual report is associated with properties of analysts' earnings forecasts. Controlling for firm- and country-level variables, I find that the level of accounting policy disclosure is significantly negatively related to forecast dispersion and forecast error. In particular, I find that accounting policy disclosures are incrementally useful to analysts over and above all other annual report disclosures. These findings suggest that accounting policy disclosures reduce uncertainty about forecasted earnings. I find univariate but not multivariate support for the hypothesis that accounting policy disclosures are especially helpful to analysts in environments where firms can choose among a larger set of accounting methods. [source] Auditor Quality and the Accuracy of Management Earnings Forecasts,CONTEMPORARY ACCOUNTING RESEARCH, Issue 4 2000PETER M. CLARKSON Abstract In this study, we appeal to insights and results from Davidson and Neu 1993 and McConomy 1998 to motivate empirical analyses designed to gain a better understanding of the relationship between auditor quality and forecast accuracy. We extend and refine Davidson and Neu's analysis of this relationship by introducing additional controls for business risk and by considering data from two distinct time periods: one in which the audit firm's responsibility respecting the earnings forecast was to provide review-level assurance, and one in which its responsibility was to provide audit-level assurance. Our sample data consist of Toronto Stock Exchange (TSE) initial public offerings (IPOs). The earnings forecast we consider is the one-year-ahead management earnings forecast included in the IPO offering prospectus. The results suggest that after the additional controls for business risk are introduced, the relationship between forecast accuracy and auditor quality for the review-level assurance period is no longer significant. The results also indicate that the shift in regimes alters the fundamental nature of the relationship. Using data from the audit-level assurance regime, we find a negative and significant relationship between forecast accuracy and auditor quality (i.e., we find Big 6 auditors to be associated with smaller absolute forecast errors than non-Big 6 auditors), and further, that the difference in the relationship between the two regimes is statistically significant. [source] The Effect of National Governance Codes on Firm Disclosure Practices: Evidence from Analyst Earnings ForecastsCORPORATE GOVERNANCE, Issue 6 2008John Nowland ABSTRACT Manuscript Type: Empirical Research Question: This study examines whether voluntary national governance codes have a significant effect on company disclosure practices. Two direct effects of the codes are expected: 1) an overall improvement in company disclosure practices, which is greater when the codes have a greater emphasis on disclosure; and 2) a leveling out of disclosure practices across companies (i.e., larger improvements in companies that were previously poorer disclosers) due to the codes new comply-or-explain requirements. The codes are also expected to have an indirect effect on disclosure practices through their effect on company governance practices. Research Findings/Results: The results show that the introduction of the codes in eight East Asian countries has been associated with lower analyst forecast error and a leveling out of disclosure practices across companies. The codes are also found to have an indirect effect on company disclosure practices through their effect on board independence. Practical Implications: This study shows that a regulatory approach to improving disclosure practices is not always necessary. Voluntary national governance codes are found to have both a significant direct effect and a significant indirect effect on company disclosure practices. In addition, the results indicate that analysts in Asia do react to changes in disclosure practices, so there is an incentive for small companies and family-owned companies to further improve their disclosure practices. [source] An Approximate Bayesian Algorithm for Combining Forecasts,DECISION SCIENCES, Issue 3 2001Kim-Hung Li Abstract In this paper we propose a consensus forecasting method based on a convex combination of individual forecast densities. The exact Bayesian updating of the convex combination weights is very complex and practically prohibitive. We propose a simple sequential updating alternative method based on function approximation. Several examples illustrate the method. [source] Combining Time-Series Components for Improved ForecastsDECISION SCIENCES JOURNAL OF INNOVATIVE EDUCATION, Issue 1 2008Frank G. Landram First page of article [source] Conservation value of degraded habitats for forest birds in southern Peninsular MalaysiaDIVERSITY AND DISTRIBUTIONS, Issue 5 2006Kelvin S.-H. ABSTRACT Clearance of tropical forest for agricultural purposes is generally assumed to seriously threaten the survival of forest species. In this study, we quantified the conservation value, for forest bird species, of three degraded habitat types in Peninsular Malaysia, namely rubber tree plantations, oil palm plantations, and open areas. We surveyed these degraded habitats using point counts to estimate their forest bird species richness and abundance. We assessed whether richness, abundance, and activities of different avian dietary groups (i.e. insectivores and frugivores) varied among the habitats. We identified the critical habitat elements that accounted for the distribution of forest avifauna in these degraded habitats. Our results showed that these habitats harboured a moderate fraction of forest avifauna (approximately 46,76 species) and their functions were complementary (i.e. rubber tree plantations for moving; open habitats for perching; shrubs in oil palm plantations for foraging). In terms of species richness and abundance, rubber tree plantations were more important than oil palm plantations and open habitats. The relatively high species richness of this agricultural landscape was partly due to the contiguity of our study areas with extensive forest areas. Forecasts of forest-species presence under various canopy cover scenarios suggest that leaving isolated trees among non-arboreal crops could greatly attract relatively tolerant species that require tree canopy. The conservation value of degraded habitats in agricultural landscapes seems to depend on factors such as the type of crops planted and distance to primary forest remnants. [source] Transport and environment: policy directions for europeENVIRONMENTAL POLICY AND GOVERNANCE, Issue 3 2001Robert Tinch Transport externalities are among the most important environmental problems affecting quality of life in Europe. Forecasts suggest that past environmental improvements may now be rolled back by traffic growth, and current traffic trends are not sustainable. The theory of environmental policy proposes pricing external costs at their marginal social costs as one solution. Although full marginal social cost pricing is impracticable, advances in tolling technology and environmental valuation mean that it is now a viable option to approximate such charging. There are signs that the European Commission and other bodies are starting to favour pricing over regulatory instruments. However, often overlooked is the potential for non-convexities in the transport sector or between transport and the rest of the economy. For example it may be that small increases in resources for public transport would not result in welfare gains, whereas large increases would. Non-convexities would mean that market forces under marginal social cost pricing might lead away from the optimal transport system. This is one reason why pricing instruments cannot in themselves be a panacea for transport externalities or bring about a sustainable transport system. Copyright © 2001 John Wiley & Sons, Ltd and ERP Environment [source] IPO Underpricing, Firm Quality, and Analyst ForecastsFINANCIAL MANAGEMENT, Issue 2 2007Steven X. Zheng We find that IPO underpricing is positively related to post-IPO growth in sales and EBITDA, but is not significantly related to growth in earnings. Our evidence suggests that accrual reversals or earnings management may cause this inconsistency. We interpret the growth rates of sales and EBITDA as measures of firm quality, and conclude that our evidence supports the notion that IPO firms with greater underpricing are of better quality. Our tests on analysts' earnings forecast errors show that analysts are less positively biased in their earnings forecasts for IPO firms that have greater underpricing. [source] Monetary Policy and Forecasts for Real GDP Growth: An Empirical Investigation for the Federal Republic of GermanyGERMAN ECONOMIC REVIEW, Issue 4 2001Gebhardt Kirschgässner Using quarterly data for the Federal Republic of Germany, we generate four-quarter-ahead forecasts for real GDP growth. Throughout the 1970s and 1980s, other monetary indicators like real M1 or short-run interest rates clearly outperform forecasts which are based on interest rate spreads. This holds for within as well as for ex-post predictions. The same holds for the development after 1992. Moreover, it is shown that simple forecasts based on M1 or on short-run interest rates outperform the common biannual GNP forecasts of the group of German economic research institutes. [source] Seasonal and inter-annual variability of the moisture sources for Alpine precipitation during 1995,2002INTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 7 2010Harald Sodemann Abstract This study presents a first quantitative climatology of the moisture sources for precipitation in the European Alps, covering a 7-year period from January 1995 to August 2002. Using a Lagrangian moisture source diagnostic and data from the ERA-40: European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis, the contribution of the following moisture sources to annual mean precipitation has been diagnosed: North Atlantic ocean 39.6%, Mediterranean 23.3%, North Sea and Baltic Sea 16.6%, and European land surface 20.8%. However, strong seasonal variability of the influence of various moisture sources is evident. Most notably, moisture transport to the Alps changes from an oceanic mode characterised by dominantly North Atlantic moisture sources during winter to a continental mode during summer with a marked contribution from Central European land areas. The method identifies inter-annual variability with respect to the location of the moisture sources in the North Atlantic, and the importance of precipitation recycling during summer. Despite the smoothed Alpine orography in the ERA-40 model, the Alps act as an effective barrier for meridional moisture transport, leading to distinct mean moisture source locations at their northern and southern slopes. The Northern Alps are predominantly influenced by the North Atlantic ocean and Central European land sources with a clear seasonality and limited monthly variability. In contrast, the Southern Alps receive a large fraction of precipitation from the Mediterranean with considerable month-to-month variability. Possible implications of these differences for precipitation extremes and stable isotopes in precipitation are discussed. Copyright © 2009 Royal Meteorological Society [source] The surface radiation budget over North America: gridded data assessment and evaluation of regional climate modelsINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 15 2009Marko Markovic Abstract While surface station observations of downwelling radiation offer accuracy at high temporal resolution, they do not easily allow an evaluation of model surface radiation budgets (SRB) over a wide geographical area. We evaluate three gridded SRB data sets against detailed observations from six surface radiation sites from the US surface radiation (SURFRAD) network. We subsequently use the most accurate surrogate observational data set for evaluation of model-simulated SRB. The data sets assessed are: ERA40,reanalysis of European Centre for Medium-Range Weather Forecasts (ECMWF), North American Regional Reanalysis (NARR),regional reanalysis of National Centres for Environmental Prediction (NCEP) and the surface radiative budget (SRB) from the International Satellite Cloud Climatology Project (ISCCP). Due to varying constraints with respect to temporal coverage of each data set, the evaluation period used in this study is 1996,2001, inclusive. The ERA40 downwelling longwave radiation (DLR) appears the most accurate surrogate observation, while both ERA40 and ISCCP show accurate results when the incoming shortwave radiation (ISR) is considered across the annual cycle. Winter DLR is less accurate in ISCCP with a positive bias and lack of very low (<200 Wm,2) flux values. The NARR SRB shows a large positive bias in the ISR throughout the annual cycle, linked to a significant underestimate of cloud cover. The ERA40 data are subsequently used to evaluate the simulated SRB in three regional climate models across North America. With respect to solar radiation, cloud cover biases are seen to be crucial, while for longwave fluxes both cloud fraction and in-cloud water content are important to simulate correctly. Inclusion of trace gases beyond H2O, CO2 and O3 appears necessary for an accurate calculation of clear-sky longwave radiation. Error compensation frequently occurs between the various components contributing to a model total-sky SRB. This is important to consider when trying to identify the underlying causes of errors in the simulated total SRB. Copyright © 2009 Royal Meteorological Society [source] Global atmospheric energetics from NCEP,Reanalysis 2 and ECMWF,ERA40 ReanalysisINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 2 2009Carlos A. F. Marques Abstract The global atmospheric energy cycle is estimated on an annual basis using Reanalysis 2 data from the National Centers for Environmental Prediction and National Center for Atmospheric Research (NCEP/NCAR), and ERA 40 Reanalyses from the European Centre for Medium-Range Weather Forecasts (ECMWF) for the period 1979,2001. A formalism to avoid belowground data on pressure levels intercepted by topography is adopted. No appreciable differences were found between the two datasets from the energetics point of view. The so-called ,, and v·grad z formulations were both used for the conversions from zonal available potential energy into zonal kinetic energy (CZ) and from eddy available potential energy into eddy kinetic energy (CE). Results with both formulations are comparable only when using the formalism preventing belowground data to enter into the computations. Atmospheric energetics are also computed using ECMWF Reanalyses for the period 1958,1978. A significant increase was found in the eddy kinetic and eddy available potential energies from the early period to the later period, likely related to the assimilation in the reanalyses of satellite data after 1979. The conversion rate, CZ, was found to change its sign throughout the years. The atmospheric energy cycle using the ECMWF Reanalyses data is compared with five previous estimates. Differences in the direction of the conversion rate, CZ, between the various estimates may be explained by the different time periods chosen for averaging. Owing to the omission of belowground data, the conversion from zonal available potential energy into eddy available potential energy (CA) was somewhat smaller in ECMWF Reanalyses than in the previous estimates. Despite those differences, an overall agreement may be found between the various estimates for the atmospheric energy cycle. Copyright © 2008 Royal Meteorological Society [source] Atmospheric moisture budget over Antarctica and the Southern Ocean based on the ERA-40 reanalysisINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 15 2008Hanna Tietäväinen Abstract The atmospheric moisture budget over Antarctica and the Southern Ocean was analysed for the period 1979,2001 on the basis of the ERA-40 reanalysis of the European Centre for Medium-Range Weather Forecasts. Meridional transport by transient eddies makes the largest contribution to the southward water vapour transport. The mean meridional circulation contributes to the northward transport in the Antarctic coastal areas, but this effect is compensated by the southward transport by stationary eddies. The convergence of meridional water vapour transport is at its largest at 64,68°S, while the convergence of zonal transport is regionally important in areas of high cyclolysis. Inter-annual variations in water vapour transport are related to the southern annular mode (SAM). The eastward transport has a significant (95% confidence level) positive correlation with the SAM index, while the northward transport has a significant negative correlation with SAM near 60°S. Hydrological balance is well-achieved in the ERA-40 reanalysis: the difference between the water vapour flux convergence (based on analysis) and the net precipitation (precipitation minus evaporation, based on 24-h forecasts) is only 13 mm yr,1 (3%) over the Southern Ocean and , 8 mm yr,1 (5%) over the continental ice sheet. Over the open ocean, the analysis methodology favours the accuracy of the flux convergence. For the whole study region, the annual mean flux convergence exceeded net precipitation by 11 mm yr,1 (3%). The ERA-40 result for the mean precipitation over the Antarctic continental ice sheet in 1979,2001 is 177 ± 8 mm yr,1, while previous estimates range from 173 to 215 mm yr,1. For the period 1979,2001, the ERA-40 data do not show any statistically significant trend in precipitation over the Antarctic grounded ice sheet and ice shelves. From the ERA-40 data, the annual average net evaporation (evaporation minus condensation) is positive over the whole continent. Copyright © 2008 Royal Meteorological Society [source] Simulation of Indian summer monsoon: sensitivity to cumulus parameterization in a GCMINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 8 2007S. K. Deb Abstract Hindcasts for the Indian summer monsoons (ISMs) of 2002 and 2003 have been produced from a series of numerical simulations performed with a general circulation model using different cumulus parameterization schemes. Ten sets of ensemble simulations have been produced without using any vegetation scheme but by prescribing the monthly observed SST from the ECMWF (European Centre for Medium Range Weather Forecasts) analyses. For each ensemble, ten simulations have been realised with different initial conditions that are also prepared from the ECMWF data: five each from the April and May analyses of both the years. Stream function, velocity potential with divergent winds at 200 hPa, winds at 850 hPa and rainfall patterns with their anomalies have been analysed and interpreted. The large-scale upper and lower level circulation features are simulated satisfactorily. The spatial structure of predicted July monsoon rainfall over India shows a fair agreement with the GPCP (observed) pentad rainfall distribution. The variability associated with all-India June,July simulated rainfall time series matches reasonably well with the observations in 2003, but the model fails to simulate the observed variability in July 2002. Further evaluation of the model-produced precipitation in seasonal simulations is done with the help of empirical orthogonal functions (EOFs) of the GPCP rainfall over India. Since the first four EOFs explain a significant part of the total variance of the observed rainfall, the simulated precipitation is projected on to these modes. Thus, the differences in simulated and observed rainfall fields manifest in the time series of their expansion coefficients, which are utilised for inter-comparison/evaluation of model simulations. Copyright © 2006 Royal Meteorological Society [source] | |||||||||||||||||||||||||||||||||||||||||||||||||