The ECMWF re-analysis project is a meteorological reanalysis project.The first reanalysis product, ERA-15, generated re-analyses for approximately 15 years, from December 1978 to February 1994. The second product, ERA-40 begins in 1957 and covers 45 years to 2002. As a precursor to a revised extended reanalysis product to replace ERA-40, ECMWF has recently released ERA-Interim, which covers the period from 1979 to present.In addition to re-analysing all the old data using a consistent system, the reanalyses also make use of much archived data that was not available to the original analyses. This allows for the correction of many historical hand-drawn maps where the estimation of features was common in areas of data sparsity. The ability is also present to create new maps of atmosphere levels that were not commonly used until more recent times. Wikipedia.
Tellus, Series A: Dynamic Meteorology and Oceanography | Year: 2017
This paper reports on the influence of taking the slanted satellite viewing geometry better into account in the simulation and assimilation of sounding radiances. The traditional approach is to use a vertical profile extracted at the geo-location information provided with the data. The present work instead investigates using a slanted profile, extracted from model fields along the instrument's line of sight. Taking the viewing geometry better into account leads to significant improvements in the simulation of brightness temperatures from model fields compared to the traditional approach. This is particularly noticeable for larger zenith angles, for channels that peak in the upper troposphere or higher and have relatively low noise, and for high and mid-latitudes. The finding also suggests that the model fields capture useful information on horizontal gradients, at least on the relevant spatial scales. The improved simulations of the sounder radiances lead to significant reductions in the size of the analysis increments at mid and high latitudes and particularly in the stratosphere during the assimilation. The system shows a statistically improved self-consistency out to the day-3 forecast range. © 2017 European Centre for Medium-Range Weather Forecasts (ECMWF).
Quarterly Journal of the Royal Meteorological Society | Year: 2017
Although the quality of medium-range forecasts has increased considerably over the decades since the start of operational forecasts at the European Centre for Medium-Range Weather Forecasts (ECMWF), individual forecasts still occasionally experience very large errors. Often the phrasing ‘drop-outs’ or ‘forecast busts’ is used for such episodes. The aim of this report is to use a combination of methods to track errors in three cases of extreme forecast errors between 2014 and 2016, to understand the error sources better. Manual error tracking and ensemble sensitivity are used to give a first guess for the source region and relaxation experiments are used to confirm the result. In the three cases investigated, the errors originated from the tropical eastern Pacific, western/central Canada and western Atlantic, respectively. The mechanisms behind the errors are discussed in the report. The results from this study can form a basis for further investigations of these cases and the methodology explained can be applied to understand future bust cases, to increase our knowledge of the origin and propagation of forecast errors. © 2017 Royal Meteorological Society
Joly M.,Meteo - France |
Atmospheric Environment | Year: 2012
The observation sites that make up air quality monitoring networks can have very different characteristics (topography, climatology, distance to emission sources, etc), which are partially described in the meta-information provided with data sets. At the scale of Europe, the description of the sites depends on the institute(s) in charge of the air quality monitoring in each country, and is based on specific criteria that can be sometimes rather subjective. The purpose of this study is to build an objective, homogeneous, and pollutant-specific classification of European air quality monitoring sites, primarily for the purpose of model verification and chemical data assimilation. Most studies that tackled this issue so far were based on limited data sets, and often took into account additional external data such as population density, emission estimates, or land cover maps. The present study demonstrates the feasibility of a classification only based on the past time series of measured pollutants. The underlying idea is that the true fingerprint of a given monitoring site lies within its past observation values. On each site to be categorized, eight indicators are defined to characterize each pollutant time series (O 3, NO 2, NO, SO 2, or PM 10) of the European AirBase and the French BDQA (Base de Données de Qualité de l'Air) reference sets of validated data over the period 2002-2009. A Linear Discriminant Analysis is used to best discriminate the rural and urban sites. After projection on the Fisher axis, ten classes are finally determined on the basis of fixed thresholds, for each molecule. The method is validated by cross-validation and by direct comparison with the existing meta-data. The link between the classes obtained and the meta-data is strongest with NO, NO 2, and PM 10. Across Europe, the classification exhibits interesting large-scale features: some contrasts between different regions depend on the pollutant considered. Comparing the classes obtained for different pollutants at the same site reveals an interesting consistency between the separate classifications. The robustness of the method is finally assessed by comparing the classifications obtained for two distinct subsets of years. The robustness - and thus the skill of the objective classification - is satisfying for all of the species, and is highest with NO and NO 2. © 2011 Elsevier Ltd.
Journal of Geophysical Research: Atmospheres | Year: 2011
The sensitivity of European Centre for Medium-Range Weather Forecasts (ECMWF) numerical weather prediction analyses to the empirical refractivity coefficients used to assimilate bending angles derived from GPS radio occultation measurements has been investigated. We have compared the Smith and Weintraub (1953) coefficients with the "best average" values proposed by Reger (2002). The Reger values produce simulated bending angles in the upper troposphere and stratosphere that are larger by ∼0.115%. This produces a cooling in the troposphere by around ∼-0.1 K, which improves the fit to radiosonde geopotential height measurements in the Northern Hemisphere but degrades the fit in the tropics and Southern Hemisphere. The cooling is caused primarily by Reger's increase in the "k1" refractivity coefficient, which accounts for the dry air contribution to the total refractivity. It is confirmed that this cooling can be reduced by introducing nonideal gas effects in the hydrostatic integration of the forward model. However, the Reger k1 coefficient should also be adjusted to k 1 = 77.643 K hPa-1 if it is used in a forward model that includes nonideal gas effects when evaluating the refractivity from the model state. Furthermore, if the nonideal gas effects are introduced in a consistent way, we find that the Reger coefficients plus nonideal gas effects produce very similar results to the Smith and Weintraub values, where nonideal gas effects are neglected. © 2011 by the American Geophysical Union.
Quarterly Journal of the Royal Meteorological Society | Year: 2014
The impact of Radio Occultation observations from Global Positioning System satellites (GPSRO) on global Numerical Weather Prediction (NWP) has been analysed with a recent version of the European Centre for Medium-range Weather Forecasting (ECMWF) Integrated Forecasting System. As in previous studies, the use of GPSRO was found to improve the NWP forecast skill and to drastically decrease model-induced temperature biases in the analysis. The maximum forecast impact is in the lower and middle stratosphere, where the GPSRO observations have the smallest errors, but it is also visible in the troposphere. The tropospheric impact of GPSRO comes in part from direct tropospheric measurements and in part from stratosphere-troposphere interactions: this second mechanism is found to be particularly important during the Northern Hemisphere winter. The forecast impact of GPSRO observations is compared with that of conventional and hyperspectral satellite nadir sounders. It is found that although GPSRO data have a smaller impact than those of either class of nadir sounders, they are still able to account for a considerable fraction (30-70%) of the global forecast error reduction afforded by the use of the full observing system over a system that uses only conventional observations. When forecast verification is performed against radiosonde observations, GPSRO is found to be the most valuable satellite observing system in the lower stratosphere. This is remarkable in view of the relative sparseness of the GPSRO spatial and temporal coverage and an indication of the potential improvements that a denser GPSRO observing network would be able to provide. The forecast impact of GPSRO observations is also evaluated in the context of a data denial assimilation experiment with respect to the full observing system. Results are found to be consistent with those from the reduced baseline observational network and also indicate a statistically significant positive impact on tropospheric synoptic skill scores. © 2013 Royal Meteorological Society.
Journal of Geophysical Research: Oceans | Year: 2012
Ocean waves play an important role in processes that govern the fluxes across the air-sea interface and in the upper-ocean mixing. Equations for current and heat are presented that include effects of ocean waves on the evolution of the properties of the upper ocean circulation and heat budget. The turbulent transport is modeled by means of the level-21/2 Mellor-Yamada scheme, which includes an equation for the production and destruction of Turbulent Kinetic Energy (TKE). The TKE equation in this work includes production due to wave breaking, production due to wave-induced turbulence and/or Langmuir turbulence, effects of buoyancy and turbulent dissipation. As a first test, the model is applied to the simulation of the daily cycle in SST at one location in the Arabian sea for the period of October 1994 until October 1995. For this location, the layer where the turbulent mixing occurs, sometimes called the Turbocline, is only a few meters thick and fairly thin layers are needed to give a proper representation of the diurnal cycle. The dominant processes that control the diurnal cycle turn out to be buoyancy production and turbulent production by wave breaking, while in the deeper layers of the ocean the Stokes-Coriolis force plays an important role. © 2012. American Geophysical Union. All Rights Reserved.
Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences | Year: 2014
The steady path of doubling the global horizontal resolution approximately every 8 years in numerical weather prediction (NWP) at the European Centre forMedium RangeWeather Forecasts may be substantially altered with emerging novel computing architectures. It coincides with the need to appropriately address and determine forecast uncertainty with increasing resolution, in particular, when convectivescale motions start to be resolved. Blunt increases in the model resolution will quickly become unaffordable and may not lead to improved NWP forecasts. Consequently, there is a need to accordingly adjust proven numerical techniques. An informed decision on the modelling strategy for harnessing exascale, massively parallel computing power thus also requires a deeper understanding of the sensitivity to uncertainty-for each part of the model-and ultimately a deeper understanding of multi-scale interactions in the atmosphere and their numerical realization in ultra-high-resolution NWP and climate simulations. This paper explores opportunities for substantial increases in the forecast efficiency by judicious adjustment of the formal accuracy or relative resolution in the spectral and physical space. One path is to reduce the formal accuracy by which the spectral transforms are computed. The other pathway explores the importance of the ratio used for the horizontal resolution in gridpoint space versus wavenumbers in spectral space. This is relevant for both high-resolution simulations as well as ensemble-based uncertainty estimation. © 2014 The Author(s) Published by the Royal Society. All rights reserved.
Agency: GTR | Branch: NERC | Program: | Phase: Research Grant | Award Amount: 378.72K | Year: 2012
There is currently a large effort in the development of general circulation model (GCM)-based seasonal to decadal prediction systems to provide climate forecasts. Such techniques are rather complex, technically challenging and still in their infancy. Any weather or climate forecast will be subject to three sources of uncertainty, namely observation uncertainty, the model-component of initial uncertainty, and model uncertainty over the forecast period. The aim of this proposal is to improve the reliability of extended range forecast of weather and climate, mainly focusing on the ocean component of the coupled system. We propose to develop and incorporate various tools based on stochastic physics to improve the reliability of forecasts focusing on a more accurate representation of ocean observations and model uncertainties. The individual impacts of the different developments on the reliability of the forecasts will be quantified to provide estimates of the different sources of uncertainties in the forecasts. The development of reliable extended range forecasts can be extremely beneficial with major economical and societal consequences.
Agency: GTR | Branch: NERC | Program: | Phase: Research Grant | Award Amount: 344.28K | Year: 2011
Scarcity of water has been identified as the most serious environmental threat facing the health and security of people living in the tropics. Pressures on water supply undermine stability through stresses on food availability and spread of disease e.g., malaria and meningitis. Yet predictions of precipitation show very high uncertainty in the Tropics and especially the arid climatic zones such as sub-Saharan Africa where the vulnerability of the population is amongst the highest in the world. The outlook for Sahel precipitation in coupled simulations of the twenty-first century remains very uncertain with no consensus as to whether there will be more or less rain in the future, or how the frequency and intensity of high impact weather will change. Skillful forecasts of rainfall would be of enormous benefit across all timescales ranging from hours to decades. In particular, short-range forecasts (up to 2 days) for the public and aviation industry, and medium-range forecasts (10-30 days) for agriculture, hydrology and health information. This is challenging since rainfall is organised through a complex interplay of large-scale wave patterns, weather systems and isolated deep convective updrafts. The locations of individual convective updrafts are not predictable and even the occurrence and evolution of mesoscale weather systems are poorly represented in Numerical Weather Prediction (NWP) models. However, there is some hope for greater predictability since the pattern of active and inactive regions of convection is often determined by large-scale wave structure. Examples of such phenomena include African Easterly Waves (AEWs) and equatorial waves. Owing to the waves, there is potential predictability for high impact weather events occurring simultaneously in several locations at once. For example, if several storms are spawned within a large-scale wave, each one of them could present a significant natural hazard, with safety and financial implications (such correlated events are not accounted for in the risk models used by the insurance industry). Unfortunately, there are severe deficiencies in the simulation of tropical large-scale waves which typically decay far too quickly in forecasts and propagate too slowly. However, it is difficult to amend models to improve the simulation of large-scale tropical waves because underpinning theory for tropical waves is currently too weak to unpick the problem. It is necessary to formulate better how different processes influence wave evolution so that modifications can be aimed at improving wave representation. The aim of the proposed project is to develop the theory behind large-scale waves in the tropics to the level where it can be applied in the quantitative diagnosis of observed weather systems. In doing so we aim to identify the processes that are most important in wave initiation, maintenance and propagation, and ways in which they are misrepresented in models, with a view to improving weather forecasts. The research will study the interplay between large-scale waves and convective rainfall through three stages of complexity: A) the dynamics of waves assuming small amplitude, B) large-amplitude aspects including vacillations between jet strength and wave amplitude, and C) explaining deficiencies in state-of-the-art forecasts of tropical waves using the new theory developed. The anticipated benefit of the research is improvement in weather forecasts of rainfall throughout the tropics at lead times of a day to a season. Stage C will be advanced through collaboration with project partners from two world-leading operational forecast centres: the Met Office and European Centre for Medium-Range Weather Forecasts.
News Article | March 3, 2017
The next-generation supercomputer that will drive Europe’s medium-range weather forecasts looks set to be housed in Bologna, Italy, from 2020. It would succeed the current system based in Reading, UK. Member states of the European Centre for Medium-range Weather Forecasts (ECMWF) made the indicative decision to relocate the facility on Wednesday. Detailed negotiations will now be held with Italian authorities. The intention is to confirm the choice in June. That is the date of the next full Council meeting of the ECMWF. The bid from Italy's Emilia-Romagna Region to erect a new €50m (£43m) building on the site of an old tobacco factory was regarded as the leading contender, according to an evaluation panel. A proposal from Finland is back-up should the legal, financial and technical discussions over the next few months suddenly fall over. The ECMWF is an independent intergovernmental organisation supported by 22 full member states from Europe, with another 12 co-operating nations. Its supercomputer system ingests weather observations to run models that construct forecasts out to 15 days ahead. These forecasts are then shared with the member national meteorological agencies, such as Meteo France and the UK's Met Office. The ECMWF's HQ has been sited at Shinfield Park on the outskirts of Reading since the organisation's set-up four decades ago. Its first supercomputer, a CRAY-1A, was installed in 1978. The machines have been regularly updated, but the existing Reading buildings are not considered capable of meeting the technical requirements of the next device. The dual CRAY-XC40 system currently running the numerical models will therefore be the last supercomputing to be done at Shinfield Park. "It has been clear for a while now that the current data centre facility does not offer the required flexibility for future growth and changes in high-performance computing technology," ECMWF's Director-General Florence Rabier said in a statement. "As laid out in our 2025 Strategy launched last September, we believe that continuing to improve weather predictions relies heavily on our ability to support our science with proportionate computing power. Intermediary goals to 2020 already require that the Centre’s next supercomputers should provide a tenfold increase in our computational capacity." ECMWF staff do not need to be in the same location as the supercomputing facilities and there is no plan to move them as well. The centre employs more than 300 people in Reading, many of them engaged in advanced meteorological research. They will, for example, be working very closely with the European Space Agency later this year when it launches the British-built Aeolus satellite. This spacecraft is due to gather the first truly global, three-dimensional view of winds on Earth, providing a significant boost to the skill of medium-range forecasting. A spokesperson for the centre said the movement of data storage and supercomputing out of the UK would have no impact on research activities in the UK. The ECMWF remained committed to Reading, she told the BBC. Half of its €100m (£85m) budget comes through direct contributions from member states. The other half comes from the European Union, which contracts the ECMWF to perform climate change and atmospheric monitoring under its Copernicus environmental programme. Brexit should have no impact on that arrangement, the spokesperson said, as the ECMWF already includes non-EU member states. Jonathan.Amos-INTERNET@bbc.co.uk and follow me on Twitter: @BBCAmos