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.
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 | December 6, 2016
After a historically mild November, the start of meteorological winter is shaping up to be extremely cold and snowy for parts of the North America, including the U.S. For weeks now, ultra cold air has been building up in Siberia, as the polar vortex has been wobbling around like a bad figure skater, displaced outside of the Arctic. Now it appears the Russian Arctic will warm up dramatically, relative to normal at least, as North America cools off — potentially big time. The frigid air is coming in two waves. The first is already spilling across the U.S. The second, potentially more potent one, is on tap for next week. SEE ALSO: Google's data centers, offices will use 100% renewable energy in 2017 The Upper Midwest, parts of the Plains states, the Rocky Mountains and the Pacific Northwest are already being affected by the first cold burst of air. In some areas, temperatures are 20 to 30 degrees Fahrenheit below average for this time of year. By far the coldest air is setting up shop across Alberta, where daily highs are likely to remain below zero Fahrenheit through the end of the week. In other areas it's just seasonably cold. In the northern Rockies and northern Plains, high temperatures may stay in the single digits on Wednesday and Thursday this week, as the worst of the cold settles in. The cold air mass will moderate somewhat as it shifts eastward, affecting the Mid-Atlantic and Northeast this weekend. Of greater interest, however, is what may lie ahead. Some computer models are hinting at a potentially far more formidable shot of cold weather during the second week of December, with a lobe of the polar vortex rotating south out of Canada, into the Southeastern U.S. The main polar vortex is a circulation of air enveloping a near-permanent area of low pressure that exists in the upper atmosphere, above typical cruising altitudes for commercial jetliners, over the Arctic. When these winds weaken, as has been happening recently, pieces of the vortex can break off, and meander south into the U.S., Europe and parts of Asia. If the second Arctic blast is as impressive as some model runs are showing, then temperatures could fall well below average for this time of year, possibly more than 30 degrees below average across the Midwest, East and Southeast. Meanwhile, in the West, milder Pacific air would move in, potentially leading to coastal rain and mountain snows. The GFS model is among the more aggressive ones projecting the second Arctic blast, showing high temperatures in the single digits along the East Coast by Dec. 16, and overnight lows well below zero. However, it has support from the more reliable Euro model as well, which lends this scenario more credibility (though still far from certainty). Such severe cold so early in the season would be rare, and is typically only seen when a solid snowpack is in place to allow for more of the sun's heat to be reflected back out into space. "Mid-December on the calendar can surely see extreme cold (and snow) but it's not quite the dead or middle of winter," said Ryan Maue, a meteorologist with WeatherBell Analytics, in a Twitter message with Mashable. "Warmer, Pacific modified air will directly compete over the Western United States," Maue says. "This would mean beneficial rainfall for California coast and huge snowfall totals for mountains." ECMWF model projection showing ultra-cold air (dark blue/green) associated with a lobe of the polar vortex rotating into the U.S. As for the track of the coldest air, Maue said the heart of the cold may track across the Ohio River Valley and into the Mid-Atlantic and Northeast. "Current model tracks of the 'tropospheric polar vortex' are for the vorticity maximum at 500-mb to swing like a pendulum through Manitoba and Ontario with the coldest Arctic air on the backside reaching as far south as the Ohio River," Maue said. To decode that a bit: The 500 millibar level he referred to equates to an altitude of about 18,000 feet. And vorticity essentially means atmospheric spin. Euro model ensemble forecast for Dec. 15, showing unusually cold conditions across the Northeast. The details on this second cold air outbreak are unclear at this time, since it's at least a week away and some computer models are not showing the truly severe cold that others are. However, the potential is there for a headline-grabbing bout of frigid weather that is similar in magnitude to the 2014 "polar vortex" winter event, when Chicago was nicknamed "Chiberia," and sea smoke was seen on the Hudson River in New York City. However, before you freak out about weeks spent indoors and run to buy long underwear and a new North Face coat, wait a few days as the forecast evolves. Stay tuned for updates, and remember that the polar vortex is not some monstrous storm that invades your neighborhood, but rather describes weather patterns high in the atmosphere. Still, just in case, maybe start pricing out vacation options in the Caribbean? BONUS: Google Earth Timelapse shows how man has altered the planet in 32 years
News Article | October 26, 2016
What did I learn from the 2016 annual European Meteorological Society (EMS) conference that last week was hosted in Trieste (Italy)? I think the biggest news from the conference was that new reanalyses are soon to be released by the European Centre for Medium-ranged Weather Forecasts (ECMWF). One new product known as ERA-5 will replace the older called ERAINT, and preliminary results suggest a significant improvement in addition to higher spatial resolution. Check this webportal for ECMWF’s different reanalysis products. By the way, the naming convention of these reanalyses is rather strange and seems to defy any logic (first there was ERA-15, then ERA-40, followed be ERAINT, ERA-20C,…). A coupled reanalyses known as CERA-20 was also presented, which breaks with the traditional atmosphere-only products. A coupled assimilation scheme for both atmosphere and ocean seems to give better quality and more consistent results. Some of the results presented at the conference involved trends in temperature and precipitation statistics, and we are now seeing more intense rainfall. This is not entirely new, but we are getting a clearer picture on intense hourly rainfall. Also, observations suggest more drought in eastern Mediterranean, which is a region affected by both subtropical and mid-latitudinal weather phenomena. If I were to pick one out of several good candidates, then perhaps the most interesting talk in the synoptic climatology session (for which I was co-convener) was on the ocean’s heat loss to atmosphere connected with surface turbulence. The message was that most of the heat exchange takes place over short time intervals, and that the most extreme magnitudes of heat exchange seem to be associated with high pressure system with cold air outbreak and an interaction with cyclones. One tradition of the ESM conferences is to award the silver medal, and this year’s EMS Silver medal was given to Michel Jarraud, who, according to my notes, said that he regards meteorology as the leading edge in science and that numerical weather prediction is one of the great success stories. He also observed that weather was significant in the propagation of ebola, and that there is an urgency to act on climate change mitigation and adaptation. Another message was that we should not try to be perfect – it’s too costly and inefficient. Much of our knowledge is good enough for action on climate change. Another concern was about capacity building and that some nations soon may have meteorological services which will run without meteorologists. Another impression was that climate adaptation seems to be stuck (also see recent post on mid-latitude storms) with limited resources devoted to climate services and little demand for climate information for decision making. There is still a question of added value for people who make the effort to incorporate such information in their business model or in governance (also see the post on added-value). The conference had several parallel sessions and that spanned over a wide range of themes on applied meteorology and climatology, such as communication, TV meteorology, and forecasting, in addition to common climate research issues (check the conference website). I could not cover all, so I may have missed some of the interesting results.
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