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Andreas Andersson
,
Anna Rutgersson
, and
Erik Sahlée

Abstract

During the years 2010–13, atmospheric eddy covariance measurement of oxygen was performed at the marine site Östergarnsholm in the Baltic Sea. The fast response optode Microx TX3 was used with two different types of tapered sensors. In spite of the increased lifetime, the optical isolated sensor is limited by the slower response time and is unsuitable for ground-based eddy covariance measurements. The sensor without optical isolation shows a −⅔ slope within the inertial subrange and attains sufficient response time and precision to be used in air–sea applications during continuous periods of 1–4 days. Spectral and cospectral analysis shows oxygen measured with the nonoptical isolated sensor to follow the same shape as for CO2 and water vapor when normalized. The sampling rate of the Microx TX3 is 2 Hz; however, the sensor was found to have a limited response and resolution, yielding a flux loss in the frequency range f > 0.3 Hz. This can be corrected for by applying cospectral similarity simultaneously using measurements of latent heat as the reference signal. On average the magnitude of the cospectral correction added 20% to the uncorrected oxygen flux during neutral atmospheric stratification.

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Carla Cardinali
,
Lars Isaksen
, and
Erik Andersson

Abstract

The use of automated aircraft data [Aircraft Meteorological Data Relay (AMDAR) and Aircraft Communication Addressing and Reporting System (ACARS)] has recently been extended in ECMWF's operational 4DVAR data assimilation system. Herein, a modified data selection procedure is reported on that allows the use of more aircraft profiling data during the aircraft's ascending and descending phase, and more of the most frequent reports at cruise level. It is shown that the accuracy of analyzed jet streams is improved through these changes, as verified against independent (non–real time) aircraft data that had not been used in the experiments. The modifications are shown to have a clear positive impact on the short- and medium-range forecast performance. The revised aircraft usage was implemented operationally in January 2002.

The impact in 4DVAR of profiles from American and European automated aircraft in ascending and descending phase has been tested in a data denial impact study, for January and July 2001. This particular impact study was run partly on the request of the WMO/Commission for Basic Systems (CBS) Expert Team on data requirements and the redesign of the global observing system. Their interest is in testing whether a modern data assimilation system (such as 4DVAR) obtains substantial benefit from the aircraft profiles, which sample very irregularly in space and time, given that America and Europe are relatively well covered by radiosondes and wind profilers. The results show a substantial positive impact of the profiling aircraft data on analysis and forecast accuracy. The short-range forecast performance is improved over North America, the North Atlantic, and Europe. In the medium range a clear positive impact is found in the North Atlantic, the European, and Arctic areas in the winter period, and beyond day 6 in the summer period. These results are statistically significant and support the ongoing WMO initiative for further expansion of the AMDAR/ACARS coverage. The results also illustrate the effectiveness of 4DVAR with respect to observations that are irregularly distributed in space and time.

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Johannes Gjerstad
,
Svein Erik Aasen
,
Helge I. Andersson
,
Iver Brevik
, and
Jørgen Løvseth

Abstract

New data are presented for the spectrum of turbulent wind energy under maritime conditions in the frequency region 1.0–0.03 mHz. The corresponding measurements were made at five levels on a mast 46 m high on a small islet off the coast of central Norway. Twelve time series of length 10 h 40 min have been analyzed. The mean wind speeds of the series are in the range 11–19 m s−1, and the wind directions are westerly, which have maritime conditions upwind.

Four of the time series were characterized by unstable atmospheric conditions (mean lapse rate −∂T/∂z in the range 12–20 K/km) and show little or no indication of a spectral gap for heights above 40 m. Four other lime series with stable to neutral conditions (mean lapse rate 3–7 K/km) do show a gap in the wind speed spectra around 0.5 mHz, in agreement with the Kansas (1972) and Minnesota (1978) experiments. The remaining series, with lapse rates fluctuating around the neutral value of 9.8 K/km, show intermediate behavior.

The temperature spectra at 45-m height do not show a gap even for stable to neutral conditions.

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Ad Stoffelen
,
Gert-Jan Marseille
,
Erik Andersson
, and
David G. H. Tan
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Ad Stoffelen
,
Jean Pailleux
,
Erland Källén
,
J. Michael Vaughan
,
Lars Isaksen
,
Pierre Flamant
,
Werner Wergen
,
Erik Andersson
,
Harald Schyberg
,
Alain Culoma
,
Roland Meynart
,
Martin Endemann
, and
Paul Ingmann

The prime aim of the Atmospheric Dynamics Mission is to demonstrate measurements of vertical wind profiles from space. Extensive studies conducted by the European Space Agency over the past 15 years have culminated in the selection of a high-performance Doppler wind lidar based on direct-detection interferometric techniques. Such a system, with a pulsed laser operating at 355-nm wavelength, would utilize both Rayleigh scattering from molecules and Mie scattering from thin cloud and aerosol particles; measurement of the residual Doppler shift from successive levels in the atmosphere provides the vertical wind profiles. The lidar would be accommodated on a satellite flying in a sun-synchronous orbit, at an altitude of ~400 km, providing near-global coverage; target date for launch is in 2007. Processing of the backscatter signals will provide about 3000 globally distributed wind profiles per day, above thick clouds or down to the surface in clear air, at typically 200-km separation along the satellite track. Such improved knowledge of the global wind field is crucial to many aspects of climate research and weather prediction. Knowledge over large parts of the Tropics and major oceans is presently quite incomplete—leading to major difficulties in studying key processes in the climate system and in improving numerical simulations and predictions; progress in climate modeling is indeed intimately linked to progress in numerical weather prediction. The background studies, potential impact on climate and weather prediction, choice of measurement specifications, and the lidar technology are discussed.

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Erik Andersson
,
Peter Bauer
,
Anton Beljaars
,
Frederic Chevallier
,
Elías Hólm
,
Marta Janisková
,
Per Kållberg
,
Graeme Kelly
,
Philippe Lopez
,
Anthony McNally
,
Emmanuel Moreau
,
Adrian J. Simmons
,
Jean-Noël Thépaut
, and
Adrian M. Tompkins

Several new types of satellite instrument will provide improved measurements of Earth's hydrological cycle and the humidity of the atmosphere. In an effort to make the best possible use of these data, the modeling and assimilation of humidity, clouds, and precipitation are currently the subjects of a comprehensive research program at the European Centre for Medium-Range Weather Forecasts (ECMWF). Impacts on weather prediction and climate reanalysis can be expected. The preparations for cloud and rain assimilation within ECMWF's four-dimensional variational data assimilation system include the development of linearized moist physics, the development of fast radiative transfer codes for cloudy and precipitating conditions, and a reformulation of the humidity analysis scheme.

Results of model validations against in situ moisture data are presented, indicating generally good agreement—often to within the absolute calibration accuracy of the measurements. Evidence is also presented of shortcomings in ECMWF's humidity analysis, from the operational data assimilation and forecasting system in 2002, and from the recently completed ERA-40 reanalysis project. Examples are shown of biases in the data and in the model that lead to biased humidity analyses. Although these biases are relatively small, they contribute to an overprediction of tropical precipitation and to an overly intense Hadley circulation at the start of the forecast, with rapid adjustments taking place during the first 6–12 h. It is shown that with an improved humidity analysis this long-standing “spindown” problem can be reduced.

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Vincent-Henri Peuch
,
Richard Engelen
,
Michel Rixen
,
Dick Dee
,
Johannes Flemming
,
Martin Suttie
,
Melanie Ades
,
Anna Agustí-Panareda
,
Cristina Ananasso
,
Erik Andersson
,
David Armstrong
,
Jérôme Barré
,
Nicolas Bousserez
,
Juan Jose Dominguez
,
Sébastien Garrigues
,
Antje Inness
,
Luke Jones
,
Zak Kipling
,
Julie Letertre-Danczak
,
Mark Parrington
,
Miha Razinger
,
Roberto Ribas
,
Stijn Vermoote
,
Xiaobo Yang
,
Adrian Simmons
,
Juan Garcés de Marcilla
, and
Jean-Noël Thépaut

Abstract

The Copernicus Atmosphere Monitoring Service (CAMS), part of the European Union’s Earth observation program Copernicus, entered operations in July 2015. Implemented by the European Centre for Medium-Range Weather Forecasts (ECMWF) as a truly European effort with over 23,500 direct data users and well over 200 million end users worldwide as of March 2022, CAMS delivers numerous global and regional information products about air quality, inventory-based emissions and observation-based surface fluxes of greenhouse gases and from biomass burning, solar energy, ozone and UV radiation, and climate forcings. Access to CAMS products is open and free of charge via the Atmosphere Data Store. The CAMS global atmospheric composition analyses, forecasts, and reanalyses build on ECMWF’s Integrated Forecasting System (IFS) and exploit over 90 different satellite data streams. The global products are complemented by coherent higher-resolution regional air quality products over Europe derived from multisystem analyses and forecasts. CAMS information products also include policy support such as quantitative impact assessment of short- and long-term pollutant-emission mitigation scenarios, source apportionment information, and annual European air quality assessment reports. Relevant CAMS products are cited and used for instance in IPCC Assessment Reports. Providing dedicated support for users operating smartphone applications, websites, or TV bulletins in Europe and worldwide is also integral to the service. This paper presents key achievements of the CAMS initial phase (2014–21) and outlines some of its new components for the second phase (2021–28), e.g., the new Copernicus anthropogenic CO2 emissions Monitoring and Verification Support capacity that will monitor global anthropogenic emissions of key greenhouse gases.

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