Richard J. Engelen
European Centre for Medium-Range Weather Forecasts
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Featured researches published by Richard J. Engelen.
Journal of Geophysical Research | 2009
Angela Benedetti; J.-J. Morcrette; Olivier Boucher; A. Dethof; Richard J. Engelen; M. Fisher; H. Flentje; N. Huneeus; L. Jones; Johannes W. Kaiser; Stefan Kinne; Alexander Mangold; M. Razinger; A. J. Simmons; Martin Suttie
[1] This study presents the new aerosol assimilation system, developed at the European Centre for Medium-Range Weather Forecasts, for the Global and regional Earth-system Monitoring using Satellite and in-situ data (GEMS) project. The aerosol modeling and analysis system is fully integrated in the operational four-dimensional assimilation apparatus. Its purpose is to produce aerosol forecasts and reanalyses of aerosol fields using optical depth data from satellite sensors. This paper is the second of a series which describes the GEMS aerosol effort. It focuses on the theoretical architecture and practical implementation of the aerosol assimilation system. It also provides a discussion of the background errors and observations errors for the aerosol fields, and presents a subset of results from the 2-year reanalysis which has been run for 2003 and 2004 using data from the Moderate Resolution Imaging Spectroradiometer on the Aqua and Terra satellites. Independent data sets are used to show that despite some compromises that have been made for feasibility reasons in regards to the choice of control variable and error characteristics, the analysis is very skillful in drawing to the observations and in improving the forecasts of aerosol optical depth.
Journal of Geophysical Research | 2004
Richard J. Engelen; Erik Andersson; F. Chevallier; A. Hollingsworth; Marco Matricardi; A. P. McNally; Jean-Noël Thépaut; Philip Watts
[1] Atmospheric CO2 concentrations have been obtained from the Atmospheric Infrared Sounder (AIRS) radiance data within the European Centre for Medium-Range Weather Forecasts data assimilation system. A subset of channels from the AIRS instrument on board the NASA Aqua platform has been assimilated providing estimates of tropospheric and stratospheric column-average CO2 mixing ratios. Although global estimates are obtained, the information content of the tropospheric estimates at middle and high latitudes is limited, and results are therefore only presented for the tropical region. First results for February and August 2003 show considerable geographical variability compared to the background with values ranging between 371 and 380 ppmv. These CO2 values are representative for a layer between the tropopause and about 600 hPa. The monthly mean random error is about 1%. Careful error analysis has been carried out to minimize any systematic errors. This study has demonstrated the feasibility of global CO2 estimation using AIRS data in a numerical weather prediction data assimilation system. In the future the system will be improved to treat CO2 as a full three-dimensional atmospheric variable, including transport. INDEX TERMS: 3337 Meteorology and Atmospheric Dynamics: Numerical modeling and data assimilation; 0365 Atmospheric Composition and Structure: Troposphere—composition and chemistry; 1610 Global Change: Atmosphere (0315, 0325); KEYWORDS: AIRS, carbon dioxide, data assimilation
Journal of Geophysical Research | 2009
F. Chevallier; Richard J. Engelen; C. Carouge; T. J. Conway; Philippe Peylin; Christopher Pickett-Heaps; Michel Ramonet; P. J. Rayner; I. Xueref-Remy
This paper demonstrates an inversion of surface CO2 fluxes using concentrations derived from assimilation of satellite radiances. Radiances come from the Atmospheric Infrared Sounder (AIRS) and are assimilated within the system of the European Centre for Medium-Range Weather Forecasts. We evaluate the quality of the inverted fluxes by comparing simulated concentrations with independent airborne measurements. As a benchmark we use an inversion based on surface flask measurements and another using only the global concentration trend. We show that the AIRS-based inversion is able to improve the match to the independent data compared to the prior estimate but that it usually performs worse than either the flask-based or trend-based inversion.
Journal of Geophysical Research | 2001
Graeme L. Stephens; Richard J. Engelen; Mark A. Vaughan; Theodore L. Anderson
This paper introduces a method that can incorporate different information into the lidar retrieval problem as an attempt to address the backscatter-to-extinction ambiguity that plagues the usefulness of lidar backscattering measurements. The approach, suited for application to spaceborne lidar data, inverts the lidar equation via an optimal estimation method. This method is illustrated using three examples drawn from LITE data. Retrievals using only lidar backscatter as input were compared to retrievals performed using an iterative solution to the lidar inversion with the same input. The two methods produced essentially identical results. The new method, however, offers a number of advantages compared to other methods, including (1) the ability to incorporate different kinds of information under a common retrieval philosophy. This feature is illustrated with the formal introduction of optical depth into the lidar inversion. In this paper, optical depth information, derived from the ldar transmission estimates, is combined with backscatter measurements making it possible to retrieve the backscatter-to-extinction ratio in addition to extinction profiles given certain caveats noted in the paper. (2) The method provides a number of ways for evaluating the quality of the retrieval. Notably, the retrieval approach predicts full error diagnostics identifying sources of error due to measurement uncertainty (instrument noise and calibration uncertainty), model error (containing all the assumptions built into the lidar equation and its parameters), as well as a priori error due to the influence of compiled databases on lidar backscatter of aerosol and cloud. When no optical depth information is available, the retrieval errors are largely dominated by the (large) uncertainty attached to the backscatter-to-extinction coefficient k. Under these circumstances the retrievals are only meaningful to the extent that k and its related uncertainty is known. When optical depth is introduced as a form of measurement, the error contributions shift to the extent that retrieval errors become dominated by the measurement error attached to the optical depth itself.
Journal of Geophysical Research | 1997
Richard J. Engelen; Graeme L. Stephens
This paper introduces a radiative transfer model for the 9.6-μm ozone band that specifically matches the TIROS operational vertical sounder (TOVS) channel 9. The model is based on a spectral Malkmus band model for transmission. Band parameters were calculated by comparing to MODTRAN3 derived radiances. The effect of pressure on absorption is dealt with using a four-parameter approximation, and the improvements of this approximation over the more common Van de Hulst-Curtis-Godson scaling approximation are assessed. While this new model is exploited in the development of the retrieval described in this paper, the result has wider applicability to ozone climate problems requiring calculation of the radiative forcing associated with changing ozone. A two-layer version of the radiative transfer model is implemented in a retrieval scheme to obtain total ozone amounts from radiances measured by the TOVS instrument. Because the TOVS ozone channel is mainly sensitive to lower stratospheric ozone, ozone columns of the upper layer (above 30 hPa and with mean pressure of 10 hPa) are prescribed as a function of latitude. Ozone columns of the lower layer (mean pressure of 105 hPa) are then retrieved. The retrieval is based on a nonlinear optimal estimation algorithm and provides definition of error characteristics for every retrieval, which makes it possible to obtain a spatial distribution of the errors in the retrieval together with the spatial distribution of the retrieved total ozone column itself. This global distribution of the retrieval error and also of the contribution of a priori knowledge to the retrieval is presented to provide a validity of the ozone retrievals. Total ozone mapping spectrometer (TOMS) statistics are used as a priori information in the retrieval, and the 40-layer model is used to estimate the forward model error of the two-layer model. Comparisons of ozone retrievals for 1989 with TOMS total ozone measurements show good agreement both in time and in space with a rms difference between 1% and 3% for zonal means and 10% for global gridded measurements.
Journal of Geophysical Research | 2000
Richard J. Engelen; Laura D. Fowler; Peter J. Gleckler; Michael F. Wehner
Brightness temperatures derived from polar-orbiting satellites are valuable for the evaluation of global climate models. However, the effect of orbital constraints must be taken into account to ensure valid comparisons. As part of the Atmospheric Model Intercomparison Project II climate model comparisons, this study seeks to evaluate the monthly mean simulated brightness temperature differences of possible model output sampling strategies with respect to the exact satellite sampling and whether they can be practically implemented to provide meaningful comparisons with these satellite observations. We compare various sampling strategies with a proxy satellite data set constructed from model output and actual TIROS operational vertical sounder orbital trajectories, rather than with the observations themselves. To a large extent, this enables isolation of the sampling error from errors caused by deficiencies in the modeled climate processes. Our results suggest that the traditional method of calculating brightness temperatures from monthly mean temperature and moisture profiles yields biases from both nonlinear effects and the removal of the diurnal cycle that may be unacceptable in many applications. However, we also find that a brightness temperature calculation every hour of the simulation provides substantially lower sampling biases provided that there are two or more properly aligned satellites. This is encouraging because it means that for many applications modelers need not accurately mimic actual satellite trajectories in the sampling of their simulations. If only one satellite is available for comparison with simulations, more sophisticated sampling seems necessary. For such circumstances, we introduce a simple procedure that serves as a useful approximation to the rather complex procedure required to sample a model exactly as a polar-orbiting satellite does the Earth. With all sampling methods, removal of biases associated with cloud cover is problematic and deserves further study.
Science | 2012
Sander Houweling; Bakr Badawy; D. F. Baker; Sourish Basu; Dmitry Belikov; P. Bergamaschi; P. Bousquet; Grégoire Broquet; Tim Butler; Josep G. Canadell; Jing M. Chen; F. Chevallier; Philippe Ciais; G. James Collatz; Scott Denning; Richard J. Engelen; I. G. Enting; Marc L. Fischer; A. Fraser; Christoph Gerbig; Manuel Gloor; Andrew R. Jacobson; Dylan B. A. Jones; Martin Heimann; Aslam Khalil; Thomas Kaminski; Prasad S. Kasibhatla; Nir Y. Krakauer; M. Krol; Takashi Maki
The steady rise in atmospheric long-lived greenhouse gas concentrations is the main driver of contemporary climate change. The Mauna Loa CO2 time series (1, 2), started by C. D. Keeling in 1958 and maintained today by the Scripps Institution of Oceanography and the Earth System Research Laboratory (ESRL) of NOAA, is iconic evidence of the effect of human-caused fossil fuel and land-use change emissions on the atmospheric increase of CO2. The continuity of such records depends critically on having stable funding, which is challenging to maintain in the context of 3- to 4-year research grant funding cycles (3), and is currently threatened by the financial crisis. The ESRL Global Monitoring Division maintains a network of about 100 surface and aircraft sites worldwide at which whole air samples are collected approximately every week for analysis of CO2, CH4, CO, halocarbons, and many other chemical species (4). This is complemented by high-frequency measurements at the Mauna Loa, Barrow, American Samoa, and South Pole observatories, and about 10 North American tall towers. The success of the NOAA program has inspired similar efforts in Europe (5), China (6), India (7), and Brazil (8), with the United Nations World Meteorological Organization providing guidance and precision requirements through the Global Atmosphere Watch program (9), but no funding. The data collected by NOAA and its worldwide partners have been used not only to demonstrate the unassailable rise of atmospheric greenhouse gas concentrations, but also to infer the magnitudes, locations, and times of surface-atmosphere exchange of those gases based on small concentration gradients between sites (10). Important findings from analysis of these records include the detection of a significant terrestrial carbon sink at northern mid-latitudes (11) and subsequent research aimed at identifying the mechanisms by which that sink must operate. Long-term, high-quality, atmospheric measurements are crucial for quantifying trends in greenhouse gas fluxes and attributing them to fossil fuel emissions, changes in land-use and management, or the response of natural land and ocean ecosystems to climate change and elevated CO2 concentrations. Greenhouse gas measurements along tall towers in the interior continents allow quantification of regional sources and sinks, which has a very high relevance for measuring the effectiveness of climate policy. NOAA ESRL provides measurements that are critical for the U.S. national security in that they provide independent verification and early warning of changing greenhouse gas emissions from countries involved in efforts to mitigate greenhouse gases. Dedicated carbon-observing satellites such as GOSAT and OCO-2 are needed to fill in the missing geographical information required for verification of carbon flux mitigation efforts. However, satellite retrievals do not yet provide sufficient information to deliver new constraints on surface fluxes, although quick progress is being made in this direction. In situ observations are crucial for anchoring space-borne measurements, for detecting potential biases of remote sensing techniques, and for providing continuity given the finite lifetime of satellites. Despite the growing importance of greenhouse gas observations to humanity, substantial budget cuts at NOAA have resulted in curtailment of our ability to observe and understand changes to the global carbon cycle. Already, a dozen surface flask-sampling sites have been removed from NOAAs operational network and aircraft profiling sites have been eliminated and reduced in frequency at the remaining NOAA sites. The planned growth in the tall tower program has stopped, and plans for closing some towers are being developed. The U.S. budget process in this election year, with the added risk of mandatory across-the-board cuts due to the 2011 Budget Control Act, foretells more bleak news for greenhouse gas monitoring at NOAA and could cause further retreat from the goal of recording ongoing changes in atmospheric composition. As scientists, we believe that preserving the continuity of these vital time series must remain a priority for U.S. carbon cycle research.
Journal of Geophysical Research | 1996
Richard J. Engelen
Strong planetary wave activity enhanced by the external forcing of a persisting anticyclone system can cause large total ozone zonal deviations. In January 1992 such a situation was observed with a high-pressure system and associated low total ozone concentrations situated over Northern Europe. In this article, measurements from the total ozone mapping spectrometer (TOMS) are analyzed with a simple model based on the linearized stationary ozone continuity equation. It is shown that in such a meteorological situation, vertical advection of ozone caused by the wavenumber-one quasi-stationary planetary wave is the most important monthly mean transport mechanism. This is different from the climatological situation, where horizontal and vertical advection are almost equally important and where wavenumbers two and three contribute more to the total ozone zonal deviations. The dominance of vertical motions, which are in phase throughout the lower and middle stratosphere, also explains the high correlations found between temperatures at 50 hPa from National Meteorological Center analyses and total ozone. Under these special meteorological conditions, the high planetary wave activity is responsible for total ozone columns with about 60 Dobson units less ozone over the anticyclonic region than under normal conditions.
Science | 2012
Sander Houweling; Bakr Badawy; D. F. Baker; Sourish Basu; Dmitry Belikov; P. Bergamaschi; P. Bousquet; Grégoire Broquet; T. Butler; Josep G. Canadell; Jing M. Chen; F. Chevallier; Philippe Ciais; G.J. Collatz; S. Denning; Richard J. Engelen; I. G. Enting; Marc L. Fischer; A. Fraser; Christoph Gerbig; Manuel Gloor; Andrew R. Jacobson; Dylan B. A. Jones; Martin Heimann; Aslam Khalil; Thomas Kaminski; Prasad S. Kasibhatla; Nir Y. Krakauer; M. Krol; Takashi Maki
The steady rise in atmospheric long-lived greenhouse gas concentrations is the main driver of contemporary climate change. The Mauna Loa CO2 time series (1, 2), started by C. D. Keeling in 1958 and maintained today by the Scripps Institution of Oceanography and the Earth System Research Laboratory (ESRL) of NOAA, is iconic evidence of the effect of human-caused fossil fuel and land-use change emissions on the atmospheric increase of CO2. The continuity of such records depends critically on having stable funding, which is challenging to maintain in the context of 3- to 4-year research grant funding cycles (3), and is currently threatened by the financial crisis. The ESRL Global Monitoring Division maintains a network of about 100 surface and aircraft sites worldwide at which whole air samples are collected approximately every week for analysis of CO2, CH4, CO, halocarbons, and many other chemical species (4). This is complemented by high-frequency measurements at the Mauna Loa, Barrow, American Samoa, and South Pole observatories, and about 10 North American tall towers. The success of the NOAA program has inspired similar efforts in Europe (5), China (6), India (7), and Brazil (8), with the United Nations World Meteorological Organization providing guidance and precision requirements through the Global Atmosphere Watch program (9), but no funding. The data collected by NOAA and its worldwide partners have been used not only to demonstrate the unassailable rise of atmospheric greenhouse gas concentrations, but also to infer the magnitudes, locations, and times of surface-atmosphere exchange of those gases based on small concentration gradients between sites (10). Important findings from analysis of these records include the detection of a significant terrestrial carbon sink at northern mid-latitudes (11) and subsequent research aimed at identifying the mechanisms by which that sink must operate. Long-term, high-quality, atmospheric measurements are crucial for quantifying trends in greenhouse gas fluxes and attributing them to fossil fuel emissions, changes in land-use and management, or the response of natural land and ocean ecosystems to climate change and elevated CO2 concentrations. Greenhouse gas measurements along tall towers in the interior continents allow quantification of regional sources and sinks, which has a very high relevance for measuring the effectiveness of climate policy. NOAA ESRL provides measurements that are critical for the U.S. national security in that they provide independent verification and early warning of changing greenhouse gas emissions from countries involved in efforts to mitigate greenhouse gases. Dedicated carbon-observing satellites such as GOSAT and OCO-2 are needed to fill in the missing geographical information required for verification of carbon flux mitigation efforts. However, satellite retrievals do not yet provide sufficient information to deliver new constraints on surface fluxes, although quick progress is being made in this direction. In situ observations are crucial for anchoring space-borne measurements, for detecting potential biases of remote sensing techniques, and for providing continuity given the finite lifetime of satellites. Despite the growing importance of greenhouse gas observations to humanity, substantial budget cuts at NOAA have resulted in curtailment of our ability to observe and understand changes to the global carbon cycle. Already, a dozen surface flask-sampling sites have been removed from NOAAs operational network and aircraft profiling sites have been eliminated and reduced in frequency at the remaining NOAA sites. The planned growth in the tall tower program has stopped, and plans for closing some towers are being developed. The U.S. budget process in this election year, with the added risk of mandatory across-the-board cuts due to the 2011 Budget Control Act, foretells more bleak news for greenhouse gas monitoring at NOAA and could cause further retreat from the goal of recording ongoing changes in atmospheric composition. As scientists, we believe that preserving the continuity of these vital time series must remain a priority for U.S. carbon cycle research.
Science | 2012
Sander Houweling; Bakr Badawy; D. F. Baker; Sourish Basu; Dmitry Belikov; P. Bergamaschi; P. Bousquet; Grégoire Broquet; T. Butler; Josep G. Canadell; Jing M. Chen; F. Chevallier; Philippe Ciais; G.J. Collatz; S. Denning; Richard J. Engelen; I. G. Enting; Marc L. Fischer; A. Fraser; Christoph Gerbig; Manuel Gloor; Andrew R. Jacobson; Dylan B. A. Jones; Martin Heimann; Aslam Khalil; Thomas Kaminski; Prasad S. Kasibhatla; Nir Y. Krakauer; M. Krol; Takashi Maki
The steady rise in atmospheric long-lived greenhouse gas concentrations is the main driver of contemporary climate change. The Mauna Loa CO2 time series (1, 2), started by C. D. Keeling in 1958 and maintained today by the Scripps Institution of Oceanography and the Earth System Research Laboratory (ESRL) of NOAA, is iconic evidence of the effect of human-caused fossil fuel and land-use change emissions on the atmospheric increase of CO2. The continuity of such records depends critically on having stable funding, which is challenging to maintain in the context of 3- to 4-year research grant funding cycles (3), and is currently threatened by the financial crisis. The ESRL Global Monitoring Division maintains a network of about 100 surface and aircraft sites worldwide at which whole air samples are collected approximately every week for analysis of CO2, CH4, CO, halocarbons, and many other chemical species (4). This is complemented by high-frequency measurements at the Mauna Loa, Barrow, American Samoa, and South Pole observatories, and about 10 North American tall towers. The success of the NOAA program has inspired similar efforts in Europe (5), China (6), India (7), and Brazil (8), with the United Nations World Meteorological Organization providing guidance and precision requirements through the Global Atmosphere Watch program (9), but no funding. The data collected by NOAA and its worldwide partners have been used not only to demonstrate the unassailable rise of atmospheric greenhouse gas concentrations, but also to infer the magnitudes, locations, and times of surface-atmosphere exchange of those gases based on small concentration gradients between sites (10). Important findings from analysis of these records include the detection of a significant terrestrial carbon sink at northern mid-latitudes (11) and subsequent research aimed at identifying the mechanisms by which that sink must operate. Long-term, high-quality, atmospheric measurements are crucial for quantifying trends in greenhouse gas fluxes and attributing them to fossil fuel emissions, changes in land-use and management, or the response of natural land and ocean ecosystems to climate change and elevated CO2 concentrations. Greenhouse gas measurements along tall towers in the interior continents allow quantification of regional sources and sinks, which has a very high relevance for measuring the effectiveness of climate policy. NOAA ESRL provides measurements that are critical for the U.S. national security in that they provide independent verification and early warning of changing greenhouse gas emissions from countries involved in efforts to mitigate greenhouse gases. Dedicated carbon-observing satellites such as GOSAT and OCO-2 are needed to fill in the missing geographical information required for verification of carbon flux mitigation efforts. However, satellite retrievals do not yet provide sufficient information to deliver new constraints on surface fluxes, although quick progress is being made in this direction. In situ observations are crucial for anchoring space-borne measurements, for detecting potential biases of remote sensing techniques, and for providing continuity given the finite lifetime of satellites. Despite the growing importance of greenhouse gas observations to humanity, substantial budget cuts at NOAA have resulted in curtailment of our ability to observe and understand changes to the global carbon cycle. Already, a dozen surface flask-sampling sites have been removed from NOAAs operational network and aircraft profiling sites have been eliminated and reduced in frequency at the remaining NOAA sites. The planned growth in the tall tower program has stopped, and plans for closing some towers are being developed. The U.S. budget process in this election year, with the added risk of mandatory across-the-board cuts due to the 2011 Budget Control Act, foretells more bleak news for greenhouse gas monitoring at NOAA and could cause further retreat from the goal of recording ongoing changes in atmospheric composition. As scientists, we believe that preserving the continuity of these vital time series must remain a priority for U.S. carbon cycle research.