lmd_Li2010_abstracts.html

2010 .

(12 publications)

F. M. O'Connor, O. Boucher, N. Gedney, C. D. Jones, G. A. Folberth, R. Coppell, P. Friedlingstein, W. J. Collins, J. Chappellaz, J. Ridley, and C. E. Johnson. Possible role of wetlands, permafrost, and methane hydrates in the methane cycle under future climate change: A review. Reviews of Geophysics, 48:4005, December 2010. [ bib | DOI | ADS link ]

We have reviewed the available scientific literature on how natural sources and the atmospheric fate of methane may be affected by future climate change. We discuss how processes governing methane wetland emissions, permafrost thawing, and destabilization of marine hydrates may affect the climate system. It is likely that methane wetland emissions will increase over the next century. Uncertainties arise from the temperature dependence of emissions and changes in the geographical distribution of wetland areas. Another major concern is the possible degradation or thaw of terrestrial permafrost due to climate change. The amount of carbon stored in permafrost, the rate at which it will thaw, and the ratio of methane to carbon dioxide emissions upon decomposition form the main uncertainties. Large amounts of methane are also stored in marine hydrates, and they could be responsible for large emissions in the future. The time scales for destabilization of marine hydrates are not well understood and are likely to be very long for hydrates found in deep sediments but much shorter for hydrates below shallow waters, such as in the Arctic Ocean. Uncertainties are dominated by the sizes and locations of the methane hydrate inventories, the time scales associated with heat penetration in the ocean and sediments, and the fate of methane released in the seawater. Overall, uncertainties are large, and it is difficult to be conclusive about the time scales and magnitudes of methane feedbacks, but significant increases in methane emissions are likely, and catastrophic emissions cannot be ruled out. We also identify gaps in our scientific knowledge and make recommendations for future research and development in the context of Earth system modeling.

W. J. Collins, S. Sitch, and O. Boucher. How vegetation impacts affect climate metrics for ozone precursors. Journal of Geophysical Research (Atmospheres), 115:23308, December 2010. [ bib | DOI | ADS link ]

We examine the effect of ozone damage to vegetation as caused by anthropogenic emissions of ozone precursor species and quantify it in terms of its impact on terrestrial carbon stores. A simple climate model is then used to assess the expected changes in global surface temperature from the resulting perturbations to atmospheric concentrations of carbon dioxide, methane, and ozone. The concept of global temperature change potential (GTP) metric, which relates the global average surface temperature change induced by the pulse emission of a species to that induced by a unit mass of carbon dioxide, is used to characterize the impact of changes in emissions of ozone precursors on surface temperature as a function of time. For NO_x emissions, the longer-timescale methane perturbation is of the opposite sign to the perturbations in ozone and carbon dioxide, so NO_x emissions are warming in the short term, but cooling in the long term. For volatile organic compound (VOC), CO, and methane emissions, all the terms are warming for an increase in emissions. The GTPs for the 20 year time horizon are strong functions of emission location, with a large component of the variability owing to the different vegetation responses on different continents. At this time horizon, the induced change in the carbon cycle is the largest single contributor to the GTP metric for NO_x and VOC emissions. For NO_x emissions, we estimate a GTP₂₀ of -9 (cooling) to +24 (warming) depending on assumptions of the sensitivity of vegetation types to ozone damage.

L. Zou, T. Zhou, L. Li, and J. Zhang. East China Summer Rainfall Variability of 1958-2000: Dynamical Downscaling with a Variable-Resolution AGCM. Journal of Climate, 23:6394-6408, December 2010. [ bib | DOI | ADS link ]

M. T. Woodhouse, K. S. Carslaw, G. W. Mann, S. M. Vallina, M. Vogt, P. R. Halloran, and O. Boucher. Low sensitivity of cloud condensation nuclei to changes in the sea-air flux of dimethyl-sulphide. Atmospheric Chemistry & Physics, 10:7545-7559, August 2010. [ bib | ADS link ]

The emission of dimethyl-sulphide (DMS) gas by phytoplankton and the subsequent formation of aerosol has long been suggested as an important climate regulation mechanism. The key aerosol quantity is the number concentration of cloud condensation nuclei (CCN), but until recently global models did not include the necessary aerosol physics to quantify CCN. Here we use a global aerosol microphysics model to calculate the sensitivity of CCN to changes in DMS emission using multiple present-day and future sea-surface DMS climatologies. Calculated annual fluxes of DMS to the atmosphere for the five model-derived and one observations based present day climatologies are in the range 15.1 to 32.3 Tg a^-1 sulphur. The impact of DMS climatology on surface level CCN concentrations was calculated in terms of summer and winter hemispheric mean values of ΔCCN/ΔFlux_DMS, which varied between -43 and +166 cm^-3/(mg m^-2 day^-1 sulphur), with a mean of 63 cm^-3/(mg m^-2 day^-1 sulphur). The range is due to CCN production in the atmosphere being strongly dependent on the spatial distribution of the emitted DMS. The relative sensitivity of CCN to DMS (i.e. fractional change in CCN divided by fractional change in DMS flux) depends on the abundance of non-DMS derived aerosol in each hemisphere. The relative sensitivity averaged over the five present day DMS climatologies is estimated to be 0.02 in the northern hemisphere (i.e. a 0.02% change in CCN for a 1% change in DMS) and 0.07 in the southern hemisphere where aerosol abundance is lower. In a globally warmed scenario in which the DMS flux increases by ˜1% relative to present day we estimate a ˜0.1% increase in global mean CCN at the surface. The largest CCN response occurs in the Southern Ocean, contributing to a Southern Hemisphere mean annual increase of less than 0.2%. We show that the changes in DMS flux and CCN concentration between the present day and global warming scenario are similar to interannual differences due to variability in windspeed. In summary, although DMS makes a significant contribution to global marine CCN concentrations, the sensitivity of CCN to potential future changes in DMS flux is very low. This finding, together with the predicted small changes in future seawater DMS concentrations, suggests that the role of DMS in climate regulation is very weak.

K. Goubanova, L. Li, P. Yiou, and F. Codron. Relation between Large-Scale Circulation and European Winter Temperature: Does It Hold under Warmer Climate? Journal of Climate, 23:3752-3760, July 2010. [ bib | DOI | ADS link ]

J. E. Williams, R. Scheele, P. van Velthoven, I. Bouarar, K. Law, B. Josse, V.-H. Peuch, X. Yang, J. Pyle, V. Thouret, B. Barret, C. Liousse, F. Hourdin, S. Szopa, and A. Cozic. Global Chemistry Simulations in the AMMA Multimodel Intercomparison Project. Bulletin of the American Meteorological Society, 91:611-624, May 2010. [ bib | DOI | ADS link ]

R. Roca, J.-C. Bergès, H. Brogniez, M. Capderou, P. Chambon, O. Chomette, S. Cloché, T. Fiolleau, I. Jobard, J. Lémond, M. Ly, L. Picon, P. Raberanto, A. Szantai, and M. Viollier. On the water and energy cycles in the Tropics. Comptes Rendus Geoscience, 342:390-402, April 2010. [ bib | DOI | ADS link ]

The water and energy cycles are major elements of the Earth climate. These cycles are especially active in the intertropical belt where satellites provide the most suitable observational platform. The history of Earth observations of the water cycle and of the radiation budget viewed from space reveals that the fundamental questions from the early times are still relevant for today's research. The last 2 decades have seen a number of milestones regarding the documentation of rainfall, mesoscale convective systems (MCS), water vapour and radiation at the top of the atmosphere (TOA). Beyond dedicated missions that provided enhanced characterizations of some elements of the atmospheric water cycle and field campaigns that allowed the gathering of validation data, the advent of the long record of meteorological satellites lead to new questioning on the homogenisation of the data time series, etc. The use of this record to document the tropical climate brought new results of the distribution of humidity and reinforced the understanding of some robust features of the African monsoon. Challenges for the immediate future concerns the deepening of the understanding of the role of cloud systems in the monsoon circulation, the downscaling of the documentation of the water and energy cycle at the scale of these cloud systems, the research of better adequation between the users and the satellite estimate of rainfall and finally a much needed methodological effort to build exploitable time series for the estimation of climatic trends in the water and energy cycle in the Tropics. The required observations to address these challenges are rapidly presented with emphasis on the upcoming Megha-Tropiques (MT) mission.

O. Marti, P. Braconnot, J.-L. Dufresne, J. Bellier, R. Benshila, S. Bony, P. Brockmann, P. Cadule, A. Caubel, F. Codron, N. de Noblet, S. Denvil, L. Fairhead, T. Fichefet, M.-A. Foujols, P. Friedlingstein, H. Goosse, J.-Y. Grandpeix, E. Guilyardi, F. Hourdin, A. Idelkadi, M. Kageyama, G. Krinner, C. Lévy, G. Madec, J. Mignot, I. Musat, D. Swingedouw, and C. Talandier. Key features of the IPSL ocean atmosphere model and its sensitivity to atmospheric resolution. Climate Dynamics, 34:1-26, January 2010. [ bib | DOI | ADS link ]

This paper presents the major characteristics of the Institut Pierre Simon Laplace (IPSL) coupled ocean-atmosphere general circulation model. The model components and the coupling methodology are described, as well as the main characteristics of the climatology and interannual variability. The model results of the standard version used for IPCC climate projections, and for intercomparison projects like the Paleoclimate Modeling Intercomparison Project (PMIP 2) are compared to those with a higher resolution in the atmosphere. A focus on the North Atlantic and on the tropics is used to address the impact of the atmosphere resolution on processes and feedbacks. In the North Atlantic, the resolution change leads to an improved representation of the storm-tracks and the North Atlantic oscillation. The better representation of the wind structure increases the northward salt transports, the deep-water formation and the Atlantic meridional overturning circulation. In the tropics, the ocean-atmosphere dynamical coupling, or Bjerknes feedback, improves with the resolution. The amplitude of ENSO (El Niño-Southern oscillation) consequently increases, as the damping processes are left unchanged.

F. Hourdin, I. Musat, F. Guichard, P. M. Ruti, F. Favot, M.-A. Filiberti*, M. Pham, J.-Y. Grandpeix, J. Polcher, P. Marquet, A. Boone, J.-P. Lafore, J.-L. Redelsperger, A. Dell'Aquila, T. L. Doval, A. K. Traore, and H. Gallée. AMMA-Model Intercomparison Project. Bulletin of the American Meteorological Society, 91:95, 2010. [ bib | DOI | ADS link ]

T. Wu, R. Yu, F. Zhang, Z. Wang, M. Dong, L. Wang, X. Jin, D. Chen, and L. Li. The Beijing Climate Center atmospheric general circulation model: description and its performance for the present-day climate. Climate Dynamics, 34:149-150, January 2010. [ bib | DOI | ADS link ]

The Beijing Climate Center atmospheric general circulation model version 2.0.1 (BCC_AGCM2.0.1) is described and its performance in simulating the present-day climate is assessed. BCC_AGCM2.0.1 originates from the community atmospheric model version 3 (CAM3) developed by the National Center for Atmospheric Research (NCAR). The dynamics in BCC_AGCM2.0.1 is, however, substantially different from the Eulerian spectral formulation of the dynamical equations in CAM3, and several new physical parameterizations have replaced the corresponding original ones. The major modification of the model physics in BCC_AGCM2.0.1 includes a new convection scheme, a dry adiabatic adjustment scheme in which potential temperature is conserved, a modified scheme to calculate the sensible heat and moisture fluxes over the open ocean which takes into account the effect of ocean waves on the latent and sensible heat fluxes, and an empirical equation to compute the snow cover fraction. Specially, the new convection scheme in BCC_AGCM2.0.1, which is generated from the Zhang and McFarlanes scheme but modified, is tested to have significant improvement in tropical maximum but also the subtropical minimum precipitation, and the modified scheme for turbulent fluxes are validated using EPIC2001 in situ observations and show a large improvement than its original scheme in CAM3. BCC_AGCM2.0.1 is forced by observed monthly varying sea surface temperatures and sea ice concentrations during 1949-2000. The model climatology is compiled for the period 1971-2000 and compared with the ERA-40 reanalysis products. The model performance is evaluated in terms of energy budgets, precipitation, sea level pressure, air temperature, geopotential height, and atmospheric circulation, as well as their seasonal variations. Results show that BCC_AGCM2.0.1 reproduces fairly well the present-day climate. The combined effect of the new dynamical core and the updated physical parameterizations in BCC_AGCM2.0.1 leads to an overall improvement, compared to the original CAM3.

D. Koch, M. Schulz, S. Kinne, C. McNaughton, J. R. Spackman, Y. Balkanski, S. Bauer, T. Berntsen, T. C. Bond, O. Boucher, M. Chin, A. Clarke, N. de Luca, F. Dentener, T. Diehl, O. Dubovik, R. Easter, D. W. Fahey, J. Feichter, D. Fillmore, S. Freitag, S. Ghan, P. Ginoux, S. Gong, L. Horowitz, T. Iversen, A. Kirkevåg, Z. Klimont, Y. Kondo, M. Krol, X. Liu, R. Miller, V. Montanaro, N. Moteki, G. Myhre, J. E. Penner, J. Perlwitz, G. Pitari, S. Reddy, L. Sahu, H. Sakamoto, G. Schuster, J. P. Schwarz, Ø. Seland, P. Stier, N. Takegawa, T. Takemura, C. Textor, J. A. van Aardenne, and Y. Zhao. Corrigendum to ”Evaluation of black carbon estimations in global aerosol models” published in Atmos. Chem. Phys., 9, 9001-9026, 2009. Atmospheric Chemistry & Physics, 10:79-81, January 2010. [ bib | ADS link ]

No abstract available.