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Natalie P. Thomas, Michael G. Bosilovich, Allison B. Marquardt Collow, Randal D. Koster, Siegfried D. Schubert, Amin Dezfuli, and Sarith P. Mahanama

et al. 2011 ; Wu et al. 2012 ; Teng et al. 2013 ; Kornhuber et al. 2019 ; Röthlisberger et al. 2019 ). Lehmann and Coumou (2015) reported a link between storm track activity and heat extremes. For daytime heat waves, land–atmosphere interactions are also highly relevant, as daytime heat leads to depletion of soil moisture and a subsequent reduction in evaporative cooling ( Fischer et al. 2007 ; Miralles et al. 2014 ). Thus, droughts and heat waves are often linked, although the strength of

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Laura M. Hinkelman

differences that exceed the EBAF uncertainties of Table 1 and the corresponding flux values are indicated by bold type. Uncertainties are not applied to land and ocean fluxes. “Trans.” = Transmittance. 1) Top of the atmosphere For both MERRA and MERRA-2, most TOA radiative flux terms agree to within about 3 W m −2 of EBAF under all-sky conditions. MERRA-2 incoming shortwave (SW) and outgoing longwave (LW) are slightly improved over MERRA. However, MERRA-2 has a substantially higher (~8%) planetary

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Krzysztof Wargan and Lawrence Coy

data ( Homeyer et al. 2010 ). Given an enhanced planetary wave activity during SSW events, it is reasonable to ask whether anticyclonic wave breaking at the tropopause contributes to the increased observed in Figs. 1a , 2b , and 4 . We will argue that such a contribution exists but plays only a minor role. Figures 5a and 5b show the distribution of and relative vorticity at the tropopause between 75° and 86°N in two 2-week periods before and immediately after the SSW. The distributions

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Lawrence Coy, Paul A. Newman, Steven Pawson, and Leslie R. Lait

their vertical extent. By April, easterlies completely surround the separated upper-westerly jet. In summary, during the November–February period, the average lower-stratospheric EP fluxes extended from north to south across the equator as expected for planetary waves propagating from the NH to the SH. A complete understanding of theses waves and their relatively large contribution to the momentum budget and flux ( Figs. 4 and 5 ) needs further investigation. Fig . 6. Monthly averaged zonal mean

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Ronald Gelaro, Will McCarty, Max J. Suárez, Ricardo Todling, Andrea Molod, Lawrence Takacs, Cynthia A. Randles, Anton Darmenov, Michael G. Bosilovich, Rolf Reichle, Krzysztof Wargan, Lawrence Coy, Richard Cullather, Clara Draper, Santha Akella, Virginie Buchard, Austin Conaty, Arlindo M. da Silva, Wei Gu, Gi-Kong Kim, Randal Koster, Robert Lucchesi, Dagmar Merkova, Jon Eric Nielsen, Gary Partyka, Steven Pawson, William Putman, Michele Rienecker, Siegfried D. Schubert, Meta Sienkiewicz, and Bin Zhao

leverages recent developments at GMAO in modeling and data assimilation to address some of the known limitations of MERRA but also provides a stepping stone to GMAO’s longer-term goal of developing an integrated Earth system analysis (IESA) capability that couples assimilation systems for the atmosphere, ocean, land, and chemistry. Toward the latter goal, MERRA-2 includes aerosol data assimilation, thereby providing a multidecadal reanalysis in which aerosol and meteorological observations are jointly

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C. A. Randles, A. M. da Silva, V. Buchard, P. R. Colarco, A. Darmenov, R. Govindaraju, A. Smirnov, B. Holben, R. Ferrare, J. Hair, Y. Shinozuka, and C. J. Flynn

analyzed aerosol fields that are radiatively coupled to the atmosphere. To our knowledge, this is the first multidecadal reanalysis within which meteorological and aerosol observations are jointly assimilated into a global assimilation system, although other operational forecasting centers are actively developing similar capabilities (e.g., Benedetti et al. 2009 ; Sekiyama et al. 2010 ; Lynch et al. 2016 ). Previously, the GMAO had performed an offline aerosol reanalysis (the MERRA Aerosol

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Gloria L. Manney and Michaela I. Hegglin

: Observations: Atmosphere and surface. Climate Change 2013: The Physical Science Basis , T. F. Stocker et al., Eds., Cambridge University Press, 159–254. Held , I. M. , 1993 : Large-scale dynamics and global warming . Bull. Amer. Meteor. Soc. , 74 , 228 – 241 , doi: 10.1175/1520-0477(1993)074<0228:LSDAGW>2.0.CO;2 . 10.1175/1520-0477(1993)074<0228:LSDAGW>2.0.CO;2 Held , I. M. , and A. Y. Hou , 1980 : Nonlinear axially symmetric circulations in a nearly inviscid atmosphere . J. Atmos. Sci. , 37

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Krzysztof Wargan, Gordon Labow, Stacey Frith, Steven Pawson, Nathaniel Livesey, and Gary Partyka

1. Introduction Atmospheric reanalyses produce global high spatial and temporal resolution long-term records of meteorological fields and composition of Earth’s atmosphere by utilizing the data assimilation methodology ( Cohn 1997 ; Kalnay 2003 ), whereby satellite and ground-based observations are combined with general circulation model (GCM) simulations in a statistically optimal way. The Modern-Era Retrospective Analysis for Research and Applications (MERRA: Rienecker et al. 2011 ) was the

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