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James J. Riley and Erik Lindborg

Abstract

Several existing sets of smaller-scale ocean and atmospheric data appear to display Kolmogorov–Obukov–Corrsin inertial ranges in horizontal spectra for length scales up to at least a few hundred meters. It is argued here that these data are inconsistent with the assumptions for these inertial range theories. Instead, it is hypothesized that the dynamics of stratified turbulence explain these data. If valid, these dynamics may also explain the behavior of strongly stratified flows in similar dynamic ranges of other geophysical flows.

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Louis J. Battan and James J. Riley

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Jackson R. Herring, James J. Riley, G. S. Patterson Jr., and Robert H. Kraichnan

Abstract

Computer simulators are made of the growth of the difference-velocity field for pairs of realizations of isotropic, three-dimensional turbulence at Reynolds number R&lambda≈40. The simulations involve full-scale integration of the Navier-Stokes equation in the Fourier representation. It is found that the difference-velocity variance (error energy) grows with time even when the initial difference-velocity is confined to wave numbers strongly damped by viscosity. The numerical integrations are compared with results of the direct-interaction approximation (DIA). It is found that the DIA gives reasonably satisfactory quantitative agreement for the evolution of the error energy and the error. energy spectrum. What discrepancies there are represent an underestimate of error energy growth by the DIA. This is explained by theoretical analysis of the approximation.

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Li Xu, Qing Zhu, William J. Riley, Yang Chen, Hailong Wang, Po-Lun Ma, and James T. Randerson

Abstract

Fire-emitted aerosols play an important role in influencing Earth’s climate, directly by scattering and absorbing radiation and indirectly by influencing cloud microphysics. The quantification of fire–aerosol interactions, however, remains challenging and subject to uncertainties in emissions, plume parameterizations, and aerosol properties. Here we optimized fire-associated aerosol emissions in the Energy Exascale Earth System Model (E3SM) using the Global Fire Emissions Database (GFED) and AERONET aerosol optical depth (AOD) observations during 1997–2016. We distributed fire emissions vertically using smoke plume heights from Multiangle Imaging SpectroRadiometer (MISR) satellite observations. From the optimization, we estimate that global fires emit 45.5 Tg yr−1 of primary particulate organic matter and 3.9 Tg yr−1 of black carbon. We then performed two climate simulations with and without the optimized fire emissions. We find that fire aerosols significantly increase global AOD by 14% ± 7% and contribute to a reduction in net shortwave radiation at the surface (−2.3 ± 0.5 W m−2). Together, fire-induced direct and indirect aerosol effects cause annual mean global land surface air temperature to decrease by 0.17° ± 0.15°C, relative humidity to increase by 0.4% ± 0.3%, and diffuse light fraction to increase by 0.5% ± 0.3%. In response, GPP declines by 2.8 Pg C yr−1 as a result of large positive drivers (decreases in temperature and increases in humidity and diffuse light), nearly cancelling out large negative drivers (decreases in shortwave radiation and soil moisture). Our analysis highlights the importance of fire aerosols in modifying surface climate and photosynthesis across the tropics.

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