Multi-year global climatic effects of atmospheric dust from large bolide impacts

The global climatic effects of dust generated by the impact of a 10 km-diameter bolide was simulated using a one-dimensional (vertical only) globally-averaged climate model by Pollack et al. The goal of the simulation is to examine the regional climate effects, including the possibility of coastal refugia, generated by a global dust cloud in a model having realistic geographic resolution. The climate model assumes the instantaneous appearance of a global stratospheric dust cloud with initial optical depth of 10,000. The time history of optical depth decreases according to the detailed calculations of Pollack et al., reaching an optical depth of unity at day 160, and subsequently decreasing with an e-folding time of 1 year. The simulation is carried out for three years in order to examine the atmospheric effects and recovery over several seasons. The simulation does not include any effects of NOx, CO2, or wildfire smoke injections that may accompany the creation of the dust cloud. The global distribution of surface temperature changes, freezing events, precipitation and soil moisture effects and sea ice increases will be discussed

A 3-dimensional numerical simulation of the atmospheric injection of aerosols by a hypothetical basaltic fissure eruption

Researchers simulated the atmospheric response to a hypothetical basaltic fissure eruption using heating rates based on the Roza flow eruption. The simulation employs the Colorado State University Regional Atmospheric Model (RAMS) with scavenging effects. The numerical model is a three-dimensional non-hydrostatic time-split compressible cloud/mesoscale model. Explicit microphysics include prediction of cloud, rain, crystal, and hail precipitation types. Nucleation and phoretic scavenging are predicted assuming that the pollutant makes an effective cloud droplet nucleus. Smoke is carried as a passive tracer. Long and short wave radiation heating tendencies, including the effects of the smoke, are parameterized. The longwave emission by the lava surface is neglected in the parameterization and included as an explicit heating term instead. A regional scale domain of 100 x 100 km in the horizontal and 22 km high is used. The horizontal grid spacing is taken to be 2 km and the vertical spacing is taken to be 0.75 km. The initial atmospheric state is taken to be horizontally homogenous and based on the standard atmospheric sounding. The fissure is assumed to be 90 km long and oriented in a zig/zag pattern

Acute effects of a large bolide impact simulated by a global atmospheric circulation model

The goal is to use a global three-dimensional atmospheric circulation model developed for studies of atmospheric effects of nuclear war to examine the time evolution of atmospheric effects from a large bolide impact. The model allows for dust and NOx injection, atmospheric transport by winds, removal by precipitation, radiative transfer effects, stratospheric ozone chemistry, and nitric acid formation and deposition on a simulated Earth having realistic geography. Researchers assume a modest 2 km-diameter impactor of the type that could have formed the 32 km-diameter impact structure found near Manson, Iowa and dated at roughly 66 Ma. Such an impact would have created on the order of 5 x 10 to the 10th power metric tons of atmospheric dust (about 0.01 g cm(-2) if spread globally) and 1 x 10 to the 37th power molecules of NO, or two orders of magnitude more stratospheric NO than might be produced in a large nuclear war. Researchers ignore potential injections of CO2 and wildfire smoke, and assume the direct heating of the atmosphere by impact ejecta on a regional scale is not large compared to absorption of solar energy by dust. Researchers assume an impact site at 45 N in the interior of present day North America

AN EXPERIMENTAL PARAMETERIZATION FOR SENSIBLE HEAT FLUX AND COMPUTATION OF SURFACE AIR TEMPERATURE FOR VARIOUS DESERT AREAS

Program year: 1975/1976Digitized from print original stored in HDRThe energy flux terms in the surface heat balance equation were computed using parameterizations and mean monthly temperature, precipitation, planetary albedo, cloudiness, and vapor pressure data for 85 very dry locations. The major flux terms, solar radiation absorbed (S), net longware radiation (I), and sensible heat flux (H), for January and July are presented for 60 stations in North Africa. Sensible heat exchange between the air and surface was then parameterized by a regression procedure using the mean ,monthly values computed as residuals in the heat balance equation. H was found to be a function of S and the proximity of the station to a major water body (D). Larger H surface losses occur for larger values of S and/or smaller values of D. The regression equation for H explains 96% of the variance of the original computations. Knowing approximate expressions for all the terms in the heat balance equation, mean monthly surface air temperature was computed to test the efficacy of the H parameterization. The computed temperatures (Tc) show a combination of systematic and random deviations from the observed temperatures to the extent that the average root-mean-square error of Tc for all stations is 10°C. Thus, the derived expression for H has limited computational usefulness. Improvements in the parameterization could perhaps be made by replacing constants with simple functions or by dividing the stations into two or more geographical regions for separate study

Recent Advances in Paleoclimate Modeling: Toward Better Simulations of Warm Paleoclimates

Numerical climate models have been applied to problems of paleoclimatology for several decades. During that time, climate models have progressed in complexity from relatively simplistic Energy Balance Models (EBMs) to sophisticated three-dimensional General Circulation Models (GCMs) of the atmosphere and oceans. Recent advances in climate modeling, mainly the incorporation of climate system processes once generalized or ignored and the interactive ‘coupling’ of climate system components, are leading toward more realistic paleoclimate simulations and a new understanding of warm paleoclimate dynamics. The future promises even more comprehensive models running at higher resolutions, allowing paleoclimate modeling studies to focus on subcontinental to regional-scale problems. However, as the models gain sophistication, paleoclimate modeling strategies become more complex. The set-up and initialization of GCMs using Atmospheric General Circulation Models (AGCMs) coupled to full-depth, dynamical Ocean General Circulation Models (OGCMs) will provide one of the primary challenges for the paleoclimate modeling community in coming years

Deep Water Formation and Poleward Ocean Heat Transport in the Warm Climate Extreme of the Cretaceous (80 Ma)

An ocean simulation of the “greenhouse” climate of the Late Cretaceous, about 80 million years ago (Ma), demonstrates that warm salty deep water, consistent with proxy climate data, can be formed by cooling in the high latitude Southern Hemisphere. This is contrary to the long standing hypothesis of deep water formation due to evaporation over low latitude marginal seas. A reduced equator to pole temperature gradient is maintained with a poleward ocean heat transport that is not larger than today\u27s