The albedo-OLR distribution in E3SM matches well with CERES observations (ocean only, 12°S to 12°... more The albedo-OLR distribution in E3SM matches well with CERES observations (ocean only, 12°S to 12°N, 150°E-170°E) E3SM hi res. (25x25 km) c. Defining MCS life-cycle stages
The new Energy Exascale Earth System Model Version 1 (E3SMv1) developed for the U.S. Department o... more The new Energy Exascale Earth System Model Version 1 (E3SMv1) developed for the U.S. Department of Energy has significant new treatments of aerosols and light-absorbing snow impurities as well as their interactions with clouds and radiation. This study describes seven sets of new aerosol-related treatments (involving emissions, new particle formation, aerosol transport, wet scavenging and resuspension, and snow radiative transfer) and examines how they affect global aerosols and radiative forcing in E3SMv1. Altogether, they give a reduced total aerosol radiative forcing (−1.6 W/m 2) and sensitivity in cloud liquid water to aerosols, but an increased sensitivity in cloud droplet size to aerosols. A new approach for H 2 SO 4 production and loss largely reduces a low bias in small particles concentrations and leads to substantial increases in cloud condensation nuclei concentrations and cloud radiative cooling. Emitting secondary organic aerosol precursor gases from elevated sources increases the column burden of secondary organic aerosol, contributing substantially to global clear-sky aerosol radiative cooling (−0.15 out of −0.5 W/m 2). A new treatment of aerosol resuspension from evaporating precipitation, developed to remedy two shortcomings of the original treatment, produces a modest reduction in aerosols and cloud droplets; its impact depends strongly on the model physics and is much stronger in E3SM Version 0. New treatments of the mixing state and optical properties of snow impurities and snow grains introduce a positive present-day shortwave radiative forcing (0.26 W/m 2), but changes in aerosol transport and wet removal processes also affect the concentration and radiative forcing of light-absorbing impurities in snow/ice. Plain Language Summary Aerosol and aerosol-cloud interactions continue to be a major uncertainty in Earth system models, impeding their ability to reproduce the observed historical warming and to project changes in global climate and water cycle. The U.S. DOE Energy Exascale Earth System Model version 1 (E3SMv1), a state-of-the-science Earth system model, was developed to use exascale computing to address the grand challenge of actionable predictions of variability and change in the Earth system critical to the energy sector. It has been publicly released with new treatments in many aspects, including substantial modifications to the physical treatments of aerosols in the atmosphere and light-absorbing impurities in snow/ice, aimed at reducing some known biases or correcting model deficiencies in representing aerosols, their life cycle, and their impacts in various components of the Earth system. Compared to its predecessors (without the new treatments) and observations, E3SMv1 shows improvements in characterizing global distributions of aerosols and their radiative effects. We conduct sensitivity experiments to understand the impact of individual changes and provide guidance for future development of E3SM and other Earth system models.
• New Earth system model configuration with improved treatment of sea ice and aerosols • Extended... more • New Earth system model configuration with improved treatment of sea ice and aerosols • Extended marine biogeochemistry enables cloud nucleation to depend on prognostic marine emissions • Climate sensitivity is little changed but adjusted radiative forcing is stronger in modified model
We conduct sensitivity experiments using a climate model that has an explicit water source taggin... more We conduct sensitivity experiments using a climate model that has an explicit water source tagging capability forced by prescribed composites of sea ice concentrations (SIC) and corresponding SSTs to understand the impact of sea ice anomalies on regional evaporation, moisture transport, and sourcereceptor relationships for precipitation over Antarctica. Surface sensible heat fluxes, evaporation, and 5 column-integrated water vapor are larger over Southern Ocean (SO) areas with lower SIC, but changes in Antarctic precipitation and its source attribution with SICs reflect a strong spatial variability. Among the tagged source regions, the Southern Ocean (south of 50°S) contributes the most (40%) to the Antarctic total precipitation, followed by more northerly ocean basins, most notably the S. Pacific Ocean (27%), S. Indian Ocean (16%) and S. Atlantic Ocean (11%). The annual mean Antarctic precipitation is about 150 10 Gt/year more in the "low" SIC case than in the "high" SIC case. This difference is larger than the modelsimulated interannual variability of Antarctic precipitation (99 Gt/year). The contrast in contribution from the S. Ocean, 102 Gt/year, is even more significant, compared to the interannual variability of 35 Gt/year in Antarctic precipitation that originates from the S. Ocean. The horizontal transport pathways from individual vapor source regions to Antarctica are largely determined by large-scale atmospheric 15 circulation patterns. Vapor from lower latitude source regions takes elevated pathways to Antarctica. In contrast, vapor from the Southern Ocean moves southward within the lower troposphere to the Antarctic continent, so the contribution of nearby sources also depends on regional coastal topography. The impact of sea ice anomalies on regional Antarctic precipitation also depends on atmospheric circulation changes that result from the prescribed composite SIC/SST perturbations. In particular, regional wind anomalies 20 along with surface evaporation changes determine regional shifts in the zonal and meridional moisture fluxes that can explain some of the resultant precipitation changes.
Proceedings of the National Academy of Sciences of the United States of America, Feb 7, 2017
Polycyclic aromatic hydrocarbons (PAHs) have toxic impacts on humans and ecosystems. One of the m... more Polycyclic aromatic hydrocarbons (PAHs) have toxic impacts on humans and ecosystems. One of the most carcinogenic PAHs, benzo(a)pyrene (BaP), is efficiently bound to and transported with atmospheric particles. Laboratory measurements show that particle-bound BaP degrades in a few hours by heterogeneous reaction with ozone, yet field observations indicate BaP persists much longer in the atmosphere, and some previous chemical transport modeling studies have ignored heterogeneous oxidation of BaP to bring model predictions into better agreement with field observations. We attribute this unexplained discrepancy to the shielding of BaP from oxidation by coatings of viscous organic aerosol (OA). Accounting for this OA viscosity-dependent shielding, which varies with temperature and humidity, in a global climate/chemistry model brings model predictions into much better agreement with BaP measurements, and demonstrates stronger long-range transport, greater deposition fluxes, and substantia...
Abstract We explore the impact of injecting a precursor of sulfate aerosols into the middle atmos... more Abstract We explore the impact of injecting a precursor of sulfate aerosols into the middle atmosphere where they would act to increase the planetary albedo and thus counter some of the effects of greenhouse gase forcing. We use an atmospheric general circulation ...
Abstract A recently proposed geo-engineering scheme to limit greenhouse warming is the injection ... more Abstract A recently proposed geo-engineering scheme to limit greenhouse warming is the injection of sulfur into the stratosphere to increase the Earth's albedo. This is expected to reduce tropospheric temperatures, as observed following large volcanic eruptions (for ...
JT Kiehl, JJ Hack, GB Bonan, B Boville NASA 19980147981, 1996. This report presents the details o... more JT Kiehl, JJ Hack, GB Bonan, B Boville NASA 19980147981, 1996. This report presents the details of the governing equations, physical parameterizations, and numerical algorithms defining the version of the NCAR Community Climate Model designated CCM3. ...
JT Kiehl, JJ Hack, GB Bonan, B Boville NASA 19980147981, 1996. This report presents the details o... more JT Kiehl, JJ Hack, GB Bonan, B Boville NASA 19980147981, 1996. This report presents the details of the governing equations, physical parameterizations, and numerical algorithms defining the version of the NCAR Community Climate Model designated CCM3. ...
ABSTRACT We present results on detecting and isolating the forcing and response processes in the ... more ABSTRACT We present results on detecting and isolating the forcing and response processes in the climate system by applying multiple pseudo-random perturbations of sea surface temperature (SST) patterns across various ocean regions using CAM5 and Hadley Center GCM. As a reasonable first step, we have simplified the original idea of forcing the climate system by seeding sea salt aerosols in the marine boundary layer by directly imposing the SST perturbations. Our aim is to generate worldwide transfer functions between pseudo random sea spray patterns or SST perturbations and the corresponding climate responses. This will help us to understand good and bad times and regions for imposing such perturbations, especially to avoid any adverse effects on climate. Our preliminary study involves a control simulation using background SST data from a previous coupled AOGCM run. The next three simulations use SST anomalies over three different ocean regions, namely North Pacific, South Pacific, and South Atlantic respectively as obtained from a previous work by Jones et al. [2009] over and above the background SST data. The last simulation is carried out using independent pseudo-random binary sequences of the three SST anomalies in addition to the background SST data. Correlations between the responses to the pseudo random SST variations are being compared with previously predicted model results to understand and isolate the individual forcing and response processes. We plan to extend our study by introducing more complex perturbations spatially, temporally and possibly to cloud albedo directly using a coupled AOGCM like CCSM. Reference: Jones A, J. Hayward, and O. Boucher (2009), Climate impacts of geoengineering marine stratocumulus clouds, J. Geophys. Res., 114, doi:10.1029/2008JD011450
ABSTRACT The Global Modeling Initiative (GMI) science team has developed a three dimensional chem... more ABSTRACT The Global Modeling Initiative (GMI) science team has developed a three dimensional chemistry and transport model (CTM) to evaluate the impact of the exhaust of supersonic aircraft on the stratosphere. An important goal of the GMI is to test modules for numerical transport, photochemical integration, and model dynamics within a common framework. This work is focussed on the dependence of the overall assessment on the wind and temperature fields used by the CTM. Three meteorological data sets for the stratosphere were available to GMI: the National Center for Atmospheric Research Community Climate Model (CCM2), the Goddard Earth Observing System Data Assimilation System (GEOS-DAS), and the Goddard Institute for Space Studies general circulation model (GISS-2'). Objective criteria were established by the GMI team to evaluate which of these three data sets provided the best representation of trace gases in the stratosphere today. Tracer experiments were devised to test various aspects of model transport. Stratospheric measurements of long-lived trace gases were selected as a test of the CTM transport. This presentation describes the criteria used in grading the meteorological fields and the resulting choice of wind fields to be used in the GMI assessment. This type of objective model evaluation will lead to a higher level of confidence in these assessments. We suggest that the diagnostic tests shown here be used to augment traditional general circulation model evaluation methods.
Although the influence of El~Niño on inducing drought in equatorial Southeast Asia is relatively ... more Although the influence of El~Niño on inducing drought in equatorial Southeast Asia is relatively well understood, less is known about feedbacks between El Niño, biomass burning and aerosol forcing in this region Fires associated with El~Niño are a new phenomenon, arising from recent increases in human population and agriculture. We examined the impact of El Niño-induced fire aerosols on regional climate using the Community Climate System Model (CCSM), and the Global Fire Emissions Dataset (GFED) for 1997--2006. In our first experiment, we forced the CCSM and a slab ocean model (SOM) with two single-year emissions datasets, one representing a high fire year (1997) and the other a low fire year (2000). In our second experiment the CCSM, coupled with a data ocean model (DOM) of fixed sea surface temperatures (SSTs), was forced with multi-year emissions, consisting of the 10 year GFED record plus an additional 'buffer' year of 'mean' fire emissions. Climate responses to fire aerosols in the two experiments were determined by analyzing ensembles of forty (SOM) and five (DOM) simulations, respectively.Our results show links between fire, aerosols, and decreases in regional precipitation. The inclusion of fire emissions and their climate effects generally improves agreement between simulations and several satellite datasets, including MODIS, MISR and ISCCP. In the first experiment, fires produce aerosol optical depth (AOD) anomalies of 1.0--1.4 over the areas with the most fire in 1997. In the areas with the highest aerosol concentration, solar absorption by these carbonaceous aerosols increases solar heating rates between the surface and 100 hPa upwards of 0.2--0.3 K day-1 during the peak fire season (August--October). This intense heating stabilizes the troposphere, suppresses convection, and ultimately decreases precipitation the region. In peak fire season, fire-emitted aerosols reduced precipitation by more than 30% in the areas of highest AOD. This reduces soil moisture by 1--2% nearly uniformly in the region. These results suggest that recent increases in deforestation and fire emissions in equatorial Southeast Asia may intensify El~Niño-induced drought.
... Snow Charlie Zender, Mark Flanner, and Jim Randerson Department of Earth System Science, Univ... more ... Snow Charlie Zender, Mark Flanner, and Jim Randerson Department of Earth System Science, University of California, Irvine ... K. Lo, S. Menon, R. Miller, P. Minnis, T. Novakov, V. Oinas, J. Perl-witz, J. Perlwitz, D. Rind, A. Romanou, D. Shindell, P. Stone, S. Sun, ...
The albedo-OLR distribution in E3SM matches well with CERES observations (ocean only, 12°S to 12°... more The albedo-OLR distribution in E3SM matches well with CERES observations (ocean only, 12°S to 12°N, 150°E-170°E) E3SM hi res. (25x25 km) c. Defining MCS life-cycle stages
The new Energy Exascale Earth System Model Version 1 (E3SMv1) developed for the U.S. Department o... more The new Energy Exascale Earth System Model Version 1 (E3SMv1) developed for the U.S. Department of Energy has significant new treatments of aerosols and light-absorbing snow impurities as well as their interactions with clouds and radiation. This study describes seven sets of new aerosol-related treatments (involving emissions, new particle formation, aerosol transport, wet scavenging and resuspension, and snow radiative transfer) and examines how they affect global aerosols and radiative forcing in E3SMv1. Altogether, they give a reduced total aerosol radiative forcing (−1.6 W/m 2) and sensitivity in cloud liquid water to aerosols, but an increased sensitivity in cloud droplet size to aerosols. A new approach for H 2 SO 4 production and loss largely reduces a low bias in small particles concentrations and leads to substantial increases in cloud condensation nuclei concentrations and cloud radiative cooling. Emitting secondary organic aerosol precursor gases from elevated sources increases the column burden of secondary organic aerosol, contributing substantially to global clear-sky aerosol radiative cooling (−0.15 out of −0.5 W/m 2). A new treatment of aerosol resuspension from evaporating precipitation, developed to remedy two shortcomings of the original treatment, produces a modest reduction in aerosols and cloud droplets; its impact depends strongly on the model physics and is much stronger in E3SM Version 0. New treatments of the mixing state and optical properties of snow impurities and snow grains introduce a positive present-day shortwave radiative forcing (0.26 W/m 2), but changes in aerosol transport and wet removal processes also affect the concentration and radiative forcing of light-absorbing impurities in snow/ice. Plain Language Summary Aerosol and aerosol-cloud interactions continue to be a major uncertainty in Earth system models, impeding their ability to reproduce the observed historical warming and to project changes in global climate and water cycle. The U.S. DOE Energy Exascale Earth System Model version 1 (E3SMv1), a state-of-the-science Earth system model, was developed to use exascale computing to address the grand challenge of actionable predictions of variability and change in the Earth system critical to the energy sector. It has been publicly released with new treatments in many aspects, including substantial modifications to the physical treatments of aerosols in the atmosphere and light-absorbing impurities in snow/ice, aimed at reducing some known biases or correcting model deficiencies in representing aerosols, their life cycle, and their impacts in various components of the Earth system. Compared to its predecessors (without the new treatments) and observations, E3SMv1 shows improvements in characterizing global distributions of aerosols and their radiative effects. We conduct sensitivity experiments to understand the impact of individual changes and provide guidance for future development of E3SM and other Earth system models.
• New Earth system model configuration with improved treatment of sea ice and aerosols • Extended... more • New Earth system model configuration with improved treatment of sea ice and aerosols • Extended marine biogeochemistry enables cloud nucleation to depend on prognostic marine emissions • Climate sensitivity is little changed but adjusted radiative forcing is stronger in modified model
We conduct sensitivity experiments using a climate model that has an explicit water source taggin... more We conduct sensitivity experiments using a climate model that has an explicit water source tagging capability forced by prescribed composites of sea ice concentrations (SIC) and corresponding SSTs to understand the impact of sea ice anomalies on regional evaporation, moisture transport, and sourcereceptor relationships for precipitation over Antarctica. Surface sensible heat fluxes, evaporation, and 5 column-integrated water vapor are larger over Southern Ocean (SO) areas with lower SIC, but changes in Antarctic precipitation and its source attribution with SICs reflect a strong spatial variability. Among the tagged source regions, the Southern Ocean (south of 50°S) contributes the most (40%) to the Antarctic total precipitation, followed by more northerly ocean basins, most notably the S. Pacific Ocean (27%), S. Indian Ocean (16%) and S. Atlantic Ocean (11%). The annual mean Antarctic precipitation is about 150 10 Gt/year more in the "low" SIC case than in the "high" SIC case. This difference is larger than the modelsimulated interannual variability of Antarctic precipitation (99 Gt/year). The contrast in contribution from the S. Ocean, 102 Gt/year, is even more significant, compared to the interannual variability of 35 Gt/year in Antarctic precipitation that originates from the S. Ocean. The horizontal transport pathways from individual vapor source regions to Antarctica are largely determined by large-scale atmospheric 15 circulation patterns. Vapor from lower latitude source regions takes elevated pathways to Antarctica. In contrast, vapor from the Southern Ocean moves southward within the lower troposphere to the Antarctic continent, so the contribution of nearby sources also depends on regional coastal topography. The impact of sea ice anomalies on regional Antarctic precipitation also depends on atmospheric circulation changes that result from the prescribed composite SIC/SST perturbations. In particular, regional wind anomalies 20 along with surface evaporation changes determine regional shifts in the zonal and meridional moisture fluxes that can explain some of the resultant precipitation changes.
Proceedings of the National Academy of Sciences of the United States of America, Feb 7, 2017
Polycyclic aromatic hydrocarbons (PAHs) have toxic impacts on humans and ecosystems. One of the m... more Polycyclic aromatic hydrocarbons (PAHs) have toxic impacts on humans and ecosystems. One of the most carcinogenic PAHs, benzo(a)pyrene (BaP), is efficiently bound to and transported with atmospheric particles. Laboratory measurements show that particle-bound BaP degrades in a few hours by heterogeneous reaction with ozone, yet field observations indicate BaP persists much longer in the atmosphere, and some previous chemical transport modeling studies have ignored heterogeneous oxidation of BaP to bring model predictions into better agreement with field observations. We attribute this unexplained discrepancy to the shielding of BaP from oxidation by coatings of viscous organic aerosol (OA). Accounting for this OA viscosity-dependent shielding, which varies with temperature and humidity, in a global climate/chemistry model brings model predictions into much better agreement with BaP measurements, and demonstrates stronger long-range transport, greater deposition fluxes, and substantia...
Abstract We explore the impact of injecting a precursor of sulfate aerosols into the middle atmos... more Abstract We explore the impact of injecting a precursor of sulfate aerosols into the middle atmosphere where they would act to increase the planetary albedo and thus counter some of the effects of greenhouse gase forcing. We use an atmospheric general circulation ...
Abstract A recently proposed geo-engineering scheme to limit greenhouse warming is the injection ... more Abstract A recently proposed geo-engineering scheme to limit greenhouse warming is the injection of sulfur into the stratosphere to increase the Earth's albedo. This is expected to reduce tropospheric temperatures, as observed following large volcanic eruptions (for ...
JT Kiehl, JJ Hack, GB Bonan, B Boville NASA 19980147981, 1996. This report presents the details o... more JT Kiehl, JJ Hack, GB Bonan, B Boville NASA 19980147981, 1996. This report presents the details of the governing equations, physical parameterizations, and numerical algorithms defining the version of the NCAR Community Climate Model designated CCM3. ...
JT Kiehl, JJ Hack, GB Bonan, B Boville NASA 19980147981, 1996. This report presents the details o... more JT Kiehl, JJ Hack, GB Bonan, B Boville NASA 19980147981, 1996. This report presents the details of the governing equations, physical parameterizations, and numerical algorithms defining the version of the NCAR Community Climate Model designated CCM3. ...
ABSTRACT We present results on detecting and isolating the forcing and response processes in the ... more ABSTRACT We present results on detecting and isolating the forcing and response processes in the climate system by applying multiple pseudo-random perturbations of sea surface temperature (SST) patterns across various ocean regions using CAM5 and Hadley Center GCM. As a reasonable first step, we have simplified the original idea of forcing the climate system by seeding sea salt aerosols in the marine boundary layer by directly imposing the SST perturbations. Our aim is to generate worldwide transfer functions between pseudo random sea spray patterns or SST perturbations and the corresponding climate responses. This will help us to understand good and bad times and regions for imposing such perturbations, especially to avoid any adverse effects on climate. Our preliminary study involves a control simulation using background SST data from a previous coupled AOGCM run. The next three simulations use SST anomalies over three different ocean regions, namely North Pacific, South Pacific, and South Atlantic respectively as obtained from a previous work by Jones et al. [2009] over and above the background SST data. The last simulation is carried out using independent pseudo-random binary sequences of the three SST anomalies in addition to the background SST data. Correlations between the responses to the pseudo random SST variations are being compared with previously predicted model results to understand and isolate the individual forcing and response processes. We plan to extend our study by introducing more complex perturbations spatially, temporally and possibly to cloud albedo directly using a coupled AOGCM like CCSM. Reference: Jones A, J. Hayward, and O. Boucher (2009), Climate impacts of geoengineering marine stratocumulus clouds, J. Geophys. Res., 114, doi:10.1029/2008JD011450
ABSTRACT The Global Modeling Initiative (GMI) science team has developed a three dimensional chem... more ABSTRACT The Global Modeling Initiative (GMI) science team has developed a three dimensional chemistry and transport model (CTM) to evaluate the impact of the exhaust of supersonic aircraft on the stratosphere. An important goal of the GMI is to test modules for numerical transport, photochemical integration, and model dynamics within a common framework. This work is focussed on the dependence of the overall assessment on the wind and temperature fields used by the CTM. Three meteorological data sets for the stratosphere were available to GMI: the National Center for Atmospheric Research Community Climate Model (CCM2), the Goddard Earth Observing System Data Assimilation System (GEOS-DAS), and the Goddard Institute for Space Studies general circulation model (GISS-2'). Objective criteria were established by the GMI team to evaluate which of these three data sets provided the best representation of trace gases in the stratosphere today. Tracer experiments were devised to test various aspects of model transport. Stratospheric measurements of long-lived trace gases were selected as a test of the CTM transport. This presentation describes the criteria used in grading the meteorological fields and the resulting choice of wind fields to be used in the GMI assessment. This type of objective model evaluation will lead to a higher level of confidence in these assessments. We suggest that the diagnostic tests shown here be used to augment traditional general circulation model evaluation methods.
Although the influence of El~Niño on inducing drought in equatorial Southeast Asia is relatively ... more Although the influence of El~Niño on inducing drought in equatorial Southeast Asia is relatively well understood, less is known about feedbacks between El Niño, biomass burning and aerosol forcing in this region Fires associated with El~Niño are a new phenomenon, arising from recent increases in human population and agriculture. We examined the impact of El Niño-induced fire aerosols on regional climate using the Community Climate System Model (CCSM), and the Global Fire Emissions Dataset (GFED) for 1997--2006. In our first experiment, we forced the CCSM and a slab ocean model (SOM) with two single-year emissions datasets, one representing a high fire year (1997) and the other a low fire year (2000). In our second experiment the CCSM, coupled with a data ocean model (DOM) of fixed sea surface temperatures (SSTs), was forced with multi-year emissions, consisting of the 10 year GFED record plus an additional 'buffer' year of 'mean' fire emissions. Climate responses to fire aerosols in the two experiments were determined by analyzing ensembles of forty (SOM) and five (DOM) simulations, respectively.Our results show links between fire, aerosols, and decreases in regional precipitation. The inclusion of fire emissions and their climate effects generally improves agreement between simulations and several satellite datasets, including MODIS, MISR and ISCCP. In the first experiment, fires produce aerosol optical depth (AOD) anomalies of 1.0--1.4 over the areas with the most fire in 1997. In the areas with the highest aerosol concentration, solar absorption by these carbonaceous aerosols increases solar heating rates between the surface and 100 hPa upwards of 0.2--0.3 K day-1 during the peak fire season (August--October). This intense heating stabilizes the troposphere, suppresses convection, and ultimately decreases precipitation the region. In peak fire season, fire-emitted aerosols reduced precipitation by more than 30% in the areas of highest AOD. This reduces soil moisture by 1--2% nearly uniformly in the region. These results suggest that recent increases in deforestation and fire emissions in equatorial Southeast Asia may intensify El~Niño-induced drought.
... Snow Charlie Zender, Mark Flanner, and Jim Randerson Department of Earth System Science, Univ... more ... Snow Charlie Zender, Mark Flanner, and Jim Randerson Department of Earth System Science, University of California, Irvine ... K. Lo, S. Menon, R. Miller, P. Minnis, T. Novakov, V. Oinas, J. Perl-witz, J. Perlwitz, D. Rind, A. Romanou, D. Shindell, P. Stone, S. Sun, ...
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