scholarly journals A Consistent Prescription of Stratospheric Aerosol for Both Radiation and Chemistry in the Community Earth System Model (CESM1)

2015 ◽  
Vol 8 (12) ◽  
pp. 10711-10734 ◽  
Author(s):  
R. R. Neely ◽  
A. Conley ◽  
F. Vitt ◽  
J. F. Lamarque
Keyword(s):  
Temperature Response ◽  
Coupled Model ◽  
Stratospheric Aerosol ◽  
Earth System Model ◽  
System Model ◽  
Aerosol Layer ◽  
Earth System ◽  
Global Mean Temperature ◽  
Pinatubo Eruption ◽  
Community Earth System Model

Abstract. Here we describe an updated parameterization for prescribing stratospheric aerosol in the Community Earth System Model (CESM1). The need for a new parameterisation is motivated by the poor global response of most models in Coupled Model Inter-comparison Project 5 (CMIP5) to colossal volcanic perturbations to the stratospheric aerosol layer (such as the 1991 Pinatubo eruption or the 1883 Krakatau eruption) in comparison to observations. In particular, the scheme used in the CMIP5 simulations by CESM1 simulated a global temperature decrease by a factor 2 larger than was observed. The new parameterisation takes advantage of recent improvements in historical stratospheric aerosol databases to allow for varying both the mass loading and effective radius of the prescribed aerosol. Simulations utilizing the new scheme are shown to now reproduce the observed global mean temperature response as well as the temperature response of the stratosphere due to local aerosol heating after the 1991 Pinatubo eruption.

scholarly journals A consistent prescription of stratospheric aerosol for both radiation and chemistry in the Community Earth System Model (CESM1)

2016 ◽  
Vol 9 (7) ◽  
pp. 2459-2470 ◽  
Author(s):  
Ryan Reynolds Neely III ◽  
Andrew J. Conley ◽  
Francis Vitt ◽  
Jean-François Lamarque
Keyword(s):  
Surface Temperature ◽  
Temperature Response ◽  
Stratospheric Aerosol ◽  
Earth System Model ◽  
System Model ◽  
Earth System ◽  
Climate System Model ◽  
Pinatubo Eruption ◽  
Community Earth System Model ◽  
Global Mean

Abstract. Here we describe an updated parameterization for prescribing stratospheric aerosol in the National Center for Atmospheric Research (NCAR) Community Earth System Model (CESM1). The need for a new parameterization is motivated by the poor response of the CESM1 (formerly referred to as the Community Climate System Model, version 4, CCSM4) simulations contributed to the Coupled Model Intercomparison Project 5 (CMIP5) to colossal volcanic perturbations to the stratospheric aerosol layer (such as the 1991 Pinatubo eruption or the 1883 Krakatau eruption) in comparison to observations. In particular, the scheme used in the CMIP5 simulations by CESM1 simulated a global mean surface temperature decrease that was inconsistent with the GISS Surface Temperature Analysis (GISTEMP), NOAA's National Climatic Data Center, and the Hadley Centre of the UK Met Office (HADCRUT4). The new parameterization takes advantage of recent improvements in historical stratospheric aerosol databases to allow for variations in both the mass loading and size of the prescribed aerosol. An ensemble of simulations utilizing the old and new schemes shows CESM1's improved response to the 1991 Pinatubo eruption. Most significantly, the new scheme more accurately simulates the temperature response of the stratosphere due to local aerosol heating. Results also indicate that the new scheme decreases the global mean temperature response to the 1991 Pinatubo eruption by half of the observed temperature change, and modelled climate variability precludes statements as to the significance of this change.

scholarly journals An Online Ensemble Coupled Data Assimilation Capability for the Community Earth System Model: System Design and Evaluation

2021 ◽  
Author(s):  
Jingzhe Sun ◽  
Yingjing Jiang ◽  
Shaoqing Zhang ◽  
Weimin Zhang ◽  
Lv Lu ◽  
...  
Keyword(s):  
Data Assimilation ◽  
Coupled Model ◽  
Model Atmosphere ◽  
Earth System Model ◽  
System Model ◽  
Ocean Temperature ◽  
Earth System ◽  
Cross Covariance ◽  
Community Earth System Model ◽  
Coupled Data Assimilation

Abstract. The Community Earth System Model (CESM) developed at the National Center of Atmospheric Research (NCAR) has been used worldwide for climate studies. This study extends the efforts of CESM development to include an online (i.e., in-core) ensemble coupled data assimilation system (CESM-ECDA) to enhance CESM’s capability for climate predictability studies and prediction applications. The CESM-ECDA system consists of an online atmospheric data assimilation (ADA) component implemented to both the finite-volume and spectral-element dynamical cores, and an online oceanic data assimilation (ODA) component. In ADA, surface pressures (Ps) are assimilated, while in ODA, gridded sea surface temperature (SST) and ocean temperature and salinity profiles at real Argo locations are assimilated. The system has been evaluated within a perfect twin experiment framework, showing significantly reduced errors of the model atmosphere and ocean states through “observation”-constraints by ADA and ODA. The weakly CDA in which both the online ADA and ODA are conducted during the coupled model integration shows smaller errors of air-sea fluxes than the single ADA and ODA, facilitating the future utilization of cross-covariance between the atmosphere and ocean at the air-sea interface. A three-year CDA reanalysis experiment is also implemented by assimilating Ps, SST and ocean temperature and salinity profiles from the real world spanning the period 1978 to 1980 using 12 ensemble members. Results show that Ps RMSE is smaller than 20CR and SST RMSE is better than ERA-20C and close to CFSR. The success of the online CESM-ECDA system is the first step to implement a high-resolution long-term climate reanalysis once the algorithm efficiency is much improved.

scholarly journals Regional Climate Simulations With the Community Earth System Model

2018 ◽  
Vol 10 (6) ◽  
pp. 1245-1265 ◽  
Author(s):  
A. Gettelman ◽  
P. Callaghan ◽  
V. E. Larson ◽  
C. M. Zarzycki ◽  
J. T. Bacmeister ◽  
...  
Keyword(s):  
Regional Climate ◽  
Earth System Model ◽  
System Model ◽  
Earth System ◽  
Climate Simulations ◽  
Community Earth System Model

scholarly journals Evaluating simplified chemical mechanisms within present-day simulations of the Community Earth System Model version 1.2 with CAM4 (CESM1.2 CAM-chem): MOZART-4 vs. Reduced Hydrocarbon vs. Super-Fast chemistry

2018 ◽  
Vol 11 (10) ◽  
pp. 4155-4174 ◽  
Author(s):  
Benjamin Brown-Steiner ◽  
Noelle E. Selin ◽  
Ronald Prinn ◽  
Simone Tilmes ◽  
Louisa Emmons ◽  
...  
Keyword(s):  
Computational Cost ◽  
Earth System Model ◽  
Chemical Mechanism ◽  
System Model ◽  
Earth System ◽  
Chemical Mechanisms ◽  
Trade Offs ◽  
Community Earth System Model ◽  
Time Periods ◽  
Fast Mechanism

Abstract. While state-of-the-art complex chemical mechanisms expand our understanding of atmospheric chemistry, their sheer size and computational requirements often limit simulations to short lengths or ensembles to only a few members. Here we present and compare three 25-year present-day offline simulations with chemical mechanisms of different levels of complexity using the Community Earth System Model (CESM) Version 1.2 CAM-chem (CAM4): the Model for Ozone and Related Chemical Tracers, version 4 (MOZART-4) mechanism, the Reduced Hydrocarbon mechanism, and the Super-Fast mechanism. We show that, for most regions and time periods, differences in simulated ozone chemistry between these three mechanisms are smaller than the model–observation differences themselves. The MOZART-4 mechanism and the Reduced Hydrocarbon are in close agreement in their representation of ozone throughout the troposphere during all time periods (annual, seasonal, and diurnal). While the Super-Fast mechanism tends to have higher simulated ozone variability and differs from the MOZART-4 mechanism over regions of high biogenic emissions, it is surprisingly capable of simulating ozone adequately given its simplicity. We explore the trade-offs between chemical mechanism complexity and computational cost by identifying regions where the simpler mechanisms are comparable to the MOZART-4 mechanism and regions where they are not. The Super-Fast mechanism is 3 times as fast as the MOZART-4 mechanism, which allows for longer simulations or ensembles with more members that may not be feasible with the MOZART-4 mechanism given limited computational resources.

scholarly journals Development of hybrid 3-D hydrological modeling for the NCAR Community Earth System Model (CESM)

2015 ◽  
Author(s):  
Xubin Zeng ◽  
◽  
Peter Troch ◽  
Jon Pelletier ◽  
Guo-Yue Niu ◽  
...  
Keyword(s):  
Hydrological Modeling ◽  
Earth System Model ◽  
System Model ◽  
Earth System ◽  
Community Earth System Model

scholarly journals Quantifying the role of fire in the Earth system – Part 1: Improved global fire modeling in the Community Earth System Model (CESM1)

2012 ◽  
Vol 9 (11) ◽  
pp. 16753-16814 ◽  
Author(s):  
F. Li ◽  
S. Levis ◽  
D. S. Ward
Keyword(s):  
Carbon Emissions ◽  
Anthropogenic Impacts ◽  
Earth System Model ◽  
System Model ◽  
Burned Area ◽  
Earth System ◽  
Alternative Scheme ◽  
System Perspective ◽  
Community Earth System Model ◽  
Peat Fires

Abstract. Modeling fire as an integral part of an Earth system model (ESM) is vital for quantifying and understanding fire-climate-vegetation interactions on a global scale and from an Earth system perspective. In this study, we introduce to the Community Earth System Model (CESM) the new global fire parameterization proposed by Li et al. (2012), now with a more realistic representation of the anthropogenic impacts on fires, with a parameterization of peat fires, and with other minor modifications. The improved representation of the anthropogenic dimension includes the first attempt to parameterize agricultural fires, the economic influence on fire occurrence, and the socioeconomic influence on fire spread in a global fire model; also an alternative scheme for deforestation fires. The global fire parameterization has been tested in CESM1's land component model CLM4 in a 1850–2004 transient simulation, and evaluated against the satellite-based Global Fire Emission Database version 3 (GFED3) for 1997–2004. The simulated 1997–2004 average global totals for the burned area and fire carbon emissions in the new fire scheme are 338 Mha yr−1 and 2.1 Pg C yr−1. Its simulations on multi-year average burned area, fire seasonality, fire interannual variability, and fire carbon emissions are reasonable, and show better agreement with GFED3 than the current fire scheme in CESM1 and modified CTEM-FIRE. Moreover, the new fire scheme also estimates the contributions of global fire carbon emissions from different sources. During 1997–2004, the contributions are 8% from agricultural biomass burning, 27% from tropical deforestation and degradation fires, 5% from global peat fires (3.7% from tropical peat fires), and 60% from other fires, which are close to previous assessments based on satellite data, government statistics, or other information sources. In addition, we investigate the importance of direct anthropogenic influence (anthropogenic ignitions and fire suppression) on global fire regimes during 1850–2004, using CESM1 with the new fire scheme. Results show that the direct anthropogenic impact is the main factor driving the trends of global burned area in the whole period and fire carbon emissions only before ~ 1870.

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