scholarly journals The HadGEM3-GA7.1 radiative kernel: the importance of a well-resolved stratosphere

2020 ◽  
Author(s):  
Christopher J. Smith ◽  
Ryan J. Kramer ◽  
Adriana Sima
Keyword(s):  
General Circulation ◽  
Climate Model ◽  
Coupled Model ◽  
Circulation Model ◽  
Atmospheric Model ◽  
Stratospheric Temperature ◽  
Linear Behaviour ◽  
Intercomparison Project ◽  
Stratospheric Cooling ◽  
The Uk

Abstract. We present top-of-atmosphere and surface radiative kernels based on the atmospheric component (GA7.1) of the HadGEM3 general circulation model developed by the UK Met Office. We show that the utility of radiative kernels for forcing adjustments in idealised CO2 perturbation experiments is most appropriate where there is sufficiently high resolution in the stratosphere in both the target climate model and the radiative kernel. This is because stratospheric cooling to a CO2 perturbation continues to increase with height, and low-resolution or low-top kernels or climate model output are unable to fully resolve the full stratospheric temperature adjustment. In the sixth phase of the Coupled Model Intercomparison Project (CMIP6), standard atmospheric model data is available up to 1 hPa on 19 pressure levels, which is a substantial advantage compared to CMIP5. We show in the IPSL-CM6A-LR model where a full set of climate diagnostics are available that the HadGEM3-GA7.1 kernel exhibits linear behaviour and the residual error term is small. From kernels available in the literature we recommend three kernels for adjustment calculations to CO2 and well-mixed greenhouse gas perturbations based on their stratospheric resolution: HadGEM3-GA7.1, ECMWF-Oslo, and ECHAM6. The HadGEM3-GA7.1 radiative kernels are available at https://doi.org/10.5281/zenodo.3594673 (Smith, 2019).

scholarly journals The HadGEM3-GA7.1 radiative kernel: the importance of a well-resolved stratosphere

2020 ◽  
Vol 12 (3) ◽  
pp. 2157-2168 ◽  
Author(s):  
Christopher J. Smith ◽  
Ryan J. Kramer ◽  
Adriana Sima
Keyword(s):  
General Circulation ◽  
Climate Model ◽  
Temperature Response ◽  
Coupled Model ◽  
Circulation Model ◽  
Atmospheric Model ◽  
Stratospheric Temperature ◽  
Linear Behaviour ◽  
Stratospheric Cooling ◽  
The Uk

Abstract. We present top-of-atmosphere and surface radiative kernels based on the atmospheric component (GA7.1) of the HadGEM3 general circulation model developed by the UK Met Office. We show that the utility of radiative kernels for forcing adjustments in idealised CO2 perturbation experiments is greatest where there is sufficiently high resolution in the stratosphere in both the target climate model and the radiative kernel. This is because stratospheric cooling to a CO2 perturbation continues to increase with height, and low-resolution or low-top kernels or climate model output are unable to fully resolve the full stratospheric temperature adjustment. In the sixth phase of the Coupled Model Intercomparison Project (CMIP6), standard atmospheric model data are available up to 1 hPa on 19 pressure levels, which is a substantial advantage compared to CMIP5. We show in the IPSL-CM6A-LR model where a full set of climate diagnostics are available that the HadGEM3-GA7.1 kernel exhibits linear behaviour and the residual error term is small, as well as from a survey of kernels available in the literature that in general low-top radiative kernels underestimate the stratospheric temperature response. The HadGEM3-GA7.1 radiative kernels are available at https://doi.org/10.5281/zenodo.3594673 (Smith, 2019).

scholarly journals The FAMOUS climate model (versions XFXWB and XFHCC): description update to version XDBUA

2011 ◽  
Vol 4 (4) ◽  
pp. 3047-3065
Author(s):  
R. S. Smith
Keyword(s):  
Water Budget ◽  
General Circulation ◽  
Climate Model ◽  
Circulation Model ◽  
Model Description ◽  
Model Intercomparison ◽  
Ocean Atmosphere ◽  
Atmosphere General Circulation Model ◽  
Intercomparison Project ◽  
The Uk

Abstract. FAMOUS is an ocean-atmosphere general circulation model of low resolution, based on version 4.5 of the UK MetOffice Unified Model. Here we update the model description to account for changes in the model as it is used in the CMIP5 EMIC model intercomparison project (EMICmip) and a number of other studies. Most of these changes correct errors found in the code. The EMICmip version of the model (XFXWB) has a better-conserved water budget and additional cooling in some high latitude areas, but otherwise has a similar climatology to previous versions of FAMOUS. A variant of XFXWB is also described, with changes to the dynamics at the top of the model which improve the model climatology (XFHCC).

scholarly journals The FAMOUS climate model (versions XFXWB and XFHCC): description update to version XDBUA

2012 ◽  
Vol 5 (1) ◽  
pp. 269-276 ◽  
Author(s):  
R. S. Smith
Keyword(s):  
Water Budget ◽  
General Circulation ◽  
Climate Model ◽  
Circulation Model ◽  
Model Description ◽  
Model Intercomparison ◽  
Ocean Atmosphere ◽  
Atmosphere General Circulation Model ◽  
Intercomparison Project ◽  
The Uk

Abstract. FAMOUS is an ocean-atmosphere general circulation model of low resolution, based on version 4.5 of the UK MetOffice Unified Model. Here we update the model description to account for changes in the model as it is used in the CMIP5 EMIC model intercomparison project (EMICmip) and a number of other studies. Most of these changes correct errors found in the code. The EMICmip version of the model (XFXWB) has a better-conserved water budget and additional cooling in some high latitude areas, but otherwise has a similar climatology to previous versions of FAMOUS. A variant of XFXWB is also described, with changes to the dynamics at the top of the model which improve the model climatology (XFHCC).

scholarly journals Impact of an observational time window on coupled data assimilation: simulation with a simple climate model

2017 ◽  
Vol 24 (4) ◽  
pp. 681-694 ◽  
Author(s):  
Yuxin Zhao ◽  
Xiong Deng ◽  
Shaoqing Zhang ◽  
Zhengyu Liu ◽  
Chang Liu ◽  
...  
Keyword(s):  
Data Assimilation ◽  
General Circulation ◽  
Climate Model ◽  
Time Window ◽  
Coupled Model ◽  
Circulation Model ◽  
Scale Interactions ◽  
Climate Signals ◽  
Coupled Data Assimilation ◽  
Climate Analysis

Abstract. Climate signals are the results of interactions of multiple timescale media such as the atmosphere and ocean in the coupled earth system. Coupled data assimilation (CDA) pursues balanced and coherent climate analysis and prediction initialization by incorporating observations from multiple media into a coupled model. In practice, an observational time window (OTW) is usually used to collect measured data for an assimilation cycle to increase observational samples that are sequentially assimilated with their original error scales. Given different timescales of characteristic variability in different media, what are the optimal OTWs for the coupled media so that climate signals can be most accurately recovered by CDA? With a simple coupled model that simulates typical scale interactions in the climate system and twin CDA experiments, we address this issue here. Results show that in each coupled medium, an optimal OTW can provide maximal observational information that best fits the characteristic variability of the medium during the data blending process. Maintaining correct scale interactions, the resulting CDA improves the analysis of climate signals greatly. These simple model results provide a guideline for when the real observations are assimilated into a coupled general circulation model for improving climate analysis and prediction initialization by accurately recovering important characteristic variability such as sub-diurnal in the atmosphere and diurnal in the ocean.

scholarly journals The Effect of a Well-Resolved Stratosphere on Surface Climate: Differences between CMIP5 Simulations with High and Low Top Versions of the Met Office Climate Model

2012 ◽  
Vol 25 (20) ◽  
pp. 7083-7099 ◽  
Author(s):  
S. C. Hardiman ◽  
N. Butchart ◽  
T. J. Hinton ◽  
S. M. Osprey ◽  
L. J. Gray
Keyword(s):  
General Circulation ◽  
Climate Model ◽  
Southern Oscillation ◽  
Coupled Model ◽  
Circulation Model ◽  
Climate Simulation ◽  
Reanalysis Dataset ◽  
Quasi Biennial Oscillation ◽  
Surface Climate ◽  
The Impact

Abstract The importance of using a general circulation model that includes a well-resolved stratosphere for climate simulations, and particularly the influence this has on surface climate, is investigated. High top model simulations are run with the Met Office Unified Model for the Coupled Model Intercomparison Project Phase 5 (CMIP5). These simulations are compared to equivalent simulations run using a low top model differing only in vertical extent and vertical resolution above 15 km. The period 1960–2002 is analyzed and compared to observations and the European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis dataset. Long-term climatology, variability, and trends in surface temperature and sea ice, along with the variability of the annular mode index, are found to be insensitive to the addition of a well-resolved stratosphere. The inclusion of a well-resolved stratosphere, however, does improve the impact of atmospheric teleconnections on surface climate, in particular the response to El Niño–Southern Oscillation, the quasi-biennial oscillation, and midwinter stratospheric sudden warmings (i.e., zonal mean wind reversals in the middle stratosphere). Thus, including a well-represented stratosphere could improve climate simulation on intraseasonal to interannual time scales.

scholarly journals Long-term Surface Temperature (LoST) database as a complement for GCM preindustrial simulations

2019 ◽  
Vol 15 (3) ◽  
pp. 1099-1111 ◽  
Author(s):  
Francisco José Cuesta-Valero ◽  
Almudena García-García ◽  
Hugo Beltrami ◽  
Eduardo Zorita ◽  
Fernando Jaume-Santero
Keyword(s):  
Surface Temperature ◽  
General Circulation ◽  
Ground Surface ◽  
Coupled Model ◽  
Circulation Model ◽  
Research Unit ◽  
Large Spread ◽  
Intercomparison Project ◽  
Past Millennium

Abstract. Estimates of climate sensitivity from general circulation model (GCM) simulations still present a large spread despite the continued improvements in climate modeling since the 1970s. This variability is partially caused by the dependence of several long-term feedback mechanisms on the reference climate state. Indeed, state-of-the-art GCMs present a large spread of control climate states probably due to the lack of a suitable reference for constraining the climatology of preindustrial simulations. We assemble a new gridded database of long-term ground surface temperatures (LoST database) obtained from geothermal data over North America, and we explore its use as a potential reference for the evaluation of GCM preindustrial simulations. We compare the LoST database with observations from the Climate Research Unit (CRU) database, as well as with five past millennium transient climate simulations and five preindustrial control simulations from the third phase of the Paleoclimate Modelling Intercomparison Project (PMIP3) and the fifth phase of the Coupled Model Intercomparison Project (CMIP5). The database is consistent with meteorological observations as well as with both types of preindustrial simulations, which suggests that LoST temperatures can be employed as a reference to narrow down the spread of surface temperature climatologies on GCM preindustrial control and past millennium simulations.

Sensitivity of the Aerosol Indirect Effect to Subgrid Variability in the Cloud Parameterization of the GFDL Atmosphere General Circulation Model AM3

2011 ◽  
Vol 24 (13) ◽  
pp. 3145-3160 ◽  
Author(s):  
Jean-Christophe Golaz ◽  
Marc Salzmann ◽  
Leo J. Donner ◽  
Larry W. Horowitz ◽  
Yi Ming ◽  
...  
Keyword(s):  
General Circulation Model ◽  
Indirect Effect ◽  
General Circulation ◽  
Coupled Model ◽  
Circulation Model ◽  
Atmospheric Model ◽  
Radiation Balance ◽  
Cloud Drop ◽  
Aerosol Indirect Effect ◽  
Alternate Model

Abstract The recently developed GFDL Atmospheric Model version 3 (AM3), an atmospheric general circulation model (GCM), incorporates a prognostic treatment of cloud drop number to simulate the aerosol indirect effect. Since cloud drop activation depends on cloud-scale vertical velocities, which are not reproduced in present-day GCMs, additional assumptions on the subgrid variability are required to implement a local activation parameterization into a GCM. This paper describes the subgrid activation assumptions in AM3 and explores sensitivities by constructing alternate configurations. These alternate model configurations exhibit only small differences in their present-day climatology. However, the total anthropogenic radiative flux perturbation (RFP) between present-day and preindustrial conditions varies by ±50% from the reference, because of a large difference in the magnitude of the aerosol indirect effect. The spread in RFP does not originate directly from the subgrid assumptions but indirectly through the cloud retuning necessary to maintain a realistic radiation balance. In particular, the paper shows a linear correlation between the choice of autoconversion threshold radius and the RFP. Climate sensitivity changes only minimally between the reference and alternate configurations. If implemented in a fully coupled model, these alternate configurations would therefore likely produce substantially different warming from preindustrial to present day.

Quantification of uncertainty in reference evapotranspiration climate change signals in Belgium

2016 ◽  
Vol 48 (5) ◽  
pp. 1391-1401 ◽  
Author(s):  
Parisa Hosseinzadehtalaei ◽  
Hossein Tabari ◽  
Patrick Willems
Keyword(s):  
Climate Change ◽  
General Circulation ◽  
Reference Evapotranspiration ◽  
Coupled Model ◽  
Circulation Model ◽  
Change Context ◽  
Intercomparison Project ◽  
Projected Changes ◽  
Availability Assessment ◽  
Comparable Magnitude

Projections of evapotranspiration form the basis of future runoff and water availability assessment in a climate change context. The scarcity of data or insufficiency of time/funds compels the application of simple reference evapotranspiration (ETo) methods requiring less meteorological inputs for ETo projections which adds uncertainty to the projected changes. This study investigates the bias in ETo climate change signals derived from seven simple temperature- and radiation-based methods (Blaney–Criddle, Hargreaves–Samani, Schendel, Makkink, Turc, Jensen–Haise, Tabari) compared with that from the standard Penman–Monteith FAO 56 method on the basis of 12 general circulation model (GCM) outputs from the Coupled Model Intercomparison Project Phase 5 for central Belgium for four future greenhouse gas scenarios (RCP2.6, RCP4.5, RCP6.0, RCP8.5). The results show the lack of conformity on the amount of ETo changes between the simple and standard methods, with biases of over 100% for some simple methods. The uncertainty affiliated with ETo methods for monthly ETo changes is smaller but of comparable magnitude to GCM uncertainty, which is usually the major source of uncertainty, and larger for daily extreme ETo changes. This emphasizes the imperative of addressing the uncertainty associated with ETo methods for quantifying the hydrological response to climate change.

scholarly journals Climate and African precipitation changes in the mid-Holocene simulated using an Earth System Model MIROC-ESM

2012 ◽  
Vol 8 (4) ◽  
pp. 3277-3343 ◽  
Author(s):  
R. Ohgaito ◽  
T. Sueyoshi ◽  
A. Abe-Ouchi ◽  
T. Hajima ◽  
S. Watanabe ◽  
...  
Keyword(s):  
General Circulation ◽  
Coupled Model ◽  
Circulation Model ◽  
Earth System Model ◽  
System Model ◽  
Earth System ◽  
African Monsoon ◽  
Proxy Records ◽  
Intercomparison Project ◽  
Precipitation Changes

Abstract. The importance of evaluating models using paleoclimate simulations is becoming more recognized in efforts to improve climate projection. To evaluate an integrated Earth System Model, MIROC-ESM, we performed simulations in time-slice experiments for the mid-Holocene (6000 yr before present, 6 ka) and preindustrial (1850 AD) times under the protocol of the Coupled Model Intercomparison Project 5/Paleoclimate Modelling Intercomparison Project 3. We first overview the simulated global climates by comparing with simulations using a previous version of the MIROC model (MIROC3), which is an atmosphere-ocean coupled general circulation model, and then comprehensively discuss various aspects of climate change with 6 ka forcing. We also discuss the 6 ka African monsoon activity. The 6 ka precipitation change over northern Africa according to MIROC-ESM does not differ dramatically from that obtained with MIROC3, which means that newly developed components such as dynamic vegetation and improvements in the atmospheric processes do not have significant impacts on representing the 6 ka monsoon change suggested by proxy records. Although there is no drastic difference in the African monsoon representation between the two models, there are small but significant differences in the precipitation enhancement in MIROC-ESM, which can be related to the representation of the sea surface temperature rather than the vegetation coupling, at least in MIROC-ESM.

scholarly journals Sensitivity of Pliocene climate simulations in MRI-CGCM2.3 to respective boundary conditions

2016 ◽  
Vol 12 (8) ◽  
pp. 1619-1634 ◽  
Author(s):  
Youichi Kamae ◽  
Kohei Yoshida ◽  
Hiroaki Ueda
Keyword(s):  
Boundary Conditions ◽  
General Circulation ◽  
Model Comparison ◽  
Climate Model ◽  
Phase 1 ◽  
Regional Climate ◽  
Circulation Model ◽  
Poleward Heat Transport ◽  
Climate Simulations ◽  
Intercomparison Project

Abstract. Accumulations of global proxy data are essential steps for improving reliability of climate model simulations for the Pliocene warming climate. In the Pliocene Model Intercomparison Project phase 2 (PlioMIP2), a part project of the Paleoclimate Modelling Intercomparison Project phase 4, boundary forcing data have been updated from the PlioMIP phase 1 due to recent advances in understanding of oceanic, terrestrial and cryospheric aspects of the Pliocene palaeoenvironment. In this study, sensitivities of Pliocene climate simulations to the newly archived boundary conditions are evaluated by a set of simulations using an atmosphere–ocean coupled general circulation model, MRI-CGCM2.3. The simulated Pliocene climate is warmer than pre-industrial conditions for 2.4 °C in global mean, corresponding to 0.6 °C warmer than the PlioMIP1 simulation by the identical climate model. Revised orography, lakes, and shrunk ice sheets compared with the PlioMIP1 lead to local and remote influences including snow and sea ice albedo feedback, and poleward heat transport due to the atmosphere and ocean that result in additional warming over middle and high latitudes. The amplified higher-latitude warming is supported qualitatively by the proxy evidences, but is still underestimated quantitatively. Physical processes responsible for the global and regional climate changes should be further addressed in future studies under systematic intermodel and data–model comparison frameworks.

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