Temperature and precipitation extremes and their potential future changes are evaluated in an ensemble of global coupled climate models participating in the Intergovernmental Panel on Climate Change (IPCC) diagnostic exercise for the Fourth Assessment Report (AR4). Climate extremes are expressed in terms of 20-yr return values of annual extremes of near-surface temperature and 24-h precipitation amounts. The simulated changes in extremes are documented for years 2046–65 and 2081–2100 relative to 1981–2000 in experiments with the Special Report on Emissions Scenarios (SRES) B1, A1B, and A2 emission scenarios. Overall, the climate models simulate present-day warm extremes reasonably well on the global scale, as compared to estimates from reanalyses. The model discrepancies in simulating cold extremes are generally larger than those for warm extremes, especially in sea ice–covered areas. Simulated present-day precipitation extremes are plausible in the extratropics, but uncertainties in extreme prec...

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Changes in temperature and precipitation extremes in the IPCC ensemble of global coupled model simulations

http://www.jstage.jst.go.jp/article/jmsj/90A/0/90A_2012-A02/_pdf

A New Global Climate Model of the Meteorological Research Institute: MRI-CGCM3 —Model Description and Basic Performance—

. Implications of 21st century climate change on the hydrology and water resources of the Colorado River Basin were assessed using a multimodel ensemble approach in which downscaled and bias corrected output from 11 General Circulation Models (GCMs) was used to drive macroscale hydrology and water resources models. Downscaled climate scenarios (ensembles) were used as forcings to the Variable Infiltration Capacity (VIC) macroscale hydrology model, which in turn forced the Colorado River Reservoir Model (CRMM). Ensembles of downscaled precipitation and temperature, and derived streamflows and reservoir system performance were assessed through comparison with current climate simulations for the 1950–1999 historical period. For each of the 11 GCMs, two emissions scenarios (IPCC SRES A2 and B1, corresponding to relatively unconstrained growth in emissions, and elimination of global emissions increases by 2100) were represented. Results for the A2 and B1 climate scenarios were divided into three periods: 2010–2039, 2040–2069, and 2070–2099. The mean temperature change averaged over the 11 ensembles for the Colorado basin for the A2 emission scenario ranged from 1.2 to 4.4°C for periods 1–3, and for the B1 scenario from 1.3 to 2.7°C. Precipitation changes were modest, with ensemble mean changes ranging from −1 to −2% for the A2 scenario, and from +1 to −1% for the B1 scenario. An analysis of seasonal precipitation patterns showed that most GCMs had modest reductions in summer precipitation and increases in winter precipitation. Derived April 1 snow water equivalent declined for all ensemble members and time periods, with maximum (ensemble mean) reductions of 38% for the A2 scenario in period 3. Runoff changes were mostly the result of a dominance of increased evapotranspiration over the seasonal precipitation shifts, with ensemble mean runoff changes of −1, −6, and −11% for the A2 ensembles, and 0, −7, and −8% for the B1 ensembles. These hydrological changes were reflected in reservoir system performance. Average total basin reservoir storage and average hydropower production generally declined, however there was a large range across the ensembles. Releases from Glen Canyon Dam to the Lower Basin were reduced for all periods and both emissions scenarios in the ensemble mean. The fraction of years in which shortages occurred increased by approximately 20% by period 3 for both emissions scenarios.

/pdf/a-multimodel-ensemble-approach-to-assessment-of-climate-2tl5ef5n1h.pdf

A multimodel ensemble approach to assessment of climate change impacts on the hydrology and water resources of the Colorado River Basin

A numerical study of the contributions of dust source regions to the global dust budget

Simulations of the stratosphere from thirteen coupled chemistry-climate models (CCMs) are evaluated to provide guidance for the interpretation of ozone predictions made by the same CCMs. The focus of the evaluation is on how well the fields and processes that are important for determining the ozone distribution are represented in the simulations of the recent past. The core period of the evaluation is from 1980 to 1999 but long-term trends are compared for an extended period (1960–2004). Comparisons of polar high-latitude temperatures show that most CCMs have only small biases in the Northern Hemisphere in winter and spring, but still have cold biases in the Southern Hemisphere spring below 10 hPa. Most CCMs display the correct stratospheric response of polar temperatures to wave forcing in the Northern, but not in the Southern Hemisphere. Global long-term stratospheric temperature trends are in reasonable agreement with satellite and radiosonde observations. Comparisons of simulations of methane, mean age of air, and propagation of the annual cycle in water vapor show a wide spread in the results, indicating differences in transport. However, for around half the models there is reasonable agreement with observations. In these models the mean age of air and the water vapor tape recorder signal are generally better than reported in previous model intercomparisons. Comparisons of the water vapor and inorganic chlorine (Cly) fields also show a large intermodel spread. Differences in tropical water vapor mixing ratios in the lower stratosphere are primarily related to biases in the simulated tropical tropopause temperatures and not transport. The spread in Cly, which is largest in the polar lower stratosphere, appears to be primarily related to transport differences. In general the amplitude and phase of the annual cycle in total ozone is well simulated apart from the southern high latitudes. Most CCMs show reasonable agreement with observed total ozone trends and variability on a global scale, but a greater spread in the ozone trends in polar regions in spring, especially in the Arctic. In conclusion, despite the wide range of skills in representing different processes assessed here, there is sufficient agreement between the majority of the CCMs and the observations that some confidence can be placed in their predictions.

/pdf/assessment-of-temperature-trace-species-and-ozone-in-3wnn6d5e2j.pdf

Assessment of temperature, trace species, and ozone in chemistry-climate model simulations of the recent past

A new version of a global coupled atmosphere-ocean general circulation model (MRI-CGCM2) has been developed at the Meteorological Research Institute (MRI). The model can be used to explore climate change associated with anthropogenic forcings. We aimed to reduce the drawbacks of the former version of the model (MRI-CGCM1, Tokioka. et. al., 1996) and achieve a more realistic climatic mean and variability to predict climate changes with greater accuracy.   In a preliminary analysis of the control run, the model showed generally good performance in reproducing the mean climate (including seasonal variation) in representative aspects; surface air temperature, precipitation, snow and sea ice distribution, and ocean structure and circulation. The model is capable of making a stable integration longer than 200 years. The sea ice distribution is much improved and is close to the observed extent and thickness. The model simulates realistic strength of meridional overturning in the Atlantic Ocean that MRI-CGCM1 failed to simulate. The model realistically simulates variabilities such as Arctic Oscillation (AO) and ENSO.    Temporal variation of the sea surface temperature (SST) anomaly in the NINO3 region (150°W to 90°W, 4°S to 4°N) shows a large positive value (max. +4°C) with several years interval. The SST anomaly pattern is similar to the observed El Nino with a strong positive anomaly in the central-eastern equatorial Pacific. The model still has some biases at present. The surface air temperature in winter at high latitude has a warm bias due to weaker stability in the boundary layer. The surface temperature over land in summer also shows a warm bias associated with a problem concerning the hydrological process.

/pdf/xin-qi-xiang-yan-jiu-suo-jie-he-moderu-mri-cgcm2-z4evm66z0f.pdf

新気象研究所結合モデル (mri-cgcm2)

MASINGAR, a global tropospheric aerosol chemical transport model coupled with MRI/JMA98 GCM: Model description

大気大循環モデル (mri/jma98) による対流圏、成層圏、中間圏のシミュレーション

大気大循環モデルmri/jma98と結合した全球対流圏エーロゾル化学輸送モデル masingar

An atmospheric general circulation model developed in the Meteorological Research Institute is described. The model has 23 vertical layers from the earth's surface to approximately 70km in the middle mesosphere. It uses the spectral transform method with a rhomboidal 24 truncation. The model includes all major physical processes. It has been run for ten years with climatological sea surface temperatures (SSTs). The model generally simulates the features of the general atmospheric circulation in the troposphere and the stratosphere reasonably well. Some drawbacks exist, however, such as the lack of equatorial quasi-biennial oscillation (QBO). It should be emphasized that the model is successful in simulating the interannual variation in stratospheric circulation in the extratropics without any interannual changes in SSTs or external forcing.

柴田清孝

Papers

新気象研究所結合モデル (mri-cgcm2)

MASINGAR, a global tropospheric aerosol chemical transport model coupled with MRI/JMA98 GCM: Model description

大気大循環モデル (mri/jma98) による対流圏、成層圏、中間圏のシミュレーション

大気大循環モデルmri/jma98と結合した全球対流圏エーロゾル化学輸送モデル masingar

The description of the MRI atmospheric spectral GCM (MRI-GSPM) and its mean statistics based on a 10-year integration

柴田 清孝

Papers

新気象研究所結合モデル (mri-cgcm2)

MASINGAR, a global tropospheric aerosol chemical transport model coupled with MRI/JMA98 GCM: Model description

大気大循環モデル (mri/jma98) による対流圏、成層圏、中間圏のシミュレーション

大気大循環モデルmri/jma98と結合した全球対流圏エーロゾル化学輸送モデル masingar

The description of the MRI atmospheric spectral GCM (MRI-GSPM) and its mean statistics based on a 10-year integration

柴田清孝