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

Landslides in a changing climate

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.

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

For most of the global land area poleward of about 40° latitude, snow plays an important role in the water cycle. The (seasonal) timing of runoff in these areas is especially sensitive to projected losses of snowpack associated with warming trends, whereas projected (annual) runoff volume changes are primarily associated with precipitation changes, and to a lesser extent, with changes in evapotranspiration (ET). Regional studies in the USA (and especially the western USA) suggest that hydrologic adjustments to a warming climate have been ongoing since the mid-twentieth century. We extend the insights extracted from the western USA to the global scale using a physically based hydrologic model to assess the effects of systematic changes in precipitation and temperature on snow-affected portions of the global land area as projected by a suite of global climate models. While annual (and in some cases seasonal) changes in precipitation are a key driver of projected changes in annual runoff, we find, as in the western USA, that projected warming produces strong decreases in winter snow accumulation and spring snowmelt over much of the affected area regardless of precipitation change. Decreased snowpack produces decreases in warm-season runoff in many mid- to high-latitude areas where precipitation changes are either moderately positive or negative in the future projections. Exceptions, however, occur in some high-latitude areas, particular in Eurasia, where changes in projected precipitation are large enough to result in increased, rather than decreased, snow accumulation. Overall, projected changes in snowpack and the timing of snowmelt-derived runoff are largest near the boundaries of the areas that currently experience substantial snowfall, and at least qualitatively, they mirror the character of observed changes in the western USA. Copyright © 2008 John Wiley & Sons, Ltd.

Implications of global climate change for snowmelt hydrology in the twenty-first century.

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)

Experiments related to twentieth century historical climate changes and the twenty-first century scenario are performed with the latest version of the MRI climate model, MRI-CGCM2.3. The model reproduces globally averaged surface air temperature (SAT) variations in the twentieth century with satisfactory agreement with interdecadal changes of the observed trend, as well as with the overall SAT increase of 0.5°C at the present-day compared to the pre-industrial level. The globally averaged SAT rises 2.4°C in the late twenty-first century in the experiment for scenario A1B of the Special Report on Emissions Scenarios (SRES) by the Intergovernmental Panel on Climate Change (IPCC). The spatial structures of the simulated trends for the late twentieth century are validated in various atmospheric fields through comparisons with observed data, which indicate that the model demonstrates reasonable agreement with the observed trend in each field. Most of the simulated changes for the twenty-first century reveal spatial patterns similar to those in the trends that appeared in the late twentieth century. The simulated trend patterns of the sea-level pressure (SLP) in both hemispheres bear a resemblance to the observed trends, with each spatial structure reminiscent of the annular modes in the northern and southern hemispheres (NAM and SAM). These SLP trend patterns are consistent with the trends in the SAT, precipitation, and zonal mean zonal wind fields, as in the NAM and SAM. The coherent trend structures of these fields are projected to be enhanced in twenty-first century climate changes. Changes of ocean and sea-ice in association with these atmospheric changes are also described.

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Climate changes of the twentieth through twenty-first centuries simulated by the MRI-CGCM2.3

The MRI atmospheric general circulation model has been used to study the effect of horizontal resolution on the simulation of Asian summer monsoon. The model has been integrated for an eight year period with three different horizontal resolutions designated as Low (4°lat X 5°long), Medium (3°lat X 3.3°long) and High (2°lat X 2.5°long), respectively. The results indicate that the increase of horizontal resolution improved the simulation of mean sea level pressure and precipitation patterns. The high resolution model simulates a heat low and monsoon trough in agreement with the observations, while the low resolution model simulates an abnormal heat low over north India. The high resolution model simulates the precipitation maxima over the Bay of Bengal and the south Indian ocean, and a dry region over the Tarim basin better, while the low resolution model better simulates the precipitation maximum over the Arabian sea. All the models simulate weaker monsoon circulation while the increase of horizontal resolution leads to further weakening of low level monsoon westerlies. The results of this study conclude that the increase of horizontal resolution improved the simulation of many observed features of the Asian summer monsoon circulation, but certain features deteriorated indicating that the model parameterizations may need to be suitably modified.

鬼頭昭雄

Papers

新気象研究所結合モデル (mri-cgcm2)

Climate changes of the twentieth through twenty-first centuries simulated by the MRI-CGCM2.3

Mri gcm-iiによるアジアの夏季モンスーンのシミュレーションに対する水平解像度の効果

鬼頭 昭雄

Papers

新気象研究所結合モデル (mri-cgcm2)

Climate changes of the twentieth through twenty-first centuries simulated by the MRI-CGCM2.3

Mri gcm-iiによるアジアの夏季モンスーンのシミュレーションに対する水平解像度の効果

鬼頭昭雄