2017 Abstract
Area Theme C: Integrated Climate Change Projection
Japan Meteorological Business Support Center: Izuru Takayabu
As a successor of "Program for Risk Information on Climate Change (SOUSEI)" carried out for 5 years (FY2012-2016), the Ministry of Education, Culture, Sports, Science and Technology (MEXT) has established an advanced program for 5 years (FY2017-2021), "Integrated Research Program for Advancing Climate Models (TOUGOU)" with 4 themes from A to D:
Theme A: Prediction and Projection of Large-Scale Climate Changes Based on Advanced Model Development;
Theme B: Sophisticated Earth System Model for Evaluating Emission Reductions Needed;
Theme C: Integrated Climate Change Projection; and
Theme D: Integrated Hazard Projection.
This program aims to further develop climate models and to reflect the knowledge gained through them in the adaptation plans of actual regions to the questions that society needs answers for in this process will open the door to a new type of science. Using the world-class supercomputers, such as Earth Simulator, we are pursuing research and development in which all themes are organically linked. Our research and development include prediction and diagnosis of imminent global climate change expected to occur within a few years or decades, research on greenhouse gas emission scenarios and associated long-term climate change projections, development of probabilistic climate change projection techniques, and development of technology for precise impact assessment, etc.
International society is seeking stronger cooperation with "the physical science basis" of Working Group I (WGI) and "impacts, adaptation and vulnerability" of Working Group II (WGII) within the Intergovernmental Panel on Climate Change (IPCC). In Japan, the development of global warming adaptation measures for all the local government units and various types of information on warming projections for use in those measures are being sought.
Among warming projections, the change in the probability of extreme weather, for example typhoons and heavy rainfall during the rainy season, has recently drawn a lot of attention. High-resolution and precise global and regional climate models will be used in this theme and with the aim of elucidating how and why extreme weather changes that can have such a major impact on regional climates occur. The data from warming projection calculations can then be used it examine the types of impact they will have on society. Data that meets all of the types of demand for it therefore needs to be output.
In area Theme C, we intend to carry out future projections and experiments for use in reproducing current climates in various scenarios and experiments that reproduce past climates through assimilating data. Then, by assessing the adequacy of the resulting data, we can provide the various users of it with guidelines for them to use in making the decision on which data they can best use. In addition, we intend to develop a new and high-resolution downscaling model system to ensure that the data can then be utilized in a greater variety of fields, in warming impact assessment of environmental contamination, and in agriculture and renewable energy etc. The studies will be used in coordinated studies that include staff exchanges with other countries that are vulnerable to global warming (e.g. Southeast Asian countries) as well as in domestic coordinated studies. In this way, the studies can then contribute to warming projections for use at actual sites and studies on their utilization.
Sub-theme (i): Development of high-precision models integrated with climate-relevant processes
Japan Meteorological Business Support Center: Masayoshi Ishii
For further improvement of future-projection products used for climate change adaptation and mitigation, we are developing global and regional coupled models of high resolution, which is a revision of the present earth system model of the Meteorological Research Institute of the Japan Meteorological Agency. So far, we conducted time-slice experiments with high-resolution atmospheric models for future changes in extreme weather and climate events such as typhoon and strong precipitation. The versions of the same model have been used under consecutive domestic global-warming research programs called KYOSEI, KAKUSHIN, and SOUSEI. The model performances are still the best among atmospheric modes used for global warming studies world-wide. However, the models ignore air-sea coupling and they produce atmospheric states only. That is why we introduce coupled models for conducting future projections with time-slice experiments. Such coupled experiments provide us more physically consistent products than ever and these should be informative in relation to understand future climate changes in extreme events as well as mean states. We also plan to examine the possibility of atmospheric chemistry products by introducing chemistry models including complicated chemical processes and transportation. These physical and chemical products will hopefully respond to various social demands.
Needless to say, understanding past climates for more than 100 years is as important as predicting future climates in the next 100 years. At present, the past climates are limitedly known particularly before the International Geophysical Year (1957-1958). Even in the past climate, strong typhoons landed on Japan islands, and the old Japan experienced severe disasters due to heavy rain and drought. It is beneficial to modeling and climate predictions to understand how and why these events occurred in long-term climate fluctuations. Therefore, a study for 150-year climate reanalysis is incorporated in this sub-theme. Here, we will develop a system of long-term data assimilation with sparse observations.
Sub-theme (ii): Development of climate scenarios for multi-stakeholder applications and understanding the mechanisms of climate change
a: Development of climate scenarios for multi-stakeholder applications and understanding the mechanisms of future changes in extreme events
Japan Meteorological Business Support Center: Toshiyuki Nakaegawa
We performed a present-day climate simulation with future climate projection system using global and regional climate models with 20, 5 and 2 km horizontal resolutions to quantify the natural variabilities in atmosphere and are performing a future climate simulation at the late 21st century under the RCP2.6 scenario. We are also performing a seamless long-term simulation for more than 100 years with 60 and 20 km versions of the global and regional climate models, respectively. The experimental designs were determined after discussion with the Theme C and D members.
We examined the effects of spatial pattern of future sea surface temperatures on changes in severe meteorological phenomena and their uncertainties. Extreme precipitation is influenced by the level of neutral buoyancy as well as well-known increase in precipitable water based on the Clausius-Clapeyron relationship. Large ensemble simulations of the Database for Policy Decision-making for Future Climate Change (d4PDF) allow us to reveal the robust future changes in occurrences, existence, and severe intensity of tropical cyclones under a +4˚C world with statistical significance. The occurrence of tropical cyclones in the future climate is projected to globally decrease by 33%. We started analyzing the characteristics of mean states and climate extremes in our future climate projections with MRI-AGCM3.2S/H among the CMIP5 model ensemble. The mean states of the present-day climate simulation of MRI-AGCM3.2S/H are as well reproduced as those of CMIP5 multi-model ensemble mean.
Analyses on the NHRCMs show that extreme precipitation in the 2-km present-day climate simulation reproduces better compared to the 5-km one. Future changes in extreme precipitation in northwestern part of Hokkaido Island is due to the enhanced westerly wind in the future climate rather than to the increase in precipitable water. Cloud-resolving present-day climate simulation with 2-km resolution and simulation with 5-km convection-scheme shows different relationship between elevations and annual maximum snow depth. We also performed additional and extension simulations of d4PDF and found that the interannual variabilities in annual number of days with greater than 100 mm/day are correlated with the interannual variabilities in sea surface temperatures and induced large-scale circulations in some areas but not so in others.
b: High-resolution simulation of typhoons and extreme events
Nagoya University: Kazuhisa Tsuboki
Most extreme phenomena are caused by typhoons: heavy rainfall, violent winds and storm surges. The purposes of the present study are to clarify the mechanisms of extreme phenomena associated with typhoons using a high-resolution model and their future changes in association with the climate change using pseudo-global warming (PGW) experiments and dynamic downscaling experiments. In this year, we performed simulations of the most intense typhoon in the 21st century and examined the process and mechanism of the development. The impact of ocean coupling was also shown. A dynamic downscaling experiment of future typhoons was begun using a cloud-resolving model.
Typhoon Megi (2010) is the most intense typhoon in the 21st century. It attained the minimum sea level pressure of 885 hPa after the rapid intensification. The high-resolution simulation experiment showed that the storm developed rapidly when the sea surface temperature (SST) has a peak at the storm center while the development of the storm stops when the SST at the center is lower than that of the surrounding area. The result indicates that a detailed SST distribution is necessary for accurate prediction of development of a very intense typhoon.
The future change of typhoon-related heavy rainfall is another important research topic. A record-breaking rainfall amount was brought by four typhoons which made landfall in the northern Japan in August 2016. The future change of such extreme events is a big issue for typhoon disaster prevention. To answer this problem, we performed PGW experiments of one of the four typhoons. The result of the PGW experiments showed that the northward movement speed was slower and the minimum central pressure was lower in the PGW experiments than the simulation experiment. The rainfall distribution was more localized and was more intense. The rainfall in the region far distance from the typhoon becomes more intense owing to the large moisture flux to the northeast of the typhoon center.
A dynamic downscaling experiment was started using CReSS and d4PDF data to examine the future change of typhoons approaching the northern Japan. We expect to obtain high-resolution data of typhoons and associated heavy rainfalls by further experiments of the d4PDF typhoons.
Sub-theme (iii): Advancing international collaboration through the application of a high-performing climate model over many countries in the Asia-Pacific region
Japan Meteorological Business Support Center: Hidetaka Sasaki
1) Climate change projections in vulnerable areas
Six researchers were invited to the Meteorological Research Institute (MRI) in order to conduct collaborative researches on climate change projection around their homelands in FY2017. Invited researcher from Thailand carried out some sensitivity tests of NHRCM over Thailand as reproducibility of NHRCM varies by region. According to the results, climate change projection over whole Thailand was executed by using 5-km grid spacing NHRCM (NHRCM05). Two climate change scenarios whose horizontal grid space was 2-km were made over Mekong river basin and Nan and Yom river basin by using the calculated result of NHRCM05 for the boundary conditions of them. Invitee from Vietnam simulated the present climate by using NHRCM05 over whole Vietnam region. The reproducibility of wind and precipitation is good in Vietnam. Philippines researcher carried out only sensitivity tests to precipitation in this fiscal year. No researcher was invited from Indonesia in this fiscal year, however, the present climate simulation was conducted by using NHRCM05 for the reason that Theme D requested the climate change scenario around Batang Hari River basin. Two convective parameterization schemes were validated in Panama. Precipitation bias was small, but space correlation was low in Grell scheme. On the other hand, in Kain-Fritsch scheme, precipitation was largely overestimated, but space correlation was high as compared with in Grell scheme.
2) Intercomparison of climate change projections
The simulation of the present climate has been started by using 20-km grid spacing AGCM in order to participate in the HighResMIP, which is an international project to compare the results of high resolution global models. Downscaling experiments from ERA-Interim reanalysis and AGCM were conducted by using 20-km grid spacing NHRCM over the East Asian region in order to participate in CORDEX-EA. The characteristic that the precipitation in eastern part of Asia is little as compared to the other region in winter was well reproduced in NHRCM. The precipitation due to modification of air mass over the Japan Sea was also well reproduced on the Japan Sea coast in winter. On the other hand, the precipitation was overestimated around the Himalayas and underestimated over the plain area in Vietnam in summer.