2019 Abstract
Area Theme C: Integrated Climate Change Projection
Japan Meteorological Business Support Center: Izuru Takayabu
TOUGOU-C＇s targets are, (1) arranging the synthesized climate change projection data around
Japan and Asian countries, and (2) preparing a high accuracy, local scale climate change data,
especially of extreme events.
Internationally, the process of writing the 6th assessment report (AR6) of IPCC WGI has already
started. It is planned to be published in 2021. In AR6, handshaking among WGI (aims to assess the
physical science basis), WGII (assesses the vulnerability, socio-economic and natural systems), and
WGIII (focuses on climate change mitigation) is strongly recommended.
In Japan, establishing the climate adaptation plan is an urgent issue. Cabinet has decided ＂National
Plan for Adaptation to the impacts of Climate Change＂ in November 2015. Following this decision,
MOE has started the action of A-PLAT (Climate Change Adaptation Platform) in August 2016, where
many local scale climate change information appeared. Finally, ＂Climate Change Adaptation Act＂ has
been promulgated on June 2018, and come into force on 1 December 2018. The purpose of this Act is
to promote Climate Change Adaptation through establishing necessary measures such as formulating
plans for Climate Change Adaptation and providing information on the Climate Change Impact and
Climate Change Adaptation, thereby contributing to the health and cultural life of the Japanese people
both at the present and in the future in recognition of the impact that global warming and other climate
change has on daily life, society, economics, and the natural environment, and the risk that this impact
will increase over the long term. In order to promote a policy for Climate Change Adaptation
comprehensively and systematically, the government shall establish a plan for Climate Change
Adaptation. And our program has to prepare a national climate change scenario for that purpose. (Act
on Promotion of Global Warming Counter-measures (Act No. 117 of 1998))
MOE set up CCCA (Center for Climate Change Adaptation) in NIES, and it starts to promote
adaptation and research related to climate change adaptation in the local government. To promote
these activities, high resolution, high accuracy climate change projection data is needed.
Figure 1 indicates the role of Theme-C in the whole activity in translating/using the climate change
data. To bridge between the CMIP products and the impact studies, our mission, to downscale the
global climate model data into a local scale, is an indispensable process.
Figure 2 indicates the flow chart for producing national climate change scenario. We expect five-year
cycle of producing valuable data for making county base climate adaptation plan. We need to
project more accurate and less uncertain information of climate change in local scale to distribute
valuable data for this cycle.
For this purpose, we have designed our project as shown in Fig. 3. We have three sub-programs in
it, and many co-workings or relations have been established with many domestic and international
climate change projects or activities.
Fig.1 Schematic representation of Theme C in the whole project activities
Fig.2 The flow chart of making national climate change scenario
Fig.3 The role of the project of theme C
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 based on 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 former 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 models used for global warming studies world-wide. However, the models do not include air-sea coupling processes, 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 to understand future climate changes in extreme events as well as mean states. We also plan to examine 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 poorly known particularly before the International Geophysical Year (1958-59). In the past, we experienced big typhoons landed on Japan and severe disasters such as flood and drought. It is beneficial to modelling and climate predictions to understand how and why these events occurred as a result of 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
In sub-theme (ii) Development of climate scenarios for multi-stakeholder applications and understanding the mechanisms of climate change, we develop a set of future climate projection under a changing climate with high horizontal resolution of atmospheric global and regional climate models with high reliability so that it is widely used for impact assessments and risk managements for water resources, agriculture, and health sectors and for the mechanism research on future changes in climate extremes. Moreover, intensive experiments on future changes in typhoons are performed with atmosphere-ocean coupled regional model and uncertainty in future climate projection of typhoons is tackled from the viewpoint of the mechanisms. In this fiscal year, following research topics are investigated.
Climatological mean precipitation in East Asia or Japan is influenced by future changes in surface air temperature in the Eurasian Continent as well as by those of sea surface temperatures (SSTs) as revealed in the last fiscal year. One-hundred-fifty-year simulations show no long-term trend in climatological mean precipitation which cannot be seen in our time-sliced 20-year simulations. On the other hand, the simulations have an increasing trend in extreme precipitation. Future changes in extreme precipitation is examined with the database for policy decision making for future climate change (d4PDF). Future changes in extreme precipitation is decomposed into thermodynamic effect (Clausius-Clapeyron relation) and dynamical effect (circulation field) and these two contributions to the future changes are analyzed. Pseudo-non-global-warming approach shows that water vapor field and vertical atmospheric stability enhance and reduce, respectively, future changes in extreme precipitation, suggesting that the balance between the two determines the changes in extreme precipitation.
Typhoons influencing climates in Japan are also investigated with different approaches. Pseudo-global-warming approach applies to Typhoon Hagibis devastating Japanese archipelago in October 2019. This analysis reveals the current global warming increases total precipitation of Typhoon Hagibis by 3％ to 5％. Typhoons attacking Japanese archipelago in recent years also have stronger maximum wind speeds and/or more precipitation amount due to the current global warming. In addition, typhoon translation speed in mid latitudes around Japan is projected to reduce in a future warming climate simulated in d4PDF. Dynamical downscaling with cloud-resolving regional model reveals the enhancement of the minimum central pressure.
The fundamental future climate projection with the atmospheric global climate model with 20-km grid spacing and with the atmospheric regional climate model with 5-km and 2-km grid spacing in Japan are steadily performed. These results from the atmospheric global climate model are assessed by comparing the CMIP5 multi-model ensembles. The 150-year simulations with the atmospheric global climate model with 60-km grid spacing and with the atmospheric regional climate model with 20-km spacing in Japan are also performed with 4 RCP scenarios under the convention of High Resolution Model Intercomparison Project to evaluate transient climate changes.
b: High-resolution simulation of typhoons and extreme events
Nagoya University: Kazuhisa Tsuboki
The purpose of the present study is a future change projection of typhoon intensity and precipitation intensity/amount in the mid-latitude with the climate change. Using a cloud-resolving model and a regional atmosphere-ocean coupled model, dynamical downscaling experiments of d4PDF typhoons, pseudo-global warming experiments, and simulation experiments of observed intense typhoons were performed.
To understand the impacts of global warming on tropical cyclones (TCs) in midlatitude regions, typhoons that traveled over the sea east of Japan were selected from the current climate (98 cases) and 4K-increased climate (125 cases) of d4PDF, and dynamical downscaling experiments were performed using the 4-km-mesh cloud-resolving model with a one-dimensional slab ocean model. The results show that the maximum intensity of typhoon increases and higher intensity reaches higher latitude while no significant northward migration of the maximum intensity latitude was found. The baroclinicity around Japan is weakened with the climate change and the SST increases 3～ 5℃. As a result, an extra-tropical transition is delayed and the axisymmetric structure tends to be maintained during northward moving.
Pseudo-global warming experiments using the coupled model were performed for the three typhoons that caused heavy rainfall over the northern Japan in late August 2016. In the all cases, the typhoon intensity increased under the future warmer climate. The ratio of frequency of intense rainfall in the eastern Hokkaido also increased. The rainfall amount associated with landfall increased for all typhoons, owing the intensification of the secondary circulation of typhoon.
Using the cloud-resolving model and the coupled model, simulation experiments of Typhoon Trami (2018) were performed. Since Trami moved very slowly, the difference between these models was significant and only the coupled model simulated the characteristic large eye and slow movement of Trami. This indicates that the coupled model is necessary to simulate the characteristics of slow-moving typhoons, because SST changes due to three-dimensional motion of sea water could have a considerable impact on the development and structure of typhoon.
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: Akihiko Murata
1) Climate change projection in vulnerable areas
Four researchers were invited to MRI from SE-Asian Countries in order to conduct collaborative researches on climate change projection around their homelands in FY2019. First, the non-hydrostatic regional climate model (NHRCM) was used to simulate present and future climate in the central part of Vietnam with a grid spacing of 2 km. Generally, the spatial distribution of orographically induced precipitation is well reproduced by the model with 2-km grid spacing when compared with that produced by 5-km grid spacing. In the future climate, the annual precipitation increases by 20～40％. This tendency also holds true in winter although precipitation in the northern region of the model domain decreases in summer. The reduction of the summertime precipitation to the north seems to be attributed to a foehn phenomenon. Next, simulations for the present and future climate over Peninsular Malaysia were conducted using NHRCM with 2-km grid spacing. The simulations reproduce two peaks of monthly precipitation in April and November over the western half of Peninsular Malaysia and a peak in December over the eastern half. In terms of future changes in precipitation, the results show a 20～30％ increase over the western and southern domain in winter and a 25～40％ increase over the western domain in summer. In fall, precipitation increases by 30～40％, whereas does not change appreciably in spring. Finally, simulations for the present and future climate over Indonesia were performed using NHRCM with 5-km grid spacing. Ten years of simulations out of 20 years, for each present and future climate, have so far been finished. Preliminary results show that reproduced seasonal precipitation is consistent with that derived from a gridded dataset based on observations. In the future climate, shapes of probability distribution functions imply that the magnitude of the variance, in addition to the mean, in seasonal precipitation increases in winter.
2) International comparison of climate change projection
The simulation of the future climate was completed by using 20-km grid spacing AGCM in order to participate in international project to compare the results of high-resolution global models (HighResMIP). Downscaling experiments from ERA-Interim and AGCM for the future climate were completed by using 20-km grid spacing NHRCM over East Asia region in order to participate in Coordinated Regional Climate Downscaling Experiment-East Asia (CORDEX-EA).
2018 Abstract
Area Theme C: Integrated Climate Change Projection
Japan Meteorological Business Support Center: Izuru Takayabu
Main mission of Theme C is to bridge the climate change data and their users, especially, impact
study researchers of climate change.
Internationally, the process of writing the sixth assessment report (AR6) of IPCC has already
started. It is planned to be published in 2021. In AR6, handshaking among WGI (aims to assess the
physical science basis), WGII (assesses the vulnerability, socio-economic and natural systems), and
WGIII (focuses on climate change mitigation) is strongly recommended.
Fig.1 Schematic representation of Theme C in the whole projects activities.
Figure 1 indicates the role of Theme C in the whole activity in translating/using the climate change data. To bridge between the global climate change products and the impact studies, our mission, to downscale the global climate model data into a local scale is an indispensable process.
Fig.2 Design of the project of Theme C (red rectangular).
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 current global climate model of the Meteorological Research Institute (MRI) 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
heavy 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 models used for global warming studies worldwide.
However, in order to keep the model bias minimum, the models use specified sea surface
temperatures, ignoring air-sea coupling processes. 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 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, big 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 as a
result of 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
Mechanism of future changes in extreme climate phenomena and uncertainties were investigated
based on numerical experiments using MRI-atmospheric general circulation model (MRI-AGCM) and
dynamical downscaling with Non-Hydrostatic Regional Climate Model (NHRCM).
Our projections by MRI-AGCM with different experiment setups have shown large uncertainties in
future changes in the rainy season in Japan, Baiu. New ensemble experiments with MRI-AGCM in a
60 km grid spacing were conducted with future changes in sea surface temperatures (SSTs) projected
by atmosphere-ocean coupled models (AOGCMs) participating in the Coupled Model
Intercomparison Project phase 5 (CMIP5). It is revealed that future changes in precipitation amount in
Japan is highly uncertain, while those in a larger region such as East Asia is robust. Future changes in
precipitation are also investigated by the MRI-AGCM experiments partially including atmosphereocean
coupled processes, indicating that coupled process tends to shift the Baiu rain band more
southward than in the experiments without the processes under a future climate, as well as less
increase in convective activities in the Philippine Sea. In global scale, the MRI-AGCM experiments
suggest that future changes in extreme one-day precipitation is strongly relevant to the future changes
in the mid-tropospheric upward motion.
Performance of the future climate projection by MRI-AGCM is evaluated in comparison with the
CMIP5 multi-model ensemble (MME). The present-day precipitation in MRI-AGCM with a 60 km
grid is simulated very well in global 26 regions compared with the CMIP5 MME. The uncertainties in
the ensemble with different convection schemes and different future change patterns in SST in the
MRI-AGCM experiments are relatively large in low latitudes while they are small in mid- and high-latitudes.
Performance of the future projection by NHRCM is also evaluated. It is revealed that a dominant
process of future changes in extreme hourly precipitation in the seas around Japan is different from
each region: dynamical process for Okinawa region and thermodynamical process for Kii-offshore
region. The event attribution is applied to the heavy rainfall event and heat waves observed in July
2018 for evaluating the influence of the global warming on them, using regional d4PDF, which was
donwscaled from global d4PDF. An east-west surface pressure dipole is simulated during the heavy
rainfall event in global d4PDF and enhances meso-scale phenomena. Regional d4PDF enables to
evaluate the influence of global warming on recent local heavy precipitation events in western Japan.
The recent change in the heavy precipitation events appears in the western Kyushu, but it does not so
in the eastern Kyushu. The changes in the western Kyushu region are explained by the
thermodynamical effect estimated with the Clausius-Clapeyron relation under the current global
warming. These researches with d4PDF are performed in cooperation with Theme A and Theme C.
Future climate projections with dynamical downscaling from high-resolution MRI-AGCM with a 20
km grid are conducted continuously to increase ensemble members. NHRCMs with a 5-km grid and a
2-km grid are used for this regional projection under RCP2.6 scenario. These future projection data of
Theme C are continuously provided to Theme D researchers.
b: High-resolution simulation of typhoons and extreme events
Nagoya University: Kazuhisa Tsuboki
The purpose of the present study is to estimate future changes of maximum intensity, associated
rainfall amount and northward shift of maximum intensity position of very intense typhoons with the
climate change by high resolution simulations, pseudo-global warming experiments, and sensitivity
experiments. This study uses a cloud-resolving model, Cloud Resolving Storm Simulator (CReSS) and
a regional coupled atmosphere-ocean model, Non-hydrostatic Ocean model for the Earth Simulator
(CReSS-NHOES).
Using CReSS, we performed a simulation experiment of Supertyphoon Lan (2017), which was the
most intense typhoon in 2017. The simulation result was compared with observation and was found
that it agreed well with the observation. The process of intensification of Typhoon Lan was studied
using the simulation result. We found that latent heating due to intense convection within the radius of
maximum wind speed and forced descending motion caused the central pressure decrease of the
typhoon. Since the Sea surface temparature (SST) decrease due to typhoon motion was considered in
the simulation, the intensity of Typhoon Lan was correctly simulated. This indicates that the ocean
process is important for the accurate simulation of typhoon even though the movement speed of
typhoon is large.
Dynamic downscaling simulations (DDSs) of typhoons in a GCM simulation were also performed
using d4PDF data for initial and boundary conditions. Northward-moving typhoons to the east of
Japan in the d4PDF data were selected for the DDSs, because they have large impact on the midlatitude
countries including Japan. The numbers of the selected typhoons are 98 and 125 for the
present climate and 4 K increased climate, respectively. They showed that points of the maximum
intensity shift northward and the northward-moving speed of typhoon decreased in the 4 K increased
climate. According to DDSs of the northward-moving typhoons of d4PDF, rainfall amount of typhoon
increases over the Pacific to the north of Kanto. These experiments were combined with the pseudo-global
warming experiments of the four typhoons moved northward to the east of Japan in 2016 to
study future change of rainfall amount and intensity of typhoons with the global warming.
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
Three researchers were invited to MRI in order to conduct collaborative researches on climate
change projection around their homelands in FY2018. First of all, the non-hydrostatic regional climate
model (NHRCM) is used to simulate present and future climate in Malaysia with a grid spacing of 5
km. Generally, the spatial distribution and annual cycles of both variables are well reproduced by the
model with slightly cold (for temperature) and wet (for rainfall) biases particularly over the
mountainous area of East Malaysia. Second, NHRCM is used to simulate the rainfall and temperature
over Vietnam at 5 km horizontal resolution for present and far future climate driven by MRIAGCM20
data. The simulations capture the spatial distribution of rainfall quite well as compared with
Vietnam Gridded Precipitation (VnGP) Dataset. Third, NHRCM is used to dynamically downscale the
MRI-AGCM3.2 model output for the Philippines at 5 km resolution, which is then further downscaled
for Mindanao at 2 km resolution. Present and far future climate with RCP8.5 scenarios are simulated.
Initial analysis shows that NHRCM is able to capture the spatial distribution of boreal summer rainfall
over Mindanao for 1981-2000, which is overestimated in comparison with APHRODITE but
underestimated in comparison with Climate Hazards Group InfraRed Precipitation with Station data
(CHIRPS). The interannual boreal summer mean rainfall averaged over Mindanao also shows this
disagreement in the bias in comparison with the observation data used. These results highlight the
need for understanding the inherent biases of the observation dataset. The present climate simulation
was conducted by using NHRCM05 around Batang Hari River basin in Indonesia in the previous
financial year. After confirming the reproducibility of the data, future climate projection was carried
out there and calculated results were provided to Theme D in this fiscal year.
2) International comparison of climate change projection
The simulation of the present climate was completed by using 20 km grid spacing AGCM in order
to participate in international project to compare the results of high-resolution global models
(HighResMIP). Downscaling experiments from ERA-Interim and AGCM were completed by using 20
km grid spacing NHRCM over East Asia region in order to participate in Coordinated Regional
Climate Downscaling Experiment-East Asia (CORDEX-EA).
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， 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.
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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.