**3.2.2 Tropical cyclone and tornado**

Murata et al. (2003) was the first to apply MRI-NHM to a typhoon. They numerically simulated the major spiral rainband in typhoon Flo (T9019), which was the subject of an international model intercomparison (COMPARE III; Nagata et al., 2001), with several horizontal resolutions (20, 14, 10, 7 and 5 km). The effects of precipitation schemes and horizontal resolution on the representation of the simulated rainband were studied.

Effects of ice-phase processes and evaporation from raindrops on the development and structures of tropical cyclones were studied by Sawada and Iwasaki (2007; 2010). Wada (2009; 2012) and Wada et al. (2010) used an atmosphere-wave-ocean coupled version of NHM to examine the effect of the ocean on tropical-cyclone intensity and structural change. Wong et al. (2010) developed a new parameterization scheme of air-sea momentum, heat, and moisture fluxes, considering the saturation properties of bulk transfer coefficients under a high winds regime, and tested its impact on tropical cyclone intensity. Kanada et al. (2012) compared PBL schemes and examined their impact on the development of intense tropical cyclones.

In May 2008, Cyclone Nargis hit southern Myanmar and claimed more than 100,000 lives there in one of the largest meteorological disasters in Southeast Asia, mainly due to the storm surge. Numerical modeling studies of this event were performed as part of the research project "International Research for Prevention and Mitigation of Meteorological Disasters in Southeast Asia" (see 3.2.3). Kuroda et al. (2010) conducted a forecast experiment of Nargis and its associated storm surge using NHM with a horizontal resolution of 10 km and the Princeton Ocean Model (POM) with a horizontal resolution of 3.5 km. The impact of SST in the Bay of Bengal and ice phase on Nargis' rapid development was also examined.

resolution of 5 km. The detailed structure of the rainfall system at the intense rain stage was also investigated by NHM with a horizontal resolution of 1 km and sensitivity

A flood was caused by heavy rainfall that lasted for several days from late January to early February 2007 in Jakarta and its vicinity. Trilaksono et al. (2012) investigated spatiotemporal modulation of precipitation using time-lagged ensemble. The National Centers for Environmental Prediction (NCEP) Global Analyses with a horizontal resolution of 1° × 1° was used for the initial and boundary conditions of NHM with a horizontal resolution of 20 km. They demonstrated that the event associated with a cold surge was preceded by a Borneo vortex event. Trilaksono et al. (2011) conducted downscaling experiments for the Jakarta Flood, and studied the dependence of heavy precipitation simulated by the model on the horizontal resolution. The downscale runs with higher resolutions (2, 4, and 5 km) demonstrated the ability to reproduce a region of strong convective activity to the north of

Seko et al. (2012) investigated generation mechanisms of convection cells in tropical regions. Convection cells near Sumatra Island were reproduced using the reanalysis data of the JMA Climate Data Assimilation System (JCDAS) and downscale experiments with a horizontal grid interval of 1 km. Updrafts of gravity waves that were trapped in the lower atmosphere

Murata et al. (2003) was the first to apply MRI-NHM to a typhoon. They numerically simulated the major spiral rainband in typhoon Flo (T9019), which was the subject of an international model intercomparison (COMPARE III; Nagata et al., 2001), with several horizontal resolutions (20, 14, 10, 7 and 5 km). The effects of precipitation schemes and

Effects of ice-phase processes and evaporation from raindrops on the development and structures of tropical cyclones were studied by Sawada and Iwasaki (2007; 2010). Wada (2009; 2012) and Wada et al. (2010) used an atmosphere-wave-ocean coupled version of NHM to examine the effect of the ocean on tropical-cyclone intensity and structural change. Wong et al. (2010) developed a new parameterization scheme of air-sea momentum, heat, and moisture fluxes, considering the saturation properties of bulk transfer coefficients under a high winds regime, and tested its impact on tropical cyclone intensity. Kanada et al. (2012) compared PBL schemes and examined their impact on the development of intense tropical

In May 2008, Cyclone Nargis hit southern Myanmar and claimed more than 100,000 lives there in one of the largest meteorological disasters in Southeast Asia, mainly due to the storm surge. Numerical modeling studies of this event were performed as part of the research project "International Research for Prevention and Mitigation of Meteorological Disasters in Southeast Asia" (see 3.2.3). Kuroda et al. (2010) conducted a forecast experiment of Nargis and its associated storm surge using NHM with a horizontal resolution of 10 km and the Princeton Ocean Model (POM) with a horizontal resolution of 3.5 km. The impact of SST in the Bay of Bengal and ice phase on Nargis' rapid

horizontal resolution on the representation of the simulated rainband were studied.

experiments.

Java Island during the flood.

triggered new convection cells.

cyclones.

**3.2.2 Tropical cyclone and tornado** 

development was also examined.

The greatest typhoon damage in Japan was caused by 'Isewan Typhoon' (Vera) and its associated storm surge in 1959. Kawabata et al. (2012) performed a reanalysis experiment of the typhoon using JNoVA, assimilating drop sonde observations taken by the US Air Force.

Mashiko et al. (2009) performed a numerical simulation of tornadogenesis in an outerrainband minisupercell of a typhoon using NHM with a grid spacing of 50 m.

#### **3.2.3 International research for prevention and mitigation of meteorological disasters in Southeast Asia**

In 2007, Kyoto and MRI started the project "International Research for Prevention and Mitigation of Meteorological Disasters in Southeast Asia" (http://www-mete. kugi.kyotou.ac.jp/project/MEXT/) with institutions in southeast Asia. This project was supported for fiscal years 2007 through 2009 by the Asia S & T Strategic Cooperation Program of the Ministry of Education, Culture, Sports, Science and Technology of Japan (MEXT) Special Coordination Funds for Promoting Science and Technology. Numerical experiments were performed at the Institut Technologi Bandung (ITB) in Indonesia, Hong Kong Observatory, Nanyang Technological University in Singapore, National Center for Hydro-Meteorological Forecasting of Vietnam, and CSIR Centre for Mathematical Modelling and Computer Simulation in India.

MRI was a major participating institution in Japan, and was responsible for NWP model development and application. Case studies with downscale prediction and statistical verifications of forecast accuracy around Japan and Southeast Asia were performed. Hayashi et al. (2008) compared NHM and the Weather Research Forecasting (WRF) model for two seasons (July 2007 and January 2008) with the same initial and boundary conditions and the same domain size and resolutions. Tools were prepared for numerical experimentations with NHM using the JMA global analysis, the global model forecast, and the JMA one-week global ensemble forecast. Saito et al. (2010a) conducted ensemble predictions of Nargis and the associated storm surge employing perturbations from the JMA one-week global ensemble forecast. Ensemble prediction results were used as input data for the decision support system developed by Kyoto University (Otsuka and Yoden, 2011).

Data assimilation experiments were conducted by modifying the JMA Meso 4D-VAR system to apply to tropical areas. A tropical cyclone (TC) bogus procedure was developed for the Bay of Bengal, and the impact on TC forecasts was investigated by Kunii et al. (2010b). Nearreal-time (NRT) analysis of precipitable water vapor using the international ground based GPS network around the Bay of Bengal was performed to demonstrate its positive impact on the Nargis forecast (Shoji et al., 2011).

A comprehensive description of this international project including newsletters, the users' guide to the decision support tool, and links to related published papers has been published as a technical report of MRI (Saito et al., 2011b).

#### **3.3 Cloud simulations**

#### **3.3.1 Winter monsoon snow clouds over the Sea of Japan**

Ikawa et al. (1991) implemented a bulk parameterization scheme of cloud microphysics to MRI-NHM, and performed a numerical simulation of the convective snow cloud over the Sea of Japan. Sensitivity experiments to ice nucleation rates were conducted to simulate the

The JMA Nonhydrostatic Model and Its Applications to Operation and Research 97

interval of 5 km were performed using the Earth Simulator in the MEXT Research Revolution 2002 project. Kanada et al. (2005) used this version of NHM and examined structure of mesoscale convective systems (MCSs) during the late Baiu season in the global warming climate. Sasaki et al. (2008) performed five-year integrations of the non-hydrostatic regional climate model (NHRCM) with a 4 km grid interval, and successfully reproduced monthly precipitation, seasonal change, and regional features in Japan. The relationship between precipitation and elevation in the present climate by NHRCM was compared with observation by Sasaki and Kurihara (2008). The climatological features of warming events over Toyama Plain, central Japan, were investigated with NHRCM by Ishizaki and

A single-layered square prism urban canopy (SPUC) scheme for NHM was developed by Aoyagi and Seino (2011). The SPUC run more accurately reproduced the expected behavior

As shown in Fig. 1, QPF performance of operational mesoscale NWP at JMA has been remarkably improved in these ten years for weak to moderate rains. However, there are still many difficulties in producing predictions of severe mesoscale phenomena that specify their intensity, location, and timing. Convective rains without strong synoptic or orographic forcing are still very hard to predict due to the smallness of their spatiotemporal scales and their sensitivity to the small perturbations in the initial condition. To overcome these difficulties, research and development on mesoscale data assimilation and ensemble forecast

Water vapor is one of the most important parameters in weather forecasting, and GPS is a powerful tool for retrieving accurate water vapor information. In Japan, the Geospatial Information Authority of Japan has been operating a nationwide permanent dense GPS array, the GPS Earth Observation Network (GEONET), since 1994. Shoji (2009) developed a near real-time (NRT) analysis system of TPWV derived from GEONET data to contribute to water vapor monitoring and NWP. Ishikawa (2010) applied this system to the operational GPS TPWV data assimilation at JMA using JNoVA and contributed to improve the MSM's

On 28 July 2008, a local heavy rainfall occurred over the Hokuriku and Kinki districts, central Japan. Shoji et al. (2009) used Meso 4DVAR to perform data assimilation experiments of GEONET TPWV data for this event, and demonstrated that the rainfall forecast was improved. Further improvements were obtained by adding TPWV derived from GPS

Seko et al. (2010) used the Meso 4D-Var system for a heavy rainfall event in northern Japan on 16 July 2004 to investigate the impacts of three kinds of GPS-derived water vapor data: TPWV, slant water vapor along the path from the GPS satellite to the receiver (SWV), and radio occultation (RO) data along the path from the GPS satellite to the CHAllenging Minisatellite Payload (CHAMP) satellite. When SWV and RO data were assimilated simultaneously, both

Takayabu (2009).

have been conducted.

QPF performance (see 2.2.4).

of the urban canopy effect than the slab run did.

**3.5.1 Mesoscale assimilation of GPS data** 

**3.5 Mesoscale data assimilation and ensemble forecast** 

stations of the International GNSS Service in Korea and China.

the rainfall region and rainfall amount were similar to the observed ones.

cloud more realistically and to examine the effects of an increase in the number concentration of ice crystals on the formation of the convective snow cloud.

Saito et al. (1996) conducted sensitivity experiments on the orographic snowfall over the mountainous region of northern Japan, and investigated the orographic effect on the snowfall from cloud microphysical aspects. A 2-dimensional model with a horizontal resolution of 2 km was employed. In the experiments with full cloud microphysics, the precipitation amount over the land increased significantly with mountain heights exceeding the height of the cloud base. However, in the experiments with a warm-rain process, the precipitation amount was only 1/3 that of the experiments with an ice phase. A seeding experiment in which ice nucleation rates were enhanced over a specified zone in the Sea of Japan demonstrated the possibility of artificial modification of the snowfall. A further seeding experiment was conducted by Hashimoto et al. (2008), and seedability of the winter orographic snow clouds over northern Japan was assessed using a nested NHM with a horizontal resolution of 1 km.

Saito (2001) conducted a numerical simulation of cloud bands during a cold air outbreak over the Sea of Japan with a horizontal resolution of 3 km, and showed outstanding similarity between the satellite image and simulated clouds. Four nodes of the HITAC SR8000 of MRI were employed. A higher resolution (1 km) simulation of the snow clouds over the southern coastal area of the Japan Sea was conducted by Eito et al. (2005). Eito et al. (2010) extended the simulation area to (2000 km)2 and examined the structure and formation mechanism of transversal cloud bands using the Earth Simulator.

Yanase et al. (2002) conducted high-resolution simulation of an observed polar low over the Japan Sea on 21 January 1997 with the 2-km horizontal resolution MRI-NHM. The simulation successfully reproduced the observed features of the polar low (*e.g.,* its horizontal scale, movement, spiral bands, and a cloud-free eye). Detailed three-dimensional structures of the simulated polar low were clarified, and its development mechanism was investigated. Futher siumulations of the polar low were conducted by Yanase et al. (2004) and Yanase and Niino (2007).

#### **3.3.2 Maritime boundary layer clouds and spectral bin methods**

Nagasawa et al. (2006) conducted numerical simulation of *Yamase* clouds, typical maritime boundary-layer clouds over the sea off the east coast of northern Japan. NHM with a high resolution of 100 m was employed to simulate convective structures observed from satellite images.

Iguchi et al. (2008) implemented a bin-based microphysics scheme for cloud into NHM to reproduce realistic and inhomogeneous condensation nuclei (CN) fields. Nested simulations were performed for two precipitation events over an area of the East China Sea, where the general features of the horizontal distributions of variables (*e.g.,* effective droplet radius derived from satellite data retrieval) were reproduced. Iguchi et al. (2012) evaluated the binbased cloud microphysical scheme through comparison with observation data by shipborne Doppler and spaceborne cloud profiling radars.

#### **3.4 Regional climate modelling and urban simulation**

A regional climate model version of NHM employing spectral boundary coupling (SBC) was developed by Yasunaga et al. (2005). Forty-day simulations with a horizontal grid

cloud more realistically and to examine the effects of an increase in the number

Saito et al. (1996) conducted sensitivity experiments on the orographic snowfall over the mountainous region of northern Japan, and investigated the orographic effect on the snowfall from cloud microphysical aspects. A 2-dimensional model with a horizontal resolution of 2 km was employed. In the experiments with full cloud microphysics, the precipitation amount over the land increased significantly with mountain heights exceeding the height of the cloud base. However, in the experiments with a warm-rain process, the precipitation amount was only 1/3 that of the experiments with an ice phase. A seeding experiment in which ice nucleation rates were enhanced over a specified zone in the Sea of Japan demonstrated the possibility of artificial modification of the snowfall. A further seeding experiment was conducted by Hashimoto et al. (2008), and seedability of the winter orographic snow clouds over northern

Saito (2001) conducted a numerical simulation of cloud bands during a cold air outbreak over the Sea of Japan with a horizontal resolution of 3 km, and showed outstanding similarity between the satellite image and simulated clouds. Four nodes of the HITAC SR8000 of MRI were employed. A higher resolution (1 km) simulation of the snow clouds over the southern coastal area of the Japan Sea was conducted by Eito et al. (2005). Eito et al. (2010) extended the simulation area to (2000 km)2 and examined the structure and formation

Yanase et al. (2002) conducted high-resolution simulation of an observed polar low over the Japan Sea on 21 January 1997 with the 2-km horizontal resolution MRI-NHM. The simulation successfully reproduced the observed features of the polar low (*e.g.,* its horizontal scale, movement, spiral bands, and a cloud-free eye). Detailed three-dimensional structures of the simulated polar low were clarified, and its development mechanism was investigated. Futher siumulations of the polar low were conducted by Yanase et al. (2004)

Nagasawa et al. (2006) conducted numerical simulation of *Yamase* clouds, typical maritime boundary-layer clouds over the sea off the east coast of northern Japan. NHM with a high resolution of 100 m was employed to simulate convective structures observed from satellite

Iguchi et al. (2008) implemented a bin-based microphysics scheme for cloud into NHM to reproduce realistic and inhomogeneous condensation nuclei (CN) fields. Nested simulations were performed for two precipitation events over an area of the East China Sea, where the general features of the horizontal distributions of variables (*e.g.,* effective droplet radius derived from satellite data retrieval) were reproduced. Iguchi et al. (2012) evaluated the binbased cloud microphysical scheme through comparison with observation data by shipborne

A regional climate model version of NHM employing spectral boundary coupling (SBC) was developed by Yasunaga et al. (2005). Forty-day simulations with a horizontal grid

concentration of ice crystals on the formation of the convective snow cloud.

Japan was assessed using a nested NHM with a horizontal resolution of 1 km.

mechanism of transversal cloud bands using the Earth Simulator.

**3.3.2 Maritime boundary layer clouds and spectral bin methods** 

Doppler and spaceborne cloud profiling radars.

**3.4 Regional climate modelling and urban simulation** 

and Yanase and Niino (2007).

images.

interval of 5 km were performed using the Earth Simulator in the MEXT Research Revolution 2002 project. Kanada et al. (2005) used this version of NHM and examined structure of mesoscale convective systems (MCSs) during the late Baiu season in the global warming climate. Sasaki et al. (2008) performed five-year integrations of the non-hydrostatic regional climate model (NHRCM) with a 4 km grid interval, and successfully reproduced monthly precipitation, seasonal change, and regional features in Japan. The relationship between precipitation and elevation in the present climate by NHRCM was compared with observation by Sasaki and Kurihara (2008). The climatological features of warming events over Toyama Plain, central Japan, were investigated with NHRCM by Ishizaki and Takayabu (2009).

A single-layered square prism urban canopy (SPUC) scheme for NHM was developed by Aoyagi and Seino (2011). The SPUC run more accurately reproduced the expected behavior of the urban canopy effect than the slab run did.
