**3.2 Tropical meteorology**

## **3.2.1 Tropical convection and heavy rainfall**

A model intercomparison for a tropical squall line observed during the Ttropical Ocean/Global Atmosphere Coupled Ocean-Atmosphere Response Experiment (TOGA COARE) was conducted in the GEWEX Cloud Systems Study (GCSS). Redelsperger et al. (2000) compared results from eight cloud-resolving models including NHM. Most of the models were able to predict similar rainfall and integrated water content evolutions and agreed quantitatively, but the apparent heat and moisture sources indicated some quantitative differences.

The diurnal evolution of tropical island convection observed during the Maritime Continent Thunderstorm Experiment (MCTEX; Keenan et al., 2000) was simulated by Saito et al (2001b) using NHM nested with the Australian Bureau of Meteorology Research Centre's

observed in Hokkaido, northern Japan, using the 2-dimensional AE model. Inspired by their works, Saito and Ikawa (1991) conducted 2-dimensional simulation of the local downslope wind *Yamaji-kaze* in Shikoku, western Japan. The averaged orography of Shikoku Island in the east-west direction was regarded as the typical orography, and the development and propagation of an internal hydraulic jump were simulated by a numerical experiment using

Saito (1993) conducted numerical experiments using the real orography of Shikoku Island with the surface friction, and studied the geographical characteristics of the Yamaji-kaze. Smith's (1980) linear analytic solution of the mountain flow over an isolated mountain was extended to the flow over a mountain range with a col, and compared with the non-linear

Saito (1994) developed a double-nested model to reproduce the Yamaji-kaze of the 27 September 1991 windstorm. A realistic simulation of the observed phenomena was first conducted in Japan using a nested nonhydrostatic model with a horizontal resolution of 2.5 km. Good agreement between the simulation and the observed time evolution of surface

The Kii Peninsula, central Japan, is famous for its abundant rainfall which reaches 3000 to 4000 mm a year. Airflow over the Kii Peninsula and its relation to the orographic enhancement of rainfall has been studied by Saito et al. (1994) and Murata (2009). Saito et al. (1998) compared the Deutscher Wetterdienst nonhydrostatic regional model(DWD LM)and MRI-NHM for numerical solutions of the 3-dimensional mountain waves, focusing on the computational efficiency of HI-VI and HE-VI schemes. Fujibe et al. (1999) studied diurnal wind variation in the lee of a mountain range using MRI-NHM and demonstrated agreement with the daytime advance of downslope wind in the Canterbury

A model intercomparison of mountain flow over a steep mountain was conducted by Satomura et al. (2003) as the Steep Mountain Model Intercomparison Project (St-MIP). To examine the accuracy of the terrain-following coordinates, mountain waves over twodimensional bell-shaped mountains with various half-widths and heights were compared

A model intercomparison for a tropical squall line observed during the Ttropical Ocean/Global Atmosphere Coupled Ocean-Atmosphere Response Experiment (TOGA COARE) was conducted in the GEWEX Cloud Systems Study (GCSS). Redelsperger et al. (2000) compared results from eight cloud-resolving models including NHM. Most of the models were able to predict similar rainfall and integrated water content evolutions and agreed quantitatively, but the apparent heat and moisture sources indicated some

The diurnal evolution of tropical island convection observed during the Maritime Continent Thunderstorm Experiment (MCTEX; Keenan et al., 2000) was simulated by Saito et al (2001b) using NHM nested with the Australian Bureau of Meteorology Research Centre's

the observed thermal stratification and time-changing wind profile.

wind was obtained when a strong typhoon approached western Japan.

with theoretical calculations and among models, including NHM.

aspect of the simulated flow.

Plains in New Zealand.

**3.2 Tropical meteorology** 

quantitative differences.

**3.2.1 Tropical convection and heavy rainfall** 

Limited-Area Assimilation and Prediction System (BMRC LAPS). The left panel of Fig. 2 presents the visible satellite images over Melville and Bathurst Islands, Northern Territory of Australia, on 27 November 1995. At 1200 CST, shallow convective clouds corresponding to Rayleigh–Benard convection covered the interior of the islands. Along the southern coasts of the two islands, line-shaped clouds suggest organization associated with the sea breeze front (SBF). At 1300 CST, the clouds merged and organized at the central part of the islands in the form of an east–west line. An hour later (1400 CST), deep convection (*Hector*) developed at the southwestern part of Melville Island and along the southern coast of Bathurst Island. The right panel of Fig. 2 indicates the corresponding simulation with a 1 km NHM. Details of the observed evolution of the clouds on this day (Rayleigh–Benard convection, cloud merger along the convergence zone between the two SBFs, and succeeding explosive growth of deep convection) were very well reproduced.

Fig. 2. Left: Visible image on 27 Nov 1995: (a) at 0230 UTC (1200 CST), (b) at 0330 UTC (1300 CST), and (c) at 0430 UTC (1400 CST). Right: Fields derived from the 1 km NHM simulation. (a) Cloud water mixing ratio at *z* = 1.46 km and *t* = 180 min (1300 CST). Contour interval is 0.1 g Kg-1. (b) Vertically accumulated cloud water at *t* = 240 min (1400 CST). Contour interval is 0.1 Kg m-2. (c) Simulated cloudtop temperature at *t* = 300 min (1500 CST). Contour interval is 5 K. After Saito et al. (2001b).

On 26 July 2005, an intense rainfall system caused heavy rain in excess of 900 mm at Mumbai, on the west coast of India. This system was simulated by Seko et al. (2008) using the global analysis data of JMA as the initial condition of NHM. A maximum rainfall exceeding 1,100 mm in 17 hours was reproduced by the simulation with a horizontal

The JMA Nonhydrostatic Model and Its Applications to Operation and Research 95

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 outer-

**3.2.3 International research for prevention and mitigation of meteorological disasters** 

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

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

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

rainband minisupercell of a typhoon using NHM with a grid spacing of 50 m.

**in Southeast Asia** 

the Nargis forecast (Shoji et al., 2011).

**3.3 Cloud simulations** 

as a technical report of MRI (Saito et al., 2011b).

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

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 experiments.

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 Java Island during the flood.

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 triggered new convection cells.
