To attain these objectives, all the regional experiments for GAME will be conducted during the IOP with the full operational and adhoc observing systems, combined with the enhanced operational and adhoc radiosonde observations (2 times/day for the full IOP period, 4 times/day for some core IOP periods). The full data archive of TRMM satellite, which will provide 5-day to monthly rainfall rate over the full IOP period, is one of the indispensable conditions for the IOP, in addition to the full data archives of the three geostationary satellites (GMS-5, FY-2 and INSAT) over the monsoon region.

Considering the necessary conditions mentioned above, we planned about a half year in 1998, starting from April to October, as the most suitable period of the extended IOP. The two core periods of the IOP with enhanced radiosonde observations of 4 times/day, one for the onset phase and the other for the mature monsoon phase have also been decided as mentioned in 6.2.

6.2.1 Radiosonde network

The intensive upper air soundings of temperature, humidity, pressure and wind field over the whole of monsoon Asian region, based on the current operational radiosonde network and adhoc radiosonde stations in some data-sparse areas, will provide most essential data set for estimating the atmospheric energy and water budget during IOP. The aerial coverage of the radiosonde network for GAME IOP is shown in Fig.6.2-1. Since the convective activity shows a remarkable diurnal cycle during monsoon season, the upper air soundings should be made at least 2 times per day for the whole IOP, and hopefully 4 times per day in the core IOP, to resolve the full diurnal cycle. The stations where 4 times/day observations are expected to be implemented during the core IOP period are also shown in Fig. 6.2-1. These stations, including several adhoc stations in Tibetan Plateau area and in Thailand, correspond to the radiosonde network for the three regional experiments. The enhanced observations at the stations over and around the South China Sea will also be implemented, associated with the IOP of the South China Sea Monsoon Experiment (SCSMEX). Data archive of the radiosonde data should include data of all significant levels, in addition to the standard mandatory levels, which is required particularly for regional and meso-scale energy budget analysis. The core IOP will be described in 6.2.4.

6.2.2 In-situ observation network

6.2.3 Satellite observations

One of the most essential satellite observations for GAME area, particularly in the tropics and subtropics including the Tibetan Plateau is rainfall (precipitation) rate measurement by TRMM, which will be launched in November of 1997. The 5-day mean through 1-month mean rainfall amounts over the GAME area including the surrounding oceans need to be validated based on in-situ intensive observations and other satellite-derived atmospheric moisture quantity such as from SSM/I, some of which will be deployed as part of GAME regional experiments. These rainfall data will be used for aerial mean energy and water budget analysis of regional and/or basin scales. This data set is also important for validation of precipitation in GCM and regional model experiments.

To resolve the diurnal cycles of convective activity and water vapor content, visible, infrared and water-vapor channel data from geostationary satellites from GMS, FY-II and INSAT need to be intensively archived and combined together to get the time-space structure of convective activity over the whole GAME/SCSMEX domain.

6.2.4 Time phasing of IOP

The GAME IOP focuses on the energy and water cycle processes and land-atmosphere interactions in the seasonal evolution of Asian summer monsoon system. To examine these processes in the boundary season of the monsoon year (Yasunari, 1990) or the predictability barrier phase (Webster and Yang, 1992), IOP need to start from boreal spring. The data availability of TRMM is also crucial for the quantitative estimates of precipitation and hydrological processes in the atmosphere.

To satisfy these conditions, GAME IOP has tentatively been decided to be six months starting from the beginning of April and ending at the end of September in 1998. During the IOP, we have set three sub-stages (Phase-I, II and III) of about one month, which focuses on the processes in the pre-monsoon season, the onset phase of monsoon and the maturing phase of monsoon, respectively. A tentative time phasing of these three sub-stages may be as follows;

Phase I: pre-monsoon late March to late April

Phase II: onset mid May to mid June

Phase III: mature monsoon July to August

Phase I primarily focuses on the land-surface/atmosphere interaction, including snow cover over the Tibetan Plateau and soil moisture/evaporation and pre-monsoon rain processes in the tropics and subtropics. Land surface hydrological processes, surface radiation and heat fluxes and PBL processes will be intensively observed. In Southeast Asia, particularly over Indo-China peninsula, this stage includes the onset of summer monsoon. In this area, role of soil moisture change from dry pre-monsoon condition to wet post-onset condition is one of the targets of the intensive surface observation.

Phase II corresponds to the onset phase over major part of the Asian monsoon region, including India, Tibetan Plateau, South China Sea. In east Asia (China, Japan, Korea), this phase also corresponds to the onset of the frontal rain season (called Meiyu in China, Baiu in Japan or Changma in Korea). The full onset of monsoon over South China Sea is nearly consistent with this phase (Lau, 1995). In Siberia, rapid snow melt and seasonal warming of the surface and atmosphere occurs nearly concurrently.

Phase III corresponds to the mature phase of the monsoon in the tropics and Tibetan Plateau area. In east Asia, this phase is nearly consistent with the withdrawal phase of the frontal rain season. Precipitation reaches its maximum in the northern part of the continent.

In these two phases, the roles of surface-atmosphere interaction and convective activity in the continental- as well as regional-scale fields should be solved in the time scales of diurnal cycle, intraseasonal variability and seasonal cycle. These studies need to be based on highly-resolved 4-DDA data, which requires implementation of enhanced radiosonde observation with 4 times/day over the whole Asian monsoon region covering East Asia, South China Sea, Southeast Asia, South Asia and the Tibetan Plateau. To cover the atmosphere-ocean interaction in the surrounding oceans, collaboration with other national and international projects are highly expected to be deployed concurrently. Particularly, the joint implementation of IOP with SCSMEX is very crucial for GAME IOP.

At the second session meeting of the GAME-ISP held in Cheju Island, Korea on March 24-25, 1997, the members of the ISP and the observers from related countries discussed the details of the implementation plan of the enhanced radiosonde observations during the IOP, and finalized the plan as follows:

The radiosonde observations of full 2 times/day will be implemented from April 1 through September 30, 1998. The unified enhanced observation periods for the whole domain has been set to the two phases; the first phase (onset phase) is one month from May 16 to June 15, and the second phase (mature phase) is one full month of July. Each regional project or country will have some different schedule of enhanced radiosonde observations, depending upon the regional monsoon conditions and the scientific objectives of their own. for example, GAME-Tropics will implement longer enhanced radiosonde observation, since the southeast Asia has the longer monsoon season with two major rain spells in May to June, and August to September. The time-schedules of the enhanced observation for each region (project) and country is shown in Fig.6.3-1. The countries involved in this project are expected to be, Japan, China (including Hongkong), Korea, Taiwan, Thailand, Philippines, Vietnam, Thailand, Malaysia, Singapore, Indonesia, Myanmar, India, Bangladesh and Nepal.

In addition to these stations involved in GAME (HUBEX, Tropics, Tibet), TIPEX, and SCSMEX, 16 upper air stations in China, located between HUBEX and TIPEX region, are going to be involved in the IOP, as part of Japan-China cooperative study on Asian monsoon.

Korea will implement the enhanced radiosonde observations during IOP, as part of KORMEX enhanced observation. The meso-scale meteorological research group of Meteorological Research Institute (MRI), Tsukuba, is going to cooperate with this IOP, by deploying the enhanced radiosonde and and radar observations over East China Sea. JMA also will implement the enhanced observations at some stations in south-western part of Japan, in cooperation with TRMM validation program in Okinawa islands.

Fig.6.2-1 The aerial coverage of the radiosonde network for GAME IOP.

Fig.6.3-1 The time-schedules of the enhanced observation for each region (project) and country.

Table 6.3-1