09:15 〜 09:30
[ACG37-02] Challenges for a systematic understanding of the precipitation process in Asian countries
キーワード：夏季アジアモンスーン、降水過程、大気陸面過程、観測および数値実験、大気水循環
Asian countries exist in tropical, subtropical, temperate, and subarctic zones, which includes semi-arid and highland area; therefore, a background synoptic-scale forcing and a surface boundary forcing for regional-scale climate differ depending on the regions. Toward the establishment of a new Regional Hydro-climate Project for the Asian monsoon region under WCRP/GEWEX/GHP, we propose several challenges for understandings of (1) precipitation variability over multiple-timescales and their interactions by means of in-situ observation, space and ground remote sensing, and modeling, (2) key processes that affect precipitation variability in multiple-timescales, (3) possible contributions of surface conditions including SST, land cover, soil moisture, snow, and topography to precipitation variability.
As an example, the largest annual precipitation amount is recorded over the Meghalaya Plateau in South Asia, which would be caused by a complex interaction of diurnal, intra-seasonal, and seasonal variations during the Asian summer monsoon season. Fujinami et al. (2017, JGR) suggests that a low-level barrier jet is accelerated over a stable layer in the nighttime and transports moist air effectively to the south of the Meghalaya Plateau, which is a key mechanism to cause heavy precipitation (Fig. 1). The meso-scale convective systems (MCSs) developed over the South Asia also would be a hot topic in terms of heavy precipitation occurrence, a moistening in the lower stratosphere, and moisture transport over the Himalayas and the Tibetan Plateau (e.g., Dong et al. 2016, Nature Communications). For these issues, an intensive observation under the cooperative system among the Asian counties is essential to reveal the diurnal variation in the planetary boundary layer (PBL) structure and the atmospheric water cycle in the multi-sphere. Meanwhile, the high resolution experiments (less than 2km) could be conducted using regional climate models because of a current progress of computational resources, which would be valuable for evaluations of a diurnal variation in precipitation characteristics over the precipitous mountains (e.g., the Himalayas and the Meghalaya Plateau) and impacts of the surface conditions on precipitation processes.
The new findings obtained from the studies in the South Asia, such as the occurrence of nocturnal low-level jet, the effect of the MCS on the moisture transport, impacts of SST and land surface condition on precipitation, and the simulation skill of regional climate model for the heavy precipitation over the complex topography etc., should be compared them in other Asian countries and/or could be applied to the understanding of their physical processes in other regions. The understanding of global common and regional/seasonal-dependent sensitivities of precipitation characteristics to the surface conditions over the various climate conditions is also interesting.
As an example, the largest annual precipitation amount is recorded over the Meghalaya Plateau in South Asia, which would be caused by a complex interaction of diurnal, intra-seasonal, and seasonal variations during the Asian summer monsoon season. Fujinami et al. (2017, JGR) suggests that a low-level barrier jet is accelerated over a stable layer in the nighttime and transports moist air effectively to the south of the Meghalaya Plateau, which is a key mechanism to cause heavy precipitation (Fig. 1). The meso-scale convective systems (MCSs) developed over the South Asia also would be a hot topic in terms of heavy precipitation occurrence, a moistening in the lower stratosphere, and moisture transport over the Himalayas and the Tibetan Plateau (e.g., Dong et al. 2016, Nature Communications). For these issues, an intensive observation under the cooperative system among the Asian counties is essential to reveal the diurnal variation in the planetary boundary layer (PBL) structure and the atmospheric water cycle in the multi-sphere. Meanwhile, the high resolution experiments (less than 2km) could be conducted using regional climate models because of a current progress of computational resources, which would be valuable for evaluations of a diurnal variation in precipitation characteristics over the precipitous mountains (e.g., the Himalayas and the Meghalaya Plateau) and impacts of the surface conditions on precipitation processes.
The new findings obtained from the studies in the South Asia, such as the occurrence of nocturnal low-level jet, the effect of the MCS on the moisture transport, impacts of SST and land surface condition on precipitation, and the simulation skill of regional climate model for the heavy precipitation over the complex topography etc., should be compared them in other Asian countries and/or could be applied to the understanding of their physical processes in other regions. The understanding of global common and regional/seasonal-dependent sensitivities of precipitation characteristics to the surface conditions over the various climate conditions is also interesting.