[AAS02-05] Reproducibility of an extremally high-temperature event in d4PDF regional climate model experiment
Keywords:extremely high-temperature event, d4PDF, foehn winds
In this study, we confirm whether extremely high-temperature events in the future can be expressed in regional climate model experiment of the database for Policy Decision making for Future climate change (d4PDF-RCM). Multiple dynamical downscaling (DDS) experiments from d4PDF-RCM with Weather Research and Forecasting model (WRF) were conducted and the downscaled temperature and wind fields around Niigata city on EHT event were compared with the d4PDF-RCM. In a DDS experiment with a horizontal resolution of 3 km (WRF3), the daily maximum temperature is about 3 ℃ higher than the d4PDF-RCM. In a DDS experiment with the topography of the d4PDF-RCM and a horizontal resolution of 20 km (WRF20d), the daily maximum temperature is about 2 ℃ higher than that of the d4PDF-RCM.
The reason for these differences in daily maximum temperatures is that the horizontal resolution of the d4PDF-RCM and its topography was too coarse to express small-scale phenomena such as the foehn winds. The spatio-temporal structure of foehn winds is clearly expressed in WRF3. On the other hand, in the d4PDF-RCM, the structure cannot be expressed at all. Therefore, it can be not enough to directly analyze d4PDF-RCM to discuss the regional EHT events in the future climate. In addition, the spatio-temporal structure of foehn winds in WRF20d is not clearer than that of WRF3. From these results, we concluded that the DDS experiment with appropriate horizontal-resolution and topography needs to be performed to discuss regional EHT events in the future climate.
The results of the WRF3 and a DDS experiment without topography shows that foehn winds have a contribution of about 2.0 ℃ on this EHT event. This result suggests that more than half of the difference between the maximum temperature of the WRF3 and d4PDF-RCM was brought by the topography effect. This contribution of foehn winds is almost the same as that in the current EHT event, shown in the previous study.
Acknowledgments: This research was supported by the Environment Research and Technology Development Fund (2-1905) of the Environmental Restoration and Conservation Agency of Japan. This study used d4PDF produced with the Earth Simulator jointly by science programs (SOUSEI, TOUGOU, SI-CAT, DIAS) of the Ministry of Education, Culture, Sports, Science, and Technology (MEXT), Japan.
The reason for these differences in daily maximum temperatures is that the horizontal resolution of the d4PDF-RCM and its topography was too coarse to express small-scale phenomena such as the foehn winds. The spatio-temporal structure of foehn winds is clearly expressed in WRF3. On the other hand, in the d4PDF-RCM, the structure cannot be expressed at all. Therefore, it can be not enough to directly analyze d4PDF-RCM to discuss the regional EHT events in the future climate. In addition, the spatio-temporal structure of foehn winds in WRF20d is not clearer than that of WRF3. From these results, we concluded that the DDS experiment with appropriate horizontal-resolution and topography needs to be performed to discuss regional EHT events in the future climate.
The results of the WRF3 and a DDS experiment without topography shows that foehn winds have a contribution of about 2.0 ℃ on this EHT event. This result suggests that more than half of the difference between the maximum temperature of the WRF3 and d4PDF-RCM was brought by the topography effect. This contribution of foehn winds is almost the same as that in the current EHT event, shown in the previous study.
Acknowledgments: This research was supported by the Environment Research and Technology Development Fund (2-1905) of the Environmental Restoration and Conservation Agency of Japan. This study used d4PDF produced with the Earth Simulator jointly by science programs (SOUSEI, TOUGOU, SI-CAT, DIAS) of the Ministry of Education, Culture, Sports, Science, and Technology (MEXT), Japan.