Asuka Suzuki-Parker

Modeling high-impact weather and climate: lessons from a tropical cyclone perspective

Although the societal impact of a weather event increases with the rarity of the event, our current ability to assess extreme events and their impacts is limited by not only rarity but also by current model fidelity and a lack of understanding and capacity to model the underlying physical processes. This challenge is driving fresh approaches to assess high-impact weather and climate. Recent lessons learned in modeling high-impact weather and climate are presented using the case of tropical cyclones as an illustrative example. Through examples using the Nested Regional Climate Model to dynamically downscale large-scale climate data the need to treat bias in the driving data is illustrated. Domain size, location, and resolution are also shown to be critical and should be adequate to: include relevant regional climate physical processes; resolve key impact parameters; and accurately simulate the response to changes in external forcing. The notion of sufficient model resolution is introduced together with the added value in combining dynamical and statistical assessments to fill out the parent distribution of high-impact parameters.

Mechanism of Precipitation Increase with Urbanization in Tokyo as Revealed by Ensemble Climate Simulations

AbstractThis study examines how urbanization affects the precipitation climatology in Tokyo, Japan. A unique aspect of this study is that an ensemble, regional climatological simulation approach is used with sensitivity experiments to reduce uncertainty arising from nonlinearity in the precipitation simulations. Another aspect is that the robustness of the precipitation response is tested with “stress response” simulations with increasing urban forcing. The results show that urbanization causes a robust increase in the amount of precipitation in the Tokyo metropolitan area and a reduction in the inland areas. These anomalies are statistically significant at the 95% and 99% levels in some parts. There is no measureable change in the surrounding rural and ocean areas. These precipitation responses are attributed to an increase of surface sensible heat flux in Tokyo, which destabilizes the atmosphere and induces an anomalous surface low pressure pattern and the convergence of grid-scale horizontal moisture f...

Assessment of the Impact of Metropolitan-Scale Urban Planning Scenarios on the Moist Thermal Environment under Global Warming: A Study of the Tokyo Metropolitan Area Using Regional Climate Modeling

Using a high-resolution regional climate model coupled with urban canopy model, the present study provides the first attempt in quantifying the impact of metropolitan-scale urban planning scenarios on moist thermal environment under global warming. Tokyo metropolitan area is selected as a test case. Three urban planning scenarios are considered: status quo, dispersed city, and compact city. Their impact on the moist thermal environment is assessed using wet-bulb globe temperature (WBGT). Future projections for the 2070s show a 2–4°C increase in daytime mean WBGT relative to the current climate. The urban scenario impacts are shown to be small, with a −0.4 to

Assessing the Sustainability of Ski Fields in Southern Japan under Global Warming

This is the first study in assessing the impact of climate change on Japanese ski fields with ensemble dynamical downscaling simulations. We target three ski fields in Ehime Prefecture, a southern border area for skiing in Japan. Our field survey revealed that a field located above 1200 m altitudes currently operates on natural snow supply, but those located at lower altitudes depend solely or partially on artificial snow supply. Fields are currently open for 82∼105 days. We analyzed ensemble high-resolution (5 km) dynamical downscaling simulations for future ski season durations with natural and artificial snow supplies. The future projection results for the end of the twenty-first century suggested that there would be virtually no natural snow accumulation in the study area for skiing. With artificial snow supply, a field located above 1200 m would be able to retain more than two months of ski season duration. Fields located at lower altitudes would only be able to open for 37∼43 days even with artificial snow supply. While the above projections suggest a severe outlook for the targeted ski fields, it is important to note that there is a strong demand from local skiers at beginner/intermediate levels for these ski fields. Thus, as long as these demands remain in the future, and if a business model to maximize profit during short opening periods is established, it may be possible to offset profit loss due to climate change.

An Application of a Physical Vegetation Model to Estimate Climate Change Impacts on Rice Leaf Wetness

AbstractA physical vegetation model [the Two-Layer Model (2LM)] was applied to estimate the climate change impacts on rice leaf wetness (LW) as a potential indicator of rice blast occurrence. Japan was used as an example. Dynamically downscaled data at 20-km-mesh resolution from three global climate models (CCSM4, MIROC5, and MRI-CGCM3) were utilized for present (1981–2000) and future (2081–2100) climates under the representative concentration pathway 4.5 scenario. To evaluate the performance of the 2LM, the LW and other meteorological variables were observed for 108 days during the summer of 2013 at three sites on the Pacific Ocean side of Japan. The derived correct estimation rate was 77.4%, which is similar to that observed in previous studies. Using the downscaled dataset, the changes in several precipitation indices were calculated. The regionally averaged ensemble mean precipitation increased by 6%, although large intermodel differences were found. By defining a wet day as any day in which the daily...