Abstract
This study evaluated the performance of the Weather Research and Forecasting (WRF) model version 3.7 for simulating a series of rainfall events in August 2014 over Japan and investigated the impact of uncertainty in sea surface temperature (SST) on simulated rainfall in the record-high precipitation period. WRF simulations for the heavy rainfall were conducted for six different cases. The heavy rainfall events caused by typhoons and rain fronts were similarly accurately reproduced by three cases: the TQW_5km case with grid nudging for air temperature, humidity, and wind and with a horizontal resolution of 5 km; W_5km with wind nudging and 5-km resolution; and W_2.5km with wind nudging and 2.5-km resolution. Because the nudging for air temperature and humidity in TQW_5km suppresses the influence of SST change, and because W_2.5km requires larger computational load, W_5km was selected as the baseline case for a sensitivity analysis of SST. In the sensitivity analysis, SST around Japan was homogeneously changed by 1 K from the original SST data. The analysis showed that the SST increase led to a larger amount of precipitation in the study period in Japan, with the mean increase rate of precipitation being 13 ± 8% K−1. In addition, 99 percentile precipitation (100 mm d−1 in the baseline case) increased by 13% K−1 of SST warming. These results also indicate that an uncertainty of approximately 13% in the simulated heavy rainfall corresponds to an uncertainty of 1 K in SST data around Japan in the study period.
Highlights
In recent years, climate change has occurred as a consequence of global warming
These results indicate that an uncertainty of approximately 13% in the simulated heavy rainfall corresponds to an uncertainty of 1 K in sea surface temperature (SST) data around Japan in the study period
The climate change results in severe precipitation events with more intense and more frequent rainfall, according to the Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report [1]. This is because the saturation pressure of water vapor increases due to the air temperature rise under the global warming, and the amount of water vapor supplied from the sea increases due to the rise in sea surface temperature (SST)
Summary
The climate change results in severe precipitation events with more intense and more frequent rainfall, according to the Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report [1]. This is because the saturation pressure of water vapor increases due to the air temperature rise under the global warming, and the amount of water vapor supplied from the sea increases due to the rise in sea surface temperature (SST). While daily extreme precipitation intensities typically increase with a warming atmosphere by within the rate expected from the CC relationship [6,7], changes in shorter duration precipitation extremes may well exceed the rate [6]. In terms of SST, it is virtually certain that the upper ocean (0–700 m) warmed from 1971 to 2010 [1], and SST around Japan will increase by about 0.6–2.1 K by 2100 [8]
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