Abstract
This paper investigates the sensitivity of projected future climate changes over China to the horizontal resolution of a regional climate model RegCM4.4 (RegCM), using RCP8.5 as an example. Model validation shows that RegCM performs better in reproducing the spatial distribution and magnitude of present-day temperature, precipitation and climate extremes than the driving global climate model HadGEM2-ES (HadGEM, at 1.875° × 1.25° degree resolution), but little difference is found between the simulations at 50 and 25 km resolutions. Comparison with observational data at different resolutions confirmed the added value of the RCM and finer model resolutions in better capturing the probability distribution of precipitation. However, HadGEM and RegCM at both resolutions project a similar pattern of significant future warming during both winter and summer, and a similar pattern of winter precipitation changes including dominant increase in most areas of northern China and little change or decrease in the southern part. Projected precipitation changes in summer diverge among the three models, especially over eastern China, with a general increase in HadGEM, little change in RegCM at 50 km, and a mix of increase and decrease in RegCM at 25 km resolution. Changes of temperature-related extremes (annual total number of daily maximum temperature > 25 °C, the maximum value of daily maximum temperature, the minimum value of daily minimum temperature in the three simulations especially in the two RegCM simulations are very similar to each other; so are the precipitation-related extremes (maximum consecutive dry days, maximum consecutive 5-day precipitation and extremely wet days’ total amount). Overall, results from this study indicate a very low sensitivity of projected changes in this region to model resolution. While fine resolution is critical for capturing the spatial variability of the control climate, it may not be as important for capturing the climate response to homogeneous forcing (in this case greenhouse gas concentration changes).
Highlights
In this paper, using different resolutions of the regional climate model RegCM4.4 driven by the global climate model HadGEM2-ES, we investigate future changes of temperature, precipitation and climate extremes at the end of the twenty-first century over mainland China with a focus on the high emission forcing scenario (RCP8.5)
Comparison between the two regional climate models (RCMs) simulations shows that the overall performance are similar, and the 50 km simulation performs slightly better for mean climate while the 25 km simulation performs slightly better for climate extremes
The global and regional climate models exhibit some differences in the future climate change over China
Summary
Coupled global atmosphere–ocean general circulation models (GCMs) are the primary tools used to investigate the response of the climate system to increases in greenhouse. Gao et al (2006) conducted RCM experiments with the resolution change across the range of 60–360 km over East Asia, and the results show that the model resolutions of 60 km or higher are needed to accurately simulate the distribution of precipitation. This finding was further confirmed by a follow up study on the spatial variability of monsoon precipitation (Gao et al 2008).
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