中国气候变化信息网 China Climate Change Info-Net
Validation and Climate Change Responses of Hadley
Centre GCMs over China
XU Yinlong
Agrometeorology Institute, CAAS, Beijing, 100081 China
Now in: Hadley Centre for Climate Prediction and Research, UK
Abstract. In this paper, the capacity of Hadley Centre GCMs to simulate
present climate over China has been validated using station observations and
CRU gridded climatological datasets. Analysing the performance of HadCM2, HadCM3,
and HadAM3H shows that the Hadley Centre GCMs perform well over East China and
the high resolution atmospheric GCM, HadAM3H, improves the simulation greatly,
especially over Northwest China and the Tibetan Pleteau. Overall, the models
have a tendency to be too cold in winter and summer with these biases reduced
in HadAM3H in winter and reversed in summer. In contrast, precipitation is over-estimated
in winter and in summer over many central areas but underestimated in summer
over the north-west and some coastal regions. Analysing the seasonal cycle of
surface air temperature and precipitaion shows that for temperature the patterns
in HadAM3H are obviously improved from those in HadCM2. Also, the simulated
patterns of precipitation are improved in HadAM3H but still show reasonably
large biases (over 2mm/day locally).
A preliminary analysis has also been made of the response to climate change
under the SRES A2 scenario in the HadCM3 and HadAM3H experiments. Annual mean
warming over China ranges from 3.5K in the south to 5.5K in the north. Winter
warming in HadCM3 has maxima of 6K over central and north-east China. The pattern
of response in HadAM3H is similar but with slightly higher values (maximum of
6.5K). The summer warming in HadCm3 is largest in northern regions with a maximum
of 7K. Again the HadAM3H patterns are similar though in contrast the maximum
is slightly reduced (6.5 K). Annual mean precipitation increases over almost
all of the country but with little or no change in northern and especially north-western
China. HadCM3 predicts increased winter precipitation over the whole country
with a maximum of 0.8mm/day in the east whereas in HadAM3H increases are smaller
and with decreases in the south east. In summer the response patterns are more
similar with decreases in the north west and central eastern regions (maximum
of 1mm/day in the latter) and increases (maximum 2mm/day) in the south and in
the north east. It is likely from the senario analyses that the precipitation
would increase over the catchment of Yangzi River and North China Plain, which
could relieve the drought in the North China Plain but increase the risk of
flooding over the Yangzi River.
These analyses provide essential background to the setting up of PRECIS (Providing Regional Climates for Impacts Studies) over China and understanding its predictions because the PRECIS RCM will be driven by HadAM3H at its lateral boundaries and thus inherit the large-scale characteritics of HadAM3H.
Key words: Model's validation, HadCM2, HadCM3, HadAM3H, Observation datasets, CRU, Surface air temparearture, Precipitaion, Total downward surface shortwave flux, A2 & B2 greenhouse gases emission senarios, Climate senarios
Watching Slides:http://www.ami.ac.cn/Sino_UK/workshop/Xu_hadleywork.ppt
Source: http://www.ami.ac.cn/Sino_UK