Introduction
NCC/GU-WG is a weather generator developed at National Climate Center of China (NCC) and Gothenburg University (GU) for Assessment of Climate Impact in China. It can simulate daily precipitation, maximum temperature, minimum temperature, radiation, relative humidity and wind speed. In version 1.0, only precipitation simulation is available. The stochastic model is based on two states first order Markov Chain and two parameters Gamma distribution (Liao et al., 2004). Simulation of other variables will
be added in later versions. Simulation of precipitation can be made at 672 stations in China (Figure blow shows the station locations). Models parameters are derived from the history daily records between 1960 and 2000 at each station.

How to run NCC/GU-WG
You should extract the downloaded package firstly to a folder which include four parameter files named Province.txt 、StationProvince.txt 、StationName.txt 、Parameters.txt and an executable file named BCCWG..exe. These files must be put in the same folder and should not be modified. The program is run by double clicking BCCWG..exe.

How to use NCC/GU-WG
In BCCWG version 1.0, there are 672 stations for selection when you want to simulate precipitation. You can select station you want to simulate either by station number or by province name. After the station is chosen, you can select simulation length from 1 year to 1000 years by clicking the vertical scrollbar. When both station and simulation length are selected, double click OK button and the program will prompt a save interface to you to create a file. The simulation result will be written to the file you created. The output file is a text file with three columns. The first column is the number of year, the second is the number of day and the last is the daily precipitation rate simulated (mm/day).

Application of NCC/GU-WG
Firstly, Weather generator is an important tool to study impact of climate change. Because it can generate daily records in the future based on a certain climate scenario and its results can be usedin models to simulate climate change impact. Secondly, Weather generator is an important tool to study extreme climate event and its risk analysis. Extreme climate events are rare processes that occur occasionally. The length of observed time series is often too short to allow estimate of the probability of extreme events. However, weather generator can do it. It can simulate weather data statistically to history records long enough. Thirdly, weather generator can simulate the weather time-series to unobserved locations. Through it, quantitative assessment of impact of climate condition in such area becomes realized. Fourthly, weather generator is an important tool for preliminary assessment of climate impact, because it can simulate daily data in the future used in impact models successfully based on short-term forecasting result.

Further Developments
Simulation of maximum temperature, minimum temperature, radiation, relative humidity, wind speed etc will be added to the NCC/GU-WG in the coming versions. Further, the new versions will be able to deal with future climate change scenario, seasonal climate prediction, and generation of daily weather records for unobserved locations.

References
Liao Yaoming, Zhang Qiang, Chen Deliang. 2004: Developing a Weather Generator and its Precipitation Simulation in China. Journal of Geographical Science (in press).

Contact Points
Liao Yaoming(Division of Climate Assessment and Environment Operation, National Climate Center, China Meteorology Administration. Telephone: +86-10-68409546, Email: LYMZXR@SOHU.COM )
Chen Deliang (National Climate Center, China Meteorology Administration; Earth Science Center, Gothenburg University, Sweden. Telephone: +46-31-7734813, Fax: +46-31-7731986, Email: DELIANG@GVC.GU.SE, Personal Home Page: http://www.gvc.gu.se/ngeo/deliang/deliang.htm )