Rights: The University of Waikato Published 18 June 2008 Download

Dr Peyman Zawar-Reza, from the University of Canterbury, discusses how scientists often develop models to help them solve problems. In this case, students wanted to find out what effect a city (Christchurch) has on the weather for that region and developed a model to combine multiple variables mathematically. When the variables were changed, the model predicted changes in weather patterns.


With any sort of problem-solving you have two things – you have an initial condition and you actually have the definition of the problem, which you try to solve with the model. I asked the students to tell me whether Christchurch has any effect on local climate in the Canterbury region, and if it does, what is that effect? So the problem was, does Christchurch have an effect on local climate? What you need to solve a problem, is you need a problem definition – does Christchurch have an effect? And another thing… information you need is initial conditions. Well, the students did a really good project, and they used a weather forecasting model, and they did a simulation of one day’s Christchurch weather, with Christchurch represented in the model. And you can do that, you can specify an area as being urban. You know dark surfaces, rough surfaces, not green, very little humidity on the surface, that sort of a thing – all the things that make a difference in the climate system. Then, how do you know whether Christchurch actually has any effect on the local climate? Well, they did two things. They did another simulation where they came in and manually erased Christchurch from the surface of the planet. They made it all grassland, or tussock land, or jungle, I can't remember, and they redid the weather forecasting exercise. Then they did another scenario where they came and converted the whole Canterbury region with urban zones, sort of like a Christchurch becoming a mega city in 20 years from now. And it was really astonishing to them, because they could actually see effects on local climate from manipulating urban zones. And one of the things that they said might happen is that, if Canterbury goes toward more urbanisation, then the effect of having rainfall will increase over the Canterbury region, might increase. And that is how they solved the problem, which you can not do by any other means.

P. Stadler