Ask A Scientist: How can we predict tomorrow's weather?
QUESTION: How can we predict tomorrow's weather?
ANSWER: Weather forecasting is a nice example of how science can help predict the future. The general procedure for how scientists make a prediction goes like this: First, they observe how various quantities change over time in a phenomenon they are trying to predict. Second, they create a model that can explain the changes observed. Finally, they input the current condition into the model to estimate what is most likely to occur next.
Once a prediction is made, it is compared to what actually occurred later to assess how accurate the prediction was. If it was not accurate enough, scientists go back to the second stage and revise their model.
Science is all about model building. Here, a model means a simple representation of something you want to understand. If your model captures relationships between past, present and future (such relationships are called dynamics), it can give you the power of future prediction. Such models may be mathematical (e.g., equations), computational (e.g., computer simulations), visual (e.g., diagrams), physical (e.g., miniatures), narrative (e.g., key concepts), etc.
The models that meteorologists use to forecast the weather are complex mathematical equations (written in the form of "nonlinear partial differential equations") that describe how various meteorological quantities in the atmosphere, such as air pressure, temperature, humidity, wind speed and cloud density, will change over time in a three-dimensional space.
These models have been studied and developed by a number of scientists for nearly a century, and they have been improved to become more and more accurate over the years. Meteorologists enter a lot of data into these models, such as current and past weather conditions, barometric pressure measurements, and information collected by meteorological radar, radiosondes and weather satellites.
Solving the equations requires a lot of computational power, so sometimes they use "supercomputers" to compute the model equations. Once the computational results are in, the meteorologists carefully assess them and develop a final forecast using their scientific expertise and experience. This is what we see on TV as weather forecasting.
One thing I should mention is that no matter how accurate the models become to predict the weather for the next few days, it is still impossible to do the same for the next 30 days. This is not because scientists and meteorologists are doing a lazy job. Instead, it is because these kinds of models are fundamentally "chaotic" due to their mathematical properties. Such "chaotic" systems are highly sensitive to any small changes in their variables, so it is practically impossible to predict their long-term behaviors. In fact, nature is full of such chaotic systems, for which all we could do is to predict the future for only a short period of time, but not any longer.
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MEET THE STUDENT ASKING THE QUESTION
Name: Joseph Tiderencel
School: St. John the Evangelist, Diocese of Syracuse
Teacher: Anu Rai
Career interest: NBA basketball player
MEET THE SCIENTIST
Answered by: Hiroki Sayama
Title: Director, Collective Dynamics of Complex Systems Research Group, Binghamton University
Research area: Complex systems, artificial life, mathematical biology, computer and information sciences
Interests/hobbies: Traveling, walking, swimming