Simulation of precipitation in 40 alpha world cities for the 20th century by means of random walk

Totally unexpected and unpredictable droughts and floods frequently occur around the world. The unexpectedness and unpredictability strongly suggest that random factors should play an important role in those unexpected and unpredictable droughts and floods. The historical precipitations provide an important way to analyze the precipitation trend and also provide a possibility to use various models to simulate the historical precipitations, which is important too because it is almost impossible to conduct a controlled experiments on precipitations to illustrate their patterns and results. In this study, we use the random walk to simulate the annual precipitation in 40 alpha world cities for the 20
^th
century. The results show that the random walk can simulate the year-to-year precipitations and can catch their general trend. Thus this study provides a way to describe the unexpectedness and unpredictability of precipitation patterns in these cities during this period of time.