Examine the graph labeled December 2014 Precipitation from the Exploratorium’s Environmental Field Station. What is being measured? Where were the measurements taken? What time period do they cover? What patterns do you see in the data? Do you notice anything unusual about any of the measurements?
The graph shows that more than 20 inches (51 cm) of rain fell in one day, on December 31, 2014. Does this seem likely?
What do scientists do when they find data that seem unusual? Ideally, they repeat the experiment, but that’s not possible in this case, because rainfall is a natural event. However, we can look at other local data to help verify or refute the data from Pier 15.
Look at the NOAA California Climate Station Precipitation Summary and find the average annual precipitation for San Francisco (the far right-hand column).
Look at the NOAA Monthly Precipitation Averages for Bay Area Cities and find the average monthly precipitation data for “San Francisco City.”
The National Weather Service collects precipitation data at a weather station not far from the Exploratorium, so we can compare their data to ours. Look at the information you obtained from the NOAA National Weather Service Forecast Center website. What do you notice? Which measurement for December 31 seems more likely—more than 20 inches (51 cm) in one day or 0 inches (0 cm) in one day?