Naomi, Mark, and Sammy are three friends that met playing video games online. One day they were discussing the best time for them to log in to play together. They discovered that they are all in the same time zone. Not only that, they used Google Maps to find out that they also live at the same longitude, 86 W. Sammy lives in Alabama and said that the weather there is warm most of the year, and does not get too cold during the wintertime. Mark's hometown is in Kentucky, and mentioned the weather there is warm half of the year, and the other half is cold. Naomi, on the other hand is from Michigan where it is cold for a good portion of the year.
Where Naomi, Mark, and Sammy Live
The map shows the longitudinal line that goes from 86W through 31N. All three friends live along this line.
The three friends wanted to make a visual representation of the temperature across the latitude span of their hometown to see how the temperature changed over time. So, after some research, they decided to make a Hovmöller (also known as Hovmoller) Plot, which shows data such as temperature, along a selected longitude or latitude over a period of time.
Hovmöller plot of the Temperature over Naomi, Mark, and Sammy's Homes
Hovmöller Plot on the longitude line 86W between Alabama and Michigan, latitudes 44N to 32N from June 2006 through 2008
Naomi, Mark and Sammy created the color-coded plot and saw how different the temperatures were from Alabama to Michigan even during the same season. Reds and oranges represent temperatures between 68F (20C) to 90F (32C). The color yellow and green colors represent 42F (6C) to 66F (19C). And the temperatures for blue to purple are 41F (5C) to 17F (-8C).
Hovmöller plot of the Temperature over Naomi's Home
Here we have the Hovmöller Plot for the latitude around Naomi's hometown. We can see how the blue and purple take up a good portion during the months of December through March. We can also notice how from the end of September to the beginning of December it has yellow and green showing cooler temperatures. Finally, May through September are red orange in color, but it is not a dark red, indicating that it does not get extremely hot there.
Hovmöller plot of the Temperature over Mark's Home
In Mark's hometown, the plot shows how there is a good spread between the hotter colors, and colder or cooler colors. Notice that there are cold temperatures, but there is not a lot of purple, meaning it does not get below freezing very often. We can also see that there is dark red in the graph, showing that high temperatures occur, especially in late summer.
Hovmöller plot of the Temperature over Sammy's Home
We can see that at Sammy's hometown there is a lot of dark red across the plot, and small stretches of time where there is yellow and some green. This shows that it is warm most of the year and the weather cools off during the winter. We can also see that there is no blue nor purple indicating that in Sammy's hometown does not get cold at all.
Hovmöller Plot between Alabama and Michigan from june 2006 through June 2008
Hovmöller Plot on the longitude 86W between Alabama and Michigan, latitudes 44N to 32N from June 2006 through June 2008
Here we have the whole Hovmöller Plot and we can see the changes in temperature as you go along the latitude and over time. The higher the latitude the colder it gets, the lower the latitude the warmer it gets. We can also see the temperature change in cycles as time passes.
Moving on to other Applications of the Hovmöller Plot
Now that they understand how to make these types of plots, the three friends decide to look for other patterns in the world. Sammy, who wants to be an oceanographer, decides to create a Hovmöller plot at the mouth of the Amazon River to look at changes in salinity there.
Salinity is important to track to be able to understand ocean circulation. It changes the density of seawater and makes it sink or float, and influences deep ocean currents. Evaporation and precipitation, ice formation and melting, and river runoffs influence salinity. Combined with other oceanographic information, they can find out how it affects climate in the short term as well as in the long term.