The search for the Central Valley's climate analogues

 About a year ago, during a heatwave at the end of summer, after several months without a drop of rain, I was walking on a shaded path in an old Oak grove by the Sacramento River, and wondered: are there other places like this in the world? Not just other Mediterranean climates, with hot dry summers and cool rainy winters, I knew there were many places classified that way. I wanted to know if there were other places with the same average temperatures, rainfall, and humidity every month of the year as my home in the Central Valley. I tried all kinds of Google searches and couldn't find an answer as specific as I wanted.

Consulting climate maps, like the ubiquitous Köppen climate classification map, was not much help. According to this map, Sacramento's climate should be the same as the French Riviera, or Istanbul, but the summer temperatures in Marseilles are 10 degrees (F) cooler than in Sacramento, and in Istanbul it snows in the Winter.

Köppen climate map (yellow is Csa, which most of the Central Valley falls in)

I hoped to narrow it down a little better than Köppen did. 

I wanted to find out if Sacramento, or Fresno, or Bakersfield (all with slightly different climates) had any identical climate twins out there in the world. This is what led me to GIS technology.

GIS (short for Geographic Information System) software lets you search and display map-based data in many different ways. Through trial and error, I was able to bring worldwide climate data into a GIS program called ArcGIS, and run searches with temperature ranges and humidity ranges for different times of the year (future posts will go more in depth for anyone who wants to try this themselves). 

The result is a series of maps with 5 zones: purple, blue, teal, green, and orange. Each color corresponds with a different climate of inland valleys in California. Blue, Sacramento's zone, has the "Delta breeze" which cools it off a little in the summer, while Bakersfield and Redding in the green zone are too far from the water to get this tempering effect. 

Redding gets more rain in the winter than Bakersfield does, but in this mapping I focused on temperature and humidity (the main factors for human comfort), not rainfall. I'm planning to experiment with this in the future to see how adding rainfall to the criteria changes things.

As an architect I was more interested in temperature and humidity because these are the main factors of climate that are the most challenging for a building to moderate. To deal with rainfall all you need is a good roof and decent site drainage. To deal with heat and cold you need a variety of different strategies, and humidity helps determine which strategies are most appropriate. There is much more to talk about on this topic, but for now enjoy the maps!

Purple, blue, teal, green, and orange colors each represent slightly different climates of the inland valleys in California.  

climate analogues on a world map

detail of Algeria and Tunisia. Constantine and Sacramento are climate analogues.

detail of Jordan, Palestine, Israel, and Egypt. Jordan has several important cities in or near the blue zone.

detail of Morocco and Southern Spain and Portugal. Granada, Evora, Meknes, and Fez are all climate analogues with Sacramento. Marrakesh falls just outside the green zone.

detail of Argentina and Chile. Santiago has a similar climate to Napa or Fairfield. Mendoza and Santa Rosa in Argentina have climates similar to parts of the Central Valley.