Tool For Comparing City Climates And Finding Similar Cities

I've added a new tool that lets you find and compare cities with similar climates...

Data

I used the CRUTS data set (you might have heard of HadCRUT...it's the CRUT in that) for everything in this except for humidity. I used NASA's dataset for humidity. 

Methodology

The process has a massive number of steps, so I'll just provide a basic summary:

• calculate the monthly average for each variable from 1990 - 2009 at each lat/lon location
• use bilinear interpolation with each city's lat/lon location to get the monthly averages for each variable for each city; fallback to nearest neighbor and repeat for invalid data
• using something very similar to a RSS equation for each variable, calculate for all combinations of cities with a variety of weighting terms to scale all errors to be roughly the same scale
• adjust the weighting so that it's roughly 30% how hot it gets, 30% how cold it gets, 20% how much it rains, 10% how sunny it is, and 10% how humid it is; to handle north and south of the equator being flipped, each variable is sorted and the sorted lists are compared
• for each city, calculate the error comparing with ever other city using the equation determined in the previous steps, and rank these
• remove cities that are too close together from the rankings for each city so that you get an interesting spread (e.g., no one cares if two cities 5 miles apart have similar climates); the radius I picked is roughly the size of New York and Pennsylvania put together

City List

I have ~1100 cities at the time of writing. I started with a list of the largest cities in the world, mapped them, and then started filling in gaps in the map. I added a lot more once I found that a few cities that I tested had no good matches. I think I have pretty decent coverage at this point, and almost every major population center on Earth should be within 50 miles or so of a city in this tool.

My Favorites

So this is actually a tool I've wanted forever and was the original reason I started this site, so I've played with it a lot. My favorite random similar cities are:

• Iquitos, Peru and Timika, Indonesia
• Lviv, Ukraine and Muskegon (Michigan), USA
• Salt Lake City (Utah), USA and Tblisi, Georgia
• Panama City, Panama and Manila, Phillipines

Feeback

If you want this tool to do other stuff or you find bugs, feel free to let me know in the comments. I had the ability to pick the cities using the map, but it was kind of hard to use and I couldn't figure out a better way to do it. It worked well for ~50 cities, but above that became annoying. I also only tested this on a ZenFone so it might be awful on mobile.

In case you missed the link at the top, it is here:

http://cityprojections.com/CompareCityClimates.html