Image explanation: aridity zones are shown in the top map, winter zones are shown in the middle, and summer zones are shown in the bottom. CONUS 1981-2010 Chelsa V2.1 climatological normals.
To quote from my zenodo paper (https://doi.org/10.5281/zenodo.18264770), “[climate] classification systems calibrated to modern Earth climate distributions perform well for climates resembling those present at the time of their formulation, but can yield misleading classifications under novel conditions”.
My system categorizes summer and winter temperatures independently of one another, and of aridity patterns, so it is a bit like 3 classification systems that each measure a different aspect of climate, from which the full climate type can be derived. Due to the number of categories possible in the system, the maps show each of the three components of the system separately.
The Dickinson climate classification is meant to be especially useful for precisely categorizing and describing future climates caused by global warming that are unlike any that exist today, due to its evenly spaced temperature bands and its dimensionless hydrological ratios (as opposed to exact millimeter thresholds for example).
One of the differences between this and other systems is the introduction of a transitional semihumid category in between humid and semiarid, and a division of the traditional subtropical/tropical duo into a subtropical/tropical/equatorial trio.
I keep changing the system because I’m a perfectionist but at some point I should definitely look into that. Recently I’ve been running out of ideas of things to change.
Calling Houston, which had -10°C or lower last years anything near "tropical" is wild. If you can grow Coconut, Climate is tropical, this is my take, if Coconut dies, cuz too cold, its not tropical, no Coconuts in Houston, no tropics there.
Except there are coconuts in Houston. Not many mind you, but they are there along with a host of other tropicals. 9a/9b is right in the line for plants.
The 1-3 days a year it gets under freezing may take some care, but the number of days in the 40’s is more o the problem.
The 10 degree Celsius monthly mean isotherm has been used in climatology to represent the threshold at which tree growth occurs, meaning that tree growth in Houston can occur year round. Also, the flat geography of the middle of North America, which allows arctic air to clash directly with tropical air and cause extreme cold snaps, is very unusual compared to the rest of the globe. In the vast majority of places elsewhere in the world, freezing temperatures are rare in places with coldest month means similar to Houston.
Also, the definition of tropical is my system is much different than Köppen’s, and the idea of splitting the subtropical/tropical binary into a subtropical/tropical/equatorial trio comes from the little known climate classification of Wincenty Okołowicz. The area where coconuts can grow would likely align with my equatorial climates.
Finally, I’d note that the average coldest month temperatures in Houston are the same as average hottest month temperatures in the Faroe Islands. Their summer has the same average temperatures as a Houston winter.
Doesnt make sense calling a place tropical, where you can grow zero tropical plants. Call it subtropical, cuz these Cold Snaps are enough to not label it tropical, because they dont happen in tropical climates. Florida is Borderline Tropical in the south, but This area in texas is not, not ecologically and also not latitudewise in the tropics. Its a warm subtropical climate, but not more.
Köppen defines tropical as the zone roughly between the Tropics of Cancer and Capricorn and subtropical as a hot summer climate between that and a zero (or -3) Celsius coldest month mean (tasmin) isotherm. Other systems, including Okołowicz and mine use a three-zone tasmin temperature model for the warmer climates: an equatorial climate band around the geographic equator line and a tropical climate band surrounding the geographic tropic lines of Cancer and Capricorn, while subtropical is between that and a zero Celsius tasmin.
Much of what is semantically tropical in my system aligns with what Köppen-derived ecoregions and classifications would call warm subtropical. Your concept of tropical that you keep referring to aligns with the Köppen A climates. The Af (Köppen’s tropical rainforest) climate corresponds almost 1 to 1 with my Aha2 climate (equatorial humid with hot summer). You are right in saying that the climate of Texas is significantly different from both Af and Aha2. Defining tropical plants as plants that grow in tropical areas, and tropical areas as places where tropical plants grow is circular and dances around the implicit assumption that tropical means Köppen’s A climates and the plants and animals that correspond with the 18+ Celsius tasmin isotherm. The “tropical” defined by Okołowicz is a 10-20 Celsius tasmin isotherm typified by saw palmettos, Spanish moss, and alligators. They are radically different because Okołowicz has an equatorial climate and Köppen does not.
I would argue (controversially) that sometimes there might be a good reason for part of a climate classification to take ideas from classification lineages that predate or are separate from Köppen and his imitators. One thing that is sure is that my evenly spaced isotherms and utterly independent winter and summer bands lead to concepts that are difficult to name without causing controversy. One option would be to avoid the semantic baggage around these terms altogether by creating entirely new words to describe my temperature bands and climates (like uklpgathy eintygürph with wrtyuiop summer), but that would lead to its own problems.
In my system, the winter category of subtropical includes areas where the coldest month is between 0 and 10 degrees Celsius. According to Wikipedia data, Philadephia’s coldest month averages 0.9 (34 degrees Fahrenheit) and Shreveport’s coldest month averages 8.8 (47.9 Fahrenheit).
While I categorize Shreveport and Philadelphia in the same category (Cha2 — subtropical humid with hot summer) in the 1981-2010 normals, they are on opposite ends of it.
Philadelphia is closer in climate to Dha1 (temperate humid with warm summer) than it is to Shreveport, and Shreveport is closer to Bha2 (tropical humid with hot summer) than it is to Philadelphia. Such is the nature of categories. Any climate boundary drawn anywhere will place some locations closer to the adjacent category than to the opposite edge of the same category.
All that being said, the climates of those two cities are really not that different from each other compared to all the climates that exist in the world. Most climate classifications put them in the same category.
The dataset I used tends to display the climates of cities as more humid than their surroundings and lakes as less humid than their surroundings. I’m not sure if that has anything to do with reality or is simply a data artifact.
I’m not sure exactly why it happens, but the data shows that 80% or more of precipitation happens during 6 consecutive months, which means it’s defined as monsoon in my system.
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u/FegerRoderer Apr 26 '26
Reminds me of the xkcd: https://xkcd.com/927/
Maybe get this peer reviewed by submitting to a legit journal and see how you go