Since the development of Wladimir Köppen’s Köppen Climate Classification system, many different classification models have been developed and modifications of the said system also existed. One of which is the Köppen-Trewartha Climate Classification model. In 1968, Glenn Thomas Trewartha produced his modification of Köppen’s and the final version was done in 1980. The modified version’s objective was to adjust the original criteria for temperature and the thresholds that separate dry and wet climatic regions and to better correspond to the observed boundaries of natural landmasses. This, and the original version were the most widely-used models in contemporary times.
Trewartha’s maps did a lot more to define the climate zones in the mid-latitudes, especially in North America and Asia, to reflect vegetative zones and present a more useful map. The Trewartha model is divided into six climate types, and each also has its subtypes and like the Köppen-Geiger, they are represented by letters. Types A, C, D, E and F have heat as the determining factor and B, the dry climate is in similar manner to the original Köppen system. Air temperature and amounts of precipitation are the determining factors of the Trewartha climate classification, just like of Köppen’s.
Below is the model’s climate types and their subtypes:
Köppen-Trewartha Climate Classification
Climate Types
Tropical (A) - Frost is limited in continental locations; in marine areas the average monthly temperature is above 18°C (64.4°F). It's subtypes are :
Dry (B) - Potential evaporation equals or exceeds precipitation
Subtropical (C) - At least 8 months have average temperatures above 10°C (50°F)
Temperate (D) - At least 4 months have average temperatures above 10°C (50°F)
Boreal (E) - The warmest month has an average temperature above 10°C (50°F)
Polar (F) - All months have average temperatures below 10°C (50°F)
Subtypes:
Tropical wet (Ar) - all months average above 18°C (64.4°F) and no dry season
Tropical wet-dry (Aw) - same as AR but at least 2 months dry in winter
Tropical/subtropical semiarid (BSh) - Evaporation exceeds precipitation, and all months average above 0°C (32°F)
Tropical/subtropical arid (BWh) - one-half or below the precipitation of BSh, and all months average above 0°C (32°F)
Temperate semiarid (BSk ) - same as BSh but with at least one month of average below 0°C (32°F)
Temperate arid (BWk) - same as BWh but with at least one month average below 0°C (32°F)
Subtropical dry summer (Mediterranean) (Cs) - 8 months average above 10°C (50°F), coldest month average below 18°C (64.4°F), and a dry summer
Subtropical humid (Cf) - same as Cs but no dry season
Temperate oceanic (Do) - 4-7 months average above 10°C (50°F), coldest month average above 0°C (32°F)
Tundra (Ft) - all months average below 10°C (50°F)
Polar ice cap (Fi) - all months average below 0°C (32°F)
References:
CLIMATE CHANGE | The KoppenTrewartha Climate Classification System. (2017, September 30). Geography and You. https://geographyandyou.com/the-koppen-trewartha-climate-classification-system/
Climate Classification Systems. (n.d.). Oregon State University. https://open.oregonstate.education/permaculturedesign/chapter/climate-classification-systems/
Hi, it's me again. So this is another example of a classification model. I have also included a world climate map, to show an example.
Thanks for reading. <3
