Hello! Welcome back to our exploration of global climate systems.
In our last lesson, we learned the "language" of the Köppen climate classification system. We broke down the meaning of the three-letter codes, understanding how they represent broad climate groups (A, B, C, D, E), precipitation patterns, and temperature characteristics.
Today, we will move from theory to practice. Our goal is to apply the Köppen climate classification system to identify major climate types. You will learn the systematic process geographers use to take raw temperature and precipitation data and assign a specific climate code to a location. This is a core practical skill in climatology and a perfect way to build on your interest in the subject.
1. The Tools for Climate Classification
To classify a climate, we need two essential tools: a source of data and a set of rules.
Tool 1: The Climograph
Our primary data source is the climograph (also called a climatograph). As we saw briefly in the last lesson, a climograph is a chart that displays the average monthly temperature and precipitation for a specific location.
To see how these are constructed and read, let's watch a short segment from the "Earth Explained" video we used previously.
Köppen Climate Classification
This clip quickly explains what a climograph is and how it graphically represents the key data we need for classification.
Watch from 01:52 to 04:14. Focus on how the bar graph represents precipitation and the line graph represents temperature over the 12 months of the year.
Typically:
- Temperature is shown as a line graph.
- Precipitation is shown as a bar graph.
- The x-axis represents the 12 months of the year.
Tool 2: The Classification Key
The second tool is the set of rules. In the last lesson, you looked at a decision chart. This is formally known as a classification key. It's a flowchart that guides you through a series of yes/no questions about a location's temperature and precipitation values to arrive at the correct Köppen code. It ensures the process is objective and repeatable.
We will use the key provided in the following resource for our practical application.
C2: What Is Your Climate Classification?
This document from GLOBE provides a step-by-step guide and the necessary classification key. We'll be using it extensively.
Please open this PDF and scroll to 'Appendix C: Köppen-Geiger Climate Classification Key' (page 23). Keep this key open in a separate tab or window, as we will refer to it throughout the next section. Notice it's broken into 'Part 1 – Major Climate Types' and 'Part 2 – Sub-climate Classification'.
2. A Guided Application: Classifying New Delhi
Let's now walk through the process together, step-by-step. We will classify the climate of New Delhi, India, using the data and instructions from the same GLOBE document.
C2: What Is Your Climate Classification?
This resource provides a worked example for classifying New Delhi. We will follow its logic to see how the key is applied to real data.
Read 'Activity 1' from page 4 to page 6. You don't need to do the calculations yourself; the answers are provided in Tables 2A and 2B. Your focus should be on following the logic: how they use the data in the tables to answer the questions in the classification key (Appendix C) you just opened.
Let's break down the process you just read about.
Step 1: Determine the Major Climate Group (First Letter)
You start with Part 1 of the key. You have the following data for New Delhi from Table 2A:
Tmax(Warmest Month Temp): 32.72°CTmin(Coldest Month Temp): 13.53°CPann(Annual Precipitation): 710.16 mmPth(Precipitation Threshold): 77.40 mm
Now, you follow the key:
-
Is
Tmax< 10°C?- No (32.72 is not < 10). Go to question 2.
-
Is
Pann< 10 xPth?- Yes (710.16 is < 10 x 77.40 = 774).
- The key directs you to ARID (B).
We have successfully identified the first letter: New Delhi has a B climate.
Step 2: Determine the Sub-classification (Second and Third Letters)
Now we move to the section of the key specifically for Arid (B) climates (page 25 of the PDF).
-
Is
Pann> 5 xPth?- Yes (710.16 is > 5 x 77.40 = 387).
- The key directs you to STEPPE (S).
-
Next, we determine the third letter.
- Is
Tann(Annual Temp) > 18°C? - Yes (The annual average temp, 24.70°C, is > 18°C).
- The key directs you to HOT (h).
- Is
By systematically following the rules, we have determined the full Köppen classification for New Delhi: BSh - Arid, Steppe, Hot.
This structured process is fundamental to climatology. It transforms raw numbers into a meaningful classification that tells a story about a place's long-term weather patterns.
3. A Tour of the World's Major Climates
Now that you understand the process of classification, let's explore the characteristics of the major climate types you might identify. What does it actually mean to live in a Cfa or an ET climate?
The following video provides a concise tour of the Köppen zones. We'll go through it group by group. As you watch, try to locate the described regions on the world climate map below.
The Koppen-Geiger Climate Classification System
This video from Geodiode gives excellent, real-world descriptions and examples for each of the major climate zones.
Watch from 03:29 to 11:13. The video is sectioned by climate group (A, B, C, D, E), making it easy to follow. I recommend pausing after each group to reflect on its characteristics.
For a more detailed textual reference, you can use the following resource, which provides descriptions, locations, controlling factors, and example climographs for each type. It's a great companion to the video.
Appendix 2: Köppen Climate Classification System
This webpage from a physical geography lab manual offers detailed descriptions of all the climate types. It's an excellent resource to read alongside the video or to consult for more detail.
Skim through the sections on Tropical (A), Dry (B), Moist Subtropical (C), Moist Continental (D), and Polar (E) climates. You don't need to read every word, but notice the structure: each climate type is described with its key characteristics, typical locations, and controlling weather factors.
Test your understanding!
You are given a climograph for a city. The line graph shows that the coldest month averages -5°C and the warmest month averages 23°C. The bar graphs show that precipitation is fairly consistent throughout the year. Based on this information alone, what is the most likely three-letter Köppen classification? Explain your reasoning letter by letter.
Show answer
The most likely classification is Dfa.
- D (Continental): The coldest month is -5°C, which is less than -3°C, so it must be a D or E climate. The warmest month is 23°C, which is greater than 10°C, so it cannot be an E climate. Therefore, the first letter is D.
- f (Fully Humid): Precipitation is "fairly consistent throughout the year," indicating no dry season. Therefore, the second letter is f.
- a (Hot Summer): The warmest month's average temperature is 23°C, which is greater than 22°C. This defines a hot summer. Therefore, the third letter is a.
This climate, Dfa, is a Humid Continental climate with a hot summer and precipitation all year round, typical of places like Chicago or New York City.
Conclusion
In this lesson, you have taken a major step from theory to practice. You've learned how to use the tools of a climatologist—climographs and classification keys—to systematically identify a location's climate type. You've also taken a tour of the world's major climates to understand the real-world meaning behind the Köppen codes.
Key Takeaways:
- Systematic Application: The Köppen system is applied using a classification key, a decision tree that uses specific temperature and precipitation thresholds to ensure an objective outcome.
- Data to Classification: You can determine a location's three-letter Köppen code by analyzing its climograph data and following the rules of the key.
- Global Climate Patterns: Each Köppen code corresponds to a distinct set of climate characteristics and is found in specific regions of the world, often in predictable latitudinal bands.
Preview of the Next Lesson:
In our next lesson, we will focus more deeply on the first tool we used today: the climograph. The learning outcome is to analyze climographs to determine the temperature and precipitation characteristics of a specific location. While today we used them to find a classification, next time we will use them to tell a detailed story about a place's climate, describing its seasonality, temperature ranges, and moisture patterns in detail.