What does BW stand for as per the Koeppen climate classification?

In the Köppen climate classification system, the capital letter 'B' designates dry climates where evaporation exceeds precipitation [3]. These dry climates are further subdivided using capital letters 'S' and 'W' to indicate the degree of aridity. Specifically, 'BS' stands for steppe or semi-arid climate, while 'BW' stands for desert or arid climate [5]. The 'W' in BW is derived from the German word 'Wüste', meaning desert [5]. These desert climates are often further categorized by temperature using a third letter: 'h' for subtropical/hot deserts (BWh) and 'k' for mid-latitude/cold deserts (BWk) [4]. In contrast, Tundra is represented by 'ET' under the 'E' (Polar) group, and Mesothermal climates are represented by the letter 'C' [2]. Therefore, BW specifically identifies the desert climate within the arid group.

Sources

1. [1] FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 11: World Climate and Climate Change > Dry Climates : B > p. 93
2. [3] FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 11: World Climate and Climate Change > K OEPPE N ' S SCHEME OF CLASSIFICATION OF CLIMATE > p. 92
3. [5] https://en.wikipedia.org/wiki/K%C3%B6ppen_climate_classification
4. [2] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 30: Climatic Regions > 30.3. B – Dry Climate > p. 440
5. [4] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 30: Climatic Regions > Major Climatic Types According to Koppen > p. 421