Which Köppen code is used for a tropical savanna climate with a dry winter? The answer is Aw.
The Köppen code Aw describes a tropical savanna, or tropical wet-and-dry, climate whose pronounced dry season occurs during the local winter. The first letter A indicates a tropical climate, defined by a mean temperature of at least 18°C in every month. The w denotes dry winter conditions.
Aw climates have a driest month with less than 60 millimetres of precipitation and below the relevant Köppen threshold based on annual rainfall. Their wet season is substantial but not wet enough to qualify as Af tropical rainforest or, under the classification rules, Am tropical monsoon climate.
Savanna landscapes often contain tall grasses with scattered trees, reflecting seasonal water availability. Aw is not universal for every tropical savanna: As is used where the dry season occurs during the high-sun summer period. BWh, by contrast, is a hot desert code, while Af means rainfall remains sufficiently year-round.