Q: You are given a sentence and a question in the input. The information provided in the sentence should be enough to answer the question. You're expected to write the correct answer. Do not use any facts other than those provided in the sentence.
Sentence: Under Köppen's climate classification, portions of the city with lower elevations have a humid subtropical climate (Cwa), while portions of the city with higher elevations generally have a subtropical highland climate. 
Question: What is the Köppen abbreviation for a humid subtropical climate?
A:
Cwa.