Phonetic transliteration:
阿 ā (A-) +
娜 nà (-na).
娜 is one of the most common characters used for the feminine -na/-nna ending in foreign names — see also
安娜 (Anna),
黛安娜 (Diana),
苏珊娜 (Susanna).
阿娜 is the rendering favored for the Spanish/Portuguese form Ana (without the doubled n).