The standard PRC rendering of the desert 'Sahara' is
撒哈拉 (Sǎhālā), with
撒 not
萨.
萨哈拉 is a less standard variant — you'll see it in older translations, Taiwan/HK media, and in personal names. Famous Taiwanese writer
三毛 (Sān Máo) titled her bestselling memoir 《
撒哈拉的故事》 ('Stories of the Sahara'), cementing
撒哈拉 as the dominant form.