text: Sometimes , a surge of dry air called the Saharan Air Layer ( SAL ) follows a tropical wave , leaving cloudless skies , as convection is capped by the dry layer inversion .
simplified: Periodically , a surge of intensely dry air known as the Saharan Air Layer ( SAL ) is entrained behind a tropical wave , resulting in cloudless or nearly cloudless skies as convection is limited by the dry layer inversion .