I discovered how to do this and am updating my post for the benefit of anyone who wants an answer to this question.
Here’s the snippet of code I wrote to cycle through all users and email an alert to those with have a user level of 2 (Author).
$users = $wpdb->get_results(“SELECT user_email, ID FROM $wpdb->users”);
foreach ( $users as $user ) {
$user_info = get_userdata($user->ID);
$email = $user->user_email;
$level = $user_info->user_level;
if ($level == 2) {
mail($email, $subject, $message);
}
}