Welcome email on new subscriber

Is there a way to send the welcome email when creating a new subscriber?
I see the admin panel does something like this:
```ruby
send_welcome_email: 1, 
channel: {
  welcome_email_subject: 'Welcome email subject',
  welcome_email_body:	'<p>Welcome email body</p>'
}
```
but I can't seem to get it to work using the API.