Is there a way to pay annually?

There is no annual payment option for iCloud Storage, only monthly. There are two methods by which you can add credit to your Apple ID sufficient to cover a year's subscription: you could buy sufficient ' iTunes and App Store' (not Apple Store) gift cards and redeem them in your account in iTunes/Apple Music, or you could use your registered payment method to add credit to your account - please see  Add money to your Apple ID balance - Apple Support

Note that in both cases this credit will also be used for any music,movie or app purchases so you would have to take that into account.