How to clear AWS RDS Aurora MySQL local storage?

I got a warning message about running out of AWS RDS local storage. > The free storage capacity for DB Instance: {MY INSTANCE NAME} is low > at 2% of the provisioned storage [Provisioned Storage: 157.36 GB, Free > Storage: 3.35 GB]. You may want to increase the provisioned storage to > address this issue. According to the AWS document, local storage depends on instance type and can be increased by scale up : https://aws.amazon.com/premiumsupport/knowledge-center/aurora-mysql-local-storage/?nc1=h_ls But, I would like to clear the local storage instead of scaling up the instance because only one instance of the read cluster has insufficient local storage. I restarted Aurora instance but the local storage is still almost full. How can I clear local storage? It's MySQL version is 5.6.