The payment of all funds shall be by checks or warrants signed by the city clerk and countersigned by the mayor, provided, however, a facsimile thereof may be used for such signing. During the absence of the mayor from the corporate limits of the city, and necessity therefore arising, checks or warrants may be countersigned by the mayor pro-tem designated by the mayor to act in his (her) stead. All such disbursements shall be authorized by resolution of the commission.