A method of controlling a wind turbine by means of indirect turbulence measurements, the wind turbine comprising a wind turbine tower, a nacelle arranged on top of the wind turbine tower, a rotor with at least two wind turbine blades arranged rotatably relative to the nacelle, and a wind turbine control system comprising a controller and a sensor unit (13, 14), wherein the controller is configured to control the operation of the wind turbine, and the sensor unit (13, 14) is electrically connected to the controller and configured to measure a vibration signal of the wind turbine, wherein the sensor unit (13, 14) comprises a vibration sensor, wherein the method comprises the steps of: - measuring a vibration signal of the wind turbine indicative of turbulence by use of the vibration sensor, - calculating a severity indicator based on the vibration signal, wherein the severity indicator is a signal indicative of the severity level of the current vibrations of the wind turbine, - determining an operational limit parameter as a function of the severity indicator, wherein the operational limit parameter indicates a minimum or maximum limit of an operational range of an operational parameter of the wind turbine, - determining a control signal for controlling the operational parameter based on the operational limit parameter, and - controlling the operation of the wind turbine according to the control signal, wherein the step of determining an operational limit parameters comprises, - dividing a range of the severity indicator into operational zones defined by threshold values (27, 28), wherein the threshold values (27, 28) comprise a first threshold value and a second threshold value, and - comparing the severity indicator with the threshold values (27, 28), wherein if the severity indicator is below the first threshold value, a first operational limit parameter is determined, then the wind turbine is operated in an alert mode, and the wind turbine is put in a reduced operation mode in order to detect any extreme wind gusts; and if the severity indicator is above the second threshold value, a second operational limit parameter (20") is determined, then the wind turbine is operated in a reduced load mode, and the operation of the wind turbine is reduced to reduce extreme loads. - measuring a vibration signal of the wind turbine indicative of turbulence by use of the vibration sensor, - calculating a severity indicator based on the vibration signal, wherein the severity indicator is a signal indicative of the severity level of the current vibrations of the wind turbine, - determining an operational limit parameter as a function of the severity indicator, wherein the operational limit parameter indicates a minimum or maximum limit of an operational range of an operational parameter of the wind turbine, - determining a control signal for controlling the operational parameter based on the operational limit parameter, and - controlling the operation of the wind turbine according to the control signal, wherein the step of determining an operational limit parameters comprises, - dividing a range of the severity indicator into operational zones defined by threshold values (27, 28), wherein the threshold values (27, 28) comprise a first threshold value and a second threshold value, and - comparing the severity indicator with the threshold values (27, 28), wherein if the severity indicator is below the first threshold value, a first operational limit parameter is determined, then the wind turbine is operated in an alert mode, and the wind turbine is put in a reduced operation mode in order to detect any extreme wind gusts; and if the severity indicator is above the second threshold value, a second operational limit parameter (20") is determined, then the wind turbine is operated in a reduced load mode, and the operation of the wind turbine is reduced to reduce extreme loads. if the severity indicator is below the first threshold value, a first operational limit parameter is determined, then the wind turbine is operated in an alert mode, and the wind turbine is put in a reduced operation mode in order to detect any extreme wind gusts; and if the severity indicator is above the second threshold value, a second operational limit parameter (20") is determined, then the wind turbine is operated in a reduced load mode, and the operation of the wind turbine is reduced to reduce extreme loads.