ICSE Class 9 Answered

(i) For weather forecasting: If the barometer height on a particular day is less than normal height, it shows fall in pressure. If fall in pressure is steep it could mean dust storm or rain. However, if there is gradual drop in pressure, it means that weather will change from normal to windy. If there is no change in height, it is fair weather. If there is a rise in barometric height it means dry or anticyclonic weather.

(ii) Altimeter: It has been established that for a vertical rise in 105 m, the barometric height drops by 1 m. This fact is used in the construction of altimeter, where fall in length of mercury column is calibrated as height of a place.