A hygrometer is an easy to use tool for measuring the amount of humidity in the atmosphere. There are two main types of hygrometers – a dry and wet bulb psychrometer and a mechanical hygrometer.

The overall amount of ozone is essentially stable in a natural cycle. This has been true for millions of years .
Since some decades, according to atmospheric measurements, ozone layer is getting thinner. Ozone depletion has been most severe at the poles, specially over Antarctica, where a seasonal ozone layer "hole" appears ( in the NASA image the blue color means lack of ozone). It is not technically a “hole” where no ozone is present, but is actually a region of exceptionally depleted ozone in the stratosphere over the Antarctic that happens at the beginning of Southern Hemisphere spring (August-October).