Weather Glossary - Y
The interval required for the earth to complete one revolution around the sun. A sidereal year, which is the time it takes for the earth to make one absolute revolution around the sun, is 365 days, 6 hours, 9 minutes and 9.5 seconds. The calendar year begins at 12 o'clock midnight local time on the night of December 31st-January 1st. Currently, the Gregorian calendar of 365 days is used, with 366 days every four years, a leap year. The tropical year, also called the mean solar year, is dependent on the seasons. It is the interval between two consecutive returns of the sun to the vernal equinox. In 1900, that took 365 days, 5 hours, 48 minutes, and 46 seconds, and it is decreasing at the rate of 0.53 second per century. This decrease is due to the slow precession of the Earth's axis of rotation.
The heat currently affecting southeastern Australia is rare, not just for this time of year but even for summer, covering an unusually large area.
As South Australia continues to heat up in unseasonably hot weather, the Country Fire Service (CFS) has issued an extreme fire danger rating for the Mount Lofty Ranges and the state's lower south-east.
A Western Queensland grazier who has overcome depression says he will not allow the current drought to drag him back into the dark days of negative thinking.