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.
Sydney-siders have been spoilt for choice in the surf department over the past few days.
Severe thunderstorms sparked up just to the west of Lochington yesterday late morning, tearing through many parts of southeast Queensland into late last night.
A very cold airmass coupled with vigorous a low pressure system caused snow to fall to low levels in Tasmania last night and into this morning, leading to road delays and closures.