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.
No rain fell in Perth at all during the month of April for only the fourth time in the past 140 years, according to the Bureau of Meteorology.
There were two decent rounds of alpine snow last month and much of Australia's southeast shivered through their coldest temperatures in at least six months last week.
A front is bringing a colder showery change to southern Australia, dropping temperatures by five-to-10 degrees.