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.
Tropical Cyclone Alfred has weakened to a tropical low as it begins to make landfall on the Gulf of Carpentaria's southern coast.
Some homes in the community of Borroloola on the Gulf of Carpentaria were evacuated with 74 residents sheltering elsewhere, as they waited for Cyclone Alfred to make landfall about sunrise on Tuesday.
WA's Kimberley is in the midst of one of its biggest wet seasons on record, causing headaches for emergency services, remote communities and cattle stations cut off by flooding, but it has not been all bad news for the region.