SOLSTICE today.

[3488]

At 11:28 HRS UTC, the Earth reaches the Solstice (Northern Summer / Southern Winter) today.

For us in the northern hemisphere, we have just had the Shortest night of 2010, today the longest day.

Andrew Brown.

 

[orionrider]

Thanks Andrew
We woke up with the same thought, but mine led to a surprising revelation. Check this related post: viewtopic.php?t=24853

 

[MeteorWayne]

A few comments of the solstice. It is of course the day when the sun takes the highest track across the sky in the northern hemisphere, and the lowest in the southern.

But it's a good time to think 3D about the solar system. It's the day that the earth's axis of rotation's north pole points toward the sun. If you have a globe with the 23 1/2 degree tilt, get it out, and place the globe in orbit around a light bulb (representing the sun). Today, that tilt is in the direction of the sun/bulb. As you make a circle around the sun (light bulb) the axis continues to point in the same direction, so that in 6 months the north pole points away from the sun. It always points at the north star. I love giving this 3D demo during my astronomy lectures. It really helps people "get it".

MW

 

[charliebigspuds]

OK I am missing something, why is it hotter in July / August than around the date of the summer solstice?

 

[MeteorWayne]

Primarily because of how long it takes to warm the land, and especially the ocean water on the earth's surface. There is a time lag involved. Here in the US, the peak temperature is about July 15th (hence meteorological summer being the months of June, July, and August, often abbreviated JJA). For the UK, which is an island surrounded by water that takes longer to warm than land, I believe Andrew has said the peak temperature comes later, in early August.

It's also why the coldest US temps are in mid January, and meteorological winter (the coldest 3 months) are Dec, Jan, and Feb..DJF). Just as it takes time to warm up the water and land in Summer, it takes time for the stored warmth to radiate to space in winter.

And BTW, at least here in NJ, the last two weeks of August are the time when the first cooler airmasses start to feel really good

 

[MeteorWayne]

Bing....it is now the Solstice

 

[3488]

That's true Wayne, our hottest day of the year usually occurs between the 7th & 25th August, sometimes earlier in July, very, very rarely in June, the last time in 2000, before that 1968, last year was the 5th August, so very slightly earlier than normal.

In fact it is more likely to occur in September nearer the Autumn Equinox than the Summer Solsticein June. In 1992, 12th September was the hottest day, 1998, 2002, 2004, also hottest days were in September, it is because as Wayne says the surrounding seas take time to heat up.

Last year on 21st June, it was 19 C / 64 F. On 23rd September it was 27 C / 81 F. It often, though not always pans out like that here.

Another thing I would like to add, is that the earliest Sunrise & latest Sunset do NOT occur on the solstice. Here we had the earliest Sunrise on the 17th June & the latest Sunset will be on the 24th June. However the 21st June is still the longest day. We have something similar in Winter, earliest Sunset 12th December, Shortest Day 22nd December, latest Sunrise 2nd January. This is due to the eccentricity of the Earth's orbit around the Sun, a slightly different issue.

Andrew Brown.