Sorry, but I have a question that I need to get out of my system. The BBC describes the seasons:
Our wonky planet The central axis that goes through the poles is tilted at an angle of 23.5 degrees, so it's not at right angles to the way we're travelling. As we move around the Sun during the year, the amount of light each area of the planet receives varies in length. Here's a description of how the seasons change in the northern hemisphere. (If you live in the southern hemisphere, then you need to reverse the seasons). |
| Summer The day the north pole is nearest the Sun is called the 'summer solstice'. (You can see this from the picture on the right). Looking from Earth, the Sun reaches its highest point in the sky all year. This means it takes the most amount of time to cross the sky. So this is the longest day of the year and happens around 21 June. Astronomers call this the start of summer and after this date, days start getting shorter. Autumn As we continue our journey around the Sun, the north pole moves away from the Sun. The Sun rises lower in the sky so the days continue getting shorter. When the Sun is at its mid-point in the sky, we reach the 'autumn equinox', around 22 September. Day and night are both 12 hours long and its the beginning of autumn. Winter The day when the north pole is furthest from the Sun is called the 'winter solstice'. The Sun crosses the sky at its lowest point all year. Therefore it crosses the sky in the quickest time so this is the shortest day of the year. Winter solstice happens around 22 December and marks the start of winter. From then on, the days start getting longer. Spring The Earth continues on its path, and our north pole starts moving towards the Sun again. The Sun moves upwards in our skies and the days continue getting longer. Again, we reach a midpoint when day and night are both 12 hours long. This is called the 'vernal (or spring) equinox' and happens around 21 March. |
I understand how the dates of the equinoxes and solstices were determined and I'm okay with that. But how about the season start dates? We use different ways to define the seasons. Take summer for instance. If we define "summer" by its day lengths, wouldn't that make June 21 the middle of summer in the northern hemisphere? Shouldn't the longest day of the year be the middle of summer? What do you think about that?
What if we use another measure, say temperature. Well, I've lived in Vermont, Utah, and California and I would have to say that the 3 warmest months in each of those states are July, August, and September. So I guess saying that June 21 is the first day of summer is acceptable if you're measuring the seasons by temperature.
If you are a gardener or farmer, when do you plant your crops? If you go by average last frost dates, for many states, it's usually safe to plant your summer veggies during some time in May. The growing season is usually June, July, August, and September. Okay, I guess June 21 as the start of summer is good for growing too.
Why am I thinking about the seasons? Well, the main reason is because I'm upside down. I just left the Indian Summer of California and I'm headed into Summer Down Under. The SF Bay Area is at 37.7* North latitude, Los Angeles at 34*, and Sydney is at 33.9* South latitude, Melbourne at 38*. We both have Mediterranean like weather with dry summers and wet winters. (One of the reasons why I'm so into Australian plants. They do so well in California!) So I figured that the weather would be similar to that in Cali. And so it might be. I haven't been here long enough to see and people are telling me that the weather we've been having since I got here 3 weeks ago, is not typical. All I know is, it's raining a lot and when the sun is shining, it's hot and humid (60%! I really liked how dry it was in Utah.). And it's only November 14, "spring". What's summer gonna be like?!
Let me know what you think!
Cyn
PS: Australia is the only (?) country where the seasons start on the first of the month and not on the 21st or 22nd.
PPS: In the tropical northern parts of Australia, there are really only 2 seasons, the wet and the dry (May-November).
I have no idea hahaha
ReplyDeleteHi Cyn, this is Nick. I'm not a climatologist, but I'm pretty sure there is a big thermal lag combined with ocean effects that causes the summer to lag the solstice by a considerable margin and accounts for the humidity differences. It's the same reason why London has a dramatically different climate to Moscow, despite it being on the same latitude.
ReplyDeleteThe thing that really freaked me about the southern hemisphere is the fact that the sun goes backwards across the sky. It took me a while to figure out what was going on!
Loving the blog. Keep it up!
Hi Cyn, this is Linda. I'm not sure what he's talking about, but it's November 12, and the high today was 80 degrees and the humidity was 84%, according to the weather app, and it was a very very pleasant day. How hot is it there?
ReplyDeleteSorry, I didn't understand anything Nick wrote. Maybe if I read it 10 more times I'll figure it out. 30*C, which is 86*F and 70% humidity. Way too sticky and a little too hot for me. Gorgeous except for about 2 hours. It rained for about 30 minutes. And Linda, it can't be the 12th. I might be across the International Date Line but not more than 24 hours!
ReplyDeleteHmmm. Don't know about the date thing. Possible I mixed that up, though I'm pretty sure you're 12 hours ahead, give or take.
ReplyDelete