Naked Science Forum

Life Sciences => The Environment => Topic started by: Don_1 on 12/05/2013 01:19:24

Title: What did I say about the British weather?
Post by: Don_1 on 12/05/2013 01:19:24

Back in August 2008, some damn fool joined thisy here forum and posed thisy here question:

http://www.thenakedscientists.com/forum/index.php?topic=16682.msg192114#msg192114
We are being told by marine biologists, meteorologists and a host of others, that the ocean's temperatures are rising. Cited as evidence for this is the retreat of the polar ice caps and migration of fish toward the cooler waters, amongst other natural phenomena.

Would I be right, therefore, in coming to this conclusion?

The higher ocean temperatures result in more evaporation. This increase in evaporation leads to more condensation when the water vapour laden air reaches land causing the increase in cloud cover and precipitation that the British mainland is currently experiencing. As this cloud cover prevents the Sun’s rays from warming the land, the condensation increases, the cloud cover increases and so it goes on in a vicious circle.

If this is correct, can we in Britain expect to see a repetition of this type of summer weather in future years?

Now I don't want to suggest that I was right back then, but.........

I wonder, could the weather itself actually have an effect upon itself? Could the cold air being sucked south from the artic by the jet stream being far to the south, be preventing the jet stream from driftting north?

Title: Re: What did I say about the British weather?
Post by: CliffordK on 12/05/2013 04:26:12

I do believe that heat may cause more precipitation.  However, the hotter the temperature, the more water vapor that can be carried by the air, and thus, perhaps just more vapor, not more rain.

Keep in mind that weather is only one part of "climate". 

This is one of the driest springs we have ever had.  It is rare that I would admit looking forward to the rain in the forecast next week.

Depending on the place, we tend to get more precipitation in the winter than the summer, so it must be more complicated than heat producing rain.

I'm not sure about the jet stream.

Title: Re: What did I say about the British weather?
Post by: dlorde on 12/05/2013 20:31:17

Quote from: CliffordK on 12/05/2013 04:26:12

I do believe that heat may cause more precipitation.  However, the hotter the temperature, the more water vapor that can be carried by the air, and thus, perhaps just more vapor, not more rain.

Yes, it only precipitates as rain when conditions are suitable.

Quote

I'm not sure about the jet stream.

As I understand it, the (circumpolar) jet stream follows the meandering boundary of the cold polar air and the warmer temperate and tropical air, and is driven by the rotation of the Earth and the temperature and pressure differences across the cold/warm air boundary.  The greater the temperature difference, the greater the speed of the jet stream. On the north side of this boundary, you encounter  more of the polar air currents and winds, to the south of it, more tropical winds.

As global temperature rises, the poles are warming faster than the tropics, which is reducing the temperature differential across the jet stream boundary, robbing energy from and slowing the jet stream. As it slows, it tends to meander more, and these meanders move more slowly. In recent times, these meanders have extended further north and south than usual, and have tended to slow to a stall, causing extended periods of unusually cold or warm weather over the corresponding regions.