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If the basic driving force in the atmosphere is a difference between high pressure and low pressure, there should be no driving gradient in the jet stream since it is a continuous flow around the world.

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I have a hard problem with using a density difference between daytime and nighttime since the argument can be used to explain flow in either direction.

Probably is a blind shot, but I would like to ask if somebody has calculated the impact in global warming of the direct heat. I am thinking for example in the human population (almost 7 billion with a constant  average temperature of 36.5 º C). And not only that, but the average temperature of all the cattle in the world kept by humans, (billions of animals that otherwise wouldn´t exist). Also we could think in the heat from fires (both wildfires and the small ones) and the heat that escapes from our homes, vehicules or industries.

I spotted these stones used to make walls in Gozo, Malta (see photo). What aspect of composition and weathering led to their distinctive indented appearance?

Richard James, Cardiff, UK

The two trails of cirrus cloud seem to show that there is wind travelling in opposite directions, and are very cleanly separated - is this likely ?

Generally things dry out more slowly the colder it is, yet as soon as winter arrives my hands become so dry the skin splits.

Bernard Marie, Lille, France

When scientists say no snowflake is the same as another and they are all different how did they find this out? What makes them think out of the trillions and trillions of snowflakes that have fallen two aren't the same and how have they proved this?

Sometimes, after a heavy rainfall, while watching a puddle to see if there are still raindrops falling in it, I see a tiny bow wave racing across the puddle as if caused by a flea in a speedboat. What causes this?

Also, if one lives above or below a road, sirens and other traffic noises often vary with the time of day, etc. The standard explanation is diffraction, but maybe others have additional angles or insights to lend.