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> But several thousand eyars ago the Sahara was arable land. I think the desert status of the Sahara has more to do with a combination of oceanic gyre patterns

by lainga 4y ago

> But several thousand eyars ago the Sahara was arable land. I think the desert status of the Sahara has more to do with a combination of oceanic gyre patterns and the structure of the Hadley circulation. The Sahara and other latitudes around 30N are constantly under a high-pressure zone of descending hot dry air which is part of the northern Hadley cell. The exception is over India where the Eurasian landmass pulls the ITCZ (ascending side of the Hadley cell) way far North and causses the monsoons. I don't think flooding the Sahara would change its aridity any more than the Arabian peninsula, despite being surrounded by water, is still a desert away from the immediate coastline. It's a matter of air moisture, not sea or ground moisture. You could try irrigation, though. The Libyans abortively tried that under Gaddhafi.

lordofgibbons 4y ago
I'm not an expert in any of this but from what I know, portions of the Arabian peninsula sure do get plenty of rain for agriculture from the red sea in the western part. >don't think flooding the Sahara would change its aridity any more than the Arabian peninsula There's something to be said about the lake effect. It certainly happens in U.S and Canada where areas just east of the Great Lakes get much more precipitation than other parts
- lainga 4y ago
  I think the lake effect requires air which is colder than the water. The lowermost level of air warms and accepts water vapor, which immediately rises, re-freezes, and is entrained as ice and blown out onto land. Lake-effect precipitation does form over seas, but you need the air temperature above the surface layer to fall below zero. As for the rain in Saudi Arabia, there is a mountain range along the coast south of Mecca, and I think the area gets rain because of orographic uplift. When the wind blows across the Red Sea it does pick up a lot of moisture, just not enough to cause rain, because the air is so hot and can hold so much moisture overall. But it gets forced up over the mountains, cools, and passes saturation humidity, and the excess water becomes rain. You can see where the mountain range ends on an annual precipitation map of SA. Sorry to rain on your parade.

by lainga 4y ago

lordofgibbons 4y ago

I'm not an expert in any of this but from what I know, portions of the Arabian peninsula sure do get plenty of rain for agriculture from the red sea in the western part. >don't think flooding the Sahara would change its aridity any more than the Arabian peninsula There's something to be said about the lake effect. It certainly happens in U.S and Canada where areas just east of the Great Lakes get much more precipitation than other parts

lainga 4y ago
I think the lake effect requires air which is colder than the water. The lowermost level of air warms and accepts water vapor, which immediately rises, re-freezes, and is entrained as ice and blown out onto land. Lake-effect precipitation does form over seas, but you need the air temperature above the surface layer to fall below zero. As for the rain in Saudi Arabia, there is a mountain range along the coast south of Mecca, and I think the area gets rain because of orographic uplift. When the wind blows across the Red Sea it does pick up a lot of moisture, just not enough to cause rain, because the air is so hot and can hold so much moisture overall. But it gets forced up over the mountains, cools, and passes saturation humidity, and the excess water becomes rain. You can see where the mountain range ends on an annual precipitation map of SA. Sorry to rain on your parade.