2021-03-21
Bluebell flowers carpet the Hallerbos forest floor, Flanders, Belgium (© Jason Langley/plainpicture)
覆盖了Hallerbos森林地面的蓝铃花，比利时佛兰德 (© Jason Langley/plainpicture)
What color do you normally associate with a forest? Well, in the Hallerbos forest of Belgium, that would be blue, for reasons you can clearly see here. For about 10 days every year, usually in late April or early May, this very old forest floor is transformed as bluebell hyacinths wake up from their winter slumber and carpet the forest floor in blue.
Bluebell flowers carpet the Hallerbos forest floor, Flanders, Belgium (© Jason Langley/plainpicture)
覆盖了Hallerbos森林地面的蓝铃花，比利时佛兰德 (© Jason Langley/plainpicture)
What color do you normally associate with a forest? Well, in the Hallerbos forest of Belgium, that would be blue, for reasons you can clearly see here. For about 10 days every year, usually in late April or early May, this very old forest floor is transformed as bluebell hyacinths wake up from their winter slumber and carpet the forest floor in blue.
2021-03-22
Château de Joux in the Jura mountains of France (© Ivoha/Alamy)
汝拉山中的Chateau de Joux堡，法国 (© Ivoha/Alamy)
Overlooking the valley linking France to Switzerland (the Cluse de Pontarlier), Joux castle – with its keep, towers, drawbridges, surrounding walls and fort – offers fantastic evidence of the way fortifications have developed over the years. Built in the 11th century, then modified by Vauban in the 17th century, people will discover 10 centuries of history there.
Château de Joux in the Jura mountains of France (© Ivoha/Alamy)
汝拉山中的Chateau de Joux堡，法国 (© Ivoha/Alamy)
Overlooking the valley linking France to Switzerland (the Cluse de Pontarlier), Joux castle – with its keep, towers, drawbridges, surrounding walls and fort – offers fantastic evidence of the way fortifications have developed over the years. Built in the 11th century, then modified by Vauban in the 17th century, people will discover 10 centuries of history there.
2021-03-23
Satellite image of the Mania River in Madagascar (© NASA Earth Observatory image by Joshua Stevens, using Landsat data from the US Geological Survey)
马尼亚河的卫星图像，马达加斯加 (© NASA Earth Observatory image by Joshua Stevens, using Landsat data from the US Geological Survey)
A satellite view of the Mania River in Madagascar allows us to see a curious cloud pattern. It's common for cool, moist marine air to rise and form dense clouds over bodies of water, then for the clouds to evaporate as they drift over warmer, drier land. The opposite is happening here: Puffs of clouds are forming over land, but not over water. That's because Madagascar's tropical rainforests are warm and wet enough that evaporating moisture rises as the day heats up. When it rises high enough, the moisture encounters cooler air, which condenses the water into clouds. Generally speaking, clouds will form where the air is rising, which in this case is only over the land. Above the river, the air is cooler and descending, so no clouds are forming there.
Satellite image of the Mania River in Madagascar (© NASA Earth Observatory image by Joshua Stevens, using Landsat data from the US Geological Survey)
马尼亚河的卫星图像，马达加斯加 (© NASA Earth Observatory image by Joshua Stevens, using Landsat data from the US Geological Survey)
A satellite view of the Mania River in Madagascar allows us to see a curious cloud pattern. It's common for cool, moist marine air to rise and form dense clouds over bodies of water, then for the clouds to evaporate as they drift over warmer, drier land. The opposite is happening here: Puffs of clouds are forming over land, but not over water. That's because Madagascar's tropical rainforests are warm and wet enough that evaporating moisture rises as the day heats up. When it rises high enough, the moisture encounters cooler air, which condenses the water into clouds. Generally speaking, clouds will form where the air is rising, which in this case is only over the land. Above the river, the air is cooler and descending, so no clouds are forming there.