FYFD

Tag: mountains

  • Lenticular Landscape

    Lenticular Landscape

    Mountain ridgelines push oncoming winds up and over their peaks, creating the conditions for some spectacular condensation. If the displaced air is moist enough, it cools and condenses into a cloud that appears to hover over the peak. In reality, winds are constantly moving up and over the mountain, condensing into visible cloud where the temperature is cool enough and then morphing back to water vapor once temperatures increase. This process can create stacked lenticular clouds like those seen here. This spot in New Zealand sees lenticular clouds so often that the formation has its own name: Taieri Pet! (Image credit: satellite image – L. Dauphin, b/w – National Library; via NASA Earth Observatory)

    Black-and-white photo of an instance of the Taieri Pet lenticular cloud structure.
    Black-and-white photo of an instance of the Taieri Pet lenticular cloud structure.
  • Jumps in Stratified Flows

    Jumps in Stratified Flows

    One of the factors that complicates geophysical flows is that both the atmosphere and the ocean are stratified fluids with many stacked layers of differing densities. These variations in density can generate instabilities, trap rising or sinking fluids, and transmit waves. The animations above show flow over two ridges with dye visualization (top), velocity (middle), and contours of density (bottom). The upstream influence of the left ridge creates a smooth, focused flow that quickly becomes turbulent after the crest. The jet rebounds as a turbulent hydraulic jump before slowing again upstream of the second ridge. Like the first ridge, the second ridge also generates a hydraulic jump on the lee side. Clearly both stratification and the local topography play a big role in how air moves over and between the ridges. If prevailing winds favor these kinds of flows, it can help generate local microclimates. (Image credit and submission: K. Winters, source videos)