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Narration |
Visual |
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rotating earth
[Introductory title]
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Hundreds of miles above us, a fleet of NASA spacecraft constantly scans the Earth.
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One of these has dramatically improved our ability to study severe weather. |
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TRMM, the Tropical Rainfall Measuring Mission, observes weather systems with the world's only space based precipitation radar. |
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TRMM peers down through clouds revealing their internal structure.
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[annotation pointing to "Hurricane Bonnie"]
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Using TRMM measurements, scientists identified a dramatic feature in the structure of Hurricane Bonnie.
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[fade out VIRS, fade in PR]
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Towering rain clouds close to the eye wall nearly reached the
stratosphere. |
["Hot Tower" annotation]
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These structures, called "hot towers", extended higher than commercial jets
fly. |
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Research into these observations has lead scientists to new insights about hurricanes.
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[keep moving around PR] |
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Let's look at the role "hot towers" play in hurricanes. |
[keep moving around PR] |
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A hurricane's eye is an intense low pressure system.
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[illustrations] |
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Near the ocean's surface, air spirals
inward in an attempt to fill the low pressure region. |
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As air nears the eye, it rises rapidly until forced outward at the barrier formed by the warm tropopause. |
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The net effect is a cycle of air moving inward near the ocean surface, upward at the eye wall, and outward at high altitudes. |
[add lines showing ocean and tropopause, maybe cloud cartoon] |
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The air picks up energy from the warm ocean water through evaporation.
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This warm, moist air rises in the eye wall and releases it's energy through condensation, sustaining the hurricane.
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"Hot
towers" act like express elevators accelerating the movement of energy into high altitude clouds. |
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This energy boost tends to strengthen the hurricane.
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What causes these "hot towers" to form? |
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There's a big
difference in wind speeds between the fierce eye wall and the
relatively calm winds inside the eye. |
[add "calm" annotation to center]
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These rapid changes in wind speeds cause instabilities that can spin up intense vortices just inside the eye wall. |
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Near the surface, air spiraling inward collides with these vortices forcing the air upwards creating an updraft.
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[freeze time]
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A very strong updraft in the eye wall carries moisture much higher than normal creating a "Hot Tower". |
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High resolution computer simulations of hurricanes show the formation of "Hot Towers",
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[data fades in]
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In this simulation of Hurricane Bonnie, "Hot Towers" are clearly visible. |
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The arrows show winds swirling near the surface where energy is picked up from the warm ocean. |
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Some of this air moves into the hot
tower and rises rapidly, boosting the
hurricane's strength. |
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But, it's more complicated than that, because hot towers move with the hurricane; and, there are often multiple updrafts.
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[start showing multiple time steps]
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When air passes into a hot tower, it rapidly rises higher. |
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Conditions are more favorable for
vortices to form updrafts on one side of the hurricane because wind
shear amplifies colliding winds in that area. |
[ nadir at start ]
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Wind shear causes these updrafts to weaken in other areas of the eye. |
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Vortices can also pump high
energy air from the eye into the eye wall, boosting the strength of the
updrafts and intensifying the hurricane.
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Scientists have confirmed a connection between hot towers and hurricane
intensification; but, forecasting intensification remains a difficult
problem. |
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Combining
satellite observations with super-computer simulations
provides a powerful tool for studying Earth's complex systems. |
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end credits |
