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I just read that to form a hurricane the sea would need to be at least 26°C warm and a lot of condensation need to occur.
The wikipedia article says:
This makes me wonder, since with all the talk about global warming the number of hurricanes would have to increase.
The wikipedia article says:
Structurally, a tropical cyclone is a large, rotating area of clouds, wind and thunderstorm activity. The primary energy source of a tropical cyclone is the release of the heat of condensation from water vapor condensing at high altitudes. Because of this, a tropical cyclone can be thought of as a giant vertical heat engine.
The ingredients for a tropical cyclone include a pre-existing weather disturbance, warm tropical oceans, moisture, and relatively light winds aloft. If the right conditions persist long enough, they can combine to produce the violent winds, incredible waves, torrential rains, and floods associated with this phenomenon.
This use of condensation as a driving force is the primary difference which distinguishes tropical cyclones from other meteorological phenomena. Mid-latitude cyclones, for example, draw their energy mostly from pre-existing temperature gradients in the atmosphere. In order to continue to drive its heat engine, a tropical cyclone must remain over warm water, which provides the atmospheric moisture needed. The evaporation of this moisture is driven by the high winds and reduced atmospheric pressure present in the storm, resulting in a sustaining cycle. As a result, when a tropical cyclone passes over land, its strength will diminish rapidly.
A hurricane can be viewed as a localized, runaway greenhouse effect. The driving force, the source of the energy, is the sun. The sun warms the water and leads to increased evaporation. Water vapor is an effective greenhouse gas. The heating of the oceanic water is never quite uniform. When locally there is increased temperature, there will be increased evaporation providing a positive feedback mechanism. As the heated air expands and rises, the air pressure is lowered. The air cannot rise indefinitely and will spread at higher altitudes, where the vapor will condense and form clouds. The clouds shield the underlaying water by reflecting the solar radiation. This enhances the localizing effect. The Coriolis effect provides for the circular motion.
The ingredients for a tropical cyclone include a pre-existing weather disturbance, warm tropical oceans, moisture, and relatively light winds aloft. If the right conditions persist long enough, they can combine to produce the violent winds, incredible waves, torrential rains, and floods associated with this phenomenon.
This use of condensation as a driving force is the primary difference which distinguishes tropical cyclones from other meteorological phenomena. Mid-latitude cyclones, for example, draw their energy mostly from pre-existing temperature gradients in the atmosphere. In order to continue to drive its heat engine, a tropical cyclone must remain over warm water, which provides the atmospheric moisture needed. The evaporation of this moisture is driven by the high winds and reduced atmospheric pressure present in the storm, resulting in a sustaining cycle. As a result, when a tropical cyclone passes over land, its strength will diminish rapidly.
A hurricane can be viewed as a localized, runaway greenhouse effect. The driving force, the source of the energy, is the sun. The sun warms the water and leads to increased evaporation. Water vapor is an effective greenhouse gas. The heating of the oceanic water is never quite uniform. When locally there is increased temperature, there will be increased evaporation providing a positive feedback mechanism. As the heated air expands and rises, the air pressure is lowered. The air cannot rise indefinitely and will spread at higher altitudes, where the vapor will condense and form clouds. The clouds shield the underlaying water by reflecting the solar radiation. This enhances the localizing effect. The Coriolis effect provides for the circular motion.
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