Hot tower
Encyclopedia
Tropopause
The tropopause is the atmospheric boundary between the troposphere and the stratosphere.-Definition:Going upward from the surface, it is the point where air ceases to cool with height, and becomes almost completely dry...
, i.e. it reaches out of the lowest layer of the atmosphere, the troposphere
Troposphere
The troposphere is the lowest portion of Earth's atmosphere. It contains approximately 80% of the atmosphere's mass and 99% of its water vapor and aerosols....
, into the stratosphere
Stratosphere
The stratosphere is the second major layer of Earth's atmosphere, just above the troposphere, and below the mesosphere. It is stratified in temperature, with warmer layers higher up and cooler layers farther down. This is in contrast to the troposphere near the Earth's surface, which is cooler...
. In the tropics, the tropopause typically lies at least 15 km above sea level. These towers are called "hot" because they rise high due to the large amount of latent heat released as water vapor condenses into liquid and freezes into ice.
The hot tower hypothesis was proposed in 1958 by Herbert Riehl
Herbert Riehl
Herbert Riehl was a German-born American meteorologist who is widely regarded as the father of tropical meteorology...
and Joanne Simpson
Joanne Simpson
Joanne Simpson was the first woman to ever receive a Ph.D. in meteorology. She eventually became NASA's lead weather researcher and authored or co-authored over 190 articles. Simpson contributed to many areas of the atmospheric sciences, particularly in the field of tropical meteorology...
(then Joanne Malkus) after extensive study of moist static energy
Moist static energy
The moist static energy is a thermodynamic variable that describes the state of an air parcel, and is similar to the equivalent potential temperature. The moist static energy is a combination of a parcels kinetic energy due to an air parcel's temperature, its potential energy due to its height...
profiles in the tropics. Prior to 1958, the mechanism driving the global-scale circulation pattern called Hadley cell
Hadley cell
The Hadley cell, named after George Hadley, is a circulation pattern that dominates the tropical atmosphere, with rising motion near the equator, poleward flow 10–15 kilometers above the surface, descending motion in the subtropics, and equatorward flow near the surface...
s was poorly understood. Riehl and Simpson proposed that the energy feeding these convective
Convection
Convection is the movement of molecules within fluids and rheids. It cannot take place in solids, since neither bulk current flows nor significant diffusion can take place in solids....
cells was supplied by the release of latent heat
Latent heat
Latent heat is the heat released or absorbed by a chemical substance or a thermodynamic system during a process that occurs without a change in temperature. A typical example is a change of state of matter, meaning a phase transition such as the melting of ice or the boiling of water. The term was...
during condensation and subsequent freezing of warm, moist air in areas of convection about 5 kilometres (3.1 mi) wide. The large horizontal extent of these convective cells provides a buffer from the dry air surrounding the convective region that allows the parcel to rise at nearly the moist adiabatic lapse rate. In 2007, the National Aeronautics and Space Administration (NASA) hypothesized that the wind shear
Wind shear
Wind shear, sometimes referred to as windshear or wind gradient, is a difference in wind speed and direction over a relatively short distance in the atmosphere...
between the eye and the eyewall could enhance updraft and be a purely dynamic generator of convection.
Hot towers may appear when the hurricane is about to intensify. A particularly tall hot tower rose above Hurricane Bonnie
Hurricane Bonnie (1998)
Hurricane Bonnie was a major hurricane that made landfall in North Carolina, United States, inflicting severe crop damage. The second named storm, first hurricane, and first major hurricane of the 1998 Atlantic hurricane season, Bonnie developed from a tropical wave that emerged off the coast of...
in August 1998 as the storm intensified before striking North Carolina
North Carolina
North Carolina is a state located in the southeastern United States. The state borders South Carolina and Georgia to the south, Tennessee to the west and Virginia to the north. North Carolina contains 100 counties. Its capital is Raleigh, and its largest city is Charlotte...
, United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
. Bonnie caused more than $1 billion in damage and three deaths, according to the National Oceanic and Atmospheric Administration
National Oceanic and Atmospheric Administration
The National Oceanic and Atmospheric Administration , pronounced , like "noah", is a scientific agency within the United States Department of Commerce focused on the conditions of the oceans and the atmosphere...
and the National Hurricane Center
National Hurricane Center
The National Hurricane Center , located at Florida International University in Miami, Florida, is the division of the National Weather Service responsible for tracking and predicting weather systems within the tropics between the Prime Meridian and the 140th meridian west poleward to the 30th...
.
External links
- Hurricane Multimedia Gallery. - A Hurricane Multimedia page.
- UCAR slides: "Hot Towers and Hurricanes: Early Observations, Theories and Models"