1f. Short Waves in the Upper Atmosphere and Their Effect on Surface
ConditionsWhile Rossby waves play a role in establishing regions of
upper-level divergence and convergence, they are not the only waves in
the atmosphere that do so The atmosphere also contains smaller eddies.
Some of these, called short waves, are smaller ripples superimposed on
the larger Rossby waves. These eddies migrate downwind within the Rossby
waves and exert their own impact on the life cycle of midlatitude
cyclones. Depending on where they are located within the Rossby waves,
they can either enhance or reduce the local divergence or
convergence.The Role of Temperature AdvectionThe formation of short
waves depends on temperature advection, the horizontal transport of warm
or cold air by the wind. Because air in the upper troposphere is well
removed from the direct source of atmospheric heating (the surface),
the temperature changes we experience from day to night are barely
perceptible in the upper atmosphere.Upper-level air changes temperature
very slowly as it moves from one region to another, and air flowing
horizontally from a warm region can retain its high temperature as it
moves into a region otherwise occupied by cold air. We refer to the
horizontal movement of relatively warm air as warm air advection. The
opposite, of course, is called cold air advection. Both types of
temperature advection appear on Rossby waves and, as we wilt see, affect
the development of surface cyclones.FIGURE 10-4-1 Barotropic and
Barodinic Atmospheres. (a) A barotropic atmosphere exists where the
isotherms (the dashed lines showing the temperature distribution) and
height contours (solid lines) are aligned in the same direction. No
temperature advection occurs when the atmosphere is barotropic. A
baroclimc atmosphere occurs where the isotherms intersect the height
contours. Cold air advection is occurring in (b), warm air advection in
(c)....Detecting Warm and Cold Air AdvectionA useful method for
detecting warm and cold air advection on a map of the upper atmosphere
is to compare the orientation of height contours and isotherms. Figure
10-4-1 illustrates three possible patterns of 500 mb height levels and
temperature advection. In Figure 10-4-1a, parallel height contours
(solid lines) are aligned in a west-to-east direction so that a
geostrophic wind flows from west to east. The isotherms (the dashed
lines showing the temperature distribution at the 500 mb level) run
parallel to the height contours and indicate a northward decrease in
temperature. Because the airflow is parallel to the height contours (and
in this case the isotherms), the temperature is the same (just less
than −25 °C) at positions 1 and 2, and there is neither cold nor warm
air advection. When the height contours and isotherms are in alignment,
the atmosphere is said to be barotropic.In Figure 10-4-1b, the height
contours are parallel to each other, as are the isotherms. But in this
instance the height contours and isotherms intersect each other, and the
temperature increases from position 3 (below −25 °C) to position 4
(above −20 °C), This is an example of cold air advection, wherein a
parcel of colder air is transported from 3 to 4. The opposite situation,
warm air advection, occurs in Figure 10-4-1c, where the temperature
decreases in the direction of airflow. When the height contours and the
isotherms intersect, as in both parts (b) and (c), the atmosphere is
said to be barodinic.Effects of Advection in a Rossby WaveRefer to
Figure 10-4-2 and observe the two baroclinic zones at positions 1 (cold
advection) and 2 (warm advection). Where cold advection exists, the
entering air is denser than the air ahead of it because of its lower
temperature. This gives it a negative buoyancy that causes it to sink
downward, bringing cold air toward the surface. Cold air advection
typically occurs behind a cold front, thereby enhancing the temperature
contrast found on either side of the front. Where warm advection occurs,
entering air is warmer and more buoyant than the air ahead of it and
therefore rises. The warm and cold air advection thus cause vertical
motions similar to those associated with statically unstable air
(Chapter 6). This situation is called baroclinic instability, an
important mechanism in creating low pressure at the surface.In addition
to undergoing rising or sinking motions, the air in areas of warm or
cold air advection undergoes a slight turning—to the right in areas of
cold air advection and to the left in regions of warm air advection.
These motions are what cause the ripples (short waves) to form on the
Rossby waves. When a short wave is located downwind of a Rossby wave
trough axis, the divergence is enhanced and surface cyclones
intensify.FIGURE 10-4-2 Warm and Cold Air Advection Around a Rossby
Wave. The air at position 1 flows from colder to warmer air, resulting
in cold air advection. Along a zone of cold air advection, sinking
motions and a turning of the air to the right tend to take place. Warm
air advection occurs at position 2 along with a rising of the
air....What are warm and cold air advection? Get solution
2f. Short Waves in the Upper Atmosphere and Their Effect on Surface ConditionsWhile Rossby waves play a role in establishing regions of upper-level divergence and convergence, they are not the only waves in the atmosphere that do so The atmosphere also contains smaller eddies. Some of these, called short waves, are smaller ripples superimposed on the larger Rossby waves. These eddies migrate downwind within the Rossby waves and exert their own impact on the life cycle of midlatitude cyclones. Depending on where they are located within the Rossby waves, they can either enhance or reduce the local divergence or convergence.The Role of Temperature AdvectionThe formation of short waves depends on temperature advection, the horizontal transport of warm or cold air by the wind. Because air in the upper troposphere is well removed from the direct source of atmospheric heating (the surface), the temperature changes we experience from day to night are barely perceptible in the upper atmosphere.Upper-level air changes temperature very slowly as it moves from one region to another, and air flowing horizontally from a warm region can retain its high temperature as it moves into a region otherwise occupied by cold air. We refer to the horizontal movement of relatively warm air as warm air advection. The opposite, of course, is called cold air advection. Both types of temperature advection appear on Rossby waves and, as we wilt see, affect the development of surface cyclones.FIGURE 10-4-1 Barotropic and Barodinic Atmospheres. (a) A barotropic atmosphere exists where the isotherms (the dashed lines showing the temperature distribution) and height contours (solid lines) are aligned in the same direction. No temperature advection occurs when the atmosphere is barotropic. A baroclimc atmosphere occurs where the isotherms intersect the height contours. Cold air advection is occurring in (b), warm air advection in (c)....Detecting Warm and Cold Air AdvectionA useful method for detecting warm and cold air advection on a map of the upper atmosphere is to compare the orientation of height contours and isotherms. Figure 10-4-1 illustrates three possible patterns of 500 mb height levels and temperature advection. In Figure 10-4-1a, parallel height contours (solid lines) are aligned in a west-to-east direction so that a geostrophic wind flows from west to east. The isotherms (the dashed lines showing the temperature distribution at the 500 mb level) run parallel to the height contours and indicate a northward decrease in temperature. Because the airflow is parallel to the height contours (and in this case the isotherms), the temperature is the same (just less than −25 °C) at positions 1 and 2, and there is neither cold nor warm air advection. When the height contours and isotherms are in alignment, the atmosphere is said to be barotropic.In Figure 10-4-1b, the height contours are parallel to each other, as are the isotherms. But in this instance the height contours and isotherms intersect each other, and the temperature increases from position 3 (below −25 °C) to position 4 (above −20 °C), This is an example of cold air advection, wherein a parcel of colder air is transported from 3 to 4. The opposite situation, warm air advection, occurs in Figure 10-4-1c, where the temperature decreases in the direction of airflow. When the height contours and the isotherms intersect, as in both parts (b) and (c), the atmosphere is said to be barodinic.Effects of Advection in a Rossby WaveRefer to Figure 10-4-2 and observe the two baroclinic zones at positions 1 (cold advection) and 2 (warm advection). Where cold advection exists, the entering air is denser than the air ahead of it because of its lower temperature. This gives it a negative buoyancy that causes it to sink downward, bringing cold air toward the surface. Cold air advection typically occurs behind a cold front, thereby enhancing the temperature contrast found on either side of the front. Where warm advection occurs, entering air is warmer and more buoyant than the air ahead of it and therefore rises. The warm and cold air advection thus cause vertical motions similar to those associated with statically unstable air (Chapter 6). This situation is called baroclinic instability, an important mechanism in creating low pressure at the surface.In addition to undergoing rising or sinking motions, the air in areas of warm or cold air advection undergoes a slight turning—to the right in areas of cold air advection and to the left in regions of warm air advection. These motions are what cause the ripples (short waves) to form on the Rossby waves. When a short wave is located downwind of a Rossby wave trough axis, the divergence is enhanced and surface cyclones intensify.FIGURE 10-4-2 Warm and Cold Air Advection Around a Rossby Wave. The air at position 1 flows from colder to warmer air, resulting in cold air advection. Along a zone of cold air advection, sinking motions and a turning of the air to the right tend to take place. Warm air advection occurs at position 2 along with a rising of the air....Explain what barodinic instability is and where it would be identified on a 500 mb map. Get solution
2f. Short Waves in the Upper Atmosphere and Their Effect on Surface ConditionsWhile Rossby waves play a role in establishing regions of upper-level divergence and convergence, they are not the only waves in the atmosphere that do so The atmosphere also contains smaller eddies. Some of these, called short waves, are smaller ripples superimposed on the larger Rossby waves. These eddies migrate downwind within the Rossby waves and exert their own impact on the life cycle of midlatitude cyclones. Depending on where they are located within the Rossby waves, they can either enhance or reduce the local divergence or convergence.The Role of Temperature AdvectionThe formation of short waves depends on temperature advection, the horizontal transport of warm or cold air by the wind. Because air in the upper troposphere is well removed from the direct source of atmospheric heating (the surface), the temperature changes we experience from day to night are barely perceptible in the upper atmosphere.Upper-level air changes temperature very slowly as it moves from one region to another, and air flowing horizontally from a warm region can retain its high temperature as it moves into a region otherwise occupied by cold air. We refer to the horizontal movement of relatively warm air as warm air advection. The opposite, of course, is called cold air advection. Both types of temperature advection appear on Rossby waves and, as we wilt see, affect the development of surface cyclones.FIGURE 10-4-1 Barotropic and Barodinic Atmospheres. (a) A barotropic atmosphere exists where the isotherms (the dashed lines showing the temperature distribution) and height contours (solid lines) are aligned in the same direction. No temperature advection occurs when the atmosphere is barotropic. A baroclimc atmosphere occurs where the isotherms intersect the height contours. Cold air advection is occurring in (b), warm air advection in (c)....Detecting Warm and Cold Air AdvectionA useful method for detecting warm and cold air advection on a map of the upper atmosphere is to compare the orientation of height contours and isotherms. Figure 10-4-1 illustrates three possible patterns of 500 mb height levels and temperature advection. In Figure 10-4-1a, parallel height contours (solid lines) are aligned in a west-to-east direction so that a geostrophic wind flows from west to east. The isotherms (the dashed lines showing the temperature distribution at the 500 mb level) run parallel to the height contours and indicate a northward decrease in temperature. Because the airflow is parallel to the height contours (and in this case the isotherms), the temperature is the same (just less than −25 °C) at positions 1 and 2, and there is neither cold nor warm air advection. When the height contours and isotherms are in alignment, the atmosphere is said to be barotropic.In Figure 10-4-1b, the height contours are parallel to each other, as are the isotherms. But in this instance the height contours and isotherms intersect each other, and the temperature increases from position 3 (below −25 °C) to position 4 (above −20 °C), This is an example of cold air advection, wherein a parcel of colder air is transported from 3 to 4. The opposite situation, warm air advection, occurs in Figure 10-4-1c, where the temperature decreases in the direction of airflow. When the height contours and the isotherms intersect, as in both parts (b) and (c), the atmosphere is said to be barodinic.Effects of Advection in a Rossby WaveRefer to Figure 10-4-2 and observe the two baroclinic zones at positions 1 (cold advection) and 2 (warm advection). Where cold advection exists, the entering air is denser than the air ahead of it because of its lower temperature. This gives it a negative buoyancy that causes it to sink downward, bringing cold air toward the surface. Cold air advection typically occurs behind a cold front, thereby enhancing the temperature contrast found on either side of the front. Where warm advection occurs, entering air is warmer and more buoyant than the air ahead of it and therefore rises. The warm and cold air advection thus cause vertical motions similar to those associated with statically unstable air (Chapter 6). This situation is called baroclinic instability, an important mechanism in creating low pressure at the surface.In addition to undergoing rising or sinking motions, the air in areas of warm or cold air advection undergoes a slight turning—to the right in areas of cold air advection and to the left in regions of warm air advection. These motions are what cause the ripples (short waves) to form on the Rossby waves. When a short wave is located downwind of a Rossby wave trough axis, the divergence is enhanced and surface cyclones intensify.FIGURE 10-4-2 Warm and Cold Air Advection Around a Rossby Wave. The air at position 1 flows from colder to warmer air, resulting in cold air advection. Along a zone of cold air advection, sinking motions and a turning of the air to the right tend to take place. Warm air advection occurs at position 2 along with a rising of the air....Explain what barodinic instability is and where it would be identified on a 500 mb map. Get solution
