Some things to notice about this image...
The location of the Tropopause, the red line.
The location of the upper-level jet streaks, the blue lines. Notice how you are looking through the entrance regions of the jet streaks here.
The stability of the Stratosphere compared with that of the Troposphere.
Notice also how the jet streaks are all located in the mid- to upper-Troposphere. You can see how the 3 Tropopause folds occur to the left of the jet streak entrances, which is consistant with what we know about upper-level jet streak circulations in the entrance regions, with convergence and sinking air to the left (left rear quadrant), pulling down the Stratospheric air, and divergence and rising air to the right (right rear quadrant), forcing up the Tropospheric air.
*This image from Lecture 8 notes.
Please note this is an upper-level jet streak.
As air enters the jet streak, PGF becomes dominant, pulling it to the left, causing convergence in the left rear quadrant and divergence in the right rear quadrant. Once the air exits the jet streak, Coriolis becomes dominant, pulling the air to the right, causing convergence in the right front quadrant and divergence in the left front quadrant.
Please also note the Transverse Circulations of the entrance and exit regions. In the entrance, sinking air to the left and rising air to the right causes counterclockwise motion (as you are looking through the jet streak horizontally). This is the formation of the Low Level Jet, or LLJ. This is called a Direct Transverse Circulation because this particular circulation forces warm air to rise and cold air to sink. This also acts to weaken or destroy any thermal gradient in place. In the exit, rising air to the left and sinking air to the right causes clockwise motion (again, looking through the jet streak horizontally). This LLJ circulation is called an Indirect Transverse Circulation, because it forces cold air to rise and warm air to sink. This acts to create or enhance any existing thermal gradient.
Lastly, it should be noted that these Transverse Circulations and the way they create thermal gradients ahead of the jet streak and destroy thermal gradients behind it is what causes the movement of the jet streak itself, not wind advection.
Lastly, in straight-line flow, vorticity is created only by shear. Cyclonic shear to the left of the jet streak causes a vort. max. to form to the left; anticyclonic shear to the right causes a vort. min. to form to the right. PVA occurs ahead of the vort. max. because it is advecting FROM the area of maximum vorticity, and NVA occurs behind it because you are advecting TO the area of maximum vorticity, so it can only advect negatively onto the vort. max. NVA occurs ahead of the vort. min. because you are advecting FROM the area of minimum vorticity, and PVA occurs behind the vort. min. because you are advecting TO the area of minimum vorticity, and it can only be increased by any advections to it.
*I created this image.
This image is again a 300mb jet streak. The difference here is that it is cyclonically curved(NH). Cyclonic shear and cyclonic curvature combine to form a strong vort. max to the left, and anticyclonic curvature roughly negate one another, leaving you with no substantial area of vorticity, and subsequently no substantial vorticity advections to the right. There are also no substantial VV's on the right side. Because of the strong Vort. Max. on the left side, strong PVA occurs ahead of the vort. max. and strong NVA occurs behind it.
*I created this image.
This image is a 300mb jet streak, once again. This jet streak is anticyclonically curved(NH). Anticyclonic shear and cyclonic curvature negate one another on the left, leaving you with no substantial area of vorticity, and subsequently no substantial vorticity advections to the right. There are also no substantial VV's on the left side. Anticyclonic shear and anticyclonic curvature combine to form a strong vort. min. on the right side. Because of this, strong NVA occurs ahead of the vort. min. and strong PVA occurs behind it.
*I created this image.
This image is an 850mb jet streak. Please, PLEASE PLEASE PLEEEEEEEEASE be aware that a lower-level jet streak causes very different results in terms of VV's (vertical velocities). The convergence still occurs in the left rear and right front quadrants, and divergence still occurs in the right rear and left front quadrants. However, in the lower levels, convergence causes air to rise and divergence causes air to sink. Due to this, sinking air happens in the right rear and left front quadrants, and rising air happens in the left rear and right front quadrants.
*I created this image.
.BT
Thanks for the guides
ReplyDeleteYah, no worries mate.
ReplyDeleteabout to take a synoptic test tomorrow... thank you so much for you great help!!!!
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