Chapter2 part 2

Question 1

ENSO

Answer 1

(coupled ocean-atmospheric phenomenon)

El Nino - Southern Oscillation

Question 2

ENSO components:

Answer 2

1. Trade Winds
2. Pressure Distribution (zonal distribution)
3. Walker Circulation
4. Precipitation

Question 3

compare between Normal and Elnino

Answer 3

Normal:

• walker circulation
  
  • rise is west and sinks in east (clockwise)
• Pressure system and SST
  
  • Cold upwelling in South america (HIGH) and warm above Australia (LOW)
• trades
  
  • Southeast
• thermocline
  
  • high towards SA and low towards australia
• precipitation
  
  • on the western side

Elnino:

• Walker Circulation
  
  • rise in east and sinking is west
  • Walker circulation either weekns or reverse
• Pressure and SST
  
  • cold above australia (HIGH) and warm SST in central and east pacific equator (LOW)
• trades
  
  • become weeker and may reverse (depending on SST)
• Thermocline
  
  • sinks in east and rises in west
• Precipitation:
  
  • on the eastern side

Question 4

what is thermocline?

Answer 4

Zone of transition (similar to front)

occur in cold water (places of fish)

Question 5

difference between normal circulation and la nina

Answer 5

la nina is stronger than normal circulation (area of thermocline rises near to the surface)

Question 6

Southern Oscillation:

Answer 6

The seesaw variation between the surface atmospheric pressure of the eastern and western pacific

Question 7

what is SOI?

Answer 7

the southern oscillation index

pressure of tahiti - pressure of darwin

Question 8

compare different SOI values

Answer 8

In normal Circulation SOI>0

In El Nino SOI<0

Question 9

to asses the strength of el nino you should

Answer 9

devide the pacific basin into three nino regions (eastern, center, western) the eastern and central witness more significant changes

Question 10

the trade wind charactaristics:

Answer 10

• steady but have inter annual variations (IAV)
• mean velocity 3.6-7.2 m/s
  
  • stronger in winter because the meridional temperature gradient is strong
  • weaker in summer

Question 11

trades layer structure:

Answer 11

• Sub cloud layer (bellow the cloud base)
• cloud layer
• Inversion layer (stable layer with NEGATIVE lapse rate)(Temp increasing w/ht)
  
  • this is called trade wind inversion

Question 12

trade wind inversion location

Answer 12

• Decending branch of the hadley cell and subsidence in the subtropical anticyclone

Question 13

trade wind inversion structure:

Answer 13

two dimentional variation in space (zonal and meridional variation)

• the inversion height and strength vary spacially (2D variation) –> zonally and meridionally

Question 14

compare between zonally and merionally variability

Answer 14

Zonally:

• Height: Inversion increase towards west
• strenth decrease towards west

meridionally:

• Height: Inversion increases towards the equator
• strength: decrease towards equator

subsidence - upwelling cold currents —> more intense

Question 15

formation and maintenece of TWT depends on

Answer 15

the factos that lead to dO-/dz >0 (static stability)

Question 16

factors that contribute to static stability:

Answer 16

1. strong divergence (anticyclone) because of anticyclone it decreases E to W & 30 to the equator
2. sensible heat flux (cold in surface making the air cold above it) its more in the east (air is warmer than the cold ocean currents or cold upwelling water)

Question 17

Factors to distroy (destabilize) TWI

Answer 17

• NORMAL CONDITIONS: warm SST’s to the west (east upwelling and west warmest) lead to:
  
  • More unstable
  • Weakening of TWI
• The presence of Clouds
  
  • through sensible heating
  • turbulent mixing
    
    • turbulent mixing occure only in thunderstorm clouds (trap long wave rad and reflect more radiation from the top)
    • give rise to temperature decrease with height (unstable)
• Descending branch brings warm O- downwards (mixing). the ascending branch brings colder O-‘s upwards. this will cause weekening as the warmer heat flux is directed downwards weakening TWI.
  
  • In clouds in general O- increases with height while temperature decrease with height

Question 18

The ITCZ:

Answer 18

• Region of convergence of the trades from each hemisphere
• thermally generated trough of low pressure

Question 19

structure of ITCZ:

Answer 19

• confluence zone. zone of:
  
  • lowest pressure
  • highest temp
  • max wind
• convergence zone. zone of:
  
  • maximum cloudiness and
  • rainfall

Question 20

distance between confluence and conv.

Answer 20

300 - 1000 km

Question 21

the seperation of the regions of …………. is necessary for the ……….

Answer 21

maximum temperature and pressure (confluence) and maximum cloudiness (divergence) is necessary for the maintenance of the thermal trough

Question 22

speration between regions of maximum temperature and pressure (confluence) and maximum cloudiness (divergence) is necessary for the maintenance of the thermal trough because

Answer 22

maximum cloudiness decreases solar energy (-ve feedback) for mainaining ITCZ

Question 23

explation the seperation of the two zones

Answer 23

1. corriolis force turns the cross equatorial flow anti cyclonically
2. in the regions of maximum anticyclonic curvatire the flow is faster
3. the deceleration of the flow downstream (the same direction the wind is moving) results in convergence before reaching the equatorial trough)

Question 24

the position and movement of ITCZ:

Answer 24

the mean position is 15N and 5 s in northern hemisphere and southern hemispherre in summer

Question 25

What would happen to the ITCZ if the earth surface was uniform:

Answer 25

* the ITCZ would be parallel to the latitude * its annual migration would be symmetric with a reference to the equator

Question 26

the asymetry in the .................... is due to ............

Answer 26

position and migration is due to land - ocean contrast

Question 27

circulation associated with ITCZ:

Answer 27

* trade wind trough (closer to the equator) - trade wind confluence with no directional shift across the trough * monsoon trough: trough with directional shift along the equator

Question 28

......................... is proportional to .....................

Answer 28

the variation of zonal wind with height is proportional to the meridional temperature gradient do ug/do z is proportional to -do T/do y (thermal wind relationship)

Question 29

if temperature decreases poleward

Answer 29

westerlies increase with ht (ug\>0) easterlies decrease with ht (ug\<0)