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Tropical Meteorology > Chapter2 part 2 > Flashcards

Chapter2 part 2 Flashcards

1
Q

ENSO

A

(coupled ocean-atmospheric phenomenon)

El Nino - Southern Oscillation

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2
Q

ENSO components:

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

compare between Normal and Elnino

A

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
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4
Q

what is thermocline?

A

Zone of transition (similar to front)

occur in cold water (places of fish)

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5
Q

difference between normal circulation and la nina

A

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

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6
Q

Southern Oscillation:

A

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

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7
Q

what is SOI?

A

the southern oscillation index

pressure of tahiti - pressure of darwin

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8
Q

compare different SOI values

A

In normal Circulation SOI>0

In El Nino SOI<0

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9
Q

to asses the strength of el nino you should

A

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

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10
Q

the trade wind charactaristics:

A
  • 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
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11
Q

trades layer structure:

A
  • 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
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12
Q

trade wind inversion location

A
  • Decending branch of the hadley cell and subsidence in the subtropical anticyclone
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13
Q

trade wind inversion structure:

A

two dimentional variation in space (zonal and meridional variation)

  • the inversion height and strength vary spacially (2D variation) –> zonally and meridionally
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14
Q

compare between zonally and merionally variability

A

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

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15
Q

formation and maintenece of TWT depends on

A

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

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16
Q

factors that contribute to static stability:

A
  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)
17
Q

Factors to distroy (destabilize) TWI

A
  • 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
18
Q

The ITCZ:

A
  • Region of convergence of the trades from each hemisphere
  • thermally generated trough of low pressure
19
Q

structure of ITCZ:

A
  • confluence zone. zone of:
    • lowest pressure
    • highest temp
    • max wind
  • convergence zone. zone of:
    • maximum cloudiness and
    • rainfall
20
Q

distance between confluence and conv.

A

300 - 1000 km

21
Q

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

A

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

22
Q

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

A

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

23
Q

explation the seperation of the two zones

A
  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)
24
Q

the position and movement of ITCZ:

A

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

25
Q

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

A
  • the ITCZ would be parallel to the latitude
  • its annual migration would be symmetric with a reference to the equator
26
Q

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

A

position and migration is due to land - ocean contrast

27
Q

circulation associated with ITCZ:

A
  • 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
28
Q

……………………. is proportional to …………………

A

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)

29
Q

if temperature decreases poleward

A

westerlies increase with ht (ug>0)

easterlies decrease with ht (ug<0)

Tropical Meteorology (16 decks)

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