Chapter 1: Characteristics of tropical regions

Question 1

tropical weather is influenced by

Answer 1

• its geography
• its control over weather systems
  
  • movement and development

Question 2

factors that effect the development and movement of weather in tropics

Answer 2

• the districution of land and water (sea)
  
  • land and sea breeze
    
    • local scale
    • durinal scale
  • monsoon
    
    • large scale
    • seasonal
• the effect of mountain chains on the motion of weather systems
  
  • moonsoon
    
    • hemalaian mountains deflect monsoon wind to keep it in Asia

Question 3

tropical geography:

Answer 3

1. less land in tropics than at higher latitudes (36 % of the earths land mass is in tropics)
   
   1. generate monsoon flows of the tropical zones
   2. provides the moisture that drives the tropical heat engine (moisture releases latent heat)
2. in tropics more land to the north than to the south of the equator
   
   1. brings more rain to the north of the equator due to the formation of heat low over the land
3. the tropical zone has a dissproportionality large amount of high land (more mountain ranges) ex: himalayas, SE asian mountains
   
   1. guid and block the movement of weather systems

Question 4

Major differences between tropics and midlatitude

Answer 4

1. corriolis parameter is small in the tropics
2. weather systems in tropics are dominated by convection and the effects of water vapor and latent heating (in mid latitude dominated by waves)
   because of convection the planetary boundary layer is much deeper in tropics
3. tropopause is much higher and cooler in the tropics
4. sea level pressure exhibits durinal and semi diurinal cycle due to gravitaional and thermal tides in the atmosphere

Question 5

implications of corriolis parameter being small in the tropics

Answer 5

1. winds cannot be assumed geostrophic or quasigeostrophic
2. the relationship (dynamic link) between divergence/ convergence & vorticity tendency is much weaker than in higher latitudes
3. circulations are much larger (in tropics circulation penetrates more into the land)

Question 6

what is the corriolis parameter

Answer 6

f= 2(omega) sin (theta)

omega= 7.292 x 10^-5 s^-1

theta = latitude

Question 7

planetary boundary layer

Answer 7

1 km layer near the surface that is influenced by turbulences. if turbulences and convection is more the height will increase (tropics)

Question 8

tropopause height in the equator and near the poles

Answer 8

13 km

8 km

Question 9

Horizontal momentum equation (simplified) in vector form:

Answer 9

Question 10

Horizontal momentum equation (simplified) in vector form: (explain the terms)

Answer 10

Question 11

if you apply the scale analysis to Horizontal momentum equation

Answer 11

you will see a balance between PGF and corriolis terms. The terms on the RHS are larger. If the ratio between the PGF and corriolis force will determine if the acceleration term can be neglected

Question 12

in the tropic corriolis force is almost

Answer 12

zero

Question 13

Breakdown of geostrophic approximation

Answer 13

(A) acceleration (inertial)

(B) Pressure gradient force ( required for air to move from one place to another)

(C) corriolis force (change with latitude)

Question 14

The rossby number

Answer 14

(R₀) ratio of the inertial force (term A) to the corriolis force (Term C)

Question 15

Express the Rossby number

Answer 15

Question 16

R₀ may be

Answer 16

• <<0
  
  • In extratropics and higher latitudes R₀ almost 0.1 (SYNOPTIC SCALE)
  • corriolis force is large
    
    • inertial forces are unimportant
    • balance between PGF and Corriolis ofrce (Geostrophic balance)
• >>1
  
  • In tropics R>0.1 (SYNOPTIC SCALE)
  • corriolis force is small
    
    • coriois force is unimportant
    • balance between inertial force (acceleration) and pressure gradient force (cyclostrophic balance)
• almost 1
  
  • occure in mesoscale systems (hurricanes, tornadoes) in tropics and extra tropics
  • Corriolis force and inertial force are of the same order
    
    • No term can be neglected
    • gradient wind balance

Question 17

geostrophic approximation validation

Answer 17

• in tropics (NOT VALID)
• in high latitudes (VALID)

Question 18

when wind is geostrophic it follows

Answer 18

isobars (you will be able to measure wind from isobars)

Question 19

isobaric analysis is important in

Answer 19

extra tropics

Question 20

we cannot use isobaric analysis in tropics due to

Answer 20

• lack of simple wind pressure relationship (geostrophic wind relationship)
• pressure gradients are week in tropics

Question 21

instead of isobaric analysis ……………. is used in the tropics

Answer 21

stream line analysis and isotach analysis

Question 22

in tropics we analyse …………

in extratropics we analyse …………

Answer 22

wind

pressure

Question 23

the two most important levels for tropical wind analysis

Answer 23

• the gradient wind level
  
  • the lowest level at which frictional force is not important
  • just above the PBL
  • almost at 850 hpa
• the 200 hPa level

Question 24

stream lines

Answer 24

lines that are parallel to the wind

Question 25

common features in streamline analysis

Answer 25

1. Asymptotes
2. cusps
3. neutral point (col)
4. Influent and outflow
5. cyclone and anticyclone

Question 26

asymptotes

Answer 26

streamlines form with other streamlines

• diffluent
• confliunt

Question 27

cusps

Answer 27

intermediate between a wave and a developing closed circulation

(when you see a cusp expect circulation to form)

Question 28

neutral point (col)

Answer 28

occure at intersection of two asymptotes of opposite sign ( one confliuent one difluent)

Question 29

in the tropics the wind is

Answer 29

ageostrophic which gives rise to convergence and divergence (plays a prominant role in tropics than midlatitude)

Question 30

Divergence and convergence patterns can be infered from

Answer 30

cloud patterns on a sattelite image

Question 31

a distinct cloud feature on a satellite image indicate

Answer 31

a convergent asymptote at low levels

a divergent asymptote at higher levels

Question 32

a large cloud free area indicates

Answer 32

a divergent asymptote at low levels

a convergent asymptote at high levels

Question 33

sunglint on the visible image indicate

Answer 33

(reflection from the surface of the ocean)

• light winds
• can help locate
  
  • ridge axes
  • neutral points

Question 34

absolute vorticity

Answer 34

(ع+f)

Question 35

the synoptic scale vorticity equation can be written as:

Answer 35

d/dt(ع+f)= -(ع+f) -/.v

Question 36

when del . v is

Answer 36

+ve then divergence then (ع+f) decreases

-ve then convergence then (ع+f) increases

Question 37

charactaristics of absolute vorticity in the tropics:

Answer 37

• the absolute vorticity is week (small) in tropics beceause f is small
• a given amount of conv and div will have a much smaller effect on abs vort in tropics than in mid lat
• strong anticyclones are not common in tropics

Question 38

atmospheric tides:

Answer 38

the large amplitude, durinal and semi durinal variation of sea level pressure due to solar heating (not due to gravitational force)

Question 39

solar heating excites

Answer 39

three pressure oscillations having periods 24 hrs, 12 hrs, 8 hrs

all of which differ in horizontal and vertical structure

Question 40

the 12 hr (semi durinal) oscillation:

Answer 40

• the largest amplitude occur at the surface at a range of 1 to 2 mb
• the amplitude decreases with height and is less than 0.5 mb at the tropopause
• the pressure maximum occur at 10 and 22 and the pressure minimum occur at 04 and 16

Question 41

explain how the tidal range varies

Answer 41

• greater near the equator and decreases polewards
• greater overland than over water