1. ATOC 4720 class 40: Thermally-driven circulation in tropics
Maintenance of thermal wind equilibrium;
The monsoon circulation;
3. Circulation over the troical oceans: ITCZ;

2. Previous class: Symmetric Hadley Cells (f=0)
High P
Pressure
High P
High P
Low P

3. OBSERVATIONS:
WINTER EQ

4. EFFECT OF ROATION!
Assume an air parcel at EQ, u=0
Westerly winds!
Geostrophic winds: parallel to isobars!

5. Maintenance of thermal wind equilibrium
CF: generate
Motion “along isobars”

6. OBSERVATIONS: monsoon&ITCZ
SUMMER

7. OBSERVED MONTHLY WIND AND PRECIPITATION
JAN
ITCZ
APR
ITCZ
JULY
MONSOON
OCT
ITCZ

8. NCEP winds and satellite TRMM SST
JAN
APR
JULY
OCT

9. Heavy precipitation in the tropics are characterized by:
[1] SST slightly higher than surroundings;
[2]A slight depression (low level low pressure, high level high
pressure (upward bulge) of p surfaces);
[3]Cyclonic flow in the lower and anticyclonic flow in the upper
troposphere;
[4] Lower tropospheric convergence and upper level divergence;
[5]An upward mass-flux with mamximum values in the middle
Troposphere (rising motion);

10. Dynamical and thermodynamial explanations using
the equations we have learnt:
Demonstrate on blackboard;

11. Idealized monsoon circulation: no rotation

12. Realistic surface feature of the monsoon

13. ITCZ: refer to previous figures
Low pressure beult;
Wind convergence; part of Hadley Cell;
Higher SST;
Heavy precipitation;