On global summer monsoonal drought mechanics

  • M. Sankar-Rao
  • S. V. Sachidananda
Article
  • 38 Downloads

Abstract

It is shown that within the framework of a linear five-level quasi-geostrophic steady state global model the middle latitude systems can always have significant influence on the Asian summer monsoonal system through the lower tropospheric monsoonal westerly window region around 80°E. It is hypothesized that quasistationarity of the middle latitude longwave systems results in stronger teleconnections through this window and the consequent monsoon breaks when the phase is right.

Keywords

Monsoon break Rossby waves middle latitudes teleconnections 

List of Symbols

B =

−(RPs/U f Pδ) (1/a) (∂T/∂φ)

b =

−(RPs/U0d2T f PT) (1/a) (∂T0T/∂ Φ)

D

any dependent variable

D

time mean ofD =D0 +D*

D0

zonal mean ofD

D*

Axially asymmetric perturbation part =D exp (im λ)

D

amplitude ofD*

d =

−(RPs/U0Tf PT)

f=

2 Ω sin Φ

K0 =

[(∂T0/∂P) −(RT0/PCp)]−1

l

Ekman friction constant

M =

−(RPs/Uf Pδ)U0 δ gρδ/Ka)

m

longitudinal wave number

N =

RPs/Uf Pδ

P

pressure

Ps

surface standard pressure

S1 =

f2PK0/RPs2

S2 =

[-f2(∂/∂P) (PKA12BC0660)]RPS

S3 =

(1/U0) [(1/a)(∂η0/∂Φ) + (f∂/∂P) (K0/a) (∂T0/∂Φ)]

T

temperature

u

eastward velocity

v

northward velocity

ζ

relative vorticity

η =

f + ζ, the absolute vorticity

λ

longitude

v =

(RPs/U f Pδ) (gPδ l/Ka)

ξ

P/Ps, the usual coordinate in many GCMs

ρ

density

Φ

latitude

Ω

angular velocity of the earth

ω =

dp/dt

2

horizontal spherical Laplacian SuffixesT and δ denote top and bottom of the atmosphere considered

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Copyright information

© Indian Academy of Sciences 1987

Authors and Affiliations

  • M. Sankar-Rao
    • 1
  • S. V. Sachidananda
    • 1
  1. 1.Department of Aerospace Engineering and Centre for Atmospheric SciencesIndian Institute of ScienceBangaloreIndia

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