* Indian Institute of Technology, Kharagpur

forestercuckooΜηχανική

27 Οκτ 2013 (πριν από 3 χρόνια και 7 μήνες)

67 εμφανίσεις

Mihir Kumar Dash*, Dhrubajyoti Samanta* and P. C.
Pandey**

* Indian Institute of Technology, Kharagpur

* Indian Institute of Technology, Bhubaneswar

Outline


Introduction



Data and Methodology



Rossby wave breaking
and
circulation over the West Asia




Convective inhibition over the Indian subcontinent




Summary

Indian Institute of Technology, Kharagpur

Introduction

Indian Institute of Technology, Kharagpur

Major

200
-
hPa

circulation

anomalies

accompanied

with

climatological

zonal

wind

(shading

>
15
m)

from

June

to

September

.

The

dotted

line

indicates

the

zero

zonal

wind

line

in

200
-
hPa

Adopted

from

Ding

Q
.

2008



Westerly Jet or wave guide




High Pressure regions

Indian Institute of Technology, Kharagpur

Krishnan et al. 2009



Low over WCI




Blocking high
over south
eastern china

Ten
-
day back trajectories from central India.
Dry
spell for trajectories terminating at 850
(green)
and 700
(red)
hPa

(from
Krishnamurti

et al, 2010)

1
8 June 2009

4
th

August
2009

16
th

July 2002

30
th

August 2001

Indian Institute of Technology, Kharagpur

Western
Asia Dry Air
Incursion

Indian Institute of Technology, Kharagpur

Rossby Wave Breaking

Overturning

of

PV

event

at

350
-
K

PV


(a)
Anticyclonic


(b)

Cyclonic
.

contoured

every

2

potential

vorticity

units
.

From

Strong

and

Magnusdottir
,

2009

Data and Methodology



D
aily
wind
fields (u, v, w)
and
temperature fields
at
eleven different pressure levels at a resolution of 2.5
°

×

2.5
°

from NCEP
-
NCAR reanalysis



Geopotential

height from NCEP

NCAR reanalysis



Precipitation from TRMM

𝐼𝑃𝑉
=


(
𝜁
𝛳
+

)
𝜕𝛳
𝜕𝑝

𝑄
𝐶𝑝
=

(
𝜕𝑇
𝜕𝑡
+
𝑣
.
𝛁
T +
𝛚

𝜕𝑇
𝜕𝑝
)

Indian Institute of Technology, Kharagpur

Climatology of Isentropic
Potential
Vorticity

and
horizontal wind at 350K Level

Indian Institute of Technology, Kharagpur

Sample cases of Rossby Wave
Breaking and intensification of
circulation over the western
India

Potential
Vorticity

and Wind Field anomalies at 350K Over Asia and Africa

Geopotential

Height and Temperature anomalies at 500hPa Over Asia and Africa

Indian Institute of Technology, Kharagpur

Meridional

Cross
-
section of Specific humidity over Central India

Thermodynamics of the upper
-
troposphere

Thermodynamics of the upper
-
troposphere

Hadley Circulation during
Breaking condition

Summary

Rossby Wave
Breaking over the
Western/Western
Central Asia

Formation of
blocking high
over Western
Central Asia

Descending of
dry air from
western and
central Asia
forming a
inversion layer
over Indian sub
-
continent

Modification of
Hadley
circulation over
the Indian
Subcontinent

Suppression
of convection
over the
Indian

subcontinent
and Drought

THANK YOU