M.R.Ramesh Kumar and S Sankar

National Institute of Oceanography

Dona Paula, Goa – 403004

Email: kramesh@nio.org

On Some Aspects of Active and

Break Monsoon Conditions Over

the Indian Subcontient

Rainfall in cmRainfall Over India during Summer Monsoon

Rainfall in cmRainfall Over India during Summer Monsoon

• To identify breaks and active monsoon conditions over

the Indian subcontinent for the period of 1901-2004.

• To identify break and active monsoon conditions over

the Indian subcontinent and compare them with earlier

estimates.

• To study the role of various air sea interaction

parameters on Break and Active monsoon conditions.

• To check whether there is any increasing or

decreasing trend in Breaks or Active monsoon

conditions for the recent decades.

Objectives

• Pentad values of SST, W, PWAT, Evaporation, sensible and latent heat flux from 1988-2002 were extracted from HOAPS (Grassl et al., 2000) More details can be had from www.hoaps.zmaw.de

• Pentad values of Rainfall were extracted from GPCP data. More details can be had from cics.umd.edu/GPCP from 1988-2002.

• Daily OLR data were extracted from www.cdc.noaa.gov/cdc/data.interp_OLR.html for the period 1988-2002.

• High Resolution Daily Rainfall for the period 1901 - 2004

Data

Monsoon Onset over Kerala coast

Synoptic systems (Lows, Depressions,

Cyclonic storms etc)

Active / Break in monsoon conditions

Quantum of monsoon rainfall

Monsoon Variability

Onset Dates Summer Monsoon over the

Indian subcontinent

IMD

Withdrawal Dates of Summer Monsoon

IMD

Monsoon Onset over Kerala (1901-2008)

MONSOON ONSET KERALA

Mean Onset Date : 01 June

Earliest Onset date : 11 May (1918)

Most delayed Onset: 18 June (1972)

Standard Deviation : 8 days

Some statistics of MOK

The number of synoptic systems

such as Lows, Depressions and

Cyclonic systems were maximum in

the years 1980 and 1988, there were

17 each. In addition to giving copious

amount of rainfall to the various

meteorological sub-divisions, they

also help in the progress of the

northern limit of the monsoon.

Synoptic Systems

Tracks of storms during monsoon

IMD

Trends in Monsoon Depression Frequency

y = -0.0675x + 12.058

0

3

6

9

12

15

1891 1901 1911 1921 1931 1941 1951 1961 1971 1981 1991 2001

Dep

ressio

ns (

Ju

n-S

ep

)

y = -0.0295x + 10.984

0

2

4

6

8

10

12

14

16

1891 1901 1911 1921 1931 1941

Dep

ressio

ns (Ju

n-S

ep

)

y = -0.0928x + 8.6548

0

2

4

6

8

10

12

1951 1961 1971 1981 1991 2001

It does not rain everyday within the

monsoon life cycle of 122 days (1st June

to 30th September), some days it rains

quite heavily, such days we call as active

days, some days the rains are quite weak,

these we call it break. During the break

days, the rainfall is quite low over the

entire Indian subcontinent .

ACTIVE BREAK CYCLE

• Ramamurthy ‘s study (1969)of 80 years(1888-1967)

Reveals the following situations responsible for

break.

(i)The migration of the trough to the foothills of the

Himalayas.

(ii)The absence of the low level Easterly winds over

the northern India.

(iii)The increased rainfall activity in the foothills of

Himalaya and decrease of rainfall over rest of the

country.

Traditional definition of break

% of Departure in Rainfall during Break

Ramamurthy (1969)

• Study of 89 years(1901-1989)

(i) Studied the breaks over the Indian

subcontinent using the rainfall over the

monsoon zone, which they feel is a true

representative of the monsoon rainfall.

(ii)Obtained a –ve CC of –0.56 between the

monsoon rainfall and the no. of break days.

Gadgil and Joseph (2003)

Classification of Days

• Break : If rainfall < 9mm/day & persists

for a minimum of 3 days.

• Active : If rainfall >15mm/day & persists

for a day

• Normal : If rainfall > 9mm/day & rainfall

<15mm/day

Ramesh Kumar and Uma (2004)

• Study of 102 years(1901-2002)

(i) Studied the breaks over the Indian subcontinent using the All India Daily Rainfall,which they feel is a true representative of the monsoon rainfall.

(ii)Obtained a –ve CC of –0.78 between the monsoon rainfall and the no. of break days and a + ve CC of 0.59 with active days which is more robust than most of the previous studies.

Ramesh Kumar and Uma (2004)

Duration of

Breaks

(Days)

Ramamurthy

(1969)

Gadgil &

Joseph (2003)

Ramesh &

Uma (2004)

3-4 49.5 44.8 45.4

5-6 19.8 22.8 23.2

7-8 16.2 14.3 11.7

9-10 6.3 6.7 6.1

11-12 4.5 4.8 3.6

13-14 1.0 3.8 3.4

>15 2.7 2.8 2.2

Comparison of the % of duration of breaks.

Year Gadgil &

Joseph (2003)

De et al

(1998)

Krishnan

et al., (2000)

Ramesh &

Uma (2004)

1975 (E) 24-28J 23-25J, 24-26J

1979 (D) 2-6J, 15-31A 17-23J, 15-31A 1-6J, 18-22J, 12-

27A

2-7J,17-20J, 13-

31A

1982(D) 1-8J 1-7J 1-11J, 15-18J,

26-31A

1983(E) 8-9J, 24-26A 22-25A 4-8J 5-10J, 24-28A

1987(D) 16-17J,23-24J,

31J-4A, 11-13A

28J-1A 14J-3A 11-13J, 15J-6A,

8-11A, 15-18A

1988(E) 14-17A 5-8J, 13-15 A 13-16A, 29-31A

Comparison of Break Days for Selected Deficit

(D) & Excess (E) years

Year Webster et al (1998) Joseph &

Sijikumar (2004)

Ramesh &

Uma (2004)

1980 29 May –3 Jun, 14 – 16 Jul ,

15 - 20 Aug

21 Jun – 7 Jul 1 – 3 Jul

1983 18 – 24 Jun, 19 – 22 Jul,

9 – 11 Sept.

11 – 15 Aug 25 – 27 Jul

1986 9 - 14 Jun, 17 - 21 Jul,

5 – 10 Aug, 7 – 10 Sept.

19 – 27 Jun, 16- 21

Jul, 6 –11 Aug

12 – 14 Aug

1988 4 – 8 Jun, 15 – 18 Jul,

21 – 25 Sept

15 – 20 Jul

31 Jul - 2 Aug

16 – 19 Jul

1989 9 – 14 Jun, 21 – 23 Jul,

19 –22 Aug, 15 – 18 Sept

21 – 26 Jul 21 – 25 Jul

Comparison of Active Days for Selected year

Ramesh Kumar and Uma (2004)

Scatter plot of seasonal monsoon rainfall and Break and Active days .

Swapna and Ramesh Kumar (2002)

Swapna and Ramesh Kumar (2002)

Rainfall During Break Monsoon

Composite

Rainfall During Active Monsoon Composite

Rainfall During Active Monsoon

Composite

An event is called IRE, if R is more than 10 cm/day.

Intense Rainfall Events

24 hour Rainfall recorded at

0830IST on 02 July 1984

Colaba - 54cm

Santacruz - 24cm

24 hour Rainfall recorded at

0830IST

on 27 July 2005

Colaba - 7cm

Santacruz - 94cmColaba

Santacruz

Low & Moderate events

Heavy events (>10cm)

V. Heavy events (>15cm)

Goswami et al., 20006

In the Global Warming scenario,the SST of EIO has warmed muchmore than the other tropical oceansduring the period 1950 to thepresent. Indian ocean has warmedthrough about 1.50 C during thisperiod.

Rapid Warming of the EIO

0C

Joseph and Sabin -2008

RAPID WARMING OF EIO 1950 to 2003 (June-

Sept SST 1999-2003 minus 1950-1954)

SST Trend over I.O. during 1951-2008

Ramesh Kumar et al (2009

))))))

((((((

20N030S

))))

((((

TEJSTJ

( )

MHC with its Ascending limb at 20N and descending limb

at 30S shown. With increasing SST near equator when

equatorial convection strengthens, the MHC gets weakened

which weakens both TEJ and STJ.

LLJ

Year July August

Break/Year Break Days/

year

Break./ Year Break days

/ Year

1951-

1960

1.9 9.5 2.4 13.1

1961-

1970

1.6 8.7 1.9 13.7

1971-

1980

1.5 7.1 2.4 13.5

1981-

1990

1.8 9.9 2.5 15.5

1991-

2000

1.7 10.3 2.7 14.8

2001 –

2007

1.7 13.3 2.6 14.4

Decade Type I Type II Total

No. of

Breaks

% of

Type II

to the

total J A T J A T

1951-

1960

15 21 36 3 4 7 43 16

1961-

1970

14 12 26 3 6 9 35 26

1971-

1980

14 18 32 2 5 7 39 18

1981-

1990

15 19 34 3 6 9 43 21

1991-

2000

9 30 39 7 7 14 43 33

2001-

2007

7 12 19 5 4 9 28 32

SST Trend over E.E I.O. during 1951-2008

Ramesh Kumar et al (2009

Ramesh Kumar et al (2009)

VIMT Trend to Peninsular India

during 1951-2008

1. We are likely to get more prolonged

monsoon breaks in the coming

decades, which can lead to droughts.

2. IRE occurrences are on the increase

3. SST over the equatorial Indian ocean

is increasing rapidly

Summary

THANK YOU

Guha Thakurtha P. and Rajeevan M (2008)

INCREASE/DECREASE IN RAINFALL

(MM) IN 100 YEARS

Monsoon Rainfall for 2009

IMD

Monsoon Rainfall for 2009

Monsoon on line (IITM)

Average Rainfall Monsoon Zone and

Active / Break Days for 2009

IMD, Pune

Composite tracks of systems over BB and NWP Ocean for

monsoon months a) June b) July c) August and d) September

during the deficit monsoon years

Ramesh Kumar et al (2009b)

Composite tracks of systems over BBand NWP Ocean for monsoon

months a) June b) July c) August and d) September during the

Excess monsoon years

Ramesh Kumar et al (2009b)

Composite picture of the systems (represented by stars and circles)

formed during the excess (circle) and deficit (star) monsoon years

for the peak monsoon month of July. Values given in each quadrant

are the number of the systems formed and the percentage is given

in the parenthesis. .Number of systems during the excess and

deficit monsoon years are 18 and 35 respectively.

Ramesh Kumar et al (2009b)

Tracks systems over BB in 2009

Tracks systems over NWP in 2009

Causes for the deficit in rainfall in

Monsoon 2009

• One of the important feature of 2009

monsoon season was the relatively

low number of monsoon depressions.

Only 2 depressions formed in Bay of

Bengal .

• The number of convective systems in

the NWP were 18 in number in 2009.

IMD,New Delhi: www.mausam.gov.in

IITM, Pune. www.tropmet.res.in

NIO, Goa: www.nio.org

Some websites with useful Information

Southwest Monsoon – Y.P. Rao

The Monsoons – P.K.Das

Monsoon Dynamics – T.N.Krishnamurti

Monsoon Meteorology – C.S. Ramage

Monographs of India Meteorological

Department, New Delhi.

Some Books on Monsoons