monsoon variability of the past · 2020-05-08 · the role of water vapor and cloud feedback on the...

The role of water vapor and cloud feedback on the evolution of the Indian summer monsoon

over the last 22,000 years

Chetankumar Jalihal

Guided by: Prof. J. Srinivasan &Prof. Arindam Chakraborty

jalihal@iisc.ac.in Indian Institute of Science

mailto:jalihal@iisc.ac.in

Short version

OBJECTIVE

DIFFERENT SENSITIVITY OF

MONSOON TO INSOLATION

1

TraCE21K simulation

Model: CCSM3, fully coupled ESM, with transient boundary conditions,3.75ᵒ x 3.75ᵒ

Duration: 22 Kyrs

OBJECTIVE

OBJECTIVE

Identify the feedbacks.

Quantify the role of forcings and feedbacks.

2

𝑮𝑴𝑺 = −𝑃

𝐵

𝑃𝑇𝑼.𝛁𝒎 + 𝝎

𝜕𝒎𝜕𝑝

𝑑𝑝

𝐿𝑣 𝑃𝐵

𝑃𝑇𝑼.𝛁𝒒 + 𝝎

𝜕𝒒𝜕𝑝

𝑑𝑝

𝑷 − 𝑬 =𝑸𝒅𝒊𝒗𝑮𝑴𝑺

METHOD

ENERGETICS FRAMEWORK(Neelin & Held 1987; Raymond 2009)

3

Net energy flux into atmosphere

Gross Moist Stability

RESULTS

GMS IS A UNIQUE FUNCTION OF

WATER VAPOR

4

𝑷 − 𝑬 =𝑸𝒅𝒊𝒗𝑮𝑴𝑺

𝑷 − 𝑬 =𝑸𝒅𝒊𝒗

ൗ𝟖𝟎. 𝟒 𝑪𝑾𝑽 − 𝟏. 𝟑

Jalihal et al. (2019) Nat. Comm.

RESULTS

(P-E) OVER THE LAST 22,000 YRS

5

𝑷 − 𝑬 =𝑸𝒅𝒊𝒗

ൗ𝟖𝟎. 𝟒 𝑪𝑾𝑽 − 𝟏. 𝟑

Jalihal et al. (2019) Nat. Comm.

RESULTS

QDIV DRIVES (P-E) DURING

HOLOCENE

6

𝑷 − 𝑬 =𝑸𝒅𝒊𝒗

ൗ𝟖𝟎. 𝟒 𝑪𝑾𝑽 − 𝟏. 𝟑

CWV fixed at pre-industrial values.

Jalihal et al. (2019) Nat. Comm.

RESULTS

WATER VAPOR PLAYS CRUCIAL

ROLE DURING DEGLACIAL

7

𝑷 − 𝑬 =𝑸𝒅𝒊𝒗

ൗ𝟖𝟎. 𝟒 𝑪𝑾𝑽 − 𝟏. 𝟑

Qdiv fixed at pre-industrial values.

Jalihal et al. (2019) Nat. Comm.

RESULTS

GREENHOUSE GASES AND ICE

SHEETS AFFECT GMS ALONE

8

𝑷 − 𝑬 =𝑸𝒅𝒊𝒗

ൗ𝟖𝟎. 𝟒 𝑪𝑾𝑽 − 𝟏. 𝟑GHG and ice sheets do not influence Qdiv

Jalihal et al. (2019) Nat. Comm.

Qdiv

(m

m d

ay

-1)

Qdiv

(m

m d

ay

-1)

RESULTS

ORBITAL FORCING AFFECTS BOTH

GMS AND QDIV

9

𝑷 − 𝑬 =𝑸𝒅𝒊𝒗

ൗ𝟖𝟎. 𝟒 𝑪𝑾𝑽 − 𝟏. 𝟑

Even though both Qdiv and GMS are influenced, GMS is dominant, when boundary conditions are that of LGM.

Jalihal et al. (2019) Nat. Comm.

Qdiv

(m

m d

ay

-1)

Energy available

GHG & Ice sheets

Total column water vapor

Surface temperature

Precipitation

1 2

1 - Dominant during the Deglacial

2 - Dominant during the Holocene

Insolation

Jalihal et al. (2019) Nat. Comm.

Long version

MOTIVATION

INSOLATION OVER LAST 22,000 YRS

1

HoloceneDeglacial

Summer insolation over India

MOTIVATION

THIS VARIATION IS DUE TO

PRECESSION OF EARTH

1

HoloceneDeglacial

23,000 yrs

OBJECTIVE

DIFFERENT SENSITIVITY OF

MONSOON TO INSOLATION

2

TraCE21K simulation

Model: CCSM3, fully coupled ESM, with transient boundary conditions,3.75ᵒ x 3.75ᵒ

Duration: 22 Kyrs

OBJECTIVE

DIFFERENT SENSITIVITY OF

MONSOON TO INSOLATION

2

Deglacial forcings: Insolation greenhouse gasesice sheets

Holocene forcings: Mainly insolation

OBJECTIVE

OBJECTIVE

Identify the feedbacks.

Quantify the role of forcings and feedbacks.

3

Method

4

Based on the equations for conservation of moisture & Moist Static Energy.

න

𝑃𝑡

𝑃𝑏

𝑈. 𝛻𝑚 + 𝜔𝜕𝑚

𝜕𝑝𝑑𝑝 = 𝑔[𝐹𝑏 − 𝐹𝑡]

න

𝑃𝑡

𝑃𝑏

𝑈. 𝛻𝑞 + 𝜔𝜕𝑞

𝜕𝑝𝑑𝑝 = 𝑔[𝐸 − 𝑃]

m - Moist Static Energy;

(m = Cp*T + g*Z + Lv *q)

Fb - Bottom Fluxes

Ft - Fluxes at Top of Atm.

u - x component of velocity

METHOD

ENERGETICS FRAMEWORK

q - Specific Humidity (kg/Kg)

ω - Vertical velocity (Pa/s)

Pb - Surface Pressure

Pt - Top Pressure

v - y component of velocity

5

𝑷 − 𝑬 =𝑸𝒅𝒊𝒗𝑮𝑴𝑺

METHOD

ENERGETICS FRAMEWORK(Neelin & Held 1987; Raymond 2009)

6

𝑮𝑴𝑺 = −𝑃

𝐵

𝑃𝑇𝑼.𝛁𝒎+ 𝝎

𝜕𝒎𝜕𝑝

𝑑𝑝

𝐿𝑣 𝑃𝐵

𝑃𝑇𝑼.𝛁𝒒 + 𝝎

𝜕𝒒𝜕𝑝

𝑑𝑝

𝑮𝑴𝑺 = −𝑃

𝐵

𝑃𝑇𝑼.𝛁𝒎 + 𝝎

𝜕𝒎𝜕𝑝

𝑑𝑝

𝐿𝑣 𝑃𝐵

𝑃𝑇𝑼.𝛁𝒒 + 𝝎

𝜕𝒒𝜕𝑝

𝑑𝑝

𝑷 − 𝑬 =𝑸𝒅𝒊𝒗𝑮𝑴𝑺

METHOD

ENERGETICS FRAMEWORK(Neelin & Held 1987; Raymond 2009)

6

Net energy flux into atmosphere (top + bottom)

Over land net surface energy fluxes are small.

𝑷 − 𝑬 =𝑸𝒅𝒊𝒗𝑮𝑴𝑺

METHOD

ENERGETICS FRAMEWORK(Neelin & Held 1987; Raymond 2009)

6

m

ω𝑮𝑴𝑺 = −

𝑃𝐵

𝑃𝑇𝑼.𝛁𝒎 + 𝝎

𝜕𝒎𝜕𝑝

𝑑𝑝

𝐿𝑣 𝑃𝐵

𝑃𝑇𝑼.𝛁𝒒 + 𝝎

𝜕𝒒𝜕𝑝

𝑑𝑝

Gross Moist Stability.

Primarily depends on vertical profile of m and ω

𝑮𝑴𝑺 = −𝑃

𝐵

𝑃𝑇𝑼.𝛁𝒎 + 𝝎

𝜕𝒎𝜕𝑝

𝑑𝑝

𝐿𝑣 𝑃𝐵

𝑃𝑇𝑼.𝛁𝒒 + 𝝎

𝜕𝒒𝜕𝑝

𝑑𝑝

𝑷 − 𝑬 =𝑸𝒅𝒊𝒗𝑮𝑴𝑺

METHOD

ENERGETICS FRAMEWORK(Neelin & Held 1987; Raymond 2009)

6

m

ω

Qdiv = TOA_Net_SW - TOA_OLR + SFC_RAD + SHF + LHF

TOA_Net_SW- Net Short Wave at Top of Atm

TOA_OLR - Net Outgoing Longwave Radiation

Qnet

RESULTS

A CLOSER LOOK AT QDIV

7

Qdiv over land is influenced by insolation and cloud radiative feedback.

Results

8

RESULTS

GMS IS A UNIQUE FUNCTION OF

WATER VAPOR

9

Jalihal et al. (2019) Nat. Comm.

RESULTS

GMS IS A UNIQUE FUNCTION OF

WATER VAPOR

9

𝑷 − 𝑬 =𝑸𝒅𝒊𝒗𝑮𝑴𝑺

𝑷 − 𝑬 =𝑸𝒅𝒊𝒗

ൗ𝟖𝟎. 𝟒 𝑪𝑾𝑽 − 𝟏. 𝟑

Jalihal et al. (2019) Nat. Comm.

RESULTS

(P-E) OVER THE LAST 22,000 YRS

10

𝑷 − 𝑬 =𝑸𝒅𝒊𝒗

ൗ𝟖𝟎. 𝟒 𝑪𝑾𝑽 − 𝟏. 𝟑

Jalihal et al. (2019) Nat. Comm.

RESULTS

QDIV DRIVES (P-E) DURING

HOLOCENE

10

𝑷 − 𝑬 =𝑸𝒅𝒊𝒗

ൗ𝟖𝟎. 𝟒 𝑪𝑾𝑽 − 𝟏. 𝟑

CWV fixed at pre-industrial values.

Jalihal et al. (2019) Nat. Comm.

RESULTS

WATER VAPOR PLAYS CRUCIAL

ROLE DURING DEGLACIAL

10

𝑷 − 𝑬 =𝑸𝒅𝒊𝒗

ൗ𝟖𝟎. 𝟒 𝑪𝑾𝑽 − 𝟏. 𝟑

Qdiv fixed at pre-industrial values.

Jalihal et al. (2019) Nat. Comm.

Role of different forcings

11

RESULTS

GREENHOUSE GASES AFFECT GMS

ALONE

12

𝑷 − 𝑬 =𝑸𝒅𝒊𝒗

ൗ𝟖𝟎. 𝟒 𝑪𝑾𝑽 − 𝟏. 𝟑

GHG does not influence Qdiv

Jalihal et al. (2019) Nat. Comm.

Qdiv

(m

m d

ay

-1)

RESULTS

ICE SHEETS AFFECT GMS ALONE

13

𝑷 − 𝑬 =𝑸𝒅𝒊𝒗

ൗ𝟖𝟎. 𝟒 𝑪𝑾𝑽 − 𝟏. 𝟑

Ice sheets do not influence Qdiv

Jalihal et al. (2019) Nat. Comm.

Qdiv

(m

m d

ay

-1)

RESULTS

ORBITAL FORCING AFFECTS BOTH

GMS AND QDIV

14

𝑷 − 𝑬 =𝑸𝒅𝒊𝒗

ൗ𝟖𝟎. 𝟒 𝑪𝑾𝑽 − 𝟏. 𝟑

Even though both Qdiv and GMS are influenced, GMS is dominant.

Jalihal et al. (2019) Nat. Comm.

Qdiv

(m

m d

ay

-1)

RESULTS

ORBITAL FORCING WITH GLACIAL

BOUNDARY CONDITIONS

15

𝑷 − 𝑬 =𝑸𝒅𝒊𝒗

ൗ𝟖𝟎. 𝟒 𝑪𝑾𝑽 − 𝟏. 𝟑

ORB: orbital parameters only. Constant LGM values for all other boundary conditions.

During cold periods, orbital forcing drives monsoon through GMS.

Jalihal et al. (2019) Nat. Comm.

Qdiv

(m

m d

ay

-1)

Energy available

Precipitation

1 2

Insolation

GMS

1 - Dominant during the Deglacial

2 - Dominant during the Holocene

Jalihal et al. (2019) Nat. Comm.

Energy available

GHG & Ice sheets

Precipitation

1 2

1 - Dominant during the Deglacial

2 - Dominant during the Holocene

Insolation

GMS

Jalihal et al. (2019) Nat. Comm.

Energy available

GHG & Ice sheets

Total column water vapor

Surface temperature

Precipitation

1 2

1 - Dominant during the Deglacial

2 - Dominant during the Holocene

Insolation

Jalihal et al. (2019) Nat. Comm.

Conclusions

19

CONCLUSIONS

CONCLUSIONS

• Changes in insolation is an initial trigger, final response involves feedbacks as well.

• Water vapor feedback amplifies solar forcing during deglacial.

• Cloud radiative feedback influences monsoon during Holocene.

20

CONCLUSIONS

CONCLUSIONS

• Insolation can drive monsoon through two different pathways.

• Greenhouse gases and ice sheets only affect GMS.

20

• Through energy available during warm periods, and through GMS during cold periods

Thank you

21

Extra Slides

22