Challenges in the study of the american monsoon systems
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Challenges in the study of the American Monsoon Systems. Carolina Vera CIMA (UBA-CONICET) DCAO/Facultad de Ciencias Exactas y Naturales Buenos Aires, Argentina. Monsoon societal relevance.

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Challenges in the study of the american monsoon systems

Challenges in the study of the American Monsoon Systems

Carolina Vera

CIMA (UBA-CONICET)

DCAO/Facultad de Ciencias Exactas y Naturales

Buenos Aires, Argentina


Monsoon societal relevance

Monsoon societal relevance

  • A large percentage of the world population live under monsoonclimate,and receive benefits as well as damages from monsoon precipitation and hydrological processes.

  • Most of the countries under monsoon climates are developing countriesor semi-developed countries, where coordination for monsoon seasonal prediction is highly required.

  • Large uncertainties exist in predicting (or projecting) all the regional monsoon climatesassociated with natural & anthropogenic (GHGs increase, aerosol increase, and LCLU changes) forcings due to lack of understanding of the hydro-climate processes of monsoons.

(WCRP/IMS 2008)


Challenges in monsoon system study

Challenges in monsoon system study

  • The monsoon systems are manifested as land-atmosphere-ocean coupled systems, exhibiting a variety of time and space scales that are governed by complex physical processes and their interactions.

(WCRP/IMS 2008)


Multi scale interaction in the tropics and monsoon regions

Multi-scale interaction in the tropics and monsoon regions

Solar forcing

Diurnal

Cycle

Seasonal

Cycle

Subseasonal

Variability

Interanual

Variability

Land-Atmosphere-Ocean Interactions

Orographic forcings

(WCRP/IMS 2008)


Challenges in monsoon system study1

Challenges in monsoon system study

  • Due to our lack of understanding of these processes and interactions, large uncertainties still exist in prediction of the monsoons on local, regional, and continental-scales.

  • Monsoon predictions require better models, and better models require improved physical parameterizations, which in turn require more comprehensive observations. 

(WCRP/IMS 2008)


Challenges in monsoon system study2

Challenges in monsoon system study

  • Since the monsoon systems possess a large range of variability from diurnal to decadal time scales, prediction is a challenging test for the modeling community. 

  • Given the importance of the monsoons in driving the energy and water cycle, improving model physics in monsoon regions will result in better models for other applications such as global change, and water resource assessments.

(WCRP/IMS 2008)


Challenges in the study of the american monsoon systems

Outline

  • Description of some features of the:

    • Seasonal Cycle

    • Diurnal Cycle

    • Intraseasonal Variability

    • Interannual Variability

  • Focusing on:

    • Current ability of global models in describing those features


Challenges in the study of the american monsoon systems

Monsoon Mature phase

NAMS

SAMS

Climatological seasonal mean precipitation (shaded, NCEP reanalysis), & vertically integrated moisture fluxes (arrows, CMAP)

(Vera et al., 2006, J. Climate)


Challenges in the study of the american monsoon systems

Seasonal Cycle of precipitation from WCRP/CMIP3 models

OBS

(1970-1999 period) (Vera et al., 2006, GRL)


Challenges in the study of the american monsoon systems

Surface temperature Bias

DJF

(1979-1999)

(20 Models)

(Vera and Gonzalez, 2008)


Challenges in the study of the american monsoon systems

Summer surface temperature bias in WCRP/CMIP3 models

Multi-model Ensemble Mean – Observed Mean

Observations (CRU)

20 Models

(Vera and Gonzalez, 2008)


Challenges in the study of the american monsoon systems

Precipitation Bias

DJF

(1979-1999)

(Vera and Gonzalez, 2008)


Challenges in the study of the american monsoon systems

Summer precipitation bias in WCRP/CMIP3 models

Observations (CMAP)

(mm/day)

Multi-model Ensemble Mean – Observed Mean (mm/day)

20 Models

(Vera and Gonzalez, 2008)


Diurnal cycle and mesoscale variability

Diurnal Cycle and Mesoscale Variability


Challenges in the study of the american monsoon systems

The Diurnal Cycle in South America

Temporal frequency of cold clouds (infrared brightness temperature Tb 235 K)

Falvey and Garreaud (2008)


Challenges in the study of the american monsoon systems

MCS activity in South America

Subtropical South America has the largest fractional contribution of PFs with MCSs to rainfall of anywhere on earth between 36 N and 36 S

(Zipser et al. BAMS, 2006)


Challenges in the study of the american monsoon systems

MCS activity in South America

05Z ~ 02 LST

MCS event on 17 January 2003

Afternoon (SACZ)

Night (LPB)

MCS mature stage time occurrence frequency. Bars in green represent the period November 15 to December 31, in black January 1 to February 15 (Zipser et al. 2004)


Challenges in the study of the american monsoon systems

Diurnal Cycle – MCS - Synoptic Waves

00 UTC

06 UTC

Frequency of Convection (2000-2003)

SALLJ Days

  • During SALLJ Days:

  • Higher frequency of MCS occurrence (41%)

  • Synoptic waves associated with SALLJ events provide the favorable enviroment for MCS development

  • MCS are bigger and last longer

  • MCS tend to be nocturnal in both SALLJ and NO SALLJ dates over northern Argentina and Paraguay and diurnal over southern Brazil

12 UTC

18 UTC

00 UTC

06 UTC

NO SALLJ

Days

18 UTC

12 UTC

(Salio et al. 2007)


Intraseasonal variability

Intraseasonal Variability


Challenges in the study of the american monsoon systems

Intraseasonal variability in South America

L

H

+ T. anom

- T. anom

H

L

+ T. anom

- T. anom

H

L

Intensified SACZ

Inhibited SALLJ poleward progression

Weakened SACZ

Intensified SALLJ poleward progression

1st EOF leading pattern of 10-90-day filtered OLR variability

Higher frequency of extreme daily rainfall events at the subtropics

(Liebmann, Kiladis, Saulo, Vera, and Carvalho, 2004)

(Gonzalez, Vera, Liebmann, Kiladis, 2007)

Higher frequency of heat waves and extreme daily temperature events at the subtropics

(Cerne , Vera, and Liebmann, 2007)

SOUTH AMERICAN SEE-SAW PATTERN

Nogues-Paegle and Mo (1997)

Diaz and Aceituno (2003)


Challenges in the study of the american monsoon systems

Intraseasonal variability from WCRP/CMIP3 Models

EOF-1 (10-90 days) Filtered OLR

EOF-1 Spectral Density

Regressions EOF-1 & 200-hPa v´

40-60 days

20-40 days

OBS

GFDL

MPI

(González, and Vera, 2008)


Challenges in the study of the american monsoon systems

OBS

GFDL

MPI

LAG -15 Days

LAG -10 Days

Regressions between

EOF-1 (10-90 days Band)

&

OLR´

LAG -5 Days

LAG 0 Days

(González and Vera, 2008)


Challenges in the study of the american monsoon systems

GFDL

MPI

NCEP/NCAR

Day -10

Day -5

Regressions EOF-1 & 850-hPa v´

(Divergence shaded)

Day 0

González, and Vera, 2008)


Interannual variability

Interannual Variability


Challenges in the study of the american monsoon systems

ENSO

Percentage of (c) El Niño and (d) La Niña peaks showing a maximum

amplitude located in the western, central and eastern Pacific

(Leloup et al. 2008)


Challenges in the study of the american monsoon systems

Precipitation Interannual Variability in South America

OND (1970-1999)

OBS

Vera and Silvestri (2008)


Challenges in the study of the american monsoon systems

ENSO

OND (1979-1999)

Correlations between ElNino3.4 SST anomalies and (left) precipitation and (right) 500-hPa geopotential height anomalies. Significant values at 90, 95 and 99% are shaded. NCEP reanalysis data.

(Vera and Silvestri, 2007)


Challenges in the study of the american monsoon systems

ENSO signal in SH Circulation anomalies from WCRP/CMIP3 models

OBS

OND (1970-1999)

Correlations between ENSO index and 500-hPa geopotential height anomalies. Significant values at 90, 95 and 99% are shaded.

Vera and Silvestri (2008)


Challenges in the study of the american monsoon systems

ENSO signal in precipitation anomalies from WCRP/CMIP3 models

OBS

OND (1970-1999)

Correlations between ENSO index and precipitation anomalies. Significant values at 90, 95 and 99% are shaded.

Vera and Silvestri (2008)


Challenges in the study of the american monsoon systems

Southern Annular Mode (SAM)

OND (1979-1999)

Correlations between SAM index and (left) precipitation and (right) 500-hPa geopotential height anomalies. Significant values at 90, 95 and 99% are shaded. NCEP reanalysis data.

Vera and Silvestri (2008)


Challenges in the study of the american monsoon systems

SAM signal in SH circulation anomalies from WCRP/CMIP3 models

OBS

OND (1970-1999)

Correlations between SAM index and 500-hPa geopotential height anomalies. Significant values at 90, 95 and 99% are shaded.

Vera and Silvestri (2008)


Challenges in the study of the american monsoon systems

SAM signal in precipitation anomalies from WCRP/CMIP3 models

OBS

OND (1970-1999) Correlations between SAM index and 500-hPa geopotential height anomalies. Significant values at 90, 95 and 99% are shaded.

Vera and Silvestri (2008)


Challenges in the study of the american monsoon systems

Some of the relevant processes to American Monsoon climate

that need to be better understood and simulated

  • Dynamics over complex terrain like the Andes and the Brazilian plateau

  • Land-Atmosphere interaction (Land use changes)

  • Air-Sea interaction in the surrounding oceans

  • Diurnal cycle of precipitation

    • Diurnal evolution of the PBL

    • Diurnal cycle of the LLJ

  • Feedbacks within the physical climate system (climate & biogeochemical cycles)

  • Cloud related processes and associated phenomena (including aerosol-cloud interactions)


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