Continental Tropical Convergence Zone CTCZ Programme

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Continental Tropical Convergence Zone (CTCZ)
Programme under the Indian Climate Research
Programme (ICRP)
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(No Transcript)
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Main Focus

• Understanding monsoon variability on timescales
  ranging from sub-seasonal to inter annual and
  decadal, and its impact on critical national
  resources
• Observational
• Modeling
• Data Analysis
• Inter-Agency Multi-Institutional

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ICRP Experiments
Bay of Bengal Monsoon Experiment (BOBMEX)
1998-1999 Arabian Sea
Monsoon Experiment (ARMEX)
Jun-Aug 2002, Mar - June 2003 , April-May 2005
1998
July 26, 2005 Mumbai 940 mm
BOBMEX 1998-99 Air-sea Coupling Rapid SST
Recovery Northward Propagation North-South
gradients (Bhat et al, BAMS, 2001)

• ARMEX 2002-2003, 2005
• Intense Rainfall Events on WC
• Warm pool build up Collapse
• Monsoon Onset over Kerala
• Mausam Jan. 2005 (Special Issue)

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ORV Sagar Kanya
Indian Oceanographic Research Vessel 110 m
long 31 Scientists 65 Crew
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North Bay SST- maintenance
OLR, Rainfall (GPCP) (shaded) (cont.)
June-Sept. 1978-95

• Maximum Precipitation
• Region of highest clouding in the
  entire region
• Cloud systems - Cut off solar radiation
• Wind speed
  generally increases
• SST decreases
• How SST is
  maintained above the
• threshold
  level (28oC)
• Top fresh water layer shallow mixed layer
• (solar
  penetration, Debasis, et al.
• 
  GRL, 2002)

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ARMEX 1. Intense Rainfall
Events on West Coast 2. Warm pool dynamics
Year 1998
(Source NIOT Buoy data)
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Temp
salinity
Density
(ARMEX BOBMEX)
Differences in the Ocean Mixed Layer North Bay
and Arabian Sea (AS)
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BAY weak winds High RH
lower LHF NLW
AS Winds stronger Lower RH
High LHF
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• Continental Tropical Convergence Zone (CTCZ)
  Programme
• under the
• Indian Climate Research Programme (ICRP)
• Pilot2008
• Main expt from 2009

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Fig 1a INSAT picture of the CTCZ on an acttive
monsoon day7 August 2007
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Fig 1b Winds at 1.5 km above sea-level on 7
August 07
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Figure 2 Average June-September rainfall the
approximate limits of the monsoon zone indicated
by red dashed lines
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• The major objective the CTCZ programme of the
  Indian Climate Research Programme is to
  understand the mechanisms leading to space-time
  variation of the CTCZ and the embedded monsoon
  disturbances during the summer monsoon.

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• A multiscale approach with study of the major
  interacting scales viz. planetary, regional,
  synoptic and mesoscale is essential. For
  adequate observations on all important
  time-scales from diurnal to intraseasonal and
  interannual, a multi-year programme is required.

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Science foci and objectives

• A. Phenomena
• a Links of monsoon variability with the
  convection over the surrounding oceans

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• to understand the underlying mechanisms of the
  three basic elements of the variation of
  convection over the ocean on synoptic and larger
  scales viz.
• genesis of synoptic scale cloud systems over the
  warm oceans around the subcontinent
• fluctuations in the intensity of the TCZ
• propagations of the synoptic scale systems and
  of the TCZ emanating from
• the oceanic regions
• (iv) the variation of convection over the
  critical regions of the (i) Bay of Bengal and
  eastern Arabian Sea and (ii) equatorial Indian
  Ocean EEIO, WEIO, on intraseasonal and
  interannual scales

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Active spells, weak spells and monsoon breaks
Fig. 3 Variation of the daily rainfall over
central India during June-September 1972,75
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b Important phases of the monsoon

• Unravelling the factors that determine the
  life-span of active and weak spells of the CTCZ
  and
• Understanding the role of land hydrological
  feedbacks and aerosols in the transitions between
  active and weak spells and hence the life-span of
  these spells.

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B Process studies

• Under the CTCZ programme, detailed studies of
  such processes specific to the CTCZ such as the
  atmosphere- hydrosphere biosphere feedbacks (in
  which land surface processes, and aerosols will
  be important) are planned. The focus will be on
  features of the variation/ events (such as active
  spells and breaks, propagation of systems) in
  which these processes play an important role.
  Special observational sites will be located in
  regions which are considered critical for
  understanding such processes and events.

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Hot Spots
Fig.4. Regions over which variation of soil
moisture has an impact on rainfall (derived from
12 atmospheric general circulation models
participating in GLACE the Global Land
Atmosphere Coupling Experiment)
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(ii) Aerosols role in the variability of the
monsoon

• Elucidation of the space-time variation of
  aerosols particularly over regions which are
  considered to be critical for impact on the
  monsoon, of aerosol sources and sinks, aerosol
  life cycles in clouds, impact of aerosols on
  atmospheric radiation, is one of the objectives
  of the CTCZ

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(iii) Interaction between different scales of
convection

• In the observational programme, a major goal will
  be the elucidation of the nature of the cloud
  systems in the CTCZ. The microphysics of warm and
  cold clouds, the characteristics of the meso and
  synoptic scale cloud systems in the CTCZ will be
  studied. Special observations aimed at
  elucidating the nature and variation of cloud
  condensation nuclei and aerosols (natural and
  anthropogenic) over the land and some oceanic
  regions, and cloud microphysics and
  aerosol-cloud-precipitation interactions are
  planned.