Transcript Slide 1

Outstanding Scientific Challenge for the
Proposed Asian Monsoon Year Study
and the Scientific Strategy for its
implementation
Devraj Sikka
40 Mausam Vihar, New Delhi, India
Asian Monsoon System and its
Sub-Systems
• The Asian Summer Monsoon is a Key Element of
General Circulation
• Comes with remarkable regularity
• Exhibits substantial variability on data of arrival (7-12
days in different components), temporal scale of
synoptic, medium Intra seasonal rainfall variability (3-7
days 10-20 days and 30-60 days). Quantum of inter
annual variability, varying from 10-50 percent in different
sub-regions, with profound economic consequences
• Influence extends on large horizontal scale and even on
global climate
• Large system which comprises of South Asian Summer
Monsoon (SASM) East Asian Summer Monsoon
(EASM), South China Sea Summer Monsoon (SCSM)
and Western North Pacific Summer Monsoon (WNPSM)
• All these regional monsoon have their respective subregional characteristics
Somali Coast, Indonesian and Western Pacific Channels are prominent
in Lower Troposphere
Synoptic Disturbances of Asian Monsoon
Regional Monsoon Experiments in India since MONEX
and over South China Sea
• MONTBLEX and LASPEX (1989-96), BOBMEX (199899) and ARMEX (2002-03) in India and South China Sea
Monsoon Experiment (SCSMEX 1996-2001), GEWEX
Asian Monsoon Experiment (GAME 1995 onwards) etc
in East Asian region.
• As a result of research through field progammes great
understanding of Regional Monsoon Systems, their
fluctuations role of land-ocean processes, ISV and IAV
achieved.
• Understanding not resulted in high improvement in
prediction of extreme weather (meso-scale) and extreme
climate events (Intra-annual Scale) some key elements
perhaps missing
• Integration of processes not achieved due to attention
mainly focused on sub-regional processes on Grand
Asian Scale.
Equatorial Cloud Clusters Locked to Madden
Julian Oscillation
Need for Comprehensive Study of All
Component of Asian Summer Monsoon System
• Asian Summer Monsoon System evolves almost simultaneously
during May-September
• Undergoes onset, peak and withdrawal periods at different phases
of the system
• Processes in one component influence the other particularly with
respect to major sub-seasonal oscillations produced by low
frequency modes (10-20 days and 30-60 days) which encompass
synoptic variability.
• The trough (ridge) of the two modes lying in phase enhance
(suppress) convection with same phase lag over different regions as
the 10-20 days mode moves westward from West Pacific toward
Bay of Bengal and 30 day mode moves east wind from India to West
Pacific.
• These two modes are therefore the connecting links between
the two major regions. Hence modulations of different subregional components need deeper study.
Sub-Seasonal Variability, Role of Land
Surface and Aerosols – New Facets
• Sub-seasonal variability of the monsoon in each region
controlled by meso-scale and synoptic scale disturbances
which distribute rainfall.
• Knowledge, particularly on meso-scale, needs considerable
improvement by analyzing these disturbances with respect to
land surface hetrogenities, heating and cooling of land surface
under dry and moist episodes.
• Incursion of dry and dusty air (which may even be
anthropogenically charged with soot particles)
into the
Gangetic Valley, Yangtze Valley and North China under
prolonged dry spells. Indirect Aerosol effect likely to dominate
in mid-season breaks
• Current great interest to understand role of aerosols in spring
heating of the upper troposphere along the foot hills of
Himalayas and Tibet which might impact on the rainfall in early
monsoon season.
Role of Remote SST Forcing (ENSO) and Regional SST Forcing (IOD)
and KUROSHIO (on Asian monsoon)
Need for Targeted Observations over
Specific Areas
• Gangetic Plain and Yangtze Valley (meso-scale)
• South China Sea on Tropical Disturbances and their WNW Passage
(large scale)
• East Tibetan Area – for influence on Meiyu season (meso-scale)
• Tracking of LLJ over West Arabian Sea, South of Sri Lanka, Central
B.B. (Large Scale)
• Indo-China, Yangtze Valley (Large Scale)
• Inter play of Monsoon active-break over India with Meiyu and
N.China Sea Systems (Large Scale)
• Passage of MJO and bifurcating meridionally propagating
convective episodes (Large Scale)
• Passage of westerly troughs north of Tibet and Western Sector of
India (Large Scale)
• Air-sea interactions B.B & SCS regions (medium and large scales)
• Build up of EQUINO and role of ISO on it
• These would help in diagnosing interactions between different
components of sectoral monsoon components
Strategy for Implementation of AMY
• Co-ordination with CTCZ (India), MAIRS, West
Pacific Mahasri and other initiatives.
• Co-ordination
for
Field
Phase
Regional
Managements to implement overall objectives
• Modelling for Better Prediction on meso, synoptic
and Extended Range Scales.
• Information and Data Exchange and Co-ordinated
Research.
• AMY would contribute to WMO/CLIVAR,
THORPEX, CEOP, GEWEX, TMRP
• International co-ordination necessary to
achieve objectives for Integrated Asian
Monsoon Studies on multi-year basis (20082011).
AMY to be a Multi-Year Programme
• Hence active exchange of ideas through
scientific workshops – one or two each
year needed in different participating
countries to keep focus on major research
objectives
• Primary goal of better Predictability
through Modelling Framework
• Success of Program to depend on
Societal
Impacts
through
better
predictability and Water Resource
Management
THANK YOU VERY MUCH