Transcript - Centre for Climate Change Research (CCCR)

Role of Soil Moisture Coupling on the
Surface Temperature Variability Over the Indian Subcontinent
J. Sanjay
M.V.S Rama Rao and R. Krishnan
Centre for Climate Change Research (CCCR)
Indian Institute of Tropical Meteorology (IITM), Pune
(An Autonomous Institute of the
Ministry of Earth Sciences, Govt. of India)
Email: [email protected]
• Soil moisture is a key variable of the climate system
• It is involved in a number of feedbacks at the local,
regional and global scales, and plays a major role in
climate-change projections (Seneviratne et al. 2010)
• In this study we focus on soil moisture-temperature
feedbacks, and their possible modifications with
climate change
• The Indian summer monsoon rainy season (JuneSeptember) is characterized by variations on a wide
range of timescales across diurnal, synoptic,
intraseasonal, interannual and decadal scales
• Surface temperatures over north-central India can
increase rapidly to above-normal values during break
monsoon periods (e.g., Raghavan 1973)
• During recent decades, a significant increase in the
incidence of prolonged monsoon-breaks has been
observed during the core monsoon rainy months of
July and August over India (Ramesh Kumar et al. 2009)
Changing characteristics of break monsoon spells
during the recent three decades
• Active and break events are defined as periods
during the peak Indian monsoon months of July and
August, in which the normalized anomaly of the
rainfall over the monsoon core zone exceeds +1.0 or
is less than −1.0 respectively, provided the
criterion is satisfied for at least three consecutive
days (Rajeevan et al. 2010)
• This methodology was applied to two
observed daily precipitation datasets
• APHRODITE
(Asian Precipitation—
Highly-Resolved Observational Data
Integration Towards Evaluation of Water
Resources ; Yatagai et al. 2012; 0.5o x 0.5o)
• IMD
(India Meteorological Department;
Rajeevan et al. 2005 ; 1o x 1o)
Frequeny of Break Days during the recent 3 decades
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APHRODITE
Observed Active and Break Day Anomaly Composite
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for the recent three decades
Rain
Tair
• Indicates to the role of local feedbacks such as land-atmosphere
coupling in maintaining higher break monsoon temperatures over a
wider region in recent decades
Soil moisture–Air temperature Coupling during Monsoon Season
• Derived using the global multimodel analysis (MMA) of land surface state variables and fluxes
from the Global Soil Wetness Project-2 (GSWP-2; Dirmeyer et al. 2006; 1°X1° grid; 1986-1995)
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• The SM-temperature coupling is
expected to be strongest in
transitional zones between dry and
wet climates where a strong
dependency of ET on SM (ie.,
moisture limited) is superposed
with large mean ET and its
variability (Seneviratne et al., 2010).
Processes contributing to soil moisture–temperature coupling and
feedback loop
Estimations of soil moisture–temperature coupling diagnosed with JJA ρ(E,T)
Role of soil moisture changes for changes in summer
climate variability under different climate regimes
(CTL vs SCEN, i.e present vs future)
• In this hypothetical scenario, the mean seasonal cycle of SM in the
present-climate conditions is largely confined within a range where it
does generally not limit ET (radiation-limited ET regime)
• It shifts to a SM-limiting regime during the summer season under the
future-climate conditions
GSWP-2 MMA Wet and Soil Conditions Anomaly Composite
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Moist to Transitional SM regime
Energy-limited to SM-limited EF regime
• The dry composite shows strong
SM-temperature coupling
In Conclusion
• The latest ensemble of climate models participating in the
Coupled Model Intercomparison Project phase 5 (CMIP-5)
consistently projects significant increases in day-to-day
rainfall variability during Indian summer monsoon season
under unmitigated climate change (Menon et al. 2013)
• Hence this observation-based analysis, by taking into
account the respective period of the summer monsoon
season where SM is most likely to be limiting over some
parts of India, suggests that the sub-seasonal SMtemperature coupling is going to play a dominant role while
assessing the regional climate change impacts on livelihood
• Proper representation of these aspects of landatmosphere interactions in CORDEX RCMs will enhance
the confidence in providing regional climate projections
with them
Many Thanks to:
•
•
CORDEX Workshop Organisers
ICIMOD, Kathmandu, Nepal
Thanks for your attention
Email: [email protected]