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Evaluation of diurnal scale precipitation and associated cloud and dynamical processes in observations and
models over central India
Presented byMalay GanaiIITM, Pune
INDIA
Collaborators: Dr. P. Mukhopadhyay, Dr. Phani Muralikrishna, M. Mahakur
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Outline
1. Significance
2. Data used
3. Analysis with Observational data
4. Analysis of Model output
5. Major findings
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Significance..
Bring out the diurnal scale rainfall variability over central Indian region and set up a causal relationship with cloud and dynamical processes.
The study also highlights the diurnal variability of rainfall and cloud processes during active and break period of Indian summer monsoon.
Finally, model (CFSv2) analysis has been carried out to identify its biases.
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Relatively high and homogeneous rainfall variability.
All India Rainfall Index (AIRI) strongly positively correlated with CI.
TCZ establishes at the culmination of onset phase of ISM over this region.
Central India
Hoyos and Webster (2007), Rajeevan et al. (2010), Goswami
(2005)
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Data used Duration Parameters
TRMM 10 years (1999-2008) Rainfall
Kalpana-1 8 years (2005-2012) OLR
MERRA 10 years (1999-2008) Cloud water, cloud ice, MCONV, ω
ISCCP 20 years (1990-2009) Low cloud and High cloud fractions
TRMM VIRS 15 years (1998-2012) Congestus clouds
CFSv2-T126 5 years free run at output frequency of 3 hrs
Model output
CFSv2-T382 Same as T126 Model output
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Observational aspects…
(d)
Rainfall (mmhr-1), OLR (Wm-2), CIMR/CWMR (Kgm-2), High/low cloud (%)
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Moisture convergence (x 10-8 S-1) and vertical velocity (PaS-1) over CI
Moisture convergenceVertical p-velocity
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To investigate the diurnal variability during active (wet) and break (dry) phases of
Indian Summer Monsoon….
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Year
Time series of 10-90 days filtered precipitation anomalies averaged over CI (18N-26N,74E-83E) for JJAS from 1999-2008 using TRMM, normalized by its
standard deviation (3.79 mm day-1 ). Active (break) phases correspond to the index > +1 (< -1).
Goswami and Xavier (2003), Abhik et al. 2013
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During Active (black line) and Break (red line) phases..
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Moisture convergence (x 10-7 S-1) during active (black line) and break (red line) phases
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Vertical velocity (PaS-1) during active (black line) and break (red line) phases
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Model Analysis..
CFSv2-T382CFSv2-T126
OLR is higher in model
Model precipitates earlier than observation
Cloud water and low cloud peaks later than observation
Cloud ice and high cloud show weak diurnal cycle compared to observation
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All the time lighter (0.0-0.5 mmhr-1)category dominates. Afternoon time moderate (0.5-1.5 mmhr-1) rain rate increases
Lighter rain is more all the time than TRMM. Can’t able to separate
moderate and heavy rainfall properly.
Increased resolution possibly is not the only
way out !!!WE NEED TO HAVE
BETTER CLOUD PARAMETERIZATION
SCHEME.
(c)
(b)
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Rain rate (mmhr-1)
OL
R (
Wm
-2)
Scatter plot: OLR vs Rainfall
Observation shows deepening of convection in the afternoon hours.
Model simulated convection is shallower for all the times.
230 Wm-2
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Central IndiaObserved peak
Low Congestus High
Cloud Cloud hydrometeors
Cloud water Ice
1730 IST 1130-1430 1300-1500 1730-2030 1430 IST 1730 IST
Rainfall
Major findings…
The magnitude of diurnal rainfall is influenced by the large scale monsoon regime but the time of peak rainfall is mostly decided by the local forcing.
The CFSv2 (T126 and T382) has significant biases in capturing the diurnal cycles of rainfall and associated clouds and dynamical parameters over central India.
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We have proposed a mechanism which builds a bridge betweendiurnal rainfall variation and its PDF distribution with cloud
and dynamical processes.
Based on the observational findings over CI….
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Enhanced in
solatio
n & m
oisture
Detrainment
Proposed mechanism
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ACKNOWLEDGEMENTS
WWOSC Organizing Committee
Dr. P. Mukhopadhyay
WMO
Director, IITM
Ministry of Earth Sciences, Govt. of India
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