Evaluation of diurnal scale precipitation and associated cloud and dynamical processes in observations and models over central India Presented by Malay Ganai IITM, Pune INDIA Collaborators: Dr. P. Mukhopadhyay, Dr. Phani Muralikrishna, M. Mahakur

Outline 1.Significance 2.Data used 3.Analysis with Observational data 4.Analysis of Model output 5.Major findings

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.

 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)

Data usedDurationParameters TRMM10 years ( )Rainfall Kalpana-18 years ( )OLR MERRA10 years ( )Cloud water, cloud ice, MCONV, ω ISCCP20 years ( )Low cloud and High cloud fractions TRMM VIRS15 years ( )Congestus clouds CFSv2-T1265 years free run at output frequency of 3 hrs Model output CFSv2-T382Same as T126Model output

Observational aspects… (d) Rainfall (mmhr -1 ), OLR (Wm -2 ), CIMR/CWMR (Kgm -2 ), High/low cloud (%)

Moisture convergence (x S -1 ) and vertical velocity (PaS -1 ) over CI Moisture convergence Vertical p-velocity

To investigate the diurnal variability during active (wet) and break (dry) phases of Indian Summer Monsoon….

Standardized rainfall anomaly Year Time series of days filtered precipitation anomalies averaged over CI (18N-26N,74E-83E) for JJAS from 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

During Active (black line) and Break (red line) phases..

Moisture convergence (x S -1 ) during active (black line) and break (red line) phases

Vertical velocity (PaS -1 ) during active (black line) and break (red line) phases

Model Analysis.. CFSv2-T382 CFSv2-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

All the time lighter ( mmhr -1 ) category dominates. Afternoon time moderate ( 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)

Rain rate (mmhr -1 ) OLR (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

Central India Observed peak LowCongestusHigh CloudCloud hydrometeors Cloud waterIce 1730 IST IST1730 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.

We have proposed a mechanism which builds a bridge between diurnal rainfall variation and its PDF distribution with cloud and dynamical processes. Based on the observational findings over CI….

Morning hours Shallow convection Lighter rainfall Noon-early afternoon hours Increased instability and high cloud liquid water low cloud maxima and growing up to congestus stage Afternoon-early evening hours Deep convection High cloud and Cloud ice maximum Moderate/heavy rainfall Enhanced insolation & moisture Detrainment Proposed mechanism

ACKNOWLEDGEMENTS WWOSC Organizing Committee Dr. P. Mukhopadhyay WMO Director, IITM Ministry of Earth Sciences, Govt. of India