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

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 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

Observational aspects…

(d)

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

Moisture convergence (x 10-8 S-1) and vertical velocity (PaS-1) over CI

Moisture convergenceVertical p-velocity

To investigate the diurnal variability during active (wet) and break (dry) phases of

Indian Summer Monsoon….

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

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

Moisture convergence (x 10-7 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-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

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)

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

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.

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….

Enhanced in

solatio

n & m

oisture

Detrainment

Proposed mechanism

ACKNOWLEDGEMENTS

WWOSC Organizing Committee

Dr. P. Mukhopadhyay

WMO

Director, IITM

Ministry of Earth Sciences, Govt. of India