Utilisation of MT-Satellite observations at NCMRWF : Plan & prospects

A. K. Bohra, M. Das Gupta, John P. Geogre, R. Ashrit & A.K. Mitra

National Centre for Medium Range Weather Forecasting

NOIDA, India

Objectives of NCMRWF

Development of operational Global and regional scale NWP models for forecasting weather in medium range(3-10 days) time scale taking full advantage of existing and concurrent developments in this field

To inform and guide the farmers in advance to undertake various farming activities based on the expected weather

Research on various aspects of NWP

A near real time numerical weather prediction (NWP) suite is being run operationally at NCMRWF since 1st June 1994 to issue medium range weather forecasts over Indian subcontinent

NWP NWP Models at NCMRWF

Global ModelsT-80 [ 150 km x 150km resolution]T-170 [ 75kmx75km resolution]

Meso-scale ModelsMM5 [Nested 90, 30, 10 km resolution]Eta [ 48km resolution]RSM [50km]

Ocean Wave ModelWAVEWATCH-III at 1 deg.for global ocean

Forecast to different Forecast to different SectorsSectors

NCMRWFForecast

Agriculture

Adventure

Tourism

PowerWater

Resources

Armed Forces

Shipping &FisheriesSpace

• To make a accurate forecast it is important to know the current weather

• Global observations are continuously downloaded through GTS and ftp access and fed into the assimilation system

• about 106 observations are processed in each assimilation cycle

Global Satellite Obsn.

Global Aircraft Obsn.

DATA PROCESSING

&QUALITY CONTROL

DATA RECEPTION & DECODING

at NCMRWF(1/2 hrly)

RTHNEW DELHI

FTP Satellite Data MSMR, SSMI etc.

Ships &Buoys

Surfaceobservations

Aircraft RS/RW

Satellite data

PilotBalloon

PREVIOUS (6HR.)ANALYSIS

ANALYSISSURFACE

BOUNDARYCONDITIONS

DATA PROCESSING AND

QUALITY CONTROL

PREVIOUS (6 HOURS)ANALYSIS

SSI ANALYSIS

T80 GLOBAL SPECTRAL FORECAST MODEL

SURFACEBOUNDARYCONDITIONS

MEDIUM RANGE WEATHER FORECAST BASED ON 00 UTC ANALYSIS

  

GTSDATA

Global Data assimilation System (GDAS) operational at NCMWRF

• 6-hrly intermittent

• 3D-VAR analysis (SSI)

• conventional and satellite obsn.

Repeated four times a day

00,06,12 & 18 UTC

Satellite data assimilated at NCMRWF

• Classical CMVs from GOES, METEOSAT,GMS and Kalpana

• High resolution winds from METEOSAT-5(63ºE)

• ATOVS (120km) temperature and total precipitable water(TPW) (500km TOVS)

• SSM/I, (MSMR) wind speed• QSCAT, (ERS-2) winds

Satellite data utilisation in data assimilation – forecast system

Some of the recent studies carried out at NCMRWF

• Impact of satellite derived temperature profile data on medium range forecasts (TOVS NOAA-12/14 coarse resolution - 500 km)  ’Global Ocean Atmosphere Systems , 1998’

• TOVS temperature profile data at its full resolution ( With IMD / HRPT -85 Km ) Meteorology & Atmos. Physics, 1999’

• Improve the quality of INSAT derived CMVs Height re-assignment by employing guess fields from global forecast model ( With IMD ) ‘Meteorology & Atmos. Physics, 2002’

• The divergent part of the wind was improved by using INSAT OLR information as input in analysis system( with IITM )

‘Meteorology & Atmospheric Physics, 1997’

• Derive synthetic moisture profiles from INSAT IR data JMA and BMRC type technique ‘Int. J of Remote Sensing, 2002’ /

‘Atmosfera, 2001’

• Assimilation of MSMR data in NCMRWF global data assimilation system (with IIT-D), Meteorology and Atmospheric Physics, 2002

• Impact of ATOVS temperature and moisture profiles, Mausam, 2003

• Impact of ERS-2 scatterometer winds ‘Mausam, 2002

• Impact of High Density Atmospheric Motion Vectors, 6th International Winds Workshop, 2002

• Analyses of Orissa Super Cyclone using TRMM (TMI), DMSP (SSM/I) and OceanSat-I (MSMR) Derived Data, The Global Atmosphere and Ocean System, 2003

• Observed daily large-scale rainfall patterns during BOBMEX-99, Earth & Planetary Science, 2003

• Daily Rainfall for Indian Monsoon Region from Merged satellite and Rain-Guage Values: Large-Scale Analysis from Real Time data, Journal of Hydrometeorology, 2003

Impact studies with SSM/I and MSMR wind speed & TPW

Impact of SSM/I wind speed and TPW

Comparison of SSM/I and MSMR wind speed with Buoy obsn.

Experiments with TRMM/TMI Data

Orissa Super Cyclone – October 1999

TPWC , Wind Speed from:-

TMI / TRMM

SSM/I

MSMR

METEOSAT - 5

20 – 31 Oct 1999 / TPWC & Wind

Exp1: TRMM 25 km

Exp2: TRMM averaged to 75 km

Exp3: SSM/I averaged to 75 km

EXP4: MSMR 75 km

Best simulated track is from the analyses with TRMM (25 km) and METEOSAT-5 (not shown)

However, forecast quality was still poor even in T170 version and with 25 km TRMM data

Vertical structure is important;

ATOVS type data might improve

Simulated track of super-cyclone based on 00UTC 24 Oct 2005

Experiments with ATOVS (NOAA 15 &16) temperate and moisture (global model)

Temperature at 850 hPa NOAA 15 & 16 00UTC 29 Sept 2001

Specific Humidity at 850 hPa NOAA 15 & 16 00UTC 29 Sept 2001

TPWC (mm) NOAA 15&16 00UTC 290901

TPWC (mm) SSM/I 00UTC 290901

SSM/I obsn. more moist over Tropics

(mm)

as expected analyses with SSM/I are more moist than analyses with ATOVS

SSM/I - more rainfall over Ocean

ATOVS - rainfall reduced over Ocean

more over Indian land

with ATOVS

with SSM/I

OBS

D1-FCST

Total rainfall Sept. 2001

Experiments with ATOVS (NOAA 15 &16) temperate and moisture

(Mesoscale model MM5 3DVAR)

without ATOVS with ATOVSAnalyses of a monsoon low with & without ATOVS (temp. & moisture)

850 hPa height & wind 00UTC 27th, 28th & 29th July 2004

In analyses with ATOVS, low is better organized, with centre of circulation coinciding with contour low

without ATOVS with ATOVS 24hr., 48hr. 72 hr. prediction based on 00UTC 26th July 2004

with & without ATOVS (temp. & moisture)

850 hPa height & wind

system is predicted more intense, in with ATOVS run

Validation of radiative fluxes

Validation of Net Radiatve Fluxes using LASPEX data set over Anand

Summer Monsoon

Post-Monsoon Winter

T80 simulation of net radiative fluxes matches well with observation in clear sky condition

Recent Heavy Rainfall Episode over West Coast of India

With NCMRWF analysis With UKMO analysis

Unprecedented Heavy Rainfall(~95cm) over Mumbai on 26th July 2005, very localized event over a region 20-30kms

• NCMRWF’s operational models could not predict such high rainfall with initial condition from its 3D-VAR assimilation system (without radiance)

• Same event is better simulated with initial condition generated by 4DVAR (with radinace) assimliatiion (obtained from UKMO)

Studies related with different physical parameterization schemes conducted at NCMRWF

Convection : KUO/RAS/SAS

PBL : Local / Non-Local closure

Radiation: GFDL / Harshavardhan

Satellite – rain gauge merged rainfall analysis (real time product for model validation)

Satellite – rain gauge merged product (NCMRWF)

CMAP (XIE-ARKIN) Rainfall

Total rainfall Sept 2001

heavy rainfall over peninsular India and over Nepal and adjoining NE India is captured better in NCMRWF product

Comparison of Analysed rainfall amount June 2001

Northern part ofwest coast

Southern part ofwest coast

East coast & north BOB

Central India & monsoon trough reg.

R

ain

fall

in

cm

(OBS)

Megha-tropique satellite is proposed to carry three scientific instruments:

Multi-frequency Microwave Scanning Radiometer, MADRAS

• rain above the oceans & surface winds, • integrated water vapour content, • liquid water in clouds, • convective rain

Multi-channel Microwave Instrument, SAPHIR• vertical humidity profile in the atmosphere

Multi-channel instrument, SCARAB• earth's radiation budget

Expected observations from Megha-tropique satellite

Possible Use of Megha-Tropiques data at NCMRWF

Input to the NWP models

Model validation

1. Input to the NCMRWF assimilation- forecast system:-

• Ocean surface wind, integrated water vapor and rain (MADRAS)

• Water vapor profiles in the cloud free troposphere (SAPHIR).

Use of these parameters in assimilation system may improve the distribution of the water vapor over the tropical oceans in analysis, which may ultimately improve the convection and other precipitation processes in the model.

• Cloud liquid water and ice (MADRAS)

can be used an input to the model, which may improve the computation of cloud optical properties (input to the radiation scheme) in the model and hence the radiation fluxes and

heating/cooling rates.

2. Model validation

• Shortwave and Longwave radiation (ScaRaB) measurements are useful for the validation of the radiation scheme over the tropical areas. The radiative fluxes observation in this mission is a valuable data to validate the model generated

cloud radiative forcing.

• Deep convection areas, cloud liquid water, precipitation, cloud top ice, anvil areas and humidity profiles (SAPHIR, MADRAS) useful for the validation of the parameterization of convection and other precipitation processes in the model

Proposed studies using observations from Megha-Tropiques satellite

(1) Data Assimilation

direct radiance assimilation

assimilation of surface wind, TPW

rainfall assimilation (nudging / 4DVAR)

observing system experiments

(2) Convection-Radiation Study

initiation and life cycle of convective systems over the Asian Monsoon Region has to be studied using Mesoscale/Cloud Resolving Model (MCRM) and data from Megha-Tropiques

preparation of cloud climatology for Asian Monsoon Regime

ScaRab radiation data will be used for comparing and ultimately improving radiation budget of numerical models

(3) Large scale & intra-seasonal monsoon variability

Hadley Walker circulations, Water vapour transport

Feedbacks on radiation

Madden-Julian oscillations

Onset, break and variations of monsoons

Ocean-Atmosphere interactions

(4) Local retrieval

retrieval through RT models using MW & SCARAB

Use NCMRWF’s meso-scale NWP outputs

Improved temp. , mositure and rainfall

(5) Rainfall analysis

calibration of IR rainfall with MW rainfall

technique for blending of rainfall data from Megha-Tropiques, TRMM, SSM/I and other geo-stationary satellite to

generation of grided rainfall dataset at different required (synoptic and meso scales) resolution