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Climate Forecast System Version 2.0

      The NCEP Climate Forecast System version 2 (CFSv2; Saha et al. 2013) is a state-of-the-art coupled climate model developed by the National Center for Environmental Prediction (NCEP), USA and it has been implemented to the Prithvi High Performance Computer (HPC) at Indian Institute of Tropical Meteorology (IITM), Pune. It is a fully coupled ocean- atmosphere-land model with advanced physics, increased resolution and refined initialization as compared to earlier version (CFSv1).

The atmospheric component of CFSv2 is Global Forecast System (GFS) with spectral resolution of T382 and 64 hybrid vertical levels and the ocean component is Geophysical Fluid Dynamics Laboratory (GFDL) Flexible Modeling System (FMS) & Modular Ocean Model version 4 (MOM4; Griffies et al. 2004). The convective parameterization utilizes simplified Arakawa-Schubert convection with momentum mixing. The model also implements orographic gravity wave drag based on Kim and Arakawa (1995) approach and sub-grid scale mountain blocking (Lott and Miller 1997).

The model employs Rapid radiative transfer model shortwave radiation with maximum random cloud overlap (Iacono et al. 2000; Clough et al. 2005). In addition, it has a four layer NOAH land surface model (Ek et al. 2003) and a two layer dynamical sea ice model (Wu et al. 1997; Winton 2000) coupled together with the Atmosphere and Ocean components in Earth System Modeling Framework (ESMF).

The skill of the CFS T382L64 model Hindcast has been analysed and found to provide better forecasts compared to the low-resolution (T126) configuration (Ramu et al. 2016).

Type of system: Coupled Ocean-Atmospheric Dynamical System (Numerical)

System produces: probabilistic and deterministic forecast

Model type and resolution: T382L64

Ensemble size: 12 members for hindcast and 40 members for forecast

Details of forecasts period: 9 months

Lead-time: One-month lead forecasts

Period of verification: three-month

Period of Hindcast: 1981-2009

List of regions for each parameter. For all parameters: Northern Extratropics, Tropics, Southern Extratropics

Lead times for verification running season: 0, 1

Period of verification: 1981 – 2009 for MAM, JJA, SON and DJF and all running Season

List of parameters:Precipitation , T2m and SST

Details of verification data sets used :Precipitation: GPCP,T2m: ERA40, SST:NCEP



Seasonal Forecast Model

     The seasonal forecast system of the IMD is a probabilistic system build on a 10 member ensemble originally developed by Experimental Climate Prediction Center (ECPC) and global sea surface temperature (SST) forecasts from NCEP Coupled Forecasting System (CFS) version 2 model was used as boundary forcing for the SFM model. To provide global monthly and seasonal forecasts initialized on each month throughout the years.

Type of system: Atmospheric General Circulation Model (Numerical)

System produces probabilistic forecasts

Model type and resolution: T62L28

Ensemble size: 10 members for forecast and hindcast

Details of forecasts period: 4 months

Lead-time: Zero lead

Period of verification: three-month

Period of Hindcast: 1982-2010

LAF = Lagged Average Forecasts

Boundary conditions specifications: Forecast SST as Boundary condition (CFS-V2 SST, 40 ensemble member from first 10 days)

List of parameters being assessed: t2m, Precipitation

List of regions for each parameter. For all parameters: Northern Extratropics, Tropics, Southern Extratropics

Lead times available for each parameter. For all season: 0, 1

Period of verification: 1982 – 2010 for MAM, JJA, SON and DJF and all running Season

Number of hindcasts (available) : 30 full years (Jan.1982 - Dec.2010)

Details of verification data sets used:Precipitation: GPCP , T2m: ERA40