National Centre for Medium Range Weather Forecasting

About: National Centre for Medium Range Weather Forecasting is a government organization based out in Noida, India. It is known for research contribution in the topics: Monsoon & Weather Research and Forecasting Model. The organization has 176 authors who have published 368 publications receiving 4749 citations.

A combined passive–active microwave retrieval of ocean surface wind speed from SARAL-AltiKa microwave radar altimeter and radiometer

Abstract: SARAL (Satellite with Argos and AltiKa) is the first satellite radar altimetry mission to fly a Ka-band instrument (AltiKa), which has completed 5 years in orbit on 25th February 2018. Ka-band SARAL-AltiKa suffers larger signal attenuation due to atmospheric water content and also exhibits a different relationship with wind speed than at Ku and C band. Here an augmentation of our earlier geophysical model function (GMF) that was developed based on first principles for wind speed retrieval from SARAL-AltiKa is proposed. This GMF is further augmented here, taking advantage of the co-aligned passive microwave radiometer making measurements of brightness temperature (BT) along with the primary active radar AltiKa measurements of radar backscatter (RB) and significant wave height (SWH) in conjunction with a large matched database of wind speed from Jason-2, respectively. The retrieved wind speed from currently modified algorithm provides an accuracy of 1.34 ms−1 in root mean square deviation with global buoys. Finally, the new algorithm has been used successfully in demonstrating its applicability in capturing regional to global wind field features and compared with other independent satellite measurements like OceanSat scatterometer, Jason-2 altimeter and DMSP-SSM/I radiometer.

Variation of coastal atmospheric boundary layer characteristics with convective activity along the west coast of India during the Arabian Sea Monsoon Experiment (ARMEX) 2002

Abstract: This paper investigates the characteristic features of the coastal atmospheric boundary layer (CABL) along the west coast of India during the south-west monsoon (SWM) 2002. Extensive surface and upper-air findings were obtained during the same period from the Arabian Sea Monsoon Experiment (ARMEX; 15th June to 15th August 2002) 2002. The operational general circulation model (GCM) of the National Centre for Medium Range Weather Forecasting (NCMRWF) was used in this study to see the spatial variation of the CABL during two specific convective episodes that led to heavy rainfall along the west coast of India. The impact of a non-local closure (NLC) scheme employed in the NCMRWF GCM was carried out in simulating the CABL. The same episodes were also simulated using a similar parameterization scheme employed in the high resolution mesoscale modelling system (MM5). The diurnal variation of CABL is better represented from MM5 simulation. Comparing the MM5 simulation with that of the coarser grid NCMRWF GCM, we observed that the NCMRWF GCM underestimates the values of both latent heat flux (LHF) and the coastal atmospheric boundary layer height (CABLH). Results from MM5 therefore indicate that the best way to move forward in addressing the short-comings of coarse grid-scale GCMs is to provide a parameterization of the diurnal effects associated with convection processes.

An assessment of a very severe cyclonic storm in the Arabian sea using the COSMO model

Abstract: Accurate and reliable representation of convective processes is one of the major sources of uncertainty in numerical weather prediction (NWP) models, especially for those operating in the grey zone resolutions. The performance of NWP models become more sensitive to their grid resolutions, when they are used for simulation of severe weather events, such as a cyclonic storm. In this paper, we present a detailed assessment of an intense convective episode with heavy precipitation associated with the passage of a very severe cyclonic storm “OCKHI” using the Consortium for Small-scale Modelling (COSMO). A set of distinct numerical simulations are carried out using COSMO to address the impact of grid resolution and the treatment of explicit and implicit convection. Results obtained from the present investigation indicate that explicit treatment of convection in the COSMO model led to improved prediction of the cyclonic event in terms of sea level pressure, maximum sustained surface wind speeds and the accumulated rainfall, but reduction of the spatial grid resolution from 7 to 3 km did not show appreciable differences in the forecast fields. Conclusively, the current study recommends switching off the convection parameterization scheme at a grid resolution of 7 km for improved predictability of tropical cyclones.