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.

Effect of the variation in the lower tropospheric temperature on the wind onset of the Indian summer monsoon

Abstract: There is a large thermal contrast between the Arabian Peninsula and India (Δθ AI) at the mature stage of the Indian summer monsoon (ISM). The forming process of Δθ AI is investigated analyzing various datasets. It forms earlier in the lower troposphere than in the middle and upper layers. The potential temperature in the lower troposphere over the west coast of India (θ IW) abruptly decreases in advance of the rapid enhancement of the westerly wind over the Arabian Sea corresponding to the ISM onset. Such a process was observed for all the target years and the rapid decrease in θ IW could trigger the ISM onset. The decrease in θ IW had two patterns. In one case, cooler air is brought by the strong winds around a cyclone over the Arabian Sea. In another case, θ IW decreases gradually by a synergy of a southwesterly wind over the Arabian Sea and the enlargement of Δθ AI.

Spatial-temporal variation and mechanism associated with mini-cold pool off the southern tip of India during summer and winter monsoon season

Abstract: Sea surface temperature (SST) from different sources suggests that the occurrence of a mini-cold pool (MCP) off the southern tip of India (STI) is a persistent phenomenon which occurs during both the summer and the winter monsoon seasons. However, the associated mechanism is different in both scenarios and, hence, numerical experiments are conducted to study and ascertain the mechanism. The dynamics that govern the occurrence of MCP during the summer season is mainly due to upwelling, caused by the divergence in the near-surface circulation off STI, advection of the cold upwelled water from the western Arabian Sea and the southwest coast of India. In contrast, during the winter monsoon, the model studies suggest that circulations driven by positive Ekman dynamics and outgoing heat flux are mainly responsible for the formation of MCP off STI during December–February. The cold water intrusion in both seasons occurs in accordance with the monsoon and coastal currents, which underlines the importance of advection. The position and extent of cooling differs during both seasons because wind stress varies significantly.

Global spectra of energy and enstrophy and their fluxes during July 1979

Abstract: Transient and stationary spectra of kinetic energy (KE), available potential energy (APE) and enstrophy (EN), and their spectral fluxes as a function of the two-dimensional wavenumbern were computed for July 1979. Triangular truncation at zonal wavenumber 42 was used for computation. The slopes of various spectra in the wavenumber range 14≤n≤25 were obtained by fitting a straight line in log-log scale by the least square method. The transientKE, APE andEN spectra in the lower (upper) troposphere had slopes −2·21 (−2·30), −2·65 (−2·64) and −0·36 (−0·46), respectively. The effect of stationary and divergent motion on the slope values was investigated. The possible correlation between the slope and percentage of transient component in the combined energy and enstrophy was examined to identify the transient motion of the atmosphere with the two-dimensional homogeneous isotropic turbulence. The vertically averaged slope of kinetic energy and enstrophy in the lower (upper) troposphere was close to the value at 700 (200) hPa level.

A case study on the vertical distribution and characteristics of aerosols using ground-based raman lidar, satellite and model over Western India

Abstract: Ahmedabad is an urban site in western region of India. Dust loading and its variability are very high over this semi-arid location. A state-of-the-art ground-based Raman lidar has been used for the...

Numerical simulation of the marine boundary layer characteristics over the Bay of Bengal as revealed by BOBMEX-98 Pilot experiment

Abstract: An attempt has been made to study the marine boundary layer characteristics over Bay of Bengal using BOBMEX (Bay of Bengal and Monsoon Experiment) pilot experiment data sets, which was conducted between 23rd October and 12th November 1998 on board ORV Sagar Kanya. A one-dimensional multilevel atmospheric boundary layer with TKE-e closure scheme is employed to study the marine boundary layer characteristics. In this study two synoptic situations are chosen: one represents an active convection case and the other a suppressed convection. In the present article the marine boundary layer characteristics such as temporal evolution of turbulent kinetic energy, height of the boundary layer and the airsea exchange processes such as sensible and latent heat fluxes, drag coefficient for momentum are simulated during both active and suppressed convection. Marine boundary layer height is estimated from the vertical profiles of potential temperature using the stability criterion. The model simulations are compared with the available observations.