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.

Mechanism of ENSO influence on the South Asian monsoon rainfall in global model simulations.

Abstract: Coupled ocean atmosphere global climate models are increasingly being used for seasonal scale simulation of the South Asian monsoon. In these models, sea surface temperatures (SSTs) evolve as coupled air-sea interaction process. However, sensitivity experiments with various SST forcing can only be done in an atmosphere-only model. In this study, the Global Forecast System (GFS) model at T126 horizontal resolution has been used to examine the mechanism of El Nino-Southern Oscillation (ENSO) forcing on the monsoon circulation and rainfall. The model has been integrated (ensemble) with observed, climatological and ENSO SST forcing to document the mechanism on how the South Asian monsoon responds to basin-wide SST variations in the Indian and Pacific Oceans. The model simulations indicate that the internal variability gets modulated by the SSTs with warming in the Pacific enhancing the ensemble spread over the monsoon region as compared to cooling conditions. Anomalous easterly wind anomalies cover the Indian region both at 850 and 200 hPa levels during El Nino years. The locations and intensity of Walker and Hadley circulations are altered due to ENSO SST forcing. These lead to reduction of monsoon rainfall over most parts of India during El Nino events compared to La Nina conditions. However, internally generated variability is a major source of uncertainty in the model-simulated climate.

Characteristics of observed rainfall over Odisha: An extreme vulnerable zone in the east coast of India

Abstract: The present study investigates the spatiotemporal characteristics of rainfall events during the summer monsoon season over Odisha (one of the vulnerable zone for heavy rainfall) with the main aim for heavy-to-extreme rainfall events. India Meteorological Department (IMD) station observations and gridded rainfall analysis datasets for a period of 34 years (1980–2013) are used and four frequency indices (heavy-to-extreme, light-to-moderate, dry days, and wet spells) and four intensity indices (daily maximum rainfall, 5-day maximum rainfall, seasonal rainfall total, and daily intensity index) from both the datasets are evaluated. Furthermore, the above-stated indices are analysed over the four meteorological zones of Odisha, as classified by IMD. The analysis reveals that both the heavy-to-extreme rainfall days and dry days are increasing, while the light-to-moderate rainfall days and wet days are decreasing. It is also found that the rate of increase in rainfall amount and number of wet-day are higher in the southern than northern Odisha. This implies that the climate is becoming drier as one move from south to north and the gradient is also increasing with time. The climatological analysis suggests not only the heavy-to-extreme rainfall days and intensity are more in urban (Khordha) and highly elevated (Eastern Ghat; height ~ 1.6 km) areas but also the trend is increasing over those regions. The Murphy skill score of daily rainfall between two datasets is 0.94; however, the number of the extreme rainfall events is more in station data (297) than the gridded data (150) during the study period.

Mesoscale model forecast verification during monsoon 2008

Abstract: There have been very few mesoscale modelling studies of the Indian monsoon, with focus on the verification and intercomparison of the operational real time forecasts. With the exception of Das et al (2008), most of the studies in the literature are either the case studies of tropical cyclones and thunderstorms or the sensitivity studies involving physical parameterization or climate simulation studies. Almost all the studies are based on either National Center for Environmental Prediction (NCEP), USA, final analysis fields (NCEP FNL) or the reanalysis data used as initial and lateral boundary conditions for driving the mesoscale model. Here we present a mesoscale model forecast verification and intercomparison study over India involving three mesoscale models: (i) the Weather Research and Forecast (WRF) model developed at the National Center for Atmospheric Research (NCAR), USA, (ii) the MM5 model developed by NCAR, and (iii) the Eta model of the NCEP, USA. The analysis is carried out for the monsoon season, June to September 2008. This study is unique since it is based entirely on the real time global model forecasts of the National Centre for Medium Range Weather Forecasting (NCMRWF) T254 global analysis and forecast system. Based on the evaluation and intercomparison of the mesoscale model forecasts, we recommend the best model for operational real-time forecasts over the Indian region. Although the forecast mean 850 hPa circulation shows realistic monsoon flow and the monsoon trough, the systematic errors over the Arabian Sea indicate an easterly bias to the north (of mean flow) and westerly bias to the south (of mean flow). This suggests that the forecasts feature a southward shift in the monsoon current. The systematic error in the 850 hPa temperature indicates that largely the WRF model forecasts feature warm bias and the MM5 model forecasts feature cold bias. Features common to all the three models include warm bias over northwest India and cold bias over southeast peninsula. The 850 hPa specific humidity forecast errors clearly show that the Eta model features dry bias mostly over the sea, while MM5 features moist bias over large part of domain. The RMSE computed at different levels clearly establish that WRF model forecasts feature least errors in the predicted free atmospheric fields. Detailed rainfall forecast verification further establishes that the WRF model forecast rainfall skill remains more or less same in day-2 and day-3 as in day-1, while the forecast skill in the MM5 and Eta models, deteriorates in day-2 and day-3 forecasts.

Multi year changes of Aerosol Optical Depth in the monsoon region of the Indian Ocean since 1986 as seen in the AVHRR and TOMS data

Abstract: Aerosol Optical Depth (AOD) data based on AVHRR and TOMS was analyzed to find out the changes in the Indian Ocean from 1981 to 2004. Four regions covering Indian Ocean north of 10° S were studied in detail. The results strongly suggest that the mean value of AOD in these regions decreased from 1986–1990 to 1995–1999. The Arabian Sea and Bay of Bengal show increase thereafter whereas in the equatorial part it decreased further, during 2000–2004. The drop in AOD from the first to second period is evident in AVHRR and TOMS in the case of the Arabian Sea (North West Indian Ocean). The decrease in this case is prominent in summer. These results in general agree with the recently reported global decrease in AOD, "global brightening" and also the reversal of trend in some of the anthropogenic emissions.