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Sultānpur Lodhi, India

Rajeevan M.,Earth System Science Organization | Sikka D.R.,40 Mausam Vihar | Tyagi A.,Earth System Science Organization
International Journal of Climatology | Year: 2015

The trends and epochal variability of southwest monsoon over the country as a whole and four homogeneous regions are examined using monthly rainfall data (1901-2011) of 640 political districts of India. The district rainfall data is computed from station rainfall data. The same station data is used to analyse the trends in the frequency of rainfall events of different intensities for examining extreme rainfall events. The existence of the multidecadal epochal variability of rainfall is clearly established in the all-India monsoon rainfall as well as monsoon rainfall over the four homogenous regions. However, over different homogenous regions, the phases of multidecadal variability are found to be different. Principal component analysis brings out Northeast India (NEI) rainfall as more dominant mode for all-India rainfall. Significant decrease in southwest monsoon rainfall over NEI is observed during the post 1950 period. Decreasing trends are also observed over the monsoon core region during the post-1950 period. Over these regions, monsoon rainfall has increased significantly during the pre-1950 period. It has been shown that the decreasing trend in monsoon rainfall during the post 1950 period is the result of multidecadal epochal variability. Geographical regions that experienced significant changes in the frequency of days of rainfall with different intensities are also identified. Significant change/turning points are also detected in the southwest monsoon rainfall. Frequency of moderate rainfall events (5mm≤daily rainfall<100mm) decreased significantly during the period 1951-2010 over the monsoon core region of India whereas no significant changes are observed in the frequencies of heavy (daily rainfall >100mm) or very heavy rain (daily rainfall >150mm) during the southwest monsoon season. Climatic shift or change point in monsoon rainfall in India is also detected by an established statistical test. © 2015 Royal Meteorological Society. Source

Kumar T.S.,Indian National Center for Ocean Information Services | Kumar Ch.P.,Indian National Center for Ocean Information Services | Nayak S.,Earth System Science Organization
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences - ISPRS Archives | Year: 2010

The Indian Tsunami Early Warning System (ITEWS) based at Indian National Center for Ocean Information Services (INCOIS), Hyderabad is responsible for issuing tsunami advisories to authorized officials from the Ministry of Home Affairs (MHA) and Ministry of Earth Sciences (MoES) in India. The centre operates on 24x7 basis and has the functions of monitoring seismological stations, bottom pressure recorders (BPRs) and tidal stations throughout the Indian Ocean Basin to evaluate potentially tsunamigenic earthquakes and disseminating tsunami warning information. A database of all possible earthquake scenarios for the Indian Ocean is used to identify the regions under risk at the time of event. Timely tsunami advisories (Warning/Alert/Watch/Information) are generated following pre-set decision support rules and standard operating procedure (SOP). The end-to-end system performance was very well tested for the first time after its establishment against the earthquake and tsunami event on September 12, 2007 Off the west coast of Sumatra. The Indian system equipped with world-class computational, communication and technical support facility is capable of detecting tsunamis in the Indian Ocean. With this capability INCOIS has begun providing regional tsunami watch services on a trial basis from its national system for the Indian Ocean region. Source

In this study, analysis of the long term climatology, variability and trends in the daily rainfall events of ≥5 mm [or daily rainfall (DR) events] during the southwest monsoon season (June-September) over four regions of India; south central India (SCI), north central India (NCI), northeast India (NEI) and west coast (WC) have been presented. For this purpose, a new high spatial resolution (0.25° × 0.25°) daily gridded rainfall data set covering 110 years (1901-2010) over the Indian main land has been used. The association of monsoon low pressure systems (LPSs) with the DR events of various intensities has also been examined. Major portion of the rainfall over these regions during the season was received in the form of medium rainfall (≥5-100 mm) or moderate rainfall (MR) events. The mean seasonal cycle of the daily frequency of heavy rainfall (HR) (≥100-150 mm) or HR events and very heavy rainfall (VHR) (≥150 mm) or VHR events over each of the four regions showed peak at different parts of the season. The peak in the mean daily HR and VHR events occurred during middle of July to middle of August over SCI, during late part of June to early part of July over NCI, during middle of June to early July over NEI, and during late June to middle July over WC. Significant long term trends in the frequency and intensity of the DR events were observed in all the four geographical regions. Whereas the intensity of the DR events over all the four regions showed significant positive trends during the second half and the total period, the signs and magnitude of the long term trends in the frequency of the various categories of DR events during the total period and its two halves differed from the region to the region. The trend analysis revealed increased disaster potential for instant flooding over SCI and NCI during the recent years due to significant increasing trends in the frequency (areal coverage) and intensity of the HR and VHR events during the recent half of the data period. However, there is increased disaster potential over NEI and WC due to the increasing trends in the intensity of the rainfall events. There is strong association between the LPS days and the DR events in both the spatial and temporal scales. In all the four regions, the contributions to the total MR events by the LPS days were nearly equal. On the other hand, there was relatively large regional difference in the number of combined HR and VHR events associated with LPS days particularly that associated with monsoon depression (LPS stronger than monsoon depression) days. The possible reasons for the same have also been discussed. The increasing trend in the monsoon low (low pressure) days post 1970s is the primary reason for the observed significant increasing trends in the HR and VHR events over SCI and NCI and decreasing trend in HR events over NEI during the recent half (1956-2010). This is in spite of the decreasing trend in the MD days. © 2014 Springer-Verlag Berlin Heidelberg. Source

Prakash P.,Indian National Center for Ocean Information Services | Prakash S.,Indian National Center for Ocean Information Services | Rahaman H.,Indian National Center for Ocean Information Services | Ravichandran M.,Indian National Center for Ocean Information Services | Nayak S.,Earth System Science Organization
Geophysical Research Letters | Year: 2012

Recent studies of satellite-derived Chlorophyll concentrations (Chl-a) in the western Arabian Sea (AS) have suggested an increasing temporal trend, but the length of the records used have typically been too short to resolve longer-term trends, if any. Our analysis of a long term satellite ocean color data shows a change of trend in the summer chlorophyll for the western AS before and after 2003; Chl-a concentration was indeed increasing till 2003, but appears to be declining since then, indicating a secular multi-year trend in Chl-a variability. However, this trend is not uniform over the entire region. Analysis of wind, sea surface temperature (SST), Sea Level Anomaly (SLA) and thermocline depth, suggests that the declining summer monsoon chlorophyll-a (Chl-a) concentration may be due to increasing SLA in this region. The earlier observed biological changes in the western AS could be an artifact of the change in local winds and ocean dynamics, which may be a part of the natural long-term variability. © 2012. American Geophysical Union. All Rights Reserved. Source

Abhilash S.,Indian Institute of Tropical Meteorology | Abhilash S.,University of Miami | Sahai A.K.,Indian Institute of Tropical Meteorology | Borah N.,Indian Institute of Tropical Meteorology | And 6 more authors.
Journal of Applied Meteorology and Climatology | Year: 2015

This study describes an attempt to overcome the underdispersive nature of single-model ensembles (SMEs). As an Indo-U.S. collaboration designed to improve the prediction capabilities of models over the Indian monsoon region, the Climate Forecast System (CFS) model framework, developed at the National Centers for Environmental Prediction (NCEP-CFSv2), is selected. This article describes a multimodel ensemble prediction system, using a suite of different variants of the CFSv2 model to increase the spread without relying on very different codes or potentially inferior models. The SMEs are generated not only by perturbing the initial condition, but also by using different resolutions, parameters, and coupling configurations of the same model (CFS and its atmosphere component, the Global Forecast System). Each of these configurations was created to address the role of different physical mechanisms known to influence error growth on the 10-20-day time scale. Last, the multimodel consensus forecast is developed, which includes ensemble-based uncertainty estimates. Statistical skill of this CFS-based Grand Ensemble Prediction System (CGEPS) is better than the best participating SME configuration, because increased ensemble spread reduces overconfidence errors. © 2015 American Meteorological Society. Source

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