Browsing by Author "D.R. Pattanaik"

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An apparent relationship between Madden–Julian Oscillation and the advance of Indian summer monsoon
(John Wiley and Sons Ltd, 2017) M. Singh; R. Bhatla; D.R. Pattanaik
A marked seasonality in the occurrence of Madden–Julian Oscillation (MJO) events is well known. The core region of oscillation is located at low latitudes (between the equator and 15°) in the summer hemisphere. The eastward progression of MJO signal interacts with the monsoon circulation and modulates the advance period of Indian summer monsoon (ISM). The analyses suggest that the mean advance period of ISM (41 days) is comparable with the life cycle of the MJO (30–60 days). The advance period of ISM has been categorised into normal, fast and slow-advance years to decide the pace of the monsoon during progression of monsoon. During the period 1983–2015, the fastest progress of the monsoon was seen in the year 2013 (fastest advancement in the last 33 years) and slowest progress of monsoon was seen in the year 2002 (most lethargic advancement in the last 33 years). The results of the analyses show that variation in daily MJO-amplitude during fast-advancement years is more as compared with the normal and slow-advancement years. The normal-advancement years mostly occur during MJO phase 1 and phase 2 and fast-advancement years frequently occur during MJO phase 2; however, slow-advancement years are found to occur during MJO phase 5 and phase 6. The MJO phase 2 is the most frequent phase and MJO phase 8 is the least frequent phase during advance of monsoon. However, the highest amplitude is recorded during MJO phase 8. The strong (weak) monsoon current is modulated by strong (weak) MJO phases. © 2016 Royal Meteorological Society
Effect of unusual dust event on meteorological parameters & aerosol optical and radiative properties
(India Meteorological Department, 2018) V.K. Soni; Sanjay Bist; R. Bhatla; S.C. Bhan; Gajendra Kumar; M. Sateesh; Siddhartha Singh; D.R. Pattanaik
A very unusual dust plume generated from dust-storm activities over the Arabian Peninsula and Southwest Asia affected the north-west region of India between March 20 and 23, 2012, causing significant reductions in air quality and consequently changes in meteorological parameters. Ground based measurements of aerosol optical depth at 500 nm reached 1.015 ± 0.24 and 0.837 ± 0.042 at Jodhpur while Angstrom exponent dropped to-0.030 and-0.065 on March 20 and 21, 2012 respectively. The AOD reached 0.959 in Delhi while Angstrom exponent dropped to 0.006 on March 21, 2012. PM10 concentration peaked at an unusually high value of more than 1800 μgm-3 during dust storm hours of March 20, 2012 at Delhi. Moderate Resolution Imaging Spectrometer (MODIS) retrieved aerosol optical depth also exhibited high values as well along the path of dust storm and dust plume. The intensity of the dust plume was such that it caused significant cooling at the surface. The large reduction in the radiative flux at the surface level had caused a drop in surface temperature by approximately 2-10 °C. Shortwave and longwave Direct Aerosol Radiative Forcing was calculated using SBDART during the dust period. © 2018, India Meteorological Department. All rights reserved.
Impact of Madden-Julian oscillation on onset of summer monsoon over India
(Springer-Verlag Wien, 2017) R. Bhatla; Madhu Singh; D.R. Pattanaik
The Madden-Julian oscillation (MJO) is identified as the dominant mode of intraseasonal variabilities (ISVs) in the tropical atmosphere. It is one of the most influencing factors, which can influence the onset phase of monsoon over India giving rise to early/delayed onset of summer monsoon onset over Kerala (MOK) in the southern tip of India. The aim of the present study is to find years in which northward propagating ISVs significantly contribute to the early/delayed MOK. Climatology of early and delayed onset of Indian summer monsoon is analyzed in association with MJO state for the period of 37 years (1979–2015). The results indicate strong MJO events are frequent and show relatively better association with the onset of summer monsoon over India as compared to the weak MJO events. With respect to the MJO phase, the result suggests that the MOK occur mostly in association with MJO phases 1, 2, 3, and 8. Out of these, the MJO phase 2 (convection centre over western equatorial Indian Ocean) is mostly associated with pre-onset (early onset) years, MJO phase 8 (convection center over western hemisphere) is mostly associated with post-onset (late onset) years, and MJO phases 1 and 3 (convection centers over eastern equatorial Indian Ocean or western hemisphere) are mostly associated with normal-onset years. © 2016, Springer-Verlag Wien.