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Moorthy K.K.,Vikram Sarabhai Space Center | Beegum S.N.,Vikram Sarabhai Space Center | Babu S.S.,Vikram Sarabhai Space Center | Smirnov A.,NASA | And 5 more authors.
Journal of Geophysical Research: Atmospheres | Year: 2010

Analysis of the continuous and collocated measurements of columnar spectral aerosol optical depths (AODs) and mass size distributions in the marine atmospheric boundary layer (MABL) over the Bay of Bengal (BoB), carried out from 27 December 2008 to 29 January 2009 during the Winter Integrated Campaign for Aerosols, Gases and Radiation Budget (W-ICARB), revealed distinct regional features in the spatial variations of the aerosol properties in the MABL and column. In general, AODs were high over the northern and northwestern parts of the BoB, with pockets of very high values, within which the AODs were as high as ∼0.8 while the smallest values (∼0.1) were observed over the northeastern BoB, off the Myanmar and Bangladesh coasts. Interestingly, though, this region had the highest Angstrom wavelength exponent α(∼1.5), notwithstanding the generally high values that prevailed over the eastern as well as northern coastal regions of India. Back trajectory analyses revealed the significant role of the advected aerosols in the observed spatial pattern. Within the MABL, high accumulation mode mass concentrations (MA) prevailed over the entire BoB with the accumulation fraction ranging from 0.6 to 0.95, whereas very high fine-mode (r < 0.1 μm) aerosol mass fractions (∼0.8) were observed over the northeastern and western coastal BoB adjoining the Indian mainland (where α was high to very high). The vertical distributions, inferred from the columnar and MABL properties as well as from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations data, revealed better homogeneity in the northeastern and eastern BoB, whereas significant heterogeneity was seen over other regions. Copyright 2010 by the American Geophysical Union. Source


Nair V.S.,Vikram Sarabhai Space Center | Suresh Babu S.,Vikram Sarabhai Space Center | Krishna Moorthy K.,ISRO Head Quarters | Satheesh S.K.,Indian Institute of Science
Journal of Quantitative Spectroscopy and Radiative Transfer | Year: 2014

The effects of radiative coupling between scattering and absorbing aerosols, in an external mixture, on the aerosol radiative forcing (ARF) due to black carbon (BC), its sensitivity to the composite aerosol loading and composition, and surface reflectance are investigated using radiative transfer model simulations. The ARF due to BC is found to depend significantly on the optical properties of the 'neighboring' (non-BC) aerosol species. The scattering due to these species significantly increases the top of the atmospheric warming due to black carbon aerosols, and significant changes in the radiative forcing efficiency of BC. This is especially significant over dark surfaces (such as oceans), despite the ARF due to BC being higher over snow and land-surfaces. The spatial heterogeneity of this effect (coupling or multiple scattering by neighboring aerosol species) imposes large uncertainty in the estimation ARF due to BC aerosols, especially over the oceans. © 2014 Elsevier Ltd. Source


Rao A.R.,Tata Institute of Fundamental Research | Malkar J.P.,Tata Institute of Fundamental Research | Hingar M.K.,Tata Institute of Fundamental Research | Agrawal V.K.,Tata Institute of Fundamental Research | And 17 more authors.
Astrophysical Journal | Year: 2010

We present the results of an analysis of hard X-ray observations of the C2.7 solar flare detected by the RT-2 experiment on board the Coronas-Photon satellite. We detect hard X-ray pulsations at periods of 12s and 15s. We find a marginal evidence for a decrease in period with time. We have augmented these results using the publicly available data from the RHESSI satellite. We present a spectral analysis and measure the spectral parameters. © 2010. The American Astronomical Society. Source


Kompalli S.K.,Vikram Sarabhai Space Center | Babu S.S.,Vikram Sarabhai Space Center | Moorthy K.K.,ISRO Head Quarters | Manoj M.R.,Vikram Sarabhai Space Center | And 3 more authors.
Atmospheric Research | Year: 2014

In a first of its kind study over the Indian region, concurrent and extensive measurements of black carbon (BC) concentration and atmospheric boundary layer parameters are used to quantify the role of atmospheric boundary layer in producing temporal changes in BC. During this study, 18months (2011-12) data of continuous measurements of BC aerosols, made over a semi-urban location, Nagpur, in Central India are used along with concurrent measurements of vertical profiles of atmospheric thermodynamics, made using weekly ascents of GPS aided Radiosonde for a period of 1year. From the balloon data, mixed layer heights and ventilation coefficients are estimated, and the monthly and seasonal changes in BC mass concentration are examined in the light of the boundary layer changes. Seasonally, the BC mass concentration was highest (~4573±1293ngm-3) in winter (December-February), and lowest (~1588±897ngm-3) in monsoon (June-September), while remained moderate (~3137±1446ngm-3) in pre-monsoon (March-May), and post-monsoon (~3634±813ngm-3) (October-November) seasons. During the dry seasons, when the rainfall is scanty or insignificantly small, the seasonal variations in BC concentrations have a strong inverse relationship with mixed layer height and ventilation coefficient. However, the lowest BC concentrations do not occur during the season when the mixed layer height (MLH) is highest or the ventilation coefficient is the highest; rather it occurs when the rainfall is strong (during summer monsoon season) and airmass changes to primarily of marine origin. © 2014 Elsevier B.V. Source


Deb S.K.,Space Applications Center | Kishtawal C.M.,Space Applications Center | Kumar P.,Space Applications Center | Kiran Kumar A.S.,ISRO Head Quarters | And 3 more authors.
Atmospheric Research | Year: 2016

The advanced Indian meteorological geostationary satellite INSAT-3D was launched on 26 July 2013 with an improved imager and an infrared sounder and is placed at 82°E over the Indian Ocean region. With the advancement in retrieval techniques of different atmospheric parameters and with improved imager data have enhanced the scope for better understanding of the different tropical atmospheric processes over this region. The retrieval techniques and accuracy of one such parameter, Atmospheric Motion Vectors (AMV) has improved significantly with the availability of improved spatial resolution data along with more options of spectral channels in the INSAT-3D imager. The present work is mainly focused on providing brief descriptions of INSAT-3D data and AMV derivation processes using these data. It also discussed the initial quality assessment of INSAT-3D AMVs for a period of six months starting from 01 February 2014 to 31 July 2014 with other independent observations: i) Meteosat-7 AMVs available over this region, ii) in-situ radiosonde wind measurements, iii) cloud tracked winds from Multi-angle Imaging Spectro-Radiometer (MISR) and iv) numerical model analysis. It is observed from this study that the qualities of newly derived INSAT-3D AMVs are comparable with existing two versions of Meteosat-7 AMVs over this region. To demonstrate its initial application, INSAT-3D AMVs are assimilated in the Weather Research and Forecasting (WRF) model and it is found that the assimilation of newly derived AMVs has helped in reduction of track forecast errors of the recent cyclonic storm NANAUK over the Arabian Sea. Though, the present study is limited to its application to one case study, however, it will provide some guidance to the operational agencies for implementation of this new AMV dataset for future applications in the Numerical Weather Prediction (NWP) over the south Asia region. © 2015 Elsevier B.V.. Source

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