Impact of dust storm on the atmospheric boundary layer: a case study from western India     

Saha  Sourita  Sharma  Som  Chhabra  Abha  Kumar  Kondapalli Niranjan  Kumar  Prashant  Kamat  Dharmendra  Lal  Shyam 《Natural Hazards》2022,113(1):143-155

Natural Hazards - The present study focuses on investigating the impacts of a sudden dust storm on the atmospheric boundary layer (ABL) over Ahmedabad (23.02°N, 72.57°E), an urban site...  相似文献   

Paleo-ocean chemistry records in marine opal: Implications for fluxes of trace elements, cosmogenic nuclides (Be and Al), and biological productivity     

D. Lal  C. Charles  J.N. Goswami  L. McHargue 《Geochimica et cosmochimica acta》2006,70(13):3275-3289

Here, we provide evidence suggesting that marine (diatom) opal contains not only a high fidelity record of dissolved oceanic concentrations of cosmic ray-produced radionuclides, ¹⁰Be and ²⁶Al, but also a record of temporal variations in a large number of trace elements such as Ti, Fe, Zn and Mn. This finding is derived from measurements in purified biogenic opal that can be separated from detrital materials using a newly developed technique based on surface charge characteristics. Initial results from a sediment core taken near the present-day position of the Antarctic Polar Front (ODP Site 1093) show dramatic changes in the intrinsic concentrations of, Be, Al, Ti, Fe, Mn and Zn in the opal assemblages during the past ∼140 kyr BP. The results imply appreciable climatically controlled fluctuations in the level of bioreactive trace elements. The time series of total Be, Al, Ti, Fe and ¹⁰Be in the sediment core are all well correlated with each other and with dust records in the polar ice cores. The observations suggest that a significant flux of these trace metals to oceans is contributed by the aeolian dust, in this case, presumably from the Patagonia. This observation also allows determination of fluxes of dust-contributed ¹⁰Be to the Antarctica ice sheets. However, our data show that the relationships among the various metals are not perfectly linear. During periods of higher dissolved concentrations of trace elements (indicated by Fe and Ti) the relative concentrations of bioreactive elements, Be, Al, Mn and Zn are decreased. By contrast, the Fe/Zn and Fe/Mn ratios decrease significantly during each transition from cold to warm periods. The relative behavior could be consistent with any of the following processes: (i) enhanced biological productivity due to greater supply of the bioreactive elements (e.g. Zn) during cold periods (ii) increased biological and inorganic scavenging of particle active elements (e.g. Be and Al) during early interglacial periods (iii) differential uptake/removal of the metals by the various diatom taxa whose relative productivity or growth rate changes with large scale climate. In any case, with one sedimentary phase and in single sedimentary sections, we now have the potential to compare directly a proxy for aeolian input of micronutrients (e.g. Fe or Ti), with a proxy for production (e.g. ²⁶Al/Al ratios). We expect that studies of the temporal records of trace elements and cosmogenic nuclides in contrasting regions of upwelling and productivity, which exhibit different sensitivities to global climate fluctuations and micronutrient inputs, would lead to a direct and comprehensive test of ideas such as the hypothesis of iron control of atmospheric carbon dioxide [Martin, J.H., 1990. Glacial-interglacial CO₂ change: the iron hypothesis. Paleoceanography5, 1-13]. Our present data from a single site do not show that increases in dissolved Fe concentrations, per se, were responsible for increased biological productivity. However, a much clearer picture of the effect of increased dust fluxes should emerge when we have data for trace elements and the cosmogenic nuclides, ¹⁰Be and ²⁶Al from various oceanic provinces.  相似文献   

Deep multi-frequency radio imaging in the Lockman Hole using the GMRT and VLA – I. The nature of the sub-mJy radio population     

Edo Ibar  R. J. Ivison  A. D. Biggs  D. V. Lal  P. N. Best  D. A. Green 《Monthly notices of the Royal Astronomical Society》2009,397(1):281-298

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Computable extensions of generalized fractional kinetic equations in astrophysics     

Vinod Behari Lal Chaurasia  Shared Chander Pandey 《中国天文和天体物理学报》2010,10(1)

Fractional calculus and special functions have contributed a lot to mathematical physics and its various branches.The great use of mathematical physics in distinguished astrophysical problems has attracted astronomers and physicists to pay more attention to available mathematical tools that can be widely used in solving several problems of astrophysics/physics.In view of the great importance and usefulness of kinetic equations in certain astrophysical problems,the authors derive a generalized fractional kin...  相似文献   

Giant Metrewave Radio Telescope observations of X-shaped radio sources     

Dharam Vir Lal  A. Pramesh Rao 《Monthly notices of the Royal Astronomical Society》2007,374(3):1085-1102

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Activity of water during granulite metamorphism around Anakapalle,Vishakhapatnam District,A.P.     

S. N. Lal 《Journal of Earth System Science》1995,104(1):79-84

A refined mathematical equation is proposed to quantify the ambient activity of water during granulite fades metamorphism. The thermodynamic calculations point to the low activity of water during metamorphism in the area around Anakapalle, Vishakhapatnam district, A.P. Carbonic metamorphism seems to be responsible for the low activity of water during this metamorphism. Calc-silicate rocks in the area, could have been the source of the CO₂.  相似文献   

Terrestrial radiation balance in the atmosphere over NW-India     

Dr. M. Lal 《Theoretical and Applied Climatology》1973,21(2-3):233-242

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New age constraints on the cooling and unroofing history of the Trans-Himalayan Ladakh Batholith (Kargil area), N. W. India     

Rasoul B Sorkhabi  Arvind K Jain  Susumu Nishimura  Tetsumaru Itaya  Nand Lal  R M Manickavasagam  Takahiro Tagami 《Journal of Earth System Science》1994,103(1):83-97

Thermotectonic history of the Trans-Himalayan Ladakh Batholith in the Kargil area, N. W. India, is inferred from new age data obtained here in conjunction with previously published ages. Fission-track (FT) ages on apatite fall around 20±2 Ma recording cooling through temperatures of ∼100°C and indicating an unroofing of 4 km of the Ladakh Range since the Early Miocene. Coexisting apatite and zircon FT ages from two samples in Kargil show the rocks to have cooled at an average rate of 5–6°C/Ma in the past 40 Ma. Zircon FT ages together with mica K−Ar cooling ages from the Ladakh Batholith cluster around 40–50 Ma, probably indicating an Eocene phase of uplift and erosion that affected the bulk of the batholith after the continental collision of India with the Ladakh arc at 55 Ma. Components of the granitoids in Upper Eocene-Lower Oligocene sediments of the Indus Molasse in Ladakh supports this idea. Three hornblende K−Ar ages of 90 Ma, 55 Ma, and 35 Ma are also reported; these distinctly different ages probably reflect cooling through 500–550°C of three phases of I-type plutonism in Ladakh also evidenced by other available radiometric data: 102 Ma (mid-Cretaceous), 60 Ma (Palaeocene), and 40 Ma (Late Eocene); the last phase being localised sheet injections. The geodynamic implications of the age data for the India-Asia collision are discussed.  相似文献   

Water　Resources　of　the　South　Asian　Region　in　a　Warmer　Atmosphere   总被引：1，自引：0，他引：1  

M.Lal 《大气科学进展》1994,11(2):239-246

The global mean surface temperature may rise by about 0.3oC per decade during the next Few decades as a result of anthropogenic greenhouse gas emissions in the earth’s atmosphere. The data generated in the greenhouse warming simulations (Business-as-Usual scenario of IPCC) with the climate models developed at Max Planck Institute for Meteorology, Hamburg have been used to assess future plausible hydrological scenario for the South Asian region. The model results indicate enhanced surface warming (2.7oC for summer and 3.6oC for winter) over the land regions of South Asia during the next hundred years. While there is no significant change in the precipitation over most of the land regions during winter, substantial increase in precipitation is likely to occur during summer. As a result, an increase in soil moisture is likely over central India, Bangladesh and South China during summer but a statistically sig-nificant decline in soil moisture is expected over central China in winter. A moderate decrease in surface runoff may occur over large areas of central China during winter while the flood prone areas of NE-India. Bangladesh and South China are likely to have an increase in surface runoff during summer by the end of next century.  相似文献   

Thermoluminescence dating of pottery from Sringaverapura—A Ramayana site     

D P Agrawal  N Bhandari  B B Lal  A K Singhvi 《Journal of Earth System Science》1981,90(2):161-172

The first thermoluminescence (TL) dates of pottery from aRamayana associated site are reported. The TL dates for pre-NBPW Black-Slipped Ware levels are 730 and 765 B.C., while radiocarbon date takes the earliest Black Slipped Ware level (for which no TL dates are available) to 905 B.C. (uncorrected). For the OCW level, three TL dates are available which range from 1035 B.C. to 875 B.C. The early NBPW period believed to be associated with theRamayana episode will thus be post-750 B.C.  相似文献