• Devendraa Siingh

      Articles written in Journal of Earth System Science

    • Chemistry of snow and lake water in Antarctic region

      Kaushar Ali Sunil Sonbawane D M Chate Devendraa Siingh P S P Rao P D Safai K B Budhavant

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      Surface snow and lake water samples were collected at different locations around Indian station at Antarctica, Maitri, during December 2004-March 2005 and December 2006-March 2007.Samples were analyzed for major chemical ions. It is found that average pH value of snow is 6.1. Average pH value of lake water with low chemical content is 6.2 and of lake water with high chemical content is 6.5.The Na+ and Cl are the most abundantly occurring ions at Antarctica. Considerable amount of SO$^{2-}_{4}$ is also found in the surface snow and the lake water which is attributed to the oxidation of DMS produced by marine phytoplankton.Neutralization of acidic components of snow is mainly done by NH$^{+}_{4}$ and Mg2+. The Mg2+, Ca2+ and K+ are nearly equally effective in neutralizing the acidic components in lake water.The NH$^{+}_{4}$ and SO$^{2-}_{4}$ occur over the Antarctica region mostly in the form of (NH4)2SO4.

    • The ion–aerosol interactions from the ion mobility and aerosol particle size distribution measurements on January 17 and February 18, 2005 at Maitri, Antarctica – A case study

      Devendraa Siingh Vimlesh Pant A K Kamra

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      A case study for the ion–aerosol interactions is presented from the simultaneous measurements of mobility spectra of atmospheric ions in the mobility range of 2.29 to 2.98 × 10−4 cm2 V−1 s−1 (diameter range 0.41–109 nm) and of size distribution of atmospheric aerosol particles in the size ranges of 4.4–700 nm and 500–20,000 nm diameters made at Maitri (70° 45′ 52′′S, 11° 44′ 2.7′′E; 130 m above mean sea level), Antarctica, on two days January 17 and February 18, 2005, with contrasting meteorological conditions. In contrast to January 17, on February 18, winds were stronger from the morning to noon and lower from the noon to evening, atmospheric pressure was lower, cloudiness was more, the land surface remained snow-covered after a blizzard on February 16 and 17 and the airmass over Maitri, descended from an altitude of ∼3 km after an excursion over ocean. On these days mobility spectra showed two modes, corresponding to intermediate ions and light large ions and an indication of additional one/two maxima for small/cluster ions and heavy large ions. The small ions generated by cosmic rays, and the nucleation mode particles generated probably by photochemical reactions grew in size by condensation of volatile trace gases on them and produced the cluster and intermediate ion modes and the Aitken particle mode in ion/particle spectra. Particles in the size range of 9–26 nm have been estimated to grow at the rate of 1.9 nm h−1 on February 18, 2005. Both, ions and aerosol particles show bimodal size distributions in the 16–107 nm size range, and comparison of the two size distributions suggests the formation of multiple charged ions. Attachment of small ions to particles in this bimodal distribution of Aitken particles together with the formation of multiple charged ions are proposed to result in the light and heavy large ion modes. Growth of the nucleation mode particles on February 18, 2005 is associated with the passage of the airmass over ocean. In contrast, though the ion size distributions were not much different, the aerosol size distributions did not show a dominant peak for the formation and growth of nucleation mode particles on January 17. More measurements are needed before the conclusion of this case study is generalized.

    • Tidal and gravity waves study from the airglow measurements at Kolhapur (India)

      R N Ghodpage Devendraa Siingh R P Singh G K Mukherjee P Vohat A K Singh

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      Simultaneous photometric measurements of the OI 557.7 nm and OH (7, 2) band from a low latitude station, Kolhapur (16.8°N, 74.2°E) during the period 2004–2007 are analyzed to study the dominant waves present in the 80–100 km altitude region of the atmosphere. The nocturnal intensity variations of different airglow emissions are observed using scanning temperature controlled filter photometers. Waves having period lying between 2 and 12 hours have been recorded. Some of these waves having subharmonic tidal oscillation periods 4, 6, 8 and 12 hours propagate upward with velocity lying in the range 1.6–11.3 m/s and the vertical wave length lying between 28.6 and 163 kms. The other waves may be the upward propagating gravity waves or waves resulting from the interaction of inter-mode tidal oscillations, interaction of tidal waves with planetary waves and gravity waves. Some times, the second harmonic wave has higher vertical velocity than the corresponding fundamental wave. Application of these waves in studying the thermal structure of the region is discussed.

    • The influence of wind speed on surface layer stability and turbulent fluxes over southern Indian peninsula station

      M N Patil R T Waghmare T Dharmaraj G R Chinthalu Devendraa Siingh G S Meena

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      Surface to atmosphere exchange has received much attention in numerical weather prediction models. This exchange is defined by turbulent parameters such as frictional velocity, drag coefficient and heat fluxes, which have to be derived experimentally from high-frequency observations. High-frequency measurementsof wind speed, air temperature and water vapour mixing ratio (eddy covariance measurements), were made during the Integrated Ground Observation Campaign (IGOC) of Cloud Aerosol Interaction and Precipitation Enhancement Experiment (CAIPEEX) at Mahabubnagar, India (16◦44'N, 77◦59'E) in the south-west monsoon season. Using these observations, an attempt was made to investigatethe behaviour of the turbulent parameters, mentioned above, with respect to wind speed. We found that the surface layer stability derived from the Monin–Obukhov length scale, is well depicted by the magnitude of wind speed, i.e., the atmospheric boundary layer was under unstable regime for wind speeds greater than 4 m s−1; under stable regime for wind speeds less than 2 m s−1 and under neutral regime for wind speeds in the range of 2–3 m s$^{−1}$. All the three stability regimes were mixed for wind speeds 3–4 m s$^{−1}$. The drag coefficient shows scatter variation with wind speed in stable as well as unstable conditions.

    • Distribution of lightning in relation to topography and vegetation cover over the dry and moist regions in the Himalayas

      Sunil Oulkar Devendraa Siingh Upal Saha Adarsh Kumar Kamra

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      The impacts of elevation, terrain slope and vegetation cover on lightning activity are investigated for contrasting environments in the north-east (NE) (21–29$^{\circ}$N; 86–94$^{\circ}$E) and the north-west (NW) (28–36$^{\circ}$N; 70–78$^{\circ}$E) regions of the Himalayan range. Lightning activity is more at a higher terrain slope/elevation in the dry NW region where vegetation cover is less, whereas it is more at a lower terrain slope/elevation in the moist NE region where vegetation cover is more. In the wet NE, 86% (84%) of the annual lightning flash rate density (LFRD) occurs at an elevation < 500 m (terrain slope < 2%) and then sharply falls off at a higher elevation (terrain slope). However, only 49% (47%) of LFRD occurs at an elevation of < 500 m (terrain slope < 2%) and then rather gradually falls off at a higher elevation (terrain slope) in the dry NW. The ratio of the percentages of LFRD and elevation points is much higher in the NW than in the NE above an elevation of ${\sim}$1000 m. The impacts of terrain slope and elevation in enhancing the lightning activity are stronger in the dry NW than in the moist NE. The correlation coefficient of the LFRD with the normalised difference vegetation index is higher in the NW than in the NE on both the regional and annual scales. Results are discussed as a caution in using any single climate variable as a proxy for projecting a change in the lightning–climate relationships in the scenario of global warming.

    • Observations of carbon dioxide and turbulent Cuxes during fog conditions in north India


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      The occurrence of thick fog for longer duration in the northern regions of India disturbs the aviation, roadtransportation and other day to day activities. To understand the turbulence properties during fog period,we measured the atmospheric turbulent parameters along with carbon dioxide concentrations in theatmospheric boundary layer using eddy covariance system. These measurements were conducted over the agricultural station, Hisar, India, during the months of January–February of the year 2017 and 2018.During this period, total five thick fog events and three moderate fog events were captured. The turbulentparameter such as friction velocity, stability, sensible and latent heat fluxes are presented with respect tofog events. During the study period, the western disturbance persists over the north Pakistan andneighborhood region which advects the large amount of moisture into the lower troposphere and furtherthrough evaporation. It enforces stable and clear sky atmospheric conditions and reduces the surfacetemperature leading to the formation of strong surface-based temperature inversion which facilitatesthe fog formation in the study region. The land surface processes with neutral stability conditions in thesurface layer, play significant role to sustain fog in the study region. The observations show substantialincrease of carbon dioxide concentration during the thick fog events. The foggy days did not depict thediurnal pattern in flux of $\rm{CO}_{2}$. The anomalies of the meteorological parameters during foggy days and clear sky are analyzed. The foggy conditions (04:00–10:00 h, IST) are found to be characterized with low wind speed, high relative humidity with remarkable fluctuations in dew point temperature. Also, the sensible and latent heat flux shows remarkable changes during foggy and clear sky conditions.

    • Fair-weather atmospheric electric Beld measurements at Gulmarg, India


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      In the present study, the atmospheric electric Beld observations are reported at Gulmarg station, Kashmir (34°05'N; 74°42'E) for a period of 1 year: June 2019–May 2020. The observation site is situated in an area with high thunderstorm activity and very high radon concentration. Diurnal characteristics of PG are explained with electrode effect under summer/dry surface conditions and evaporation effect under winter/ wet surface conditions associated with sunrise. The latter effect is highly responsible for the diurnal peak of PG observed in afternoon (1300 LT) hours along with the water vapour pressure under low temperature. Similarly, excess positive charges found at the electrode layer shift the diurnal peak to an earlier time ${\sim}$1000–1100 LT under turbulent exchange from the surface. Therefore, the annual mean curve is the resultant of these two effects that act in different seasons. In addition, the annual diurnal variation of the potential gradient is in agreement with some other continental stations having two maxima and higher values of PG during the winter months. The secondary diurnal maximum (2000 LT) is likely due to African thunderstorm activity being reflected strongly at our measurement site. Comparison of our results with Carnegie leads to a weak correlation between the two, which is due to the difference in the nature of observation sites, while a comparison with the observations of B N Raina (August 1970–October 1973) at the same observatory reveals a similar nature of PG variation. Finally, simple correlation plots of PG with meteorological parameters and radon concentration have been shown. The results indicate that radon concentration and meteorological parameters like temperature, relative humidity in addition to water vapour pressure are important local factors influencing the surface PG measurements at our site.

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