Articles written in Journal of Earth System Science

    • 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.

    • Characterisation of particulate matter at a high-altitude site in southwest India: Impact of dust episodes


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      Observations on a particulate matter $\rm{(PM_{10}}$ and $\rm{PM_{2.5})}$ were carried out during March 2015 to February 2017 over a high-altitude location Mahabaleshwar in the Western Ghats region in southwest India. Apart from temporal variation of PM and the ratio of $\rm{PM_{2.5}/PM_{10}}$, impacts of local meteorological parameters on the concentration of PM are examined. $\rm{PM_{10}}$ showed a maximum concentration during pre-monsoon, whereas $\rm{PM_{2.5}}$ showed it in winter. The monsoon season showed the lowest concentrations for both $\rm{PM_{10}}$ and $\rm{PM_{2.5}}$. Concentrations were significantly reduced in 2016 due to the washout effect from enhanced rainfall during that year. Diurnal variations of PM were related to the variation in a planetary boundary layer, mountain valley winds as well as changes in different local sources. Dominance of primary particles was observed from the $\rm{PM_{2.5}/PM_{10}}$ ratio. The Central Pollution Control Board (CPCB) threshold limit for PM was exceeded on several days mainly during pre-monsoon due to transported dust from the Arabian Peninsula and Thar Desert apart from an increase in the tourist activity. A typical case for transported dust event during March 2016 is studied. Organics and sulphate particles showed a significant enhancement during dust event. Overall, the study indicated emissions from mixed sources for PM from local as well as distant source regions over Mahabaleshwar.

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