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Mass loading and chemical composition of atmospheric aerosols over the Arabian Sea during the pre-monsoon months of April and May have been studied as a part of the Integrated Campaign for Aerosols, gases and Radiation Budget (ICARB). These investigations show large spatial variabilities in total aerosol mass loading as well as that of individual chemical species. The mass loading is found to vary between 3.5 and 69.2 μg m?3, with higher loadings near the eastern and northern parts of Arabian Sea, which decreases steadily to reach its minimum value in the mid Arabian Sea. The decrease in mass loading from the coast of India towards west is estimated to have a linear gradient of 1.53 μg m?3/° longitude and an e?1 scale distance of ～2300 km. SO 4 2? , Cl? and Na+ are found to be the major ionic species present. Apart from these, other dominating watersoluble components of aerosols are NO 3 ? (17%) and Ca2+ (6%). Over the marine environment of Arabian Sea, the non-sea-salt component dominates accounting to ～76% of the total aerosol mass. The spatial variations of the various ions are examined in the light of prevailing meteorological conditions and airmass back trajectories. 相似文献
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I A Girach Narendra Ojha Prabha R Nair Yogesh K Tiwari K Ravi Kumar 《Journal of Earth System Science》2018,127(1):15
In situ measurements of near-surface ozone (\(\hbox {O}_{3})\), carbon monoxide (CO), and methane (\(\hbox {CH}_{4})\) were carried out over the Bay of Bengal (BoB) as a part of the Continental Tropical Convergence Zone (CTCZ) campaign during the summer monsoon season of 2009. \(\hbox {O}_{3}\), CO and \(\hbox {CH}_{4}\) mixing ratios varied in the ranges of 8–54 ppbv, 50–200 ppbv and 1.57–2.15 ppmv, respectively during 16 July–17 August 2009. The spatial distribution of mean tropospheric \(\hbox {O}_{3}\) from satellite retrievals is found to be similar to that in surface \(\hbox {O}_{3}\) observations, with higher levels over coastal and northern BoB as compared to central BoB. The comparison of in situ measurements with the Monitoring Atmospheric Composition & Climate (MACC) global reanalysis shows that MACC simulations reproduce the observations with small mean biases of 1.6 ppbv, –2.6 ppbv and 0.07 ppmv for \(\hbox {O}_{3}\), CO and \(\hbox {CH}_{4}\), respectively. The analysis of diurnal variation of \(\hbox {O}_{3}\) based on observations and the simulations from Weather Research and Forecasting coupled with Chemistry (WRF-Chem) at a stationary point over the BoB did not show a net photochemical build up during daytime. Satellite retrievals show limitations in capturing \(\hbox {CH}_{4}\) variations as measured by in situ sample analysis highlighting the need of more shipborne in situ measurements of trace gases over this region during monsoon. 相似文献
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Thara V. Prabha Anandakumar Karipot Michael W. Binford 《Boundary-Layer Meteorology》2007,123(2):239-261
Large-eddy simulation is used to study secondary circulations in the convective boundary layer modulated as a result of horizontally
varying surface properties and surface heat fluxes over flat terrain. The presence of heat flux heterogeneity and its alignment
with respect to geostrophic wind influences the formation, strength and orientation of organized thermals. Results show boundary-attached
roll formation along heat flux maxima in the streamwise direction. The streamwise organization of the updrafts and downdrafts
formed downwind of heterogeneities leads to counter-rotating secondary circulations in the crosswind plane. The distribution
of resolved-scale pressure deviations shows large pressure gradients in the crosswind plane. Spanwise and vertical velocity
variances and heat flux profiles depict considerable spatial variability compared to a homogeneous forest simulation. Secondary
circulations are observed for various ambient wind scenarios parallel and perpendicular to heterogeneities. In the presence
of increased wind speed, thermals emerging from the heat flux heterogeneity are elongated, and organize along and downwind
of large-scale heterogeneity in the streamwise direction. Simulation with a reduced heat flux shows a shallower circulation
with a lower aspect ratio. Point measurements of heat flux inside the roll circulation could be overestimated by up to 15–25%
compared to a homogeneous case. 相似文献
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Rajesh Sharma Prabha Joshi P. D. Pant 《Journal of the Geological Society of India》2009,73(2):237-248
Talc deposits of Rema area in the Kumaun Inner Lesser Himalaya are hosted within high magnesium carbonates of the Proterozoic
Deoban Formation. These deposits occur as irregular patches or pockets mainly within magnesite bodies, along with impurities
of magnesite, dolomite and clinochlore. Textures represent different phases of reactions between magnesite and silica to produce
talc. Petrography, XRD and geochemistry reveal that the talc has primarily developed at the expense of magnesite and silica,
leaving dolomite largely un-reacted. Early fluid inclusions in magnesite and dolomite associated with talc are filled with
H2O+NaCl+KCl ± MgCl2 ± CaCl2 fluids, which represent basin fluid system during diagenesis of carbonates. Their varied degree of re-equilibration was although
not pervasive but points to increased burial, and hence requires careful interpretation. H2O-CO2 fluid with XCO2 between 0.06 and 0.12 was equilibrated with talc formation. The reaction dolomite+quartz → talc was not extensive because
T-XCO2 was not favourable, and talc was developed principally after magnesite+quartz. 相似文献
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Murugavel P. Malap N. Balaji B. Mehajan R. K. Prabha T. V. 《Theoretical and Applied Climatology》2017,130(1-2):467-476
Based on the precipitable water observations easily available from in situ and remote sensing sensors, a simple approach to define the lifting condensation level (LCL) is proposed in this study. High-resolution radiosonde and microwave radiometer observations over peninsular Indian region during the Cloud Aerosol Interaction and Precipitation Enhancement Experiment Integrated Ground Observational Campaign (CAIPEEX-IGOC) during the monsoon season of 2011 are used to illustrate the unique relationship. The inferences illustrate a linear relationship between the precipitable water (PW) and the LCL temperature. This relationship is especially valuable because PW is easily available as a derived parameter from various remote sensing and ground-based observations. Thus, it could be used to estimate the LCL height and perhaps also the boundary layer height. LCL height and PW correlations are established from historical radiosonde data (1984–2012). This finding could be used to illustrate the boundary layer-cloud interactions during the monsoon and is important for parameterization of boundary layer clouds in numerical models. The relationships are illustrated to be robust and seem promising to get reasonable estimates of the LCL height over other locations as well using satellite observations of PW.
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Phiros Shah R. Sajeev K. J. Thara Grinson George Muhammad Shafeeque S. Akash 《Marine Geodesy》2019,42(1):64-84
An attempt has been made to develop a holistic understanding of upwelling and downwelling along the south-west coast of India. The main objective was to elucidate the roles of different forcings involved in the vertical motion along this coast. The south-west coast of India was characterized by upwelling during the south-west monsoon (May to September) and by downwelling during the north-east monsoon and winter (November to February). The average vertical velocity calculated along the south-west coast from the vertical shift of the 26?°C isotherm is 0.57?m/day during upwelling and 0.698?m/day during downwelling. It was concluded that upwelling along the south-west coast of India is driven by offshore Ekman transport due to the alongshore wind, Ekman pumping, horizontal divergence of currents and by the propagation of coastally trapped waves. Whereas downwelling along the coast is driven only by convergence of currents and the propagation of coastally trapped Kelvin waves. Along the west coast of India, the downwelling-favorable Kelvin waves come from the equator and upwelling-favorable waves come from the Gulf of Mannar region. 相似文献
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Time series of soil surface and subsurface temperatures, soil heat flux, net radiation, air temperature and wind speed were
measured at two locations in Kalpakkam, coastal southeast India. The data were analysed to estimate soil thermal diffusivity,
thermal conductivity, volumetric heat capacity and soil heat flux. This paper describes the results and discusses their implications. 相似文献
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Land surface parameterization schemes play a significant role in the accuracy of meso-local scale numerical models by accounting for the exchange of energy and water between the soil and the atmosphere. The role of land surface processes during large-scale cold-pooling events was studied with two land surface schemes (LSMs) in the Advanced Research Weather Forecasting model (ARW). Model evaluation was complex due to the surface and boundary layer interactions at different temporal and spatial scales as revealed by a scale dependent variance analysis. Wavelet analysis was used for the first time to analyze the model errors with specific focus on land surface processes. The ARW model was also evaluated for the formation of a low-level jet (LLJ). It is shown that vertical resolution in the model boundary layer played a significant role in determining the characteristics of LLJ, which influenced the lower boundary layer structure and moisture distribution. The results showed that the simulated low-level jet over southern Georgia was sensitive to the land surface parameterization and led to a significant difference in the boundary layer exchange. The jet shear played a crucial role in the maintenance of turbulence and weak shear caused excessive radiative cooling leading to unrealistic cold pools in the model. The results are important for regional downscaling as the excessive cold pools that are simulated in the model can go unnoticed. 相似文献