Books by Bomidi Lakshmi Madhavan
Papers by Bomidi Lakshmi Madhavan
Copernicus GmbH, Feb 14, 2017
Interactive comment on "Multiresolution analysis of the spatiotemporal variability in global radi... more Interactive comment on "Multiresolution analysis of the spatiotemporal variability in global radiation observed by a dense network of 99 pyranometers during the HOPE campaign" by Bomidi Lakshmi Madhavan et al. Bomidi Lakshmi Madhavan et al.
Remote Sensing
In recent years (2017–2019), several moderate volcanic eruptions and wildfires have perturbed the... more In recent years (2017–2019), several moderate volcanic eruptions and wildfires have perturbed the stratospheric composition and concentration with distinct implications on radiative forcing and climate. The Stratospheric Aerosol and Gas Experiment III instruments onboard the International Space Station (SAGE III/ISS) have been providing aerosol extinction coefficient (EC) profiles at multiple wavelengths since June 2017. In this study, a method to invert the spectral stratospheric aerosol optical depth (sAOD) or EC values from SAGE III/ISS (to retrieve the number/volume size distributions and other microphysical properties) is presented, and the sensitivity of these retrievals is evaluated. It was found that the retrievals are strongly dependent on the choices of wavelengths, which in turn determine the shapes of the calculated curves. Further, we examine the changes in stratospheric aerosol spectral behavior, size distribution properties, time evolution (growth/decay) characteristi...
Atmospheric Environment, 2022
Vertical distribution of aerosols and their composition in the lower troposphere is critically im... more Vertical distribution of aerosols and their composition in the lower troposphere is critically important for assessing the Earth's radiation budget and their impact on monsoon circulation. We combine the extinction coefficient, particulate depolarization ratio obtained from CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) for period of 11 years (2008-2018) over the Indian region to provide an unprecedented climatological overview of the physical and optical characteristics of quasi-aerosol layers and their source and formation mechanism throughout its annual life cycle in the free troposphere. The key findings includes: i)The quasi aerosol layer over the Indian region are found to be persistent between 4-6 km during all seasons and occasionally reach above 6 km and exhibited strong seasonal and regional dependency, ii) Layer thickness varies between 2.0-3.0 km corresponds to primary peak are more frequent of about 80-90 % of cases over all six regions and while secondary layer occasionally forms (10-20 %), iii) The aerosol layer thickness increases by about 36.7 and 25% during summer and fall season compared to that of spring, and winter, iv) Layer-AOT showed year-to-year variations of up to a factor of two with a relative variability of about 15-23% (1σ), v) Trend in layer AOT is not very conspicuous and showed oscillatory pattern, vi) Depolarization ratios generally increase with height suggesting that the irregularity of aerosol shape increases with altitude, vii) The polluted dust and smoke are the major aerosol components of the observed quasi aerosol layer between 4 to 6 km for spring and fall season while these are the polluted dust during winter and summer.
The HD(CP)2 Observational Prototype Experiment (HOPE) was performed as a major 2-month field expe... more The HD(CP)2 Observational Prototype Experiment (HOPE) was performed as a major 2-month field experiment in Jülich, Germany, in April and May 2013, followed by a smaller campaign in Melpitz, Germany, in September 2013. HOPE has been designed to provide an observational dataset for a critical evaluation of the new German community atmospheric icosahedral non-hydrostatic (ICON) model at the scale of the model simulations and further to provide information on land-surface–atmospheric boundary layer exchange, cloud and precipitation processes, as well as sub-grid variability and microphysical properties that are subject to parameterizations. HOPE focuses on the onset of clouds and precipitation in the convective atmospheric boundary layer. This paper summarizes the instrument set-ups, the intensive observation periods, and example results from both campaigns. HOPE-Jülich instrumentation included a radio sounding station, 4 Doppler lidars, 4 Raman lidars (3 of them provide temperature, 3 ...
Background: Cytokine levels have been extensively described in pregnant subjects under normal and... more Background: Cytokine levels have been extensively described in pregnant subjects under normal and pathological conditions, including mood-related disorders. Concerning chemokines, very few studies have reported their association with psychiatric disorders during pregnancy. Therefore, we explored the chemokine profile in women exhibiting anxiety and depression during late pregnancy in the present study. Methods: One hundred twenty-six pregnant women in the 3rd trimester of pregnancy, displaying moderate to severe anxiety (ANX) alone and women exhibiting moderate to severe anxiety with comorbid depression (ANX + DEP), and 40 control pregnant women without affective disorders (CTRL) were evaluated through the Hamilton Anxiety Rating Scale (HARS) and the Hamilton Depression Rating Scale (HDRS). Serum chemokine levels of MCP-1 (CCL2), RANTES (CCL5), IP-10 (CXCL10), Eotaxin (CCL11), TARC (CCL17), MIP-1α (CCL3), MIP-1β (CCL4), MIG (CXCL9), MIP-3α (CCL20), ENA-78 (CXCL5), GROα (CXCL1), I-TAC (CXCL11) and IL-8 (CXCL8)] were measured by immunoassay. Clinical, biochemical, and sociodemographic parameters were correlated with HARS and HDRS score values. Results: Serum levels of most chemokines were significantly higher in the ANX and in the ANX + DEP groups, when compared to the CTRL group. Positive correlations were observed between MIP-1α/CCL3, MIP-1β/CCL4, MCP-1/CCL2, MIP-3α/CCL20, RANTES/CCL5, Eotaxin/CCL11, and I-TAC/CXCL11 with high scores for anxiety (HARS) (p < 0.05) and for depression (HDRS) (p < 0.004). After controlling clinical measures for age + gwk + BMI, chemokines such as IL-8/ CXCL8, MCP-1/CCL2 and MIP-1β/CCL4 were found associated with high scores for anxiety (p < 0.05) in the ANX group. TARC/CCL17 and Eotaxin/CCL11 showed significant associations with high scores for depression (p < 0.04) whereas, MCP-1/CCL2 and MIP-1α/CCL3 were significantly associated with high scores for anxiety (p < 0.05) in the ANX + DEP group. Using a multivariate linear model, high serum levels of MIP-1β/CCL4 and Eotaxin/CCL11 remained associated with depression (p < 0.01), while, IL-8/CXCL8, MIP-1β/CCL4, MCP-1/CCL2, and MIP-1α/CCL3 were associated with anxiety (p < 0.05) in the symptomatic groups. Conclusions: Our data show that serum levels of distinct chemokines are increased in women exhibiting high levels of affective symptoms during late pregnancy. Our results suggest that increased levels of anxiety, depressive
Over last two decades, South Asia has witnessed a rapid increase in population, industrialization... more Over last two decades, South Asia has witnessed a rapid increase in population, industrialization, and energy demands. Consequently, 2-6 fold increase in the emission of particulate matter (PM) and trace gases were reported. Air pollution in South Asia has more adverse impact and is linked to nearly 1 million premature deaths and around 10 million tonnes of crop loss in a year. So, monitoring of trace gases and PM concentrations over urban centers has received significant attention among scientists, policymakers, health regulatory agencies, and the media. Particularly over the Indian region, this becomes significant, as the observation of trace gases and PM concentrations with fairly good temporal and spatial resolutions is limited. Concerns about air quality and transport pathways on a regional scale also place more stringent demand on observations and modeling effort. Quantifying the source contribution (regional emission due to various anthropogenic activities such as city traffi...
The possible interaction and modification of cloud properties due to aerosols is one of the most ... more The possible interaction and modification of cloud properties due to aerosols is one of the most poorly understood mechanisms within climate studies, resulting in the most significant uncertainty as regards radiation budgeting. In this study, we explore direct ground based remote sensing methods to assess the Aerosol-Cloud Indirect Effect directly, as space-borne retrievals are not directly suitable for simultaneous aerosol/cloud retrievals. To illustrate some of these difficulties, a statistical assessment of existing multispectral imagers on geostationary (e.g., GOES)/Moderate Resolution Imaging Spectroradiometer (MODIS) satellite retrievals of the Cloud Droplet Effective Radius (R eff) showed significant biases especially at larger solar zenith angles, further motivating the use of ground based remote sensing approaches. In particular, we discuss the potential of using a combined Microwave Radiometer (MWR)-Multi-Filter Rotating Shadowband Radiometer (MFRSR) system for real-time monitoring of Cloud Optical Depth (COD) and Cloud Droplet Effective Radius (R eff), which are combined with aerosol vertical properties from an aerosol lidar. An iterative approach combining the simultaneous observations from MFRSR and MWR are used to retrieve the COD and R eff for thick cloud cases and are extensively validated using the DoE Southern Great Plains (SGP) retrievals as well as regression based parameterized model retrievals. In addition, we account for uncertainties in background aerosol, surface albedo and the combined measurement uncertainties from OPEN ACCESS Atmosphere 2012, 3 469 the MWR and MFRSR in order to provide realistic uncertainty estimates, which is found to be ~10% for the parameter range of interest in Aerosol-Cloud Interactions. Finally, we analyze a particular case of possible aerosol-cloud interaction described in the literature at the SGP site and demonstrate that aerosol properties obtained at the surface can lead to inconclusive results in comparison to lidar-derived aerosol properties near the cloud base.
IEEE Transactions on Geoscience and Remote Sensing, 2014
Sun photometric measurements are an important method of measuring the column amount and optical p... more Sun photometric measurements are an important method of measuring the column amount and optical properties of atmospheric aerosols and are frequently used to better understand the impact of aerosols on the Earth's radiative budget. This paper assesses two calibration techniques used for multifilter rotating shadowband radiometers (MFRSRs) and presents the results obtained at Long Island, NY, during the July 2011 Aerosol Life Cycle Intensive Operational Period (IOP) campaign. The instrument calibration constants are validated internally against each other and against an independent quantitative technique based on the solar irradiance at the top of the atmosphere, convolved with the MFRSR filter response. In addition, the aerosol optical parameters obtained from the MFRSR are assessed against the same parameters retrieved with a recently calibrated CIMEL sun/sky radiometer collocated with the MFRSR instrument. These comparisons indicate generally good agreement between the two instruments for both calibration techniques. The advantages and disadvantages of the two techniques are presented. Additionally, an analysis of the optical and physical properties of aerosols from the MFRSR and their chemical compositions obtained by an in situ high-resolution time-of-flight aerosol mass spectrometer, together with back trajectories, indicate that the principal source of high concentrations of fine aerosols observed during July 18-24 was forest fires in western Canada.
IEEE Transactions on Geoscience and Remote Sensing, 2013
Understanding of chemical, physical, and radiative processes-emissions, transport, deposition, an... more Understanding of chemical, physical, and radiative processes-emissions, transport, deposition, and modification of aerosol optical properties due to ageing-is of major importance to global and regional climate simulations and projections as well as health impairment. This paper presents aerosol optical properties retrieved with the Multifilter Rotating Shadowband Radiometers (MFRSRs) and the source attribution based on back trajectories and in situ aerosol chemical composition analysis obtained during the Aerosol Life Cycle Intensive Observational Period at Brookhaven National Laboratory on Long Island, NY, during July and August 2011. The aerosol optical properties retrieved with the MFRSR exhibit excellent agreement with those obtained with a colocated Cimel sunphotometer. Apportioning aerosol optical depths by size modes reveals several episodes of high loading of fine aerosol (diameter less than 2.5 μm). Analysis of optical and physical properties of aerosols as well as their chemical composition obtained by an in situ high-resolution timeof-flight aerosol mass spectrometer together with back trajectories indicates that the principal source of high concentrations of fine aerosols observed during July 18-24 was forest fires in western Canada, consistent with reports by the Canadian Forest Service and satellite observations by the Moderate Resolution Imaging Spectroradiometer (MODIS).
Atmospheric Measurement Techniques, 2016
As part of the <b>H</b>igh Definition Clouds and Precipitation for advancing Climate ... more As part of the <b>H</b>igh Definition Clouds and Precipitation for advancing Climate Prediction <b>O</b>bservational <b>P</b>rototype <b>E</b>xperiment (HOPE), a high-density network of 99 silicon photodiode pyranometers was set up around Jülich (10 km × 12 km area) from April to July 2013 to capture the small-scale variability of cloud-induced radiation fields at the surface. In this paper, we provide the details of this unique setup of the pyranometer network, data processing, quality control, and uncertainty assessment under variable conditions. Some exemplary days with clear, broken cloudy, and overcast skies were explored to assess the spatiotemporal observations from the network along with other collocated radiation and sky imager measurements available during the HOPE period.
Arabian Journal of Geosciences
Atmospheric Measurement Techniques Discussions
As part of the High Definition Clouds and Precipitation for advancing Climate Prediction Observat... more As part of the High Definition Clouds and Precipitation for advancing Climate Prediction Observational Prototype Experiment (HOPE), a high spatial density network of 99 silicon photodiode pyranometers was set up around Jülich (10 km x 12 km area) from April to July 2013, to capture the variability in the radiation field at the surface induced by small-scale cloud inhomogeneity. Each of these autonomously operated pyranometer stations was equipped with weather sensors for simultaneous measurements of ambient air temperature and relative humidity. In this paper, we provide the details of this unique setup of the pyranometer network and the data analysis with initial quality screening procedure we adopted. We also present some exemplary cases consisting of the days with clear, broken cloudy and overcast skies to assess our spatio-temporal observations from the network, and validate their consistency with other collocated radiation measurements available during the HOPE period.
Atmospheric Chemistry and Physics
The time series of global radiation observed by a dense network of 99 autonomous pyranometers dur... more The time series of global radiation observed by a dense network of 99 autonomous pyranometers during the HOPE campaign around Jülich, Germany, are investigated with a multiresolution analysis based on the maximum overlap discrete wavelet transform and the Haar wavelet. For different sky conditions, typical wavelet power spectra are calculated to quantify the timescale dependence of variability in global transmittance. Distinctly higher variability is observed at all frequencies in the power spectra of global transmittance under broken-cloud conditions compared to clear, cirrus, or overcast skies. The spatial autocorrelation function including its frequency dependence is determined to quantify the degree of similarity of two time series measurements as a function of their spatial separation. Distances ranging from 100 m to 10 km are considered, and a rapid decrease of the autocorrelation function is found with increasing frequency and distance. For frequencies above 1∕3 min<sup>...
Atmospheric Chemistry and Physics
The HD(CP)<sup>2</sup> Observational Prototype Experiment (HOPE) was performed as a m... more The HD(CP)<sup>2</sup> Observational Prototype Experiment (HOPE) was performed as a major 2-month field experiment in Jülich, Germany, in April and May 2013, followed by a smaller campaign in Melpitz, Germany, in September 2013. HOPE has been designed to provide an observational dataset for a critical evaluation of the new German community atmospheric icosahedral non-hydrostatic (ICON) model at the scale of the model simulations and further to provide information on land-surface–atmospheric boundary layer exchange, cloud and precipitation processes, as well as sub-grid variability and microphysical properties that are subject to parameterizations. HOPE focuses on the onset of clouds and precipitation in the convective atmospheric boundary layer. This paper summarizes the instrument set-ups, the intensive observation periods, and example results from both campaigns. <br><br> HOPE-Jülich instrumentation included a radio sounding station, 4 Doppler lidars, 4 Ram...
Atmospheric Chemistry and Physics Discussions, 2016
The "HD(CP)<sup>2</sup> Observational Prototype Experiment" (HOPE) was exec... more The "HD(CP)<sup>2</sup> Observational Prototype Experiment" (HOPE) was executed as a major 2-month field experiment in Jülich, Germany, performed in April and May 2013, followed by a smaller campaign in Melpitz, Germany in September 2013. HOPE has been designed to provide a critical evaluation of the new German community atmospheric Icosahedral non-hydrostatic (ICON) model at the scale of the model simulations and further to provide information on land-surface-atmospheric boundary layer exchange, cloud and precipitation processes as well as on sub-grid variability and microphysical properties that are subject to parameterizations. HOPE focuses on the onset of clouds and precipitation in the convective atmospheric boundary layer. The paper summarizes the instrument set-ups, the intensive observation periods as well as example results from both campaigns. <br><br> HOPE-Jülich instrumentation included a radio sounding station, 4 Doppler lidars, 4 Raman...
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Books by Bomidi Lakshmi Madhavan
Papers by Bomidi Lakshmi Madhavan