Articles | Volume 32, issue 2
https://doi.org/10.5194/angeo-32-175-2014
© Author(s) 2014. This work is distributed under
the Creative Commons Attribution 3.0 License.
the Creative Commons Attribution 3.0 License.
https://doi.org/10.5194/angeo-32-175-2014
© Author(s) 2014. This work is distributed under
the Creative Commons Attribution 3.0 License.
the Creative Commons Attribution 3.0 License.
ANGEO Communicates
| 
21 Feb 2014
ANGEO Communicates |
| 21 Feb 2014
Signatures of Rossby wave modulations in aerosol optical depth over the central Himalayan region
D. V. Phanikumar
Aryabhatta Research Institute of observational Sciences, Nainital, India
K. Niranjan Kumar
Masdar Institute of Science and Technology, Abu Dhabi, United Arab Emirates
K. K. Shukla
Aryabhatta Research Institute of observational Sciences, Nainital, India
Pt. Ravishankar Shukla University, Raipur, Chhatisgarh, India
H. Joshi
Aryabhatta Research Institute of observational Sciences, Nainital, India
M. Venkat Ratnam
National Atmospheric Research Laboratory, Gadanki, India
Aryabhatta Research Institute of observational Sciences, Nainital, India
K. Reddy
Department of Physics, Yogi Vemana University, Kadapa, India
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K. K. Shukla, K. Niranjan Kumar, D. V. Phanikumar, R. K. Newsom, V. R. Kotamarthi, T. B. M. J. Ouarda, and M. V. Ratnam
Atmos. Meas. Tech. Discuss., https://doi.org/10.5194/amt-2016-162, https://doi.org/10.5194/amt-2016-162, 2016
Revised manuscript not accepted
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Estimation of Cloud base height was carried out by using various ground based instruments (Doppler Lidar and Ceilometer) and satellite datasets (MODIS) over central Himalayan region for the first time. The present study demonstrates the potential of Doppler Lidar in precise estimation of cloud base height and updraft velocities. More such deployments will be invaluable inputs for regional weather prediction models over complex Himalayan terrains.
K. Niranjan Kumar, D. V. Phanikumar, T. B. M. J. Ouarda, M. Rajeevan, M. Naja, and K. K. Shukla
Ann. Geophys., 34, 123–132, https://doi.org/10.5194/angeo-34-123-2016, https://doi.org/10.5194/angeo-34-123-2016, 2016
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The link between upper-tropospheric planetary-scale Rossby waves and surface meteorological parameters is examined. The propagating Rossby waves along with undulations in the subtropical jet create convergence and divergence regions in the mid-troposphere. The surface relative humidity, wind speeds, and temperature are synchronized with the phase of the propagating Rossby waves. The present study finds important implications for medium-range forecasting through Rossby wave propagation.
Vadassery Neelamana Santhosh, Bomidi Lakshmi Madhavan, Sivan Thankamani Akhil Raj, Madineni Venkat Ratnam, Jean-Paul Vernier, and Frank Gunther Wienhold
EGUsphere, https://doi.org/10.5194/egusphere-2024-2861, https://doi.org/10.5194/egusphere-2024-2861, 2024
This preprint is open for discussion and under review for Atmospheric Chemistry and Physics (ACP).
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Our study examines a lesser-known atmospheric feature, the Asian Tropopause Aerosol Layer, located high above Earth. We investigated how different aerosols, such as sulfates, nitrates, and pollutants, influence heat entering and leaving the atmosphere. The results show that these particles can alter temperature patterns, especially during the Asian summer monsoon. This research improves our understanding of how human activities may affect regional climate.
Vishnu Thilakan, Dhanyalekshmi Pillai, Jithin Sukumaran, Christoph Gerbig, Haseeb Hakkim, Vinayak Sinha, Yukio Terao, Manish Naja, and Monish Vijay Deshpande
Atmos. Chem. Phys., 24, 5315–5335, https://doi.org/10.5194/acp-24-5315-2024, https://doi.org/10.5194/acp-24-5315-2024, 2024
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This study investigates the usability of CO2 mixing ratio observations over India to infer regional carbon sources and sinks. We demonstrate that a high-resolution modelling system can represent the observed CO2 variations reasonably well by improving the transport and flux variations at a fine scale. Future carbon data assimilation systems can thus benefit from these recently available CO2 observations when fine-scale variations are adequately represented in the models.
Amit Kumar Pandit, Jean-Paul Vernier, Thomas Duncan Fairlie, Kristopher M. Bedka, Melody A. Avery, Harish Gadhavi, Madineni Venkat Ratnam, Sanjeev Dwivedi, Kasimahanthi Amar Jyothi, Frank G. Wienhold, Holger Vömel, Hongyu Liu, Bo Zhang, Buduru Suneel Kumar, Tra Dinh, and Achuthan Jayaraman
EGUsphere, https://doi.org/10.5194/egusphere-2023-2236, https://doi.org/10.5194/egusphere-2023-2236, 2023
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This study investigates the formation mechanism of a tropopause cirrus cloud layer observed at extremely cold temperatures over Hyderabad in India during the 2017 Asian summer monsoon using balloon-borne sensors. Ice crystals smaller than 50 microns were found in this optically thin cirrus cloud layer. Combined analysis of back-trajectories, satellite, and model data revealed that the formation of this layer was influenced by gravity waves and stratospheric hydration induced by typhoon Hato.
Prajjwal Rawat, Manish Naja, Evan Fishbein, Pradeep K. Thapliyal, Rajesh Kumar, Piyush Bhardwaj, Aditya Jaiswal, Sugriva N. Tiwari, Sethuraman Venkataramani, and Shyam Lal
Atmos. Meas. Tech., 16, 889–909, https://doi.org/10.5194/amt-16-889-2023, https://doi.org/10.5194/amt-16-889-2023, 2023
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Satellite-based ozone observations have gained importance due to their global coverage. However, satellite-retrieved products are indirect and need to be validated, particularly over mountains. Ozonesondes launched from a Himalayan site are used to assess the Atmospheric Infrared Sounder (AIRS) ozone retrieval. AIRS is shown to overestimate ozone in the upper troposphere and lower stratosphere, while the differences from ozonesondes are more minor in the middle troposphere and stratosphere.
Hazel Vernier, Neeraj Rastogi, Hongyu Liu, Amit Kumar Pandit, Kris Bedka, Anil Patel, Madineni Venkat Ratnam, Buduru Suneel Kumar, Bo Zhang, Harish Gadhavi, Frank Wienhold, Gwenael Berthet, and Jean-Paul Vernier
Atmos. Chem. Phys., 22, 12675–12694, https://doi.org/10.5194/acp-22-12675-2022, https://doi.org/10.5194/acp-22-12675-2022, 2022
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The chemical composition of the stratospheric aerosols collected aboard high-altitude balloons above the summer Asian monsoon reveals the presence of nitrate/nitrite. Using numerical simulations and satellite observations, we found that pollution as well as lightning could explain some of our observations.
Hossain Mohammed Syedul Hoque, Kengo Sudo, Hitoshi Irie, Alessandro Damiani, Manish Naja, and Al Mashroor Fatmi
Atmos. Chem. Phys., 22, 12559–12589, https://doi.org/10.5194/acp-22-12559-2022, https://doi.org/10.5194/acp-22-12559-2022, 2022
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Nitrogen dioxide (NO2) and formaldehyde (HCHO) are essential trace graces regulating tropospheric ozone chemistry. These trace constituents are measured using an optical passive remote sensing technique. In addition, NO2 and HCHO are simulated with a computer model and evaluated against the observations. Such evaluations are essential to assess model uncertainties and improve their predictability. The results yielded good agreement between the two datasets with some discrepancies.
Varaha Ravi Kiran, Madineni Venkat Ratnam, Masatomo Fujiwara, Herman Russchenberg, Frank G. Wienhold, Bomidi Lakshmi Madhavan, Mekalathur Roja Raman, Renju Nandan, Sivan Thankamani Akhil Raj, Alladi Hemanth Kumar, and Saginela Ravindra Babu
Atmos. Meas. Tech., 15, 4709–4734, https://doi.org/10.5194/amt-15-4709-2022, https://doi.org/10.5194/amt-15-4709-2022, 2022
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We proposed and conducted the multi-instrumental BACIS (Balloon-borne Aerosol–Cloud Interaction Studies) field campaigns using balloon-borne in situ measurements and ground-based and space-borne remote sensing instruments. Aerosol-cloud interaction is quantified for liquid clouds by segregating aerosol and cloud information in a balloon profile. Overall, the observational approach proposed here demonstrated its capability for understanding the aerosol–cloud interaction process.
Shohei Nomura, Manish Naja, M. Kawser Ahmed, Hitoshi Mukai, Yukio Terao, Toshinobu Machida, Motoki Sasakawa, and Prabir K. Patra
Atmos. Chem. Phys., 21, 16427–16452, https://doi.org/10.5194/acp-21-16427-2021, https://doi.org/10.5194/acp-21-16427-2021, 2021
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Long-term measurements of greenhouse gases (GHGs) in India and Bangladesh unveiled specific characteristics in their variations in these regions. Plants including rice cultivated in winter and summer strongly affected seasonal variations and levels in CO2 and CH4. Long-term variability of GHGs showed quite different features in their growth rates from those in Mauna Loa. GHG trends in this region seemed to be hardly affected by El Niño–Southern Oscillation (ENSO).
Rohit Chakraborty, Arindam Chakraborty, Ghouse Basha, and Madineni Venkat Ratnam
Atmos. Chem. Phys., 21, 11161–11177, https://doi.org/10.5194/acp-21-11161-2021, https://doi.org/10.5194/acp-21-11161-2021, 2021
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In this study, urbanization-induced surface warming has been found to trigger prominent changes in upper-troposphere–lower-stratosphere regions leading to stronger and more frequent lightning extremes over India. Consequently, the implementation of this hypothesis in global climate models reveals that lightning frequency and intensity values across India will rise by ~10–25 % and 15–50 %, respectively, by 2100 at the current urbanization rate, which should be alarming for present policymakers.
Saginela Ravindra Babu, Madineni Venkat Ratnam, Ghouse Basha, Shantanu Kumar Pani, and Neng-Huei Lin
Atmos. Chem. Phys., 21, 5533–5547, https://doi.org/10.5194/acp-21-5533-2021, https://doi.org/10.5194/acp-21-5533-2021, 2021
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The present study explores the detailed structure, dynamics, and trace gas variability in the Asian summer monsoon anticyclone (ASMA) in the extreme El Niño of 2015/16. The results find the structure of the ASMA shows strong spatial variability between July and August. A West Pacific mode of the anticyclone is noticed in August. A significant lowering of tropospheric tracers and strong increase in stratospheric tracers are found. The tropopause temperatures also exhibit a warming in the ASMA.
Kizhathur Narasimhan Uma, Siddarth Shankar Das, Madineni Venkat Ratnam, and Kuniyil Viswanathan Suneeth
Atmos. Chem. Phys., 21, 2083–2103, https://doi.org/10.5194/acp-21-2083-2021, https://doi.org/10.5194/acp-21-2083-2021, 2021
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Reanalysis data of vertical wind (w) are widely used by the atmospheric community to determine various calculations of atmospheric circulations, diabatic heating, convection, etc. There are no studies that assess the available reanalysis data with respect to observations. The present study assesses for the first time all the reanalysis w by comparing it with 20 years of radar data from Gadanki and Kototabang and shows that downdrafts and peaks in the updrafts are not produced in the reanalyses.
Teresa Jorge, Simone Brunamonti, Yann Poltera, Frank G. Wienhold, Bei P. Luo, Peter Oelsner, Sreeharsha Hanumanthu, Bhupendra B. Singh, Susanne Körner, Ruud Dirksen, Manish Naja, Suvarna Fadnavis, and Thomas Peter
Atmos. Meas. Tech., 14, 239–268, https://doi.org/10.5194/amt-14-239-2021, https://doi.org/10.5194/amt-14-239-2021, 2021
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Balloon-borne frost point hygrometers are crucial for the monitoring of water vapour in the upper troposphere and lower stratosphere. We found that when traversing a mixed-phase cloud with big supercooled droplets, the intake tube of the instrument collects on its inner surface a high percentage of these droplets. The newly formed ice layer will sublimate at higher levels and contaminate the measurement. The balloon is also a source of contamination, but only at higher levels during the ascent.
Sreeharsha Hanumanthu, Bärbel Vogel, Rolf Müller, Simone Brunamonti, Suvarna Fadnavis, Dan Li, Peter Ölsner, Manish Naja, Bhupendra Bahadur Singh, Kunchala Ravi Kumar, Sunil Sonbawne, Hannu Jauhiainen, Holger Vömel, Beiping Luo, Teresa Jorge, Frank G. Wienhold, Ruud Dirkson, and Thomas Peter
Atmos. Chem. Phys., 20, 14273–14302, https://doi.org/10.5194/acp-20-14273-2020, https://doi.org/10.5194/acp-20-14273-2020, 2020
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During boreal summer, anthropogenic sources yield the Asian Tropopause Aerosol Layer (ATAL), found in Asia between about 13 and 18 km altitude. Balloon-borne measurements of the ATAL conducted in northern India in 2016 show the strong variability of the ATAL. To explain its observed variability, model simulations are performed to deduce the origin of air masses on the Earth's surface, which is important to develop recommendations for regulations of anthropogenic surface emissions of the ATAL.
Ghouse Basha, M. Venkat Ratnam, and Pangaluru Kishore
Atmos. Chem. Phys., 20, 6789–6801, https://doi.org/10.5194/acp-20-6789-2020, https://doi.org/10.5194/acp-20-6789-2020, 2020
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This study explores the variability of the Asian summer monsoon anticyclone (ASMA) spatial variability and trends using long-term observational and reanalysis data sets. The decadal variability of the anticyclone is very large at the edges compared with the core region. We propose that the transport process over the Tibetan Plateau and the Indian region is significant in active monsoon, strong monsoon and strong La Niña years. Thus, different phases of the monsoon are important in UTLS analyses.
Ghouse Basha, M. Venkat Ratnam, Pangaluru Kishore, S. Ravindrababu, and Isabella Velicogna
Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-2019-743, https://doi.org/10.5194/acp-2019-743, 2019
Preprint withdrawn
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The Asian Summer Monsoon Anticyclone (ASMA) plays an important role in confining the trace gases and aerosols for a longer period. This study explores the variability of tropopause parameters, trace gases and aerosols and its relation with ENSO and QBO in ASMA. Further, the influence of the Indian summer monsoon activity on the ASMA trace gases and aerosols is studied with respect to active and break spells of monsoon, strong and weak monsoon years and strong La Niña, El Niño years.
Rohit Chakraborty, Bijay Kumar Guha, Shamitaksha Talukdar, Madineni Venkat Ratnam, and Animesh Maitra
Atmos. Chem. Phys., 19, 12325–12341, https://doi.org/10.5194/acp-19-12325-2019, https://doi.org/10.5194/acp-19-12325-2019, 2019
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The present study investigates the plausible aspects which influence the probability of drought occurrences over three Indian regions during the southwest Asian mid-monsoon period. The investigation reveals that an increasing tendency of dry day frequency (DDF) over urbanized regions in the last few decades has significant association with the abundance of anthropogenic aerosols. Additionally, future projections of DDF indicate a five-fold rise which can be a crucial concern for policy makers.
Rohit Chakraborty, Madineni Venkat Ratnam, and Shaik Ghouse Basha
Atmos. Chem. Phys., 19, 3687–3705, https://doi.org/10.5194/acp-19-3687-2019, https://doi.org/10.5194/acp-19-3687-2019, 2019
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Intense convective phenomena are a common climatic feature in the Indian tropical region which occur during the pre-monsoon to post-monsoon seasons (April–October) and are generally accompanied by intense thunderstorms, lightning, and wind gusts with heavy rainfall. Here we show long-term trends of the parameters related to convection and instability obtained from 27 radiosonde stations across six subdivisions over the Indian region during the period 1980–2016.
Simone Brunamonti, Teresa Jorge, Peter Oelsner, Sreeharsha Hanumanthu, Bhupendra B. Singh, K. Ravi Kumar, Sunil Sonbawne, Susanne Meier, Deepak Singh, Frank G. Wienhold, Bei Ping Luo, Maxi Boettcher, Yann Poltera, Hannu Jauhiainen, Rijan Kayastha, Jagadishwor Karmacharya, Ruud Dirksen, Manish Naja, Markus Rex, Suvarna Fadnavis, and Thomas Peter
Atmos. Chem. Phys., 18, 15937–15957, https://doi.org/10.5194/acp-18-15937-2018, https://doi.org/10.5194/acp-18-15937-2018, 2018
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Based on balloon-borne measurements performed in India and Nepal in 2016–2017, we infer the vertical distributions of water vapor, ozone and aerosols in the atmosphere, from the surface to 30 km altitude. Our measurements show that the atmospheric dynamics of the Asian summer monsoon system over the polluted Indian subcontinent lead to increased concentrations of water vapor and aerosols in the high atmosphere (approximately 14–20 km altitude), which can have an important effect on climate.
Khadak Singh Mahata, Maheswar Rupakheti, Arnico Kumar Panday, Piyush Bhardwaj, Manish Naja, Ashish Singh, Andrea Mues, Paolo Cristofanelli, Deepak Pudasainee, Paolo Bonasoni, and Mark G. Lawrence
Atmos. Chem. Phys., 18, 14113–14132, https://doi.org/10.5194/acp-18-14113-2018, https://doi.org/10.5194/acp-18-14113-2018, 2018
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This paper presents the first-time simultaneous measurement of CO and O3 at multiple sites in the Kathmandu Valley bottom, its mountain rim and a river outlet, providing their spatial, temporal and seasonal–diurnal variations. Our study reveals that high O3, especially during premonsoon, in observed sites is of high concern for human health and ecosystems in the region. We also estimated CO emission flux to be 2–14 times higher than widely used emission databases (EDGAR HTAP, REAS and INTEX-B).
Piyush Bhardwaj, Manish Naja, Maheswar Rupakheti, Aurelia Lupascu, Andrea Mues, Arnico Kumar Panday, Rajesh Kumar, Khadak Singh Mahata, Shyam Lal, Harish C. Chandola, and Mark G. Lawrence
Atmos. Chem. Phys., 18, 11949–11971, https://doi.org/10.5194/acp-18-11949-2018, https://doi.org/10.5194/acp-18-11949-2018, 2018
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This study provides information about the regional variabilities in some of the pollutants using observations in Nepal and India. It is shown that agricultural crop residue burning leads to a significant enhancement in ozone and CO over a wider region. Further, the wintertime higher ozone levels are shown to be largely due to local emissions, while regional transport could be important in spring and hence shows the role of regional sources versus local sources in the Kathmandu Valley.
Nelli Narendra Reddy, Madineni Venkat Ratnam, Ghouse Basha, and Varaha Ravikiran
Atmos. Chem. Phys., 18, 11709–11727, https://doi.org/10.5194/acp-18-11709-2018, https://doi.org/10.5194/acp-18-11709-2018, 2018
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Cloud vertical structure affects large-scale atmosphere circulation by altering gradients in total diabatic heating and cooling and latent heat release. Detailed cloud vertical structure in all seasons, including diurnal variation over the Indian region, is made for the first time. The detected cloud layers are verified with independent observations using cloud particle sensor sonde. Heating and cooling in the troposphere and lower stratosphere due to these cloud layers are also investigated.
Sivan Thankamani Akhil Raj, Madineni Venkat Ratnam, Daggumati Narayana Rao, and Boddam Venkata Krishna Murthy
Ann. Geophys., 36, 149–165, https://doi.org/10.5194/angeo-36-149-2018, https://doi.org/10.5194/angeo-36-149-2018, 2018
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Ozone and water vapor are two potent greenhouse gases in the atmosphere. They influence the temperature structure greatly, particularly in the upper troposphere and lower stratosphere. We have investigated the long-term trends in these trace gases over the Indian region using long-term data (1993–2015) constructed from multi-satellite observations. A decreasing trend in ozone associated with NOx chemistry in the tropical middle stratosphere and a good correlation between N2O and O3 is found.
Khadak Singh Mahata, Arnico Kumar Panday, Maheswar Rupakheti, Ashish Singh, Manish Naja, and Mark G. Lawrence
Atmos. Chem. Phys., 17, 12573–12596, https://doi.org/10.5194/acp-17-12573-2017, https://doi.org/10.5194/acp-17-12573-2017, 2017
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The paper provides an overview of CH4, CO2, and CO mixing ratios, including diurnal and seasonal variation, and discusses the association of potential sources and meteorology with the observed temporal variation in the Kathmandu Valley. The study will provide an important dataset for a poorly studied region and will be useful for validating estimates from emission inventories, regional models, and satellite observations and assisting in the design of mitigation measures in the region.
Dipesh Rupakheti, Bhupesh Adhikary, Puppala Siva Praveen, Maheswar Rupakheti, Shichang Kang, Khadak Singh Mahata, Manish Naja, Qianggong Zhang, Arnico Kumar Panday, and Mark G. Lawrence
Atmos. Chem. Phys., 17, 11041–11063, https://doi.org/10.5194/acp-17-11041-2017, https://doi.org/10.5194/acp-17-11041-2017, 2017
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For the first time, atmospheric composition was monitored during pre-monsoon season of 2013 at Lumbini (UNESCO world heritage site as birthplace of the Buddha). PM and O3 frequently exceeded WHO guidelines. Pollution concentration, diurnal characteristics and influence of open burning on air quality in Lumbini were investigated. Potential source regions were also identified. Results show that air pollution at this site is of a great concern, requiring prompt attention for mitigation.
Sanjay Kumar Mehta, Madineni Venkat Ratnam, Sukumarapillai V. Sunilkumar, Daggumati Narayana Rao, and Boddapaty V. Krishna Murthy
Atmos. Chem. Phys., 17, 531–549, https://doi.org/10.5194/acp-17-531-2017, https://doi.org/10.5194/acp-17-531-2017, 2017
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Study of the diurnal variation of the atmospheric boundary layer (ABL) height is important for the knowledge of pollutant dispersion, crucial for all living beings. The most difficult part in the study of the diurnal variation is in identification of the stable boundary layer which occurs ~ 50% of times only and mostly during nighttime winter. Surface temperature and clouds directly affect the diurnal pattern of the ABL. Thus, stronger (weaker) diurnal variation found during pre-monsoon (winter).
Madineni Venkat Ratnam, Alladi Hemanth Kumar, and Achuthan Jayaraman
Atmos. Meas. Tech., 9, 5735–5745, https://doi.org/10.5194/amt-9-5735-2016, https://doi.org/10.5194/amt-9-5735-2016, 2016
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Launch of INSAT-3D carrying a multi-spectral imager by the ISRO made it possible to obtain profiles of temperature and water vapour over India with higher temporal and vertical resolutions. Initial validation is made with the radiosonde, other satellites and reanalysis data sets. Good correlation between INSAT-3D and in situ measurements is noticed with a few cautions. Temperature data from INSAT-3D are of high quality and can be directly assimilated for better forecasts over India.
M. Venkat Ratnam, S. Ravindra Babu, S. S. Das, G. Basha, B. V. Krishnamurthy, and B. Venkateswararao
Atmos. Chem. Phys., 16, 8581–8591, https://doi.org/10.5194/acp-16-8581-2016, https://doi.org/10.5194/acp-16-8581-2016, 2016
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The impact of cyclones that occurred over the north Indian Ocean during 2007–2013 on the STE process is quantified using satellite observations. It is shown that cyclones have a significant impact on the tropopause structure, ozone and water vapour budget, and consequentially STE in the UTLS region. The cross-tropopause mass flux from the stratosphere to the troposphere for cyclonic storms is found to be 0.05 ± 0.29 × 10−3 kg m−2, and for very severe cyclonic storms it is 0.5 ± 1.07 × 10−3 kg m−2.
K. K. Shukla, K. Niranjan Kumar, D. V. Phanikumar, R. K. Newsom, V. R. Kotamarthi, T. B. M. J. Ouarda, and M. V. Ratnam
Atmos. Meas. Tech. Discuss., https://doi.org/10.5194/amt-2016-162, https://doi.org/10.5194/amt-2016-162, 2016
Revised manuscript not accepted
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Estimation of Cloud base height was carried out by using various ground based instruments (Doppler Lidar and Ceilometer) and satellite datasets (MODIS) over central Himalayan region for the first time. The present study demonstrates the potential of Doppler Lidar in precise estimation of cloud base height and updraft velocities. More such deployments will be invaluable inputs for regional weather prediction models over complex Himalayan terrains.
Siddarth Shankar Das, Madineni Venkat Ratnam, Kizhathur Narasimhan Uma, Kandula Venkata Subrahmanyam, Imran Asatar Girach, Amit Kumar Patra, Sundaresan Aneesh, Kuniyil Viswanathan Suneeth, Karanam Kishore Kumar, Amit Parashuram Kesarkar, Sivarajan Sijikumar, and Geetha Ramkumar
Atmos. Chem. Phys., 16, 4837–4847, https://doi.org/10.5194/acp-16-4837-2016, https://doi.org/10.5194/acp-16-4837-2016, 2016
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The present study examines the role of tropical cyclones in the enhancement of tropospheric ozone. The most significant and new observation reported is the increase in the upper-tropospheric ozone by 20–50 ppbv, which has extended down to the middle and lower troposphere. The descent rate of enhanced ozone layer during the passage of tropical cyclone is 0.8–1 km day−1. Enhancement of surface ozone concentration by ~ 10 ppbv in the daytime and 10–15 ppbv at night-time is observed.
Sanjeev Dwivedi, M. S. Narayanan, M. Venkat Ratnam, and D. Narayana Rao
Atmos. Chem. Phys., 16, 4497–4509, https://doi.org/10.5194/acp-16-4497-2016, https://doi.org/10.5194/acp-16-4497-2016, 2016
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Monsoon inversion (MI) over the Arabian Sea is one of the important characteristics associated with the monsoon activity over Indian region. The initiation and dissipation times of MI, their percentage of occurrence, strength etc., has been examined. We suggest MI could also be included as one of the semi-permanent features of southwest monsoon.
K. Niranjan Kumar, D. V. Phanikumar, T. B. M. J. Ouarda, M. Rajeevan, M. Naja, and K. K. Shukla
Ann. Geophys., 34, 123–132, https://doi.org/10.5194/angeo-34-123-2016, https://doi.org/10.5194/angeo-34-123-2016, 2016
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The link between upper-tropospheric planetary-scale Rossby waves and surface meteorological parameters is examined. The propagating Rossby waves along with undulations in the subtropical jet create convergence and divergence regions in the mid-troposphere. The surface relative humidity, wind speeds, and temperature are synchronized with the phase of the propagating Rossby waves. The present study finds important implications for medium-range forecasting through Rossby wave propagation.
A. K. Pandit, H. S. Gadhavi, M. Venkat Ratnam, K. Raghunath, S. V. B. Rao, and A. Jayaraman
Atmos. Chem. Phys., 15, 13833–13848, https://doi.org/10.5194/acp-15-13833-2015, https://doi.org/10.5194/acp-15-13833-2015, 2015
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We present the longest (1998 to 2013) cirrus cloud climatology over a tropical station using a ground-based lidar. A statistically significant increase is found in the altitude of sub-visible cirrus clouds. Also a systematic shift from thin to sub-visible cirrus cloud type is observed. Ground-based lidar is found to detect more number of sub-visible cirrus clouds than space-based lidar. These findings have implications to global warming and stratosphere-troposphere water vapour exchange studies.
S. Ravindra Babu, M. Venkat Ratnam, G. Basha, B. V. Krishnamurthy, and B. Venkateswararao
Atmos. Chem. Phys., 15, 10239–10249, https://doi.org/10.5194/acp-15-10239-2015, https://doi.org/10.5194/acp-15-10239-2015, 2015
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The effect of tropical cyclones (TCs) that occurred over the north Indian Ocean in the last decade on the tropical tropopause parameters has been quantified for the first time. The vertical structure of temperature and tropopause parameters within the 5º radius away from the cyclone centre during TC period is also presented. The water vapour variability in the vicinity of TC is investigated.
It is demonstrated that the TCs can significantly affect the tropical tropopause and thus STE processes.
M. Pramitha, M. Venkat Ratnam, A. Taori, B. V. Krishna Murthy, D. Pallamraju, and S. Vijaya Bhaskar Rao
Atmos. Chem. Phys., 15, 2709–2721, https://doi.org/10.5194/acp-15-2709-2015, https://doi.org/10.5194/acp-15-2709-2015, 2015
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Sources and propagation characteristics of high-frequency gravity waves observed in the mesosphere using airglow emissions from Gadanki and Hyderabad, India, are investigated using reverse ray tracing. Wave amplitudes are also traced back, including both radiative and diffusive damping. Interestingly, large vertical shears in the horizontal wind are noticed near the ray terminal points (at 10-12km altitude) and are thus identified to be the source for generating the observed gravity waves.
K. Ramesh, A. P. Kesarkar, J. Bhate, M. Venkat Ratnam, and A. Jayaraman
Atmos. Meas. Tech., 8, 369–384, https://doi.org/10.5194/amt-8-369-2015, https://doi.org/10.5194/amt-8-369-2015, 2015
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The study of atmospheric convection is important for the understanding of evolution of diurnal cycles of rainfall. High-resolution observations of vertical profiles of temperature and relative humidity are very useful for understanding the behaviour of these convections. Microwave radiometers are becoming useful tools for it. In this paper, we propose a new method to retrieve these profiles based on adaptive neuro-fuzzy interface systems and find that this method has a better skill of retrieval.
R. Kumar, M. C. Barth, S. Madronich, M. Naja, G. R. Carmichael, G. G. Pfister, C. Knote, G. P. Brasseur, N. Ojha, and T. Sarangi
Atmos. Chem. Phys., 14, 6813–6834, https://doi.org/10.5194/acp-14-6813-2014, https://doi.org/10.5194/acp-14-6813-2014, 2014
M. Venkat Ratnam, N. Pravallika, S. Ravindra Babu, G. Basha, M. Pramitha, and B. V. Krishna Murthy
Atmos. Meas. Tech., 7, 1011–1025, https://doi.org/10.5194/amt-7-1011-2014, https://doi.org/10.5194/amt-7-1011-2014, 2014
P. Kishore, M. Venkat Ratnam, I. Velicogna, V. Sivakumar, H. Bencherif, B. R. Clemesha, D. M. Simonich, P. P. Batista, and G. Beig
Ann. Geophys., 32, 301–317, https://doi.org/10.5194/angeo-32-301-2014, https://doi.org/10.5194/angeo-32-301-2014, 2014
R. Kumar, M. C. Barth, G. G. Pfister, M. Naja, and G. P. Brasseur
Atmos. Chem. Phys., 14, 2431–2446, https://doi.org/10.5194/acp-14-2431-2014, https://doi.org/10.5194/acp-14-2431-2014, 2014
