Current Science

S. K. Satheesh ¹

Affiliations
1 Centre for Atmospheric and Oceanic Sciences and Divecha Centre for Climate Change, Indian Institute of Science, Bengaluru 560 012, IN

Abstract

No Abstract.

Full Text

   

S. Seetha , S. K. Satheesh

Abstract

No Abstract.

Full Text

   

K. Krishna Moorthy , S. K. Satheesh , V. R. Kotamarthi

Abstract

Climate change has great significance in Asia in general, and India in particular due to its diverse geographical features and high population density. It is now well known that atmospheric aerosols have a decisive role in perturbing regional and global climate. Ground-based and satellite-borne measurements have shown that the Indo-Gangetic Plains (IGP), which extends from western desert, across the plains and over to the Bay of Bengal and one of the densely populated and rapidly developing regions of the subcontinent, has some of the highest and persistent aerosol optical depths (AOD)/loading, especially during the dry winter and pre-monsoon seasons.

Full Text

   

K. Krishna Moorthy ¹, S. K. Satheesh ¹, V. R. Kotamarthi ²

Affiliations
1 Centre for Atmospheric and Oceanic Sciences, Indian Institute of Science, Bengaluru 560 012, IN
2 Environmental Science Division, Argonne National Laboratory, Argonne, IL, US

Abstract

Climate change has great significance in Asia in general, and India in particular; and atmospheric aerosols have a decisive role in this. The climate forcing potential of aerosols is closely linked to their optical, microphysical and chemical properties. Systematic efforts to characterize these properties over the Indian region started about 5 decades ago, and evolved over the years through concerted efforts in the form of long-term scientific programmes as well as concerted fields experiments. All these have resulted in this activity becoming one of the most vibrant fields of climate research in India and have brought several important issues in the national and international foci. The field experiment, RAWEX-GVAX (Regional Aerosol Warming Experiment-Ganges Valley Aerosol Experiment), conducted during 2011-12 jointly by the US Department of Energy, Indian Space Research Organization and Department of Science and Technology, has emerged as a direct outcome of the above efforts. This overview provides a comprehensive account of the development of aerosol-climate research in India and south Asia, and the accomplishment and newer issues that warranted the above field campaign. Details of RAWEX-GVAX, the major outcomes and the subsequent and more recent efforts are presented, followed by the way forward in this field for the next several years to come.

Keywords

Aerosols, Climate Change, ICARB, RAWEX–GVAX.

Full Text

   

N. Srivastava ¹, S. K. Satheesh ², Nadege Blond ³, K. Krishna Moorthy ⁴

Affiliations
1 Department of Physics, Birla Institute of Technology, Mesra, Ranchi 835 215, IN
2 Centre for Atmospheric and Oceanic Sciences, Indian Institute of Science, Bengaluru 560 012, IN
3 Laboratoire Image Ville Environnement, UMR7362 CNRS, Université de Strasbourg, Strasbourg, FR
4 ISRO HQ, Antariksh Bhavan, Bengaluru 560 231, IN

Abstract

In order to understand the regional climate implications of aerosols over Indo-Gangetic Plains (IGP), a major Indo-US field experiment, Ganges Valley Aerosol Experiment (GVAX) was conducted during 2011-12. Atmospheric Radiation Measurement (ARM) mobile facility (AMF) was deployed at the northern Indo-Gangetic Plain over the high-altitude site, Manora Peak, Nainital (29°21^'33.84^"N, 79°27^'29.27^"E, 1980 m amsl) in Central Himalayas, for an year-round measurement of aerosols, clouds and other climate-relevant atmospheric parameters. One of the objectives of GVAX was examining the ability of models to simulate aerosols over Indian region and validate the simulations. In part-1 of this two-part paper, we examine use of the chemical transport model 'CHIMERE' to simulate aerosol fields over Indian region (4-37.5°N; 67-88.5°E) for multiple years (2006, 2007 and 2008) by simulating the spatial and temporal distribution of PM10, BC mass concentrations and OC/BC ratios. It is seen that the model successfully captures the broad features of the regional distribution of aerosols, including the most conspicuous IGP hotspot and its seasonality.

Keywords

Aerosols, Black Carbon, Chemistry Transport Model, CHIMERE, GVAX.

Full Text

   

N. Srivastava ¹, S. K. Satheesh ², Nadege Blond ³, K. Krishna Moorthy ⁴

Affiliations
1 Department of Physics, Birla Institute of Technology, Mesra, Ranchi 835 215, IN
2 Centre for Atmospheric and Oceanic Sciences, Indian Institute of Science, Bengaluru 560 012, IN
3 Laboratoire Image Ville Environnement, UMR7362 CNRS, Université de Strasbourg, Strasbourg, FR
4 ISRO HQ, Antariksh Bhavan, Bengaluru 560 231, IN

Abstract

In this paper, we evaluate the performance of the chemical transport model 'CHIMERE' over large Indian region (4-37.5°N; 67-88.5°E) for multiple years (2006, 2007 and 2008) by comparing the model simulations with concurrent aerosol measurements from different locations. Model simulated near-surface black carbon mass concentrations agreed satisfactorily with measurements at various locations (oceanic, inland and island sites), in general, except during monsoon months, when the model underpredicted the measurements. Similar results were obtained when model simulated column integrated PM₁₀ mass concentrations were correlated with MODIS-derived aerosol optical depth (AOD), using AOD as a proxy for aerosol loading. The underperformance of the model during monsoon arises, at least partly, due to the model-simulated rainfall being higher than the actual rainfall over the Indian domain, during the monsoon season. Notwithstanding these, the general performance of the CHIMERE model to simulate aerosol loading over Indian domain during dry months is, in general, found to be satisfactory.

Keywords

Aerosols, Black Carbon, Chemistry Transport Model.

Full Text

   

D. V. Phanikumar ¹, K. K. Shukla ¹, M. Naja ¹, N. Singh ¹, S. Sahai ², R. Sagar ³, S. K. Satheesh ⁴, K. K. Moorthy ⁴, V. R. Kotamarthi ⁵, Rob K. Newsom ⁶

Affiliations
1 Aryabhatta Research Institute of Observational Sciences, Nainital 263 002, IN
2 Amity University, Noida 201 303, IN
3 Aryabhatta Research Institute of Observational Sciences, Nainital 263 002
4 Centre for Atmospheric and Oceanic Sciences, Indian Institute of Science, Bengaluru 560 012, IN
5 Argonne National Laboratory, Argonne, IL, US
6 Pacific Northwest National Laboratory, Richland, Washington, US

Abstract

The RAWEX-GVAX field campaign has been carried out from June 2011 to March 2012 over a high altitude site Manora Peak, Nainital (29.4°N; 79.2°E; 1958 m amsl) in the central Himalayas to assess the impacts of absorbing aerosols on atmospheric thermodynamics and clouds. This paper presents the preliminary results of the observations and data analysis of the Doppler Lidar, installed at Nainital. Strong updrafts with vertical winds in the range of ~2-4 ms^-1 occurred during the daytime and throughout the season indicating thermally driven convection. On the other hand during nighttime, weak downdrafts persisted during stable conditions. Plan Position Indicator scan of Doppler Lidar showed north-northwesterly winds in the boundary layer. The mixing layer height, derived from the vertical velocity variance, showed diurnal variations, in the range ~0.7-1 km above ground level during daytime and very shallow during nighttime.

Keywords

Boundary Layer, Doppler Lidar, GVAX.

Full Text

   

Narendra Singh ¹, Raman Solanki ¹, N. Ojha ², M. Naja ¹, U. C. Dumka ¹, D. V. Phanikumar ¹, Ram Sagar ¹, S. K. Satheesh ³, K. Krishna Moorthy ⁴, V. R. Kotamarthi ⁵, S. K. Dhaka ⁶

Affiliations
1 Aryabhatta Research Institute of Observational Sciences, Nainital 263 002, IN
2 Department of Atmospheric Chemistry, Max Planck Institute for Chemistry, Mainz, DE
3 Center for Atmospheric and Oceanic Sciences, Indian Institute of Science, Bengaluru 560 012, IN
4 ISRO Head Quarters, Bengaluru 560 231, IN
5 Environmental Science Division, Argonne National Laboratory, Illinois, US
6 Radio and Atmospheric Physics Lab., Rajdhani College, University of Delhi, Delhi 110 015, IN

Abstract

We present the measurements of cloud-base height variations over Aryabhatta Research Institute of Observational Science, Nainital (79.45°E, 29.37°N, 1958 m amsl) obtained from Vaisala Ceilometer, during the nearly year-long Ganges Valley Aerosol Experiment (GVAX). The cloud-base measurements are analysed in conjunction with collocated measurements of rainfall, to study the possible contributions from different cloud types to the observed monsoonal rainfall during June to September 2011. The summer monsoon of 2011 was a normal monsoon year with total accumulated rainfall of 1035.8 mm during June-September with a maximum during July (367.0 mm) and minimum during September (222.3 mm). The annual mean monsoon rainfall over Nainital is 1440 ± 430 mm. The total rainfall measured during other months (October 2011-March 2012) was only 9% of that observed during the summer monsoon. The first cloud-base height varied from about 31 m above ground level (AGL) to a maximum of 7.6 km AGL during the summer monsoon period of 2011. It is found that about 70% of the total rain is observed only when the first cloud-base height varies between surface and 2 km AGL, indicating that most of the rainfall at high altitude stations such as Nainital is associated with stratiform low-level clouds. However, about 25% of the total rainfall is being contributed by clouds between 2 and 6 km. The occurrences of high-altitude cumulus clouds are observed to be only 2-4%. This study is an attempt to fill a major gap of measurements over the topographically complex and observationally sparse northern Indian region providing the evaluation data for atmospheric models and therefore, have implications towards the better predictions of monsoon rainfall and the weather components over this region.

Keywords

Ceilometer, Central Himalaya, Cloud-Base, GVAX, Monsoon.

Full Text

   

Manish Naja ¹, Piyush Bhardwaj ¹, Narendra Singh ¹, Phani Kumar ¹, Rajesh Kumar ², N. Ojha ¹, Ram Sagar ³, S. K. Satheesh ⁴, K. Krishna Moorthy ⁵, V. R. Kotamarthi ⁶

Affiliations
1 Aryabhatta Research Institute of Observational Sciences, Nainital 263 002, IN
2 National Center for Atmospheric Research, Boulder, Colorado, US
3 Indian Institute of Astrophysics, Bengaluru 560 034, IN
4 Centre for Atmospheric and Oceanic Sciences, Indian Institute of Science, Bengaluru 560 012, IN
5 Indian Space Research Organization, Head Quarters, Bengaluru 560 231, IN
6 Argonne National Laboratory, Argonne, IL, US

Abstract

An extensive field study, RAWEX-GVAX, was carried out during a 10-month (June 2011-March 2012) campaign at ARIES, Nainital and observations on a wide range of parameters like physical and optical properties of aerosols, meteorological parameters and boundary layer evolution were made. This work presents results obtained from high-frequency (four launches per day), balloon-borne observations of meteorological parameters (pressure, temperature, relative humidity, wind speed and wind direction). These observations show wind speed as high as 84 m/s near the subtropical jet. It is shown that reanalysis wind speeds are in better agreement at 250 hPa (altitude of subtropical jet) than those above or below this value (100 hPa or 500 hPa). These observations also demonstrate that AIRS-derived temperature profiles are negatively biased in the lower altitude region, whereas they are positively biased near the tropopause. WRF simulated results are able to capture variations in temperature, humidity and wind speed profile reasonable well. WRF and AIRS-derived tropopause height, tropopause pressure and tropopause temperature also show agreement with radiosonde estimates.

Keywords

Aerosols, Radiosonde, Subtropical Jet, Tropopause Folding, Vertical Profiling.

Full Text

   

S. K. Satheesh ¹, K. Krishnamoorthy ²

Affiliations
1 Divecha Centre for Climate Change, Centre for Atmospheric and Oceanic Sciences, Indian Institute of Science, Bengaluru 560 012, IN
2 Centre for Atmospheric and Oceanic Sciences, Indian Institute of Science, Bengaluru 560 012, IN

Abstract

The Earth’s climate is changing and the global temperature has been rising since the middle of the last century. The anthropogenic emission of greenhouse gases is widely accepted as the major contributor to this warming. The prediction of future trends by climate models indicates that human beings will face serious challenges by the end of this century. Some of these are sea-level rise, coastal inundation, melting of polar ice caps and mountain glaciers, reduction in agricultural productivity and spread of vector-borne diseases. Based on the scientific findings, there is an increasing demand for actions to urgently control the emissions that are perturbing our climate. Climate change is, thus, one of the major challenges of this century and India will be among the worst affected.

Full Text

   

Anil V. Kulkarni , S. K. Satheesh

Abstract

Himalayan cryology

The Himalayan region, including Karakoram, possesses a large concentration of mountain glaciers. In addition, large area is also covered by seasonal snow during winter. Snow and glacier melt during summer provides water to the major Indian rivers. This makes these rivers perennial and they are considered as the lifeline of millions of people living along the banks. However, water availability can be affected due to changes in global and regional climate. This will have a profound impact on the livelihood of millions of people living in the region. Therefore, understanding changes in the cryosphere is important to assess future changes in water availability and its influence on the people. In this context, this special section in Current Science highlights the latest understanding of the Himalayan cryosphere.

Full Text

   

S. K. Satheesh ¹

Affiliations
1 Divecha Centre for Climate Change, and Centre for Atmospheric and Oceanic Sciences, Indian Institute of Science, Bengaluru 560 012, IN

Abstract

The Intergovernmental Panel on Climate Change (IPCC) reports have shown that global warming is due to increase in greenhouse gases (GHGs). Several studies have linked extreme weather to global warming and the frequency of extreme weather events is increasing. Global warming is projected to pose a major threat to the aviation sector; the direct consequence arising from the reduced lift (dependent on air density). It is projected that under extreme conditions, it would be difficult for aircraft to take-off during summer in the tropics. Storms such as cyclones and tornadoes pose challenges to the aviation sector. Cyclones can cause flooding of airfields and terminals. Underground power utilities are likely to short due to inundation, which can cause power outages. Strong winds can damage control towers and other ground equipment and installations. Due to the recent floods (August 2018), the international airport at Kochi, one of the busy airports of India, was shut down for nearly two weeks, consequent to extreme precipitation in the catchment areas of rivers. One of Japan’s busiest airports, Kansai International Airport in Osaka, had to be closed recently (September 2018) because of flooding caused by typhoon Jebi, the strongest to hit Japan in 25 years. Flood waters covered runways, leaving several planes submerged up to their engines and more than 1000 flights were cancelled. Just a few years ago, the Chennai International Airport was completely shut down after the unusually heavy precipitation flooded the airfield. Blizzards and other extreme cold weather conditions can cause icy runways and frozen fuelling equipment. Icy runways make safe take-offs and landings extremely difficult. Airports need to close during heavy blizzards. Necessary safety precautions for open airports include gritting of runways and de-icing of aircraft.

Full Text

   

A. Ajay ¹, K. Krishna Moorthy ², S. K. Satheesh ³, G. Ilavazhagan ¹

Affiliations
1 Hindustan Institute of Technology and Science, Chennai 603 103, IN
2 Centre for Atmospheric and Oceanic Sciences, Indian Institute of Science, Bengaluru 560 012, IN
3 Divecha Centre for Climate Change, Indian Institute of Science, Bengaluru 560 012, IN

Abstract

Continuous analytical measurements of the loading and optical properties of near-surface aerosols over the megacity Bengaluru, in south India, are examined for the impact of the national lockdown (LD) associated with COVID-19 pandemic. The near total shutdown of rail, road, and air traffic as well as total closure of most of the business establishments and IT industry, especially during the first phase of the LD, is found to dramatically reduce black carbon (BC) abundance. Within one week of the first week of the LD phase 1 (LD1), the ambient BC concentration at the urban centre came down to levels comparable to those reported for remote rural locations, primarily due to >60% reduction in BC from fossil fuel (BCff) emissions. On the other hand, BC from biomass burning (BCwb) did not show any conspicuous impact. Consequently, the fraction of BCwb to BC more than doubled and the spectral absorption coefficient increased from ~1.15 to ~1.4. The single scattering albedo increased from its prevailing mean value 0.66 before LD to 0.74 during LD1 and then gradually decreased to 0.68 with increasing relaxations on vehicular traffic. The results reveal the unequivocal role of vehicular emissions in impacting the aerosol loading and their optical properties over Bengaluru. The study also shows how the environment responded to the gradual relaxations in the subsequent phases of LD. It is interesting to note that a few spells of strong rainfall towards the fourth phase of the LD impacted the aerosols non-selectively leading to sharp decrease in all the quantities. However, owing to the non-selective nature of the washout this large reduction in loading did not impact the single scattering albedo, unlike the case with the LD.

Keywords

Black Carbon, COVID-19 Lockdown, Scattering Coefficients, Single Scattering Albedo.

Full Text

   

A. Ajay ¹, K. Krishna Moorthy ², S. K. Satheesh ³, G. Ilavazhagan ¹

Affiliations
1 Hindustan Institute of Technology and Science, Chennai 603 103, IN
2 Centre for Atmospheric and Oceanic Sciences, Indian Institute of Science, Bengaluru 560 012, IN
3 Divecha Centre for Climate Change, Indian Institute of Science, Bengaluru 560 012, IN

Abstract

Long-term and continuous measurements of aerosol concentration and optical properties from the Challakere Climate Observatory, located in a remote rural semi-arid region northwest of Bengaluru, are examined for the impact of the prolonged and phased national lockdown during the COVID-19 pandemic. The analyses revealed that the lockdown, which almost brought all the anthropogenic activities (particularly associated with fossil fuel use such as in transport and industrial sectors) to a standstill and then slowly relaxed in phases, had very little impact on the aerosol properties at this remote site, in sharp contrast to the impacts seen in the major urban conglomerate, Bengaluru, located about 230 km southeast to Challakere. Rather than impacts from anthropogenic sources associated with fossil fuel combustion, the aerosol characteristics at Challakere are strongly influenced by regional and synoptic meteorology. The findings re-emphasize that the emissions from fossil fuel combustion in industrial and automobile sector are the major source of aerosols (especially absorbing type) over urban and semi-urban environments.

Keywords

Anthropogenic Emissions, Black Carbon, COVID-19 Lockdown, Rural Aerosols, Scattering Coefficients, Single Scattering Albedo.

Full Text

   

S. K. Satheesh ¹

Affiliations
1 Centre for Atmospheric and Oceanic Sciences, and Divecha Centre for Climate Change, Indian Institute of Science, Bengaluru 560 012, IN

Abstract

No abstract.

Keywords

No keywords.

Full Text

   

S. K. Satheesh ¹

Affiliations
1 Divecha Centre for Climate Change, and Centre for Atmospheric and Oceanic Sciences, Indian Institute of Science, Bengaluru 560 012, India, IN

Abstract

No Abstract.

Full Text

   

S. K. Satheesh ¹

Affiliations
1 Current Science Association, Bengaluru 560 080., IN

Abstract

No Abstract.

Full Text

   

S. K. Satheesh ¹

Affiliations
1 Divecha Centre for Climate Change & Centre for Atmospheric and Oceanic Sciences, Indian Institute of Science, Bengaluru 560 012, IN

Abstract

No Abstract.

Keywords

No Keywords.

Full Text

   

S. K. Satheesh ¹

Affiliations
1 Divecha Centre for Climate Change & Centre for Atmospheric and Oceanic Sciences, Indian Institute of Science, Bengaluru 560 012, IN

Abstract

No Abstract.

Keywords

No Keywords.

Full Text