Current Science

Ram Sagar ¹, U. C. Dumka ¹, Manish Naja ¹, Narendra Singh ¹, D. V. Phanikumar ¹

Affiliations
1 Aryabhatta Research Institute of Observational Sciences, Manora Peak, Nainital 263 002, IN

Abstract

ARIES, acronym for Aryabhatta Research Institute of Observational Sciences, located in the Central Gangetic Himalayan (CGH) region is emerging as one of the unique sites for climate change studies. The long-term, in situ, precise measurements of aerosols and trace gases obtained from this region provide valuable inputs for climate studies. Atmospheric scientists from ARIES are actively involved in nearsurface measurements for meteorology, aerosols and trace gases as well as vertical profiling. The Institute is also providing the observational infrastructure and research support to three major projects of the Indian Space Research Organization, Geosphere Biosphere Programme, which basically deals with the measurement of aerosols, trace gases and boundary-layer experiments. The upcoming stratosphere-troposphere radar and high-power micro-pulse lidar observational facilities will be utilized for the continuous vertical profiling of winds, aerosol and cloud properties at a very fine resolution in time and space. Apart from this, atmospheric scientists of ARIES also have active national and international research collaborations. The important results obtained from these research activities are highlighted and upcoming major observational facilities in the field of atmospheric sciences are discussed. They clearly demonstrate the importance of the unique geographical location of ARIES for climate change studies in the CGH region. These measurements and routine meteorological observations provide the necessary atmospheric corrections to the astrophysical observations taken using optical telescopes located at the site.

Keywords

Aerosols, Air Pollution, Climate Change, Trace Gases, Wind Profiler.

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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.

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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.

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