Browsing by Author "Dipesh Rupakheti"

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Aerosol Properties Over Tibetan Plateau From a Decade of AERONET Measurements: Baseline, Types, and Influencing Factors
(Blackwell Publishing Ltd, 2019) Manisha Pokharel; Jie Guang; Bin Liu; Shichang Kang; Yaoming Ma; Brent N. Holben; Xiang'ao Xia; Jinyuan Xin; Kirpa Ram; Dipesh Rupakheti; Xin Wan; Guangming Wu; Hemraj Bhattarai; Chuanfeng Zhao; Zhiyuan Cong
In this study, a decade long measurement of aerosol optical properties at two AERONET stations (Nam Co during 2006–2016 and QOMS during 2009–2017) in the Tibetan Plateau (TP), a region sensitive to climate change and human perturbation, is presented. The baseline value of aerosol optical depth (AOD) was 0.029 and 0.027 at Nam Co and QOMS, respectively, which are comparable to or even lower than those at some Arctic and remote ocean locations. The seasonality of AOD values were the order of spring > summer > winter > autumn. Based on AOD and Ångström exponent (α), major aerosol types over the TP were further identified as continental background, biomass burning, and dust. Although continental background aerosol was the main feature in remote areas of TP, biomass burning plumes frequently occurred, especially during spring (March–April). In one of such biomass burning event in April 2014, MODIS observations demonstrated that intensive open fires occurred in South Asia, covering the foothills of Himalayas and Indo-Gangetic Plain. The air mass back trajectories and CALIOP observations further revealed that biomass burning plume could be uplifted to higher altitudes and reach the Himalayas. Moreover, an occasional dust event detected in April 2008 over the TP demonstrated that the dust from Taklamakan Desert may impact the main body of TP episodically, although the local dust from the inside of TP cannot be excluded and warrants further study. ©2019. American Geophysical Union. All Rights Reserved.
Historical Black Carbon Reconstruction from the Lake Sediments of the Himalayan-Tibetan Plateau
(American Chemical Society, 2019) Bigyan Neupane; Shichang Kang; Pengfei Chen; Yulan Zhang; Kirpa Ram; Dipesh Rupakheti; Lekhendra Tripathee; Chhatra Mani Sharma; Zhiyuan Cong; Chaoliu Li; Juzhi Hou; Min Xu; Poonam Thapa
Black carbon (BC) is one of the major drivers of climate change, and its measurement in different environment is crucial for the better understanding of long-term trends in the Himalayan-Tibetan Plateau (HTP) as climate warming has intensified in the region. We present the measurement of BC concentration from six lake sediments in the HTP to reconstruct historical BC deposition since the pre-industrial era. Our results show an increasing trend of BC concurrent with increased anthropogenic emission patterns after the commencement of the industrialization era during the 1950s. Also, sedimentation rates and glacier melt strengthening influenced the total input of BC into the lake. Source identification, based on the char and soot composition of BC, suggests biomass-burning emissions as a major contributor to BC, which is further corroborated by open-fire occurrence events in the region. The increasing BC trend continues to recent years, indicating increasing BC emissions, mainly from South Asia. © 2019 American Chemical Society.