scholarly journals Response to review comments of "Impact of topography on black carbon transport to the southern Tibetan Plateau during pre-monsoon season and its climatic implication"

2020 ◽  
Author(s):  
Zhang Meixin
Keyword(s):  
Tibetan Plateau ◽  
Black Carbon ◽  
Monsoon Season ◽  
Southern Tibetan Plateau ◽  
Climatic Implication ◽  
Carbon Transport

scholarly journals Impact of topography on black carbon transport to the southern Tibetan Plateau during the pre-monsoon season and its climatic implication

2020 ◽  
Vol 20 (10) ◽  
pp. 5923-5943 ◽  
Author(s):  
Meixin Zhang ◽  
Chun Zhao ◽  
Zhiyuan Cong ◽  
Qiuyan Du ◽  
Mingyue Xu ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Black Carbon ◽  
Radiative Forcing ◽  
Monsoon Season ◽  
Radiative Heating ◽  
The Tibetan Plateau ◽  
Complex Topography ◽  
Meridional Transport ◽  
Near Surface ◽  
Mass Volume

Abstract. Most previous modeling studies about black carbon (BC) transport and its impact over the Tibetan Plateau (TP) conducted simulations with horizontal resolutions coarser than 20 km that may not be able to resolve the complex topography of the Himalayas well. In this study, the two experiments covering all of the Himalayas with the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) at the horizontal resolution of 4 km but with two different topography datasets (4 km complex topography and 20 km smooth topography) are conducted for pre-monsoon season (April 2016) to investigate the impacts of topography on modeling the transport and distribution of BC over the TP. Both experiments show the evident accumulation of aerosols near the southern Himalayas during the pre-monsoon season, consistent with the satellite retrievals. The observed episode of high surface BC concentration at the station near Mt. Everest due to heavy biomass burning near the southern Himalayas is well captured by the simulations. The simulations indicate that the prevailing upflow across the Himalayas driven by the large-scale westerly and small-scale southerly circulations during the daytime is the dominant transport mechanism of southern Asian BC into the TP, and it is much stronger than that during the nighttime. The simulation with the 4 km topography resolves more valleys and mountain ridges and shows that the BC transport across the Himalayas can overcome the majority of mountain ridges, but the valley transport is more efficient. The complex topography results in stronger overall cross-Himalayan transport during the simulation period primarily due to the strengthened efficiency of near-surface meridional transport towards the TP, enhanced wind speed at some valleys and deeper valley channels associated with larger transported BC mass volume. This results in 50 % higher transport flux of BC across the Himalayas and 30 %–50 % stronger BC radiative heating in the atmosphere up to 10 km over the TP from the simulation with the 4 km complex topography than that with the 20 km smoother topography. The different topography also leads to different distributions of snow cover and BC forcing in snow. This study implies that the relatively smooth topography used by the models with resolutions coarser than 20 km may introduce significant negative biases in estimating light-absorbing aerosol radiative forcing over the TP during the pre-monsoon season. Highlights. The black carbon (BC) transport across the Himalayas can overcome the majority of mountain ridges, but the valley transport is much more efficient during the pre-monsoon season. The complex topography results in stronger overall cross-Himalayan transport during the study period primarily due to the strengthened efficiency of near-surface meridional transport towards the TP, enhanced wind speed at some valleys and deeper valley channels associated with larger transported BC mass volume. The complex topography generates 50 % higher transport flux of BC across the Himalayas and 30 %–50 % stronger BC radiative heating in the atmosphere up to 10 km over the Tibetan Plateau (TP) than the smoother topography, which implies that the smooth topography used by the models with relatively coarse resolution may introduce significant negative biases in estimating BC radiative forcing over the TP during the pre-monsoon season. The different topography also leads to different distributions of snow cover and BC forcing in snow over the TP.

scholarly journals Spatial–temporal variations in riverine carbon strongly influenced by local hydrological events in an alpine catchment

2021 ◽  
Vol 18 (10) ◽  
pp. 3015-3028
Author(s):  
Xin Wang ◽  
Ting Liu ◽  
Liang Wang ◽  
Zongguang Liu ◽  
Erxiong Zhu ◽  
...  
Keyword(s):  
Organic Matter ◽  
Tibetan Plateau ◽  
Headwater Streams ◽  
Monsoon Season ◽  
Temporal Variations ◽  
Large Rivers ◽  
Frozen Soils ◽  
Headwater Catchments ◽  
Carbon Transfer ◽  
Carbon Transport

Abstract. Headwater streams drain >70 % of global land areas but are poorly monitored compared with large rivers. The small size and low water buffering capacity of headwater streams may result in a high sensitivity to local hydrological alterations and different carbon transport patterns from large rivers. Furthermore, alpine headwater streams on the “Asian water tower”, i.e., Qinghai–Tibetan Plateau, are heavily affected by thawing of frozen soils in spring as well as monsoonal precipitation in summer, which may present contrasting spatial–temporal variations in carbon transport compared to tropical and temperate streams and strongly influence the export of carbon locked in seasonally frozen soils. To illustrate the unique hydro-biogeochemistry of riverine carbon in Qinghai–Tibetan headwater streams, here we carry out a benchmark investigation on the riverine carbon transport in the Shaliu River (a small alpine river integrating headwater streams) based on annual flux monitoring, sampling at a high spatial resolution in two different seasons and hydrological event monitoring. We show that riverine carbon fluxes in the Shaliu River were dominated by dissolved inorganic carbon, peaking in the summer due to high discharge brought by the monsoon. Combining seasonal sampling along the river and monitoring of soil–river carbon transfer during spring thaw, we also show that both dissolved and particulate forms of riverine carbon increased downstream in the pre-monsoon season due to increasing contribution of organic matter derived from thawed soils along the river. By comparison, riverine carbon fluctuated in the summer, likely associated with sporadic inputs of organic matter supplied by local precipitation events during the monsoon season. Furthermore, using lignin phenol analysis for both riverine organic matter and soils in the basin, we show that the higher acid-to-aldehyde (Ad/Al) ratios of riverine lignin in the monsoon season reflect a larger contribution of topsoil likely via increased surface runoff compared with the pre-monsoon season when soil leachate lignin Ad/Al ratios were closer to those in the subsoil than topsoil solutions. Overall, these findings highlight the unique patterns and strong links of carbon transport in alpine headwater catchments with local hydrological events. Given the projected climate warming on the Qinghai–Tibetan Plateau, thawing of frozen soils and alterations of precipitation regimes may significantly influence the alpine headwater carbon transport, with critical effects on the biogeochemical cycles of the downstream rivers. The alpine headwater catchments may also be utilized as sentinels for climate-induced changes in the hydrological pathways and/or biogeochemistry of the small basin.

scholarly journals Strong Light Absorption Induced by Aged Biomass Burning Black Carbon over the Southeastern Tibetan Plateau in Pre-monsoon Season

2020 ◽  
Author(s):  
Tianyi Tan ◽  
Min Hu ◽  
Zhuofei Du ◽  
Gang Zhao ◽  
Dongjie Shang ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Black Carbon ◽  
Biomass Burning ◽  
Climate Warming ◽  
Light Absorption ◽  
Monsoon Season ◽  
Absorption Enhancement ◽  
The Tibetan Plateau ◽  
Mixing State ◽  
Strong Light

Abstract. During the pre-monsoon season, biomass burning (BB) activities are intensive in southern Asia. Facilitated by westerly circulation, those BB plumes can be transported to the Tibetan Plateau (TP). Black carbon (BC), the main aerosol species in BB emissions, is an important climate warming agent, and its absorbing property strongly depends on its size distribution and mixing state. To elucidate the influence of those transported BB plumes on the TP, a field campaign was conducted on the southeast edge of the TP during the pre-monsoon season. It was found that the transported BB plumes substantially increased the number concentration of the atmospheric BC particles by 13 times, and greatly elevated the number fraction of thickly-coated BC from 52 % up to 91 %. Those transported BC particles had slightly larger core size and much thicker coatings than the background BC particles. However, the coating mass was not evenly distributed on BC particles with different sizes. The smaller BC cores were found to have larger shell/core ratios than the larger cores. Besides, the transported BB plumes strongly affected the vertical variation of the BC's abundance and mixing state, resulting in a higher concentration, larger number fraction and higher aging degree of BC particles in the upper atmosphere. Resulted from both increase of BC loading and aging degree, the transported BB plumes eventually enhanced the total light absorption by 15 times, in which 21 % was contributed by the BC aging and 79 % was contributed from the increase of BC mass. Particularly, the light absorption enhancement induced by the aging process during long-range transport has far exceeded the background aerosol light absorption, which implicates a significant influence of BC aging on climate warming over the TP region.

scholarly journals Impact of topography on black carbon transport to the southern Tibetan Plateau during pre-monsoon season and its climatic implication

2019 ◽  
Author(s):  
Meixin Zhang ◽  
Chun Zhao ◽  
Zhiyuan Cong ◽  
Qiuyan Du ◽  
Mingyue Xu ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Black Carbon ◽  
South Asian ◽  
Radiative Forcing ◽  
Large Scale ◽  
Climate Models ◽  
Monsoon Season ◽  
Global Climate Models ◽  
Radiative Heating ◽  
The Tibetan Plateau

Abstract. Most of previous modeling studies about black carbon (BC) transport and impact over the Tibetan Plateau conducted simulations with horizontal resolutions coarser than 10 km that may not be able to resolve well the complex topography of the Himalayas. In this study, the experiments with WRF-Chem at two horizontal resolutions (20 km and 4 km) are conducted for pre-monsoon season (April, 2016) to investigate the impacts of topography on modeling the transport and distribution of BC over the TP. The simulations at both resolutions show evident accumulation of aerosols near the southern Himalayas during the pre-monsoon season, consistent with the satellite retrievals. The observed episode of high surface BC concentrations at the station near the Mt. Everest due to heavy biomass burning near the TP is well captured by the simulations. The simulations at both resolutions indicate that the prevailing up-flow across the Himalayas driven by the large-scale circulation during the daytime is the dominant transport mechanism of South Asian BC into the TP, and is much stronger than that during the nighttime. The valley wind can strengthen the prevailing up-flow transport. The simulations at coarse resolution (20 km) and fine resolution (4 km) show large differences in representing the distributions of topography of the Himalayas. The simulation at 4 km resolution resolves more valleys and thus produces much stronger transport fluxes, which indicates that although the transport of South Asian BC across the Himalayas can overcome the mountain ridges, the valley transport is more efficient and cannot be ignored. This results in 50 % higher transport flux of BC across the Himalayas and 30–40 % stronger BC radiative heating in the atmosphere over the TP from the simulation at 4 km than that at 20 km resolution. The different topography also leads to different distributions of snow cover and BC forcing in snow. This study implies that global climate models generally with even coarser resolutions than 20 km may introduce significant negative biases in estimating light absorbing aerosol radiative forcing over the TP.

scholarly journals Measurement report: Strong light absorption induced by aged biomass burning black carbon over the southeastern Tibetan Plateau in pre-monsoon season

2021 ◽  
Vol 21 (11) ◽  
pp. 8499-8510
Author(s):  
Tianyi Tan ◽  
Min Hu ◽  
Zhuofei Du ◽  
Gang Zhao ◽  
Dongjie Shang ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Black Carbon ◽  
Biomass Burning ◽  
Climate Warming ◽  
Light Absorption ◽  
Monsoon Season ◽  
Absorption Enhancement ◽  
The Tibetan Plateau ◽  
Mixing State ◽  
Strong Light

Abstract. During the pre-monsoon season, biomass burning (BB) activities are intensive in southern Asia. Facilitated by westerly circulation, those BB plumes can be transported to the Tibetan Plateau (TP). Black carbon (BC), the main aerosol species in BB emissions, is an important climate warming agent, and its absorbing property strongly depends on its size distribution and mixing state. To elucidate the influence of those transported BB plumes on the TP, a field campaign was conducted on the southeast edge of the TP during the pre-monsoon season. It was found that the transported BB plumes substantially increased the number concentration of the atmospheric BC particles by a factor of 13 and greatly elevated the number fraction of thickly coated BC from 52 % up to 91 %. Those transported BC particles had slightly larger core size and much thicker coatings than the background BC particles. However, the coating mass was not evenly distributed on BC particles with different sizes. The smaller BC cores were found to have larger shell / core ratios than the larger cores. Besides, the transported BB plumes strongly affected the vertical variation in the BC's abundance and mixing state, resulting in a higher concentration, larger number fraction, and higher aging degree of BC particles in the upper atmosphere. Resulting from both increase in BC loading and aging degree, the transported BB plumes eventually enhanced the total light absorption by a factor of 15, of which 21 % was contributed by the BC aging, and 79 % was contributed from the increase in BC mass. Particularly, the light absorption enhancement induced by the aging process during long-range transport has far exceeded the background aerosol light absorption, which implicates a significant influence of BC aging on climate warming over the TP region.

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