The Deep Atmospheric Boundary Layer and Its Significance to the Stratosphere and Troposphere Exchange over the Tibetan Plateau

Chen, Xuelong; Añel, Juan Antonio; Su, Zhongbo; Torre, Laura de la; Kelder, H.; Peet, Jacob C. A. van; Ma, Yaoming

doi:10.1371/journal.pone.0056909

Cited by 73 publications

(84 citation statements)

References 56 publications

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“…area to study atmospheric dynamics, and difficult for modelling so it can serve as a test case to see if the dynamics in the model are correctly implemented. On 25 February 2008 a stratosphere-troposphere exchange event was observed in GOME-2 data (Chen et al, 2013), which can also be observed in the assimilation output. In Fig.…”

Section: Case Studysupporting

confidence: 61%

Simultaneous assimilation of ozone profiles from multiple UV-VIS satellite instruments

Peet

Kelder

et al. 2018

Atmos. Chem. Phys.

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Abstract. A three-dimensional global ozone distribution has been derived from assimilation of ozone profiles that were observed by satellites. By simultaneous assimilation of ozone profiles retrieved from the nadir looking satellite instruments Global Ozone Monitoring Experiment 2 (GOME-2) and Ozone Monitoring Instrument (OMI), which measure the atmosphere at different times of the day, the quality of the derived atmospheric ozone field has been improved. The assimilation is using an extended Kalman filter in which chemical transport model TM5 has been used for the forecast. The combined assimilation of both GOME-2 and OMI improves upon the assimilation results of a single sensor. The new assimilation system has been demonstrated by processing 4 years of data from 2008 to 2011. Validation of the assimilation output by comparison with sondes shows that biases vary between −5 and +10 % between the surface and 100 hPa. The biases for the combined assimilation vary between −3 and +3 % in the region between 100 and 10 hPa where GOME-2 and OMI are most sensitive. This is a strong improvement compared to direct retrievals of ozone profiles from satellite observations.

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Section: Case Studysupporting

confidence: 61%

Simultaneous assimilation of ozone profiles from multiple UV-VIS satellite instruments

Peet

Kelder

et al. 2018

Atmos. Chem. Phys.

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“…This result strongly suggests that the topography of the Tibetan Plateau can exert an influence on the lower stratosphere and upper troposphere. Škerlak et al (2014) compiled a global 33 yr climatology of STE from 1979 to 2011 and concluded that the Tibetan Plateau is one of the global hot spots for deep STE, where the very high orography combined with a high mixing layer enables quasi-horizontal transport into the Planetary boundary layer (PBL) (Chen et al, 2013 (Tang et al, 1995;Klausen et al, 2003;Wang et al, 2006;Xu et al, 2011) and, on the southern rim, for the Nepal Climate Observatory-Pyramid (NCO-P; 27.95 • N, 86.80 • E; 5079 m a.s.l.) in the Himalaya range (Cristofanelli et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

Influence of air mass downward transport on the variability of surface ozone at Xianggelila Regional Atmosphere Background Station, southwest China

Lin

Zheng

et al. 2014

Atmos. Chem. Phys.

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Abstract. In situ measurements of ozone (O 3 ), carbon monoxide (CO) and meteorological parameters were made from December 2007 to November 2009 at the Xianggelila Regional Atmosphere Background Station (28.006 • N, 99.726 • E; 3580 m a.s.l.), southwest China. It was found that both O 3 and CO peaked in spring while the minima of O 3 and CO occurred in summer and winter, respectively. A normalized indicator (marked as "Y ") on the basis of the monthly normalized O 3 , CO and water vapor, is proposed to evaluate the occurrence of O 3 downward transport from the upper, O 3 -rich atmosphere. This composite indicator has the advantage of being less influenced by the seasonal or occasional variations of individual factors. It is shown that the most frequent and effective transport occurred in winter (accounting for 39 % of the cases on the basis of a threshold of the Y value larger than 4) and they can make a significant contribution to surface O 3 at Xianggelila. A 9.6 ppb increase (21.0 %) of surface ozone is estimated based on the impact of deep downward transport events in winter. A case of strong O 3 downward transport event under the synoptic condition of a deep westerly trough is studied by the combination of the Y indicator, potential vorticity, total column ozone and trajectory analysis. Asian monsoon plays an important role in suppressing O 3 accumulation in summer and fall. The seasonal variation of O 3 downward transport, as suggested by the Y indicator at Xianggelila, is consistent with the seasonality of stratosphere-to-troposphere transport and the subtropical jet stream over the Tibetan Plateau.

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“…Radiosonde observations over the Tibetan Plateau (TP) reveal a high frequency (~80% of all profiles) of multiple thermal tropopauses during winter . Stable potential temperature (hereafter referred to as theta) and low RH over the Tibetan Plateau during winter can potentially enhance the downward transport of O3 rich dry eddies of stratospheric origin as a part of BrewerDobson circulation (Chen et al, 2013;Bracci et al, 2012;Hocking et al, 2007). Model calculations, surface observations, and back trajectories suggest that stratospheric intrusions in the Himalayan region occur most frequently during winter and early spring Chen et al 2013).…”

Section: Introductionmentioning

confidence: 99%

“…Stable potential temperature (hereafter referred to as theta) and low RH over the Tibetan Plateau during winter can potentially enhance the downward transport of O3 rich dry eddies of stratospheric origin as a part of BrewerDobson circulation (Chen et al, 2013;Bracci et al, 2012;Hocking et al, 2007). Model calculations, surface observations, and back trajectories suggest that stratospheric intrusions in the Himalayan region occur most frequently during winter and early spring Chen et al 2013). STE events have also been detected during winter over the Indian plains (Gupta et al, 2007) and at the edge of the Himalayan foothills (Ojha et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

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Transport and Distribution of Short-lived Climate Pollutants in the Himalaya

Dhungel¹

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Major combustion sources in the Indo-Gangetic Plain (IGP) of southern Asia form persistent haze layers, also known as atmospheric brown clouds (ABC), from December through early June. ABC is a mixture of high concentrations of reactive trace gases and lightabsorbing and light-scattering particles like black carbon (BC) and ozone (O3) precursors. Models and satellite imagery suggest that strong wind systems within deep Himalayan valleys are major pathways by which pollutants from the IGP are transported to the higher Himalaya. However, there is a lack of observational evidence to elucidate Himalayan valleys as major pollutant pathways. To evaluate the pathway of pollutants from IGP to higher Himalaya, I measured BC, O3, and associated meteorological conditions within the Kali-Gandaki Valley (KGV), Nepal, from January 2013 to July 2015. High concentrations of BC and O3 were observed during pre-monsoon (March-June) and post-monsoon (September-February) seasons. Frequent episodes of BC concentrations two to three fold higher than average persisted from several days to a week during non-monsoon months. Observation of increases in BC concentration and fluxes in the valley were found during pre-and post-monsoon seasons and in conjunction with widespread agricultural burning and wildfires over the IGP.In addition to surface sources, tropospheric O3 can also be transported from the stratosphere that contributes significantly to background concentrations. Tropospheric O3 modulates the atmospheric lifetime of many atmospheric gases and like BC influences climate via direct and indirect radiative forcing. I collected ozonesonde data from Pokhara, Nepal in winter (December 2015 -January 2016) focusing on the distribution and sources of tropospheric O3 in the Himalayan region. Stratospheric influence was inferred when tropospheric air masses had potential vorticity (PV) above 1.5 PVU, relative humidity (RH) under 20% and potential temperature (theta) above 320 K. I found that the ozonesondes that stayed south of the Himalaya measured higher O3 concentrations between 3 and 10 km and ozonesondes launched during high PV period were 10-20 ppbv higher between 9 and 13 km. I also found that the topography and surface temperature induced a consistent thermal structure over the Tibetan plateau. When the jet was positioned south of the thermal gradient, high O3 concentrations were observed above 8 km. Higher O3 concentrations were detected when the jet stream had high wind speeds (above 60 ms -1 ) and during periods of high PV given the location of the SJS was south of the thermal gradient. Layers of diffused air masses were frequently detected with PV values showing both stratospheric and tropospheric origin. This dissertation supports the hypothesis that trans-Himalayan valleys are important conduits for transport of pollutants from the IGP to TP and provides insight, for the first time, on the vertical concentrations O3 adjacent to Himalaya using MERRA-2 as a tool to understand the role of SJS and the influence of stratosph...

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The Deep Atmospheric Boundary Layer and Its Significance to the Stratosphere and Troposphere Exchange over the Tibetan Plateau

Cited by 73 publications

References 56 publications

Simultaneous assimilation of ozone profiles from multiple UV-VIS satellite instruments

Simultaneous assimilation of ozone profiles from multiple UV-VIS satellite instruments

Influence of air mass downward transport on the variability of surface ozone at Xianggelila Regional Atmosphere Background Station, southwest China

Transport and Distribution of Short-lived Climate Pollutants in the Himalaya

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