scholarly journals The topography contribution to the influence of the atmospheric boundary layer at high altitude stations

2017 ◽  
Author(s):  
Martine Collaud Coen ◽  
Elisabeth Andrews ◽  
Diego Aliaga ◽  
Marcos Andrade ◽  
Hristo Angelov ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Atmospheric Boundary Layer ◽  
High Altitude ◽  
Geometric Mean ◽  
Convective Transport ◽  
Transport Processes ◽  
The Tibetan Plateau ◽  
Diurnal Cycles ◽  
Air Convection ◽  
Aerosol Parameters

Abstract. High altitude stations are often emphasized as free tropospheric measuring sites but they remain influenced by atmospheric boundary layer (ABL) air masses due to convective transport processes. The local and meso-scale topographical features around the station are involved in the convective boundary layer development and in the formation of thermally induced winds leading to ABL air lifting. The station altitude is not a sufficient parameter to characterize the ABL influence. Topography data from the global digital elevation model GTopo30 were used to calculate 5 parameters for 46 high altitude stations situated in five continents. The geometric mean of these 5 parameters determines a topography based index called ABL-TopoIndex which can be used to rank the high altitude stations as a function of the ABL influence. To construct the ABL-TopoIndex, we rely on the criteria that the ABL influence will be low if the station is one of the highest points in the mountainous massif, if there is a large altitude difference between the station and the valleys or plateaus, if the slopes around the station are steep, and finally if the drainage basin for air convection is small. All stations on volcanic islands exhibit a low ABL-TopoIndex whereas stations in the Himalaya and the Tibetan Plateau have high ABL-TopoIndex values. Spearman's rank correlation between aerosol optical properties and number concentration from 28 stations and the ABL-TopoIndex, the altitude and the latitude are used to validate this topographical approach. Statistically significant (s.s.) correlations are found between the 5 and 50 percentiles of all aerosol parameters and the ABL-TopoIndex whereas no s.s. correlation is found with the station altitude. The diurnal cycles of aerosol parameters seem to be best explained by the station latitude although a s.s. correlation is found between the amplitude of the diurnal cycles of the absorption coefficient and the ABL-TopoIndex. Finally, the main flow paths for air convection were calculated for various ABL heights.

scholarly journals Identification of topographic features influencing aerosol observations at high altitude stations

2018 ◽  
Vol 18 (16) ◽  
pp. 12289-12313 ◽  
Author(s):  
Martine Collaud Coen ◽  
Elisabeth Andrews ◽  
Diego Aliaga ◽  
Marcos Andrade ◽  
Hristo Angelov ◽  
...  
Keyword(s):  
Boundary Layer ◽  
High Altitude ◽  
Drainage Basin ◽  
Geometric Mean ◽  
Convective Transport ◽  
Transport Processes ◽  
High Plains ◽  
The Tibetan Plateau ◽  
Diurnal Cycles ◽  
Aerosol Parameters

Abstract. High altitude stations are often emphasized as free tropospheric measuring sites but they remain influenced by atmospheric boundary layer (ABL) air masses due to convective transport processes. The local and meso-scale topographical features around the station are involved in the convective boundary layer development and in the formation of thermally induced winds leading to ABL air lifting. The station altitude alone is not a sufficient parameter to characterize the ABL influence. In this study, a topography analysis is performed allowing calculation of a newly defined index called ABL-TopoIndex. The ABL-TopoIndex is constructed in order to correlate with the ABL influence at the high altitude stations and long-term aerosol time series are used to assess its validity. Topography data from the global digital elevation model GTopo30 were used to calculate five parameters for 43 high and 3 middle altitude stations situated on five continents. The geometric mean of these five parameters determines a topography based index called ABL-TopoIndex, which can be used to rank the high altitude stations as a function of the ABL influence. To construct the ABL-TopoIndex, we rely on the criteria that the ABL influence will be low if the station is one of the highest points in the mountainous massif, if there is a large altitude difference between the station and the valleys or high plains, if the slopes around the station are steep, and finally if the inverse drainage basin potentially reflecting the source area for thermally lifted pollutants to reach the site is small. All stations on volcanic islands exhibit a low ABL-TopoIndex, whereas stations in the Himalayas and the Tibetan Plateau have high ABL-TopoIndex values. Spearman's rank correlation between aerosol optical properties and number concentration from 28 stations and the ABL-TopoIndex, the altitude and the latitude are used to validate this topographical approach. Statistically significant (SS) correlations are found between the 5th and 50th percentiles of all aerosol parameters and the ABL-TopoIndex, whereas no SS correlation is found with the station altitude. The diurnal cycles of aerosol parameters seem to be best explained by the station latitude although a SS correlation is found between the amplitude of the diurnal cycles of the absorption coefficient and the ABL-TopoIndex.

scholarly journals Stable Atmospheric Boundary Layers and Diurnal Cycles: Challenges for Weather and Climate Models

2013 ◽  
Vol 94 (11) ◽  
pp. 1691-1706 ◽  
Author(s):  
A. A. M. Holtslag ◽  
G. Svensson ◽  
P. Baas ◽  
S. Basu ◽  
B. Beare ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Wind Speed ◽  
Atmospheric Boundary Layer ◽  
Climate Models ◽  
Model Performance ◽  
Weather Forecast ◽  
The Arctic ◽  
Diurnal Cycles ◽  
Low Wind Speed ◽  
Weather And Climate

The representation of the atmospheric boundary layer is an important part of weather and climate models and impacts many applications such as air quality and wind energy. Over the years, the performance in modeling 2-m temperature and 10-m wind speed has improved but errors are still significant. This is in particular the case under clear skies and low wind speed conditions at night as well as during winter in stably stratified conditions over land and ice. In this paper, the authors review these issues and provide an overview of the current understanding and model performance. Results from weather forecast and climate models are used to illustrate the state of the art as well as findings and recommendations from three intercomparison studies held within the Global Energy and Water Exchanges (GEWEX) Atmospheric Boundary Layer Study (GABLS). Within GABLS, the focus has been on the examination of the representation of the stable boundary layer and the diurnal cycle over land in clear-sky conditions. For this purpose, single-column versions of weather and climate models have been compared with observations, research models, and large-eddy simulations. The intercomparison cases are based on observations taken in the Arctic, Kansas, and Cabauw in the Netherlands. From these studies, we find that even for the noncloudy boundary layer important parameterization challenges remain.

scholarly journals Transport of short-lived halocarbons to the stratosphere over the Pacific Ocean

2020 ◽  
Vol 20 (2) ◽  
pp. 1163-1181
Author(s):  
Michal T. Filus ◽  
Elliot L. Atlas ◽  
Maria A. Navarro ◽  
Elena Meneguz ◽  
David Thomson ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Lower Stratosphere ◽  
Atmospheric Transport ◽  
Convective Transport ◽  
Transport Processes ◽  
Lagrangian Model ◽  
Convection Scheme ◽  
Model Calculations ◽  
Upper Troposphere ◽  
Tropical Troposphere

Abstract. The effectiveness of transport of short-lived halocarbons to the upper troposphere and lower stratosphere remains an important uncertainty in quantifying the supply of ozone-depleting substances to the stratosphere. In early 2014, a major field campaign in Guam in the western Pacific, involving UK and US research aircraft, sampled the tropical troposphere and lower stratosphere. The resulting measurements of CH3I, CHBr3 and CH2Br2 are compared here with calculations from a Lagrangian model. This methodology benefits from an updated convection scheme that improves simulation of the effect of deep convective motions on particle distribution within the tropical troposphere. We find that the observed CH3I, CHBr3 and CH2Br2 mixing ratios in the tropical tropopause layer (TTL) are consistent with those in the boundary layer when the new convection scheme is used to account for convective transport. More specifically, comparisons between modelled estimates and observations of short-lived CH3I indicate that the updated convection scheme is realistic up to the lower TTL but is less good at reproducing the small number of extreme convective events in the upper TTL. This study consolidates our understanding of the transport of short-lived halocarbons to the upper troposphere and lower stratosphere by using improved model calculations to confirm consistency between observations in the boundary layer, observations in the TTL and atmospheric transport processes. Our results support recent estimates of the contribution of short-lived bromocarbons to the stratospheric bromine budget.

scholarly journals Climatological perspectives of air transport from atmospheric boundary layer to tropopause layer over Asian monsoon regions during boreal summer inferred from Lagrangian approach

2012 ◽  
Vol 12 (13) ◽  
pp. 5827-5839 ◽  
Author(s):  
B. Chen ◽  
X. D. Xu ◽  
S. Yang ◽  
T. L. Zhao
Keyword(s):  
Boundary Layer ◽  
Atmospheric Boundary Layer ◽  
Large Scale ◽  
Transport Model ◽  
Asian Summer Monsoon ◽  
Indian Subcontinent ◽  
Policy Implications ◽  
Boreal Summer ◽  
The Tibetan Plateau ◽  
Source Regions

Abstract. The Asian Summer Monsoon (ASM) region has been recognized as a key region that plays a vital role in troposphere-to-stratosphere transport (TST), which can significant impact the budget of global atmospheric constituents and climate change. However, the details of transport from the boundary layer (BL) to tropopause layer (TL) over these regions, particularly from a climatological perspective, remain an issue of uncertainty. In this study, we present the climatological properties of BL-to-TL transport over the ASM region during boreal summer season (June-July-August) from 2001 to 2009. A comprehensive tracking analysis is conducted based on a large ensemble of TST-trajectories departing from the atmospheric BL and arriving at TL. Driven by the winds fields from NCEP/NCAR Global Forecast System, all the TST-trajectories are selected from the high resolution datasets generated by the Lagrangian particle transport model FLEXPART using a domain-filling technique. Three key atmospheric boundary layer sources for BL-to-TL transport are identified with their contributions: (i) 38% from the region between tropical Western Pacific region and South China Seas (WP) (ii) 21% from Bay of Bengal and South Asian subcontinent (BOB), and (iii) 12% from the Tibetan Plateau, which includes the South Slope of the Himalayas (TIB). Controlled by the different patterns of atmospheric circulation, the air masses originated from these three source regions are transported along the different tracks into the TL. The spatial distributions of three source regions keep similarly from year to year. The timescales of transport from BL to TL by the large-scale ascents r-range from 1 to 7 weeks contributing up to 60–70% of the overall TST, whereas the transport governed by the deep convection overshooting become faster on a timescales of 1–2 days with the contributions of 20–30%. These results provide clear policy implications for the control of very short lived substances, especially for the source regions over Indian subcontinent with increasing populations and developing industries.

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

PLoS ONE ◽  
2013 ◽  
Vol 8 (2) ◽  
pp. e56909 ◽  
Author(s):  
Xuelong Chen ◽  
Juan A. Añel ◽  
Zhongbo Su ◽  
Laura de la Torre ◽  
Hennie Kelder ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Tibetan Plateau ◽  
Atmospheric Boundary Layer ◽  
The Tibetan Plateau

scholarly journals Investigation of the atmospheric boundary layer dynamics during the ESCOMPTE campaign

2007 ◽  
Vol 25 (3) ◽  
pp. 597-622 ◽  
Author(s):  
F. Saïd ◽  
A. Brut ◽  
B. Campistron ◽  
F. Cousin
Keyword(s):  
Boundary Layer ◽  
Atmospheric Boundary Layer ◽  
Lower Layer ◽  
Lower Troposphere ◽  
Sea Breeze ◽  
Transport Processes ◽  
Topographic Effects ◽  
Pollution Transport ◽  
Data Set ◽  
Diurnal Variability

Abstract. This paper presents some results about the behavior of the atmospheric boundary layer observed during the ESCOMPTE experiment. This campaign, which took place in south-eastern France during summer 2001, was aimed at improving our understanding of pollution episodes in relation to the dynamics of the lower troposphere. Using a large data set, as well as a simulation from the mesoscale non-hydrostatic model Meso-NH, we describe and analyze the atmospheric boundary layer (ABL) development during two specific meteorological conditions of the second Intensive Observation Period (IOP). The first situation (IOP2a, from 22 June to 23 June) corresponds to moderate, dry and cold northerly winds (end of Mistral event), coupled with a sea-breeze in the lower layer, whereas sea-breeze events with weak southerly winds occurred during the second part of the period (IOP2b, from 24 June to 26 June). In this study, we first focus on the validation of the model outputs with a thorough comparison of the Meso-NH simulations with fields measurements on three days of the IOP: 22 June, 23 June and 25 June. We also investigate the structure of the boundary layer on IOP2a when the Mistral is superimposed on a sea breeze. Then, we describe the spatial and diurnal variability of the ABL depths over the ESCOMPTE domain during the whole IOP. This step is essential if one wants to know the depth of the layer where the pollutants can be diluted or accumulated. Eventually, this study intends to describe the ABL variability in relation to local or mesoscale dynamics and/or induced topographic effects, in order to explain pollution transport processes in the low troposphere.

scholarly journals The Vertical Variability of Black Carbon Observed in the Atmospheric Boundary Layer during DACCIWA

2019 ◽  
Author(s):  
Barbara Altstädter ◽  
Konrad Deetz ◽  
Bernhard Vogel ◽  
Karmen Babić ◽  
Cheikh Dione ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Atmospheric Boundary Layer ◽  
Black Carbon ◽  
West African Monsoon ◽  
Transport Processes ◽  
Small Scale ◽  
Scale Modelling ◽  
Research Aircraft ◽  
Reactive Trace Gases ◽  
Vertical Variability

Abstract. The vertical variability of the black carbon (BC) mass concentration in the atmospheric boundary layer (ABL) is analysed during the West-African Monsoon (WAM) season. BC was measured with a micro aethalometer (model AE51, AethLabs) integrated in the payload bay of the unmanned research aircraft ALADINA (Application of Light-weight Aircraft for Detecting IN situ Aerosol) as part of the field experiment of the DACCIWA (Dynamics-Aerosol-Chemistry-Cloud Interactions in West Africa) project. In total, 53 measurement flights were performed at the local airfield of Save, Benin, in the period of 2–16 July 2016. The mean results show a high variability of BC (1.79 to 2.42 ± 0.31 μg/m3) influenced by the stratification of the ABL during the WAM. The model COSMO-ART (Consortium for Small-scale Modelling–Aerosols and Reactive Trace gases) was applied for the field campaign period and used in order to investigate possible sources of the measured BC. The model output was compared with the BC data on two selected measurement days (14 and 15 July 2016). The modeled vertical profiles of BC show that the observed BC was already altered, as the size was mainly dominated by the accumulation mode. Further, the calculated vertical transects of wind speed and BC showed that the measured BC layer was transported from the south with maritime inflow, but was mixed vertically after to the onset of the nocturnal low-level jet (NLLJ) at the measurement site. The validations and the ground observations of gas concentrations NOx and CO confirm that primary emission could be excluded during the case study, in contrast to initially expected. The case underlines the important role of BC transport processes in the WAM area.

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