Convective boundary layer evolution to 4 km asl over High‐alpine terrain: Airborne lidar observations in the Alps

Nyeki, S.; Kalberer, Markus; Colbeck, I.; Wekker, Stephan F. J. De; Furger, Markus; Gäggeler, H. W.; Koßmann, M.; Lugauer, M.; Steyn, D. G.; Weingärtner, E.; Wirth, Martin; Baltensperger, Urs

doi:10.1029/1999gl010928

Cited by 67 publications

(66 citation statements)

References 12 publications

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“…A so called injection (or aerosol) layer can form above the CBL top which intermittently receives CBL air (Henne et al, 2004). It has been shown from airborne Lidar observations (Nyeki et al, 2000) and model studies ) that JFJ can be situated well within the injection layer during summer, day-time, fair-weather conditions. It is clear from Fig.…”

Section: Selection Of Data Representative Of Free Troposphere Airmentioning

confidence: 99%

1997–2007 CO trend at the high Alpine site Jungfraujoch: a comparison between NDIR surface in situ and FTIR remote sensing observations

Dils

Cui²,

Henne

et al. 2011

Atmos. Chem. Phys.

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Abstract. Within the atmospheric research community, there is a strong interest in integrated datasets, combining data from several instrumentations. This integration is complicated by the different characteristics of the datasets, inherent to the measurement techniques. Here we have compared two carbon monoxide time series (1997 till 2007) acquired at the high-Alpine research station Jungfraujoch (3580 m above sea level), with two well-established measurement techniques, namely in situ surface concentration measurements using Non-Dispersive Infrared Absorption technology (NDIR), and ground-based remote sensing measurements using solar absorption Fourier Transform Infrared spectrometry (FTIR). The profile information available in the FTIR signal allowed us to extract an independent layer with a top height of 7.18 km above sea level, appropriate for comparison with our in situ measurements. We show that, even if both techniques are able to measure free troposphere CO concentrations, the datasets exhibit marked differences in their overall trends (−3.21 ± 0.03 ppb year −1 for NDIR vs.−0.8 ± 0.4 ppb year −1 for FTIR). Removing measurements that are polluted by uprising boundary layer air has a strong impact on the NDIR trend (now −2.62 ± 0.03 ppb year −1 ), but its difference with FTIR remains significant. Using the LAGRANTO trajectory model, we show that both measurement techniques are influenced by different source regions and therefore are likely subject to exhibit significant differences in their overall trend behaviour. However the observation that the NDIR-FTIR trend difference is as significant before as after 2001 is at odds with available emission databases which claim a significant Asian CO increase after 2001 only.

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Section: Selection Of Data Representative Of Free Troposphere Airmentioning

confidence: 99%

1997–2007 CO trend at the high Alpine site Jungfraujoch: a comparison between NDIR surface in situ and FTIR remote sensing observations

Dils

Cui²,

Henne

et al. 2011

Atmos. Chem. Phys.

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“…The literature describes the convective boundary layer as a PBL that follows the terrain (Wekker et al 2004) or as a layer that is decoupled from the terrain (Kossmann et al 1998). On the other hand, an aerosol layer is nearly uniform in height and generally does not follow the underlying terrain on a scale up to tens of km (Nyeki et al 2000;Wekker 2002). The difference between the aerosol layer and PBL follows a daily cycle, and at night the aerosol or residual layer is deeper than the stable boundary layer.…”

Section: Ceilometer Versus Wind Profiler Pbl Determinationmentioning

confidence: 99%

“…The mechanisms responsible for advecting the PBL air up to the JFJ station altitude are of convective and mechanical nature. Namely the PBL air is uplifted by the convective PBL growth process and mountain venting (Nyeki et al 2000;Henne et al 2005;Collaud Coen et al 2011). Previous PBL studies at the JFJ site identified elevated aerosol layers that are transported by advection to the site .…”

Section: Introductionmentioning

confidence: 99%

Investigation of the Planetary Boundary Layer in the Swiss Alps Using Remote Sensing and In Situ Measurements

Ketterer

Zieger

Bukowiecki

et al. 2014

Boundary-Layer Meteorol

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The development of the planetary boundary layer (PBL) has been studied in a complex terrain using various remote sensing and in situ techniques. The high-altitude research station at Jungfraujoch (3,580 m a.s.l.) in the Swiss Alps lies for most of the time in the free troposphere except when it is influenced by the PBL reaching the station, especially during the summer season. A ceilometer and a wind profiler were installed at Kleine Scheidegg, a mountain pass close to Jungfraujoch, located at an altitude of 2,061 m a.s.l. Data from the ceilometer were analyzed using two different algorithms, while the signal-to-noise ratio of the wind profiler was studied to compare the retrieved PBL heights. The retrieved values from the ceilometer and wind profiler agreed well during daytime and cloud-free conditions. The results were additionally compared with the PBL height estimated by the numerical weather prediction model COSMO-2, which showed a clear underestimation of the PBL height for most of the cases but occasionally also a slight overestimation especially around noon, when the PBL showed its maximum extent. Air parcels were transported upwards by slope winds towards Jungfraujoch when the PBL was higher than 2,800 m a.s.l. during cloud-free cases. This was confirmed by the in situ aerosol measurements at Jungfraujoch with a significant increase in particle number concentration, particle light absorption and scattering coefficients when PBL-influenced air masses reached the station in the afternoon hours. The continuous aerosol in situ measurements at Jungfraujoch were clearly influenced by the local PBL development but also by long-range transport phenomena such as Saharan dust or pollution from the south.

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“…Convergence near mountain peaks further enhances the export of boundary-layer air to the free troposphere. In aggregate, mountain ranges create an injection layer above and within their lee (Henne et al, 2005;Nyeki et al, 2000) which is dynamically decoupled from the convective boundary layer but has similar tracer concentrations. In order to feed the vertical transport, boundary-layer air is drawn towards the base of the mountains from up to 80 km away over the course of a day (Weissmann et al, 2005).…”

Section: Introductionmentioning

confidence: 99%

Surface-to-mountaintop transport characterised by radon observations at the Jungfraujoch

et al. 2014

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Abstract. Atmospheric composition measurements at Jungfraujoch are affected intermittently by boundary-layer air which is brought to the station by processes including thermally driven (anabatic) mountain winds. Using observations of radon-222, and a new objective analysis method, we quantify the land-surface influence at Jungfraujoch hour by hour and detect the presence of anabatic winds on a daily basis. During 2010-2011, anabatic winds occurred on 40 % of days, but only from April to September. Anabatic wind days were associated with warmer air temperatures over a large fraction of Europe and with a shift in air-mass properties, even when comparing days with a similar mean radon concentration. Excluding days with anabatic winds, however, did not lead to a better definition of the unperturbed aerosol background than a definition based on radon alone. This implies that a radon threshold reliably excludes local influences from both anabatic and non-anabatic vertical-transport processes.

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Convective boundary layer evolution to 4 km asl over High‐alpine terrain: Airborne lidar observations in the Alps

Cited by 67 publications

References 12 publications

1997–2007 CO trend at the high Alpine site Jungfraujoch: a comparison between NDIR surface in situ and FTIR remote sensing observations

1997–2007 CO trend at the high Alpine site Jungfraujoch: a comparison between NDIR surface in situ and FTIR remote sensing observations

Investigation of the Planetary Boundary Layer in the Swiss Alps Using Remote Sensing and In Situ Measurements

Surface-to-mountaintop transport characterised by radon observations at the Jungfraujoch

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