A portrayal of an orographic Warm Conveyor Belt using observations from aircraft, lidar and radar

2020 ◽  
Author(s):  
Maxi Boettcher ◽  
Andreas Schäfler ◽  
Harald Sodemann ◽  
Michael Sprenger ◽  
Stefan Kaufmann ◽  
...  
Keyword(s):  
Western Europe ◽  
Field Experiments ◽  
Marine Boundary Layer ◽  
Conveyor Belt ◽  
Western Mediterranean ◽  
Air Mass ◽  
Conveyor Belts ◽  
The Alps ◽  
The Baltic ◽  
Warm Conveyor Belts

<p>Warm conveyor belts (WCBs) are important airstreams in extratropical<br>cyclones, leading to the formation of intense precipitation<br>and the transport of substantial amounts of water vapour upward and<br>poleward. This study presents a scenario of a WCB that ascended from<br>western Europe towards the Baltic Sea using aircraft, lidar and<br>radar observations from the field experiments HyMeX and<br>T-NAWDEX-Falcon in October 2012.<br>Trajectories based on the ensemble data assimilation<br>system of the ECMWF are used to quantify probabilistically<br>the occurrence of the WCB and Lagrangian matches<br>between different observations. Despite severe limitations<br>for research flights over Europe, the DLR Falcon successfully<br>sampled WCB air masses during different phases of<br>the ascent. The overall picture of the WCB trajectories revealed<br>measurements in several WCB branches: trajectories<br>that ascended from the East Atlantic over northern France<br>while others had their inflow in the western Mediterranean<br>region and passed across the Alps. For the latter ones, Lagrangian<br>matches coincidentally occurred between lidar water<br>vapour measurements in the inflow of the WCB south,<br>radar measurements during the ascent at and its outflow<br>north of the Alps during a mid-tropospheric flight leg over<br>Germany.<br>The comparison of observations and ensemble analyses<br>reveals a moist bias of the analyses in parts of the WCB inflow<br>and an underestimation of cloud water species in the<br>WCB during ascent. In between, the radar instrument measured<br>strongly precipitating WCB air mass with embedded<br>linking trajectories directly above the melting layer while<br>orographically ascending at the southern slops of the Alps.<br>An inert tracer air mass could confirm the long pathway<br>of WCB air from the inflow in the marine boundary layer<br>until the outflow in the upper troposhpere near the Baltic<br>sea several hours later. This case study illustrates the complexity<br>of the interaction of WCBs with the Alpine topography,<br>which leads to (i) various pathways over and around<br>the Alpine crest and (ii) locally steep WCB ascent with increased<br>cloud content that might result in enhancement<br>of precipitation where the WCB flows over the Alps. The<br>combination of observational data and detailed ensemble-based<br>trajectory calculations reveals important aspects of<br>orographically-modified WCBs.</p>

scholarly journals Lagrangian matches between observations from aircraft, lidar and radar in an orographic warm conveyor belt

2020 ◽  
Author(s):  
Maxi Boettcher ◽  
Andreas Schäfler ◽  
Michael Sprenger ◽  
Harald Sodemann ◽  
Stefan Kaufmann ◽  
...  
Keyword(s):  
Baltic Sea ◽  
Western Europe ◽  
Field Experiments ◽  
Conveyor Belt ◽  
Western Mediterranean ◽  
Wind Fields ◽  
The Baltic Sea ◽  
The Alps ◽  
The Baltic ◽  
Warm Conveyor Belts

Abstract. Warm conveyor belts (WCBs) are important airstreams in extratropical cyclones, often leading to the formation of intense precipitation and the amplification of upper-level ridges. This study presents a case study that involves aircraft, lidar and radar observations in a WCB ascending from western Europe towards the Baltic Sea during the field experiments HyMeX and T-NAWDEX-Falcon in October 2012. Trajectories were used to link different observations along the WCB, that is to establish so-called Lagrangian matches between observations. To this aim, wind fields of the ECMWF ensemble data assimilation system were used, which allowed for a probabilistic quantification of the WCB occurrence and the Lagrangian matches. Despite severe air traffic limitations for performing research flights over Europe, the DLR Falcon successfully sampled WCB air masses during different phases of the WCB ascent. The WCB trajectories revealed measurements in two distinct WCB branches: one branch ascended from the eastern North Atlantic over southwestern France, while the other had its inflow in the western Mediterranean. Both branches passed across the Alps, and for both branches, Lagrangian matches coincidentally occurred between lidar water vapour measurements in the inflow of the WCB south of the Alps, radar measurements during the ascent at the Alps, and in situ aircraft measurements by Falcon in the WCB outflow north of the Alps. An airborne release experiment with an inert tracer could confirm the long pathway of the WCB from the inflow in the Mediterranean boundary layer to the outflow in the upper troposphere near the Baltic Sea several hours later. The comparison of observations and ensemble analyses reveals a moist bias in the analyses in parts of the WCB inflow but a good agreement of cloud water species in the WCB during ascent. In between these two observations, a precipitation radar measured strongly precipitating WCB air located directly above the melting layer while ascending at the southern slopes of the Alps. The trajectories illustrate the complexity of a continental and orographically influenced WCB, which leads to (i) WCB moisture sources from both the Atlantic and Mediterranean, (ii) different pathways of WCB ascent affected by orography, and (iii) locally steep WCB ascent with high radar reflectivity values that might result in enhanced precipitation where the WCB flows over the Alps. The linkage of observational data by ensemble-based WCB trajectory calculations and confirmed by an inert tracer, and the model evaluation using the multi-platform observations are the central elements of this study and reveal important aspects of orographically modified WCBs.

scholarly journals Lagrangian matches between observations from aircraft, lidar and radar in a warm conveyor belt crossing orography

2021 ◽  
Vol 21 (7) ◽  
pp. 5477-5498
Author(s):  
Maxi Boettcher ◽  
Andreas Schäfler ◽  
Michael Sprenger ◽  
Harald Sodemann ◽  
Stefan Kaufmann ◽  
...  
Keyword(s):  
Baltic Sea ◽  
North Atlantic ◽  
Western Europe ◽  
Hydrological Cycle ◽  
Conveyor Belt ◽  
Western Mediterranean ◽  
The Baltic Sea ◽  
The Alps ◽  
The Mediterranean ◽  
The Baltic

Abstract. Warm conveyor belts (WCBs) are important airstreams in extratropical cyclones, often leading to the formation of intense precipitation and the amplification of upper-level ridges. This study presents a case study that involves aircraft, lidar and radar observations in a WCB ascending from western Europe towards the Baltic Sea during the Hydrological Cycle in the Mediterranean Experiment (HyMeX) and T-NAWDEX-Falcon in October 2012, a preparatory campaign for the THORPEX North Atlantic Waveguide and Downstream Impact Experiment (T-NAWDEX). Trajectories were used to link different observations along the WCB, that is, to establish so-called Lagrangian matches between observations. To this aim, an ensemble of wind fields from the global analyses produced by the European Centre for Medium-Range Weather Forecasts (ECMWF) Ensemble of Data Assimilations (EDA) system were used, which allowed for a probabilistic quantification of the WCB occurrence and the Lagrangian matches. Despite severe air traffic limitations for performing research flights over Europe, the German Aerospace Center (DLR) Falcon successfully sampled WCB air masses during different phases of the WCB ascent. The WCB trajectories revealed measurements in two distinct WCB branches: one branch ascended from the eastern North Atlantic over southwestern France, while the other had its inflow in the western Mediterranean. Both branches passed across the Alps, and for both branches Lagrangian matches coincidentally occurred between lidar water vapour measurements in the inflow of the WCB south of the Alps, radar measurements during the ascent at the Alps and in situ aircraft measurements by Falcon in the WCB outflow north of the Alps. An airborne release experiment with an inert tracer could confirm the long pathway of the WCB from the inflow in the Mediterranean boundary layer to the outflow in the upper troposphere near the Baltic Sea several hours later. The comparison of observations and ensemble analyses reveals a moist bias in the analyses in parts of the WCB inflow but a good agreement of cloud water species in the WCB during ascent. In between these two observations, a precipitation radar measured strongly precipitating WCB air located directly above the melting layer while ascending at the southern slopes of the Alps. The trajectories illustrate the complexity of a continental and orographically influenced WCB, which leads to (i) WCB moisture sources from both the Atlantic and Mediterranean, (ii) different pathways of WCB ascent affected by orography, and (iii) locally steep WCB ascent with high radar reflectivity values that might result in enhanced precipitation where the WCB flows over the Alps. The linkage of observational data by ensemble-based WCB trajectory calculations, the confirmation of the WCB transport by an inert tracer and the model evaluation using the multi-platform observations are the central elements of this study and reveal important aspects of orographically modified WCBs.

scholarly journals Effect of anthropogenic aerosol emissions on precipitation in warm conveyor belts in the western North Pacific in winter – a model study with ECHAM6-HAM

2016 ◽  
Author(s):  
Hanna Joos ◽  
Erica Madonna ◽  
Kasja Witlox ◽  
Sylvaine Ferrachat ◽  
Heini Wernli ◽  
...  
Keyword(s):  
North Pacific ◽  
Aerosol Particles ◽  
Conveyor Belt ◽  
Radiation Balance ◽  
Anthropogenic Aerosol ◽  
Model Study ◽  
Conveyor Belts ◽  
Winter Time ◽  
Warm Conveyor Belts ◽  
Aerosol Emissions

Abstract. While there is a clear impact of aerosol particles on the radiation balance, whether and how aerosol particles influence precipitation is controversial. Here we use the ECHAM6-HAM global cli- mate model coupled to an aerosol module to analyse whether an impact of anthropogenic aerosol particles on the timing and the amount of precipitation from warm conveyor belts in low pressure systems in the winter time North Pacific can be detected. We conclude that while polluted warm con- veyor belt trajectories start with 5–10 times higher black carbon concentrations, the overall amount of precipitation is comparable in pre-industrial and present-day conditions. Precipitation formation is however supressed in the most polluted warm conveyor belt trajectories.

scholarly journals On the Co-Occurrence of Warm Conveyor Belt Outflows and PV Streamers*

2014 ◽  
Vol 71 (10) ◽  
pp. 3668-3673 ◽  
Author(s):  
Erica Madonna ◽  
Sebastian Limbach ◽  
Christine Aebi ◽  
Hanna Joos ◽  
Heini Wernli ◽  
...  
Keyword(s):  
Life Cycle ◽  
Three Dimensional ◽  
Conveyor Belt ◽  
Rossby Wave Breaking ◽  
Weather Forecasts ◽  
Three Dimensional Objects ◽  
The North ◽  
Conveyor Belts ◽  
Diabatic Processes ◽  
Warm Conveyor Belts

Abstract The co-occurrence of warm conveyor belts (WCBs), strongly ascending moist airstreams in extratropical cyclones, and stratospheric potential vorticity (PV) streamers, indicators for breaking Rossby waves on the tropopause, is investigated for a 21-yr period in the Northern Hemisphere using Interim European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-Interim) data. WCB outflows and PV streamers are respectively identified as two- and three-dimensional objects and tracked during their life cycle. PV streamers are more frequent than WCB outflows and nearly 15% of all PV streamers co-occur with WCBs during their life cycle, whereas about 60% of all WCB outflows co-occur with PV streamers. Co-occurrences are most frequent over the North Atlantic and North Pacific in spring and winter. WCB outflows are often located upstream of the PV streamers and form earlier, indicating the importance of diabatic processes for downstream Rossby wave breaking. Less frequently, PV streamers occur first, leading to the formation of new WCBs.

scholarly journals 3-D visualization of ensemble weather forecasts – Part 2: Forecasting warm conveyor belt situations for aircraft-based field campaigns

2015 ◽  
Vol 8 (2) ◽  
pp. 2161-2212 ◽  
Author(s):  
M. Rautenhaus ◽  
C. M. Grams ◽  
A. Schäfler ◽  
R. Westermann
Keyword(s):  
System Integration ◽  
Visual Analysis ◽  
Weather Forecasting ◽  
Conveyor Belt ◽  
Ensemble Prediction ◽  
Wind Fields ◽  
Uncertainty Visualization ◽  
Ensemble Prediction System ◽  
Conveyor Belts ◽  
Warm Conveyor Belts

Abstract. We present the application of interactive 3-D visualization of ensemble weather predictions to forecasting warm conveyor belt situations during aircraft-based atmospheric research campaigns. Motivated by forecast requirements of the T-NAWDEX-Falcon 2012 campaign, a method to predict 3-D probabilities of the spatial occurrence of warm conveyor belts has been developed. Probabilities are derived from Lagrangian particle trajectories computed on the forecast wind fields of the ECMWF ensemble prediction system. Integration of the method into the 3-D ensemble visualization tool Met.3D, introduced in the first part of this study, facilitates interactive visualization of WCB features and derived probabilities in the context of the ECMWF ensemble forecast. We investigate the sensitivity of the method with respect to trajectory seeding and forecast wind field resolution. Furthermore, we propose a visual analysis method to quantitatively analyse the contribution of ensemble members to a probability region and, thus, to assist the forecaster in interpreting the obtained probabilities. A case study, revisiting a forecast case from T-NAWDEX-Falcon, illustrates the practical application of Met.3D and demonstrates the use of 3-D and uncertainty visualization for weather forecasting and for planning flight routes in the medium forecast range (three to seven days before take-off).

scholarly journals The Baroclinic Moisture Flux

2016 ◽  
Vol 145 (1) ◽  
pp. 25-47 ◽  
Author(s):  
Ron McTaggart-Cowan ◽  
John R. Gyakum ◽  
Richard W. Moore
Keyword(s):  
Vertical Motion ◽  
Moisture Flux ◽  
Conveyor Belt ◽  
Mean Flow ◽  
Conveyor Belts ◽  
Moist Processes ◽  
The Mean ◽  
Rain Events ◽  
The Many ◽  
Warm Conveyor Belts

Abstract As subsaturated air ascends sloping isentropic surfaces, adiabatic expansion results in cooling and relative moistening. This process is an effective way to precondition the atmosphere for efficient moist processes while bringing parcels to saturation, and thereafter acts to maintain saturation during condensation. The goal of this study is to develop a diagnostic quantity that highlights circulations and regions in which the process of parcel moistening by isentropic ascent is active. Among the many features that rely on this process for the generation of an important fraction of their energy are oceanic cyclones, transitioning tropical cyclones, warm conveyor belts, diabatic Rossby vortices, and predecessor rain events. The baroclinic moisture flux (BMF) is defined as moisture transport by the component of vertical motion associated with isentropic upgliding. In warm conveyor belt and diabatic Rossby vortex case studies, the BMF appears to be successful in identifying the portion of the circulation in which this process is actively bringing parcels to saturation to promote the formation of clouds and precipitation. On a broader scale, the climatological maxima of the BMF highlight regions in which parcel moistening by isentropic ascent is anticipated to have a nonnegligible impact on the atmospheric state either through the action of the mean flow or via the repeated occurrence of isolated large-BMF events. The process-centric foundation of the BMF makes it useful as a filtering or exploratory variable, with the potential for extension into predictive applications.

scholarly journals Effect of anthropogenic aerosol emissions on precipitation in warm conveyor belts in the western North Pacific in winter – a model study with ECHAM6-HAM

2017 ◽  
Vol 17 (10) ◽  
pp. 6243-6255 ◽  
Author(s):  
Hanna Joos ◽  
Erica Madonna ◽  
Kasja Witlox ◽  
Sylvaine Ferrachat ◽  
Heini Wernli ◽  
...  
Keyword(s):  
North Pacific ◽  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Aerosol Particles ◽  
Conveyor Belt ◽  
Radiation Balance ◽  
Anthropogenic Aerosol ◽  
Conveyor Belts ◽  
Warm Conveyor Belts

Abstract. While there is a clear impact of aerosol particles on the radiation balance, whether and how aerosol particles influence precipitation is controversial. Here we use the ECHAM6-HAM global climate model coupled to an aerosol module to analyse whether an impact of anthropogenic aerosol particles on the timing and amount of precipitation can be detected in North Pacific warm conveyor belts. Warm conveyor belts are the strongest precipitation-producing airstreams in extratropical cyclones and are identified here with a Lagrangian technique, i.e. by objectively identifying the most strongly ascending trajectories in North Pacific cyclones. These conveyor belts have been identified separately in 10-year ECHAM6-HAM simulations with present-day and pre-industrial aerosol conditions. Then, the evolution of aerosols and cloud properties has been analysed in detail along the identified warm conveyor belt trajectories. The results show that, under present-day conditions, some warm conveyor belt trajectories are strongly polluted (i.e. high concentrations of black carbon and sulfur dioxide) due to horizontal transport from eastern Asia to the oceanic region where warm conveyor belts start their ascent. In these polluted trajectories a weak delay and reduction of precipitation formation occurs compared to clean warm conveyor belt trajectories. However, all warm conveyor belts consist of both polluted and clean trajectories at the time they start their ascent, and the typically more abundant clean trajectories strongly reduce the aerosol impact from the polluted trajectories. The main conclusion then is that the overall amount of precipitation is comparable in pre-industrial conditions, when all warm conveyor belt trajectories are clean, and in present-day conditions, when warm conveyor belts consist of a mixture of clean and polluted trajectories.

scholarly journals Direct dating reveals the early history of opium poppy in western Europe

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Aurélie Salavert ◽  
Antoine Zazzo ◽  
Lucie Martin ◽  
Ferran Antolín ◽  
Caroline Gauthier ◽  
...  
Keyword(s):  
Western Europe ◽  
Western Alps ◽  
Western Mediterranean ◽  
Opium Poppy ◽  
Radiocarbon Dates ◽  
Macrobotanical Remains ◽  
History Of ◽  
Temperate Europe ◽  
Radiocarbon Chronology ◽  
Botanical Remains

AbstractThis paper aims to define the first chrono-cultural framework on the domestication and early diffusion of the opium poppy using small-sized botanical remains from archaeological sites, opening the way to directly date minute short-lived botanical samples. We produced the initial set of radiocarbon dates directly from the opium poppy remains of eleven Neolithic sites (5900–3500 cal BCE) in the central and western Mediterranean, northwestern temperate Europe, and the western Alps. When possible, we also dated the macrobotanical remains originating from the same sediment sample. In total, 22 samples were taken into account, including 12 dates directly obtained from opium poppy remains. The radiocarbon chronology ranges from 5622 to 4050 cal BCE. The results show that opium poppy is present from at least the middle of the sixth millennium in the Mediterranean, where it possibly grew naturally and was cultivated by pioneer Neolithic communities. Its dispersal outside of its native area was early, being found west of the Rhine in 5300–5200 cal BCE. It was introduced to the western Alps around 5000–4800 cal BCE, becoming widespread from the second half of the fifth millennium. This research evidences different rhythms in the introduction of opium poppy in western Europe.

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