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

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.

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Review of “Effect of anthropogenic aerosol emissions on precipitation in warm conveyor belts in the western North Pacific in winter - a model study with ECHAM6-HAM”, by Joos et. al.

10.5194/acp-2016-722-rc2 ◽

2016 ◽

Author(s):

Anonymous

Keyword(s):

North Pacific ◽

Western North Pacific ◽

Anthropogenic Aerosol ◽

Model Study ◽

Conveyor Belts ◽

Warm Conveyor Belts ◽

Aerosol Emissions

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

Journal of the Atmospheric Sciences ◽

10.1175/jas-d-14-0119.1 ◽

2014 ◽

Vol 71 (10) ◽

pp. 3668-3673 ◽

Cited By ~ 12

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.

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

10.5194/egusphere-egu2020-18794 ◽

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

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

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

Geoscientific Model Development Discussions ◽

10.5194/gmdd-8-2161-2015 ◽

2015 ◽

Vol 8 (2) ◽

pp. 2161-2212 ◽

Cited By ~ 2

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).

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The Baroclinic Moisture Flux

Monthly Weather Review ◽

10.1175/mwr-d-16-0153.1 ◽

2016 ◽

Vol 145 (1) ◽

pp. 25-47 ◽

Cited By ~ 4

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.

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Toward a systematic evaluation of warm conveyor belts in numerical weather prediction and climate models. Part II: Verification of operational reforecasts

Journal of the Atmospheric Sciences ◽

10.1175/jas-d-20-0385.1 ◽

2021 ◽

Author(s):

Jan Wandel ◽

Julian F. Quinting ◽

Christian M. Grams

Keyword(s):

North Atlantic ◽

North Pacific ◽

Regression Models ◽

Weather Prediction ◽

Systematic Evaluation ◽

Logistic Regression Models ◽

The North ◽

Conveyor Belts ◽

The North Atlantic ◽

Warm Conveyor Belts

AbstractWarm conveyor belts (WCBs) associated with extratropical cyclones transport air from the lower troposphere into the tropopause region and contribute to upper-level ridge building and the formation of blocking anticyclones. Recent studies indicate that this constitutes an important source and magnifier of forecast uncertainty and errors in numerical weather prediction (NWP) models. However, a systematic evaluation of the representation of WCBs in NWP models has yet to be determined. Here, we employ the logistic regression models developed in Part I to identify the inflow, ascent, and outflow stages of WCBs in the European Centre for Medium-Range Weather Forecasts (ECMWF) sub-seasonal reforecasts for Northern Hemisphere winter in the period January 1997 to December 2017. We verify the representation of these WCB stages in terms of systematic occurrence frequency biases, forecast reliability, and forecast skill. Systematic WCB frequency biases emerge already at early lead times of around 3 days with an underestimation for the WCB outflow over the North Atlantic and eastern North Pacific of around 40% relative to climatology. Biases in the predictor variables of the logistic regression models can partially explain these biases in WCB inflow, ascent, or outflow. Despite an overconfidence in predicting high WCB probabilities, skillful WCB forecasts are on average possible up to a lead time of 8–10 days with more skill over the North Pacific compared to the North Atlantic region. Our results corroborate that the current limited forecast skill for the large-scale extratropical circulation on sub-seasonal time scales beyond 10 days might be tied to the representation of WCBs and associated upscale error growth.

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Light conveyor belts. Test method for the measurement of the electrostatic field generated by a running light conveyor belt

10.3403/01717182 ◽

1999 ◽

Keyword(s):

Electrostatic Field ◽

Conveyor Belt ◽

Test Method ◽

Conveyor Belts

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Light conveyor belts. Determination of the electrostatic field generated by a running light conveyor belt

10.3403/30106621 ◽

2006 ◽

Keyword(s):

Electrostatic Field ◽

Conveyor Belt ◽

Conveyor Belts

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The local and remote atmospheric impacts of Africa’s 21st century aerosol emission trajectory

10.5194/egusphere-egu21-14417 ◽

2021 ◽

Author(s):

Chris Wells ◽

Apostolos Voulgarakis

Keyword(s):

Regional Climate ◽

Emission Region ◽

Anthropogenic Aerosol ◽

Remote Locations ◽

Aerosol Emission ◽

Radiation Fluxes ◽

The World ◽

Aerosol Emissions ◽

The Impact ◽

Lower Biomass

Aerosols are a major climate forcer, but their historical effect has the largest uncertainty of any forcing; their mechanisms and impacts are not well understood. Due to their short lifetime, aerosols have large impacts near their emission region, but they also have effects on the climate in remote locations. In recent years, studies have investigated the influences of regional aerosols on global and regional climate, and the mechanisms that lead to remote responses to their inhomogeneous forcing. Using the Shared Socioeconomic Pathway scenarios (SSPs), transient future experiments were performed in UKESM1, testing the effect of African emissions following the SSP3-RCP7.0 scenario as the rest of the world follows SSP1-RCP1.9, relative to a global SSP1-RCP1.9 control. SSP3 sees higher direct anthropogenic aerosol emissions, but lower biomass burning emissions, over Africa. Experiments were performed changing each of these sets of emissions, and both. A further set of experiments additionally accounted for changing future CO2 concentrations, to investigate the impact of CO2 on the responses to aerosol perturbations. Impacts on radiation fluxes, temperature, circulation and precipitation are investigated, both over the emission region (Africa), where microphysical effects dominate, and remotely, where dynamical influences become more relevant.&#160;

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