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.

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.

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

Atmospheric Chemistry and Physics ◽

10.5194/acp-17-6243-2017 ◽

2017 ◽

Vol 17 (10) ◽

pp. 6243-6255 ◽

Cited By ~ 7

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.

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Coupled 1-D physical–biological model study of phytoplankton production at two contrasting time-series stations in the western North Pacific

Journal of Oceanography ◽

10.1007/s10872-015-0341-1 ◽

2016 ◽

Vol 72 (3) ◽

pp. 509-526 ◽

Cited By ~ 8

Author(s):

Yoshikazu Sasai ◽

Chisato Yoshikawa ◽

S. Lan Smith ◽

Taketo Hashioka ◽

Kazuhiko Matsumoto ◽

...

Keyword(s):

Time Series ◽

North Pacific ◽

Western North Pacific ◽

Biological Model ◽

Phytoplankton Production ◽

Model Study

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The Lagged Effect of Anthropogenic Aerosol on East Asian Precipitation during the Summer Monsoon Season

Atmosphere ◽

10.3390/atmos11121356 ◽

2020 ◽

Vol 11 (12) ◽

pp. 1356

Author(s):

Su-Jung Lee ◽

Yong-Cheol Jeong ◽

Sang-Wook Yeh

Keyword(s):

North Pacific ◽

Korean Peninsula ◽

Western North Pacific ◽

Monsoon Season ◽

East Asian ◽

Eastern China ◽

Anthropogenic Aerosols ◽

Anthropogenic Aerosol ◽

The North ◽

Lagged Effect

The authors investigated the lagged effect of anthropogenic aerosols (AAs) during the premonsoon season (April–May–June) on the East Asian precipitation during the postmonsoon season (July–August) using the aerosol optical depth (AOD) from a satellite dataset and reanalysis datasets. When the AOD is high in Eastern China during the premonsoon season, the amount of precipitation increases in the western North Pacific, including the Korean Peninsula and Japan, during the postmonsoon season. The amount of cloud in the western-to-central North Pacific in the premonsoon season increases during the high-AOD period. Subsequently, it cools the sea surface temperature until the postmonsoon season, which strengthens the North Pacific High. The strengthened North Pacific High in the postmonsoon season expands to the western North Pacific, which leads to the enhancement of the moisture flows from the ocean. This results in the increase in precipitation in the western North Pacific, including the Korean Peninsula and Japan, during the postmonsoon season.

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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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