AMIP simulations of a Global Model for Unified Weather‐Climate Forecast: Understanding Precipitation Characteristics and Sensitivity over East Asia

Abstract. Understanding the exchange processes between the atmospheric boundary layer and the free troposphere is crucial for estimating hemispheric transport of air pollution. Most studies of hemispheric air pollution transport have taken a large-scale perspective using global chemical transport models with fairly coarse spatial and temporal resolutions. In support of United Nations Task Force on Hemispheric Transport of Air Pollution (TF HTAP; www.htap.org), this study employs two high-resolution atmospheric chemistry models (WRF-Chem and CMAQ; 36×36 km) driven with chemical boundary conditions from a global model (MOZART; 1.9×1.9°) to examine the role of fine-scale transport and chemistry processes in controlling pollution export and import over the Asian continent in spring (March 2001). Our analysis indicates the importance of rapid venting through deep convection that develops along the leading edge of frontal system convergence bands, which are not adequately resolved in either of two global models compared with TRACE-P aircraft observations during a frontal event. Both regional model simulations and observations show that frontal outflows of CO, O3 and PAN can extend to the upper troposphere (6–9 km). Pollution plumes in the global MOZART model are typically diluted and insufficiently lofted to higher altitudes where they can undergo more efficient transport in stronger winds. We use sensitivity simulations that perturb chemical boundary conditions in the CMAQ regional model to estimate that the O3 production over East Asia (EA) driven by PAN decomposition contributes 20% of the spatial averaged total O3 response to European (EU) emission perturbations in March, and occasionally contributes approximately 50% of the total O3 response in subsiding plumes at mountain observatories (at approximately 2 km altitude). The response to decomposing PAN of EU origin is strongly affected by the O3 formation chemical regimes, which vary with the model chemical mechanism and NOx/VOC emissions. Our high-resolution models demonstrate a large spatial variability (by up to a factor of 6) in the response of local O3 to 20% reductions in EU anthropogenic O3 precursor emissions. The response in the highly populated Asian megacities is 40–50% lower in our high-resolution models than the global model, suggesting that the source-receptor relationships inferred from the global coarse-resolution models likely overestimate health impacts associated with intercontinental O3 transport. Our results highlight the important roles of rapid convective transport, orographic forcing, urban photochemistry and heterogeneous boundary layer processes in controlling intercontinental transport; these processes may not be well resolved in the large-scale models.

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Future projections of precipitation characteristics in East Asia simulated by the MRI CGCM2

Advances in Atmospheric Sciences ◽

10.1007/bf02918481 ◽

2005 ◽

Vol 22 (4) ◽

pp. 467-478 ◽

Cited By ~ 41

Author(s):

Akio Kitoh ◽

Masahiro Hosaka ◽

Yukimasa Adachi ◽

Kenji Kamiguchi

Keyword(s):

East Asia ◽

Future Projections ◽

Precipitation Characteristics

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Precipitation Characteristics over East Asia in Early Summer: Effects of the Subtropical Jet and Lower-Tropospheric Convective Instability

Journal of Climate ◽

10.1175/jcli-d-16-0724.1 ◽

2017 ◽

Vol 30 (20) ◽

pp. 8127-8147 ◽

Cited By ~ 10

Author(s):

Chie Yokoyama ◽

Yukari N. Takayabu ◽

Takeshi Horinouchi

Keyword(s):

East Asia ◽

Convective Instability ◽

Large Scale ◽

Early Summer ◽

Shallow Convection ◽

The South ◽

Subtropical Jet ◽

High Dependency ◽

Precipitation Characteristics ◽

Stratiform Precipitation

Abstract A quasi-stationary front, called the baiu front, often appears during the early-summer rainy season in East Asia (baiu in Japan). The present study examines how precipitation characteristics during the baiu season are determined by the large-scale environment, using satellite observation three-dimensional precipitation data. Emphasis is placed on the effect of subtropical jet (STJ) and lower-tropospheric convective instability (LCI). A rainband appears together with a deep moisture convergence to the south of the STJ. Two types of mesoscale rainfall events (REs; contiguous rainfall areas), which are grouped by the stratiform precipitation ratio (SPR; stratiform precipitation over total precipitation), are identified: moderately stratiform REs (SPR of 0%–80%) representing tropical organized precipitation systems and highly stratiform REs (SPR of 80%–100%) representing midlatitude precipitation systems associated with extratropical cyclones. As the STJ becomes strong, rainfall from both types of mesoscale precipitation systems increases, with a distinct eastward extension of a midtropospheric moist region. In contrast, small systems appear regardless of the STJ, with high dependency on the LCI. The results indicate that the STJ plays a role in moistening the midtroposphere owing to ascent associated with secondary circulation to the south of the STJ, producing environments favorable for organized precipitation systems in the southern part of the rainband. The horizontal moisture flux convergence may also contribute to precipitation just along the STJ. On the other hand, the LCI plays a role in generating shallow convection. In high-LCI conditions, deep convection can occur without the aid of mesoscale organization.

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Intercomparison of precipitation datasets for summer precipitation characteristics over East Asia

Climate Dynamics ◽

10.1007/s00382-018-4303-3 ◽

2018 ◽

Vol 52 (5-6) ◽

pp. 3005-3022 ◽

Cited By ~ 2

Author(s):

Kwang-Yul Kim ◽

Jinwon Kim ◽

Kyung-On Boo ◽

Sungbo Shim ◽

Youngmi Kim

Keyword(s):

East Asia ◽

Summer Precipitation ◽

Precipitation Characteristics

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Precipitation characteristics related to atmospheric rivers in East Asia

International Journal of Climatology ◽

10.1002/joc.6843 ◽

2020 ◽

Author(s):

Jinwon Kim ◽

Hyejin Moon ◽

Bin Guan ◽

Duane E. Waliser ◽

Juntae Choi ◽

...

Keyword(s):

East Asia ◽

Atmospheric Rivers ◽

Precipitation Characteristics

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Seasonal Prediction Skills in the CAMS-CSM Climate Forecast System

10.21203/rs.3.rs-202011/v1 ◽

2021 ◽

Author(s):

Bo Liu ◽

Jingzhi SU ◽

Libin MA ◽

Yanli TANG ◽

Xinyao RONG ◽

...

Keyword(s):

East Asia ◽

Air Temperature ◽

Lead Time ◽

Southern Oscillation ◽

Seasonal Prediction ◽

Good Prediction ◽

Climate Forecast ◽

Forecast System ◽

Climate Forecast System ◽

Enso Events

Abstract The seasonal predictability in the CAMS-CSM climate forecast system is evaluated with a set of retrospective forecast experiments during the period of 1981-2019. The CAMS-CSM, which has been registered for the sixth phase of the coupled model intercomparison project (CMIP6), is an atmosphere-ocean-land-sea ice fully coupled general model. The assimilation scheme used in the forecast system is the 3-dimentional nudging, including both the atmospheric and oceanic components. The analyses mainly focus on the seasonal predictable skill of sea surface temperature, 2-m air temperature, and precipitation anomalies. The analyses revealed that the model shows a good prediction skill for the SST anomalies, especially in the tropical Pacific, such as El Niño-Southern Oscillation (ENSO) events. The anomaly correlation coefficient (ACC) score for ENSO can reach 0.75 at 6-month lead time. Furthermore, the extreme warm/cold Indian Ocean dipole (IOD) events are successfully predicted at 3- and even 6-month lead times. The whole ACC of IOD events between the observation and the prediction can reach 0.51 at 2-month lead time. There are reliable seasonal prediction skills for 2-m air temperature anomalies over most of the Northern Hemisphere, where the correlation is mainly above 0.4 at 2-month lead time, especially over the East Asia, North America and South America. However, the seasonal prediction for precipitation still faces a big challenge. The source of precipitation predictability over the East Asia can be partly related to strong ENSO events. Additionally, the anomalous anticyclone over the western North Pacific (WPAC) which connects the ENSO events and the East Asian summer monsoon (EASM) can be well predicted at 6-month lead time.

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Quantifying pollution inflow and outflow over East Asia through coupling regional and global models

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-10-109-2010 ◽

2010 ◽

Vol 10 (1) ◽

pp. 109-152 ◽

Cited By ~ 1

Author(s):

M. Lin ◽

T. Holloway ◽

G. R. Carmichael ◽

A. M. Fiore

Keyword(s):

Boundary Layer ◽

Air Pollution ◽

High Resolution ◽

East Asia ◽

Global Model ◽

Free Troposphere ◽

Regional Models ◽

Global Models ◽

Limited Ability ◽

Surface O3

Abstract. Understanding the exchange processes between the atmospheric boundary layer and the free troposphere is crucial for estimating hemispheric transport of air pollution. Most studies of hemispheric air pollution transport have taken a large-scale perspective: using global chemical transport models and focusing on synoptic-scale export events. These global models have fairly coarse spatial and temporal resolutions, and thus have a limited ability to represent boundary layer processes and urban photochemistry. In support of United Nations Task Force on Hemispheric Transport of Air Pollution (TF HTAP; http://www.htap.org), this study employs two high-resolution atmospheric chemistry models (WRF-Chem and CMAQ; 36×36 km) coupled with a global model (MOZART; 1.9×1.9°) to examine the importance of fine-scale transport and chemistry processes in controlling pollution export and import over the Asian continent. We find that the vertical lifting and outflow of Asian pollution is enhanced in the regional models throughout the study period (March 2001) as contrast to the global model. Episodic outflow of CO, PAN, and O3 to the upper troposphere during cold frontal passages is twice as great in the WRF-Chem model as compared with the MOZART model. The TRACE-P aircraft measurements indicate that the pollution plumes in MOZART are too weak and too low in the altitude, which we attribute to the global model's inability to capture rapid deep convection that develops along the leading edge of the convergence band during frontal events. In contrast to pollution export from Asia, we find little difference in the regional vs. global model transport of European (EU) pollution into surface air over East Asia (EA). Instead, the local surface characteristics – sensitivity – strongly influence surface O3 responses. For instance, the O3 response to 20% decreases in EU emissions imported into our regional model domain is strongest (0.4–0.6 ppbv) over mountainous regions and weakest (0.1–0.3 ppbv) in megacities. The spatial averaged O3 response over EA estimated by our regional models is ~0.1 ppbv lower than global model estimates. Our results suggest that global models tend to underestimate the total budget of Asian pollutants exported to the free troposphere given their limited ability to properly capture vertical convection and lifting. Due to the compensating effects on surface O3 responses over downwind continents, future high-resolution hemispheric model analysis should provide additional insights into how the export and import processes interact, and will help to narrow the uncertainty of intercontinental source-receptor relationships.

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