Features and interdecadal variability of droughts in the homogeneous rainfall zones over the East Asian monsoon region

Awan, Jehangir Ashraf; Bae, Deg‐Hyo

doi:10.1002/joc.4471

Cited by 7 publications

(10 citation statements)

References 42 publications

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“…The large AOD appears over eastern China, especially over the Sichuan Basin and east-central China, with a maximum exceeding 0.6. The aerosol loading gradually decreases from eastern China through Japan up to the North Pacific along midlatitude westerlies, similarly to the climatological annual mean AOD (Bao et al, 2009). As spring is a transitional season, relatively weak northwesterlies prevail at the low-level troposphere (850 hPa) over northern East Asia, while southern China and the north of mainland South East Asia are mainly controlled by the southwesterly wind, where the AOD is also relatively high.…”

Section: Variation In Spring Aerosolsmentioning

confidence: 66%

“…the regions with significant aerosol changes are different between the findings of Sun et al (2018) and . However, spring sees the highest aerosol optical depth (AOD) over East Asia in the annual cycle, which is related to the dust and anthropogenic emissions (Kim et al, 2007;Bao et al, 2009). Carbonaceous aerosols (CAs) from South Asia (Zhang et al, 2010b) and South East Asia (Lin et al, 2009;Yadav et al, 2017) can be transported to East Asia during this season.…”

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confidence: 99%

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El Niño–Southern Oscillation (ENSO) effect on interannual variability in spring aerosols over East Asia

Zhu

Deng

et al. 2021

Atmos. Chem. Phys.

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Abstract. Effects of the El Niño–Southern Oscillation (ENSO) on the interannual variability in spring aerosols over East Asia are investigated using the Modern Era Retrospective analysis for Research and Applications Version 2 (MERRA-2) reanalysis aerosol data. Results show that the ENSO has a crucial effect on the spring aerosols over mainland South East Asia, southern China, and the ocean south of Japan. The above-normal (below-normal) aerosols are found over these regions during the ensuing spring of El Niño (La Niña). In contrast to the local aerosol diffusion in winter, the ENSO affects East Asian aerosols in the following spring mainly via the modulation of upstream aerosol generation and transport processes. The underlying physical mechanism is that during the ensuing spring of El Niño (La Niña), the dry (wet) air and reduced (enhanced) precipitation are beneficial for the increase (reduction) in biomass burning activities over northern mainland South East Asia, resulting in more (fewer) carbonaceous aerosol emissions. On the other hand, the anomalous anticyclone (cyclone) over the north-western Pacific (WNP) associated with El Niño (La Niña) enhances (weakens) the low-level south-westerly wind from northern mainland South East Asia to southern Japan, which transports more (less) carbonaceous aerosol downstream. Anomalous precipitation plays a role in reducing aerosols over the source region, but its washout effect over the downstream region is limited. The ENSO's impact on the ensuing spring aerosols is mainly attributed to the eastern Pacific ENSO rather than the central Pacific ENSO.

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Section: Variation In Spring Aerosolsmentioning

confidence: 66%

mentioning

confidence: 99%

El Niño–Southern Oscillation (ENSO) effect on interannual variability in spring aerosols over East Asia

Zhu

Deng

et al. 2021

Atmos. Chem. Phys.

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“…The long-term linear trend is removed from each field in advance. Because the ENSO is a significant inter-annual mode, a Fourier analysis is performed IMPACT OF NPSTF ON ENSO e731 to obtain the inter-annual variability via removing the first three waves (Awan and Bae, 2016).…”

Section: Datamentioning

confidence: 99%

“…Normalized time series of the spring NPSTF index and that of the following-winter Niño-3.4 index for the period of1961-2016 in the x coordinate are labelled according to each December.…”

mentioning

confidence: 99%

Impact of the North Pacific subtropical sea surface temperature front on El Niño‐Southern Oscillation

Zhang

Shi

et al. 2018

Intl Journal of Climatology

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The North Pacific subtropical front (NPSTF) of sea surface temperature (SST) is an important subtropical feature in the North Pacific. In this study, we reveal that the inter‐annual variability of the spring NPSTF has a robust correlation with the El Niño‐Southern Oscillation (ENSO) in the following winter over the period of 1961–2016. When there is a strong spring NPSTF, anomalous cyclonic and anticyclonic circulations in the low troposphere occur to its north and south, respectively. The northeasterly wind anomaly associated with the anticyclonic circulation increases the climatological northeasterly wind over the subtropical Northeast Pacific, resulting in SST decrease via the wind–evaporation–SST feedback. The SST and wind perturbations propagate southwards from the subtropical to the eastern central equatorial Pacific in summer and grow via the Bjerknes feedback from summer to winter, eventually leading to a La Niña event in winter. A strong spring NPSTF induces an anomalous anticyclonic circulation to its south through both transient eddy activity and atmospheric heat source anomaly. The enhanced air temperature gradient due to a strong NPSTF increases the atmospheric baroclinicity, favouring an enhanced transient eddy activity over the NPSTF and to the north. The enhanced transient eddy activity triggers a significant negative height anomaly to the north via high‐frequency transient eddy feedback forcing, which is conductive to an anticyclonic circulation over the subtropical North Pacific through the downstream effect of Rossby waves. On the other hand, the convergence and increased atmospheric baroclinicity related to the strong NPSTF act to enhance precipitation over the NPSTF and to the north, corresponding to the increased atmospheric heat source, which can also excite an anomalous anticyclonic circulation over the subtropical North Pacific.

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“…APHRODITE dataset is freely available for the period of 1951–2007. We used the data from 1977 to 2007 considering a density of rain gauge stations used in the dataset preparation, which was significantly high in this period compared to the earlier period (Awan and Bae, ).…”

Section: Study Area and Datasetsmentioning

confidence: 99%

Drought prediction over the East Asian monsoon region using the adaptive neuro‐fuzzy inference system and the global sea surface temperature anomalies

Awan

Bae

2016

Intl Journal of Climatology

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Prediction of droughts has a great importance in the management and planning of water resources. This study developed an adaptive neuro-fuzzy inference system (ANFIS) based model for prediction of droughts, and evaluated its applicability in the seven homogeneous rainfall zones of the East Asian monsoon region (20 ∘ -50 ∘ N, 103 ∘ -149 ∘ E). Standardized Precipitation Index (SPI) was used to characterize the drought events. SPI series were computed for each zone using a 30-year (1978-2007) gridded rainfall dataset (0.5 ∘ grid resolution) at the corresponding grid points. The influence of sea surface temperature anomalies (SSTA) on droughts was assessed using a lagged-correlation between global gridded SSTA (0.2 ∘ grid resolution) and the SPI of each zone. SSTA were used as a potential predictor variable based on the premise that the land-sea thermal contrast is a major driver of the monsoon. The model was trained and validated using a 25-year (1978-2002) dataset, with different configurations to obtain the optimum model structure and a set of suitable predictors. The performance of the model was demonstrated by comparing the model simulated results with the observed drought index and drought categories using a 5-year (2003-2007) independent checking dataset. The model predicted the drought categories accurately for 50 to 70% cases in checking period for different zones. The results showed the viability of the proposed model for drought prediction with substantial enhancement in accuracy when past SSTA were used as a predictor compared with the use of only past SPI data. Figure 1. The homogeneous rainfall zones over the East Asian monsoon region .

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Features and interdecadal variability of droughts in the homogeneous rainfall zones over the East Asian monsoon region

Cited by 7 publications

References 42 publications

El Niño–Southern Oscillation (ENSO) effect on interannual variability in spring aerosols over East Asia

El Niño–Southern Oscillation (ENSO) effect on interannual variability in spring aerosols over East Asia

Impact of the North Pacific subtropical sea surface temperature front on El Niño‐Southern Oscillation

Drought prediction over the East Asian monsoon region using the adaptive neuro‐fuzzy inference system and the global sea surface temperature anomalies

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