Observed variability of intertropical convergence zone over 1998—2018

Liu, Chunlei; Liao, Xiaoqing; Qiu, Juliao; Yang, Yazhu; Feng, Xiahong; Allan, Richard P.; Cao, Ning; Long, Jingchao; Xu, Jianjun

doi:10.1088/1748-9326/aba033

Cited by 30 publications

(36 citation statements)

References 64 publications

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“…A significant anticorrelation between summertime Sahel precipitation and NAO has been reported by previous studies on a multidecadal scale (Folland et al, 2009;Linderholm et al, 2009) caused by the northward displacement of ITCZ shifting the "rain belt" into the Sahel region in response to a warmer North Atlantic (Sheen et al, 2017;Yuan et al, 2018). By locating the maximum rainfall within 0°-20°N, 30°-0°W following Liu et al, (2020), we found an average https://doi.org/10.5194/egusphere-2022-18 Preprint. Discussion started: 28 February 2022 c Author(s) 2022.…”

Section: Weakened Trans-atlantic Dust Transport Under Droughtssupporting

confidence: 71%

Reduced surface fine dust under droughts over the southeastern United States during summertime: observations and CMIP6 model simulations

Wang

2022

Preprint

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Abstract. Drought is an extreme hydroclimate event that has been shown to cause the increase of surface fine dust near source regions, while the drought-dust relationship in regions predominantly influenced by long-range transported dust such as the southeastern US (SEUS) has received less attention. Using long-term surface fine dust observations, weekly US Drought Monitor (USDM), and monthly Standardized Precipitation-Evapotranspiration Index (SPEI), this study unmasks spatial disparity in drought-dust relationships where the SEUS stands out as being abnormous in that it shows a decrease in surface dust concentrations during drought in contrast to the expected increase in dust found in other contiguous US (CONUS) regions. Surface fine dust was found to decrease by ~0.5 µg/m3 with a unit decrease of SPEI in the SEUS, as opposed to an increase of ~0.15 µg/m3 in the west. The anomalies of elemental ratios, satellite aerosol optical depth (AOD), and dust extinction coefficients suggest that both the emissions and trans-Atlantic transport of African dust are weakened when the SEUS is under droughts. Through the teleconnection patterns of negative North Atlantic Oscillation (NAO), a lower than normal and more northeastward displacement of the Bermuda High (BH) was present during SEUS droughts which resulted in less dust being transported into the SEUS. At the same time, enhanced precipitation in Sahel associated with the northward shift of the Intertropical Convergence Zone (ITCZ) leads to lower dust emissions therein. Of the four selected models participating in the sixth phase of the Coupled Model Intercomparison Project (CMIP6), GISS-E2-1-G was found to perform the best in capturing the drought-dust sensitivity in the SEUS. This study reveals the mechanism of how regional-scale droughts influence aerosol abundance through changing long-range transport of dust.

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Section: Weakened Trans-atlantic Dust Transport Under Droughtssupporting

confidence: 71%

Reduced surface fine dust under droughts over the southeastern United States during summertime: observations and CMIP6 model simulations

Wang

2022

Preprint

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“…The surface energy budget includes downward and upward surface shortwave and longwave radiative fluxes and the latent heat (evapotranspiration) and sensible heat turbulent fluxes. The asymmetric hemispheric distribution of the net downward TOA radiative flux and the net surface flux are closely related to crossequatorial energy transports in both atmosphere and oceans (Loeb et al 2018b;Liu et al 2017), as well as the position of the intertropical convergence zone (ITCZ) (Donohoe et al 2013;Frierson and Hwang 2012;Kang et al 2018;Liu et al 2020). More than 90% of the energy accumulating in the Earth system is taken up by the ocean (Cheng et al 2017).…”

Section: Introductionmentioning

confidence: 99%

Variability in the global energy budget and transports 1985–2017

et al. 2020

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The study of energy flows in the Earth system is essential for understanding current climate change. To understand how energy is accumulating and being distributed within the climate system, an updated reconstruction of energy fluxes at the top of atmosphere, surface and within the atmosphere derived from observations is presented. New satellite and ocean data are combined with an improved methodology to quantify recent variability in meridional and ocean to land heat transports since 1985. A global top of atmosphere net imbalance is found to increase from 0.10 ± 0.61 W m−2 over 1985–1999 to 0.62 ± 0.1 W m−2 over 2000–2016, and the uncertainty of ± 0.61 W m−2 is related to the Argo ocean heat content changes (± 0.1 W m−2) and an additional uncertainty applying prior to 2000 relating to homogeneity adjustments. The net top of atmosphere radiative flux imbalance is dominated by the southern hemisphere (0.36 ± 0.04 PW, about 1.41 ± 0.16 W m−2) with an even larger surface net flux into the southern hemisphere ocean (0.79 ± 0.16 PW, about 3.1 ± 0.6 W m−2) over 2006–2013. In the northern hemisphere the surface net flux is of opposite sign and directed from the ocean toward the atmosphere (0.44 ± 0.16 PW, about 1.7 ± 0.6 W m−2). The sea ice melting and freezing are accounted for in the estimation of surface heat flux into the ocean. The northward oceanic heat transports are inferred from the derived surface fluxes and estimates of ocean heat accumulation. The derived cross-equatorial oceanic heat transport of 0.50 PW is higher than most previous studies, and the derived mean meridional transport of 1.23 PW at 26° N is very close to 1.22 PW from RAPID observation. The surface flux contribution dominates the magnitude of the oceanic transport, but the integrated ocean heat storage controls the interannual variability. Poleward heat transport by the atmosphere at 30° N is found to increase after 2000 (0.17 PW decade−1). The multiannual mean (2006–2013) transport of energy by the atmosphere from ocean to land is estimated as 2.65 PW, and is closely related to the ENSO variability.

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“…From February to May, the result is for all SH ITCZs. There were no SH ITCZs from TRMM datasets in May Generally, there is a strong relationship between the ITCZs position and the intensity, as found by C. Liu et al (2020). Additionally, the ITCZ location is closely associated with the warmest SST (Bain et al, 2011), given the fact that SST annual cycle in the EP is lagging by roughly two months after the solar insolation (Karnauskas, Seager, Kaplan, Kushnir, & Cane, 2009).…”

Section: Itczs Characteristics On Intermonthly Timescalementioning

confidence: 77%

“…Keep in mind that all SH ITCZs occurring in Pacific ITCZs January are S-SITCZ during extreme El Niño events. From the annual cycle, it can be concluded that the NH ITCZs location, width and convection intensity are significantly correlated (p-value <0.05) as stated by C Liu et al (2020),. although the full width peaks one month earlier than other features.…”

mentioning

confidence: 85%

“…It is the expression of the general circulation of the atmosphere, tropical dynamic and thermodynamic coupling and air-sea interaction. More than 30% of the global precipitation is produced within the ITCZ, and its variability greatly affects people living in the tropics (C. Liu et al, 2020). Seasonal variation in the geographical position of the ITCZ is sensitive to local-scale processes such as air-surface interactions (Suzuki, 2011).…”

Section: Introductionmentioning

confidence: 99%

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Objective Identification and Characterisation of Pacific ITCZs using ERA5, GPCP and TRMM

Homoudi

Barfus

Bedbur

et al. 2022

Preprint

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Despite the intense research on the tropical climate and its features, primarily the Intertropical Convergence Zone (ITCZ), fewer studies investigated the state of the ITCZ through an objective and automated algorithm, particularly the double ITCZ. The study combines the European Centre for Medium-Range Weather Forecasts Reanalysis (ERA5) variables, Global Precipitation ClimatologyProject (GPCP), and TRMM (TMPA 3B42 Daily) datasets to objectively and automatically identify the zonally elongated convergence regions (i.e. ITCZs) in the Pacific and provide 42 years climatologies. The algorithm utilises layer- and time-averaged winds in the lower troposphere (pressure levels between 1000 and 850 hPa) to obtain characteristics of ITCZs that include centre latitude, boundaries, widths, and additionally precipitation intensities using GPCP and TRMM datasets. The Northern Hemisphere (NH) ITCZs are found near 8° N, while the Southern Hemisphere (SH) ITCZs are near5° S. On the one hand, these results suggest that the NH ITCZs reach their northernmost centre latitude and the highest centre precipitation intensity in September and their southernmost in March; the full width peaks in August. On the other hand, the SH ITCZs start near the equator and migrate to reach the southernmost latitude in May. During their seasonal migration, the widths fluctuate with decreasing intensities. Generally, as found by previous studies, the NH ITCZs shift equatorward, narrow and intensify. The SH ITZCs shift poleward, narrow, and intensify under global warming.

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Observed variability of intertropical convergence zone over 1998—2018

Cited by 30 publications

References 64 publications

Reduced surface fine dust under droughts over the southeastern United States during summertime: observations and CMIP6 model simulations

Reduced surface fine dust under droughts over the southeastern United States during summertime: observations and CMIP6 model simulations

Variability in the global energy budget and transports 1985–2017

Objective Identification and Characterisation of Pacific ITCZs using ERA5, GPCP and TRMM

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