Harmonious inter-decadal changes of July–August upper tropospheric temperature across the North Atlantic, Eurasian continent, and North Pacific

Zhou, Tianjun; Zhang, Jie

doi:10.1007/s00376-009-9020-8

Cited by 28 publications

(26 citation statements)

References 33 publications

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“…Thus such a poor correlation between the summer APO and the previous winter possibly implies a weaker influence of the previous winter Pacific SST on the boreal summer APO and associated climate anomalies. Moreover, some simulations also showed a weaker forcing of SST anomalies to the APO-like phenomenon (Zhou and Zhang 2009;Zhao et al 2010aZhao et al , 2011b. However, we do not understand the seasonal dependence of the SST-APO relationship.…”

Section: Summary and Discussionmentioning

confidence: 77%

Boreal summer continental monsoon rainfall and hydroclimate anomalies associated with the Asian-Pacific Oscillation

Zhao¹,

Wang

Zhou

2012

Clim Dyn

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With the twentieth century analysis data for atmospheric circulation, precipitation, Palmer drought severity index, and sea surface temperature (SST), we show that the Asian-Pacific Oscillation (APO) during boreal summer is a major mode of the earth climate variation linking to global atmospheric circulation and hydroclimate anomalies, especially the Northern Hemisphere (NH) summer land monsoon. Associated with a positive APO phase are the warm troposphere over the Eurasian land and the relatively cool troposphere over the North Pacific, the North Atlantic, and the Indian Ocean. Such an amplified land-ocean thermal contrast between the Eurasian land and its adjacent oceans signifies a stronger than normal NH summer monsoon, with the strengthened southerly or southwesterly monsoon prevailing over tropical Africa, South Asia, and East Asia. A positive APO implies an enhanced summer monsoon rainfall over all major NH land monsoon regions: West Africa, South Asia, East Asia, and Mexico. Thus, APO is a sensible measure of the NH land monsoon rainfall intensity. Meanwhile, reduced precipitation appears over the arid and semiarid regions of northern Africa, the Middle East, and West Asia, manifesting the monsoon-desert coupling. On the other hand, surrounded by the cool troposphere over the North Pacific and North Atlantic, the extratropical North America has weakened low-level continental low and upper-level ridge, hence a deficient summer rainfall. Corresponding to a high APO index, the African and South Asian monsoon regions are wet and cool, the East Asian monsoon region is wet and hot, and the extratropical North America is dry and hot. Wet and dry climates correspond to wet and dry soil conditions, respectively. The APO is also associated with significant variations of SST in the entire Pacific and the extratropical North Atlantic during boreal summer, which resembles the Interdecadal Pacific Oscillation in SST. Of note is that the Pacific SST anomalies are not present throughout the year, rather, mainly occur in late spring, peak at late summer, and are nearly absent during boreal winter. The season-dependent APO-SST relationship and the origin of the APO remain elusive.

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Section: Summary and Discussionmentioning

confidence: 77%

Boreal summer continental monsoon rainfall and hydroclimate anomalies associated with the Asian-Pacific Oscillation

Zhao¹,

Wang

Zhou

2012

Clim Dyn

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“…However, even if the apparent cooling in the reanalysis data is real, it occurred before 1977 (Figures 9 and 10) [Zhou and Zhang, 2009], and it is centered to the northeast of the TP with a maximum around 300 hPa (Figure 11) [Yu and Zhou, 2007], rather than at the height of the TP (around 700 hPa). Furthermore, a heating change over the TP would have a direct impact on the SASM, yet Figures 10a-b show much weaker trends than those for the EASM (Figures 8 and 9).…”

Section: Appendix B: the Apparent Tropospheric Cooling Over East Asiamentioning

confidence: 99%

“…[53] Many studies [e.g., Yu et al, 2004;Yu and Zhou, 2007;Zhou and Zhang, 2009] have investigated the large cooling over East Asia in the reanalysis data, which peaks around 300 hPa and in April and July-August [Yu and Zhou, 2007] and occurred primarily from the 1950s to the early 1970s [Zhou and Zhang, 2009]. The atmospheric fields from the reanalyses before the modern satellite era (since 1979) are Figure B1.…”

Section: Appendix B: the Apparent Tropospheric Cooling Over East Asiamentioning

confidence: 99%

The relative roles of upper and lower tropospheric thermal contrasts and tropical influences in driving Asian summer monsoons

Dai

Sun³

et al. 2013

JGR Atmospheres

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111

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[1] Summer thermal structure and winds over Asia show a larger land-ocean thermal gradient in the upper than in the lower troposphere, implying a bigger role of the upper troposphere in driving the Asian summer monsoon circulation. Using data from atmospheric re-analyses and model simulations, we show that the land-ocean thermal contrast in the mid-upper (200-500 hPa) troposphere (TCupper) contributes about three times as much as the thermal contrast in the mid-lower (500-850 hPa) troposphere (TClower) in determining both the strength and variations of Asian summer monsoon circulations. Tropical sea surface temperature anomalies associated with the annual cycle, El Niño-Southern Oscillation, decadal changes, and global warming all are accompanied with much larger variations and changes in TCupper than in TClower, partly due to enhanced latent heating aloft from convection. The variations and changes in TCupper and TClower are highly correlated with the strength of the South Asian Summer Monsoon (SASM) and the East Asian Summer Monsoon (EASM) in their respective sectors during the past 50-60 years. In particular, the weakening of the EASM since the 1950s is caused by the weakening mainly in TCupper and secondarily in TClower induced mainly by recent tropical surface warming, although spurious cooling over East Asia seen in reanalysis data may have enhanced this weakening. However, the strength of the SASM and EASM monsoons follows TCupper but decouples with TClower in the global warming case in the 21 st century. The results suggest that the TCupper plays a dominant role and provides an efficient mechanism through which tropical oceans can influence extratropical monsoons.

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“…The APO is actually a local manifestation of the asymmetric zonal change in the tropospheric temperature in the Northern Hemisphere based on the works of Zhou and Zhang [51], and Zhou et al [52]. EASM variability is a consequence of the land-sea thermal contrast between Asia and the adjacent ocean; thus, it is appropriate to investigate the long-term variations of the EASM using the APO over the last millennium.…”

Section: Apomentioning

confidence: 99%

Forced response of atmospheric oscillations during the last millennium simulated by a climate system model

Man

Zhou

2011

Chin. Sci. Bull.

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Variations in global atmospheric oscillations during the last millennium are simulated using the climate system model FGOALS_gl. The model was driven by reconstructions of both natural forcing (solar variability and volcanic aerosol) and anthropogenic forcing (greenhouse gases and sulfate aerosol). The model results are compared against proxy reconstruction data. The reconstructed North Atlantic Oscillation (NAO) was out of phase with the Pacific Decadal Oscillation (PDO) in the last millennium. During the Medieval Warm Period (MWP), the NAO was strong while the PDO was weak. During the Little Ice Age (LIA), the NAO was weak while the PDO was strong. A La Niña-like state prevailed in the MWP, while an El Niño-like state dominated in the LIA. This phenomenon is particularly obvious in the 15th, 17th and 19th centuries. Analysis of the model output indicates that the NAO was generally positive during 1000-1400 AD and negative during 1650-1900 AD. There is a discrepancy between the simulation and reconstruction during 1400-1650 AD. The simulated PDO generally varies in parallel with the reconstruction, which has a negative phase during the MWP and a positive phase during the LIA. The correlation coefficient between the reconstruction and simulation is 0.61, and the correlation is statistically significant at the 1% level. Neither the La Niña-like state of the MWP nor the El Niño-like state of the LIA is reproduced in the model. Both the reconstructed and the simulated Antarctic Oscillations had a negative phase in the early period of the last millennium and a positive phase in the late period of the last millennium. The Asian-Pacific Oscillation was generally strong during the WMP and weak during the LIA, and the correlation coefficient between the simulation and reconstruction is 0.50 for the period 1000 -1985 AD. The analysis suggests that the specified external forcings significantly affected the evolution of atmospheric oscillation during the last millennium. millennial climate, atmospheric oscillation, external forcing, climate system model Citation:Man W M, Zhou T J. Forced response of atmospheric oscillations during the last millennium simulated by a climate system model.

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Harmonious inter-decadal changes of July–August upper tropospheric temperature across the North Atlantic, Eurasian continent, and North Pacific

Cited by 28 publications

References 33 publications

Boreal summer continental monsoon rainfall and hydroclimate anomalies associated with the Asian-Pacific Oscillation

Boreal summer continental monsoon rainfall and hydroclimate anomalies associated with the Asian-Pacific Oscillation

The relative roles of upper and lower tropospheric thermal contrasts and tropical influences in driving Asian summer monsoons

Forced response of atmospheric oscillations during the last millennium simulated by a climate system model

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