Indian summer monsoon influence on the climate in the North Atlantic–European region

AbstractThe Asian monsoon is an important component of the global climate system. Seasonal variations in wind, rainfall, and temperature associated with the Asian monsoon systems affect a vast expanse of tropical and subtropical Asia. Speleothem-derived summer monsoon variation in East Asia was previously found to be closely associated with millennial-scale change in temperature in the North Atlantic region between 75 and 10 ka. New evidence recovered from East Asia, however, suggests that the teleconnection between summer monsoon in East Asia and temperature change in the North Atlantic region may have significantly reduced during 120 to ~ 110 ka, a period directly after the full last interglaciation and corresponding roughly to marine oxygen isotope stage 5d. This reduction may be due to the low ice volume in the North Hemisphere at that time, which makes the millennial-scale change in temperature in the North Atlantic region less effective in influencing the Asian summer monsoon. This is important for investigating the mechanisms controlling the Asian summer monsoon and the paleoclimatic teleconnection between East Asia and the North Atlantic region, and for predicting monsoon-associated precipitation in East Asia under a global-warming trend.

Download Full-text

Very low zonally asymmetric ozone values in March 1997 above the North Atlantic-European region, induced by dynamic processes

Annales Geophysicae ◽

10.1007/s00585-999-0933-4 ◽

1999 ◽

Vol 17 (7) ◽

pp. 933-940 ◽

Cited By ~ 5

Author(s):

G. Entzian ◽

D. Peters

Keyword(s):

North Atlantic ◽

Total Ozone ◽

Meteorological Parameters ◽

Middle Atmosphere ◽

European Region ◽

Dynamic Processes ◽

Decadal Change ◽

The North ◽

Pattern Correlation ◽

The North Atlantic

Abstract. The total ozone distribution in March 1997 showed very low values in the North Atlantic-European region, even lower than in the years before. A spatial pattern correlation between the zonally asymmetric part of total ozone and that of the 300 hPa surface geopotential of the Northern Hemisphere was applied to examine the spatial structure of the low ozone values and its dynamic dependence. A trend analysis in the North Atlantic-European region was carried out to determine to what extent the low March 1997 ozone values are related to the decadal change of meteorological parameters in the lower stratosphere, observed since the 1980s, in comparison to the interannual variability. The conclusion is that the very low ozone values above the North Atlantic-European region in March 1997 were mainly induced by dynamic processes, namely their decadal change as well as their interannual variability.Key words. Meteorology and atmospheric dynamics (climatology; middle atmosphere dynamics)

Download Full-text

Recent trends in summer atmospheric circulation in the North Atlantic/European region: is there a role for anthropogenic aerosols?

Journal of Climate ◽

10.1175/jcli-d-20-0665.1 ◽

2021 ◽

pp. 1-49

Author(s):

Buwen Dong ◽

Rowan T. Sutton

Keyword(s):

Atmospheric Circulation ◽

North Atlantic ◽

General Circulation ◽

European Region ◽

Northern Europe ◽

Anthropogenic Aerosols ◽

The North ◽

The North Atlantic ◽

The Mediterranean ◽

Fast Responses

AbstractThe variability of the westerly jet stream and storm track is crucial for summer weather and climate in the North Atlantic/European region. Observations for recent decades show notable trends in the summer jet from 1970s to 2010s, characterized by an equatorward migration over the North Atlantic accompanied by a poleward migration and weakening of the Mediterranean jet over Europe. These changes in atmospheric circulation were associated with more cyclonic storms traveling across the UK into northern Europe, and fewer over the Mediterranean, leading to wet summers in northern Europe and dry summers in southern Europe.In this study we investigate the potential drivers and processes that may have been responsible for the observed changes in summer atmospheric circulation, with a particular focus on the role of anthropogenic aerosols (AA). We conduct attribution experiments with an atmospheric general circulation model (AGCM) forced with observed changes in sea surface temperatures/sea ice extent (SST/SIE), greenhouse gas concentrations and AA precursor emissions. Comparison between the model results and observations strongly suggests that fast responses to AA changes were likely the primary driver of the observed poleward migration and weakening of the Mediterranean jet, with changes in SST/SIE playing a secondary role. The simulated response shows good agreement with the observed changes in both magnitude and vertical structure, which suggests that common mechanisms - involving aerosol-radiation and aerosol-cloud interactions - are responsible. By contrast, changes in the North Atlantic jet are influenced in the model experiments by changes in both Atlantic SST/SIE (which may themselves have been influenced by changes in AA) and fast responses to AA. In this case, however, there are significant differences between the model response and the observed changes; we argue these differences may be explained by biases in the model climatology.

Download Full-text

A southern and northern control on speleothem-based Asian summer monsoon variability during MIS 4

Quaternary Research ◽

10.1017/qua.2019.36 ◽

2019 ◽

Vol 92 (3) ◽

pp. 738-753

Author(s):

Dianbing Liu ◽

Shushuang Liu ◽

Yifan Fang

Keyword(s):

Summer Monsoon ◽

North Atlantic ◽

Southern China ◽

Asian Summer Monsoon ◽

Phase Correlation ◽

The North ◽

Asian Summer ◽

The North Atlantic ◽

Freshwater Inputs

AbstractA 20-year-resolution speleothem δ18O record from southern China reveals a detailed Asian summer monsoon (ASM) history between 73.6 and 62.3 ka. ASM changes during Interstadial 19 and late MIS 4 matched Greenland temperature variations but were antiphased with Antarctic temperatures. However, long-term strengthening of the ASM in early MIS 4 agrees well with the gradual Antarctic warming, when Greenland remained in a stable cold state. More specifically, the ASM was less variable during peak interstadials in contrast to striking instabilities during stadials. These observations suggest that the factors dominating ASM variability change through time. During early MIS 4, negligible freshwater perturbations occurred in the North Atlantic, and sea-surface temperatures in the low- to midlatitude Pacific Ocean reached the modern level. Thus, an expansion of the Intertropical Convergence Zone (ITCZ) was likely important for the long-term ASM rise. In late MIS 4, the antiphase correlation between ASM and Antarctic temperature could be attributed to freshwater inputs into the North Atlantic and a southerly positioned ITCZ. Consequently, meridional ITCZ shifts, although within a limited latitudinal band, would result in an antiphase relationship between interhemispheric climate changes. Otherwise, an in-phase correlation could be expected if the centroid of ITCZ is stable along the equator.

Download Full-text