Validation of δ18O as a proxy for past monsoon rain by multi-GCM simulations

Midhun, M.; Ramesh, R.

doi:10.1007/s00382-015-2652-8

Cited by 45 publications

(53 citation statements)

References 41 publications

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“…The model is forced with observed sea surface temperatures, while the large‐scale wind fields and temperature are constrained with the observations (NCEP reanalysis II; Kanamitsu et al, ) using the spectral nudging technique (Yoshimura & Kanamitsu, ). The nudging technique helps in simulating a more realistic atmospheric circulation and thereby improves the ISM simulation (Midhun & Ramesh, ). Reference is made to Yoshimura et al () for further details about IsoGSM and model setup.…”

Section: Methodsmentioning

confidence: 99%

“…In the limited observations over the ISM region, the amount effect shows a large spatial variation (Breitenbach et al, ; Laskar et al, ; Lekshmy et al, , ; Midhun & Ramesh, ; Yadava et al, ). From the three long‐term stations in India (New Delhi, Mumbai, and Kozhikode) only New Delhi shows a significant amount effect during ISM on the monthly timescale.…”

Section: Introductionmentioning

confidence: 99%

“…Among these, only New Delhi shows a significant amount effect during ISM on a monthly timescale. Simulations of ISM from multiple isotope‐enabled General Circulation Models (GCMs) also show a noisy pattern in the simulated amount effect over the continent but a strong, consistent amount effect over the ocean (Midhun & Ramesh, ). This suggests that the controlling factors of the rainfall‐ 18 O relation over ocean and continent are quite different.…”

Section: Introductionmentioning

confidence: 99%

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The Effect of Monsoon Circulation on the Stable Isotopic Composition of Rainfall

et al. 2018

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Understanding the factors that control the variability of oxygen isotopic ratios (δ18O) of Indian Summer Monsoon (ISM) rainfall (δ18Op) is of vital importance for the interpretation of δ18Op derived from climate proxies (e.g., speleothem and tree ring cellulose) of this region. Here we demonstrate the importance of moisture transport pathways on spatiotemporal variations of ISM δ18Op using a new set of daily observations from central and northern India and previously reported data aided by simulations from an isotope‐enabled General Circulation Model. 18O‐depleted rain events are characterized by a higher number of air parcel back trajectories through the Bay of Bengal branch of moisture transport, while those through the Arabian Sea branch are associated with 18O enriched rain events. This effect is observed on intraseasonal to interannual timescales in the long‐term observations at New Delhi as well. Thus, the shift in moisture transport regimes must be considered when interpreting δ 18Op from climate proxies of the ISM region.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The Effect of Monsoon Circulation on the Stable Isotopic Composition of Rainfall

et al. 2018

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“…Model runs of isotope general circulation models available for Indian continent (e.g. Hoffman and Heimann, 1997;Midhun and Ramesh, 2016) suggest that the models tend to underestimate the amplitude of seasonal changes of δ 18 O, particularly in northern India. A more comprehensive isotope modelling of monsoon circulation would be needed to quantify the above-outlined mechanisms of moisture recycling and their impact on the measured stable isotope composition of precipitation in the region.…”

Section: Evolution Of δ 18 O During Ism Periodmentioning

confidence: 99%

Isotopic composition of daily precipitation along the southern foothills of the Himalayas: impact of marine and continental sources of atmospheric moisture

et al. 2018

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Abstract. The flow of the Himalayan rivers, a key source of fresh water for more than a billion people primarily depends upon the strength, behaviour and duration of the Indian summer monsoon (ISM) and the western disturbances (WD), two contrasting circulation regimes of the regional atmosphere. An analysis of the 2 H and 18 O isotope composition of daily precipitation collected along the southern foothills of the Himalayas, combined with extensive backward trajectory modelling, was used to gain deeper insight into the mechanisms controlling the isotopic composition of precipitation and the origin of atmospheric moisture and precipitation during ISM and WD periods. Daily precipitation samples were collected during the period from September 2008 to December 2011 at six stations, extending from Srinagar in the west (Kashmir state) to Dibrugarh in the east (Assam state). In total, 548 daily precipitation samples were collected and analysed for their stable isotope composition. It is suggested that the gradual reduction in the 2 H and 18 O content of precipitation in the study region, progressing from δ 18 O values close to zero down to ca. −10 ‰ in the course of ISM evolution, stems from regional, large-scale recycling of moisture-driven monsoonal circulation. Superimposed on this general trend are short-term fluctuations of the isotopic composition of rainfall, which might have stem from local effects such as enhanced convective activity and the associated higher degree of rainout of moist air masses (local amount effect), the partial evaporation of raindrops, or the impact of isotopically heavy moisture generated in evapotranspiration processes taking place in the vicinity of rainfall sampling sites. Seasonal footprint maps constructed for three stations representing the western, central and eastern portions of the Himalayan region indicate that the influence of monsoonal circulation reaches the western edges of the Himalayan region. While the characteristic imprint of monsoonal air masses (increase of monthly rainfall amount) can be completely absent in the western Himalayas, the onset of the ISM period in this region is still clearly visible in the isotopic composition of daily precipitation. A characteristic feature of daily precipitation collected during the WD period is the gradual increase of 2 H and 18 O content, reaching positive δ 2 H and δ 18 O values towards the end of the period. This trend can be explained by the growing importance of moisture of continental origin as a source of daily precipitation. High deuterium-excess (d-excess) values of daily rainfall recorded at the monitoring stations (38 cases in total, range from 20.6 to 44.0 ‰) are attributed to moisture of continental origin released into the atmosphere during the evaporation of surface water bodies and/or soil water evaporation.

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“…A number of studies with isotope-enabled general circulation models (GCMs) also suggest a significant inverse relationship between ISM upstream summer (June to September) rainfall amount and δ 18 Op variations over the Indian Subcontinent (e.g., Vuille et al, 2005;Pausata et 155 al., 2011;Berkelhammer et al, 2012;Sinha et al, 2015;Midhun and Ramesh, 2016). As such, the low and high δ…”

Section: Proxy Interpretationmentioning

confidence: 99%

Timing and Structure of the 4.2 ka BP Event in the Indian Summer Monsoon Domain from an Annually-Resolved Speleothem Record from Northeast India

Kathayat

Cheng

Sinha

et al. 2018

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Validation of δ18O as a proxy for past monsoon rain by multi-GCM simulations

Cited by 45 publications

References 41 publications

The Effect of Monsoon Circulation on the Stable Isotopic Composition of Rainfall

The Effect of Monsoon Circulation on the Stable Isotopic Composition of Rainfall

Isotopic composition of daily precipitation along the southern foothills of the Himalayas: impact of marine and continental sources of atmospheric moisture

Timing and Structure of the 4.2 ka BP Event in the Indian Summer Monsoon Domain from an Annually-Resolved Speleothem Record from Northeast India

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