Variability and Predictability of the Northeast India Summer Monsoon Season Rainfall (Neir)

Sharma, Devabrat; Das, Suparna; Goswami, B. N.

doi:10.2139/ssrn.4067274

Cited by 5 publications

(6 citation statements)

References 39 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We note that TRUE cases exhibit a barotropic convergence over NE India (Figure 4), consistent with what was reported by Sharma et al. (2023). The black geopotential height contours in Figure 4 depict topography (500 m contour emphasized in thick magenta contour).…”

Section: Driver Of Nepremon and Causalitysupporting

confidence: 92%

“…Nevertheless, the consistency of our results with the results of Sharma et al. (2023) is intriguing. We also performed some additional analysis, comparing excess and deficit composites of NE premon to check the robustness of our analysis (Robustness analysis in Supporting Information ).…”

Section: Driver Of Nepremon and Causalitysupporting

confidence: 89%

“…Sharma et al. (2023) found that May rainfall over NE comes from the interaction of the large‐scale circulation with the local orography. The extra‐tropical low‐frequency waves drive a barotropic convergence interacting with the local orography.…”

Section: Driver Of Nepremon and Causalitymentioning

confidence: 99%

See 2 more Smart Citations

A Pre‐Monsoon Signal of False Alarms of Indian Monsoon Droughts

Goswami

2024

Geophysical Research Letters

View full text Add to dashboard Cite

Current knowledge suggests a drought Indian monsoon (perhaps a severe one) when the El Nino Southern Oscillation and Pacific Decadal Oscillation each exhibit positive phases (a joint positive phase). For the monsoons, which are exceptions in this regard, we found northeast India often gets excess pre‐monsoon rainfall. Further investigation reveals that this excess pre‐monsoon rainfall is produced by the interaction of the large‐scale circulation associated with the joint phase with the mountains in northeast India. We posit that a warmer troposphere, a consequence of excess rainfall over northeast India, drives a stronger monsoon circulation and enhances monsoon rainfall over central India. Hence, we argue that pre‐monsoon rainfall over northeast India can be used for seasonal monsoon rainfall prediction over central India. Most importantly, its predictive value is at its peak when the Pacific Ocean exhibits a joint positive phase and the threat of extreme drought monsoon looms over India.

show abstract

Section: Driver Of Nepremon and Causalitysupporting

confidence: 92%

Section: Driver Of Nepremon and Causalitysupporting

confidence: 89%

See 1 more Smart Citation

A Pre‐Monsoon Signal of False Alarms of Indian Monsoon Droughts

Goswami

2024

Geophysical Research Letters

View full text Add to dashboard Cite

show abstract

“…The conventional wisdom has been that the May rainfall is "pre-monsoon" and the India meteorological Department (IMD) defines "Onset" of monsoon over the NEI by about 3 rd June 7 . However, a recent study using monthly data 8 argue that the May rainfall is indeed summer monsoon rainfall and inclusion of May rainfall in the monsoon seasonal rainfall significantly influences the variability and predictability of the NEI seasonal (MJJAS) rainfall. On a broader context, it is important to recognize the eastwest asymmetry of the length of the Indian monsoon rainy season (LRS) as the climate change may impact it differently over the NEI compared to that over the CI and NWI.…”

Section: Introductionmentioning

confidence: 99%

“…based on rainfall averaged over a number of stations (large-scale nature)4 , later definitions either explicitly or implicitly include parameters representing the convectively coupled nature of the phenomenon3,[5][6][7][8][9] .While there is a fair degree of agreement on the principle of defining the MoK, there is little or no agreement in the definition of 'progress' or 'local onset' north of Kerala, whether over the Andaman and Nicobar Island, NEI or interior CI6,[10][11][12] . The 'local onset' or 'local withdrawal', by necessity is based only on some traits of local rainfall6,[10][11][12] .…”

mentioning

confidence: 99%

Present and Future of the South Asian Summer Monsoon’s Rainy Season over Northeast India

Goswami

saha

Mahanta

2023

Preprint

View full text Add to dashboard Cite

An iconic aspect of the Indian Summer Monsoon Rainfall (ISMR), a rainy season that lasts longer than June to September over Northeast India (NEI) and considerably shorter over Northwest India, is expected to be significantly altered by climate change. The lack of a physically based objective definition of the monsoon rainy season over the NEI introduces significant uncertainty in impact assessment, variability, and predictability studies of ISMR. Here, we objectively define the ‘Length of the Rainy Season’ (LRS) for NEI and show that the El Nino and Southern Oscillation is a primary drivers of LRS over NEI. In contrast to a significant decreasing trend of LRS and LRS-rainfall during the historical period over NEI, the projected LRS under SSP5-8.5 continues to decrease while the LRS rainfall acquires a significant increasing trend. Implications of the findings on variability and predictability of NEI-rainfall and in the context of large-scale ISMR are discussed.

show abstract

Dynamics of May ‘onset’ of Indian summer monsoon over Northeast India

Das,

Goswami,

Mahanta

et al. 2024

Quart J Royal Meteoro Soc

View full text Add to dashboard Cite

Acknowledging the prolonged duration of the rainy season in Northeast India (NEI) compared to Central India, the official onset of the Indian summer monsoon over NEI is traditionally marked around 5 June, with May rainfall categorized as ‘pre‐monsoon’. However, our study reveals that May rainfall in NEI occurs in active/break spells driven by persistent synoptic‐scale systems, contributing to a significant monsoon heat source during this period. Through an objective analysis, we determine that the climatological ‘onset’ in NEI actually occurs around 18 May, with withdrawal around 14 October, resulting in an extended rainy season of approximately 150 days. The enigma of the May onset, while the Intertropical Convergence Zone remains proximate to the equator, is addressed by identifying a conducive climate in May. This climate is characterized by low‐level cyclonic vorticity over the region, influenced by the interannual strengthening (weakening) by the Atlantic Niño (El Niño). The introduction of potential vorticity from extratropical transient Rossby waves in May significantly amplifies low‐level cyclonic vorticity by 3–4 times, acting as a catalyst for the monsoon onset in NEI. Furthermore, a 5–6 times intensification of northward moisture transport from the Bay of Bengal sustains the monsoon heat source post onset. The May onset is made feasible by the uplifting of low‐level cyclonic winds, facilitated by the horseshoe‐shaped orography around the Brahmaputra valley. This process is complemented by an increased local moisture content resulting from evapotranspiration. Our findings challenge conventional notions by demonstrating that a component of Indian summer monsoon rainfall in NEI is not directly related to the Intertropical Convergence Zone. This challenges the fundamental definition of the South Asian Monsoon and calls for a reassessment of the prevalent belief that the Indian monsoon season is confined to June–September in NEI.

show abstract

Variability and Predictability of the Northeast India Summer Monsoon Season Rainfall (Neir)

Cited by 5 publications

References 39 publications

A Pre‐Monsoon Signal of False Alarms of Indian Monsoon Droughts

A Pre‐Monsoon Signal of False Alarms of Indian Monsoon Droughts

Present and Future of the South Asian Summer Monsoon’s Rainy Season over Northeast India

Dynamics of May ‘onset’ of Indian summer monsoon over Northeast India

Contact Info

Product

Resources

About