Westward Propagating Predecessors of Monsoon Depressions

Saha, Kshudiram; Sanders, Frederick; Shukla, J.

doi:10.1175/1520-0493(1981)109<0330:wppomd>2.0.co;2

Cited by 113 publications

(103 citation statements)

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“…The broad consensus among previous authors has been that high typhoon-activity in NWP decreases ISMR (e.g., Kumar and Krishnan 2005). However, there have been occasions where the remnants of NWP typhoons moved westwards, crossed over to the northern parts of the Bay of Bengal and provided the nucleus for the formation of monsoon depressions (Saha et al 1981). Therefore, the path of NWP storm determines the favourable or adverse impact of storms on the monsoon rainfall of India.…”

Section: Introductionmentioning

confidence: 77%

The Indian drought of 2002—a sub‐seasonal phenomenon?

Bhat

2006

Quart J Royal Meteoro Soc

107

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SUMMARYA major drought occurred over India in the year 2002 with a seasonal rainfall deficit of 21.5%, a result of 56% below normal rainfall in the month of July. The largest anomalies occurred in the western parts of India, when an Indian monsoon field experiment was in progress there. The present study is based primarily on data collected from a research ship that was deployed 100-250 km off the west coast of India for the experiment. Surface and upper air observations made over the eastern Arabian Sea during July 2002 are presented. Sea-surface conditions were favourable for supporting deep convection over the study area. Strong atmospheric inversions around 800 hPa prevented the growth of cumulonimbus during the first half and towards the end of July. A second inversion above the melting level was also prominently present. The strength and persistence of the inversions are unusual. Backtrajectory analysis reveals a major change in the low-level circulation during July 2002 with frequent advection of dry air from over the deserts around the eastern Arabian Sea instead of marine air from across the equator.

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Section: Introductionmentioning

confidence: 77%

The Indian drought of 2002—a sub‐seasonal phenomenon?

Bhat

2006

Quart J Royal Meteoro Soc

107

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“…Thus, this seed cyclonic circulation appears as a residual disturbance of the MJO. Similarly, di¤erent sources reports that westward propagating residual disturbances of the TCs that occur in the western North Pacific transformed into monsoon depressions in the Bay of Bengal (Krishnamurti et al 1977;Saha et al 1981;Chen and Weng 1999). Note that the o¤-equatorial residual component shown in Fig.…”

Section: Could Iso Provide a Seed For Tc Genesis?mentioning

confidence: 99%

Formation of Tropical Cyclones in the Northern Indian Ocean Associated with Two Types of Tropical Intraseasonal Oscillation Modes

Kikuchi

Wang

2010

Journal of the Meteorological Society of Japan

134

102

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Over the northern Indian Ocean (NIO), a substantial number (@ 60%) of tropical cyclones (TCs) form in association with significant intraseasonal oscillation (ISO) events (i.e., Nargis [2008]). In this paper the relationship between TC genesis and ISO in the NIO was studied using 30-year (1997-2008) observations. Because NIO TCs mainly occur in transitional seasons when climatological environmental forcing favors TC genesis, two types of ISO modes, boreal summer intraseasonal oscillation (BSISO) and Madden-Julian oscillation (MJO), which represents boreal winter ISO, were objectively and quantitatively defined, and their connection with TC genesis was examined. It was found that over 70% of ISO-related genesis is associated with the northward propagating BSISO mode and up to 30% with the eastward propagating MJO mode. The BSISO mode primarily a¤ects TC formation in May-June and September-November, while the MJO mode a¤ects TC formation primarily from November-December. Because of their distinct structures and lifecycles, the BSISO and MJO modes a¤ect TC formation di¤erently. For the BSISO mode, TC formation is enhanced during its wet phases overlaying the NIO. For the MJO mode, TC formation is enhanced after the convection passes over the Malay Peninsula and when the Indian Ocean is in a dry phase. The BSISO mode enhances TC genesis by creating favorable environmental forcing for TC genesis, while the MJO mode does not. The most salient feature is that both the ISO modes favor TC genesis by providing a synoptic-scale seeding disturbance at least six days prior to TC formation. The seeding disturbance provided by the BSISO is a cyclonic vorticity anomaly to the north of the equatorial convection/westerly wind burst, whereas the seeding provided by the MJO is a convectively coupled Rossby wave that breaks away from the major body of the MJO convection. The seasonality of the NIO TC genesis, intensity, and prevailing tracks are also explained in terms of the e¤ect of environmental forcing on TC genesis potential, steering flow, and maximum potential intensity. The results imply that monitoring the evolution of the two types of ISO modes, especially the BSISO, may provide a useful medium-range forecast for NIO cyclogenesis.

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“…tropical cyclones, perturbations, and monsoon lows) over the SCS by short wave train anomalies emanating from the western tropical Pacific (Saha et al, 1981;Chen and Weng, 1999;Chen and Yoon, 2000) and (2) an east-west inter-annual seesaw response to the tropical Pacific sea-surface temperature (SST) anomalies, the so-called Walker circulation for the Indo-Pacific inter-annual interaction (Chen and Yoon, 2000). The SASM rainfall over the Indochina Peninsula can be interpreted as a result of northward seasonal rain belt migration, in an east-west oriented precipitation belt called the inter-tropical convergence zone (ITCZ), over the equatorial Indian Ocean in the Boreal summer.…”

Section: Introductionmentioning

confidence: 99%

Relationship between the tropical Pacific and Indian Ocean sea‐surface temperature and monthly precipitation over the central highlands, Vietnam

Nguyen

Uvo

Rosbjerg

2007

Intl Journal of Climatology

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Abstract:The relationship between monthly sea-surface temperature (SST) in the tropical Pacific and the Indian Ocean and monthly precipitation over the Vietnamese central highlands (VCH) has been investigated by means of singular value decomposition. The seasonal variation of SST plays a critical role in the onset of the monsoon season and convective rain band movement in the inter-tropical convergence zone.The relationships between precipitation and SST in both oceans vary significantly through the rainy season. In April, ENSO is strongly correlated with precipitation over the VCH, while the Indian Ocean SST only shows a significant correlation with precipitation in the northern VCH. In May, there is no significant relationship between precipitation and SST in either of the oceans. In June, precipitation over the VCH is negatively correlated with the northern Indian Ocean and the southern Pacific SST. Through July to September, no significant relationships were found between the Indian Ocean SST and precipitation patterns. The equatorial central to the eastern Pacific SST, in turn, is positively correlated with precipitation in a small area from the north to the south of the VCH. In October, precipitation over the VCH is strongly related to ENSO and positively correlated with the equatorial eastern Indian Ocean SST. For November, the north-western Pacific as well as the equatorial eastern Indian Ocean SST is positively and strongly correlated with precipitation over the VCH.Lag-time analyses demonstrate a potential link between the Pacific SST and monthly precipitation patterns through the rainy season from one to three months in advance, and between the Indian Ocean SST and monthly precipitation patterns in October and November from one to two months in advance. The analysed results provide a strong basis for a predictive scheme, but further analysis of skill levels needs to be developed.

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Westward Propagating Predecessors of Monsoon Depressions

Cited by 113 publications

References 0 publications

The Indian drought of 2002—a sub‐seasonal phenomenon?

The Indian drought of 2002—a sub‐seasonal phenomenon?

Formation of Tropical Cyclones in the Northern Indian Ocean Associated with Two Types of Tropical Intraseasonal Oscillation Modes

Relationship between the tropical Pacific and Indian Ocean sea‐surface temperature and monthly precipitation over the central highlands, Vietnam

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