On the relationship between Arabian Sea warm pool and formation of onset vortex over east-central Arabian Sea

Deepa, R.; Gnanaseelan, C.; Seetaramayya, P.; Nagar, S. G.

doi:10.1007/s00703-010-0095-7

Cited by 6 publications

(3 citation statements)

References 15 publications

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“…The composite sea‐surface temperature (SST) demonstrates a positive mean anomaly (maximum warming of 0.45 °C) in the forward sector of the system for both DD and CS categories (Figure 10a). The positive anomaly of SST in MOVs may be attributed to the presence of the Arabian Sea mini‐warm‐pool region, as outlined in the previous studies (Rao and Sivakumar, 1999; Vinayachandran et al, 2007; Deepa et al ., 2007; 2010; 2012). A cooling of 0.3 °C is noted in the rear sector of the MOV at DD and CS stages (Figure 10a), while the 2 m temperature (T2m) shows an average cooling (negative anomaly) up to −1 °C within a 5° radius (Figure 10b).…”

Section: Resultsmentioning

confidence: 99%

“…Deepa et al (2007) studied the genesis of an MOV that formed in 2001 and found that in addition to the presence of the ASMWPR, a horizontal wind shear along the northern boundary of the LLJ at 850 hPa level is needed. Subsequent studies (Deepa et al, 2010) suggested that a decrease in the vertical wind shear during the monsoon onset period might be one of the necessary conditions for the formation of MOV. Moreover, the absence of a warm SST region can preclude the formation and maintenance of MOV even if the environment is favourable (Deepa et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

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Machine learning and dynamics based error‐index method for the detection of monsoon onset vortex over the Arabian Sea: Climatology and composite structures

Sasanka

Osuri

Niyogi

2023

Quart J Royal Meteoro Soc

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Monsoon onset vortex (MOV) forms over the Arabian Sea near the northern flank of the low-level jet during the monsoon onset over Kerala (MOK). The study concerns the development and evaluation of an algorithm for detecting and tracking MOVs in regional/global analyses. The first step involves preparing the first-guess database of MOV locations based on geopotential height, surface and 850 hPa wind magnitude and circulation from ERA5 reanalysis for 1982-2020. Three different approaches: (a) error-index of MOV, (b)machine-learning (ML), and (c) combination of error-index and ML models, are employed to detect MOV. The error-index method, in which the detected vortex is compared with the idealized vortex, achieves an accuracy of 0.6 with a 0.95 true-positive-rate and 0.55 false-positive-rate. The best ML models can identify the MOVs in the training samples with maximum accuracy of 0.99. However, their accuracy is limited in tracking the MOVs continuously in the global analyses as they are not trained with wind circulation. The combined error-index and ML models could detect all the 27 observed MOVs in the ERA5 reanalysis with 5 false-positives. This approach is tested on IMDAA reanalysis, and the success rate is 0.79 with 6 false-positives. Temporal analyses show that ∼95% of the MOVs occur during −10 to +20 days from MOK. Composite structures indicate that the MOVs exhibit higher sea-surface temperatures (>0.3 • C) in the forward sector with 85% cloud cover in the left-rear sector. Rainfall of 4-5 mm⋅hr −1 is seen in the left sector. Upper-level (700-200 hPa) warm core (>3.5 • C) and lower-level (1000-700 hPa) cold-core (<1 • C) is evident. The composite structures of MOVs are almost similar to that of monsoon depressions with higher asymmetry in the forward-rear sectors. This study may help explore future projections of MOV activity from climate models and its relationship with monsoon rainfall activity.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Machine learning and dynamics based error‐index method for the detection of monsoon onset vortex over the Arabian Sea: Climatology and composite structures

Sasanka

Osuri

Niyogi

2023

Quart J Royal Meteoro Soc

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“…The extent and intensity of warm pool depend on the type of monsoon. Maximum core temperature and wide coverage of warm pool occur during the excess monsoon years compared to normal and deficient monsoon years (Deepa et al, 2010;Neema et al, 2011).…”

Section: Inferences From Trmm Observationsmentioning

confidence: 99%

Aerosol Features during Drought and Normal Monsoon Years: A Study Undertaken with Multi-Platform Measurements over a Tropical Urban Site

Vijaykumar

Devara

Simha

2012

Aerosol Air Qual. Res.

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This paper reports the results of aerosol optical characteristics over a tropical urban station at Pune, India, during drought and normal monsoon years, based on ground-based and satellite observations for the period 2008-2010. Ground-based data from MICROTOPS-II and AERONET, and satellite data products from Moderate Resolution Imaging Spectroradiometer (MODIS) and Ozone Monitoring Instrument (OMI) sensors, were utilized in the study. Detailed analysis of this data revealed that the maximum values of aerosol optical depth (AOD) and minimum values of precipitable water content (PWC) were observed during a drought year (2009) compared to normal monsoon years (2008 and 2010). In order to characterize aerosols further, the Ångström parameters α and β were evaluated. Using the least squares method, α is calculated in the spectral interval of 380-1020 nm, along with the coefficients a 1 and a 2 of the second-order polynomial fitted to the plotted logarithm of AOD versus the logarithm of wavelength. Meteorological parameters, such as temperature and relative humidity, have been measured during the course of the study, as well as the variations in monthly rainfall over the experimental site. The high surface temperatures and low rainfall amounts during the pre-monsoon and monsoon seasons of 2009 lead to an increase in AOD as compared to those in 2008 and 2010. The ground-based observations from MICROTOPS-II reveal good correlation with satellite observations of the MODIS and OMI sensors, and also correlate with the AERONET observations, corroborating the results. Discrimination of aerosol types from radiometric measurements and the tropospheric circulation obtained from the NCEP/NCAR (National Centers for Environmental Prediction/National Center for Atmospheric Research) reanalysis were also discussed, and found to be consistent.

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Triggering effect of an unusual northwestward-moving tropical cyclone over the Bay of Bengal on the extremely early Indian summer monsoon onset

et al. 2022

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On the relationship between Arabian Sea warm pool and formation of onset vortex over east-central Arabian Sea

Cited by 6 publications

References 15 publications

Machine learning and dynamics based error‐index method for the detection of monsoon onset vortex over the Arabian Sea: Climatology and composite structures

Machine learning and dynamics based error‐index method for the detection of monsoon onset vortex over the Arabian Sea: Climatology and composite structures

Aerosol Features during Drought and Normal Monsoon Years: A Study Undertaken with Multi-Platform Measurements over a Tropical Urban Site

Triggering effect of an unusual northwestward-moving tropical cyclone over the Bay of Bengal on the extremely early Indian summer monsoon onset

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