Remote influences on the Indian monsoon low-level jet intraseasonal variations

Swathi, Maratt Satheesan; Izumo, Takeshi; Lengaigne, Matthieu; Vialard, Jérôme; Kumar, M. R. Ramesh

doi:10.1007/s00382-019-05108-1

Cited by 7 publications

(2 citation statements)

References 62 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…An important dynamical feature of ISM is the formation of the strong cross‐equatorial jet at lower levels (850 hPa), which is also known as the Findlater jet (Joseph & Raman, 1966; Findlater, 1969). This low‐level jet (LLJ) is an essential source of moisture for the Indian monsoon (Findlater, 1969; Swathi et al., 2020). All the model simulations are able to capture the mean LLJ reasonably well, but CFSv2‐T126 is simulated as a weak LLJ (Figures 1b–1d), which implies lesser moisture availability to the monsoon circulation.…”

Section: Resultsmentioning

confidence: 99%

“…An important dynamical feature of ISM is the formation of the strong cross-equatorial jet at lower levels (850 hPa), which is also known as the Findlater jet (Joseph & Raman, 1966;Findlater, 1969). This low-level jet (LLJ) is an essential source of moisture for the Indian monsoon (Findlater, 1969;Swathi et al, 2020 robust south-westerly mean flow over the Indian Ocean and the Indian landmass, whereas relatively weaker south-easterlies over the southern Indian Ocean compared to the CFSv2-T126. WRFOML simulated strong south-westerlies over the AS and equatorial Indian Ocean region (Figure 1g) compared to CFSv2-T126 and WRFCTL, which helps to transport more moisture to AS and Central Indian region and thereby reduces the dry bias in WRFOML.…”

Section: Simulation Of Important Climatological Features Of Ismmentioning

confidence: 99%

See 1 more Smart Citation

Reducing Systematic Biases Over the Indian Region in CFS V2 by Dynamical Downscaling

Prasad

Ramu

Rao

et al. 2021

Earth and Space Science

View full text Add to dashboard Cite

The usefulness of dynamical downscaling of seasonal reforecasts of Indian Monsoon is explored to address the seasonal mean biases in the reforecasts. Almost all the current generation global coupled models, including the Climate Forecast System version 2 (CFSv2, T126 ∼110 km), exhibit systematic mean dry bias over the central Indian region during the summer monsoon season. Cold sea surface temperature (SST) biases in the Indian Ocean and a weak monsoon circulation due to a colder tropospheric temperature contribute to this dry bias. Such systematic biases restrict the use of skillful forecasts from these models in climate applications (such as agriculture or hydrology). Dynamical downscaling of seasonal forecasts (∼110 km resolution) using the Weather Research and Forecasting (WRF) model coupled to a simple ocean mixed layer model (OML; WRFOML) at 38 km resolution significantly reduces the majority of the systematic biases reported earlier. The seasonal mean dry bias reduces to 16% in WRFOML as compared to 44% (33%) in the CFSv2‐T126 (WRFCTL) over the Indian land region. Warmer SSTs in the Indian Ocean and a more robust monsoon circulation emanating from a realistic simulation of the tropospheric temperature reduced the systematic biases in WRFOML compared to CFSv2‐T126 and WRFCTL. Additionally, category‐wise rainfall distributions are also improved drastically in the downscaled simulations (WRFOML). Downscaled reforecasts with reduced systematic biases have better suitability for climate applications.

show abstract

Section: Resultsmentioning

confidence: 99%

Section: Simulation Of Important Climatological Features Of Ismmentioning

confidence: 99%

Reducing Systematic Biases Over the Indian Region in CFS V2 by Dynamical Downscaling

Prasad

Ramu

Rao

et al. 2021

Earth and Space Science

View full text Add to dashboard Cite

show abstract

Identification of the Asian summer monsoon anticyclone based on tropical easterly and subtropical westerly jets during active and break phases

Musaid,

Mehta,

Tegtmeier

et al. 2024

Intl Journal of Climatology

View full text Add to dashboard Cite

The Asian summer monsoon anticyclone (ASMA) plays a vital role in the transport and redistribution of the tracers in the upper troposphere and lower stratosphere during transient monsoon conditions. The ASMA can be identified using various diagnostics such as winds and divergence, potential vorticity, the Montgomery stream function or geopotential height. Its representation based on the commonly‐used existing method that takes a climatological range of the geopotential height (GPH) at a given pressure level is not robust and fails in several circumstances. In this study, we propose a new GPH method to define the ASMA for the active and break phases of the monsoon based on the GPH values at the tropical easterly jet (TEJ) and subtropical westerly jet (STJ) locations. The proposed method compares the GPH values at the locations corresponding to the wind speed maxima of TEJ and STJ at 100 hPa with the maximum GPH at 100 hPa and selects the one with the minimum difference to define the ASMA extent. The same procedures were applied to obtain the ASMA extent at 150 hPa. The ASMA extents are obtained using the method proposed here and the existing fixed GPH method for the 30 active and 27 break phases from 2005 to 2023. The fixed GPH method provides a larger ASMA extent for 24 active and 21 break phases, which appears to be an unrealistic estimation compared to the proposed method. Our proposed method identifies the ASMA extent that is larger and centred around the Iranian side during the active phases while it is smaller and centred around the Tibetan side during the break phases. Furthermore, the minimum concentration of ozone (O3), and maximum concentrations of carbon monoxide (CO) and water vapour (H2O) are also found to be centred near the Iranian side during the active phases and on the Tibetan side during the break phases. The tracer concentrations are generally higher for CO, H2O and O3 during the active phase than in the break phase. Tracer concentrations within the ASMA extent using the fixed GPH method are higher for O3 while lesser for CO and H2O when compared to the proposed method.

show abstract

South Asian Monsoon Extremes and Climate Change

Yadav

2022

Extremes in Atmospheric Processes and Phenomenon: Assessment, Impacts and Mitigation

View full text Add to dashboard Cite

Remote influences on the Indian monsoon low-level jet intraseasonal variations

Cited by 7 publications

References 62 publications

Reducing Systematic Biases Over the Indian Region in CFS V2 by Dynamical Downscaling

Reducing Systematic Biases Over the Indian Region in CFS V2 by Dynamical Downscaling

Identification of the Asian summer monsoon anticyclone based on tropical easterly and subtropical westerly jets during active and break phases

South Asian Monsoon Extremes and Climate Change

Contact Info

Product

Resources

About