Structural Transformation of the Monsoon Low Level Jetstream on its Passage over the South Asian Region
Abstract
One of the important semi-permanent components of the Indian Summer monsoon is the Low Level jet stream (LLJ) seen around 1.5 km altitude. The variability of the strength of LLJ is directly related to the monsoon condition over the south Asian region. The LLJ had its origin in the easterly trade winds of the South Indian Ocean (SIO). It crosses the equator in a narrow belt close to the east African coast. It further turns anti-cyclonically over the Arabian Sea near the Somali coast and passed through peninsular India and the Bay of Bengal. It carries the moisture generated by the winds over the south Indian Ocean and the Arabian Sea to the monsoon rainfall over south Asia.
The study aims to know about the structural transformation of the LLJ at various locations over the summer monsoon region. The cross-sectional structure of LLJ along its path over the South Indian Ocean (SIO), cross-equatorial path, Arabian Sea, Indian land area and Bay of Bengal has been investigated by analyzing the vertical cross-section perpendicular to the direction of flow. The study reveals that the core speed of the wind varies both spatially and temporally. The maximum wind speed of LLJ is observed over Arabian Sea, of about 24 ms-1 at 900 hPa. The core height of the LLJ varies depending on the underlying topography of the location. The maximum speed of LLJ is situated at lower height (925 hPa) over Indian Ocean region, whereas the core height rise around 850 hPa over the continental region due to the convective forcing and lower boundary effect. The changes noted in the monsoon low level jet in deficient monsoon years is attributed to the increased number of break in rainfall days observed in the recent decades. The outcome of the study is expected to provide some interesting information of the nature of the spatial as well as the temporal variability of the monsoon low level Jetstream over the south Asian region.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.A53M2681R
- Keywords:
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- 3305 Climate change and variability;
- ATMOSPHERIC PROCESSESDE: 3319 General circulation;
- ATMOSPHERIC PROCESSESDE: 3337 Global climate models;
- ATMOSPHERIC PROCESSESDE: 3373 Tropical dynamics;
- ATMOSPHERIC PROCESSES