Scholarlink

<p>Over the past two decades, the summer monsoon rainfall has shown decreasing trends over central India, with the Indo-Gangetic plains showing the most prominent changes. In particular, Bundelkhand, a subregion in the Gangetic plains, has experienced an increase in the frequency and severity of meteorological droughts. We analyse long-term rainfall data revealing two types of droughts in Bundelkhand: Type-1 droughts that coincide with the large-scale Indian monsoon droughts, and Type-2 droughts, which are localised to Bundelkhand. Our focus in this work is on the spatio-temporal evolution of rainfall during the latter category of droughts. We find that there is a distinct dipole structure in rainfall on a subseasonal scale, characterised by increased rainfall in the western India region and a decreased rainfall in east central India during July and August. Furthermore, we analyse the upper- and lower-level atmospheric circulation changes responsible for the subsidence during Type-2 droughts. The rainfall deficit during July and August appear to be associated with a midlatitude stationary Rossby wave which induces an anomalous anticyclone over western North Pacific which drives easterlies over the south China Sea into east central India, that in turn reduce the regional moisture influx. At the same time, the Rossby wave also induces an anomalous cyclonic circulation over northwest India and Pakistan, increasing moisture convergence from the Arabian Sea, leading to enhanced convection over west India. During September, the high-pressure region over Tibetan Plateau migrates further southward into central India, increasing (decreasing) subsidence (convection). Taken together, a combined effect of intraseasonal variations in the midlatitude jet and the circulation over western North Pacific and Tibetan Plateau are responsible for the observed rainfall dipole pattern. At the downstream end, we find that the enhanced soil stress (dryness) owing to reduced rain may have a role to play in the much-reported depletion of groundwater storage in northwest India in general.</p>

错误：搜索内容不能为空，请输入英文关键词
错误：关键词超出字数限制，请精简
高级检索

The subseasonal evolution of Indian rainfall dipole and its local impact in recent decades

  • 期刊论文

  • 发表日期：

    2026年1月13日

查看全文
  • C. Sarat,
  • V. Venugopal,
  • Sekhar Muddu

摘要

Over the past two decades, the summer monsoon rainfall has shown decreasing trends over central India, with the Indo-Gangetic plains showing the most prominent changes. In particular, Bundelkhand, a subregion in the Gangetic plains, has experienced an increase in the frequency and severity of meteorological droughts. We analyse long-term rainfall data revealing two types of droughts in Bundelkhand: Type-1 droughts that coincide with the large-scale Indian monsoon droughts, and Type-2 droughts, which are localised to Bundelkhand. Our focus in this work is on the spatio-temporal evolution of rainfall during the latter category of droughts. We find that there is a distinct dipole structure in rainfall on a subseasonal scale, characterised by increased rainfall in the western India region and a decreased rainfall in east central India during July and August. Furthermore, we analyse the upper- and lower-level atmospheric circulation changes responsible for the subsidence during Type-2 droughts. The rainfall deficit during July and August appear to be associated with a midlatitude stationary Rossby wave which induces an anomalous anticyclone over western North Pacific which drives easterlies over the south China Sea into east central India, that in turn reduce the regional moisture influx. At the same time, the Rossby wave also induces an anomalous cyclonic circulation over northwest India and Pakistan, increasing moisture convergence from the Arabian Sea, leading to enhanced convection over west India. During September, the high-pressure region over Tibetan Plateau migrates further southward into central India, increasing (decreasing) subsidence (convection). Taken together, a combined effect of intraseasonal variations in the midlatitude jet and the circulation over western North Pacific and Tibetan Plateau are responsible for the observed rainfall dipole pattern. At the downstream end, we find that the enhanced soil stress (dryness) owing to reduced rain may have a role to play in the much-reported depletion of groundwater storage in northwest India in general.