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An investigation of the onsets of the 1999 and 2000 monsoons in central Nepal

Publication ,  Journal Article
Lang, TJ; Barros, AP
Published in: Monthly Weather Review
January 1, 2002

The Marsyandi River basin in the central Nepalese Himalayas is a topographically complex region, with strong spatial gradients of precipitation over various timescales. A meteorological network consisting of 20 stations was installed at a variety of elevations (528-4435 m) in this region, and measurements of rainfall were made during the 1999 and 2000 summer monsoons. The onsets of the 1999 and 2000 monsoons in central Nepal were examined at different spatial scales by using a combination of rain gauge. Meteosat-5, Tropical Rainfall Measuring Mission (TRMM), ECMWF analysis, and Indian radiosonde data. At the network, the onsets manifested themselves as multiday rain events, which included a mixture of stratiform and convective precipitation. Moist and unstable upslope flow was associated with the occurrence of heavy rainfall. During each onset, 2-day rainfall reached as high as 462 mm, corresponding to 10%-20% of the monsoon rainfall. Differences among rain gauges were up to a factor of 8, reflecting the role of small-scale terrain features in modulating rainfall amounts. At the larger scale, the onsets were associated with monsoon depressions from the Bay of Bengal that moved close enough to the Himalayas to cause the observed upslope flow from the winds on their eastern flank. During the 1999 onset, convection in this eastern flank collided with the mountains in the vicinity of the network. In 2000 no major collision occurred, and 33%-50% less rain than 1999 fell. Analysis of observations for a 5-yr period (1997-2001) suggests that the interannual variability of the monsoon onset along the Himalayan range is linked to the trajectories and strength of these depressions.

Duke Scholars

Published In

Monthly Weather Review

DOI

ISSN

0027-0644

Publication Date

January 1, 2002

Volume

130

Issue

5

Start / End Page

1299 / 1316

Related Subject Headings

  • Meteorology & Atmospheric Sciences
  • 3701 Atmospheric sciences
  • 0401 Atmospheric Sciences
  • 0102 Applied Mathematics
 

Citation

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ICMJE
MLA
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Lang, T. J., & Barros, A. P. (2002). An investigation of the onsets of the 1999 and 2000 monsoons in central Nepal. Monthly Weather Review, 130(5), 1299–1316. https://doi.org/10.1175/1520-0493(2002)130<1299:AIOTOO>2.0.CO;2
Lang, T. J., and A. P. Barros. “An investigation of the onsets of the 1999 and 2000 monsoons in central Nepal.” Monthly Weather Review 130, no. 5 (January 1, 2002): 1299–1316. https://doi.org/10.1175/1520-0493(2002)130<1299:AIOTOO>2.0.CO;2.
Lang TJ, Barros AP. An investigation of the onsets of the 1999 and 2000 monsoons in central Nepal. Monthly Weather Review. 2002 Jan 1;130(5):1299–316.
Lang, T. J., and A. P. Barros. “An investigation of the onsets of the 1999 and 2000 monsoons in central Nepal.” Monthly Weather Review, vol. 130, no. 5, Jan. 2002, pp. 1299–316. Scopus, doi:10.1175/1520-0493(2002)130<1299:AIOTOO>2.0.CO;2.
Lang TJ, Barros AP. An investigation of the onsets of the 1999 and 2000 monsoons in central Nepal. Monthly Weather Review. 2002 Jan 1;130(5):1299–1316.

Published In

Monthly Weather Review

DOI

ISSN

0027-0644

Publication Date

January 1, 2002

Volume

130

Issue

5

Start / End Page

1299 / 1316

Related Subject Headings

  • Meteorology & Atmospheric Sciences
  • 3701 Atmospheric sciences
  • 0401 Atmospheric Sciences
  • 0102 Applied Mathematics