The atmospheric branch of the hydrological cycle over the Indus, Ganges, and Brahmaputra river basins
The atmospheric branch of the hydrological cycle over the Indus, Ganges, and Brahmaputra river basins (IRB, GRB, and BRB respectively) in the South Asian region was investigated. The 3-dimensional model FLEXPART v9.0 was utilized. An important advantage of this model is that it permits the compu...
Main Authors: | , , , , |
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Format: | Article |
Language: | English |
Published: |
Copernicus Publications
2017-12-01
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Series: | Hydrology and Earth System Sciences |
Online Access: | https://www.hydrol-earth-syst-sci.net/21/6379/2017/hess-21-6379-2017.pdf |
Summary: | The atmospheric branch of the hydrological cycle over the Indus,
Ganges, and Brahmaputra river basins (IRB, GRB, and BRB respectively) in the
South Asian region was investigated. The 3-dimensional model FLEXPART v9.0
was utilized. An important advantage of this model is that it permits the
computation of the freshwater budget on air parcel trajectories both backward and forward
in time from 0.1 to 1000 hPa in the atmospheric vertical column.
The analysis was conducted for the westerly precipitation regime (WPR)
(November–April) and the monsoonal precipitation regime (MPR) (May–October)
in the period from 1981 to 2015. The main terrestrial and oceanic climatological
moisture sources for the IRB, GRB, and BRB and their contribution to
precipitation over the basins were identified. For the three basins, the most
important moisture sources for precipitation are (i) in the continental
regions, the land masses to the west of the basins (in this case called western Asia), the Indian region (IR), and the basin itself, and (ii) from the ocean,
the utmost sources being the Indian Ocean (IO) and the Bay of Bengal (BB), and
it is remarkable that despite the amount of moisture reaching the Indus and
Ganges basins from land sources, the moisture supply from the IO seems to be
first associated with the rapid increase or
decrease in precipitation over the
sources in the MPR. The technique of the composites was used to analyse how
the moisture uptake values spatially vary from the sources (the budget of
evaporation minus precipitation (<i>E</i> − <i>P</i>) was computed in a backward experiment
from the basins) but during the pre-onset and pre-demise dates of the
monsoonal rainfall over each basin; this confirmed that over the last days of
the monsoon at the basins, the moisture uptake areas decrease in the IO. The
Indian region, the Indian Ocean, the Bay of Bengal,
and the basins themselves are the main sources of moisture responsible for
negative (positive) anomalies of moisture contribution to the basins during
composites of driest (wettest) WPR and MPR. |
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ISSN: | 1027-5606 1607-7938 |