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ID 776
file
title alternative
土壌水分変動とその大気へのインパクト : スリランカにおける事例
creator
Yamanaka, Tsutomu
Kaihotsu, Ichirow
Shimada, Jun
Nandakumar, Vythilingam
subject
Soil moisture
Rainfall
Feedback mechanism
Time series analysis
Sri Lanka
abstract
Time series analyses of soil moisture, rainfall, air temperature and other hydrometeorological components observed at inland area of Sri Lanka in 1994 were carried out. Auto-correlation analysis gives a time scale from 10 to 30 days as persistency of soil moisture anomaly, which is considerably small relative to that under midlatitude temperate climate and is shorter than that for atmospheric temperature. Two dominant periodicities are detected from spectral analysis : 45-60-day period (especially for large rainfall and soil moisture at all depths) and 22.5-30-day period (for small rainfall and shallow soil moisture). The two intraseasonal variations are also detected for satellite-remote-sensed outgoing longwave radiation (OLR) over and around Sri Lanka. Band-pass filtered OLR anomaly for the former periodicity propagates from around Sri Lanka to the west and is strengthened through the process of its westward propagation. On the other hand, OLR anomaly for the latter periodic component has its origin at east ocean-region and propagates westward to Sri Lanka. For the 45-60-day period, band-pass filtered anomaly propagates from rainfall to soil moisture, soil temperature, wet-bulb temperature and back to rainfall, indicating a feedback loop. In contrast, propagation of anomaly through hydrometeorological variables is not found for the 22.5-30-day period. These statistical results indicate that external forcing causes the latter periodic and also that the former periodicity is introduced by an enhancement of the latter variation once in its two cycles due to negative feedback between soil moisture and rainfall. The selective enhancement against different periodic variations appears to be associated with characteristic time-scale of the soil moisture persistence.
journal title
Memoirs of the Faculty of Integrated Arts and Sciences, Hiroshima University. IV, Science reports
volume
Volume 27
start page
77
end page
93
date of issued
2001-12
publisher
広島大学総合科学部
contributor
国立情報学研究所
date of created
2006-03-21
issn
1340-8364
ncid
SelfDOI
language
eng
nii type
Departmental Bulletin Paper
HU type
Departmental Bulletin Papers
DCMI type
text
format
application/pdf
text version
publisher
department
Graduate School of Integrated Arts and Sciences
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