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 Soil moisture variability and its possible impact on the atmosphere: A case in Sri Lanka

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Author(s)

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

  • Science reports

    Science reports 27, 77-93, 2001

    Hiroshima University

Cited by:  1

Codes

  • NII Article ID (NAID)
    110000482401
  • NII NACSIS-CAT ID (NCID)
    AN10435936
  • Text Lang
    ENG
  • Article Type
    Journal Article
  • Journal Type
    大学紀要
  • ISSN
    13408364
  • NDL Article ID
    6071453
  • NDL Source Classification
    ZM2(科学技術--科学技術一般--大学・研究所・学会紀要)
  • NDL Call No.
    Z14-649
  • Data Source
    CJPref  NDL  NII-ELS 
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