Penman 式で用いられる有効長波放射量推定式の係数に関する考察  [in Japanese] Coefficients in Net Long Wave Radiation Equations for Penman-type Evapotranspiration Equation  [in Japanese]

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Abstract

本報文では,高精度で長波放射量が観測されている世界中の18観測所での観測結果をもとに,一般的な有効長波放射量推定式で用いられている係数の気候依存性,および推定式を構成する雲の効果に関する係数の妥当性について検討し,以下のことを明らかにした.(1)快晴時の大気の射出率を表すBrunt式の2つの係数は相関係数−0.98となる高い相関がある.(2)Brunt式の係数は,年平均蒸気圧と相関があり,気候依存性が認められる.(3)雲の効果を快晴時の全天日射量と実際の全天日射量の比を変数とする一次式で表すとき,その係数は年平均蒸気圧および年平均気温と相関があり,気候依存性がある.(4)雲の効果を表す係数は,下向き長波放射量に雲の効果を算入する本来の機能とともに,地表面温度と気温との差を調整する機能を担っていると考えられ,物理的意味を持たない係数となっている.

This paper discusses the climate-dependency of three coefficients in general long wave radiation equations and the validity of the cloudiness factor in general equations, based on data at 18 high accuracy stations for long wave radiation fluxes. The following became apparent: (1) two coefficients of Brunt's formula for the air humidity correction factor under clear-sky conditions have a correlation coefficient of −0.98; (2) the coefficient of the Brunt's formula has a correlation with annual mean vapor pressure and is assumed to be climate-dependent; (3) the coefficient of the original cloudiness factor which is a linear function of a rate of short wave radiation under a clear sky to actual short wave radiation have a correlation with annual mean vapor pressure and annual mean air temperature and is also climate-dependent; (4) the cloudiness factor in general equations is considered as the fitting parameter which considers not only cloud radiation but the temperature difference between air and surface.

Journal

  • Transactions of The Japanese Society of Irrigation, Drainage and Rural Engineering

    Transactions of The Japanese Society of Irrigation, Drainage and Rural Engineering 81(1), 75-80, 2013-02-25

    The Japanese Society of Irrigation, Drainage and Rural Engineering

References:  7

Codes

  • NII Article ID (NAID)
    10031171476
  • NII NACSIS-CAT ID (NCID)
    AA12240517
  • Text Lang
    JPN
  • Article Type
    ART
  • ISSN
    18822789
  • NDL Article ID
    024317591
  • NDL Call No.
    Z18-365
  • Data Source
    CJP  NDL  J-STAGE 
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