(1) Institute of Observational Research for Global Change, Japan Agency for Marine-Earth Science and Technology
(3) Institute of Observational Research for Global Change, Japan Agency for Marine-Earth Science and Technology / Institute of Low Temperature Science, Hokkaido University
Downward longwave radiation (DLR) is an important incoming radiation component in high latitude area, especially during winter and snowmelt season. In the Eastern Siberia, DLR during winter (from October and next April) is strongly affected by the surface temperature inversion layer which is developed in conjunction with remarkable air temperature decrease on the land surface. Few estimation schemes for the DLR at land surface represent the effect of strong surface inversion as appeared in Eastern Siberia. In the present study, an estimation of DLR under clear sky during winter based on the relationship between DLR and surface temperature inversion was examined using observed DLR data and upper air data in 2000 (during GAME-Siberia experiments) in Yakutsk. Generally DLR is estimated based on Stefan-Boltzmann radiation law using atmospheric emissivity (¥åA) associated with accumulated water vapor content and effective temperature, normally air temperature at screen height. Radiation chart is used for estimating DLR under clear sky condition and calculating back to the effective temperature in order to detect the effect of inversion layer. Both precipitable waters using NCEP/NCAR reanalysis data and estimated from surface humidity can be used for the calculation of ¥åA in winter. As the effective temperature, the effect of surface inversion layer (dTe) is added to the surface air temperature. A difference between surface air temperature and mean temperature in inversion layer is highly correlated with dTe. In addition, this inversion temperature difference has liner relationship with surface air temperature below -10¢ªC. Comparing with this estimation, observed DLR at the top of the tower in larch forest in Yakutsk is comparable throughout a winter. However the result applying the estimation to the polar site (Tiksi) is quite low comparing with observed DLR, and it is needed to clarify other effect of atmospheric conditions, such as wind speed and cloudiness.
Submittal Information
Name :
Date :
Yoshihiro Iijima
30-Jul-04-16:03:30
Organization :
Theme :
Institute of Observational Research for Global Change, Japan Agency for Marine-Earth Science and Technology