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Volume 58, Issue 2
Displaying 1-5 of 5 articles from this issue
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Nobutaka MONJI, Ken HAMOTANI, Ryuichi TOSA, Toshifumi FUKAGAWA, Kazuto ...2002 Volume 58 Issue 2 Pages 63-69
Published: June 10, 2002
Released on J-STAGE: February 25, 2010
JOURNAL FREE ACCESSTwo types of the modified gradient method for CO2 and water vapor flux estimation, in which the eddy correlation is applied only to the sensible heat flux, are presented. One type uses the eddy diffusivity for the sensible heat flux, and the other establishes the flux-gradient relation in the form of the product Φm Φh as a function of the gradient Richardson number. The latter method can be used even in heavy rains.
In order to confirm the applicability of these methods, the dimensionless profile relations for momentum, sensible heat, latent heat and CO2 are estimated over a mangrove forest. Although these dimensionless profiles indicate smaller values than the Businger-Dyer representation under stable conditions, they indicate similar tendency with each other.
The two modified gradient methods agree with each other although the scatter in the individual comparison is large.View full abstractDownload PDF (800K) -
Nobutaka MONJI, Ken HAMOTANI, Yoshiharu HAMADA, Yukari AGATA, Takashi ...2002 Volume 58 Issue 2 Pages 71-77
Published: June 10, 2002
Released on J-STAGE: February 25, 2010
JOURNAL FREE ACCESSCharacteristics of CO2 and heat fluxes over a mangrove forest are investigated during dry and wet seasons in southern Thailand. Fluxes are estimated by the modified gradient method presented in Monji et al. (2002). Turbulent fluxes show considerable differences between wet and dry seasons. When it rains the latent heat flux exceeds the net radiation considerably and the sensible heat flux shows large negative values. CO2 flux during the rain is slightly upward. The relationship between global solar radiation and CO2 flux was not significantly different between dry and wet seasons.
CO2 stored inside the canopy atmosphere during the night was found to be consumed in the morning by its photosynthesis. The storage rate is large when wind is low and its magnitude is not negligible in the CO2 exchange process.View full abstractDownload PDF (757K) -
Naru TAKAYAMA, Seiji HAYAKAWA, Satoshi ONOMOTO, Tamon TSUJI2002 Volume 58 Issue 2 Pages 79-92
Published: June 10, 2002
Released on J-STAGE: February 25, 2010
JOURNAL FREE ACCESSThe 1-km-mesh nocturnal minimum temperatures in winter were estimated for all of Kyushu by using variational analysis. The 1-km-mesh is not sufficient for prediction of frost occurrence and prediction of road freezing. So, a method to convert the nocturnal minimum temperatures from 1-km-mesh to 50-m-mesh was examined. The estimated deviation for 1-km-mesh nocturnal minimum temperature (DTr-m) was computed by subtracting 1-km-mesh nocturnal minimum temperature from observed nocturnal minimum temperature at JH (Japan Highway) weather stations. Each day from December 1, 1997 to February 28, 1998 was classified into one of five kinds of weather condition days. The properties of DTr-m distribution for each weather condition were investigated by rank sum test and by using GIS with a DEM (GTOPO30). The values of DTr-m tended to become nearly zero on rainy days, with large positive or negative values on fine days. But, in areas where flat topography predominates, the values of DTr-m were distributed around zero regardless of the weather conditions. On fine days, the values of DTr-m were large and positive in mountainous regions, and were large and negative in the West sea coastal area. The differences in the degree of localized cooling between JH weather and AMeDAS stations which depend on geographical and topographical features may cause the variation in the DTr-m values.
The difference of the degree of basin (BDJ-A) was calculated from 50-m-mesh elevation data for the JH weather stations and the nearest AMeDAS stations. The values of BDJ-A have a negative relationship to the median of DTr-m frequency. These results show that 1-km-mesh temperature may be convertible to 50-m-mesh temperature by using BDJ-A.View full abstractDownload PDF (5657K) -
Yoshitaka KUROSE, Kazuhiko OHBA, Atsushi MARUYAMA, Taichi MAKI2002 Volume 58 Issue 2 Pages 93-101
Published: June 10, 2002
Released on J-STAGE: February 25, 2010
JOURNAL FREE ACCESSThe cold air formed in the Aso Basin flows out from the valley of the Aso somma under conditions of nocturnal radiative cooling. It is thought that this local wind influences agricultural production in this region. So, meteorological observations and mobile observations were carried out at Aso region, and then the characteristics of this local wind were clarified as follows. The local wind was named “Aso Oroshi”.
1) The wind speed of the “Aso Oroshi” was closely related to the temperature inversion in the Aso Basin. The wind speed of the “Aso Oroshi” was strong when temperature inversion developed.
2) The maximum wind speed of the “Aso Oroshi” was 6m/s and the maximum instantaneous wind speed was 9m/s. It is therefore thought that no wind damage occur due to “Aso Oroshi” because no damage occur by wind with a speed less than 10m/s.
3) Air temperature along the valley of Aso somma changed more than the dry adiabatic lapse rate as the “Aso Oroshi” wind speed exceed 3.8m/s. This result strongly suggests “Aso Oroshi” received heat from air above with higher potential temperature.
4) The air temperature decreased by “Aso Oroshi” at the higher altitudes above 230m. On the other hand, the decrease in air temperature was small due to “Aso Oroshi” at the lower altitudes below 230m. It is thought that the “Aso Oroshi” becomes a meteorological resource which prevents frost damage in the lower altitude below 230m.
5) The potential temperature was constant from lon. 130°54′E towards windward, but decreased towards leeward from lon. 130°54′E. Lon. 130°54′E point is located at the exit of the Aso somma valley.View full abstractDownload PDF (2779K) -
Yoshitaka KUROSE, Kazuhiko OHBA, Atsushi MARUYAMA, Taichi MAKI2002 Volume 58 Issue 2 Pages 103-113
Published: June 10, 2002
Released on J-STAGE: February 25, 2010
JOURNAL FREE ACCESSThe strong easterly wind formed in the valley of the Aso somma is known as “Matsubori Kaze”. This local wind causes wind damage in this region. Therefore, the characteristics of this local wind and its wind damage to barley were investigated. Meteorological observations were carried out at Aso region from April 9, 1999 to May 31, 2000 and from April 1 to May 31, 2001, and the damage to barley was investigated at harvest in 1999, 2000 and 2001.
The airflow over mountains is formed in Aso somma under conditions of stable stratification and the prevailing southeastly wind speed was over 10m/s at the level of about 850hPa. The airflow over mountains converges in the valley of Aso somma, creating a strong wind with a speed over 10m/s. It is thought that this strong wind is “Matsubori Kaze”.
“Matsubori Kaze” removes the awn of barley, thus obstructing the ripening of the grain by eliminating photosynthesis by the awn. In 1999 “Matsubori Kaze” blew at early stage of ripening removing the awn of barley. Thousand grain weight of barley decreases by 10 to 20% when compared with the leeward zone where there was no wind damage in 1999. “Matsubori Kaze” negatively affects barley in this region.View full abstractDownload PDF (6908K)
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