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Volume 50 (1999)
- Issue 4 Pages 125-
- Issue 3 Pages 97-
- Issue 2 Pages 65-
- Issue 1 Pages 1-
Volume 50, Issue 2
Displaying 1-3 of 3 articles from this issue
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A. Chandrasekar, D. V. Bhaskar Rao, Akio Kitoh1999 Volume 50 Issue 2 Pages 65-80
Published: 1999
Released on J-STAGE: July 25, 2006
JOURNAL FREE ACCESSThe MRI atmospheric general circulation model has been used to study the effect of horizontal resolution on the simulation of Asian summer monsoon. The model has been integrated for an eight year period with three different horizontal resolutions designated as Low (4°lat X 5°long), Medium (3°lat X 3.3°long) and High (2°lat X 2.5°long), respectively. The results indicate that the increase of horizontal resolution improved the simulation of mean sea level pressure and precipitation patterns. The high resolution model simulates a heat low and monsoon trough in agreement with the observations, while the low resolution model simulates an abnormal heat low over north India. The high resolution model simulates the precipitation maxima over the Bay of Bengal and the south Indian ocean, and a dry region over the Tarim basin better, while the low resolution model better simulates the precipitation maximum over the Arabian sea. All the models simulate weaker monsoon circulation while the increase of horizontal resolution leads to further weakening of low level monsoon westerlies. The results of this study conclude that the increase of horizontal resolution improved the simulation of many observed features of the Asian summer monsoon circulation, but certain features deteriorated indicating that the model parameterizations may need to be suitably modified.View full abstractDownload PDF (2977K) -
Susumu Iwakura, Kikuo Okada1999 Volume 50 Issue 2 Pages 81-90
Published: 1999
Released on J-STAGE: July 25, 2006
JOURNAL FREE ACCESSThe relation between prevailing visibility and relative humidity measured at Tokyo International Airport was studied by taking aerosol mass concentration into consideration. The period used for the analysis is from December 1995 to March 1996, and from December 1996 to March 1997. An empirical equation which shows the relation was proposed and it has three parameters α, β and γ. The parameter α is the ratio of extinction coefficient (evaluated from visibility) to aerosol mass concentration in dry conditions. The parameter γ is an exponent which determines the ratio α (1-ƒ) γ at relative humidity ƒ. The parameter β is the correction value for measured aerosol mass concentration. In this study, the values of the parameters α, β and γ were calculated to be 3.0m2g-1, 32μgm-3 and -0.51, respectively. The value α -1 of 0.33gm-2 is almost the same as that of 0.32±0.02gm-2 reported by Waggoner and Weiss (1980), even if the cutoff radius of aerosols in this study (≤5μm) was larger than that in their measurements. The growth rate of aerosol particles with increasing relative humidity estimated in this study was equal to the value for the “normal” particles described in Kasten (1969).
The calculated visibility in another period of 15-21 February 1994 was obtained by using the parameters α, β and γ evaluated in this study, aerosol mass concentration and relative humidity measured during this period. The comparison showed that the calculated visibility coincided with observed visibility in this case.View full abstractDownload PDF (862K) -
Hirotada Kanehisa1999 Volume 50 Issue 2 Pages 91-96
Published: 1999
Released on J-STAGE: July 25, 2006
JOURNAL FREE ACCESSGlobally balanced equations for a localized meso-scale disturbance embedded in a large-scale flow are derived. The “globally” means that integrated(i.e., averaged) quantities over the meso-scale region are subjected to the equations. The integrated quantities are the velocity potential and stream function of the horizontal velocity, and the energy. From these, large-scale counterparts, which are integrated (i.e., averaged) on the outside surface of the meso-scale region, have been subtracted.
The results show the followings. The translating velocity of the meso-scale disturbance is equal to the large-scale velocity averaged just outside of the disturbance, to O(Ro) (i.e., neglecting O(Ro2)), where Ro is the Rossby number of the large-scale flow. The averaged-subtracted energy is conserved, to O(Ro). Both the averaged-subtracted velocity potential and stream function oscillate with a frequency f (equal to Coriolis parameter), to O(Ro). In particular, if the averaged-subtracted velocity, potential and stream function are, respectively zero and equal to the averaged-subtracted energy divided by f initially, then they remain so to O(Ro).View full abstractDownload PDF (465K)
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