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The diurnal variation and long-term variation of the kinetic energy generation and dissipation are investigated with the wind and geopotential data observed twice a day a t 00 and 12 GMT over North America during a 5-yr. period.The generation from the work done by the horizontal pressure force and the dissipation are significantly and consistently greater at 00 GMT than at 12 GMT. The diurnal variation is especially pronounced during the summer. The annual march of the seasons and the year-to-year variation of the kinetic energy parameters are also significant.By the use of twice-a-day observations for an extended period, the study over North America is increased in generality a8 an approximation to hemispherical features. However, some uncertainty remains in this respect because of the possible effects of the semidiurnal variations and unconfirmed radiation errors in the radiosonde observations. The previously reported double maxima of the generation and dissipation in the planetary boundary layer and a t the jet stream level derived from limited data are confirmed in this study. The multi-annual mean of the dissipation is estimated as 4.12 watts/m.z About half of the estimated dissipation takes place in the boundary layer, and the other half takes place in the free atmosphere.

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Energy transformations involved in the maintenance of kinetic energy in the winter monsoon over the Kuroshio region are investigated with the AMTEX 74 and 75 upper-air observations. The kinetic energy level is very high and the energy transformations are very intense in the winter monsoon over the region. Both the kinetic energy generation and dissipation in the mid and upper troposphere are a few to several times stronger than those in major cyclones of a continental region. A large amount of kinetic energy is supplied to the mid and lower troposphere from the source in the upper troposphere.We may view the winter monsoon over the region as part of the intense kinetic energy transformations in the general circulation of the Northern Hemisphere winter with the source in the upper and midtroposphere.The cold air outbreak is essentially a surge of energy. The winter monsoon thus maintained over the ocean is then expected to absorb latent and sensible heat from the ocean surface to increase the available potential energy in the general circulation.

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