Advection Type Research Articles

A Flux Formulation of the Spectral Atmospheric Equations Suitable for Use in Long-Term Climate Modeling

Previous1y, spectral modeling has been limited to prognostic equations Of the advective type. An alternative approach in which the equations have been recast in flux form is presented here. The latter type is more. appropriate to model vertical boundary conditions, and also guarantees mass conservation—an important consideration in extended range climatic integrations. A comparison of the two approaches is made. Each of the formulations have been successfully employed in a two-level atmospheric climate model. Results from trial integrations of the two model types are presented also.

Meteorology of long-range transport

The increasing attention to regional-scale transport of pollution has resulted in numerous air quality networks, models and large scale field studies to relate the sources of pollution to subsequent air quality measurements and thence to the effects of pollution. We compare observed air quality and trajectory data to calculations to quantitatively evaluate the differences. Methods of preparing air trajectories are described with emphasis on the Air Resources Laboratories' trajectory model and an accompanying diffusion model. The comparison of observed atmospheric transport with calculated trajectories shows that large computational errors can occur and more importantly that these may be systematic, but different, depending on the type of advection (cold vs warm) and whether the transport is over land or over the sea. We describe the use of tetroon recovery locations in trajectory analysis and show that such data can be obtained over distances up to 4000 km. Computed trajectories based on the geostrophic assumption and on the observed wind field are compared to observations to determine the adjustments required to obtain the best comparisons. Directional adjustments of up to 40° and changes in speed by a factor of two are sometimes necessary. We make suggestions for studies to improve the capability of calculating trajectories, including experiments using balloons and controlled tracer releases. Both of these techniques are applicable over regional scales. Finally we show the global distribution of sulfur from the industrial areas of the Northern Hemisphere, as calculated by an efficient computer model, as a step in the determination of the global sulfur budget.

Advection and Evapotranspiration of Wide‐Row Sorghum in the Central Great Plains1

AbstractThis study was conducted to evaluate the importance of advection as a source of energy for evapotranspiration from grain sorghum planted in 1‐m rows with both irrigated and dryland conditions. Detailed measurements of temperature, water vapor content, and wind speed were made within and above the canopy at various times and positions within the field during August 1967. Evapotranspiration was also measured by soil moisture sampling. Three types of advection were observed. Withincanopy advection resulted from the large amount of exposed dry soil between rows, which caused soil temperature between the rows to be as much as 20 C higher than plant temeprature. About 64% of the energy used to heat up the soil was used for transpiration in the irrigated plot, whereas only about 21% of the energy was used for transpiration in the dryland plot. Border advection, manifested by horizontal temperature and water vapor gradients, occurred over most of the plot irrigated but was most evident from 0 to 40 m from the upwind edge. This type of advection yielded sufficient energy to account for about 30% of the energy used for evapotranspiration from the irrigated plot. Large scale advection, manifested by temperature inversions, was found to occur during the night and probably yielded very little energy used for evapotranspiartion.

移流型方程式およびプリミティヴ方程式の数値解を求める際, 境界条件によって生ずる誤差

The boundary errors in numerical integrations of hydrodynamical equations are discussed. If the advective type equation is solved on an open domain, adopting centered difference scheme, an extra boundary condition is needed at the outflow point and it brings some errors. It is shown that these errors result from the false reflection of a computational mode wave, synchronized with the incident physical wave. By assuming the situation that in a semi-infinite domain, the incident physical wave and the reflected suprious wave are in balanced state, the rate of reflection of the computational mode is estimated. It was found that if the quantity at the outflow boundary point is extrapolated from the interior of the domain with l-th order continuity, the reflection rate is tan (l+1)(p/2), +where p is the wave number of the incident wave measured in grid unit.The same method of analysis is applied to the examination of boundary conditions of primitive equations. It was revealed that adopting some boundary conditions, the reflection rates of computational mode of gravity wave exceed unity, while a certain condition does not bring artificial reflection at all. Discussions are made about the differences between the Platzman's analyses (1954) and the present results.

The field of vertical motion in selected weather situations

The effect of vertical motion on pressure and temperature changes is briefly discussed, and the role of vertical velocities in the process of condensation is stressed. Two independent methods for the measurement of vertical velocities are outlined, and a practical technique for computation is described. The effect of vertical velocities in bringing about changes in sky condition and weather is illustrated in two cases. The field of vertical velocity from the surface to thirteen kilometers through a Colorado Low is illustrated by means of a cross‐section showing in the vertical plane the projections of streamlines of air flow, pressure changes, type of temperature advection, and the locations of the tropopause and the trough line.