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Yutaka Izumi and Henry A. Brown

Abstract

The time and height variations of temperature, wind speed, and moisture content observed at the Cedar Hill tower during the dissipation of a low-level jet on the morning of 14 May 1962 are presented and discussed. Three distinct stages of significant variations occur before sunrise at the upper levels of the tower. The three stages art: 1) a period of an abrupt and simultaneous warming and drying; 2) a period of steady temperature, mixing ratio, and wind speed; and 3) a period of pronounced decreases in temperature and wind speed and a marked increase in mixing ratio that occur progressively later with increasing height. It is proposed that these variations are produced by horizontal and vertical advection and by turbulent mixing.

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Tetsuya Fujita and Henry A . Brown

Five mesosystems, occurring on 4 to 5 June 1953 in an area 500 by 600 mi near Chicago, were analysed with the use of data from regular synoptic stations. Four of the systems were of the well known type having a pressure-surge line, a thunderstorm high, and a wake depression. The fifth system, a trough 500 mi in length, traveled at the rate of 60 kn.

By using radar pictures taken every minute, the movement of echoes was also studied. The echo velocities, which were approximately 20 kn while a pressure-surge line was 100 mi distant, increased up to 40 kn with the approach of the line. The individual echoes in the line moved in an east-northeast direction while the pressure-surge line, oriented southwest to northeast, proceeded towards the south-southeast. The centers of the mesosystems moved in the same direction as the individual echoes in the squall line.

Hourly precipitation amounts accompanying each system were integrated with respect to time and “time integrated” precipitation charts were then constructed.

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Henry E. Fuelberg and Peter A. Browning

Abstract

Contibutions of divergent and rotational wind components to the synoptic-scale kinetic energy balance are described using rawinsonde data at 3 and 6 h intervals from NASA’s fourth Atmospheric Variability Experiment (AVE 4). Two intense thunderstorm complexes occurred during the period. Energy budgets am described for the entire computational region and for limited volumes that enclosed storm-induced, upper-level wind maxima touted poleward of the convection.

Although small in magnitude, the divergent wind component played an important role in the cross-contour generation and horizontal flux divergence of kinetic energy. The importance of V D appears directly related to the presence and intensity of convection. Although K D usually comprised lm than 10% of the total kinetic energy content generation of kinetic energy by V D was a major factor in the creation of upper-level wind maxima to the north of the storm complexes. Omission of the divergent wind apparently would lead to serious misrepresentations of the energy balance. A random error analysis is presented to assess confidence limits in the various energy parameters.

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