I. Foehn Winds of Southern California.II. Foehn Wind Cyclo-Genesis.III. Weather Conditions Associated With the Akron Disaster.IV. The Los Angeles Storm of December 30, 1933 to January 1, 1934

Geology;Meterology

Krick, Irving Parkhurst ; von Kármán, Theodore

University:California Institute of Technology

Department:Geological and Planetary Sciences

关键词: Geology;    Meterology;   

Others  :  https://thesis.library.caltech.edu/8611/1/Krick%201934.pdf

美国|英语

来源: Caltech THESIS

【 摘 要 】

I. Foehn winds of southern California.
An investigation of the hot, dry and dust laden windsoccurring in the late fall and early winter in the Los AngelesBasin and attributed in the past to the influences of the desertregions to the north revealed that these currents were of afoehn nature. Their properties were found to be entirely dueto dynamical heating produced in the descent from the high levelareas in the interior to the lower Los Angeles Basin. Any dustassociated with the phenomenon was found to be acquired from theLos Angeles area rather than transported from the desert. It wasfound that the frequency of occurrence of a mild type foehn of thisnature during this season was sufficient to warrant its classificationas a winter monsoon. This results from the topography ofthe Los Angeles region which allows an easy entrance to the airfrom the interior by virtue of the low level mountain passes northof the area. This monsoon provides the mild winter climate ofsouthern California since temperatures associated with the foehncurrents are far higher than those experienced when maritime airfrom the adjacent Pacific Ocean occupies the region.

II. Foehn wind cyclo-genesis.
Intense anticyclones frequently build up over the high levelregions of the Great Basin and Columbia Plateau which lie betweenthe Sierra Nevada and Cascade Mountains to the west and the RockyMountains to the east. The outflow from these anticyclones produceextensive foehns east of the Rockies in the comparatively lowlevel areas of the middle west and the Canadian provinces ofAlberta and Saskatchewan. Normally at this season of the year verycold polar continental air masses are present over this territoryand with the occurrence of these foehns marked discontinuity surfacesarise between the warm foehn current, which is obliged to slide overa colder mass, and the Pc air to the east. Cyclones areeasily produced from this phenomenon and take the form of unstablewaves which propagate along the discontinuity surface between thetwo dissimilar masses. A continual series of such cyclones wasfound to occur as long as the Great Basin anticyclone is maintainedwith undiminished intensity.

III. Weather conditions associated with the Akron disaster.
This situation illustrates the speedy development andpropagation of young disturbances in the eastern United Statesduring the spring of the year under the influence of the conditionallyunstable tropical maritime air masses which characterise theregion. It also furnishes an excellent example of the superiorityof air mass and frontal methods of weather prediction for aircraftoperation over the older methods based upon pressure distribution.

IV. The Los Angeles storm of December 30, 1933 to January 1, 1934.
This discussion points out some of the fundamental interactionsoccurring between air masses of the North Pacific Ocean in connectionwith Pacific Coast storms and the value of topographic andaerological considerations in predicting them. Estimates of rainfallintensity and duration from analyses of this type may be made andwould prove very valuable in the Los Angeles area in connection withflood control problems.