Observation of progressive convective interactions from the Rocky Mountain slopes to the Plains
Date
1979
Authors
Philipp, Ceri Burns, author
Vonder Haar, Thomas H., advisor
Cotton, William R., committee member
Meiman, James R., committee member
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Abstract
Geosynchronous satellite data were employed for a climatological study of two summers' data and for a specific case study to observe convective interactions between the eastern slopes of the Colorado Rocky Mountains and the plains of eastern Colorado and western Kansas. The climatological study involved imagery for May-August 1976 and 1977 for a study region defined from eastern Utah to western Kansas that was divided into five areas. Development and movement of convective activity from the mountains to the plains was identified by the satellite imagery analysis for 12% of the 1976 summer days (13 out of 108) and 17% of the 1977 summer days (16 out of 94). When precipitation records for stations in western Kansas were consulted, it was found that these satellite- identified development and movement days made a significant contribution to the monthly and seasonal total precipitation for this area. There were instances when the contribution was greater than 90% (for some months) and greater than 50% (for seasonal total). Further results from the climatological study showed that cumulus clouds were most likely to form in the southwestern and central Colorado mountains between 0700 and 1000 MDT (1300 to 1600 GMT). Mountain regions were generally clearing remnants of old cells during the late afternoon, evening and night hours with development and growth of new cells occurring in the early morning to early afternoon. Plains regions generally were clearing remnants during morning and early afternoon hours with convection developing in late afternoon, evening and night hours. A quantitative case study was performed for 4 August 1977 when 3-minute rapid scan satellite data were available. It was a day when optimum conditions for development and movement from the mountains to the plains existed. Computer programs on the All Digital Video Imaging System for Atmospheric Research (ADVISAR) were used to study changes in cloud size, cloud number, and cloud brightness for two areas in Colorado. The first area was in the northeastern Colorado Rocky Mountains where the primary storm system moved through. The second area was in southern Colorado (near Pueblo) which included both mountains and plains regions and primarily stationary convective activity. From the quantitative study, no definite correlation was found between changes in cloud number and changes in cloud brightness. Differences in both quantities over 3-minute intervals were found to be significant and were sometimes larger than 6 or 9-minute changes. Both areas showed varying patterns of increasing and decreasing cloud number and brightness. The first area with the active moving system tended to have greater mean brightness and more time periods with large clouds than the stationary system area. It also had larger "largest clouds" over the time period studied (1100 - 1624 MDT) than the second area.
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Subject
Cumulus
Clouds -- Colorado
Clouds -- Photographs from space