Publications

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https://hdl.handle.net/10217/200693

This digital collection includes publications by faculty, researchers, and/or students in the Department of Atmospheric Science.

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Open Access
Role of angular momentum transports in tropical storm dissipation over tropical oceans
(Colorado State University. Libraries, 1968-12) Wachtmann, Ronald F., author
The mean wind field is investigated around eleven tropical storms which dissipated over tropical waters south of 20° north latitude. Wind data at 850 mb and 200 mb are composited in a circular area of 12° latitude radius from the storm center for two periods in the life of these storms: (1) their intensification and mature stages, and (2) their dissipation stage. Vertical shears between these two levels are also composited. Wind data in the composites are converted to radial profiles of mean tangential wind for the two periods of storm life. These profiles are compared to similar profiles found in previous studies for intensifying tropical depressions and for mature tropical storms. The most significant differences are found in the low level wind field north of the storm centers. The broad easterly flow to the north of the intensifying tropical depressions is also found north of the dying storms during their intensification and mature stages. However, during the dissipation stage the easterly flow has weakened and become westerly over a part of the area. As a result, the mean tangential wind is significantly reduced at all radii thus reducing the import of relative angular momentum into the storm by the mean radial circulation. A deficiency in angular momentum results from a loss to the ocean greater than the import through the boundaries in at least some of the cases investigated. It is concluded that a lack of angular momentum import through the lateral boundaries may in some cases be an important factor in storm weakening or dissipation. Angular momentum import into storms at low latitudes is performed by the surrounding anticyclones at the outer radii. Maintenance and control of storm intensity is thus directly related to the position and intensity of these anticyclones.
Open Access
Monthly climatological wind fields associated with tropical storm genesis in the West Indies
(Colorado State University. Libraries, 1968-12) Sartor, James W., Jr., author; Department of Atmospheric Science, Colorado State University, publisher
An empirical study is presented which investigates the relationship of monthly climatological wind fields to tropical storm genesis in the Gulf of Mexico and the western Caribbean. The parameters investigated are tropospheric vertical wind shear and 850 mb relative vorticity. These parameters have been shown by Gray (1967) to be strongly correlated with early intensification of tropical disturbances. The magnitude of the individual mean monthly deviations of these parameters from the long term monthly mean is specified. An estimate of the daily variations of these parameters and the ratio of daily to monthly deviations is also determined. Correlations of these parameter deviations with tropical storm genesis is presented. Monthly vertical wind shear deviations are small, yet they show favorable correlations. Positive deviations of mean monthly 850 mb relative vorticity is strongly correlated with genesis in the Gulf of Mexico and is also favorably correlated with genesis in the western Caribbean. It is concluded that there are general circulation changes, with periods of a month or more, which produce favorable or unfavorable genesis conditions.
Open Access
An operational adaptation program of weather modification for the Colorado River Basin
(Colorado State University. Libraries, 1969-10) Chappell, Charles F., author; Crow, Loren W., author; Mielke, Paul W., Jr., author; Rasmussen, James L., author; Shobe, William E., author; Stockwell, Homer, author; Wykstra, Ronald A., author; Department of Atmospheric Science, Colorado State University, publisher; Grant, Lewis O., editor
Interim report for the period July 1968-June 1969.
Open Access
Conference on cloud physics
(Colorado State University. Libraries, 1970-08) Colorado State University. Department of Atmospheric Science, author
The manuscripts reproduced in this collection of preprints are unrefereed papers presented at the Conference on Cloud Physics held on August 24-27, 1970 in Fort Collins, Colorado.
Open Access
Larimer County, Colorado, air pollution and outlook
(Colorado State University. Libraries, 1970-12) Riehl, Herbert, author; Herkhof, Dirk, author; Department of Atmospheric Science, Colorado State University, publisher
Planning for economic and population growth in presently rural areas would be considerably aided from the standpoint of air quality, if an assessment of future air pollution in terms of expected population growth, as a parameter, could be made. This paper attempts to make such an estimate for the foothills area just east of the Colorado Rockies near the northern border of the state. Three problems are taken up in succession, limiting attention to particulate pollution. At first, "pollution potential", defined as the probability of incidence of air pollution episodes of some minimum duration, is calculated from winds obtained during a field experiment. On the average, 10 episodes per winter taking up one quarter of a winter's time may be expected; this is a substantial fraction of total time. Next, the mechanisms of present air pollution accumulation and depletion were studied preliminary to developing daytime and nighttime models for future pollution. It is shown that a nighttime model without turbulence can reconstruct the present pollution map quite faithfully, whereas turbulent upward flux must be added in daytime, not unexpectedly. In the models, it is possible to express future pollution density in terms of wine speed and pollution source strength. Assuming a rate of 50 per cent population increase per decade, estimates of average pollution and so of pollution distribution are prepared until the year 2000.
Open Access
On temperature and humidity observations at the surface of the tropics
(Colorado State University. Libraries, 1972-02) Riehl, Herbert, author; Department of Atmospheric Science, Colorado State University, publisher
Open Access
Summary and conclusions of an independent analysis of the weather modification program in the San Luis Valley
(Colorado State University. Libraries, 1973-02-12) Grant, Lewis O., author; Brier, Glen W., author; Mielke, Paul W., Jr., author
A comprehensive analysis of the cloud seeding activities in the San Luis Valley of southern Colorado is in progress. Several more months will be required for its completion. Certain tentative conclusions are now possible. These are presented in summary form and in ·some detail in the following sections. It is planned that a technical report will be prepared and submitted to a scientific journal for publication at the completion of the study.
Open Access
Vortex structure and dynamics of Florida Keys waterspouts: 1974 field experiment, final report
(Colorado State University. Libraries, 1974) Sinclair, P. C., author; Department of Atmospheric Science, Colorado State University, publisher
From direct penetrations of the waterspout funnel by specially instrumented aircraft, a quantitative description of the dynamic-thermodynamic structure of the waterspout has been developed. The Navier-Stokes equations of motion for the waterspout vortex are simplified by an extensive order of magnitude analysis of each term in the equations. The reduced set of equations provides a realistic mathematical model of the waterspout vortex. Further simplification shows that the cyclostrophic-Rankine combined vortex model accounts for, on the average, approximately 63% of the measured pressure drop from the environment to the waterspout core. The penetration measurements show that the waterspout funnel consists of a strong rotary and vertical field (radial component is smaller) of motion which results in a combined flow pattern similar to that of a helical vortex. In general, the measurements indicate that this one-cell vortex structure is the dominate configuration. However, several penetrations suggest reduced positive vertical velocities near the funnel core, and in one case, a downdraft core with vertical velocity of -0.8 msec-1. These measurements indicate that waterspout vortex may in some stages of development have a structure more closely described by the two-cell vortex such as discovered by Sinclair (1966, 1973) for the dust devil vortex. The temperature and pressure structure show that the waterspout, like the dust devil, is a warm core (ΔT = 0.1 to 0.5°C), low pressure (ΔP = -0.6 to -8.4 mb) vortex. All aircraft penetrations of the visible funnels were made within 150 m of cloud base at speeds of 55-65 msec-1.
Open Access
A pilot project of weather modification for the San Juan Mountains of the Colorado River Basin: final report
(Colorado State University. Libraries, 1974-02) Grant, Lewis O., author; Chappell, Charles F., author; Crow, Loren W., author; Fritsch, J. Michael, author; Mielke, Paul W., Jr., author; Department of Atmospheric Science, Colorado State University, publisher
This is the final report on the preparation of a design program to apply results from experimental programs for augmenting orographic precipitation to a Pilot Project that would have the goal of providing "...sound scientific and engineering evaluation of precipitation creases over a large area by operational-type application of cloud seeding techniques...", (Kahan, 1969). The report describes: (1) the purpose of the project; (2) the scientific and technological basis; (3) the design constraints; and, (4) the details of the design. The design itself includes descriptions of: (1) the experimental hypothesis; (2) the site selection; (3) the experimental procedures (randomization. etc.); (4) the data collection requirements; (5) the operations procedures; and, (6) the evaluation techniques to be employed.
Open Access
Radiation measurements from polar and geosynchronous satellites
(Colorado State University. Libraries, 1974-02) Vonder Haar, T. H., author; Department of Atmospheric Science, Colorado State University, publisher
Annual report for National Aeronautics and Space Administration grant NGR-06-002-102 for period: 1 October 1972-30 September 1973.
Open Access
Radiation measurements from polar and geosynchronous satellites
(Colorado State University. Libraries, 1974-12) Vonder Haar, T. H., author; Department of Atmospheric Science, Colorado State University, publisher
Annual report for National Aeronautics and Space Administration grant NGR-06-002-102 for period: 1 October 1973-30 September 1974.
Open Access
On the variability of hemispheric scale energy parameters
(Colorado State University. Libraries, 1975) McGuirk, James P., author; Reiter, Elmar R., author; Barbieri, Ann M., author; Colorado State University, publisher
Hemispheric scale energy parameters have been computed and their variability on an annual time scale and a scale of a few weeks is identified and discussed. Based on data for 15 winter seasons, the annual variability of available potential energy is linked to fluctuations of elements of the general circulation, such as the jet streams. This link establishes a relationship between simply computed hemispheric scale parameters and regional weather conditions affecting man's economic wellbeing. Daily statistics on three winter seasons of hemispheric energy modes have been analyzed with the ultimate goal of understanding and reproducing the behavior of the hemispheric energy cycle. Two phenomena are discussed: (1) A strong 22-26 day cycle in the energy modes which may be linked to synoptic scale systems and the atmospheric index cycle; and (2) A large midwinter "dip" in zonal available potential energy which is tentatively linked to a possible movement of the Hadley cell. This "dip" is shown to have a profound effect on the meridional temperature gradient, particularly in midlatitudes.
Open Access
GATE convection subprogramme: field phase report
(Colorado State University. Libraries, 1975-02) Betts, A. K., author; Rodenhuis, D. R., author; Department of Atmospheric Science, Colorado State University, publisher
A summary of the in-field decisions affecting the GATE Convection Subprogramme (C.S.P.) objectives
Open Access
Causes and effects of atmospheric interannual variability: progress report to National Science Foundation
(Colorado State University. Libraries, 1977-06) Reiter, Elmar R., author; Department of Atmospheric Science, Colorado State University, publisher
During the present grant period we examined in some detail the 24-day vacillation in the atmospheric energy cycle. We arrived at the conclusion that this cycle is tied to baroclinic instabilities and to the amplification of cyclonic disturbances upon which feed the planetary wave modes. We also examined cases of sudden stratospheric warming. They are generally characterized by prolonged decreases in hemispheric zonal available potential energy, by the development of a blocking ridge over the Gulf of Alaska and by a tendency towards below-normal temperatures over the Eastern United States. A feasibility study of hemispheric monthly precipitation anomalies revealed that large anomalies, indeed, exist simultaneously and with same sign over the continents of the northern hemisphere. From this conclusion the importance of the hydrological cycle in atmospheric variability studies has to be emphasized again. Another source of atmospheric interannual variability has been identified in the sensible and latent heat transfers between ocean and atmosphere. The 24-day vacillation appears to be influenced by these heat transfers, especially in regions with large sea surface temperature (SST) anomalies. The SST anomalies in the North Pacific between 40 and 50°N appear to be caused by fluctuations in the water transport around the Pacific gyro. This transport, in turn, seems to respond to long-term and large-scale fluctuations in the v-component of the trade winds in both hemispheres. Such fluctuations also appear to influence the global mean annual temperature, perhaps due to variations in the release of latent heat within the intertropical convergence zone.
Open Access
Modeling atmospheric dispersion of lead particulates from a highway
(Colorado State University. Libraries, 1977-10) Katen, Paul C., author; Department of Atmospheric Science, Colorado State University, publisher
Open Access
Radiation measurements from polar and geosynchronous satellites
(Colorado State University. Libraries, 1978-06) Vonder Harr, Thomas H., author; Kidder, Stanley, Q., author; Hillger, Donald W., author; Ellis, James S., author; Department of Atmospheric Science, Colorado State University, publisher
This is the Annual report for period 1 November 1976-31 October 1977 and the Final report, 10 October 1970-31 July 1978 for National Aeronatuics and Space Administratin grant NGR-06-002-102.
Open Access
Satellite studies during the 1976-77, 1977-78 Sierra Cooperative Pilot Project: final report to the Office of Atmospheric Resources Management, Bureau of Reclamation
(Colorado State University. Libraries, 1979-02) Morris, K. Robert, author; Reynolds, David W., author; Vonder Haar, Thomas H., author; Department of Atmospheric Science, Colorado State University, publisher
Digital imagery from the SMS-2 geostationary satellite was recorded for analysis in support of the Sierra Cooperative Pilot Project. Imagery of five storms during the 1976-77 and 1977-78 seasons of the project have been analyzed in detail using the CSU ADVISAR. Temporal variations in cloud top temperature were charted and synoptic and mesoscale cloud features have been studied. Results show the highest precipitation and lowest cloud top temperatures below -35°C, occur about one or two hours ahead of the surfacecold front within the frontal band. Following the frontal passage an unstable convective orographic cloud remains over the Sierra for up to 8 hours with cloud top temperatures around -15°C well within the seeding window range. Mesoscale features including banded and cellular convection and cloud streets have been observed by the satellite with their effects often showing up in the precipitation gage records. Large convective lines and cells were tracked onshore and were found to move with the winds somewhat below the 50 kPa level. Cells intensify in the Central Valley of California usually dissipating as they climb the Sierra Trajectories of large cells curve to the left upon encountering the foothills becoming nearly parallel to the mountains under certain conditions. Precipitation is greatest on the west slopes of the Sierra due to the orographic effect. Lee-side precipitation appears to be dependent on the presence of high cold cloud tops which lead to precipitation particles being carried over the crest.
Open Access
On the adjustment of simple atmospheric currents
(Colorado State University. Libraries, 1980-03) Fischer, Günter, author; Nehrkorn, Thomas, author; Schubert, Wayne, author
A disturbance of geostrophic equilibrium in the form of an unbalanced vortex of finite lateral extension or an unbalanced zonal current of finite width is suddenly injected into upper atmospheric layers between 8 and 16 km at time t = 0. We consider the changes of motion, temperature and pressure caused by the initially unbalanced velocity field which seeks to gain a stationary geostrophic equilibrium, and compare the final to the initial state. To this end the linearized hydro-thermodynamical equations are solved on the assumption that the basic state of the horizontally unlimited atmosphere is in rest and the lapse rate of temperature vanishes or, in a second example, is adiabatic. We show that the solutions for these baroclinic disturbances are obtained by a superposition of solutions for barotropic disturbances
Open Access
A cross-spectral study of the spatial relationships in the North Pacific sea-suface temperature anomaly field
(Colorado State University. Libraries, 1980-03) Middleton, John W., author; Department of Atmospheric Science, Colorado State University, publisher
Open Access
Atlas of linear trends in northern-hemisphere tropospheric geopotential height and temperature patterns
(Colorado State University. Libraries, 1981-05) Reiter, Elmar R., author; Westhoff, Daniel R., author; Department of Atmospheric Science, Colorado State University, publisher
Gridded NMC data for 500-mb geopotential height, 300/500-mb and 500/700-mb thickness for the period 1951 to 1978 were subjected to linear trend analyses. These analyses were performed for each calendar month. Significant geographical and seasonal distributions of cooling and warming patterns emerged. An atmospheric cooling trend over the North Pacific during the winter months appears to be associated with oceanic cooling in that region, but also to planetary-wave adjustments, suggesting that ocean-atmosphere feedback mechanisms are effectively at work over climatic time scales. Consistently large temperature trends also appear over the Asian continent. Comparisons between thickness trends in the 1ayer 300/500-mb with those in the layer 500/700-mb reveal well-pronounced patterns of stabilization and destabilization.