Malkus Joanne Starr

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  • Technical Report
    Concerning the structure of some cumulus clouds which penetrated the high tropical troposphere
    (Woods Hole Oceanographic Institution, 1954-03) Malkus, Joanne Starr ; Ronne, Claude
    Some extremely large oceanic trade-mind cumulonimbus clouds extending upwards of 40,000 ft. into a region of strong winds and intense vertical shear have been studied by means of time-lapse photography. A simultaneous still picture of the clouds taken a known distance and direction away from the motion pictures permits triangulation upon the clouds and calculation of the vertical and horizontal motions of several of the individual towers. By means of a nearby radiosonde observation, it is established that the air forming the strongest of these towers must have risen from near cloud base with little or no dilution of its buoyancy by mixing with the clear-air surroundings. The model of Malkus and Scorer (1954) concerning the erosion of cumulus towers is reviewed and tested upon these towers with satisfactory results. A minimum horizontal cloud dimension is apparently required for the production of undiluted towers. The horizontal motion of the clouds relative to the air is also estimated from the model and tested by the observations and the net upward transport of latent heat in water vapor is calculated approximately.
  • Technical Report
    Cloud structure and distributions over the tropical Pacific : part II
    (Woods Hole Oceanographic Institution, 1961-08) Malkus, Joanne Starr ; Riehl, Herbert ; Ronne, Claude ; Gray, William S.
    This is the second part in three of an observational study of tropical oceanic clouds and their relation to the large-scale flow patterns. The first part appeared in preliminary form in 1959 in a volume entitled "Cloud Structure am.d Distributions over the Tropical Pacific. Part I", an unpublished Technical Report (Reference No.58-62) of the Woods Hole Oceanographic Institution. The four authors were the same as those of this report. In addition, a very brief summary of the work (by J. Malkus and C. Ronne) was published in Monograph No.5 of the American Geophysical Union in 1960. A review of the cloud code evolved during this program has been published by M. Alaka in the Bulletin of World Meteorological Organization for April, 1960. The basic material for this study consists of three photographic flights made during July and August 1957 on Military Air Transport (MATS) cargo aircraft flying on regular schedules between San Francisco and the Phillipines. The photographer was Claude Ronne of Woods Hole, accompanied by Joanne Malkus om. the third flight. The appropriate synoptic data were kindly collected by Prof. Colin Ramage of the University of Hawaii and were analyzed by Professor Riehl (then at the University of Chicago) and his colleague Mr. W.S.Gray. The first report described the purposes and methods of the inquiry and presented the results of the first trans-Pacific flight. This report is concerned primarily with the results of the Second flight. A third report on the last flight is planned later, as well as eventual publication of all three parts together. The part of the program reported here has been supported jointly by the Office of Naval Research and the National Science Foundation.
  • Technical Report
    On the structure of trade-wind air below cloud
    (Woods Hole Oceanographic Institution, 1956-08) Malkus, Joanne Starr
    The moisture and temperature structure of the trade-wind mixed layer are compared under conditions of strong versus weak trade. The data used are two series of aircraft psychrograph soundings made over the ocean near Puerto Rico in early spring. The first in conditions of strong undisturbed trade and high zonal index (April 10 - 28, 1946) and the second under conditions of weak rather disturbed trade and low zonal index (March 18 - April 7, 1953). The weak trade soundings show a less homogeneous moisture distribution and a less stable temperature lapse rate. Considerable variation in structure of the lowest air accompanies changes in the trade regime which may give rise to significant fluctuations in energy input at the source region for atmospheric circulations. The importance of wind stirring in the upward transfer of moisture is indicated, which may affect the formation of trade cumulus clouds. Further studies investigating the relation between air and ocean structure at their boundary are suggested by the evidence herein, which may relate to the formation of tropical storms.
  • Book
    On the structure of the trade wind moist layer
    (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1958-08) Malkus, Joanne Starr
    The trade-wind moist layer is itself subdivided in the vertical into two superposed layers of different convective regime, because of the occurrence of water vapor condensation at about 600-700 m above the tropical oceans. Below the condensation level, in the so-called "subcloud" layer, unsaturated convective turbulence predominates. Eddies 50-150 m across are characteristic and recent studies suggest that larger scales of motion with dimensions 10-50 km (size of cloud groups) are also significant. No evidence of cloud-scale motions below cloud base have been found, except in precipitating downdrafts. Above the condensation level, cumulus convection is the major transport process; small-scale turbulence is confined to the neighborhood of clouds, which form in bunches separated by wider, weakly subsiding clear areas. The lower four-fifths of the subcloud layer is well-stirred and has been christened the "mixed layer". The lapse rate is close to dry adiabatic and the moisture content of the air is nearly constant with height, decreasing only 3-6% from 15m above the sea to its top at about 550 m. The thickness of the mixed layer commonly shows variations of 20% in space and as much as 100% in time, with extreme day-to-day variations of about 300-700 m. Recent evidence suggests that its space variations on a 10-50 km scale are associated with the bunchy grouping of trade cumuli. It appears that the clouds are grouped in places where the mixed layer is thickened, reaching close to the condensation level of the air within it. The trade-wind mixed layer thus plays the crucial role of a "valve" in the earliest phases of the atmosphere's energy supply. Its structure regulates both the input from the sea below through evaporation and the output aloft through cumulus formation. The present study has therefore been divided into three parts. Part I examines the structure of air below cloud; Part II is concerned with the features of the cloud layer and cumulus convection; and Part III attempts to construct a physical model of the operation of the moist layer as a whole.
  • Technical Report
    On the formation and structure of downdrafts in cumulus clouds
    (Woods Hole Oceanographic Institution, 1954-08) Malkus, Joanne Starr
    Downdrafts, exhibiting speeds and mass transports comparable to those of the main updrafts, are a common feature of the cumulus clouds studied by the Woods Hole Oceanographic Institution's FBI aircraft in the trade-wind region. These downdrafts are observed to be most pronounced at the extreme downshear edge of the visible cloud and are generally stronger the greater the age of the cloud tower, although they are normally present at the edge of even rapidly growing turrets.
  • Technical Report
    On the structure of the trade wind moist layer
    (Woods Hole Oceanographic Institution, 1957-01) Malkus, Joanne Starr
    Comparison of the lower trade-wind air under conditions of strong versus weak circulation is continued, Moisture and thermal structure and transports from the top of the mixed layer up to the trade-wind inversion are investigated. Much less difference is found at those levels between weak and strong circulation period than was found in the lowest or mixed layer. It is shown that the development of trade cumulus convection is dependent primarily upon conditions below cloud while for immense cumulonimbus build-ups convergence in the large-scale flow appears to be necessary. A physical model of the moist layer is constructed which describes the interaction of cloud populations with their surroundings, It shows how the cloud groups, though they average level-for-level both virtually and potentially colder than the clear, are thermally direct circulations providing heat and moisture to the trade. The model is built up from numerical calculations based primarily upon the aircraft soundings made in the undisturbed trade near Puerto Rico in April 1946 and March - April, 1953.
  • Technical Report
    Some results of a trade cumulus cloud investigation
    (Woods Hole Oceanographic Institution, 1953-05) Malkus, Joanne Starr
    Cross sections through two trade cumulus clouds are presented, showing the temperatures, turbulence, and water vapor content of the clouds and their nearby environment, the cloud slope, and the external wind profile. The two clouds were studied over the Caribbean Sea on the same afternoon in June, 1952, and were in widely differing phases of their life cycles. The measurements were made from a slow-flying aircraft equipped with sensing instruments and whose behavior as a meteorological tool had been previously studied. Numerous calculations are made from the cross sections, including total and dynamic entrainment, drafts, slopes, and liquid water content. These are, where possible, checked against the corresponding observations. In addition to testing previously evolved theoretical models, and the usefulness of the steady-state hypothesis, the data provide some evidence concerning the formation and growth of larger trade cumulus clouds from several smaller ones and by successive stages.
  • Book
    Vertical distribution of temperature and humidity over the Caribbean Sea
    (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1949) Bunker, Andrew F. ; Haurwitz, B. ; Malkus, Joanne Starr ; Stommel, Henry M.
    The observations presented and discussed in this paper were obtained as part of a research project conducted under contract NObs-2083 with the Bureau of Ships of the U. S. Navy by the Woods Hole Oceanographic Institution. The observations and their original reduction were carried out under the direction of Jeffries Wyman. The airplane soundings were undertaken by Kenneth McCasland and Alfred Woodcock. The sea surface temperature was measured on the surface ships by David F. Barnes and Roger Patterson. The necessary airplane (PBY-SA) and surface boats (PC's) were made available by the U. S. Navy. All observations were made during the spring of 1946 at about 19.5°N latitude, 66°W longitude, north of San Juan, Puerto Rico, and at about lO°N latitude, 79.5°W longitude, north of Coco Solo, Panama. An extensive preliminary report on the results of the expedition with a limited circulation was prepared by Wyman and his collaborators during the summer of 1946. The present paper deals with certain phases of the work in a more detailed fashion. Special attention is given to the temperature and humidity distributions in the vertical and to their interpretation in the light of meteorological principles. A discussion of atmospheric turbulence based on airplane measurements has already been published elsewhere (Langwell, 1948), and an application of the airplane soundings to the theory of cumulus clouds has been studied by Stommel (1947). The second and third chapters of this publication deal with the description of observational techniques used by the expedition, with the methods of reduction and present the data on which the later discussion is based. It has been thought desirable to publish these data in extenso because they may be of interest to other meteorologists in view of the sparsity of upper-air observations in this region. The actual preparation of Chapters II and III is largely the work of Bunker and Stommel. In order to show how the observations made off Puerto Rico fit into the general pattern of climatic and weather conditions in the Caribbean area Chapter iv presents a survey of the climate of this region and of the weather conditions during the time when the observations were taken. This Chapter was contributed by Joanne Malkus. It is pertinent to include in this general introduction the conclusion drawn in Chapter IV namely that the weather situations encountered represented, in general, a relatively undisturbed trade-wind regime of early spring. The homogeneous layer of nearly dry-adiabatic lapse-rate of temperature and almost constant mixing ratio is one of the most characteristic phenomena in the lowest atmosphere of this region. It is also of utmost importance for the energy budget of the hydrosphere and the atmosphere. Therefore, a special discussion of this layer by Bunker is given in Chapter V. Because of the nearly dry-adiabatic lapse-rate in the homogeneous layer most of the heat transfer between water and air in the trade-wind zone must be in the form of latent heat of vaporization, a conclusion whose thermodynamic implications were discussed thoroughly by Ficker (1936). For this reason the distribution of water vapor deserves special attention, and Chapter VI deals with this variable as a problem in turbulent mass exchange. The analysis presented in this chapter is due to Haurwitz and Stommel.
  • Book
    Observational studies of the air flow over Nantucket Island during the summer of 1950
    (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1952-10) Malkus, Joanne Starr ; Bunker, Andrew F.
    The observations presented here were undertaken as a continuation of a broader program to investigate atmospheric convection. One phase of this study concerns the relation between convective motions, their energy sources, and the structure of the atmosphere prior to their onset. The structure of the atmosphere is described in terms of such parameters as temperature, humidity, velocity, turbulence, and distribution of these in space. An oceanic island was chosen as the site for this phase of the study primarily because it serves as a localized and clearly defined energy source for convective motions. Nantucket was selected from the many accessible islands in the Woods Hole area, nearly all known to produce convective cloud streets, mainly because of its flat, smooth topography. Because its elevation never exceeds 15 meters above sea level and because it contains no large trees, hills or other obstructions, the effect of heating the air from below is rather well isolated due to minimization of the barrier and frictional effects. Previous observational work (Malkus, Bunker, and McCasland, 1949) indicates that such heating is the main energy source for the observed convective motions and constitutes a necessary but not suffcient condition for their production. This conclusion is corroborated and extended by the present data.