Search Results

You are looking at 1 - 10 of 32 items for

  • Author or Editor: Toby N. Carlson x
  • All content x
Clear All Modify Search
TOBY N. CARLSON

Abstract

The development and motion of fronts associated with lee-side troughs on large mountain barriers has been investigated. These fronts differ from ordinary cold fronts in their horizontal temperature field, which is characterized by a sinusoidal thermal ridge. The thermal ridge intensifies, while remaining stationary with respect to the mountains, and moves eastward upon the approach of a Pacific cold front.

An equation is derived, showing that changes in the thermal pattern can be described by changes in a potential thermal vorticity equation, which consists of three terms: (1) one representing an advection of the potential thermal vorticity by the 500-mb. wind; (2) one representing the advection of 500-mb. absolute vorticity by the thermal wind; and (3) a purely orographic term.

An idealized sinusoidal model of the thickness pattern is used in conjunction with the prognostic equation to explain the development and motion of lee-side thermal ridges. Actual examples from synoptic maps are chosen to corroborate the theory. The conclusions are: (1) the thermal ridge will develop when the surface flow is such as to produce large-scale descent on the lee slopes of the mountains; (2) no thermal ridging will appear when the 500-mb. ridge lies east of the lee slopes; (3) thermal ridging will appear with the approach of a 500-mb. ridge from the west; and (4) the thermal ridge will move eastward upon the passage of the 500-mb. ridge.

Full access
TOBY N. CARLSON

Abstract

An analysis of sea-surface temperatures over the tropical Atlantic for the past 5 yr shows a correlation between the number of tropical storms formed between July 10 and September 20 and the ocean temperatures over a wide area centered near 10°N and 35°W.

Full access
TOBY N. CARLSON

Abstract

During October 12–15, 1965, the southern part of Florida received an unusually heavy and prolonged rainstorm. Although the conventional isobaric analyses did not reveal any obvious pre-existing disturbance which would be expected to produce such a result, isentropic charts suggest that intense convection was being initiated and sustained by an organized lift of conditionally unstable air to saturation. Accompanying the heavy rainfall was the formation in the lower troposphere during the 14th of a tropical depression which is thought to have been of convective origin.

Full access
Toby N. Carlson

Abstract

Airflow through a developing midlatitude disturbance is analyzed in a relative-wind isentropic system in order to provide insight into how the cloud pattern evolves into the familiar comma shape. The model presented makes use of various concepts such as that of the conveyor belt and explores the relationship between the configuration of the major airstreams and such features as the jet streams and the dry tongue. The model also relates vertical motion and precipitation to the origin and vertical displacement of the airstreams and attaches special significance to airstream boundaries, which manifest themselves as sharp discontinuities in cloud and weather patterns.

Full access
TOBY N. CARLSON

Abstract

Surface and upper air (700 mb) analyses along with high-quality satellite photographs are presented for a 2-week period during August and September 1967. These show, in particular, the structure and motion over the continent of Africa of four major wave disturbances, three of which later became Atlantic hurricanes. The evolution of cloudiness and convection and the intensification of the disturbance at low levels over West Africa are examined in detail and related to certain climatological features of the area. Some general characteristics of the disturbances are discussed.

Full access
Toby N. Carlson
Full access
Toby N. Carlson

A simple one-layer, quasi-geostrophic model of vertical motion and surface pressure tendency is derived and used to illustrate relationships between various parameters such as stability, latitude, wind speed, and the sea-level pressure tendency for sinusoidal disturbances in a baroclinic current. It is shown in the model that the wavelength at which the maximum surface pressure tendency occurs varies with the Rossby radius of deformation, as well as with the zonal wind speed and amplitude of the disturbance. In the case of a simulated polar cyclone, which exists at high latitudes under conditions of low static stability and shallow atmospheric depth, the wavelength of maximum growth rate is relatively short.

The primary virtue of this model is that it can be used as a pedagogical tool for explaining quantitatively, but without lengthy calculations, the behavior of surface pressure systems.

Full access
TOBY N. CARLSON

Abstract

Analyses drawn from the synoptic data gathered over the eastern Caribbean in Project ECCRO, October 1965, revealed the presence of an upper tropospheric cold Low. (With assumption of state motion), the fields of wind, height, temperature, water vapor, vertical velocity, clouds, and weather were transferred to a relative coordinate system traveling with the motion of the cold Low. This process yielded composite fields in which the 6 days of data were combined into 1. These fields, showing the structure of the cold Low at five different levels in the troposphere, are presented and the evolution of cloud and moisture patterns are discussed.

Full access
TOBY N. CARLSON

Abstract

A daily analysis of the 2,000- and 10,000-ft streamlines over West Africa was made for a 3½-mo period beginning in July 1968. With the aid of satellite photographs and auxiliary sea-level pressure data, a total of 33 synoptic scale wave perturbations were observed to move across West Africa and the tropical Atlantic Ocean during this period. Some general features of these disturbances are summarized, including facts on their origin, speed, intensity, distribution of sea-level pressure, appearance on the satellite photographs, and movement over the Atlantic Ocean. The effects of the large-scale circulation and the influence of sea-surface temperatures on the movement and intensity of disturbances are also discussed.

Full access
Toby N. Carlson

Abstract

Using VHRR brightness data obtained from the NOAA 3 satellite, isopleths of aerosol Optical depth for Saharan dust have been drawn for seven days during summer 1974 over a portion of the eastern equatorial North Atlantic. The large-scale patterns reveal an elongated dust plume which emerges from a narrow region along the African coast. Thereafter, the plume moves westward and spreads laterally though maintaining rather discrete boundaries associated with sharp gradients of turbidity, especially along the southern border. Exceptionally large values of optical depth (>2.0) are found near the centers of some dust outbreaks but these high values contribute Little to the total dust loading, which, in typical episodes, are estimated to represent a loss of topsoil from Africa of ∼8 million metric tons of material in a period of 4–5 days. There appeared to be no direct intrusion of the dust plume into the ITCZ or north of 25°N in that region. Outbreaks of dust appear often to be no to the rear of a well-de-veloped easterly wave disturbance and inverted V-shaped cloud pattern. This paper demonstrates the feasibility of using satellite brightness data to quantitatively map dust outbreaks.

Full access