440 research outputs found
Turbulence and turbulent fluxes over the Indian Ocean
Originally issued as Reference No. 68-62, series later renamed WHOI-.A C-54Q aircraft equipped with meteorological instruments was flown
three times to India to participate in the International Indian Ocean Expedition.
Flights were made out of Bombay, Gan, and Aden to observe winds,
temperatures, humidities, clouds, radiation, carbon dioxide, tritium,
turbulence, and turbulent fluxes of heat, water vapor, momentum and kinetic
energy. The present paper reports the values of 405 measurements of the
turbulence and turbulent fluxes and interprets them in terms of the monsoon
circulation and the effect upon currents and temperatures of the
Arabian Sea. Analyses of other data have been reported and interpreted
elsewhere. The aircraft turbulence measuring system used was developed earlier
by Bunker (1955) (1960). It consisted of a vertical accelerometer, a
strain-guage air-speed transducer, a vertical gyro, a platinum wire
thermometer and a microwave refractometer for humidity measurements. The
data was recorded on a nine-channel oscillograph. A digitizing reader
was used to read and punch the data on cards. The turbulent quantities
and fluxes were computed and tabulated by machine. The accuracy and limitations
of the system are discussed. While much is left to be desired in
terms of accuracies and spectral range, the results are meteorologically
useful and comparison shows good agreement with other techniques.Submitted to the National Science Foundation
under Grants G-22389 and GA-1490
Stress, turbulence, and heat flow measurements over the Gulf of Maine and surrounding land
Originally issued as Reference No. 56-65, series later renamed WHOI-.This report presents turbulence, flux, temperature and water
vapor data obtained from an airplane flying over the Gulf of Maine and
adjacent shores. Measurements of the root-mean-square turbulent deviation
velocities, shearing stresses, and heat flows were made at many
heights and offshore distances in air masses moving from land to water.
Stability effects on the turbulence and fluxes of heat and momentum
have been Observed over a wide range of conditions as air flowed over
cooler or warmer surfaces.
The following conclusions have been drawn from a study of
the data:
(1) The magnitudes of the root-mean-square turbulent deviation
velocities δw and δu 3 increases with height in the lowest 100
meters and then decreases slowly with height up to the inversion where
the velocities drop to very low values. (2) Shearing stresses were found to increase with height
up to the 100 to 200 in level and then drop off with height. This
height variation is in contrast to the generally accepted notion of
a decrease of the stress from the surface to the geostrophic level.
These observations confirm the findings of Scrase (1930) and others
and demand an investigation of the acceleration of the air and the
effects of thermal winds.
(3) Both the horizontal and vertical components of the turbulent
wind are increased by hydrostatic instability and decreased by
stability. The horizontal component is affected less than the vertical
component by stability differences. (4) The decrease in the turbulent velocities as air passes from
land to cooler water is great and rapid while the increase in turbulent
velocities as the air passes over warmer water is slight and slow.
(5) The observed heat fluxes also first increase and then decrease
with height and usually become negative near the top of the mixed
ground layer where the potential temperature gradient becomes strongly
positive.
(6) The stability of the air above about 50 m is a very poor
indicator of the temperature difference existing between the underlying
surface and the air of the main mixed layer. Diffusion of heat downward
from a layer of warm air above the ground layer frequently is the cause
of a stable lapse rate regardless of the relative temperature of the surface
below.
(7) No comparison of the coefficient of turbulent mass exchange
for water vapor, heat flow and momentum could be made since the temperature
gradient was stable even when heat was flowing upward, and no wind
profiles were made over the water.Office of Naval Research under
contract Nonr-1721(00) (NR-082-021
Air-sea interaction for the International Indian Ocean Expedition
Originally issued as Reference No. 68-8, series later renamed WHOI-A C-54Q aircraft was bailed to the Woods Hole Oceanographic
Institution to participate in the International Indian Ocean
Expedition and other research projects in the fields of meteorology and oceanography. With the joint support of the Office of
Naval Research and the National Science Foundation, the aircraft
was modified and instrumented for meteorological research.Submitted to the National Science Foundation
on Work Accomplished under Grant G 22389 to
the Woods Hole Oceanographic Institution
Measurements of the vertical water vapor transport and distribution within unstable atmospheric ground layers and the turbulent mass exchange coefficient
The series of observations described in this
report were planned with the double purpose of measuring the evaporation and transport of water vapor from the ocean into an unstable atmosphere, and of studying the diffusion processes operating
in air of this stability class. Measured values of
the evaporation from ocean surfaces were conspicuously
absent from the meteorological literature
until Craig and Montgomery (1949) published
values for hydrostatically stable air. The present
set of measurements extends our knowledge to
include evaporation into a hydrostatically unstable
air mass. In addition to evaporation values at the
surface, net transports of water vapor at many
levels up to 2000 meters have been measured
New Star Forming Galaxies at z\approx 7 from WFC3 Imaging
The addition of Wide Field Camera 3 (WFC3) on the Hubble Space Telescope
(HST) has led to a dramatic increase in our ability to study the z>6 Universe.
The increase in the near-infrared (NIR) sensitivity of WFC3 over previous
instruments has enabled us to reach apparent magnitudes approaching 29 (AB).
This allows us to probe the rest-frame ultraviolet (UV) continuum, redshifted
into the NIR at . Taking advantage of the large optical depths at this
redshift, resulting in the Lyman-alpha break, we use a combination of WFC3
imaging and pre-existing Advanced Camera for Surveys (ACS) imaging to search
for z approx 7 over 4 fields. Our analysis reveals 29 new z approx 7 star
forming galaxy candidates in addition to 16 pre-existing candidates already
discovered in these fields. The improved statistics from our doubling of the
robust sample of z-drop candidates confirms the previously observed evolution
of the bright end of the luminosity function.Comment: 15 pages, accepted in MNRA
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