ARM Enhanced Shortwave Experiment

Project Description
ARESE, the ARM Enhanced Shortwave Experiment, concluded a very
successful deployment to Oklahoma on November 1, 1995. The purpose of
this five week long campaign was to conduct a series of instrumented
flights to measure the interaction of solar energy with clear and
cloudy skies to provide additional insight into recent observations of
enhanced absorption in cloudy atmospheres.As such, ARESE focused on
two scientific objectives: (1) the direct measurement of the
absorption of solar radiation by clear and cloudy atmospheres and the
placement of bounds on these measurements; and

(2) the investigation of the possible causes of absorption in excess
of the model predictions.

To accomplish these objectives, ARESE used a combination of satellite,
aircraft, and ground observations to make highly accurate solar flux
measurements at different altitudes throughout the atmospheric
column. At the heart of this was a carefully "stacked" Twin Otter
and Egrett "cloud sandwich" with the Otter at 1500 - 5000 ft and the
Egrett at 43,000 ft. This was overflown by an ER-2 flying at 65,000
ft, which because of its much higher speed did not stay in constant
alignment with the Twin Otter/Egrett stack but did provide periodic
coincidences with these other aircraft. All three aircraft carried
identical up- and down-looking "Valero" radiometers and flew over
identical up-looking radiometers at the CART central and extended
facilities. Radiance measurements from the GOES satellites were used
to retrieve top-of-the atmosphere fluxes. These flux measurements
were supplemented by a variety of cloud property measurements from
the ground, the Egrett and the ER-2, including! radar, lidar and
multispectral measurements.

These baseline ARESE flights were conducted at the CART site from
September 25 through November 1. During that time we flew twelve
scientific data flights and accumulated approximately 60 hours of
in-flight data under a variety of atmospheric conditions ranging from
clear to solid overcast. These flights are detailed in the table below
and include: cloud forcing experiments under scattered, broken, and
solid overcast conditions including low, mid-, and high-level cloud
decks; clear sky column absorption and surface albedo measurements;
clear sky flux profiling measurements; and in-flight, co- altitude
intercomparisons of flux measurements made from the two aircraft. The
data appear to be of excellent quality and comprise a unique data set
for testing our understanding of the absorption of solar radiation in
both clear and cloudy atmospheres.

In addition to these baseline solar absorption experiments, the ER-2
also performed some key calibration experiments. These used highly
accurate spectral radiance measurements from the MODIS Airborne
Simulator (MAS) to calibrate radiance measurements from the GOES
satellite and to improve retrieval algorithms for converting spectral
radiances to spectral fluxes.

The success of this deployment was the result of the tremendous
efforts of a multi-laboratory multiagency team comprised of five DOE
Laboratories, three NASA Centers, about a dozen universities and three
aircraft companies. The ARM Program sponsored the ground-based
measurements, ARM-UAV (Unmanned Aerospace Vehicle) the coordinated
Egrett and Otter measurements, and ARM and NASA the ER-2
flights. Funding was provided through the DOE's ARM Program and
through DoD's Strategic Environmental Research and Development Program

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