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Albany, NY 12203

Instruments development

We have developed two instruments for solar radiation as well as for remote sensing aerosols and clouds.

Multi-scan Spectrometer

We proposed a new technique for simultaneously retrieving cloud optical depth and effective radius for low LWP clouds as well as aerosol optical properties and particle size [Min and Duan 2005]. The radiance of the solar aureole, the forward scattering lobe of aerosol and cloud particles, corresponding to a shadowband strip is obtained by differentiating the blocked and unblocked irradiances measured by a Lambertian detector. The advantage of the shadowband technique is that the forward scattering lobe and the total-horizontal irradiance are simultaneously measured by the same detector. It allows accurate determination of atmospheric transmittances without requiring absolute calibration: Langley regression of the direct-normal irradiance with the associated forward scattering lobe taken on stable clear days can be used to extrapolate the instrument's response to top of the atmosphere (TOA), and this calibration can then be applied to the total horizontal irradiance. Transmittances are calculated subsequently under all-sky conditions as the ratio of the uncalibrated signal to the extrapolated TOA value.

High resolution oxygen A-band spectrometer

Because oxygen is a well-mixed gas in the atmosphere, the pressure dependence (as a surrogate of altitude) of oxygen A-band absorption line parameters provides a vehicle for retrieving photon path length distributions from spectrometry of the oxygen A-band [More to see Surface Remote Sensing]. A high resolution oxygen A-band spectrometer can be used to study the links between cloud microphysics and 3D geometry and cloud radiative transfer, validate the BoardBand Heating Rate Profile products directly, and test radiative transfer models and cloud overlap schemes used in GCMs.

A DIfferential Absorption Radar for Barometry (DIAR-Bar)

Atmospheric pressure is the primary driving force for atmospheric dynamics and generates wind fields which transport mass, moisture and momentum. All weather predictions of Numerical weather prediction (NWP) models are critically based on the pressure fields and dynamics. Good knowledge of sea surface air pressure can considerably improve tropical storm tracks and intensities as shown by our Observing System Simulations (OSS). Although it is one of the most important atmospheric variables, surface air pressure currently can only be measured by limited numbers of in-situ observations conducted by buoys, ships, or dropsondes over oceans which are sparse in spatial coverage and expensive to implement. At the 50~55 GHz O2 absorption band, the total extinction of radar echoes from surfaces is strongly correlated to atmospheric column O2 amounts, thus, atmospheric path lengths and surface air pressures. The novelty of our technique is to use the absorption difference from the echoes of a dual-frequency O2-band radar to estimate the surface pressure, which can measure surface air pressure under all weather conditions over oceans. The high-altitude (>15 km) airborne system under development is to demonstrate the capability of space measurements and to remotely sense pressure fields for hurricane dynamics, which will lay the foundation for future satellite barometric observation.

The rotating shadowband spectroradiometer (RSS) at the Southern Great Plains (SGP)

A high-resolution oxygen A-band and water vapor band spectrometer