Summary of the Skywatch Suite of Instruments http://skywatch.colorado.edu/ Samuel LeBlanc1,2, Peter Pilewskie1,2, Scott Kittelman1, Katja Friedrich1 1Department of Atmospheric and Oceanic Sciences, University of Colorado 2Laboratory for Atmospheric and Space Physics Introduction. The Skywatch suite is composed of radiation/remote sensing instruments and Current Instruments precipitation instruments located on the roof of the Duane Physics building. Two broadband Radiometers measure downwelling solar and infrared radiation that Radiometers is sensitive to clouds, aerosols, and water vapor. A determines cloud Ceilometer base altitude and the boundary layer height. A Sun Photometer measures the . • Active cloud base height sensing system directly transmitted solar irradiance in narrow spectral bands which can be used • -like mode (905nm wavelength laser) to determine aerosol loading. A Solar Spectral Flux Radiometer measured . Broadband Shortwave • Determines up to 3 cloud base heights hyperspectral radiance and irradiance, complementary to the broadband Irradiance (310 to 2800 nm) • Measures backscatter from cloud droplets radiation measurements. It will be operated in two modes: zenith pointing and • Atmospheric Boundary layer determination sky-scanning to derive aerosol properties.  Clear sky on • Using the minimum negative gradient of the The is the instrument of choice for the in situ measurement of drop 10/17 to 10/18 backscatter to determine the boundary layer height size distributions, while the Micro-Rain Radar is used as the remote sensing Irradiance only depends profiler. The is the absolute rain amount detector. on sun angle

Purpose Pyrgeometer • Teaching tool for undergraduates and graduates alike. . Longwave Irradiance (4.5 μm • Information source for present weather and sky conditions to 42 μm) • Cloud/aerosol/precipitation remote sensing. • Develop novel instrumentation and retrieval methods for aerosol optical thickness, size, and composition using hyperspectral radiance Overcast to clear • Integration and merging of data from multiple instruments on 11/15 to 11/16 My Research Goals: Disdrometer Solar Spectral Flux Radiometers • Active 2D laser beam sensing • Dual head, hyperspectral full hemispheric • Hydrometeor detection by shadow size Boundary Layer height increase radiometer • particle partially blocks the laser path, Cloud base descends with rain event with daytime heating • Wavelengths range from 300 to 1700 nm between the emitter head and the receiver • Si and InGaAs solid state Linear head. diode array • Hydrometeor speed • 9 to 12 nm resolution detection by amount Micro Rain Radar • 366 mm-1 and 179 mm-1 of time blocking the • Zenith pointing flat field grating laser beam Doppler radar (24.1 GHz) Hydrometeors • Reflectivity and Velocity gives the drop size Almucantar Tracking System distribution

• Development of 2-axis tracking system • Construct active sun-tracking method with 4-quadrant photodiode Fibre optics Heads • Test and calibrate Tracking system • Liquid water Sun content Solar Almucantar determination Uses:• Aerosol optical thickness determination • Hyperspectral abilities for aerosol size distribution • Possible particle shape determination by use of polarization • Relationship of speed and size, Narrow field of View Collimator gives the rain rate(R), and the • Construction of a narrow field of view fore optics Radar Reflectivity(Z), can be • Will give a factor of 106 used to find the correct Z-R stray light rejection relationship • Particle Fall Velocity determination • Change SSFR from hemispheric irradiance (64 doppler frequency bins) detector to radiance • Profiling rain rate measurements • Use in CALNEX for spring of 2010 Future Instruments • Potential design for the collimating hyperspectral courtesy André Ehrlich, Leipzig University fore optic Rain Gauge Sun Photometer References • Weighing system measures total liquid water • Passive sun-tracking system • Löffler-Mang, M., and J. Joss, 2000:An optical disdrometer for measuring size and velocity of content of precipitation • Grating spectrometer with 2048 channel Si CCD hydrometeors. J. Atmos.Ocean. Tech., vol.17, pp.130-139. • Automated absolute amount measurements • 350 – 1050 nm Wavelength range • Kurt Nemeth and Martin Löffler-Mang, 2006: OTT PARSIVEL® - Enhanced Precipitation Identifier for • Antifreeze combination for subzero temperatures • Will help determine atmospheric aerosol loading present Weather, Drop Size Distribution and Radar Reflectivity, OTT MESSTECHNIK GmbH & Co. KG • 1° degree half angle field of view • Jacqueline Gordon, 1985:New Uses for the Solar Almucantar, Applied optics, vol.24, No. 20, pp.3381-3389

Samuel LeBlanc, [email protected] Phone: (303) 492-6401