Allison Parker Remote Sensing of the Oceans and Atmosphere Abstract The milli meter wavelength cloud radar MMCR is the first fully operational unattended radar for the sole purpose of remote sensing of clouds The MMCR operates at wavelengths about ten times smaller than conventional radar systems allowing for better remote sensing of non precipitating clouds There are several MMCRs currently in use by the Atmospheric Radiation Measurement ARM program in Oklahoma Alaska and the western south Pacific These MMCRs provide statistical surveys of cloud location and frequency information about cloud microphysical characteristics and produce data for basic research into cloud microphysics The data provided by the MMCRs is important for research into climate change and cloud radiative processes Atmospheric Radiation Measurement Program ARM Created in 1989 with funding from the US DOE Primary Objective Improved scientific understand of physics related to interactions of clouds and radiative feedback processes in atmosphere Main Sites Oklahoma Alaska and Western Pacific ARM Field Research Sites Southern Great Plains Oklahoma Dedicated Nov 1992 Chosen because homogenous geography easy accessibility variability of climate cloud type and surface flux properties and variation of temperature and humidity Source www arm gov ARM Field Research Sites High Latitudes North Slope of Alaska Dedicated July 1997 Data being used to refine models and parameterizations as they related to the Arctic Reasons to study climate change in high latitudes include ice snow dry climate major pumps for global ocean currents Source www arm gov ARM Field Research Sites Tropical Western Pacific Located in Australia Nauru Island Papua New Guinea Region plays a large role in El Nino Pacific warm pool supplies heat and moisture for deep convective cloud systems that produce high altitude cirrus clouds Source www arm gov Milli Meter Wavelength Cloud Radar MMCR Developed by the ARM Program for quantifying properties of radiatively important clouds Main purpose is to determine cloud boundaries radar reflectivity up to 20km Doppler capability for measurement of cloud constituent vertical velocities Primary Measurements Horizontal Wind Radar Doppler Radar Reflectivity Vertical Velocity Source www arm gov MMCR Design Vertically pointing single polarization Doppler system operating at 35Ghz 8 7 mm or 94 Ghz 3 1mm Low peak power transmitter for long term reliability High gain antenna and pulse compressed wave forms to maximize sensitivity and resolution Sources Moran et al Characteristic Values for Meteorological Radars Examples of MMCR Data Examples of MMCR Data Mode 1 Samples lowest kilometers only with high sensitivity Mode 2 Most sensitive above 3 km Mode 3 Good general mode not as sensitive to thin clouds as Mode 2 Mode 4 Less sensitive than modes 2 and 3 but does not Contributions of the MMCR to the ARM Program Statistical Surveys of Cloud Location Frequency MMCR data is compared with climate simulations weather forecast models and cloud resolving models 1 km resolution Contributions of the MMCR to the ARM Program Retrievals of Cloud Microphysical Characteristics Liquid water content vs height ice water Cloud particle phase Cloud droplet size distribution number of particles per radius size Contributions of the MMCR to the ARM Program Basic Research into Cloud Microphysics How does the precipitation process actually work When do clouds begin to precipitate Sources Atmospheric Radiation Measurement Program www arm gov 4 23 08 Clothiaux E M Miller B Albrecht T Ackerman J Verlinde D Babb R Peters and W Syrett 1995 An Evaluation of a 94 GHz Radar for Remote Sensing of Cloud Properties J Atmos Oceanic Technol 12 201 229 Moran K P B E Martner M J Post R A Kropfli D C Welsh and K B Widener 1998 An Unattended Cloud Profiling Radar for Use in Climate Research Bull Amer Meteor Soc 79 443 455