HR: 15:30h
AN: A33E-08    [Abstracts]
TI: Detection of Mixed-Phase Clouds over the Arctic Using MODIS 6.7-12 micron Data
AU: * Spangenberg, D A
EM: d.a.spangenberg@larc.nasa.gov
AF: Analytical Services & Materials, Inc., 1 Enterprise Parkway, Suite 300, Hampton, VA 23666 United States
AU: Minnis, P
EM: p.minnis@nasa.gov
AF: NASA-Langey Research Center, Building 1250, Mail Stop 420, Hampton, VA 23681 United States
AU: Shupe, M D
EM: Matthew.Shupe@noaa.gov
AF: NOAA Environmental Technology Laboratory, 325 Broadway, Boulder, CO 80305 United States
AU: Poellot, M R
EM: poellot@aero.und.edu
AF: University of North Dakota, Box 9007, Grand Forks, ND 58202 United States
AU: Wang, Z
EM: ZWang@uwyo.edu
AF: University of Wyoming, 1000 E. University Ave., Laramie, WY 82071 United States
AB: Over the Arctic, clouds containing both ice crystals and supercooled liquid droplets are a common occurrence and need to be taken into account in determining cloud microphysical properties. Presently, these mixed-phase (MIXP) clouds are detected fairly well by ground-based techniques, however, no information on their spatial extent is available. Satellite data has excellent spatial coverage and provides a means to extend the information on cloud phase away from the ground sites. To accomplish this goal, an Arctic cloud phase model is developed to detect MIXP clouds using Moderate Resolution Imaging Spectroradiometer (MODIS) data taken onboard the Terra and Aqua satellites. The model utilizes three water vapor and two cloud-top temperature channels in the 6.7-12 μm wavelength range. To develop the model, a wide range of cloud systems were sampled where the brightness temperature (BT) data from MODIS was compared to surface-based phase retrievals at the Atmospheric Radiation Measurement (ARM) North Slope of Alaska (NSA) Barrow site. Cloud phase can be linked to specific sets of thermal and moisture structures existing between the upper part of the cloud and the upper troposphere. These structures are, in turn, reflected in the MODIS BT data. Results from the ARM MODIS cloud-phase model (AMCPM) are compared to surface-based retrievals over the ARM-NSA Barrow site and to in-situ data from the Citation aircraft which flew during the ARM Mixed-Phase Arctic Cloud Experiment. Since the AMCPM only uses channels in the infrared part of the spectrum, it can be applied to both daytime and nighttime scenes with no discontinuities in the output phase. Preliminary results are encouraging with an agreement between MODIS and the surface-based retrievals of over 75 %. The MIXP clouds considered here are those having generally between 10 and 90 % liquid water out of the total water content. The model should be applied to high-latitude regions only and even there, it is unclear how it will perform for scenes containing highly elevated terrain. Two main types of MIXP clouds were found over the Arctic. The dominant type is the low-level MIXP cloud topped with mostly supecooled liquid. MODIS 8.5, 11, and 12 μm (3CHIR) data confirms this since they have nearly identical signatures to those clouds containing just liquid. This type of MIXP cloud is trapped under the surface temperature inversion. The second, and less common, type of MIXP cloud rises above the temperature inversion or occurs with no inversion. These are normally thick clouds and often extend well into the mid troposphere. MODIS 3CHIR signatures show that they have mostly ice crystals at their tops.
DE: 3310 Clouds and cloud feedbacks
DE: 3360 Remote sensing
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005