Comparison of Cloud Fraction, Height/Temperature, and Microphysical Properties
Between GISS SCM, NASA MODIS, and DOE ARM SGP Data
PI: Xiquan Dong, University of North Dakota
Co-Is, Dr. Tony Del Genio, NASA GISS; Dr. Pat Minnis, NASA LaRC
This proposed research is in response to the announcement of NASA NN-H-04-Z-YS-008-N, in particular for “a new Cloud Modeling and Analysis Initiative (CMAI)”, using three data sets: NASA GISS Single Column Model (SCM) simulations, NASA MODIS satellite results, and DOE ARM surface data over the ARM Southern Great Plains (SGP) site during the period of 1997-2004. Based on several years of three data sets, we propose the following two objectives:
Objective 1: After providing and comparing the long-term CF variations and their vertical distributions, we will further classify clouds into the following 10 categories:
- Single-layer low cloud (<3km, no middle/high clouds above it)
- Single-layer middle cloud (3-6 km, no high cloud above it, and no low cloud below it)
- Single-layer high cloud (>6km, no low/middle clouds below it)
- Middle cloud over low cloud (contiguous)
- Middle cloud over low cloud (not contiguous)
- High cloud over middle cloud (contiguous)
- High cloud over middle cloud (not contiguous)
- High cloud over low
- High over middle, and middle over low cloud (contiguous)
- High over middle, and middle over low cloud (not contiguous)
The surface radar-lidar observed 10 categories of cloud amounts will be used as cloud truth for comparing the corresponding satellite-derived cloud amounts, and for studying the percentages of low/middle clouds under high cloud and low cloud under middle cloud missed by satellite, and finally for reconciling the surface and satellite estimations of cloud amounts. Eventually we will compare both surface and satellite results with the model simulations, understand the physical processes associated with cloud formation, maintenance, and dissipation, and modify the existing cloud parameterizations if necessary.
Objective 2: We will do the similar study to the first objective, but focus on the microphysical/optical properties of single-layer low and high clouds, as well as deep convective clouds. From the comparison, we want to know if they agree to each other if all of three data sets have correct cloud microphysical properties. If not, what are the reasons for leading to this discrepancy? We will test and evaluate each cloud parameterization in the GISS SCM using both satellite and surface data as a baseline, make some improvements, and then apply the modified parameterization in the model until the model simulations close to the observations.
There are 3 steps for this proposed research:
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Step 1: Analyze 8-yr (1997-2004) ARM SGP surface data only to provide cloud truth
Step 2: Compare 5-yr surface-satellite (2000-2004) and 3-yr surface-SCM data (1999-2001), respectively.
Step 3: Finally, compare 2-yr surface-satellite-SCM data (2000-2001).
We have set up a permanent website for publishing the results to the scientific community (http://people.aero.und.edu/~dong/result.html). It is our goal to eventually improve the representation of clouds in climate models and to have more accurate climate predications using satellite and surface observations.
