Computer Modeling Laboratory 9

Written report due: 8 November

Passive remote sensing of clouds.

RELATED MATERIALS:
Lecture 19

ADDITIONAL MATERIALS:
Platnick, S., et al., 2003: The MODIS cloud products: Algorithms and examples from Terra. IEEE Trans. Geosci. Remote Sens., 41, 459-473.
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TASK 1

Instruction:to compute the TOA radiances click on RUN RT code

The solar reflectance technique enables to retrieve the optical depth and effective drop size of clouds using radiances measured by a passive satellite sensor in the solar spectrum (see Lecture 19).

Using MODIS 2.1 and 0.86 μm channels, investigate whether this technique is capable of retrieving the optical depth and effective particle size of low level clouds over bright deserts (Asur = 0.3). Both MODIS channels have a band width of 0.05 μm. Take same solar and viewing zenith angles as in Figure 19.9, Lecture 19.

 

TASK 2

To access MODIS Cloud Products:

  • To access MODIS RGB images: Images -> MODIS Standard -> L1B Granules -> Launch L1b Images Page -> Terra Platform, Java Enabled -> 2008 -> Nov -> 01st
    https://modis-atmosphere.gsfc.nasa.gov/
  • Under PRODUCTS, select MODIS: Terra under All Sensors
  • Select MOD05_L2: MODIS/Terra Clouds 5-min L2 Swath 1km and 5km
  • Under TIME, select Single Data and Advanced; type in 2008-11-01 and click Save
  • Under LOCATION, select Enter Coordinates and type -10, -10, 10, 10 (for 10W, 10N, 10E, 10S)
  • Under FILES select the 10:25:00, 10:30:00, and 12:00:00 granules, then click Images
  • Download images for cloud fraction, cloud-top pressure, cloud optical depth and effective particle radius for the three time periods
  • To access MODIS RGB images: Images -> MODIS Standard -> L1B Granules -> Launch L1b Images Page -> Terra Platform, Java Enabled -> 2008 -> Nov -> 01st

1) Analyze cloud fraction images by comparing two RGB images for 10:25; 10:30 and 12:00 granules. Find a few instances when cloud fraction was retrieved incorrectly. Briefly discuss the possible reasons.
2) Using cloud-top-pressure and cloud optical depth images, identify a stratus cloud over ocean and over land. Compare retrieved effective particle radius for these cases. Do retrievals look reasonable (refer to table 9.1, Lecture 9)?
3) Identify a few cirrus clouds in RGB images and analyze retrieved cloud products, if any. Do the retrieved products look reasonable? Briefly discuss what might be causing problems in retrievals of ice clouds.