Abstract - Two methods of cloud masking tuned to Malaysian conditions have been developed, based on spectral analysis and Principal Components Analysis (PCA) of MODIS data. In the spectral approach, thresholds were applied to four reflective bands (1, 2, 3, and 4), three thermal bands (29, 31 and 32), the band 2/band_1 ratio, and the difference between band 29 and 31 in order to detect cloud. The PCA test applied a threshold to the first principal component derived from the seven quantities used for spectral analysis. Cloud detections were compared with the standard MODIS cloud mask, and their accuracy was assessed using reference images and geographical information on the study area.
Keywords: Cloud masking, spectral analysis, Principal Components Analysis , reflectance, brightness temperature
1. INTRODUCTION
Typically, 50% of the Earth’s surface is covered by cloud at any time, where cloud is defined as a visible mass of condensed water droplets or ice crystals suspended in the atmosphere above the Earth's surface. In remote sensing, clouds are generally characterized by higher reflectance and lower temperature than the background. Thick opaque cloud blocks almost all information from the surface or near surface, while thin cloud has some physical characteristics similar to other atmospheric constituents. Misinterpretation of cloud may result in inaccuracy of various remote sensing applications, ranging from land cover classification to retrieval of atmospheric constituents (e.g. in air pollution studies).
Several cloud detection and masking studies have been reported in the literature. However, most of these algorithms were designed for the global scale (Rossow & Gardner 1993; Ackerman et al 2002), and little e...
... middle of paper ...
...ration mapping. Photogrammetry Engineering and Remote Sensing, 57, p.1163-1169.
Rossow, W.B., & Gardner, 1993. Cloud detection using satellite measurement of infrared and visible radiances for ISCCP. Journal of Climate, 6, p.2341 – 2369.
Saunders, R. W. & Kriebel, K. T., 1988. An improved method for detecting clear sky and cloudy radiances from AVHRR data. International Journal of Remote Sensing, 9, p.123 –150.
Saunders, R.W., 1986. An automated scheme for the removal of cloud contamination form AVHRR radiances over Western Europe. International Journal of Remote Sensing, 7, p.867 – 886.
Swain, P. H., & Davis, S. M., 1978. Remote Sensing: The Quantitative Approach. New York: McGraw-Hill.
Yhann, S. R. & Simpson, J. J., 1995. Application of neural networks to AVHRR cloud segmentation. IEEE Transactions on Geoscience and Remote Sensing, 33, p.590 – 604.
Hess, D., McKnight, T. L., & Tasa, D. (2011). McKnight's physical geography (Custom ed. for California State University, Northridge ; 2nd Calif. ed.). New York: Learning Solutions.
National Weather Service. National Oceanic and Atmospheric Association, 5 Jan. 2010. Web. 2 Feb. 2010. .
Landsat Project Science Officeat NASA’s Goddard Space Flight Center. Landsat Glacier Bay. 2003. USA. Visible Earth NASA. Web. 16. Mar. 2014.
scattering of thin, high clouds. From a vantage point atop one of seven hills I
Stephen V. Stehman, “Selecting and interpreting measures of thematic classification accuracy”. Remote Sensing of Environment, Vol. 62, No.1, pp.77–89, 1997.
Glickman, Todd S. (ed.) (2000). Glossary of Meteorology (2nd ed.). American Meteorological Society. ISBN 978-1-878220-34-9.
2. Nemery B, HoetPH. Nemmar A. (2001). The Meuse Valley Fog of 1930: an air pollution disaster. Lancet. 357(9257): 704-8
Ever wonder what the atmosphere consists of? What's it made out of, what type of weather patterns are there, what does a hurricane look like, or other natural phenomenon's of today's weather ? Well America, hopefully now we can! Meteorology is the study of the atmosphere and the effects it has on our weather. Climatology focuses on how atmospheric changes alter the world’s climates, aeronomy is the study of the upper parts of the atmosphere. Meteorology focuses on the lower parts of the atmosphere, primarily the troposphere, where most weather takes place. It has been released that under the supervision of NASA, President Dwight D Eisenhower and the National Oceanic and Atmospheric Association (NOAA) that they have launched a satellite called TIROS 1 out of Cape Canaveral, Florida that will observe, record, and transmit data back to headquarters. The first ever weather satellite has arrived and with much hope will change weather prediction for the future.
"The Optical SETI Resource for Planet Earth." The Columbus Optical SETI Observatory. 1999. Columbus Observatory. 27 January 2000 http://www.coseti.org/.
"Climate and CO2 in the Atmosphere." Climate and CO2 in the Atmosphere. University of California, San Diego, 2002. Web. 26 June 2014. .
Now what causes all this chaos is a mixture of gases. “Greenhouse gases are transparent to certain wavelengths of the suns radiant energy, allowing them to penetrate deep into the atmosphere or all the way into the Earth’s surfac...
The observed changes on Earth generally depict a positive feedback loop, because surface, air, and water temperatures are warming and albedo is decreasing. Research is clear that the changes in temperature, ocean ice cover, and albedo are contributing to a positive feedback cycle. However, clouds remain a massive source of uncertainty in predicting how much the climate will change.
Web. The Web. The Web. March 26, 2014 Ncdc.noaa.gov. Web.
Atmospheric scientists first used the term “Greenhouse-Effect” in the early 1800’s. It was used to describe the naturally occurring functions of trace gases in the atmosphere and did not have any negative connotations. In the recent decades, we often hear about the term greenhouse effect in somewhat negative terms. It is important to know that without the greenhouse effect life on earth as we know it would be impossible. In the atmospheric greenhouse effect, the type of surface that sunlight first encounters is the most important factor. Forests, grasslands, oceans’ surface, ice caps, deserts, and cities all absorb, reflect, and radiate radiation differently. Sunlight falling on a white glacier surface strongly reflects back into space, resulting in minimal heating of the surface. Sunlight falling on a dark desert soil is strongly absorbed and contributes to significant heating of the surface and lower atmosphere. Cloud covers also affect greenhouse warming by both reducing the amount of solar radiation reaching the earth’s surface and reducing the amount of radiation energy emitted into space. Although the greenhouse effect is a naturally- occurring process, humans have recently ampl...
Precipitation: Clouds in the air drop rain on land in the form of water, hail or snow.