Figure 11Research flowchart.
an idealization of atmospheric motion. In the form of isobaric coordinate, the horizontal
pressure gradient force can be transformed with the function of geopotential so that the
equation becomes
27 ..
..........
ˆ
p
h v
k f
Dt h
v D
It can be seen that the gradient of geopotential implicit the same horizontal wind
speed at all heights in the atmosphere whereas in height coordinates the velocity of
horizontal wind depends on the rate of pressure gradient which varies directly with
changes in air density.
III METHODOLOGY 3.1
Location and Time
The study
was conducted
in the
Laboratory of Meteorology and Atmospheric Pollution,
Department of Geophysics and Meteorology, Bogor Agricultural University and
in the Division of Climate Modelling,
National Institute of Aeronautics and Space LAPAN
Bandung from February until May 2011.
3.2 Tools and Materials
The sofwares used in this study are listed as follows:
ENVI 4.5, ER Mapper 7.1, Global Mapper v12, Ferret v6.7, ArcGIS 9.3,
Matlab R2010b,
Notepad++ 5.9,
Microsoft Office 2007 The materials consist of three main sources of
data: a. MODIS Terra level 1B L1B data;
covering Bogor and its surroundings. Data acquisition date: October 1,
2006. Band used: Thermal Infrared Bands TIR 31
10.780 m - 11.280 m and 32 11.770 m - 12.270
m. Spatial resolution: 1 km. http:ladsweb.nascom.nasa.govdata
search.html b. DEM data Digital Elevation Model
with 90 x 90 m spatial resolution http:srtm.csi.cgiar.org
3.3 Data Processing
The approaching method in this study is derived from the momentum equations based
on Newton’s second law of motion which
applied to TerraMODIS L1B data set. Generally, the steps taken can be seen in
Figure 11.
3.3.1 Bowtie Correction
The MODIS L1B data set contains calibrated
and geolocated
at-aperture radiances for 36 discrete bands covering the
part from 0.4
m to 14.4 m of
electromagnetic spectrum. These data were generated from MODIS level 1A scans of raw
radiance MOD01. Although the level 1B data have been calibrated and geolocated, it
needs to be corrected due to distortion caused by the characteristics of MODIS sensor and
the Earth’s curvature; known as the Bowtie effect. The elimination of bowtie effect was
done with Modistool in ENVI.
