How to read TRMM hdf data by Matlab (1A,2A )

Maybe lots of people also face the same problem when they try to use TRMM data. Here, I want to write down every steps as detail as possible to make sure that people who have no idea can operate this useful data easily.


Step1: Make sure your personal computer is installed with Matlab(any version is available )

Step2：Download the data from NASA website
http://mirador.gsfc.nasa.gov/cgi-bin/mirador/presentNavigation.pl?tree=project&project=TRMM&dataGroup=Orbital&CGISESSID=66232b166b683630dfde5075b086bba4&location=(-90,-180),(90,180)
and choose by date and make sure the orbits of TRMM in your data can cover the domain you want to select.
(in 2A25 you can find a logo near the size information, you can use it to check the orbit of your data)












Step3 :Use Matleb intrinsic function hdftool

Step4: There will be a message box popping out

Step 5:expand the column and select the data that you want to import
EX: find the scan navigation,which can show the track of your satellite.
you can use "import" bottom or the import command to get the matrix you want.

Step6:the dimension of matrixes have different meanings

if the dimension is 9249*1--->9249=time step,1=the value of measure on the Nadir(星下點)
if the dimension is 9249*49--> 9249=time step,49=the 49 pixels near the Nadir
if the dimension is 9249*49*2 (or 9249*49*6)--> 2 and 6 can be different parameter for the RADAR function
if the dimension is 9249*49*80--> 80 means the vertical measurement(cross section)


For more detail information can be found in the guide book
http://www.eorc.jaxa.jp/TRMM/document/text/handbook_e.pdf

Interesting raining in winter Taiwan

                                          http://www.cwb.gov.tw/V7/observe/radar/?type=2

This RADAR reflectivity  shows one of the most common raining type in winter Taiwan.

(1) Local precipitation due to winter monsoon(north-easterly) and topography (raining region is concentrated in 宜蘭  and 基隆). The cloud of this type precipitation is relative shallow(stratus cloud) and the maximum diabatic heating level is around 850hPa
(2)The convergence zone between land-sea breeze and winter monsoon , its raining region is near the east coast of Taiwan. This type of raining is getting stronger in the midnight when the land breeze is the strongest. It's heating profile is close to deep convection but more stationary (it can last over 3 days)
 (3)"Overrunning". the warm-moisture air from south China sea is tilting by northeasterly, and when the free troposphere is stable(with strong stratification), the feature of gravity wave becomes more obvious. Its raining region can go across from south to north Taiwan.

The speed of gravity wave we saw on the RADAR is around 70km/hr=19.45m/s. It's easy to say this is 3or 4th internal mode from a simplification wave speed diagnostic equation. The maximum heating level is around
800hPa~700hPa.

External Mode~300m/s
1st internal mode~60m/s
2st internal mode~(60/2)=30 m/s
3st internal mode~(60/3)=20 m/s
4st internal mode~(60/4)=15m/s
...
nth. internal mode~(60/n)=... (m/s)
..
and the maximum heating profile is also easy to find on the following  picture.