2.8 Observing wind and waves:
hurricane Katrina

Wind and waves observed in the case of an extreme meteorological event.

Hurricane Katrina, in August 2005, was one of the most devastating hurricanes in the US history.

Data used

We will take advantage of the fact that several satellites were providing data at the time (August 2005), and use the GDRs from Envisat, Jason-1, Topex/Poseidon and GFO.

Methodology

We will use the Basic Radar Altimetry Toolbox to have a loook at significant wave heights and wind speed modulus as provided in the standard datasets.

Geographic extraction

We will be looking at individual ground tracks (one for each satellite), between 17°N and 30°N

Data selection and BRAT Datasets definition

We have to select the tracks we wish to work on.
To select the right tracks, you can have a look at the ground track maps that may be provided with the data handbook.

Katrina at different dates with T/P (red) and Jason-1 (blue) passes, Envisat (and ERS-2), and GFO passes. The images were taken within 20 minutes of the altimeter passes. (Credits NOAA/Altimetrics LLC)

The tracks and cycles closest to hurrican Katrina are:
-   Envisat, cycle 040, pass #351
-   Jason-1, cycle 134, pass #026
-   Topex/Poseidon, cycle 477, pass #026
-   GFO, cycle 157, pass #409

Name the dedicated BRAT workspace you are using for this job. Within this workspace, name your datasets; We will need 4 datasets: one for each satellite, with one file in each of them.

BRAT Operations definition

In the 'Operations' menu, name your operation (you will need 4 operations, too, one for each satellite), then select your dataset and data record. In 'Data mode' keep Y=F(X) for a plot.
Enter your data expression:
we will define two data fields, one for Significant Wave Height in Ku band, one for Wind speed modulus.
For the X field the variable is the latitude (beware that default is longitude, so you have to change it, and change the data type)

The only thing we will put in 'Select expression' is the ocean flag. "Classical" data editing (the one provided as pre-defined formula within BRAT) is not in order here, since we are dealing with a phenomena out of the ordinary (and thus over usual thresolds). Optionally, you can constrain the number of values used to compute a 1Hz value (depending on the satellite; see the ocean data editing for ideas of significant values) and the wet tropospheric correction (between -1 and 1 m)