gsMAP rainfall

[Nguyen Hong Quang]

Good morning,

I am using gsMAP raifall of JAXA as precipitation input to the KINEROS2 model.

The data include images in hdf extension.

I just clip the rainfall images for my study area and do average and then get a series of rain depth for the event.

Dose anyone know the best way to use these data? Is there any option to use the images (*.hdf) directly?

I looking for your helps, thanks!

Best regards,

Quang

[Shea]

Hi Quang,

K2 cannot read the JAXA GSMaP files directly. You should be able to download files from the TXT folder on the GSMaP FTP site and use the extracted CSV files in ArcMap via the Add XY Data followed by the Point to Raster Tool. You could also download the binaries and convert them to rasters using the *Float to Raster tool in ArcMap. To use the data from the converted rasters in K2, you could do a zonal average of each raster using the watershed as your zone, and then sum the zonal averages to get total precipitation depth. When creating the precipitation file in AGWA, you can use the user-defined depth option and enter the total precipitation depth and number of timesteps to disaggregate the event into a hyetograph using the SCS Type II methodology.

Alternatively, instead of summing the zonal averages for a total precipitation depth and having AGWA disaggregate it into a hyetograph, you could use the zonal average of each raster as hourly breakpoint data for creating your own hyetograph. The precipitation file could be created using either the user-defined hyetograph option in AGWA or by creating the precipitation file using a text editor using an existing file as a guide.

Hope that's helpful, and apologies for not responding sooner, I lost track of the support forum for several months.

Shea

*Converting the binary dat files the GSMaP data comes in was a multi-step process and a little tricky because of the way it uses longitude from 0 to 360 instead of -180 to 180, so if the CSV data works for you I'd recommend using that. If you want to use the binary files, read on. After extracting the gsmap_nrt.YYYYMMDD.HHNN.dat file, the extension needs to be changed to .flt for ArcMap to recognize it. Then a header file needs to be created with the same name as the .flt file but with the extension .hdr. Even though the DataFormatDescription.pdf that comes with the data indicates the upper-left corner is 0.05 degrees East and 59.95 degrees North, the header file requires the lower left corner, so YLLCENTER should be -59.95, and the XLLCENTER should be -179.95 because ArcMap doesn't recognize a 0 to 360 longitude system. Because the raster has been shifted 180 degrees east, a custom projection must be created and used with this raster where the Prime Meridian is shifted 180 east to compensate. The CSV files are split up regionally and have the correct coordinates based on a -180 to 180 longitude system, so the Prime Meridian shift and custom projection are not necessary to use them.

NCOLS 3600
NROWS 1200
XLLCENTER -179.95
YLLCENTER -59.95
CELLSIZE 0.1
NODATA_VALUE -99.0
BYTEORDER LSBFIRST

[Nguyen Hong Quang]

Dear Shea,

many thanks for the response. I did it in the same way as your second option.

I think your answer is still valuable for me and others who would like to use JAXA GSMaP rainfall.

Thanks again and have a nice day!

Best wishes,

Quang

Vào ngày 8:08 Thứ Sáu, 10 tháng 2 2017, Shea <isb...@gmail.com> đã viết: