Does anyone know how to download TRMM 3B42 time series data? - r

Question

I'm trying to download TRMM 3B42 3-hour binary data for a given time span from this NASA FTP server.
There is an excellent code made by Florian Detsch to download the daily product (here is the link: https://github.com/environmentalinformatics-marburg/Rsenal/blob/master/R/downloadTRMM.R) included in the GitHub-only Rsenal package. Unfortunately it is not working for the 3-hour data.
I changed the code:
downloadTRMM <- function(begin, end, dsn = ".", format = "%Y-%m-%d.%H") {
## transform 'begin' and 'end' to 'Date' object if necessary
if (!class(begin) == "Date")
begin <- as.Date(begin, format = format)
if (!class(end) == "Date")
end <- as.Date(end, format = format)
## trmm ftp server
ch_url <-"ftp://disc2.nascom.nasa.gov/data/TRMM/Gridded/3B42_V7/"
## loop over daily sequence
ls_fls_out <- lapply(seq(begin, end, 1), function(i) {
# year and julian day (name of the corresponding folder)
tmp_ch_yr <- strftime(i, format = "%Y%m")
#tmp_ch_dy <- strftime(i, format = "%j")
# trmm date format
tmp_dt <- strftime(i+1, format = "%Y%m%d.%H")
# list files available on server
tmp_ch_url <- paste(ch_url, tmp_ch_yr, "", sep = "/")
tmp_ch_fls <- tmp_ch_fls_out <- character(2L)
for (j in 1:2) {
tmp_ch_fls[j] <- paste0("3B42.", tmp_dt, "z.7.precipitation",
ifelse(j == 1, ".bin"))
tmp_ch_fls[j] <- paste(tmp_ch_url, tmp_ch_fls[j], sep = "/")
tmp_ch_fls_out[j] <- paste(dsn, basename(tmp_ch_fls[j]), sep = "/")
download.file(tmp_ch_fls[j], tmp_ch_fls_out[j], mode = "wb")
}
# return data frame with *.bin and *.xml filenames
tmp_id_xml <- grep("xml", tmp_ch_fls_out)
data.frame(bin = tmp_ch_fls_out[-tmp_id_xml],
xml = tmp_ch_fls_out[tmp_id_xml],
stringsAsFactors = FALSE)
})
## join and return names of processed files
ch_fls_out <- do.call("rbind",ls_fls_out)
return(ch_fls_out)
}
getwd()
setwd("C:/Users/joaoreis/Documents/Bases_Geograficas/trmm_3h/")
fls_trmm <- downloadTRMM(begin = "2008-01-01.00", end = "2008-01-05.00")
fls_trmm
But I get the following error:
trying URL
'ftp://disc2.nascom.nasa.gov/data/TRMM/Gridded/3B42_V7//200801//3B42.20080102.00z.7.precipitation.bin'
Error in download.file(tmp_ch_fls[j], tmp_ch_fls_out[j], mode = "wb")
: cannot open URL
'ftp://disc2.nascom.nasa.gov/data/TRMM/Gridded/3B42_V7//200801//3B42.20080102.00z.7.precipitation.bin'
In addition: Warning message: In download.file(tmp_ch_fls[j],
tmp_ch_fls_out[j], mode = "wb") : InternetOpenUrl failed: '' Called
from: download.file(tmp_ch_fls[j], tmp_ch_fls_out[j], mode = "wb")
Does anyone know how to fix it using R?
Thanks!

Answer 1

As of commit 909f98a, I have enabled the automated retrieval of 3-hourly data from ftp://disc3.nascom.nasa.gov/data/s4pa/TRMM_L3. Make sure you have the latest version of Rsenal installed using
devtools::install_github("environmentalinformatics-marburg/Rsenal")
and then have a look at the examples in ?downloadTRMM. For now, the function supports both character (requires 'format' argument passed on to strptime) and POSIXlt input. For example, something like
downloadTRMM(begin = "2015-01-01 12:00", end = "2015-01-03 12:00",
type = "3-hourly", format = "%Y-%m-%d %H:%M")
to download 3-hourly data from 1-3 January 2015 (noon to noon) should now work just fine.
Note that in contrast to the FTP server you mentioned, the data comes in .HDF format and a rasterize method has not been implemented so far, meaning that you have to deal with the container files yourself. I'll try to figure out something more convenient soon regarding the automated rasterization of the data.