[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

20010816: 20010815: mail returned regarding NEXRAD data

Wil,

The National Climatic Data Center archives Level II data as part of
their federal mission. The fees charged are part of the cost recovery
process. Unidata has nothing to do with that. 

The level III data are available on NOAAPORT as well as the
weather.noaa.gov ftp server (the ftp server has additional fields not
available on NOAAPORT at this time).

Steve Chiswell
Unidata User Support



>From: Wil Wollheim <address@hidden>
>Organization: UCAR/Unidata
>Keywords: 200108161206.f7GC6l126598

>
>
>Hi Steve,
>
>Sorry for the hastle about the return e-mail - it should be fixed now.
>
>Thanks for responding to the radar query.  It sounds like we will be able
>to get ascii data from the NEXRAD III files (via gradr and glist), but
>that the data will only be in relatively broad categories.  
>
>With regard to the the NEXRAD level II data, is that  available only for a
>fee?  It seems expensive (the NCDC web site said $ 100 for two days and 25
>for each additional day).  Do unidata members have access to this data
>without the steep cost?  If not, the level III categories will probably
>work for us as well.
>
>Thanks again for your help.
>
>Wil
>
>Water Systems Analysis Group
>Complex Systems Research Center
>Morse Hall
>University of New Hampshire
>Durham NH 03824
>Voice: (603) 862-0812
>FAX: (603) 862-0587
>E-mail: address@hidden
>
>On Wed, 15 Aug 2001, Unidata Support wrote:
>
>> 
>> Wil,
>> 
>> Your return address on your computer sending mail:
>> address@hidden 
>> is apparently invalid. That should be corrected to properly identify 
>> what your return address is.  I have re-attatched my response below.
>> 
>> I know Tim received my reply.
>> 
>> Steve Chiswell
>> Unidata User Support
>> 
>> 
>> 
>> Will,
>> 
>> The NEXRAD data on the NOAAPORT broadcast are NEXRAD Level III
>> products. That is, the data have already been discretized into
>> data ranges and have had sampling algorithms applied.
>> For raw data, you would want LEVEL II archived data from NCDC.
>> 
>> The documentation on NEXRAD Level III data is available from the
>> National weather service interface control documents:
>> http://www.roc.noaa.gov/ssb/cm/icd_downloads.asp
>> a synopsis of the radar data header from the RDA->RPG control
>> document above is: http://www.ofa.noaa.gov/~amd/1-90019-ex5.pdf
>> 
>> A higher level description of the data is in our online email archives:
>> http://www.unidata.ucar.edu/projects/coohl/mhonarc/MailArchives/datastream/m
> sg01569.html
>> 
>> 
>> All the packages (GEMPAK, McIDAS, and WXP) have routines which can display
>> the data products, but do not readily provide a method for interrogating
>> the data since the products have already been processed into the radial or 
>> raster displays at the radar PUP.
>> 
>> Unidata does not provide any access to WXP. You would have to contact
>> Unisys directly for that package.
>> 
>> GDRADR is a program I developed for GEMPAK and provided in the
>> releases including and since 5.6.C.1. This program allows the user to
>> create a gridded data set from the NEXRAD Level III (NIDS) products.
>> Once the data is in a grid point format, you could use any of the
>> GEMPAK grid programs to manipulate the data. GDLIST will list out the data
>> values from a gridded data set in ascii. GEMPAK provides a library of
>> grid functions (such as the GWFS gaussian weighted sampling function)
>> which can be used to manipulate the data.
>> 
>> When you say you want "actual numbers", you need to understand that
>> the NIDS data, as products, are sample groups. That is, all values
>> in a range are assigned a discrete integer (0 - 15). So the products
>> are generally 8 or 16 levels of data bins. So, a "6" may represent
>> precipitation from 1.5" to 2.0" for example. As I mentioned above, if
>> you want the actual radar value, say 1.643", you would want to use Level II
>> data.
>> 
>> Steve Chiswell
>> Unidata User Support
>> address@hidden
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> >From: Wil Wollheim <address@hidden>
>> >Organization: UCAR/Unidata
>> >Keywords: 200108131408.f7DE8s119785
>> 
>> >
>> >Dear Steve,
>> >
>> >We are trying to convert the radar images (NTPxxx) we receive via ldm into
>> >a format that we can import into a GIS system.  Among the things we are
>> >trying to do is:
>> >
>> >1) clip the radar image from any given radar station to relatively small
>> >areas (about 100 - 200 km2 areas)
>> >
>> >2) calculate average precipitation for those areas, so we would like to
>> >use the actual numbers for each grid cell (i.e. we would like to
>> >have the radar data in ascii format).
>> >
>> >My question is, how do we proceed to do this?  We've looked through
> >the documentation and haven't been able to track down a method.  Did
>> >we miss something obvious?  Among the questions we have is 
>> >
>> >1) what format is the radar data in when we get it via the ldm
>> >
>> >2) how do we convert that format into ascii text?
>> >
>> > We are members of Unidata and have Gempak on our server.  Will your new
>> >program, gdradr, be able to do this?  How do we get a hold of gdradr or do
>> >we need to reload the new version of Gempak?  
>> > 
>> >Also, can unidata users use WXP provided by UNISYS? In particular, they
>> >have rad and radcvt programs that we thought we could use, but these
>> >require a licence.  Just wondering if unidata covers that as well.
>> >
>> >Thanks for your help!
>> >
>> >Wil Wollheim
>> >
>> >
>> >
>> >Water Systems Analysis Group
>> >Complex Systems Research Center
>> >Morse Hall
>> >University of New Hampshire
>> >Durham NH 03824
>> >Voice: (603) 862-0812
>> >FAX: (603) 862-0587
>> >E-mail: address@hidden
>> >
>> >
>> >
>> >
>> 
>> ****************************************************************************
>> Unidata User Support                                    UCAR Unidata Program
>> (303)497-8644                                                  P.O. Box 3000
>> address@hidden                                   Boulder, CO 80307
>> ----------------------------------------------------------------------------
>> Unidata WWW Service                        http://www.unidata.ucar.edu/     
>> ****************************************************************************
>> 
>> --QAA21358.997820989/eos-f.sr.unh.edu--
>> 
>> 
>> 
>> ------- End of Forwarded Message
>> 
>> 
>
>
>