******************************************************************************* * * * Welcome to the NCEP/NCAR Reanalysis CD-ROM. This CD-ROM contains one year * * of selected analyses from the NCEP/NCAR Reanalysis Project. * * * * Problems and questions should be directed to: * * * * Dr. Wesley Ebisuzaki * * Climate Prediction Center W/NP52 * * 5200 Auth Road Room 605 * * Camp Springs, MD 20746 USA * * * * email:wd51we@sun1.wwb.noaa.gov * * * * * * * * ************************************************************************* * * * To run the demo from Windows95, enter E:\DEMO.BAT at the RUN * * * * option from the START menu, assuming the cd-rom is device E:. * * * * To run the demo from MS-DOS or the MS-DOS prompt, enter * * * * E: * * * * DEMO * * * ************************************************************************* * * * * * ******************************************************************************* TABLE OF CONTENTS ----- -- -------- I) Introduction II) Data Organization and Access Software III) The 30-Second Plot IV) Other Important CD-ROM Documents V) Changes I. INTRODUCTION This CD-ROM contains one year of selected fields from the NCEP/NCAR Reanalysis Project. The goal of this reanalysis project is to provide the climate research, monitoring, and modeling communities with analyses that span the last 40 years that have been generated from a stable, invariant analysis system. To date, there has been little choice but to use analyses that supported real-time weather forecasting, and changes in these systems introduced inhomogeneities that could be erroneously interpreted as changes in the 'climate'. The quality of these analyses should be superior to earlier 'operational' analyses because: o a state-of-the-art data assimilation system is used, o more observations (later data cut-off time) are used, o quality control has been improved, and o the model/data assimilation procedure will remain essentially unchanged during the entire NCEP/NCAR Reanalysis project (1957-1995) and for the CDAS (Climate Diagnostics Assimilation System). (Of course there will be some changes as the types and numbers of observations changes over the years.) A more comprehensive description of the NCEP/NCAR Reanalysis Project can be found in file "TEXT\INTRO\REANAL.INF" (published BAMS, March 1996). II DATA ORGANIZATION and ACCESS SOFTWARE The vast majority of the reanalysis products on this CD were written in GRIdded Binary (GRIB), which is a self-documenting, international standard. For those who desire more information about GRIB, see documentation in file "TEXT\GRIB\GUIDE.TXT". However, since GRIB can be difficult to read without the proper software, we have provided two methods for accessing the GRIB data on this CD. First, the PC version of "Grid Analysis and Display System" (GrADS) is included. GrADS is an extremely powerful, useful, and easy-to-use data manipulation and display package that was developed by Brian Doty of the Center for Ocean-Land-Atmosphere Studies in Calverton, Maryland. The Unix versions of GrADS are available at no charge (see PROGRAMS\GRADS.DOC). The PC version of GrADS is in the "PROGRAMS\PCGRADS" directory. This version requires a PC with a 386 with a math co-processor, 486DX or a Pentium CPU. For more information on GrADS, including instructions on obtaining the latest version of pc-GrADS, see the file "PROGRAMS\GRADS.DOC". The second method to access GRIB data is through the use of a C language program developed at NCEP called 'wgrib', which is also provided on this CD. This program requires a C compiler and a 32-bit (or more) computer and was written expressly for support of the NCEP/NCAR Reanalysis project. Complete documentation for 'wgrib' appears in file "PROGRAMS\WGRIB\README" on this CD. 'wgrib' performs the following functions: o inventories files, o deletes records, o rearranges records, o converts GRIB to IEEE, binary and text. The data is stored in the following formats. 'Horizontal' fields (maps) are stored in GRIB on either: a) 144 x 73, 2.5 x 2.5 degree grid b) 192 x 94 Gaussian grid (flux data) The first data point is for the northern-most point at 0E. The second point is is slightly east of the first point. Vertical Cross-sections are stored in f77 IEEE on either: a) 73 x 17 vertical cross section prs levels: 1000 925 850 700 600 500 400 300 250 200 150 100 70 50 30 20 10 b) 73 x 11 vertical cross section theta surfaces: 270 280 290 300 315 330 350 400 450 550 650 For more information, see TEXT\TABLE.IDS. A program, PROGRAMS\X2GRAD\X2GRAD.C can be used to make the files GrADS compatible. III The 30-Second Plot One goal in the design of this CD-ROM was to make if fast to use. Suppose you happen to be interested in the weather on February 2, 1962. You should be able to take the CD-ROM for 1962, put it into your computer, and be looking at the 500 mb heights in half a minute. 0) GrADS must be installed. A version of GrADS for the PC is on the CD-ROM, see README.DOS. Workstation versions are available from Brian Doty, COLA (see PROGRAMS\GRADS.MSG). 1) Insert CD-ROM in to PC, or workstation (10 seconds) 2) On a workstation, you must mount the cd-rom (system specific) (6 seconds) Assume the cd-rom is mounted at /cdrom (Unix) or e: (MS-DOS). 3) Start GrADS (4 seconds) 4) Open a control file (5 seconds) example: ga> open /cdrom/ctl/at00z12z/hgt.prs (UNIX, lower-case cd-rom file names) example: ga> open /cdrom/CTLUC/AT00Z12Z/HGT.PRS (UNIX, upper-case cd-rom file names) example: ga> open /cdrom/CTLSEMIC/AT00Z12Z/HGT.PRS;1 (UNIX, upper-case with semicolon cd-rom file names) example: ga> open e:/ctl/at00z12z/hgt.prs (MS-DOS, assuming cd-rom is device e:) Note: to check the contents of the file, type ga> query file 5) Display a plot (5 seconds) example: ga> set time 2feb62 ga> set lev 500 ga> d hgt Note: The 30-second plot will only work on PC's and certain UNIX workstations (see README.UNX). A complete listing of the data files and contents can be found in TEXT\LISTS\FILELIST and TEXT\TABLE.IDS. IV) Other Important CD-ROM Documents See file(s) ___________ 1) About the NCEP/NCAR Reanalysis Project .... TEXT\INTRO\REANAL.INF 2) Directory structure of this CD ............ CD.ORG 3) Data organization, access information ..... README.DOS, README.UNX, CD.ORG 4) Table of data fields on this CD ........... TEXT\TABLE.IDS (units, filename interpretation, i.e., Rosetta stone) (list of data files) TEXT\LISTS\FILELIST 5) About GRIB (GRIdded Binary) ............... TEXT\GRIB\GUIDE.TXT 6) Details about the Reanalysis Project ...... TEXT\DETAILS\*.* 7) Data Access Software ...................... - Analysis & Display ("GrADS") ........... PROGRAMS\GRADS.MSG, README.DOS PROGRAMS\PCGRADS\GRADSCRU.TXT - Read/inventory/convert ("wgrib")......... PROGRAMS\WGRIB\README V) Changes 6/98: CD-ROMS for years before 1974 will not have observed outward long wave radiation for obvious reasons. 6/98: updated demo (references to obs OLR deleted) 6/98: updated FILELIST, DATALIST 5/15/98: GPCPRAIN.GRB (monthly observed/estimated precipitation) from GPCP has been updated. 5/15/98: MRGDRAIN.GRB (monthly observed/estimated precipitation) has been deleted. 5/15/98: CMPORAIN.GRB (monthly observed/estimated precipitation) from Xie-Arkin has been added. This is the so-called cmapo product. CPC Merged Analysis of Precipitation CPC Merged Analysis of Precipitation (CMAP) is constructed by merging gauge observations and 6 kinds of satellite estimates (GPI, OPI, MSU, SSM/I scattering and SSM/I emission). First, to reduce the random error inherent in the individual data sources, the 6 kinds of satellite estimates are combined linearly through the Maximum Likelyhood Estimation Method in which the combination coefficients are inversely proportional to the individual error variances. The output of this first step is then blended with the gauge data to remove the bias, in which the first step output is used to define the 'shape' while the gauge data are used to determine the magnitude of the precipitation fields. Validation tests showed that the merged analysis has improved quality compared to the individual data sources, with both the random error and bias reduced significantly. Reference: Xie, P, and P.A. Arkin (1997): Global Precipitation: A 17-year monthly analysis based on gauge observations, satellite estimates and numerical model outputs. Bull. Amer. Meteor. Soc., 78, 2539- 2558. 5/15/98 upgraded wgrib from the ftp site 5/15/98 grib2ctl has been replaced by the perl version 9/23/96 GPCPRAIN.GRB and MRGDRAIN.GRB (monthly observed/estimated precipitation) were both changed from the BAMS (1996) CD-ROM. Updated versions can be found in DATA\OBSERVED. For documentation see BAMS (1996). 9/23/96 EMC's corrected precipitation fields were added to DATA\DAILY and MONTHLY\SFC. (look for "Reanalysis" under http://www.ncep.noaa.gov). This new field has units of Kg/m/m/s and GRIB identifier of 180. 9/23/96 Daily averaged snow amount (WEASD) was removed for lack of space. Note that text and software may not reflect these last minute changes.