ECMWF 1 COM INTRO 2004: MARS Introduction MARS Introduction and basic concepts Computer User Training Course 2004 Carsten Maaß & Manuel Fuentes User Support, Data and Services Section

ECMWF 2 COM INTRO 2004: MARS Introduction Contents Introduction Meteorological content MARS language MARS architecture Retrieving data Practicals

ECMWF 3 COM INTRO 2004: MARS Introduction Introduction M eteorological A rchival and R etrieval S ystem Meteorological data (GRIB: fields, BUFR: observations) Large amount of data (size & number) Operational & Research environment Batch & interactive modes Large number of users with different requirements: large datasets rarely few fields very often Heterogeneous environment

ECMWF 4 COM INTRO 2004: MARS Introduction Introduction – MARS components Client/Server architecture Clients: workstations, supercomputers Servers: supercomputers, dedicated servers Several databases Tape library

ECMWF 5 COM INTRO 2004: MARS Introduction Introduction – Some figures 760 TBytes of data in fields Growing daily by 750 GByte: – 250 GB Operational data – 500 GB Research requests ( fields) per day Analysis, forecast and observations since 1957 (ERA-40) Operational forecast since 1985

ECMWF 6 COM INTRO 2004: MARS Introduction Meteorological content – Atmospheric model Atmospheric model (T511 L60) Analysis (synoptic hours: 00, 06, 12 and 18 UTC) – Surface – Model levels (60) – Pressure levels (21) – Isentropic levels Forecast (10 day forecast based on 00/12 UTC Analysis) – 3 hourly steps from 3 to 72 hours – 6 hourly steps from 72 to 240 hours

ECMWF 7 COM INTRO 2004: MARS Introduction Meteorological content – Wave model Wave model Coupled with atmospheric model Analysis (00, 06, 12 and 18 UTC) Forecast (to 10 days) European Shelf Model (Mediterranean) Analysis Forecast to 5 days

ECMWF 8 COM INTRO 2004: MARS Introduction Meteorological content – Boundary conditions Boundary Conditions Project (T511 L60) Analysis (3dVar at 00, 06, 12 and 18 UTC) Forecast (at 00/06/12/18 UTC to 96 hours)

ECMWF 9 COM INTRO 2004: MARS Introduction Meteorological content – EPS Ensemble Prediction System (T255 L40 at 00/12 UTC) 50 different forecasts with perturbed initial conditions Control forecast (to 21 days) Perturbed forecasts (to 10 days) Ensemble mean and standard deviation Extreme forecast index Forecast probabilities Clusters Tubes

ECMWF 10 COM INTRO 2004: MARS Introduction Meteorological content – Other ensemble FC Seasonal Forecast Atmospheric + Wave + Ocean models (00 UTC to 6 months) Ensemble forecast techniques (40 members) Different methods: with and without ocean data assimilation Monthly means Monthly Forecast Every two weeks (00 UTC to 32 days) Atmospheric + Wave + Ocean models Ensemble forecast techniques (50 members)

ECMWF 11 COM INTRO 2004: MARS Introduction Meteorological content - Multi-Analysis Ensemble Analyses from 4 Centres – NCEP – UK Met Office – Meteo-France – DWD 5 Forecasts (to 10 days at 12 UTC): 4 centres + 1 consensus

ECMWF 12 COM INTRO 2004: MARS Introduction Meteorological content – Monthly Means Averaged over each calendar month Atmospheric – Analysis – Forecast Wave – Analysis – Forecast

ECMWF 13 COM INTRO 2004: MARS Introduction Meteorological content – Special datasets Special Projects – ECMWF Re-Analyses (ERA-15, ERA-40) – DEMETER: Multimodel Ensemble for seasonal to Interannual prediction – PROVOST – ECSN-Hyretics ECMWF Research experiments Member States Research experiments Member States own model data

ECMWF 14 COM INTRO 2004: MARS Introduction Meteorological content – ERA-40 ERA-40 period: Sep 1957 – Aug 2002 Resolution: – Horizontal: T159L60, N80 (~1.125º) – Vertical: 60 ML, 23 PL, 15 PT, PV=±2 Analyses (3dVar) at 00/06/12/18 Forecasts at 06/18 to 6h and 00/12 to 36 h Monthly means, vertical integrals, observations … All Analysis data on-line 1 file per 1 month of data

ECMWF 15 COM INTRO 2004: MARS Introduction Meteorological content – Observations & Feedback Observations –Surface data –Vertical soundings –Upper-air data –Satellite Feedback Analysis Input Analysis Feedback

ECMWF 16 COM INTRO 2004: MARS Introduction Meteorological content – Archive plans Early delivery system Multi-model Seasonal Forecast Revised Monthly Forecast Forecast satellite images

ECMWF 17 COM INTRO 2004: MARS Introduction Meteorological content – Data formats WMO formats Fields in GRIB (GRid In Binary), ECMWF local extensions – Spherical Harmonics (upper-air fields, T511) – Gaussian Grid (surface fields, N256) – Latitude/Longitude (wave and ocean products) Observations in BUFR (Binary Universal Form Representation) – Instrument specific

ECMWF 18 COM INTRO 2004: MARS Introduction MARS language Mechanism to name archived fields Request syntax: verb, parameter1= value1, …= value2, parameterN= valueN verb: action to be taken (e.g. retrieve, list, read) parameter: predefined keyword (e.g. type, date, target) value: value assigned to the parameter

ECMWF 19 COM INTRO 2004: MARS Introduction MARS language verb and parameter=value separated by commas, but last one Spaces and tab characters are ignored *, ! and # comment until end-of-line Directives are not case sensitive Values: predefined names, numeric values or strings (filenames) Abbreviations: enough letters to uniquely identify keyword Acronyms: usually initial letters of names / is used as list separator specify pathnames in quotes

ECMWF 20 COM INTRO 2004: MARS Introduction MARS language – Retrieve request retrieve, action class= od, identification stream= oper, expver= 1, date= -3, date & time related time= 12, type= analysis, data related levtype= model levels, levelist= 1/to/60, param= temperature, grid= 2.5/2.5, post-processing target= analysis storage

ECMWF 21 COM INTRO 2004: MARS Introduction MARS language – Identification of archive classECMWF classification (od, rd, e4, …) stream expver repres domain origin system method origin (FC system) of the data (oper, wave, kwbc, enfo, seas, …) version of the experiment (01 operational, 11, aaaa) archived representation (sh, gg, ll) area covered by the data (Global, Mediterranean, …) origin (centre) of the data (kwbc, egrr, …) seasonal forecast operational system (1, 2) seasonal forecast ocean assimilation (0, 1, …)

ECMWF 22 COM INTRO 2004: MARS Introduction MARS language - Date & time timebase time or observation time (00, 06, 09:30, …) datebase date of the model (-1, , …) stepforecast time-step from base time (12, 24, 240, …) referencereference forecast time step for EPS tube (96,…) range observations: period in minutes from base time (360,…) ocean fields: extension of the time series/average fcmonthmonth from seasonal forecast base date (1, 6, …) fcperiodperiod, in days, for an averaged field (26-32)

ECMWF 23 COM INTRO 2004: MARS Introduction MARS language – Fields typetype of field (an, fc, …) levtypetype of level (pl, ml, sfc, pt, pv) levelistlevels for the specified levtype (off if levtype=sfc) parammeteorological parameter ( t, temperature, 130, ) numberensemble member ( 1, 2, …) channelbrightness temperature frequency band diagnostic, iterationsensitivity forecast products frequency, direction2-d wave spectra products product, section, latitude, longitude ocean products

ECMWF 24 COM INTRO 2004: MARS Introduction MARS language – Observations & images typetype of observations or images (ob, fb, ai, af, im) obstypeobservation subtype (s, air) or image channel identWMO observation station number or satellite identifier duplicateswhether duplicated observations are to be kept or not blockWMO block number for observation

ECMWF 25 COM INTRO 2004: MARS Introduction MARS language – Storage Unix pathnames (using /) have to be enclosed in quotes, e.g. target= /scratch/ms/gb/uid/analysis targetUNIX pathname where retrieved data is stored sourceUNIX pathname from where to read data fieldsettemporary storage; can be considered a MARS variable

ECMWF 26 COM INTRO 2004: MARS Introduction MARS language - Post-processing grid output grid mesh Latitude/longitude increments in degrees (2.5/2.5) Number of latitude from Pole to Equator (160) gaussiantype of Gaussian grid (regular, reduced) areadesired sub-area in degrees (north/west/south/east) framenumber of grid points from sub area inwards (5) resoltriangular truncation (319, auto, av) rotationlat/lon of South Pole accuracynumber of bits per data value in GRIB (16)

ECMWF 27 COM INTRO 2004: MARS Introduction MARS language – Execution control expectnumber of expected fields (1000, any, …) databasewhere to look for the data usehint about frequency of use (infrequent)

ECMWF 28 COM INTRO 2004: MARS Introduction MARS language – Values Single value, predefined names, numbers, mnemonics param = temperature List of values, separated by / step = 12/24/48 Range of values, using keywords: to, / and by date = /to/ step = 24/to/240/by/24

ECMWF 29 COM INTRO 2004: MARS Introduction MARS language – Values Expected number of fields is computed by multiplying number of values after expansion of ranges date = /to/ fields Certain parameters accept all as valid value levelist = all Most parameters accept off as valid value levtype = surface, levelist = off Not all possible combinations parameter = value name an archived field

ECMWF 30 COM INTRO 2004: MARS Introduction Request examples - Re-Analysis Retrieval of snow depth from the ERA-40 archive for November 1993, for all analysis base times. It retrieves 120 fields. retrieve, class= e4, stream= oper, expver= 1, date= /to/ , time= 00/06/12/18, type= an, levtype= sfc, param= sd, target= era sd

ECMWF 31 COM INTRO 2004: MARS Introduction Request examples - Ensemble forecast Retrieval of surface temperature and 10-m wind components (U and V), 20 first members of the EPS for 2 nd Jan 2001 for time steps 12, 36 and 60. It retrieves 180 fields. retrieve, class= od, stream= enfo, expver= 1, date= , time= 12, step= 12/36/60, type= pf, levtype= sfc, param= st/10u/10v, number= 1/to/20, target= perturbed.sfc

ECMWF 32 COM INTRO 2004: MARS Introduction Request examples – Operational analysis Retrieval of sea surface temperature for first 10 days of May 2002, all synoptic times. It retrieves 40 fields. retrieve, class= od, stream= oper, expver= 1, date= /to/ , time= 00/06/12/18, type= an, levtype= sfc, param= sea surface temperature, target= sst

ECMWF 33 COM INTRO 2004: MARS Introduction MARS Architecture Client/Server Protocol: MARS request Clients, C program + libemos library (GRIBEX + Interpolation) – Supercomputers – Workstations and Servers – Applications like Metview (local / at ECMWF) – Remote client for Member States (security mechanism) – WebMARS – Data Server

ECMWF 34 COM INTRO 2004: MARS Introduction MARS Architecture – Servers Reports Database (RDB), on-line observations (for Operations only) Fields Database (FDB) – Data produced by most recent cycles or experiments – Very fast access (on-line data) – Suitable for model input Main Archives (4 servers) – Dedicated IBM servers, running AIX – 9 TB disk space – Tape management SW: HPSS – StorageTek silos

ECMWF 35 COM INTRO 2004: MARS Introduction MARS Architecture - Request execution 1) Check syntax (MARS language and request syntax) 2) Print request to be processed 3) Query all Supercomputers FDB 4) Query main archives (if data not in FDB) 5) Transfer data 6) Post-processing while transferring (if needed) 7) Report on result

ECMWF 36 COM INTRO 2004: MARS Introduction Retrieving data Request scheduling Queue system Priorities: user, request age, request cost (number of tapes and fields) Data collocation MARS tree Archive objects (for OD data) – 1 file per month of AN (1 level type, all times, levels, params) – 1 file per forecast (1 level type, all steps, levels, params) – 1 file per EPS (1 level type, all steps, members, levels, params)

ECMWF 37 COM INTRO 2004: MARS Introduction Retrieving data - MARS tree

ECMWF 38 COM INTRO 2004: MARS Introduction Retrieving data - Post-processing Conversions – SH SH (reduced truncation), GG, LL – GG (reduced) GG (lower resolution or regular), LL – LL LL (lower resolution) Sub-area extractions (GG, LL, waves), reduces data volume Derived fields (e.g. U and V from vorticity and divergence) Rotation

ECMWF 39 COM INTRO 2004: MARS Introduction Retrieving data - Post-processing Truncation before interpolation, reduces necessary resources Grid increment Truncation 2.5T to 2.5T to 1.5T to 0.6T319 0 to 0.4T639

ECMWF 40 COM INTRO 2004: MARS Introduction Retrieving data – Efficiency Local Disk ($SCRATCH) Estimate amount of data (list command) – Number of fields (up to tens of thousands / request) – Data size (up to several Gigabytes / request) Check computer resources: quota, CPU time, … Reduce number of tapes involved (better scheduling) Retrieve as much data from the same tape as possible Do not create unnecessary sub-archives

ECMWF 41 COM INTRO 2004: MARS Introduction Retrieving data - Hints Default values: minimize their use No semantic check (only syntax is checked) MARS messages – INFOrequest execution and report – WARNINGunusual aspect of execution – ERRORsystem or data errors – FATALterminates execution

ECMWF 42 COM INTRO 2004: MARS Introduction Accessing MARS directives from input stream directives from file mars <<EOF retrieve, type = an, date = -1 target = $SCRATCH/my_an EOF cat > my_request <<EOF retrieve, type = an, date = -1 target = $SCRATCH/my_an EOF mars my_request

ECMWF 43 COM INTRO 2004: MARS Introduction Additional resources MARS documentation Web-MARS Data Services documentation User Guide to ECMWF forecast products EMOSLIB (GRIBEX) Documentation IFS Documentation

ECMWF 44 COM INTRO 2004: MARS Introduction Data Server – A standalone PC-Linux system outside the firewall Public (non-commercial) distribution of data – Self-registration Datasets – DEMETER, 24 GBytes – ERA-15, 1 GByte – ERA-40, 400 GBytes, 2.5º Based on Web-MARS – Disk-only MARS server – MARS client, Metview, SMS – fastCGI, Perl, MySQL

ECMWF 45 COM INTRO 2004: MARS Introduction Data Server User interface – different for each dataset – built dynamically from MySQL contents NetCDF is produced on-the-fly from GRIB (experimental) Very popular since ERA-40 made available – About 1000 users – Download about 1TB/month Useful tool for sharing data among project collaborators

ECMWF 46 COM INTRO 2004: MARS Introduction Web-MARS – Archive catalogue Content browsing of every field in the archive Real-time (dynamic access to metadata) Create MARS requests (without checking availability) Check availability of data Check for changes in the archive Cost evaluation Retrieval and plotting for few fields URL based in MARS requests (can be edited) More up to date than static content documentation

ECMWF 47 COM INTRO 2004: MARS Introduction Web-MARS – Catalogue shortcuts Overview Brings you directly into the catalogue Static page to latest datasets Suitable for new users Latest update Page updated every night Availability by source of data

ECMWF 48 COM INTRO 2004: MARS Introduction Web-MARS – Data Finder Allows to have different views of the archive – By period of time – By meteorological parameter – By data source (forecasting system) Narrow the search for data Availability Brings you directly into the catalogue

ECMWF 49 COM INTRO 2004: MARS Introduction Web-MARS – Changes in the archive addition or discontinuation of fields Web-MARS – Parameter Database GRIB table controlled view Links to IFS documentation

ECMWF 50 COM INTRO 2004: MARS Introduction Web-MARS – Server activity Show archive activity Monitor your requests Learn how the queuing system works – Reason for queued requests