We have started to put together a list of frequently asked questions regarding MERRA. Obviously, it will grow with the frequency of questions. Comments or questions posted here will also contribute to the list.
http://gmao.gsfc.nasa.gov/research/merra/faq.php
All three streams have been running, though there was some down time on the supercomputer last night. So far:
All three MERRA streams are running. Stream 1 has just finished Jan1979, so we'll be evaluating that tomorrow. Streams 2 and three are still in their final spin up period, but will be finished with the spin up by tomorrow.
We have a link to an image that is regularly updated and shows how much data of each stream has been produced, as well as how much data is left to produce.
http://gmao.gsfc.nasa.gov/operations/merra_status_production.gif
Needless to say, at this point we have much more to do.
All the updates are checked in and Stream 1 (starting 1979) has restarted. Streams 2 and 3 should also start soon.
Since the last post, we found that the coefficient update being implemented (and a required fix) also affected the MSU data for TIROS-N which is the only satellite data in early 1979. Since this is a non-zero difference, we need to rewind the 1979 MERRA stream (it had progressed to the start of NOAA-6, July 1, 1979) and rerun.
While testing the updated coefficients, some zero-difference updates to the output diagnostics were incorporated to the system. The updated tag is being handed back to operations, who should be able to restart Stream 1 (1979) before the end of this week. In looking at the first 6 months of the 1979 that is being rerun, the output seems much as we expected from validation experiments.
We still have some backlog in the computing queues for other projects, and we are going to rerun our 2006 validation experiment with the updated coefficients as a formal validation of the implementation of this update. It is important to not that the model physics and generally the data assimilation has not changed in some time, and the bug fix to these coefficients are part of the input data stream.
The MERRA Stream 1 (starting Jan 1979) has been progressing steadily, up to mid March 1979. We've had a look at Jan 1979, and it looks to be within expectations. The second two streams are on hold, mainly because there are some short experiments still being run.
However, it has also come to our attention that the CRTM team are fixing a bug in the coefficients for MSU radiances. Stream 1 won't assimilate these until July 1979, but the second stream will assimilate these immediately. The hold for the short runs will continue through next week, at which time the status of the update to these coefficients will be reevaluated. However, all indications are that the reanalysis should not proceed until these are included in the CRTM. This is an interesting development. We'll run some tests of the impact of the bug fix.
So, in the mean time, we can continue the processing of the Stream 1, and evaluate it along the way. Some results will be posted in the next couple days.
One of the last few fixes included in the system (discussed in the previous update), one that should have been minimal impact, greatly affected some code in the data assimilation. The result was that many wind observations that should have been assimilated were not. The problem was apparent (actually the system crashed), so the fix has been fixed.
There have also been several down times in the last week while some updates were made to the computing platform. So far, it looks like the data stream starting in 1979 has been running continuously (or at least regularly) over the weekend. It is up to 15 JAN 1979 after starting on Friday in December 78. So, if all goes well, by Tuesday we should see the first month of MERRA data.
With all the down time, some short reprocessing experiments that the GMAO is producing for instrument team support have been delayed. So, there is a backlog that is being cleared out. Once clear, the second two streams will be restarted from Jan 1989 and Jan 1998, respectively.
The three streams are ready to start. The first has run from Jan 1 1979 to Jan 9. However, all are on hold while system maintenance is being done (in other words, the computers are down).
By Monday, I'll be back from the 3rd International Conference on Reanalyses in Tokyo Japan, with better information. It has been a very interesting meeting, with status updates from the 20th Century reanalysis project and the NCEP CFS Reanalysis and Reforecast project (see the ppt at the CFS Site). Stay tuned to these interesting activities too!
The three spinup runs reported earlier have completed 1 year of spin up. These have provided the starting points for the MERRA production. The output diagnostics have been updated to correct minor diagnostic bugs, and when the system is rebuilt, production will begin.
I'm monitoring status from the 3rd WCRP International Conference on Reanalysis, and will this page when new information is available.
A data flag was out of place, and Stream 1 had to be backed up. All are still moving forward to the end of the December of their respective spin up phases.
Stream 1 date completed: 19781202
Stream 2 date completed: 19881124
Stream 3 date completed: 19971124
The Spin Up periods are still being processed.
Over the holidays, the last few science fixes went into the system, and the spinup periods resumed. Each of the three MERRA processing streams is presently running, with the data to be discarded for spinup.
On the MERRA WWW page, we are posting several figures showing the comparison of 5 satellite era reanalyses with GPCP and CMAP precipitation data sets. There are some similarities among the reanalyses, in their differences from the observations (Tropical precipitation, and interestingly European continental January precipitation), but also differences between the merged observation data sets (GPCP has lower tropical precipitation than CMAP, but higher January precipitation, in general). Citations are provided on the page, that provide some analysis and discussion on the sources of bias. However, there are many other aspects in comparing reanalyses to the observed data. These are only climatologies, so that interanual variability, weather scale and diurnal cycle differences are not expanded.
The WWW page is at: http://gmao.gsfc.nasa.gov/research/merra/reanalysis_precipitation_climatology.php
Please take a look, and feel free to make comments on this blog.
Just a brief post. The spinup runs are still on hold. The physics in the system seems to be set and the output diagnostics are likewise set. The main hold up is that the adaptive bias correction of a small number of channels over land is not stabilizing even after long (coarse resolution) runs, and continues to grow ultimately leading to the rejection of observations that should otherwise be accepted. A patch seems to be working, and a clean experiment is getting underway today. The spinup experiments should be restarted soon, and that will be posted here when it happens.
The GMAO started the day, presenting a summary of the system and critical improvements in recent months (Rienecker), the dynamical circulation, clouds and radiation (Suarez and Bacmeister), climate variability features (monsoons, hurricanes, low level jets (LLJ) and diurnal cycle - Schubert) and precipitation statistics and land hydrology (Bosilovich and Koster). Key points from the presentations are summarized below.
Michele Rienecker reviewed some major and critical changes to the system since the inception of the Review Group. These include improvements in the use of retrieved wind speed over the ocean, improvement in the radiance assimilation (through the latest CRTM radiative transfer coefficients), corrections to bias and jumps in the radiosonde observations and a fix for diurnal cycle of glacier surface temperatures.
In looking at zonal circulation, Max Suarez showed the differences between the GEOS-5 and other reanalysis systems for winds, temperature and humidity. For example, the GEOS-5 eddy heights compare with ECMWF operational analysis both in a mean sense, and in the interannual variability. With small contour intervals in the zonal cross-sections, differences in tropopause height can be identified among all the reanalyses. In addition, GEOS-5 reproduction of stratospheric ozone profiles is reasonable, and a limited comparison of the beginning of a quasi-biennial oscillation looks promising. One possible systematic problem is high upper troposphere humidity (as compared to ECMWF and NCEP operational analyses). The radiation fluxes have some bias, as well, but these are somewhat reduced compared to the existing reanalyses (Figure 1).
Siegfried Schubert reviewed some evaluations of monsoonal circulations, including the North American monsoon and Indian monsoon. GEOS-5 reproduces the low level winds (e.g. the Somali jet and the Great Plains LLJ) as well as the subseasonal breaks observed in the monsoonal precipitation. There are some apparent regional biases in the precipitation, but this is also true among all the existing reanalyses. The GEOS-5 North American monsoon circulation and precipitation compare well with the North American Regional Reanalysis (NARR) (for July 2004, Figure 2). Globally, the interannual variations of precipitation compares well with observations, and better than existing reanalyses. In addition, the monthly average water budget shows globally averaged analysis tendencies to be a small value (Figure 3). However, the diurnal amplitude of continental precipitation is large and the phase is shifted to a daytime maximum compared to observations. This is a problem for all reanalyses, and it persists in the GEOS-5 system.
Mike Bosilovich reviewed monthly mean precipitation, where GEOS-5 generally produces good fields compared with GPCP and CMAP, not only in the global mean, but also spatial correlation. In addition global P-E is generally small (near zero) indicating that the global analysis is relatively well balanced (but will be non zero). The GEOS-5 precipitation is reasonable in many regions and latitude bands. Comparisons for the
Figure 1 Monthly mean (Jan 2004) TOA Longwave radiation differences between CERES ERBE-like observations and several reanalyses and operational analyses.
Figure 2 Comparison of the seasonal evolution of the North American monsoon between the North American Regional Reanalysis (NARR) and GEOS5.
Figure 3 Global vertically integrated water vapor budget for July 2004 including the physical components, the analysis increment and residual.
Figure 4 
Figure: Time series of 2m air temperature at two Antarctica stations. The green line indicates GEOS5 Patch 15, Blue is patch 20 (including the fix) and the read is ECMWF operational analysis. Model data are the nearest gridpoint to the stations. Station data is marked with a black box.Just a quick post on current jobs and activities.
The validation runs for Jan-Jul and Jul-Oct 2004, Jan and Jul 2006, Jul and Aug 1987 are complete. Jan and Jul 2001 are going, and should wrap up next week. For the next two weeks a summary of the results will be pulled together.
For production, the system will run in three data streams. Each stream will be spun up for two years at a coarse (2 degrees resolution) then the native MERRA resolution for 1 year. The streams will each start at January of 1979, 1989 and 1998.
Presently, the coarse (2 degree) runs are complete and the native (1/2 degree) spin up runs have started. They are all either completed January or into February. Each stream is producing around 10 days/day when the computers are up. With reasonable up time, they should reach the nominal beginning of production by early November.
GEOS5 uses an Incremental Analysis Update (IAU) to constrain the atmospheric numerical model by observations. The following figure shows the schematic of the procedure. Starting at 09Z, a 6 hour forecast is run, and forecast data from 09Z, 12Z and 15Z are used to create the analysis (blue diamond). From the analysis and the forecast, a tendency is calculated. This tendency is applied to another model forecast cycle in the prognostic equations (green arrow and light blue box). This is called the corrector segment, so that the tendencies are nudging the model forecast in the direction of the observations at every time step.
MERRA will have two primary products. First, the analyses will consist of the model state variables written instantaneously after the analysis every 6 hours (00Z, 06Z, 12Z and 18Z). There will be model level (72 eta levels) and pressure interpolated (42 pressure levels) for each analysis time. Second, the diagnostic fields are written from the model corrector segment. These include 1 hourly average 2 dimensional (1/2 deg latitude by 2/3 degree longitude) surface, single level (e.g. H500), radiation, land specific and vertically integrated fields. In addition, 3 hourly average 3 dimensional coarse resolution 1.25 deg x 1.25 degree) atmospheric diagnostics are produced from the corrector segment. These include all the tendencies for the state variables, as well as fluxes and budget terms.
One advantage of IAU is that it allows the corrector segment data to be written. This data is exposed to the observational forcing spread out in time, rather than a large change in the initial conditions. The spin up spin down problems in the forecast, associated with initializing a forecast system with an analysis data, are much smaller. Essentially, this allows the production of 1 hourly precipitation and other physics fields. The figure below shows a global average precipitation time series (data is written at every model time step, ~30 min) using the synoptic analysis as initial conditions, IAU and a pure model forecast. Reinitializing the forecasts with the analysis causes jumps in the time series. The free running model tries to have a global precipitation rate of ~3 mm/day. The analysis tried to reduce that, but after the initial time the forecast starts to drift back to it's preferred climate state. The IAU provides forcing at every time step, constraining the system with the observations.
The ocean atmosphere interactions are one of the crucial elements in climate variability. The MERRA system does not have a coupled ocean model and data assimilation, but future reanalyses will likely go in this direction. In MERRA, seas surface temperatures are prescribed and ocean surface wind observations (from buoys and satellites) are analyzed. Downward components of the radiation would be related to the parameterized clouds and radiation calculations, as well as the input observations (radiances, temperature and moisture). The following figures prepared for validation compare some winds and fluxes with GEOS5 experiments and other reanalyses.
This following figure shows the daily time-series for Jan 2004 and 2006 U10M and V10M winds at the TAO mooring location of 165E on the equator. GEOS-5 shows good agreement with TAO and matches the minimum and maximum values everywhere. In Jan 2004 and 2006, GEOS-5 is more highly correlated with QSCAT than NCEP CDAS or JRA-25. The NCEP-CDAS analysis shows several periods of larger bias against the observations.
The next figure shows maps of monthly latent heat flux for GEOS5, JRA-25 and NCEP CDAS. GEOS-5 has much less evaporation out of the ocean than JRA-25 and NCEP CDAS, especially in the western boundary currents: Gulf Stream and Kuroshio. Mean and RMS differences between GEOS-5 and JRA-25 and GEOS-5 and NCEP CDAS are much larger than that of NCEP CDAS and JRA-25 in the above region. Similar patterns are seen in January 2004.
In three validation periods investigated so far (Jan/Jul2004 and Jan 2006), GEOS-5 net radiation is more highly correlated with TAO in the Eastern Pacific that other reanalyses.
NCEP-CDAS generally is biased low in most time-periods and TAO locations. GEOS5 also correlates well with the TAO incoming shortwave radiation observations.
The three reanalyses are fairly different in their net heat fluxes. GEOS-5 has less heat loss than both NCEP and JRA in the Kuroshio and Gulfstream areas, and more heat gain off Western Australia. In the 45S-45N band, GEOS5 and JRA have substantial differences.
Vacations in August have limited the posting, but the validation experiments are continuing. The experiments are moving well, and the system performance will be discussed in another post. Here are some of the validation comparisons for TOA radiation of some reanalyses to CERES ERBE-like data from Terra and Aqua. In the figures, the GEOS5 validation experiment is labeled d5_b10p15 (d is the 1/2 degree resolution, beta10 patch15 is the version of the data assimilation system).
The first figure is the zonal mean of the TOA LW and SW fluxes in Jan and Jul 2004. CERES observations are in red, GEOS5 is blue, JRA-25 is black and NCEP RII is green. GEOS5 shows somewhat smaller bias in the tropics LW, and also mid latitude SW. The July upward SW in the tropics seems biased high compared to the obs and other reanalyses, but otherwise, it seems in the range of the reanalyses. (Click on thumbnails to see the full figure)
The next two figures show the monthly mean maps of the comparisons. to CERES Terra. The differences between the CERES-Terra and CERES-Aqua are provided as a reference. In TOA LW, JRA-25 seems systematically biased high, while NCEP RII has strong positive and negative variations. GEOS5 leans to a high bias, but not as high as JRA. JRA and NCEP also show large positive bias in the tropics, which impling a dry upper troposphere or low cloud top. Newman et al (2000) have evaluated the interal consistency of several reanalyses, between OLR, precipitation and upper level divergence. In addition, they note that the correspondence among the reanalyses is quite low. The reanalyses OLR are all different from each other.
The shortwave biases of the reanalyses generally are similar. The exception seems to be the polar warm season. For example, TOA SW in Antarctica January is high for NCEP RII and GEOS5, but low for JRA.
Newman M., P. D. Sardeshmukh, J. W. Bergman, 2000: An Assessment of the NCEP, NASA, and ECMWF Reanalyses over the Tropical West Pacific Warm Pool. Bull. Amer. Meteror. Soc. 81, 41–48.
Smith, G. L.; Wielicki, B. A.; Barkstrom, B. R.; Lee, R. B.; Priestley, K. J.; Charlock, T. P.; Minnis, P.; Kratz, D. P.; Loeb, N.; 2004: Clouds and Earth Radiant Energy System (CERES): An overview, Advances In Space Research, 33, 1125-1131.
Wielicki, B.A., B.R. Barkstrom, E.F. Harrison, R.B. Lee, G. Louis Smith, and J.E. Cooper, 1996: Clouds and the Earth's Radiant Energy System (CERES): An Earth Observing System Experiment. Bull. Amer. Meteor. Soc., 77, 853–868.
