Status June 28

Since the last post, work has progressed on setting up the validation experiments. Initial conditions are being created and assorted other tasks to make sure the system is configured. The jobs should be close to starting. However, there are some ongoing experiments that may affect the setup. First, the data group has applied some corrections to the sonde data for known biases (e.g. radiation). I don't have the citations handy but I'll try to get them posted before long. With the corrections applied to the data, the quality control code needs to be modified to reflect that. The experiment is just a sanity check to make sure that the data and code are implemented properly.

While investigating the "sawtooth" problem discussed in earlier posts, the analysis group looked more closely at some of the statistics for the temperature assimilation. A feature in the lowest atmospheric layers of the statistics may partly contribute to the sawtooth, so they are testing a correction to the statistics. Preliminary results seem positive, and a full resolution was being started. This correction would be much more broad than the target correction already applied to fix the sawtooth. So, we will need to look closely at the experiment before it is implemented for validation.

In parallel, the code is being engineered to work on a newer supercomputer at GSFC called Discover. This will be where MERRA production is carried out. The system is running well there. However, occasional random crashes are being investigated. A likely cause is a memory leak. These things happen, and the folks working on the problem should have it fixed without impact on production.

The SSMI 2 degree experiment is nearly complete (Jan 1984 - Dec 1989). The main purpose was to checkout the potential impact of the introduction of SSMI (radiances and surface ocean winds) to the data stream. Several people are still looking at it. The preliminary results show that the SSMI does not seem to have considerable impact on atmospheric moisture and precipitation. However, it is plainly apparent in the global time series of surface wind, moisture and evaporation (all increasing). There is a slight upward trend in global precipitation after the introduction of SSMI, but it does not exhibit a a shock or step (to the eye, statistical analysis would probably reflect the introduction).

One feature that this experiment has demonstrated is that the operational NOAA satellites, and their variations do seem to be influencing the precipitation time series. Firstly, the global mean precipitation (averaged for Jan 1984 - Dec1987) is lower than any experiment we have run to this point, 2.2 mm/day compared to 2.6 mm/day for GPCP and ~3mm/day for JRA25 and ERA40. Resolution might be part of the deficit. In some recent tests, we have not seen a large change in precipitation going from 1/2 to 2 degrees. However, some previous experiments did show ~0.2mm/day global deficit in the 2 degree system compared to 1/2. So, we are putting a new experiment into the validation experiments, July 1986. This will run at 1/2 degree with the latest system, and be included in the validation experiments.

Another issue from the SSMI experiment is that the precipitation bias is not uniform across the period of analysis. In 1984, precipitation is quite close to GPCP at2.4 mm/day, but it has a downward drift over the next few years, from early 1985 (NOAA 9 starts in Dec 1984) until Jan 1987 when NOAA 10 begins. The analysis increments are negative (removing water vapor) and getting more in time. There are jumps in the time series of moisture increments when the NOAA satellites change. We still have a bit of work to do on this, as well as check the 1/2 degree experiment. A more detailed evaluation is being prepared, and we have much more to investigate.

The primary validation experiments will be Jan and Jul 2004 (expected to run for six months each to make a full annual cycle). The Jul 1986 is also being put on a fast track. They should start soon, and more info will be posted then. The secondary runs, Jan/Jul 2001 and Jan 2006 will begin when CPUs become available.

Sawtooth Update June 15

The experiment testing the impact of not using AMSUA for land snow conditions progressed several more days overnight. The results show that a weaker version of the Sawtooth shows up as we get deeper into winter, even without AMSUA. AIRS radiances are still being assimilated. Further analysis shows that in Siberia (where the Sawtooth is worst) the synoptic conditions change, decreasing clouds, and the Sawtooth simultaneously appears. The figure below shows the original Sawtooth (b5_b10p9), the latest experiment restricting AMSUA (exp06g) and NCEP Operational analysis for Jan 1-11, 2006. It is important to note that the weakened Sawtooth in exp06g somewhat compares to a semi-diurnal cycle in the NCEP operational analysis (between Jan 9-11, should have been still using the SSI analysis).

The working hypothesis for why the weakened sawtooth appears is that AIRS is still prevalent in this region. Some are looking into the radiative transfer model. Also, we are not using the latest NCEP CRTM. There was some discussion on updating the CRTM to the latest, however, it quickly determined that this would require a complete update of the GSI in the GEOS5 system. Of course, that would incur significant delays.

For now, we are going to continue to monitor the experiment. But the major portion of the problem seems to be under control. Since theGEOS5 is in range of NCEP operational analyses, plans for validation will go forward. In validation we will examine further whether this feature adversely affects the science quality of the data set. The good news would be that the problem has finite bounds in, only over land snow, and only occur then when AIRS is available (starting 2002).

Just a quick note and reminder of the positive aspects of this system we have previously reported (we tend to hammer at the problems). The precipitation from the configuration for MERRA seems to be well in line with GPCP, and a good contribution compared to other reanalyses. TPW looks reasonable compared to NVAP data (though those obs may have bias). There will be data supporting the stratosphere community that should be very unique. At one-hourly intervals, the surface diagnostics should be very useful for diurnal cycle studies. These and a few other aspects should help make MERRA a reasonable contribution.

Status June 14

Just a brief update, as our regular meeting was relatively brief and focused.

Progress has been made on the sawtooth problem. The results presented today show that rejecting all AMSUA radiance over land snow conditions eliminates the sawtooth. There are some experiments ongoing to test which channels (surface peak and high peak) might be included without the instigating a sawtooth. Also, there is an experiment with all AMSUA, but with much stricter quality control. We should have the results from those experiments in a couple working days. However, the fallback position would be to not use AMSUA over snow.

During these tests, some other minor bugs and updates to the system have been found and fixed. An experiment pulling the system all together is being configured and run over the weekend. That should be evaluated next week along with the AMSUA quality checks. If all goes as expected there, validation experiments will begin soon thereafter.

The 2 degree SSMI experiment is ongoing, and producing a month every 14 hours or so. Presently it is at 16 February 1988. While we're monitoring some of the data as it progresses, some analysis of SSMI impact will be done when we have 1 year after SSMI starts (probably try to get 2 years after, eventually).

Land Fractions

One feature in the GEOS5 GCM that is different previous reanalyses is fractional surface tiles, as opposed to a land/sea mask. Each grid box contains a fraction of land, water, lake or land ice. The fractions are based on the 1km Global Land Cover Characteristics (GLCC) database. Along coast lines, the land processes are blended with sea surface processes. Inland, lakes and rivers are also included. This will require some attention of users calculating precise budgets. For example, the grid box average evaporation that would be appropriate for an atmospheric budget, may not be appropriate for in-situ data comparisons and land surface budget studies, if the lake fraction is substantial. Figures showing some examples of land and lake fractions are shown below.

To support the analysis of land water and energy budgets, a land only output data collection will be produced (tavg1_2d_lnd_Nx in the MERRA File Specification Document). These grids would be for the land only fraction of the surface. Users will be able to differentiate land evaporation from total evaporation in grid boxes near the coast and near inland water bodies. Soil water (GWET variables) will show up in grid boxes that appear to be oceanic. The model does provide an integer land/ocean mask (variable name LWI). However, this is simply a 50% cutoff between land/land ice and ocean fractions. For some specific purposes, this may not be appropriate, and users should use the land fraction to develop their own mask.

Additionally, the land fraction is subset into tiles based on the Catchment hydrology. The land collection includes data from the catchments. For more information, the interested reader should review Koster et al. (2001, J. Geophys. Res. Vol. 105 , No. D20 , p. 24,809, 2000JD900327).

Status June 5

We've had some good news and bad news. The good news is that efforts by the analysis group to revise the error statistics have had the expected positive impact on a systematic zonal wind bias in the tropics at upper levels. Further, the adjustments in the convective parameterizations by the model group have held up through this testing, and precipitation looks be reasonable compared to other reanalyses and observation data sets at the monthly time scales.

The bad news is that the "saw tooth" problem persists, but progress is being made in understanding it. In one of the data sweeper runs, we find that the analysis is reasonable, through Dec 2000, then the sawtooth begins in January 2001. This is at the same time NOAA 16 data begins to be used in the input data stream. Presently, the satellite bias corrections used in the system are being reexamined. The current thinking is that, if an inappropriate bias is included, the analysis rejects the radiance observations (near the surface), then the bias is never properly adjusted. To test this, an experiment started with zero bias is being started, this should spin up a new bias correction. Most of the system testing has simply carried bias corrections along from older systems.

So, while the system is getting closer and we are certainly learning more on the system with every experiment, the important validation experiments have not yet begun. Some minor corrections have also been identified. For example, it was found that snow was reaching the surface in regions too warm and equatorward. The snow production algorithm was not including surface temperatures, so now a check has been added.

The 2 degree experiment to test SSMI in the late eighties has progressed into 1987, and is closing on the onset of SSMI in July. However, the experiment is being removed from the priority queues. The GMAO is gearing up for operational support for TC4, which needs high priority, and also the experimentation on the sawtooth problem takes priority.

To emphasize the critical nature of the sawtooth problem, the figure below shows an example of how it looks at the worst. The time series is 850 mb temperature at a point every 6 hour analysis time. The points closest to the NCEP operational analysis are the when sondes are present (00Z and 12Z) and the very warm temperatures are when only satellite data are available. At this point, the GEOS5 surface temperature is much colder than NCEP and the surface channel radiances are being rejected by the quality controls.

June 11 Follow up: Recent experiments have shown that the AMSU channels over ice may be the root of the sawtooth problem. Further work is aimed at identifying specific channels. Result should be posted in the next status report, probably Friday June 15.

Latest on the 3rd WCRP Reanalysis Conf.

A recent Message from JRA-25 User Admin:

Dear JRA-25 reanalysis data users,

I am pleased to inform you that registration of the
Third WCRP International Conference on Reanalysis will
begin on 1 June 2007.

Please visit the conference page
(http://jra.kishou.go.jp/3rac_en.html)
and move to Instruction page.
Please note the instruction page will be available
from 1 June.
The deadline for submission of abstracts is 31 July 2007.

WCRP, GCOS and GEO may support travel costs for
participants from developing countries.

Please inform researchers who are interested in the conference of the conference.




Sincerely yours,

Secretariat of 3rd Reanalysis Conference
CPD/Japan Meteorological Agency

Status May 25

I'm on my way out to the LandFlux Workshop, so this will be a quick post.

The "sawtooth" problem first discussed in the May 18 status update is still being worked on. The bias correction that seemed like it might be a solution did not fix the problem. A short 1/2 degree experiment with limiting very strong stability in NH winter did not have an immediate response, though, GCM seasonal simulations show that this should make a big step to correct the cold bias thought to be the root of the saw tooth. This problem is also found in 2 degree experiments, so that new seasonal 2 degree experimetns are being started to assess our understanding of the problem and show that correcting the surface temperature bias corrects the sawtooth. 2 degree runs turn around much more easily than 1/2 so results should be available next week.

Unfortunately, being on travel, I'll miss the meetings that review the results, but I'll spin back up as soon as possible.

The SSMI experiment is moving forward. It is in late 1985, looking forward to July 1987 when SSMI becomes available. There should be alot to work with when I get back from Landflux (June 4).

In a general sense, we (a concensus of the GEOS5 status meetings) are very pleased with where the systems is, and were it not for the sawtooth would be moving on with the validation experiments. There is one other science issue that has come up. The Relocator (corrects the location and dynamics of tropical cyclones) was run last summer for MAP06. Somewhere along the way, the numerous updates and changes have "broken" the Relocator code. It shouldn't be difficult to fix, but will need to be tested before we go to validation.

As far as the schedule goes, a critical milepost will be the start of the validation experiments. Once validation experiments start, then we should have good ideas on the beginning of production.

Upcoming Runs and Plans

An update to the file spec was posted on the MERRA WWW page this week. No major changes, but it is still a draft.

We fully expect to have the system ready for production by mid-July. As such we are gearing up for the validation runs. The reanalysis system is also being configured for the new Discover super computing system. This provides a significant performance increase. A new partition for MERRA is being prepared.

The runs will be:

Jan/Jul 2001, Pre-AIRS period where we have legacy experiments, including the GEOS4 validation

Jan-Apr and Jul-Oct 2004: We want a full annual cycle, but that will take a substantial amount of time to run. As a shortcut, we'll run two experiments that will provide the central month of the four seasons, so most focus will be on Jan, Jul then Apr, Oct. This should show any red flags that might require us to hold production. However, we plan to keep the Jan 2004 run going beyond April, as computing cycles permit, with the idea that we will get a full annual cycle (the start of production will not be held up for that to finish, but we will evaluate it nonetheless).

Jan 2006: We have been using this case for several experiments so far, and have some familiarity with it.

We have been formulating a list of comparisons and issues to consider in validation. I'll post that separately in a couple days.

Status May 18

The SSMI 2 degree test runs is back up and running. It was started on Jan 1 1984 and completed 1984 yesterday. It will be a couple weeks before it catches up to the first SSMI observations. In the mean time we are scanning it's precipitation, temperature and heights. Most look reasonable. However, we know from previous experiments that the GEOS5 precipitation is much improved at 1/2 degrees resolution.

The system put toward validation is being finalized. We are checking and rechecking the implementation of a correction to the observational error statistics. Also, the system to be used in validation should have the entire file spec being produced. One component still being tested is the grid resolution reduction. The most voluminous data are the 3-D tendencies. I think just about every physical tendency has been included in the file spec. The 72 layer 1/2 degree data would be far too enormous for anyone to use, ( and uncomfortable to store). So, we are reducing the tendencies to 1.25x1.25 degrees and 42 pressure levels. The resolution reduction is being build inline to conserve the time doing I/O.

Recently, we found an oscillation between 6 hour analyses, with and without the radiosondes. The problem is local to high winter latitudes over land. It appears that the model has a cold surface bias, and the surface radiances are being rejected. Mid troposphere radiances still think the atmosphere is cold, and try to warm it up, but in the next analysis, the radiosondes draw the temperatures back. So, it seems to be a disagreement between a model bias (at high winter land latitudes) and differences in the radiosondes and radiances. Here, this has become known as the "sawtooth" problem, as the 500 mb time series shows a 6 hour zigzag pattern.

One possible source of the model bias is that there is no limit on the stability of the surface layer. So, Richardson numbers are very high in these conditions. In free running model, it doesn't appear to be a problem, but it decouples the land and atmosphere when observations are included. So, a limit on the Richardson number is being tested. There is also a strict criteria that limits the surface radiance increments. So that when the forecast and observation differences are large, the increment is rejected. This is strict for very good reasons (cloud clearing problems, for example). We are cautiously looking into relaxing that restriction. However, this could be risky and would only go forward if remarkable improvements can be obtained.

We also had some good news in this respect. The analysis group turned on the bias correction routines for surface temperature in GSI. This will apply a bias correction to the model background, before the surface temperatures are analyzed. So, the GSI sees a better surface temperature. These bias corrected temperaturesdo not feed back to the model forecasts (a much more difficult problem). After 15 days, the sawtooth has been corrected in many regions. East Siberia is spinning up to this a bit slower. In any event, it seems to be a reasonable fix as well.

We had not seen a problem in the system like this until recently, when running Jan 2006 as a test case. The previous winter case that was examined in detail was Jan 2001. In Jan 2006, we also include AIRS radiances. While these are thinned, AIRS still contributes 500K observations of the 1.2M observations assimilated. Away from the AIRS period, we still see the problem when we are looking for it, but it is reduced. We can also see this periodically in other operational analyses, but not nearly the degree seen in our Jan 2006 experiment.

Status May 10

We are still rebuilding the system with the latest patches and output diagnostic code. Part of this is also building on the Discover systems. It is taking time. The next round of systems tests should be the last before validation experiments. The 80's SSMI Impact tests will be run with the latest build, as well. For a timeline, Th May 3, decisions on the configuration of the system were made. The system build was completed Tue May 8. Computer systems were down May 9 for scheduled maintenance. They system is built and the jobs may start by the end of the week (May 11).

We met again today (May 9) with the GES DISC personnel working on the MERRA data distribution system. It is called MDISC, where M is for modeling (not MERRA specific). There will be several portals to the data for access and visualization. FTP will likely be the most general route people take, but there is also a subsetting routine with the FTP with a graphical interface that looks very good so far. I'll do some testing on that in the next couple days.

The working schedule for getting MERRA production going is not earlier than July 1. There are a lot of small items on the checklist for production, as well as a couple major gateways. The major gateways are: first we need a systems test that holds up in some short (one month) experiments, second take that system to run validation experiments, then analyze the results of validation and present those to both HQ and our User review group. The results of the review should indicate that we can go forward with productions. All told, it feels pretty ambitious at this point. Regardless, we are checking off the items needed to begin production.

Reanalysis paper by L. Bengtsson

An interesting paper led by Lennart Bengtsson is in this month's BAMS on the limitations, need and future role of reanalyses in climate studies. Found at AMS Online.

SSMI test delayed

The test of the MERRA system during the mid-1980s, enveloping the initiation of SSMI observations, had been running with a critical bug in the system. It was caught after the third of 5 planned years of running. The bug was a known problem in an old tag, but that tag was not adequately updated in Operations, despite being fixed in the research and development systems for months.

The purpose of this experiment is to test the impact of a significant change in the observing system, namely SSMI, on the GEOS5 time series. The system is running at a very coarse 2x2.5 degrees, 3 hourly output, which allows for much quicker throughput than we will see with the full half degree system. While the configuration is close to, but not exactly, that of the MERRA validation experiments, it should be close enough to contribute to the system validation. It will assess how sensitive the system is to the SSMI data when it first becomes available.

MERRA Status

At the development meeting today, we reviewed proposed fixes for the GSI statistics. This effort addresses a bias in the upper tropospheric zonal wind. These have been tested at coarse resolution. One fix has proved promising and the system is being rebuilt. This will be tested at the full MERRA spatial resolution. This also impacts certain aspects of the convective parameterization. So, a set of tests are being prepared and executed over the upcoming weekend. Early (but possibly incomplete) results of the tests are expected by Thursday May 10.

These tests will be used to decide the final configuration of the GEOS5 system to execute the MERRA reanalysis. Full system validation will begin with this configuration.

Also, Queen Elizabeth II will visit Goddard, May 8.

File Specification Document

The MERRA File Specification Document describes every aspect of the output data files that users will need to use the data. The file formats, grid structures, frequency and variables are all included. There are also some brief discussions on the physics and analysis.

The file can be found at: http://gmao.gsfc.nasa.gov/research/merra/MERRA_FileSpec_DRAFT_4-10-2007.doc

Full documentation of the GCM science and analysis methods are in development.

MERRA Current Status

4/19/2007

The science aspect of the MERRA is frozen. There are some final settings in the system that are awaiting a final decision. Validation of the whole system should be under way in 1-2 weeks.

This is an example of the precipitation being produced in the system.

The figure shows the difference of monthly reanalysis precipitation from GPCP. The numbers over each panel show the mean global difference (near zero is good) and the global standard deviation of the difference (smaller is better).

MERRA Introduction

NASA's Modern Era Retrospective-analysis for Research and Applications (MERRA) is intended to be a full reanalysis of the satellite era. In general, the data provided will support science research and applications.

The official MERRA WWW site is: http://gmao.gsfc.nasa.gov/merra/

This Blog is intended to be an interface between the developers and user community, and a place for status updates and Q&A regarding the MERRA production and data.