In this blog, I will describe in some detail one major roadblock in giving the U.S. state-of-the-art weather prediction: inadequate computer resources. This situation should clearly have been addressed years ago by leadership in the National Weather Service, NOAA, and the Dept of Commerce, but has not, and I am convinced will not without outside pressure. It is time for the user community and our congressional representatives to intervene. To quote Samuel L. Jackson, enough is enough. (click on image to watch him say that famous line)
|Enough is Enough! The U.S. Needs Better NWP|
|Courtesy of Bill Lapenta, EMC.|
If you would expect the U.S. has a lot more computer power to balance all these responsibilities and tasks, you would be very wrong. Right now the U.S. NWS has two IBM supercomputers, each with 4992 processors (IBM Power6 processors). One computer does the operational work, the other is for back up (research and testing runs are done on the back-up). About 70 teraflops (trillion floating points operations per second) for each machine.
|NCEP (U.S.) Computer|
The UKMET office, serving a far, far smaller country, has two newer IBM machines, each with 7680 processors for 175 teraflops per machine.
Here is a figure, produced at NCEP that compares the relative computer power of NCEP's machine with the European Centre's. The shading indicates computational activity and the x-axis for each represents a 24-h period. The relative heights allows you to compare computer resources. Not only does the ECMWF have much more computer power, but they are more efficient in using it...packing useful computations into every available minute.
|Courtesy of Bill Lapenta, EMC|
The Canadians? They have TWO machines like the European Centre's!
So what kind of system does NCEP require to serve the nation in a reasonable way?
To start, we need to double the resolution of our global model to bring it into line with ECMWF (they are now 15 km global). Such resolution allows the global model to model regional features (such as our mountains). Doubling horizontal resolution requires 8 times more computer power. We need to use better physics (description of things like cloud processes and radiation). Double again. And we need better data assimilation (better use of observations to provide an improved starting point for the model). Double once more. So we need 32 times more computer power for the high-resolution global runs to allow us to catch up with ECMWF. Furthermore, we must do the same thing for the ensembles (running many lower resolution global simulations to get probabilistic information). 32 times more computer resources for that (we can use some of the gaps in the schedule of the high resolution runs to fit some of this in...that is what ECMWF does). There are some potential ways NCEP can work more efficiently as well. Right now NCEP runs our global model out to 384 hours four times a day (every six hours). To many of us this seems excessive, perhaps the longest periods (180hr plus) could be done twice a day. So lets begin with a computer 32 times faster that the current one.
Many workshops and meteorological meetings (such as one on improvements in model physics that was held at NCEP last summer---I was the chair) have made a very strong case that the U.S. requires an ensemble prediction system that runs at 4-km horizontal resolution. The current national ensemble system has a horizontal resolution about 32 km...and NWS plans to get to about 20 km in a few years...both are inadequate. Here is an example of the ensemble output (mean of the ensemble members) for the NWS and UW (4km) ensemble systems: the difference is huge--the NWS system does not even get close to modeling the impacts of the mountains. It is similarly unable to simulate large convective systems.
|Current NWS( NCEP) "high resolution" ensembles (32 km)|
|4 km ensemble mean from UW system|
A real champion within NOAA of the need for more computer power is Tom Hamill, an expert on data assimilation and model post-processing. He and colleagues have put together a compelling case for more NWS computer resources for NWP. Read it here.
Back-of-the-envelope calculations indicates that a good first step-- 4km national ensembles--would require about 20,000 processors to do so in a timely manner--but it would revolutionize weather prediction in the U.S., including forecasting convection and in mountainous areas. This high-resolution ensemble effort would meld with data assimilation over the long-term.
And then there is running super-high resolution numerical weather prediction to get fine-scale details right. Here in the NW my group runs a 1.3 km horizontal resolution forecast out twice a day for 48h. Such capability is needed for the entire country. It does not exist now due to inadequate computer resources.
The bottom line is that the NWS numerical modeling effort needs a huge increase of computer power to serve the needs of the country--and the potential impacts would be transformative. We could go from having a third-place effort, which is slipping back into the pack, to a world leader. Furthermore, the added computer power will finally allow NOAA to complete Observing System Simulation Experiments (OSSEs) and Observing System Experiments (OSEs) to make rational decisions about acquisitions of very expensive satellite systems. The fact that this is barely done today is really amazing and a potential waste of hundreds of millions of dollars on unnecessary satellite systems.
But do to so will require a major jump in computational power, a jump our nation can easily afford. I would suggest that NWS's EMC should begin by securing at least a 100,000 processor machine, and down the road something considerably larger. Keep in mind my department has about 1000 processors in our computational clusters, so this is not as large as you think.
|For a country with several billion-dollar weather disasters a year, investment in reasonable computer resrouces for NWP is obvious.|
Yes, a lot of money, but I suspect the cost of the machine would be paid back in a few months from improved forecasts. Last year we had quite a few (over ten) billion-dollar storms....imagine the benefits of forecasting even a few of them better. Or the benefits to the wind energy and utility industries, or U.S. aviation, of even modestly improved forecasts. And there is no doubt such computer resources would improve weather prediction. The list of benefits is nearly endless. Recent estimates suggest that normal weather events cost the U.S. economy nearly 1/2 trillion dollars a year. Add to that hurricanes, tornadoes, floods, and other extreme weather. The business case is there.
As someone with an insider's view of the process, it is clear to me that the current players are not going to move effectively without some external pressure. In fact, the budgetary pressure on the NWS is very intense right now and they are cutting away muscle and bone at this point (like reducing IT staff in the forecast offices by over 120 people and cutting back on extramural research). I believe it is time for weather sensitive industries and local government, together with t he general public, to let NOAA management and our congressional representatives know that this acute problem needs to be addressed and addressed soon. We are acquiring huge computer resources for climate simulations, but only a small fraction of that for weather prediction...which can clearly save lives and help the economy. Enough is enough.