GEO on Continuing Reanalyses

GEO has published an article supporting the reanalyses development and international collaboration and coordination. Reanalyses represent a significant confrontation between the models and observations, and can be used to improve both, and produce a research quality value-added data product. While CFSR, Interim, 20CR and MERRA are all being released about the same time, they were not planned that way. So, there is a unique opportunity to have a community-wide check on our technological development in the models, assimilation, observations quality and computational resources (which affect the resolution and numerics). Generally, there will be advantages and disadvantages to each of these, which will take some time and effort to sort out. While they will be different, the important point will be is if they are making improvements on the representation of the Earth system.

In order to make progress, continuity and traceability in the system development will be crucial, but can only be attained if the respective centers have regular plans to produce the next round. If too many years go by, the next systems will be so different isolating and understanding the reasons for differences will not be possible. To little time, and the next reanalysis will not represent much difference, and the community will begin to feel the workload updating to the latest. Ideally, the next reanalyses should utilize all the information gained on the quality of the observations from the previous reanalyses, while advancing the representation of physical processes and data assimilation.

Effect of the Eyjafjallajokull eruption

Aircraft observations are a substantial part of the reanalysis system, especially over the oceans and regions where other high altitude conventional observations are infrequent. So that, the eruption of Eyjafjallajokull volcano will have many effects on reanalyses in general. Increased concentrations of aerosols can effect the remote sensing of atmospheric properties (Mount Pinatubo is the typical historical case). The aerosols will affect the radiance observations, and we will be monitoring MERRA's variational bias correction and assimilation of the radiance observations. It's also worthwhile to note that the MERRA system does not include interactive aerosols or aerosol assimialtion (currently under development), but rather incorporates only prescribed mean seasonal cycle variations.

The commercial aircraft restrictions that occurred also have affected the aircraft observing data set.The figures below show the number and locations of aircraft observations in a 6 hour window from ASDAR data system, before and after the major eruption that disrupted air travel.

It appears that the numbers of flights are beginning to recover, and the altitude of the eruption is on the order of 10km, so that the effects should be short lived, assuming the activity subsides.

Before: 12425 obs in 6 hours (green are used in the assimilation, red indicates qc rejection)
After: 6038 obs in 6 hours

MERRA real time production schedule

Stream three has finished March 2010, signifying a transition to real time production schedule. Production will lag real time by approximately 3 weeks, allowing collection of all the observations used in the retrospective periods. We are planning one week to review and quality assure each new month's data files, before being sent to the GES DISC. So, Each new month of MERRA data will be available online roughly 1 month behind present time, and will be released in 1 month segments.

Jan-Mar 2010 are currently being reviewed and should be available on the DISC within the next couple of days.