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