Known Issue #1, east Atlantic anomaly

Recently, an evaluation of the global energetics identified an anomalous feature, a bullseye, off the coast of Portugal during most of 1979 and 1980. The anomaly affects many tendencies and variables in this localized region. Figure 1 shows the JJA 1979 Analysis Increments of temperature at 500 mb, the center of the strong negative increment is a persistent radiosonde that appears to be flawed, compared to other nearby sondes. However, it was not rejected by the data assimilation's quality control. The sonde itself is being researched as to whether it is mislocated or just poor quality. Regardless, 1979 and 1980 data have a localized problem. The data will still likely be made available, as other regions around the globe, and certain global parameters are not as dramatically affected. However, we will try to alert users to this issue, as it will affect any investigation of the weather in the eastern Atlantic Ocean or possible western Europe (Figure 2).

The current plan is to re-run the affected period at a later date, however, that re-run will not replace the existing data, but be placed alongside the existing data. We will continue to use and evaluate the current 1979 and 1980 data, and if other issues arise, fixes could also be incorporated into the re-run. Also, with this problem, a new page will be created for the MERRA WWW site to catalog issues with the data as they arise, and include any actions to those issues.



Figure 1 JJA 1979 analysis increments of temperature (DTDT_ANA). The questionable sonde is causing the negative increments circled.


Figure 2 Temperature differences (MERRA-JRA25) at 850 mb for JJA 1979. The low temperatures resulting from the questionable sonde are apparent west of Portugal. The featuer is also apparent in the surface pressure fields (not shown)