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ECMWF, DWD, NCEP and JMA are providing quality monitoring reports of land surface observations based on feedback from their data assimilation (DA) systems on a daily basis. These reports include qualitative and quantitative (Observation-minus-Background, O-B, departures) information covering the following observed physical quantities: surface pressure (or geopotential height for some high-altitude stations), 2-metre temperature, 2-metre relative humidity and 10-metre wind (meridional and zonal components). The qualitative information includes a description on the usage (Status, i.e., used or not used on the assimilation) and the type of report (i.e., the Traditional Alphanumeric Code -TAC-, or the Binary Universal Format for the Representation of Meteorological Data -BUFR) of each of the above mentioned physical quantities. It is worth noting that surface pressure is the most important in situ observed quantity for global NWP forecasting, and in some cases the only observed surface quantity over land used in the global atmospheric data assimilation, e.g. in the JMA global atmospheric data assimilation system (JMA, 2019). ECMWF’s atmopsheric 4D-Var also assimilates relative humidity over land , but only at nighttime. Based on these reports (four daily, centred at the main synoptic hours, 00, 06, 12 and 18UTC), it is possible to infer the performance of the land surface network both in terms of availability and quality.
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2.2.Upper-air land observations
Currently only ECMWF, JMA and JMA DWD are providing quality monitoring reports for upper-air observations. Like the surface reports, these include qualitative as well as quantitative information. However, the The quantitative information provided is obtained by aggregating the O-B departures into two main categories: layer between the first pressure level up 100hPa to 100 hPa inclusive (Trop); and the layer from 100hPa 100 hPa up to the last reported level (Stra). The quantitative information for the aforementioned layers consists of both average the mean and standard deviation of O-B departures over the layer for the following observed physical quantities: upper-air temperature, upper-air humidity and upper-air wind. Provision of these data reports (four daily, centred at the main synoptic hours, 00, 06, 12 and 18UTC), typically happens 24 hours after the actual observation. The availability, quality and completeness of these conventional profiling observations can be easily assessed based on the information provided by these the monitoring reports. It is worth mentioning that for the high-resolution BUFR reports, two messages are disseminated on the Global Telecommunication System (GTS): a preliminary message containing the measurements from the surface up to 100h Pa (TTAA=IUK header - I, Observational data Binary coded, U, upper-air message and S, radiosonde from fixed land station up to 100 hPa) and the final message containing the entire sounding from surface to balloon burst (TTAA=IUS, header - I, Observational data Binary coded, U, upper-air message and S, radiosonde from fixed land station up to balloon burst). ECMWF and JMA use the full BUFR message (i.e., IUS bulletin), and only when if the full one is not available , they use the IUK bulletin. Therefore, both ECMWF and JMA monitoring reports reflect this, i.e., the ascent report that contains the highest level will be used to calculate the statistics (i.e., IUS bulletin). This is the a case of duplicates, however, if a radiosonde is launched 30 mins after the one that went wrong (i.e., burst at quite low altitudes), both will be used because they are not considered duplicates in those circumstances.