Medspiration â System Requirements Document - Data User Element

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Medspiration System Requirements Document same. MED-SOC-RS-001_1 Issue F SR.MDB.0220/I The colocation method will be the same for each satellite product regardless of their resolution. It is stated in the GDS that, for coarser resolution (typically 25 km), the mean of a transect of several measurements obtained within the grid cell will be preferred to a single point observation. This solution introduces a lot of complexity because of the ancillary parameters provided with the in-situ measurements (for instance ship speed or heading, location, sensor identifiers) which can’t be averaged and because in-situ observations may come from different sensors and platforms. In addition, a mean observation could be computed from both day-time or night-time measurements. It is proposed to use the same algorithm as for high resolution measurements. SR.MDB.0230/I The time and space constraints are stored in a configuration file (MDB_time_constraint and MDB_space_contraint variables) for each L2P dataset. These colocation criteria shall be defined and maintained by the GHRSST-PP International Project Office. SR.MDB.0240/I The space/time criteria shall be set as the largest as acceptable (typically 25km in space and 6 hours in time). These criteria may be strengthened when filtering out the data from the MDB at GDAC, for instance to take into account the day/night asymmetry, but not when generating the MDB records at RDAC in order to add more flexibility and extendibility. It is stated in the GDS that “because of the day-night asymmetry in the growth and decay of the diurnal thermocline, more stringent conditions for acceptable time intervals may be required during the day than at night. For these and ambiguous cases, such as close to the terminator, the smallest spatial separation and shortest possible time interval should be sought”. It is not clear if this should be taken into account for the MDB records generation or when retrieving the data records from the database, which allows more flexibility (easier to generate the most complete MDB dataset and then filter out when extracting the data). Moreover the definition and the computation of the day/night threshold need to be provided in order to ensure consistency through RDACs. SR.MDB.0250/I An in-situ measurement shall be colocated to only one pixel of each L2P dataset. This is a refinement from the GDS which states that only one instance of each in situ observation for each individual satellite sensor should occur within the MDB which is © 2004 SOC Page 50 of 193
Medspiration MED-SOC-RS-001_1 System Requirements Document Issue F ambiguous since some sensor measurements may exist in different datasets with various resolutions (eg AVHRR). SR.MDB.0260/I A satellite pixel shall be colocated to only one in situ measurement from a single in situ data file. However, the scope of the colocation process for in situ data is limited to the data files : a satellite pixel may be colocated again with another in situ measurement delivered by CORIOLIS a few days or weeks later in another datafile There is no user requirements addressing this issue. Trying to avoid a satellite pixel being colocated with more than one in situ measurement would be complex to implement while addressing very rare cases. In particular it would almost imply building a MDB to filter out these cases which is not the aim of this system. If this issue is considered as critical, it should be adressed by the GDAC MDB when ingesting its records. SR.MDB.0270/I The targeted in situ measurement for the MDB records production are the SST1m data derived from drifting/moored buoy, ship and float (Argo) observations. For some sensors, the SST1m may not be accessible : it is thus proposed to catch the closest to the 1m depth in the limits of [-5m, 0m]. It is stated in the GDS that the targeted in situ measurement for the MDB records production are the SST1m data derived from drifting/moored buoy and ship observations. After meeting with the CORIOLIS staff, it appears this may be too restrictive since very few ship observations are available beyond –5m. Relaxing this constraint allows to select more data and also to capture the floats data. 3.3.3.3 Generating the MDB records SR.MDB.0310/I All L2P confidence data each pixel stored in a MDB record must accompany the extracted data. SR.MDB.0320/I For each L2P pixel matched to an in-situ measurement, a n x n array of L2P data shall be extracted centred on this pixel and provided within the related MDB record. SR.MDB.0330/I All in situ parameters available in addition to the SST measurement should be included in the MDB record. Upgrade of the MDB format (DTD) may be necessary. Additional parameters will be submitted to GHRSST-PP through ESA in order to keep consistency (variable names, units,…). © 2004 SOC Page 51 of 193
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Medspiration â System Requirements Document - Data User Element