Medspiration â System Requirements Document - Data User Element

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Medspiration MED-SOC-RS-001_1 System Requirements Document Issue F Page Table, fig. Reference ID Text from reference documents SR entry 62 WP-ID2.2.2.5 TMI SST retrieval below 285 K 62 WP2-203 TMI retrieves SST primarily from the 10.7 GHz channel, which has decreased sensitivity (and therefore increased error) at CFD.0160 SSTs below 285K. Although the bias at lower temperatures is negligible, the standard deviation increases (as reflected in the SSES). TMI data having retrievals below 285K must be flagged according to the following GDS rule: 62 Rule WP2-204 · Rule 2.2.2.5: If a TRMM TMI SST measurement value is less than 285K, bit 2 of the L2P confidence data variable CFD.0160 2.2.2.5 MW_SST_flags should be set. 62 WP-ID2.2.2.6 High Wind retrieval, above 12 ms -1 62 WP2-205 Uncertainties in the emissivity model at high winds and increased errors in the directional model, result in larger errors CFD.0170 above 12 ms -1 . These errors should not vary temporally or spatially since they are due to uncertainty in the estimate of emissivity. Although this increased error will be reflected in the SSES, some data users may chose to simply exclude these retrievals as suspect. 62 The GDS specifies the following rule: 62 Rule WP2-206 · Rule 2.2.2.6a: If a microwave wind speed measurement contemporaneous with a microwave SST measurement is CFD.0170 2.2.2.6a greater than 12 ms -1 , bit 3 of the L2P confidence data variable MW_SST_flags should be set. 62 Rule WP2-207 · Rule 2.2.2.6b: If a contemporaneous microwave wind speed measurement is unavailable, the nearest NWP analysis CFD.0180 2.2.2.6b in space and time toi the SST measurement should be used to evaluate Rule 2.2.2.6a. 62 WP-ID2.2.2.7 Derive a Microwave Proximity Confidence Value (MPCF) 62 WP2-208 MPCV data are analogous to Infrared Proximity Confidence Values (IPCV) and provide a method to better understand the CFD0210 character of microwave SST and their relationship to the SST1m. Microwave SST measurements are known to be of a reduced quality when they are in close proximity to clearly flagged rainfall, due to side lobe contamination in the proximity of land and sea ice. Also, at wind speeds < 2 ms -1 , a cool skin effect may also exist whereas at high wind speeds the emissivity model used to derive SST is poorly defined. These factors may be used to derive a Proximity_Confidence © 2004 SOC Page 154 of 193
Medspiration MED-SOC-RS-001_1 System Requirements Document Issue F Page Table, fig. Reference ID Text from reference documents SR entry value for microwave SST retrievals that can then be used to derive a MPCV for use within the GHRSST-PP MDB and ultimately the assignment of SSES for MW SST data. The initial MPCV scheme proposed for the GDS is based on the following criteria: 62 WP2-2090 1. Physical distance of an SST measurement from the nearest rain flag. CFD0200 62 WP2-210 2. Physical distance of an SST measurement from nearest land. CFD0200 62 WP2-211 3. Physical distance of an SST measurement from nearest sea ice (held in bit 4 of MW_SST_flags). CFD.0190 62 WP2-212 4. Conditions when the surface wind speed is > 12 ms -1 and is likely to modify the emissivity conditions of the sea surface CFD.0170 in the 6-11GHz frequency range. 62 WP2-213 5. Low wind speed conditions < 2ms -1 when a cool skin/warm layer effect may be present. 62 WP2-214 6. For the special case of TMI SST, conditions when the SST is < 285K. CFD0160 63 WP2-215 The proposed scheme is an initial configuration for MPCV and further research is required within the GHRSST-PP to NASR establish an optimal scheme, which should be undertaken at RDAC once sufficient data are available within the GHRSST- PP MDB. 63 The MPCV scale is shown in Table 2.2.2.7.1. 63 Table WP2-216 Microwave proximity confidence value (MPCV) scale definitions. CFD.0210 2.2.2.7.1 63 WP2-217 If any of the test bitflags are set for the MW retrieval, the data will be flagged as questionable. CFD.0210 63 WP2-218 In addition two surface wind speed threshold values are used to delineate the wind speed conditions for which the best SST retrievals and relationship to the in situ observations is expected using the threshold parameters MPCV_wind1 and CFD.0210 CFD.0220 MPCV_wind2. 63 WP2-219 The values for MPCV_windn shown in Figure 2.2.2.7.1 are expected to vary for a given sensor and the exact value of CFD.0220 these parameters is a subject of on-going research and development within the GHRSST-PP. © 2004 SOC Page 155 of 193
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Medspiration â System Requirements Document - Data User Element

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Medspiration â System Requirements Document - Data User Element