Synthetic MSU Temperatures Using Weighting Functions

The vertical weighting function describes the relative contribution that microwave radiation emitted by a layer in the atmosphere makes to the total intensity measured above the atmosphere on board a satellite. Thus, the brightness temperature for each MSU/AMSU channel corresponds to an average temperature of the atmosphere averaged over that channel's weighting function. For the vertical profile of TLS, 90% of the emissions are generated from the layer between 150 hPa (~12 km) and 20 hPa (~26 km). In the tropics, about 20% of the emissions contributing to TLS originate below the tropopause, here TLS does not exclusively represent stratospheric temperature anomalies (Christy et al. 2003).

RSS provided the weighting functions as instantaneous values at given altitudes whilst UAH provided static mean weighting functions over 5 hPa layers. Both types of weighting functions were converted to CHAMP pressure levels (Fig. 3) and applied to CHAMP temperature climatology profiles. Due to the small differences

July 2005: CHAMP Dry Temperature (Zonal Mean)

July 2005: CHAMP Dry Temperature (Zonal Mean)

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Fig. 2 CHAMP temperature climatology for July 2005, monthly and zonal means for 10° latitude bands on 0.2 km vertical grid. Investigated regions (dashed): global (70° S to 70°N), tropics (20°S to 20°N), NH/SH extratropics (30°N to 70°N)/(30°S to 70°S) (Steiner et al. 2007)

180 165 190 195 200 205 210 215 220 225 230 235 240 245 250 255 [iq

Fig. 2 CHAMP temperature climatology for July 2005, monthly and zonal means for 10° latitude bands on 0.2 km vertical grid. Investigated regions (dashed): global (70° S to 70°N), tropics (20°S to 20°N), NH/SH extratropics (30°N to 70°N)/(30°S to 70°S) (Steiner et al. 2007)

UAH/RSS WFcts for CHAMP

UAH/RSS WFcts for CHAMP

Weighting Functions [hPa

Fig. 3 MSU/AMSU TLS weighting functions from RSS and UAH at CHAMP pressure levels. The respective vertical gridding is indicated on the height axis (right)

Weighting Functions [hPa

Fig. 3 MSU/AMSU TLS weighting functions from RSS and UAH at CHAMP pressure levels. The respective vertical gridding is indicated on the height axis (right)

of the CHAMP TLS temperatures derived with the different weighting functions, the averaged TLS temperature of the two was used for further comparison.

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