Validation of AIRS-Retrieved atmospheric temperature data over the Taklimakan Desert

The Taklimakan Desert, the world's second largest desert, plays an important role in regional climate change. Previousstudies on its spatial temperature features suffered from sparse conventional detection data, but the Atmospheric InfraredSounder (AIRS) provides excellent temperature retrievals with high spatiotemporal resolution. Validation of AIRS temperatureretrievals over desert regions with high land-surface emissivity, the key contributor to inversion error, is essential beforeusing these data in regional weather/climate modeling. This paper examines the correlation coefficients, root meansquare error (RMSE) and mean BIAS between AIRS-retrieved atmospheric temperature data and radiosonde observations(RAOBs) in the Taklimakan Desert hinterland and oases in the morning and at dusk. Firstly, the AIRS retrievals are consistentwith RAOBs and are more consistent in the morning than at dusk. The consistency is better over a small-scale desert oasisthan over a large-scale oasis in the morning and exhibits the opposite trend at dusk. The correlation coefficient over thehinterland is high in the morning but negative at dusk due to high desert-surface emissivity. Second, the RMSEs, which areall smaller than 3 K, are generally higher over desert sites than over oasis sites and slightly lower over a small-scale oasisthan over a large-scale oasis in the morning. At dusk, the RMSEs are higher over desert sites than over oases and slightlyhigher over a small-scale oasis than over a large-scale oasis. Furthermore, the RMSEs are generally higher in the morningthan at dusk over a large-scale oasis and lower in the morning than at dusk over a small-scale oasis. Third, the absolutemean BIAS values are mostly lower than 1 K. In the morning, relative to RAOB temperatures, the retrieval temperaturesare higher over desert sites but lower over oasis sites. At dusk, the retrieval temperatures are lower than RAOB temperaturesover both desert and oasis sites. The retrieval temperatures are higher than RAOB temperatures over desert sites inthe morning but slightly lower at dusk. Most absolute mean BIAS values are higher in the morning than at dusk overboth oasis and desert sites. Finally, the consistency between the AIRS and RAOB temperature data is high from 700 hPato 100 hPa in the morning and from 700 hPa to 300 hPa at dusk. The difference between the AIRS and RAOB temperaturedata is generally higher in the morning than that at dusk. The RMSE differences between the AIRS and RAOB data areslightly lower in the morning than at dusk and are lower in the middle layers between 700 hPa and 150 hPa than in the layersabove 150 hPa during both the morning and night. The BIAS is lower in the morning than at dusk below 300 hPabut higher in the upper layers. Moreover, the BIAS value is positive in the middle layers between 500 hPa and 150 hPaand negative at other levels at both times. Generally, the AIRS retrieval temperatures are reliable and can be used in furtherstudies in the Taklimakan Desert.