Deep convective cloud characterizations from both broadband imager and hyperspectral infrared sounder measurements. Issue 3 (2nd February 2017)

• Record Type: Journal Article
• Authors: Ai, Yufei; Li, Jun; Shi, Wenjing; Schmit, Timothy J.; Cao, Changyong; Li, Wanbiao
• Is Part Of: Journal of geophysical research. Volume 122:Issue 3(2017)
• Page Start: 1700
• Page End: 1712
• Publication Date: 2017-02-02
• Subjects: deep convective cloud -- broadband imager -- hyperspectral IR sounder; Atmospheric physics -- Periodicals; Geophysics -- Periodicals; 551.5
• DOI: 10.1002/2016JD025408
• Languages: English
• ISSNs: 2169-897X

Abstract

Abstract: Deep convective storms have contributed to airplane accidents, making them a threat to aviation safety. The most common method to identify deep convective clouds (DCCs) is using the brightness temperature difference (BTD) between the atmospheric infrared (IR) window band and the water vapor (WV) absorption band. The effectiveness of the BTD method for DCC detection is highly related to the spectral resolution and signal‐to‐noise ratio (SNR) of the WV band. In order to understand the sensitivity of BTD to spectral resolution and SNR for DCC detection, a BTD to noise ratio method using the difference between the WV and IR window radiances is developed to assess the uncertainty of DCC identification for different instruments. We examined the case of AirAsia Flight QZ8501. The brightness temperatures ( T b s) over DCCs from this case are simulated for BTD sensitivity studies by a fast forward radiative transfer model with an opaque cloud assumption for both broadband imager (e.g., Multifunction Transport Satellite imager, MTSAT‐2 imager) and hyperspectral IR sounder (e.g., Atmospheric Infrared Sounder) instruments; we also examined the relationship between the simulated T b and the cloud top height. Results show that despite the coarser spatial resolution, BTDs measured by a hyperspectral IR sounder are much more sensitive to high cloud tops than broadband BTDs. As demonstrated in this study, a hyperspectral IR sounder can identify DCCs with better accuracy. Key Points: Discussion of DCC detection with BNR from different instruments Uncertainty in the DCC identification using broadband and hyperspectral infrared instruments Relationship between the DCC top height and infrared BTD