Abstract
Abstract. Measuring atmospheric conditions above convective storms using spaceborne instruments is challenging. The operational retrieval framework of current hyperspectral infrared sounders adopts a cloud-clearing scheme that is unreliable in overcast conditions. To overcome this issue, previous studies have developed an optimal estimation method that retrieves the temperature and humidity above high thick clouds by assuming a slab of cloud. In this study, we find that variations in the effective radius and density of cloud ice near the tops of convective clouds lead to non-negligible spectral uncertainties in simulated infrared radiance spectra. These uncertainties cannot be fully eliminated by the slab-cloud assumption. To address this problem, a synergistic retrieval method is developed here. This method retrieves temperature, water vapor, and cloud properties simultaneously by incorporating observations from active sensors in synergy with infrared radiance spectra. A simulation experiment is conducted to evaluate the performance of different retrieval strategies using synthetic radiance data from the Atmospheric Infrared Sounder (AIRS) and cloud data from CloudSat/CALIPSO. In this experiment, we simulate infrared radiance spectra from convective storms through a combination of a numerical weather prediction model and a radiative transfer model. The simulation experiment shows that the synergistic method is advantageous, as it shows high retrieval sensitivity to the temperature and ice water content near the cloud top. The synergistic method more than halves the root-mean-square errors in temperature and column integrated water vapor compared to prior knowledge based on the climatology. It can also improve the quantification of the ice water content and effective radius compared to prior knowledge based on retrievals from active sensors. Our results suggest that existing infrared hyperspectral sounders can detect the spatial distributions of temperature and humidity anomalies above convective storms.
Highlights
Water vapor in the upper troposphere and lower stratosphere (UTLS) plays an essential role in the Earth’s climate system due to its important radiative effects (Huang et al, 2010; Dessler et al, 2013) and chemical effects (Shindell, 2001; Kirk-Davidoff et al, 1999; Anderson et al, 2012).Our understanding of UTLS water vapor has long been informed by accurate in situ observations carried out during aircraft and balloon campaigns
We evaluate the performance of retrieval strategies that use the slab-cloud and synergistic methods following a simulation experiment emulating an implementation based on the Atmospheric Infrared Sounder (AIRS) L1B and DARDAR-Cloud products
By conducting the simulation experiment, this study evaluated the ability of existing hyperspectral infrared sounders to detect temperature and humidity fields above convective storms
Summary
Water vapor in the upper troposphere and lower stratosphere (UTLS) plays an essential role in the Earth’s climate system due to its important radiative effects (Huang et al, 2010; Dessler et al, 2013) and chemical effects (Shindell, 2001; Kirk-Davidoff et al, 1999; Anderson et al, 2012).Our understanding of UTLS water vapor has long been informed by accurate in situ observations carried out during aircraft and balloon campaigns. Long-term records provided by balloon-borne observations have suggested a decadal increase in stratospheric water vapor (Oltmans et al, 2000; Rosenlof et al, 2001; Hurst et al, 2011) but a decadal cooling in tropical tropopause temperature over the same period (Rosenlof et al, 2001; Randel et al, 2004). These contradictory trends in water vapor and temperature are not reproduced well by reanalysis products (Davis et al, 2017), and the key processes at play are still under debate. While balloon-borne instruments suggest possible changes in UTLS water vapor, aircraft campaigns reveal that UTLS water vapor can be highly
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
