Mathematical aspects in the meteorological interpretation of satellite hyperspectral infrared measurements part II: estimates of the cloud absorption vertical profile of Hurricane Ioke on 28 August 2006
This study processes and analyses hyperspectral measurements from the Atmospheric Infrared Sounder on 28 August 2006 covering day and night scenes of Hurricane Ioke with a temporal spacing of 12 hours. A semi-discrete multilevel cloud model is used to describe the perturbation of the outgoing thermal radiation caused by cloudiness in the field of view (FOV) of a satellite instrument. Cloud spectral effects in the model are represented by an effective cloud absorption vertical profile (CAVP). The CAVP estimate is considered an indicator of the presence of clouds at specific atmospheric layers. The CAVP estimates are compared with lidar measurements. Results indicate a realistic characterization of cloud top and cloud vertical scale. The spatial distribution of the CAVP estimates is used to describe the spatial structure of the hurricane and to monitor its changes over time. Comparison of daytime and night-time CAVP estimates shows that the effective hurricane radius is drastically reduced from about 578 km during the day to about 463 km at night at an atmospheric layer above 212 hPa and from about 604 km to about 499 km at atmospheric layer above 300 hPa. In addition, there is indication of a significant presence of ice crystals in the upper troposphere 10–14 km at night over the large areas adjacent to the hurricane. These crystal clouds have the potential to affect the hurricane energy budget by reducing the night-time cooling rate and trapping heat and moisture in the lower atmospheric layers.