Jean Lionel Lacour

A correlation method for volcanic ash detection using hyperspectral infrared measurements

Remote satellite detection of airborne volcanic ash is important for mitigating hazards to aviation and for calculating plume altitudes. Infrared sounders are essential for detecting ash, as they can distinguishing aerosol type and can be used day and night. While broadband sensors are mainly used for this purpose, they have inherent limitations. Typically, water and ice can mask volcanic ash, while wind blown dust can yield false detection. High spectral resolution sounders should be able to overcome some of these limitations. However, existing detection methods are not easily applicable to hyperspectral sounders and there is therefore a pressing need for novel techniques. In response, we propose a sensitive and robust volcanic ash detection method for hyperspectral sounders based on correlation coefficients and demonstrate it on IASI observations. We show that the method differentiates ash from clouds and dust. Easy to implement, it could contribute to operational volcanic hazard mitigation.

Structure and Dynamical Influence of Water Vapor in the Lower Tropical Troposphere

In situ, airborne and satellite measurements are used to characterize the structure of water vapor in the lower tropical troposphere—below the height,

Observations of HDO/H2O ratio with IASI/MetOp

z_*,

Infrared satellite observations of hydrogen sulfide in the volcanic plume of the August 2008 Kasatochi eruption

z∗, of the triple-point isotherm,

Cross-validation of IASI/MetOp derived tropospheric δD with TES and ground-based FTIR observations

T_*.

Advanced exploitation of Ground-Based measurements for Atmospheric Chemistry and Climate Applications "AGACC"

T∗. The measurements are evaluated in light of understanding of how lower-tropospheric water vapor influences clouds, convection and circulation, through both radiative and thermodynamic effects. Lower-tropospheric water vapor, which concentrates in the first few kilometers above the boundary layer, controls the radiative cooling profile of the boundary layer and lower troposphere. Elevated moist layers originating from a preferred level of convective detrainment induce a profile of radiative cooling that drives circulations which reinforce such features. A theory for this preferred level of cumulus termination is advanced, whereby the difference between