Abstract
AbstractAnvil clouds cover extensive areas of the tropics, and their response to global warming can affect cloud feedbacks and climate sensitivity. A growing number of models and theories suggest that when the tropical atmosphere warms, anvil clouds rise and their coverage decreases, but observational support for this behavior remains limited. Here we use 10 years of measurements from the space‐borne CALIPSO lidar to analyze the vertical distribution of clouds and isolate the behavior of anvil clouds. On the interannual time scale, we find a strong evidence for anvil rise and coverage decrease in response to tropical warming. Using meteorological reanalyses, we show that this is associated with an increase in static stability and with a reduction in clear‐sky radiatively driven mass convergence at the anvil height. These relationships hold over a large range of spatial scales. This is consistent with the stability Iris mechanism suggested by theory and modeling studies.
Highlights
Anvil clouds cover extensive areas of the tropics, reflect solar radiation, and reduce outgoing long‐wave radiation
We further show that this behavior is consistent with the stability Iris effect suggested by theory and modeling studies
ERA5 reanalyses further show that the altitude and extent of anvils vary in phase with the altitude and strength of the radiatively driven clear‐sky mass convergence peak and that both are tightly linked to the static stability profile
Summary
Anvil clouds cover extensive areas of the tropics, reflect solar radiation, and reduce outgoing long‐wave radiation. Several studies have provided observational support for this theory, showing the rise of high clouds during the very strong 1997–1998 El Niño event (Xu et al, 2005), the invariance of high clouds temperature relative to surface temperature over a 6‐month period (Eitzen et al, 2009; Xu et al, 2007), and the good correspondence between vertical profiles of cloud fraction and radiatively driven clear‐sky mass convergence over a 10‐month period (Kubar et al, 2007) These observations were confirmed on longer periods of 4 to 6 years (Li et al, 2012; Thompson et al, 2017; Zelinka & Hartmann, 2011). We further investigate the existence of PHAT in these observations, as well as the spatial scale at which PHAT and the stability Iris potentially hold
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