The occurrence of cirrus clouds associated with eastward propagating equatorial n = 0 inertio‐gravity and Kelvin waves in November 2011 during the CINDY2011/DYNAMO campaign

Abstract

AbstractCirrus cloud variability associated with n = 0 eastward inertio‐gravity equatorial waves and equatorial Kelvin waves (both with the period of ~4 days) and equatorial Kelvin wave with another periodicity (~16 days) were observed in the tropical Indian Ocean (8.0°S, 80.5°E) in November of 2011 during the Cooperative Indian Ocean experiment on intraseasonal variability in the Year 2011 (CINDY2011)/Dynamics of the Madden‐Julian Oscillation (DYNAMO) field campaign using balloon‐borne cryogenic frostpoint hygrometers, Vaisala radiosondes, and a shipborne high spectral resolution lidar system. During early to mid‐November, the cirrus cloud appearance corresponded primarily with high supersaturation and high relative humidity caused by the temperature disturbances associated with the ~4 day waves between 12 km altitude and the cold‐point tropopause. The cirrus clouds disappeared under the unfavorable (downward wind and dry) conditions that were caused by the ~4 day waves, although the ~16 day wave was generating favorable conditions. Our multi‐instrument cirrus measurements revealed that we must consider the phases of various overlapping waves when estimating dehydration efficiency caused by cirrus clouds around the cold‐point tropopause.