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Unprecedented Observations of a Nascent In Situ Cirrus in the Tropical Tropopause Layer
Author(s) -
Reinares Martínez I.,
Evan S.,
Wienhold F. G.,
Brioude J.,
Jensen E. J.,
Thornberry T. D.,
Héron D.,
Verreyken B.,
Körner S.,
Vömel H.,
Metzger J.M.,
Posny F.
Publication year - 2021
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2020gl090936
Subject(s) - cirrus , tropopause , ice crystals , atmospheric sciences , hygrometer , environmental science , backscatter (email) , effective radius , stratosphere , remote sensing , geology , climatology , physics , meteorology , astrophysics , humidity , telecommunications , galaxy , computer science , wireless
A nascent in situ cirrus was observed on January 11, 2019 in the tropical tropopause layer (TTL) over the southwestern Indian Ocean, with the use of balloon‐borne instruments. Data from cryogenic frost point hygrometer (CFH) and Compact Optical Backscatter and AerosoL Detector (COBALD) instruments were used to characterize the cirrus and its environment. Optical modeling was employed to estimate the cirrus microphysical properties from the COBALD backscatter measurements. Newly fomed ice crystals with radius <1 μm and concentration ∼500 L −1 were reported at the tropopause. The relatively low concentration and CFH ice supersaturation (1.5) suggests a homogeneous freezing event stalled by a high‐frequency gravity wave. The observed vertical wind speed and temperature anomalies that triggered the cirrus formation were due to a 1.5‐km vertical‐scale wave, as shown by a spectral analysis. This cirrus observation shortly after nucleation is beyond remote sensing capabilities and presents a type of cirrus never reported before.