In Situ Measurements of Cirrus Clouds on a Global Scale

Gary Lloyd,Martina Krämer,Petzold Andreas,Martin Gallagher,Thomas Choularton,Darrel Baumgardner

doi:10.3390/atmos12010041

Abstract

Observations of high-altitude cirrus clouds are reported from measurements made during the routine monitoring of cloud properties on commercial aircraft as part of the In-Service Aircraft for a Global Observing System. The increasing global scale of the measurements is revealed, with 7 years of in situ data producing a unique and rapidly growing dataset. We find that cloud fractions measured ≥ 10 km at aircraft cruise altitude are representative of seasonal trends associated with the mid-latitude jet stream in the Northern Hemisphere, and the relatively higher cloud fractions are found in tropical regions such as the Inter-Tropical Convergence Zone and South East Asia. Both stratospheric and tropospheric data were used to calculate the cloud fractions routinely experienced by commercial aircraft. Further work is needed for a direct comparison with previous studies that limit cloud fraction calculations to tropospheric data only. The characteristics of these clouds are discussed and the potential different formation mechanisms in different regions assessed.

Highlights

In-Service Aircraft for a Global Observing System (IAGOS) is a European ResearchInfrastructure that combines the scientific expertise of its member institutions with the infrastructure of civil aviation to make near continuous measurements of the atmosphere on a global scale
IAGOS is an opportunity to add to the global cirrus climatology, and here we describe some of the initial results from this global in situ dataset
Our measurement period is limited in the context of the El Nińo Southern Oscillation (ENSO) signal, this is consistent with the findings reported by Virts and Wallace that found a shift in peak cloudiness towards the maritime continent during La Nina [31]

Summary

Introduction

In-Service Aircraft for a Global Observing System (IAGOS) is a European ResearchInfrastructure that combines the scientific expertise of its member institutions with the infrastructure of civil aviation to make near continuous measurements of the atmosphere on a global scale. Routine measurements by commercial aircraft over the past 25 years have enabled research on a multitude of essential climate variables (ECVs) [2] on a time scale that is important in the context of global climate change. This has included temperature trends [3], greenhouse gases including CO2 , CH4 , CO and H2 O [4,5] climatologies of O3 , CO and

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Findings

Discussion

Conclusion