Abstract

Abstract. In this study the temporal and spatial characteristics of the liquid water path (LWP) of low, middle and high level clouds are analysed using space-based observations from the Spinning Enhanced Visible and Infrared Imager (SEVIRI) instrument onboard the Meteosat Second Generation 2 (MSG 2) satellite. Both geophysical quantities are part of the CLAAS (CLoud property dAtAset using SEVIRI) data set and are generated by EUMETSAT's Satellite Application Facility on Climate Monitoring (CM SAF). In this article we focus on the statistical properties of LWP, retrieved during daylight conditions, associated with individual cloud types. We analysed the intrinsic variability of LWP, that is, the variability in only cloudy regions and the variations driven by cloud amount. The relative amplitude of the intrinsic diurnal cycle exceeded the cloud amount driven amplitude in our analysed cases. Our results reveal that each cloud type possesses a characteristic intrinsic LWP distribution. These frequency distributions are constant with time in the entire SEVIRI field of view, but vary for smaller regions like Central Europe. Generally the average LWP is higher over land than over sea; in the case of low clouds this amounts to 15–27% in 2009. The variance of the frequency distributions is enhanced as well. Also, the average diurnal cycle of LWP is related to cloud type with the most pronounced relative diurnal variations being detected for low and middle level clouds. Maps of the relative amplitude and the local time of maximum LWP show the variation throughout the SEVIRI field of view.

Highlights

  • An essential parameter for monitoring climate variability is the large-scale view of the cloud-field distribution

  • Both variables are derived from the Spinning Enhanced Visible and Infrared Imager (SEVIRI) onboard the Meteosat Second Generation 2 (MSG 2) satellite

  • The general features of liquid water path (LWP), for example, frequency distribution, average value and diurnal cycle are specified to serve as characteristic measures in atmospheric numerical modelling

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Summary

Introduction

An essential parameter for monitoring climate variability is the large-scale view of the cloud-field distribution. We go beyond the simplified type of cloud approach and analyse and discuss the relationship between cloud type and liquid water path as they are categorised by CM SAF (EUMETSAT’s Satellite Application Facility on Climate Monitoring) Both variables are derived from the Spinning Enhanced Visible and Infrared Imager (SEVIRI) onboard the Meteosat Second Generation 2 (MSG 2) satellite. The general features of LWP, for example, frequency distribution, average value and diurnal cycle are specified to serve as characteristic measures in atmospheric numerical modelling They can be used to conduct process studies, assist in the evaluation of microphysical measurement experiments such as the airborne probing of clouds and serve as input for cloud generators and radiative transfer studies on a wide range of spatial scales.

Generation of LWP and CTY from SEVIRI measurements
Cloud type classification
Cloud liquid water path derivation
Analysis
Diurnal cycle
Findings
Conclusions
Full Text
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