Variability of Liquid Water Path in Marine Boundary Layer Clouds

Introduction and Motivation Climatology Model Evaluation Variability of Cloud Liquid Water Conclusions and Future Work

Schematic of Tropical Circulation

Introduction and Motivation Climatology Model Evaluation Variability of Cloud Liquid Water Conclusions and Future Work

Conclusions Part 1 We’ve exploited the availability of a 30-year satellite record to construct a comprehensive climatology of global regions dominated by MBL cloud Discussed the applicability of using Lower Tropospheric Stability as an indirect measure of inversion strength and hence Cloud Fraction. In addition to a dependence on LTS, there is an additional, weaker dependence on the absolute temperature. The seasonal cycle in LTS is governed by the potential temperature at 700hPa in the northern hemisphere, and by SST in the Southern Hemisphere regions. These two factors can to a certain extent explain some of the differences in interregional behaviour.

Introduction and Motivation Climatology Model Evaluation Variability of Cloud Liquid Water Conclusions and Future Work

Introduction and Motivation Climatology Model Evaluation Variability of Cloud Liquid Water Conclusions and Future Work

Horvath and Davies, JGR, 2007

Seethala and Horvath, JGR, 2010

27 Scene Average Scene Average Simultaneous Retrievals – possible biases Simultaneous Retrievals – possible biases Assumes Small Particle size Assumes Small Particle size Poor spatial resolution relative to visible spectrum Poor spatial resolution relative to visible spectrum

28

Introduction and Motivation Climatology Model Evaluation Variability of Cloud Liquid Water Conclusions and Future Work

Conclusions The A-Train instruments provide the opportunity to use independent collocated measurements of LWP. LWP can be strongly influenced by the large scale atmosphere Increased Lower Tropospheric Stability acts to decrease in-cloud LWP This partially offsets increased CRF due to increased fraction of overcast cloud at high stabilities Wind speed and Potential Temperature at 700 hPa are good indicators of cloud properties for overcast cloud Large scale atmospheric factors can also have a significant impact on droplet effective radius, possibly through cloud lifetime effects Further work is needed to establish mechanisms fort he observed results.

Future Work Extend our analysis to different regions Extend time span of current study Investigate seasonal cycle of LWP in terms of large scale variables Extend e.g. LWP-LTS results to different cloud fractions, develop technique to deal with systematic bias. Apply similar method to evaluation of model representation of liquid water.