Vertical Variation of Cloud Droplet Size Using Ship and Space-borne R/S Data
Li, Z., University of Maryland
Chen, R, R Wood, Z Li, R Ferraro, and F Chang. 2008. "Studying the vertical variation of cloud droplet effective radius using ship and space-borne remote sensing data." Journal of Geophysical Research 113, doi:10.1029/2007JD009596.
Figure 1. Coincident images of C-band radar reflectivity and MODIS cloud profile at UTC 15:55, Oct. 18, 2001. a) RHB C-band radar reflectivity image. b) MODIS estimation of droplet effective radius at cloud top (re1). c) MODIS estimation of droplet effective radius at cloud ba
se (re2). d) MODIS LWP estimation.
Figure 2. Scatter plot of reflectivities over upper 1/3 portion of cloud la
yer (Zupper-third) and reflectivities over lower 1/3 portion of cloud la yer (Zlower-third) with data from MMCR. Color of the scatter plots represents the column maximum radar reflectivity.
Low level stratiform liquid water clouds have a significant influence on the earth’s climate due to their strong shortwave radiative forcing. Such clouds cover large regions of the earth’s oceans [Klein and Hartmann 1993]. The shortwave optical depth of liquid water clouds depends upon both the bulk condensate amount and the size of the cloud drops. Dependence on the latter is expressed conveniently as an effective radius. The vertical variation of cloud droplet effective radius (re) is an important cloud property that reflects both condensation and coalescence growth. Satellite observation is the only practical means to infer cloud re globally. Solar reflectance measurements from a visible channel and a single near infrared (NIR) channel are used widely to estimate cloud optical depth and cloud top re. The retrieved values only represent a thin la
Using data from the EPIC 2001 Stratocumulus Study, this study investigates the cloud re vertical variation for drizzling and non-drizzling clouds. Estimates of the partitioning of liquid water content between drizzle drops and small cloud droplets is carried out using millimeter wave cloud radar (MMCR) data in drizzling stratocumulus by incorporating simultaneous liquid water path (LWP) estimates from a passive microwave radiometer. Satellite reflectance measurements from the moderate-resolution imaging spectroradiometer (MODIS) on the Terra satellite are used to estimate the trend of vertical re variation. Using drizzle rates estimated with a scanning C-band radar we show that the cloud re can decrease with height in clouds with sufficiently strong drizzle. For non-drizzling clouds, the re generally increases with height in accordance with the growth of cloud droplets by condensation. For drizzling clouds, at cloud ba
Both re at cloud ba