1 / 2

Motivation

levi-medina
Télécharger la présentation

Motivation

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Statistical characteristics of cloud variability observed at three ARM sites. To improve understanding and parameterization of subgrid variability in climate models, Scientists at Brookhaven and Argon National Laboratories examined the decade-long retrieval products of cloud Liquid Water Path (LWP) from three permanent sites of DOE’s Atmospheric Radiation Measurement (ARM) program for key statistical characteristics, probability density function and their dependence on averaging scales. It is found that the standard deviation, relative dispersion (the ratio of the standard deviation to the mean) and skewness all increase quickly with the averaging window size when the window size is small and become more or less flat when the window size exceeds 12 hours. There is a positive correlation between the mean LWP and the standard deviation. The skewness is found to be closely related to the relative dispersion with a correlation coefficient of 0.6. Comparison further shows that the lognormal, Weibull, and Gamma PDFs reasonably explain the observed relationship between skewness and relative dispersion over a wide range of scales. These results provide observational evidence for subgrid cloud variability and useful insights into how to represent the subgrid variability in climate models. Reference:Huang, D., E. Campos, and Y. Liu. (2014): Statistical characteristics of cloud variability, Part I: retrieved cloud Liquid Water Path at three ARM sites J. Geophys. Res. Accepted. Contact: Dorothy Koch, SC23.1, 301-903-0105

  2. Statistical characteristics of cloud variability observed at three ARM sites • Motivation • What are the statistical characteristics of observed subgrid cloud variability useful for parameterization development? • Approach • The decade-long data at three permanent ARM sites are used to examine for key statistics, PDF, and their scale-dependence. • Result • The variability and skewness of cloud LWP increase with the averaging window size. There is a positive correlation between the mean LWP and the standard deviation. The lognormal, Weibull, and Gamma distributions reasonably explain the observed relationship between skewness and relative dispersion over a wide range of scales. The scatter plot of the skewness and relative dispersion of cloud Liquid Water Path calculated in 3-hour windows using the data from the TWP, SGP, and NSA sites for the period of 1999 to 2002. The color in the scatter plot indicates the density of data points. The solid curves correspond to the truncated Gaussian, gamma, lognormal, and Weibull distributions commonly used in the PDF-based parameterizations. Huang, D., E. Campos, and Y. Liu. (2014): Statistical characteristics of cloud variability, Part I: retrieved cloud Liquid Water Path at three ARM sites. J. Geophys. Res., Accepted.

More Related