Accession Number:

ADA522470

Title:

A Model Study of Global Variability in Mesospheric Cloudiness

Descriptive Note:

Journal article

Corporate Author:

NAVAL RESEARCH LAB WASHINGTON DC E O HULBURT CENTER FOR SPACE RESEARCH

Report Date:

2005-01-01

Pagination or Media Count:

14.0

Abstract:

We have performed microphysical calculations of mesospheric cloudiness which are driven by output vertical wind, water vapor mixing ratio and temperature from a two-dimensional 2D global chemicaldynamical model. The variations in the 2D model output drive variations in the simulated clouds which can be compared with cloud observations. The specific cloud observables we model are ice content, altitude, peak backscatter at 532nm and albedo at 252 nm. We categorize these parameters in terms of their variations with latitude, solar activity and hemisphere north vs. south. In agreement with observations, we find brighter clouds in the Northern Hemisphere NH relative to the south and at solar minimum relative to solar maximum. Also we find that cloud altitudes are higher in the Southern Hemisphere SH relative to the NH. Quantitatively, compared with observations, it appears that the model may overstate the magnitude of these variations. Thus, the entire range of observed cloud altitudes, poleward of 65-70 deg, is about 2km 83-85 km, whereas the range in the calculated heights range extends up to 5km 83-88 km. In addition, the calculated solar cycle brightness change of up to an order of magnitude appears larger than the limited available observations. Since the model H2O variation in the 80-90km region with respect to solar activity is relatively small 10-40, it is not the cause of our large model cloud variability. Rather, for both hemispheric variation and solar cycle changes, we suggest that the model temperature variability may be too great.

Subject Categories:

  • Atmospheric Physics
  • Meteorology

Distribution Statement:

APPROVED FOR PUBLIC RELEASE