NASA Logo, External Link
Facebook icon, External Link to NASA STI page on Facebook Twitter icon, External Link to NASA STI on Twitter YouTube icon, External Link to NASA STI Channel on YouTube RSS icon, External Link to New NASA STI RSS Feed AddThis share icon
 

Record Details

Record 43 of 18263
A Comparison of the Lower Stratospheric Age-Spectra Derived from a General Circulation Model and Two Data Assimilation Systems
Author and Affiliation:
Schoeberl, Mark R.(NASA Goddard Space Flight Center, Greenbelt, MD, United States)
Douglass, Anne R.(NASA Goddard Space Flight Center, Greenbelt, MD, United States)
Zhu, Zhengxin(Science Systems and Applications, Inc., Greenbelt, MD, United States)
Pawson, Steven(Maryland Univ., Baltimore, MD, United States)
Abstract: We use kinematic and diabatic back trajectory calculations, driven by winds from a general circulation model (GCM) and two different data assimilation systems (DAS), to compute the age spectrum at three latitudes in the lower stratosphere. The age-spectra are compared to chemical transport model (CTM) calculations, and the mean ages from all of these studies are compared to observations. The age spectra computed using the GCM winds show a reasonably isolated tropics in good agreement with observations; however, the age spectra determined from the DAS differ from the GCM spectra. For the DAS diabatic trajectory calculations there is too much exchange between the tropics and mid-latitudes. The age spectrum is thus too broad and the tropical mean age is too old as a result of mixing older mid latitude air with tropical air. Likewise the mid latitude mean age is too young due to the in mixing of tropical air. The DAS kinematic trajectory calculations show excessive vertical dispersion of parcels in addition to excessive exchange between the tropics and mid latitudes. Because air is moved rapidly to the troposphere from the vertical dispersion, the age spectrum is shifted toward the young side. The excessive vertical and meridional dispersion compensate in the kinematic case giving a reasonable tropical mean age. The CTM calculation of the age spectrum using the DAS winds shows the same vertical and meridional dispersive characteristics of the kinematic trajectory calculation. These results suggest that the current DAS products will not give realistic trace gas distributions for long integrations; they also help explain why the extra tropical mean ages determined in a number of previous DAS driven CTM s are too young compared with observations. Finally, we note trajectory-generated age spectra . show significant age anomalies correlated with the seasonal cycles. These anomalies can be linked to year-to-year variations in the tropical heating rate. The anomalies are suppressed in the CTM spectra suggesting that the CTM transport scheme is too diffusive.
Publication Date: Jan 01, 2002
Document ID:
20030032196
(Acquired May 01, 2003)
Subject Category: METEOROLOGY AND CLIMATOLOGY
Document Type: Preprint
Meeting Information: AGU 2002 Fall Meeting; 6-10 Dec. 2002; San Francisco, CA; United States
Meeting Sponsor: American Geophysical Union; Washington, DC, United States
Financial Sponsor: NASA Goddard Space Flight Center; Greenbelt, MD, United States
Organization Source: NASA Goddard Space Flight Center; Greenbelt, MD, United States
Description: 2p; In English
Distribution Limits: Unclassified; Publicly available; Unlimited
Rights: Copyright
NASA Terms: ATMOSPHERIC GENERAL CIRCULATION MODELS; CYCLES; COMPUTATION; LATITUDE; STRATOSPHERE; SPECTRA; TRACE CONTAMINANTS; ANOMALIES; DATA SYSTEMS; HEAT TRANSFER; KINEMATICS; ADIABATIC FLOW; TRACE ELEMENTS; TROPICAL REGIONS
Availability Source: Other Sources
Availability Notes: Abstract Only
› Back to Top
Find Similar Records
NASA Logo, External Link
NASA Official: Gerald Steeman
Site Curator: STI Program
Last Modified: August 22, 2011
Contact Us