Climate And Weather of the Sun-Earth System

A new SCOSTEP Program for 2004-2008

Global Observing Campaign

The purpose of this campaign is to characterize tides and their influence from the Troposhpere to the Thermosphere.


Although atmospheric tides were the first of the large scale global waves to be identified in the atmosphere, our understanding of their behaviour remains incomplete. They are closely linked to solar heating throughout the atmosphere but their source mechanisms are not fully understood and non-linear interactions are likely to play a role in the creation of some modes. The sun-synchronous (migrating) diurnal and semi-diurnal tides have been extensively studied but even for these modes, the short term variability, vertical structure and dissipation remains unresolved. Recent work has identified the existence of strong non-sun synchronous (non-migrating) modes and their role in geographic variations in the strength of observed diurnal and semidiurnal oscillations.

Above the stratosphere, the influence of tides is ubiquitous. They dominate the dynamical variability, significantly impact the local time variations in constituents and the associated chemistry and strongly modulate the propagation conditions experienced by upward propagating gravity waves. In the ionosphere they are thought to cause the observed Sq variations in the current systems.

In current general circulation models, tidal modes are closely linked to the parameterizations of radiative heating, convection, clouds and latent heat. As such comparisons between models and observed tidal signatures provide a sensitive means of evaluating and validating these parameterizations. For the most part, the study of tidal modes (other than the migrating diurnal tide) in general circulation models has been neglected.

The resolution of many of the outstanding problems concerning the existence and impact of tides in the atmosphere requires global and extensive observation campaigns, a vigorous analysis effort and comparison with global models.

It is recognized that comparisons with models will provide insights into the mechanisms involved in the propagation and influence of tides and the observations will serve as a means of model validation. To foster interaction between the modelling community and the observing community, model runs for similar time periods as the observing campaigns are solicited and considered an integral part of this observing campaign.

Goals and Organization

The purpose of this project is:

These goals will be achieved through global observations campaigns and the associated analysis of the data. Two workshops will be held to support the analysis of this data and comparison with model results. The first workshop will be held after several successful observing campaigns and will concentrate primarily on presenting the observations and the second will be held a couple of years later and will concentrate on the analysis of the data and comparison with and validation of global models.

The activities associated with this effort will be facilitated by a team with a broad range of expertise and international representation. They will select the timing for the observation campaigns, promote and coordinate participation in these campaigns, assist in the setting up of the resulting data sets, and ensure the scientific community is aware of this data and involved in its analysis.

Campaign Description

Several global observing campaigns are proposed for the characterization of tides in the Earth's atmosphere. The time periods will be chosen to sample the conditions during several seasons, allow the associated variations in the tidal modes to be determined. To explore possible correlations with ENSO and the QBO a campaign during the the NH spring solstice season will be scheduled for every year. The first of these campaigns is scheduled for September/October, 2005.

The observations for each campaign will be identified and made accessible for the scientific community through appropriate agreements with the scientists associated with the various data sets.

Observations are solicited which will allow the diagnosis of:

It is envisioned that the resulting data set will be used both for direct analyses of the conditions present in the atmosphere during the observing campaign and for comparisons with conditions diagnosed in models of various complexities. As a result in addition to the observations, model simulations of conditions appropriate to the various observing campaigns are also solicited.

For more information on this campaign or to express interest in participating contact William Ward ().

CAWSES Office, Center for Space Physics, Boston University, 725 Commonwealth Ave. Boston, MA 02215 USA; Phone: 617/353-5990; FAX: 617/353-6463;

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