Remote Sensing of Mesosphere and Lower Thermosphere Dynamical Tracers from Space

Dear Colleagues,

Remote observations of long-lived trace gases in the mesosphere and lower thermosphere (MLT), depicting the dynamics of this atmospheric region, are often used to quantify dynamical phenomena that are otherwise difficult to measure (i.e., winds, waves, diffusion, etc.). Over the past few decades, satellite technology has provided a wealth of global measurements of tracers’ distributions in the MLT, which have already reached a continuous coverage over close to two solar cycles from single instruments in some cases. The availability of these datasets has resulted in a big step forward in understanding the dynamics of the MLT, i.e., global circulation, wave­–wave and wave–mean flow interactions, coupling to atmospheric regions below and above, name a few "after" response to sudden stratospheric warmings.

There are no clear prospects of a space mission being launched in the near future with the main objective of monitoring tracers with coverage from the lower mesosphere to the lower thermosphere. Providing continuity to the present observations is crucial for tracking variations of the MLT dynamics, particularly under a changing climate scenario. Moreover, it is critical to identify causes for disagreement between available measurements, not only in order to build up merged datasets to determine long-term variations, but also to provide recommendations for future instrumentation.

In the advent of a potential time gap in MLT tracer monitoring in the case of undesired failure of the space instruments currently in operation, it is timely to assess the quality of the available datasets, their drifts due to aging, the reasons for disagreement between datasets, and the pitfalls in their merging. This should be done for at least three reasons: (i) for an accurate evaluation of the climate change impact on MLT dynamics; (ii) because these datasets are used as diagnostics for accuracy of numerical model simulations and contribute to improvement of predictions; and (iii) with the ultimate aim of providing the scenario for future developments. In addition, it is also timely to highlight achievements in the knowledge of the dynamics of the MLT using available tracer datasets in order to demonstrate their need to decision makers.

In this Special Issue, we welcome manuscripts describing tracer measurements from space and evaluating their quality, more specifically related to the following aspects:

• Retrievals, uncertainties, and error assessment;
• Comparisons between datasets (including ground-based observations) and evaluation of biases or instrumental drifts;
• Climatologies and variations at any time-scale;
• Recommendations for future satellite instrumentation (and also ground-based instrumentation in support to satellite technology).

Manuscripts highlighting the value of tracers’ observations from space through comparisons with model simulations or including scientific analysis and broadening the knowledge on MLT dynamics are also more than welcome.

Dr. Maya Garcia Comas
Guest Editor

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• Mesosphere and lower thermosphere
• Dynamics
• Tracers
• Remote sensing
• Future instrumentation
• Climate change