Predictability of the mesosphere and lower thermosphere based on initialized hindcast experiments

Monday, July 15, 2019

The ability to predict conditions in Earth’s ionosphere and thermosphere is of increasing societal relevance due to the growing dependence on, for example, satellite based communications and navigation (e.g., GPS) systems. The ionosphere and thermosphere are known to vary significantly from day-to-day, and this day-to-day weather is largely driven by processes originating in the lower atmosphere (below ~50 km), especially during periods of low solar and geomagnetic activity.

Graph depicting global normalized root mean square error for wavenumbers
Global normalized root mean square error for wavenumbers 0-6 in different seasons at (a) 1.0, (b) 0.1, (c) 0.01, and (d) 0.001 hPa in WACCMX+DART hindcast experiments verified against WACCMX+DART analysis fields. Solid lines indicate the median of all hindcast experiments, and shading indicates the lower and upper quartiles.

Accurate forecasting of the ionosphere-thermosphere variability thus partially depends on the ability to accurately forecast the component that originates in the lower atmosphere. This study makes use of the recent developments in whole atmosphere models to provide the first comprehensive investigation of current capabilities to forecast the lower atmospheric drivers of ionosphere-thermosphere day-to-day variability. We evaluate the present capabilities of the Whole Atmosphere Community Climate Model eXtended version with data assimilation (WACCMX+DART) to forecast conditions at altitudes (~60-120 km) that are relevant for generating the day-to-day variability in the ionosphere and thermosphere. The forecast skill is evaluated based on a set of hindcast experiments that were initialized on the 1st and 15th of each month of 2009 and 2010. The results demonstrate that the forecast skill decreases with increasing altitude, and also decreases for smaller spatial scales. Furthermore, it is found that, on average, the primary drivers of spatial and temporal variability in the ionosphere can be forecast several days in advance. The forecast skill of the ionosphere is typically thought to be less than ~24 hours; however, the results of the present study illustrate that the forecast skill of the ionosphere can potentially be increased by incorporating forecasts of the lower atmospheric drivers.

Publication Name: Space Weather
First HAO Author's Name: Nick Pedatella