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# The Impact of Solar Activity on Forecasting the Upper Atmosphere via Assimilation of Electron Density Data

Kodikara, Timothy and Zhang, Kefei and Pedatella, Nick and Borries, Claudia (2021) The Impact of Solar Activity on Forecasting the Upper Atmosphere via Assimilation of Electron Density Data. Space Weather. Wiley. doi: 10.1029/2020SW002660. ISSN 1542-7390. (Submitted)

 PDF - Postprint version (accepted manuscript) 16MB

## Abstract

This study presents a comprehensive comparison of the impact of solar activity on forecasting the upper atmosphere through assimilation of radio occultation (RO)-derived electron density ($Ne$) into a physics-based model (TIE-GCM) using an ensemble Kalman filter (KF). Globally abundant RO-derived $Ne$ offers one of the most promising means to test the effect of assimilation on the model forecasted state on a global scale. This study emphasizes the importance of understanding how the assimilation results vary with solar activity, which is one of the main drivers of thermosphere-ionosphere dynamics. This study validates the forecast states with independent RO-derived GRACE (Gravity Recovery and Climate Experiment mission) $Ne$ data. The principal result of the study is that the agreement between forecast $Ne$ and data is better during solar minimum than solar maximum. The results also show that the agreement between data and forecast is mostly better than that of the standalone TIE-GCM driven with observed geophysical indices. The results emphasize that TIE-GCM significantly underestimate $Ne$ in altitudes below 250~km and the assimilation of $Ne$ is not as effective in these lower altitudes as it is in higher altitudes. The results demonstrate that assimilation of $Ne$ significantly impacts the neutral mass density ($\rho$) estimates via the KF state vector---the impact is larger during solar maximum than solar minimum relative to a nonassimilation run. The results are useful to explain the inherent model bias, to understand the limitations of the data, and to demonstrate the capability of the assimilation technique.

Item URL in elib:https://elib.dlr.de/139405/
Document Type:Article
Title:The Impact of Solar Activity on Forecasting the Upper Atmosphere via Assimilation of Electron Density Data
Authors:
AuthorsInstitution or Email of AuthorsAuthor's ORCID iD
Kodikara, TimothyTimothy.Kodikara (at) dlr.dehttps://orcid.org/0000-0003-4099-9966
Zhang, KefeiRMIT, Australiahttps://orcid.org/0000-0001-9376-1148
Pedatella, NickUCAR, CO, USAhttps://orcid.org/0000-0002-8878-5126
Borries, Claudiaclaudia.borries (at) dlr.dehttps://orcid.org/0000-0001-9948-3353
Date:8 March 2021
Journal or Publication Title:Space Weather
Refereed publication:Yes
Open Access:Yes
Gold Open Access:No
In SCOPUS:Yes
In ISI Web of Science:Yes
DOI :10.1029/2020SW002660
Publisher:Wiley
ISSN:1542-7390
Status:Submitted
Keywords:TIE-GCM, data assimilation, ionosphere forecasts, ensemble Kalman filter, neutral mass density forecasts, COSMIC
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Space
HGF - Program Themes:Earth Observation
DLR - Research area:Raumfahrt
DLR - Program:R EO - Earth Observation
DLR - Research theme (Project):R - Solar-Terrestrial Physics SO
Location: Neustrelitz
Institutes and Institutions:Institute for Solar-Terrestrial Physics > Solar-Terrestrial Coupling Processes
Deposited By: Kodikara, Dr Timothy
Deposited On:22 Mar 2021 09:06