General comments:

The manuscript describes the impact of Aeolus observations on the forecast of Hurricane Ida (2021) and a mesoscale convective system that occurred during NASA’s CPEX-AW field campaign. The authors claim that the novelty of this investigation is that it evaluates the potential impact of the “near-real-time” assimilation of this data set. As mentioned in the paper, previous work has focused on observing system experiments (OSEs). As a matter of fact, OSEs mimic near-real-time impacts as they use observations that were available at the time of the experiment. Thus, I don’t understand what the limitations of earlier investigations are. In fact, these earlier studies used all the observations that were available for assimilation – not just conventional data.

The findings of this study are limited to one single hurricane and one single mesoscale system, which makes it impossible to draw any general conclusions. Therefore, the evaluation of the impact of Aeolus is over-emphasized. In addition, some of the technical elements are not well described. An example are the observations errors. Those are critical in data assimilation as reported in previous Aeolus data impact studies. The paper doesn’t show any statistics of background/analysis departures either that are critical to evaluate the behavior of the assimilation algorithms used here.  

More detailed comments:

L74: What is the meaning of near-real-time HLOS here – and what is different from the methodology used in previous studies (OSEs)? What is new in this study since only focuses on one single hurricane?

L99: Is the assimilated done in the parent domain, the inner domain or both?

Fig.2: Are the Aeolus values observations or background simulations? Also, is the y-axis the instrument error or the observation error? It is not clear to this reviewer how the observation errors are estimated.

In a real-time environment, all available observations would be assimilated – not just conventional data. Why is it not done here? Are the reconnaissance data been assimilated?