Spatio-Temporal Analysis of Valley Wind Systems in the Complex Mountain Topography of the Rolwaling Himal, Nepal

Round 1

Reviewer 1 Report

The authors present an interesting study on the spatio-temporal features of valley wind systems in a complex mountain topography. The article is well organized and writtend. I have no suggestions for the improvement of the mansucript. It is suggested the aticle be accepted. 

Author Response

Dear Reviewer,

thanks a lot for your kind comments on our paper.

Best regards,
Johannes Weidinger and Helge Jentsch

Reviewer 2 Report

It was not clearly for me the the wind directions are representative for up/down valley... The accuracy of the measurements should be taken in account. Also, I guess that low resolution of ERA5-Land is not suitable (as described in the manuscript). Have you WRF simulation (at 1 km resolution for instance)?! The authors should analyse the use of decimals for the averages respected to the accuracy of the instruments...

Comments for author File: Comments.pdf

Author Response

Dear Reviewer,

thanks a lot for your thorough and critical read and helpful comments on our manuscript.
Please find our responses in the response letter below and our comments in the reviewed manuscript as .pdf.

Best regards,
Johannes Weidinger and Helge Jentsch

_______________________________________________________________________________

Response to Reviewer 2 Comments

Point 1: It was not clearly for me the the wind directions are representative for up/down valley...

Response 1: We added additional information on the dominant wind directions, the valley orientation and attached wind rose plots for all VWDs and the two stations within the results (Figures 4 and 6). Additionally, wind rose plots for all remaining stations are now in the appendix. We hope this is now much clearer than in the previous manuscript version.

 

Point 2: The accuracy of the measurements should be taken in account.

Response 2: Please see Response 4 for this point, too.

 

Point 3: Also, I guess that low resolution of ERA5-Land is not suitable (as described in the manuscript). Have you WRF simulation (at 1 km resolution for instance)?!

Response 3: For more consistency within the utilized data sets (for the valley wind days (VWD) selection in a data scarce mountain region), we switched to implement only ERA5 data sets and the in situ measurements from the AWS network for the identification of VWDs. ERA5-Land data is now excluded within our approach. We only use ERA5 data for parts of the subsetting of our observation period to (VWDs). It is a product with mediocre spatial resolution (~31km) compared to ERA5-Land (~9km), but instead has all the required parameters ‘mean sea level pressure’ and the wind speeds at the 500 hP level (‘U-component of wind’ and ‘V-component of wind’). These parameters are rather spatially consistent and tend not to vary too much, especially over our research domain with approx. 10 km horizontal extension. Unfortunately, we do not have access to very high WRF simulations (at 1km resolutions for our research area), otherwise this would be the perfect data source for our identification of VWDs. For further research in a follow-up paper we are planning to use the knowledge of our working group in dynamical downscaling to further improve the selection of VWDs. There are several optimization techniques to adjust this selection towards monsoon influenced mountain regions, such as the central Himalayas.

 

Point 4: The authors should analyse the use of decimals for the averages respected to the accuracy of the instruments...

Response 4: Thanks for this hint. We appreciate a critical look at accuracies and sensor sensitivities within meteorological observations. We tried to be precise with our measurements and the argumentation within the manuscript. Whenever we are discussing mean values, we used two decimal points, since we have 5 x 4 = 20 measurements per hour. With 120 VWDs in total, this is a robust number of measurements (~2400 repetitions per hour on VWDs). When we use single observations in our reasoning (e.g., in the results section with Figure 5 and 6), we only use one decimal place. The accuracy of the wind speed sensors from the manufacturer is given with ±1.1 m s^-1 over the whole measurement range between 0 and 76 m s^-1, but additionally the measurement inaccuracy is maximum 4,0 % of the current sensor reading. Moreover, the measurement accuracy includes the minimal sensitivity of 1 m s^-1 starting threshold, which adds additional ‘artificial’ uncertainty at lower wind speeds. Thus, with slower wind speeds, where our measurements are located (0 – 8 m s^-1), they can be regarded as more precise than the accuracy over the whole range. Before we shipped the AWS stations to Nepal, we tested them thoroughly within our laboratory and can confirm that especially at lower wind speeds (1 to 10 m s^-1) the sensor readings are accurate. Multiple sensor changes and recalibrations within our measurement period from 2013 until today substantiate our consistent and precise observations.

Author Response File: Author Response.pdf

Reviewer 3 Report

This is a nicely written paper and I enjoyed reading it. A few comments and suggestions for the authors to consider:

1. The figures look great overall. For Figures 3 and 4, it will be more meaningful to consider using additional windrose plots to illustrate speed and directions. May even consider plotting wind roses for individual representative hours during the most representative periods.

2. Figures 3 and 4 - it seems you have precisely picked the local time zone (i.e., GMT+5.45) for data post-analysis, can you explain why in (b) both air temperature and incoming solar radiation still peak earlier than noon time (12 PM)?

3. Please spell out "SD" error although readers can guess it should be "standard deviation".

4. Figures 5 and 6 - please add the scale bar for wind vectors if the arrows are proportional to wind speed.

Author Response

Dear Reviewer,

thanks a lot for your thorough and critical read and helpful comments on our manuscript.
Please find our responses in the response letter below.

Best regards,
Johannes Weidinger and Helge Jentsch

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

the authors did most of my points raised at the previous round