Fog and Low Stratus Obstruction of Wind Lidar Observations in Germany—A Remote Sensing-Based Data Set for Wind Energy Planning

Comments

Answers

1.

Line 79: define the acronym DEM

Added definition as suggested see line 79 in manuscript.

2.

2. Very rough resolution along the coast – colors spills into the sea. Improve.

Imrpoved all figures in manuscript as suggested.

3.

Line 101: Explain and give an impression on how big the height difference is.

Added the average height difference to the manuscript. See line 101

4.

Line 105: not clear for me, please clarify how two measurements levels fall in the

same bin!

Added further information about the measurement levels see lines 107-110 in manuscript.

5.

4: Cloud free is marked in blue and CBA<=100 m in red. This is opposite to the

way it is done in Fig. 5 and Fig. 6. Please be consistent.

Good point. Colors in figure 5 and 6 is now adapted to beconsistent with figure 4.

6.

I note that in Fig. 4 at a height of 150m the availability of the measurements is about

70%. In Fig. 5 (diurnal variation), all measurements fall below the 80% threshold,

but in Fig. 6 all measurements from march to September (7 months) are above the

threshold level. The results in Fig. 6 seems contra-intuitively for me when looking

at Fig. 4 and 5 and needs a thorough discussion.

Due to the non associative property of the mean function the total mean can differ from the mean of the groups (month) if the groups have different numbers of items. Therefore it seems that the numbers in figures 4 and 5 don’t match those of figure 6.

7.

7. Add availability on the islands in the figure. Here the results are shown for a

height of 130m and not 152.5m as in the foregoing figures. Any reason for the

change of height – at least it is not explained. I suggest to be consistent and show

the results for the same height throughout the manuscript – e. g. 130m.

The availability on the islands was fixed together with point 2. There actually is no change in height. Based on the threshold definition the maps are valid for heights above 130m a.s.l.. See expanded explanation in the manuscript lines 113-116

8.

9. Add the height in the legend.

Good point. The information was added to the figure captions where missing.

9.

10. It is not clear (explained???) what P8, P13, GWS HM and SWA refers to. Please

clarify.

Further information regarding the weather types and fog patterns were added to the manuscript. See lines 179-182.

10.

11. Same as for fig. 10.

See point 9.

Comment

Answers

1.

Line 12, suggest to delete “due to availabilities...”.

Removed as suggested.

2.

Line 42, suggest to replace “stronger” with “considerable”.

Here a comparison to the non-fog situations is made. As the decrease of the CNR curve is stronger than in the non-fog situation, we chose the formulation “stronger” - not “considerable”.

3.

Line 46, suggest to replace “advantageous” with “important”.

The word “important” may suggest some kind of necessity. Currently, this information is not available for the optimization of measurement strategies, but the planning process would benefit from this kind of information. From the authors point of view, it is an advantage to have an estimate. Therefore, we suggest to keep the current wording.

4.

Line 47, suggest to add “lidar data” in front of “availability”.

“lidar data” was inserted as suggested

5.

Line 48, replace “spatial impact is” with “spatial and temporal variabilities are”.

The wording was adapted as suggested

6.

Line 53, replace “from data of” with “obtained from”.

“obtained from” was inserted instead of using “of” (line 53).

7.

Line 65-67, move “, which has a temporal...,” between “2014-2017” and “were used”. Yes, it

should be “were” instead of “was”.

The order of the sentence was changed as suggested. Since the sentence refers to a single data set (the MSG data set), we suggest to keep the wording “was” here. (lines 65-67).

8.

Line 79, Again, should be “were”, same for line 80, should be “These data were utilized to...”.

Here also we suggest to keep the word “was” since the DEM is a single data set (lines 79-80).

9.

Line 87, add comma before “were available”.

Added as suggested (line 87).

10.

Line 88, should be “in percentage”.

“percent” is kept since it refers to the unit of the data (line 88).

11.

Line 99, consider to rephrase as “...within one pixel in some complex terrain,...”

“in” was changed to “within” as suggested (line 99).

12.

Line 108, “were not representative...” and remove “was” before “left out”.

Changed “was” to “were” to reflect the plural form of data and removed the second “were” to streamline the sentence (lines 110-111).

13.

Two lines below, what is “intervals” here?

“Intervals” refers to the time period each data point comprises as described in the chapter “Lidar data”. For clarity “(data points”) was inserted (three lines below previous comment).

14.

Line 123-125, this sentence needs to be broken up or rephrased. Here is my suggestion, but the

author probably has better way to do it. It should be “turbines in Germany have been featured a

hub height of...”, and put period after “in the future”. The rest should be a separate sentence.

The sentence was split up as suggested to increase readability (lines 127-129).

15.

Line 125, delete “measurements”.

“CDWL measurements” was removed from the sentence since it should be clear from the context (line 129).

16.

Line 132, should be “are often characterized”

The order of the words in the manuscript is grammatically equivalent to the suggested change. Therefore we suggest to keep the current word order. (line 136).

17.

Line 134-136, this sentence is also confusing. I get what the author is trying to say, but there is sure cleaner way to do it. Also, the author might add some statement why this leads to higher uncertainty of HYFOG.

Further information regarding the impact of the higher uncertainty was added to the manuscript. The higher uncertainty of HYFOG during the summer itself is a fact based on the validation presented in the cited article. From the authors point of view a discussion of the reasons for the higher uncertainty is out of the scope of this manuscript.

18.

Line 146, add comma after “Other factors” and another comma after “periods”. Also, in addition to referring to the reference (16), the author may consider add some statement on why clean air during cloud free condition reduces the lidar data availability.

Commas added as suggested. “low aerosol backscatter” was added as a hint for reduced availability when using lidars (lines 155-156).

19.

Line 151-153, long sentence needs to be rephrased. Delete “half of the year”. Move “on the other hand” to the beginning of the sentence.

“on the other hand” was moved to the beginning as suggested. “(Oct-Mar) was added to clarify “winter half of the year” (lines 161-162).

20.

Line 154, please address more specifically what kind of “special care” is referring to.

“temporal representativity” was added to clarify (line 164).

21.

Line 168, delete “half year” and add commas before “as shown” and after “10 a)” .

Commas added as suggested. For “winter half year” see point 19 (lines 178-179).

22.

Line 171, add comma after “December”.

Comma added as suggested (line 181).

23.

Line 188-191, This is another long sentence that is a little difficult to follow. Try rephrase it.

The sentence was rephrased (lines 203-206).