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Peer review report 2 on “A multi-scale analysis of Namibian rainfall over the recent decade – comparing TMPA satellite estimates and ground observations”
Journal of Hydrology: Regional Studies 9 (2017) 105–106
Contents lists available at ScienceDirect
Journal of Hydrology: Regional Studies journal homepage: www.elsevier.com/locate/ejrh
Peer Review Report
Peer review report 2 on “A multi-scale analysis of Namibian rainfall over the recent decade – comparing TMPA satellite estimates and ground observations”
1. Original Submission 1.1. Recommendation Major Revision 2. Comments to Author The authors employed a continuous 6-year record of ground observations collected at Weltevrede Guest Farm Namibia to evaluate the TMPA 3B42 0.25-degree (∼25 km) 3-hourly satellite rainfall estimates over the area. The validation of satelliteprecipitation over remote areas with scarce ground observation is interesting and useful. Although there are apparent limitations caused by the scarcity of observations, it can still be useful for other investigations with similar data situation or providing complementary information for other related studies over the same domain. However, the authors should make sure not over-interpret the information from the very limited data which quality is even not known. Comparison of single point rainfall measurement with areal precipitation estimation can be very risk with lots of uncertainties, which deserves a more depth discussion reminding the cautions of the uncertainty. I would recommend the authors should perform a major revision to significantly improve the quality of the manuscript, particularly in the following two aspects: (1) Perform a thorough comparison of the TMPA and gauge data. Comparison of TMPA rainfall and gauge data was only based on scatter plots showing the correlation, while quantitative bias information was lacking. How does the bias very over seasons and in wet/dry years, and in terms of intensity? This information will interest readers and also provide a basis for the adjustment of the TMPA toward gauge data for the trend analysis which is a main part of the study. A PDF comparison would be suggested. (2) The trend analysis was based on the bias adjusted TRMM data. The adjustment will have significant impacts on the PDF of the TRMM rainfall thus on the trend analysis. However, how was the adjustment performed was not described at all, which is surprising. Was the bias-correction performed at annual, monthly or daily scales? Was there a PDF matching? Why should we believe the simple bias correction can lead to a more reliable trend rather than just using the raw TMPA data itself which should be more homogeneous at least for the analysis? What would be the difference in the trends between the TMPA raw data, and the adjusted data? The authors should better address the concerns. Some detailed comments: #Abstract can be better organized, for example by saying the potential values of this study all together in one or two sentences. Line 114, what does it mean by saying of “calibration”? Lines 163–165: How was the annual bias correction performed? Be clear.
DOI of the original article:http://dx.doi.org/10.1016/j.ejrh.2016.07.003. 2214-5818/$ – see front matter http://dx.doi.org/10.1016/j.ejrh.2016.12.042
106
Peer Review Report / Journal of Hydrology: Regional Studies 9 (2017) 105–106
Lines 181–189: It is not quite clear to me the definition of the Ei and Ci even with the formula. What is the Pj and mean P? Please make it clearer. Lines 194–201: Well said. However, it is not clear how the situation was handled in this study. Please provide more discussion. Use TMPA instead of TRMM to correct the product name throughout the manuscript. Anonymous
Contents lists available at ScienceDirect
Journal of Hydrology: Regional Studies journal homepage: www.elsevier.com/locate/ejrh
Peer Review Report
Peer review report 2 on “A multi-scale analysis of Namibian rainfall over the recent decade – comparing TMPA satellite estimates and ground observations”
1. Original Submission 1.1. Recommendation Major Revision 2. Comments to Author The authors employed a continuous 6-year record of ground observations collected at Weltevrede Guest Farm Namibia to evaluate the TMPA 3B42 0.25-degree (∼25 km) 3-hourly satellite rainfall estimates over the area. The validation of satelliteprecipitation over remote areas with scarce ground observation is interesting and useful. Although there are apparent limitations caused by the scarcity of observations, it can still be useful for other investigations with similar data situation or providing complementary information for other related studies over the same domain. However, the authors should make sure not over-interpret the information from the very limited data which quality is even not known. Comparison of single point rainfall measurement with areal precipitation estimation can be very risk with lots of uncertainties, which deserves a more depth discussion reminding the cautions of the uncertainty. I would recommend the authors should perform a major revision to significantly improve the quality of the manuscript, particularly in the following two aspects: (1) Perform a thorough comparison of the TMPA and gauge data. Comparison of TMPA rainfall and gauge data was only based on scatter plots showing the correlation, while quantitative bias information was lacking. How does the bias very over seasons and in wet/dry years, and in terms of intensity? This information will interest readers and also provide a basis for the adjustment of the TMPA toward gauge data for the trend analysis which is a main part of the study. A PDF comparison would be suggested. (2) The trend analysis was based on the bias adjusted TRMM data. The adjustment will have significant impacts on the PDF of the TRMM rainfall thus on the trend analysis. However, how was the adjustment performed was not described at all, which is surprising. Was the bias-correction performed at annual, monthly or daily scales? Was there a PDF matching? Why should we believe the simple bias correction can lead to a more reliable trend rather than just using the raw TMPA data itself which should be more homogeneous at least for the analysis? What would be the difference in the trends between the TMPA raw data, and the adjusted data? The authors should better address the concerns. Some detailed comments: #Abstract can be better organized, for example by saying the potential values of this study all together in one or two sentences. Line 114, what does it mean by saying of “calibration”? Lines 163–165: How was the annual bias correction performed? Be clear.
DOI of the original article:http://dx.doi.org/10.1016/j.ejrh.2016.07.003. 2214-5818/$ – see front matter http://dx.doi.org/10.1016/j.ejrh.2016.12.042
106
Peer Review Report / Journal of Hydrology: Regional Studies 9 (2017) 105–106
Lines 181–189: It is not quite clear to me the definition of the Ei and Ci even with the formula. What is the Pj and mean P? Please make it clearer. Lines 194–201: Well said. However, it is not clear how the situation was handled in this study. Please provide more discussion. Use TMPA instead of TRMM to correct the product name throughout the manuscript. Anonymous