the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Multi-scale temporal analysis of evaporation on a saline lake in the Atacama Desert
- 1Meteorology and Air Quality, Wageningen University, Wageningen, The Netherlands
- 2Department of Hydraulic and Environmental Engineering, Pontificia Universidad Católica de Chile, Santiago Chile
- 3Centro de Desarrollo Urbano Sustentable (CEDEUS), Santiago Chile
- 4Centro de Excelencia en Geotermia de los Andes (CEGA), Santiago Chile
- 5Department of Civil Engineering, Universidad de Chile, Santiago, Chile
- 1Meteorology and Air Quality, Wageningen University, Wageningen, The Netherlands
- 2Department of Hydraulic and Environmental Engineering, Pontificia Universidad Católica de Chile, Santiago Chile
- 3Centro de Desarrollo Urbano Sustentable (CEDEUS), Santiago Chile
- 4Centro de Excelencia en Geotermia de los Andes (CEGA), Santiago Chile
- 5Department of Civil Engineering, Universidad de Chile, Santiago, Chile
Abstract. We investigate how evaporation changes depending on the scales in the Altiplano region of the Atacama Desert. More specifically, the temporal evolution from the climatological to the sub-diurnal scales on a high-altitude saline lake ecosystem. We analyse the evaporation trends over 70 years (1950–2020) at a high-spatial resolution. The method is based on the downscaling of 30-km hourly resolution ERA5 reanalysis data to 0.1-km spatial resolution data, using artificial neural networks to analyze the main drivers of evaporation. To this end, we use the Penman open water evaporation equation, modified to compensate for the energy balance non-closure and the ice cover formation on the lake during the night. Our estimation of the hourly climatology of evaporation shows a consistent agreement with eddy-covariance measurements and reveals that evaporation is controlled by different drivers depending on the time scale. At the sub-diurnal scale, mechanical turbulence is the primary driver of evaporation, and at this scale, it is not radiation-limited. At the seasonal scale, more than 70 % of the evaporation variability is explained by the radiative contribution term. At the same scale, and using a large-scale moisture tracking model, we identify the main sources of moisture to the Chilean Altiplano. In all cases, our regime of precipitation is controlled by large-scale weather patterns closely linked to climatological fluctuations. Moreover, seasonal evaporation influences significantly the saline lake surface spatial changes. From an interannual scale perspective, evaporation increased by 2.1 mm per year during the entire study period, according to global temperature increases. Finally, we find that yearly evaporation depends on the El Niño Southern Oscillation (ENSO), where warm and cool ENSO phases are associated with higher evaporation and precipitation rates, respectively. Our results show that warm ENSO phases increase evaporation rates by 15 %, whereas cold phases decrease it by 2 %.
Felipe Lobos-Roco et al.
Status: closed
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RC1: 'Comment on hess-2022-20', Anonymous Referee #1, 04 Mar 2022
The comment was uploaded in the form of a supplement: https://hess.copernicus.org/preprints/hess-2022-20/hess-2022-20-RC1-supplement.pdf
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AC1: 'Reply on RC1', Felipe Lobos Roco, 24 Mar 2022
We thank the reviewer for his/her constructive comments and valuable contribution to our manuscript. In the attached document, we answered the line-by-line comments in blue font and indicated if, how, and where we introduced changes in the revised manuscript in a colored font.
Felipe Lobos Roco
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AC1: 'Reply on RC1', Felipe Lobos Roco, 24 Mar 2022
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RC2: 'Comment on hess-2022-20', Stephanie Kampf, 13 Mar 2022
This manuscript is an interesting multi-scale, multi-method evaluation of evaporation and water balance at the Salar del Huasco in Chile. The paper contributes insight into climate drivers of evaporation variability and illustrates how dominant controls on evaporation vary with time scale. The manuscript is well-written, with methods carefully documented.
My suggestion of major revisions is due to concerns about influences on evaporation that appear to be neglected:
1) Salinity reduces evaporation rates, and as far as I can tell this effect is not included in the site-adapted Penman equation. See Mor et al. 2018 WRR
2) Although open water evaporation rates are likely highest, water can also evaporate from areas with salt crusts (see Kampf et al. 2005 JOH, though probably some more recent references are also available). Because the salt crust areas may be large relative to the open water, they likely do have a substantial effect on the basin water balance. An interesting study on salt crust changes over time in Bowen et al. 2017, Geomorphology.
Please incorporate these effects into the analysis, or explain why they can be neglected.
Other minor suggestions:
line 214: "Evaporation estimates are obtained from the downscaled ERA5 and precipitation" - presumably precipitation data are not used to calculate evaporation. Should this state "precipitation-adjusted evaporation estimates"?
line 215: how is the lake depth determined?
lines 257-258: "we observe that and coefficients". Should the "and" be deleted here, or is another word missing?
Table 2, 1st row: "addapted"
Table 2, what is "m" column?
Figure 5: Time series are great to see, but I would suggest (1) plotting as lines rather than columns for easier viewing, and (2) paring this with a scatterplot of met station vs ERA5, so the reader can more easily evaluate the performance comparison. Consider also adding precipitation to the time series to visualize how these changes in evaporation correspond with year-to-year and seasonal variability in precipitation. This time series information about precipitation would be a helpful addition to the combined year precipitation data in Fig 6.
Figure 9: Similarly, I am curious what these patterns look like as a time series rather than aggregated to monthy means and ranges. The complete time series (or an example series of years) would illustrate how much the lake area changes from year to year & how those area changes relate to precipitation and evaporation.
Lake water balance, paragraph starting line 369: I am not entirely following the water balance calculations and results. Could you show the water balance graphically?
Figure 9: b and c are plotting mean monthly values? Related to the comment above about showing full time series - this monthly aggregation illustrates the average role of evaporation in determining lake surface area, but it misses the interannual variability and how precipitation influences area. If the lake surface area lags behind the precipitation because of the slower moving groundwater, then comparing one month's area to the same month's precipitation will not necessarily be helpful. You could try correlations between precipitation and area using the full time series, but instead of comparing same months, lag the lake area month until you find the lag time at which precipitation and lake area are best correlated.
A3: energy balance non-closure coefficient - from Figure A-3, it looks like this is the slope (m) in each scatter relationship? Please connect "m" from the figure to the energy balance non-closure coefficient variable.
Ice coefficient: on what basis did you choose the number of hours below freezing for ice coefficient values? Did you consider salinity effects on freezing?
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AC2: 'Reply on RC2', Felipe Lobos Roco, 24 Mar 2022
We thank Dr. Stephanie Kampf for her constructive comments and valuable contribution to our manuscript. In the attached document, we answered the line-by-line comments in blue font and indicated if, how, and where we introduced changes in the revised manuscript in a colored font.
Felipe Lobos Roco
-
AC2: 'Reply on RC2', Felipe Lobos Roco, 24 Mar 2022
Status: closed
-
RC1: 'Comment on hess-2022-20', Anonymous Referee #1, 04 Mar 2022
The comment was uploaded in the form of a supplement: https://hess.copernicus.org/preprints/hess-2022-20/hess-2022-20-RC1-supplement.pdf
-
AC1: 'Reply on RC1', Felipe Lobos Roco, 24 Mar 2022
We thank the reviewer for his/her constructive comments and valuable contribution to our manuscript. In the attached document, we answered the line-by-line comments in blue font and indicated if, how, and where we introduced changes in the revised manuscript in a colored font.
Felipe Lobos Roco
-
AC1: 'Reply on RC1', Felipe Lobos Roco, 24 Mar 2022
-
RC2: 'Comment on hess-2022-20', Stephanie Kampf, 13 Mar 2022
This manuscript is an interesting multi-scale, multi-method evaluation of evaporation and water balance at the Salar del Huasco in Chile. The paper contributes insight into climate drivers of evaporation variability and illustrates how dominant controls on evaporation vary with time scale. The manuscript is well-written, with methods carefully documented.
My suggestion of major revisions is due to concerns about influences on evaporation that appear to be neglected:
1) Salinity reduces evaporation rates, and as far as I can tell this effect is not included in the site-adapted Penman equation. See Mor et al. 2018 WRR
2) Although open water evaporation rates are likely highest, water can also evaporate from areas with salt crusts (see Kampf et al. 2005 JOH, though probably some more recent references are also available). Because the salt crust areas may be large relative to the open water, they likely do have a substantial effect on the basin water balance. An interesting study on salt crust changes over time in Bowen et al. 2017, Geomorphology.
Please incorporate these effects into the analysis, or explain why they can be neglected.
Other minor suggestions:
line 214: "Evaporation estimates are obtained from the downscaled ERA5 and precipitation" - presumably precipitation data are not used to calculate evaporation. Should this state "precipitation-adjusted evaporation estimates"?
line 215: how is the lake depth determined?
lines 257-258: "we observe that and coefficients". Should the "and" be deleted here, or is another word missing?
Table 2, 1st row: "addapted"
Table 2, what is "m" column?
Figure 5: Time series are great to see, but I would suggest (1) plotting as lines rather than columns for easier viewing, and (2) paring this with a scatterplot of met station vs ERA5, so the reader can more easily evaluate the performance comparison. Consider also adding precipitation to the time series to visualize how these changes in evaporation correspond with year-to-year and seasonal variability in precipitation. This time series information about precipitation would be a helpful addition to the combined year precipitation data in Fig 6.
Figure 9: Similarly, I am curious what these patterns look like as a time series rather than aggregated to monthy means and ranges. The complete time series (or an example series of years) would illustrate how much the lake area changes from year to year & how those area changes relate to precipitation and evaporation.
Lake water balance, paragraph starting line 369: I am not entirely following the water balance calculations and results. Could you show the water balance graphically?
Figure 9: b and c are plotting mean monthly values? Related to the comment above about showing full time series - this monthly aggregation illustrates the average role of evaporation in determining lake surface area, but it misses the interannual variability and how precipitation influences area. If the lake surface area lags behind the precipitation because of the slower moving groundwater, then comparing one month's area to the same month's precipitation will not necessarily be helpful. You could try correlations between precipitation and area using the full time series, but instead of comparing same months, lag the lake area month until you find the lag time at which precipitation and lake area are best correlated.
A3: energy balance non-closure coefficient - from Figure A-3, it looks like this is the slope (m) in each scatter relationship? Please connect "m" from the figure to the energy balance non-closure coefficient variable.
Ice coefficient: on what basis did you choose the number of hours below freezing for ice coefficient values? Did you consider salinity effects on freezing?
-
AC2: 'Reply on RC2', Felipe Lobos Roco, 24 Mar 2022
We thank Dr. Stephanie Kampf for her constructive comments and valuable contribution to our manuscript. In the attached document, we answered the line-by-line comments in blue font and indicated if, how, and where we introduced changes in the revised manuscript in a colored font.
Felipe Lobos Roco
-
AC2: 'Reply on RC2', Felipe Lobos Roco, 24 Mar 2022
Felipe Lobos-Roco et al.
Felipe Lobos-Roco et al.
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