the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 07 Dec 2023
Observations of the macrophysical properties of cumulus cloud fields over the tropical western Pacific and their connection to meteorological variables
Abstract. The poor representation of the macrophysical properties of shallow oceanic cumuli in climate models contributes to the large uncertainty in cloud feedback. These properties are also difficult to measure because it requires high-resolution satellite imagery that are seldomly collected over ocean. Here, we examine cumulus cloud macrophysical properties, their size, shape, and spatial distributions, over the tropical western Pacific using 170 15-m resolution scenes from Terra’s Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) collected during the 2019 Cloud, Aerosol and Monsoon Processes Philippines Experiment (CAMP2Ex) mission. The average cloud fraction (CF) was 0.12, half of which was contributed by clouds less than 1.6 km in area-equivalent diameter. This compared well to Terra’s Multiangle Imaging Spectroradiometer (MISR) resolution-corrected CF of 0.13, but less than the 0.19 measured by Terra’s Moderate Resolution Imaging Spectroradiometer (MODIS). The cloud size distribution exhibited a power law form with exponent of 2.93 and an area-perimeter power law with dimension of 1.24. ASTER, MISR, and CAMP2Ex aircraft lidar showed excellent agreement in the cloud top height (CTH) distribution peak altitude of ~750 m. We examined cumulus properties in relation to meteorological variables and found that the variation in mean CTH is most controlled by the total column water vapor, lower-tropospheric stability (LTS), and estimated inversion strength (EIS). The variation in CF is most controlled by surface wind speed and near-cloud relative humidity instead of LTS/EIS, suggesting the need to improve low cloud parameterizations in climate models that use LTS/EIS based on stratocumulus studies.
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RC1: 'Comment on egusphere-2023-2852', Anonymous Referee #1, 03 Jan 2024
The manuscript presents an analysis of the macrophysical properties of cumulus cloud fields over the tropical western Pacific using high-resolution ASTER satellite data during the CAMP2Ex mission. This study also reveals the correlations between these properties and various meteorological variables. The authors show that the average cloud fraction is notably contributed by smaller clouds and that the variation in mean cloud top height is significantly affected by total column water vapor and LTS. Overall, this paper is well-written with clear scientific merit. However, the uncertainties and causality need to be strengthened. With this, I would recommend the publication of this manuscript with the following major revisions.
Specific comments:
1. This work can strengthen the discussions of uncertainties associated with deriving cloud macrophysical properties from ASTER data. This discussion would benefit from a more comprehensive examination of potential biases and errors that could impact the interpretation of results, especially when using high-resolution satellite imagery.
2. The manuscript utilizes R-squared values to infer meteorological controls over cloud properties. However, there is an imitation of correlations as an indicator, particularly if there are other confounding factors, such as synoptic patterns, that can affect both meteorology and cloud properties simultaneously. The correlation does not clearly reveal the causality.
3. While the impact of meteorological parameters on cloud top height and fraction is explored, this work can discuss more on the key parameters controlling cloud size, such as cloud equivalent diameter. Including an analysis of the impacts of factors on the cloud size could provide a more comprehensive understanding of the cumulus clouds.
4. The study could be strengthened by including analyses of planetary boundary layer (PBL)-related parameters, like PBL height and PBL stability, given their known influence on cumulus cloud modulation. This inclusion would provide a more in-depth perspective on the interactions between the PBL and cloud properties.
Citation: https://doi.org/10.5194/egusphere-2023-2852-RC1 -
RC2: 'Comment on egusphere-2023-2852', Anonymous Referee #2, 06 Feb 2024
Overall, I think the manuscript is well-written and is worthy of rapid publication. Very minor suggestions are provided below.
A few references could be added, for a more complete literature review.
Lines 35-36:
You discuss the morphology of clouds, but I think you need other references in addition to Tobin et al., (2013). This issue and the issue of cloud heterogeneity are discussed in many recent papers. The following references should be considered:Rampal, N., & Davies, R. (2020). On the factors that determine boundary layer albedo. Journal of Geophysical Research: Atmospheres, 125(15), e2019JD032244.
Lang, F., Ackermann, L., Huang, Y., Truong, S. C., Siems, S. T., & Manton, M. J. (2022). A climatology of open and closed mesoscale cellular convection over the Southern Ocean derived from Himawari-8 observations. Atmospheric Chemistry and Physics, 22(3), 2135-2152.
Lang, F., Siems, S. T., Huang, Y., Alinejadtabrizi, T., & Ackermann, L. (2024). On the relationship between mesoscale cellular convection and meteorological forcing: comparing the Southern Ocean against the North Pacific. Atmospheric Chemistry and Physics, 24(2), 1451-1466.
Goren, T., Sourdeval, O., Kretzschmar, J., & Quaas, J. (2023). Spatial Aggregation of Satellite Observations Leads to an Overestimation of the Radiative Forcing Due To Aerosol‐Cloud Interactions. Geophysical Research Letters, 50(18), e2023GL105282.Lines 80 - 85, could use more recent references such as :
Lewis, H., Bellon, G., & Dinh, T. (2023). Upstream Large-Scale Control of Subtropical Low-Cloud Climatology. Journal of Climate, 36(10), 3289-3303.I encourage the authors to add other more recent references too.
Citation: https://doi.org/10.5194/egusphere-2023-2852-RC2 -
AC1: 'Final response to referee comments on egusphere-2023-2852', Michie Vianca De Vera, 11 Mar 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2023-2852/egusphere-2023-2852-AC1-supplement.pdf
Status: closed
-
RC1: 'Comment on egusphere-2023-2852', Anonymous Referee #1, 03 Jan 2024
The manuscript presents an analysis of the macrophysical properties of cumulus cloud fields over the tropical western Pacific using high-resolution ASTER satellite data during the CAMP2Ex mission. This study also reveals the correlations between these properties and various meteorological variables. The authors show that the average cloud fraction is notably contributed by smaller clouds and that the variation in mean cloud top height is significantly affected by total column water vapor and LTS. Overall, this paper is well-written with clear scientific merit. However, the uncertainties and causality need to be strengthened. With this, I would recommend the publication of this manuscript with the following major revisions.
Specific comments:
1. This work can strengthen the discussions of uncertainties associated with deriving cloud macrophysical properties from ASTER data. This discussion would benefit from a more comprehensive examination of potential biases and errors that could impact the interpretation of results, especially when using high-resolution satellite imagery.
2. The manuscript utilizes R-squared values to infer meteorological controls over cloud properties. However, there is an imitation of correlations as an indicator, particularly if there are other confounding factors, such as synoptic patterns, that can affect both meteorology and cloud properties simultaneously. The correlation does not clearly reveal the causality.
3. While the impact of meteorological parameters on cloud top height and fraction is explored, this work can discuss more on the key parameters controlling cloud size, such as cloud equivalent diameter. Including an analysis of the impacts of factors on the cloud size could provide a more comprehensive understanding of the cumulus clouds.
4. The study could be strengthened by including analyses of planetary boundary layer (PBL)-related parameters, like PBL height and PBL stability, given their known influence on cumulus cloud modulation. This inclusion would provide a more in-depth perspective on the interactions between the PBL and cloud properties.
Citation: https://doi.org/10.5194/egusphere-2023-2852-RC1 -
RC2: 'Comment on egusphere-2023-2852', Anonymous Referee #2, 06 Feb 2024
Overall, I think the manuscript is well-written and is worthy of rapid publication. Very minor suggestions are provided below.
A few references could be added, for a more complete literature review.
Lines 35-36:
You discuss the morphology of clouds, but I think you need other references in addition to Tobin et al., (2013). This issue and the issue of cloud heterogeneity are discussed in many recent papers. The following references should be considered:Rampal, N., & Davies, R. (2020). On the factors that determine boundary layer albedo. Journal of Geophysical Research: Atmospheres, 125(15), e2019JD032244.
Lang, F., Ackermann, L., Huang, Y., Truong, S. C., Siems, S. T., & Manton, M. J. (2022). A climatology of open and closed mesoscale cellular convection over the Southern Ocean derived from Himawari-8 observations. Atmospheric Chemistry and Physics, 22(3), 2135-2152.
Lang, F., Siems, S. T., Huang, Y., Alinejadtabrizi, T., & Ackermann, L. (2024). On the relationship between mesoscale cellular convection and meteorological forcing: comparing the Southern Ocean against the North Pacific. Atmospheric Chemistry and Physics, 24(2), 1451-1466.
Goren, T., Sourdeval, O., Kretzschmar, J., & Quaas, J. (2023). Spatial Aggregation of Satellite Observations Leads to an Overestimation of the Radiative Forcing Due To Aerosol‐Cloud Interactions. Geophysical Research Letters, 50(18), e2023GL105282.Lines 80 - 85, could use more recent references such as :
Lewis, H., Bellon, G., & Dinh, T. (2023). Upstream Large-Scale Control of Subtropical Low-Cloud Climatology. Journal of Climate, 36(10), 3289-3303.I encourage the authors to add other more recent references too.
Citation: https://doi.org/10.5194/egusphere-2023-2852-RC2 -
AC1: 'Final response to referee comments on egusphere-2023-2852', Michie Vianca De Vera, 11 Mar 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2023-2852/egusphere-2023-2852-AC1-supplement.pdf
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