Abstract
In situ observations of cloud effective radius (reff), droplet number concentration (Nd), and thermodynamic phase from 11 wintertime flights over the Southern Ocean (43–45°S, 145–148°E) are compared to products from MODerate-resolution Imaging Spectroradiometer (MODIS) and Cloud-Aerosol Lidar with Orthogonal Polarization. The in situ observations were in close alignment with A-train overpasses for a 30-min window. For open mesoscale cellular convection, which was predominantly observed, clouds were commonly found to be intermittently drizzling, patchy, and mixed phase. Compared to the in situ observations of the cloud thermodynamic phase, the Cloud-Aerosol Lidar with Orthogonal Polarization and MODIS cloud phase optical property products consistently underestimated the occurrence of mixed-phase clouds, whereas the MODIS infrared-based phase product showed a better qualitative agreement despite a frequent classification of uncertainty. The MODIS reff_2.1 overestimated the in situ reff for nondrizzling clouds (by ~13 μm on average) and, to a lesser extent, for lightly drizzling cases. Conversely, MODIS reff_2.1 underestimated the in situ reff for heavily drizzling cases by ~10 μm on average. The overestimation of reff is much greater than that for the stratocumulus over the Southeast Pacific shown in other studies. An examination on subpixel heterogeneity, droplet size variability, a bimodal distribution, and solar zenith angle suggests that all of these factors have measurable impacts on the MODIS reff bias. The MODIS Nd is largely consistent with the in situ observations. However, the Nd of the two high Nd cases (closed mesoscale cellular convection) are highly underestimated. An error analysis suggests that the Nd biases are likely a result of a compensating error effect.
| Original language | English |
|---|---|
| Pages (from-to) | 11120-11140 |
| Number of pages | 21 |
| Journal | Journal of Geophysical Research: Atmospheres |
| Volume | 123 |
| Issue number | 19 |
| DOIs | |
| Publication status | Published - 16 Oct 2018 |
Keywords
- aircraft observations
- boundary layer clouds
- cloud droplet number concentration
- effective radius
- precipitation
- satellite observations
Cite this
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A comparison of cloud microphysical properties derived from MODIS and CALIPSO with in-situ measurements over the wintertime Southern Ocean. / Ahn, Eunmi; Huang, Yi; Siems, Steven T.; Manton, Michael J.
In: Journal of Geophysical Research: Atmospheres, Vol. 123, No. 19, 16.10.2018, p. 11120-11140.Research output: Contribution to journal › Article › Research › peer-review
TY - JOUR
T1 - A comparison of cloud microphysical properties derived from MODIS and CALIPSO with in-situ measurements over the wintertime Southern Ocean
AU - Ahn, Eunmi
AU - Huang, Yi
AU - Siems, Steven T.
AU - Manton, Michael J.
PY - 2018/10/16
Y1 - 2018/10/16
N2 - In situ observations of cloud effective radius (reff), droplet number concentration (Nd), and thermodynamic phase from 11 wintertime flights over the Southern Ocean (43–45°S, 145–148°E) are compared to products from MODerate-resolution Imaging Spectroradiometer (MODIS) and Cloud-Aerosol Lidar with Orthogonal Polarization. The in situ observations were in close alignment with A-train overpasses for a 30-min window. For open mesoscale cellular convection, which was predominantly observed, clouds were commonly found to be intermittently drizzling, patchy, and mixed phase. Compared to the in situ observations of the cloud thermodynamic phase, the Cloud-Aerosol Lidar with Orthogonal Polarization and MODIS cloud phase optical property products consistently underestimated the occurrence of mixed-phase clouds, whereas the MODIS infrared-based phase product showed a better qualitative agreement despite a frequent classification of uncertainty. The MODIS reff_2.1 overestimated the in situ reff for nondrizzling clouds (by ~13 μm on average) and, to a lesser extent, for lightly drizzling cases. Conversely, MODIS reff_2.1 underestimated the in situ reff for heavily drizzling cases by ~10 μm on average. The overestimation of reff is much greater than that for the stratocumulus over the Southeast Pacific shown in other studies. An examination on subpixel heterogeneity, droplet size variability, a bimodal distribution, and solar zenith angle suggests that all of these factors have measurable impacts on the MODIS reff bias. The MODIS Nd is largely consistent with the in situ observations. However, the Nd of the two high Nd cases (closed mesoscale cellular convection) are highly underestimated. An error analysis suggests that the Nd biases are likely a result of a compensating error effect.
AB - In situ observations of cloud effective radius (reff), droplet number concentration (Nd), and thermodynamic phase from 11 wintertime flights over the Southern Ocean (43–45°S, 145–148°E) are compared to products from MODerate-resolution Imaging Spectroradiometer (MODIS) and Cloud-Aerosol Lidar with Orthogonal Polarization. The in situ observations were in close alignment with A-train overpasses for a 30-min window. For open mesoscale cellular convection, which was predominantly observed, clouds were commonly found to be intermittently drizzling, patchy, and mixed phase. Compared to the in situ observations of the cloud thermodynamic phase, the Cloud-Aerosol Lidar with Orthogonal Polarization and MODIS cloud phase optical property products consistently underestimated the occurrence of mixed-phase clouds, whereas the MODIS infrared-based phase product showed a better qualitative agreement despite a frequent classification of uncertainty. The MODIS reff_2.1 overestimated the in situ reff for nondrizzling clouds (by ~13 μm on average) and, to a lesser extent, for lightly drizzling cases. Conversely, MODIS reff_2.1 underestimated the in situ reff for heavily drizzling cases by ~10 μm on average. The overestimation of reff is much greater than that for the stratocumulus over the Southeast Pacific shown in other studies. An examination on subpixel heterogeneity, droplet size variability, a bimodal distribution, and solar zenith angle suggests that all of these factors have measurable impacts on the MODIS reff bias. The MODIS Nd is largely consistent with the in situ observations. However, the Nd of the two high Nd cases (closed mesoscale cellular convection) are highly underestimated. An error analysis suggests that the Nd biases are likely a result of a compensating error effect.
KW - aircraft observations
KW - boundary layer clouds
KW - cloud droplet number concentration
KW - effective radius
KW - precipitation
KW - satellite observations
UR - http://www.scopus.com/inward/record.url?scp=85054394671&partnerID=8YFLogxK
U2 - 10.1029/2018JD028535
DO - 10.1029/2018JD028535
M3 - Article
VL - 123
SP - 11120
EP - 11140
JO - Journal of Geophysical Research: Atmospheres
JF - Journal of Geophysical Research: Atmospheres
SN - 2169-897X
IS - 19
ER -