An Analysis of the Short-term Cloud Feedback Using MODIS Data

TitleAn Analysis of the Short-term Cloud Feedback Using MODIS Data
Publication TypeJournal Article
Year of Publication2013
JournalJournal of Climate
Number13
Pages4803–4815
Date Published07/2013
Abstract / Summary

The cloud feedback in response to short-term climate variations is estimated from cloud measurements combined with offline radiative transfer calculations. The cloud measurements are made by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA'sTerrasatellite and cover the period 2000–10. Low clouds provide a strong negative cloud feedback, mainly because of their impact in the shortwave (SW) portion of the spectrum. Midlevel clouds provide a positive net cloud feedback that is a combination of a positive SW feedback partially canceled by a negative feedback in the longwave (LW). High clouds have only a small impact on the net cloud feedback because of a close cancellation between large LW and SW cloud feedbacks. Segregating the clouds by optical depth, it is found that the net cloud feedback is set by a positive cloud feedback due to reductions in the thickest clouds (mainly in the SW) and a cancelling negative feedback from increases in clouds with moderate optical depths (also mainly in the SW). The global average SW, LW, and net cloud feedbacks are +0.30 ± 1.10, −0.46 ± 0.74, and −0.16 ± 0.83 W m−2K−1, respectively. The SW feedback is consistent with previous work; the MODIS LW feedback is lower than previous calculations and there are reasons to suspect it may be biased low. Finally, it is shown that the apparently small control that global mean surface temperature exerts on clouds, which leads to the large uncertainty in the short-term cloud feedback, arises from statistically significant but offsetting relationships between individual cloud types and global mean surface temperature.

URLhttp://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-12-00547.1
DOI10.1175/JCLI-D-12-00547.1
Journal: Journal of Climate
Year of Publication: 2013
Number: 13
Pages: 4803–4815
Date Published: 07/2013

The cloud feedback in response to short-term climate variations is estimated from cloud measurements combined with offline radiative transfer calculations. The cloud measurements are made by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA'sTerrasatellite and cover the period 2000–10. Low clouds provide a strong negative cloud feedback, mainly because of their impact in the shortwave (SW) portion of the spectrum. Midlevel clouds provide a positive net cloud feedback that is a combination of a positive SW feedback partially canceled by a negative feedback in the longwave (LW). High clouds have only a small impact on the net cloud feedback because of a close cancellation between large LW and SW cloud feedbacks. Segregating the clouds by optical depth, it is found that the net cloud feedback is set by a positive cloud feedback due to reductions in the thickest clouds (mainly in the SW) and a cancelling negative feedback from increases in clouds with moderate optical depths (also mainly in the SW). The global average SW, LW, and net cloud feedbacks are +0.30 ± 1.10, −0.46 ± 0.74, and −0.16 ± 0.83 W m−2K−1, respectively. The SW feedback is consistent with previous work; the MODIS LW feedback is lower than previous calculations and there are reasons to suspect it may be biased low. Finally, it is shown that the apparently small control that global mean surface temperature exerts on clouds, which leads to the large uncertainty in the short-term cloud feedback, arises from statistically significant but offsetting relationships between individual cloud types and global mean surface temperature.

DOI: 10.1175/JCLI-D-12-00547.1
Citation:
Zhou, C, MD Zelinka, AE Dessler, and P Yang.  2013.  "An Analysis of the Short-term Cloud Feedback Using MODIS Data."  Journal of Climate 4803–4815.  https://doi.org/10.1175/JCLI-D-12-00547.1.