TY - JOUR
T1 - Characteristics of cirrus clouds in the tropical lower stratosphere
AU - Iwasaki, Suginori
AU - Luo, Zhengzhao Johnny
AU - Kubota, Hisayuki
AU - Shibata, Takashi
AU - Okamoto, Hajime
AU - Ishimoto, Hiroshi
N1 - Funding Information:
We would like to thank Prof. Pao Wang in University of Wisconsin-Madison for helpful comments and his insight. SI was supported by the JSPS Grant-in-Aid for Young Scientists (B) 24710024 . ZJL acknowledges support by NASA grant NNX12AC13G associated with SEAC 4 RS field campaign and travel support by the NSF/NCAR CONTRAST Science Team . TS and SI are supported by the JSPS Kakenhi Grant-in-Aid for Scientific Research (A) Grant Number 25257201 . HO is supported by the JSPS Kakenhi Grant-in-Aid for Scientific Research (A) Grant Number 25247078 . Data from CloudSat and CALIOP were obtained from the CloudSat Data Processing Center and the Atmospheric Sciences Data Center (ASDC).
Publisher Copyright:
© 2014 Elsevier B.V.
PY - 2015/10/1
Y1 - 2015/10/1
N2 - A unique type of cloud in the tropical lower stratosphere, which we call "stratospheric cirrus", is described in this study. Stratospheric cirrus clouds are generally detached from overshooting deep convection and are much smaller than subvisual cirrus often observed near the tropical tropopause. We analyzed two cases of stratospheric cirrus in the tropical and subtropical lower stratosphere captured by the space-borne lidar, Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP). Both cases occurred 2-3 hours after the most active phase of the nearby convective cloud clusters. Case 1 has a double-layer structure above the cold point height (CPH); the CPH and two cloud top heights are, respectively, 17.8, 18.9, and 19.9 km. Case 2 has a single cloud layer where CPH and the cloud top height are, respectively, 16.5 and 18.7 km. The mode radius and ice water content of the stratospheric cirrus clouds are estimated to be 4-10μm and 0.2-0.8 mg/m3 based on the radar-lidar method and consideration of the cloud particle terminal velocity. Comparisons with previous numerical model simulation studies suggest that the double-layer stratospheric cirrus clouds are likely from an overshooting plume, pushed up into the stratosphere in an overshoot when warm stratospheric air is inhomogeneously mixed with cold overshooting air. The single-layer stratospheric cirrus cloud is associated with some non-negligible wind shear, so it could be a jumping cirrus cloud, although we cannot rule out the possibility that it came from an overshooting plume because of the similarity in cloud characteristics and morphology between the two cases. Guided by the case studies, an automatic algorithm was developed to select stratospheric cirrus clouds for global survey and statistical analysis. A total of four years of CALIPSO and space-borne cloud radar (CloudSat) data were analyzed. Statistical analysis suggests that stratospheric cirrus clouds occur on the order of 3.0×103 times a year between 30 °S and 30 °N. Many of the stratospheric cirrus clouds are found in the pre-monsoon season in the South and Southeast Asia, where convection is deep and intense.
AB - A unique type of cloud in the tropical lower stratosphere, which we call "stratospheric cirrus", is described in this study. Stratospheric cirrus clouds are generally detached from overshooting deep convection and are much smaller than subvisual cirrus often observed near the tropical tropopause. We analyzed two cases of stratospheric cirrus in the tropical and subtropical lower stratosphere captured by the space-borne lidar, Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP). Both cases occurred 2-3 hours after the most active phase of the nearby convective cloud clusters. Case 1 has a double-layer structure above the cold point height (CPH); the CPH and two cloud top heights are, respectively, 17.8, 18.9, and 19.9 km. Case 2 has a single cloud layer where CPH and the cloud top height are, respectively, 16.5 and 18.7 km. The mode radius and ice water content of the stratospheric cirrus clouds are estimated to be 4-10μm and 0.2-0.8 mg/m3 based on the radar-lidar method and consideration of the cloud particle terminal velocity. Comparisons with previous numerical model simulation studies suggest that the double-layer stratospheric cirrus clouds are likely from an overshooting plume, pushed up into the stratosphere in an overshoot when warm stratospheric air is inhomogeneously mixed with cold overshooting air. The single-layer stratospheric cirrus cloud is associated with some non-negligible wind shear, so it could be a jumping cirrus cloud, although we cannot rule out the possibility that it came from an overshooting plume because of the similarity in cloud characteristics and morphology between the two cases. Guided by the case studies, an automatic algorithm was developed to select stratospheric cirrus clouds for global survey and statistical analysis. A total of four years of CALIPSO and space-borne cloud radar (CloudSat) data were analyzed. Statistical analysis suggests that stratospheric cirrus clouds occur on the order of 3.0×103 times a year between 30 °S and 30 °N. Many of the stratospheric cirrus clouds are found in the pre-monsoon season in the South and Southeast Asia, where convection is deep and intense.
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U2 - 10.1016/j.atmosres.2015.06.009
DO - 10.1016/j.atmosres.2015.06.009
M3 - Article
AN - SCOPUS:84932627906
SN - 0169-8095
VL - 164-165
SP - 358
EP - 368
JO - Atmospheric Research
JF - Atmospheric Research
ER -