Regional and vertical distribution of semitransparent cirrus clouds over the tropical Indian region derived from CALIPSO data

• Published in: Journal of atmospheric and solar-terrestrial physics Vol. 73; no. 13; pp. 1967 - 1979
• Main Authors: Meenu, S., Rajeev, K., Parameswaran, K.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.08.2011; Elsevier
• Subjects: CALIPSO; Cloud lifetime; Earth, ocean, space; Exact sciences and technology; External geophysics; Indian region; Physics of the ionosphere; Physics of the magnetosphere; Semitransparent cirrus; Indian Ocean; Asia; Bay of Bengal; India; ISW, Bangladesh, Bengal Bay; Cloud lifetime; Indian region; Semitransparent cirrus; CALIPSO; High altitude; physical properties; Occurrence frequency; Vertical distribution; Regional scope; tropical zone; monthly average; Summer monsoon; Ice cloud; Vertical gradient; Lifetime; optical properties; Spatial distribution; Cirrus; Tropopause; spatial variations; Optical thickness
• ISSN: 1364-6826; 1879-1824
• DOI: 10.1016/j.jastp.2011.06.007

Monthly mean spatial and vertical distributions of the frequency of occurrence ( F STC) of semitransparent cirrus (STC) and their physical and optical properties over the Indian region are investigated using multiyear CALIPSO data. Over the Bay of Bengal (BoB), F STC above the lapse-rate tropopause is >30% during the summer monsoon season, most of which has optical depth <0.03. Based on spatial variations of the observed STC properties away from deep convective regions, we propose that the presence of high-altitude clouds below STCs over the BoB and Indian regions during summer monsoon reduces dissipation of STCs, resulting in their longer lifetime (∼1–2 days). ► Considerable occurrence of cirrus above tropopause over Bay of Bengal during monsoon. ► Higher cirrus base height at descending limb of Hadley cell than at ITCZ. ► Evidence for reduced cirrus dissipation when it occurs above high-altitude clouds. ► Potential mechanism for longer cirrus lifetime over Indian region during monsoon. ► On average, cirrus with optical depth <0.3 contributes ∼80–91% of the total cirrus.