Anvil Cirrus Outflow During the Maritime Continent Thunderstorm Experiment:A Case Study
Michael P. Jensen1, Thomas P. Ackerman1 and Stephen M. Sekelsky2
1 Department of Meteorology, Pennsylvania State University
2 Department of Electrical Engineering, University of Massachusettes
abstract
The Maritime Continent Thunderstorm Experiment (MCTEX) took place from 13 November to 10 December 1995 on the Tiwi Islands, Australia. The primary objective of the experiment was to study the lifecycles of the thunderstorms which occur almost daily on these islands from the transition from wet and dry seasons. This study is concerned with the cirrus outflow and its impact on the radiation budget. As part of MCTEX, a suite of remote sensing instruments, including a dual-wavelength millimeter radar, a 10cm vertically pointing radar and broad-band solar and IR radiometers were deployed at Garden Point located on the northwest corner of the Tiwi Islands. A scanning C-band Doppler radar was also located in Nguiu approximately 50 km to the south of Garden Point. The MCTEX dataset lends itself to the pursuit of several case studies in order to describe the radiative effects of these tropical cirrus anvils. This study investigates the cirrus anvil observed on 27 November. Microphysoical retrievals of median particle diameter and number density calculated using a dual-wavelength technique are used in a Mie theory calculationin order to determine the optical properties of the cloud layer. Combining the cloud radar reflectivity, with the IWC calculated from the microphysical retrievals, a Z-IWC parameterization will be chosen, which best fits the data for the observed cloud. This parameterization is then applied to the C-pol reflectivities to describe the optical depth over the rest of the areal extent of theanvil, such that a 2-d contour of optical depth is drawn for different stages in the development of the anvil. Once a description of the optical depth of the cloud layer is made, the effect of the cloud on the radiation field at different stages in its development is investigated using a two-stream radiative transfer model and an independent pixel approach.
