Convective-stratiform rainfall separation by cloud content
Journal
Journal of Geophysical Research Atmospheres
Journal Volume
112
Journal Issue
14
Date Issued
2007
Author(s)
Abstract
A method is proposed to separate the convective component of the precipitation from the remainder based on threshold values of vertically integrated content of ice clouds (ice water path, IWP), water clouds (liquid water path, LWP), and their ratio (cloud ratio). These cloud variables can be retrieved from satellite measurements and are physically linked to the cloud microphysics as demonstrated by an analysis of simulated cloud microphysics budgets in a two-dimensional cloud-resolving model subject to the imposed forcing from the Tropical Ocean Global Atmosphere Coupled Ocean-Atmosphere Response Experiment (TOGA COARE). Our analysis suggests that rainfall can be designated convective when the corresponding value of cloud ratio < 0.2 or the value of IWP > 2.55 mm. The remaining grids are classified as mixed and stratiform when the corresponding range of cloud ratio is 0.2-1.0 and greater than 1, respectively. The method is evaluated by the vertical velocity (w) data. The frequency distribution of w shows that w in the convective region has a wide distribution of w, with maximum values exceeding 15 m s-1. In the designated stratiform region, the distribution is narrow, with absolute values of w confined within 5 m s-1. The statistics of w and the budgets of cloud microphysics are consistent with corresponding physical characteristics of the convective and stratiform regions of precipitation. The consideration of features like fractional cloud covers, rainrates, w profiles, and the corresponding wave response leads us to regard the mixed and stratiform regions as the non-convective region. Copyright 2007 by the American Geophysical Union.
SDGs
Type
journal article