Jin, D; Oreopoulos, L; Lee, D; Tan, J; Kim, KM (2020). Large-Scale Characteristics of Tropical Convective Systems Through the Prism of Cloud Regime. JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES, 125(6), e2019JD031157.

We employ the cloud regime concept to identify large-scale tropical convective systems and investigate their characteristics in terms of organization and precipitation. The tropical cloud regimes (TCRs) are derived from Moderate Resolution Imaging Spectroradiometer cloud optical thickness and cloud top pressure two-dimensional joint histograms. We focus on the TCRs that have relatively low cloud top pressures and high cloud optical thicknesses, as well as heavy precipitation, namely, TCR1 (convective core-dominant), TCR2 (various high clouds), and TCR3 (anvils). The horizontal size of aggregates of TCR1, TCR2, or TCR3 occurrences (TCR123) is identified as the number of contiguous 1 degrees x 1 degrees grid cells occupied by either of these three TCRs. For the small- to intermediate-size aggregates (TCR123 size 20 to 160 one-degree grid cells), there is large variability in the fraction of the aggregate each TCR occupies, but generally, TCR2 exhibits the highest fraction. As the total system size grows, the variability shrinks and for the largest systems ratios eventually converge to 0.3, 0.2, and 0.5 for TCR1, TCR2, and TCR3, respectively. The mean precipitation of convective core-rich TCR1 is generally high for the systems of intermediate size (80-160 one-degree grid cells) but with the highest mean coming from smaller systems of 20-40 grid cells. For the largest systems, their mean precipitation in areas containing cores (TCR1) are relatively low with suppressed variation. The mean precipitation rates of TCR2 and TCR3 in a TCR123 aggregate tend to be stronger when accompanying TCR1 mean precipitation rate is also high. Plain Language Summary Tropical convection systems often grow larger than several thousand kilometers in diameter. In this study, we identify these large systems using gridded satellite observations of cloud extinction and cloud top height. Using the concept of "cloud regime" that helps to classify and assign cloud observations to preset cloud classes, we can quantify the characteristics of large-scale tropical convective systems such as the area of the system occupied by the most intense convection. This area varies widely for systems of smaller sizes but is confined to a limited range around 30% of the total area for the largest systems. In addition, the mean precipitation in the area of strongest convective activity is not the heaviest for the largest systems but rather for the systems of moderate size. As the systems become larger, both area fraction and precipitation variabilities decrease.