Systematic Cloud-Dependent Characteristics of Covariances between ABI Channel 10 Brightness Temperature and Vertical Profile of Model State Variables

Abstract

The assimilation of all-sky infrared brightness temperatures (BTs) into short-term convective-scale forecasts has led to forecast improvements. While most studies employ an ensemble-based approach to achieve this, some limitations, such as the treatment of sampling errors and insufficient model spread, have been addressed in different ways. With the ultimate goal of informing more flexible cloud-adaptive treatments of these issues, the present study aims to better understand the vertical structure of systematic relationships between different atmospheric state variables and BT under different cloud and precipitation conditions. In particular, results are evaluated for high-altitude clouds, both with and without robust precipitation present, and for midaltitude clouds with cloud tops both above and below 400 mb (1 mb = 1 hPa). The systematic relationships to BTs are described across the different cloud categories defined within the study, and case studies are used to connect the systematic results to physical processes or features. In the high-cloud categories, the conclusions made came from a mesoscale convective system. For high-precipitating high clouds, BTs were related to the overall strength of convection and the proximity to the localized updrafts. In nonprecipitating high clouds, BT anomalies were related to the depth and hydrometeor concentration of anvil-like clouds as well as midlevel temperature and dewpoint anomalies associated with organized convection. Results in the midlevel cloud categories appeared to be generally dominated by synoptic-scale features. When cloud tops were above 400 mb, BTs were mainly related to ice-phase hydrometeors. When cloud tops were below 400 mb, BTs were mainly related to liquid-phase hydrometeors and included a contribution from what is considered the clear-air regime above the cloud.