Led by ARM's Chief Scientist, working groups are the principal organizational structure within the ARM Science Team. These groups, focused by sub-discipline, provide a forum for ARM scientists to help shape the program direction and collaborate with each other. Each group includes an infrastructure translator and a science leader to ensure program completeness. Though the maturity of the ARM Program has resulted in some blurring of the boundaries between these working groups, they still provide a sound organizational structure for describing program progress.
The primary objective of ARM's aerosol research is to quantify the impact of aerosols on the radiative balance of Earth's climate system, both directly and indirectly, through their influence on clouds. To this end, ARM uses in situ and remote sensing observations from surface-based, airborne, and satellite platforms together with process-modeling to global-scale modeling.
This working group addresses the critical issue of relating observations and data analysis to climate model development and evaluation. Their research principally involves (1) single column models to represent the vertical profile evolution of temperature, water vapor, and clouds averaged over a single grid-box of a global climate model, and (2) high-resolution cloud resolving models to represent convective and cloud processes over a limited area. Results from these studies are then used to improve cloud parameterizations in global climate models. Prior to 2006, the Cloud Modeling Working Group was known as Cloud Parameterization and Modeling.
The broad goal of the Cloud Properties Working Group is to develop and implement algorithms that characterize the physical state of the cloudy atmosphere, including cloud occurrence, cloud condensed water amount, and cloud optical properties. The algorithms must deal with the complexity of cloud types, condensate phase, and cloud geometry that are encountered in real situations. They are also concerned with the problem of appropriately aggregating cloud temporal and spatial properties from scales of observation to climate model scales.
Clouds with Low Optical [Water] Depths (CLOWD)
The goal of the ad-hoc (short-term) CLOWD Working Group is to determine the best strategy for measuring clouds with low optical depths and low liquid water paths (LWP) at ACRF locales. Currently, the primary instrument used to measure the cloud LWP is the microwave radiometer, which does not have the required accuracy for LWP below approximately 100 g m-2. While it is possible to retrieve low optical depth values, different retrieval techniques produce different values of uncertain accuracy. Because clouds with low LWP and low optical depth occur frequently over ARM locales, it is important to resolve these problems.
The objective of this working group is to test radiation parameterizations at the accuracy required for climate studies. Due to research successes and advances in instrumentation capabilities, as well as the identification of climatically significant anomalies between observed and model calculated quantities, much of the research activity has migrated from longwave to shortwave radiation and from clear to cloudy-sky problems. Prior to 2006, the Radiative Processes Working Group was known as the Instantaneous Radiative Flux Working Group.