Assessing the Vertical Structure of Radiative Heating Using Radar/Lidar/AERI for Cirrus Cloud Events at SGP

Lori Borg University of Wisconsin, Madison
David Tobin University of Wisconsin, Madison
David Turner National Oceanic and Atmospheric Administration
Robert Holz University of Wisconsin/CIMMS
Daniel DeSlover University of Wisconsin
Edwin Eloranta University of Wisconsin
Robert Knuteson University of Wisconsin-Madison
Henry Revercomb University of Wisconsin, Madison
Leslie Moy University of Wisconsin, Madison

Category: Radiation

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Figure 1: Optical depth fraction sensed by radar versus optical depth measured by Lidar: Based on 3 years of single-layer cirrus cloud events at SGP when Lidar not attenuated. Median values are shown with interquartile ranges, including zero points (blue) and without(red).

Cirrus clouds play a significant role in the energy budget of the atmosphere and represent a major source of uncertainty in understanding climate and climate change. A large part of this uncertainty lies in the modeling of the cloud, which requires assumptions and simplifications of the cloud morphology. In this study, uniform cirrus cloud events at the Atmospheric Radiation Measurement (ARM) Climate Research Facility (ACRF) Southern Great Plains (SGP) site are investigated using various data sources (radar, lidar, atmospheric emitted radiance interferometer [AERI], atmospheric infrared sounder [AIRS], and combinations thereof) to derive cloud microphysical and optical properties. These properties are used to compute longwave heating rate profiles and top-of-atmosphere (TOA) and surface (SFC) fluxes using the rapid radiative transfer model (RRTM). Computed fluxes are compared with observations and computed heating rates with the ARM Broadband Heating Rate Profile (BBHRP). Additionally these cloud properties are used to compute upwelling and downwelling radiances for comparisons with AERI and AIRS observations. Results indicate, that to first order, accurate calculation of heating rates and TOA and SFC fluxes is driven by the cloud optical depth and cloud boundaries with ice crystal effective radius and habit being secondary effects. Radar alone can miss significant upper level cirrus, and combinations of measurements are needed to characterize thin cirrus. The figure depicts the fraction of optical depth (OD) sensed by the radar as a function of the OD measured by the lidar for approximately three years of single-layer cirrus cases when the lidar is not attenuated. For clouds with a total lidar OD less than 1, the radar often does not detect a significant amount of the cloud OD. For clouds with a total lidar OD greater than 2, the radar sees only approximately 80% of total Lidar OD.

This poster will be displayed at ARM Science Team Meeting.

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