Title: Can liquid cloud microphysical processes be used for vertically pointing cloud radar calibration?

Abstract

Cloud radars are unique instruments for observing cloud processes, but uncertainties in radar calibration have frequently limited data quality. Thus far, no single robust method exists for assessing the calibration of past cloud radar data sets. Here, we investigate whether observations of microphysical processes in liquid clouds such as the transition of cloud droplets to drizzle drops can be used to calibrate cloud radars. Specifically, we study the relationships between the radar reflectivity factor and three variables not affected by absolute radar calibration: the skewness of the radar Doppler spectrum (γ), the radar mean Doppler velocity (W), and the liquid water path (LWP). For each relation, we evaluate the potential for radar calibration. For γ and W, we use box model simulations to determine typical radar reflectivity values for reference points. We apply the new methods to observations at the Atmospheric Radiation Measurement (ARM) sites North Slope of Alaska (NSA) and Oliktok Point (OLI) in 2016 using two 35 GHz K_a-band ARM Zenith Radars (KAZR). For periods with a sufficient number of liquid cloud observations, we find that liquid cloud processes are robust enough for cloud radar calibration, with the LWP-based method performing best. We estimate that, in 2016, the radarmore » reflectivity at NSA was about 1±1 dB too low but stable. For OLI, we identify serious problems with maintaining an accurate calibration including a sudden decrease of 5 to 7 dB in June 2016.« less

Authors:

Maahn, Maximilian ;

• Search DOE PAGES for author "Maahn, Maximilian"
• Search DOE PAGES for ORCID "0000-0002-2580-9100"

Hoffmann, Fabian ;

• Search DOE PAGES for author "Hoffmann, Fabian"
• Search DOE PAGES for ORCID "0000-0001-5136-0653"

Shupe, Matthew D.; de Boer, Gijs; Matrosov, Sergey Y.; Luke, Edward P.

Publication Date:

Thu Jun 13 00:00:00 EDT 2019

Research Org.:

Brookhaven National Laboratory (BNL), Upton, NY (United States); Univ. of Colorado, Boulder, CO (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Biological and Environmental Research (BER)

OSTI Identifier:

1526077

Alternate Identifier(s):

OSTI ID: 1561246; OSTI ID: 1673429

Report Number(s):

BNL-212055-2019-JAAM
Journal ID: ISSN 1867-8548

Grant/Contract Number:  

SC0013306; SC0012704

Resource Type:

Published Article

Journal Name:

Atmospheric Measurement Techniques (Online)

Additional Journal Information:

Journal Name: Atmospheric Measurement Techniques (Online) Journal Volume: 12 Journal Issue: 6; Journal ID: ISSN 1867-8548

Publisher:

European Geosciences Union

Country of Publication:

Germany

Language:

English

Subject:

54 ENVIRONMENTAL SCIENCES