Precipitation Observations During the SCHUSS Observing CampaignLeah Campbell, John McMillen, Trevor Alcott, Jon Zawislak, Tim Garrett,

Ed Zipser, and W. James SteenburghDepartment of Atmospheric Sciences, University of Utah, Salt Lake City, Utah

Introduction

• From 22 October to 21 November 2011 the University of Utah Atmospheric Sciences Department used a portable, dual-polarized Doppler weather radar (DOW6) provided by the Center for Severe Weather Research and the National Science Foundation as part of Storm CHasing Utah Style Study (SCHUSS).

• The examination of data from the DOW6, a 24GHz vertically pointing Micro Rain Radar (MRR), and a hydrometeor videosonde (HYVIS) snowflake camera system provides a unique look into winter precipitation events in some of the snowiest terrain in the interior United States.

AcknowledgementsThe Center for Severe Weather Research provided the use of the DOW6 without which this research would not be possible. University of Utah students operated the DOW during the Fall of 2011. Thanks to Sandra Yuter and Nate Hardin for providing access to the MRR data, and Kristen Yeager for her work on NEXRAD derived SWE accumulation. This work is supported by the National Science Foundation under Grant No. AGS-0938611. Any opinions, findings, and conclusions or recommendations expressed here are those of the authors and do not necessarily reflect the views of the National Science Foundation.

SCHUSS Objectives• Allow students to plan and execute a comprehensive

observing campaign.

• Gather a unique and high quality data set for further study by students and faculty.

• Gain insight into winter precipitation processes (synoptic, orographic, and lake-effect) and their interactions in complex terrain.

IOP 5 (5 Nov 2011)• Unprecedented observation of an organized lake-effect band

of cellular convection. This IOP also includes observations of synoptic scale and orographic precipitation.

IOP 6 (12-13 Nov 2011)• Period includes observation of pre-frontal orographic

precipitation processes over the Wasatch, frontal passage and precipitation shadowing in the Salt Lake Valley.

IOP 8 (18-19 Nov 2011)

• Period includes observation of frontal precipitation, post-frontal precipitation and orographic enhancement.

Map Of SCHUSS Operating Environment

Great Salt Lake

Salt Lake Valley

Wasatch M

ountains

DOW IOP 6,7,8

KMTX Radar

Micro-Rain Radar

Camera

RH

I IOP

5

RHI IOP 6,7,8

DOW IOP 5

5 Nov 2011 1245 UTC Horizontal Reflectivity RHI along 355° (see map)

Note 30+ dBZ echo in cross section of the lake-effect band.

dBZ

km

IOP 7 (13 Nov 2011)

• Period includes observation of orographically enhanced precipitation over the Wasatch Mountains.

IOP 7IOP 5 Future Work

• Further analyze the additional dual-polarized radar data parameters to explore the microphysical evolution of the precipitation events observed during each IOP.

• Explore the correlation between differential reflectivity values and hydrometeor type that is apparent in visual comparison of HYVIS images with differential reflectivity images from the DOW6.

5 Nov 2011 12:42 UTC Horizontal Reflectivity, 2.2°

Note 30+ dBZ lake-effect band extending from upper left.

5 Nov 2011 12-16 UTCNEXRAD Derived Total SWE

Note largest accumulations along lake-effect band axis.

dBZ

km Wasatch Mountains

12 Nov 2011 1441 UTC Horizontal Reflectivity, 4.2°

Note 30 dBZ echo aligned over the Wasatch Mountains.

dBZ

km

12-13 Nov 2011 14-04 UTCNEXRAD Derived Total SWE

Note the largest accumulation over the Wasatch Mountains.

Wasatch Mountains

12 Nov 2011 1437 UTC Horizontal Reflectivity RHI along 87° (see map)

Note 30 dBZ echo aligned over Wasatch Mountains.

dBZ

km

Wasatch Mountains MRR

dBZ

km

13 Nov 2011 1206 UTC Horizontal Reflectivity RHI along 87° (see map)

Note 30 dBZ echo aligned over Wasatch Mountains.

Wasatch Mountains MRR

dBZ

km

13 Nov 2011 1314 UTC Horizontal Reflectivity, 4.2°

Note 30 dBZ echo aligned over the Wasatch Mountains.

13 Nov 2011 05-20 UTCNEXRAD Derived Total SWE

Note the largest accumulation over the Wasatch Mountains.

Wasatch Mountains

dBZ

km

19 Nov 2011 0353 UTC Horizontal Reflectivity RHI along 87° (see map)Note wave structure over Wasatch Mountains.

Wasatch Mountains MRR

dBZ

km

19 Nov 2011 0322 UTC Horizontal Reflectivity, 4.2°

Note 30 dBZ echo to the northwest of DOW and over Wasatch Mountains.

18-19 Nov 2011 23-11 UTCNEXRAD Derived Total SWE

Note slightly higher accumulation over the Wasatch Mountains.

Wasatch MountainsdBZ

km

13 Nov 2011 0944 UTC Differential Reflectivity RHI along 87° (see map)

Note positive differential reflectivity throughout the echo.

• Positive differential reflectivity indicates non-spherical hydrometeors with a larger horizontal axis.

• HYVIS images (inset) reveal dendrites, which preferentially fall with their largest axes horizontally oriented.

09:33:23

09:35:03 09:35:57 09:35:58 09:47:35

09:47:3609:48:10

09:49:2709:51:4109:50:39

Wasatch Mountains HYVIS

12 Nov 2011 2038 UTC Differential Reflectivity RHI along 87° (see map)

Note zero/negative differential reflectivity throughout the echo.

• Zero differential reflectivity indicates spherical hydrometeors.

• Negative differential reflectivity indicates non-spherical hydrometeors with a larger vertical axis.

• HYVIS images (inset) reveal graupel and heavily rimed dendrites; heavily rimed dendrites approach a spherical shape and graupel preferentially falls with its largest axes vertically oriented.

20:29:45

20:33:37

20:35:05

20:36:1220:36:26 20:36:27 20:38:29

20:39:21

20:39:4420:40:03

20:40:06

20:40:2920:41:19

dBZ

km

Wasatch Mountains HYVIS

12 -13 Nov 2011 MRR Reflectivity Time Series

13 Nov 2011 MRR Reflectivity Time Series

18-19 Nov 2011 MRR Reflectivity Time Series