2011 - Cooperative Institute for Research in Environmental Sciences ...

through an increased knowledge of regional and global
water cycle processes.
Milestone 1. Plan and execute the 2011 Hydrometeorology
Testbed, HMT-West field campaign, an annual
series of field efforts conducted in the northern
California American River basin, located in the Sierra
Nevada Mountains west of Lake Tahoe and east of
Sacramento. CIRES investigators will be key participants
and contributors to these activities.
The Hydrometeorology Testbed (HMT)-West 2011
field season was conducted from Dec. 1, 2010, to
March 8, 2011, with a break from Dec. 22-27 (94 total
days of operations). This deployment was unique
due to significant contributions to the existing
HMT-West infrastructure from the California Energy
Commission (CEC) and the California Department
of Water Resources (CADWR). The CEC is building
on the existing HMT-West instrumentation network
through CalWater (http://www.esrl.noaa.gov/psd/
calwater/), a program complementary to HMT-West
that aims to examine the role of aerosols in precipitation
as well as to quantify the temporal and spatial
variability of atmospheric rivers (ARs) and their
representation in climate models. These objectives
involve specialized monitoring of the Sierra Barrier
Jet (SBJ), which profoundly affects transports of both
water vapor and aerosols, and ultimately redistributes
orographic precipitation and modifies AR conditions
(each of importance to HMT). Observational assets
deployed for HMT-West 2011 (Figure 1) included:
• SkyWater C-band radar at Lincoln;
• Supplemental upper air soundings at Lincoln;
• S-band precipitation profilers at Sugar Pine and Mariposa;
• Atmospheric River Observatory at Concord;
• GPS-met observations at Fort Bragg and Shasta
Overall there were seven SBJ-focused Intensive Operating
Periods, with 295 hours of SkyWater radar operations,
and 88 special radiosondes launched (71 by the Earth System
Research Laboratory Physical Sciences Division from
Lincoln, plus 17 supplemental soundings by the National
Weather Service from Oakland or Reno). In addition,
specialized HMT-West numerical model simulations were
conducted in real-time, and daily forecasts and field team
deployment decisions were made throughout the period.
Milestone 2. Develop and test an approach for a synergetic
use of C-band scanning polarimetric radar (C-POL)
and vertically pointing 8-mm wavelength radar (MMCR)
for simultaneous retrievals of parameters in stratiform
precipitating systems at the Tropical Western Pacific
(TWP) Darwin Atmospheric Radiation Measurement (ARM)
Climate Research Facility (ACRF). This remote sensing
approach will aim to estimate liquid cloud water path
and rain water path in the liquid hydrometer layer and
simultaneously retrieve an ice water content profile and
ice water path in the same vertical atmospheric column.
In addition to measurements from radars that are currently
available at the Darwin ACRF, the ground-based
rain gauge and disdrometer data will be used to constrain
retrievals. The suggested remote sensing approach will be
tested using data from a number of experimental events.
The retrieval uncertainties will be evaluated.
Figure 1: Observational assets deployed for HMT-West 2011
A remote sensing
approach for simultaneous
retrievals of
cloud and rainfall
parameters in the
vertical column above
the U.S. Department
of Energy’s (DOE) Climate
Research Facility
at the TWP Darwin
site in Australia was
developed. This approach
uses vertically
pointing measure-
Figure 2: A measurement example
in a rain system
ments from Ka-band radar and scanning measurements
from a nearby C-band radar pointing toward the TWP
Darwin site. Rainfall retrieval constraints are provided
by an impact disdrometer. The approach is applicable
to stratiform precipitating systems when a separation
between the liquid hydrometeor layer, which contains
rainfall and liquid water clouds, and the ice hydrometeor
layer is provided by the radar bright band. Absolute
C-band reflectivities and Ka-band vertical reflectivity
gradients in the liquid layer are used for retrievals of the
mean layer rain rate and cloud liquid water path. Figure 2
shows a measurement example in a rain system. Different
slopes of Ka-band radar reflectivity (MMCR) corresponds
to different attenuation rates caused by differing amounts
of liquid phase while C-band data (CPOL) used as a proxy
for non-attenuated reflectivities show very little vertical
variability.
CIRES Annual Report 2011 103