Pacific Jets Experiment 2003 (PACJET-03)

BACKGROUND

The Pacific Land-falling Jets Experiment (PACJET) is an ongoing study of land-falling winter storms on the U.S. West Coast. The project is operated by the National Oceanic and Atmospheric Administration (NOAA) in collaboration with a number of universities and other government agencies. The field research is designed to increase the scientific understanding of these powerful and often destructive storms and to test the use of new observing systems and products to aid National Weather Service (NWS) forecasters.

Map of PACJET project area and close-up of microphysical array area.

PACJET-2003 FIELD OPERATIONS

As in past winters dating back to the 1997/98 El Niño, PACJET will again this winter operate a network of 915-MHz wind profiling radars along the Pacific coast from northern Oregon to southern California, as well as others in California's central valley and Sierra foothills. In Jan. and Feb. 2003, PACJET will also conduct focused observations in the vicinity of Fort Ross, CA, on the rugged coastline north of San Francisco, an area that has particularly poor coverage by the NWS's operational network of WSR-88D radars. These PACJET observations will employ additional advanced-technology instruments, including a polarimetric, Doppler X-band scanning weather radar, a pair of S-band precipitation profiling radars, raindrop disdrometers, and special high-resolution rain gauges.

PACJET-2003 GOALS

  • Examine the structure and kinematics of storms as they approach the coastline and ascend the coastal mountains, and determine the role of low-level wind jets in precipitation formation and location.
  • Document storm features that slip beneath coverage of the nearest WSR-88D radars, and send the PACJET radar images to NWS forecast offices via the Web.
  • Study the microphysical features and orographic precipitation mechanisms in storm clouds over the coastal mountains.
  • Continue testing experimental polarimetric radar estimations of rainfall rate.
  • Develop embryonic foundations for a regional Hydrometeorological Testbed as a conduit to infuse new observing technology to the NWS.
  • Evaluate a suite of operational and research models through comparison to radar wind profiler and surface meteorological data.

Data Collection Dates

Core Season January 10 - February 17 2003 Intensive measurements at Fort Ross (FRS) and Cazadero (CZC/CZD), California
Full Season December 11, 2002 - April 10 2003 Continuous operation of wind profilers and surface met stations at several West Coast sites

Intensive Operating Periods Within Core Season

1 11 JAN 03 - 14 JAN 03 5" rain at FRS; fluctuating periods of deep and shallow cloud
2 21 JAN 03 - 23 JAN 03 1.5" rain at FRS; warm front followed by cold front; many sondes
3 12 FEB 03 - 13 FEB 03 0.4" rain at FRS; disorganized showers
4 15 FEB 03 - 16 FEB 03 1.4" rain at FRS; cold front and convective cells; persistent mid- level dry layer

Other Intense Weather Events Outside of the Core Season

A1 13 DEC 02 - 16 DEC 02 20" rain at CZC
A2 26 DEC 02 - 31 DEC 02 10" rain at CZC
A3 13 MAR 03 - 15 MAR 03 6" rain at CZC

Instrumentation Operations Overview

Instrument Site Data Period Comments
X-band Polarimetric Radar (ETL) FRS 10 JAN 03 - 17 FEB 03 data collection mainly during precipitation
S-band Precip Profiler (ETL) FRS 10 JAN 03 - 17 FEB 03 amplifier problem 5 FEB 03 - 13 FEB 03
S-band Precip Profiler (ETL) CZC 10 DEC 02 - 10 APR 03  
JW Raindrop Disdrometer (ETL) FRS 10 JAN 03 - 6 FEB 03  
FRS-Fort 7 FEB 03 - 17 FEB 03 Call Ranch site
CZC 18 FEB 03 - 10 APR 03  
JW Raindrop Disdrometer (UW) CZC 10 JAN 03 - 10 APR 03 data problems until 23 JAN 03
Radiosonde Launches (ETL) FRS 10 JAN 03 - 17 FEB 03 28 launches, episodic
Hasse Ship Rain Gauge (UW) CZC 10 JAN 03 - 10 APR 03  
Qualimetrics 6" Rain Gauge (UW) CZC 26 JAN 03 - 10 APR 03  
Hot-Plate Precip Mass Gauge (DRI) FRS 15 JAN 03 - 17 FEB 03  
GWINDEX (CIMSS) Ocean 6 JAN 03 - 31 MAR 03 GOES Satellite Winds
8-inch Orifice Rain Gauges (ETL)
#1 FRS 10 JAN 03 - 17 FEB 03  
#2 SLP 10 JAN 03 - 17 FEB 03 Salt Point
#3 FRS-VC 10 JAN 03 - 17 FEB 03 Park Visitor Center
Surface Met Stations (ETL) FRS 11 DEC 02 - 10 APR 03 data outage 14 JAN 03
CZC 11 DEC 02 - 10 APR 03  
West Coast 915-MHz Wind Profilers + Surface Met Stations (ETL)
many sites operated beyond the Pacjet period
Newport, OR NPT 11 DEC 02 - 10 APR 03  
Eureka, CA ERK 22 DEC 02 - 10 APR 03  
Bodega Bay, CA BBY 11 DEC 02 - 01 MAR 03 Profiler data problems
Chico, CA CCO 11 DEC 02 - 10 APR 03  
Grass Valley, CA GVY 11 DEC 02 - 10 APR 03  
Pt. Piedras Blancas, CA PPB 11 DEC 02 - 10 APR 03  
Lost Hills, CA LHS 11 DEC 02 - 10 APR 03  
Goleta, CA GLA 11 DEC 02 - 10 APR 03  
San Nicholas Is., CA SNI 11 DEC 02 - 10 APR 03  

Instrumentation

Boundary Layer Profiler Network

The NOAA/ETL boundary layer windprofiler network is a portable, configurable network of wind profilers, meteorological observation towers and RASS units for the observation of regional weather systems impacting air quality and severe weather.

Disdrometers

The Distromet LTD Model RD-80 disdrometer uses the momentum of falling raindrops to measure the size distribution of rain. The amplitude of the pulse generated as a drop hits the disdrometer's electromechanical transducer is roughly proportional to the drop's momentum and, ultimately, the drop's diameter. The size range of drops that can be measured spans from 0.3 mm to 5 mm. Drops larger than 5 mm are rare because they tend to be unstable and breakup into smaller drops. By comparing disdrometer measurements from coastal and inland mountain sites, we will learn more about the microphysical processes associated with orographic precipitation, one of the underlying goals of PACJET. The disdrometer measurements will also shed light on the microphysical information derived from the X-band polarimetric scanning radar and the S-band vertically pointing radars deployed for PACJET-2003. The integrated size distribution measured by the disdrometer is a direct measurement of the rainfall intensity, which will be compared to the rainfall intensities measured by a variety of other rain gauges and estimated by the radars. These comparisons will be used to diagnose the strengths and limitations of various in situ and remote sensing measurement techniques used to provide rainfall intensity.

GWINDEX: GOES Rapid-Scan WINDs EXperiment

The automated satellite-derived winds processing developed at UW-CIMSS uses a sequence of geostationary satellite images to generate three dimensional wind products by the following procedures:

  • Check image registration
  • Track targets
  • Assign target height
  • Calculate displacement vectors
  • Perform quality control steps

S-band Profiler

The S-band vertical profiler is based on existing S-band and UHF profiler technology which has been modified for research. It's dynamic range has been extended to study moderate to heavy precipitation which would not be otherwise possible. The S-band has been calibrated through a side-by-side comparison with the Ka-band radar. In a typical cloud profiling mode of operation, the sensitivity is -14 dBZ at 10 km. Examples taken from a recent field campaign illustrate the profiler's ability to measure vertical velocity and radar reflectivity profiles in clouds and precipitation.

X-band Radar

ETL developed this state-of-the-art X-band radar primarily for observations of the ocean surface, rain, snow, storm airflow patterns, and for hydrological applications. It has Doppler, dual-polarization, and full scanning capability, including the ability to scan downward beneath the horizon for ocean work. Fine-scale measurements are possible with selectable range resolution from 7.5 to 150 meters. Polarization options include switching between H and V, or using the "split" H/V, configuration that has been proposed for future NEXRAD upgrades. The polarization measurements include differential phase (Kdp), and differential reflectivity (ZDR), which can used for more accurate estimates of rainfall rate and identification of precipitation particle types. The radar uses ETL's new Radar Acquisition and Display System (RADS), which allows various options for scan control and computing derived parameters in realtime. The radar is transportable in North America on its own trailer bed or it can be shipped overseas in standard sea containers. ETL engineers are working toward implementing fully automated, unattended operation and remote control of this system.