The Intermountain Precipitation Experiment

Operations Plan

Last Revision: 6 December 1999
David Schultz
NOAA/National Severe Storms Laboratory and
Cooperative Institute for Mesoscale Meteorological Studies
1313 Halley Circle
Norman, OK 73069
(405) 366-0453

James Steenburgh
Department of Meteorology, University of Utah
NOAA/Cooperative Institute for Regional Prediction
135 South 1460 East, Room 819
Salt Lake City, UT 84112-0110
(801) 581-8727

Thanks to Terry Schuur for the MEaPRS Ops Plan, which served as a model!
IPEX Home Page (University of Utah)

IPEX Home Page (NSSL)

Table of Contents


1. Introduction and Motivation

Improvements in quantitative-precipitation forecasting over the western United States require advances in several areas including: (1) the understanding of dynamical and microphysical processes during orographic-precipitation events, (2) the numerical simulation and parameterization of orographically-induced circulations and precipitation microphysics, (3) the assimilation of diverse datasets by numerical models in complex terrain, and (4) the use of multiple sensors, including high-elevation radars, to estimate accumulated precipitation. Although recent field programs such as COAST (Bond et al. 1997) and CAL-JET (Ralph et al. 1998) have examined the influence of coastal orography on landfalling fronts and precipitation systems, there is an ongoing need for field programs that utilize multiple observing platforms to examine the interaction between mesoscale dynamics and cloud microphysics during orographic-precipitation events (Smith et al. 1997; Fritsch et al. 1998). Data is needed from regions with differing topography and climatological conditions to understand the spectrum of orographic precipitation processes.

Eta model quantitative-precipitation forecast (QPF) skill is lower over the Intermountain West and eastern Rocky Mountains than over any other region of the U.S. (Gartner et al. 1998). Precipitation prediction over the Intermountain West, in particular, provides a unique scientific challenge for several reasons. First, the organization of clouds and precipitation associated with cyclones and fronts is greatly perturbed by upstream mountain ranges, such as the Cascades and Sierra Nevada, as well as the various ranges of the Great Basin. Second, microphysical processes occur in a continental airmass that is characterized by cold cloud conditions, large cloud condensation nuclei (CCN) concentrations, and large cloud droplet concentrations. Finally, the major mountain ranges of the Great Basin feature relatively small cross-barrier length scales, are steeply sloped on both the windward and leeward slopes, and are separated by broad lowland regions that are tens of kilometers in width. Climatologically, these narrow, two-dimensional mountain ranges receive approximately 5 times as much precipitation as their adjacent lowland regions.

In northern Utah, intense vertical relief and lake-land surface contrasts contribute to the development of orographic and lake-effect precipitation that impact transportation, commerce, and public safety along the densely populated Wasatch Front urban corridor, which includes the cities of Ogden, Salt Lake, and Provo. Annual snowfall in the Wasatch Mountains approaches 1300 cm, with record storm and 24-h accumulations at Alta ski area of 267 and 141 cm, respectively (Pope and Brough 1996). On average, Alta observes 49 (21) days per year with at least 12.5 (25) cm of snowfall. In lowland regions, lake-effect snowbands associated with the GSL produce heavy accumulations several times each winter (Steenburgh et al. 1999). Snowstorms over the state of Utah have produced $100 million of property damage over the past six years. Major events include the 24-26 February 1998 lake-effect and orographic snowstorm that produced accumulations of up to 130 cm in the Salt Lake City metropolitan area (Slemmer 1998).

Despite the dramatic socio-economic impacts of orographic and lake-effect precipitation events over the Intermountain West, there are significant gaps in our understanding of these phenomena. Enhanced mesoscale and microphysical datasets are needed to improve our understanding of orographic precipitation, to improve data assimilation and numerical weather prediction in regions of complex terrain, and to improve precipitation estimates from high-elevation radars. To address these needs, the primary mission of IPEX is to improve the understanding, analysis, and prediction of precipitation processes over complex terrain. The program is thus directly related to two foci of the U.S. Weather Research Program (Emanuel et al. 1995; Smith et al. 1997): quantitative-precipitation forecasting and the optimal mix of observations in numerical weather prediction. Specific IPEX goals are:

2. Specific Scientific Objectives

To meet the goals described above, the IPEX field phase involves the collection of data required to document the dynamical, kinematic, and microphysical processes involved in orographic and lake-effect snowstorms. The following specific scientific objectives have been developed to guide field-phase planning and operations:

3. Facilities

Approved or existing facilities identified in black. Funding pending for items in red.
Facility Institution Location Purpose/Mission
P-3 research aircraft NOAA/AOC SLC Airport In-situ and radar-derived observation of kinematic and microphysical storm structure
Mobile CLASS rawinsonde labs (2) NSSL Locomotive Springs and Ogden or western Desert at the "Oasis" Vertical profiles of temperature, wind, and RH; dynamical response to Wasatch and GSL; PBL modification by GSL
915-Mhz Wind Profiler U.S. Army Dugway Proving Grounds Dugway Proving Grounds Vertical wind profiles; dynamical response to regional orography
Three-hourly regional soundings NWS SLC, LKN, BOI, GJT (6-h), DRA (18 Z only) Regional-scale storm structure; data assimilation
Utah Mesonet University of Utah High density over northern Utah; additional sites regionally Mesoscale storm structure; surface flow kinematics; quantitative precipitation observations (SWE)
Doppler on Wheels (2) University of Oklahoma Orographic precip target area or mobile operation during lake-effect events Fine-scale spatial and temporal evolution of orographic precipitation structure and kinematics; lake-effect precipitation structure and kinematics
Dual-frequency microwave radiometer University of Utah Facility for Atmospheric Remote Sensing University of Utah Spatial and temporal evolution of integrated water vapor and CLW
KMTX WSR-88D NWS Promontory Point Forecast operations; QPE validation and development
Vertically pointing Doppler Radar NSSL/Ken Howard, Salt River Project, and Radian Portable, but usually Snowbasin QPE validation and development
Terminal Doppler Weather Radar (TDWR) FAA Centerville Forecast operations; QPE validation and development
Utah ADAS University of Utah Northern Utah Quasi-operational data assimilation; Forecast operations
Real-time MM5 (36/12 km resolution) University of Utah Northern Utah and surrounding region Forecast operations; model validation

4. Forecasting and Daily Operations

All forecasting and nowcasting operations for IPEX will be conducted from the Ops Center set up in the briefing room at the National Weather Service Forecast Office (NWSFO) in Salt Lake City (SLC). The IPEX forecasting and nowcasting support effort will operate 7 days a week for the full operational period of the experiment. An AWIPS workstation and UNIX workstation will be provided for forecasting. NWS personnel will be available for assistance in forecasting and nowcasting, as their time allows. It will be necessary for all IPEX personnel who will be working in the Ops Center in a forecasting capacity to receive training prior to the start of the experiment. The Ops Center will be reserved for approximately 1 week prior to the experiment for training purposes. Proper training will take approximately half a day.

In this document, a distinction is made between IPEX forecasting and nowcasting responsibilities. Forecasting support is defined as daily and long-term prediction, while nowcasting support is defined as short-term (less than 3 hours) prediction and real-time support of field operations. Forecasters will be drawn from participating IPEX scientists and students. The forecaster shift schedule can be found here.

4.1 Nominal Daily Schedule

The following chronology provides a working guide for daily forecasting/nowcasting operations. Much of the schedule is dictated by operational constraints of the P-3 aircraft, which requires advance notice of takeoff (TO) time well in advance of specified missions (specific details of the P-3 operational constraints are addressed later in this document). The typical daily schedule is listed below. This schedule will be adjusted for early P-3 departures.

Following the departure of the P-3 from SLC, communication via VHF radio and flight phone is established between the IPEX Operations Director and the P-3 chief scientist. The Remote Aircraft Tracker System (RATS) will provide P-3 location on the NSSL (Radar Algorithms and Display System) RADS display of KTMX data running in real-time in the Ops Center.

4.2 Forecast Products and Dissemination  

A variety of forecast products, described in the table below, will be prepared by the forecast team for daily meetings and forecast verification. These products have been selected based on program needs and the desire to limit as much as possible the ambiguous validation of forecasts. Forecast products will be archived via a world wide web page and available over the internet. The forecast team will present their forecasts at the 12 MST briefing that will be attended by the Operations Coordination Team and other interested scientists.

IPEX Forecast Entry Page

IPEX Forecasts To Date

4.3 Forecast Comments

Guidance for forecasting lake-effect snowstorms can be derived from the recent paper by Steenburgh et al. (1999). Additional information concerning lake-effect of the Great Salt Lake is provided in Carpenter (1993) and Onton (1999). According to Steenburgh et al. (1999), lake-effect precipitaiton is most common overnight and in the early morning hours. Therefore, lake-effect IOPs will likely occur overnight, with operations ceasing in the early afternoon.

Forecasting orographic precipitation is covered by Dunn (1983).

Guidance for forecasting postfrontal lightning associated with lake-effect or orographic precipitation can be found in Schultz (1999). Schultz (1999) found that lake-effect snowstorms are more likely to produce lightning when the surface temperature is greater than 2C. Similar values of 700-hPa temperature, surface-to-700-hPa temperature difference, and lifted index are -10.5C, 13.7C, and 1C, respectively. Dewpoint depression and convective available potential energy are not useful in forecasting postfrontal lightning. 4.4 Nowcaster Responsibilities  

4.5 Communications

As with any field experiment, good communications are important towards assuring the success of the project. As such, several redundant communications links will be established between the operations center and the chief scientists of the mobile laboratories and the DOWS. The primary means of communication between the operations center and the P-3 aircraft will be VHF radio (122.925 MHz), flight phone, and possibly also satellite communications; the primary means of communication between the operations center and the mobile laboratories and DOWs will be cell phone. It will also be possible for the mobile laboratories to directly coordinate operations with the P-3 using VHF radio.

Should communication systems fail, the mobile laboratory, DOW, and P-3 Chief Scientists will exercise their best judgments based on their most recent communications with the Operations Director.

4.6 Decision Responsibilities

At 12:00 MST, the forecast team will brief the Operations Coordination Team on the daily and longer range outlooks. The discussion will also include issues such as facility status reports, budget considerations, and instrument availability. Based on the 6-24 hour forecast and facility reports, the Operations Coordination Team will collectively decide whether to operate (GO/NO GO), and given a GO decision will develop an effective mission strategy. Based on the 24-48-hour outlook, a decision about operating on the following day would be rendered (GO/NOGO/STANDBY). Given a GO decision, the P-3 Chief Scientist will alert the NOAA/AOC representative of the anticipated takeoff time and initial target point for the day's mission. The Operations Director will have the authority to make the final decision on daily operations.

5. Mobile Laboratory Operations

All participating vehicles must have tire chains and/or 4WD with snow tires, as required by the state of Utah. Sleeping bags should also be carried in the vehicles in case of emergency.

5.1. Mobile Laboratories

During IPEX, two mobile laboratories from the JMRF will participate in mobile ballooning operations. These two mobile laboratories will be known as NSSL1 and NSSL2. Though some evolution in the mobile laboratory design has occurred over the past decade, the basic structure of the mobile laboratory and its data systems, as well as a short discussion of mobile ballooning operations, is presented by Rust (1989).

In most cases, the mobile laboratories will be deployed to locations predetermined and will remain fixed. In the event of possible lightning activity in the region, NSSL1 may be redirected to lauch EFMs. Since a large number of instruments may be in the air at any given time, it is critical that the mobile laboratory chief scientists coordinate frequency allocations prior to each mission. The P-3 pilots request the following information (to be provided by the P-3 Chief Scientist in coordination with the mobile laboratories): 1) the launch location (lat/lon) and time of each balloon launch, and 2) the approximate shortest distance from the airborne balloon to the P-3 flight track.

In addition to mobile ballooning operations, when possible, mobile laboratory crews will make efforts to measure snow type and rate observations.

5.2 Mobile Ballooning Instrumentation

As stated earlier, the primary data collection responsibility of mobile laboratory crews will be to launch balloon-borne radiosondes and EFMs. For NSSL5 (Showell), it will typically be necessary for a 5 person crew when launching electrical instrumentation. For NSSL4, only a 2-3 person crew will be necessary. There should be ample opportunity prior to the start of IPEX to train students and scientists to fill in at one or more of the key positions. The SLC tower (section 5.2) number is 325-9660.

5.3 Balloon Launch Strategies

Once an IOP begins, sondes will be launched every 3-h to coincide with synoptic times, where possible.

Capt. Howard at Hill AFB would like notification as far in advance as possible of an IOP, then call the Hill AFB Tower 1 hour prior to all launches. Below are the contact numbers for Hill and Ogden Airport for your records.

1. Capt. Howard (Hill AFB): 801-775-6752
Call for notification of an IOP/Balloon Launch as far in advance as possible.

2. Hill AFB Tower: 801-777-1604
Call 1 h prior to launch of all radiosonde launches. This must be done at both Oasis and Ogden airport. I'm not sure if we need to worry about it for Locomotive Springs.

3. Clark Taylor (Ogden Tower): 801-625-5569
I'm not sure if this number is the direct line to the tower, but it is the number we've been using to contact Clark. Suggest that Les verifies the tower number when he visits before IPEX starts.

4. SLC: We have an OK from them....Tom is hunting down the tower number.

6. Ground-based Radar Operations

Ground-based radar operations during IPEX will include the collection of dual-Doppler radar data over northern Utah. In this section, National Weather Service (NWS) and FAA TDWR single-Doppler radar data collection within the IPEX experimental domain and the coordination of the northern Utah WSR-88D NWS radars with DOW data collection are discussed.

6.2 Dual-Doppler Radar Coverage 6.3 DOWs

See the separate document (draft) of the DOW Ops Plan.

All participating vehicles must have tire chains and/or 4WD with snow tires, as required by the state of Utah. Sleeping bags should also be carried in the vehicles in case of emergency.

6.4 Scanning Strategies

Archive of Level II data will be performed.

7. Aircraft Operations

One NOAA P-3 aircraft has been committed to IPEX for 57 research flight hours. The two primary responsibilities of the P-3 will be to gather pseudo-dual-Doppler and in-situ cloud microphysical data in support of IPEX objectives.

7.1 Operational Constraints

AOC has developed several rules regarding P-3 flight missions to ensure safe operations yet allow maximum flexibility to adjust to changing weather and multiple scientific objectives. These constraints are summarized in Table 4.

Table 4: NOAA P-3 Operational Constraints
Constraints Limits
Anticipated next-day takeoff time Must be specified at least 24 hours in advance
Crew duty day 16 hours
Minimum crew rest between duty days 15 hours
Maximum consecutive mission days 6
Minimum pre-flight preparation time 3 hours

The anticipated next-day takeoff time specifies the start of the crew duty day. The mission must be completed within 16 hours of this time including any delays in takeoff. A "hard-down" day must be given after the sixth consecutive mission day, or following 3 consecutive late night missions. A mission day is defined as an alert day whether or not the aircraft actually flies a mission. A down day is declared at the weather briefing for the next day. The P-3 scientific personnel will also adhere to the crew duty day and crew rest operational constraints. The first day of possible flight will be no less than 12 hours after the end of the Super Bowl on 30 January 2000.

7.2 Scientific Flight Crew Positions

The operation of the specialized scientific equipment on the P-3 (lower fuselage and tail radar, cloud physics system) is normally performed by the scientific crew. Personnel from AOC monitor the performance and recording of the main data system (in-situ flight level data). The required scientific positions on the P-3 are as detailed in Table 5.

Table 5: NOAA P-3 Scientific Flight Crew Positions
Position Number of People Duties
Chief Scientist 1 Plan flight tracks in coordination with Flight Director
Supervise data collection
Coordinate with Operations Center & Mobile Laboratories
Doppler Radar 1 Monitor system performance
Maintain tape and event logs
Change tapes
Help interpret radar displays
Cloud Physics 2 Monitor system performance (1 cloud physics/ 1Q-probe)
Maintain tape and event logs
Change tapes
Help interpret PMS displays
Observers 2 (optional) Help interpret meteorology and assist Chief Scientist
Maintain scientific logs
7.3 Instrumentation

There are three basic data systems on the P-3. These include the radar data system, the cloud physics data system, and the main data system.

7.3.1 Radar Data System:

The P-3 aircraft is fitted with two research radars onboard. They are a 5 cm lower fuselage radar (LF) that measures returned power only and a 3 cm tail mounted Doppler radar (TA). The 5 cm LF is mounted below the lower surface of the aircraft and scans in a PPI mode. The radar is capable of performing complete 360 sweeps or sector scans of less than 360 and operates nominally at 2 rpm. The radar, operating at 200 PRF, has an unambiguous range of ~750 km, and can archive a maximum of 512 gates (or bins) of information. The maximum range that can be archived is simply the product of the 512 gates times the pulse length. The pulse length is variable between 125 m and 750 m in 125 m steps. Both the pulse length as well as the sector size are operator selectable. Some of the LF characteristics are given in the Table 6.

Table 6: Characteristics of the NOAA P-3 Lower Fuselage Radar
Parameter Value
Scanning method PPI
Wavelength 5.59 cm (C-band)




1.1 deg 

 4.1 deg

Gain 37.5 dB
Sidelobe (dB down from main lobe) -23 dB
Scan rate 2 RPM
Tilt elevation range (10 deg
Range resolution 750 m (maximum; half pulse length)
Pulse Repetition Rate (PRF) 200 /s
Unambiguous range 750 km
Maximum range (archived) 384 km
The TA is mounted on the tail of the aircraft and scans in RHI mode which, due to forward aircraft motion, is better characterized as a helical pattern. The "French antenna" is being used for IPEX. The French antenna is a dual plate antenna with one plate directing the radar beams ~20 aft of the normal vector to the aircraft heading and the other directing the beams ~20 forward of the normal vector. As each sweep is completed, the power is alternately directed to the other antenna plate, and hence, alternating forward and aft sweeps are accomplished. The French antenna can rotate at a maximum of 10 rpm and can provide either 360 continuous sweeps or 180 sector sweeps to either side of the aircraft. Some of the characteristics of the TA are given in the Table 7.
Table 7: Characteristics of the NOAA P-3 Airborne Doppler Radar
Parameter Value
Scanning method RHI
Wavelength 3.22 cm (X-band)

 CRPE (French) flat-plate antenna 



2.07 deg/2.04( deg (aft/fore beams) 

 2.10 deg (aft and fore beams)

Polarization (along sweep axis) 

 French antenna 


Linear horizontal
Sidelobes (dB down from main lobe) 

 French antenna 



Aft beam: -57.6 dB; Fore beam: -55.6 dB 

 Aft beam: -41.5 dB; Fore beam: -41.8 dB


 French antenna 


Aft beams: 34.85 dB; Fore beams: 35.90 dB
Scan rate 0-10 RPM
Fore/Aft tilt 

 French antenna 


Aft beam: -19.48 deg; Fore beam: 19.25 deg
Pulse Repetition Frequency (PRF) 1600 /s (maximum)
Pulses averaged per radial sample 32
Unambiguous Nyquist interval (12.88 m/s (1600 /s PRF)
Unambiguous range 93.7 km
Range resolution (0.5 (s pulse duration) 75 m (half pulse length)
7.3.2 Cloud Physics Data System:

The P-3 aircraft is fitted with two optical array probes with size resolutions of 150 mm (2DG-P) and 30 mm (2DG-C), respectively. These probes are typically referred to as "grey probes" as, in addition to having a size resolution that is improved over earlier versions, they are also capable of discriminating four different shades of optical intensity. The characteristics of the 2DG-P and 2DG-C probes are given in Table 8.

Table 8: Characteristics of the NOAA P-3 Optical Array Probes
Parameter 2DG-P 2DG-C
Size range 9.6 mm 1.92 mm
Resolution 150 microns 30 microns
Ice/water discrimination No Depolarizer
Other cloud microphysics instrumentation to be flown on the P-3 during IPEX include: a 15-channel Forward Scattering Spectrometer Probe (FSSP), and a Johnson-Williams (JW) cloud liquid water probe.

7.3.3 Main Data System:

Characteristics of the main data system sensors are given in Table 9. The sensors that are serviced by the main data system are sampled at a rate of 40 Hz, and then are averaged to yield 1 sample per second. Derived parameters (such as wind) are calculated in post-processing once calibrations and biases are determined and removed.

Table 9: Characteristics of the NOAA P-3 main data system sensors
Parameter Instrument Manufacturer Accuracy Resolution
Positioning Inertial Navigation Equipment (INE) Northrop/Delco 1.5 km (after post-processing) 8.3x10-8 
Temperature Platinum resistance Rosemount 0.5 C 0.03 C
Dewpoint Cooled Mirror General Eastern 0.5 C 0.03 C
Static pressure Transducer Garrett 1.0 mb 0.1 mb
Dynamic pressure Transducer Rosemount 0.5 mb 0.1 mb
Attack pressure Transducer Rosemount 1.0% 0.1 mb
Sideslip pressure Transducer Rosemount 1.0% 0.1 mb
Absolute altitude Radar Altimeter Stewart-Warner (APN-59) 0.01% 1 m
Cloud water Hot Wire Johnson-Williams 0.2% 0.1 g/m3
In-cloud temp. CO2 radiometer (14 micron) Barnes/AOC 1.0 C 0.1 C
Ground speed INE accelerometers Northrop/Delco 0.5 m/s 0.06 m/s
Track angle INE accelerometers Northrop/Delco 0.2 deg 0.005 deg
Heading angle INE accelerometers Northrop/Delco 0.1 deg 0.005 deg
Pitch angle INE accelerometers Northrop/Delco 0.06 deg 0.005 deg
Roll angle INE accelerometers Northrop/Delco 0.06 deg 0.005 deg

8. Field Experiments

8.1 Overview of Field Experiments

Specific field experiment designs are presented in this section. One of the advantages of using the P-3 aircraft to investigate weather phenomena is the ability to adjust flight patterns to fit the pattern of storms and precipitation. The fixed terrain forcing will make P-3 operations much simpler than other projects. In addition, flight safety requirements specify that the P-3 not penetrate any convective cell where the possibility exists of damage due to turbulence, strong updrafts and downdrafts, and/or damage from hail, graupel, or icing. No penetration of convective features (as evidenced on the nose radar display) will be attempted.

8.2 Flight Modules

Module 1: Cross-barrier flight stack

2 short legs 60 to 160 km 10 - 27 minutes
3 long legs150 to 330 km25 - 55 minutes
ascents25 kft 25 minutes
TOTAL TIME:60 - 107 minutes

Module 2: Along-barrier racetracks

2 long legs60-200 km 10 to 33 minutes
2 short legs20-50 km 3 to 8 minutes

TOTAL TIME: 13 to 41 minutes

Module 3: Midlake Band flight tracks

long along-band leg150 km 25 minutes
long cross-band leg100 km 17 minutes
times 3-5 isothermal levels: 51-83 minutes
ascents25 kft25 minutes
TOTAL TIME: 76-108 minutes

9. Data Management

9.1. Operational and Research Networks

WSR-88D Radar:

The NWS WSR-88D (10-cm Doppler) radar provides two types of archives - base data and products. Base data (Archive Level II) consists of data that have been preprocessed (clutter suppressed, point target filtered, V and W moments range unfolded and return power converted to dBZ and occurs at the Radar Data Acquisition (RDA) component located at the radar tower. Level II base reflectivity data are archived at 1-km resolution out to 460 km; base velocity and spectrum width data are archived at 0.25- km resolution out to 230 km. The archive medium for Level II data is Exabyte 8-mm cartridge tape. These data are archived at NCDC and can be obtained via off-line order entry on the On-line Access and Service Information System (OASIS). NCDC typically requires a nominal fee for duplication and dissemination of archived data via magnetic tape (8 mm). The NCDC system is accessible through the NSSL CODIAC.


Regional digitized radar reflectivity composites over the U.S. are available from a commercial vendor (WSI® Corp.) at the UCAR Joint Office for Science Support (JOSS). 15-minute composite files, in McIDAS AREA file format, will be archived for a fixed sector covering the IPEX domain. A catalog of browse radar composites Gif images will be also available.

Single Site:

Gif products for the lowest 2 scans from individual radar sites can be archived for various WSR-88D radars in the IPEX domain. Arrangements must be made in anticipation of capturing sites of interest to researchers. Vertically-pointing S-band radar S-band operations will be set up at Snowbasin ski area upper parking lot. The S-band will record the vertical profile of reflectivity in the shadow of Ogden Peak which blocks the KMTX lowest radar beam. The radar records data continuously employing hard disk data storage and can be left unattended for several days. Technical specifications can be found at Continuous manning of the equipment is not needed.

Manual snow and snow water equivalent measurements

Accurate manual precipitation measurements (MPMs) are important for validation of remotely-sensed and model-predicted precipitation. The primary points for MPMs will be in the Ogden-Snowbasin area. Manual measurements will be collected at the Snowbasin base, near the vertically-pointing radar and Utah Mesonet Site, Weber State college near the Utah Mesonet site, and the Ogden airport. Measurements will include storm-total snowfall, snow water equivalent, precipitation and, during periods of heavy precipitation, 3-h or 1-h accumulations. Data will be collected using snow boards and coaring tubes. The data for Ogden airport and Weber State will be collected by members of the NSSL mobile lab team. Two volunteers will collect data at Snowbasin.

NWS Radiosonde Operations:

The National Weather Service will provide radiosonde observations from several field offices in support of the IPEX field program. When requested, soundings will be provided every 3 hours from Salt Lake City (SLC), Boise (BOI), and Elko (LKN). Grand Junction (GJT) will provide soundings every 6 h and Desert Rock (DRA) will provide a launch at 1800 UTC when requested.

NWS Offices should be provided notice 36 h prior to the start of an IOP which includes a tentative schedule for the times of radiosonde launches. Communications between the offices will be coordinated by the SLC NWSFO lead forecaster. Since data collection at the upstream offices (LKN, BOI, DRA) will likely begin 12 h or so before the start of an IOP, this will give those offices approximately a 24 h notice. Updates and possible schedule modifications will be provided on an as needed basis as an IOP approaches.

To satisfy the requirements above, IPEX planning meetings must not only discuss the possibility of a next day IOP, but the possibility of an IOP 2 days in advance. If an IOP is likely, a tentative sounding schedule should be provided to the NWS field offices.

Add SL Tower number to notify for balloon launches. 325-9660

Add 585-1403 as the operations info line.

National Weather Service standard soundings will be taken during IPEX from the existing NWS network every 12 hours (00 and 12 UTC) and every 3 hours during IOPs. The radiosondes will be radio-directionally tracked (GMD) with winds measured at one minute interval. Thermodynamic data (temperature, pressure and relative humidity using a carbon hygristor) are sampled about once per second and averaged values from the MicroART processor are stored every 6 seconds. NCDC archives the 6-sec, high resolution data; JOSS routinely quality-controls and reformats (calculates winds) from these data. The NWS soundings will be available after the field phase via CODIAC.

Table 11: NWS Sounding Sites
WMO ID Site Latitude Longitude Elev (m)
72572 SLC Salt Lake City, UT 40.78 -111.97 1288
99999 RIW Riverton, WY 43.07 -108.45 1664
72681 BOI Boise, ID 43.57 -116.22 874
????? LKN northeastern NV
72476 GJT Grand Junction, CO 39.11 -108.53 1475
MCLASS soundings:

The Cross-chain LORAN Atmospheric Sounding System uses Vaisala RS-80L LORAN radiosondes to profile temperature, pressure, humidity (Humicap) and winds. Thermodynamic parameters are transmitted directly from the radiosonde to the mobile laboratory every 4 sec. A 20-sec average every 10 seconds is archived for the thermodynamic variables, while a 30-sec average is used for winds. A WMO- coded message can be prepared and transmitted to the IPEX Operations Center, if needed. All CLASS data will be archived at NSSL. 10-sec sounding files will be available through the interactive data catalog.

MCLASS electrification:

As noted earlier in this document, a balloon-borne instrument to measure cloud electrification properties will be flown during IPEX.

Utah Mesonetwork:

The Utah Area Mesoscale surface Network (Utah Mesonet) is operated by the University of Utah School of Meteorology and consists of XXX automated sites. 5-minute data are received at UU, where they are quality controlled and archived. All mesonet sites measure the standard surface meteorological parameters, with some sites taking additional measurements from specialized instruments.

GOES satellite imagery:

Satellite imagery is routinely ingested at UU and archived to tape. Visible and Infrared imagery are nominally available every 30 minutes, at 4-km resolution. The capability exists to acquire a high resolution (1-km) sector centered over the IPEX domain, if requested by researchers. Additionally, 12-km resolution images of water vapor channel are also available. These data are received from both GOES-8 and GOES-9 satellites.

Aircraft Data:

NOAA's Aircraft Operations Center (NOAA/AOC, Tampa, FL) operates a Lockheed Orion WP-3D aircraft, a four-engine turboprop, which will be based out of Salt Lake Airport. The P-3 will be available from 31 January to 28 February 2000 for approximately XX research hours. The aircraft routinely measures flight level state parameters (temperature, moisture, winds) and basic microphysical variables (liquid water, PMS probe data) as well as data collected by its two radars. All aircraft data systems are recorded on 4-mm DAT media.

Flight-level Data:

Flight level meteorological data (temperature, moisture, winds) and other data systems from the P-3 will be collected, quality controlled and processed by the AOC. The data will be catalogued and archived at NSSL. CODIAC will have an inventory of take-off, landing times and could contain flight track information. The aircraft data manager will provide flight track information to the IPEX Field Catalog after each flight.

Aircraft Radar Data:

The NOAA WP-3D research aircraft carries two radars, the horizontally scanning lower fuselage (LF) radar and a vertically scanning tail (TA) radar. The LF radar is non-coherent and the TA radar is Doppler (3-cm). Both radars are three-axis stabilized, where the TA antenna is nominally directed perpendicular to the aircraft ground track but can be skewed fore and aft in order to perform pseudo dual-doppler scanning. Both antennas rotate a full 360 . Reflectivity and velocity data from the radars are recorded on 4-mm DAT media. The aircraft data manager, John Daugherty will provide a few radar summary images after each flight for documentation in the IPEX Field Catalog. All aircraft radar data will be available from the data manager after the field phase.

Lightning Network:

Cloud-to-ground flash information is routinely received at NSSL from the Lightning Location and Protection (LLP/GAI) system. Data for time, location, polarity, signal strength and number of returned strokes are available for purchase at the end of the calendar year from Global Atmospherics, Inc. Model data:

Operational model-derived gridpoint data are available to UU data feed or the Unidata/Local Data Manager (LDM) feed. These files are routinely archived. Data will be available, off-line, through the interactive data catalog. UU typically receives Eta and RUC-2 gridpoint data files in GEMPAK format.

MM5 at NSSL:

The NCAR / Penn State Mesoscale Model (MM5) is run at UU. Arrangements will be made for archival and distribution of MM5 grid fields, if requested by IPEX investigators.

9.2 Operations Summary / Field Data Catalog

NSSL, in collaboration with the UCAR Joint Office for Science Support (JOSS) has developed the capability of maintaining a World Wide Web (WWW)-based field data catalog. The on-line catalog capability allows investigators limited perusal and display of preliminary data products during the field phase. The catalog will also provide in-field project summaries (daily or otherwise as required) and summarize data collection activities. The field data catalog will provide access to daily operations and weather forecasts relating to IPEX activities. The NSSL field catalog can be reached at The Web-based field catalog is also valuable in providing information to investigators that may be located away from the Operations Center.

A number of forecast / nowcast products will be available to the Operations Director and the Nowcaster at the IPEX Operations Center. The Operations Center will be housed in the NWSFO SLC.

9.3 Interactive Data Catalog and Archive

Central to the NSSL data management is the on-line, interactive, catalog, archival and distribution system (CODIAC) which offers scientists a means to identify data sets of interest, the facilities to view selected data and associated metadata, and the ability to automatically obtain data from geographically dispersed data centers via Internet file transfer (FTP) or separate media (tapes, CD-ROM, disks, etc.). Links will also be provided from the NSSL CODIAC to other data centers holding cooperative project data and other relevant information to IPEX research. The NSSL CODIAC system can be reached at

10. Participants