Rationale—Tier 1

1. Rationale—Tier 1 The principal rationale for a dense network of soundings, profilers and radars in Tier 1, together with rain gauges, is to describe and understand the diurnal cycle of precipitation and the structure of precipitation in the core region of the NAMS and to better understand regimes associated with intra-seasonal variability, including the influences of surges, jets, surface fluxes and topographic blocking. These observations are critical for budget studies and model validation.

2. Objectives to which soundings, radars and profilers contribute… • Observe and describe statistically the daily evolution of “ordinary” convective rainfall • over the high Sierra Madre Occidental, the western and eastern slopes, the Gulf of California • coastal plain, and the southern Gulf region. • Clarify the relationship of convection on east and west slopes of the Sierra Madre Occidental • and water vapor transport from the Gulf of Mexico and the Gulf of California. • Observe and describe statistically the location and amplitude of “organized” mesoscale • rainfall systems within the diurnal cycle. • Observe and diagnose the principal mechanisms that force or maintain mesoscale rainfall • systems so that the effects of these may be adequately represented in models • (e.g. convectively-generated cold pools, sea and land breeze fronts, microphysics, other • diurnally-varying and/or topographically-influenced aspects). • Assist in the identification of local properties and processes associated with variability in • the precipitation (e.g. anomalous surface latent or sensible heat fluxes, quasi-permanent • convergence zones)

3. Objectives-con’t • Observe the development and propagation of southerly surges and associated low-level jets • in the Gulf of California in the broader regional context of tropical easterly waves and • mid-latitude westerly trough passages. • Clarify the relationship of southerly surges/jets to the forcing, organization and northward • propagation of convectively-generated precipitation.

4. Instrumentation and DesignConstraints • The plan is to maximize use of observing systems currently operated by the SMN and to augment • these with research systems currently maintained by U.S. agencies. There are five SMN sounding • sites in Tier 1 – Guaymas, Mazatlan, Torreon, Chihuahua, and La Paz. There are four 5-cm • Doppler radars in Tier 1 – Obregon, Gusave, Cabo San Lucas, and Palmito. • The sounding sites are presumed to be fully functional, so experimental design constraints mainly • concern the frequency and scheduling of soundings and the provision of expendables as may be • required. All of the radars are operational, however, none currently meet standards for systematic • recording of calibrated 3-D reflectivity and velocity data required to address the scientific • objectives.

5. Instruments/Sites UHF wind profilers (some with Radio-Acoustic Sounding System (RASS) capabilities) provide winds through ~ 6 km plus virtual temperature soundings to ~ 2 km. NOAA/AL and ETL. Virtual Integrated Sounding Systems, VISS (co-located SMN sounding + UHF profiler) NCAR Integrated Sounding Systems, ISS, (UHF profiler + RASS + rawinsonde); ISS and VISS will provide continuous wind profiles in the low-to-mid troposphere along with full tropospheric thermodynamic and wind soundings. SMN 5 cm Doppler radars A 10 cm Doppler-polarimetric radar (NASA N-POL, NCAR S-POL); providing rainfall estimates, structure of convection, airflow patterns The Ron Brown shipboard platform (VISS, 5 cm Doppler radar) Crtitical GofC location for surges.

6. Integrated Sounding Systems Seatainer-packaged: UHF Doppler wind profiler (~ 0.1–7km agl) Radio-Acoustic Tv profiler (~0.2 – 2 km agl) GPS rawinsonde sounding system automated surface met obs Applicable to regional analyses, breezes, surges, cold pools, gravity waves, etc. Soundings, > 2/day + event-based

7. NCAR S-pol radar 10 cm Doppler, polarimetric radar Highly portable, six 20 ft. seatainers Diesel generator powered Easy set up Peak power 1 Mw 1 degree beamwidth antenna Suite of Doppler and polarimetric variables Doppler measurements, polarimetric-based rainfall maps, hydrometeor identification Internet ready Deployment costs through NSF deployment pool for NSF-supported research

8. NASA N-pol radar 10 cm Doppler, polarimetric radar Highly portable, four 20 ft. seatainers Diesel generator powered Easy set up Peak power 50 kw 1.4 degree beamwidth antenna Suite of Doppler and polarimetric variables Internet ready Leverage NAME for TRMM and GPM validation studies—NASA funding

10. Rationale for Experimental Design Concentration of observations in the southern Gulf region is based on the climatology of rainfall, the apparent geographical origin of surge events, and diurnal tendency in this region for rainfall to propagate westward, down the SMO slopes, onto the coastal plain and into the GoC itself. A set of continuous, high resolution and reliable deep tropospheric precipitation, wind and thermodynamic measurements utilizing radar, profiler and sounding observations over the southern one half of the SMO and GoC are critical to the proper initialization and validation of both regional and cloud resolving numerical models. The co-location of RAOB and profilers will minimize uncertainties in the significance of data from each individual observing system and increase the quantitative applications of both. Observations over the GoC channel, including SST and interfacial fluxes, are also critically important.

11. Deployment Issues

12. Schedule Perform SMA radar modifications and training (spring 2003). Install and conduct limited operation of 3 UHF profilers (June-July 2003) and routine operations of modified SMA radars (June- Sept 2003). Evaluation of UHF and SMA radar data, (Fall-winter, 2003-4) Installation of ISSs, UHF profilers for VISS sites, and 10 cm radar (spring 2004) Field phase: a six-to-eight week operation (July-August) of ISSs and VISS sites (sounding frequency @ six per day during IOPs, twice per day otherwise, average 4/day) 24/7 operations of polarimetric radar. 50 day operation for the R/V Brown. Conduct QC and archival of sounding, profiling and radar data continually throughout and immediately following operational periods ( UCAR/JOSS, NCAR/ATD, NOAA/AL/ETL, as appropriate).

13. Deployment Issues Services Provided by NCAR/ATD 4 Integrated Sounding Systems operated for 4 months on the mainland $ 800 K* (Average of 4 sondes per day, 60 days) S-POL Doppler-Polarimetric radar operated for 2-3 months $ 500 K* Upgrades, calibrations and staff training for all four SMN radars ~$ 200 K *Eligible for NSF Field Deployment Pool funds Science Overview Document due at NSF in December 2002 Services Provided by NOAA/ETL and/or AL 3 UHF profilers operated for 2 months in 2003 TBD 6 UHF profilers operated for 4 months in 2004 TBD

14. R/V Ronald H. Brown • Instruments • Radar (Scanning C-band Doppler; Vertically pointing Ka-band Doppler) • Rawinsonde • 915 MHz wind profiler • DIAL/Mini-MOPA LIDAR • Multi-spectral radiometers • Air-sea flux system • Meteorological observation (T,RH, P), rain gauges and ceilometer • Oceanographic measurements including SST, CTD and ADCP

15. Ronald Brown Sounding-Derived Winds and w During EPIC PBL w PBL w CG Flash count x 10= R T R T T R Zonal Wind Meridional Wind • Soundings launched 6X/day from 11 September-1 October 2001 • Passage of 3 Easterly Waves (V and U wind signatures). • Peak instability/lightning 0-2 days prior to trough passage

16. 1 dBZ R T R R T T 30 dBZ R T R R T T 40 dBZ R T R R T T 9/11 9/15 9/19 9/23 9/27 10/01 Convective Structure: Filtered Echo Height Distributions vs. Time

17. Height (km) Frequency of Occurrence Distribution of 30 dBZ Echo Tops During EPIC • Mean and mode of echo top distribution is “flat” • Tail of distribution (most intense convection) extends to greatest height near 02 L