Florida Bay Rainfall Study

Clouds and Climate
(960930H1 Aircraft 42RF -- single aircraft)

Scientific Crew

Chief Scientist -- Michael Black

Radar/Doppler Scientist -- John Gamache

Cloud Physics -- Bob Black

Observer -- Jack Stamates (OAD)

This document is divided into 3 sections (Each section is written by the Chief Scientist):

Mission Briefing

HRD crew arrived in Opa-Locka airport to meet NOAA42 at 1600 UTC for a 1700 takeoff. The mission objective was to observe in-situ wind and thermodynamic variables, radar reflectivity and Doppler velocities in low-level penetrations of tropical rain showers. Penetrations of both convective and stratiform rain areas was desired. The areas of interest, in order of priority, were; 1) The southern Florida Peninsula, particularly the southern Everglades, 2) Florida Bay, and 3) Adjacent coastal waters. If time and weather conditions permitted, Paul Willis would drive an instrumented van to the land areas for possible over flights of the P-3. Multiple altitudes below 5000 ft would be employed and the mission duration would be 4-5 h.

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Mission Synopsis

Takeoff was at 1702 UTC when NOAA42 headed west over the Everglades to hunt for rain showers. We penetrated two small showers at 2000 ft near the Dade-Collier County line but, unfortunately the radar was down. From 1830-2000 UTC we penetrated a east-west line of convective cells that extended from near the intersection of Highway 29 and Interstate 75 to the coast near Ft. Meyers. We flew through this line at 3000, 4000, and 5000 ft altitudes. Reflectivities in the cells sometimes exceeded 55 dBZ. During the penetrations, we encountered moderate turbulence and traversed broad up- and downdrafts with vertical velocities as strong as 10 m/s. Occasional lightning flashes were observed. After working the east-west line, we headed SSE along a convective line that intersected the E-W one. We followed this line into Florida Bay, just SSE of Naples. We then reversed course, descended from 3000 ft to 2200 ft, and flew the line inland to a point near the intersections of Highways 29 and 41. We flew into a couple of small showers on route to the Dade-Collier training airfield before heading back to Opa-Locka. We landed at 2139 UTC.

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Mission Evaluation and Problems

A broad range of precipitation types were traversed during this flight, ranging from light, stratiform rain to moderate to heavy rain showers and thunderstorms. The cells were moving fairly rapidly to the NW at 10-15 m/s. The tail radar indicated strong vertical shear as the tops (8-12 km) of the cells were tilted downwind. The strongest flow was experienced at 4000 ft altitude with wind speeds sometimes exceeding 20 m/s. Although we could not fly below 3000 ft for most of the flight, we did sample the rain events at 2200, 3000, 4000, and 5000 ft altitudes. Later, we confirmed that Paul Willis was sampling the rain showers in the van near the time and location that the aircraft was flying overhead. Overall, I believe that the mission objectives were satisfied and that the data collected will help to contribute to the clouds and climate project.

The radar system was down occasionally for brief periods for the first half of the flight. The Doppler data appeared noisy for the first hour but after some adjustment by Jim Roles (AOC), the data looked good. The 2-D precipitation probe appeared to have some missing bytes which resulted in noisy data. Whether or not the data can be smoothed or recovered is uncertain. Since we were flying under IFR conditions, air-traffic control would not clear us below 3000 ft, except for a brief period at 2200 ft. A similar flight earlier in the year, albeit in more scattered precipitation, was flown under VFR rules, hence eliminating the altitude restrictions. The aircraft did not have an air phone onboard, thereby providing no direct way to communicate with Paul Willis on his cell phone on the ground. (I understand that the use of cell phones onboard flights is illegal). I could have tried a phone patch via radio, but based on my discussion with Paul prior to takeoff, I was sure that he would be sampling the same area of rain that we were flying through. Some form of direct communications with personnel on the ground for this mission (and others) is highly desirable.

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