Florida Bay Rainfall Study

Clouds and Climate Over the Everglades
(960809I Aircraft 43RF -- single aircraft)

Scientific Crew

Chief Scientist -- Marks

Doppler Scientist -- Dodge

Doppler Operator -- Landsea

Cloud Physics Scientist -- R. Black

Observers -- Murillo (FSU), Guertin (PSU)

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

Mission Briefing

The planned mission was Clouds and Climate over the Everglades in support of the Florida Bay Rainfall Study. The primary purpose of the mission is to collect radar and cloud microphysics data in convective precipitation systems over the Florida Bay watershed, which includes the Everglades from Lake Okeechobee to Florida Bay. The aircraft measurements will be attempted within 100 km of the Miami WSR-88D radar (KAMX) and in conjunction with surface based disdrometer measurements from the HRD/AOC instrumented van and the HRD/OAD Joss disdrometer. The instrumented van will be sampling along the Tamiami Trail near Ochopee and the intersection with highway 29 (roughly 25.9°N, 81.4°W), while the disdrometer is located at the National Park Service Agricultural Test Station in Everglades National Park at 25.39°N, 80.68°W.

A secondary purpose for the mission is to continue testing the PMS probe orientation and location measurements begun last season by R. Black. These measurements are designed to determine the effect of the airflow around the wing on the microphysics sampling. A tertiary purpose is to test the instrumentation (radar system, dropsonde, field mills, etc.) on N43RF prior to any field program deployments.

The mission plan calls for N43RF to depart from Opa Locka around 1730 UTC and ferry to the W coast of Florida to coordinate patterns with Paul Willis in the van via cellphone. Paul will contact us when he is in position, approximately 1815 UTC. After attempting to fly a coordinated mission with the van, N43RF will pick targets of opportunity. Maximum mission duration will be <5 h.

Return to Top

Mission Synopsis

N43RF departed Opa Locka (25.91°N, 80.27°W) at 1748 UTC. After takeoff we ferried to the west coast of Florida, passing a convective precipitation system, composed of a 30-40 km long line oriented roughly E-W, located between the Tamiami Trail and Alligator Alley (I-75) approaching Paul's target area. We did a true airspeed calibration over Florida Bay from 1826-1828 UTC while waiting to contact Paul Willis in the van. During the true airspeed calibration we contacted Paul via Airphone and gave the location of the convective precipitation system approaching the Trail. Paul was in precipitation and making measurements, so we proceeded to intercept the precipitation system. The first pass was W-E along the N side of the precipitation system at 10000 ft with the tail radar in perpendicular scan mode, starting at 1833 UTC (25.85°N, 81.3°W). We exited the system on the E side at 1842 UTC (25.9°N, 80.7°W, almost over Dade-Collier airport) and performed a spiral descent to 1500 ft. At 1855 UTC we started E-W 1500 ft pass through same cells along the N side of the Tamiami Trail (upwind) with the tail radar in F/AST mode. The leg ended at 1900 UTC E of Everglades City. We reversed course and made another W-E pass at 1500 ft starting at 1906 UTC (25.9°N, 81.17°W). This pass the cells were getting pretty stratiform. The leg ended at 1909 UTC where we turned over Dade-Collier airport to track WSW once more at 1912 UTC. We made two more passes at 1500 ft: (1) WSW-ENE starting at 1917 UTC; and (2) ENE-WSW starting at 1921 UTC. At the end of the last leg we talked with Paul in the van and started a climb to 10000 ft over Florida Bay to look for other targets, and to restart the radar system which froze around 1930 UTC.

As we were loitering over Florida Bay we noticed that the convective precipitation system we had just sampled continued to regenerate as it moved SE toward the disdrometer at the Agricultural Test Station. By 2000 UTC the precipitation system was nearly over the disdrometer location (25.39°N, 80.68°W). Hence, a pattern was set up to sample the system once again as it passed over the disdrometer. The first leg was at 10000 ft on a SSE track passing a few mile E of the disdrometer location starting at 2012 UTC. The tail radar was in perpendicular scan mode on this traverse. The traverse was followed at 2018 UTC by an attempt to box the system, starting to the W of the feature, with the tail radar in F/AST mode. Plenty of CG lightning was noted around the system. We completed the box with another 10000 ft leg NNW-SSE through the convective system starting at 2029 UTC (25.61°N, 80.58°W). After completing the box, we made a spiral descent to 1500 ft (shortly after reaching 1500 ft ATC requested we return to 2000 ft for the duration of our penetrations). We then proceeded to make four roughly N-S passes through the convective system over the disdrometer site with the tail radar in F/AST mode. The first pass we skirted W (upwind) of the heavy precipitation core sitting over the disdrometer site, passing roughly 3 nm W of the disdrometer. The second and third passes we went right over the disdrometer in precipitation (we could see the Agricultural Test Site buildings in the rain both times), passing overhead at 2049 and 2054 UTC, respectively. The last leg starting at 2101 UTC passed roughly 2 nm E of the disdrometer which was no longer in the heavy core. We noted a lot of CG lightning on the last three legs. At the end of the fourth 2000 ft leg, we climbed back up to 10000 ft at 2104 UTC, did a final true airspeed calibration over Florida Bay S of the convective system, and then returned to Opa Locka at 2144 UTC.

Return to Top

Mission Evaluation and Problems

This mission went much better than expected considering it was the first research mission of the season and posed some tricky logistical challenges. Fortunately for us the weather cooperated, providing two good convective precipitation systems, one over the area where Paul was making measurements with the van, and the second (likely a direct descendant of the first system) was sampled directly over the disdrometer at the Agricultural Test Station. Because of uncertainty in the performance of the new AOC crew members and the desire to take it easy on this first mission, my leg selection and mission planning were very tentative and conservative on the first system flown, resulting in little heavy rain sampled. By the second system, my confidence in the AOC crew and their confidence in our intentions made for more aggressive sampling of the heavy precipitation core, despite lightning and the low altitude. The AOC crew was fantastic, making the mission execution as easy as possible. Communications with the van worked pretty good, thanks to the help of Damon San Souci from AOC, who used the Airphone on the plane to communicate with Paul. In the future we may want to use just another cellphone on the plane, as AOC claims that should work at that close range. Either way we need to work out a slightly better scheme for communicating with the van.

We recorded FAST (40 Hz), as well as, SLOW (1 Hz) data records from the main aircraft data system. Both record types are stored on a single DAT. We also recorded 2 DATs with radar data (one before and one after the system crash), and 1 DAT of cloud physics data. A box of ODWs (8 sondes) was baselined, with 2 sondes failing the PTH baseline. We left the sondes on the aircraft for future use. We also transmitted 1 min ASDL flight level data to test communications between the aircraft and NHC.

1. The radar data system went down twice during the mission. The first time, at the beginning of the mission, when the LF radar wouldn't transmit. Terry Lynch and Jim Roles replaced the LF R/T. The second time the radar system froze after the first set of convective penetrations and Peter Dodge restarted the system.

2. The 2D-P data seemed noisy with a lot of records with clear air updating. The 2D-C data seemed cleaner. R. Black will check the tapes to see how bad the problem is. The clear air updating will likely compromise the sample volume for rainfall estimation.

3. Communications with the Airphone was problematic. We could call Paul and he could call us. However, once a connection was made it was often broken or badly garbled. We need to try a cellphone the next time.

4. There are now four video cameras onboard N43RF (and likely also on N42RF). We need to start carrying 4 super VHS cassettes for each flight.

Return to Top