Instrument Names: DC-8 Microwave Temperature Profiler (MTP/DC8), ER-2 Microwave Temperature Profiler (MTP/ER2)

Principal Investigator: Dr. Michael J. ("MJ") Mahoney, JPL/Caltech

Recent Missions: On the DC-8, the MTP has flown on SOLVE, PEM Tropics B, SONEX, SUCCESS, and TOTE/VOTE. On the ER-2, it has flown on SOLVE, CIREX, STRAT and POLARIS. On the WB-57F, the MTP has flown on ACCENT, ACCENT II and WAM. Also, in 2000, the MTP flew on the NCAR L-188C in the Texas Air Quality Study. Since the late 1980s, MTPs have an enviable performance record of more than 450 successful flights and 2800 flight hours.

Overview: The MTP retrieves profiles of air temperature versus altitude along an aircraft flight track. It does this by measuring the natural thermal microwave emission from oxygen molecules in the earth’s atmosphere, and then performing a statistical retrieval inversion procedure, based on an archive of thousands of radiosondes, to obtain the most likely temperature profile given the measurements. On the DC-8 this retrieved profile displays on monitors throughout the aircraft, and can be used for real time flight planning. On the ER-2 the MTP operates autonomously, and the data is processed after recovery.

Objectives: During CAMEX-4, MTPs will make measurements of the temperature field about the DC-8 and ER-2 flight tracks. Temperature is a primary state variable of the atmosphere, and its measurement is essential to place in situ and remote measurements of chemical species and aerosols in proper meteorological context. MTP data will also be used to verify numerical weather models, especially on mesoscales, where satellite measurements are inadequate. MTP measurements will also be used to validate satellite data.

Experiment Operations: The JPL DC-8 Microwave Temperature Profiler, a passive microwave radiometer, will measure natural thermal emission from oxygen molecules at three frequencies (55.51, 56.66 and 58.79 GHz). The instrument views ten elevation angles between –80 and +80 degrees by using a scanning mirror – located behind a microwave window on the sensor unit – to change the viewing direction. The real-time display consists of air temperature versus altitude, from near the surface to 24 km, which is updated every 14 seconds. The ER-2 MTP operation is similar, but it is adapted to the higher flight altitude (20 km) of the ER-2, and produces a temperature profile every 10 seconds. The ER-2 MTP weighs only 10 kg (22 lbs) and is contained in two small packages about the size of a shoebox.

Benefits: MTP temperature measurements will help scientists understand the effect of diabatic heating and cooling, which is associated with water phase changes, on hurricane dynamics. Together with moisture and wind, temperature is one of the primary state variables needed to initialize numerical weather prediction models, and hence to understand the model's ability to track hurricanes and predict their intensity at landfall. MTPs will also be able to contribute to the validation of satellite temperature measurements, especially in non-clear sky conditions. And they will provide support for the remote water vapor measurements planned for CAMEX-4, in that the temperature profile allows a vapor density profile to be converted to a relative humidity profile, and thus the saturation state of the atmosphere can be determined. Finally, the MTP data will be used to carry out independent research such as studying the role of convectively-generated gravity waves in atmospheric dynamics.