rafclouds -- compute incloud temperature, vapor, and total water mixing ratio
rafclouds tau_temp tau_mr tau_mrt mrtlag
Rafclouds expects a Candis file on the standard input containing NCAR/RAF aircraft data concatenated into a single variable slice. The standard output produces a similar file with some or all of the additional fields cleanatb, oat2, ctemp, cmr, and cmrt.
The field cleanatb is derived from the Rosemount temperature, atb, and the FSSP liquid water content, plwcf. Basically, Rosemount values in and near a region of liquid water are replaced by values linearly interpolated across the region. Values of liquid water > 10 g/m^3 are rejected as being unreasonable, and the result of a flakey instrument. (The FSSP probe does this sometimes.)
The field oat2 is derived from the Ophir radiometer temperature, xato, and simply is a despiked version of oat. (In some configurations the Ophir instrument produces apparently useless calibration spikes.)
The field mruv2 is derived from the UV hygrometer, and is a despiked version of xmruv. If the UV hygrometer is not available, the Lyman alpha instrument is calibrated and used instead to produce mruv2.
The field ctemp is derived from oat2 and cleanatb. The low pass filtered part of cleanatb is combined with the scaled high pass part of oat2. The command line argument tau_temp is the filtering time constant for this calculation. Ctemp should be a valid in-cloud temperature if the cloud transit time is much less than tau_temp.
The field cmr is derived from mr, the vapor mixing ratio produced by a dewpoint instrument, and mruv2, the despiked vapor mixing ratio produced by the UV hygrometer. The low pass filtered part of mr is combined with the scaled high pass part of mruv. The command line argument tau_mr is the filtering time constant for this calculation. Cmr should be a valid in-cloud vapor mixing ratio if the cloud transit time is much less than tau_mr.
The field cmrt is derived from mr and xmrtow, the experimental total water probe. This probe evaporates all water with a heater and then measures the mixing ratio with a wetbulb-drybulb combination. Since xmrtow can drift a small amount relative to mr, cmr, the low pass part of mr combined with the scaled high pass part of xmrtow, is computed. Xmrtow suffers a lag relative to other devices, due to transit time of air through the system. Xmrtow is delagged by the amount specified in the command line parameter mrtlag (given in an integer number of seconds) before combination with mr. A good starting point is mrtlag = 2 sec. Cmrt should be a valid in-cloud total water mixing ratio if the cloud transit time is much less than tau_mrt. Care must be taken in interpreting the output, as xmrtow appears to have a response time of order a second or two.
Setting tau_temp = tau_mr = tau_mrt = 100 sec is a good starting point. Current scaling values and despiking parameters are incorporated as parameters in the output file. See the source code for their precise meaning.
If the precursor fields for any computation are missing, the resultant field is neither computed nor incorporated in the output file.
Standard RAF variable names are assumed. Deviations (and time evolution of names) will cause confusion.
The output of this program is highly experimental at this point. In particular, be sure that the wetbulb in xmrtow has not dried out. A symptom of this is unreasonably high mixing ratios in xmrtow.
Rafread, rafdap.