Friday, May 23, 2008
Overview of suspect data for 0000 UTC 23 May 2008:
Superadiabatic layer(s) aloft:
LBF UNR SLE TWC FWD LIX TLH LCH MFL BUF
Additionally - the LBF flight was incomplete; the MHX flight was missing all winds except that at the surface; the LIX flight also exhibited a warm spike and extremely noisey data; the JAN flight was terminated.
Overview of suspect data for 1200 UTC 23 May 2008:
Superadiabatic layer(s) aloft:
LBF UNR TWC FWD OUN TLH MHX DVN BMX BNA APX RNK
Additionally - the UNR and MFL flights exhibited extreme noise in the RH data and the bizarre TLH flight was terminated.
Thursday, May 22, 2008
Visually obvious problems appear in the sounding data as per:
Warm spikes at GGW RIW
Superadiabatic layers aloft at GJT GGW(3) SHV TOP OMA AMA JAN TLH MFL(2)
Suspect layer (Opposite of wet bulb superadiabatic) at UIL SLE MFR APX
Some of these are quite amazing. The sounding data can be easily viewed at Univ. of WY's upper air page:
Note that two of the suspect soundings are from non RRS stations - TOP which flew into an MCS and MFR which showed a weak Op-Super layer from its VIZ instrument.
I call the strange layers "Op-Super" that occur when sonde exits cloud into drier and warmer air and T increases rapidly but RH stays at 100% for a while. This likely indicates a hygrister problem vs wet bulbing under same conditions which indicates a wetted thermister.
Friday, May 16, 2008
I have had time to take a quick pass through the morning soundings.
Soundings having a super-adiabatic layer aloft include:
MAF BRO LIX TLH MHX GYX
Soundings having a warm spike aloft between 0 and -10C include:
GJT LIX IAD
Too busy today to take a careful look at any of these.
Thursday, May 15, 2008
AMA FWD BNA LBF LZK JAN LCH
The problem at LBF was due to an intense warm spike.
The too cool layers in several of these soundings cause computed CAPE to be inaccurate.
I cross-checked the NCAR RAP plots with those at Wyoming this morning, and all the above
problem soundings were similar at each web page.
LCH is the most bizarre sounding of the bunch. The instrument apparently was launched into
a thunderstorm or deep convection.
Data were missing for for a short period.
Operator interpolated data for the missing period.
A saturated point was interpolated with T/Td spread shown as //
The NCAR Rap sounding decoder did not interpret the // correctly,
producing the very strange sounding on their web page.
The decoders at Wyoming and SPC plotted the data correctly.
Wednesday, May 14, 2008
Figure 1 - KFGZ
This sounding indicates a very dry layer of almost 100 mb vertical extent just above 700 mb. It had been raining for several hours and at the time of release Flagstaff was reporting moderate to heavy snowfall. The snow continued for several hours after sounding time. The dry layer certainly does not seem physically realistic, given the steady precipitation event that was underway.
Figure 2 - KFWD
This morning's sounding at FWD indicates a strongly super-adiabatic lapse at about 710 mb. This excursion causes a layer that appears to be several degrees too cool from about 710 to 550 mb. The net result is that sounding analysis software routines would produce CAPE values that were likely too great. Since the sonde did not, apparently, rise into a very dry layer, the reason for the super-adiabatic layer aloft is not clear.
Both of these soundings may illustrate random instabilities within these two RSS sonde's internal electronics, but this is just a guess on my part.
Thursday, May 08, 2008
My quick look at the soundings last evening identified two RSS flights that exhibited strongly super-adiabatic lapse rates in shallow layers aloft. These soundings were taken at Birmingham, AL, and Sterling, VA.
Note that the RRS operational procedures indicate that layers such as these should be removed via manual editing by the operator, and provide instructions for how this should be done.
Figure 1 (00Z BMX)
The layer of interest here extends from about 630 mb to 610 mb. The sonde apparently had moisture on the thermistor, and perhaps on the hygristor. When the instrument exited a deep, cloudy layer it encountered very dry air aloft and evaporative cooling of the sensors probably produced the super-adiabatic layer.Figure 2 (00Z IAD)
The layer of interest here is only about 10 mb deep and is located near 740 mb. The reason for this super-adiabatic layer is not obvious, since the entir atmosphere appears to be quite moist. The sounding apparently did not exit cloud into a very dry layer above. It is possible that the instrument was in a saturated updraft and exited the updraft suddenly. It is also possible that the hygristor did not respond adequately to a layer that was considerably drier than the data indicate.
During the next few months I'll be paying particular interest in identifying soundings in which bad data have complicated the diagnosis of CAPE or potentially caused forecasting difficulties.
If readers note soundings that seem to be candidates, as per above, for closer examination, please feel free to alert me to them. Thanks, Bob firstname.lastname@example.org
Wednesday, May 07, 2008
Today's winning example of a strange sounding is that taken at Ft. Worth TX at 1200 UTC.