dynamo-iss3: SOUNDING Messages: 11 Entries..

Radiosonde aspiration test

Aspirating on ladder next to surface met tower 23:20-23:26Z
Aspirating on ground at usual location 23:28-23:37Z
Launched 23:42:50Z

Sonde appearing to be about 1 mb lower, 1C higher and 5% RH lower than surface met.

Sonde ID 1830714 file D20120115_234246

Cloudy with occasional rain.  Profiler showing melting layer aloft so used 40 cuft of Helium and put some Pam on the balloon.

Radiosonde aspiration test

Aspirating on ladder next to surface met tower 11:45 - 11:55Z
Aspirating on ground at usual location 11:57 - 12:02Z
Launched

Sonde appearing to be about 1 mb lower, 0.2 - 0.5C higher and 5-8% RH lower than surface met.

Sonde ID 18300711 file D20120115_120331

Partly cloudy during tests (with occasional short bursts of sun) but then a squall with heavy persistent rain started as sonde was launched.

On the 0z sounding this morning I had 3 sondes showing up to 6 sats before going out to fill the balloon. All 3 either lost gps at launch or had lost it by the time I returned with the balloon. Squalls were in the area and passing over the site.

Radiosonde aspiration test

Repeated aspiration test from yesterday.   

Aspirating on ladder next to surface met tower 18:25 - 17:02Z
Aspirating on ground at usual location 17:02 - 17:15Z
Launched

Sonde ID 1830709 file D20120114_171505

Some dew earlier in evening so possible inversion?

Radiosonde aspiration test

Repeated aspiration test from yesterday.   

Aspirating on ground at usual location 11:09 - 11:12Z
Aspirating on ladder next to surface met tower 11:15 - 11:30Z
Aspirating on ground at usual location 11:32 - 11:42Z
Launched

Sonde appearing to be about 1 mb lower, 0.2 - 0.5C higher and 2 - 4% RH higher than surface met.

For another point of comparison, at 11:30 kestrel was measuring 27.2C 88% RH and 1005.4 hPa.

Sonde ID 1840947 file D20120114_114533
(note typo in operator notes in D file, should be 11:15-11:30, not 23:15-23:30)

Radiosonde aspiration test.

There has been an apparent RH bias between the radiosonde surface data and the surface met, particularly at night.
June asked us to aspirate a sonde up directly next to the surface met as a check to see if a night-time inversion close to the ground might be contributing.

At 9pm local (15Z) set up a test whereby the aspirator is mounted on a step ladder at the 2m level directly next to the surface met tower.
Mounted from approx 14:55 to 15:33. At surface met comparison point in GAUS software,
sonde was measuring about 1.2 mb lower, 0.1C higher and 1.5% RH higher than surface met.

Apsirator fan cut in and out.  Was okay running from 1520 to 1533.
From 1536 to 1547 sonde was on aspirator on ground as usual location near conntainers.

In this case wasn't a clear difference to the eye between ground aspiration and aspiration on the ladder next to the met tower, however we should analyse the raw data later to check.

The sonde was released about 1548 and allowed to fly to 400 mb before begin terminated.

The sonde ID is 1840953 and the data file is D20120113_154822_P.1

Field Olive Oil Deployment (FOOD)

FOOD hypothesis:

Olive oil is hydrophobic, and thus, despite adding weight to the balloon by applying olive oil, the balloon surface should not accrue as much water, keeping the balloon lighter throughout its flight. Further, prevention of a water coat on the balloon surface reduces the chance of riming near and above the freezing level, which would otherwise increase balloon weight at an exponential rate.

FOOD Field-phase:

06Z sounding on 10/9/11 (moderate to heavy rain):

Applied olive oil to entire balloon surface. Used outside canopy to assist in rolling balloon around during application. Balloon was filled to 35 cub. ft. Success! Burst level: 49 mb, 20 km. Flight time: 2:11.

09Z sounding on 10/9/11 (moderate to heavy rain):

Applied olive oil to balloon surface while it was about half full and still attached to helium hose. Proved difficult to apply olive oil to entire balloon surface in this manner, so only applied to top half (assuming that this might be sufficient). Balloon was filled to 35 cub. ft. Failure! Never made through freezing level (~550 mb). Bobbed up and down at least four times between ~550 and ~650 mb before falling from ~550mb, after apparently developing a slow leak and accelerating downward from ~10 to ~35 m/s, after which point the sounding was deemed compromised and the channel was closed.

12Z sounding on 10/9/11 (very light rain):

In an effort to redeem the last failed launch, balloon surface was covered in a manner similar to the 06Z balloon (filled balloon to 35 cub. ft. and used overhang to assist in applying olive oil to the entire balloon surface). Success! Burst level: 41 mb, 32 km. Flight time: 1:26.

Concluding remarks:

The sample size for heavy rain is at this time only two launches, so it is difficult to draw concrete conclusions. However, it appears that full-balloon olive oil coverage might be necessary for successful passage through the freezing level, and we'll continue this practice for subsequent heavy rain launches (fill to 35 cub. ft. and use overhang to assist in full-balloon surface olive oil application).

Interesting observation (food for thought): perhaps consistent with a prominence of observed supersaturated layers (e.g., 104% RH) in recent soundings, in cases when the balloon succumbs to the freezing layer, it is observed to lose upward speed and accelerate downward in a very rapid manner (e.g., all within ~3-5 minutes), almost precisely after reaching 0C. This suggests that, in the presence of saturation (supersaturation with respect to ice), riming on the balloon surface immediately commences once at/below freezing temperature and it becomes exposed to mixed-phase hydrometeors. I.e., if the environment is at/below the freezing point and saturated (supersaturated) with respect to water (ice), it is reasonable to assume that there is a plethora of frozen hydrometeors that can initiate a rapid freezing process on the balloon surface, which is likely covered in liquid water at that point.

Acknowledgments:

We thank Paul Ciesielski for his suggestion of using Pam Spray during inclement weather to prevent icing issues, which motivated the decision to try olive oil when Pam Spray was unavailable. We also thank Bill Brown for acquiring olive oil of the best kind on Diego Garcia, and for his continued support in the launching of weather balloons. Cheers.

ooZ launch:
First attempted sounding iced up at freezing level and began falling. Cut it off to launch another, but data looked good so chose "Good Sounding." Did relaunch at 2355 UTC 7 with 32 ft^3 to try to get higher (Bill says use 35 whenever raining). Same thing happened, but eventually shed ice and made it through freezing level. Cut off at about 230mb to get onto GTS. Only received sonde profile log for first launch, and it didn't contain any GTS message. Both sounding files exist (232117 and 000138) in /data_source/class/, and both WMO messages are present in /data_source/wmo. Questions we're left with:
Will Pam spray solve the problem?
Do we report "Bad Sounding" when closing first launch if doing a relaunch?

03Z launch:
Iced up again and bobbed around several times. Never made it through freezing level, so terminated at GTS deadline. Didn't get a sonde profile log again, so "sounding field log" will need to be updated with exact details. New file and wmo message are present, so behind-the-scene processes seem okay.

Oct 2 0Z sounding lost GPS at 450 mb so I didn't mark it as a good sounding,
however this means it wasn't transmitted to the GTS.
At Charlies suggestion I edited the D20111001_232654_P.1 file on the
sounding PC to change the operator standard comments line (near the end)
to say "Good Sounding" and saved it as D20111001_232655_P.1
(ie, added one second to the title) - this allowed Aspen to generate and WMO
message and sent it to the GTS.
Apparently it is acceptable to the GTS processes to have soundings like
this with some missing data.

ISS3 soundings on Diego Garcia.

A NCAR GAUS sounding rack using Vaisala RS92-SGPD soundings will be used.

A test sounding was launched at 5Z Sep 30, and another will be launched
about 1130Z the same day.

IOP soundings will start at 0Z tomorrow morning (Oct 1), every 3 hours.
Soundings will be launched between 45 and 30 minutes before nominal time
(ie, the 0Z sounding will be launched between 2315 and 2330Z). 

Soundngs will be logged in a spread sheet sounding_field_log.xls
Significant issues will also be noted in tklog.

Soundings will be transmitted to the GTS using aspen to generate a WMO file.
The WMO call sign is DRG. 

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CLASS LAUNCH LOG						 version:951116
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1. Clone the original sounding log file.
2. Enter information before launch.
3. Enter post-termination data.
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SITE INFO
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Site Name: 
date yymmdd: 
launch time UTC: 
Sonde coef tape #:

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MET INFO
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Pressure mb	: 
Temp C		: 
RH %		: 

		For Surface Data
Pressure mb	: 
Temp C		: 
RH%		: 
Wind Spd m/s	: 
Wind Dir deg	: 

Pre-Launch		Note conditions not observable by automatic systems
Weather Description	( visibility, sea state, cloud coverage and cloud type, 
		          rain, virga, etc. )


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POST TERMINATION
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Termination Pressure mb	: 
Termination Altitude km	: 
Reason for Termination	: 

Post-Termination Weather Description: 

For Surface Data
		Pressure mb	: 
     		Temp C		: 
		RH %		: 
		Wspd m/s 	: 
		Wdir deg	: 
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COMMENTS (data quality, unusual meteorolical features, launch problems, etc.)
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