GATNDOR: Minutes of 1 February 2013 quarterly Phone Call

NOTES: GATNDOR telecon – Friday, 1 February 2013
11 AM EST – call began
12:10 PM EST – call ended

Participants:
Alessandro Fasso’, Peter Thorne, Rosalba Ignaccolo, Tony Reale, Bomin Sun, Dian Seidel, John Dykema, Tom Gardiner (only at start of call)
Not available:
June Wang, David Whiteman, Hannes Vogelmann, Belay Demoz, Greg Bodeker

Fabio chaired the call.
Notes by Dian Seidel.

1. Topic work progress

1.1 Atmospheric measurement co-location – Alessandro summarized main points of the draft manuscript he had circulation to the group earlier, describing basic approach and application of the method to relative humidity observations from Beltsville and Sterling radiosonde data. Tom asked about Table 1 and units of uncertainties. They are variance of percent RH. Dian asked why focus on relative humidity first. This was addressed in Tokyo – RH has more uncertainty than, for example, pressure, and more components of the uncertainty budget will come into play. Bomin asked why no value is given in Table to for effect of spatial separation (natural variability). It is in the “bias” term, but there are only two points so it cannot be directly estimated. Bomin mentioned Sun et al. collocation study, Alessandro mentioned differences in approach (global vs two sites). Dian asked how best to provide comments to authors. Agreed that GATNDOR members should send comments to Alessandro before ICM5 and we can discuss these at ICM5. Target is to submit to Atm. Meas. Tech. soon (by ICM5, or within a few months afterward).

1.2 Quantifying the value of complementary measurements – Fabio summarized the draft he sent, which is more preliminary than the Fasso et al. study. Goal is to find a metric for the effects of redundancy on measurement uncertainty, and entropy is a good candidate. Data from Potenza will be used, possibly also Sodankyla. Want to know quantitative effect of additional measurements on uncertainty reduction. Also want to know something about the effects of averaging. Alessandro commented on the importance of de-trending time series as depicted in Fig. 1 of the draft manuscript. The purpose is to avoid having to address calibration issues. Alessandro commented on Fig. 2, consider adding a profile for entropy associated with Lidar/Aeri. Also Sonde/Aeri. Alessandro commented on Fig. 5, which seems counter-intuitive, why is variance larger for longer averaging period of data?

2. Update from TT measurement scheduling and from SASBE activity –
Tom summarized ongoing activities related to scheduling. Literature review has been made and main findings have been summarized in a document currently circulating among the team. Some information for trend uses, but much less for other GRUAN data uses. Dave has made a proposal to NASA regarding stratospheric temperature trends. Using 6-hourly Lindenberg, tests are being made to examine effects of sampling/scheduling on trend estimates. More details will be given at ICM5. Dian asked about stratospheric temperature. Tom agreed it could be a future focus but has not been to date.
Site Atmospheric State Best Estimate (SASBE) project – John described work by Tony showing how upper-tropospheric water vapor information from radiosondes is not being adequately used. A potential targeted objective for GATNDOR would be to demonstrate value of water vapor in the upper-troposphere (1) in assimilations (?) (2) satellite vs aircraft measurements of filamentary water vapor field – use sonde data to examine vertical and horizontal extent of filaments and effects on satellite observations.

3. ICM-5 (TT cross-meeting and possible GATNDOR launch meeting(?)) – Fabio asked group’s views on joint meetings or separate GATNDOR meeting. Peter indicated a 90 min slot on Tuesday (4:30 – 6:00 pm) at ICM5 for Task Teams and GATNDOR. Dian suggested small discussion on co-location manuscript, no dedicated GATNDOR meeting. Fabio and group decided to wait for final agenda to see if there is a good time (over lunch near the end of the week) to meet to evaluate future GATNDOR plans and entrain new people with appropriate expertise.

5. Update and news from conferences –
No news regarding potential PhD student with Ulrike Langematz at Free Univ. Berlin. Fabio suggested we keep this topic alive at ICM5.
June would like to encourage research in GATNDOR using GRUAN data with its uncertainty information. Also CSU student comparing GRUAN data with Vaisala RS92 data.
Fabio agreed to serve as GATNDOR chair until new people are recruited to participate in GATNDOR over the coming year, and at that time leadership rotation will be addressed.
Fabio thanked Rosalba, Tony and Bomin for participating in the call.
6. AOB (next telecon TBD maybe in or after De Bilt) – none

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