GNSS-based water vapor estimation and validation during the MOSAiC expedition

Männel, Benjamin; Zus, Florian; Dick, Galina; Glaser, Susanne; Semmling, Maximilian; Balidakis, Kyriakos; Wickert, Jens; Maturilli, Marion; Dahlke, Sandro; Schuh, Harald

doi:https://doi.org/10.5194/amt-2021-79

Preprints

https://doi.org/10.5194/amt-2021-79

Preprints

08 Apr 2021

Review status: this preprint is currently under review for the journal AMT.

GNSS-based water vapor estimation and validation during the MOSAiC expedition

Benjamin Männel¹, Florian Zus¹, Galina Dick¹, Susanne Glaser¹, Maximilian Semmling², Kyriakos Balidakis¹, Jens Wickert^1,3, Marion Maturilli⁴, Sandro Dahlke⁴, and Harald Schuh^1,5 Benjamin Männel et al.

Show author details

¹GFZ German Research Centre for Geosciences, Telegrafenberg, Potsdam, Germany
²DLR-SO Institute for Solar-Terrestrial Physics, Neustrelitz, Germany
³Technische Universität Berlin, Chair GNSS Remote Sensing, Navigation, and Positioning, Berlin, Germany
⁴Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung, Bremerhaven, Germany
⁵Technische Universität Berlin, Chair Satellite Geodesy, Berlin, Germany

Received: 12 Mar 2021 – Accepted for review: 02 Apr 2021 – Discussion started: 08 Apr 2021

Abstract. Within the transpolar drifting expedition MOSAiC (Multidisciplinary drifting Observatory for the Study of Arctic Climate), GNSS was used among other techniques to monitor variations in atmospheric water vapor. Based on 15 months of continuously tracked GNSS data including GPS, GLONASS, and Galileo, epoch-wise coordinates and hourly zenith total delays (ZTD) were determined using a kinematic precise point positioning (PPP) approach. The derived ZTD values agree to 1.1 ± 0.2 mm (RMS of the differences 10.2 mm) with the numerical weather data of ECMWF’s latest reanalysis, ERA5, computed for the derived ship’s locations. This level of agreement is also confirmed by comparing the on-board estimates with ZTDs derived for terrestrial GNSS stations in Bremerhaven and Ny Ålesund and for the radio telescopes observing Very Long Baseline Interferometry in Ny Ålesund. Preliminary estimates of integrated water vapor derived from frequently launched radiosondes are used to assess the GNSS-derived integrated water vapor estimates. The overall difference of 0.08 ± 0.04 kg m⁻² (RMS of the differences 1.47 kg m⁻²) demonstrates a good agreement between GNSS and radiosonde data. Finally, the water vapor variations associated with two warm air intrusion events in April 2020 are assessed.

Benjamin Männel et al.

Status: open (until 03 Jun 2021)

Post a comment Subscribe to comment alert

RC1: 'Comment on amt-2021-79', Anonymous Referee #1, 16 Apr 2021 reply

Review of GNSS-based water vapor estimation and validation during the

MOSAiC expedition, by Mannel et al, amt-2021-79

This is an article on our present day ability to derive good quality

ZTDs from GNSS data obtained on a moving platform, in this case a slow

moving ship.

It is interesting, wellwritten, easy to read, and deserves publication.

In principle the manuscript can be published as is, but

I have a few suggestions for improvements for the authors to consider.

1 The term "crows nest" will to most readers mean something else.

Consider to just remove the first entry and say "top of ship" or "top

of mast" in the second.

2 Consider to include statistics on ZTDs from NYA2 versus ERA, possibly

also from NE Greenland if you have easy access to GNSS data from there.

Those from NYA2 you have already.

3 The processing is done after the expedition. Include a few sentences

whether the quality of the GNSS ZTDs would be different was it done

in near real-time, which is important for the potential use of ZTDs from

ships in NWP.

4 Ground based ZTDs are (to my knowledge) not assimilated in ERA, which

strengthen then use of ERA as an independent data source. You

could mention that.

Then two comments that are more ment for eventual future work.

Presumably a research wessel will carry a high quality pressure sensor. It can be

expected to provide better quality ZHD than ERA on average. On top, with

respect to daily variability it will be effected by the earthly and

atmospheric tides as the ZHD proper, while those effects are not well

represented in an NWP model such as ERA. The

barometer could be used for the derivation of ZHD, to

derive ZWD from the GNSS ZTD.

The on-board barometer could also provide an

a priori for the ZHD in the GNSS data processing, when deriving GNSS ZWD to

obtain the GNSS ZTD. As humidity levels are very very low in part of the

year in the Arctic, a dominant part of the ZWD estimated in the GNSS data

processing is in reality due to variability of the pressure (and

hence ZHD). Using a better apriori for ZHD would reduce the problem

that the mapping functions for ZHD and ZWD are not identical in the GNSS data processing.

Reply

Citation: https://doi.org/10.5194/amt-2021-79-RC1

Benjamin Männel et al.

Viewed

Total article views: 189 (including HTML, PDF, and XML)

HTML	PDF	XML	Total	BibTeX	EndNote
157	28	4	189	1	2

HTML: 157
PDF: 28
XML: 4
Total: 189
BibTeX: 1
EndNote: 2

Views and downloads (calculated since 08 Apr 2021)

Month	HTML	PDF	XML	Total
Apr 2021	157	28	4	189

Cumulative views and downloads (calculated since 08 Apr 2021)

Month	HTML	PDF	XML	Total
Apr 2021	157	28	4	189

Viewed (geographical distribution)

Total article views: 179 (including HTML, PDF, and XML) Thereof 179 with geography defined and 0 with unknown origin.

Country	#	Views	%

Latest update: 19 Apr 2021

Short summary

Within the MOSAiC expedition, GNSS was used to monitor variations in atmospheric water vapor. Based on 15 months of continuously tracked data, coordinates and hourly zenith total delays (ZTD) were determined using kinematic precise point positioning. The derived ZTD values agree within few millimeters to ERA5 and terrestrial GNSS and VLBI stations. The derived integrated water vapor corresponds to the frequently launched radiosondes (0.08 ± 0.04 kg m⁻², RMS of the differences 1.47 kg m⁻²).


Total:	0
HTML:	0
PDF:	0
XML:	0