The SPARC water vapor assessment II: intercomparison of satellite and ground-based microwave measurements
Gerald E. Nedoluha1,Michael Kiefer2,Stefan Lossow2,R. Michael Gomez1,Niklaus Kämpfer3,Martin Lainer3,Peter Forkman4,Ole Martin Christensen4,Jung Jin Oh5,Paul Hartogh6,John Anderson7,Klaus Bramstedt8,Bianca M. Dinelli9,Maya Garcia-Comas10,Mark Hervig11,Donal Murtagh4,Piera Raspollini12,William G. Read13,Karen Rosenlof14,Gabriele P. Stiller2,and Kaley A. Walker15Gerald E. Nedoluha et al. Gerald E. Nedoluha1,Michael Kiefer2,Stefan Lossow2,R. Michael Gomez1,Niklaus Kämpfer3,Martin Lainer3,Peter Forkman4,Ole Martin Christensen4,Jung Jin Oh5,Paul Hartogh6,John Anderson7,Klaus Bramstedt8,Bianca M. Dinelli9,Maya Garcia-Comas10,Mark Hervig11,Donal Murtagh4,Piera Raspollini12,William G. Read13,Karen Rosenlof14,Gabriele P. Stiller2,and Kaley A. Walker15
1Remote Sensing Division, Naval Research Laboratory, Washington, DC, USA
2Karlsruhe Institute of Technology, Institute of Meteorology and
Climate Research, Karlsruhe, Germany
3Institute of Applied Physics, University of Bern, Bern, Switzerland
4Onsala Space Observatory, Department of Radio and Space Science,
Chalmers University of Technology, Onsala, Sweden
5Sookmyung Women's University, Seoul, South Korea
6Max Planck Institute for Solar System Research, Göttingen, Germany
7Hampton University, Hampton, Virginia, USA
8University of Bremen, Institute of Environmental Physics, Bremen,
Germany
9Istituto di Scienze dell'Atmosfera e del Clima del Consiglio Nazionale
delle Ricerche, Bologna, Italy
10Instituto de Astrofisica de Andalucia, CSIC, Granada, Spain
11GATS Inc., Driggs, Idaho, USA
12Istituto di Fisica Applicata “Nello Carrara” (IFAC) del Consiglio
Nazionale delle Ricerche (CNR), Florence, Italy
13Jet Propulsion Laboratory, California Institute of Technology,
Pasadena, California, USA
14University of Colorado, Atmospheric Chemistry Observations &
Modeling Laboratory, Boulder, Colorado, USA
15University of Toronto, Department of Physics, Toronto, Ontario,
Canada
1Remote Sensing Division, Naval Research Laboratory, Washington, DC, USA
2Karlsruhe Institute of Technology, Institute of Meteorology and
Climate Research, Karlsruhe, Germany
3Institute of Applied Physics, University of Bern, Bern, Switzerland
4Onsala Space Observatory, Department of Radio and Space Science,
Chalmers University of Technology, Onsala, Sweden
5Sookmyung Women's University, Seoul, South Korea
6Max Planck Institute for Solar System Research, Göttingen, Germany
7Hampton University, Hampton, Virginia, USA
8University of Bremen, Institute of Environmental Physics, Bremen,
Germany
9Istituto di Scienze dell'Atmosfera e del Clima del Consiglio Nazionale
delle Ricerche, Bologna, Italy
10Instituto de Astrofisica de Andalucia, CSIC, Granada, Spain
11GATS Inc., Driggs, Idaho, USA
12Istituto di Fisica Applicata “Nello Carrara” (IFAC) del Consiglio
Nazionale delle Ricerche (CNR), Florence, Italy
13Jet Propulsion Laboratory, California Institute of Technology,
Pasadena, California, USA
14University of Colorado, Atmospheric Chemistry Observations &
Modeling Laboratory, Boulder, Colorado, USA
15University of Toronto, Department of Physics, Toronto, Ontario,
Canada
Correspondence: Gerald E. Nedoluha (nedoluha@nrl.navy.mil)
Received: 22 Jun 2017 – Discussion started: 20 Jul 2017 – Revised: 12 Oct 2017 – Accepted: 27 Oct 2017 – Published: 06 Dec 2017
Abstract. As part of the second SPARC (Stratosphere–troposphere Processes And their Role in Climate) water vapor assessment (WAVAS-II), we present measurements taken from or coincident with seven sites from which ground-based microwave instruments measure water vapor in the middle atmosphere. Six of the ground-based instruments are part of the Network for the Detection of Atmospheric Composition Change (NDACC) and provide datasets that can be used for drift and trend assessment. We compare measurements from these ground-based instruments with satellite datasets that have provided retrievals of water vapor in the lower mesosphere over extended periods since 1996.
We first compare biases between the satellite and ground-based instruments from the upper stratosphere to the upper mesosphere. We then show a number of time series comparisons at 0.46 hPa, a level that is sensitive to changes in H2O and CH4 entering the stratosphere but, because almost all CH4 has been oxidized, is relatively insensitive to dynamical variations. Interannual variations and drifts are investigated with respect to both the Aura Microwave Limb Sounder (MLS; from 2004 onwards) and each instrument's climatological mean. We find that the variation in the interannual difference in the mean H2O measured by any two instruments is typically ∼ 1%. Most of the datasets start in or after 2004 and show annual increases in H2O of 0–1 % yr−1. In particular, MLS shows a trend of between 0.5 % yr−1 and 0.7 % yr−1 at the comparison sites. However, the two longest measurement datasets used here, with measurements back to 1996, show much smaller trends of +0.1 % yr−1 (at Mauna Loa, Hawaii) and −0.1 % yr−1 (at Lauder, New Zealand).
As part of the second SPARC (Stratosphere–troposphere Processes And their Role in Climate) water vapor assessment (WAVAS-II), we present measurements taken from or coincident with seven sites from which ground-based microwave instruments measure water vapor in the middle atmosphere. In the lower mesosphere, we quantify instrumental differences in the observed trends and annual variations at six sites. We then present a range of observed trends in water vapor over the past 20 years.
As part of the second SPARC (Stratosphere–troposphere Processes And their Role in Climate) water...
