The SPARC water vapor assessment II: intercomparison of satellite and ground-based microwave measurements

Abstract

Abstract. As part of the second SPARC (Stratospheretroposphere 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 groundbased 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 H 2 O and CH 4 entering the stratosphere but, because almost all CH 4 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 H 2 O measured by any two instruments is typically ∼ 1%. Most of the datasets start in or after 2004 and show annual increases in H 2 O 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).

On the Anthropogenic Impact on Long‐Term Evolution of Noctilucent Clouds

“…(see, e.g., Nedoluha et al, 2017). We have determined the relative contributions of the two sources of H 2 O using recent satellite observations of H 2 O and CH 4 from the instrument SOFIE (Solar Occulation For Ice Experiment) on the AIM satellite (Aeronomy of Ice in the Mesosphere) at the stratopause (H 2 O = 7.5 ppmv and CH 50km 4 = 100 ppbv; Rong et al, 2016).…”

Observed Responses of Mesospheric Water Vapor to Solar Cycle and Dynamical Forcings

“…The H 2 O trends of Figure are smaller than the secular trends from the model study of Garcia et al () and somewhat smaller than the analyzed trends from HALOE data in Randel et al (), both for the time span of 1992–2002. On the other hand, Nedoluha et al () reported on H 2 O trends at 0.46 hPa for 1996 through 2005 from ground‐based microwave measurements at two sites (Mauna Loa, Hawaii at 19.5°N, 204°E, and Lauder, New Zealand at 45°S, 170°E). Their trends are between ±1% per decade and are consistent with observed trends of H 2 O entering the lower stratosphere.…”

“…Section 5 contains the updated results of the responses of H 2 O and temperature to the solar forcings and extends those findings through the lower mesosphere. Section 6 shows the associated H 2 O trends and compares them with ones reported by Nedoluha et al (2017) for 1992-2005 from two ground-based microwave radiometer sites. Section 7 reports on results from a separate simultaneous temporal and spatial (STS) analysis method that accounts for diurnal effects and for any biases due to changes in the sampling with latitude from HALOE.…”

HO Generation Above Sprite‐Producing Thunderstorms Derived from Low‐Noise SMILES Observation Spectra

“…Global warming is predicted to increase tropospheric lightning activity (5–10% for every 1° of warming) (Krause et al, ; Michalon et al, ; Price & Rind, ; Romps et al, ; Trapp et al, ) although the prediction has a large uncertainty in the lightning parameterization (Finney et al, ). Long‐term trends of increase in mesospheric carbon dioxide (CO ) and water vapor (H O) have been reported owing to recent improvement in the accuracy of global measurements (Chandra et al, ; Nath et al, ; Nedoluha et al, ; Qian et al, ). These trends, approximately +5.5% of CO and 10% of H O per decade, are related to anthropogenic CO and methane (CH ) emissions, respectively, and affect radiative forcing and mesospheric composition.…”