GEWEX Water Vapor Assessment: Validation of AIRS Tropospheric Humidity Profiles With Characterized Radiosonde Soundings

Trent, Tim; Schröder, Marc; Remedios, J. J.

doi:10.1029/2018jd028930

Cited by 24 publications

(29 citation statements)

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“…Identification of such sites, in addition to measurements that provide additional information for sun glint oceans or collocation uncertainty would be a focus of future PBL XH 2 O algorithm development. Overall GOSAT PBL H 2 O biases show a similar performance to AIRS Version 6 water vapour profile biases below 850 hPa (Trent et al [56]) at global and climate radiosonde sites, which is very promising for climate studies.…”

Section: Validation At Global Radiosonde Sitesmentioning

confidence: 52%

“…One of the challenges when validating any GOSAT product is collocating with enough in situ measurements in order to calculate meaningful statistics. For this study we adopt and adapt the criteria outlined in Trent et al [56]. First a GOSAT footprint is considered collocated spatially if it is within 100 km of the ARSA launch site.…”

Section: Collocation Of Gosat With Arsamentioning

confidence: 99%

“…As the seasons progress into summer the collocation densities increase in the north, but in the southern hemisphere sees little change in collocation numbers. This, however is also the result of the lower number of radiosonde ground truth sites that can be used for validation, and presents a challenge when validating denser IR sounder measurements (Trent et al [56]). To add confidence to the validation results, a consistency test based on Immler et al [58] was calculated seasonally on a global 5 • × 5 • grid from the available collocations (Figure 10).…”

Section: Validation At Global Radiosonde Sitesmentioning

confidence: 99%

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Observing Water Vapour in the Planetary Boundary Layer from the Short-Wave Infrared

et al. 2018

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Water vapour is a key greenhouse gas in the Earth climate system. In this golden age of satellite remote sensing, global observations of water vapour fields are made from numerous instruments measuring in the ultraviolet/visible, through the infrared bands, to the microwave regions of the electromagnetic spectrum. While these observations provide a wealth of information on columnar, free-tropospheric and upper troposphere/lower stratosphere water vapour amounts, there is still an observational gap regarding resolved bulk planetary boundary layer (PBL) concentrations. In this study we demonstrate the ability of the Greenhouse Gases Observing SATellite (GOSAT) to bridge this gap from highly resolved measurements in the shortwave infrared (SWIR). These new measurements of near surface columnar water vapour are free of topographic artefacts and are interpreted as a proxy for bulk PBL water vapour. Validation (over land surfaces only) of this new data set against global radiosondes show low biases that vary seasonally between −2% to 5%. Analysis on broad latitudinal bands show biases between −3% and 2% moving from high latitudes to the equatorial regions. Finally, with the extension of the GOSAT program out to at least 2027, we discuss the potential for a new GOSAT PBL water vapour Climate Data Record (CDR).

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Section: Validation At Global Radiosonde Sitesmentioning

confidence: 52%

Section: Collocation Of Gosat With Arsamentioning

confidence: 99%

Section: Validation At Global Radiosonde Sitesmentioning

confidence: 99%

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Observing Water Vapour in the Planetary Boundary Layer from the Short-Wave Infrared

et al. 2018

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“…Thus, large scale differences in q and T data records are observed in the upper troposphere. The retrieval of absolute humidity in the upper troposphere is a challenging task for the majority of observing systems [36,37], including radiosondes which are an anchor element during assimilation in reanalysis [22]. Thus, G-VAP will continue to analyse the quality of q and T profiles in the upper troposphere, among others, using the NOAA Products Validation System [38].…”

Section: Analysis Of Gridded Water Vapour and Temperature Profilesmentioning

confidence: 99%

The GEWEX Water Vapor Assessment: Overview and Introduction to Results and Recommendations

et al. 2019

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To date, a large variety of water vapour data records from satellite and reanalysis are available. It is key to understand the quality and uncertainty of these data records in order to fully exploit these records and to avoid data being employed incorrectly or misinterpreted. Therefore, it is important to inform users on accuracy and limitations of these data records based on consistent inter-comparisons carried out in the framework of international assessments. Addressing this challenge is the major objective of the Global Water and Energy Exchanges (GEWEX) water vapor assessment (G-VAP) which was initiated by the GEWEX Data and Assessments Panel (GDAP).Here, an overview of G-VAP objectives and an introduction to the results from G-VAP's first phase are given. After this overview, a summary of available data records on water vapour and closely related variables and a short introduction to the utilized methods are presented. The results from inter-comparisons, homogeneity testing and inter-comparison of trend estimates, achieved within G-VAP's first phase are summarized. The conclusions on future research directions for the wider community and for G-VAP's next phase are outlined and recommendations have been formulated.For instance, a key recommendation is the need for recalibration and improved inter-calibration of radiance data records and subsequent reprocessing in order to increase stability and to provide uncertainty estimates. This need became evident from a general disagreement in trend estimates (e.g., trends in TCWV ranging from −1.51 ± 0.17 kg/m 2 /decade to 1.22 ± 0.16 kg/m 2 /decade) and the presence of break points on global and regional scale. It will be a future activity of G-VAP to reassess the stability of updated or new data records and to assess consistency, i.e., the closeness of data records given their uncertainty estimates. aimed at the consolidation of the G-VAP strategy and the technical implementation. Results from these workshops and feedback from GDAP were used to establish the G-VAP assessment plan. G-VAP organises annual workshops to provide opportunities for (i) presenting state-of-the-art of water vapour retrievals and products, (ii) discussion of results from inter-comparisons exercises and quantifying the sources of observed differences, and (iii) providing recommendations for future directions and roadmap. It was consensus at the G-VAP workshops to continue G-VAP beyond the finalisation of the World Climate Research Programme (WCRP) report on G-VAP, with support from GDAP. Details of the future of G-VAP were discussed and agreed upon at the 7th workshop in October 2017. The assessment plan and minutes from the G-VAP workshops are available at http://gewex-vap.org/?page_id=19 and partly workshop summaries have been published in the GEWEX News (see http://www.gewex.org/resources/gewex-news/).Prior to analysis, an inventory of available satellite and reanalysis data records has been carried out and made available online at http://gewex-vap.org/?pageid=13. A subset of these data rec...

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“…However, the majority of these instruments can 30 only measure columns of water vapour, or partial column profiles. Most satellite instruments are capable of measuring water vapour down to 300 hPa, or roughly 9 km altitude (Hegglin et al, 2013), but a few like the AIRS satellite can accurately measure down to the surface (Trent et al, 2019). However, while satellite measurements provide excellent global coverage, their vertical resolutions are typically on the order of kilometers which limits their ability to capture water vapour's large variability with altitude.…”

Section: Introductionmentioning

confidence: 99%

A Raman Lidar Tropospheric Water Vapour Climatology and Height-Resolved Trend Analysis over Payerne Switzerland

Hicks–Jalali¹,

Sica²,

Haefele³

et al. 2020

Preprint

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Abstract. Water vapour is the strongest greenhouse gas in our atmosphere and its strength and its dependence on temperature leads to a strong feedback mechanism in both the troposphere and the stratosphere. Raman water vapour lidars can be used to make high vertical resolution measurements, on the order of 10s of meters, making height-resolved trend analyses possible. Raman water vapour lidars have not typically been used for trends analyses, primarily due to the lack of long enough time series. However, the RAman Lidar for Meteorological Observations (RALMO), located in Payerne, Switzerland, is capable of making operational water vapour measurements and has one of the longest ground-based and well-characterized data sets available. We have calculated a 11.5-year water vapour climatology using RALMO measurements in the troposphere. Our study uses nighttime measurements during mostly clear conditions, which creates a natural selection bias. We have also calculated the geophysical variability of water vapour. The climatology shows that the highest water vapour specific humidity concentrations are in the summer months, and the lowest in the winter months. The percent variability of water vapour in the free troposphere is larger than of the boundary layer. We have also determined water vapour trends from 2009&#8211;2019. We first calculate precipitable water vapour trends for comparison with the majority of water vapour trend studies. We detect a precipitable water vapour trend of 2.1&#8201;mm/decade using RALMO measurements, which is significant at the 90&#8201;% level. The trend is consistent with a 1.38&#8201;&#176;C/decade surface temperature trend detected by coincident radiosonde measurements under the assumption that relative humidity remains constant;however, it is larger than previous water vapour trend values. For the first time, we show height-resolved increases in water vapour through the troposphere. We detect positive tropospheric water vapour trends ranging from 5% change in specific humidity per decade to 15% specific humidity per decade depending on the altitude. The water vapour trends at 5 layers are statistically significant at or above the 90% level.

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GEWEX Water Vapor Assessment: Validation of AIRS Tropospheric Humidity Profiles With Characterized Radiosonde Soundings

Cited by 24 publications

References 50 publications

Observing Water Vapour in the Planetary Boundary Layer from the Short-Wave Infrared

Observing Water Vapour in the Planetary Boundary Layer from the Short-Wave Infrared

The GEWEX Water Vapor Assessment: Overview and Introduction to Results and Recommendations

A Raman Lidar Tropospheric Water Vapour Climatology and Height-Resolved Trend Analysis over Payerne Switzerland

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