Roger Saunders

Met Office · R&D

This paper gives an update of the RTTOV (Radiative Transfer for TOVS) fast radiative transfer model, which is widely used in the satellite retrieval and data assimilation communities. RTTOV is a fast radiative transfer model for simulating top-of-atmosphere radiances from passive visible, infrared and microwave downward-viewing satellite radiometer...

Simulated stratospheric temperatures over the period 1979–2016 in models from the Chemistry-Climate Model Initiative are compared with recently updated and extended satellite data sets. The multimodel mean global temperature trends over 1979–2005 are −0.88 ± 0.23, −0.70 ± 0.16, and −0.50 ± 0.12 K/decade for the Stratospheric Sounding Unit (SSU) cha...

This paper gives an update of the RTTOV (Radiative Transfer for TOVS) fast radiative transfer model which is widely used in the satellite retrieval and data assimilation communities. RTTOV is a fast radiative transfer model for simulating top of atmosphere radiances from passive visible, infrared and microwave downward-viewing satellite radiometers...

Sea Surface Temperature (SST) observations from space have been made by the Along Track Scanning Radiometers (ATSRs) providing 20 years (August 1991-April 2012) of high quality data. As part of the ESA Climate Change Initiative (CCI) project, SSTs have been retrieved from the ATSRs. Here, the quality of CCI SST (Phase 1) from ATSRs is validated aga...

Global dynamical reanalyses of the atmosphere and ocean fundamentally rely on observations, not just for the assimilation (i.e., for the definition of the state of the Earth system components) but also in many other steps along the production chain. Observations are used to constrain the model boundary conditions, for the calibration or uncertainty...

The European Reanalysis of Global Climate Observations 2 (ERA-CLIM2) is a European Union Seventh Framework Project started in January 2014 and due to be completed in December 2017. It aims to produce coupled reanalyses, which are physically consistent datasets describing the evolution of the global atmosphere, ocean, land surface, cryosphere, and t...

Upper tropospheric humidity (UTH) contributes significantly to the atmospheric greenhouse effect by having a strong influence on the outgoing longwave radiation. UTH can be measured either by radiosondes or satellite instruments. However, the radiosonde humidity measurements can suffer from significant biases in the upper troposphere. Satellite obs...

A new set of Infrared Atmospheric Sounding Interferometer (IASI) channels was re-selected from 314 EUMETSAT channels. In selecting channels, we calculated the impact of the individually added channel on the improvement in the analysis outputs from a one-dimensional variational analysis (1D-Var) for the Unified Model (UM) data assimilation system at...

Land surface temperature (LST) observations from a variety of satellite instruments operating in the infrared have been compared to estimates of surface temperature from the Met Office operational numerical weather prediction (NWP) model. The comparisons show that during the day the NWP model can under predict the surface temperature by up to 10 K...

To investigate the characteristics of Spinning Enhanced Visible and Infrared Imager (SEVIRI)-derived products from the UK Met Office algorithm, one year of cloud occurrence frequency (COF) and cloud-top height (CTH) data from May 2013 to April 2014 was analysed in comparison with Cloud Profiling Radar (CPR) and Cloud-Aerosol LiDAR with Orthogonal P...

To better understand the impacts of climate change, environmental monitoring capabilities must be enhanced by deploying additional and more accurate satellite- and ground-based (including in situ) sensors. In addition, reanalysis of observations collected decades ago but long forgotten can unlock precious information about the recent past. Historic...

Sea Surface Temperature (SST) is an important geophysical parameter for both climate and weather applications. Drifting buoys are the backbone of the SST observational array because they provide global coverage in comparison to moored buoys and better quality observations in comparison to ships. Also, they are used widely for the calibration and/or...

Volcanic eruptions are natural hazards with dire consequences to life and economy. As most volcanoes are in remote areas, satellites play a vital role in providing observations and input to models used for forecasting volcanic plume evolution. Radiances from the Infrared Atmospheric Sounding Interferometer (IASI) on board the MetOp polar orbiting m...

Two methods to generate synthetic satellite images in the visible spectrum from data generated by numerical weather prediction models are compared: the implementation of the discrete ordinate method in RTTOV and the look-up table based method MFASIS, which is several orders of magnitude faster. It is shown that after compensating for different assu...

Sea surface temperature (SST) is a geophysical parameter important for both weather forecasting and climate monitoring. Satellite instruments provide SST measurements by using a retrieval method to convert the observed signals to SST. The satellite SST retrieval can be calibrated using in-situ observations, and its quality is validated against in-s...

We present a comparison of a reference and a fast radiative transfer model using numerical weather prediction profiles for the Zeeman-affected high-altitude Special Sensor Microwave Imager/Sounder channels 19–22. We find that the models agree well for channels 21 and 22 compared to the channels' system noise temperatures (1.9 and 1.3 K, respectivel...

Satellite-based layer-average stratospheric temperature (T) climate data records (CDRs) now span more than three decades and so can elucidate climate variability associated with processes on multiple time scales. We intercompare and analyze available published T CDRs covering at least two decades, with a focus on Stratospheric Sounding Unit (SSU) a...

We present a comparison of a reference and a fast radiative transfer model using numerical weather prediction profiles for the Zeeman-affected high altitude Special Sensor Microwave Imager/Sounder channels 19–22. We find that the models agree well for channels 21 and 22 compared to the channels' system noise temperatures (1.9 and 1.3 K, respectivel...

ATSR-1 onboard ERS-1, ATSR-2 onboard ERS-2 and AATSR onboard ENVISAT are radiometers built specifically with the requirement for climate observations in mind, i.e. high accuracy and stability, in order to provide high quality Sea Surface Temperature (SST) observations from space. SST is an essential climate variable (ECV) with observations availabl...

Sea Surface Temperature (SST) is an Essential Climate Variable (ECV) for which there are observations since 1850. Because of its importance for climate, weather forecasting and oceanography SST observations from space have been made by dedicated instruments, for example ATSR-1 on board ERS-1 from August 1991 and its successor instruments ATSR-2 and...

Met Office, Satellite Applications Technical Memo 19

There is a need to find a candidate instrument that can bridge the gap between AATSR and SLSTR climate quality IR observations. Due to restrictions relating to the orbit of ENVISAT and Sentinel-3 only MODIS on TERRA and AVHRR on MetOp-A could potentially provide observations for a period that will overlap significantly with SLSTR. Here, the use of...

Sea Surface Temperature (SST) is an Essential Climate Variable (ECV) for which there are observations since 1850. Because of its importance for climate, weather forecasting and oceanography SST observations from space have been made by dedicated instruments, for example ATSR-1 on board ERS-1 from August 1991 and its successor instruments ATSR-2 and...

Here, the Climate Symposium 2014, organized by the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT) and the World Climate Research Programme (WCRP), with support from the European Commission (EC), European Space Agency (ESA), and other agencies, took place in Darmstadt, Germany, from 13 to 17 October 2014. Around 5...

This report summarises the conclusions of discussions between climate experts and the metrology community (in this context national metrology institutes) held over two days at the National Physical Laboratory in May 2015. The objectives of the workshop and the framework for the discussions were established by leading climate experts including those...

As the societal impacts of hazardous weather and other environmental pressures grow, the need for integrated predictions that can represent the numerous feedbacks and linkages between sub-systems is greater than ever. This was well illustrated during winter 2013/2014 when a prolonged series of deep Atlantic depressions over a 3 month period resulte...

Stratospheric Sounding Units (SSU) on the NOAA polar orbiting satellites measured infrared radiances in the 15 micron CO2 band between late 1978 and mid-2006. From these radiances a time series of layer mean stratospheric temperatures has been derived by several groups. Discrepancies in these temperature analyses have been highlighted recently and...

The three-way error analysis is a powerful tool that enables the derivation of the standard deviation of error inherent in each observation. It is based on the use of three independent observations of the same quantity and does not require any previous knowledge about the bias of these observations types. The main assumption behind the analysis is...

Sea Surface Temperature (SST) is an Essential Climate Variable (ECV) for which there are observations since 1850. Because of its importance for climate, weather forecasting and oceanography SST observations from space have been made by dedicated instruments, for example ATSR-1 on board ERS-1 from August 1991 and its successor instruments ATSR-2 and...

Infrared satellite measurements were used to track the volcanic plume from Grímsvötn, Iceland in 2011. Following the explosive eruption, the plume was sheared by the atmosphere into two distinct volcanic clouds, one was ash-rich and the other was mainly composed of sulphur dioxide (SO2) gas. Satellite retrievals of the volcanic ash were found to be...

[1] Co-located SEVIRI retrieved and GERB fluxes at the top of atmosphere are used to provide, for the first time, an observationally based estimate of the cloud-free net direct radiative effect (DRE) of mineral dust aerosol from geostationary satellite observations, providing new insights into the influence of time of day on the magnitude and sign...

Sea surface temperature (SST) measurements are important for meteorology, climate and oceanography. The ATSRs provided the most accurate satellite measurements of SST from 1991 to 2012, due to their dual view capability and the onboard blackbody calibration. Their heritage will be continued with the SLSTR instrument onboard Sentinel 3, which is pla...

Observations of the Earth from space have been made for over 40 years and have contributed to advances in many aspects of climate science. However, attempts to exploit this wealth of data are often hampered by a lack of homogeneity 30 and continuity, and by insufficient understanding of the products and their uncertainties. There is, therefore, a n...

The Along-Track Scanning Radiometer (ATSR) Reprocessing for Climate (ARC) project aims to create an independent climate data record of sea surface temperatures (SSTs) covering recent decades that can be used for climate change analysis. Here, theARCSSTs are assessed using comparisons with collocated drifting buoy observations and a three-way error...

We use multiple observations and climate model simulations to study upper tropospheric humidity (UTH) in tropical descent regions. A satellite simulator is used to generate UTH from model fields to ensure a like-to-like comparison. We have shown that HadGEM2 is generally able to reproduce the patterns and magnitude of UTH in these regions. In both...

Radiances measured by satellite radiometers are often subject to biases due to limitations in their radiometric calibration. In support of the Global Space-based Inter-Calibration System project, to improve the quality of calibrated radiances from atmospheric sounders and imaging radiometers, an activity is underway to compare routinely measured ra...

A new record of sea surface temperature (SST) for climate applications is described. This record provides independent corroboration of global variations estimated from SST measurements made in situ. Infrared imagery from Along-Track Scanning Radiometers (ATSRs) is used to create a 20 year time series of SST at 0.1° latitude-longitude resolution, in...

A robust method to detect volcanic ash, using data from the infrared channels of the Spinning Enhanced Visible and Infrared Imager instrument mounted on-board Meteosat Second Generation, is presented. The simultaneous retrieval of quantitative volcanic ash physical properties using a one-dimensional variational analysis framework is also described....

During volcanic eruptions that eject ash into the atmosphere Volcanic Ash Advisory Centers issue statements on the forecast dispersion of the ash so that the aviation industry can manage airspace to avoid aircraft encountering volcanic ash. Observations, such as those from satellites, are compared with the forecasts from an atmospheric dispersion m...

The fast Radiative Transfer for Television Infrared Observation Satellite (TIROS) Operational Vertical Sounder (RTTOV) (Version 9.3) model was used for simulating the effect of East Asian dust on top of atmosphere radiances. The size distribution of Asian dust was retrieved from nine years of sky radiometer measurements at Dunhunag located in the e...

Simultaneous nadir overpasses (SNOs) of polar-orbiting satellites are most frequent in polar areas but can occur at any latitude when the equatorial crossing times of the satellites become close owing to orbital drift. We use global SNOs of polar orbiting satellites to evaluate the intercalibration of microwave humidity sounders from the more frequ...

The Pathfinder sea surface temperature (SST) data set, from the Advanced Very High Resolution Radiometer (AVHRR), is an important climate data record for SST due to the longevity of the sensor series of potentially 38years (from 1981 to 2020). However high amounts of aerosol in the atmosphere, such as after a major volcanic eruption, lead to a cool...

There are many sea surface temperature (SST) datasets derived from various satellite instruments with different characteristics in terms of orbit, coverage, retrieval, calibration, accuracy and measurement type. This paper presents the results of a project to combine SSTs from two instruments: the Along-Track Scanning Radiometer (ATSR) SSTs and the...

“Targeted observations” refers to the augmentation of the regular observing network with additional, specially chosen observations to be assimilated into operational numerical weather prediction models. Observation locations are chosen in order to improve forecasts of high-impact weather events of importance to society. Examples include dropwindson...

In this paper, we will presents our results in accelerating Radiative Transfer for TOVS (RTTOV) Radiative Transfer Model (RTM) scheme on many-core NVIDIA graphics processing units (GPUs). GPUs have evolved into a highly parallel, multi-threaded, many-core processors with tremendous computational speed and a high memory bandwidth. We will discuss ho...

A Tool to Estimate Land Surface Emissivities at Microwave frequencies (TELSEM) has been developed for use with the Radiative Transfer for the Television and infrared Observation satellite operational Vertical Sounder (RTTOV) model. Its objective is to provide a good estimate of the microwave surface emissivity to improve the retrieval of atmospheri...

The radiative transfer for television operational vertical sounder (RTTOV) is a widely-used radiative transfer model (RTM) for calculation of radiances for satellite infrared and microwave sensors, including the 8461-channel infrared atmospheric sounding interferometer (IASI) and the 15-band Advanced Microwave Sounding Unit-A (AMSU-A). In the era o...

We develop a Graphics Processing Unit (GPU)-based high-performance RTTOV-7 forward model. The RTTOV forward model performs the fast computation of the radiances, brightness temperatures, overcast radiances, surface to space transmittances, surface emissivities and pressure level to space transmittances for a given profile vector. A special optimize...

The new ESA Climate Change Initiative (CCI) approved in 2009 is in the process of being set up. The overall objective of the CCI, as laid out in the Programme declaration approved by ESA member states is: "To realize the full potential of the long-term global "Earth Observation" archives that ESA together with its Member states have established ove...

A multi-spectral rainfall estimation algorithm has been developed for the Sahel region of West Africa with the purpose of producing accumulated rainfall estimates for drought monitoring and food security. Radar data were used to calibrate multi-channel SEVIRI data from MSG, and a probability of rainfall at several different rain-rates was establish...

The Met Office has been using data from the Spinning Enhanced Visible and Infrared Imager (SEVIRI) on board the Meteosat Second Generation (MSG) satellites for nowcasting, assimilation in numerical weather prediction (NWP) and for providing guidance to forecasters since September 2004. This paper describes the cloud mask derived from MSG imagery wh...

Geostationary satellites are ideal for monitoring dust and aerosols due to their rapid development. The Spinning Enhanced Visible and Infrared Imager (SEVIRI) onboard the Meteosat Second Generation (MSG) series provides a unique opportunity to detect the presence of dust and to retrieve mineral dust optical thickness using brightness temperatures i...

A fast radiative transfer model (RTM) to compute emitted infrared radiances for a very high resolution radiometer (VHRR), onboard the operational Indian geostationary satellite Kalpana has been developed and verified. This work is a step towards the assimilation of Kalpana water vapor (WV) radiances into numerical weather prediction models. The fas...

The Fourth Assessment Report (AR4) of the Intergovernmental Panel on Climate Change (IPCC) concluded that global warming is "unequivocal" and that most of the observed increase since the mid-twentieth century is very likely due to the increase in anthropogenic greenhouse gas concentrations, with discernible human influences on ocean warming, contin...

Near real-time rainfall estimates are crucial in sub-Saharan Africa for a variety of humanitarian and agricultural purposes. However, for economic and infrastructural reasons, regularly reporting rain-gauges are sparse and precipitation radar networks extremely rare. Satellite rainfall estimates, particularly from geostationary satellites such as M...

We describe the approach to be adopted for a major new initiative to derive a homogeneous record of sea surface temperature for 1991–2007 from the observations of the series of three along-track scanning radiometers (ATSRs). This initiative is called (A)RC: (Advanced) ATSR Re-analysis for Climate. The main objectives are to reduce regional biases i...

Using collocations of three different observation types of sea surface temperatures (SSTs) gives enough information to enable the standard deviation of error on each observation type to be derived. SSTs derived from the Advanced Along-Track Scanning Radiometer (AATSR) and Advanced Microwave Scanning Radiometer for Earth Observing System (EOS; AMSR-...

NWP forecast skill is partly controlled by the quality of the initial state, or analysis. In variational data assimilation schemes the analysis is derived by minimizing a cost function made up of a departure from the background and a departure from the observations. How close the analysis pulls towards the observations is determined by the balance...

The latest Met Office cloud-top height retrieval using Meteosat Second Generation (MSG) SEVIRI data is described, and the impact of some proposed changes is investigated. For one particular case study, comparisons with coincident radiosonde data show that, for low-cloud situations, the resulting cloud-top height values are systematically and signif...

A system of assimilating SEVIRI cloud products directly into the Met Office NAE forecast model via four-dimensional variational assimilation has been developed. This has been trialled over both Summer and Winter seasons. Forecast impact in Summer is generally slightly positive overall, due to improved precipitation and surface temperature. The impa...

Top of atmosphere brightness temperatures and skin sea surface temperatures (SSTs) at 10 arc minute spatial resolution from the Advanced Along Track Scanning Radiometer (AATSR) on ENVISAT have now been collected at the Met Office in near-real time since 2002. Various processing have been performed on these data to convert from skin to foundation SS...

Using co-locations of three different observation types of sea surface temperatures (SSTs) gives enough information to enable the standard deviation of error on each observation type to be derived. SSTs derived from the Advanced Along-Track Scanning Radiometer (AATSR) and Advanced Microwave Scanning Radiometer (AMSR-E) instruments are used, along w...

The Joint World Meteorological Organization (WMO)-Intergovernmental Oceanographic Organization (WMO)-Intergovernmental Oceanographic Commission (IOC) Technical Commission for Oceanography and Marine Meteorology (JCOMM) Workshop on Advances in Marine Climatology (CLIMAR)/ International Workshop on Advances in the Use of Historical Marine Climate Dat...

A comparison of radiative transfer models for simulating radiances from the Atmospheric Infrared Sounder (AIRS), has been undertaken. Results from 14 line-by-line and fast parameterized infrared models were submitted. Several aspects of the models were compared. First, the forward model calculations for all 2378 AIRS channels for 52 diverse atmosph...

This paper describes the direct assimilation of water vapour (WV) clear-sky radiance (CSR) data from geostationary satellites within the context of the ECMWF four-dimensional variational assimilation (4D-Var) system. The assimilation of Meteosat–7 WV CSR data became operational on 9 April 2002. As 4D-Var includes a time dimension, the high temporal...

A near-continuous series of global retrievals of sea surface temperature (SST) has been made from the Along-Track Scanning Radiometer (ATSR) series of instruments from 1991 to 2005. To analyze possible long-term trends in the global or regional SST throughout the period daily anomalies are computed using a 1961–90 daily climatology, averaged into g...

Many of the results of this study are presented in the paper included in the ITSC-14 proceedings by Saunders et. al. (2005) and a paper by Saunders et. al. (2006) about to be published. This paper therefore only summarizes the final conclusions of the study.

Validation has been performed on the Advanced-Along Track Scanning Radiometer (AATSR) Sea Surface Temperature (SST) Meteo product data at the Met Office on a daily basis. Meteo product skin SSTs have been compared with point measurements of buoy SST, and a 1-degree climate SST analysis field compiled from in situ measurements and Advanced Very High...

The Advanced Along Track Scanning Radiometer (AATSR) Sea Surface Temperature (SST) Meteo product, a fast-delivery level-2 product at 10 arc min spatial resolution, has been available from the European Space Agency (ESA) since 19 August 2002. Validation has been performed on these data at the Met Office on a daily basis, with a 2-day lag from data r...

The Advanced Along-Track Scanning Radiometer (AATSR) was launched on Envisat in March 2002. The AATSR instrument is designed to retrieve precise and accurate global sea surface temperature (SST) that, combined with the large data set collected from its predecessors, ATSR and ATSR-2, will provide a long term record of SST data that is greater than 1...

A method of estimating surface rain-rate from SEVIRI data is presented. The new scheme extends the Met Office's Nimrod nowcasting system satellite precipitation scheme from the existing two-channel method relevant to Meteosat-7, by way of the inclusion of additional SEVIRI channels. Comparisons are made with the existing scheme, and also with some...

The Met Office has been using data from the Meteosat Second Generation (MSG) satellite, Meteosat-8, both for data assimilation and forecast guidance applications since September 2004. This paper gives an overview of the range of MSG products developed at the Met Office and now being used by the nowcasting system, numerical weather prediction models...

Both science and society need changes in global sea surface temperature (SST) over recent decades to be more robustly quantified. We present here plans to do this by exploiting the series of space-based sensors, the (A)ATSRs, in a project that recently received confirmation of funding and will commence late in 2005. (A)ATSR SSTs produced to date ar...

ERA-40 is a re-analysis of meteorological observations from September 1957 to August 2002 produced by the European Centre for Medium-Range Weather Forecasts (ECMWF) in collaboration with many institutions. The observing system changed considerably over this re-analysis period, with assimilable data provided by a succession of satellite-borne instru...

ERA-40 is a re-analysis of meteorological observations from September 1957 to August 2002 produced by the European Centre for Medium-Range Weather Forecasts (ECMWF) in collaboration with many institutions. The observing system changed considerably over this re-analysis period, with assimilable data provided by a succession of satellite-borne instru...

At the workshop for Soundings from High Spectral Resolution Observations in May 2003, an AIRS radiative transfer model comparison was proposed under the auspices of the ITWG. Results from 14 models have been submitted. The aim of the intercomparison was (i) to compare the forward model calculations for all AIRS channels from all models for 52 diver...

The Advanced Along-Track Scanning Radiometer (AATSR) Meteo product has been available in near-real time since 19 August 2002. Validation has been performed on these data on a daily basis. Skin and bulk SSTs, which have been calculated from the Meteo product, have been compared with alternative measurements in the form of buoy data, a climate SST an...

Reprocessing of the second Along Track Scanning Radiometer (ATSR-2) Clear-Sea Consolidated Averaged Brightness Temperature (CSCABT) dataset to high quality, high spatial resolution Sea Surface Temperatures (SSTs) from the 2nd ATSR upon the ERS-2 satellite have been completed for the period June 1995 to December 2000. Validation results of these ATS...

Principal aspects of the development of Gastropod, a fixed-pressure-grid fast radiative transfer model for the Atmospheric Infrared Sounder (AIRS), are described. Performance of the forward and gradient operators is characterized, and the impact of radiative transfer model errors on retrieval accuracy is quantified in a minimum-variance linear retr...

Satellite-based retrievals of sea-surface temperature (SST) hold great potential for augmenting and improving existing global climate analyses. However, optimal blending of satellite data with in situ measurements of SST requires an accurate estimate of the temperature difference between radiometric skin and bulk water sampled below the skin. Conte...

1] Satellite instruments specifically designed to monitor atmospheric carbon dioxide concentrations have not been flown to date but, high-resolution infrared sounders, being launched in the next few years, may offer the possibility of at least a basic carbon dioxide monitoring capability. This paper explores the sensitivity of this new generation o...

RESUME The AATSR Meteo product became available in near-real time as BUFR formatted files updated on an ESA ftp server from 19 August 2002. Since that time, data have been downloaded in near-real time and a series of routine monitoring and validation activities have been performed at the Met Office, UK. The Meteo product SST was compared to point m...

Observations from the Atmospheric Infrared Sounder (AIRS) are assimilated into the Met Office's Numerical Weather Prediction (NWP) model. The processing methodology is described with emphasis on cloud detection and quality control. The impact of the AIRS observations is an improvement in forecast skill of 0.5-1.0% which is a satisfactory result giv...

Gastropod is a fast radiative transfer code designed to meet the requirements of a day one radiative transfer operator for AIRS (and eventually IASI) for use in variational data assimilation systems. This paper gives an overview of the model methodology adopted, and summarises the results from line-by-line radiative transfer model validation of the...

Over three years of bulk SSTs were derived using ATSR-2 cloud-cleared skin SSTs (averaged at a resolution of 0.5 degrees), using a skin to bulk temperature model. The algorithm is based on a physical skin model and covers all surface wind speed ranges. The near-surface diurnal thermocline is also modelled with the aim of rejecting those observation...

The goals of this study are the evaluation of current fast radiative transfer models (RTMs) and line-by-line (LBL) models. The intercomparison focuses on the modeling of 11 representative sounding channels routinely used at numerical weather prediction centers: 7 HIRS (High-resolution Infrared Sounder) and 4 AMSU (advanced microwave sounding unit)...

Enhanced wind datasets of the European satellite Meteosat are now provided every 90 mins together with the quality indicator (QI) derived by the quality control of the Meteorological Product Extraction Facility (MPEF) at the European Organisation for the Exploitation of Meteorological Satellites. All three channel cloud motion winds and clear sky w...

An intercomparison of radiation codes used in retrieving upper-tropospheric humidity (UTH) from observations in the v2 (6.3 μm) water vapor absorption band was performed. This intercomparison is one part of a coordinated effort within the Global Energy and Water Cycle Experiment Water Vapor Project to assess our ability to monitor the distribution...