Nineteen limb-viewing data sets (occultation, pas-sive thermal, and UV scattering) and two nadir upper tro-pospheric humidity (UTH) data sets are intercompared andalso compared to frost-point hygrometer balloon sondes.The upper troposphere considered here covers the pressurerange from 300-100 hPa. UTH is a challenging measure-ment, because concentrations vary between 2-1000 ppmv(parts per million by volume), with sharp changes in verti-cal gradients near the tropopause. Cloudiness in this regionalso makes the measurement challenging. The atmospherictemperature is also highly variable ranging from 180-250 K.The assessment of satellite-measured UTH is based on co-incident comparisons with balloon frost-point hygrometersondes, multi-month mapped comparisons, zonal mean timeseries comparisons, and coincident satellite-to-satellite com-parisons. While the satellite fields show similar features inmaps and time series, quantitatively they can differ by a fac-tor of 2 in concentration, with strong dependencies on theamount of UTH. Additionally, time-lag response-correctedVaisala RS92 radiosondes are compared to satellites andthe frost-point hygrometer measurements. In summary, mostsatellite data sets reviewed here show on average ~ 30 % agreement amongst themselves and frost-point data but withan additional ~ 30 % variability about the mean bias. TheVaisala RS92 sonde, even with a time-lag correction, showspoor behavior for pressures less than 200 hPa.
The SPARC Water Vapor Assessment II: assessment of satellite measurements of upper tropospheric humidity
Bianca M. Dinelli;Piera Raspollini;
2022
Abstract
Nineteen limb-viewing data sets (occultation, pas-sive thermal, and UV scattering) and two nadir upper tro-pospheric humidity (UTH) data sets are intercompared andalso compared to frost-point hygrometer balloon sondes.The upper troposphere considered here covers the pressurerange from 300-100 hPa. UTH is a challenging measure-ment, because concentrations vary between 2-1000 ppmv(parts per million by volume), with sharp changes in verti-cal gradients near the tropopause. Cloudiness in this regionalso makes the measurement challenging. The atmospherictemperature is also highly variable ranging from 180-250 K.The assessment of satellite-measured UTH is based on co-incident comparisons with balloon frost-point hygrometersondes, multi-month mapped comparisons, zonal mean timeseries comparisons, and coincident satellite-to-satellite com-parisons. While the satellite fields show similar features inmaps and time series, quantitatively they can differ by a fac-tor of 2 in concentration, with strong dependencies on theamount of UTH. Additionally, time-lag response-correctedVaisala RS92 radiosondes are compared to satellites andthe frost-point hygrometer measurements. In summary, mostsatellite data sets reviewed here show on average ~ 30 % agreement amongst themselves and frost-point data but withan additional ~ 30 % variability about the mean bias. TheVaisala RS92 sonde, even with a time-lag correction, showspoor behavior for pressures less than 200 hPa.File | Dimensione | Formato | |
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