Can surface pressure be used to remove atmospheric contributions from GRACE data with sufficient accuracy to recover hydrological signals?

The Gravity Recovery and Climate Experiment (GRACE) satellite mission will resolve temporal variations in gravity orders of magnitude more accurately and with considerably higher resolution than any existing satellite. Effects of atmospheric mass over land will be removed prior to estimating the gravitational field, using surface pressure fields generated by global weather forecast centers. To recover the continental hydrological signal with an accuracy of 1 cm of equivalent water thickness down to scales of a few hundred kilometers, atmospheric pressure must be known to an accuracy of 1 mbar or better. We estimate errors in analyzed pressure fields and the impact of those errors on GRACE surface mass estimates by comparing analyzed fields with barometric surface pressure measurements in the United States and North Africa/Arabian peninsula. We consider (1) the error in 30-day averages of the pressure field, significant because the final GRACE product will average measurements collected over 30-day intervals, and (2) the short-period error in the pressure fields which would be aliased by GRACE orbital passes. Because the GRACE results will average surface mass over scales of several hundred kilometers, we assess the pressure field accuracy averaged over those same spatial scales. The atmospheric error over the 30-day averaging period, which will map directly into GRACE data, is generally < 0.5 mbar. Consequently, analyzed pressure fields will be adequate to remove the atmospheric contribution from GRACE hydrological estimates to subcentimeter levels. However, the short-period error in the pressure field, which would alias into GRACE data, could potentially contribute errors equivalent to 1 cm of water thickness. We also show that given sufficiently dense barometric coverage, an adequate surface pressure field can be constructed from surface pressure measurements alone. Copyright 2001 by the American Geophysical Union

An Analysis of ENSO Prediction Skill in the CFS Retrospective Forecasts

Abstract The present study documents the so-called spring prediction and persistence barriers in association with El Niño–Southern Oscillation (ENSO) in the National Centers for Environmental Prediction (NCEP) Climate Forecast System (CFS) retrospective forecasts. It is found that the spring prediction and persistence barriers in the eastern equatorial Pacific sea surface temperature (SST) are preceded by a boreal winter barrier in the western equatorial Pacific zonal wind stress. The time of the persistence barrier is closely related to the time of the ENSO phase transition, but may differ from the time of the lowest variance. The seasonal change of the signal-to-noise ratio cannot explain the persistence barrier. While the noise may lead to a drop of skill around boreal spring in the western equatorial Pacific zonal wind stress, its impacts on the skill of eastern equatorial Pacific SST is small. The equatorial Pacific zonal winds display an excessive response to ENSO-related SST anomalies, which leads to a longer persistence in the equatorial Pacific thermocline depth anomalies and a delayed transition of the eastern equatorial Pacific SST anomalies. This provides an interpretation for the prediction skill drop in boreal spring in the eastern equatorial Pacific SST. The results suggest that improving the atmospheric model wind response to SST anomalies may reduce the spring prediction barrier

Atlas of climatology and variability of monthly mean Northern Hemisphere sea level pressure, 700 mb geopotential height, and 1000-700 mb thickness, 1950-1992 /

"September 1993."Shipping list no.: 93-0600-P.Includes bibliographical references (p. 10-11).Mode of access: Internet

Drivers of the 2013/14 winter floods in the UK

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