期刊名称：Tellus A: Dynamic Meteorology and Oceanography
电子版ISSN：1600-0870
出版年度：2001
卷号：53
期号：2
页码：192-214
DOI：10.3402/tellusa.v53i2.12186
摘要：The feasibility of assimilating the GPS total zenith delay into atmospheric models is investigatedwithin the framework of the ‘‘Observing System Simulation Experiment.’’ The total zenith delayis made up of two terms: one is proportional to the pressure at the site of the GPS groundbasedreceiver and the other to the overlying amount of water vapor. Using the MM5 mesoscalemodel and its adjoint, a set of 4-dimensional variational (4DVAR) experiments is performed.Results from the assimilation of simulated precipitable water observations are used as thebenchmark. The model domain covers Southern California. The observations are simulatedwith a 10 km horizontal resolution model that includes full physics, while a 20-km resolutionand a less comprehensive physics package are used in the 4DVAR experiments. Both, the 10-kmand 20-km models employ the same set of 15 vertical levels. Moisture fields retrieved from thetotal zenith delay are found to compare very well with those retrieved from the precipitablewater. Verified against the observations, the vertically integrated moisture is found to be veryaccurate. An overall improvement is also achieved in the vertical profiles of the moisture fields.The use of the so-called background term and model initialization are shown to greatly reducethe negative impact that the sole assimilation of the total zenith delay can have on the pressurefield and integrated water vapor. The adverse effect stems from the poor resolution of thetopography needed to evaluate the model pressure at the GPS sites. The analysis incrementsof all model fields are found to be similar to the counterparts obtained from the assimilationof the precipitable water. The same is true for the short-range precipitation forecasts initiatedfrom the 4DVAR-optimal initial conditions.
