Showing papers on "Meteorological reanalysis published in 1997"

A high resolution global reanalysis highlighting the winter monsoon. Part I, reanalysis fields

Abstract: This study entails a reanalysis of the TOGA-COARE, CEPEX period covering the months December 1992 through March 1993. Four times daily data sets were reanalyzed for the period. The unique aspect of this reanalysis is that (i) it incorporates physical initialization i.e. assimilation of rainfall from raingauge and satellite (OLR and microwave radiometric data), (ii) this reanalysis is carried out at a very high resolution, T170, global spectral model (space resolution of roughly 70 km at equator) and (iii) ECMWF reanalysis is used as a first guess field for this study. This analysis is global and is carried out at 15 vertical levels using the FSU global spectral model. In this study we have analyzed a large number of meterological variables such as wind, temperature, humidity, surface pressure, vertical velocity, cloud, rainfall, surface fluxes and diabatic heating. In this part of the paper we present the monthly mean and samples of daily fields of the reanalysis. Some of the major results of the reanalysis include the relationships among the flow fields and the ITCZ convection; the shallow northeast monsoon current and its rapid turning towards westerlies with height; an overabundance of middle clouds over the region of the ITCZ; and the distribution of heat sources and sinks. A motivation for this reanalysis is the forthcoming Indian Ocean Experiment (INDOEX), which is an international field experiment to be conducted during the winter monsoon time frame in 1999.

Arctic precipitation as represented in the NCEP/NCAR reanalysis

Abstract: Arctic prec ipita tion as depicted in the l\\'a tiona l Center for Environmental Prediction (l\\CEP) and the National Center for Atmospheric Research (NCAR) reana lysis effort is evaluated using 6 hourly model output for the period 198693 in conjunction with ga uge-corrected climatologies. Climatologica l field s fi'om the model agree favo rably with observations in terms of general spatio-tempora l pa tterns, but with some notable diITerences. In pa rticul a r, the precipitat ion max imum over the centra l Arctic (the region north of 70° N ) is depicted inJuly, onc month too ea rly. Values arc too low from August through D ecember, resulting in underes timates of annua l precipitation of about 40 mm. Despite these shortcomings, the modeled precipita tion fi elds appear to be sufficiently reali stic to represent a base for blending with other data to prov ide g ridded fi eld s suitable for use in climate studies and sea-ice models.

New meteorological data assimilation model for real-time emergency response

Abstract: We are developing a new meteorological data assimilation model for the Atmospheric Release Advisory Capability (ARAC) project at Lawrence Livermore National Laboratory, which provides real-time dose assessments of airborne pollutant releases. The model, ADAPT (Atmospheric Data Assimilation and Parameterization Techniques), builds three-dimensional meteorological fields, which can be used to drive dispersion models or to initialize or evaluate mesoscale models. ADAPT incorporates many new features and substantial improvements over the current ARAC operational models MEDIC/MATHEW, including the use of continuous-terrain variable-resolution grids, the ability to treat assorted meteorological data such as temperatures, pressure, and relative humidity, and a new algorithm to produce mass-consistent wind fields. In this paper, we will describe the main features of the model, current work on a new atmospheric stability parameterization, and show example results.

Data Assimilation for High-Resolution Limited-Area Models (gtSpecial IssueltData Assimilation in Meteology and Oceanography: Theory and Practice)

Abstract: The present status of development of data assimilation techniques for high resolution limited area models is reviewed and various candidates for a new generation of a data assimilation system are compared. It is concluded that data assimilation based on 3-dimensional or 4-dimensional variational techniques is the most promising approach. Further investigations are needed, however, to find out whether variational data assimilation is feasible over "limited" model integration areas or whether global/hemispheric model integration areas have to be introduced for high resolution limited area data assimilation purposes. The main problem in this connection is the rapid propagation of forecast errors on a global or at least hemispheric atmospheric scale within a time-scale of a few days.

Technical Report Series on Global Modeling and Data Assimilation. Volume 13; Interannual Variability and Potential Predictability in Reanalysis Products

Abstract: ABSTRACTThis technical memorandum documents the longwave radiation parameterization developedat the Climate and Radiation Branch, NASA/Goddard Space Flight Center, for a wide variety ofweather and climate applications. Based on the 1996-version of the Air Force GeophysicalLaboratory H/TRAN data base (Rothman et al., 1998), the parameterization includes theabsorption due to major gaseous absorption (water vapor, C02, 03) and most of the minor tracegases (N20, CH 4, CFC's), as well as clouds and aerosols. The thermal infrared spectrum isdivided into nine bands. To achieve a high degree of accuracy and speed, various approaches ofcomputing the transmission function are applied to different spectral bands and gases. Thegaseous transmission function is computed either using the k-distribution method or the tablelook-up method. To include the effect of scattering due to clouds and aerosols, the opticalthickness is scaled by the single-scattering albedo and asymmetry factor. The optical thickness,the single-scattering albedo, and the asymmetry factor of clouds are parameterized as functions ofthe ice and water content and the particle size. The parameterization can accurately computefluxes to within 1% of the high spectral-resolution line-by-line calculations. The cooling rate canbe accurately computed in the region extending from the surface to the O.Ol-hPa level.The computer code for this longwave parameterization is very easy to use. It has beenimplemented in atmospheric models for cloud, weather, and climate studies at many governmentinstitutes and universities. The code and sample calculations are accessible athttp://climate.gsfc.nasa.gov/-chou/clirad_lw.

Meteorological Support to ALPTRAC

Abstract: SNOWMET was designed as a meteorological support study data for ALPTRAC. Its aims were thus related to the meteorological interpretation of the field measurements made by the other groups, including investigation of source areas and the role of vertical transport process (boundary layer versus free troposphere). Synoptic-scale trajectories were computed, and operational meteorological data were collected for several sites in the Alps. Trajectories were statistically evaluated together with aerosol measurements to find potential source regions relevant for the Alps.