The Land Surface Analysis in the NCEP Climate Forecast System Reanalysis

Abstract The NCEP Climate Forecast System Reanalysis (CFSR) uses the NASA Land Information System (LIS) to create its land surface analysis: the NCEP Global Land Data Assimilation System (GLDAS). Comparing to the previous two generations of NCEP global reanalyses, this is the first time a coupled land–atmosphere data assimilation system is included in a global reanalysis. Global observed precipitation is used as direct forcing to drive the land surface analysis, rather than the typical reanalysis approach of using precipitation assimilating from a background atmospheric model simulation. Global observed snow cover and snow depth fields are used to constrain the simulated snow variables. This paper describes 1) the design and implementation of GLDAS/LIS in CFSR, 2) the forcing of the observed global precipitation and snow fields, and 3) preliminary results of global and regional soil moisture content and land surface energy and water budgets closure. With special attention made during the design of CFSR GLDAS/LIS, all the source and sink terms in the CFSR land surface energy and water budgets can be assessed and the total budgets are balanced. This is one of many aspects indicating improvements in CFSR from the previous NCEP reanalyses.

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A Hybrid Global Ocean Data Assimilation System at NCEP

Monthly Weather Review ◽

10.1175/mwr-d-14-00376.1 ◽

2015 ◽

Vol 143 (11) ◽

pp. 4660-4677 ◽

Cited By ~ 35

Author(s):

Stephen G. Penny ◽

David W. Behringer ◽

James A. Carton ◽

Eugenia Kalnay

Keyword(s):

Data Assimilation ◽

Initial Conditions ◽

Global Ocean ◽

Climate Forecast ◽

Forecast System ◽

Climate Forecast System ◽

Ocean Data Assimilation ◽

Data Assimilation System ◽

Ncep Climate Forecast System ◽

Assimilation System

Abstract Seasonal forecasting with a coupled model requires accurate initial conditions for the ocean. A hybrid data assimilation has been implemented within the National Centers for Environmental Prediction (NCEP) Global Ocean Data Assimilation System (GODAS) as a future replacement of the operational three-dimensional variational data assimilation (3DVar) method. This Hybrid-GODAS provides improved representation of model uncertainties by using a combination of dynamic and static background error covariances, and by using an ensemble forced by different realizations of atmospheric surface conditions. An observing system simulation experiment (OSSE) is presented spanning January 1991 to January 1999, with a bias imposed on the surface forcing conditions to emulate an imperfect model. The OSSE compares the 3DVar used by the NCEP Climate Forecast System (CFSv2) with the new hybrid, using simulated in situ ocean observations corresponding to those used for the NCEP Climate Forecast System Reanalysis (CFSR). The Hybrid-GODAS reduces errors for all prognostic model variables over the majority of the experiment duration, both globally and regionally. Compared to an ensemble Kalman filter (EnKF) used alone, the hybrid further reduces errors in the tropical Pacific. The hybrid eliminates growth in biases of temperature and salinity present in the EnKF and 3DVar, respectively. A preliminary reanalysis using real data shows that reductions in errors and biases are qualitatively similar to the results from the OSSE. The Hybrid-GODAS is currently being implemented as the ocean component in a prototype next-generation CFSv3, and will be used in studies by the Climate Prediction Center to evaluate impacts on ENSO prediction.

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A 10-yr Climatology of Tibetan Plateau Vortices with NCEP Climate Forecast System Reanalysis

Journal of Applied Meteorology and Climatology ◽

10.1175/jamc-d-13-014.1 ◽

2014 ◽

Vol 53 (1) ◽

pp. 34-46 ◽

Cited By ~ 25

Author(s):

Xinyuan Feng ◽

Changhai Liu ◽

Roy Rasmussen ◽

Guangzhou Fan

Keyword(s):

Tibetan Plateau ◽

Effective Diameter ◽

Climate Forecast ◽

Forecast System ◽

Climate Forecast System ◽

Climate Forecast System Reanalysis ◽

Average Life Span ◽

Near Surface ◽

Late Night ◽

Ncep Climate Forecast System

AbstractA plateau vortex refers to a shallow meso-α-scale cyclonic vortex that is usually confined to near-surface levels (500 hPa) over the Tibetan Plateau during warm seasons. It is the major precipitation-producing weather system over the plateau, but the knowledge of its climatology and understanding of generation mechanisms are limited because of the lack of adequate observations in this harsh mountainous region. In this study, the high-resolution NCEP Climate Forecast System Reanalysis data have been used to perform a statistical survey of these vortices over 10 warm seasons (April–October of 2000–09). The purpose is to document their climatological features, including genesis, size, life cycle, propagation, and diurnal variation.Results show that ~103 plateau vortices occur on average every year. Most are detected from May through August, with the maximum monthly count in July. The primary area of origin exhibits a west–east orientation in correspondence with a large-scale confluence zone, and the most concentrated source lies in the area of 33°–36°N, 84°–90°E in the high elevated central and western plateau. Significant diurnal variations are observed, characteristic of a preferential genesis during late afternoon to evening hours and a late night dissipation peak. The vortex events have an average life span of ~15 h and an average horizontal dimension (effective diameter) of ~280 km. In accordance with the steering environmental flow, an overwhelming majority travel eastward with a mean translation speed of ~10 m s−1. A small fraction of systems (approximately nine cases annually) move off the plateau, predominantly from the eastern edge.

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