A Comparison of Extratropical Cyclones in Recent Reanalyses ERA-Interim, NASA MERRA, NCEP CFSR, and JRA-25

2011 ◽  
Vol 24 (18) ◽  
pp. 4888-4906 ◽  
Author(s):  
K. I. Hodges ◽  
R. W. Lee ◽  
L. Bengtsson
Keyword(s):  
The Other ◽  
Extratropical Cyclones ◽  
Forecast System ◽  
Climate Forecast System ◽  
Climate Forecast System Reanalysis ◽  
Spatial Differences ◽  
The Mean ◽  
Using Data ◽  
Modern Era ◽  
Ncep Climate Forecast System

Abstract Extratropical cyclones are identified and compared using data from four recent reanalyses for the winter periods in both hemispheres. Results show the largest differences occur between the older lower resolution 25-yr Japanese Reanalysis (JRA-25) when compared with the newer high resolution reanalyses, particularly in the Southern Hemisphere (SH). Spatial differences between the newest reanalyses are small in both hemispheres and generally not significant except in some common regions associated with cyclogenesis close to orography. Differences in the cyclone maximum intensitites are generally related to spatial resolution except in the NASA Modern Era Retrospective-Analysis for Research and Applications (NASA MERRA), which has larger intensities for several different measures. Matching storms between reanalyses shows the number matched between the ECMWF Interim Re-Analysis (ERA-Interim) and the other reanalyses is similar in the Northern Hemisphere (NH). In the SH the number matched between JRA-25 and ERA-Interim is lower than in the NH; however, for NASA MERRA and the NCEP Climate Forecast System Reanalysis (NCEP CFSR), the number matched is similar to the NH. The mean separation of the identically same cyclones is typically less than 2° geodesic in both hemispheres for the latest reanalyses, whereas JRA-25 compared with the other reanalyses has a broader distribution in the SH, indicating greater uncertainty. The instantaneous intensity differences for matched storms shows narrow distributions for pressure, while for winds and vorticity the distributions are much broader, indicating larger uncertainty typical of smaller-scale fields. Composite cyclone diagnostics show that cyclones are very similar between the reanalyses, with differences being related to the intensities, consistent with the intensity results. Overall, results show NH cyclones correspond well between reanalyses, with a significant improvement in the SH for the latest reanalyses, indicating a convergence between reanalyses for cyclone properties.

scholarly journals The Land Surface Analysis in the NCEP Climate Forecast System Reanalysis

2012 ◽  
Vol 13 (5) ◽  
pp. 1621-1630 ◽  
Author(s):  
Jesse Meng ◽  
Rongqian Yang ◽  
Helin Wei ◽  
Michael Ek ◽  
George Gayno ◽  
...  
Keyword(s):  
Surface Energy ◽  
Surface Analysis ◽  
Land Surface ◽  
Climate Forecast ◽  
Forecast System ◽  
Climate Forecast System ◽  
Climate Forecast System Reanalysis ◽  
Data Assimilation System ◽  
Ncep Climate Forecast System ◽  
Assimilation System

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.

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

2014 ◽  
Vol 53 (1) ◽  
pp. 34-46 ◽  
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.

Ocean–Atmosphere Characteristics of Tropical Instability Waves Simulated in the NCEP Climate Forecast System Reanalysis

2012 ◽  
Vol 25 (18) ◽  
pp. 6409-6425 ◽  
Author(s):  
Caihong Wen ◽  
Yan Xue ◽  
Arun Kumar
Keyword(s):  
Cloud Cover ◽  
Surface Wind ◽  
Heat Fluxes ◽  
Forecast System ◽  
Climate Forecast System ◽  
Climate Forecast System Reanalysis ◽  
Instability Waves ◽  
Tropical Instability Waves ◽  
Ncep Climate Forecast System

Abstract The NCEP Climate Forecast System Reanalysis (CFSR) represents a new effort with the first guess from a high-resolution coupled system and offers prospects for improved simulation of mesoscale air–sea coupled variability. This study aims to describe the characteristics of ocean–atmosphere covariability associated with tropical instability waves (TIWs) in the Pacific for the CFSR, and to assess how well they agree with in situ and satellite observations. Multiyear daily high-resolution CFSR data are used to describe variability associated with TIWs. Results show that TIW-induced SST variations exhibit pronounced seasonal and interannual variability that are tightly connected with cold tongue variations. The analysis illustrates coherent patterns associated with TIWs, both in the ocean and the atmosphere. Moisture and air temperature maximums are located west of SST maximums, leading to downstream displacement of surface pressure minimums relative to SST maximums. Surface winds accelerate (decelerate) over warm (cold) water, and a thermally direct circulation is created. Significant signals are observed in low-level cloud cover, which are closely in phase with surface wind convergences. The magnitudes of TIW-induced surface wind, surface pressure, and cloud cover perturbations agree well with in situ and satellite observations. Further analysis shows that surface net heat flux perturbations are dominated by latent heat fluxes and have a large negative feedback on TIW SST variability (~40 W m−2 °C−1). Water vapor perturbation is the primary factor contributing to changes in latent heat fluxes, while SST-induced wind perturbation plays a secondary role. The analysis presented here highlights that the CFSR provides an unprecedented opportunity to study the physical mechanisms for the TIWs, as well as their influences on climate variability.

An assessment of the surface climate in the NCEP climate forecast system reanalysis

2010 ◽  
Vol 37 (7-8) ◽  
pp. 1601-1620 ◽  
Author(s):  
Wanqiu Wang ◽  
Pingping Xie ◽  
Soo-Hyun Yoo ◽  
Yan Xue ◽  
Arun Kumar ◽  
...  
Keyword(s):  
Climate Forecast ◽  
Forecast System ◽  
Climate Forecast System ◽  
Climate Forecast System Reanalysis ◽  
Surface Climate ◽  
Ncep Climate Forecast System

The NCEP Climate Forecast System Reanalysis

2010 ◽  
Vol 91 (8) ◽  
pp. 1015-1058 ◽  
Author(s):  
Suranjana Saha ◽  
Shrinivas Moorthi ◽  
Hua-Lu Pan ◽  
Xingren Wu ◽  
Jiande Wang ◽  
...  
Keyword(s):  
Climate Forecast ◽  
Forecast System ◽  
Climate Forecast System ◽  
Climate Forecast System Reanalysis ◽  
Ncep Climate Forecast System

An assessment of oceanic variability in the NCEP climate forecast system reanalysis

2010 ◽  
Vol 37 (11-12) ◽  
pp. 2511-2539 ◽  
Author(s):  
Yan Xue ◽  
Boyin Huang ◽  
Zeng-Zhen Hu ◽  
Arun Kumar ◽  
Caihong Wen ◽  
...  
Keyword(s):  
Climate Forecast ◽  
Forecast System ◽  
Climate Forecast System ◽  
Climate Forecast System Reanalysis ◽  
Ncep Climate Forecast System ◽  
Oceanic Variability

scholarly journals The Reliability of Antarctic Tropospheric Pressure and Temperature in the Latest Global Reanalyses

2012 ◽  
Vol 25 (20) ◽  
pp. 7138-7146 ◽  
Author(s):  
Thomas J. Bracegirdle ◽  
Gareth J. Marshall
Keyword(s):  
Surface Energy Balance ◽  
Surface Air Temperature ◽  
Radiosonde Data ◽  
Positive Trend ◽  
Forecast System ◽  
Climate Forecast System ◽  
Sea Level Pressure ◽  
Climate Forecast System Reanalysis ◽  
Near Surface ◽  
Modern Era

Abstract In this study, surface and radiosonde data from staffed Antarctic observation stations are compared to output from five reanalyses [Climate Forecast System Reanalysis (CFSR), 40-yr ECMWF Re-Analysis (ERA-40), ECMWF Interim Re-Analysis (ERA-Interim), Japanese 25-year Reanalysis (JRA-25), and Modern Era Retrospective-Analysis for Research and Applications (MERRA)] over three decades spanning 1979–2008. Bias and year-to-year correlation between the reanalyses and observations are assessed for four variables: mean sea level pressure (MSLP), near-surface air temperature (Ts), 500-hPa geopotential height (H500), and 500-hPa temperature (T500). It was found that CFSR and MERRA are of a sufficiently high resolution for the height of the orography to be accurately reproduced at coastal observation stations. Progressively larger negative Ts biases at these coastal stations are apparent for reanalyses in order of decreasing resolution. However, orography height bias cannot explain large winter warm biases in CFSR, JRA-25, and MERRA (11.1°, 10.2°, and 7.9°C, respectively) at Amundsen–Scott and Vostok, which have been linked to problems with representing the surface energy balance. Linear trends in the annual-mean T500 and H500 averaged over Antarctica as a whole were found to be most reliable in CFSR, ERA-Interim, and MERRA, none of which show significant trends over the period 1979–2008. In contrast JRA-25 shows significant negative trends over 1979–2008 and ERA-40 gives significant positive trends during the 1980s (evident in both T500 and H500). Comparison to observations indicates that the positive trend in ERA-40 is spurious. At the smaller spatial scale of individual stations all five reanalyses have some spurious trends. However, ERA-Interim was found to be the most reliable for MSLP and H500 trends at station locations.

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