Characteristics of the JRA-25 Dataset from the Viewpoint of Global Energetics

Abstract

In this study, the global circulation represented by JRA-25 is examined from the viewpoint of global energetics, compared with ERA-40 and NCEP/NCAR reanalysis. Although the peak and slope of the spectrum for JRA-25 are consistent with those of the other datasets, the magnitude of energy or energy conversion is generally ERA-40 > JRA-25 > NCEP. For short waves, a rapid decrease of amplitude with increasing wave number is shown for NCEP/NCAR reanalysis and ERA-40. The energy conversion from zonal available potential energy to zonal kinetic energy, caused by zonalmean meridional circulation, is the largest for JRA-25, which is the result of a large amount of cancellation of the local conversion term in the Hadley cell. IntroductionThe Japanese 25-year reanalysis (JRA-25) is an up-todate dataset produced by the Japan Meteorological Agency (JMA) and the Central Research Institute of Electric Power Industry (CRIEPI). The dataset contains global data, with multiple layers from the surface to the middle stratosphere; it is very useful for the study of various meteorological and climatological phenomena.In order to diagnose the new reanalysis dataset and improve a future reanalysis, it is essential to examine features of the dataset from a variety of perspectives. Some of the advantages and deficiencies of JRA-25 were reported in connection with the impact of some newlyproduced observational data, which was summarized by Onogi et al. (2005). In this study, we examine the characteristics of global circulation represented by the JRA-25 data, from the viewpoint of global energetics. Data usedThe JRA-25 dataset used in this study was downloaded from the JRA-25 homepage (http://jra.kishou.go. jp/). Resolution of given data is 2.5°× 2.5°intervals in longitude/latitude and 23 vertical levels (1000, 925, 850, 700, 600, 500, 400, 300, 250, 200, 150, 100, 70, 50, 30, 20, 10, 7, 5, 3, 2, 1 and 0.4 hPa). Field variables used for computing the energy cycle are the horizontal wind (u, v), temperature (T), and dew-point depression (T Td), which is available in 8 levels up to 300 hPa.Two other reanalysis datasets were compared with the JRA-25. Both have the same horizontal resolution as JRA-25 (2.5°× 2.5°). One is the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis (hereafter NCEP1) dataset (Kalnay et al. 1996), which is available from the Climate Diagnostics Center (CDC) of the National Oceanic and Atmospheric Administration (NOAA)-Cooperative Institute for Research in Environmental Sciences (CIRES) (http://www.cdc.noaa.gov/ cdc/reanalysis/), which has a vertical resolution of 17 levels (1000, 925, 850, 700, 600, 500, 400, 300, 250, 200, 150, 100, 70, 50, 30, 20 and 10 hPa). The other dataset used in this study is the European Centre for MediumRange Weather Forecasts (ECMWF) 40-year reanalysis (ERA-40) dataset (Uppala et al. 2005), obtained from the ECMWF Data Server (http://data.ecmwf.int/data/), which has a vertical resolution of 23 levels (1000, 925, 850, 775,...

A Detailed Normal-Mode Energetics of the General Circulation of the Atmosphere

“…The three reanalysis show identical spectra for A and K in the zonal wavenumber domain, except at wavenumbers n a 25 for NCEP-R2, There is a rapid decrease in the spectra of NCEP-R2 at « s 36, previously reported by Watarai and Tanaka (2007) for NCEP-Rl and also by Marques et al, (2010) for NCEP-R2, In addition, it may be seen that both energy spectra for NCEP-R2 starts to decrease more rapidly than those for ERA-40 and JRA-25 at wavenumbers n s 25, Most of A resides in the baroclinic modes, whereas for K there are comparable amounts of energy among the barotropic and baroclinic modes.…”

Future Changes in Atmospheric Conditions for the Seasonal Evolution of the Baiu as Revealed from Projected AGCM Experiments

“…This dataset has a temporal resolution of six hours and a spatial resolution of 1.25°, the same resolution as the MRI-AGCM3.2S. The JRA-55 has been extensively improved since the Japanese 25-year Reanalysis (JRA-25) (Takahashi et al 2006;Onogi et al 2007;Watarai and Tanaka 2007).…”

Climatological Evolution of the Okinawa Baiu and Differences in Large-Scale Features during May and June

“…We use meteorological data from the Japanese 25-yr Reanalysis (JRA-25) (Takahashi et al 2006;Onogi et al 2007;Watarai and Tanaka 2007) and precipitation data from the Global Precipitation Climatology Project (GPCP; Huffman et al 2001) for the 10 years from 1997 through 2006. The JRA-25 dataset is provided 6-hourly at a horizontal resolution of 1.258 3 1.258 (longitude 3 latitude).…”