Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Hayashi Spectra of the Northern Hemisphere Mid-latitude Atmospheric
  Variability in the NCEP and ERA 40 Reanalyses   We compare 45 years of the reanalyses of NCEP-NCAR and ECMWF in terms of
their representation of the mid-latitude winter atmospheric variability for the
overlapping time frame 1957-2002. We adopt the classical approach of computing
the Hayashi spectra of the 500 hPa geopotential height fields. Discrepancies
are found especially in the first 15 years of the records in the
high-frequency-high wavenumber propagating waves and secondly on low
frequency-low wavenumber standing waves. This implies that in the first period
the two datasets have a different representation of the baroclinic available
energy conversion processes. In the period starting from 1973 a positive impact
of the aircraft data on the Euro-Atlantic synoptic waves has been highlighted.
Since in the first period the assimilated data are scarcer and of lower quality
than later on, they provide a weaker constraint to the model dynamics.
Therefore, the resulting discrepancies in the reanalysis products may be mainly
attributed to differences in the models' behavior.

22
The categories of this paper are: chao-dyn
1
The categories of this paper are: cs
28
The categories of this paper are: alg-geom
31
The categories of this paper are: ao-sci
29
The categories of this paper are: funct-an
2
The categories of this paper are: math
12
The categories of this paper are: nucl-th
8
The categories of this paper are: hep-ex
26
The categories of this paper are: bayes-an
18
The categories of this paper are: econ
4
The categories of this paper are: cond-mat
32
The categories of this paper are: atom-ph
10
The categories of this paper are: q-bio
25
The categories of this paper are: patt-sol
24
The categories of this paper are: dg-ga
11
The categories of this paper are: hep-lat