Middle-latitude climates - The Global Climate System: Patterns, Processes, and Teleconnections - page 96

Chapter 4
Middle-latitude climates
4.1 Introduction
In geographical terms, the middle-latitude climate zone is generally located
between the poleward edges of the subtropical high pressure systems (approxi-
mately 358 N and S), and the beginnings of the polar circulations (approximate
608 N and S). For many years the middle-latitude climates were referred to as
climates of the temperate zone. This proves a definitive misnomer, for while the
zone contains some of the most equable of climates, it also has some of the most
extreme. In the Northern Hemisphere (NH), the middle-latitude climates have
some of the highest measure of continentality, an index that is essentially a
measure of seasonal extremes.
This chapter examines various aspects of middle-latitude climates. It begins
with an essay providing details of the development and significance of reana-
lysis. This recent analytical method draws upon a state-of-the-art data assimila-
tion system to reprocess all past atmospheric environmental observations,
combining them with short forecasts in order to derive the best estimate of the
state and evolution of the environment. Since the statistical combination of the
forecast and observations is denoted in operational applications as ''analysis,''
the new method is usually known as reanalysis. Thereafter, an account of
selected aspects of middle-latitude climates of the NH is followed by a discus-
sion of the much-neglected climates of the Southern Hemisphere (SH).
4.2 Data availability
Those studying the climate of the middle latitudes in the NH have been relatively
fortunate in terms of data availability. It is there that temperature and precipita-
tion have been measured in reasonably accurate form for several hundred years.
The longest range from some 300 years in Central England (Manley 1953 )to
about 200 years for a few locations in Europe and the eastern United States. Most
of the stations that make up today's observational network have been kept for
little more than 100 years.
Until the advent of weather satellites in 1966, when the Applications
Technology Satellite (ATS1) was launched, SH and ocean data were sparse.
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