|Air temperature of the Giant Mts in the light of atmospheric circulation – an attempt to compare between northern and southern slopes|
|Termika powietrza w świetle cyrkulacji atmosferycznej w Karkonoszach – próba porównania stoków o północnej i południowej makroekspozycji|
|Piotr Pawliczek; Sobik Mieczysław|
|warunki termiczne, topoklimat, efekt fenowy|
|thermal conditions, topoclimate, foehn effect|
Paper aims to shed new look at the issue of air temperature on the slopes of the Giant Mountains. During one measurement
year, automatic recorders operated at measurement sites in Jakuszyce and on the northern slope of Szrenica Mt. From the
southern part of the Giant Mountains, measurement data from the Pec pod Sněžkou weather station, were included. A synoptic
calendar was prepared with 6 hours interval, defi ning both the character (cyclonic/anticyclonic) and the direction of air circulation
(8 directions). The temperature differences between measurement sites were analyzed with reference to the accompanying
synoptic conditions. Multi-day periods of anomalous course of air temperature between the stations has been designate. In that
section, the analysis has been focused on the role of synoptic situation, the infl uence of the terrain relief and the deformation of
air fl ow through the main ridge. Monthly average temperature was always lowest in Jakuszyce and usually highest on the slope
of Szrenica. Flow direction, perpendicular to the main ridge caused foehn effects on the leeward slope which were stronger at
the northern side of the Giant Mountains and occurred frequently, especially in cold part of the year. In extreme situations, the
daily average temperature on the slope of Szrenica was more than 10°C higher than at other stations. The obtained results were
confronted with the existing opinions on climatic regionalization of the Polish part of the Giant Mountains. There is no reason to
join the plateau of the JizeraMts and Giant Mountains into a common climatic region. The former area is at comparable altitude
signifi cantly cooler than the latter, moreover it is not infl uenced by warm and dry foehn wind.
Celem pracy jest nowe spojrzenie na zagadnienia temperatury powietrza w środkowym piętrze wysokościowym w Karkonoszach.
W ciągu jednego roku pomiarowego, zainstalowano automatyczne termohigrografy w Jakuszycach i na stoku Szrenicy.
Ponadto dołączono dane pomiarowe ze stacji synoptycznej z Pecu pod Śnieżką. Stworzono kalendarz synoptyczny defi niujący charakter
(cyklonalny/antycyklonalny) i cyrkulację (8 kierunków) co 6 godzin. Różnice temperatury powietrza pomiędzy stanowiskami
zanalizowano w odniesieniu do panujących warunków atmosferycznych. Zidentyfi kowano i scharakteryzowano wybrane okresy z
anomalnym przebiegiem temperatury pomiędzy stacjami. Analiza ta skupiała się na roli sytuacji synoptycznej, wpływie ukształtowania
terenu i deformacji przepływu powietrza przez Grzbiet Główny Karkonoszy. Średnia miesięczna temperatura zawsze była najniższa
w Jakuszycach i zazwyczaj najwyższa na stoku Szrenicy. Przepływ powietrza prostopadły do Grzbietu Głównego powodował efekty
fenowe po zawietrznej. Były one silniejsze i zdarzały się częściej po północnej stronie Karkonoszy, szczególnie w chłodnym półroczu. W
sytuacjach ekstremalnych, stok Szrenicy był ponad 10°C cieplejszy w ujęciu średnio-dobowej temperatury niż pozostałe stanowiska.
Rezultaty przeprowadzonej analizy zostały odniesione do istniejącego podziału na subregionyklimatyczne polskiej części Karkonoszy.
Nie ma uzasadnienia dla łączenia Gór Izerskich i Karkonoszy w jeden region klimatyczny. Wierzchowina Gór Izerskich na porównywalnej
wysokości jest wyraźnie chłodniejsza od Karkonoszy, ponadto brak jest na niej ocieplającego i osuszającego wpływu fenu.
|Air temperature is one of the most important|
elements of climate; and for this reason one of
the most common studied. Even in a relatively small
mountain range, like the Giant Mountains, quite large
local climatic contrasts exist caused by location within
different landforms. The study aims to present and
explain differences between adjacent stations situated
on both Polish and Czech sides of the mountains with
reference to the atmospheric circulation type.
During a period 18.04.2013-
17.04.2014 (excluding 16.09-15.10.2013) two temperature
and humidity automatic recorders operated
at two measurement sites in Jakuszyce (JAK) and
at the northern slope of Szrenica Mt. (SZS). They
were set, at a height close to 850 m above sea level.
For comparison with the southern part of the Giant
Mountains, measurement data from the Pec pod
Sněžkou (PPS) weather station, located at a similar
height were included. JAKis situated in a valley while
SZS and PPS represent slope location.
Measurement data were
collected every 10 minutes at JAK and SZS sites
and hourly at PPS. Due to the existing differences
in altitude between stations, measured values of
temperature were brought, with the use of the vertical
temperature gradient, to the reference altitude
860 m a.s.l. – the altitude of JAK station. A synoptic
calendar was prepared every 6 hours, defi ning both
the character (cyclonic/anticyclonic) and the direction
of air circulation (8 directions). The temperature differences
between measurement sites were analyzed
with reference to the accompanying synoptic conditions.
Another issue was to identify and characterize
selected multi-day periods of anomalous course of
air temperature between the stations. In that section,
the analysis has been focused on the role of synoptic
situation, the infl uence of the terrain relief and the
deformation of air fl ow through the main ridge of
the Giant Mts.
Monthly average temperatures
were always lowest at JAK and usually
highest at SZS. Differences between SZS and JAK
ranged by 0,8-3,2°C, in the case of PPS and JAK it
was 0,3-1,8°C. The thermal seasons and thermal
specifi c days have been characterized as well. SZS
was characterized by signifi cant shorter winter and
longer period with 0°C<Tavg<5°C range. Summer
lasted about one month at both SZS and PPS, while
it was a week shorteratJAK. The greatest difference
in case of thermal specifi c days was in frost days
(Tmin<0°C). The number of such days was about
aggregate 3 months at SZS, 4 months at PPS and 5 months at JAK. Number of hot days (Tmax>25°C)
was similar at all stations.
Then the temperature differences between stations
in 1273 situations with reference to the accompanying
synoptic conditions have been analyzed.
During Sa, Sc and SWa circulation, the SZS site was
about 2°C or more warmer than JAK and PPS due
to the foehn effect on the leeward side of the main
ridge of Giant Mts. When NE, NW (both type of
weather) and Nc circulation took place, PPS was
warmer than JAK and SZS about 1°C because of the
same effect. Circulation from perpendicular sectors
(N-NE-E and S-SW-W) cause greater differences
between leeward station and JAK in the cold part of
year, than in the warm part of year. Especially it was
noticeable at SZS (2,4°C warmer between November
and April compared to 1,1°C warmer between May
and October) and occurred more often.
Two situations with anomalous course of air temperature
between the stations have been presented.
Particularly high thermal contrasts developed on
18-19 December 2013 during strong S and SW circulation,
when differences of daily average temperature
between JAK and PPS compared to SZS exceeded
even 10K. It was the result of warm foehn effect at
SZS, which however did not reach the Jelenia Góra
Basin. JAK at the same time was under infl uence of the
low level cold air, which travelled from SW through
the Szklarska Pass and then, in relatively shallow
layer, down the Kamienna Valley. Thermal conditions
at JAK and PPS were similar due to the fact that both
stations were immersed in the same sub-inversion
cold air mass, while SZS experienced descending fl ow
of air on the lee side of the Giant Mts. On 27-28 April
2013 during N circulation PPS compared to JAK and
SZS was warmer up to 8K. On the windward side, the
orographic lifting occurred resulting in rainfall. On
the lee side air subsidence caused the temperature
increase and the decrease of humidity, these both
effects were enhanced by insolation. The obtained results were confronted with the
existing opinions on climatic regionalization of the
Polish part of the Giant Mountains. Existing division
into climatic subregions was developed by Kwiatkowski
and Hołdys (1985). The division based on
anemo-orographical systems which were discovered
by Jenik (1961). The concept divided Giant Mts. into
two subregions: Izera-Giant Mts. (K-Iz) and Eastern-
Giant Mts. (E-K). The K-Iz region at the same altitude
is cooler and is characterized by larger precipitation.
In the E-K subregionfoehn effects happen more
frequently. JAK which is located in basin, was used
as the reference station for the K-Izsubregion which
is mostly sloping terrain. According to Kwiatkowski
and Hołdys, thermal conditions in JAK and SZS
should be almost the same.