International Scientific Conference GEOBALCANICA 20 20 [625999]

International Scientific Conference GEOBALCANICA 20 20

THERMO -HYDROMETRIC ARGUMENTS IN THE DEMONSTRATION OF
FOEHNAL CIRCULATION IN COTNARI, ROMANIA

Lidia Maria Apopei (1)
Dumitru Mihăilă (1)
Petruț Ionel -Bistricean (2)
1 Department of Geography, Faculty of History and Geography, Stefan cel Mare University,
Suceava, Romania
2 Regional Meteorological Centre of Moldova, National Meteorological Administration,
Suceava, Romania

ABSTRACT

The foehnal circulation from Cotnari is a meteorological reality demonstrated through
the statistical, cartographic and graphical analyses realized on the basis of the data
processing of a program of hourly observations made in 12 representative points of the
researched territory, carried out for 8 months. Our analyses confirm that from a thermal
point of view the foehn brings an average thermal increase of 1.3 -1.5 ° C and a hygric
deficit of 8 -9%. In clear cases with foehn (that represent 4.5% of the time monitored),
the thermal and hygric consequences are doubled in value.

Keywords: thermo -hygrometric sensors, urban atmosphere, topoclimates

INTRODUCTION

The foehn should be defined by its characteristics and not according to its origin [1].
Although t he foehn is defined as "the wind warmed and dried by the downward
movement, generally on the sheltered slope of a mountain" [2], [The World
Meteorological Organization, 1992], the identification of the periods with foehn for
each geographical region, creat es real problems for researchers. Currently, there are no
generally accepted specific value thresholds for meteorological elements (air
temperature, relative humidity of the air, air pressure, the speed or wind direction) based
on which we can classify dyn amic manifestations in a particular area or region in the
foehn interval category [3].
The choice of foehn / non foehn limits is influenced by the regional synoptic conditions,
the particularities of the local dynamics and topography [4]. The previous clim atological
observations and analyses are important because they have indicated, in different ways,
the existence of foehnal manifestations in a certain area. The analysis and interpretation
of the foehn is at the discretion of the researcher considering th e key characteristics of
this type of wind [2]:
– the dynamics of the air and the perpendicular orientation of the wind lines when
encountering an orographic obstacle,

Physical Geography

– the increase of the air temperature and the reduction of the relative humidity on the
slope opposite to the air circulation.
The recent European studies outline through the variety of approaches (aerological
surveys, mathematical models, IT programs, graphical simulations), the ubiquity of the
foehn where the wind lines are forced to cross a orographic obstacle. Starting from the
MAP project (The Mesoscale Alpine Program, 1999), meteorologists from the
MeteoSWISS service established in 2008 the quantitative limits specific to the foehn
witin Central Europe (applying them to the geographical area adjacent to the Alps).
They have considered parameters such as wind direction / speed and pressure gradient
that was 4 hPa for the mountain floor (8 hPa for the adjacent terrain). These parameters
come from the MOS (Model Output Statistics) meteorolog ical database included in the
ECMWF (European Center for Medium Range Weather Forecasts) model and were the
basis for the development of the computer program for detecting the regional foehn. In
Romania, the foehn was analyzed from both points of view of t he thermodynamic
theory [5], [6], [7], [8] and hydraulic theory [9]. The regions in the country where the
foehn has a higher frequency are the sub -mountain areas protected by /from the
Carpathian Mountains shelter. To these regions are added the hilly peak s that oppose the
dominant circulation. From this last category we stopped at the top of the Hârlău –
Tudora Hill, where the manifestation of the foehn is demonstrated by the previous
climatic observations [7], [8], [9] and the use of the land for viticultur e purposes .

MATERIALS AND METHODS

Study area

The Cotnarilor area is located in
the northeast of Romania,
between Siret Valley and Prut
Valley, in the northern half of
Iasi County. The study area is
developed on an altitude
difference of 328 meters
(between 391 m in Humosu Hill
and 63 m in Erbiceni locality
located on the Bahlui river
valley), longitudinally about 1 °
(between 26 ° 35 'longitude E to
Tătăruși in the west and 27 ° 30
'longitude E to Re diu in the east)
and 10' latitudinal (between the
locality Deleni located in the
northern extremity at 47 ° 27 'lat.
N and the locality Rediu from
the southern extremity located at
47 ° 12' lat.N(Fig. 1).

Figure1. Geographical position of Cotnari area

International Scientific Conference GEOBALCANICA 20 20

METHODS

To carry out this study we used the meteorological data recorded at the Cotnari Weather
Station and the measurements of temperature (° C) and relative humidity (%) of the air,
at 12 weather stations. The recordings from the meteorological stations set up in their
own network were made with C EM DT 171 Data Logger sensors, placed in
meteorological shelters according to the regulations of the National Meteorological
Administration. The choice of places for monitoring the temperature and humidity of
the air was made on the north -south oriented po sts alignments and longitudinally placed
from West to East, in representative physical -geographic conditions (river valley, slope
opposite to the advection, sheltered slope, the territory from the east of the sheltered
slope on which the foehnal influence is reflected) in order to capture the regional
thermo -hygrical consequences of air dynamics. The weather stations arranged in the
order and the specified logic are found in Tab. 1 and Fig. 1. These are: Tătăruși – the
western slope of the Siret river, Heci in the river bed of Siret river, Humosu on the
opposite slope of the air advection, Deleni, Cireșeni, Cucuteni, Cotnari on the hilly
alignment Dealu Mare -Hârlău and Belcești weather stations, Focuri, Erbiceni, Movileni
in the Jijia -Bahlui hilly plain .
Tabel 1. Location of observation posts of Cotnari area
The name of
the weather
station The code
of the
weather
station Geographical position Latitude
(°lat.N.) Longitude
(°long.E.) Altitude
(m)
Tătăruși TAT The western slope of
Siret river (WSS) 47° 21' 26° 35' 323
Heci HEC The minor riverbed of
Siret 47° 21' 26° 40' 217
Humosu HUM WSS 47° 25' 26° 41' 391
Cireseni CIR The hilly alignement of
the peaaks at the west of
Cotnari (HAWC) 47° 22' 26° 50' 269
Deleni DEL HAWC 47° 27' 26° 52' 312
Cucuteni CUC HAWC 47° 16' 26° 56' 233
Stația
meteorologică
Cotnari SMC Cotnari Cuesta 47° 22' 26° 56' 289
Cotnari COT Cotnari Cuesta 47° 20' 26° 56' 170
Belcești BEL The lower plain of Jijia
and Bahlui(LPJB) 47° 19' 27° 05' 148
Focuri FOC LPJB 47° 22' 27° 12' 104
Erbiceni ERB LPJB 47° 15' 27° 13' 63
Movileni MOV LPJB 47° 20' 27° 21' 74
Rediu REB LPJB 47° 12' 27° 30' 97
We have monitored for the period 01.03.2019 – 31.10.2019 (245 days / 5880 hours) the
inter-hourly, inter -diurnal and inter -monthly evolution of the air temperature and
relative humidity in the study area. The analysis of the daily synoptic maps from the
websites www.watterbote.de, www.pogodynka.pl and www.meteoromania.ro, the aerial
surveys available on the website www.weather.uwyo ., led, initially, to the identification
of the peculiarities of the foehn in area of study.
Graphic materials were created using ArcGIS, Excel 2007 and ClimateOpenAir.

Physical Geography
RESULTS AND DISCUSSIONS

The study is based on a certain algorithm. i) First of all, we selected the cases in which
the wind has beaten from the general western sect or (SSW, SW, WSW, W, WNW, NW,
NNW). ii) Then, from the resulting database, we extracted the consecutive hourly cases
(between 5 and 20 hours) with the wind speed of over 2 m / s, considering (in agreement
with Beaufort's observations, 1805) that above this speed threshold of the wind, the
movement of the air can produce obvious foehn effects. iii) For these cases we followed
the fulfillment of other additional conditions: the increase of the air temperature and the
decrease of the relative humidity at the w eather stations located to the east of Cotnari.
Later, we analyzed the synoptic maps and the aerological surveys.

Tabel 2. Periods with foehn in Cotnari area (01.03.2019 – 31.10.2019)
Date Time
interval No.
hours Average
speed
periods
with
foehn
(m/s) Maximum wind speed
(m/s) The
average
value of
air
pressure
periods
with foehn
(mb) The
average
value of
air
temperature
periods
with foehn
(°C) The
average
value of
relative
humidity
periods
with foehn
(%) speed hour direction
01.03.2019 02:30 –
20:30 18 8.5 12.0 07:30
08:00 NNV
NV 1004.1 7.0 50.1
10.03.2019 08:30 –
19:30 11 8.4 14.0 13:30 V 1009.4 11.3 43.0
11.03.2019 07:30 –
17:30 10 8.0 13.0 12:30 NV 1005.2 12.2 37.5
23.03.2019 05:30 –
20:30 15 7.9 10.0 10:30
14:30
15:30 NV
NNV 1026.1 9.0 32.0
26.03.2019 04:30 –
19:30 13 5.0 6.0 08:30
13:30 NV 1017.0 5.4 71.9
30.03.2019 05:30 –
14:30 9 6.5 7.0 05:30
04:30 NV 1025.8 12.6 55.8
10.04.2019 02:30 –
16:30 14 5.2 7.0 07:30 NV 1007.4 15.9 65.6
20.04.2019 00:00 –
14:30 14 3.5 4.0 03:30
11:30 NV 1029.2 8.5 73.1
28.04. 2019 04:30 –
09:30 5 3.5 5.0 06:30 V 1007.9 15.6 67.5
08.05.2019 02:30 –
16:30 14 10.4 14.0 04:30
06:30 NV 1013.9 9.3 75.7
25,26.05.
2019 21:30 –
14:30 17 5.8 8.0 05:30
07.30 V 1014.1 12.6 55.8
18.06.2019 00:30 –
13:30 13 4.5 5.0 07.30
10.30 NV 1017.9 22.9 74.7
28.06.2019 05:30 –
20:30 15 8.7 10.0 05:30
17:30 NV 1013.9 21.3 52.9
22.07.2019 00:30 –
13:30 13 4.3 8.0 03:30 NV 1019.4 23.3 69.0
31.07.2019 02:30 –
14:30 12 5.8 8.0 09:30 NNV 1008.1 24.9 67.2
22.08.2019 00:30 –
20:30 20 8.0 10 02:30
05.30 NV 1023.6 21.9 69.4
03.09.2019 05:30 –
16:30 11 5.0 7.0 11:30
12:30 NV 1015.5 24.8 61.8
16.09.2019 02:30 –
10:30 8 4.7 7.0 03:30
05.30 V 1018.0 14.8 60.8
22.09.2019 02:30 –
13:30 11 4.5 7.0 04:30
05.30 V 1022.5 14.2 58.2
11.10.2019 00:00 –
14:30 14 5.2 7.0 06:30
08:30 V 1021.0 13.8 66.5
01.03.2019 -31.10.2019 266 6.2 1016.0 mb 15.0° C 60.5 %

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Based on our own observations, for the period 01.03.2019 -31.10.2019, were identified,
in the current stage of the research, twenty periods with foehn (Table 2) during which
we noticed more particularities of the weather parameters .

1.The western circulation was dominant,
during the analyzed period 01.03. 2019 –
31. 10. 2019, in the air dynamics with an
average percentage of 58% (Fig. 2, Fig. 3).
This circulation, in accordance with the
NNW -SSE arrangement of the major lines
of the relief, favors air foehnization in the
eastern sector of the s tudy area. The
synoptic maps of Europe indicated in
periods with foehn, advancements of
western air masses to the east and south –
east of the continent. In what concerns
Romania, the western air climbs the
Oriental Carpathians and flows towards the
Siret Pa ss. In this low altitude space, the
air can sediment on anticyclonic time with
clear weather and atmospheric calm favors
the thermal inversions or it can climb the western hills toward the Moldavian Plain. The
low altitudes of the orographic barrier, of on ly 400 – 500 m (Delul Mare Hârlău -Tudora
587 m) and the presence of the low subunits: Șaua Vorona (N) and Șaua Ruginoasa (S),
do not favor a major overheating as it happens in the Sub -Carpathians of Curve. ,
Făgăraș Depression, northwest of Oltenia or Alba Iulia-Turda Corridor .

Figure 3. Day/night frequency of counts by wind direction (%)
2. The incidence of foehn periods did not exclude, according to the dominant dynamics,
any of the eight analyzed (Fig. 4). The maximum number of cases with foehn was
recorded during spring and the minimum during summer. March was characterized by
identifying six periods with foehn and the most representative hourly interval with gusts
Figure 2. Annual frequency of counts by wind
direction (%)

Physical Geography
and wind speeds over 10 m / s (42 hours). In August, a foehn episode was identified,
characterized by the rapid increase of air pressure at the Cotnari weather station, from
1020 to 1025 mb / between 00:30 and 11:30 and thermal differences over 10.0 ° C /
between 05:30 and 10:30 at the observed weather station located to the east of Cotnari,
respectively: Belcești, Erbiceni, Focuri, Movileni, Rediu .

Figure 4. Monthly frequency of counts by wind direction (%)

In selecting the beginning of the hourly intervals with foehn, the increase of the wind
speed was taken into account, the foehnal intervals ending with a reduction of the speed
at the initial values. The high fre quency of the foehn was highlighted between 03:30 and
12:30, during which gusts of wind speeds of over 10 m / s were recorded, characteristic
especially of the sunrise hours between 05: 30 -08: 30 (Fig . 5a, Fig. 5b ).

Figure 5 a. Average hourly frequency of wind speed at Cotnari Weather Station (01.03.2019 -31.10.201 9)

International Scientific Conference GEOBALCANICA 20 20

Figure 5 b. The real distribution of wind speed (m / s) from the theoretical distribution at Cotnari Weather
Station (01.03.2019 -31.10.201 9)

3. After monitoring for 8 months (between 01.03.2019 at 00:30:00 and 31.10.2019 at
23:30:00) the temperature and relative humidity of the air for the 12 weather stations
located to the west and east of Cotnari and processing the data from the field, we were
able to capture several aspects.

Physical Geography

Figure 6.The thermal field at the height of 2 m from Cotnari surroundings – the average situation between
01.03.2019 at 00:30:00 and 31.10.2019 at 23:30:00 – above; thermal profile between the western and
eastern extremities of the investigated territory – below
In terms of thermal changes, we noticed the very strong increase of the air temperature
from average values around 14.5 – 15 ° C to the west and near the main hilly peak on
which Humosu weather station is located, up to 17 – 17.5 ° C between Cotnari and
Belcești, to the east of the main hilly alignment responsible for the genesis of the
foehnal circulation (Fig. 6). Taking into account the average altitude gap of 232 m
between Humosu and Cotnari -Belcești weather stations, the average thermal difference
of 2.5 ° C between them and the average thermal gradient value of 0.46 ° C / 100 m
specific to the Moldavian Plain [10 ], we can assign the additional thermal difference
that exceeds by 1.3 – 1.5 ° C the value of the vertical av erage thermal gradient (which is
1 ° C / 232 m) of the foehnal air circulation.
In terms of hygrometric changes, the effects of the foehn are transposed by decreases of
almost 8 – 9% of the average humidity values between the Humosu and Cotnari –
Belcești weather stations, under the conditions in which the vertical vertical gradient
specific to the Moldavian Plain (0.5% / 100 m – [10] it would indicate for the same
territory value decreases for this element of only 1% (Fig. 7).

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Figure 7. The relative humidity field at the height of 2 m from Cotnari surroundings – the average
situation between 01.03.2019 at 00:30:00 and 31.10.2019 at 23:30:00 – above; the hygric profile between
the western and eastern extremities of the investigated territory – below
The foehnal effects are felt more strongly in thermal and hygric plane to the east of
Humosu over a distance of about 35 -40 kilometers (Figs. 6 and 7), up to the Cotnari –
Belcești localities. To the east of the Cotnari – Belcești weather stations, towards the
Jijia-Prut valleys the temperature drops slightly, and the humidity also increases
slightly, the foehnal effects fading .

Analyzing Fig. 8, which
represents the situation of
the distribution of the
average values of air
temperature and humidity in
the space related to Cotnari
for the enti re studied period,
we can see the
materialization of a turning
point in the temperature and
humidity of air at Humosu, a
geographical landmark in
the east, where the foehnal
circulation becomes a reality
through from its thermo –
hygric effects. These
influe nces are stronger until
Belcești and then gradually
fade as the distance from
Cotnari – Belcești increases.
The characterization of the
foehn in Cotnari, during the 8 months (between 01.03.2019 at 00:30:00 and 31.10.2019
at 23:30:00), is in the beginning stage of the researches, and these will be completed
later by more case studies and for a cumulative period of two years (March 2019 -March
2021). In this way, valuable topoclimatic conclusions will be drawn regarding the
dynamics of the air in th e investigated area. The topoclimatic information will be
supplemented by the longer term climate research (1960 -2020), with the inclusion in the
analysis of data from the Cotnari weather stations, but also of other weather stations
located near it (Botoșa ni, Iași, Roman, Suceava).

Figure 8.The temperature (°C) and air humidity (%) distribution at
a height of 2 m in the geographical area of Cotnari between
01.03.2019 at 00:30:00 and 31.10.2019 at 23:30:00

Physical Geography
Case study regarding the foehn produced on 11.10.2019

Proceeding to a more detailed investigation of one of the 20 foehn cases mentioned
(Tab. 2), we could observe that in the typical situations with foehn, the temperature
increase on the E -SErn slopes of the Moldavian Coast is higher in the direction of the
Cotnary locality than indicates the average meteorological statistics (Fig. 6 and Fig.7).
According to the data and the cartographic / graphical representations, the air
temperature increase due to foehn (and which was added to the one due to the average
vertical thermal gradient of almost 1 ° C to 200 m altitude difference) was in this case of
3.5 ° C (Fig. 9 ), and the decrease of the relative humidity due to foehn of 19% (Fig.
10). In this case we will also add the hygric difference due to the gradient of this
element (of 1% / 200 m). Hence, the final result is that the hygric decrease between
Humosu and Cotnari -Belcești can be attribuited, in a percentage of 95%, to the f oehn
circulation .

Figure 9. The thermal field at the height of 2 m in Cotnari surroundings – the situation between
11.10.2019 at 00:30:00 and 11.10.2019 at 14:30:00 – above; thermal profile between the western and
eastern extremities of the investigated territory – below

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Figure 10. The field of relative humidity of the air at the height of 2 m from Cotnari surroundings – the
situation between 11.10.2019 at 00:30:00 and 11.10.2019 at 14:30:00 – up; the hygric profile between the
western and eastern extremities of the investigated territory – down

The foehn episode unfolded between 11.10.2019 at 00:30:00 and 11.10.2019 at
14:30:00, graphically analyzed through Fig. 11 presents a series of particularities: the
starting point, the extreme west of the triggering of the local foehn effects circulation is
placed near the Humosu weather station, the thermal and hygric effects of the foehn are
amplified over a distance of 25 -30 km to the east, reaching the maximum in the
perim eter of the Cotnari -Cucuteni -Belcești weather stations, after which towards the
valleys of the Jijia and the Prut, the characteristics are markedly differentiated from the
area of maximum specified leaf influence.
On 11.10.2019, in Europe the synoptic situ ation was characterized by the presence of an
anticyclonic belt developed over the Atlantic Ocean and extended in the center, south
and southwest of the continent. Northern Europe was under the influence of the
Icelandic Cyclone, the lowest pressure being in the Norwegian Sea region, and the south
was influenced by the Mediterranean Cyclone, which extended into northern Africa and
the eastern sea basin.

Physical Geography

The Cotnari geographical
area was at that time on the
front of the anticyclonal belt
that occupied the center of
Europe from west to east, in
a position where the air
circulation in the western
sector was fully favored, the
local -relief geographic
factor, playing its role of
generator and amplifier of
the observed foehn effects
(Fig. 12). Consulting the
meteorological data in the
aerological context given by
the air charts from
11.10.2019 from Bucharest (the only ones from outside the Carpathians with relevance
and for the searched territory – the source of the diagrams: LRBS Bucharest Inmh –
Banesa) I could notice the fact that the movement of the air from the target area was
carried out in a laminar flow, without significant shears and gusts (maximum wind
speed was 7 m / s), which allowed the foehn area effects to materialize very well in the
Cotnari -Cucuteni area -Belcești.

Figure 12. The synoptic situation in Europe on 11.10.2019 at 13.00 (source: www.pogodynka.pl.)

Figure 11.Temperature distribution (° C) and air humidity (%) at a
height of 2 m in the geographical area of Cotnarilor between
11.10.2019 at 00:30:00 and 11.10.2019 at 14:30:00

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Following the air temperature evolution during the night 11.10.2019 in a wider
geographical context (the air temperature map for that interval consulted on the website:
www.meteoromania.ro), we could notice the formation of the heat island in the Cotnari
area, and at neighboring weather stations, the fact that the thermal values were lower
than in the investigated area .

CONCLUSIONS

The foehn in Cotnari is a local wind with meteorological consequences that can not be
minimized. Monitoring for 8 months (between 01.03.2019 at 00:30:00 and 31.10.2019
at 23:30:00) the state of the weather in Cotnari area allowed us to draw important
concl usions regarding the consequences of regional and local circulation.
The total duration of the foehn in Cotnari according to our preliminary research is 4.5%
of the total observed time. The consequences of the foehn start at Humosu and reach the
Jijia-Prut valleys, but are stronger over a distance of 25 -40 km east of Humosu.
The area with the greatest thermo -hygrometric impact is that around the weather
stations: Cotnari, Cucuteni, Belcești.
During the researched period, the foenal circulation led to a ther mal advance of 1.3 –
1.5°C and to a hygric deficit of 8 -9%, in the territory situated at east of Humosu. In the
period between 11.10.2019 at 00:30:00 and 11.10.2019 at 14:30:00 the consequences of
the foehn were even more evident (the temperature increase wa s of 3.5 ° C in this case,
and the value of relative humidity decrease of 19% due to the foehn).
These preliminary results entitle us to continue and deepen the research regarding the
foehn in Cotnari, especially that the researched area is a vineyard of particular
importance .

Acknowledgement :
This work is supported by project POCU 125040, entitled "Development of the tertiary
university education to support the economic growth – PROGRESSIO", co -financed by
the European Social Fund under the Human Capital Operational Program 2014 -2020.

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Physical Geography
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***WMO -The World Meteorological Organization, 1992
*** www. pogodynka.pl
*** www.meteoromania.ro