Assessment of hydrological drought in the north-eastern part of Romania

On the background of amplification of hydro-climatic drought in the last decades, in this paper we try to evaluate a series of indexes for assessing hydrological droughts. To characterize the hydrological drought, minimum flow parameters are successively analyzed: percentiles from the flow duration curve, mean annual minimum flow, base flow index and recession indeces. Also was used some indices to evaluate the water deficit from streams like thereshold level method and the sequent peak algorithm. Each method was exemplified using data from hydrometric stations from Bahlui drainage basin and associated data from 2012 summer drought. The results show that in the 2002-2014 period, the average drought duration of the cold season is 23 days, but with a low water deficit due to conditions of quartering it in the form of ice and snow layer. In summer season, the average lenght of hydrological drought is 22 days, with a huge water deficit which may exceed 37.5 mil. m3 as happened in the summer of 2012

THE COLD WAVE OF THE 25 JANUARY – 18 FEBRUARY 2012 PERIOD ON THE TERRITORY OF THE REPUBLIC OF MOLDOVA

In the present article, the cold wave of January 25-February 18, 2012 is described from the climatic point of view, in terms of indicators such as average daily temperature, minimum temperature, maximum temperature, etc. Factual material was provided by the State Hydro-Meteorological Service (SHS), for a network of 18 weather stations. It is emphasized the risk aspect of the mentioned cold wave on the socio-economic life of the Republic of Moldova

Characteristics of nocturnal urban heat island of Iaşi during a summer heat wave (1-6 of august 2017)

This paper aims to investigate in details the specific of the nocturnal urban heat island in Iaşi city area during a particular heat wave in summer time. For this, we have conducted a series of expeditionary measurements on air temperature for the interval between 1 and 6 of August 2017 which was charaterized by excessive heat conditions. Air temperature measurements were made around midnight time and were performed along westeast transects crossing the city.The main results show an intensity of 3-4°C for the nocturnal urban heat island of Iaşi during heat wave condition. Beside this, the structure of the urban heat island was also influenced by the atmospheric stability which enhanced the occurence thermal inversion phenomena. In these conditions more dense cold air descends on the rivers valleys generating strong cooling of 4.0-5.0°C in low area of the city comparatively to the city center

Late snowfall and blizzards in Moldavia. April 2017 summary case of study

While these are normal phenomena for Romania’s geographical position, heavy snows and intense blizzards can have severely negative effects, especially when they occur unseasonably, before or after the typical period. The blizzard recorded on 19-20 April 2017 was particularly violent and one of the latest blizzard events in the history of meteorological observations. In comparison, the last significant late winter event, albeit lower in intensity, was recorded on 15-16 April 1996. However, the blizzard formation mechanism in the month of April in eastern regions is relatively similar. The presence of a high-pressure zone in the central-western European region led, in both cases, to fast large-scale penetrations of arctic air from high latitudes towards areas with high cyclogenetic potential in the Mediterranean Sea basin. Thus, the depressions of Mediterranean origin, which formed in the Genova Gulf area, advanced towards the Black Sea basin via trans-Balkan trajectories, where they regenerated and resulted in strong windintensification and abundant precipitation in the Moldavian region. With regard to the event this study analyses, the high thermobaric contrast and the presence of a sufficiently cold air mass favored, during the night between the 19th and the 20th of April, the occurrence of a strong blizzard event in Moldavia, following abundant wet snowfall during the day. At several meteorological stations across Moldavia and Transylvania, as well as in mountainous areas, the maximum winter snow layer thickness was exceeded on the 20th and 21st of April

THE STATUS OF ATMOSPHERIC INSTABILITY INDICES ASSOCIATED WITH HAIL EVENTS THROUGHOUT MOLDOVA

The lower pressure of water vapor of the outer eastern and south-eastern Carpathians, as well as in Dobrogea, determines within these areas an average annual number of days of under 2 days. In sheltered areas from Bârlad Plateau the average multi-annual value decreases even below 0,5 days. Hail events that affect the territory of Moldova are, in most cases, caused by thunderstorms during May and June (frequency of over 60 %). We had analysed in the present paper a representative number of statistical severe convective events causing hailstorms and material damage between 1990-2013 period. Values of atmospheric instability indices have been analyzed for these episodes as CAPE (Convective available potential energy), SWEAT (severe weather threat), Li (lifted index), KI (K index), TT (total totals) to evaluate their medium range forecast under the hail production conditions. These indicators measure the degree of atmospheric instability providing information about possible occurrence of clouds with large vertical extent. The most powerful correlations have been recorded in the case of parameter LI, for which the daily mean value was used. The status of these indices is assessed for both the days with hail, but also on previous intervals with hail to assess their capacity to forecast this extreme weather phenomenon

The influence of solar activity on action centres of atmospheric circulation in North Atlantic

We analyse the response of sea level pressure and mid-tropospheric (500 hPa) geopotential heights to variations in solar activity. We concentrate on the Northern Hemisphere and North Atlantic in the period 1948–2012. Composite and correlation analyses point to a strengthening of the North Atlantic Oscillation and weakening (i.e. becoming more zonal) of the Pacific/North American pattern. The locations of points with lowest and highest sea level pressure in the North Atlantic change their positions between low and high solar activity

EVALUATION OF ENVIRONMENTAL INDUCED SUSCEPTIBILITY TO WINDFALLS IN THE HYDROGRAPHIC BASIN OF MOLDOVA RIVER

Windfalls are caused by the interaction of several factors and occur in a meteorological context characterized mainly by high wind speeds. In the present study we tried to develop a method for predicting windfalls in a test region, determining areas of high susceptibility of this climatic risk. For this purpose we evaluated parameters regarding the morphometric (slope, exposition, altitude) and morphological (mountain side concavity/convexity, slope break) properties of the relief, the types of forest and the soil on which these grow. We gave susceptibility scores for each parameter considered, resulting in a series of classified layers. These were subsequently added up to form the final cartographic material which highlights the vulnerable areas. For validating the results we utilised LandSat images from different time periods. The existence of a major windfalls event in the studied region (March 2002) allowed us to compare the situation before and after the event, and to check if there is a correlation with the model developed in this analysis. On the basis of this study it may be possible to predict the future evolution of trees susceptibility to windfall which could be helpful in establishing silvic measures to be implemented in order to minimize the damage caused by these phenomena

Shifts in climate suitability for wine production as a result of climate change in a temperate climate wine region of Romania

International audienc