Weather and Climate Facts for Year 2019 in Bulgaria

Bulgarian Journal of Meteorology and Hydrology Национален National институт по Institute метеорология и of Meteorology хидрология and Hydrology Bul. J. Meteo & Hydro 24/2 (2020) 114-136 Weather and climate facts for year 2019 in Bulgaria Ilian Gospodinov, Liliа Bocheva, Krastina Malcheva, Boryana Tsenova, Lyubov Trifonova National Institute of Meteorology and Hydrology, Tsarigradsko shose 66, 1784 Sofia, Bulgaria Abstract: This is a review paper describing climate and weather facts for year 2019 in Bulgaria. They are based on meteorological data from the National Institute of Meteorology and Hydrology (NIMH), which is its national weather service, but also from other sources of data and information. The paper is an adapted text from the Annual hydro-meteorological bulletin of NIMH, published in March 2020. Target readers are the wider meteorological scientific community in Bulgaria and around the world. The measurements and analyses discussed here reveal that 2019 is the warmest in Bulgaria since 1930 and the annual precipitation amounts are around or below normal. Keywords: Weather, climate, national annual meteorological bulletin. 1. INTRODUCTION The National Institute of Meteorology and Hydrology (NIMH) – the national hydro- meteorological service of Bulgaria – issues a Monthly hydro-meteorological bulletin, ISSN 1314-894X. Its last edition for the previous month is available online at http:// www.meteo.bg/meteo7/sites/storm.cfd.meteo.bg.meteo7/files/Bulletin.pdf. The text is in Bulgarian. In March 2020 NIMH issued an Annual hydro-meteorological bulletin for year 2019 containing analyses and data based on the monthly bulletins for the year as well as other sources of information. It can be found online at the official web-site of NIMH http://www.meteo.bg/ but will be replaced by a new yearly 2020 issue by March 2021. This paper presents an adapted version in English of the meteorological part of the annual bulletin for 2019. The aim is to reach out the international scientific meteorological community on the pages of this journal. The information presented is divided in section devoted to atmospheric circulation and annual summary of the most important meteorological elements such as temperature, precipitation, wind, sunshine, snow cover. Time-series of temperature and precipitation for the last decades are also 114 Ilian Gospodinov et al. given. The most significant weather events for the year are listed and analyzed. The paper follows the model of similar documents of other meteorological services around the world like, for example, the UK MetOffice (Kenton et al. 2019) and the Meteorological agency of Japan and their Climate change monitoring report, 2018. The data given in the paper are from the networks of stations of NIMH. The networks comply with the standards of the World Meteorological Organization (WMO). All data undergo daily quality control before being used for climate assessment. The reference climate period is 1961-1990 as with the WMO current recommendation. For some parameters however the reference period is more recent – 1981-2010 because there are no time-series long enough to cover the recommended period 1961-1990. Most of the parameters on the maps show deviation from the climate normals. Nevertheless, to give an idea of the characteristic values of the meteorological parameters, maps of their actual annual and seasonal averages are also shown. Maps of actual monthly averages can be found in the issues of the Monthly Hydrometeorological Bulletin of NIMH for 2019 (see reference). The categories below, around, and above normal are often used and they are defined against the climate normal for the WMO recommended period 1961-⁠1990 unless stated otherwise. Rounded numbers appear often but exact numbers have been used for the computations. 2. METEOROLOGICAL FACTS FOR YEAR 2019 Year 2019 was the warmest since 1930. The mean annual temperature in average for the country is 12.5°С, which is 2°С above the climate normal for 1961-1990. The mean annual country-mean maximum temperature is 18.8°С, which is 3°С above normal. The highest measured maximum temperature was 39.4°С registered in Radnevo, region of Stara Zagora, on 3.VII. The mean annual country-mean minimum temperature is 7.2°С, which is 1.8°С above normal. The lowest measured minimum temperature is ‒24.4°С registered in the weather station on peak Mussala (2925 m) on 7 and 8.I. The lowest minimum temperature, measured in stations below altitude of 1500 m, is ‒21.5°С in Koprivshtitsa, region of Sofia, on 8.I. The annual country-mean amount of precipitation is 573 mm that is 89% of normal. The biggest daily amount of precipitation was 197 mm from rain, registered in Dermantsi, region of Lovech, on 21.V. The strongest wind speed in populated area was 40 m/s from northeast, measured in Sliven on 22.II. The deepest snow cover in populated area was 110 cm in Manastir (1500 m above sea level), region of Smolyan, registered on 16.II. The deepest snow in stations on mountain tops was measured at Rozhen (1750 m), region of Smolyan, on 1.II – 189 cm. 115 Weather and climate facts for year 2019 in Bulgaria The day with the biggest number of registered lightning flashes (49000) in the country was 24.VI. It was also the day with the highest number of flashes ever measured in Bulgaria since 2012. These statistics are based on data from ATDNet. 3. ATMOSPHERIC CIRCULATION Figure 1 shows the mean seasonal height at geopotential surface of 500 hPa as deviation from normal for all seasons of 2019. The reference period is 1981-2010. Maps are based on the atmospheric reanalysis of Kalnay et al. (1996) and are produced on the website of NOAA-ESRL Physical Sciences Division, Boulder, Colorado, http://www. esrl.noaa.gov/psd/. (a) (b) (c) (d) Fig. 1. Deviation of the mean seasonal height (m) of geopotential surface at 500 hPa relative to the seasonal average for 1981-2010 for the four seasons of 2019: (a) – winter; (b) – spring; (c) – summer, and (d) – autumn. 116 Ilian Gospodinov et al. Figure 2 shows the mean seasonal surface pressure as deviation from normal (reference period 1981-2010). The maps are based on the atmospheric reanalysis of Kalnay et al. (1996). This gives a general idea of the atmospheric circulation for each season. (a) (b) (c) (d) Fig. 2. Deviation of the mean seasonal surface pressure (mb) from the normal for 1981-2010: (a) – winter; (b) – spring; (c) – summer; (d) – autumn. In the winter1 of 2019, Bulgaria was under the influence of a zone with cyclonic activity in the Eastern Mediterranean (Fig. 1а) and the mean seasonal surface pressure was lower than normal (Fig. 2a). There was no apparent dominant circulation pattern in the region of the country in spring2 (Fig. 1b) and the mean seasonal surface pressure was close to normal (Fig. 2b). There was an anticyclonic anomaly in Central Europe in summer3 influencing Bulgaria (Fig. 1c) but the mean seasonal surface pressure was 1 Winter 2019 is the three-month period December 2018 – January 2019 – February 2019. December 2019 will be counted for winter 2020. 2 Spring is the three-month period March-April-May. 3 Summer is the three-month period June-July-August. 117 Weather and climate facts for year 2019 in Bulgaria close to normal (Fig. 2c). In autumn4 the country was on the western periphery of an area of anticyclonic circulation (Fig. 1d) but the mean seasonal surface pressure was relatively low (Fig. 2d). 4. TEMPERATURE 4.1. General analysis of temperature Figure 3 shows maps of the mean annual temperature for year 2019 and its deviation from the normal. The mean annual country-mean temperature5 is 12.5°E. Fig. 3. (a) Mean annual temperature (°С) for 2019 and (b) its deviation from normal Fig. 4. Mean annual country-mean temperature for 1930-2019 as deviation from normal. 4 Autumn is the three-month period September-October-November. 5 The mean annual country-mean temperature is based on data from all stations of NIMH with continuous time-series for the period 1930-2019. 118 Ilian Gospodinov et al. Figure 4 shows the time-series of the annual mean temperature for the period 1930- 2019 for the whole country as deviation from normal. The mean annual temperature for 2019 is 2°С above normal. It is seen that year 2019 is the warmest one since 1930. Figure 5 shows maps of the mean seasonal temperature and its deviation from normal for the four seasons. Figure 6 shows maps of the deviation from normal of the mean monthly temperature for all 12 months of 2019. (a) (b) (c) (d) (e) (f) (g) (h) Fig. 5. Mean seasonal temperature (°С) (left) and its deviation from normal (°С) (right) for the four seasons of 2019: (1st row) – winter; (2nd row) – spring; (3rd row) – summer; and (4th row) – autumn. 119 Weather and climate facts for year 2019 in Bulgaria I II III IV V VI VII VIII IX X XI XII Fig. 6. Mean monthly temperature (°С) as deviation from the norm (°С) for year 2019 Autumn is the warmest season relative to the norm. It can be seen on Figure 5. The autumn of 2019 is one the five warmest since 1950. Summer is warmer than normal too but there have been hotter summers in the recent years. Winter and spring are with mean seasonal temperature near and above normal. The mean annual country-mean maximum temperature is 18.8°С, which is 3°С above normal. The annual mean country-mean minimum temperature is 7.2°С, i.e. 1.8°С above normal. The annual highest maximum temperature is 39.4°С and was registered in Radnevo, region of Stara Zagora, on 3.VII.

Load more