Fig. 1.
The study area with the analysed synoptic stations marked.
Table 1.
Basic parameters of the analysed research stations which are arranged in the west-east direction; TN – tropical night.
| Station | Longitude | Latitude | Altitude [m a.s.l.] | TN/10 years growth |
|---|---|---|---|---|
| Szczecin | 14°37'22" | 53°23'43" | 1 | 0.12 |
| Gorzów Wielkopolski | 15°16'38" | 52°44'28" | 71 | 0.50 |
| Zielona Góra | 15°31'28" | 51°55'49" | 192 | 0.51 |
| Poznań | 16°50'09" | 52°25'02" | 88 | 0.46 |
| Wrocław | 16°54'00" | 51°06'12" | 120 | 0.25 |
| Opole | 17°58'08" | 50°37'37" | 163 | 0.30 |
| Gdańsk | 18°29'12" | 54°22'16" | 7 | 0.41 |
| Toruń | 18°35'43" | 53°02'31" | 69 | 0.32 |
| Katowice | 19°01'58" | 50°14'26" | 278 | 0.08 |
| Łódź | 19°23'59" | 51°43'24" | 174 | 0.06 |
| Kraków | 19°48'07" | 50°04'49" | 236 | 0.00 |
| Olsztyn | 20°25'22" | 53°46'16" | 133 | 0.06 |
| Kielce | 20°41'32" | 50°48'37" | 260 | 0.03 |
| Warszawa | 20°57'40" | 52°09'46" | 106 | 0.42 |
| Rzeszów | 22°02'32" | 50°06'39" | 206 | 0.34 |
| Lublin | 22°23'37" | 51°13'01" | 238 | 0.02 |
| Białystok | 23°09'44" | 53°06'26" | 148 | 0.11 |
Fig. 2.
Sum of tropical nights (TNs): A – for the entire period 1951–2024; B – for individual decades (1951–2020) and years 2021–2024.
Fig. 3.
Distribution of tropical nights (TNs) in individual years. Stations are arranged in the west-east direction.
Fig. 4.
Number of days between the occurrence of the first and last tropical night (TN) in particular years in the analysed area.
Fig. 5.
Time range of the occurrence of tropical nights (TNs) in individual years, together with the number of stations at which tropical nights occurred simultaneously.
Fig. 6.
Number of days, total number of tropical nights (TNs), and number of cities where tropical nights (TNs) occurred in individual years.
Table 2.
Tropical nights divided by month at individual synoptic stations.
| Station | Month | |||||
|---|---|---|---|---|---|---|
| May | June | July | August | September | Sum | |
| Szczecin | 0 | 5 | 24 | 16 | 2 | 47 |
| Gorzów Wielkopolski | 0 | 10 | 34 | 25 | 2 | 71 |
| Zielona Góra | 1 | 26 | 73 | 59 | 2 | 161 |
| Poznań | 0 | 13 | 34 | 24 | 2 | 73 |
| Wrocław | 0 | 6 | 13 | 15 | 1 | 35 |
| Opole | 0 | 4 | 23 | 16 | 2 | 45 |
| Gdańsk | 0 | 1 | 38 | 36 | 0 | 75 |
| Toruń | 0 | 14 | 23 | 20 | 2 | 59 |
| Katowice | 0 | 4 | 10 | 5 | 0 | 19 |
| Łódź | 0 | 4 | 20 | 12 | 0 | 36 |
| Kraków | 0 | 2 | 7 | 4 | 0 | 13 |
| Olsztyn | 1 | 5 | 13 | 6 | 1 | 26 |
| Kielce | 0 | 3 | 3 | 3 | 0 | 9 |
| Warszawa | 0 | 10 | 31 | 21 | 0 | 62 |
| Rzeszów | 0 | 3 | 21 | 8 | 1 | 33 |
| Lublin | 0 | 2 | 7 | 6 | 0 | 15 |
| Białystok | 0 | 1 | 6 | 1 | 0 | 8 |
| Sum | 2 | 113 | 380 | 277 | 15 | 787 |
| Percentage | 0.25 | 14.36 | 48.28 | 35.20 | 1.91 | 100.00 |
Table 3.
Tropical nights (TNs) divided by month in individual decades (1951–2020) and years 2021–2024.
| Decade | Month | |||||
|---|---|---|---|---|---|---|
| May | June | July | August | September | Sum | |
| 1951–1960 | 0 | 4 | 18 | 5 | 0 | 27 |
| 1961–1970 | 0 | 4 | 11 | 16 | 0 | 31 |
| 1971–1980 | 0 | 3 | 15 | 10 | 0 | 28 |
| 1981–1990 | 1 | 3 | 33 | 13 | 0 | 50 |
| 1991–2000 | 0 | 9 | 38 | 45 | 0 | 92 |
| 2001–2010 | 1 | 10 | 117 | 25 | 0 | 153 |
| 2011–2020 | 0 | 45 | 86 | 116 | 11 | 258 |
| 2021–2024 | 0 | 35 | 62 | 47 | 4 | 148 |
| Sum | 2 | 113 | 380 | 277 | 15 | 787 |
| Percentage | 0.25 | 14.36 | 48.28 | 35.20 | 1.91 | 100 |
Table 4.
Duration of tropical nights in stations which are arranged in the west-east direction.
| Station | Duration | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| 1 day | 2 days | 3 days | 4 days | 5 days | 6 days | 7 days | 8 days | 9 days | Number of periods | Total days | |
| Szczecin | 44 | 1 | 45 | 47 | |||||||
| Gorzów Wielkopolski | 45 | 10 | 2 | 57 | 71 | ||||||
| Zielona Góra | 77 | 20 | 7 | 1 | 2 | 1 | 108 | 161 | |||
| Poznań | 50 | 10 | 1 | 61 | 73 | ||||||
| Wrocław | 33 | 1 | 34 | 35 | |||||||
| Opole | 37 | 4 | 41 | 45 | |||||||
| Gdańsk | 30 | 10 | 3 | 1 | 1 | 1 | 46 | 75 | |||
| Toruń | 41 | 6 | 2 | 49 | 59 | ||||||
| Katowice | 19 | 19 | 19 | ||||||||
| Łódź | 30 | 3 | 33 | 36 | |||||||
| Kraków | 11 | 1 | 12 | 13 | |||||||
| Olsztyn | 20 | 3 | 23 | 26 | |||||||
| kielce | 9 | 9 | 9 | ||||||||
| Warszawa | 41 | 6 | 3 | 50 | 62 | ||||||
| Rzeszów | 27 | 3 | 30 | 33 | |||||||
| Lublin | 15 | 15 | 15 | ||||||||
| Białystok | 8 | 8 | 8 | ||||||||
| Sum | 537 | 77 | 19 | 2 | 3 | 0 | 1 | 0 | 1 | 640 | 787 |
Fig. 7.
Location of synoptic stations relative to city centres. The figure was made based on maps from website: klimat.imgw.pl/pl/meta-dane/.