Fig. 1.
Course of average annual air temperature (°C) and annual totals of sunshine duration (SD in hours) in Kraków (1951–2020).
Fig. 2.
Ranges of variability of annual air temperature (°C) and annual sums of sunshine duration (SD in hours) in Kraków in the years 1951–1988 and 1988–2020.
Fig. 3.
Course of annual cloudiness values (oktas) in Kraków in the period 1951–2020, and ranges of its variability in periods 1951–1988 and 1988–2020.
Table 1.
Correlation coefficients (r) and their statistical significance (p) between the annual frequency of cloud types and annual sunshine duration (SD), average annual air temperature (T), and cloudiness (N) in Kraków in the years 1951–2020 (bold values are significant in level p < 0.05).
| Element | Cloud genera | Cloudless sky | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Ci | Cc | Cs | Ac | As | Ns | Sc | St | Cu | Cb | |||
| SD | r | 0.61 | 0.62 | 0.10 | 0.01 | –0.45 | –0.37 | 0.25 | –0.41 | 0.59 | 0.14 | –0.03 |
| p | 0.000 | 0.000 | 0.395 | 0.942 | 0.000 | 0.002 | 0.040 | 0.000 | 0.000 | 0.264 | 0.800 | |
| T | r | 0.49 | 0.40 | 0.01 | 0.08 | –0.53 | –0.46 | 0.38 | –0.55 | 0.52 | 0.30 | –0.17 |
| p | 0.000 | 0.001 | 0.913 | 0.491 | 0.000 | 0.000 | 0.001 | 0.000 | 0.000 | 0.012 | 0.149 | |
| N | r | –0.02 | 0.16 | 0.48 | 0.01 | 0.58 | 0.60 | –0.09 | 0.64 | –0.04 | –0.48 | –0.52 |
| p | 0.851 | 0.190 | 0.000 | 0.966 | 0.000 | 0.000 | 0.456 | 0.000 | 0.735 | 0.000 | 0.000 | |
Fig. 4.
Ranges of variability in the number of days with observations of frontal clouds (As, Ns, St) and clouds occurring in unstable weather conditions in Kraków during the periods 1951–1988 and 1988–2020.
Fig. 5.
The course of the observed mean annual air temperature (°C) in Kraków (Obs) and the estimated air temperature based on sunshine duration (est) from 1951 to 2020. The trend values are marked in boxes (with the standard error of estimation values in parentheses).
Table 2.
Correlation coefficients (r) and their statistical significance (p) between monthly and annual air temperature and the annual sunshine duration (SD) in Kraków, the North Atlantic Oscillation PC DJFM Hurrell index (NAO), and radiative forcing (△F) during the years 1951–2020 (bold values are significant in level p < 0.05).
| Month | SD | NAO | ΔF | |||
|---|---|---|---|---|---|---|
| R | p | r | p | r | p | |
| I | 0.35 | 0.003 | 0.51 | 0.000 | 0.24 | 0.045 |
| II | 0.22 | 0.074 | 0.40 | 0.001 | 0.28 | 0.020 |
| III | 0.26 | 0.027 | 0.54 | 0.000 | 0.33 | 0.006 |
| IV | 0.51 | 0.000 | 0.24 | 0.043 | 0.43 | 0.000 |
| V | 0.29 | 0.014 | 0.07 | 0.593 | 0.36 | 0.002 |
| VI | 0.63 | 0.000 | 0.13 | 0.292 | 0.45 | 0.000 |
| VII | 0.59 | 0.000 | 0.19 | 0.112 | 0.45 | 0.000 |
| VIII | 0.68 | 0.000 | 0.28 | 0.019 | 0.55 | 0.000 |
| IX | 0.49 | 0.000 | 0.18 | 0.130 | 0.21 | 0.074 |
| X | 0.16 | 0.187 | 0.08 | 0.526 | 0.16 | 0.175 |
| XI | 0.29 | 0.014 | –0.16 | 0.176 | 0.20 | 0.105 |
| XII | 0.25 | 0.036 | 0.18 | 0.145 | 0.17 | 0.154 |
| year | 0.76 | 0.000 | 0.54 | 0.000 | 0.64 | 0.000 |
Fig. 6.
The course of the North Atlantic Oscillation principal components (NAO PC) DJFM Hurrell index from 1951 to 2020 and the ranges of its variability in the periods 1951–1988 and 1988–2020.
Fig. 7.
Course of the observed mean annual air temperature (°C) in Kraków (Obs) and the estimated (est) from the course of two variables: sunshine duration (SD) and North Atlantic Oscillation (NAO) in the years 1951–2020. The trend values are marked in the boxes (with standard error of estimation values in parentheses).
Fig. 8.
Course of the observed mean annual air temperature (°C) in Kraków (Obs) and the estimated (Est) from the course of radiative forcing in the years 1951–2020.
Fig. 9.
The course of the observed annual average air temperature (°C) in Kraków (Obs) and the estimated (est) temperature based on the course of three variables: sunshine duration (SD), North Atlantic Oscillation (NAO), and △F from 1951 to 2020.
Fig. 10.
Course of the observed average annual air temperature (°C) in Kraków (Obs) and the estimated temperature (Est) based on the course of two variables sunshine duration (SD) and North Atlantic Oscillation (NAO) and three variables (SD, NAO, and △F) in the years 1951–2020. Trend lines are marked. The differences between the observed temperature trend and the estimated temperature trend based on three variables are so small (0.001°C · year−1) that they overlap in the graphical representation