The results of this study are discussed zone-wise and thereafter the new findings of the Karakoram anomaly. Considering the importance of the Karakoram region, climate extremes are also presented for each station in this region.
2.1 Zone wise results
The differences between the two-time slices (1991-2019 and 1962-1990) were tested for possible significance in temperature and precipitation on a seasonal basis. A significant increase in temperature during DJF and MAM and a significant decrease during JJA and SON was observed as shown in Table 2. Precipitation increased significantly during all seasons except JJA. The Mann-Kendall tests’ results for maximum, minimum temperature and precipitation are shown in Table 3. For zone 1, the MK statistic for precipitation shows significantly decreasing trend with value -0.06.18. The values of MK statistic for maximum and minimum temperature are 0.07.52 and 0.07.62, respectively, indicating increasing trends. The MK test’s results support the Karakoram anomaly during the 1962-1990 given in Table 5, however, the decadal analysis during the 1990-2019 offers complex results (discussed in details under Present climatic status of Karakoram Anomaly). During the last decade, the trend analysis show that precipitation and temperature have decreasing and increasing trends, respectively, in most parts of the Karakoram.
Most of the temperature extremes are significantly increased during 1991-2019. Results related to climates’ extremes are given in Figures 3-4 for all zones. The number of frost days decreased significantly while growing season length and summer days increased significantly in zone 1 (Northern Pakistan). Interestingly, TN10P shows a significantly decreasing trend in 1991-2019 while increasing in 1962-1990. TX10P and TX90P have significantly decreasing and increasing trends during 1991-2019 and increasing and decreasing trends, respectively during 1962-1990. Most of the precipitation extremes have increasing trends during 1962-1990 and decreasing trends during 1991-2019. For example, PRCPTOT, R10mm, R20mm and R25mm have significantly increasing and significantly decreasing trend during 1962-1990 and 1991-2019, respectively. R95P decreased but R99P increased in zone 1. Spatial distribution of changes in selected temperatures’ extremes are presented in Figures 6-8 while changes in selected precipitations’ extremes are mentioned in Figure 9 for all climate zones.
The distribution of the number of CWD is displayed in Figure 5 and Figure 11 for all zones. For zone 1, the average number of CWD increased from 16 to 19 in 1991-2019 compared to 1962-1990. A strong increase in variability was observed during 1991-2019. The maximum number of CDD was 60 and 40 during 1962-1990 and 1991-2019, respectively. The number of Frost days (FD0) has decreased from 110 to 88 during 1991-2019 compared to 1962-1990 as shown in Figure 12.
The results of t-statistic (Table 2) show a significant increase in average temperature during MAM and JJA, increase during DJF, and insignificantly decrease during SON. MK results for maximum and minimum temperature indicate significantly increasing trends with values 0.0293 and 0.0938, respectively. On the other hand, average precipitation increased significantly throughout in all seasons. The MK tests’ results (Table 3) show a significantly decreasing trend in precipitation with a magnitude of -0.0141.
Interestingly, this is the only region with the increasing number of frost days and decreasing GSL in both time slices. The SU25, TMAXMean, TN90p, TR20 and TX90p increased during the 1991-2019. The TMINMean increased significantly while TX10p and TN10p both decreased significantly during the 1991-2019. The CWD, WSDI, R10mm, R20mm and R25mm decreased during the 1991-2019. The CSDI, PRCPTOT, R95p and R99p decreased during the 1991-2019. The RX1day (Max 1-day precipitation amount) and Rx5day (Max 5-day precipitation amount) increased significantly and decreased during the 1962-1990 and 1991-2019, respectively.
The average number of CWD increased from 22 to 26 in the recent period. The standard deviation of CWD has increased from 8 (during 1962-1990) to 11 (during 1991-2019). The CDD (Figure 10) slightly reduced, with insignificant variability. The average FD0 recently increased from 34 to 47.
The average temperature significantly increased in this region, except a significantly decreased for JJA with a value of -0.42. In contrast, the average precipitation increased significantly throughout except an insignificant increase during the DJF. The results of MK test show decreasing trends in precipitation change and minimum temperature change while an increasing trend for maximum temperature change with the values -0.0890, -0.0637 and 0.0645, respectively.
GSL and SU25 have increased in the recent period. TMAXMean has decreasing and significantly increasing trends in the first and second-time slice, respectively. The results of TMINMean are in contrast with TMAXMean. TN10P, TN90P, TNN, TNX, TR20 decreased in the recent time period. A significantly decreasing and increasing trends were found in TX10P and TX90P in the second time slice, respectively. In addition, most of the precipitation extremes indicate an increasing trend during the first time slice except CDD, CSDI and WSDI with decreasing trends. In contrast, most of these extremes are decreasing except CDD, R10mm, R25mm and WSDI which have increasing trends during the 1991-2021. R95P, R99P and PRCPTOT have decreasing trend in the second time slice.
The average CWD and standard deviation reduced from 8 and 6 during 1962-1990 to 7 and 3 during 1991-2019. The CDD (Figure 10) drastically decreased from 330 to 170 during 1962-1990 to 1991-2019 with decreased variability in the recent period. The average number of FD0 (Figure 12) reduced from 55 to 34 during 1962-1990 to 1991-2019.
The average precipitation and temperature changes in zone 4 are given in table 2. The average temperature changed significantly with an increase during DJF, MAM, SON and decrease during JJA. The magnitude of change during DJF and JJA were highest with values 0.6908 and -0.1703, respectively. In addition, precipitation increased significantly only during JJA and SON. The MK test shows a decreasing trend in precipitation and maximum temperature with values -0.0986 and -0.0212, respectively. The change in minimum temperature has significantly increasing trend with value a value of 0.158.
During the second time slice, GSL and SU25 increased and decreased, respectively. TMAXMean show an increasing trend in contrast to the significant decreasing trend of TMINMean. TN10P decreased during the second period compared to the first time slice. On the other hand, TN90P significantly increased during the second time slice. TX10P and TX90P shows an insignificant decrease and increase during the second time slice, respectively. During the second time slice, all precipitation extremes have decreasing trend except an increase in CWD.
The average number of CWD (Figure 5) has increased from 7 to 8 annually. The standard deviation of CWD increased from 3 to 5 during the 1991-2019. The maximum number of CWD were 19 during 1991-2019. The maximum number of CDD reduced from 225 to 149 during 1962-1990 and 1991-2019, respectively. No significant change with the average number of zero were observed in the distribution of FD0 (Figure 12).
The average temperature shows a significant increase except JJA with an insignificant change. Changes in average precipitation, except MAM are highly significant. There is a significantly decreasing trends in precipitation and maximum temperature while significantly increasing trend for minimum temperature in this zone. The values of MK test statistic for precipitation, maximum, and minimum temperature are -0.0224, -0.0157 and 0.0560, respectively.
GSL, SU25, TMINMean, and TMAXMean have increasing trends during both time slices. TN10P has decreasing trend throughout while TN90P has decreasing and significantly increasing trends in the first and second time slice, respectively. TX10P and TX90P have decreasing trends during the second time period. Most of the precipitation extremes have increasing trends during both time slices. CDD, CSDI, R99P and WSDI have decreasing trends during the first time period while CSDI, PRCPTOT, R10mm, R95P and SDII have decreasing trends during the second time period.
The average number of CWD slightly increased from 15 to 17 annually from 1962-1990 to 1991-2019 (Figure 5). In contrast, the standard deviation of CWD decreased from 8 to 6 during 1962-1989 to 1991-2019. The distribution of CDD increased from 75 to 92 during 1962-1990 to 1991-2019. The number of FD0 reduced considerably from 8 to 2 during 1962-1990 to 1991-2019 (Figure 12).
2.2 Present climatic status of Karakoram Anomaly
The widely known Karakoram anomaly is investigated to see its present status utilizing the updated observed meteorological data from the North of Pakistan as shown in Table 1. The stations are located between an altitude of 1,250 m a.s.l. at Chilas and 2,317 m a.s.l. at Skardu station. The data was analyzed seasonally to assess the contemporary climate change. The average temperature shows an interesting pattern, specifically in winter (DJF), a significant increase at high altitude station (Skardu) of 0.97 and a significant decrease at the lowest station (Chilas) of –0.56 given in Table 4. Almost similar pattern was observed during MAM with the maximum increased at Astore and decrease at Chilas station. During JJA, average temperature has been decreased at all meteorological stations. Maximum and minimum decrease in the average temperature was noted at Gopis (with the magnitude of -1.42 oC) and Darosh (with magnitude of -0.01 oC). These changes are highly significant except at Chilas meteorological station. In SON, the average temperature shows an increasing trend at all stations other than Bunji, Chilas and Gopis with decreasing trend.
Table 5 shows the seasonal trends in precipitation, maximum, and minimum temperature during 1962-1990. During DJF, precipitation has significantly increasing trend except Gopis where the trend is insignificantly decreasing. Maximum and minimum temperature results show significantly decreasing trend during JJA except Astore with insignificant decrease in maximum temperature. These results are in lines with Karakoram Anomaly during the 1962-1990. Table 6-8 show seasonal trend analysis for precipitation, maximum temperature and minimum temperature during 1990-1999, 2000-2009 and 2010-2019, respectively. Table 6 shows a comparison among three decades (1990-1999, 2000-2009, 2010-2019) using MK test for precipitation. During 1990-1999, precipitation in Gilgit and Bunji increased while in Gopis and Skardu the trends decreased in DJF. On the contrary, the trend during 2000-2009 remained increasing. The trend changed again and decreased during 2010-2019 except Gilgit with an insignificant increasing trend. The comparison of these three decades for maximum temperature is shown in Table 7. In JJA, the maximum temperature shows a decreasing trend during 1990-1999 except Gilgit and during 2000-2009 in Gopis in JJA. The trend during 2010-2019 changed and increased in most of the stations except Gilgit with insignificant decreasing trend in JJA. Minimum temperature shows increasing trend in some parts (Bunji and Gilgit) and decreasing trend in others (Gopis and Skardu) during 1990-1999 and 2000-2009 as shown in Table 8. In contrast, during 2010-2019, minimum temperature shows increasing trend. These results show conflicting signals in climate. In the most recent decade of 2010-2019, precipitation decreases in DJF and temperature (maximum and minimum) increases in JJA. It is interesting to see a consistently decreasing trend in the SON in temperature (maximum and minimum) considering the overall thirty years period (1990-2019).
The station-wise climate extremes in the northern Pakistan are shown in Figure 13. The results show that SU25 increased throughout except Skardu during 1991-2019. TN10P (cold nights) has significantly decreased at most parts of the Northern Pakistan. TN90P (warm nights), TX90P (warm days) TR20 (tropical nights) have decreasing trend during the 1991-2019 in most parts of the region. TX90P (warm days) have mixed trend, decreasing at Darosh, Gilgit and Skardu and increasing trend at the remaining station.
Figure 14 shows decreasing trend precipitation extremes except CDD and WSDI in western and eastern parts. However, CWD, R10mm, R20mm, R25mm, R95 show increasing trends while CWD and PRECPTOT show decreasing trends in the eastern-central Karakoram.