Long‐term drought monitoring and its assessment are of great importance for meteorological disaster risk management. The recurrent spells of heat waves and droughts have severely affected the environmental conditions worldwide, including Pakistan. The present work sought to investigate the spatiotemporal changes in drought characteristics over Pakistan during Rabi and Kharif cropping seasons. The role of large‐scale circulation and interannual mode of climate variability is further explored to identify the physical mechanisms associated with droughts in the region. Monthly precipitation and temperature data (1983–2019) from 53 meteorological stations were used to study drought characteristics, using the standardized precipitation evapotranspiration index (SPEI). The nonparametric Mann–Kendall, Sen's Slope, and Sequential Mann–Kendall tests were applied on the drought index to determine the statistical significance and magnitude of the historical trend. The state‐of‐the‐art Bayesian Dynamic Linear model was further used to analyse large‐scale climate drivers of droughts, revealed an increase in drought severity, mostly over arid to semiarid regions for both cropping seasons. While temperature played a significant role in defining droughts over dry and hot seasons, rainfall is influential over the western disturbances influenced region. The analysis of atmospheric circulation patterns revealed that large‐scale changes in wind speed, air temperature, relative humidity, and geopotential height anomalies are the likely drivers of droughts in the region. We found that Niño4, sea surface temperature, and multivariate El Niño‐Southern Oscillation (ENSO4.0) Index are the most influential factors for seasonal droughts across Pakistan. Overall, the findings provide a better understanding of drought‐prone areas in the region, and this information is of potential use for mitigating and managing drought risks.

Extreme hydro-meteorological events occur more frequently with global warming, which have a great impact on ecology, environment and hydrology. Hydrometeorological variables often exhibit disturbances of non-stationary characteristics.In this paper, we take a typical ecological function reserve (Poyang Lake Basin) as an instance to study the trend and probability characters of extreme streamflow based on stationary and non-stationary generalized extreme value (GEV) models. Time and large-scale climate factors such as Southern Oscillation (SO), North Atlantic Oscillation (NAO), Arctic Oscillation (AO), Pacific Decadal Oscillation (PDO), Atlantic multidecadal oscillation (AMO), NINO3 SST (NINO3) and NINO3.4 SST (NINO3.4) are incorporated as covariates to establish non-stationary model. The main results

The meteorological drought (MD) is the precursor of the hydrological drought (HD), and understanding the propagation process from MD to HD is of great significance for the early warning of HD. Based on the theory of run and Bayesian networks, this study uses the standardized precipitation index (SPI), standardized precipitation evapotranspiration index (SPEI) and standardized streamflow index (SSI) to explore the characteristics and propagation of MD and HD in the regions of eastern Gansu, China. The results indicate that: (1) The region was mainly wet (dry) and the wetness (dryness) was stronger before (after) 2000 when reflected by SSI. The frequency is higher based on SPI and SPEI than that based on SSI, while the duration and magnitude are lower than those based on SSI. (2) The propagation time from MD to HD is generally within 1–10 months. After the occurrence of a certain level of MD, it is most likely to propagate to HD events that are relatively weaker than the MD. Besides, the higher the intensity level of MD, the shorter the propagation time to HD, and the shorter for cumulative occurrence probability of HD to approach 1.0. (3) The increase in temperature and decrease in precipitation, runoff and runoff coefficient may contribute to the dryness after 2000. Moreover, the weakened propagation from MD to HD may be due to the rapid increase of water resource consumption caused by intensive anthropogenic activities in the study area. From the above results, this study found some propagation characteristics from MD to HD in a semi‐arid and semi‐humid watershed, which can provide a supplement for revealing the drought mechanism and can assist in the management and planning of water resources in China.