Drought indices and drought areas assessed from reanalysis products are relatively more representative of historical droughts that had occurred in southern Pakistan. Statistically significant increasing trends (1984–1998 and 2000–2010) in monthly drought areas and occurrence are evident by CRU TS and MERRA-2 in dominant arid and semiarid regions.

The Arctic is experiencing more frequent and more severe warm extremes in recent decades and this article documents the spatial and seasonal variations of the trends in the warm extremes across the pan-Arctic region between 1979 and 2017. Using a novel approach, the trends are apportioned into a dynamic component directly related to the changes in anomalous atmospheric circulation patterns, a non-circulation-related thermodynamic component, and an interaction component.

Data from long-term weather stations in Midwest of Brazil for validating orbital data sets via the CHIRPS product.

The evolution of global sea surface temperature trend in the past century is investigated by using an adaptive and local spatial–temporally multidimensional ensemble empirical mode decomposition method. We found that the central equatorial Pacific turned from cooling to warming around the middle of last century made it one of the fastest warming regions in recent decades with other regions located in the Arctic Ocean and the western-boundary current regions and their mid-latitude extensions in both hemispheres. Spatial evolution of the ensemble empirical mode decomposition (EEMD) trend of global sea surface temperature. (a–h), EEMD trend ending in 1910, 1925, 1940, 1955, 1970, 1985, 2000, and 2015, respectively. (i) The spatial structure of temperature increase based on time-unvarying linear trend over the whole data domain from 1900 to 2015.

An evaluation of the NA-CORDEX downscaling experiment showed improvements to the representation of historical annual precipitation patterns across the western U.S., as well as improvements to the representation of various annual and semi-annual modes of precipitation with higher resolution model members performing better than lower ensemble members. To aid in future climate impact studies, the skill of individual ensemble members has performed as well as an examination into the projected changes to western U.S. precipitation by these members.

The large and complex influence exerted by the diurnal cycle on the climate system has challenged the reliability of numerical models. But the evaluation of this cycle in models raised another important difficulty: how to evaluate it. The approach of this study is relatively new, since rather than focusing on amplitude and phase, it focuses on the variance attributable to different aspects of the DC, and its comparison with the variance produced by larger-scale processes.

This study developed a resampling method to estimate the annual freezing and thawing index using monthly and annual temperature. These results suggested that, if the daily temperature can be reliably estimated using the resampling method, the thermal regimes of permafrost can also be reliably estimated using modelled monthly temperature and/or reconstructed past monthly/annual temperature. These estimations can also be used to validate modelled paleo-permafrost and its variations.

Composites of daily surface air temperature anomalies are positive in MJO phases 1 and 8 and negative in MJO phases 3–4 with broader region positive tendencies also in MJO phases 2 and 7, and negative tendencies in MJO phases 5–6. This variability is associated with horizontal temperature advection, whereby the southerly (northward) winds act to heat and the northerly (southward) winds cool Iran, in association with the MJO.

The problem of determining, with adequate statistical significance, the relationship between teleconnection pattern indices and precipitation at climatological time scales has been addressed through a novel technique based on a rainfall zonation. Pearson correlation was performed to evaluate the mesoscale influence on precipitation in Calabria (southern Italy) over the 1951–2010 time period, by means of a database of 79 rain gauges, divided in five rainfall zones (RZs). Seven teleconnection pattern indices, relevant to the Mediterranean region, are used searching where results were significant (significance level < 0.05) and with an absolute correlation value over a prefixed threshold (OT) equal to 0.2 (see figure).

Under the global warming, the evaporation experienced an increased trend. While the precipitation, runoff and soil water over the global drylands, except the drylands of North Africa and South Africa, experienced a decreased trend. Because of the anomalous warm over tropical, the local Hadley circulation will be intensified. It will enhance the downward motion over the middle-latitude. These regions are recognized as the main drylands. Thus, the water-cycle of global drylands, except the North Africa and South Africa, experienced a weakening trend.

Aerosol's effects on the cloud properties and precipitation over the drylands of East Asia during 1850–2300 are investigated. The effects of aerosols on cloud are saturated when the AODs reach 0.21 and 0.15 over the arid region and semiarid region, respectively. With the AOD decreasing from 2006 to 2300, cloud number concentration tends to decline but the cloud water path and precipitation increase.

Temperature anomalies series of 114 European cities are examined by using fractional integration. Most of the series display positive trends, supporting thus climate warming. The results confirm the hypothesis of long-memory in the series examined. Darker stations represent stations with stronger long-memory behaviour. Darker points are located especially next to the Baltic Sea and the Atlantic Ocean. Continental stations are characterized by weaker long-memory behaviour.

The copula-based approach is used to understand the joint dependence of drought duration and severity. The study is carried out over major river basins in India. Investigates the exceedance probability and joint return period of different drought events. Additionally, the conditional approach is also applied to probability and return period. We used a bivariate copula-based approach to understand the joint dependence of drought duration and severity of three different drought types. From the investigation, it is observed that the river basins in the Southern part of India have a higher exceedance probability and smaller joint return period compared to the Western river basins of India. Further, investigation suggests that drought events in the Western and Central India are more severe and longer whereas the ones in the south Indian river basins are more frequent but less severe.

The CEEMDAN-MFFA method is proposed to accurately quantify the precipitation complexity. Traditional MFDFA method generally overestimates precipitation complexity. Regulation of the forest ecosystems can alleviate the complex precipitation process. The results may provide valuable information for precipitation forecast and risk assessment.

After filtering out synoptic-scale disturbances at mid-high latitude, southerly winds at the lower level were strengthened, leading to the northward transport of warm/wet advection that changed the thermal structure of the lower troposphere. The subsequent formation of divergence and high pressure in the upper troposphere caused increased precipitation over these regions.

Observational diagnosis shows that the extreme warm and rainy winter in Shanghai in 2019 arose from southerly anomalies associated with an anticyclone, which was attributed to V-shaped upper-tropospheric Rossby wave activity fluxes, originated from the North Atlantic and the tropical Indian Ocean. Numerical model experiments indicate that the anomalous heat source in the tropical Indian Ocean played a dominant role (~65%) in causing the local anomalous circulation, while the heating in North Atlantic also played a role (~35%). Further analysis revealed that an extreme warm winter in the past did not coincide with an extreme wet winter.

Contrast to the quite thoroughly exploration in the influence of mean temperature shifting, the impact of high-frequency variability, especially that related to the weather disturbance, remains poorly understood. This study reveals the close linkage (p < .05) between spring vegetation greenness and weather disturbance over Siberia. We found that spring NDVI anomaly significantly covary with the synchronous synoptic temperature variance, and the cold temperature events related to weather activity likely play a role in influencing NDVI anomaly.

Composite field of intraseasonal anomalies (denoted by a prime, ') of mean temperature (Tm′) for the 191 intraseasonal heat waves identified in Maule (within Central Chile, CCh) during DJF 1872–2010 using 20CR. Individual events correspond to the first day of each HW. Shading depicts Tm′ every 0.5°C; zero contour omitted. The SD of all events is shown by grey curves every 0.5°C. Red and solid black (dashed black) contours represent positive (negative) sea level pressure (SLP′) every 1 hPa, starting at 2 hPa, and geopotental height at 500 hPa (Z500′) every 25 gpm, respectively. Century-long reanalysis data reveal that particular summer heat waves in central Chile (CCh) exhibit intraseasonal teleconnection patterns of both tropical and extra-tropical origin ~2 weeks in advance. Such patterns are effectively associated with an increased lagged probability of occurrence of warm events in CCh; thus, they can be interpreted as intraseasonal precursors. Using reanalyses and observations for recent decades, we suggest indices to monitor these relationships. Finally, three heat waves that occurred in DJF 2019-2020 are described as case studies.

Regression maps of sea ice concentration (SIC) anomalies during October–November (ON) against AD index (shading) from observational data for (a) 1979–1998 (P1) and (b) 1999–2017 (P2). Equivalent regression maps obtained through Pre-industrial experiments of CESM1 for (c) AD negative decades and (d) AD positive decades. The red box indicates the Barents–Kara Sea region (70–85°N, 20–80°E). The units of the regression maps are percentile, and the hatched region indicates significance at the 90% confidence level (observation) and 95% confidence level (model).

Evaluation of the general climate models in CMIP6 over Uganda.