Explore the vast range of titles available.

The role of winter sea-ice in the Labrador Sea as a precursor for precipitation anomalies over southeastern North Americaand Western Europe in the following spring is investigated. In general terms, as the sea ice increases, the precipitation alsoincreases. In more detail, however, analyses indicate that both the winter sea-ice and the sea surface temperature （SST）anomalies related to increases in winter sea-ice in the Labrador Sea can persist into the following spring. These featuresplay a forcing role in the spring atmosphere, which may be the physical mechanism behind the observational relationshipbetween the winter sea-ice and spring precipitation anomalies. The oceanic forcings in spring include Arctic sea-ice anomaliesand SST anomalies in the tropical Pacific and high-latitude North Atlantic. Multi-model Coupled Model IntercomparisonProject Phase 5 and Atmospheric Model Intercomparison Project simulation results show that the atmospheric circulationresponse to the combination of sea-ice and SST is similar to that observed, which suggests that the oceanic forcings areindeed the physical reason for the enhanced spring precipitation. Sensitivity experiments conducted using an atmosphericgeneral circulation model indicate that the increases in precipitation over southeastern North America are mainly attributableto the effect of the SST anomalies, while the increases over Western Europe are mainly due to the sea-ice anomalies. Althoughmodel simulations reveal that the SST anomalies play the primary role in the precipitation anomalies over southeastern NorthAmerica, the observational statistical analyses indicate that the area of sea-ice in the Labrador Sea seems to be the precursorthat best predicts the spring precipitation anomaly.

The Third Pole (TP) is experiencing rapid warming and is currently in its warmest period in the past 2,000 years. This paper reviews the latest development in multidisciplinary TP research associated with this warming. The rapid warming facilitates intense and broad glacier melt over most of the TP, although some glaciers in the northwest are advancing. By heating the atmosphere and reducing snow/ice albedo, aerosols also contribute to the glaciers melting. Glacier melt is accompanied by lake expansion and intensification of the water cycle over the TP. Precipitation has increased over the eastern and northwestern TP. Meanwhile, the TP is greening and most regions are experiencing advancing phenological trends, although over the southwest there is a spring phenological delay mainly in response to the recent decline in spring precipitation. Atmospheric and terrestrial thermal and dynamical processes over the TP affect the Asian monsoon at different scales. Recent evidence indicates substantial roles that mesoscale convective systems play in the TP’s precipitation as well as an association between soil moisture anomalies in the TP and the Indian monsoon. Moreover, an increase in geohazard events has been associated with recent environmental changes, some of which have had catastrophic consequences caused by glacial lake outbursts and landslides. Active debris flows are growing in both frequency of occurrences and spatial scale. Meanwhile, new types of disasters, such as the twin ice avalanches in Ali in 2016, are now appearing in the region. Adaptation and mitigation measures should be taken to help societies’ preparation for future environmental challenges. Some key issues for future TP studies are also discussed.

The local weather and climate of the Himalayas are sensitive and interlinked with global-scale changes in climate, as the hydrology of this region is mainly governed by snow and glaciers. There are clear and strong indicators of climate change reported for the Himalayas, particularly the Jammu and Kashmir region situated in the western Himalayas. In this study, using observational data, detailed characteristics of long- and short-term as well as localized variations in temperature and precipitation are analyzed for these six meteorological stations, namely, Gulmarg, Pahalgam, Kokarnag, Qazigund, Kupwara and Srinagar during 1980–2016. All of these stations are located in Jammu and Kashmir, India. In addition to analysis of stations observations, we also utilized the dynamical downscaled simulations of WRF model and ERA-Interim (ERA-I) data for the study period. The annual and seasonal temperature and precipitation changes were analyzed by carrying out Mann–Kendall, linear regression, cumulative deviation and Student's t statistical tests. The results show an increase of 0.8 ∘C in average annual temperature over 37 years (from 1980 to 2016) with higher increase in maximum temperature (0.97 ∘C) compared to minimum temperature (0.76 ∘C). Analyses of annual mean temperature at all the stations reveal that the high-altitude stations of Pahalgam (1.13 ∘C) and Gulmarg (1.04 ∘C) exhibit a steep increase and statistically significant trends. The overall precipitation and temperature patterns in the valley show significant decreases and increases in the annual rainfall and temperature respectively. Seasonal analyses show significant increasing trends in the winter and spring temperatures at all stations, with prominent decreases in spring precipitation. In the present study, the observed long-term trends in temperature (∘Cyear-1) and precipitation (mm year−1) along with their respective standard errors during 1980–2016 are as follows: (i) 0.05 (0.01) and −16.7 (6.3) for Gulmarg, (ii) 0.04 (0.01) and −6.6 (2.9) for Srinagar, (iii) 0.04 (0.01) and −0.69 (4.79) for Kokarnag, (iv) 0.04 (0.01) and −0.13 (3.95) for Pahalgam, (v) 0.034 (0.01) and −5.5 (3.6) for Kupwara, and (vi) 0.01 (0.01) and −7.96 (4.5) for Qazigund. The present study also reveals that variation in temperature and precipitation during winter (December–March) has a close association with the North Atlantic Oscillation (NAO). Further, the observed temperature data (monthly averaged data for 1980–2016) at all the stations show a good correlation of 0.86 with the results of WRF and therefore the model downscaled simulations are considered a valid scientific tool for the studies of climate change in this region. Though the correlation between WRF model and observed precipitation is significantly strong, the WRF model significantly underestimates the rainfall amount, which necessitates the need for the sensitivity study of the model using the various microphysical parameterization schemes. The potential vorticities in the upper troposphere are obtained from ERA-I over the Jammu and Kashmir region and indicate that the extreme weather event of September 2014 occurred due to breaking of intense atmospheric Rossby wave activity over Kashmir. As the wave could transport a large amount of water vapor from both the Bay of Bengal and Arabian Sea and dump them over the Kashmir region through wave breaking, it probably resulted in the historical devastating flooding of the whole Kashmir valley in the first week of September 2014. This was accompanied by extreme rainfall events measuring more than 620 mm in some parts of the Pir Panjal range in the south Kashmir.

Mountainous precipitation has different characteristics due to differences in climatic or topographical backgrounds. However, the variation characteristics of modern precipitation in the Nanling Mountains, which are located at the front edge of the Asian summer monsoon, remain poorly understood. Based on monthly precipitation data from twenty-two meteorological stations from 1959 to 2019, we analysed the spatiotemporal characteristics of seasonal and annual precipitation and discussed the possible driving mechanisms in the study region. Annual, spring, summer, and winter precipitation increased, while autumn precipitation decreased from 1959 to 2019; these variation trends will continue as inferred from the Hurst index of the R/S analysis. Annual and seasonal precipitation exhibit periods within a scale of 2–8 years, and their mutation times mostly occurred in the 1980s and 2010s. Spatially, the peak centre of precipitation shifted gradually from the south to the north from spring to winter, as it was influenced by variations in the water vapour source. The eastern and northern weather stations with bimodal patterns of monthly precipitation within the year have longer flood seasons than the southern and western stations with unimodal patterns. Due to the loss of water vapour during northwards and upwards migration, significant negative correlations existed between latitude and annual/spring/summer precipitation, as well as between altitude (below 500 m) and annual/spring precipitation. Regional comparisons revealed that mountainous precipitation exhibited significantly decreasing trends with increasing latitude in China. This study further demonstrated the vital roles of the Asian summer monsoon, sunspots, and ENSO forcings in regulating annual precipitation variations in the study region.

Colorado River streamflow has decreased 19% since 2000. Spring (March‐April‐May) weather strongly influences Upper Colorado River streamflow because it controls not only water input but also when snow melts and how much energy is available for evaporation when soils are wettest. Since 2000, spring precipitation decreased by 14% on average across 26 unregulated headwater basins, but this decrease did not fully account for the reduced streamflow. In drier springs, increases in energy from reduced cloud cover, and lowered surface albedo from earlier snow disappearance, coincided with potential evapotranspiration (PET) increases of up to 10%. Combining spring precipitation decreases with PET increases accounted for 67% of the variance in post‐2000 streamflow deficits. Streamflow deficits were most substantial in lower elevation basins (<2,950 m), where snowmelt occurred earliest, and precipitation declines were largest. Refining seasonal spring precipitation forecasts is imperative for future water availability predictions in this snow‐dominated water resource region. Plain Language Summary With over 40 million people dependent on the Colorado River, the 19% drop in streamflow since 2000 has been worrying, especially because its cause is not well understood. To explain this drop, we focused on changes to spring weather in snow‐dominated basins, which contribute over 80% of the river's water. We found spring precipitation decreases since 2000 not only reduced streamflow but also correlated with higher temperatures and evaporation rates and less cloudiness. These impacts combined to intensify streamflow declines in basins with earlier snowmelt. The importance of spring precipitation to Colorado River streamflow underscores the need to improve seasonal precipitation forecasts. Such improvements would enhance water availability predictions for the one billion people worldwide reliant on snow for water resources. Key Points Significant decreases in spring precipitation have been observed since 2000 in headwater basins of the Upper Colorado Drier springs have corresponded with greater spring potential evapotranspiration (PET) Spring precipitation decreases and PET increases explain much of the variability in observed streamflow deficits in these headwater basins

The interaction between co-occurring drought and hot conditions is often particularly damaging to crop's health and may cause crop failure. Climate change exacerbates such risks due to an increase in the intensity and frequency of dry and hot events in many land regions. Hence, here we model the trivariate dependence between spring maximum temperature and spring precipitation and wheat and barley yields over two province regions in Spain with nested copulas. Based on the full trivariate joint distribution, we (i) estimate the impact of compound hot and dry conditions on wheat and barley loss and (ii) estimate the additional impact due to compound hazards compared to individual hazards. We find that crop loss increases when drought or heat stress is aggravated to form compound dry and hot conditions and that an increase in the severity of compound conditions leads to larger damage. For instance, compared to moderate drought only, moderate compound dry and hot conditions increase the likelihood of crop loss by 8 % to 11 %, while when starting with moderate heat, the increase is between 19 % to 29 % (depending on the cereal and region). These findings suggest that the likelihood of crop loss is driven primarily by drought stress rather than by heat stress, suggesting that drought plays the dominant role in the compound event; that is, drought stress is not required to be as extreme as heat stress to cause similar damage. Furthermore, when compound dry and hot conditions aggravate stress from moderate to severe or extreme levels, crop loss probabilities increase 5 % to 6 % and 6 % to 8 %, respectively (depending on the cereal and region). Our results highlight the additional value of a trivariate approach for estimating the compounding effects of dry and hot extremes on crop failure risk. Therefore, this approach can effectively contribute to design management options and guide the decision-making process in agricultural practices.

Given the significant importance of spring precipitation for agricultural production in China and the presence of the spring predictability barrier, scientists have dedicated extensive efforts to understand the factors influencing spring precipitation variability and explore new predictors. However, the effects of Arctic stratospheric ozone (ASO) on precipitation in China during boreal spring, if any, and the underlying mechanisms remain unclear. We found the robust influences of March ASO on the differences in the precipitation and evaporation in April over Eastern China during 1980–2020. When ASO decreases in March, it tends to result in a higher and colder tropopause in the polar, a stronger subtropical jet stream, an intensified local Hadley circulation accompanied by anomalous downward motion over Eastern China, and consequently, drying in this region, and vice versa. These findings suggest that the likelihood of April moistening over East Asia may be potentially predicted by employing the ASO index. Plain Language Summary Food production in East Asia, which is home to a quarter of the world's population, holds immense importance. The spring season in this region marks the crop planting period, making the precipitation during this time crucial for agricultural production. However, it is challenging to predict spring moistening/drying over East Asia. Therefore, there is a need for new predictors to enhance our understanding of spring precipitation variability. Whether a connection exists between Arctic stratospheric ozone (ASO) and spring precipitation over EC has remained unknown. Here, we have highlighted a strong relationship between ASO in March and moistening over EC in April, particularly in the middle and lower reaches of the Yangtze River (YRB). Specifically, an increase (decrease) in March ASO corresponds to moistening (drying) over YRB in April. The implications of these findings are significant for forecasting spring precipitation over East Asia, which is crucial for agricultural planning and production. Key Points There are robust influences of March Arctic stratospheric ozone (ASO) on the precipitation in April over Eastern China (EC) during 1980–2020 Depletion of ASO in March tends to result in decreased precipitation over EC in April Decreased ASO results in the higher but warmer tropopause, stronger subtropical jet, and anomalous downward motion over EC

An obvious long‐term drying trend in recent early springs (February–March–April) is observed over southeastern China (SEC). Here, we attribute this drying to the weakened subtropical westerlies and deflected by the Tibetan Plateau (TP). Climatologically, the low‐level southwesterlies at the southeastern margin of the TP, a branch of the upstream subtropical westerly jet deflected by the TP terrain, bring water vapor to SEC and the southerlies move upward over SEC mainly through isentropic gliding mechanism, inducing persistent precipitation in early spring. However, the subtropical westerlies weakened significantly in recent decades due potentially to the decreased Eurasian snow cover. Consequently, an easterly trend appears along the southern margin of the TP with anomalous northeasterlies over SEC. These northeasterlies suppress both moisture supply and upward motions over SEC, and reduce regional early spring precipitation. Our results highlight the interaction between the TP terrain and the weakened subtropical westerlies that leads to the drying SEC. Plain Language Summary Spring precipitation in southeastern China (SEC) is a major rainband during the pre‐flood season in East Asia, which is significant for agricultural production and social economy. However, in the recent few decades, a robust long‐term drying trend has occurred over SEC in early spring. In this study, we propose a new mechanism for the decreased SEC precipitation and highlight the important influence of the weakened subtropical westerlies and their interaction with the Tibetan Plateau (TP). Deflected by the TP large terrain, the upstream weakened subtropical westerlies induce weakened westerlies and southwesterlies along the southern and southeastern margins of the TP, respectively. As a result, the weakened southwesterlies at the southeastern TP not only reduce the moisture transport downstream, but also suppress the ascending motions over SEC through the isentropic gliding mechanism. Both the water vapor and atmospheric circulation conditions finally induce the drying SEC in recent early springs. Key Points An early spring drying trend has occurred in southeastern China (SEC), much of this can be attributed to the weakened subtropical westerlies Deflected by the Tibetan Plateau (TP), the weakened subtropical westerlies decelerate downstream westerlies along the TP's southern margin The decelerated westerlies at the southeastern TP suppress moisture supply and rising motions over SEC, both processes cause the drying SEC

Previous studies suggested that the dry–wet surface state over the Indo-China Peninsula (ICP), closely associated with the local spring precipitation, is an important seasonal predictor for the East Asian summer monsoon and extreme climate. Hence, this work investigates the inter-annual variability of spring precipitation over the ICP and its relationship with El Niño-Southern Oscillation (ENSO) during 1958–2019. The results show that the spring precipitation anomalies over the ICP are highly linked to the ENSO-induced atmospheric circulation anomalies. In particular, there are large asymmetries in the precipitation anomalies for the spring following ENSO. During the decaying spring of the El Niño events, the precipitation decrease mainly occurs over the Western ICP associated with an anomalous low-level anticyclone over the western North Pacific. In contrast, during the decaying spring of the La Niña events, a stronger precipitation increase broadly extends into the Southeastern ICP. This is owing to a nonlinear effect of ENSO on the atmospheric circulation. Compared to El Niño, the abnormal center of La Niña extends too far westwards, inducing a westward movement of the anomalous atmospheric circulation, which results in a stronger effect on the spring ICP precipitation. Our findings emphasize the nonlinear responses of the spring ICP precipitation to ENSO. This has important implications for the seasonal climate prediction over the ICP, especially for the Southeastern ICP countries/regions.

Observed changes in climate of the U.S. Pacific Northwest since the early twentieth century were examined using four different datasets. Annual mean temperature increased by approximately 0.6°–0.8°C from 1901 to 2012, with corroborating indicators including a lengthened freeze-free season, increased temperature of the coldest night of the year, and increased growing-season potential evapotranspiration. Seasonal temperature trends over shorter time scales (<50 yr) were variable. Despite increased warming rates in most seasons over the last half century, nonsignificant cooling was observed during spring from 1980 to 2012. Observations show a long-term increase in spring precipitation; however, decreased summer and autumn precipitation and increased potential evapotranspiration have resulted in larger climatic water deficits over the past four decades. A bootstrapped multiple linear regression model was used to better resolve the temporal heterogeneity of seasonal temperature and precipitation trends and to apportion trends to internal climate variability, solar variability, volcanic aerosols, and anthropogenic forcing. The El Niño–Southern Oscillation and the Pacific–North American pattern were the primary modulators of seasonal temperature trends on multidecadal time scales: solar and volcanic forcing were nonsignificant predictors and contributed weakly to observed trends. Anthropogenic forcing was a significant predictor of, and the leading contributor to, long-term warming; natural factors alone fail to explain the observed warming. Conversely, poor model skill for seasonal precipitation suggests that other factors need to be considered to understand the sources of seasonal precipitation trends.