Changes In Summer Precipitation Research Articles

PDO influenced interdecadal summer precipitation change over East China in mid-18th century

There have been few case studies of the relationship between the Pacific Decadal Oscillation (PDO) and the East Asian climate before the pre-industrial era with limited anthropogenic impacts. Using the CESM Last Millennium Ensemble (CESM-LME) simulation with reconstruction evidence, we showed that there was an interdecadal transition of the summer precipitation in East China, with the pattern of “southern flooding and northern drought” in the mid-18th century. The interdecadal transition was influenced by PDO, as suggested by both the reconstruction evidence and simulation. Corresponding to the positive PDO phase change, the East Asia-Pacific pattern teleconnection wave train propagated northward and modulated the circulation and precipitation in East China, together with the southward movement of the East Asian westerly jet. The volcanic double or clustered eruptions are thought to have played a crucial role on the shift of the PDO phase and the decadal summer climate change over East China during the mid-18th century. Incorporating volcanic activity in a reasonable manner would likely improve decadal simulations of East Asian climate in the past and predictions in the future.

Multi-decadal Changes of the Impact of El Niño Events on Tibetan Plateau Summer Precipitation

Precipitation on the Tibetan Plateau (TP) has an important effect on the water supply and demand of the downstream population. Involving recent climate change, the multi-decadal variations of the impact of El Niño-Southern Oscillation (ENSO) events on regional climate were observed. In this work, the authors investigated the changes in summer precipitation over TP during 1950–2019. At the multi-decadal scale, the authors found that the inhabiting impact of El Niño events on the TP summer precipitation has strengthened since the late 1970s. The main factor contributing to this phenomenon is the significant amplification in the decadal amplitude of El Niño during 1978–2019 accompanied by a discernible escalation in the frequency of El Niño events. This phenomenon induces anomalous perturbations in sea surface temperatures (SST) within the tropical Indo-Pacific region, consequently weakening the atmospheric vapor transport from the western Pacific to the TP. Additionally, conspicuous anomalies in subsidence motion are observed longitudinally and latitudinally across the TP which significantly contributes to a curtailed supply of atmospheric moisture. These results bear profound implications for the multi-decadal prediction of the TP climate.

Reconstruction of temperature and monsoon precipitation in southwestern China since the last deglaciation

Monsoon precipitation and temperature are the crucial components of the Indian monsoon climate, yet their spatial-temporal relationship remains unclear. In this study, we reconstruct the changes in monsoon precipitation and mean annual temperature simultaneously over the past 16,000 years using multiple proxies, including isoprenoid glycerol dialkyl glycerol tetraethers (isoGDGTs) and n-alkanes, from an alpine lake in southwestern China. On the one hand, the reconstructed monsoon precipitation shows a long-term increasing trend during the last deglaciation and a gradual decrease during the Holocene, with the highest-humidity period occurring in the early Holocene. Our result displays good consistency with the changes in regional mean annual precipitation, summer precipitation, and monsoon intensity during the last deglaciation and the Holocene. On the other hand, the reconstructed mean annual temperature inferred from the n-alkane proxy shows a long-term warm trend since the last deglaciation. Our result is consistent with the regional reconstruction of both mean annual and summer temperatures during the last deglaciation, while evident seasonal differences were observed for Holocene records with a cooling trend of summer temperature and a warm trend of mean annual temperature. Comprehensive comparison reveals that monsoon precipitation in the Indian monsoon region is mainly related to changes in the Intertropical Convergence Zone (ITCZ) and land-sea thermal contrast controlled by boreal summer insolation. In addition, the increase in temperature during deglaciation is primarily attributed to the escalation of greenhouse gases (GHGs), while the divergent trend of seasonal temperature during the Holocene is mainly attributed to the changes in local seasonal insolation. Our research emphasizes that monsoon precipitation is a summer signature in the Indian monsoon region, which is consistent with the changes in summer temperature, while contrasting with the changes in mean annual temperature. Therefore, it is necessary to consider the seasonal difference in temperature changes when investigating the hydrothermal combination in Indian monsoon regions.

Arctic Sea Ice Loss Inducing Northwest Extension of Summer Precipitation over the Tibetan Plateau

Abstract Summer precipitation over the Tibetan Plateau (TP) has experienced obvious changes in recent decades, with significantly increased trends observed over the northern and western regions during 1961–2020. Results indicate that there are two pathways linking them to the reduced Arctic sea ice from late spring (April and May) to early summer (June and July). First, decreased sea ice in late spring favors wet and dry soil over the eastern Caspian Sea and northeastern TP by stimulating anomalous wavelike patterns and modulating snow melting. Furthermore, the soil moisture anomalies during late spring could maintain to July because of memory effects, strengthen the midlatitude Silk Road pattern, and contribute to the formation of a dipole mode around TP, characterized by a west cyclone and an east anticyclone. Second, through exciting an anomalous Rossby wave directly spreading from the Arctic to TP, a similar dipole pattern on 500-hPa geopotential height could be associated with the decline of sea ice in early summer. Consequently, enhanced southwesterly winds shown with the west cyclone cause more water vapor input to the western TP, while easterly anomalies along with the east anticyclone inhibit climatological westerly winds and prevent water vapor from outputting. This dipole pattern finally brings more moisture accumulated in the western and northern TP and increases the precipitation. This study links heterogeneous changes in summer precipitation over TP to Arctic sea ice changes and provides insights for further investigation into whether the TP could serve as a bridge connecting the Arctic and tropical climates.

The north–south shift of the ridge location of the western Pacific subtropical high and its influence on the July precipitation in the Jianghuai region from 1978 to 2021

The Jianghuai region is the area between the Yangtze River and the Huai River in China and is a densely populated agriculture region therefore, the economics and human activity there are significantly affected by the precipitation changes, particularly during the summer when extreme storms and droughts normally occur. It will be helpful if the summer precipitation changes can be predicted. The monthly ERA5 atmospheric reanalysis data from 1978 to 2021 are used in this study to investigate the relationship between the ridge latitudinal location of the western Pacific subtropical high (WPSH) and the precipitation in July over the Jianghuai region. The results show that the WPSH ridge location has an important impact on the amount and spatial distribution of the precipitation in this region. When the ridge was northward, an anomalous anticyclonic circulation will appear over the western Pacific, leading to the weakening of the summer monsoon and the reduction of moisture transport from the Indian Ocean, therefore decreasing precipitation in the Jianghuai region, while the situation is opposite when the ridge was southward. The Niño 3.4 index in March and the India–Burma trough intensity index in June have significant correlations with the July WPSH ridge location, and both can be used as precursors to predict the WPSH ridge location and, therefore, the precipitation in this region.

Increased southerly and easterly water vapor transport contributed to the dry-to-wet transition of summer precipitation over the Three-River Headwaters in the Tibetan Plateau

The Three-River Headwaters (TRH) region in the Tibetan Plateau is vulnerable to climate change; changes in summer (June–August) precipitation have a significant impact on water security and sustainability in both local and downstream areas. However, the changes in summer precipitation of different intensities over the TRH region, along with their influencing factors, remain unclear. In this study, we used observational and ERA5 reanalysis data and employed a precipitation categorization and water vapor budget analysis to quantify the categorized precipitation variations and investigate their possible linkages with the water vapor budget. Our results showed an increasing trend in summer precipitation at a rate of 0.9 mm per year (p < 0.1) during 1979–2020, with a significant dry-to-wet transition in 2002. The category ‘very heavy precipitation’ (≥10 mm d−1) contributed 65.1% of the increased summer precipitation, which occurred frequently in the northern TRH region. The dry-to-wet transition was caused by the effects of varied atmospheric circulations in each subregion. Southwesterly water vapor transport through the southern boundary was responsible for the increased net water vapor flux in the western TRH region (158.2%), while southeasterly water vapor transport through the eastern boundary was responsible for the increased net water vapor flux in the central TRH (155.2%) and eastern TRH (229.2%) regions. Therefore, we inferred that the dry-to-wet transition of summer precipitation and the increased ‘very heavy precipitation’ over the TRH was caused by increased easterly and southerly water vapor transport.

Impact of North Indian Atmospheric Diabatic Heating on Summer Precipitation in Central Asia

Abstract The impact of North Indian atmospheric diabatic heating variation on summer rainfall over Central Asia (CA) at an interannual scale during 1960–2019 was investigated from thermal adaptation and water vapor transportation perspective. The results showed that more precipitation in southeastern CA is associated with the southward subtropical westerly jet (SWJ), caused by the ascending motion and weakened water vapor output on the south side. When the SWJ moves southward, the high-level water vapor transportation on the south side changes from outward (−1.9 × 106 kg s−1) to inward (0.6 × 106 kg s−1), and the positive anomalous relative vorticity advections by the basic westerly winds produce ascending anomalies over southeastern CA. The position change in the SWJ was mainly related to atmospheric diabatic heating over northern India (NI). The thermal vorticity adaptation caused by a weakened heating rate over NI leads to an anomalous upper-level cyclone over southeastern CA, and the associated cold temperature advection eventually cools the upper troposphere of southeastern CA and reduces the temperature gradient at mid-to-high latitudes, leading to the southward SWJ. Thermal adaptation of the circulation and temperature anomaly over southeastern CA to the NI thermal forcing were also verified by numerical experiments. Both the abnormal ascending motions and the weakened outward water vapor associated with the southward SWJ, caused by the weakened heating rate over NI, lead to more summer rainfall in southeastern CA. The changes in diabatic heating over NI are closely related to Indian Ocean SST. When the Indian Ocean SST is warmer, the south Asian summer monsoon weakens, causing less precipitation and, thus, a weakened heating rate over NI. Significance Statement This study established that the northern Indian atmospheric diabatic heating anomalies associated with Indian Ocean SST variation play an important role in influencing precipitation in central Asia (CA). The weakening of the atmospheric diabatic heating over the NI would not only cause an abnormal cyclone and cooling over southern CA through thermal adaptation but also lead to southward subtropical westerly jet (SWJ), ascending motions, and decreased outward water vapor on the south side in southeastern CA, eventually resulting in more precipitation in southeastern CA. The results emphasize the influence of tropical SST and atmospheric heat sources on midlatitude climate and are important for understanding summer precipitation change in southeastern CA.

An emerging Asian aerosol dipole pattern reshapes the Asian summer monsoon and exacerbates northern hemisphere warming

Since the early 2010s, anthropogenic aerosols have started decreasing in East Asia (EA) while have continued to increase in South Asia (SA). Yet the climate impacts of this Asian aerosol dipole (AAD) pattern remain largely unknown. Using a state-of-the-art climate model, we demonstrate that the climate response is distinctly different between the SA aerosol increases and EA aerosol decreases. The SA aerosol increases lead to ~2.7 times stronger land summer precipitation change within the forced regions than the EA aerosol decreases. Contrastingly, the SA aerosol increases, within the tropical monsoon regime, produce weak and tropically confined responses, while the EA aerosol decreases yield a pronounced northern hemisphere warming aided by extratropical mean westerly and positive air-sea feedbacks over the western North Pacific. By scaling the observed instantaneous shortwave radiative forcing, we reveal that the recent AAD induces a pronounced northern hemisphere extratropical (beyond 30°N) warming (0.024 ± 0.010 °C decade−1), particularly over Europe (0.049 ± 0.009 °C decade−1). These findings highlight the importance of the pattern effect of forcings in driving global climate and have important implications for decadal prediction.

Spatio-Temporal Analysis of Simulated Summer Extreme Precipitation Events under RCP4.5 Scenario in the Middle and Lower Reaches of the Yangtze River Basin

In the context of global warming, the frequency and intensity of extreme climate events, especially extreme precipitation events, have increased. The middle and lower reaches of the Yangtze River Basin are important areas for economic development, and are also one of the areas where rainstorms and flood disasters frequently occur in China. Improving the prediction of future summer extreme precipitation in this region under the greenhouse gas emission pathway that aligns with sustainable economic development (Representative Concentration Pathway 4.5, RCP4.5) will help decision-makers better cope with the impact of increased natural disasters, such as floods. The medium-resolution CESM1.0 (Community Earth System Model 1.0) data (1° × 1°) has limitations in capturing regional climate differences. Therefore, we designed a downscale experiment using the WRF3.8 (Weather Research and Forecasting 3.8) model to obtain the daily summer precipitation grid data with 0.25° × 0.25° latitude and longitude resolution over the middle and lower reaches of the Yangtze River Basin from May to September in 2006–2030 (WRF025). The research shows that the WRF025 data is reliable in simulating the summer extreme precipitation events over the middle and lower reaches of the Yangtze River Basin, especially in the lower reaches of the Yangtze River. Compared to CESM1.0 data, WRF025 data significantly improves the ability to simulate the numerical value and distribution of summer extreme precipitation in the middle and lower reaches of the Yangtze River. Under the RCP4.5 scenario, compared to 2006–2014, there is no significant change in daily summer precipitation in the middle and lower reaches of the Yangtze River Basin during 2015–2030, with a significant decrease in daily summer extreme precipitation. There are significant regional differences in spatial distribution, with a significant decrease in Hunan and Hubei, and a significant increase in Jiangxi and Fujian. Under high-pressure control, the lower reaches of the Yangtze River are dominated by downdraft, resulting in more sunny days and less precipitation. The increase (decrease) in water vapor transport and divergence may be the reason for the increase (decrease) in extreme precipitation. The most direct factor leading to an increase (decrease) in extreme precipitation is the vertical movement upwards (downwards). Furthermore, the anomalous descent (ascent) can be well explained by the easterly (westerly) wind anomaly on the southern (northern) side of the anomalous anticyclone via the isentropic gliding mechanism.

Assessment of Climate Indices over the Carpathian Basin Based on ALADIN5.2 and REMO2015 Regional Climate Model Simulations

The Hungarian Meteorological Service has been conducting climate model simulations in order to assess the effects of climate change in the Carpathian Basin and provide data for impact research and stakeholders. Two regional climate models are used: ALADIN-Climate 5.2 (hereafter ALADIN5.2) and REMO2015. They were tested for the past when the lateral boundary conditions were taken from two sources. ERA-Interim reanalysis was used in the evaluation experiment, while the CNRM-CM5 and the MPI-ESM-LR global climate models (GCM) provided the forcings in the control experiments. The model outputs were compared with the CarpatClim-HU observational dataset for the 1981–2000 period. Future projections were carried out with the RCP4.5 and RCP8.5 scenarios, and the results were analyzed for 2021–2050 and 2071–2100. The evaluation of the results focused mainly on climate indices calculated from temperature and precipitation. The validation results showed that REMO2015 assessed the mean temperature well, but the indices based on the minimum and maximum temperature had a significant bias which has to be taken into account when interpreting future changes. The model overestimated the minimum temperature in summer, which might affect the number of tropical nights. Moreover, the maximum temperature was underestimated; thus, the derived indices, such as the occurrence of summer days and hot days, were profoundly underestimated. In comparison, ALADIN5.2 had smaller biases for the high temperature indices; moreover, the number of hot days and extremely cold days was overestimated. Taking future projections into account, we can clearly see that the results of REMO2015 show a much more moderate increase in temperature than ALADIN5.2. The reasons are yet unknown and require further investigation. In spring and summer, the number of wet days was slightly overestimated, while the number of heavy precipitation days was marginally underestimated. The projections showed the highest uncertainty in the changes in mean summer precipitation and other precipitation indices. Although the REMO2015 model assessed a decrease in precipitation, ALADIN5.2 projected an increase in precipitation with a similar magnitude.

Comprehensive effects of interdecadal change of sea surface temperature increase in the Indo-Pacific Ocean on the warming-wetting of the Qinghai–Tibet Plateau

The correlation characteristics between anomalous changes in summer precipitation on the Qinghai–Tibet Plateau (QTP) and the high-impact areas of global sea-surface temperature (SST) are mainly studied in this paper. The results show that the interdecadal change of the regional “warming-wetting” in China is especially prominent in the northern part of the main body of the QTP, which is therefore identified as the high-value area of precipitation variability. Investigations have revealed that the high-value areas of summer precipitation variability in the northern QTP are significantly correlated with four high-value areas of SST variability, namely the western North Pacific, the western Central Pacific, the Southwest Pacific, and the central Indian Ocean. In these four high-impact areas, a synchronous tendency is found in the SST increase and sea-surface specific humidity. Through the tracking analysis of the correlated vectors of the water vapor source for the warming-wetting of the QTP, it further confirms that the four high-value areas of SST variability in the Indo-Pacific Ocean are the major impact sources of water vapor transport for the warming-wetting of the QTP. Moreover, the comparison of the characteristics of various interdecadal global water vapor transport circulations show that from 1991 to 2020, the trans-equatorial water vapor transport from the Southern Hemisphere witnessed a notable increase, which furthermore suggests that the interdecadal change of SST increase in the Southwest Pacific and central Indian Ocean is the key reason for the warming-wetting of the QTP. In addition, a comprehensive image of high-impact marine water vapor sources for modulating the warming-wetting tendency in the QTP is proposed.

Rapid and Gradual Permafrost Thaw: A Tale of Two Sites

AbstractWarming temperatures and increasing disturbance by wildfire and extreme weather events is driving permafrost change across northern latitudes. The state of permafrost varies widely in space and time, depending on landscape, climate, hydrologic, and ecological factors. Despite its importance, few approaches commonly measure and monitor the changes in deep (&gt;1 m) permafrost conditions with high spatial resolution. Here, we use electrical resistivity tomography surveys along two transects in interior Alaska previously disturbed by wildfire and more recently by warming temperatures and extreme precipitation. Long‐term point observations of permafrost depth, temperature, and water content inform geophysical measurements which, in turn, are used to extrapolate interpretations over larger areas and with high spatial fidelity. We contrast gradual loss of recently formed permafrost driven by warmer temperatures and increased snowfall, with rapid permafrost loss driven by changes in air temperature, snow depth, and extreme summer precipitation in 2014.

Centennial Precipitation Characteristics Change in Haihe River Basin, China

Research on precipitation regularity in the past 120 years is an important link in analyzing the precipitation characteristics of watersheds. This paper systematically analyzes the characteristic changes of centennial precipitation data in the Haihe River basin with the help of CRU data, PCI, SPI, and the Pearson type III curve. The results show that the spatial and temporal distribution of precipitation in the Haihe River basin has a more obvious inconsistency. The temporal distribution shows the characteristics of relatively stable in the early period and increasing fluctuation in the later period, the concentration of precipitation gradually decreases, and the overall drought level decreases. The spatial distribution shows a general pattern of gradually decreasing from southwest to northeast, the overall trend of summer precipitation changes from stable to north–south extremes, and the distribution probability of extreme precipitation events in the basin decreases from southeast to northwest, while the drought-prone area transitions from the northeast to the west and southwest of the basin. Under the influence of both climate change and human activities, the seasonal distribution of precipitation tends to be average, the area affected by extreme precipitation rises, and the arid area shifts to the inland area.

Influence of water vapor influx on interdecadal change in summer precipitation over the source area of the Yellow River Basin

The source area of the Yellow River Basin (SYRB) is located in the northeastern Tibetan Plateau, and the precipitation in the SYRB is of great importance to the water resources throughout the whole basin. By analyzing the summer precipitation in the SYRB, we found that an 11.4% increase in precipitation occurred during 2003–2019 compared with 1982–2002. Such interdecadal increase of summer precipitation was due to significant changes of moisture contribution from external moisture source. In the past 38 years, 95.4% of the water vapor for summer precipitable water in the SYRB came from local evapotranspiration (10.6%), the Tibetan Plateau area (35.8%), central Eurasian area (22.5%), South Asia-northern Indian Ocean area (14.6%), South China Sea-western Pacific area (6.6%), and North Africa-West Asia area (5.3%). Thus, external water vapor supplied about 84.8% of summer precipitable water in the SYRB. Compared with 1990–2002, the relative growth rates of moisture contribution during 2003–2019 from the central Eurasian area, North Africa-West Asia area and South China Sea-western Pacific area increased by 2.40%, 4.55% and 15.07%, respectively. Such interdecadal changes were verified by evapotranspiration minus precipitation for it can illustrate the supply capacity of the moisture source. Water vapor supplies in these areas increased during 2003–2019, which greatly contributed to the increase of summer precipitation in the SYRB.

Dynamic boreal summer atmospheric circulation response as negative feedback to Greenland melt during the MIS-11 interglacial

Abstract. The unique alignment of orbital precession and obliquity during the Marine Isotope Stage 11 (MIS-11) interglacial produced perhaps the longest period of planetary warmth above preindustrial conditions in the past 800 kyr. Reconstructions point to a significantly reduced Greenland ice sheet volume during this period as a result, although the remaining extent and volume of the ice sheet are poorly constrained. A series of time slice simulations across MIS-11 using a coupled climate model indicates that boreal summer was particularly warm around Greenland and the high latitudes of the Atlantic sector for a period of at least 20 kyr. This state of reduced atmospheric baroclinicity, coupled with an enhanced and poleward-shifted intertropical convergence zone and North African monsoon, favored weakened high-latitude winds and the emergence of a single, unified midlatitude jet stream across the North Atlantic sector during boreal summer. Consequent reductions in the lower-tropospheric meridional eddy heat flux over the North Atlantic therefore emerge as negative feedback to additional warming over Greenland. The relationship between Greenland precipitation and the state of the North Atlantic jet is less apparent, but slight changes in summer precipitation appear to be dominated by increases during the remainder of the year. Such a dynamic state is surprising, as it bears stronger resemblance to the unified-jet state postulated as typical for glacial states than to the modern-day interglacial state.

Quantifying the role of the large-scale circulation on European summer precipitation change

Regional climate projections indicate that European summer precipitation may change considerably in the future. Southern Europe can expect substantial drying while Northern Europe could actually become wetter. Model spread and internal variability in these projections are large, however, and unravelling the processes that underlie the changes is essential to get more confidence in these projections. Large-scale circulation change is one of the contributors to model spread. In this paper we quantify the role of future large-scale circulation changes to summer precipitation change, using a 16-member single-model ensemble obtained with the regional climate model RACMO2, forced by the global climate model EC-Earth2.3 and the RCP8.5 emission scenario. Using the method of circulation analogues three contributions to the future precipitation change are distinguished. The first is the precipitation change occurring without circulation change (referred to as the thermodynamic term). This contribution is characterised by a marked drying-to-wetting gradient as one moves north from the Mediterranean. The second contribution measures the effects of changes in the mean circulation. It has a very different spatial pattern and is closely related to the development of a region of high pressure (attaining its maximum west of Ireland) and the associated anti-cyclonic circulation response. For a large area east of Ireland including parts of western Europe, it is the major contributor to the overall drying signal, locally explaining more than 90% of the ensemble-mean change. In regions where the patterns overlap, the signal-to-noise ratio of the total change is either enhanced or reduced depending on their relative signs. Although the second term is expected to be particularly model dependent, the high-pressure region west of Ireland also appears in CMIP5 and CMIP6 ensemble-mean projections. The third contribution records the effects of changes in the circulation variability. This term has the smallest net contribution, but a relatively large uncertainty. The analogues are very good in partitioning the ensemble-mean precipitation change, but describe only up to 40% of the ensemble-spread. This demonstrates that other precipitation-drivers (SST, spring soil moisture etc.) will generally strongly influence trends in single climate realisations. This also re-emphasises the need for large ensembles or using alternative methods like the Pseudo Global Warming approach where signal to noise ratios are higher. Nevertheless, identifying the change mechanisms helps to understand the future uncertainties and differences between models.

The Influence of the Tibetan Plateau Monsoon on Summer Precipitation in Central Asia

As a unique climate phenomenon induced by the Tibetan Plateau (TP) heat flux, the TP monsoon is closely connected with the global climate, especially pertaining to the TP. However, the current research focuses more on the influence of the TP monsoon on the TP and eastern China, but not including Central Asia. This paper analyzed the relationship between the TP monsoon index and Central Asia summer precipitation by JRA55 reanalysis data and Global Precipitation Climatology Centre (GPCC) monthly precipitation. The results showed a significant positive relationship between the TP monsoon index and summer precipitation in Central Asia. When the TP monsoon was strong, there was cold advection in the upper troposphere over Central Asia, and the resulting thermal wind caused a cyclonic circulation anomaly in the mid-upper troposphere over Central Asia. This in turn led to a cyclonic circulation anomaly to water vapor transport in the lower troposphere. The abnormal upward movement also caused more precipitation in this area, which explains the positive correlation between the TP monsoon and the precipitation in Central Asia. Based on this physical mechanism, the temperature of the mid-upper troposphere over Central Asia was closely related to the TP monsoon, and it was a key factor that affected summer precipitation changes in Central Asia.

Detectable anthropogenic forcing on the long-term changes of summer precipitation over the Tibetan Plateau

Detectable anthropogenic forcing on the long-term changes of summer precipitation over the Tibetan Plateau

Projected Changes to Spring and Summer Precipitation in the Midwestern United States

Spring and summer precipitation are both important factors for agricultural productivity in the Midwest region of the United States. Adequate summer precipitation, particularly in the reproductive and grain fill stages in July and August, is critical to corn and soybean success. Meanwhile, excessive spring precipitation can cause significant planting delays and introduces challenges with weed and pest management, and soil erosion and compaction. However, uncertainty especially in future summer precipitation changes, translates to uncertainties in how the joint distributions of spring and summer precipitation are expected to change by mid- and late-century across the Midwest. This study examines historical and projected changes in the characteristics of spring and summer precipitation in the Midwest using 12 dynamically downscaled simulations under the high-emission representative concentration pathway (RCP 8.5) from the NA-CORDEX project. Historical increases in spring precipitation and precipitation intensity are projected to continue into the mid- and late-century across the region, with strong model agreement. By comparison, projected changes in Midwest summer precipitation are more modest than for spring and have much less model agreement. Despite a projected three- to four-fold increase in the frequency of wet springs by late-century, relative to the model ensemble historical average, the lack of substantial and robust projected change in summer precipitation results in only a small increase in the risk of dry summers following wet springs in the Midwest by mid- and late-century.

Balanced estimate and uncertainty assessment of European climate change using the large EURO-CORDEX regional climate model ensemble

Abstract. Large multiscenario multimodel ensembles (MMEs) of regional climate model (RCM) experiments driven by global climate models (GCMs) are made available worldwide and aim at providing robust estimates of climate changes and associated uncertainties. Due to many missing combinations of emission scenarios and climate models leading to sparse scenario–GCM–RCM matrices, these large ensembles, however, are very unbalanced, which makes uncertainty analyses impossible with standard approaches. In this paper, the uncertainty assessment is carried out by applying an advanced statistical approach, called QUALYPSO, to a very large ensemble of 87 EURO-CORDEX climate projections, the largest MME based on regional climate models ever produced in Europe. This analysis provides a detailed description of this MME, including (i) balanced estimates of mean changes for near-surface temperature and precipitation in Europe, (ii) the total uncertainty of projections and its partition as a function of time, and (iii) the list of the most important contributors to the model uncertainty. For changes in total precipitation and mean temperature in winter (DJF) and summer (JJA), the uncertainty due to RCMs can be as large as the uncertainty due to GCMs at the end of the century (2071–2099). Both uncertainty sources are mainly due to a small number of individual models clearly identified. Due to the highly unbalanced character of the MME, mean estimated changes can drastically differ from standard average estimates based on the raw ensemble of opportunity. For the RCP4.5 emission scenario in central–eastern Europe for instance, the difference between balanced and direct estimates is up to 0.8 ∘C for summer temperature changes and up to 20 % for summer precipitation changes at the end of the century.